研究者詳細 - 梅原　徳次

Effect of Water on Wear of DLC Coatings in High Temperature and Pressurized Ethanol 査読有り

Tokoroyama, T; Horikawa, S; Mimata, J; Umehara, N; Murashima, M

TRIBOLOGY LETTERS 72 巻 ( 4 ) 2024年12月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology Letters

The friction and wear characteristics of a-C:H:Si and a-C:H coatings in an ethanol environment at 120 °C and 10 MPa focusing on the effects of water and dissolved oxygen in ethanol were investigated. The friction tests were conducted using an autoclave chamber, with gases (oxygen or nitrogen) and ethanol–water mixtures (0 and 6 vol.%). The wear acceleration of a-C:H:Si took place when it slid in ethanol with 6 vol.% water and pressurized by oxygen, thus the specific wear rate was the highest, approximately 1.8 × 10−7 mm3/Nm. The reason of this wear acceleration was assumed the effect of hardness reduction due to oxidation of the a-C:H:Si, so the O/C ratio by AES and the hardness of topmost surface by AFM nano-scratch were investigated. As a result, the higher O/C ratio showed higher specific wear rate due to the hardness reduction from 13.3 to 6.0 GPa. These findings highlight the role of water and dissolved oxygen in accelerating wear of a-C:H:Si coatings. Graphical abstract: (Figure presented.)

DOI： 10.1007/s11249-024-01910-z

Proposal of a model for the influence of coating area on the electric field at the tip of electrocautery for suppressing tip charring and surgical smoke generation due to blood heating 査読有り

Journal of Advanced Mechanical Design, Systems, and Manufacturing 18 巻 ( 6 ) 頁： AMDSM00210 2024年11月

Corrosion and tribological properties of ta-C/ta-C: Ta coatings: Analysis of the influence of Ta-O/Ta-C ratio 査読有り

Li, LL; Tokoroyama, T; Zhang, RX; Umehara, N

TRIBOLOGY INTERNATIONAL 198 巻 2024年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

Multilayer ta-C/ta-C: Ta coatings with varying total thicknesses (300, 600, and 1000 nm) and layer thickness ratios (1:0.5, 1:1, and 1:2) between the ta-C layer and ta-C: Ta layer were prepared. The study investigated the static corrosion resistance and tribological properties of the coatings in the NaCl solution. The static corrosion resistance positive correlation depended on the coating surface's Ta-O/Ta-C ratio. The lowest friction coefficient of 0.05 was obtained from the coating with a total thickness of 1000 nm due to the formation of the graphitized transfer film on the counterpart surface. A decreased sp2/sp3 ratio and the formation of tantalum oxide on the wear scar contributed to the lowest corrosion current, corrosive defect density, and wear rate.

DOI： 10.1016/j.triboint.2024.109916

The development of B/Cr co-doped DLC coating by FCVA deposition system and its tribological properties at 300 °C 査読有り国際共著国際誌

Zhang, RX; Lee, WY; Umehara, N; Tokoroyama, T; Murashima, M; Takimoto, Y

SURFACE & COATINGS TECHNOLOGY 487 巻 2024年7月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Surface and Coatings Technology

The diamond-like carbon (DLC) coating prepared using filtered cathodic arc deposition (FCVA) lost its promising wear resistance under high temperatures. Element-doped DLC coatings have been investigated to suppress carbon oxidation reaction and subsequently enhance the wear resistance in high-temperature environments. Previous research clarified the excellent tribological properties of boron-doped DLC (B-DLC) but identified challenge such as arc discharge extinguishment and coating declamation (under high-temperature friction test). In this study, the introduction of Argon gas (10 sccm) during the deposition process stabilized stable arc discharge, resulting in high hardness and deposition rate. Moreover, a chromium interlayer and varying concentration of Cr dopant (0.5 %, 1.0 %, 3.0 % at.) were added to B-DLC to develop a stable, co-doped DLC with low friction and high wear resistance. Raman spectroscopy and nano-indentation revealed an increase in the disordered carbon structure and reduction in hardness and Young's Modulus with Cr doping. Macroscopic ball-on-disk friction test, showed 1 % Cr-doped B-DLC (a-C:B:Cr1) coating exhibited super low friction (avg. coefficient 0.02) and a low specific wear rate (<5.0 × 10−6 mm3/Nm). Raman spectroscopy indicated that the transferred graphite-like tribo-film onto the surface of Si3N4 counterparts contributed to stable low friction. Additionally, XPS analysis on the DLC coatings' wear track suggested the rich B–B bond might contribute to its high wear resistance. This successful improvement on element-doped DLC prepared by FCVA provided valuable insights for further exploration of DLC coating applied to various working situations.

DOI： 10.1016/j.surfcoat.2024.130968

Evaluating Palm Oil Ester Base Oils as Eco-Friendly Alternatives in Lubricant Formulation 査読有り国際共著

Samihah Mustaffha, Darius El Pebrian, Mohd Muhyiddin Mustafa, Noritsugu Umehara, Nik Roselina Nik Roseley, Mohamad Ali Ahmad, Nor Azmmi Masripan

Jurnal Tribologi 43 巻頁： 158 - 168 2024年6月

Tribocatalytic Reaction Enabled by TiO2 Nanoparticle for MoDTC-Derived Tribofilm Formation at ta-C/Steel Contact 査読有り国際共著国際誌

Matsukawa, D; Park, JH; Lee, WY; Tokoroyama, T; Kim, JI; Ichino, R; Umehara, N

COATINGS 14 巻 ( 6 ) 2024年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Coatings

Tribochemically produced triboproducts are becoming increasingly important in tribosystems and serve to improve system performance by preventing friction or wear. Diamond-like carbon (DLC) is chemically stable, which features a trade-off with tribological pros and cons. Chemically stable DLC is thermally stable and suppresses surface damage in a high-temperature operating environment; however, it causes a detrimental effect that hinders the formation of a competent tribofilm. In this study, we dispersed highly reactive TiO2 nanoparticles (TDONPs) in molybdenum dithiocarbamate (MoDTC)-containing lubricant for adhering triboproducts on the DLC surface. In addition, TDONPs contributed to the decomposition of triboproducts by promoting the decomposition of MoDTC through its catalytic role. Rutile TDONPs were more helpful in reducing friction than anatase TDONPs and improved the friction performance by up to ~100%.

DOI： 10.3390/coatings14060773

Super hardening of Fe-W alloy plating by phase transformation of amorphous to metal carbides-dispersed nanocrystalline alloys and application as promising alternative for hard chromium plating 査読有り国際共著

J.H. Park, J.I. Kim, Y. Shinohara, T. Hagio, N. Umehara, R. Ichino

SURFACE & COATINGS TECHNOLOGY 477 巻頁： 130388 2024年5月

Creation of anti-frost micro-plastic texture surfaces enhancing thermal conductivity by carbon black containing in polyvinyl chloride 査読有り

T. Tokoroyama, L. Zhang, W. Wu, M. Murashima, N.Umehara

Journal of Advanced Mechanical Design, Systems, and Manufacturing 18 巻 ( 3 ) 頁： JAMDSM0032 2024年5月

Effect of PAO-4 and MoDTC + ZnDTP oil additive lubricants on the tribological performance of novel tetrahedral amorphous carbon (ta-C) coatings 査読有り国際共著国際誌

Mustafa M.M.B., Umehara N., Tokoroyama T., Murashima M., Utsumi Y., Moriguchi H., Shibata A.

Tribology International 193 巻 2024年5月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

This study was carried out to assess the effect of PAO-4 and mineral oil mixed with MoDTC and ZnDTP on the tribological performance of novel tetrahedral-amorphous-carbon (ta-C) coatings namely P:ta-C, and M:ta-C, were analysed using the Pin-on-Disk Tribo-tester with a fixed normal load, temperature, sliding distance and speed of 20 N, 80 °C, 250 m and 0.068 ms−1 for 60 min, respectively. The C:ta-C, P:ta-C, and M:ta-C showed excellent wear resistance when lubricated with MoDTC + ZnDTP. The formation of weak Zn-derived tribofilm on the P:ta-C coating contributed to the strong wear resistance and reduced friction coefficient. Moreover, the passive transfer of ferrous compounds from the SUJ2 disk induced the development of weak Zn-derived tribofilm on the P:ta-C and M:ta-C.

DOI： 10.1016/j.triboint.2024.109396

The 1 μm wear particles entrainment in situ observation via fluorescent staining silica particles by silane coupling with Rhodamine B 査読有り

T. Tokoroyama, M. Okashita, N. Fusetani, M. Murashima, N. Hashizume, R. Tsuboi, H. Shiomi, N. Umehara

FRONTIERS IN MECHANICAL ENGINEERING-SWITZERLAND 10 巻頁： 1371948 2024年4月

コハク酸イミド分散剤がATF油中摩擦におけるトライボ被膜の生成に及ぼす影響査読有り

野老山貴行, 寺井勇裕, 梅原徳次, 村島基之, 本田晃之, 足立常夫

トライボロジスト advpub 巻 ( 0 ) 2024年3月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

To elucidate the mechanism for suppressing wear of high-speed bearing steel (SUJ2) used in automatic transmission fluid (ATF), friction and wear tests were conducted in lubricating oils containing different concentrations of succinimide dispersant. The wear volume of the SUJ2 disk in the base oil was approximately 1.4×10⁴mm³. However, with the addition of 0.75 wt.% of succinimide dispersant, the wear volume decreased to about 0.4×10⁴mm³, approximately one-third of the original amount. In Fluid A and Fluid A I₀.₇₅-I₂.₇₅, the reduction in wear volume was observed only in Fluid A I₀.₇₅. This was believed to be due to the presence of succinimide dispersant, which led to the formation of iron oxide within the wear scars, and on the surface, FeS and FeS₂formed as tribofilms. In the case of Fluid A I₀.₇₅, the film hardness was higher, contributing to improved wear resistance. The sole reason for the increased hardness of the tribofilm in Fluid A I₀.₇₅was hypothesized to be the repeated friction of the tribofilm within the surface, leading to the deposition of FeS and FeS₂. This, in turn, was presumed to enhance the density of the tribofilm.

DOI： 10.18914/tribologist.23-00021

Lubricity performance of hydrogen-free CVD growth of graphene on copper particles as an additive in paraffin base oil 査読有り国際共著国際誌

Rahman, NL; Amiruddin, H; Abdollah, MFB; Umehara, N

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY 238 巻 ( 7 ) 頁： 869 - 879 2024年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology

This study aims to examine the impact of carbon precursor materials, which are oil palm fiber (OPF) and waste polystyrene (PS), on friction and wear properties of paraffin base oil added with graphene-coated copper (Cu) additive. The graphene was synthesized on Cu particles via hydrogen-free chemical vapor deposition method. The graphene was characterized using Raman spectroscopy and transmission electron microscopy. The lubricity properties of 0.6 wt.% of synthesized graphene-coated Cu additive in paraffin base oil was analyzed based on its tribological behavior using a four-ball tribometer. From the quantitative and qualitative characterization analysis, graphene-coated Cu additive synthesized using 50 wt.% OPF carbon precursors has a good-quality graphene with minimal defects and a well-ordered lattice structure. From the tribological analysis, the paraffin base oil added with graphene-coated Cu additive synthesized using 50 wt.% OPF carbon precursor has the lowest coefficient of friction of 0.07 and wear rate of 1.6 × 10−5 mm3/min. Hence, it can be suggested that incorporating graphene-coated Cu particles, synthesized from a 50 wt.% OPF carbon precursor, into base oil shows great potential as an environmentally friendly additive, particularly in terms of enhancing lubrication performance.

DOI： 10.1177/13506501241236826

The ta-C Hardness Effect on Wear Properties Under MoDTC Contained Boundary Lubrication 査読有り国際共著国際誌

Tokoroyama, T; Wang, S; Umehara, N; Murashima, M; Lee, WY

TRIBOLOGY LETTERS 72 巻 ( 1 ) 2024年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology Letters

The accelerated wear of hydrogenated amorphous carbon in the presence of molybdenum dithiocarbamate (MoDTC) lubrication is a significant challenge when considering its application in engine components. While it is presumed that the use of high-hardness tetrahedral amorphous carbon (ta-C) can effectively address wear issues, irrespective of chemical wear caused by Mo-degradable materials, we have yet to understand the impact of ta-C coating hardness on wear when combined with MoDTC. This uncertainty arises from the assumption that the quantity and structure of Mo-degradable material may be linked to contact pressure, implying that even with a highly hard ta-C coating, wear may vary with the applied load. In this study, we prepared ta-C coatings with four different hardness levels (such as approximately 18.2, 22.1, 46.6, and 53.6 GPa) and conducted friction tests to elucidate the influence of ta-C hardness on wear characteristics under boundary lubrication with MoDTC. Subsequently, we performed chemical analysis (Raman, EDS, and XPS) to identify the chemical species present in the tribofilm, with a particular focus on the 22.1 GPa ta-C coating as a representative of low-hardness ta-C coatings. Our findings revealed that wear suppression was achieved the contact pressure exceeded 200 MPa, irrespective of the coating hardness. Graphical abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s11249-023-01804-6

Clarification of the Effect of Surface Energy on Tribological Behavior of Two-Phase Lubricant Using Reflectance Spectroscopy and Hydrodynamic Analysis 査読有り国際共著国際誌

Hirata, K; Murashima, M; Umehara, N; Tokoroyama, T; Lee, WY; Hashizume, N; Sato, T; Nagata, R; Hanyuda, K; Otsuka, A; Ueda, M

TRIBOLOGY LETTERS 72 巻 ( 1 ) 2024年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology Letters

Recently, a new type of lubricant called two-phase lubricants has been developed to realize a high viscosity index. Two-phase lubricants are mixtures of two different lubricants, realizing low viscosity even at low temperatures due to the temperature dependence of the solubility of the lubricant molecules. In the present paper, the effect of surface energy on the tribological behavior of the two-phase lubricant is clarified using in situ observation with reflection spectroscopy. Sliding surfaces with high hydrogen-bonding terms in the surface energy components attracted high-polar lubricants, resulting in reduced friction. Analysis of the theoretical friction coefficient using Couette flow assumption revealed an important design concept of two-phase lubricants: the concentration of high viscosity lubricants on solid surfaces develops a viscosity distribution in the oil film, resulting in reduced friction.

DOI： 10.1007/s11249-023-01827-z

Effect of the graphite domain direction on the friction coefficient of tetrahedral amorphous carbon nitride 査読有り国際誌

Tokoroyama T., Fujiwara C., Murashima M., Yamaguchi M., Umehara N.

Diamond and Related Materials 143 巻 2024年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Diamond and Related Materials

Polarized surface-enhanced Raman scattering was applied to low- and high- friction surfaces of tetrahedral amorphous carbon nitride (ta-CNx) to reveal the presence of the graphite structure and investigate the angular dependence of the graphite domains that formed on the topmost surface. The measured D peak intensity differed along the incident electric field toward the sliding direction, from parallel to perpendicular and armchair edges may be present. The results for the low- friction surface indicated that graphite domains exist on the ta-CNx disk and transfer layer on the counter material (Si3N4) ball in directions different from the sliding friction, which suggests an incommensurate configuration.

DOI： 10.1016/j.diamond.2024.110853

In situ Observation of the Formation of MoDTC-Derived Tribofilm on a Bearing Steel with Different Surface Roughness by Using a Reflectance Spectroscopy and Its Effects on Friction 査読有り国際共著国際誌

Hashizume, N; Tokoroyama, T; Umehara, N; Murashima, M; Lee, WY; Zhang, RX; Kunisu, M; Shioji, H; Oharada, K

TRIBOLOGY LETTERS 72 巻 ( 1 ) 2024年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology Letters

In this paper, we evaluated the formation of MoDTC-derived tribofilm and its effects on friction reduction. We conducted in situ observation using reflectance spectroscopy to monitor the tribofilm's evolution during friction, allowing us to estimate its thickness and composition. The results revealed that the rough specimen (Ra= 12.7 nm) maintained a smaller friction coefficient and a larger volume fraction of MoS2 compared to the smooth specimen (Ra= 2.6 nm). Additionally, using the in situ observed composition and contact state, we inferred changes in the frictional properties of the tribofilm formed on both specimens. This analysis suggested that the pronounced direct contact of asperities, especially evident in the rough specimen, promoted the formation of a low-friction tribofilm (primarily MoS2), enabling the rough specimen to sustain lower friction. Graphical abstract: [Figure not available: see fulltext.].

DOI： 10.1007/s11249-023-01810-8

Synthesising graphene with renewably-sourced bio-carbon precursors: a brief review 査読有り国際共著国際誌

Abd Rahman F.H., Amiruddin H., Abdollah M.F.B., Mohd Zulkifli N.W., Samion S., Umehara N., Tanemura M., Honda M., Morina A.

