Calorimetric studies of the enthalpies of formation of A13Ni2, AlNi and AlNi3

Two calorimetric methods: solution and direct reaction techniques were used for determination of the enthalpies of formation of two advanced aluminides: AlNi and AlNi3 as the main candidates for the high-temperature application. The same comparison was made for Al3Ni2 due to the similarity of the structure with AIM. The special construction of solution calorimetry enables to determine the high temperature dependence of the enthalpies of formation of these intermetallic phases and to compare them with existing literature information and with theoretical calculations. Temperature dependence of the enthalpies of formation may explain the differences between experimental results and ab initio calculations at 0 K and may be attributed to the different reference state of the compound and its components. Differences between the numerical values of enthalpies of formation of these intermetallic phases are discussed in terms of structural similarities and combined with literature data of excess Gibbs energies to calculate excess entropies responsible for high temperature stability. This article reviews the progress made on calorimetric studies used for determination of the formation enthalpies of AlNi, AlNi3 and Al3Ni2 and compares them with first principle calculations as the source for verification of phase equilibria of Al-Ni system and phase diagram calculations from theoretical estimates. (C) 2003 Elsevier Ltd. All rights reserved.