La Chimie Des Plasmas Et Ses Débouchés a Court Terme Sur Des Synthèses Inorganiques a Caractère Industriel

2007

MSF

The formation of gas phase boron and carbon containing molecular species at high temperatures (thermal plasma) is investigated theoretically, by computing the equilibrium composition of the gas mixture containing boron, carbon, hydrogen and argon. The calculations are performed for the temperature range between 500 and 6000 K, B/C=1 and 2 and for the total pressure in the system of 1 bar. Use is made of the fact that the thermal plasma is plasma in local thermodynamic equilibrium, which makes possible theoretical determination (by employing the Gibbs free energy data for the compounds present in the system) of its equilibrium composition. From the calculated compositions of the investigated gas systems, presented in this paper, it was concluded that the initial molecule for cluster formation, as a connection between individual molecules and the solid state, in the case of the synthesis of solid boron carbide by means of thermal plasma should be the B2C molecule.

Section: Methods Of Calculation Of Equilibrium Compositionmentioning

confidence: 99%

Formation of Gas Phase Boron and Carbon-Containing Molecular Species at High Temperatures

2007

MSF

“…Two basic approaches are used to determine the composition of complex mixtures at high temperatures. According to one of them, thermodynamic equilibrium constants for decomposition and ionization reactions, together with the mass conservation law and electrical neutrality are employed to determine the equilibrium composition [6,7]. The other approach, used here, is based on the minimization of the Gibbs free energy.…”

Section: Methods Of Calculation Of Equilibrium Compositionmentioning

confidence: 99%

Thermodynamic Modelling of Boron Nitride Formation in Thermal Plasma

2006

MSF

The synthesis of solid BN in thermal plasma is investigated theoretically by computing the equilibrium composition of a gas mixture containing boron, nitrogen, hydrogen and argon. The calculations are done for the temperature range between 500 and 6000 K and the total pressure in the system of 1 bar. They are based on the fact that thermal plasma is in local thermodynamic equilibrium, which makes possible theoretical determination (by employing the Gibbs free energy data for the compounds present in the system) of its equilibrium composition. From the calculated compositions of investigated gas systems, the temperature zones with saturated and/or oversaturated vapour of B and B2N are determined and the formation mechanism of BN in solid state is proposed.

“…Two basic approaches are used to determine the composition of the complex mixtures at high temperatures. In the first one, the thermodynamic equilibrium constants for the decomposition and ionization reactions together with the mass conservation law and electrical neutrality are employed to determine equilibrium composition [7,8]. The second method based on minimization of the Gibbs free energy was used in this paper.…”

Section: Methods Of Calculation Of Equilibrium Compositionmentioning

confidence: 99%

Formation of Solid TiC from Thermal Plasma: Thermodynamic Consideration

2005

MSF

The synthesis process of solid TiC in thermal plasma was investigated theoretically by computing the equilibrium composition of the gas mixture containing titanium and chlorine (titanium as a reactant is assumed to be in the form of titanium tetrachloride) with argon, hydrogen and carbon (carbon as a reactant is assumed to be in the form of methane). The calculation was performed for the temperature range between 500 and 6000 K and the total pressure in the system of 1 bar. The fact that thermal plasma is plasma in (local) thermodynamic equilibrium made possible the theoretical determination (by employing the Gibbs free energy data for the compounds present in the system and assuming that the equilibrium of the system corresponds to its minimum energy state) of its equilibrium composition. From the calculated compositions of the investigated gas systems the temperature zones with saturated and/or oversaturated vapor of Ti, TiC and C were determined and the mechanism of the formation of TiC in solid state was proposed.