Thermodynamic investigations and substantiation of the aluminothermic fabrication method of calcium

Abstract

Металлургия цветных металлов Izvestiya vuzov. Tsvetnaya metallurgiya • 6 • 2015 15 ВведениеОсновным потребителем металлического каль-ция остается черная металлургия, где он и его спла-вы с кремнием и другими элементами, в том числе карбид кальция, применяются в процессах раскис- Thermodynamic investigations and substantiation of the aluminothermic fabrication method of calciumTo search the ways of solving the problem on decreasing the prime cost of producing metallic calcium, it is proposed to consider its aluminothermic production by the example of the CaO-Al system. The thermodynamic analysis implemented for this system showed that the aluminothermic reduction of calcium from its oxide is technically performable under a pressure of 5-10 Pa and temperature of 1200-1500 °C. It is revealed that the implementation of reduction under the residual pressure lower than 1 atm (101,3 Pa) considerably lowers the thermodynamic temperatures of reaction beginning. It is established that only three reactions, in the course of which, calcium aluminates 3CaO ·Al 2 O 3 , 5CaO ·3Al 2 O 3 (12CaO ·7Al 2 O 3 ), and CaO ·Al 2 O 3 are formed, can be used for practical purposes. It is proposed, depending on the final state, to separate the process into the «low-temperature» one (up to 1200 °C, the calcium yield is no higher than 64,3 %) and «high-temperature» one (up to 1500 °C, up to 75 % Ca). It is planned to further confirm these data experimentally. Keywords: calcium, aluminothermic reduction, aluminates, thermodynamics, thermodynamic temperature of reaction beginning, vacuum. Izv. vuzov. Tsvet. metallurgiya. 2015. No. 6. P. 15-22.

Electron Correlation at the MgF2(110) Surface: A Comparison of Incremental and Local Correlation Methods

“…Kulifeev et al are the only ones who published experimentally determined surface energies for MgF 2 so far . Unfortunately, a comparison to our results is impossible.…”