The role of gas-phase transport in combustion of the tantalum-carbon system

Мержанов, А. Г.; Рогачев, А. С.; Mukas'yan, A. S.; Khusid, Boris; Borovinskaya, I. P.; Хина, Б. Б.

doi:10.1007/bf00871314

Cited by 21 publications

(17 citation statements)

References 1 publication

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“…It should be noted that the possibility of the formation of an active gas phase during combustion of the Mo-B and Ta-C systems was pointed out earlier (22,23). How ever, the gas release in these systems was considered as a secondary process that "has nothing in common with the fundamentals of chemical interaction between the reactants" (24).…”

Section: Resultsmentioning

confidence: 99%

Reactants Transport in Combustion Synthesis of Ceramics

Kashireninov¹

1997

Synthesis and Characterization of Advanced Materials

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Diffusion in solids does not ensure the experimentally observed velocity of combustion wave propagation in the systems which are traditionally considered as gasless and burned in the mode of solid flames (gasless solid-state combustion). The phenomenology of indirect interactions, the thermochemistry and dynamics of the gas-phase carriers formation, as well as their participation in the reactants transport are studied in the systems Mo-B and Ta-C. The distributions of the main species in the gas phase of the combustion wave are measured in situ with the use of a dy namic mass-spectrometry (DMS) technique which allows for high tem poral and spatial resolution. The detailed chemical pathways of the proc esses were established. It was shown that the actual mechanism of com bustion in the systems under study is neither solid state nor gasless and the reactions are fully accomplished in a narrow front.For the last 30 years, the combustion synthesis of oxygenless ceramics has been drawing attention, first and foremost because of its evident technological advantages, i.e., sim plicity of the equipment, high productivity and low consumption of energy. In many cases, the combustion synthesis results in compounds, phases and materials that are im possible to be synthesized by other methods. These investigations were pioneered by A. Merzhanov and I. Borovinskaya (7). In later work they, together with their co-workers, created the essentials of the thermal theory of powder mixtures combustion and devel oped a well known method and various modifications of self-propagating hightemperature synthesis (SHS).SHS is based on layer-by-layer combustion of a metal powder mixture with an other reactant (reactants). Metal-reactant compositions can vary but have to meet the condition of adequate heat release to sustain the overall process. It has to be noted that processes of this kind have been known for many years (2), but up to the end of the I960's they were not used to synthesize materials of complex chemical composition.It is evident that SHS, by its chemical nature, is an exothermic redox reaction oc curring in the frontal mode. Metals (Ti, Zr, Cr, Mo, W and many others) are reductants,

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Section: Resultsmentioning

confidence: 99%

Reactants Transport in Combustion Synthesis of Ceramics

Kashireninov¹

1997

Synthesis and Characterization of Advanced Materials

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“…1,4,5 One important indication of the preliminary studies is that gas-phase transport agents may provide a means to influence and control product microstructure and composition. 6,7 The presence of gas transport agents is particularly important in systems where the adiabatic flame temperature is below the melting point temperatures of the reactants, products, and intermediate species. It has been proposed that combustion cannot occur in these systems without the presence of gas transport agents.…”

Section: Introductionmentioning

confidence: 99%

“…1,4,5 CO 2 has been proposed as an intermediate formed when trace oxide impurities are present in the reactant powders and carbon is used as one of the reactants. 6 Therefore, the specific goals of the investigation were to determine whether and to what extent the presence of iodine and carbon dioxide vapor affects TaC product microstructure and composition in SHS-generated materials.…”

Section: Introductionmentioning

confidence: 99%

Catalytically Assisted Self‐Propagating High‐Temperature Synthesis of Tantalum Carbide Powders

Kim

Wooldridge

2001

Journal of the American Ceramic Society

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The use of gas-phase iodine and carbon dioxide as transport agents in the tantalum/carbon/tantalum carbide combustion synthesis system has been examined to determine the effects of transport agents on product composition and microstructure. Two tantalum reactant particle sizes, a range of transport agent concentrations, and total pressures were studied. The effects of the combustion conditions on product morphology and composition were evaluated using scanning electron microscopy, nitrogen adsorption (specific surface area), and X-ray diffraction analyses. The results of the investigation indicate that the presence of the iodine vapor and carbon dioxide significantly enhances the combustion synthesis process, leading to higher conversion efficiencies and influencing product microstructure. The results are discussed in the context of gas-phase and solid-phase transport models.

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“…Merzhanov et al [13] examined the effects of trace oxygen-containing species on SHS systems; however, the oxygen containing species were present in uncontrolled amounts as adsorbed impurities in the reactants. In the works by Shtessel and Dorozhevets [6] and by Kostogorov and Dorozhevets [7], solid-phase halogen precursors (C 2 F 4 , C 6 Cl 6 , I 2 , etc.)…”

Section: Introductionmentioning

confidence: 99%

“…KIM AND M. S. WOOLDRIDGE diffusion transport by the gas-phase agents should be more rapid in the specimens made using the larger Ta, resulting in higher burning velocities. Note that the diffusion transport of the important gas phase intermediates is very rapid (Ͻ10 s for both transport systems, [10,13]), particularly in comparison to the characteristic time of the burning velocity. However, as noted previously, the iodine transport system is thermally driven.…”

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confidence: 99%

Burning velocities in catalytically assisted self-propagating high-temperature combustion synthesis systems

Kim¹,

Wooldridge²

2001

Combustion and Flame

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The current work presents an experimental study of catalytically assisted self-propagating high-temperature synthesis (SHS) of the tantalum/carbon material system. The effects of controlled amounts of two gas-phase transport agents (carbon dioxide and vaporized iodine) were examined. The gas-phase transport agents resulted in burning velocities 2 to 4 times faster than burning velocities observed in comparable catalytically assisted and unassisted Ta/C SHS systems. The gas-phase transport agents clearly augment the combustion synthesis process. The burning velocities of the catalytically assisted, non-melting SHS systems were found to be strong functions of particle size, pressure and the amount of gas-transport agent present. The results are compared with previous studies of both catalytically assisted and unassisted Ta/C SHS, and discussed in the context of proposed transport mechanisms.

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The role of gas-phase transport in combustion of the tantalum-carbon system

Cited by 21 publications

References 1 publication

Reactants Transport in Combustion Synthesis of Ceramics

Reactants Transport in Combustion Synthesis of Ceramics

Catalytically Assisted Self‐Propagating High‐Temperature Synthesis of Tantalum Carbide Powders

Burning velocities in catalytically assisted self-propagating high-temperature combustion synthesis systems

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