Thermodynamic Modelling of Boron Nitride Formation in Thermal Plasma

2006 ◽  
Vol 518 ◽  
pp. 349-354 ◽  
Author(s):  
J. Radić-Perić
Keyword(s):  
Free Energy ◽  
Thermal Plasma ◽  
Total Pressure ◽  
Local Thermodynamic Equilibrium ◽  
Equilibrium Composition ◽  
Gas Mixture ◽  
Theoretical Determination ◽  
Energy Data ◽  
Nitride Formation ◽  
Boron Nitrogen

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.

Formation of Solid TiC from Thermal Plasma: Thermodynamic Consideration

2005 ◽  
Vol 494 ◽  
pp. 303-308
Author(s):  
J. Radić-Perić
Keyword(s):  
Thermal Plasma ◽  
Titanium Tetrachloride ◽  
Local Thermodynamic Equilibrium ◽  
Energy State ◽  
Minimum Energy ◽  
Equilibrium Composition ◽  
Synthesis Process ◽  
Theoretical Determination ◽  
Thermodynamic Consideration ◽  
Minimum Energy State

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.

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

2007 ◽  
Vol 555 ◽  
pp. 171-176 ◽  
Author(s):  
J. Radić-Perić
Keyword(s):  
Gas Phase ◽  
High Temperatures ◽  
Molecular Species ◽  
Thermal Plasma ◽  
Local Thermodynamic Equilibrium ◽  
Cluster Formation ◽  
Equilibrium Composition ◽  
Theoretical Determination ◽  
Initial Molecule ◽  
Boron Carbon

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.

scholarly journals Thermodynamical consideration of the synthesis of solid AlN from thermal plasma

2001 ◽  
Vol 66 (8) ◽  
pp. 523-534 ◽  
Author(s):  
Jelena Radic-Peric ◽  
Nikola Pekas
Keyword(s):  
Thermal Plasma ◽  
Equilibrium Composition ◽  
Thermal Plasmas ◽  
Synthesis Process ◽  
Gas Mixture ◽  
Optimal Conditions ◽  
Temperature Range ◽  
Gas System ◽  
Thermodynamical Consideration

The synthesis process of solid AlN in thermal plasmas was investigated theoretically by computing the equilibrium composition of the gas mixture involving nitrogen and various amounts of aluminum, oxygen and hydrogen for the temperature range between 1000 and 5500 K. The results obtained by treating the plasma as a single-gas system were combined with those which take into account the presence of solid AlN and liquid Al, to find the optimal conditions for the deposition of solid AlN. The factors determining the efficiency of this process are discussed.

scholarly journals Thermodynamic Modeling of Ni-Si-Cr-B-C System in Air and Propane Atmosphere

2021 ◽  
Vol 346 ◽  
pp. 02027
Author(s):  
Nina Ilinykh ◽  
Anastasia Krivorigova ◽  
Boris Gelchinski ◽  
Sergey Ilinykh
Keyword(s):  
Powder Material ◽  
Thermodynamic Modeling ◽  
Total Pressure ◽  
Equilibrium Composition ◽  
Gas Mixture ◽  
Temperature Range ◽  
Gas Phases ◽  
Temperature Dependences ◽  
Initial Content

Thermodynamic modeling of a powder self-fluxing material PGSR-2 based on nickel (wt. %): Ni-79.3, C-0.5, Cr-15, Si-3.2, B-2 was carried out. Modeling was executed in the temperature range of 300-6000 K in the atmosphere of air and gas mixture “92 vol. % air + 8 vol. % propane” at a total pressure of P=105 Pa. The temperature dependences of the equilibrium composition of the condensed and gas phases formed during the heating of the investigated system were calculated. It is shown that the distribution of the components of the condensed and gas phases changes significantly when the initial content of the powder material and the composition of the plasma-forming gas are changed.

scholarly journals Potential-pH diagrams considering complex oxide solution phases for understanding aqueous corrosion of multi-principal element alloys

2020 ◽  
Vol 4 (1) ◽  
Author(s):  
Kang Wang ◽  
Junsoo Han ◽  
Angela Yu Gerard ◽  
John R. Scully ◽  
Bi-Cheng Zhou
Keyword(s):  
Solid Solution ◽  
Free Energy ◽  
Graphical Representation ◽  
Equilibrium Composition ◽  
Complex Oxide ◽  
Oxidation Products ◽  
Reaction Products ◽  
Aqueous Corrosion ◽  
Principal Element ◽  
Diagram Method