Journal of the Brazilian Society of Mechanical Sciences and Engineering 46 巻 ( 3 ) 2024年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Brazilian Society of Mechanical Sciences and Engineering

Graphene is a 2D material with exceptional properties that surpass those of many other materials in many respects. Conventional methods of graphene synthesis heavily rely on gaseous carbon (C) precursors, primarily hydrocarbons; such as methane or ethylene; that have significantly negative effects on the environment. The global shift towards sustainability and eco-conscious practices has increased the need for graphene production methods that are sustainable. As such, multiple studies have explored alternative sources of C, particularly bio-based materials, as well as waste-to-value processes. Reusing bio-based materials as C-based precursors not only addresses the urgent need for C sources that are sustainable and environmentally friendly but effectively creates a circular economy in the materials science and technology industry. As such, this present study explores the methods of synthesising, applying, and optimising the conversion of bio-based renewable solid carbon (SC) and liquid carbon (LC) precursors derived from a diverse range of C sources; such as lignocellulosic biomass, agricultural residues, and everyday vegetable oils; into high-quality graphene. The findings emphasise the promising role of renewable SC and LC precursors in the pursuit of sustainable and environmentally responsible methods of graphene production.

DOI： 10.1007/s40430-024-04743-y

The 1 μm wear particles entrainment in situ observation via fluorescent staining silica particles by silane coupling with Rhodamine B 査読有り

The Effect of Carbon Structure of DLC Coatings on Friction Characteristics of MoDTC-Derived Tribofilm by Using an In Situ Reflectance Spectroscopy 査読有り国際共著国際誌

Hashizume, N; Yamamoto, Y; Chen, C; Tokoroyama, T; Zhang, RX; Diao, DF; Umehara, N

TRIBOLOGY LETTERS 72 巻 ( 1 ) 2024年3月

Tokoroyama, T; Okashita, M; Fusetani, N; Murashima, M; Hashizume, N; Tsuboi, R; Shiomi, H; Umehara, N

FRONTIERS IN MECHANICAL ENGINEERING-SWITZERLAND 10 巻 2024年2月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Frontiers in Mechanical Engineering

Observing wear debris during friction is crucial for comprehending the wear behavior of lubrication systems. Despite various techniques attempted for observation, a persistent challenge is the oversight of wear debris with a diameter less than 1 μm, mainly due to limitations in measurement systems. Consequently, we still lack a comprehensive understanding of whether these small particles can infiltrate contact points and serve as abrasives. In this study, we conducted in-situ friction tests to investigate the entrainment of imitation wear particles at the contact point under boundary lubrication conditions. These imitation wear particles were glass beads with diameters of approximately 0.8 μm, 1.0 μm, and 3.0 μm, respectively. To address optical limitations, we stained these particles using silane coupling to attach Rhodamine B to the glass beads. We examined the effect of particle diameter on entrainment numbers under varying outside oil film thicknesses. The results showed that the entrainment number was highest when the outside oil film thickness matched the particle diameter. This clearly indicated that the outside oil film thickness significantly influenced the entrainment of particles.

DOI： 10.3389/fmech.2024.1371948

Park, JH; Kim, JI; Shinohara, Y; Hagio, T; Umehara, N; Ichino, R

SURFACE & COATINGS TECHNOLOGY 477 巻 2024年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Surface and Coatings Technology

Despite the superior hardness, wear resistance, and corrosion resistance of hard chromium (Cr) plating using toxic hexavalent chromium (Cr6+), the gradual restriction on the use of Cr6+ in industrial fields necessitates the development of an alternative, harmless plating material with excellent performance. Here, we report the fabrication of super-hard plating by the simple annealing of electrodeposited Fe–W–C plating as a promising alternative for hard Cr plating. Amorphous-structured Fe–W–C plating, including co-deposited citric acid-derived carbon, forms uniformly dispersed ternary metal carbides inside the plating during annealing, which changes the plating structure from amorphous to nano-carbide-dispersed alloys. The phase-transformed, nanocrystalline Fe–W–C alloy annealed at 700 °C exhibited a maximum hardness of 20.5 GPa, which surpassed the hardness of hard Cr plating (12.5 GPa). The ball-on-disc tribo-test and corrosion test results further demonstrated the superior wear and anti-corrosion properties of the carbide-dispersed Fe–W–C alloy plating compared with hard Cr plating. This study develops the applicability of this super-hard plating as a new hard coating material that overcomes the limitations of conventional metal plating without using any toxic chemical.

DOI： 10.1016/j.surfcoat.2024.130388

Development of an Electrocautery Surface Coating Method to Suppress Surgical Smoke 査読有り

Takayuki Tokoroyama, Motoyuki Murashima, Koki Ogawa, Noritsugu Umehara,

Journal of Surgery and Research 2024年1月

Nitrogen-containing diamond-like carbon deposited on glass substrate via filtered cathodic vacuum arc with high-frequency pulsed DC substrate bias 査読有り国際共著国際誌

Kim, JI; Lee, WY; Tanaka, K; Tokoroyama, T; Murashima, M; Umehara, N

SURFACES AND INTERFACES 44 巻 2024年1月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Surfaces and Interfaces

This research investigates the properties of nitrogen-containing diamond-like carbon (N-DLC) coatings deposited on glass substrate using a high-frequency pulsed-DC substrate bias. The study involved comprehensive investigations to understand how variations in carbon bonding affect the properties of N-DLC coatings. By adjusting the voltage, frequency and duty ratio of the pulsed bias, it was possible to deposit an optical coating with a transmittance of up to 52 % at range of 800–2500 nm while effectively preventing the peeling of the DLC coating on the glass. With increasing the clustered graphite structure in the DLC coating, the sheet resistance was lowered from 2370 kΩ/□ to 36 kΩ/□, and the electrical properties were also improved. The findings provide valuable insights for optimizing N-DLC coatings for non-conductors, e.g., glass, rubber, polymer, and engineering ceramic.

DOI： 10.1016/j.surfin.2023.103695

Creation of anti-frost micro-plastic texture surfaces enhancing thermal conductivity by carbon black containing in polyvinyl chloride 査読有り

Tokoroyama, T; Zhang, LY; Wu, WJ; Murashima, M; Umehara, N

JOURNAL OF ADVANCED MECHANICAL DESIGN SYSTEMS AND MANUFACTURING 18 巻 ( 3 ) 頁： JAMDSM0032 - JAMDSM0032 2024年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本機械学会

Frost formation poses challenges in various sectors, impacting efficiency and safety. Active methods involve energy-consuming processes like heating, while passive approaches utilize protective coatings or hydrophobic surfaces to minimize frost aggregation. However, low thermal conductivity remains a concern. In previous research, lotus leaves inspired micro-meter-sized asperities were effective in controlling frost growth. Applying this concept to plastic, particularly low-cost PVC, raised challenges due to its low thermal conductivity. The study explores utilizing carbon black (CB) waste from hard coating processes to enhance PVC's thermal conductivity, forming a micro-plastic texture (MPT). The research investigates the influence of CB amount and AC voltage frequency on MPT features and thermal conductivity, aiming for a sustainable solution to address frost-related issues. Incorporating 0.9 vol.% CB into PVC solution under a 2 kV AC electric field (6 Hz) resulted in an extensively distributed MPT on the surface. This MPT, formed under the 6 Hz condition, exhibited no in-plane bias, making it an ideal surface for preventing frost formation. Adding CB to PVC within the range of 0 to 2.1 vol.% and applying a 2 kV, 6 Hz AC electric field led to independent MPT formation at concentrations between 0.4 to 1.2 vol.%. Conducting cooling tests in atmospheric and vacuum conditions, we found that MPT with 0.9 vol.% CB displayed a thermal conductivity of approximately 0.19 kW/mK in atmospheric conditions, similar to aluminum alloy. However, with 1.2 vol.% or more CB, it decreased to about 0.15 kW/mK. In vacuum conditions, MPT with 1.2 vol.% CB exhibited a higher thermal conductivity of 0.063 kW/mK compared to the 0.055 kW/mK observed in MPT with 0 vol.% CB.

DOI： 10.1299/jamdsm.2024jamdsm0032

Active control of Lubricant Flow Using Dielectrophoresis and Its Effect on Friction Reduction 査読有り

Murashima Motoyuki, Aono Kazuma, Umehara Noritsugu, Tokoroyama Takayuki, Lee Woo-Young

Tribology Online 18 巻 ( 6 ) 頁： 292 - 301 2023年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Society of Tribologists

With the increasing demand for active friction control, we newly proposed to use dielectrophoresis to change the flow of PG-droplet-containing PAO4 to reduce the friction coefficient. The friction result with a 1-mm roller shows 20% reduction in friction coefficient (from 0.065 to 0.052) at AC 100 V, and in situ observation exhibits that PG tracks are formed over the contact area. On the other hand, at a high bias of 1000 V, the friction coefficient increases to 0.065. In this situation, in situ observation exhibits that PG forms a horseshoe-shaped track covering only the roller edges. Controlled friction tests and FEM analysis using 5-mm rollers revealed a unique behavior; a balanced bias effectively attracts the PG to the roller surface, and surface forces can resist mild dielectrophoretic forces to spread the PG across the roller surface. The present study strongly suggests the importance that the bias strength should be controlled to achieve a balance between surface force and dielectrophoretic force in order to obtain excellent lubrication conditions.

DOI： 10.2474/trol.18.292

Clarification of the effects of adsorption films of ester-blended oil on friction by in situ reflectance spectroscopy 査読有り国際共著国際誌

Hirata Kodai, Murashima Motoyuki, Umehara Noritsugu, Tokoroyama Takayuki, Hashizume Naoya, Lee Woo -Young, Takekawa Daisuke, Narita Keiichi

TRIBOLOGY INTERNATIONAL 187 巻 2023年9月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

In recent years, the demand for friction reduction in oil lubrication systems has become increasingly important due to the need to improve fuel economy and achieve carbon neutrality. Ester-based lubricants are known to show low friction and environmentally friendly, and they have high viscosity indexes. In the present paper, first, in situ reflectance spectroscopy was used to clarify the behavior of the oil-film thickness increase during sliding. The results showed that as the number of ester bonds increased from 1 to 4, the ester oil film thickened and the friction coefficient decreased from 0.10 to 0.06. In addition, oleic-acid-type lubricants were found to have superior ability to form a thicker oil film than the isostearic acid type.

DOI： 10.1016/j.triboint.2023.108718

Synthesis and characterisation of oil palm fibre-based graphene deposited on copper particles for superlubricity oil additive 査読有り国際共著国際誌

Rahman Nurul Liyana, Amiruddin Hilmi, Bin Abdollah Mohd Fadzli, Umehara Noritsugu

JURNAL TRIBOLOGI 37 巻頁： 128 - 141 2023年6月

Effects of Phosphonate Additives with Hydroxy Groups on the Tribological Properties of ta-C Coatings Under Boundary Lubrication 査読有り国際誌

Tanaka Kento, Tokoroyama Takayuki, Umehara Noritsugu, Murashima Motoyuki, Oshio Tadashi, Yagishita Kazuhiro

TRIBOLOGY LETTERS 71 巻 ( 2 ) 2023年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology Letters

Additives that are optimized for diamond-like carbon (DLC) coatings are highly demanded as their applications have expanded recently. In this study, friction tests were conducted on a tetrahedral amorphous carbon (ta-C)/ta-C tribopair using a phosphonate additive with hydroxy groups, which comprises glycerol monooleate (an additive that reduces the friction of DLC) and zinc dialkyl dithiophosphate (an additive that reduces wear), and the obtained tribolayers were analyzed using AFM, XPS, and ToF–SIMS. We found that the phosphonate additive with hydroxy groups tribochemically reacted with the ta-C coating to form a low-shear, hard tribolayer on the surface, thereby reducing the friction and wear of the ta-C coating. Our results indicate that additives with phosphonate structures and hydroxy groups are effective for DLC coatings. Graphical abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s11249-023-01734-3

An effective strategy for improving the performance of electrodeposited Fe-W alloy plating: Tailoring microstructure by graphene incorporation 査読有り国際共著国際誌

Shinohara Yu, Park Jae-Hyeok, Hagio Takeshi, Kim Jae-Il, Lee Woo-Young, Umehara Noritsugu, Ichino Ryoichi

MATERIALS & DESIGN 230 巻 2023年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials and Design

Despite the excellent performance of hard Cr plating using hexavalent chromium (Cr6+), its use is being restricted owing to recent environmental regulations. Electrodeposited Fe-W alloy is considered a possible alternative, but its high coefficient of friction (COF), high wear rate owing to tribo-oxidation, and high corrosion rate hinder its practical application. In this study, we attempted to solve these problems by modifying the microstructure of Fe-W alloy by incorporating 2D-structured graphene. The effect of graphene incorporation on the structure of the Fe-W alloy and its properties, especially microhardness, wear, and corrosion resistance, were investigated. The results showed the graphene effectively modified the columnar structure of the Fe-W alloy by inhibiting the vertical growth of clusters during electrodeposition, leading to fragmentation of the vertical cluster boundaries. This improved the hardness by as much as 17 % up to 9.1 GPa, and the corrosion resistance by changing the corrosion mechanism from localized corrosion to uniform corrosion. In addition, the graphene reduced the COF and wear rate by reducing the Fe2O3 formed by tribo-oxidation to a lower oxidation state. The structural modification of the plating by graphene incorporation thus provides an effective solution to improving the performance of Fe-W alloys.

DOI： 10.1016/j.matdes.2023.111938

Synthesis and characterisation of oil palm fibre-based graphene deposited on copper particles for superlubricity oil additive 査読有り国際共著国際誌

Rahman N.L., Amiruddin H., Abdollah M.F.B., Umehara N.

Jurnal Tribologi 37 巻頁： 128 - 141 2023年6月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Jurnal Tribologi

This paper presents the synthesis and characterisation of oil palm fibre-based graphene deposited on copper (Cu) particles for superlubricity oil additive. Oil palm fibre (OPF) is employed as a renewable carbon feedstock to grow graphene on Cu particles during Chemical Vapor Deposition (CVD) process. The surface morphology was observed using Scanning Electron Microscopy (SEM) embedded with Energy Dispersive X-Ray Analysis (EDX), and Transmission Electron Microscopy (TEM). Meanwhile, the presence and quality of graphene were validated and examined using Gaussian analysis of Raman spectroscopy. The results show that decreasing the peak D to peak G intensity ratio (ID/IG) tends to improve graphene quality with less number density of structural defects. The I2D/IG value greater than 1 is indicative of multilayer graphene growth. Increasing the full width at half maximum (FWHM) ratio of peak D to peak G (FWHMD/FWHMG) suggests a better dispersion of graphene. The uniform spread of surface ‘wrinkles’ observed by SEM and TEM implies that the distribution of graphene is more homogeneous on the surface of Cu particles. Further investigation into the synergistic effect of graphene as an oil additive can be performed to achieve superlubricity properties.

Superlubricity with Graphitization in Ti-Doped DLC/Steel Tribopair: Response on Humidity and Temperature 査読有り国際共著国際誌

Kim Jae-Il, Lee Woo-Young, Tokoroyama Takayuki, Umehara Noritsugu

ACS APPLIED MATERIALS & INTERFACES 15 巻 ( 15 ) 頁： 19715 - 19729 2023年4月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Materials and Interfaces

The anti-friction of diamond-like carbon (DLC) is achieved by a well-developed carbonaceous transfer layer, and Ti-doped DLC is developed into a robustly built-up carbonaceous transfer layer. The friction performance of DLC depends on the operating environment, e.g., ambient gas, humidity, temperature, lubricants, and mating material. In this study, we aimed to reveal the environmental sensitivities of Ti-DLC on friction characteristics. To this end, a Ti-DLC was rubbed against a steel ball, and friction behaviors were evaluated with different gas compositions, humidity, and temperature. Finally, we identified that fractional coverage of water on surfaces affected the anti-graphitization on Ti-DLC, leading to avoiding friction reduction.

DOI： 10.1021/acsami.3c01704

Influence of Defects in Graphene-Like Network of Diamond-Like Carbon on Silica Scale Adhesion 査読有り国際誌

Nakashima Y., Umehara N., Kousaka H., Tokoroyama T., Murashima M., Murakami K.

TRIBOLOGY LETTERS 71 巻 ( 1 ) 2023年2月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology Letters

Silica scale adhesion onto geothermal power plant equipment reduces the power efficiency. In our previous study, diamond-like carbon (DLC) coatings with low sp2 fractions and high hydrogen contents were found to suppress silica adhesion. Therefore, the present study was aimed at clarifying the mechanism of silica adhesion onto the graphene-like network of DLC. In-lens scanning electron microscopic imaging of silica adhered onto defective graphene indicated that the adhesion occurred on defects in the graphene-like network. First-principles calculations revealed that the graphene with hydrogen-terminated defects exhibited reduced adsorption energy between silica and the graphene-like network. Overall, the simulations and experiments helped establish a silica adhesion model in which defects in the graphene-like network of DLC behave as silica adhesion sites. Graphical Abstract: [Figure not available: see fulltext.].

DOI： 10.1007/s11249-022-01690-4

Novel friction stabilization technology for surface damage conditions using machine learning 査読有り国際共著国際誌

Murashima Motoyuki, Yamada Takazumi, Umehara Noritsugu, Tokoroyama Takayuki, Lee Woo -Young

TRIBOLOGY INTERNATIONAL 180 巻 2023年2月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

The surface damage is a serious cause of failure in tribosystems. In the present paper, we propose a new damage avoidance method that combines a contact position control system (e.g., morphing surface) and artificial-intelligence-based control (e.g., genetic algorithm: GA) to achieve stable friction and long life of sliding surfaces. In the case of the single-damage condition, the GA sequentially avoided contact with the damaged position, and finally complete damage avoidance was achieved. In the multiple-damage condition, we confirmed that learning by GA effectively stabilized friction, although the learning time was longer. In summary, the contact-position control method should provide new capabilities on real machine surfaces where unexpected damage occurs.

