研究者詳細 - 梅原　徳次

論文 - 梅原　徳次

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

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

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 査読有り国際共著国際誌

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

<p>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.</p>

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

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

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

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

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