Structure and properties of Ar–Kr solid solutions

The structural characteristics of N2–Kr alloys were studied using electron diffraction over the entire range of mutual concentrations. The samples were prepared in situ by condensing a gaseous mixture on aluminum and carbon substrates at temperatures of 5 and 20 K. The structure and solubility regions of the solutions were determined. The maximum solubility values of the components were: less than 20 mol.% for krypton in a nitrogen crystal, and less than 11 mol.%. for nitrogen in solid krypton. Phase separation of the solid solution was observed in a concentration range of 20–89 mol.% Kr. The effect of diluting the molecular matrix with krypton on the orientational ordering of N2 molecules in the solutions was investigated. An experimental dependence of the orientation order parameter on the solution composition was determined for N2-based solutions.

Structural transformations in N2–Kr alloys

Solodovnik

Mysko-Krutik

2019

Phase states and the mechanism of crystallization of condensed Ar−Kr mixtures

Solodovnik

Mysko-Krutik

2021

The structure characteristics of Ar−Kr mixtures deposited under special conditions have been investigated in the whole interval of concentrations applying the transmission electron diffraction technique (THEED). The samples were prepared in situ by condensing a gas mixture preliminary cooled down to the sub-liquid-nitrogen level onto substrates at T = 6 K and 20 K. The experimental results show that the structure and morphology of the Ar−Kr condensates are dependent on the nucleation dynamics prevailing in the course of the sample formation. It is shown that cooling a gas mixture is favorable to the clusterization of solute atoms in the gas flow. The krypton small clusters can serve as condensation clusters. The phase boundaries of the condensates have been determined. Regular Ar−Kr solutions are formed when the contents of one of the components are low (0−10 mol % Ar), (0−5 mol % Kr). The diffraction patterns of the condensates with prevailing Kr contents corresponded to a mixture of Kr-enriched fcc solutions and a dispersed phase of argon. The excess Kr contents are due to the specific morphology of the solutions dictated by condensation conditions. The Ar-based samples contained a mixture of two crystalline phases (an fcc solution and the hcp phase of nearly pure argon) and a glass phase of nearly pure krypton. In the concentration range 58−78 mol % Ar the new morphological form of the Ar−Kr condensates resembles the gel. The phase state diagram of the Ar−Kr condensates has been obtained.

Cluster growth in binary N2–Kr supersonic jets: Effect of initial gas temperature and krypton gas concentration

Konotop

Danylchenko

2023

An electron diffraction diagnostics of substrate-free clusters formed in N2–Kr binary jets expanding through a supersonic nozzle into a vacuum was carried out. Gas mixtures contained 0.5, 1, and 6 mol % krypton, the measured average sizes of aggregations in the cluster beam varied from 500 to 30000 molecules per cluster. A change in the nucleation mechanism in the jet from homogeneous to heterogeneous was revealed when the temperature of the gas mixture at the nozzle inlet T0 decreased from 120 to 100 K, which had a profound effect on the sizes, phase composition, and component composition of the clusters. The effect of cluster growth suppression by adding impurity with stronger intermolecular forces was revealed for the first time. It is shown that the effect is caused by the kinetics of gas condensation in a supersonic jet and is manifested at T0 = 120 K when the krypton gas content increases to 6 mol %. It was established that the intensification of cluster growth by inserted krypton nucleation centers at T0 = 100 K occurs through an increase in the fraction of the fcc phase compared to the hcp.