DOI： 10.1016/j.triboint.2023.108280

Long-term low-friction of Ti-overcoated and-doped DLCs: Robustly developed carbonous transfer layer with titanium 査読有り国際共著国際誌

Kim Jae-Il, Lee Woo-Young, Tokoroyama Takayuki, Umehara Noritsugu

CARBON 204 巻頁： 268 - 283 2023年2月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Carbon

Diamond-like carbon (DLC) has been under the research spotlight as an exceptional solid lubricant. Its friction performance is depending on a well-developed transfer layer upon its counterparts. Nowadays, iron-and brass-based metals have been utilized as the counterpart against DLC, however, it is reported their friction behaviors are somewhat inferior compared to titanium alloys. In this study, we tried to improve their friction behaviors and modified the contact interface from Fe/C to C/C by Ti addition in DLC. It was revealed that Ti, which has good adhesion for Fe and C, promoted the development of carbon transfer on Fe-based counterpart. Furthermore, Ti built-up a thick carbonous transfer layer and make better the friction performance of DLC sliding against Fe.

DOI： 10.1016/j.carbon.2022.12.012

Mechanical properties of maze-like carbon nanowalls synthesized by the radial injection plasma enhanced chemical vapor deposition method 査読有り国際共著国際誌

Ghodke Swapnil, Murashima Motoyuki, Christy Dennis, Van Nong Ngo, Ishikawa Kenji, Oda Osamu, Umehara Noritsugu, Hori Masaru

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 862 巻 2023年1月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering: A

The unique structural properties of vertically aligned graphene sheets or Carbon Nanowalls (CNWs) have attracted great interests for their potential for various applications in microelectronic devices, energy storage, and catalyst support materials. During the handling or operation of the devices, tension and/or pressure are often needed. Under such conditions, CNWs must undergo compression and stress. Therefore, the deformation mechanism and evolution behavior of the CNW structures under load play a critical role in the performance and reliability of the devices. In this study, the mechanical properties of a typical maze-like CNW structure synthesized by a Radial Injection Plasma Enhanced Chemical Vapor Deposition (RI-PECVD) technique were analyzed by employing the nanoindentation method. The measured compressive strength of the CNW structure was 50 MPa with an average modulus E value of ∼28 GPa, which is significantly higher than that of pyrolytic graphite and other graphene-based materials such as 3D graphene-derived carbon, commercial graphene, and reduced graphene oxide films. An elastoplastic behavior of a soft material was observed in high-resolution microscopy and a mechanism of deformation for CNWs is elucidated.

DOI： 10.1016/j.msea.2022.144428

Tribo-chemical wear of various 3d-transition metals against DLC: Influence of tribo-oxidation and low-shear transferred layer 査読有り国際共著国際誌

Kim Jae-Il, Tokoroyama Takayuki, Murashima Motoyuki, Umehara Noritsugu, Lee Woo-Young

TRIBOLOGY INTERNATIONAL 177 巻頁： 107938 - 107938 2023年1月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

Diamond-like carbon (DLC) is a promising solid lubricant owing to its excellent anti-friction and wear-resistance characteristics. However, the high hardness of DLC causes two-body abrasion to its counterpart, which generally are ferrous and brass metals having a relatively low hardness, resulting in severe wear of counterpart. Therefore, it is required to solve the wear-imbalance issue, leading to noise and vibration in tribo-system. In this study, we aimed to investigate the wear behavior of counterparts sliding against DLC. We used four-3d-transition metals (Ti, Fe, Ni, and Cu) as the counterpart of DLC, based on the chemical properties for carbon and oxygen, i.e., the activation energy of oxidation and work of separation with carbon. Our finding is suggested that the wear of transition metals was governed by oxidative wear rather than mechanical wear (e.g., adhesive wear and abrasive wear). Moreover, their oxidative wear was prevented by carbon-containing tribofilm, which is transferred from DLC continuously. It revealed that severe oxidational wear was caused in copper and iron, because of their chemical properties.

DOI： 10.1016/j.triboint.2022.107938

Carbon-based coatings for suppression of silica adhesion in geothermal power generation 査読有り国際誌

Nakashima Y., Umehara N., Kousaka H., Tokoroyama T., Murashima M., Mori D.

TRIBOLOGY INTERNATIONAL 177 巻頁： 107956 - 107956 2023年1月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

Geothermal steam, the power source in geothermal power generation, contains a large amount of silica. Silica adhesion on geothermal power generator equipment hinders stable power generation. This work aimed to suppress silica adhesion by using diamond-like carbon (DLC). DLC with various surface structures was investigated by X-ray fine structure and elastic recoil detection analysis. The adhered silica amount was drastically reduced by using DLC rather than turbine steel. Further, the optimum DLC structure to reduce silica adhesion was revealed. Reducing the sp² bond fraction and increasing the hydrogen content of the outermost surface of DLC reduce the adhered silica amount, although there was no correlation with the surface energy. Therefore, silica adhesion has a different mechanism from conventional adhesion.

DOI： 10.1016/j.triboint.2022.107956

トライボロジーの本質とこれから招待有り

梅原徳次

トライボロジスト 67 巻 ( 12 ) 頁： 813 - 813 2022年12月

The Tribological Property of a-C:H Coating with Tribolayer by Additive Having Glycerol and Phosphate Oxide Structure 査読有り国際共著国際誌

Tokoroyama T., Tanaka K., Kani T., Murashima M., Lee W-Y, Umehara N., Oshio T., Yagishita K.

TRIBOLOGY LETTERS 70 巻 ( 4 ) 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology Letters

The tribological properties of a-C:H coating sliding against a SUJ2 ball, a SUJ2 roller, and an a-C:H coated roller were investigated under temperatures ranging from 20 to 80 °C in PAO with different additives. The additives had a glycerol and hydroxyl functional group in one molecule to enhance additive adsorption for mating with the a-C:H coating disk material and to build a phosphorus oxide tribolayer. Additives with different numbers of hydroxyl groups and primary or secondary-type C6H13O structures were also prepared. The tribolayer derived from each additive was analyzed via EDS, XPS, and ToF-SIMS. XPS depth analysis for the tribolayers revealed that additives were dissociated by friction and suggested C–O bond cleavage occurred. Graphical Abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s11249-022-01659-3

Metal matrix nanocomposites in tribology: Manufacturing, performance, and mechanisms 査読有り国際共著

Pan Shuaihang, Jin Kaiyuan, Wang Tianlu, Zhang Zhinan, Zheng Long, Umehara Noritsugu

FRICTION 10 巻 ( 10 ) 頁： 1596 - 1634 2022年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Friction

Metal matrix nanocomposites (MMNCs) become irreplaceable in tribology industries, due to their supreme mechanical properties and satisfactory tribological behavior. However, due to the dual complexity of MMNC systems and tribological process, the anti-friction and anti-wear mechanisms are unclear, and the subsequent tribological performance prediction and design of MMNCs are not easily possible: A critical up-to-date review is needed for MMNCs in tribology. This review systematically summarized the fabrication, manufacturing, and processing techniques for high-quality MMNC bulk and surface coating materials in tribology. Then, important factors determining the tribological performance (mainly anti-friction evaluation by the coefficient of friction (CoF) and anti-wear assessment with wear rate) in MMNCs have been investigated thoroughly, and the correlations have been analyzed to reveal their potential coupling/synergetic roles of tuning tribological behavior of MMNCs. Most importantly, this review combined the classical metal/alloy friction and wear theories and adapted them to give a (semi-)quantitative description of the detailed mechanisms of improved anti-friction and anti-wear performance in MMNCs. To guarantee the universal applications of these mechanisms, their links with the analyzed influencing factors (e.g., loading forces) and characteristic features like tribo-film have been clarified. This approach forms a solid basis for understanding, predicting, and engineering MMNCs’ tribological behavior, instead of pure phenomenology and experimental observation. Later, the pathway to achieve a broader application for MMNCs in tribo-related fields like smart materials, biomedical devices, energy storage, and electronics has been concisely discussed, with the focus on the potential development of modeling, experimental, and theoretical techniques in MMNCs’ tribological processes. In general, this review tries to elucidate the complex tribo-performances of MMNCs in a fundamentally universal yet straightforward way, and the discussion and summary in this review for the tribological performance in MMNCs could become a useful supplementary to and an insightful guidance for the current MMNC tribology study, research, and engineering innovations. [Figure not available: see fulltext.]

DOI： 10.1007/s40544-021-0572-7

New in situ low-friction technology for diamond-like carbon coatings using surface discharge treatment in ambient air 査読有り国際共著国際誌

Murashima Motoyuki, Oyama Shintaro, Kousaka Hiroyuki, Tokoroyama Takayuki, Lee Woo-Young, Umehara Noritsugu

TRIBOLOGY INTERNATIONAL 165 巻頁： 107306 - 107306 2022年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

In the present paper, we develop a new in situ low-friction technology for diamond-like carbon coatings using surface discharge in ambient air. As a result, the friction coefficient dropped from 0.18 to 0.06 shortly after surface discharge. Surface profiles and Raman analysis revealed the effectiveness of surface discharge to provide a thick and soft transfer layer, providing the optimal low friction condition described by Halling. Finally, we clarified the optimum surface discharge design that low-energy surface discharge produced a thick transfer layer due to concentration of the produced debris, resulting in low friction.

DOI： 10.1016/j.triboint.2021.107306

Friction characteristics of amorphous carbon coating against various 3d-transition metals 査読有り国際誌

Kim Jae-Il, Lee Woo-Young, Tokoroyama Takayuki, Murashima Motoyuki, Umehara Noritsugu

TRIBOLOGY INTERNATIONAL 174 巻 2022年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

DLC has anti-friction characteristics due to the tribofilm formed by the carbon transfer to its mating material. However, its coefficient of friction depends on each mating material. This study aims to investigate a suitable mating material against diamond-like carbon coatings. We selected four 3d-transition metals (Ti, Fe, Ni and Cu) as the mating materials based on the chemical affinities for carbon, i.e., carbide formability and work of separation. Among them, Ti had the lowest coefficient of friction, followed by Fe, Ni and Cu. The structures of tribofilm formed on mating materials were characterized non-destructively using Raman spectroscopy consisting of confocal optics. It revealed that Ti could strongly attract the carbon and stably formed carbon-containing tribofilm, leading to low friction.

DOI： 10.1016/j.triboint.2022.107690

The tribological property of a-C:H coating with tribolayer by additive having glycerol and phosphate oxide structure 査読有り国際誌

T. Tokoroyama, K. Tanaka, T. Kani, M. Murashima, W.Y. Lee, N. Umehara, T. Oshio, K. Yagishita

Tribology letters 70 巻頁： 118 2022年10月

異なる表面粗さを有する金属表面においてゴムの劣化が静止摩擦に及ぼす影響査読有り

村島基之, 佐宗朋洋, 梅原徳次, 野老山貴行, 平野遼, 沖舘亮

トライボロジスト 67 巻 ( 9 ) 頁： 646 - 661 2022年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

Many studies on friction of rubber materials revealed the effect of power spectrum of surface roughness on friction. On the other hand, quantitative comparison of the effects of specific surface roughness parameters has not been sufficiently conducted as well as the effects of rubber deterioration on friction. In the present paper, the effect of rubber deterioration on static friction and its variation with surface profile (hard chromium (HCr) treatment, salt-bath nitrocarburizing (SBN) treatment, and gas nitrocarburizing (GN) treatment is clarified. The friction test results showed interesting results that the static friction coefficient of SBN surfaces decreased with rubber degradation, whereas the static friction coefficient of GN surfaces increased. Subsequently, we analyze the main characteristics of surface roughness parameters and explore the mechanism. First, due to the small skewness of the GN surface, the blockage of leakage channels is developed, resulting in the formation of oil reservoirs and a squeeze effect due to micro-slip of the rubber. Second, the surface of SBN has high peaks and the bearing area ratio of the peaks is high, which prevents the occurrence of leak-channel blockage and allows the peaks to penetrate rubber. The present paper specifically clarifies that these surface properties provide the obtained friction results.

DOI： 10.18914/tribologist.22-00001

Effect of fracture properties and surface morphology on wear of DLC coatings at severe contact condition 査読有り国際共著国際誌

Yamada Yusei, Murashima Motoyuki, Umehara Noritsugu, Tokoroyama Takayuki, Lee Woo-Young, Takamatsu Hajime, Tanaka Yoshikazu, Utsumi Yoshiharu

TRIBOLOGY INTERNATIONAL 169 巻頁： 107486 - 107486 2022年5月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

The present study shows how the fracture properties and surface morphology of diamond-like carbon (DLC) coatings affect their wear properties. Nine types of DLC coatings with different carbonaceous structures and surface roughness were prepared. Fracture toughness was quantitatively evaluated from the crack length on the coatings. Subsequently, wear tests were conducted under boundary lubrication to evaluate the wear properties. The results showed that the wear rate of DLC coatings with rough surfaces decreased with increasing fracture toughness, while that of smooth DLC is independent of fracture toughness. In the DLCs with rough surface, it was found that brittle fracture occurred, and the fracture significantly increased the wear rate. Additionally, the ratio of the stress intensity factor to the fracture toughness value (K/KIC) was presented, showing comprehensive wear behaviors.

DOI： 10.1016/j.triboint.2022.107486

Development of a new diamond-like carbon surface treatment method with electric discharge for short running-in and friction reduction 査読有り国際共著国際誌

Murashima Motoyuki, Maeda Misato, Xingrui Deng, Umehara Noritsugu, Kousaka Hiroyuki

PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY 236 巻 ( 5 ) 頁： 1020 - 1030 2022年5月

The present paper proposes a new treatment method for diamond-like carbon (DLC) coatings using electric discharge. DLC coatings exhibit excellent mechanical and tribological properties due to their unique carbonaceous structure. Several surface treatment methods were presented to achieve short running-in and low friction. However, in-situ surface treatment is needed to extend the life of machines and maintain their performance. Here, we propose an electric discharge treatment with a simple electrical circuit. As a result, the friction coefficient drastically drops from 0.3 to 0.11. Interestingly, the drop starts shortly after the discharge starts. Consequently, the running-in is shortened to about 6-m sliding compared to no discharge condition, which does not show any running-in more than 68-m sliding. Raman analysis reveals that a transfer layer on the ball surface is composed of carbonaceous material and the structure exhibits graphite-like characteristics. However, there is visible damage on the DLC surface. Another friction test shows a very low friction coefficient of 0.04 using a transfer layer-covered ball and a new DLC disk with a smooth surface. In conclusion, the combination of a transfer layer and smooth DLC surface is needed to exhibit excellent tribological performance, indicating the importance of less damage treatment. Next, pulse discharge treatment is demonstrated to achieve less damage to the DLC coating. As a result, the pulse discharge method reduces friction and surface damage. In conclusion, the proposed treatment methods using electric discharge not only show the potential for reducing friction, but also the feasibility of in-situ treatment during machine operation.

DOI： 10.1177/13506501211013126

Realization of near-less friction of ta-CNx coating under R32 refrigerant environment 査読有り国際誌

Lee Wooyoung, Murashima Motoyuki, Umehara Noritsugu, Tokoroyama Takayuki, Horaguchi Norihisa, Ishimoto Takao

TRIBOLOGY INTERNATIONAL 168 巻頁： 107404 - 107404 2022年4月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

Diamond-like carbon (DLC) has attracted attention from refrigeration industry due to their excellent tribological behaviors. This study focused on high friction-efficiency in hydrofluorocarbon (HFC) refrigerant, however, DLC coatings have not been achieved in previous research. We evaluated friction behavior of tetrahedral amorphous carbon nitride under difluoromethane (R32) and R32/polyolester (POE) mixture environment, respectively. Friction coefficients of 0.02 and 0.03 were recorded under R32 and R32/POE atmosphere, respectively. These results emphasize an importance of the tribofilm consisted of graphite-and polymer-like carbon, terminated with R32 components (C, H, and F).

DOI： 10.1016/j.triboint.2021.107404

Tribological Property of ta-CNx:Ta Deposited via Ion Beam Assisted-Filtered Arc Deposition 査読有り国際誌

Tokoroyama T., Tagami Y., Murashima M., Lee W-Y, Umehara N., Kousaka H.

TRIBOLOGY INTERNATIONAL 168 巻頁： 107450 - 107450 2022年4月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

Improving the hardness of amorphous carbon nitride with tantalum was realized by using ion beam assisted filtered arc deposition to obtain a low friction coefficient and low specific wear rate in ambient air. The coatings were prepared with different nitrogen flow during coating at different discharge cycles of tantalum. The wear scar and as-deposited surfaces were observed and analyzed by means of FESEM, AES, XPS, and Raman analysis. The lowest friction coefficient (~0.07) was obtained for ta-C:Ta200, which exhibited a low specific wear rate of < 1.0 × 10−7 mm3/Nm. The XPS analysis revealed the existence of amorphous Ta2O5, and the friction coefficient seemed to be positively correlated with oxygen desorption from the coatings.

