Topic
Carbide
About: Carbide is a research topic. Over the lifetime, 36331 publications have been published within this topic receiving 503586 citations.
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TL;DR: In this article, the synthesis of high-surface-area molybdenum carbides has been studied by the temperature-programmed carburization of molybenum trioxide MoO3.
Abstract: The synthesis of high-surface-area molybdenum carbides has been studied by the temperature-programmed carburization of molybdenum trioxide MoO3. The feedstocks used were mixtures of methane and ethane with hydrogen. The solid reaction products were characterized at selected intervals using thermogravimetric analysis differential scanning calorimetry (TGA-DSC), surface area measurement (BET), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The gaseous products of the carburization process were monitored using a gas chromatograph equipped with a mass spectrometer (GC-MS). The structural properties of the product carbides are shown to depend on the conditions of synthesis. The C2H6/H2 feedstock gave the highest-surface-area material. The presence of H2 in the feed mixture reduced the amount of amorphous carbon deposited an the molybdenum carbide material. The surface area was found to increase most rapidly during the initial H2-reduction stage. Initially, the MoO3 is re...
158 citations
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TL;DR: In this paper, the catalytic performance of molybdenum nitride (Mo2N), supported on alumina (Mo 2 C Al 2 O 3 ) was compared with commercial sulfided MoS 2Al 2O 3 > and NiMoS Al 2O3 > for hydrotreating coal-derived gas oil and residuum at 633 K (360°C) and 13.7 MPa (2000 psig).
Abstract: Unsupported molybdenum nitride (Mo2N) and molybdenum carbide supported on alumina ( Mo 2 C Al 2 O 3 ) were compared against commercial sulfided MoS 2 Al 2 O 3 > and NiMoS Al 2 O 3 for hydrotreating coal-derived gas oil and residuum at 633 K (360°C) and 13.7 MPa (2000 psig). When the catalytic rates were compared on the basis of active sites measured by chemisorption, the nitrides and carbides were estimated to have activities as much as five times that of NiMoS Al 2 O 3 and MoS 2 Al 2 O 3 . The comparison was based on sites titrated by CO on the carbide and nitride and by O2 on the sulfided catalysts. The gas oil and resid product quality from the carbide and nitride catalysts was significantly better than the thermal blank, indicating that the materials were active under practical hydrotreating conditions. X-ray photoelectron spectroscopy analysis after reaction of the Mo2N and Mo 2 C Al 2 O 3 catalysts indicated that surface sulfiding was not extensive.
158 citations
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24 Jan 2007
TL;DR: An approach for the growth of high-quality epitaxial silicon carbide (SiC) films and boules, using the Chemical Vapor Deposition (CVD) technique is described in this paper.
Abstract: An approach for the growth of high-quality epitaxial silicon carbide (SiC) films and boules, using the Chemical Vapor Deposition (CVD) technique is described here. The method comprises modifications in the design of the typical cold-wall CVD reactors, providing a better temperature uniformity in the reactor bulk and a low temperature gradient in the vicinity of the substrate, and an approach to increase the silicon carbide growth rate and to improve the quality of the growing layers, using halogenated carbon-containing precursors (carbon tetrachloride CCl 4 or halogenated hydrocarbons, CHCl 3 , CH 2 Cl 2 , CH 3 Cl, etc.), or introducing other chlorine-containing species in the gas phase in the growth chamber. The etching effect, proper ranges, and high temperature growth are also examined.
158 citations
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TL;DR: Abrasive wear tests on white cast irons were carried out using the wet rubber wheel test and the pin test on garnet and SiC commercial abrasive cloths as mentioned in this paper, and the influence of the matrix structure on abrasive wear was studied on one iron containing 28% massive carbides.
158 citations
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TL;DR: In this article, a solution of sugar in silica sol was used as parent material for the manufacture of nanocrystalline SiC powders, and the sugar was converted to carbon particles and the silica carbon mixture was heated up to the approved reaction temperatures between 1550 and 1800 °C under an argon pressure of 180 kPa.
Abstract: A solution of sugar in silica sol was used as parent material for the manufacture of nanocrystalline SiC powders. After mixing and freeze drying of the components the conversion was performed in two steps. First the sugar was converted to carbon particles and secondly the silica carbon mixture was heated up to the approved reaction temperatures between 1550 and 1800 °C under an argon pressure of 180 kPa. When the synthesis temperature was reached the pressure was reduced to 0.02 kPa what leads to a vigorous reaction resulting in extremely fine particles. The obtained powders were characterized with regard to the particle and crystallite size, the BET surface and their chemical composition. The oxygen content was < 0.5 wt% and the particles were < 0.5 μm with crystallites < 100 nm and specific surface areas in the range of 20–30 m2g−1. Conclusions concerning the synthesis parameters to the resulting powder properties are given in this paper.
158 citations