Study On Deposition Mechanisms And Properties Of Diamond Films On Graphite

Using chemical vapor deposition（CVD）technology to coat high performance diamond film on graphite substrate,it is great significance to improve the various performance of graphite.The purpose of this dissertation is to solve the technical problems that diamond films have difficult to deposit on the graphite substrate,and study on the deposition mechanisms,fabrication and properties of the diamond films based on amorphous ceramic SiO₂ interlayer.The chief contents of the dissertation are concluded as follows:1.Create mathematical modeling for diamond nucleation process based on carbon thermodynamic equilibrium phase diagram.Clarify the relationship between the pressure at the CVD nucleation process and the radius of diamond critical nuclei,the critical energy of diamond nucleation on different substrate.Summarize the feasible plan of diamond films coating on graphite combining Nano-thermodynamics analyze for diamond nucleation process,thermodynamics analyze for diamond growth process and related kinetic factors.2.Bring in amorphous ceramic SiO₂ interlayer and using hot filament CVD technology to deposit it on the graphite substrate.Coating four kinds of diamond films on graphite substrate include Undoped Micro-Crystalline Diamond,Undoped Nano-Crystalline Diamond,Boron-Doped Micro-Crystalline Diamond and Boron-Doped Nano-Crystalline Diamond.3.Characterize amorphous ceramic SiO₂ interlayer and diamond films by Scanning Electron Microscopy,Energy Disperse Spectrometer,Field Emission Scanning Electron Microscopy,X-ray Photoelectron Spectroscopy,Fourier Transform Infrared spectrometer,Atomic Force Microscope,Confocal Microscope,Confocal Raman Microscope and X-ray Diffraction.4.Study on bonding strength between diamond films and its substrate by Indentation experiment,the hardness and elastic modulus of diamond films by Nano-Indentation experiment and the electrical conductivity of diamond films by four-point probe method.The chief results of the dissertation indicate that four kinds of diamond films can be coated with high quality on the on graphite substrate which was preprocessing by amorphous ceramic SiO₂ interlayer.Boron-Doped Micro-Crystalline Diamond film coating on graphite shows better comprehensive properties,it has great significance to improve the abrasion resistance of DC brush motor.