Synthesis of Tungsten Carbides by Temperature-Programmed Reaction with CH4–H2 Mixtures. Influence of the CH4 and Hydrogen Content in the Carburizing Mixture

Giraudon, Jean‐Marc; Devassine, P.; Lamonier, Jean‐François; Delannoy, Laurent; Leclercq, Loı̈c; Leclercq, G.

doi:10.1006/jssc.2000.8859

Cited by 52 publications

(45 citation statements)

References 11 publications

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“…Thus, it is inferred that the reaction would occur through two consecutive stages: complete reduction followed by carburization. This conclusion is contrary to the earlier results reported by Leclercq et al [21] Recently, Giraudon et al [22] noticed that the carburization of tungsten occurs only when all oxygen has been removed practically from the initial solid, which agrees with the present work.…”

Section: A Effect Of Temperaturecontrasting

confidence: 79%

Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture

Ahmed

Seetharaman

2009

Metall Mater Trans B

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Ni-W-C ternary carbides were synthesized by simultaneous reduction-carburization of NiO-WO 3 oxide precursors using H 2 -CH 4 gas mixtures in the temperature range of 973 to 1273 K. The kinetics of the gas-solid reaction were followed closely by monitoring the mass changes using the thermogravimetric method (TGA). As a thin bed of the precursors were used, each particle was in direct contact with the gas mixture. The results showed that the hydrogen reduction of the oxide mixture was complete before the carburization took place. The nascent particles of the metals formed by reduction could react with the gas mixture with well-defined carbon potential to form a uniform product of Ni-W-C. Consequently, the reaction rate could be conceived as being controlled by the chemical reaction. From the reaction rate, Arrhenius activation energies for reduction and carburization were evaluated. Characterization of the carbides produced was carried out using X-ray diffraction and a scanning electron microscope (SEM) combined with electron dispersion spectroscopy (SEM-EDS) analyses. The grain sizes also were determined. The process parameters, such as the temperature of the reductioncarburization reaction and the composition of the gas mixture, had a strong impact on the carbide composition as well as on the grain size. The results are discussed in light of the reduction kinetics of the oxides and the thermodynamic constraints.

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Section: A Effect Of Temperaturecontrasting

confidence: 79%

Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture

Ahmed

Seetharaman

2009

Metall Mater Trans B

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“…Additional thermochemical data provide a similar decomposition temperature of 1327 C. 21) According to a relatively recent book of thermochemical data, 22) however, the decomposition temperature is calculated to be 442 C. Consequently, at this time, it is difficult to determine the decomposition temperature from thermochemical data. The existence of W 2 C at low temperatures was confirmed experimentally in studies of the carburization of W powders at temperatures from 350 to 1000 C [23][24][25] and solid-state reactions between carbon film and W at temperatures from 497 to 900 C. 26,27) Krishna et al 7) pointed out that W 2 C phase in flame sprayed WC coatings usually retained at room temperature even at very slow cooling rates. These facts indicate that the decomposition temperature of -W 2 C is much lower than 1300 C; consequently, the decomposition does not proceed readily during cooling.…”

Section: Product Phases and Microstructurementioning

confidence: 88%

Synthesis of W<SUB>2</SUB>C by Reactive Hot Pressing and Its Mechanical Properties

Taimatsu

Sugiyama²,

Kodaira

2008

Mater. Trans.

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Tungsten hemicarbide W 2 C with no or small amounts of W or WC was prepared by reaction-sintering from W and WC powders using a resistance-heated hot-pressing technique called spark plasma sintering. The product phases, density, microstructure, elastic moduli, hardness, and fracture toughness of the sintered bodies were determined. The stable region of the W 2 C phase had a narrow carbon content below 1860 C. W 2 C had a Poisson's ratio of 0.286, and its Young's modulus at zero porosity was determined to be 444 GPa from the true density and bulk density dependence. These values suggest that W 2 C has elastic deformation behavior similar to that of W.

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“…The tungsten metal is then mixed with the required amount of carbon and reacts at a temperature of 1400-1600°C to produce tungsten carbide. [10,11] The most important tungsten carbides are WC and W 2 C. W 2 C is thermodynamically unstable at low temperatures, while WC is stable, as confirmed by its electrochemical stability in acidic solutions. [12] Herein, we report, for the first time, on a solvent-and template-free, competent, and straightforward approach for the synthesis of inorganic WC nanotubes.…”

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confidence: 97%

Synthesis of WC Nanotubes

Pol

Gedanken

2006

Advanced Materials

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A nonaqueous, solvent‐ and template‐free, and straightforward route is described for the synthesis of inorganic WC nanotubes (see figure). The thermal decomposition of W(CO)6 in the presence of Mg powder is carried out at 900 °C under the autogenic pressure of the precursors in a closed Swagelok reactor to yield WC nanotubes for the first time. The reaction mechanism is supported by experimental data.

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Synthesis of Tungsten Carbides by Temperature-Programmed Reaction with CH4–H2 Mixtures. Influence of the CH4 and Hydrogen Content in the Carburizing Mixture

Cited by 52 publications

References 11 publications

Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture

Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture

Synthesis of W<SUB>2</SUB>C by Reactive Hot Pressing and Its Mechanical Properties

Synthesis of WC Nanotubes

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