The study describes an original approach to the synthesis of composites based on the MAX-phase Ti3SiC2 by a combined powder metallurgy technique. The described approach includes a two-stage heat treatment and consolidation of powders by solid-phase vacuum sintering and spark plasma sintering technologies. Powder mixtures 3Ti/1.2Si/2C and Ti/1.2Si/2TiC were considered as feedstocks for the synthesis. The selected mixtures were presintered in a vacuum furnace at a temperature of 1400°C for 1 h. The obtained compacts were milled with the addition of pure silicon powder and spark plasma sintered at a temperature of 1300°C and a pressure of 50 MPa. The silicon overage in each of the sintering steps promoted the phase formation of Ti3SiC2. The influence of isothermal holding time at the additional synthesis stage in the range of 5–10 min on phase composition and surface microstructure of the obtained materials was studied. The maximum content of the Ti3SiC2 phase, 77.8 vol

By the method of selective etching of Ti3AlC2 in HF solution using ultrasonic treatment, samples of Ti3C2Tx, where Tx is an F– or OH-group, have been obtained. The main stages occurring during etching and intercalation of layered structures of the MXene type have been determined and described, including formation of transcrystalline cracks in MAX-phase crystals, separation of MXene packages from each other, emergence of the layered structure, as well as complete delamination with the formation of single Ti3C2Tx plates. The best degree of separation has been observed in the sample obtained by 6-h ultrasonic treatment with HF solution followed by additional ultrasonic treatment for 2 h. It has been found that the use of ultrasonic treatment increases the etching rate of the original precursor and increases the degree of delamination.

The use of high-modulus ceramic materials under conditions simulating the screen protection of space objects from damage by fragments of space man-made debris is considered. The introduction of an aluminum jet at a speed of ~10 km/s into an aluminum barrier located behind brittle material screens was experimentally studied. A comparative analysis of the parameters of the residual cavity in the barrier made it possible to reveal the effect of the structural rearrangement of the ceramic material on the effectiveness of screen protection. Keywords: screen protection, space man-made debris, ceramic materials.

This paper studies the morphological and structural changes that occur during the graphitization of synthetic diamond powder (with highly faceted edges) and micropowder during heat treatment in air at temperatures up to 1000°C and in a vacuum at temperatures up to 1600°C. The most developed facets of the original diamond crystals are the octahedral 111 and cubic 100 faces. It is established that graphitization begins from the vertices and edges of crystals. 111 faces are more susceptible to graphitization than 100 faces. The morphological analysis of graphitized diamond AC160 in air helps us to study the kinetics of graphitization: the growth of dendritic graphite crystals and the formation of “graphitization pits” on the surface of diamond facets. It is shown for the first time that graphite of different shapes is formed on different diamond faces at different rates; thus, on the 111 faces graphite forms and grows in the form of triangles, and on the 100 faces, in the form of squares. At a high temperature, the volumetric graphitization of diamond particles is observed, accompanied by their destruction, mainly in the growth stages.

In this paper, synthesis and sintering of MAX phases in the Zr-Al-C system is described. Different mixtures of initial Zr/Al/C and Zr/Al/ZrC powders were used to synthesize the MAX phases of Zr2AlC and Zr3AlC2 compositions by a combined method (high-temperature sintering followed by spark plasma sintering [SPS]). The highest content of the Zr3AlC2 MAX-phase was obtained using initial Zr/Al/ZrC powders in a component ratio of 1:1.5:2-51.1 vol.%. The optimal temperature for the synthesis of a material based on the Zr(2)AlCMAX phase is 1525. C, and a material based on Zr3AlC2 is 1575. C. During subsequent SPS at a temperature of 1500.C, a pressure of 50 MPa, within 5 min, it was obtained a material containing up to 71.1 vol.% Zr3AlC2. The relative density of the samples synthesized and consolidated by the SPS method reaches 98.9%. The structure of the obtained synthesizedMAXmaterials includes elongated grains of the composition Zr2AlC and Zr3AlC2, which determines their high strength. The influence of the sintering time and temperature on the formation of the MAX phase of Zr3AlC2 from the initial powders of Zr/Al/ZrC is shown. Zirconium carbide, as an intermediate phase, is always present in the final products. Due to the large evaporation of aluminum, the ZrAl2 phase is also present in the synthesis products. An excess of aluminum contributes to the greatest formation of the Zr2AlC and Zr3AlC2 phases during the combined synthesis.

In this work, diamond–SiC composite materials modified with hafnium have been obtained, and their thermal stability at 1200°C in air has been studied. The phase composition, microstructure, and physical and mechanical characteristics have been determined. A higher thermal stability of sintered Hf-modified materials has been demonstrated compared to a diamond–silicon carbide composite materials with no additives.

This article considers the main stages of synthesis Ti3SiC2 and Ti3AlC2 and describes in detail the methods of obtaining these materials. Physical and mechanical properties of materials are investigated. The possibility of using materials in the field of nuclear waste management is considered.

