Papers by Author: Yu Jun Zhang

Abstract: Based on pretreatment of Cornus wilsoniana vegetable oil,and adopting the method of high temperature catalytic cracking to preparating of rich hydrocarbon bio-diesel. Cornus Wilsoniana vegetable oil was as the raw oil,the process of high temperature catalytic cracking was dwascussed,by the catalyst types and percentage, heating current and the influence of reaction time.The more ideal response condition was:The best catalyst was KF/CaO (40%,roast 4 h); The best catalyst percentage was 0.1%;the best heating current was 3.2 A; The best reaction time was 40 min;The yield of liquid was 82%;The response rate was 92%. The preparation of bio-diesel was similar to 0 # diesel.

Abstract: The novel frictional properties of hydrogenated DLC (Diamond-like Carbon) films have been reported for nearly ten years. But up to now, researchers still haven’t known the exact mechanism resulting in the super-low frictional performance of hydrogenated DLC films. Especially they have little knowledge on the molecular configuration and structural properties of these kinds of films. In this paper, CH3 radicals with different impact energies are selected as source species to deposit DLC films on diamond (100) by molecular dynamics simulation. Results show hydrogenated DLC films can be successfully obtained when impact energy is in an appropriate scope that is no less than 20eV. The depositing processes involve impinging diamond surface and bonding procedure. Some atoms, instead of bonding with substrate atoms, fly away from the diamond surface. Only suitable impact energy can improve the growth of the film. Within 30eV to 60eV, the maximum deposition ratio is attained. In addition, when carbon atoms act as the deposition sources, the deposition ratio is relatively higher. Furthermore, the authors find that species with higher concentration of carbon atoms in deposition sources lead to a better deposition rate. Carbon atoms are more reactive than hydrogen atoms. Then the relative densities of DLC films are calculated. The density curves indicate that the structures of the films vary obviously as the impact energy augments. The average relative density is generally monotone increase with the increment of impact energy. The hybridization of carbon atoms greatly affects the properties of hydrogenated DLC films. The transition between sp2 and sp3 will result in the graphitization and reduce the frictional coefficient when DLC films are used as tribo-pair in friction.