Papers by Author: Wen Zhuang Lu

Abstract: The diamond coating can improve the performance and durability of cutting tool. To obtain the structure of nano/micro CVD diamond coating, the finite element analysis of nano/micro composite CVD diamond coating on boronized cemented carbide was carried on using ANSYS. The relationship between nanoand micron diamond layer thickness and coating fall off stress was simulated. The thickness of nanodiamond and the micron diamond layer was suggested for the nano/micro CVD diamond coating on boronized cemented carbide cutting tool.

Abstract: Ti-Si-C films were prepared on cemented carbide by chemical vapor deposition. The reactive gas system was CH₄, (CH₃)₄Si, TiCl₄ and H₂. The film was analyzed and tested by SEM, AFM, EDS, XPS, microhardness tester, friction and wear tester. The results indicate that the film is continuous and dense. At higher substrate temperature, the hardness of the film will be higher. When the substrate temperature is 850°C, the adhesion of the film is highest with coefficient of friction only 0.14.

Abstract: Nanocrystalline diamond film was deposited on silicon by double bias hot filament chemical vapor deposition (HFCVD) system. The effect of substrate temperature on the microstructure and mechanical properties of the film were investigated systematically. More defects and non-diamond contents were found as the decrease of grain size, which cause the decrease of hardness and elastic modulus. It is shown that the proper substrate temperature is in the range of 720~760 . The excessively high substrate temperature leads to the °C dramatic increase of nondiamond content and the decrease of mechanical properties.

Abstract: The key question in the ice fixed abrasives (IFA) polishing is how to keep suitable ambient temperature in production process in order to avoid premature failure of the IFA. Based on above, the three dimensions finite element analysis (FEA) model of IFA polishing temperature field is built up at first. Then, the model reliability is demonstrated by experiments. Effects of ambient temperature and polishing time on temperature distribution and melting rate of the IFA pad are researched. The results show that the ambient temperature should be kept at about 10 °C in order to control the melting rate of the IFA pad effectively and keep longer polishing time. All the results provide the basis for choosing suitable ambient temperature in polishing.

Abstract: The present paper describes research on stress in freestanding diamond thick film, diameter of 60mm, prepared on Mo substrate by DC arc plasma jet chemical vapor deposition (DCPCVD) method. The stress in the CVD diamond film was investigated by X-ray diffraction and Raman spectrum. The results show that the stress in the film is compressive. The stress changes little at the same homocentric round. The compressive stress along radial direction is that the stress in the centre of the film is lower than that in the edge at both the final surface and the original surface.

Abstract: The abrasive ice disc chemical mechanical polishing (AID-CMP) is a potential polishing process in the semiconductor industry to realize superior surface finish and planarity for semiconductor wafers. In this paper we investigated the temperature field during GaAs wafer AID-CMP process for a better understanding of AID-CMP. The results show that the AID outer temperature is higher than the inner, and the highest temperature in AID is at the wafer/AID contact zone. The increases of Pc, v, eh and tp will generate more energy and cause more local melting during GaAs wafer AID-CMP process. The AID temperature and the area of highest temperature zone increase with increasing Pc, v, and eh. The nodes temperature increase in every conditions adopted as tp increases. The area of melted zone and thickness of melted ice increase with increasing Pc, v, eh and tp.

Abstract: Diamond film was deposited on spherical molybdenum substrate by DC arc plasma CVD method. Diamond film morphology, purities and orientation evolution, obtained from atomic force microscopy, scanning electron microscopy, Raman spectroscopy, X ray diffraction respectively, has showed that grains on the growth surface are compact, continuous and uniform. Characteristic diamond (111), (220), (311) peaks were found and (111) facets were predominant. It revealed that diamond film was polycrystalline texture characteristic. There is a typical diamond Raman spectrum peaks at 1332.0 cm-1, and not graphite and amorphous carbon characteristic peak. High purity diamond film was deposited. When methane concentration was increased, diamond film has more local clusters and vacancy defects such as voids, graphite inclusion, and hydrogen cluster. Therefore, some important parameters such as methane concentration and substrate temperature should be optimized in depositing diamond film.

Abstract: Although research on various diamond polishing techniques has been carried for years, some issues still need to be examined in order to facilitate application on large areas in a cost-efficient manner. A compositive technique for machining efficiently thick diamond films prepared by DC plasma arc jet is reported in the present paper. A two-stage polishing was applied on thick polycrystalline diamond films, by employing first electro-discharge machining (EDM) for rough polishing and subsequently mechanical polishing for finishing operations. Experimental results obtained clearly indicate the applicability of the proposed two-stage technique for fabricating transparent diamond films that can be used for the production of X-ray windows. Appropriate etching with EDM is an effective pretreatment method for enhancing the efficiency of rough polishing process in mechanical polishing of thick diamond film. The machined surfaces of diamond films are studied by Scanning Electron Microscope (SEM) and Raman Scattering Spectroscopy (Raman).

Abstract: The synthesis of nanocrystalline diamond film on polycrystalline molybdenum substrates was carried out by using of self-made hot filament chemical vapor deposited (HFCVD) system. Positive bias voltage on the grid electrode on top of hot filaments and negative bias voltage on the substrate were applied. High purity and extremely smooth nanocrystalline diamond films were successfully prepared by using the double bias method. Raman, SEM, XRD and AFM results show that the diamond films obtained have grain sizes less than 20nm, nucleation density higher than 1011cm-1. The mechanism of double bias is also discussed in this paper. The positive grid bias increases the active, decomposition and ionization of hydrogen and methane molecules, while negative substrate bias helps positive carbon-containing ions bombard the substrate that leads to the high nucleation density of the diamond film.

Abstract: Chemical vapor deposition (CVD) diamond is known for its superior characteristics such as hardness, toughness and wear resistance. However, due to these factors, machining CVD diamond is a difficult material removal process. A new technique to polish CVD diamond film efficiently is reported in the present paper. In the CVD deposition process, boron was doped into diamond to fabricate high-quality semi-conductive film, which make it possible to machine diamond film by electro discharged machining (EDM) method. The relationship between EDM parameter and removal processing was investigated in details. The machined surface of boron doped (B-doped) diamond films was studied by Scanning Electron Microscope (SEM) and Raman Scattering Spectroscopy (Raman). The experimental results show that EDM polishing is a highspeed material removal and low cost method for CVD diamond polishing. When the discharge current and pulse-on time increase in a certain range, the cutting-off speed and roughness will increase correspondingly. The roughness of EDM polished CVD diamond film surface is Ra<0.5μm when the discharge current is at 4A and pulse-on time is at 200μs.