Vol 514, No 1 (2024)

Doped silicon nanoparticles combine availability and biocompatibility of the material with a wide variety of functional properties. In this review, the methods of fabrication of doped silicon nanoparticles are discussed, the prevalent of those being chemical vapor deposition, annealing of substoichiometric silicon compounds, and diffusion doping. The data are summarized for the attained impurity contents, in the important case of phosphorus it is shown that impurity, excessive with respect to bulk solubility, is electrically inactive. The patterns of intraparticle impurity distributions are presented, that were studied in the previous decade with highly-informative techniques of atom probe tomography and solid-state NMR. Prospective optical and electrical properties of doped silicon nanoparticles are reviewed, significant role of the position of the impurities is exemplified with plasmonic behavior.

Heterogonous and mechanochemical synthesis of new materials based on titanium, calcium and magnesium phosphates have been developed for the first time. Final products demonstrate high sorption efficiency towards heavy metal cations and radionuclides. The combined action of the components ensures high sorption capacity towards different cations within a wide pH range. The optimal conditions of the processes providing the obtaining of composite products with given phase composition have been established. Using solid precursors and phosphorus-containing agents taken in a stoichiometric ratio, and mild hydrothermal conditions make it possible to reduce liquid waste to a minimum level. During the first step of synthesis both precipitation of titanium phosphate and formation of ammonium phosphate which is the precursor for the second step occur. The latter is the formation of calcium and magnesium phosphates. Thus, the synthesis proceeds in accordance with the principles of green chemistry.

The surface of an amorphous cobalt-based alloy of nominal composition Co75Si15Fe5Cr4.5Al0.5 was modified by nanostructures at anodizing in an ionic liquid – bis(trifluoromethane sulfonyl)imide 1-butyl-3-methyl- imidazolium. The magnetic (saturation specific magnetization and coercive force) and corrosion (corrosion potential and resistance) characteristics of an amorphous alloy before and after electrochemical modification of the surface by nanostructures are compared. Modification of the alloy surface partially changes its magnetic properties. After corrosion tests, an increase in the value of coercive force is observed. Corrosion tests were carried out by the method of polarization curves in Ringer’s solution. The corrosion resistance of alloys modified by oxide nanostructures is higher than the corrosion resistance of a polished alloy. The increase in corrosion resistance is mainly determined by the presence of nanostructures.

In this paper, new polymer composite materials (PCM) based on a mixture of the resole type phenol-formaldehyde and phthalide-containing phenol-formaldehyde binders, reinforced with polyoxadiazole fiber, were obtained, and their tribological properties were studied. The influence of the content of phthalide-containing phenol-formaldehyde polymer in a two-component mixture of binders on the hardness of the surface layer, tribological and thermofrictional properties of PCM in various units of dry friction on steel has been studied. It is shown that the resulting PCM are superior to PCM based on phenol-formaldehyde or phthalide-containing phenol-formaldehyde binders of the resole type in terms of tribological and thermal friction properties.

The six-component high-entropy carbide (HEC) (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)C has been studied. The electronic structure was calculated by using the ab initio package VASP for a supercell with 512 atoms constructed by using special quasi-random structures. The artificial neural networks potential (ANN-potential) was obtained by deep machine learning. The quality of the ANN-potential was estimated by the value of the energies, forces, and virials standard deviations. The generated ANN-potential was used to analyze both a defect-free model of the specified alloy, with 4096 atoms, and for the first time a polycrystalline HEC model, with 4603 atoms, by using the LAMMPS classical molecular dynamics package. The simulation of uniaxial cell tension was carried out, the elasticity coefficients, the all-round compression modulus, the elasticity modulus, and Poisson’s ratio were determined. The obtained values are in good agreement with the experimental and calculated data, which indicates a good predictive ability of the generated ANN-potential.