Surface Of Diamond Particles Research Articles

Pulsed laser deposition of metallic films on the surface of diamond particles for diamond saw blades

Ti or Ni films have been deposited on the diamond particle surfaces by pulsed laser deposition. Compressive resistance of the uncoated and coated diamond particles was measured, respectively, in the experiments. The compressive resistance of the Ti-coated diamonds particles was found much higher than that of the uncoated ones. It increased by 39%. The surface morphology is observed by the metallography microscope. The surface of the uncoated diamonds particles had many hollows and flaws, while the surface of Ni-coated diamond particles was flat and smooth, and the surface of Ti-coated diamond particles had some metal masses that stood out of the surface of the Ti-coated film. The components of the metallic films of diamond particles were examined by X-ray diffractometry (XRD). TiC was found formed on the Ti-coated diamond surface, which resulted in increased surface bonding strength between the diamond particles and the Ti films. Meanwhile, TiC also favored improving the bonding strength between the coated diamond particles and the binding materials. Moreover, the bending resistance of the diamond saw blade made of Ti-coated diamond was drastically higher than that of other diamond saw blades, which also played an important role in improving the blade's cutting ability and lifetime. Therefore, it was most appropriate that the diamond saw blade was made of Ti-coated diamond particles rather than other materials.

The formation and characterization of diamond crystallites by microwave plasma enhanced chemical vapor deposition—a comparison of gaseous and solid carbon sources as precursors

Commercial diamond powders are in irregular shapes and have been used as seeds for growing well crystallized fine diamond grits in this study. The surfaces of irregular diamond particles would serve as the seed for the subsequent growth of the diamond crystallites using microwave enhanced chemical vapor deposition (MPECVD). Both gaseous and solid carbon sources were used to transform the irregular shaped diamond seeds with sharp edges and corners along with the increase in size to the final equilibrium form of diamond crystallites. In case of gaseous carbon source, the effect of increasing methane content and applying negative dc bias voltage on the formation of diamond crystallites was significant. While in case of solid carbon source, well-faceted diamond crystallites can he extracted from the molten metal-carbon-hydrogen (M-C-H) system. Surface etch pits are numerous; especially noticeable after long exposure in hydrogen plasma. Both growth rates of diamond crystallite irrespective of the carbon sources tend to be parabolic at the later stage of growth.

The interface diffusion and reaction between Cr layer and diamond particle during metallization

A Cr layer with a thickness of 150 nm was successfully deposited on the surface of diamond particles using the dc magnetron sputtering technique. AES analysis indicated that the Cr layer reacted with diamond particle to form Cr 2C 3 carbide species on the interface during the deposition. With the rising of deposition power, the interface diffusion between Cr layer and diamond substrate increased. The interface diffusion and reaction between the Cr layer and diamond substrate were promoted significantly by an annealing treatment at a temperature range from 300 to 600°C in a ultrahigh vacuum (UHV). When the annealing temperature was below 500°C and annealing time was less than 4 h, CrC carbide species were formed on the interface. Higher temperature and longer time resulted in a Cr 2C carbide interlayer. The carbide species of Cr 2C was resulted from the interface diffusion and reaction which can be intensified significantly with raising the annealing temperature and time. The depletion of carbon atoms from diamond substrate and the diffusion of carbon controlled the formation of carbide layer. The apparent activation energy of interface diffusion and reaction was about 38.41 kJ/mol. The interface diffusion and reaction can be impeded by low vacuum.

Machining Performance of Heat Treated Sub-micron Diamond

Suh-micron diamond powder was heat-treated and its machining pert ormance wax tested in the texturing process or fixed disk blanks. Comparison indicated a significant increase of up to some 30% in stock rein al. as well as a reduction of 5% in surlacc roughness over the corresponding diamond as untreated. Such improvement can be related to the et lect s of an incrased friability and thus in number or edges available I or the stock removal process. Scratch marks, on the other hand. were essentially eliminated as a result of the deposition of non-diamond carbon on the surfaces of diamond particles, so much as to leave only edge projection tips uncvoered.

Diamond film formation by laser evaporation of highly dispersive diamond in a hydrogen plasma environment

Abstract Previously it has been shown that diamond films produced by laser evaporation (LE) of highly dispersive diamond (HDD) possess a broad size distribution of conglomerates. As a result the produced diamond film was not smooth and homogeneous. In this paper the method was improved by means of HDD laser ablation in hydrogen d.c. plasma (P = 10 Torr). The influence of hydrogen on the LE process has been investigated. It was shown that the introduction of H plasma yields a destruction of large agglomerates in a vapour flux and protects the diamond particles surface from reconstruction. The diamond films produced by laser ablation of diamond in hydrogen plasma atmosphere (LADH) on Si and WC-Co substrates at room temperature consist of dense packed islands with mean size about 200 A. The film thickness was 1500–2500 A.

