Novel headstand pyrocarbon cones （HPCs） with hollow structure were developed on the surfaces of pyrocarbon layers of the carbon/carbon （C/C） composites at 650-750 °C by the electromagnetic-field-assisted chem...Novel headstand pyrocarbon cones （HPCs） with hollow structure were developed on the surfaces of pyrocarbon layers of the carbon/carbon （C/C） composites at 650-750 °C by the electromagnetic-field-assisted chemical vapor deposition in the absence of catalysts. The fine microstructures of the HPCs were characterized by high-resolution transmission electron microscopy. The results show that the textural features of the HPCs directly transfer from turbostratic structure in roots to a well-ordered high texture in stems. And the degree of high texture ordering decreases gradually from the stem to the tail of the HPCs. The formation mechanism of the HPCs was inferred as the comprehensive effect of polarization induction on electromagnetic fields and particle-filler property under disruptive discharge.展开更多
A positive grid bias and a negative substrate bias voltages are applied to the self-made hot filament chemical vapor deposited （HFCVD） system. The high quality nanocrystalline diamond （NCD） film is successfully de...A positive grid bias and a negative substrate bias voltages are applied to the self-made hot filament chemical vapor deposited （HFCVD） system. The high quality nanocrystalline diamond （NCD） film is successfully deposited by double bias voltage nucleation and grid bias voltage growth. The Micro-Raman XRD SEM and AFM are used to investigate the diamond grain size, microstructure, surface morphology, and nucleation density. Results show that the obtained NCD has grain size of about 20 nm. The effect of grid bias voltage on the nucleation and the diamond growth is studied. Experimental results and theoretical analysis show that the positive grid bias increases the plasma density near the hot filaments, enhances the diamond nucleation, keeps the nanometer size of the diamond grains, and improves the quality of diamond film.展开更多
Amorphous Si O2（a-Si O2） films were synthesized on WC-Co substrates with H2 and tetraethoxysilane（TEOS） via pyrolysis of molecular precursor.X-ray diffraction（XRD） pattern shows that silicon-cobalt compounds for...Amorphous Si O2（a-Si O2） films were synthesized on WC-Co substrates with H2 and tetraethoxysilane（TEOS） via pyrolysis of molecular precursor.X-ray diffraction（XRD） pattern shows that silicon-cobalt compounds form at the interface between a-Si O2 films and WC-Co substrates.Moreover,it is observed by transmission electron microscope（TEM） that the a-Si O2 films are composed of hollow mirco-spheroid a-Si O2 particles.Subsequently,the a-Si O2 films are used as intermediate films and chemical vapor deposition（CVD） diamond films are deposited on them.Indentation tests were performed to evaluate the adhesion of bi-layer（a-Si O2 ＋ diamond） films on cemented carbide substrates.And the cutting performance of bi-layer（a-Si O2 ＋ diamond） coated inserts was evaluated by machining the glass fiber reinforced plastic（GFRP）.The results show that a-Si O2 interlayers can greatly improve the adhesive strength of diamond films on cemented carbide inserts;furthermore,thickness of the a-Si O2 interlayers plays a significant role in their effectiveness on adhesion enhancement of diamond films.展开更多
The effects of Si doping on morphology, components and structure characteristics of CVD diamond films were studied. Si-doped CVD diamond films were deposited on Si substrate by adding tetraethoxysilane （TEOS） into a...The effects of Si doping on morphology, components and structure characteristics of CVD diamond films were studied. Si-doped CVD diamond films were deposited on Si substrate by adding tetraethoxysilane （TEOS） into acetone as source of reactant gas. The morphology and microstructure of diamond films were characterized by scanning electron microcopy （SEM）. The crystalline quality of diamond films was studied by Raman spectroscopy and X-ray diffractometry （XRD）. The surface roughness of the films was evaluated with surface profilometer. The results suggest that Si doping tends to reduce the crystallite size, enhance grain refinement and inhibit the appearance of （11 I） facets. Raman spectra indicate that Si doping can enhance the formation of sp2 phase in diamond films. Moreover, Raman signal of SiC was detected, which suggests the existence of Si in the diamond films. Smooth fine-grained diamond （SFGD） film was synthesized at Si to C ratio of 1%.展开更多
基金Project (2011CB605801) supported by the National Basic Research Program of ChinaProject (2011M500127) supported by the China Postdoctoral Science Foundation+1 种基金Projects (50802115, 51102089) supported by the National Natural Science Foundation of ChinaProject supported by the Postdoctoral Fund of the Central South University, China
文摘Novel headstand pyrocarbon cones （HPCs） with hollow structure were developed on the surfaces of pyrocarbon layers of the carbon/carbon （C/C） composites at 650-750 °C by the electromagnetic-field-assisted chemical vapor deposition in the absence of catalysts. The fine microstructures of the HPCs were characterized by high-resolution transmission electron microscopy. The results show that the textural features of the HPCs directly transfer from turbostratic structure in roots to a well-ordered high texture in stems. And the degree of high texture ordering decreases gradually from the stem to the tail of the HPCs. The formation mechanism of the HPCs was inferred as the comprehensive effect of polarization induction on electromagnetic fields and particle-filler property under disruptive discharge.
