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Title: Thermodynamic Analysis of the High Temperature Processes in the System Si-C-H-Cl

Abstract

In the present work a thermodynamic analysis of the interaction processes in the Si-C-H-Cl system in the temperature interval 1000-3000 K is carried out. The optimal conditions giving the maximum yield of the silicon carbide by pyrolysis of mixture of volatile compounds of carbon and silicon have been defined.

Authors:
 [1]
  1. Department of Semiconductor Physics, Faculty of Physics, University of Sofia 'St. Kliment Ohridski', 5 J. Bourchier Blvd., 1164 Sofia (Bulgaria)
Publication Date:
OSTI Identifier:
21057224
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 899; Journal Issue: 1; Conference: 6. international conference of the Balkan Physical Union, Istanbul (Turkey), 22-26 Aug 2006; Other Information: DOI: 10.1063/1.2733362; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; HYDROGEN COMPOUNDS; MIXTURES; PYROLYSIS; SILICON CARBIDES; SILICON CHLORIDES; TEMPERATURE DEPENDENCE; THERMAL ANALYSIS; THERMODYNAMICS; VOLATILITY

Citation Formats

Lilov, Stanislav. Thermodynamic Analysis of the High Temperature Processes in the System Si-C-H-Cl. United States: N. p., 2007. Web. doi:10.1063/1.2733362.
Lilov, Stanislav. Thermodynamic Analysis of the High Temperature Processes in the System Si-C-H-Cl. United States. doi:10.1063/1.2733362.
Lilov, Stanislav. Mon . "Thermodynamic Analysis of the High Temperature Processes in the System Si-C-H-Cl". United States. doi:10.1063/1.2733362.
@article{osti_21057224,
title = {Thermodynamic Analysis of the High Temperature Processes in the System Si-C-H-Cl},
author = {Lilov, Stanislav},
abstractNote = {In the present work a thermodynamic analysis of the interaction processes in the Si-C-H-Cl system in the temperature interval 1000-3000 K is carried out. The optimal conditions giving the maximum yield of the silicon carbide by pyrolysis of mixture of volatile compounds of carbon and silicon have been defined.},
doi = {10.1063/1.2733362},
journal = {AIP Conference Proceedings},
number = 1,
volume = 899,
place = {United States},
year = {Mon Apr 23 00:00:00 EDT 2007},
month = {Mon Apr 23 00:00:00 EDT 2007}
}
  • Experimental results compiled from the literature were compared to thermodynamic calculations of the most stable proportion of condensed phases to deposit from gas mixtures of Si-C-Cl-H. The calculations indicated that the predominant gas molecules participating in a deposition process are chlorides and chlorosilanes for silicon and methane and acetylene for carbon. The mismatch of the calculated and experimentally determined phase boundaries at 1473 and 1600 K led to the conclusion that silicon deposition occurs faster than carbon deposition in proportion to their partial pressures. The probable reason is that silicon-bearing gas molecules have a greater sticking probability on polar Simore » and SiC surfaces because of their asymmetric geometries. 18 references, 8 figures, 3 tables.« less
  • Chemical vapor deposition of WSi{sub 2} was studied through thermodynamic equilibrium calculations for the W--F--Si--H and W--F--Si--H--Cl systems. The calculations were made with a computer program that minimizes the Gibbs free energy by Langrangian multiplier techniques. The parameter range for these system analyses were: temperature 473 to 1073 K, pressure from 50 to 500 mTorr, and Si/W ratios of 3 to 1000. 21 gas phase species and eight solid species were included in the calculations for the W--F--Si--H system and 39 gas phase species and 15 solid species were considered for the W--F--Si--H--Cl system. At the equilibrium condition, H{sub 2},more » SiF{sub 4}, and SiF{sub 2}H{sub 2} are the most prominent gaseous species for the W--F--Si--H system while WSi{sub 2} and Si are formed in the solid phase. For the W--F--Si--H--Cl system, WSi{sub 2} and Si are formed in the solid phase, while H{sub 2}, SiCl{sub 4}, HCl, SiF{sub 4} and SiHCl{sub 3} are the most prominent gas phase species. The SiCl{sub 2} intermediate plays a key role in the surface activated reaction for this system.« less
