Kinetics of decay of highly non-equilibrium metastable states of gas saturated amorphous ice in the presence of artificially introduced crystal centers

The conditions of the emergence of self-sustaining (explosive) crystallization in amorphous substances under intense non-steady state nucleation that occur during the formation of gas hydrates in low-temperature water-gas condensates prepared by a condensation method have been analyzed. The possibility of a spontaneous occurrence of hot crystallization centers in places of random accumulation of fluctuation-induced nuclei capable of causing local heating and transition to the explosive mode of crystallization in a non-equilibrium amorphous medium has been discussed. The stability of methane saturated amorphous ice layers with crystallization centers introduced artificially has been experimentally investigated. The presence of crystal nuclei in non-equilibrium gas-saturated amorphous condensates shifted the beginning of crystallization to the region of low temperatures. Crystallization took place in several stages. The behavior of DTA thermograms pointed to its development from different hot centers. In conditions of deep metastability, a spontaneous crystallization mode is realized, which ensures the capture of gas molecules and the formation of a gas hydrate. (C) 2019 Elsevier Ltd. All rights reserved.