Influence of high gas pressure on combustion synthesis of the solid-solid reaction of NiAl compound

We show the advantage of using high gas pressure in the improvement of comb ustion synthesis conditions for NiAl compound synthesis. Experiments on hig h pressure of argon between 10 and 500 MPa showed that the exothermicity of Ni-Al reactions was considerably reduced, with a complete reaction giving NiAl compound. Thermodynamic and kinetic studies were carried out. The resu lts indicate that pressure has relatively little influence on heat capacity or on the enthalpy of the reaction. We show that high pressure lowers the exothermicity of the reaction primarily by increasing the thermal conductiv ity of the sample, We propose an evolution of thermal conductivity as a fun ction of pressure in the range 10-500 MPa. The main interest of this study is a pressure-heating rate diagram developed for self-propagating high-temp erature synthesis (SHS) of NiAl. (C) 2000 Elsevier Science Ltd. All rights reserved.