Zuo Dunwen

Nano Hardness and Elastic Modulus of Nanocrystalline Diamond Coating

Nanocrystalline diamond (NCD) coatings were prepared on Si3N4 substrate by hot filament chemical vapor deposition (HFCVD) method with Ar/H2/CH4 gas mixture. The nano hardness and elastic modulus of the NCD coatings were evaluated using a nano indenter. The results show that the diamond grains appear to be rounded with the average grain size of less than 100 nm. The average nano hardness is ∼53.5 GPa, the elastic modulus is ∼606.8 GPa, and the elastic recovery is as high as ∼80%, for the fine NCD coatings deposited with the substrate temperature of 700°C. The nano hardness and elastic modulus of the NCD coatings will increase with the substrate temperature increasing from 600°C to 700°C.

Dispersibility of CeO2 Nanoparticles in Water–Ethanol Suspensions

In order to improve the dispersibility of CeO2 nanoparticles and reduce the environmental pressure, the dispersibility and stability of CeO2 nano-powder in water-ethanol suspensions was investigated in this paper. The results show that with the increasing of volume fraction of ethanol, the sedimentation rate of CeO2 nanoparticles firstly decreases and then increases. When the volume fraction of ethanol is between 30% and 50%, the dispersibility of CeO2 nanoparticles is better. Only mixing water and ethanol at a certain proportion as the dispersion medium can nano-sized CeO2 polishing slurry have the advantages of both and better dispersing effect.

Original Crack and Adhesion Development of Nano Diamond Coating

A theoretical original microvoid model which describes the micro structural aspects of tiny original crack was developed based on fracture mechanics to explain the interface strength between nano diamond coating (NDC) and its substrate. The expression of stress fields, displacement and stress intensity factor ( SIF ) K at interface crack tip were deduced. Based on the original microvoid model, the technique to improve the adhesion strength between the NDC and its substrate was obtained by improving the diamond nucleation density and adjusting the coating residue stress.

The effects of nitrogen partial pressure on the microstructure of amorphous carbon nitride films

ABSTRACT The amorphous carbon nitride (a-CNx) films with varying nitrogen content were deposited on Si (100) wafers substrates using radio frequency magnetron sputtering (RFMS) from graphite target at different nitrogen partial pressure. The influence of nitrogen partial pressure on the microstructure and phase composition of a-CNx films were researched systematically. The films were characterized by atom force spectroscopy (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). AFM results showed cluster structure in a range of tens to hundreds namometers existed on the surface of the films and the surface roughness increased with the increase of nitrogen partial pressure. Ratio of ID/IG increased with the nitrogen partial pressure, while the sp3 phase content from fitting results of XPS displayed reverse trend. The nanohardness of a-CNx films characterized by nanoindentation test decreased with the increase of nitrogen partial pressure, which consisted with the results of Raman and XPS. Thus high nitrogen partial pressure caused the mechanical properties of a-CNx films decrease.

Study on preparation and properties of mesh Ti/BDND electrode

ABSTRACT High-quality boron-doped nanocrystalline diamond (BDND) film was fabricated on mesh titanium substrate using hot filament chemical vapor deposition (HFCVD) system. Raman, X-ray diffraction (XRD), and scanning electron microscopy (SEM) spectroscopy were used to analyze the microstructure of the mesh Ti/BDND electrode. The SEM images show different parts of the mesh electrode surface are fully covered by the diamond film and particle sizes of that are nearly less than 1 μm on average. Additionally, the diamond film of the prepared electrode surface is relatively of high quality and the mesh electrode has a relatively small residual stress from Raman and XRD spectra, respectively. Cyclic voltammograms indicate that the mesh electrode has wide potential window, low background current and stable electrochemical properties in H2SO4 solution, suggesting that the prepared electrode is suitable for the application of wastewater treatment. The COD removal rate of the prepared mesh electrode increases by 10.4% compared with that of the plate electrode, which demonstrates that the ability of the mesh electrode in the wastewater treatment is relatively better.

Influence Research of Diamond Micro-Nano Particulates on Single Crystal Sapphire's Friction Properties

Hot-filament chemical vapor deposition (HFCVD) method was used to prepare aggregate spherical, pyramid and plane texture of micro-nano crystal diamond films on YG6 substrate surface by controlling preparation process parameters. The film surface morphology was observed using SEM. Texture type was inferred from XRD and Raman spectrum analysis. Friction and wear test was carried out innovatively using micro-nano crystal diamond film rub against single crystal sapphire. The micro-nano diamond particulates’ effect of friction on sapphire was compared. The results indicated that plane textured micro-crystal diamond film had larger average friction coefficient and better removal performance.

Preparation of Boron-Doped Nanocrystalline Diamond Electrode and Its Wastewater Treatment Performance

Boron-doped nanocrystalline diamond (BDND) films were prepared on Ti substrate by hot filament chemical vapor deposition (HFCVD) method. The morphology, phases and quality of the BDND films were characterized by Scanning electron microscopy, X-Ray diffraction, and Raman spectroscopy. Cyclic voltammograms indicated that the BDND electrodes had wide electrochemical window, low background current and good electro-oxidation performance of phenol solution. The effects of operative parameters like current density and pH initial were investigated. The results show that both of the two variables have significant influence on the degradation performance of the organic pollutants. High COD removal can be achieved using high current density in acid solutions, and there exists optimal values of both parameters considering the current efficiency and operation economics.

3-D assembly process information generation technology based on virtual assembly

The process of interactive virtual assembly contains mass of assembly process information which is described and saved by assembly hierarchical liaison model. Assembly BOM and 3-D assembly process files generation technology is presented. Data structure of single hierarchical assembly BOM is described, and mapping method of assembly data from assembly hierarchical liaison model to assembly BOM is given. Assembly process files data model is described. The generation flow of 3-D assembly animation based on Pro/Toolkit and assembly process files structure is presented. An application case is given to verify the validation of the proposed technology which can improve the process file editing efficiency.

Limiting Aspect Ratio of Diamond Microstructure Fabricated by Model Copy Technology

Model copy technology is an ideal approach for diamond patterning. However, incomplete filling were discovered in some of the diamond microstructures which were produced by model copy method. The effect of structural aspect ratio on the filling was investigated. The growth form of CVD diamond in the micro mould was analyzed. Results show that the nonuniformity of gas velocity distribution in the mould is the main course of incomplete filling, and an aspect ratio larger than 0.5 is necessary to achieve a complete filling.

Application of projection image of end mill to monitor its behaviour

End mills with smaller diameter have found their wide application with the development of high-speed cutting. It becomes more and more important to develop effective methods to monitor and control the milling process with small end mills. In this paper, a measuring system of projection image for small end mills is introduced, and the application of the projection image to monitor the behaviour of the end mill is discussed. It is found that for static state of φ2 mm end mill, the measurement accuracy of its image width can be easily controlled within 1 μm. When the end mill rotates, it is not so difficult to control the accuracy within 3 μm. By using the change in the image width, the radial wear of the end mill can be estimated. On the other hand, if the centre shift of the image is premeasured the deflection of the end mill during cutting can be estimated.