No 2 (2024)

In the last decade, the diversity of high-entropy materials (HEMs) has increased sharply, including due to the expansion of research into the field of amorphous, nano- and heterostructures. Interest in nanoscale HEMs is primarily associated with their potential application in various fields, such as renewable and green energy, catalysis, hydrogen storage, surface protection and others. The development of nanotechnology has made it possible to develop an innovative design of nanoscale HEMs with fundamentally new structures with unique physical and chemical properties. Problems of controlled synthesis with precisely specified parameters of chemical composition, microstructure and morphology are solved. At the same time, traditional technologies such as fast pyrolysis, mechanical alloying, magnetron sputtering, electrochemical synthesis, etc. are being modernized. Along with this, innovative synthesis technologies have appeared, such as carbothermic shock, the method of controlled hydrogen spillover. The review discusses various methods for the synthesis of nanoscale HEMs that have been developed in the last few 6–7 years for various applications. Some of them are modernization of traditional methods for producing HEM or nano-sized materials, while another group of techniques represents innovative solutions stimulated and inspired by the HEM phenomenon.

The fusibility diagram of the diphenyl – n-docosane system was calculated by Schroeder, UNIFAC and UNIFAC Dortmund methods, and it was shown that it belongs to the eutectic type. Individual substances and their mixtures were studied experimentally using a differential scanning microcalorimeter. The endo-effect corresponding to the melting of the eutectic was noted on the DTA heating curve of the eutectic alloy. A comparison of the eutectic coordinates calculated by these methods with experimental data is presented. Specific fusion enthalpy, molar values of entropy and enthalpy of fusion, volumetric specific fusion enthalpy and density for standard conditions were calculated for an eutectic alloy. The eutectic mixture can be used as a heat carrier, as well as a working fluid of a heat accumulator.

In 2021, Chepetsk Mechanical Plant SC put into operation the production of a zirconium sponge of nuclear purity for the production of nuclear fuel components. The purification of zirconium from hafnium is carried out by extractive rectification in a KCl–AlCl₃ melt. The experience of the plant operation has shown that the elemental analysis of the melt for the content of K, Al, Zr, Hf is not enough to determine its operational properties.

During the operation of the plant at various points of the technological scheme, the composition of the melt KCl–AlCl₃–ZrCl₄–HfCl₄ was studied by a complex of independent methods using specially developed methods.

The content of the phases ZrCl₄, K₂ZrCl₆ and AlCl₃ against the background of the matrix phase KAlCl₄ was studied in frozen melts by X-ray diffractometry. The regularities of changes in the content of ZrCl₄, AlCl₃ and K₂ZrCl₆ according to the technological scheme of the installation are established.

The content of the X-ray amorphous component, which contains up to 1.5 wt% aluminum and up to 3.5 wt% zirconium, has been established in frozen melts. By the method of reducing melting in the presence of carbon in frozen melts, the oxygen content of up to 1.8 wt% was determined, which is part of the X-ray amorphous component, presumably consisting of AlOCl and ZrOCl₂.

A method for determining the AlCl₃/KCl ratio based on the difference in the physicochemical properties of the melt components has been developed. Based on the results obtained, the melt composition was adjusted during the operation of the zirconium and hafnium chloride separation unit at ChMP JSC.