Reaction Of Diamond Research Articles

Diamond reinforced reaction-bonded boron carbide composites: Fabrication, microstructure, mechanical and tribological properties

Reaction-bonded boron carbide composites were fabricated by molten silicon infiltration of diamond-containing boron carbide preforms. The effects of diamond particle size on the microstructure, mechanical and tribological properties of reaction-bonded boron carbide composites were investigated. Fine diamond particles (≤7.7 µm) completely reacted with silicon generating nano silicon carbide particles, which bonded the boron carbide particles forming a 3-D ceramic skeleton and improving the flexural strength of the composites. Coarser diamond (≥24 µm) particles were retained protected by a dense SiC layer generated from the reaction of diamond and molten silicon. A “core-shell” structure with the retained diamond as the “core” and with the reaction formed silicon carbide as the “shell” formed. Relief structures were established on the composites’ surface during the wear process, greatly reducing the friction coefficient and improving the wear resistance.

Effect of tungsten on the oxidation kinetics of diamond nanopowder

The oxidation kinetics of ACM5 grade statically synthesized nanopowder of 0.1/0 grit size has been studied without addition and with addition of 1, 3, and 5 wt % tungsten nanopowder. It has been shown that tungsten is an inhibitor of the diamond reaction with oxygen. The kinetic scheme of the reaction that explains the mechanism of the tungsten inhibitory action has been substantiated.

Structural and mechano-chemical features of high-pressure phases forming at p, T and p-treatment of graphite

On a basis of a high-molecular model of the graphite → diamond transformation a mechanism of the synthesis of nonequilibrium stressed high-pressure phases, which form as a result of the deviation of the 3d-polymerization of 2d-nets of graphite from the route of the graphite → diamond reaction and block the diamond synthesis, has been proposed. The pressure criteria for the synthesis of main carbon high-pressure phases have been considered. Structural models of the new superhard carbon that form at the cold p-treatment of graphite suggested by American, Chinese, and Russian researchers have been discussed.

Microscale Patterning of Single Crystal Diamond Using Sidero-Metal/Diamond Thermochemical Reaction

AbstractIn this paper we propose and demonstrate micro patterning processes of single crystal diamond using thermochemical reaction of diamond with a sidero-metal and elucidate the reaction involved. Single crystal diamond processes a variety of excellent characteristics, such as hardness and wear resistance, and hence, is expected to be a new material for not only micro machining tools but also innovative micro devices. It is mandatory to develop a patterning process of diamond with high precision and at low cost. Laser processing is currently widely used, but it is a serial process and costly. Film deposition and plasma etching are other effective methods while they are time consuming. Thermochemical reaction between diamond and sidero-metals is well known in the field of mechanical machining. Diamond tools cannot machine sidero-metals, such as iron, nickel, and cobalt, when the diamond tools wear instead of the sidero-metals. We used this reaction to micro pattern single crystal diamond. We used nickel as the sidero-metal that was patterned either directly on a bulk of single crystal diamond or on a silicon substrate. We term the former and the latter processes as direct and indirect patterning processes, respectively. In the indirect patterning a bulk of single crystal diamond was placed on the substrate. The pattern was negatively transferred to the diamond after thermal treatment in the air at ˜1000K in both processes. The sidero-metal layer can be patterned by photolithography, which enables precise manufacturing and mass production. The direct and indirect patterning achieved etching rates of ˜0.5μm/min and ˜0.2μm/min, respectively, both of which increased as the annealing temperature increased while the indirect patterning did not require micro patterning of photoresist on a bulk diamond several millimeters squire and involved much less difficult processes than the direct patterning. The thermochemical reaction is reported to be caused by; diffusion of carbon from diamond into the sidero-metal, oxidation-reduction reaction between diamond and the metal, oxidation of diamond, and carbide formation. Carbide formation was not observed when we used nickel as the sidero-metal. When the direct and indirect patterning was conducted in nitrogen, the pattern transfer was observed but the etching rate was extremely low. Therefore, oxidation-reduction reaction is dominant in the direct patterning. In the indirect patterning, the etching continued even after the nickel and diamond was not in contact. The thickness of removed diamond was by far greater than the thickness of the nickel layer. Hence, we consider that diamond was etched by oxide-reduction reaction between the diamond and the metal while they were in contact at the beginning and then, the oxidation of diamond became dominant in the indirect patterning. The process proposed herein is readily applicable to manufacture micro devices that exploit excellent characteristics of single crystal diamond.

The low-pressure infiltration of diamond by silicon to form diamond–silicon carbide composites

The infiltration of fine-grained diamond preforms by molten silicon is limited by the blocking of the pores as a result of the volume increase during the reaction of diamond with SiC. Therefore in the present paper the infiltration of preforms made with diamond powders with different grain sizes was investigated. The preforms were prepared using phenolic resin as a binder. With increasing resin content the pore size increases, but the pore volume decreases. As a result the infiltration depth increases strongly for medium resin content. For the fine-grained ∼1.5 μm diamond preforms, a maximum infiltration depth of 2.5 mm is obtained at 10% resin, whereas at 5% resin only 1.25 mm could be infiltrated.

Imaging SIMS for the investigation of substrate surfaces for CVD diamond deposition

The influence of substrate surface preparation on diamond nucleation is a major topic in the investigation of CVD-diamond deposition. The substrate, polishing material, its grain size, and the resulting surface roughness all influence diamond nucleation. Diamond can nucleate at scratches or residues of the polishing process which are providing nucleation sites. In this paper the surface of molybdenum and substrates polished with SiC and diamond powder was studied by imaging (2- and 3-dimensional) secondary ion mass spectrometry. The distribution and grain size of polishing residues (SiC, diamond) were determined and the reaction of diamond with the substrate during heating to deposition temperature was investigated. In this case a laterally inhomogeneous system of carbon containing species had to be characterized. Therefore compound-specific secondary ion mass spectrometry had to be performed. The results suggested that diamond residues on molybdenum substrates are partly dissolved during the heat treatment. The measurements indicate that a fraction of the diamond residues is still present after heat treatment and can provide nucleation sites for diamond deposition.

Effect of the combined carbon of tungsten monocarbide on the reaction of diamond with a hard metal

Effect of the combined carbon of tungsten monocarbide on the reaction of diamond with a hard metal

Reaction of diamond with hard metals during the shaping of composite materials

Reaction of diamond with hard metals during the shaping of composite materials