Faculty Profiles - TOKOROYAMA, Takayuki

Papers - TOKOROYAMA, Takayuki

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Effect of Texturing on Friction Properties of CNx Coating Layer under Oil Lubrication with Imitation Wear Debris Reviewed

Takayuki TOKOROYAMA, Tomoyo KANEKO, Yosuke TSUKIYAMA, Noritsugu UMEHARA, Tetsuya SATO and Tadashi SUZUKI

Vol. 79 ( 806 ) page： 3895 - 3903 2013.10

Influence of UV irradiation for low frictional performance of CNx coatings Reviewed International coauthorship

T. Tokoroyama, M. Kamiya, N. UMEHARA, C. Wang, D.F. Diao

Lubrication Science Vol. 24 ( 3 ) page： 129- - 139 2012.4

Development of a Radio Knife Suppressing the Adhesion of Coagulated Blood Reviewed

Yuya Nakashima, Noritsugu Umehara, Takayuki Tokoroyama and Yoichi Akagami

Vol. 78 ( 786 ) page： 605-614 2012.2

The influence of interlayer for frictional property and adhesion of IBAD CNx coating Reviewed

M. Wakayama, Y. Tsukiyama, T. Tokoroyama, H. Kousaka, N. Umehara, M. Wang and T. Toihara

Vol. 77 ( 781 ) page： 3502- - 3510 2011.10

Reduction of adhesion of coagulation to a radio knife tip with filled micro-grooves Reviewed

Yuya NAKASHIMA, Noritsugu UMEHARA, Takayuki TOKOROYAMA and Yoichi AKAGAMI

Vol. 77 ( 779 ) page： 2916 - 2921 2011.7

The Effect of Ultraviolet Irradiation on Friction Coefficient of Diamond-Like Carbon Coating in Air Reviewed

Takayuki TOKOROYAMA*, Takuya HATANO, Noritsugu UMEHARA, and Yoshio FUWA

Journal of Japanese Society of Tribologists Vol. 56 ( 4 ) page： 256 - 263 2011.4

The Effect of Substrate Temperature, Nitrogen Ionbeam Acceleration Voltage, and Deposition Rate on Hardness of Carbon Nitride Coating Reviewed

T. TOKOROYAMA, R. SAITO, N. UMEHARA and Y. FUWA

Vol. 77 ( 775 ) page： 624 - 630 2011.3

窒素中で超低摩擦を発現するCNx膜の極表面層の機械的特性の評価 Reviewed

木村徳博，月山陽介，野老山貴行，梅原徳次

日本機械学会論文集（C編） Vol. 76 ( 772 ) page： 3794 - 3799 2010.12

The Effect of Ultraviolet Irradiation on Friction Coefficient of Diamond-Like Carbon Coating in Air Reviewed

T. Tokoroyama, T. Hatano, N. Umehara, Y. Fuwa

Vol. 76 ( 771 ) page： 3166 - 3171 2010.11

窒化炭素膜のトライボロジー特性に及ぼす紫外線照射の影響 Reviewed

野老山貴行，梅原徳次，神谷真人，不破良雄

トライボロジスト Vol. 55 ( 9 ) page： 659 - 665 2010.9

The influence of micro-grooves for friction dependant on sliding velocity in slide bearing under oil lubrication Reviewed

Shotaro OZU, Takayuki TOKOROYAMA, Atsushi KORENAGA, Shinya SASAKI and Noritsugu UMEHARA

Transactions of the Japan Society of Mechanical Engineers, Series C Vol. 75 ( 754 ) page： 1866 - 1871 2009.6

Influence of the Carbon-Overcoat on CNx Coating for the Friction and Wear Properties Reviewed

Huaipeng WANG, Takayuki TOKOROYAMA, Noritsugu UMEHARA, and Yoshio FUWA

Transactions of the Japan Society of Mechanical Engineers, Series C Vol. 75 ( 754 ) page： 1859 - 1865 2009.6

Superlow Friction Phenomena of Carbon Nitride Coatings Lubricated under 18 Carbon Atoms Unsaturated Fatty Acids Reviewed

Takayuki Tokoroyama, Noritsugu Umehara, Yuichiro Ogawa, Yoshio Fuwa

Journal of Japanese Society of Tribologists Vol. 54 ( 6 ) page： 406 - 411 2009.6

Superlow friction with CNx coating under oil lubrication Reviewed

Yuichiro Ogawa, Takayuki Tokoroyama, Noritsugu Umehara, Yoshio Fuwa

Transactions of the Japan Society of Mechanical Engineers, Series C Vol. 75 ( 752 ) page： 1088 - 1093 2009.4

Control of friction and wear properties of CNx coatings with rising temperature in ambient air Reviewed

Yuya Yoshikawa, Takayuki Tokoroyama, Noritsugu Umehara

Transactions of the Japan Society of Mechanical Engineers, Series C Vol. 74 ( 747 ) page： 2791 - 2796 2008.11

