Molecular Tribometry: Recent Results and Future Prospects

AbstractThe method of molecular tribometry is described. Ultrathin films of liquids are confined between parallel plates, usually of atomically smooth muscovite mica, such that the apparent area of contact equals the true area of contact. This paper consists of 5 sections. First, the phenomenon of solid lubrication by liquids is described. Second, the alternative viscous response of ultrathin liquid lubricants is described; the microviscosity is considerably enhanced over that of the isotropic liquid. Third, the critical shear strength is shown to have an extreme dependence on the normal pressure. Fourth, the materials requirements for molecular tribometry are discussed. Finally, a discussion is offered of the strengths and limitations of this new tool.

Download Full-text

Study on the Geotechnical Engineering Properties of Polluted Soil

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.659 ◽

2013 ◽

Vol 353-356 ◽

pp. 659-662 ◽

Cited By ~ 1

Author(s):

Zhen Ying Zhang ◽

Da Zhi Wu ◽

Li Jun Yan

Keyword(s):

Shear Strength ◽

Soil Mechanics ◽

Geotechnical Engineering ◽

Friction Angle ◽

Normal Pressure ◽

Polluted Soil ◽

Engineering Properties ◽

Copper Ore ◽

Cohesion Force ◽

Natural Density

To investigate the geotechnical engineering properties of polluted soil, ten soil samples are collected from Anqing copper ore, Anhui Province, China. The geotechnical engineering parameters of the polluted soil are measured in the soil mechanics laboratory. Tests results show that the natural density varies from 1.56 to 2.04t/m3, the moisture content varies from 15.36% to 27.87%, the modulus of the compression varies from 1.27 to 8.10MPa, the cohesion force varies from 32 to 210kPa, and the internal friction angle varies from 25.4 to 57.9 degree. Finally, the properties of the shear strength and the compression are studied, and find that the compressibility of the polluted soil is very big, and the relationship between shear strength and the normal pressure conforms to the law of Coulomb.

Download Full-text

Accurate Study of Normal Pressure Distribution in Entrance Region of Channel

Fluids Engineering ◽

10.1115/imece2005-80353 ◽

2005 ◽

Author(s):

Kensyuu Shimomukai ◽

Hidesada Kanda

Keyword(s):

Boundary Layer ◽

Pressure Gradient ◽

Pressure Distribution ◽

Transport Equation ◽

Normal Pressure ◽

Reynolds Numbers ◽

Entrance Region ◽

Parallel Plates ◽

The Difference ◽

Vorticity Transport

There are few implicit solutions available for the pressure distribution in the y-direction. Thus, for the flow between parallel plates, the pressure distribution in the entrance region was studied, focusing on the pressure gradient in the y-direction at Reynolds numbers (Re) between 100 and 5000. In the numerical method, the vorticity transport equation is first solved and then Poisson’s equation for pressure distribution is solved without any assumptions taken for pressure distribution. Consequently, the difference in pressure between the wall and the centerline existed near the inlet and decreased as Re increased. The pressure at the wall is lower than that in the central core for Re ≤ 5000. This result shows that (i) the boundary-layer assumptions do not hold for Re ≤ 5000 and (ii) the pressure distribution is contrary to Bernoulli’s law across parallel plates, although the law does not apply to viscous flow.

Download Full-text

Epitaxial growth manner and structure of superconducting oxide films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100173145 ◽

1990 ◽

Vol 48 (4) ◽

pp. 2-3

Author(s):

Yoshichika Bando ◽

Takahito Terashima ◽

Kenji Iijima ◽

Kazunuki Yamamoto ◽

Kazuto Hirata ◽

...

Keyword(s):

Ultrathin Films ◽

Film Surface ◽

High Energy ◽

Epitaxial Films ◽

Layer By Layer ◽

Initial Growth ◽

In Situ Growth ◽

High Quality ◽

Activated Reactive Evaporation

The high quality thin films of high-Tc superconducting oxide are necessary for elucidating the superconducting mechanism and for device application. The recent trend in the preparation of high-Tc films has been toward “in-situ” growth of the superconducting phase at relatively low temperatures. The purpose of “in-situ” growth is to attain surface smoothness suitable for fabricating film devices but also to obtain high quality film. We present the investigation on the initial growth manner of YBCO by in-situ reflective high energy electron diffraction (RHEED) technique and on the structural and superconducting properties of the resulting ultrathin films below 100Å. The epitaxial films have been grown on (100) plane of MgO and SrTiO, heated below 650°C by activated reactive evaporation. The in-situ RHEED observation and the intensity measurement was carried out during deposition of YBCO on the substrate at 650°C. The deposition rate was 0.8Å/s. Fig. 1 shows the RHEED patterns at every stage of deposition of YBCO on MgO(100). All the patterns exhibit the sharp streaks, indicating that the film surface is atomically smooth and the growth manner is layer-by-layer.

Download Full-text