DOI： 10.1016/j.triboint.2022.107450

ESEM内摩擦における凝縮液滴で評価したカーボン系硬質膜の摩擦痕表面エネルギーと摩擦係数の関係査読有り

梅原徳次, 中尾太一, 寺田真, 上坂裕之, 村島基之

トライボロジスト 67 巻 ( 2 ) 頁： 126 - 138 2022年2月

担当区分：筆頭著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

Carbonaceous hard coatings have promising tribological properties, such as low friction, high hardness and high wear resistance. In particular, CNx (Carbon Nitride) coating and a-C:H (hydrogenated amorphous carbon) coating show ultra low friction coefficient (µ < 0.01) in dry nitrogen gas. However, the mechanism of ultra low friction has not clarified. We have developed the in-situ measurement method on friction area during sliding to clarify the ultra low friction mechanism of carbonaceous hard coating. In this research, we demonstrated in-situ measurement of surface energy on friction area during friction by manufacturing friction tester in ESEM (Environmental Scanning Electron Microscope) chamber. Moreover, we estimated the effect of surface energy on friction property of carbonaceous hard coatings. We used UV irradiation to prepare the carbonaceous hard coatings, which have different surface energy. From the results, friction coefficient of carbonaceous hard coating decreased with surface energy, however the approximate line which showed the relationship between friction coefficient and surface energy did not pass through the origin. It suggested that friction occurred beneath the sliding surface in coatings or transferred layers not on the surface. Moreover, surface energy of carbonaceous hard coatings approached the value of graphite when carbonaceous hard coatings showed low friction. It suggested that structure of carbonaceous hard coatings had become graphite-like structure.

DOI： 10.18914/tribologist.21-00018

Metal matrix nanocomposites in tribology: Manufacturing, performance, and mechanisms 査読有り国際共著国際誌

Pan Shuaihang, Jin Kaiyuan, Wang Tianlu, Zhang Zhinan, Zheng Long, Umehara Noritsugu

Friction 10 巻頁： 1596 - 1634 2022年1月

The Tribological Properties of Hydrogenated DLC Coating Lubrication with Additive Having Glycerol and Phosphonate Structure 査読有り国際誌

Kani T., Tokoroyama T., Umehara N., Murashima M., Lee W.Y., Yagishita K.

Vierteljahresschrift fur Sozial und Wirtschaftsgeschichte 108 巻 ( 4 ) 頁： 263 - 270 2021年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Vierteljahresschrift fur Sozial und Wirtschaftsgeschichte

In general, several mechanical parts are subjected to friction and wear. To prevent wear and high friction coefficient under lubrication, additives can work to reduce friction force, to build up thin film on surfaces which is so-called tribofilm. Recently, Diamond-Like Carbon (DLC) is focused because it has excellent low friction and high wear proof as solid lubricant. However, several researchers already reported that tetrahedral amorphous carbon (ta-C) showed abnormal wear when it rubbed with glycerol mono-oleate (GMO) that is a kind of additive, although it showed very low friction coefficient. To improve tribological properties, new additives were developed that had both phosphate-oxide structure derived from ZnDTP which had high wear resistance and hydroxy group derived from GMO in one structure. To clarify the effects of the additives, friction tests were performed fixed-roller-on-disk type rotating friction tester. In the friction tests, hydrogenated amorphous carbon (a-C:H) disks, and a-C:H coated rollers were used under boundary lubrication condition at 20-80°C. Friction tests were conducted in Poly-α-olefin (PAO) oil with each GMO and the additives. The results exhibited that a-C:H gave ultra-low friction with the additive. Elemental analysis of the surface showed that tribofilm of phosphorus and oxygen was detected on the a-C:H surface in the additive used condition.

DOI： 10.25162/VSWG-2021-0016

In situ observation of the formation of MoDTC-derived tribofilm on a ta-C coating using reflectance spectroscopy and its effects on friction 査読有り国際共著国際誌

Hashizume Naoya, Murashima Motoyuki, Umehara Noritsugu, Tokoroyama Takayuki, Lee Woo-Young

TRIBOLOGY INTERNATIONAL 162 巻頁： 107128 2021年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

We clarify the relationships between tribofilm thickness, chemical composition, and friction coefficient by combining in situ and ex situ analyses. An in situ reflectance observation is conducted for MoDTC-derived tribofilm on a ta-C coating during friction tests. The results show that the thicker the tribofilm is, the lower the friction coefficient. In addition, the refractive index increases as friction decreases. XPS analysis shows that the topmost surface of the thick tribofilm contains a higher MoS2 concentration than the deep position. Therefore, the generated MoS2-rich tribofilm is considered to reduce friction. In addition, as the MoS2 tribofilm wears out, friction increases. In conclusion, we have developed a MoDTC-derived tribofilm formation model using a new method of in situ optical measurement.

DOI： 10.1016/j.triboint.2021.107128

Improved wear imbalance with multilayered nanocomposite nanocrystalline Cu and tetrahedral amorphous carbon coating 査読有り国際共著

Kim Jae-Il, Kim Jongkuk, Kim Do Hyun, Jang Young-Jun, Umehara Noritsugu

CERAMICS INTERNATIONAL 47 巻 ( 18 ) 頁： 25664 - 25673 2021年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Ceramics International

Tetrahedral amorphous carbon (ta-C) has a relatively high hardness, and it can be used to enhance film properties such as wear resistance. However, the high hardness of ta-C can adversely affect a counterpart and accelerate its wear, and the resulting wear imbalance between the film and its counterpart can cause vibrations. This issue may be resolved by improving the wear of the counterpart. This study aimed to reduce the hardness and improve the fracture toughness of ta-C films to enhance the durability of a tribosystem, which was achieved by toughening a composite and ductile phase. A multilayered nanocrystalline (nc)-Cu/ta-C nanocomposite film was fabricated that allowed for reductions in the wear of the film and its counterpart of more than 88% and 99%, respectively.

DOI： 10.1016/j.ceramint.2021.05.292

グリセリンおよびリン酸骨格構造を有する添加剤による水素含有DLC膜の潤滑油中トライボロジー特性査読有り

蟹拓実, 野老山貴行, 梅原徳次, 村島基之, 李義永, 八木下和宏

トライボロジスト 66 巻 ( 7 ) 頁： 570 - 578 2021年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

In general, several mechanical parts are subjected to friction and wear. To prevent wear and high friction coefficient under lubrication, additives can work to reduce friction force, to build up thin film on surfaces which is so-called tribofilm. Recently, Diamond-Like Carbon (DLC) is focused because it has excellent low friction and high wear proof as solid lubricant. However, several researchers already reported that tetrahedral amorphous carbon (ta-C) showed abnormal wear when it rubbed with glycerol mono-oleate (GMO) that is a kind of additive, although it showed very low friction coefficient. To improve tribological properties, new additives were developed that had both phosphate-oxide structure derived from ZnDTP which had high wear resistance and hydroxyl group derived from GMO in one structure. To clarify the effects of the additives, friction tests were performed fixed-roller-on-disk type rotating friction tester. In the friction tests, hydrogenated amorphous carbon (a-C:H) disks, and a-C:H coated rollers were used under boundary lubrication condition at 20-80°C. Friction tests were conducted in Poly-α-olefin (PAO) oil with each GMO and the additives. The results exhibited that a-C:H gave ultra-low friction with the additive. Elemental analysis of the surface showed that tribofilm of phosphorus and oxygen was detected on the a-C:H surface in the additive used condition.

DOI： 10.18914/tribologist.21-00001

Wear acceleration of a-C:H coatings by molybdenum-derived particles: Mixing and temperature effects 査読有り国際誌

Kassim K. A. M., Tokoroyama T., Murashima M., Lee W-Y, Umehara N., Mustafa M. M. B.

TRIBOLOGY INTERNATIONAL 159 巻頁： 106944 - 106944 2021年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

MoDTC has also been reported to degrade into other Mo-derived compounds. It is essential to analyze the effects of each type of MoDTC-degraded material on DLC. Therefore, we chose powder-type MoDTC, MoS2, Mo, MoO3, and Mo2C additives to be dispersed individually into a base oil and tested on an a-C:H sliding against a steel ball under boundary lubrication conditions at 80 °C. We then obtained surface-enhanced Raman scattering (SERS), which proved that MoS2 has the possibility of extracting hydrogen from the topmost surface as chemical wear (hydrogen content decreased from 30 to 35 at.% to 20 at.% of as-deposited) and that MoO3, MoDTC, and Mo have the possibility of catalytic reactions with carbon atoms. Mo2C exhibited abrasive accelerate of the a-C:H wear.

DOI： 10.1016/j.triboint.2021.106944

自動変速機油中の摩擦で金属材料表面に形成されたトライボ被膜の機械的特性評価査読有り

野老山貴行, 西本宇志, 村上靖宏, 本田晃之, 光井秀明, 寺井勇祐, 村島基之, 李義永, 梅原徳次

トライボロジスト 66 巻 ( 6 ) 頁： 461 - 469 2021年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

In this study, nano-scratch tests were conducted using atomic force microscope (AFM) to clarify the hardness of a tribofilm derived from an additive (Fluid A or Fluid B in automatic-transmission fluid) formed on an SKS3 cold work tool steel substrate surface. Comparisons between nano-indentation hardness tests and AFM nano-scratch tests were performed for each specimen. Prior to these tests, the tribofilms on the SKS3 substrate were examined with energy-dispersive spectroscopy (EDS). In order to calculate the hardness of the tribofilm from the nano-scratch results, we assumed that the AFM diamond tip acted as an abrasive to plough the tribofilm. The phosphorus-derived tribofilm formed from Fluid A was harder than the sulfur-derived tribofilm from Fluid B, and it was calculated that the phosphorus-derived tribofilm was approximately 2.64 GPa and the sulfur-derived tribofilm was 1.89 GPa. After 10 nano-indentation hardness tests on each tribofilm, the maximum indentation depth into the tribofilm formed from Fluid A was approximately 31 nm, while it was approximately 36 nm for Fluid B. These results are qualitatively consistent with the hardness results obtained by the AFM nano-scratch test method.

DOI： 10.18914/tribologist.20-00020

Realization of a Novel Morphing Surface Using Additive Manufacturing and Its Active Control in Friction 査読有り国際誌

Murashima Motoyuki, Imaizumi Yusuke, Kawaguchi Masato, Umehara Noritsugu, Tokoroyama Takayuki, Saito Toshiyuki, Takeshima Masayuki, Tsukiyama Yosuke, Nitta Isami

JOURNAL OF TRIBOLOGY-TRANSACTIONS OF THE ASME 143 巻 ( 5 ) 頁： 1 - 29 2021年5月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Tribology

As the need for higher efficiency of engineering components increases, so does the demand for functional surfaces. While various tribosurfaces (e.g., texturing and coatings) have been developed, many researches are aimed at static functionality. On the other hand, due to a wide range of environmental adaptability and active control, active-morphing surfaces can be highly efficient and robust. In this paper, we demonstrate a novel morphing surface and its realization using additive manufacturing (AM). By using a diaphragm structure, morphing performance is achieved even if a hard resin material is used. When air pressure is applied to the backside of the diaphragm, it changes to a convex shape and vice versa. The concept requires a complex structure for arranging airflow and a solid morphing system. The AM is one great technique to create such complex structures. As a result of actual manufacturing, the created morphing structure realizes a large morphing of 600 μm or more. In addition, the shape changes reversibly depending on the air pressure. The surface also exhibits very interesting tribological characteristics. The surface shows a friction coefficient of about 0.3 with a concavity, and then increases to 0.5-1.7 with a convexity. A real-contact area measurement reveals that the novel property occurs due to change in the real-contact area depending on surface morphology. In conclusion, the present paper provides a new concept of a novel morphing tribosurface, which selectively performs as a low-friction or break-like surface, created using AM.

DOI： 10.1115/1.4050269

Active Friction Control in Lubrication Condition Using Novel Metal Morphing Surface 査読有り国際誌

M. Murashima, T.Tokoroyama, N. Umehara

Tribology International 156 巻頁： 1 - 9 2021年5月

Nanotextured Mold Surface with DLC Coating for Reduction in Residual Ceramic Particles 査読有り国際誌

Murashima Motoyuki, Hojo Koki, Ito Shigehiro, Umehara Noritsugu, Tokoroyama Takayuki, Takahashi Tomonori, Imaeda Minoru

LANGMUIR 37 巻 ( 12 ) 頁： 3563 - 3574 2021年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Langmuir

In the ceramic industry, ceramic particles remain on a mold surface due to which the mold requires frequent cleaning during press molding, reducing productivity. Surface texturing and tetrahedral amorphous carbon (ta-C) coatings are well-known surface-energy controllable treatments developed for low adhesion, low friction, and high wear resistance. In the present paper, we demonstrate the effect of reducing ceramic residues using nanotexturing, ta-C coatings, and their combination. We compare two surface morphologies (i.e., 770 nm pitch nanotexturing and flat) and five materials (i.e., nonhardened steel, hardened steel, ta-C, and two types of nitrogen-doped ta-C (ta-CNx). Molding test results show that the ta-C coating on flat surfaces with the highest hardness of 30 GPa shows the lowest residual amount of 5.9 μg for Al2O3 ceramic particles. The amount is 82% less than that of the nonhardened steel. The ta-CNx20, made with a nitrogen flow rate of 20 sccm, shows the lowest residual amount of 234 μg for SiO2 ceramic particles, which is 81% less than that of the nontextured ta-CNx20. In conclusion, we provide design guidelines for nanotextured mold surfaces including the texturing pitch should be small enough for ceramic particles; the mold surface should be sufficiently hard; the lower the surface energy per unit area, the less residues of ceramic particles.

DOI： 10.1021/acs.langmuir.0c03435

The Clarification of Friction Mechanism in Oil Lubrication for CNx Coating by In-Situ Observation of Friction Area with Reflectance Spectroscopy 査読有り国際誌

Okamoto Tatsuya, Umehara Noritsugu, Murashima Motoyuki, Saito Koji, Manabe Kazuyoshi, Hayashi Keiji

TRIBOLOGY ONLINE 16 巻 ( 1 ) 頁： 49 - 58 2021年

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

To clarify the low friction mechanism of CNx coating in PAO oil lubrication, we measured reflectance spectrum at friction area in-situ by reflectance spectroscopy during friction test against a sapphire hemisphere pin in PAO oil. We observed and estimated the thickness of PAO oil film, the surface roughness of CNx coating, thicknesses, and polarizability of the transformed layer formed on bulk CNx coating during friction test by analyzing reflectance spectrum. We proposed that the decreasing of load ratio of boundary lubrication mode to total load is the one of governing factor to reduce friction on the basis of the increasing of Λ value. Also we proposed the increasing of adsorption of PAO oil to the CNx transformed layer is the second governing factor on the basis of the increasing of polarizability of PAO oil and transformed layer, that leads to the increasing of van der Waals force between transformed layer and PAO oil as low friction mechanism of CNx in PAO oil lubrication.

DOI： 10.2474/trol.16.49

Evaluation of Mechanical Characteristics of Tribofilm Formed on the Surface of Metal Material Due to Friction under Lubrication with Automatic Transmission Fluid 査読有り国際誌

Tokoroyama Takayuki, Nishimoto Takashi, Murakami Yasuhiro, Honda Akiyuki, Mitsui Hideaki, Terai Yusuke, Murashima Motoyuki, Lee Woo-Young, Umehara Noritsugu

TRIBOLOGY ONLINE 16 巻 ( 4 ) 頁： 255 - 262 2021年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

In this study, nano-scratch tests were conducted using atomic force microscope (AFM) to clarify the hardness of a tribofilm derived from an additive (Fluid A or Fluid B in automatic-transmission fluid) formed on an SKS3 cold work tool steel substrate surface. Comparisons between nano-indentation hardness tests and AFM nano-scratch tests were performed for each specimen. Prior to these tests, the tribofilms on the SKS3 substrate were examined with energy-dispersive spectroscopy (EDS). In order to calculate the hardness of the tribofilm from the nano-scratch results, we assumed that the AFM diamond tip acted as an abrasive to plough the tribofilm. The phosphorous-derived tribofilm formed from Fluid A was harder than the sulfur-derived tribofilm from Fluid B, and it was calculated that the phosphorous-derived tribofilm was approximately 2.64 GPa and the sulfur-derived tribofilm was 1.89 GPa. After 10 nanoindentation hardness tests on each tribofilm, the maximum indentation depth into the tribofilm formed from Fluid A was approximately 31 nm, while it was approximately 36 nm for Fluid B. These results are qualitatively consistent with the hardness results obtained by the AFM nano-scratch test method.

DOI： 10.2474/trol.16.255

The Tribological Properties of Hydrogenated DLC Coating Lubrication with Additive Having Glycerol and Phosphonate Structure 査読有り国際共著国際誌

Kani Takumi, Tokoroyama Takayuki, Umehara Noritsugu, Murashima Motoyuki, Lee Woo-Young, Yagishita Kazuhiro

TRIBOLOGY ONLINE 16 巻 ( 4 ) 頁： 263 - 270 2021年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

DOI： 10.2474/trol.16.263

New study on tribological performance of AA7075-TiB2 nanocomposites 査読有り国際共著

Pan Shuaihang, Saso Tomohiro, Yu Ning, Sokoluk Maximilian, Yao Gongcheng, Umehara Noritsugu, Li Xiaochun

TRIBOLOGY INTERNATIONAL 152 巻 2020年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

AA7075 (Al-Mg-Zn-Cu) nanocomposite is important in tribo-related applications. In this paper, we applied a new method to investigate the coefficient of friction (CoF) of AA7075 (T6)-TiB2 nanocomposite. This method is able to minimize the wear and obtain the CoF values of the nanocomposite. A distinct trend of the CoF is discovered in this study. A novel friction theory with the consideration of surface characteristics, such as hardness difference and atom transfer between friction pairs, has been developed to understand this CoF trend. The new insight from this study offers a great potential for a rational design of AA7075 nanocomposite parts to achieve reliable tribological performance.

