Details and features of the grain structure near the interface region between the AlN ceramic phase and AlSi10Mg matrix after the laser powder bed fusion (LPBF) were investigated. Aluminum nitride particles were obtained through self-propagating high-temperature synthesis and mechanically mixed with aluminum matrix powder. Optimization of the LPBF process parameters resulted in synthesized material free of pores and other defects. Optical microscopy analysis of etched cross-section and more detailed EBSD analysis revealed regions with relatively coarse grains at melting pool boundaries and fine grains in the melt pool core and near the AlN particles. Moreover, a pronounced orientation of fine elongated matrix grains towards the center of the ceramic particle was obtained. The such formed microstructure is attributed to directional heat sink during crystallization due to the higher thermal conductivity of aluminum nitride compared to the AlSi10Mg matrix. On the contrary, poor wettability of AlN by melt partly prevented the formation of such features, thus a combination of these factors determines the final microstructure of the interface in the resulting material.

Regularities of the interaction of widely dispersed industrial powders and electroexplosive aluminum nanopowder with nitrogen under atmospheric pressure in a linearly rising temperature and isothermal conditions have been investigated. The effect of the powder’s dispersion and composition, and the structure of the oxide shell and metal core of the aluminum particles on the temperature range of reaction and its kinetic parameters is shown. The relationship between the process of dehydration of hydroxides that are part of the superficial oxide shell of Al particles and the initial temperature of interaction between the powders and nitrogen was investigated. It is shown that the staged nature of weight gain for powders in a nitrogen atmosphere that is observed under conditions of linear heating results from a change in the macrokinetic regime, due to the effect of the Al nitride layer.

The regularities of the oxidation of electroexplosion iron nanopowder, produced by the wire electric explosion, heated in air under conditions of linearly increasing temperature and in the isothermal mode are examined. The oxidation process under conditions of linear heating is demonstrated to occur stepwise due to the combined influence of the fractional composition of the powder, its phase composition, and the structure of the oxide layer formed on the surface of the particles. It is shown that, under isothermal conditions (250–600°C), the oxidation of the nanopowder, as opposed to micron-sized powders, obeys a linear law and proceeds in the kinetic regime with E _a = 100 ± 7 kJ/mol. The conditions of thermogravimetry analysis at which the thermal self-ignition of the nanopowder occurs are determined. Based on the numerical evaluation of the sample surface heating parameter, the experimentally measured critical temperature is verified.

The rules governing the oxidation of aluminum nanopowders obtained by the electrical explosion of wires during heating in air under the conditions of linearly increasing temperature and in isothermal regime were studied. The influence of the composition and structure of aluminum particle oxide coating and metallic core on the parameters of the process and the phase composition and morphology of oxidation products was determined. Thermal reaction conditions were shown to depend on thermogravimetry regime, and the kinetic data were used to explain this dependence. The kinetics of oxidation was modeled taking into account the aluminum particle-size distribution function. It was shown that the structures of particles of the nanodisperse and micron electroexplosive powder fractions were different.

Tricalcium silicate (C₃S) as a binder material has a decisive influence on the processes of hardening and strength gain of cements and concretes. One of the promising directions is the introduction of dispersed additives into cement mixtures, which allow micro-level control of the composition of hydration products and change the dynamics of the structure formation of cement stone. In this paper, the effect of a microdisperse ettringite additive on the kinetics of the hydration and hardening process of tricalcium silicate was studied. It was shown that ettringite crystals selectively adsorb Ca²⁺ and OH⁻ ions from a saturated solution of calcium hydroxide, which contributes to the formation of hydrosilicate nuclei on their surface during cement hydration. Hydration of C₃S in the presence of ettringite proceeds more intensively; the addition of ettringite contributes to an increase in the content of calcium hydrosilicates in hydration products at the initial stage of the process. Addition of 10 wt.% ettringite to C₃S reduces the induction period of the beginning of the main phase of heat release by around two times and increases the amount of heat released on the 1st day of hydration by 15% compared to the control sample. According to electron microscopy data, it was found that during the first hours of hydration of modified C₃S, a significant number of nuclei of fibrous particles of calcium hydrosilicates with sizes of 0.2–2 microns were formed on the surface of ettringite crystals. According to the results of kinetic modeling of the setting process of cement pastes using the Avrami–Erofeyev model, it was shown that in the presence of the addition of microcrystals of ettringite, the setting rate is characterized by a slowdown in nucleation, whereas for a sample without an additive, this process proceeds with an acceleration of the formation of solid-phase nuclei. Based on the comparison of kinetic results and mechanical measurements, it is concluded that needle crystals of ettringite during C₃S hydration and cement stone hardening are preformed centers for the growth of hydrosilicate nuclei, and they also act as a reinforcing filler, increasing the bending strength of modified samples. The results of the work can be used in practice in the development of methods for controlling the processes of hydration and hardening of cements, as well as for controllable structure formation of cement stone which is important in particular for 3D printing of building products and constructions.