Papers by Author: Duo Sheng Li

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Authors: Duo Sheng Li, Dun Wen Zuo, Yu Li Sun, Rong Fa Chen, Wen Zhuang Lu, Bing Kun Xiang, Min Wang
Abstract: Diamond spherical shell thick film was prepared by high power DC-plasma jet CVD. Atom force microscopy, scanning electron microscopy, Raman spectroscopy and roughness-profile-meter were used to characterize microstructure, morphology, impurities and orientation evolution of diamond spherical shell thick film. The results show that, when nucleation begins, grains grow random orientation. The grain size of spherical diamond film prepared is compact, clear, uniform, continuous and no remarkable bigger grain over the whole surface of film. On the growth surface, (100) facets were dominant, and the cross-section SEM indicated that film columnar spreading grew from the substrate surface to the diamond film surface. The roughness of the growth surface was much more than that of the nucleation surface. To adjust some important parameters as methane concentrate, depositing time, and matrix temperature, and high quality diamond spherical shell thick film was deposited.
Authors: Duo Sheng Li, Dun Wen Zuo, Rong Fa Chen, Bing Kun Xiang, Li Gang Zhao
Abstract: DC-Plasma arc behavior is one of the key factors on growth of diamond film. The results show that keeping steady DC-Plasma arc can grow better quality diamond film. In a long-time growth of diamond film, there is sediment carbon on about 5mm border-entad anode annulus, which was proved to be graphite. It results in fluctuating and instability of DC-Plasma arc and in the DC-Plasma density, which causes graphite generation and much stress in the film. By means of adjusting anode annulus assembly, pausing the supply of carbon source and increasing H2, the problem of sediment carbon cab be effectively resolved. Finally, the mechanism of the effect of arc behavior on growth of diamond film is discussed.
Authors: Rong Fa Chen, Dun Wen Zuo, Duo Sheng Li, Bing Kun Xiang, Li Gang Zhao, Min Wang
Abstract: High quality diamond film wafers with different thickness are prepared by high power DC arc plasma jet CVD (DCPJ CVD) method using a CH4/Ar/H2 gas mixture. The effects of methane concentration on the growth of carbon balls in anode nozzle and arc stability are studied with theoretical analysis and experimental investigation. The results indicate that different sizes of carbon balls may rapidly grow in the anode nozzle with methane concentration higher than 2 Vol-%, symmetry and uniformity of the rotating arc are strongly affected with the occurrence of carbon balls, which will result in non-uniform deposition of diamond films over a large substrate area. The methane concentration should be controlled at a low level to keep diamond film wafers growth stable. Characterization by X-ray diffraction, Raman spectroscopy and SEM analysis are also carried out.
Authors: Duo Sheng Li, Xian Liang Zhou, Ai Hua Zou, Xiao Zhen Hua, Y.W. Yu
Abstract: The fabrication process and fracture characterization of 35 and 65 vol% SiCp particulate-reinforced Al matrix (SiCp/Al) composites have been investigated. SiCp composites having different volume fractions of the n-SiCp were synthesized via by pressureless-infiltration at near-net-shape route and were uniaxially tested at room temperature. The SiC particles were mixed with silicasol as an inorganic binder in distilled water. The mixtures were consolidated in a mold by pressing and dried in two step process, followed by calcination at 1000 °C. The SiCp/Al composites were fabricated by the infiltration of Al melt into SiC performs. The experimental results show that volume fraction of reinforced particles in SiCp/Al composites had a significant influenec on fracture section surface characterization in tensile tests. Composite with 45 vol% SiCp, fracture was firstly happen in Al matrix, shallow dimples and intergranular fractures were seen in all the fractographs. With increasing of vol% SiCp, fracture was more brittle in appearance in the composites and the fracture surfaces were flat and less plastic deformations.