DOI： 10.1016/j.triboint.2020.106565

２種混合砥粒研磨法を用いたガラス基板研磨加工による表面粗さ改善速度の向上査読有り

ベース油中CNxの摩擦界面その場反射分光分析観察による摩擦メカニズムの解明招待有り

梅原徳次

トライボロジスト 65 巻 ( 11 ) 頁： 684 - 687 2020年11月

ポリ塩化ビニル溶媒への交流電場援用マイクロプラスチック突起の創製査読有り

山田雄聖，野老山貴行，村島基之，梅原徳次

日本機械学会論文集 86 巻 ( 892 ) 頁： 20-00228 2020年11月

名古屋大学における全学技術支援の一元的組織化招待有り

梅原徳次, 古賀和司, 藤原冨未治, 澤木弘二, 山本浩治, 立花一志, 水口幾久代

精密工学会誌 86 巻 ( 9 ) 頁： 662 - 665 2020年9月

その場摩擦界面反射分光法によるカーボン系硬質膜の摩擦メカニズム招待有り

梅原徳次

表面技術 71 巻 ( 9 ) 頁： 547 - 550 2020年9月

コーティング電気メス先端の炭化物付着抑制手法の開発査読有り

野老山貴行，小林将大，村島基之，梅原徳次，小川航生，萬隆行，内田淳一

日本機械学会論文集 86 巻頁： 20-00273 2020年9月

嶽野広明, 野老山貴行, 村島基之, 梅原徳次, 千葉翔悟

砥粒加工学会誌 64 巻 ( 8 ) 頁： 428 - 435 2020年8月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：社団法人砥粒加工学会

本研究は，ガラス基板研磨における高コストなダイヤモンド砥粒の消費量を削減し，コスト低減と表面粗さの早期改善を目的として低硬度な砥粒とダイヤモンド砥粒を混合した，2種混合砥粒による研磨手法の開発を行った．低硬度砥粒としてGC砥粒の大きさの影響（約127 μm, 75 μmおよび13 μm），砥粒濃度の影響，砥粒種類の影響（WAおよびB4C）を明らかにした．また，砥粒の研磨面内の挙動をその場観察するため，砥粒をロ-ダミンにより蛍光染色して観察を行った．その結果，2種混合砥粒によって表面粗さの低減速度の向上に成功した．また，粒径の大きなGC砥粒は研磨に用いた天然シルク研磨パッドの繊維のすき間に移動あるいは挟みこまれる様子が観察された．一方，平均粒径1.0 μmのダイヤモンド砥粒は天然シルク研磨パッドとガラス基板間を繊維の向きとは無関係に移動している様子が観察された．

DOI： 10.11420/jsat.64.428

CiNii Books

金ナノ粒子法を用いた表面増強ラマン分析による炭素系薄膜の極表面分析査読有り

野老山貴行，梅原徳次，村島基之

トライボロジスト 65 巻 ( 8 ) 頁： 517 - 525 2020年8月

New study on tribological performance of AA7075-TiB2 nanocomposites 査読有り国際共著国際誌

Shualihang Pan, Tomohiro Saso, Ning Yu, Maximillan Sokoluk, Gongcheng Yao, Noritsugu Umehara, Xiaochun Li

Tribology International 152 巻頁： 106565 2020年8月

The wear classification of MoDTC-derived particles on silicon and hydrogenated diamond-like carbon at room temperature 査読有り国際誌

Kassim K. A. M., Tokoroyama T., Murashima M., Umehara N.

TRIBOLOGY INTERNATIONAL 147 巻頁： 106176 2020年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

Molybdenum dithiocarbamate (MoDTC) is well-known as a friction-modifier in engine oil but has wear accelerating effects on DLC/steel sliding contact. Since MoDTC was reported degradable to other materials, the effect of each material on wear acceleration has not been clarified yet. Therefore, it is necessary to divide which Mo-derived compound has a major role to enhance wear. Thus, powder-type MoDTC, MoO3, Mo2C, MoS2, and Mo were dispersed into Poly-alpha-olefin (PAO), and tested on a-C:H and Si-DLC against steel ball at room temperature. For Mo2C, MoDTC, and MoO3, the specific wear rate of a-C:H was approximately 3.4 × 10−5, 3.2 × 10−6 and 1.5 × 10−6 mm3/Nm, respectively. MoDTC indicated higher affection than MoO3 regardless of the particles’ hardness. Si-DLC showed better wear prevention compared to a-C:H.

DOI： 10.1016/j.triboint.2020.106176

Effect of mesh structure of tetrahedral amorphous carbon (ta-C) coating on friction and wear properties under base-oil lubrication condition 査読有り国際共著国際誌

Bin Mustafa Mohd Muhyiddin, Umehara Noritsugu, Tokoroyama Takayuki, Murashima Motoyuki, Shibata Akinori, Utsumi Yoshiharu, Moriguchi Hideki

TRIBOLOGY INTERNATIONAL 147 巻頁： 105557 2020年7月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

This study examined the tribological properties of novel mesh tetrahedral amorphous carbon (Mesh ta-C). Subsequently, comparison was made with conventional ta-C and a-C:H coatings under base-oil lubrication via cylindrical-pin-on-disk tribo-tester. Analysis of wear track was conducted using field-emission-scanning-electron-microscope (FE-SEM), atomic-force-microscopy (AFM), and Raman-spectroscopy. The friction coefficient for Mesh ta-C and conventional ta-C revealed a similar pattern with regard to loads. The Mesh ta-C had excellent wear resistance, where the wear rates at loads of 20 N was five and 20 times lower than conventional a-C:H and ta-C, respectively. High wear resistance of Mesh ta-C characterized by inhibition of brittle micro-fracture propagation, less in abrasive particle created during friction test, and suppressing the effect of graphitization-induced wear on the contact surface.

DOI： 10.1016/j.triboint.2019.01.016

Effect of defects on wear behavior in ta-C coating prepared by filtered cathodic vacuum arc deposition 査読有り国際共著国際誌

Lee Woo-Young, Jang Young-Jun, Tokoroyama Takayuki, Murashima Motoyuki, Umehara Noritsugu

DIAMOND AND RELATED MATERIALS 105 巻頁： 107789 - 107789 2020年5月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Diamond and Related Materials

This study examined the tribological behavior of a ta-C coating fabricated at a substrate bias of −100 V via filtered cathodic vacuum arc (FCVA) deposition. Defects in the ta-C coating were categorized as droplets, pores, and spikes, considering the morphological, structural, and mechanical properties of the ta-C surface. A friction test was conducted at 170 °C in ambient air using a ball-on-disk tribometer. The friction coefficient was 0.08 during the steady state and the wear rate was 4.3 × 10−6 mm3/Nm. To explain the friction and wear behavior, the morphological and structural properties of the defects in the designated area were compared among different sliding cycles.

DOI： 10.1016/j.diamond.2020.107789

The Surface Enhanced Raman Scattering Analysis for Carbonaceous Coating by Using Au Nano-Particles 査読有り国際誌

T. Takayuki, M. Murashima, N. Umehara

TRIBOLOGY ONLINE 15 巻 ( 5 ) 頁： 300 - 308 2020年5月

シェーバーのトライボロジー

野老山貴行, 梅原徳次

トライボロジスト 65 巻 ( 4 ) 頁： 236 - 241 2020年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

From time immemorial, shaving one’s beard has been continued. Using razor or electric shaver is common for all male adult to show their cleanliness recently. The custom for shaving my beard by myself was harbingered by World War I and II. Tremendous safety razors were provided by US government to frontline infantry, then they acquired a custom of “shaving by myself”. An electric shaver was invented early of the 20th century, and it is divided two shaving motion, a rotation or a reciprocation. In this article, investigating the relation between inner blade’s edge radiuses and pulling force, clarifying differences of shaving mechanism of a rotation or a reciprocation type shaver by a high speed camera with measuring pulling force simultaneously are explained.

DOI： 10.18914/tribologist.65.04_236

New droplet removal polishing method for diamond-like carbon with carbon fiber brush 査読有り国際誌

Murashima M., Imaizumi Y., Umehara N., Tokoroyama T.

International Journal of Automation Technology 14 巻 ( 2 ) 頁： 190 - 199 2020年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：富士技術出版株式会社

In this paper, we propose a new polishing method for diamond-like carbon (DLC) coatings using a carbon fiber brush (CFB). Surface finishing is an important process for DLC coating applications. A lapping process is widely used for attaining tetrahedral amorphous carbon (ta-C) coatings, which are a type of DLC coating containing many droplets, to obtain fine flat surfaces. The lapping process removes protuberant parts of droplets rather than the entire droplet. In this paper, we propose a new polish brush material made of carbon fiber, called CFB. Carbon fiber has both mechanical strength due to its hard carbonaceous material and flexibility due to its fiber structure. In polishing tests, CFB removed droplets from ta-C coatings and the removal effect increased with the shortening of the brush length. The surface profiles of the polished surfaces indicated that a shorter brush length yielded deep scratch marks on ta-C surfaces. Consequently, the arithmetic average surface roughness of the polished ta-C surfaces, Sa, had almost the same value as that of a non-polished surface. Here, we show the ability of CFB to remove the droplets without an increase in the surface roughness. The CFB with the longest brush length in the present study (12 mm) showed a ten-point average roughness SZJI S = 75 nm and Sa = 4.7 nm, which were 59% and 22% lower than those of the non-polished surface, respectively. Furthermore, the longest CFB removed the entire droplets whereas a shorter CFB merely removed the protuberant part of the droplets. The result indicates that CFB polishing can remove entire droplets, which result in abrasive wear or deterioration. From other polishing tests, the optimum polishing distance was determined. Shorter polishing distances could not remove droplets sufficiently whereas longer polishing distances caused deep scratches on ta-C surfaces due to the material transferred to the CFB. Accordingly, the polishing distance of 600 m showed the best surface finishing with SZJI N = 25 nm and Ra = 0.43 nm, which were 86% lower than and similar to those of the non-polished ta-C surface, respectively.

DOI： 10.20965/ijat.2020.p0190

二液分離油の反射分光摩擦面その場観察装置を用いたしゅう動部油膜その場分析査読有り

山田高澄, 梅原徳次, 野老山貴行, 村島基之, 佐藤卓, 大原健司, 羽生田清志

日本機械学会論文集 86 巻 ( 884 ) 頁： 1900315 2020年3月

ディーゼルエンジンオイル中ナノメートルサイズPMの交流電場による凝集を用いたろ過手法の開発査読有り

野老山貴行, 柴沢穂高, 梅原徳次

日本機械学会論文集 86 巻 ( 884 ) 頁： 2000016 2020年3月

Development of Surface Roughness Generation Model for CFRTP Manufactured by LFT-D 査読有り国際誌

Murashima Motoyuki, Murooka Takaharu, Umehara Noritsugu, Tokoroyama Takayuki

INTERNATIONAL JOURNAL OF AUTOMATION TECHNOLOGY 14 巻 ( 2 ) 頁： 208 - 216 2020年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：富士技術出版株式会社

In this study, we propose a new surface generation model for carbon fiber reinforced thermoplastics (CFRTP) manufactured by the long fiber thermoplastic-direct (LFT-D) method. CFRTP are considered to be a next-generation structural material because of their high productivity as well as high mechanical strength and lightness. Conversely, CFRTP have a rough surface, which does not meet the automotive outer panel standard of a “class A surface.” In the present study, we establish a surface roughness generation model based on a thermal shrinkage mismatch of thermoplastic resin to carbon fiber and non-uniform carbon fiber distribution. Furthermore, we construct a surface roughness estimation formula based on the model. In the calculation, a cross-sectional image of CFRTP is divided into many vertical segments. Subsequently, the thermal shrinkage of each segment is calculated with a standard deviation, an average, and a probability density of the amount of carbon fiber in each segment. The surface roughness of the manufactured CFRTP was measured using a surface profilometer. The result showed that the arithmetic surface roughness increased with the volume fraction of carbon fiber. We applied the surface roughness calculation to cross-sectional images of the specimens. Consequently, the estimated surface roughness showed the same tendency, in which the surface roughness increased with the volume fraction of carbon fiber. The slope of a regression line of the estimated surface roughness with respect to the volume fraction was 0.010, which was almost the same (0.011) as the slope of a regression line of the measured surface roughness. Furthermore, the estimation formula using a thermal shrinkage effective depth of 395 μm was able to estimate the surface roughness within a 3% average error. Using the estimation formula, it was predicted that the surface roughness increased with the standard deviation of the amount of carbon fiber in a segment. To confirm the reliability of the model and the formula, we measured the standard deviation of the amount of carbon fiber in CFRTP specimens, showing that the trend for CFRTP specimens matched the estimated values.

DOI： 10.20965/ijat.2020.p0208

Effect of Mating Material and Graphitization on Wear of a-C:H Coating in Boundary Base Oil Lubrication 査読有り国際誌

Aboua Kouami Auxence Melardot, Umehara Noritsugu, Kousaka Hiroyuki, Tokoroyama Takayuki, Murashima Motoyuki, Bin Mustafa Mohd Muhyiddin Bin, Mabuchi Yutaka, Higuchi Tsuyoshi, Kawaguchi Masahiro

TRIBOLOGY LETTERS 68 巻 ( 1 ) 頁： 24 2020年1月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology Letters

Hydrogenated amorphous carbon (a-C:H) coating exhibits different wear behaviors depending on its counterpart material in boundary lubricated sliding contact. In previous works, tribological behaviors of a-C:H coating were investigated against steel, chromium, and germanium counterpart materials. The specific wear rate of a-C:H coating was found to decrease with the ability of its counterpart material to react with or dissolve carbon. The present study investigated how graphitization of a-C:H coating's top layers and interactions of the counterpart material with carbon influence wear behaviors of a-C:H coating in boundary lubrication. Results show that a-C:H coating shows graphitization of its top layers regardless the counterpart material. Correlation with differences in wear behaviors of the a-C:H coating leads to the conclusion that graphitization will induce high wear of a-C:H coating only when there are also atomic interactions between the DLC coating and its counterpart material.

DOI： 10.1007/s11249-019-1248-6

グリセリン及びリン酸骨格構造を有する添加剤によるa-C:H膜の潤滑油中トライボロジー特性

EFFECTS OF LUBRICATION CONDITION ON FRICTION AND WEAR IN OIL LUBRICATION FOR ALUMINIUM ALLOY BEARINGS WITH VARIOUS CARBONACEOUS HARD COATINGS

Umehara Noritsugu, Kitamura Tomoki, Tokoroyama Takayuki, Murashima Motoyuki

7TH INTERNATIONAL CONFERENCE INTEGRITY-RELIABILITY-FAILURE (IRF2020) 頁： 1045 - 1046 2020年

蟹拓実, 野老山貴行, 梅原徳次, 村島基之, 八木下和宏

年次大会 2020 巻 ( 0 ) 頁： S11311 2020年

"FRICTIONLESS" DIAMOND-LIKE COATINGS AND IN-SITU OBSERVATION USING REFLECTANCE SPECTROSCOPY

Umehara, N

7TH INTERNATIONAL CONFERENCE INTEGRITY-RELIABILITY-FAILURE (IRF2020) 頁： 7 - 8 2020年

The Surface Enhanced Raman Scattering Analysis for Carbonaceous Coating by Using Au Nano-Particles 査読有り

Tokoroyama Takayuki, Murashima Motoyuki, Umehara Noritsugu

TRIBOLOGY ONLINE 15 巻 ( 5 ) 頁： 300 - 308 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

In general, Raman analysis is one of the useful candidates to obtain structure of carbonaceous coatings. To improve the depth resolution of Raman analysis, surface-enhanced Raman Scattering (SERS) using gold nanoparticles (Au nanoparticles: AuNPs) and Au sputtered particles were investigated. The analysis was conducted to approximately 1.7, 2.4, 4.7, and 10.0 nm thickness of carbon coatings on silicon substrate with a 532 nm incident wavelength laser. The results indicated that the underlying silicon substrate was detected in the results of the Au sputtering method. Contrastingly, the underlying silicon substrate was not detected by the AuNPs method. This result clarified that using the AuNPs method, the detection depth of the carbon film was approximately 1.7 nm or less. The a-C:H coating was processed using a calotester, and SERS measurements at different depths were performed for the 633 and 532 nm wavelengths using the AuNPs method. As a result, the IG peak position tended to increase from the vicinity of the inter face between the a-C:H coating and the substrate to the surface. In addition, the ID/IG ratio was as low as 0.28 near the substrate and 0.72 at 3800 nm.

