Abstract

The final qualities of interest (such as grain size, chemical purity, degree of stability, transition order) of new compounds, synthesised in solid state transformation processes (chemical reactions, phase transitions) can be controlled through the evaluation of the entropy generation in the system. Thermally activated chemical reaction (LiCoPO4 synthesis) and me chanically activated phase transition (PdSe2 transformation) are discussed as examples. The LiCoPO4 qualities of interest are grain size (less that 0.5 µm) and chemical purity (up to 98%). The pyrite structured PdSe2 qualities of interest are: transition-order and degree of stability. The requirements are first-order transition and as higher as possible degree of stability. The grain size of LiCoPO4 and degree of stability of PdSe2 have been described by the calculation of the entropy generation in the treatment process; the chemical purity of LiCoPO4 - by the reaction co-ordinate and the transition order of PdSe2 - by the behaviour of the thermodynamic potential - first partial derivative in the transition point. To compute the thermodynamic functions under request, the behaviour of the treated system has been investi gated by measuring the driving force of its conversion process. In the case of thermal treatment (LiCoPO4) the absorbed heat flux has been measured, whereas for the case of mechanical treatment (PdSe2) the applied pressure and its corresponding material's specific volume have been measured. Experiments and calculations have been carried out for LiCoPO4 to establish empirical equations, giving the relationship between the heating regime parameters and finalproduct grain size. For PdSe2, the relationships between the compression regime parameters and thermodynamic potential and the degree of stability have been received by numerical calculations.