Authors: Duo Sheng Li, Dun Wen Zuo, Rong Fa Chen, Yu Li Sun, Bing Kun Xiang, Wen Zhuang Lu
Abstract: In this paper, a new polishing technique was proposed to polish concave spherical surface by diamond spherical shell deposited by DC-Plasma Jet CVD(chemical vapor deposition), and preparation was studied from both experiment and theory. The deposited films were investigated by some techniques including: scanning electron microscopy (SEM), atom force microscopy (AFM), Raman spectroscopy, and roughness-profile-meter, which were used to analyze surface phase, microstructure, internal quality and surface roughness. The results show that the deposited diamond spherical shell film has some remarkable properties, such as high surface density, high hardness. Compared to traditional polishing techniques, it will have some potential advantages as convenient, flexible, efficient and precious. To adjust some important parameters as methane concentration, depositing time, and it can deposit the different size grain diamond spherical shell films, which are used to polish different precision degree concave spherical surfaces. Meantime, to change curvature of diamond spherical shell, it can adapt to polish various curvature radius concave spherical surfaces.
Authors: Rong Fa Chen, Dun Wen Zuo, Yu Li Sun, Duo Sheng Li, Wen Zhuang Lu, Min Wang
Abstract: Strain films in the thin film resistance strain gauge are prepared by magnetron sputtering method. Some results concerning the electromechanical and structural properties of nichrome (Ni80Cr20 wt.%) thin films are presented. As compared to the well-known Ni-Cu (constantan) alloy film, which are widely used for manufacturing pressure and force sensors, nichrome (Ni80Cr20 wt.%) thin films exhibit gauge factor values of the same order of magnitude, but they are much more corrosion resistant and adherent to the substrate. The influences of composition and post-deposition annealing on the electrical resistance, temperature coefficient of resistance (TCR) and gauge factor of nichrome (Ni80Cr20 wt.%) thin films are discussed.
Authors: Yu Li Sun, Dun Wen Zuo, Yong Wei Zhu, Duo Sheng Li, Mei Qi, Min Wang
Abstract: Formation, propagation and length of crack and hardness of single silicon wafer were investigated at different temperatures by means of Vickers indentation, using lower temperature testing unit with semiconductor refrigerating chip and higher temperature testing unit with closed electric furnace. The results show that the hardness of single silicon wafer decreases with the increase of temperature, while the length of crack increases with the increase of temperature. Ductile-brittle transition of the single silicon wafer can occur at different temperatures with the increase of load. When the load is smaller and temperature is lower, no cracks can be found.
Authors: Yu Li Sun, Dun Wen Zuo, Duo Sheng Li, Rong Fa Chen, Min Wang
Abstract: Hardness, elastic modulus and scratch resistance of single silicon wafer are measured by nanoindentation and nanoscratching using a nanoindenter. Fracture toughness is measured by indentation using a Vickers indenter. The results show that the hardness and elastic modulus at a peak indentation depth of 100 nm are 12.6 and 166.5 GPa respectively. These values reflect the properties of the silicon wafer, the bulk material. The fracture toughness value of the silicon wafer is 0.74 Mpa·m1/2. The material removal mechanisms are seen to be directly related to the normal force on the tip. The critical load and scratch depth estimated from the scratch depth profile after the scratching and the friction profile are 138.64 mN and 54.63 nm respectively. If the load and scratch depth are under the critical values, the silicon wafer will undergo plastic flow rather than fracture. The critical scratch depth is different from that calculated from the formula of critical-depth-of-cut described by Bifnao et al and some reasons are given.
Authors: Duo Sheng Li, Dun Wen Zuo, Wen Zhuang Lu, Rong Fa Chen, Bing Kun Xiang, M. Wang
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.
Authors: Bing Kun Xiang, Dun Wen Zuo, Duo Sheng Li, Rong Fa Chen, Ming Wang
Abstract: Micro-nanocrystalline diamond (M-NCD) Film may be successfully prepared on Mo substrate with DC arc plasmas jet deposition device. This paper studies the influences of carbon source concentration on the shape of M-NCD Film particles under circumstances of stable electric arc, and characterizes the grain size and quality of samples through SEM, AFM and Raman spectrum. The research result shows that, in the state of stable electric arc, relatively low carbon source concentration (1%) could deposit high-quality microcrystalline diamond film on the substrate, with a growth rate of up to 8.3μm/h and grain size of about 2~4μm; relatively high carbon source concentration (10% or 15%) could deposit high-quality nanocrystalline diamond(NCD) film on the microcrystalline diamond film at high speed, with a growth rate of up to above 12.6μm/h or 19.7μm/h, grain size of about 4~80nm and average grain size of 27.4nm.
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