ABSTRACT:For some polymers such as PTFE, the crystallization is so rapid that it is difficult to observe isothermal crystallization by differential scanning calorimetry (DSC). In this investigation, first, isothermal crystallization kinetics of PTFE was followed by DSC and the results were analyzed by the Avrami method, which showed that PTFE crystallizes one-dimensionally from preexisting nuclei, presumably impurities. Furthermore, the crystallization activation energy, the equilibrium melting point, and the nucleation rate parameter K g were calculated in the isothermal crystallization. Second, nonisothermal crystallization was also studied and the result was in accordance with the results of isothermal crystallization. Then, the Kissinger method was used to investigate the activation energy of PTFE in the nonisothermal crystallization. Third, the effect of glass fiber (used as filling) was investigated on crystallization of PTFE matrix.

A ferrography expert system for wear particle analysis can be an effective means of condition monitoring and fault diagnosis. The knowledge of the ferrography diagnosis expert system cannot be represented by certain rules because it is fuzzy and random, therefore an intelligent expert system is developed. A neural network with self-deleting nodes is employed in the intelligent expert system, and this overcomes to some degree the disadvantages of a traditional expert system and makes it possible to automatically acquire knowledge by learning from samples and to realize entirely automatic processing, from wear particle recognition to wear diagnosis.

By means of the density functional theory on the basis of generalized gradient approximation, the reaction paths of the dehydrogenation from the diamond (100) surface was deduced due to the reaction heat. Moreover, the most stable structure of the hydride diamond (100) surface was obtained. The results indicate that the dehydrogenation is easier to take place at the same C-C dimer and forms the parallel geometries. The parallel 1×1:1.5H, 2×1:H and parallel 2×1:0.5H are the intermediate products during the hydrogen desorption process, while, 2×1:H is the most stable structure of the hydride diamond (100) surfaces. The calculated reaction heat is in accordance with the experimental results.

Particle’s behavior in the slurry with power-law viscosity shows great effect on the wafer surface polishing. Hydrodynamic pressure is periodically generated on the surface asperity when particles are passing through it. Fatigue fracture occurs under the effect of periodical pressure and it begins from the top to the bottom of the asperity. Based on the energy-balance fracture theory, the removal rate is calculated and it shows good agreement with experiment data.

Diamond like carbon (DLC) films were prepared on Si wafer, using laser induced arc deposition (Laser arc) technique. Results of Raman Spectra analysis showed that the as-deposit films were amorphous, having obvious sp3 structure. Meanwhile, surface topography and micro-tribological properties were investigated by using Atomic Force Microscope and Nano-Scratch Tester. Influences of arc voltage, substrate bias voltage, target materials and substrate pre-treatment methods upon the film structures and film properties were studied.