DOI： 10.2474/trol.15.300

二液分離油の反射分光摩擦面その場観察装置を用いたしゅう動部油膜その場分析査読有り

ta-CNx膜の摩擦摩耗特性に及ぼす膜中又は摩擦相手材タンタルの影響査読有り

北條孝樹, 梅原徳次, 野老山貴行, 村島基之

日本機械学会論文集 86 巻 ( 888 ) 頁： 20-00018 - 20-00018 2020年

コーティング電気メス先端の炭化物付着抑制手法の開発査読有り

野老山貴行, 小林将大, 村島基之, 梅原徳次, 小川航生, 萬隆行, 内田淳一

日本機械学会論文集 86 巻 ( 889 ) 頁： 20-00273 - 20-00273 2020年

山田高澄, 梅原徳次, 野老山貴行, 村島基之, 佐藤卓, 大原健司, 羽生田清志

日本機械学会論文集 86 巻 ( 884 ) 頁： 19-00315 - 19-00315 2020年

ポリ塩化ビニル溶媒への交流電場援用マイクロプラスチック突起の創製査読有り

山田雄聖, 野老山貴行, 村島基之, 梅原徳次

日本機械学会論文集 86 巻 ( 892 ) 頁： 20-00228 - 20-00228 2020年

ディーゼルエンジンオイル中ナノメートルサイズPMの交流電場による凝集を用いたろ過手法の開発査読有り

野老山貴行, 柴沢穂高, 梅原徳次

日本機械学会論文集 86 巻 ( 884 ) 頁： 20-00016 - 20-00016 2020年

Intelligent tribological surfaces: from concept to realization using additive manufacturing 査読有り国際誌

Murashima Motoyuki, Yoshino Shouta, Kawaguchi Masato, Umehara Noritsugu

INTERNATIONAL JOURNAL OF MECHANICS AND MATERIALS IN DESIGN 15 巻 ( 4 ) 頁： 757 - 766 2019年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：International Journal of Mechanics and Materials in Design

In this paper, we provide a detailed account of our efforts in the design, development and prototyping of a novel intelligent surface by adapting initially curved diaphragms. Unlike the shortcomings that characterize current designs of functional surfaces, our adaptive surface design is characterised by simplicity, multifunctionality, adaptability, high flexibility and robustness as well as controlled autonomy. Four aspects of the work are accordingly examined. The first is concerned with the conceptual design of the new functional surface. The second with the development of functional prototypes of intelligent surfaces, showing its characteristics and ease of manufacturing using 3D additive manufacturing. The third with demonstrating the multi-frictional ability of the newly designed surface. Our friction test results show wide range friction control ability from the friction coefficient value 0.3 (same value of material itself) to 3 times higher value 1.1. Finally, we address the challenges that are faced in our new design and the efforts that are currently being adopted to overcome them.

DOI： 10.1007/s10999-018-9435-4

Investigating running-in behavior to understand wear behavior of ta-C coating with filtered cathodic vacuum arc deposition 査読有り国際共著国際誌

Lee Woo-Young, Tokoroyama Takayuki, Murashima Motoyuki, Umehara Noritsugu

JURNAL TRIBOLOGI 23 巻頁： 38 - 47 2019年12月

Effect of Carbon Diffusion on Friction and Wear Behaviors of Diamond-Like Carbon Coating Against Germanium in Boundary Base Oil Lubrication 査読有り国際共著国際誌

Aboua Kouami Auxence Melardot, Umehara Noritsugu, Kousaka Hiroyuki, Tokoroyama Takayuki, Murashima Motoyuki, Mabuchi Yutaka, Higuchi Tsuyoshi, Kawaguchi Masahiro

TRIBOLOGY LETTERS 67 巻 ( 2 ) 頁： 65 2019年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology Letters

Diamond-like carbon (DLC) coatings are designed to work under severe lubrication conditions. Depending on working environment, lubrication condition, and counterpart material, DLC coatings can exhibit crucial variations in their tribological behaviors. In the search of a counterpart material to improve tribological performances of DLC coatings in desired environment, we found out in previous work that carbon diffusion is an important parameter that influences the tribological behaviors of amorphous hydrogenated (a-C:H) coating in boundary lubrication. a-C:H coating exhibits high wear against steel counterpart material that has a high carbon affinity/solubility, while its exhibits lower wear against chromium counterpart material that has lower carbon affinity/solubility than steel. These recent findings imply that consideration of the carbon affinity/solubility when choosing a counterpart material for a-C:H coating in boundary lubrication might be of significant importance to improve tribological performances of a-C:H coating. This research investigates tribological behaviors of a-C:H coating against germanium counterpart material that has extremely low carbon affinity/solubility. Results show that there is no atomic interaction between a-C:H coating and germanium during friction and wear test, followed with a very low wear of a-C:H coating.

DOI： 10.1007/s11249-019-1179-2

The tribological potential of graphene growth from solid waste 査読有り国際共著

Noor Ayuma Mat Tahir, Fakulti Kejuruteraan Mekanikal, Mohd Fadzli Bin Abdollah*, Noreffendy Tamaldin, Hilmi Amiruddin, Mohd Rody Bin Mohamad Zin, Takayuki Tokoroyama and Noritsugu Umehara

Progress in Industrial Ecology – An International Journal 13 巻 ( 4 ) 頁： 401 - 413 2019年4月

Effect of oxygen on degradation of defects on ta-C coatings deposited by filtered arc deposition 査読有り国際誌

Murashima Motoyuki, Deng Xingrui, Izuoka Hiroto, Umehara Noritsugu, Kousaka Hiroyuki

SURFACE & COATINGS TECHNOLOGY 362 巻頁： 200 - 207 2019年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Surface and Coatings Technology

Among diamond-like carbon (DLC) coatings, tetrahedral amorphous carbon (ta-C) coatings show particularly high thermal stability and oxidation resistance due to their high sp 3 content and hydrogen-free structure. On the other hand, it is well known that high-temperature annealing leads to degradation of the ta-C structure, resulting in a release of stress, decrease of hardness, increase in surface roughness, and transformation of the coating nature. Although optical observation is a powerful candidate for imaging the surface conditions of ta-C coatings, strong light emission due to high temperature prevents the acquisition of clear images. In this paper, we establish a novel in situ observation method using environment scanning electron microscopy (ESEM), which allows us to view ta-C surface defects and droplets at 650 °C. A heater embedded in the ESEM increased the temperature on ta-C coatings to 650 °C at gas pressure of 120 Pa. Using a variety of gas conditions including ambient air, dry nitrogen, or dry oxygen, we clarified the effect of the gases on the degradation of the defects. In a dry oxygen atmosphere, defects grew dramatically with annealing time, whereas nitrogen caused no significant transformation to ta-C surfaces. Raman spectroscopy analysis revealed significant structural change in one type of defect, while no noticeable Raman shift was detected in the other type. A focused ion beam created a cross-section of an annealed defect on the ta-C coating. Subsequently, energy dispersive X-ray spectroscopy (EDS) revealed the characteristics of defect growth; one type of defect was associated with a droplet on the interlayer, and the other with graphitization due to oxidization of ta-C on the droplets.

DOI： 10.1016/j.surfcoat.2019.01.115

Tribological properties of ta-CNx coating sliding against steel and sapphire in unlubricated condition 査読有り国際誌

Liu Xiaoxu, Umehara Noritsugu, Tokoroyama Takayuki, Murashima Motoyuki

TRIBOLOGY INTERNATIONAL 131 巻頁： 102 - 111 2019年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

Tribo-behavior of tetrahedral amorphous carbon nitride (ta-CNx) coating in unlubricated condition was investigated in this study. Sliding against steel, low nitrogen content ta-CNx exhibits much lower friction and wear as temperature increases, with less adhesion wear than ta-C and remained relatively higher hardness (45.01 GPa). Nevertheless, against sapphire ta-C outperforms ta-CNx greatly, and graphitization could be found at 120 °C. With atmosphere humidity increasing, ta-CNx shows significantly decreased friction, implying the tribo-character of high sp3 bonding structure. Meanwhile, dry air seems to be the harshest condition for ta-CNx, since O2 in the atmosphere might lead to oxidized wear of ta-CNx even under room temperature. Furthermore, in humid N2, as an inert gas with high humidity, ta-CNx shows the lowest friction and wear.

DOI： 10.1016/j.triboint.2018.10.022

Processing thin (<10 mu m), dense, flexible alpha-Al2O3 films from nanopowders 査読有り国際共著国際誌

Takeuchi Makoto, Niedermaier Matthias, Jansohn Monika, Umehara Noritsugu, Laine Richard M.

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 127 巻 ( 2 ) 頁： 81 - 89 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人日本セラミックス協会

Normally, it is very difficult to process thin ceramic films (<10 ¯m) except by vapor deposition methods. This is because in traditional ceramics processing, initial powder particle sizes (typical average particle sizes, APSs >200 nm) make it difficult to realize mechanically robust thin films after sintering to full density due to excessive grain growth. One solution to this problem is to start with nanopowders (APSs <100 nm). Here we present efforts to use simple, easily available nano ¤-Al 2 O 3 (transition or t-Al 2 O 3 ) nanopowders (NPs) to process the subject films. Thus t-Al 2 O 3 NPs when properly dispersed, doped with 0.55 wt.% MgO and ball milled with a polymeric binder provide castable systems. Wire wound roller drawing/tape casting provides access to thin green films (1030 ¯m) with µ75 wt.% ceramic loadings. Following binder burnout and careful sintering to temperatures of up to 1500°C/7 h/air but preferably slightly lesser conditions leads to dense ¯10 ¯m films with average ¡-Al 2 O 3 grain sizes of 500800 nm. At higher MgO concentrations, spinel phase separates during sintering likely inhibiting grain growth. These relatively dense films are flexible and translucent. Such films, because of their flexibility, may offer utility as catalyst supports, electronic substrates or as hard facings for other materials.

DOI： 10.2109/jcersj2.18099

ベース油中ta-CNx膜の摩擦時反射分光分析その場観察による低摩擦メカニズムの解明査読有り

岡本竜也, 梅原徳次, 野老山貴行, 村島基之

日本機械学会論文集 85 巻 ( 875 ) 頁： 19-00071 - 19-00071 2019年

Effect of Pillar and Mesh Structure of Tetrahedral Amorphous Carbon (ta-C) Coatings on the Wear Properties and Fracture Toughness of the Coating 査読有り国際共著国際誌

Bin Mustafa Mohd Muhyiddin, Umehara Noritsugu, Tokoroyama Takayuki, Murashima Motoyuki, Shibata Akinori, Utsumi Yoshiharu, Moriguchi Hideki

TRIBOLOGY ONLINE 14 巻 ( 5 ) 頁： 388 - 397 2019年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

Wear by fracture is among the factors associated with the DLC coating failures in the tribological application. The current study investigated the link between the wear and the fracture-toughness on the novel Pillar and Mesh structure ta-C coatings, in addition to conventional ta-C coatings. The tribological properties of these coatings were examined under base-oil lubrication via ball-on-disk tribo-tester and micro indentation technique was used to characterize the fracture toughness. The wear track and the indentation mark were analyzed using the optical microscope, 3D laser microscope and FE-SEM. The friction coefficient for ta-C, Pillar ta-C and Mesh ta-C are within the range of 0.071 to 0.106. Mesh ta-C indicated the highest wear resistance, followed by the Pillar ta-C and conventional ta-C. Also, Mesh ta-C demonstrated the highest fractute‐toughtness value with 16.6 Mpa.m1/2, followed by pillar ta-c with 13.4 MPa.m1/2 in contrast to ta-C. Greater resistance to wear for ta-C with Pillar and Mesh structure was detected with an increased fracture-toughness and improvement in crack propagation inhibition. Moreover, the Pillar and Mesh ta-C provides superior rate of crack-energy dissipation as compared to the ta-C.

DOI： 10.2474/trol.14.388

Investigating running-in behavior to understand wear behavior of ta-C coating with filtered cathodic vacuum arc deposition 査読有り国際共著国際誌

Lee W.Y., Tokoroyama T., Murashima M., Umehara N.

Jurnal Tribologi 23 巻頁： 38 - 47 2019年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Jurnal Tribologi

In this study, to clarify running-in cycle and role of carbon transfer layer on wear, ta-C coatings were subjected to friction tests under 200 °C in air with a different sliding cycles. The steady state friction coefficient of 0.02 was obtained after finishing a running-in cycles approximately 2,000 cycles. During the steady state, wear rate of ta-C decreased with increasing number of cycles. Such the decrease of wear rate was explained by polished defects presented on surface and form carbon transfer layer on the counter-part material. The mechanism of those tribological properties was analyzed by Raman spectroscopy, scanning electron microscope observation and 3D measuring laser microscope.

The tribological potential of graphene growth from solid waste 査読有り国際共著国際誌

Tahir N.A.M., Abdollah M.F.B., Tamaldin N., Amiruddin H., Zin M.R.B.M., Tokoroyama T., Umehara N.

Progress in Industrial Ecology 13 巻 ( 4 ) 頁： 401 - 413 2019年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Progress in Industrial Ecology

This study aimed to identify the tribological potential of graphene growth from solid waste products on copper substrate via the chemical vapour deposition method. The study focused on graphene growth from fruit cover plastic waste (FCPW) and oil palm fibre (OPF), the graphene structure was zexamined using Raman spectroscopy. Then, the tribological testing was performed using a ball-on-disc tribometer, and the hardness was performed using a nano-indenter on both the worn and unworn surfaces. The results show that graphene was successfully grown from both sources. Meanwhile, the tribological study found that both coatings showed a higher coefficient of friction (μ) compared to pure copper. However, the wear rate (k) was contradicted by the μ where the k was found to be 60% to 75% lower than pure copper. Finally, the hardness analysis revealed that the coating was damaged at 100 m sliding as the surface hardness increased.

DOI： 10.1504/PIE.2019.102864

Effect of carbon diffusion on friction and wear behaviors of diamond-like carbon coating against Cr-plating in boundary base oil lubrication 査読有り国際誌

Melardot Aboua K.A., Umehara N., Kousaka H., Tokoroyama T., Murashima M., Mabuchi Y., Higuchi T., Kawaguchi M.

Tribology Online 13 巻 ( 5 ) 頁： 290 - 300 2018年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

Investigations on tribological behaviors of Diamond-like Carbon (DLC) coating against other materials are strongly needed for scientific and industrial purposes. Recently, carbon diffusion has been found to play a key role in the wear of hydrogenated amorphous carbon (a-C:H) DLC coating when it is rubbed against steel counterpart material in boundary lubrication. Chromium has been reported to decrease carbon diffusion due to increase of the activation energy. In this research, we investigated on the effects of carbon diffusion on friction and wear properties of a-C:H coating when rubbed against Cr plating material. Results show that compared to steel counterpart, a-C:H coating exhibits lower friction coefficient, lower wear rate, and lower carbon diffusion rate when rubbed against Cr plating counterpart.

DOI： 10.2474/trol.13.290

ベース油中CNxの摩擦界面その場反射分光分析による摩擦メカニズムの解明査読有り

岡本竜也, 梅原徳次, 村島基之, 斉藤浩二, 眞鍋和幹, 林圭二

トライボロジスト 63 巻 ( 11 ) 頁： 755 - 767 2018年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

To clarify the low friction mechanism of CNx coating in PAO oil lubrication, we measured reflectance spectrum at friction area in-situ by reflectance spectroscopy during friction test against a sapphire hemi-sphere pin in PAO oil. We observed and estimated thickness of PAO oil film, surface roughness of CNx coating, thicknesses and polarizability of transformed layer formed on bulk CNx coating during friction test by analyzing reflectance spectrum. We proposed that the decreasing of load ratio of boundary lubrication mode to total load is the one of governing factor to reduce friction on the basis of the increasing of Λ value. Also we proposed the increasing of adsorption of PAO oil to the CNx transformed layer is the second governing factor on the basis of the increasing of polarizability of PAO oil and transformed layer, that leads to the increasing of van der Waals force between transformed layer and PAO oil as low friction mechanism of CNx in PAO oil lubrication.

DOI： 10.18914/tribologist.17-00023

FCVA法によるホウ素含有炭素ターゲットを用いたta-C:B膜の成膜および300℃までのトライボロジー特性査読有り

Effect of ZnDTP Triboflim's Morphology on Friction Behaviors of DLC Coatings: Tribofilm Characterization by 3D Scanning Electron Microscope Observation 査読有り国際共著

K. A. M. Aboua, N. Umehara, H. Kousaka, T. Tokoroyama, M. Murashima, H. Abdullah Tasdemir, Y. Mabuchi, T. Higuchi

Journal of Advanced Mechanical Design, Systems, and Manufacturing 12 巻 ( 7 ) 2018年11月

根本公紀, 梅原徳次, 野老山貴行, 村島基之, 瀧本裕治, 中道健司

トライボロジスト 63 巻 ( 10 ) 頁： 699 - 705 2018年10月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

Boron doped tetrahedral amorphous carbon (ta-C:B) coatings were deposited with Filtered Cathodic Vacuum Arc (FCVA) method using boron doped graphite target (B=0, 5 and 10 at. %). The material properties and tribological properties of ta-C:B coatings were obtained at 23~300℃. The amount of boron contents in ta-C:B coatings are from 0 to 5.1 at. %, and the hardness of coatings ware more than 30 GPa. The friction coefficient of ta-C:B3.1 at 300℃ is about 0.02 in air. The specific wear rate of ta-C:B coating were lower than normal ta-C coating by 34% and 46% for ta-C:B3.1 and ta-C:B5.1, respectively. The sp2/(sp2+ sp3) ratio measured by XPS and O/C ratio measured by AES increased through the friction at 300℃ for ta-C, on the other hand both values did not change for ta-C:B. Friction coefficients of ta-C:B3.1 were shown as 0.055 at 23℃ and about 0.02 at 100~300℃. The specific wear rate of ta-C:B3.1 at 23~300℃ in air was about 2.0 × 10−6 mm3/Nm. From these results, we confirmed that ta-C:B shows lower friction and higher specific wear resistance at 23~300℃ in air than ta-C.

