Design of low-friction lubricant containing nanodiamond particles

Research Project

Project/Area Number	19K21063
Project/Area Number (Other)	18H05882 (2018)
Research Category	Grant-in-Aid for Research Activity Start-up
Allocation Type	Multi-year Fund (2019) Single-year Grants (2018)
Review Section	0301:Mechanics of materials, production engineering, design engineering, fluid engineering, thermal engineering, mechanical dynamics, robotics, aerospace engineering, marine and maritime engineering, and related fields
Research Institution	Utsunomiya University
Principal Investigator	Mabuchi Yutaka 宇都宮大学, 工学部, 教授 (00823296)
Project Period (FY)	2018-08-24 – 2020-03-31
Project Status	Completed (Fiscal Year 2019)
Budget Amount *help	¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000) Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000) Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Keywords	ナノダイヤモンド / 摩擦低減 / 潤滑油 / 同位体 / TOF-SIMS / 官能基 / エンジンオイル / トライボロジー / 摩擦 / 重水素 / 分散 / 潤滑 / オイル / 粒度分布 / 摩擦係数 / ナノ粒子 / 低摩擦 / ダイヤモンド / エンジン / 燃費
Outline of Research at the Start	エンジンCO2排出量削減3%の効果が期待されるナノダイヤモンドの潤滑油への分散について、ナノダイヤモンドと同様に不対電子の多いta-C膜（tetrahedral amorphous Carbon）での解析の知見を基に、1）摩擦を左右するナノダイヤモンド表面の官能基の直接観察、2）接触部に供給される粒子の量(分散状態)の二つの因子に着目し、摩擦係数との関係を明らかにすることで、複数の添加剤を含む潤滑油における低摩擦化設計の指標へ繋げる。
Outline of Final Research Achievements	It is known that the coefficient of friction is reduced by adding nano-diamond particles with a diameter of several nanometers to water. By clarifying the detailed mechanism of friction reduction, it can be applied to the engine oil and expected to improve the fuel efficiency. In this study, functional groups derived from solvent were added to the surface of nano-diamond for friction reduction, and its effect was maximized at sliding parts where the interplanar spacing was controlled uniformly. The interaction between various additives of engine oil (the anti-wear agent, the detergent and the dispersant) was also clarified. These findings lead to the design guideline of the engine oil in which nano-diamond is dispersed.
Academic Significance and Societal Importance of the Research Achievements	従来の摩擦解析は事後の試験片表面の解析のみであったのに対し、本研究は試験後のナダイヤモンド粒子を遠心分離で抽出し表面を直接観察すること、更に水素同位体を用いることで、低摩擦化のカギとなる粒子表面の官能基（-OH）が、使われる環境由来であることを明らかにした。この結果は、ナノダイヤモンド粒子を、-OHの供給源となる添加剤と組み合わせて用いることで、持続的に摩擦低減効果が得られることを意味しており、潤滑油を設計する際の重要な指針へと繋がった。