文摘A positive grid bias and a negative substrate bias voltages are applied to the self-made hot filament chemical vapor deposited （HFCVD） system. The high quality nanocrystalline diamond （NCD） film is successfully deposited by double bias voltage nucleation and grid bias voltage growth. The Micro-Raman XRD SEM and AFM are used to investigate the diamond grain size, microstructure, surface morphology, and nucleation density. Results show that the obtained NCD has grain size of about 20 nm. The effect of grid bias voltage on the nucleation and the diamond growth is studied. Experimental results and theoretical analysis show that the positive grid bias increases the plasma density near the hot filaments, enhances the diamond nucleation, keeps the nanometer size of the diamond grains, and improves the quality of diamond film.
基金Project(20130073110036)supported by the Research Fund for the Doctoral Program of Higher Education of China
文摘Amorphous Si O2（a-Si O2） films were synthesized on WC-Co substrates with H2 and tetraethoxysilane（TEOS） via pyrolysis of molecular precursor.X-ray diffraction（XRD） pattern shows that silicon-cobalt compounds form at the interface between a-Si O2 films and WC-Co substrates.Moreover,it is observed by transmission electron microscope（TEM） that the a-Si O2 films are composed of hollow mirco-spheroid a-Si O2 particles.Subsequently,the a-Si O2 films are used as intermediate films and chemical vapor deposition（CVD） diamond films are deposited on them.Indentation tests were performed to evaluate the adhesion of bi-layer（a-Si O2 ＋ diamond） films on cemented carbide substrates.And the cutting performance of bi-layer（a-Si O2 ＋ diamond） coated inserts was evaluated by machining the glass fiber reinforced plastic（GFRP）.The results show that a-Si O2 interlayers can greatly improve the adhesive strength of diamond films on cemented carbide inserts;furthermore,thickness of the a-Si O2 interlayers plays a significant role in their effectiveness on adhesion enhancement of diamond films.
基金Project(51275302)supported by the National Natural Science Foundation of ChinaProject(BC2012124)supported by Technical Innovation Funds for the Sci-Tech Enterprise of Jiangsu Province,China
文摘The effects of Si doping on morphology, components and structure characteristics of CVD diamond films were studied. Si-doped CVD diamond films were deposited on Si substrate by adding tetraethoxysilane （TEOS） into acetone as source of reactant gas. The morphology and microstructure of diamond films were characterized by scanning electron microcopy （SEM）. The crystalline quality of diamond films was studied by Raman spectroscopy and X-ray diffractometry （XRD）. The surface roughness of the films was evaluated with surface profilometer. The results suggest that Si doping tends to reduce the crystallite size, enhance grain refinement and inhibit the appearance of （11 I） facets. Raman spectra indicate that Si doping can enhance the formation of sp2 phase in diamond films. Moreover, Raman signal of SiC was detected, which suggests the existence of Si in the diamond films. Smooth fine-grained diamond （SFGD） film was synthesized at Si to C ratio of 1%.