AbstractThe potential-pH diagram, a graphical representation of the thermodynamically predominant reaction products in aqueous corrosion, is originally proposed for the corrosion of pure metals. The original approach only leads to stoichiometric oxides and hydroxides as the oxidation products. However, numerous experiments show that non-stoichiometric oxide scales are prevalent in the aqueous corrosion of alloys. In the present study, a room temperature potential-pH diagram considering oxide solid solutions, as a generalization of the traditional potential-pH diagram with stoichiometric oxides, is constructed for an FCC single-phase multi-principal element alloy (MPEA) based on the CALculation of PHAse Diagram method. The predominant reaction products, the ions in aqueous solution, and the cation distribution in oxides are predicted. The oxide solid solution is stabilized by the mixing free energy (or mixing entropy) and the stabilizing effect becomes more significant as the temperature increases. Consequently, solid solution oxides are stable in large regions of the potential-pH diagram and the mixing free energy mostly affects the equilibrium composition of the stable oxides, while the shape of stable regions for oxides is mostly determined by the structure of the stable oxides. Agreements are found for Ni2+, Fe2+, and Mn2+ between the atomic emission spectroelectrochemistry measurements and thermodynamic calculations, while deviations exist for Cr3+ and Co2+ possibly due to surface complexation with species such as Cl− and the oxide dissolution. By incorporating the solution models of oxides, the current work presents a general and more accurate way to analyze the reaction products during aqueous corrosion of MPEAs.

Mathematical Modeling of a Free Plasma Jet Discharging into Air and Comparison with Probe Measurements

1997 ◽  
Author(s):  
R. Bolot ◽  
M. Imbert ◽  
C. Coddet
Keyword(s):  
Local Thermodynamic Equilibrium ◽  
Argon Plasma ◽  
Plasma Jet ◽  
Equilibrium Composition ◽  
Physical Phenomena ◽  
Plasma Spraying Process ◽  
Spraying Process ◽  
Free Plasma ◽  
Argon Plasma Jet ◽  
Probe Measurements

Abstract Plasma spraying process modeling is useful to understand physical phenomena and to decrease the number of experiments. In this paper, a study of the external plasma jet is proposed: the PHOENICS™ CFD code was used with a 2D axisymmetrical geometry and a standard K-ε turbulence model. In a first step, thermodynamic and transport properties were calculated from chemical equilibrium composition, thermodynamic derivatives and kinetic theory of gases. Local Thermodynamic Equilibrium (LTE) was assumed for both plasma and surrounding gases. The proposed numerical results were computed for comparison with temperature measurements realized by Brossa and Pfender in the case of an argon plasma jet discharging into air, using enthalpy probes. The predictions were found reasonably accurate. The influence of the surrounding gas nature was also verified as the validity of the parabolic assumption.

Finite-temperature effects in enzymatic reactions — Insights from QM/MM free-energy simulations

2009 ◽  
Vol 87 (10) ◽  
pp. 1322-1337 ◽  
Author(s):  
Hans Martin Senn ◽  
Johannes Kästner ◽  
Jürgen Breidung ◽  
Walter Thiel
Keyword(s):  
Free Energy ◽  
Finite Temperature ◽  
Temperature Effects ◽  
Density Functional ◽  
Umbrella Sampling ◽  
Chorismate Mutase ◽  
Enzymatic Reactions ◽  
Energy Data ◽  
Energy Simulations ◽  
Entropic Contribution

We report potential-energy and free-energy data for three enzymatic reactions: carbon–halogen bond formation in fluorinase, hydrogen abstraction from camphor in cytochrome P450cam, and chorismate-to-prephenate Claisen rearrangement in chorismate mutase. The results were obtained by combined quantum mechanics/molecular mechanics (QM/MM) optimizations and two types of QM/MM free-energy simulations (free-energy perturbation and umbrella sampling) using semi-empirical or density-functional QM methods. Based on these results and our previously published free-energy data on electrophilic substitution in para-hydroxybenzoate hydroxylase, we discuss the importance of finite-temperature effects in the chemical step of enzyme reactions. We find that the entropic contribution to the activation barrier is generally rather small, usually of the order of 5 kJ mol–1 or less, consistent with the notion that enzymes bind and pre-organize the reactants in the active site. A somewhat larger entropic contribution is encountered in the case of chorismate mutase where the pericyclic transition state is intrinsically more rigid than the chorismate reactant (also in the enzyme). The present results suggest that barriers from QM/MM geometry optimization may often be close to free-energy barriers for the chemical step in enzymatic reactions.

Evaluation of Electrical Contact Material Stability on Mercuric Iodide

1993 ◽  
Vol 302 ◽  
Author(s):  
A. Y. Cheng
Keyword(s):  
Free Energy ◽  
Room Temperature ◽  
Electrical Contact ◽  
Radiation Detection ◽  
Electrical Contacts ◽  
Contact Material ◽  
Mercuric Iodide ◽  
Energy Data ◽  
Contact Materials ◽  
Temperature Radiation

ABSTRACTMercuric iodide detectors are leading candidates for room-temperature radiation detection applications. The inherently reactive nature of mercuric iodide limits the number of materials suitable for fabrication of electrical contacts. The theoretical stabilities of elemental contact materials on mercuric iodide were evaluated at 25°C. Additionally, the stabilities of transparent conductive compounds, for photodetector applications, were studied. Calculations were based on Gibbs free energy data, estimates and a series of hypothesized reactions with mercuric iodide. Leading candidate materials were identified and compared to experimental results.

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