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  • The dilithium bis(cyclopentadienide) species Li{sub 2}{l_brace}Me{sub 2}Si[C{sub 5}H{sub 2}-2,4-(CHMe{sub 2}){sub 2}]{sub 2}{r_brace} (Li{sub 2}Ip) reacts with ScCl{sub 3}(THF){sub 3} to afford rac-IpScCl{center_dot}LiCl(THF){sub 2} (1) and [meso-IpSc({mu}{sub 2}-Cl)]{sub 2} (2) and with YCl{sub 3}(THF){sub 3.5} to afford rac-IpYCl{center_dot}LiCl(THF){sub 2} (3) and [meso-IpY({mu}{sub 2}-Cl)]{sub 2} (4). Metalation with both scandium and yttrium chlorides yields the metallocene chlorides in approximately 3:1 racemic:meso ratios. Reaction of IpH{sub 2} with Zr(NMe{sub 2}){sub 4} yields exclusively meso-IpZr(NMe{sub 2}){sub 2} (9). Treatment of 1 or 2 with allylmagnesium bromide affords the allyl complexes rac-IpSc-({eta}{sup 3}-c{sub 3}H{sub 5}) (5) and meso-IpSc({eta}{sup 3}-C{sub 3}H{sub 5}) (6) and with crotylmagnesiummore » chloride affords rac-IPSc({eta}{sup 3}-C{sub 3}H{sub 4}Me) (7) and meso-IpSc({eta}{sup 3}-C{sub 3}H{sub 4}Me) (8). Diastereomerically pure rac dichlorometalate compounds (1 or 3) or pure meso chloro dimers (2 or 4) undergo spontaneous isomerization upon dissolution in THF-d{sub s}, above 55 C, affording an equilibrium ratio of {approximately}2:1 racemic:meso isomers. While spontaneous isomerization of 5, 6, 7, or 8 is very slow at room temperature; the isomerizations are not accelerated by light. The proposed mechanism for racemic-meso isomerization involves heterolytic dissociation of one cyclopentadienide ligand from the metal, rotation around that Si-Cp{sup {minus}} bond, and recoordination on the opposite face, effecting net epimerization. X-ray diffraction studies have been performed on rac-IpScCl{center_dot}LiCl(THF){sub 2} (1), [meso-IpY({mu}{sub 2}-Cl)]{sub 2} (4), and meso-IpZr(NMe{sub 2}){sub 2} (9).« less
  • Heat capacities of Na{sub 2}SO{sub 4}(aq) solutions have been measured from 140{degree}-300{degree}C at 200 bars using a flow-calorimeter over the molality range of 0.05-1.5 mol{center dot}kg{sup minus 1}. Using the ion-interaction or virial coefficient approach developed by Pitzer (1973, 1979, 1987) and coworkers, and approximating the pressure-dependencies of the various Na{sub 2}SO{sub 4}(aq) thermodynamic quantities with those of NaCl(aq) calculated from the equations of Rogers and Pitzer (1982), the authors measured heat capacities were combined with literature values on heat capacities, enthalpies, and osmotic coefficients at temperatures to 225{degree}C and at pressures mostly at 1 bar or vapor-saturation pressure tomore » yield a comprehensive set of equations for the thermodynamic properties of Na{sub 2}SO{sub 4}(aq) at temperatures 25{degree}-300{degree}C, pressure to at least 200 bars, and molalities to 3.0 mol{center dot}kg{sup minus 1}. Good agreement between experimental and predicted solubilities in water indicate that the ion-interaction model can be used successfully to predict mineral-solution equilibria to 300{degree}C without an explicit accounting for ion-pairs, and demonstrates that heat capacity measurements can be used to obtain reliable high-temperature and high-pressure activity properties of electrolyte solutions. The binary and ternary mixing parameters {theta}{sub ij} and {psi}{sub ijk} are required by the ion-interaction model for calculations for multicomponent mixtures. It was found sufficient to adopt previously determined values for {theta}{sub ij} at 25{degree}C without temperature dependence and, from the solubility data, to determine temperature-dependent {psi}{sub ijk} functions.« less