DOI： 10.18914/tribologist.18-00003

CiNii Books

The effects of oil additives and mating materials to the friction, wear and seizure characteristics of a-C:H coating 査読有り国際共著国際誌

bin Taib Mohd Taufik, Umehara Noritsugu, Tokoroyama Takayuki, Murashima Motoyuki

JURNAL TRIBOLOGI 18 巻頁： 1 - 19 2018年9月

The effect of UV irradiation to a-C:H on friction and wear properties under PAO oil lubrication including MoDTC and ZnDTP 査読有り国際誌

Taib M., Umehara N., Tokoroyama T., Murashima M.

Tribology Online 13 巻 ( 3 ) 頁： 119 - 130 2018年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

One of the solutions to reduce friction between two sliding surfaces in automobile engine is by applying DLC coating to engine components. However, it is critical that the effect of lubricant additives to DLC coating to be clarified before hands as to avoid components failure. In this study, tribological friction test between SUJ2 balls and as-deposited plus UV irradiated a-C:H coatings was conducted to clarify the effect of ultraviolet irradiation to DLC coating in four different additives added lubricant oils. AFM, nanoindentation hardness test, ellipsometery, Zygo, and EDS-SEM were used to investigate the effect of UV irradiation to a-C:H DLC before and after friction test. Prior the friction test, the results showed that UV irradiation presented no significant change in terms of hardness and roughness but the irradiation did penetrate into topmost surface of the a-C:H coating to several degree and created dangling bonds available to interact with lubricant additives elements. Friction test results showed that UV irradiated a-C:H coatings presented lower friction coefficient than as deposited a-C:H coatings. Worn surface analysis revealed that UV irradiated a-C:H coatings attracted more lubricant additives element to attach on its surface thus created thicker tribofilm on its own surface and its counter materials, resulted in lower friction coefficient than the as-deposited a-C:H coatings.

DOI： 10.2474/trol.13.119

Chemical modification at and within nanopowders: Synthesis of core-shell Al2O3@TiON nanopowders via nitriding nano-(TiO2)(0.43)(Al2O3)(0.57) powders in NH3 査読有り国際共著国際誌

You Fei, Sun Kai, Yi Eongyu, Nakatani Eitaro, Umehara Noritsugu, Laine Richard M.

JOURNAL OF THE AMERICAN CERAMIC SOCIETY 101 巻 ( 4 ) 頁： 1441 - 1452 2018年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the American Ceramic Society

Here, we demonstrate the potential utility of using chemical modification to reorganize metastable nanoparticles into nanostructured nanoparticles without coincidentally inducing extensive necking/sintering. The motivation for this effort derives from the concept that chemical reduction in a single component in a mixed-metal nanoparticle will create segregated islands of a second immiscible phase. Given the very high chemical energies inherent in nanoparticles, the formation of even smaller islands of a second phase can be anticipated to lead to extremely high interfacial energies that may drive these islands to diffuse to cores or surfaces to form core-shell structures that minimize such interfacial energies. Thus, ammonolysis of (TiO2)0.43(Al2O3)0.57 composition nanopowders where both elements are approximately uniformly mixed at atomic length scales, under selected conditions (1000°C) for various periods of time at constant NH3 flow rates leads primarily to the reduction in the Ti species to form TiN or TiON which then appears to diffuse to the surface of the particles. The final products consist of Al2O3@TiON core-shell nanopowders that remain mostly unaggregated pointing to a new mechanism for modifying nanopowder chemistries and physical properties.

DOI： 10.1111/jace.15303

Effect of nanoparticles as lubricant additives on friction and wear behavior of tetrahedral amorphous carbon (ta-C) coating 査読有り

Li Xiang, Murashima Motoyuki, Umehara Noritsugu

JURNAL TRIBOLOGI 16 巻頁： 15-29 2018年3月

Effect of nanoparticles as lubricant additives on friction and wear behavior of tetrahedral amorphous carbon (ta-C) coating 査読有り国際共著国際誌

Li Xiang, Murashima Motoyuki, Umehara Noritsugu

JURNAL TRIBOLOGI 16 巻頁： 15-29 2018年3月

Effect of Substrate Bias and Temperature on Friction and Wear Properties for ta-C Coating Prepared under Different Substrate Bias Voltages with Filtered Cathodic Vacuum Arc Deposition 査読有り国際共著国際誌

Lee Woo-Young, Tokoroyama Takayuki, Jang Young-Jun, Umehara Noritsugu

TRIBOLOGY ONLINE 13 巻 ( 5 ) 頁： 241 - 247 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

In this paper, the tribological behaviors of 1 μm of tetrahedral amorphous carbon (ta-C) coatings deposited with a different substrate bias of -0 V, -100 V and -300 V are examined under elevated temperature up to 600°C. It is found that wear behavior could be divided into two distinct regions according to testing temperature. The variation trend of the specific wear rate of ta-C coatings in region I at 23, 100 and 200°C are affected by abrasive particles which coincide with sp3 content of ta-C coatings. In region II at 300, 400 and 500°C, the transfer layer play a major role in reduction of wear rate as a function of substrate bias.

DOI： 10.2474/trol.13.241

Collecting micrometer-sized wear particles generated between DLC/DLC surfaces under boundary lubrication with an electric field

TOKOROYAMA Takayuki, KAMIYA Toru, AFMAD Nazeef Afifi Bin Hafiz, UMEHARA Noritsugu

Mechanical Engineering Letters 4 巻 ( 0 ) 頁： 18-00089 - 18-00089 2018年

記述言語：英語出版者・発行元：一般社団法人日本機械学会

Carbonaceous coatings such as Diamond-Like Carbon (DLC) are attractive candidates for reducing friction under boundary lubrication. However, the wear particles generated from the DLC are believed to form hard slurries that scratch surfaces like an abrasive, and they can shorten the lifetime of the DLC itself. Generally, in conventional automobiles, these wear particles are collected by oil filters. Modern engine bearings are required to reduce the friction coefficient to low levels so that low-viscosity lubricants are used to reduce resistance to flow. However, using a low-viscosity lubricant result in direct solid contact between surfaces, which disrupts the hydrodynamic lubrication and generates numerous wear particles. In this study, we carried out friction tests between DLC/DLC surfaces with kerosene as a boundary lubricant at room temperature. The friction tests were conducted over 12,000 cycles, and we replaced the lubricant after every 2000 cycles without changing the contact pair. Wear particles were collected from the lubricant using an electric field with the electrophoresis effect. The wear particles gathered near the positive electrode and fell onto a glass plate. Finally, after the kerosene evaporated, scanning electron microscope and laser optical microscope observations showed the relations between particle size and shape, the number of wear particles, and the friction coefficient.

DOI： 10.1299/mel.18-00089

Effect of ZnDTP triboflim's morphology on friction behaviors of DLC coatings: Tribofilm characterization by 3D scanning electron microscope observation 査読有り国際誌

Aboua Kouami Auxence Melardot, Umehara Noritsugu, Kousaka Hiroyuki, Tokoroyama Takayuki, Murashima Motoyuki, Tasdemir Haci Abdullah, Mabuchi Yutaka, Higuchi Tsuyoshi

JOURNAL OF ADVANCED MECHANICAL DESIGN SYSTEMS AND MANUFACTURING 12 巻 ( 7 ) 頁： JAMDSM0129 - JAMDSM0129 2018年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本機械学会

ZnDTP antiwear additive for lubricating oil is known to absorb strongly on sliding surfaces in boundary lubricated tribosystems, forming a tribofilm, which is able to reduce the wear of involved surfaces. It is also known to increase the friction coefficient in most DLC/DLC contacts, with the exception of ta-C DLC / ta-C DLC contact, for which the difference in friction behaviors between a base oil + ZnDTP additive lubricated tribosystem and a base oil lubricated tribosystem is not very significant. In this study we investigate a characterization method of the shape of the tribofilm formed on different types of DLC coatings and on the relation between the shape of the tribofilm and the friction behavior of the related DLC coating. Results show that compared to other investigated DLC types, the tribofilm formed on ta-C DLC has some unique characteristic topography features that promote lower friction coefficient.

DOI： 10.1299/jamdsm.2018jamdsm0129

Comparative study on effects of load and sliding distance on amorphous hydrogenated carbon (a-C:H) coating and tetrahedral amorphous carbon (ta-C) coating under base-oil lubrication condition 査読有り

Li Xiang, Deng Xingrui, Kousaka Hiroyuki, Umehara Noritsugu

WEAR 392 巻頁： 84 - 92 2017年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Wear

In this study, the lubricated friction and wear associated with diamond-like coatings (DLCs) of amorphous hydrogenated carbon (a-C:H) and hydrogen-free tetrahedral amorphous carbon (ta-C) were comparatively analyzed. The effects of load and sliding distance on the wear and friction behaviors of the coatings were studied under a boundary-lubrication condition using a poly-alpha-olefin base oil. The DLC-coated cylindrical specimens were slid with their central axes perpendicular to the sliding direction against a rotating steel counterface. The results show that the friction coefficient of the ta-C coating was lower than that of the a-C:H coating, though a graphitized layer was detected both inside and outside the wear scar of the a-C:H coating. Under a relatively low applied load (5 N), the specific wear rate of the ta-C coating was considerably lower than that of the a-C:H coating. When the load was increased to a critical value of 10 N, the specific wear rate of the ta-C coating increased rapidly to 3–5 times that of the a-C:H coating. However, the specific wear rate of the a-C:H coating decreased significantly when the load exceeded 10 N, which was consistently maintained thereafter. With the increase in the sliding distance, the specific wear rate of the ta-C coating increased rapidly. In comparison to the ta-C coating, the specific wear rate of the a-C:H coating decreased only slightly with the increase in the sliding distance; moreover, when the sliding distance exceeded 125 m, the specific wear rate of the a-C:H coating became much lower than that of the ta-C coating. The results of Raman spectroscopy, atomic force microscopy, and scanning electron microscopy show that the coatings were influenced by different types of wear mechanisms when slid under pure base-oil boundary-lubrication conditions.

DOI： 10.1016/j.wear.2017.09.009

Effect of oil temperature and counterpart material on the wear mechanism of ta-CNx coating under base oil lubrication 査読有り

Effect of mating materials on wear properties of amorphous hydrogenated carbon (a-C:H) coating and tetrahedral amorphous carbon (ta-C) coating in base oil boundary lubrication condition 査読有り国際誌

Li Xiang, Sawaki Toshiya, Kousaka Hiroyuki, Murashima Motoyuki, Umehara Noritsugu

JURNAL TRIBOLOGI 15 巻頁： 1-20 2017年12月

Liu Xiaoxu, Yamaguchi Ryo, Umehara Noritsugu, Murashima Motoyuki, Tokoroyama Takayuki

WEAR 390-391 巻頁： 312 - 321 2017年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Wear

Tetrahedral amorphous carbon nitride (ta-CNx), as an emerging and promising diamond-like carbon (DLC), has better mechanical properties than amorphous carbon nitride (a-CNx) to ensure the sufficient durability, and overcomes the limit of high internal stress of tetrahedral amorphous carbon (ta-C), which makes ta-CNx coatings of great worth of research for the tribological and mechanical applications. In this study, we present the effects of oil temperature and counterpart material on the wear behavior of ta-CNx coatings under base-oil lubrication, and further clarify the wear mechanism. ta-C and ta-CNx coatings with N/C atomic ratio of 2.2% and 11.0% were deposited by an ion beam assisted filtered arc deposition (IBA-FAD) system, and the tribological tests were performed using a ball-on-disk tribo-tester with ta-C and ta-CNx coated steel ball sliding against uncoated disk under base-oil lubrication. The results show that nitrogen doping tends to decrease the hardness and Young's modulus by reducing the sp3 structure. Sliding against steel disk, with increase of sliding distance ta-CNx shows obviously distinct wear behavior compared to ta-C, much more slowly increasing wear volume, exhibiting excellent wear resistance. Increasing oil temperature from room temperature to 120 °C results in rising wear rates of all the three coatings, with totally worn out ta-C and much lower wear rate of ta-CNx, which decreases by more than half than ta-C for high nitrogen content ta-CNx. However, as the counterpart material changed from steel to alumina, the wear rate presents oppositely increasing tendency with N/C ratio, probably caused by the change of deciding factor to hardness in this mechanical wear. It is found that the wear performance of ta-CNx coating has a clear dependence on the oil temperature and counterpart material. Based on the results, the better wear resistance of softer ta-CNx against steel could be attributed to the less tribo-chemical wear between carbon and iron, due to the nitrogen doping partial passivation effect.

DOI： 10.1016/j.wear.2017.08.012

Effect of carbon diffusion on friction and wear properties of diamond-like carbon in boundary base oil lubrication 査読有り国際誌

Aboua Kouami Auxence Melardot, Umehara Noritsugu, Kousaka Hiroyuki, Deng Xingrui, Tasdemir Haci Abdullah, Mabuchi Yutaka, Higuchi Tsuyoshi, Kawaguchi Masahiro

TRIBOLOGY INTERNATIONAL 113 巻頁： 389 - 398 2017年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

In order to control wear and friction in industry, Diamond like carbon (DLC) hard coatings are widely applied in recent years due to their well appreciated mechanical and tribological properties. However, those properties are not yet well understood, as well as behavior of DLC hard coatings when rubbed against other materials. Other researchers reported that DLC hard coatings film show high wear when rubbed against steel counterpart and their durability decrease with the increase of the temperature. In this research, we investigated on friction and wear properties of DLC coatings and the results reveal that carbon diffusion has a key role in the wear and friction behavior of DLC coatings when rubbed against steel.

DOI： 10.1016/j.triboint.2016.10.047

Clarification of effect of transformed layer and oil film on low friction coefficient of CNx coating in PAO oil lubrication by in-situ observation of friction area with reflectance spectroscopy 査読有り

Nishimura Hidenori, Umehara Noritsugu, Kousaka Hiroyuki, Murashima Motoyuki

TRIBOLOGY INTERNATIONAL 113 巻頁： 383 - 388 2017年9月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

In order to clarify a low friction mechanism of CNx (Carbon Nitride) coating in PAO (Poly Alpha Olefin) oil lubrication, we measured reflectance spectrum at friction area in-situ by reflectance spectroscopy. And we obtained thicknesses and polarizabilities of oil film and transformed layer formed on bulk CNx coating during friction test by analyzing reflectance spectrum. From results, we concluded that the increments of polarizabilities of transformed layer and oil film had an effect on increasing thickness of oil film, and then the lubricated condition changed from boundary to mixed lubrication. Finally CNx coating showed low friction coefficient in PAO oil lubrication.

DOI： 10.1016/j.triboint.2016.10.029

The effects of temperature, pressure and dissolved oxygen concentration (DO) in water on the wear of the hydrogenated diamond-like carbon (HDLC) at high temperature and pressurized water 査読有り

Zin Mohd Rody Bin Mohamad, Yagi Yuji, Sasaki Keiji, Inayoshi Naruhiko, Tokoroyama Takayuki, Umehara Noritsugu, Kousaka Hiroyuki, Kawara Shingo

TRIBOLOGY INTERNATIONAL 109 巻頁： 48 - 57 2017年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

The aim of this study is to clarify the wear mechanism of hydrogenated diamond-like carbon (HDLC) coating in high temperature and pressurized water. A new reciprocating autoclave wear tester was developed to conduct the wear test between DLC coated pins against SUS316 plate in high temperature and pressurized water. The results showed that the wear of HDLC in water was greatly influenced by water temperature from 23 °C to 300 °C and dissolved oxygen concentration (DO) from 0.73 mg O/L to 47.5 mg O/L (mg O/L:milligrams oxygen per liter) in water. On the other hand, water pressure in the chamber did not have significant effect on the wear of HDLC when pressure was increased from 10 MPa to 30 MPa at 300 °C. Based on surface analysis by XPS, AFM nano scratch, Raman spectroscopy, and AES on the top most surface of the wear scar of HDLC, softening and oxidation of top layer of wear scar of HDLC was found to be the mechanisms of high wear of HDLC in high temperature and pressurized water. The transformation of sp3 to sp2 at higher water temperature is believed to be responsible for the reduced hardness of the top most surface of HDLC. Oxidation also provided softening of top layer of HDLC at higher DO in water.

