Metastable nanosized diamond formation from a C-H-O fluid system

2010 ◽  
Vol 25 (12) ◽  
pp. 2336-2340 ◽  
Author(s):  
S.K. Simakov
Keyword(s):  
Experimental Data ◽  
Chemical Vapor Deposition ◽  
Synthesis Gas ◽  
Vapor Deposition ◽  
Present Model ◽  
Chemical Vapor ◽  
Cvd Diamond ◽  
Diamond Synthesis ◽  
Diamond Formation ◽  
Fluid System

The model of nanosized diamond particles formation at metastable P-T parameters from a C-H-O fluid system is presented. It explains the hydrothermal formation and growth of diamond and the specifics of chemical vapor deposition (CVD) diamond synthesis gas mixtures at low P-T parameters. Further, the model explains the genesis of interstellar nanodiamond formations in space and the genesis of metamorphic microdiamonds in shallow depth Earth rocks. In contrast to models where many possible reactions are considered, the present model makes the simplest possible assumptions about the key processes, and is then able to account for various tendencies seen in experimental data.

A spectroscopic study of optical centers in diamond grown by microwave-assisted chemical vapor deposition

1990 ◽  
Vol 5 (11) ◽  
pp. 2507-2514 ◽  
Author(s):  
A. T. Collins ◽  
M. Kamo ◽  
Y. Sato
Keyword(s):  
Chemical Vapor Deposition ◽  
Radiation Damage ◽  
Single Crystals ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Cvd Diamond ◽  
Edge Emission ◽  
Microwave Assisted ◽  
Bright Blue ◽  
Methane Concentrations

Absorption and cathodoluminescence spectra have been recorded for single crystals of diamond and polycrystalline films of diamond, grown by microwave-assisted chemical vapor deposition (CVD) using methane and hydrogen. The investigation has been carried out to see to what extent the properties of CVD diamond are similar to those of conventional diamond, and to what extent they are unique. Studies have been made of the as-grown material, which has not been intentionally doped, and also samples that have been subjected to radiation damage and thermal annealing. The single crystals grown using methane concentrations of 0.5 to 1.0% exhibit bright blue “band A” emission and also intense edge emission, similar to the cathodoluminescence spectra of some natural type IIa diamonds. This implies that the crystals are relatively free from structural and chemical defects, a conclusion which is reinforced by the absence of any zero-phonon lines in the absorption spectra of crystals which have been subjected to radiation damage and annealing at 800 °C. Before radiation damage the spectrum does, however, reveal an absorption which increases progressively to higher energies, and which may be associated with sp2-bonded carbon. The Cathodoluminescence spectra after radiation damage indicate that the crystals contain some isolated nitrogen, and the detection of H3 luminescence, following thermal annealing at 800 °C, demonstrates for the first time that these samples contain small concentrations of nitrogen pairs. All of the polycrystalline films, grown using methane concentrations between 0.3 and 1.5%, have an absorption which increases progressively to higher energies, and which again is attributed to sp2-bonded carbon. This absorption is stronger in the films grown using higher methane concentrations. Films grown at a methane concentration of 0.3% also exhibit bright blue cathodoluminescence, although the edge emission is undetectably weak. The use of higher methane concentrations produces films with evidence in the cathodoluminescence spectra of nitrogen + vacancy and nitrogen + interstitial complexes, as well as optical centers unique to CVD diamond. One particular defect produces an emission and absorption line at 1.681 eV. By implanting conventional diamonds with 29Si ions it has been confirmed that this center involves silicon, and it has been shown that the 1.681 eV luminescence is relatively more intense in implanted diamonds which have a high concentration of isolated nitrogen.

Effects of CH4 Concentration on CVD Diamond Coatings Deposited on Cemented Carbide Cutting Cools

2006 ◽  
Vol 532-533 ◽  
pp. 480-483 ◽  
Author(s):  
Wen Zhuang Lu ◽  
Dun Wen Zuo ◽  
Min Wang ◽  
Feng Xu
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Great Influence ◽  
Chemical Vapor ◽  
Cvd Diamond ◽  
Cemented Carbide ◽  
Diamond Coatings ◽  
Ch4 Concentration

Chemical vapor deposition (CVD) diamond coatings were deposited on cemented carbide cutting cools by an electron-assisted hot filament chemical vapor deposition (EACVD) equipment developed by the authors. The CVD diamond coatings were studied by Scanning Electron Microscope (SEM) and Raman Scattering Spectroscopy (Raman). The experimental results show that CH4 concentration in the source gas performs great influence on the micro-structure, surface roughness, composition, residual stress and adhesion of the CVD diamond coatings. The increase of CH4 concentration results the change of diamond crystal from {111} orientation to {100} orientation, the decrease of the surface roughness and the increase of sp2 carbon in the CVD diamond coatings. A residual compressive stress exists in the CVD diamond coatings. The residual stress decreases with increasing CH4 concentration. A higher or lower CH4 concentration tends to reduce adhesion stress of the continuous CVD diamond coatings.

Temperature Distributions in CW Laser Induced Pyrolytic Deposition

1983 ◽  
Vol 29 ◽  
Author(s):  
Klaus Piglmayer ◽  
Josef Doppelbauer ◽  
Dieter BÄuerle
Keyword(s):  
Experimental Data ◽  
Chemical Vapor Deposition ◽  
Laser Radiation ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Numerical Results ◽  
Infinite Plane ◽  
Material Parameters ◽  
Temperature Distributions ◽  
Cw Laser

ABSTRACTTemperature distributions induced by cw laser radiation absorbed on the surface of combined structures, consisting of discs or of stripes on semi - infinite plane substrates, are calculated for different material parameters and different geometries. The relevance of the numerical results is demonstrated by comparison with earlier experimental data obtained in pyrolytic laser-induced chemical vapor deposition.

Comparative Studies on the Cutting Performance of HFCVD Diamond and DLC Coated WC-Co Milling Tools in Dry Machining Al/SiC-MMC

2010 ◽  
Vol 126-128 ◽  
pp. 220-225 ◽  
Author(s):  
Bin Shen ◽  
Fang Hong Sun ◽  
Dong Can Zhang
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Arc Discharge ◽  
Chemical Vapor ◽  
Cvd Diamond ◽  
Cutting Edge ◽  
Cutting Performance ◽  
Vacuum Arc ◽  
Milling Tool ◽  
Milling Tools

The chemical vapor deposition (CVD) diamond and diamond-like carbon (DLC) films are deposited on the cobalt cemented tungsten carbide (WC-Co) cutting tools respectively using the hot filament chemical vapor deposition (HFCVD) technique and the vacuum arc discharge with a graphite cathode. The scanning electron microscope (SEM), optical interferometer profiler and Raman spectroscopy were adopted to characterize the as-deposited diamond and DLC films. The cutting performance of as-fabricated CVD diamond and DLC coated milling tools is evaluated in dry milling SiC particulate reinforced Al-metal matrix composite material (Al/SiC-MMCs), comparing with the uncoated WC-Co milling tool. The milling results demonstrate that the uncoated WC-Co milling tool suffers severest wear in its circumferential cutting edge, while the wear of DLC coated milling tool is slightly lower. Comparatively, the CVD diamond coated milling tool exhibits much stronger wear resistance. The wear on its circumferential cutting edge is less than 0.07 mm at the end of milling test, only a half of that of DLC coated milling tool. This result is attributed to the extremely high hardness and strong adhesive strength of CVD diamond film covered on the WC-Co milling tool.

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