Hydrogen Plasma Treatment of Natural and Homoepitaxial Diamond

ABSTRACTAs-polished and homoepitaxial diamond (100)- and (111)-oriented single crystals, natural diamond powders of 0.12-6 μm diameter, and high-pressure/hightemperature (HPHT) diamond powders of 50-100 μm diameter were treated in a microwave hydrogen plasma under four sets of conditions. Negligible changes in the weights (±10 μg) of the as-polished and homoepitaxial diamonds were observed.Post-treatment atomic force microscopy (AFM) showed a combination of smoothing and pit formation on (100) surfaces, the details of which were sensitive to the structure of the starting surface. Asymmetric pits formed on an as-polished (111) surface, but no qualitative changes in the structure of highly defective (100) and (111) films were observed. Natural diamond powders, which were quite irregular and rough prior to treatment, became markedly smoother and well-faceted, as observed by scanning electron microscopy (SEM). The degree of faceting was sensitive to plasma power level but was independent of H2 flow rate. The size and degree of faceting appeared to be the same after plasma treatment for isolated and closelypacked particles; however, the latter fused into a quasi-continuous film. “Regrown” crystallites were observed on the surfaces of synthetic type Ib diamond particles following plasma treatment. We argue that surface diffusion is the dominant mechanism for the observed morphological changes.

Microstructures of carbon polymorphs formed in shocked compressed diamond powder utilizing an interaction of oblique shock waves

Microstructures of carbon polymorphs formed in diamond-powder compact obtained by shock compaction were investigated using high-resolution electron microscopy. Shock compaction was performed by impacting iron-flyer plate at impact velocities of 1.6 and 2.3 km/s. The maximum shock pressure was estimated as 18 and 56 GPa by numerical simulation for an initial powder density of 60% of the bulk density. The particle-size reduction resulted from the pulverization effects due to cracking, friction rubbing between particles, and a tensile wave. The local heating of particle surfaces and plastic deformation promoted the phase transformation from diamond to low-density phases of carbon: turbostratic carbon, i-carbon, and α-carbyne. The higher the shock pressure, the more the effect of particle-size reduction and the local heating were enhanced. Chain-like and ribbon-like turbostratic carbon, and spherical “γ-carbon” developed from gaseous carbon generated by jetting from the diamond-particle surface were found at the 56 GPa region in the compact. The formation of “γ-carbon” was assumed to proceed through vapor → liquid → solid sequences.

Behaviour of Co binder phase during diamond deposition on WCCo substrate

The movement of the Co-rich binder phase and its interaction with growing diamond particles during deposition were investigated by repeated observations of the same site on a WC-Co substrate surface. Both etched and unetched (as-polished) specimens of WC-5Co were used for deposition. The diamond deposition was carried out using the tungsten filament chemical vapour deposition method. Raman spectra have shown that the quality of the diamond deposited on the etched substrate was better than that on the as-polished substrate. The facet size of the diamond film surface on the as-polished substrate was smaller than that on the etched specimen. These effects were caused by the atomic-scale interaction of Co atoms in the binder phase. A special feature of the diamond film on the as-polished specimen was a very rough diamond film surface. This phenomenon was observed to result from the abnormal movement of the Co-rich binder phase to the deposited diamond particle surface and the subsequent non-uniform growth of particles during deposition. The phenomenological characteristics of the Co-rich binder phase movement were also explained.

Study of ultradispersed diamond powders obtained using explosion energy

The physico-chemical properties of diamon-containing blacks (A1) obtained by the dynamic method in srongly nonequilibrium conditions as well as of ultradispersed diamond (UDD) obtained by the treatment of A1 in perchloric acid (A2) and in a mixture of nitric and sulphuric acids (A3) are studied. According to electron microscopy data, the characteristic particle size in sample A1 ranges from 70–100 Å. On dark-field micrographs there are reflections of graphite-like structures with the region of coherent scattering 5–10 Å and reflections of diamond particles 20–50 Å in size. The treatment of A1 with acids decreases the size of particles by some 10–15 Å, their surfaces being modified with chlorine- (A2) and sulphur- and nitrogen-containing fragments (A3). As found by Fourier-IR spectroscopy, the UDD surface has a large amount of oxygen in the form of ▪, and other groups. The presence of admixtures in the bulk and on the surface of diamond particles may cause the deviation of the lattice parameter a and density of the samples from the corresponding values for large diamond crystals. The presence of surface functional groups makes possible chemical modification of UDD.

Carbons Deposited on Diamond Surface

A preliminary study of the growth of diamond by vapor deposition has been carried out using diamond powder and labelled methane 1313CH4O. The powder substrate pre-treated with hydrogen was heated to temperatures of 800-990°C in a closed reaction chamber filled with 13CH4O at 1-10 Torr initial pressure. Considering the isotope shift of the Raman lines of diamond and disordered carbon, the following has been noted from the Raman spectra of such powders. Highly disordered carbon is always deposited on the surface of diamond particles treated under the described conditions. A spectrum indicating the presence of a small amount of diamond composed of 13C is found with the powder heated in 1 Torr 13CH4O at 800°C for 45hrs. At 10 Torr and 830°C, the deposit appears to consist entirely of disordered carbons; no indication of deposited diamond is found. Surface graphitization of the substrate occurs when heated in 1 Torr 13CH4O at 990°C.