DOI： 10.1016/j.triboint.2016.12.010

Microscopic origin of ultra-low friction coefficient between the wear track formed on carbon nitride coating and transfer layer on sliding ball in friction tests under dry N-2

Inoue Hiroshi, Muto Shunsuke, Arai Shigeo, Wasada Hiroaki, Umehara Noritsugu

SURFACE & COATINGS TECHNOLOGY 313 巻頁： 31 - 39 2017年3月

記述言語：日本語出版者・発行元：Surface and Coatings Technology

Carbon nitride (CNx) coatings have been found to exhibit an ultra-low friction coefficient (less than 0.01) after repeated sliding against a silicon nitride (Si3N4) ball in a dry nitrogen gas (N2) atmosphere. However, the mechanism for this has not yet been fully elucidated with respect to analyzing changes in the space structure of CNx. In the present study, we examined the microscopic structural changes in the near-surface structural transition layers of the wear track in the CNx coating and the transfer layer of the Si3N4 ball, using scanning transmission electron microscopy and electron energy-loss spectroscopy. We investigated the nitrogen concentration, density, and curvature of fragmented graphitic planes in the structural transition layers of both the CNx coating and the transfer layer of the Si3N4 ball by analyzing the plasmon peak and carbon K-edge. In addition, we theoretically examined the chemical bonding states of nitrogen doping in various model clusters using an ab initio molecular orbital method to clarify the role of nitrogen in the ultra-low friction behavior. The mechanism behind the ultra-low friction behavior is explained by nano-graphitization of the fragmented carbon structure with optimal nitrogen concentration passivating the contacting counter surfaces of the coating and ball formed during sliding.

DOI： 10.1016/j.surfcoat.2017.01.048

Effect of Electric Field on Adhesion of Thermoplastic Resin against Steel Plate, 査読有り

M. Murashima, N. Umehara, H. Kousaka, X. Deng

Tribology Online 12 巻 ( 2 ) 頁： 42-48 2017年2月

Microscopic origin of ultra-low friction coefficient between the wear track formed on carbon nitride coating and transfer layer on sliding ball in friction tests under dry N2. 査読有り国際誌

H. Inoue, S. Muto, S. Arai, H. Wasada, N. Umehara

Surface Coatings & Technology 313 巻頁： 31-39 2017年2月

種々の温度下におけるa-C:H膜の摩耗特性に及ぼすセラミックス相手材の影響査読有り

山之内卓弥、鄧　興瑞、田中幸雄、梅原徳次、上坂裕之

トライボロジスト 62 巻 ( 1 ) 頁： 52-58 2017年1月

H. Nishimura, N. Umehara, H. Kousaka, M. Murashima

Tribology International 113 巻頁： 383-388 2017年1月

Depth Profile of Oxygen of Diamond-Like Carbon Sliding Under Pressurized Hot Water 査読有り

M. R. B. Mohamad Zin, K. Okuno, N. Umehara, N. Inayoshi, K. Sasaki, S. Kawara,H. Kousaka

Tribology Online 12 巻 ( 1 ) 頁： 8-17 2017年1月

Tribological properties of ta-CNx coatings with different nitrogen content under oil lubrication conditions 査読有り

Deng Xingrui, Hattori Takafumi, Umehara Noritsugu, Kousaka Hiroyuki, Manabe Kazuyoshi, Hayashi Keiji

THIN SOLID FILMS 621 巻頁： 12 - 18 2017年1月

記述言語：英語出版者・発行元：Thin Solid Films

Carbon nitride (CNx) coatings exhibit a wide range of attractive properties that make them suitable for demanding mechanical and tribological applications. In this study, an ion beam assisted filtered arc deposition (IBA-FAD) method has been developed for the deposition of tetrahedral amorphous carbon nitride (ta-CNx) coatings. The ta-CNx coatings with various nitrogen contents were deposited by controlling the nitrogen flow to investigate the effects of nitrogen content on their tribological behavior. The composition and structure of the ta-CNx coatings were evaluated using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The tribological properties were examined using a ball-on-disk tribo-tester under oil lubrication condition. The results showed that nitrogen contents of ta-CNx coatings were restricted to the range of 0–11 at.% by nitrogen ion density. The hardness decreased with an increase in the nitrogen content as nitrogen decreased the fraction of sp3 carbon in the coatings. The ta-CNx coatings exhibit low friction under oil lubrication and the maximum value was obtained for samples containing 8 at.% of nitrogen. ta-CNx with 8–11 at.% of nitrogen exhibited markedly low wear rate.

DOI： 10.1016/j.tsf.2016.11.025

Tribological properties of ta-CNx coatings with different nitrogen content under oil lubrication conditions 査読有り国際誌

X. Deng, T. Hattori, N. Umehara, H. Kousaka, K. Manabe, K. Hayashi

Thin Solid Films 616 巻頁： 134-140 2017年1月

Clarification of high wear resistance mechanism of ta-CNx coating under poly alpha-olefin (PAO) lubrication 査読有り

Liu Xiaoxu, Yamaguchi Ryo, Umehara Noritsugu, Deng Xingrui, Kousaka Hiroyuki, Murashima Motoyuki

TRIBOLOGY INTERNATIONAL 105 巻頁： 193 - 200 2017年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

Tetrahedral amorphous carbon nitride (ta-CNx) is suitable for tribological application due to its excellent mechanical and adhesion properties. In this study, ta-CNx coatings with N/C ratios (0–11%) are deposited by ion beam assisted filtered arc deposition (IBA-FAD), and the tribological properties are investigated with a ball-on-disk tribo-tester. The results show that nitrogen doping decreases the fraction of sp3 bonding, hardness, Young's modulus and roughness. In oil ta-CNx presents slightly decreasing friction coefficient and improving wear resistance with the N/C ratio, indicating softer ta-CNx with better wear resistance. The lower surface roughness after friction of high nitrogen content ta-CNx makes it more likely to transit to mixed lubrication, resulting in lower contact load that can explain the better wear resistance.

DOI： 10.1016/j.triboint.2016.10.016

プラズマ・イオンプロセスによる薄膜の製造とトライボロジー

トライボロジーの未来と工学教育

梅原徳次

トライボロジスト 62 巻 ( 10 ) 頁： 609 - 609 2017年

上坂裕之, 梅原徳次

精密工学会誌 83 巻 ( 4 ) 頁： 319 - 324 2017年

固体潤滑シートを用いたチタン合金の穴あけ加工におけるバリ高さに及ぼすドリル表面テクスチャリングの影響査読有り

大山慎太郎, 梅原徳次, 上坂裕之, 鄧興瑞, 村島基之, 堀江茂, 松山洋介

日本機械学会論文集 83 巻 ( 849 ) 頁： 16-00378 - 16-00378 2017年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本機械学会

This paper describes about the effect of drill surface texturing on height of back burr in titanium alloy drilling process with solid lubricating sheet. Titanium alloy is difficult to conduct drilling because titanium alloy is hard and ductile material. And the workers cannot use plenty of liquid coolant for preventing the productivity decline when the work places are above their heads in production fields. Therefore drills are exchanged frequently even though the cost increases. In this study, we measured the cutting force by a loadcell to know the effect of drill surface texturing and solid lubricating sheet on drilling process of work pieces made of Ti-6Al-4V. As the results, drill with rough textured rake surface showed high burr height in exit of Ti-6Al-4V. On the other hand, drill with rough textured flank surface showed low burr height only if drilling with solid lubricating sheet. Moreover, drill with the specific texturing on flank surface by wire electric discharge machining showed low burr height.

DOI： 10.1299/transjsme.16-00378

Analysis of Wear Track on DLC Coatings after Sliding with MoDTC-Containing Lubricants 査読有り国際誌

Ohara Kenji, Hanyuda Kiyoshi, Kawamura Yasushi, Omura Kentaro, Kameda Imari, Umehara Noritsugu, Kousaka Hiroyuki

TRIBOLOGY ONLINE 12 巻 ( 3 ) 頁： 110-116 - 116 2017年

Friction and Wear Properties of Tetrahedral Si-Containing Hydrogenated Diamond-Like Carbon Coating under Lubricated Condition with Engine-Oil Containing ZnDTP and MoDTC 査読有り国際誌

Komori Kentaro, Umehara Noritsugu

TRIBOLOGY ONLINE 12 巻 ( 3 ) 頁： 123 - 134 2017年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

In this study, we investigated tribological properties of “tetrahedral” Si-containing hydrogenated DLC coating (TMS coating) during sliding against steel or cast-iron lubricated with engine-oil containing MoDTC and ZnDTP additives. TMS coatings derived from only tetramethylsilane were prepared using PACVD with high-bias process. TMS coating had the highly carbon sp3 bonded structure induced by Si (over 20 at.%) with high hydrogen content (30 at.%). TOF-SIMS analysis showed that TMS coating could form the additive-derived tribofilm on both of the non-ferrous coating surface and the ferrous counter surface to promote Mo-sulfide formation effectively, leading a low friction coefficient. The tribo-chemical reactions were related not only to Mo-sulfides formation, but also reduction of Mo-oxides. Mo-oxides could react with DLC material and induce hydrogen evolution and transformation into further weak carbon structure, causing an increasing wear of hydrogenated DLCs. TMS coating showed no significant wear in spite of plenty hydrogen content. Si induced sp3 bond and could act so as not to induce clustering of the sp2 phase. This could inhibit increasing wear of the DLC in the presence of MoDTC. The effectiveness of TMS coating in friction and wear behavior was shown to depend on tribo-chemical reactions and transformation of carbon bond structure.

DOI： 10.2474/trol.12.123

ループ型カーボンファイバーブラシによる軽量・低起動トルクすべり軸受の提案査読有り

志鷹拓哉, 村島基之, 梅原徳次, 月山陽介, 新田勇, 上坂裕之, 鄧興瑞

日本機械学会論文集 83 巻 ( 854 ) 頁： 17-00252 - 17-00252 2017年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本機械学会

This paper addresses a novel lightweight and low starting torque bearing with looped carbon fiber brush (LCFB). LCFB simulates bristle of living being. Moreover, the static friction coefficient is nearly equal to the kinetic friction coefficient. By applying LCFB to a slide bearings, where a shaft is supported by multiple LCFBs, it is realized low starting torque bearings as well as lightness compared to conventional ball bearings. In this paper, we manufacture prototype LCFB slide bearings. With the bearings, we compare friction torque between LCFB slide bearings, slide bearings and deep groove ball bearings. As results, the ratio of starting torque to regular torque of LCFB slide bearing is from 0.93 to 1.07 which is smaller than that of the slide bearing. When micro-spline shaft is used as a mating material of LCFB slide bearing, the torque reduces because of decrease of real contact area between LCFB and mating materials. In addition, since LCFB utilize elastic deformation of fibers, LCFB slide bearings are not endurable in heavy radial load as high as load rating of ball bearing. Therefore, we define the load capacity of LCFB slide bearing from buckling load of a carbon fiber bundle to avoid overload state. We propose the load capacity as a design guideline of LCFB slide bearings.

DOI： 10.1299/transjsme.17-00252

Depth Profile of Oxygen of Diamond-Like Carbon Sliding under Pressurized Hot Water 査読有り国際共著国際誌

Bin Mohamad Zin Mohd Rody, Okuno Kiichi, Sasaki Keiji, Inayoshi Naruhiko, Umehara Noritsugu, Kousaka Hiroyuki, Kawara Shingo

Tribology Online 12 巻 ( 1 ) 頁： 8 - 17 2017年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

The wear mechanism of diamond-like carbon (DLC) in hot, pressurized water has been studied by the oxygen depth profile of DLC films pre and post a sliding test. The sliding test between DLC films coated on chromium molybdenum steel (JIS SCM420) pins and austenitic stainless steel (JIS SUS316) plates was conducted in a water environment by using high temperatures of 100, 200, 250 and 300°C and a high-pressured (10 MPa) autoclave friction tester. The dissolved oxygen concentration (DO) was 0.52 mg/L for oxygen-poor water and 40 mg/L for oxygen-rich water. The experimental results showed that the specific wear rate of DLC was strongly related to the water temperature and the DO concentration. The specific wear rate in both cases of oxygen-poor and oxygen-rich water showed a temperature dependency. When the temperature was below 200°C, the specific wear rate of DLC did not depend on the DO concentration. On the other hand, when the water temperature was more than 200°C, the specific wear rate drastically increased with the DO concentration. In order to prove the effect of oxidation on the wear rate of DLC, the depth profile of the oxygen concentration was compared to that of the carbon concentration on the inside and outside of the wear scar of DLC after sliding tests in hot, pressurized water. When the concentration of DO in the water was low at 0.52 mg/L, the O/C ratio was not affected by the water temperature. On the other hand, when the concentration of DO in water was high at 40 mg/L, the O/C ratio of the top surface increased from 0.05 to 0.18 with an increase in the water temperature on the inside of the wear scar of DLC, where the O/C ratio on the inside of the wear scar was higher than that on the outside of the scar. On the basis of the estimated rate of reaction between DLC and oxygen, determined from a linear relationship between ln (Oxidation wear volume) and the inverse temperature, it was concluded that the oxidation of DLC governed the wear of DLC in hot, pressurized water. Friction was found to enhance the oxidation wear of DLC from the estimated activation energy.

DOI： 10.2474/trol.12.8

Effect of electric field on adhesion of thermoplastic resin against steel plate 査読有り国際誌

Murashima M., Umehara N., Kousaka H., Deng X.

Tribology Online 12 巻 ( 2 ) 頁： 42 - 48 2017年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本トライボロジー学会

This work shows new method which controls adhesion strength between acrylic resin and metal mold with electric field. Usage of electric field is considered as a new solution to control adhesion of thermoplastic resin in Carbon-Fiber-Reinforced ThermoPlastic (thermoplastic CFRP) stamping process because this method can prevent CFRP from its degradation. In this work, we establish new adhesion tester which can apply Direct Current (DC) or Alternating Current (AC) field on metal specimens. In the results, when DC -12 V/mm is imposed on metal specimens, adhesion strength increases to 0.81 MPa which is 57% higher than that of no field condition. Negative component of surface energy after imposing DC -12 V/mm on metal specimens is 7.6 mJ/m2. This value is 56% smaller than that of no field condition. When AC electric fields is imposed, adhesion strength decreases from no electric field condition. The most effective AC field condition is AC 10 V/mm with 1 MHz, in which case adhesion strength is 0.29 MPa. This value is 44% lower than that of no field condition.

DOI： 10.2474/trol.12.42

分離形熱サイフォンを用いた血液凝固付着抑制電気メスの開発査読有り

野老山貴行, 大須賀未都, 梅原徳次

日本機械学会論文集 83 巻 ( 845 ) 頁： 16-00123 - 16-00123 2017年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本機械学会

Radio knives are common tools in surgery. The adhesion of the tip of a radio knife to the human body through the coagulation of blood is a severe problem. A solution to this problem, suggested by other authors, is to cool the tip of the radio knife. However, introducing a cooling system, such as circulating water inside the tip with a pump, requires additional wires and pipes and may also distract the surgeons. To overcome these issues, we consider the possibility of embedding a separate type thermosyphon to cool the radio knife tip without any additional wires and pipes. The important parameters are the tip length, tip diameter, inner tip diameter, enclosure ratio of the working fluid, and grip length. First, to clarify the heat-transport possibilities, the top of the tip of a separate type thermosyphon radio knife was heated by a ceramic heater; this was done to measure the temperature difference between the radio knife tip surface and a heat release part. Second, suitable values for the tip length, diameter and other important parameters were considered. It was concluded that the highest cooling efficiency is obtained when the heating area is limited between 200 and 250 mm2 of the knife tip surface area. The inner pipe was indispensable to transport generated heat from the tip to the radio knife end. Consequently, it was revealed that the effective diameter of inner pipe was 0.48 mm in this research. To simulate the conventional surgery situations, the radio knife tip was immersed to blood and applied voltage to generate heat at the tip. It demonstrated 45.9 degree C at the maximum temperature while it was activated. Furthermore, the coagulation at the peripheral of the tip was observed, accordingly, the separate type thermosyphon radio knife exhibited a stop bleeding ability.

DOI： 10.1299/transjsme.16-00123

反射分光法によるカーボン系硬質膜の摩擦面構造変化層のその場評価装置

西村英典, 上坂裕之, 梅原徳次

トライボロジスト 62 巻 ( 7 ) 頁： 461 - 464 2017年

Effects of ceramic counterpart material on wear property of a-C:H coating under various temperatures 査読有り

Yamanouchi T., Xingrui D., Tanaka Y., Umehara N., Kousaka H.

Toraibarojisuto/Journal of Japanese Society of Tribologists 62 巻 ( 1 ) 頁： 52 - 58 2017年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Toraibarojisuto/Journal of Japanese Society of Tribologists

Carbon coatings have a keen attention according to its low friction, high hardness and high wear resistance properties. There are needs to apply carbon coatings into ceramic mechanical parts, such as mechanical seal. However the tribological properties of carbon coatings when slid against ceramics are still not investigated sufficiently. Generally tribological behaviors are affected by a counterpart material. Therefore more fundamental researches about counterpart material are necessary. In this research tribological behaviors of carbon coating when slid against various counterpart material, including SiC, SiC(O) that is SiC after annealing at 1000°C, Si3N4, Al2O3, Al2O3(Si) that includes more Si atomic concentration than Al2O3and Si wafer at various temperatures in air have been investigated. Carbon coating when slid against SiC showed the lowest wear rate at 23°C, and carbon coating when slid against Si3N4showed the lowest wear rate at 140°C and carbon coating when slid against SiC(O) showed the lowest friction coefficient at all temperature.