Hydrazine—Water System. II. Nonequilibrium Phase Transformations

Abstract

Although neither hydrazine nor water supercool to a large extent, their mixtures do. Aqueous solutions of hydrazine may be strongly supercooled and stabilized as rigid glasses. The values of the glass-transformation temperatures determined during warmup depend on the warmup rate, permitting the evaluation of mean values of the relaxation times characterizing the motions that are frozen in below such temperatures. The supercooled mixtures crystallize during warmup at temperatures that also depend on the warmup rate. The duration of the crystallization process exhibits a one-to-one correspondence with the temperature at which it occurs. The logarithm of the process duration varies linearly with the inverse of the absolute temperature permitting the evaluation of activation energies. Application of the theory of absolute reaction rates leads to the determination of entropy barriers. The correlation observed with the equilibrium phase transformations permits an interpretation of the processes of supercooling and crystallization during warmup. Detailed experimental results are discussed.