Nobuo Ohmae

Influence of humidity on microtribology of vertically aligned carbon nanotube film

The aim of this study is to probe the influence of water vapor environment on the microtribological properties of a forestlike vertically aligned carbon nanotube (VACNT) film, deposited on a silicon (001) substrate by chemical vapor deposition. Tribological experiments were performed using a gold tip under relative humidity varying from 0 to 100%. Very low adhesion forces and high friction coefficients of 0.6–1.3 resulted. The adhesion and friction forces were independent of humidity, due probably to the high hydrophobicity of VACNT. These tribological characteristics were compared to those of a diamond like carbon (DLC) sample.

Transformation of diamond nanoparticles into onion-like carbon by electron irradiation studied directly inside an ultrahigh-vacuum transmission electron microscope

In situ observation of the transformation of diamond nanoparticles (DNP) into onion-like carbon (OLC) was made during electron-beam irradiation inside an ultrahigh-vacuum transmission electron microscope at 300 kV with 8.5×1023e∕m2. 5 nm DNP changed into OLC within about 10 min of irradiation, while 20 nm DNP did not change to OLC but to graphite. Therefore, the size effect is critical to the formation of OLC. The mechanism of formation of OLC from DNP is discussed.

Friction and adhesion of carbon nanotube brushes

Abstract Brushes made of carbon nanotubes have been tested by use of atomic force microscopy. Two different cantilevers were used: a silicon cantilever with a spherical tip made of SiO2 and a beryllium bronze cantilever with a tip made of steel. Sliding in the lateral direction was studied to measure the friction coefficient and to examine nanotribological properties. Nanoindentation was used to measure the pull-off force. Finally, a model of adhesion was created and experimental results were compared with it.

Mechanical and tribological behaviour of carbon nanotube brushes

Abstract Carbon nanotube brushes of micrometre range height were deposited on a silicon substrate and tested by use of atomic force microscopy. The cantilevers tips were made of silicon or steel. Firstly, the effect of the structure of carbon nanotubes on indentation (mechanical behaviour) in normal direction to the substrate was studied. Moreover, to examine nanotribological properties, sliding in the lateral direction to the substrate was studied. We also studied how the resonance frequency of vibration of one kind of microfork changes with the depth, to examine the connection between friction force and depth of the measurement. Finally, a mathematical model of the mechanical and tribological properties of carbon nanotube brushes was elaborated.

Nanotribology and Nanoscale Materials Coatings for Lubricants

Abstract Nanotribology is defined as a fundamental research field of tribology viewed from the perspective of atoms and molecules. In this paper, tribology of nanomaterials is overviewed with a focus on advanced carbon materials. The recent development of surface tools with atomic resolution that can be used in nanotribology is firstly introduced in this paper. Advanced carbon materials including C60, carbon nanotube (CNT), and onion-like carbon (OLC) are considered having lubricating ability in nanoscale. The advantages and disadvantages of above-mentioned materials working as carbon-based nanolubricants are then discussed, and the manufacture process of them in large quantities is briefly reviewed. The methodology to examine the friction- reducing property of nanocarbon materials in boundary lubrication is reviewed, where OLC film showed very low friction and it is effective for reducing friction and wear when added in synthetic lubricant oil. The approaches for coating uniform films of nanolubricants (C60, CNT, and OLC film) are discussed. The high-resolution TEM (HR-TEM) image of OLC and cross section of CNT is shown in this paper, indicating both of them have atomic-scale intrusions and protrusions on surface. The nanocarbons and other lubricants in conjunction with 1D structured film formation through tribological processes are then compared in this research.