In Situ Analysis of the Tribochemical Reaction of CNx by FTIR Reviewed

Shingo Kanda, Takayuki Tokoroyama, Noritsugu Umehara, Yoshio Fuwa

Tribology Online Vol. 3 ( 2 ) page： 100 - 104 2008.4

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)

Carbon Nitride (CNx) coating was reported to show a superlow friction coefficient when it slid against a Si3N4 ball in nitrogen gas at atmospheric pressure. This superlow friction phenomenon occurred after a number of sliding cycles, in the so-called running-in period, due to the nitrogen atom desorption from the topmost CNx coating surface; its the surface became a graphite-like layer, and a transfer layer was formed on the counter material surface. However, a friction test and surface analysis should be conducted simultaneously, when detailed frictional phenomena including functional groups are observed on the topmost CNx surface. It was supposed that several functional groups were adsorbed on the topmost surface of the carbon system coating when the specimen was withdrawn from the synthesis chamber. In this study, we constructed a friction test apparatus in a FTIR analytic chamber to conduct friction tests and surface analysis without taking the friction test chamber out of the analytical chamber. The analysis results of 1500 cycles each indicated that the -OH or -NH functional group gradually increased with the number of sliding cycles. However, the group decreased suddenly as the friction coefficient decreased. Finally, these kinds of functional groups were not detected when the CNx coating showed superlow friction phenomena.

Evaluating Shaver Sharpness by Measuring the Pulling Force on Artificial Hair Reviewed

T. Tokoroyama, Norhaswira MOHD, Noritsugu UMEHARA

Journal of Advanced Mechanical Design, Systems, and Manufacturing Vol. 1 ( 5 ) page： 661 - 668 2007.11

Effect of Nitrogen atoms desorption on the friction of the CNx coating against Si3N4 ball in Nitrogen gas Reviewed

Takayuki Tokoroyama, Minoru Goto, Noritsugu Umehara, Takashi Nakamura, Fumihiro Honda

Tribology Letters Vol. 22 ( 3 ) page： 215 - 220 2006.6

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal)

Phase transition of CNx coatings by sliding against a Si3N4 ball has been studied by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) to understand this super-low friction phenomena in N2. A pin-on-disk type tribometer was constructed to determine the tribological properties of this coating when sliding against a Si3N4 ball in N2. The analytical results by AES and XPS showed that the nitrogen atoms desorbed from the top layers of the coating, and that the layers changed to a graphite-like structure without nitrogen during a friction coefficient decrease to lower than 0.01. The structural transition of CNx is discussed in this paper.

The effect of environmental gas on friction coefficient of CNx coatings and maximum concentration of O2 for the realization of ultra-low friction Reviewed

Takayuki Tokoroyama, Takashi Nakamura, Noritsugu Umehara, Hirotsugu Tomita, Yukinori Takenoshita

Journal of Japanese Society of Tribologists Vol. 50 ( 9 ) page： 683 - 689 2005.9

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal)

It was reported that CNx showed super-low friction coefficient less than 0.01 in N2. In this study, to clarify the possibility of super-low friction of CNx in air, friction tests in N2, O2, CO2, and Ar were carried out. Moreover, friction tests in each constant concentration of O2 and increasing concentration of O2 from 0 to 21% or decreasing from 21 to 0% were carried out to know the maximum concentration of O2 in ambient gas. Main results are the followings: (1) In the case of friction test carried out in O2, the transfer layer showed 7 times higher oxygen concentration than the transfer layer formed in N2. On the other hand, in the case of transfer layer indicating low concentration of oxygen, friction coefficient was lower than 0.05. (2) In order to obtain super-low friction coefficient less than 0.01, it was necessary that at least transfer layer should be formed in N2 (contained concentration of O2 lower than 0.01%) and the concentration of O2 at friction environment kept less than 2.0%.

Effect of surface roughness and transfer layer of mating ceramic parts for ultra low friction phenomena in sliding between CNx and ceramics Reviewed

Takayuki Tokoroyama, Noritsugu Umehara, Hirotsugu Tomita, Yukinori Takenoshita

Transactions of the Japan Society of Mechanical Engineers, Series C Vol. 69 ( 686 ) page： 2824 - 2829 2003.10

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal)

In order to know the running-in process for ultra low friction of CNx sliding against Si3N4 balls in N2, the effect of surface roughness of balls on friction coefficient was investigated. As results, it was shown that friction coefficient for all of Si3N4 balls decreased with sliding cycles and reached to the specific minimum values less than 0.05. For friction coefficient less than 0.01, smooth surface of ball with 30nm Ry as initial surface roughness was necessary. Smooth surfaces of CNx coating and Si3N4 ball after running-in provide ultra low friction after the transfer of tiny amount of CNx to Si3N4 ball and the generating of thin and uniform transfer film on balls.

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Papers - TOKOROYAMA, Takayuki