Carbides powders, properties

Chromium carbide is important in powder preparations designed for thermal spray apphcations of corrosion and wear-resistant coatings on tool and machine parts. Lower carbon carbides of chromium are important in hardfacing tods and electrodes for weld-apphed ovedays on machine wear surfaces. However, these carbides are usually formed in situ from Cr and C in the rod and not added as preformed carbides. The properties of Ci2C2 are hsted in Table 2. 

In this paper, we will report the electronic and catalytic reactivities of the model VC/V(110) surface, and our attempt to extend them to VC powder catalysts. By using high-resolution electron energy loss spectroscopy (HREELS) and NEXAFS techniques, we observed that the surface properties of V(110) could be significantly modified by the formation of vanadium carbide some of the experimental results on these model surfaces were published previously.3-5 We will discuss the selective activation of the C-H bond of isobutane and the C=C bond of isobutene on V(110) and on VC/V(110) model systems. These results will be compared to the catalytic performances of vanadium and vanadium carbide powder materials in the dehydrogenation of isobutane. 

Lately, the spark plasma sintering has been used gradually in practical applications. The characteristics of this new sintering process are low- temperature and short- time sintering. The features of this process are expected to solve the above problems. Therefore, we tried to sinter- bond the composition graded cemented carbide powders on steel substrate by spark plasma sintering, and evaluated the structural and mechanical properties of this composite material. This paper reports the results of these evaluations. 

Kim, E. S. Lee, T. H. Shin, S. H. Yoon, J.-S., Effect of Incorporation of Carbon Fiber and Silicon Carbide Powders Into Silicone Rubber on the Ablation and Mechanical Properties of the Silicone Rubber-Based Ablation Material. 

An alternative basket type has been developed and licensed which is constructed out of Metamic-HT, a metal matrix composite made by embedding nanoparticles of aluminum oxide and fine boron carbide powder on the grain boundaries of aluminum resulting in improved structural strength properties at elevated temperatures. This allows the basket to serve as both a structural component and a neutron absorber. 

T Ishigaki, T Sato, Y Moriyoshi, MI Boulos. Influence of plasma modification of titanium carbide powder on its sintering properties. J Mater Sci Lett 14 1694, 1995. 

The menstmum niobium—carbide process (7) utilizes either columbite [1310-23-2] mineral concentrates or ferroniobium as starting materials. A low level of TaC in soHd solution with NbC commonly occurs, as Ta and Nb occur together in ores. The properties of NbC are given in Table 1. The grayish brown NbC powder is used in cemented carbides to replace TaC. TaC—NbC soHd solutions that have 3 1, 2 1, 1 1, and 1 2 ratios and the corresponding ternary and quaternary soHd solutions with TiC and WC are common. 

The nitrides can be prepared by heating a metal powder in an N2 or NH3 atmosphere to temperatures above 1100°C. The carbides form upon heating mixtures of the metal powders with carbon to temperatures of about 2200 °C. Both the nitrides and carbides can also be made by chemical transport reactions by the van Arkel-de Boer method if the metal deposition takes place in an atmosphere of N2 or a hydrocarbon. Their remarkable properties are ... 

Most forms of carbon, except diamond, which are renowned as supports for precious metal catalysts in certain applications [3], interact strongly with MW [4]. Amorphous carbon and graphite, in their powdered form, irradiated at 2.45 GHz, rapidly (within 1 min) reach very high temperatures (>1300 K). This property has been used to explain MW-assisted syntheses of inorganic solids [5], In these syntheses carbon is either a secondary susceptor which assists the initial heating but does not react with other reactants, or is one of the reactants, e. g. in the synthesis of metal carbides. MW-carbon coupling has also been widely developed ... 

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