|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Applications of Process Engineering Principles in Materials Processing, Energy and Environmental Technologies: An EPD Symposium in Honor of Professor Ramana G. Reddy
||Vaporization Thermodynamics of Mg, K, and Rb Using Knudsen Torsion Effusion Thermogravimetry Method
||L.-N. N. Nforbi, Anjali Talekar, Dhanesh Chandra, Wen-Ming Chien, Kai Lau, Hans Hagemann, Yaroslav Filinchuk, J-C Zhao
|On-Site Speaker (Planned)
The vapor pressure and molecular weight of effusing vapors of Mg(BH4)2 (KBH4) and RbBH4 were determined by torsion-effusion gravimetric method. The Mg(BH4)2(s) → Mg(s) + 2B(s) + 4H2(g) to predominantly H2 gas (~ 95 %) with a small amount of Mg(BH4)2 (~ 5%) in the gas phase. The equations for vapor pressures for crystalline Mg(BH4)2 are given by: logPTotal (bar) = 9.2303 - 7286.2/T, logPEq. MgBH4)2(bar) = 8.2515 - 7286.2/T, and logPEq.H2(bar) = 9.1821 - 7286.2/T. The solid KBH4 disproportionated to B(s), K(g) and H2(g) during vaporization; is log PEq.(KBH4) (bar) = (8.134 ± 0.041) – (9557.7 ± 28.7)/T. Likewise the RbBH4 also disproportionated equilibrium decomposition pressure Peq equation is log PEq(RbBH4) (bar) = (10.053 ± 0.037) – (9591.4 ± 24.0)/T. The vaporization pressures, disproportionation of each of these borohydrides, partial pressures of disproptionated gases, Gibbs energy changes (ΔGº) and standard enthalpies of reaction for decomposition will be presented.
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