In this paper, a new diamond–silicon carbide ceramic composite material—Ideal—is studied and its mechanical characteristics are determined. For the first time, a comprehensive determination of Poisson’s ratio, shear modulus, bulk modulus, and transverse sound velocity is carried out. Poisson’s ratio is in the region of 0.008 to 0.01, which, in turn, indicates the absolutely brittle nature of the failure of the Ideal ceramic under loading. The criteria that allow evaluating different materials used for body armor are calculated.

As an example of the implementation of digital materials science approaches based on statistical processing of electron micrographs with the analysis of fractal parameters, the digital characteristics of microstructure of diamond–silicon carbide ceramic composite material are calculated. The lacunarity parameter characterizing the non-uniform distribution of filler particles in the matrix is found. Based on lacunarity values calculated at different scales, scale invariance parameter characterizing the dependence of lacunarity on the scale is evaluated. Voronoi entropy characterizing the structure based on the quantity of information is also calculated and used to determine the average number of neighboring particles and average distance between them. For the composites with high mechanical properties, the number of nearest neighbors approaches six, indicating an almost closest packing.

The results of a study of carbon fiber-filled samples with an epoxy amine-cured matrix are presented. Independent quasi-periodic oscillations of the density and Young's modulus were recorded for the first time, against the backdrop of a monotonic increase in the strength of the samples. The probable causes of the appearance of the vibrational kinetics of the physico-mechanical parameters of the composite are determined depending on the content of the filler in the reaction volume of constant magnitude.

We employed contact alloying in the range 1000–1860°С to study the reaction specifics between SiC and Al2O3−(t + m)ZrO2(Y2O3) oxide composition. Real-time experiments with photographic recording of the changing size and shape of the Al2O3−(t + m)ZrO2(Y2O3) sample on a SiC ceramic substrate showed that Al2O3−(t + m)ZrO2(Y2O3) compositions react with the silicon carbide substrate in the range 1720–1860°С to melt and penetrate into (impregnate) the substrate. X-ray powder diffraction patterns were measured for samples taken from the contact area of the oxide composition with SiC directly on the substrate and in a chipped-off 1-mm-deep near-surface layer. ZrС, Al2Y4O9, and Al3.21Si0.47 were formed in the contact area via redox reactions involving oxide melt, in addition to 6H-SiC, Si and Al2O3, t-ZrO2 phases, which are the initial components of the substrate and oxide composition, respectively.

The possibility of obtaining complex-shaped mechanical engineering products based on reaction-sintered silicon carbide using two methods - mechanical processing of polymerized blanks before sintering and hot slip molding under pressure, has been studied. The obtained silicon carbide ceramic materials are characterized by a low density of about 3.04…3.07 g/cm3, a porosity of ? 1 % and a bending strength of 320…360 MPa. Materials based on silicon carbide modified with boron carbide have a density of 2.72 g/cm3, a porosity of about 1 % and a bending strength of 280 MPa.

A composite material based on the B4C–SiC system with different initial carbon contents was obtained by reaction sintering (impregnation of a porous billet with liquid silicon). Carbon reacted with silicon to form a secondary silicon carbide that filled the space in the porous workpiece until a monolithic material was obtained. Boron carbide acted as the source of carbon if it was initially absent or its content was low. The obtained materials had the following characteristics: bending strength up to 320 MPa, density up to 2.85 g/cm3, microhardness up to 30 GPa.

The initial powders Zr, Al, C and Zr, Al, Sc were used for the synthesis of MAX phases of the composition Zr2AlC and Zr3AlC2. The highest content (50.4 vol%) of the MAX phase Zr3AlC2 was obtained using the initial powders Zr/Al/Zr in the ratio of components 1:1.5:2 with the addition of 5 vol% Al. The optimal temperature for the synthesis of a material based on the MAX phase Zr2AlC is 1525° C, a material based on Zr3AlC2 is 1575°C. The structure of the synthesized MAX materials obtained includes elongated grains of the composition Zr2AlC and Zr3AlC2, which determines their high strength. Zirconium carbide, as an intermediate phase, is always present in the final products. Due to the large evaporation of aluminum, the ZrO2 phase is also present in the synthesis products. Excess aluminum contributes to the greatest formation of Zr2AlC and Zr3AlC2 phases during synthesis.

We employed contact alloying in the range 1000–1860°С to study the reaction specifics between SiC and Al 2 O 3 −( t + m )ZrO 2 (Y 2 O 3 ) oxide composition. Real-time experiments with photographic recording of the changing size and shape of the Al 2 O 3 −( t + m )ZrO 2 (Y 2 O 3 ) sample on a SiC ceramic substrate showed that Al 2 O 3 −( t + m )ZrO 2 (Y 2 O 3 ) compositions react with the silicon carbide substrate in the range 1720–1860°С to melt and penetrate into (impregnate) the substrate. X-ray powder diffraction patterns were measured for samples taken from the contact area of the oxide composition with SiC directly on the substrate and in a chipped-off <1-mm-deep near-surface layer. ZrС, Al 2 Y 4 O 9 , and Al 3.21 Si 0.47 were formed in the contact area via redox reactions involving oxide melt, in addition to 6H-SiC, Si and Al 2 O 3 , t -ZrO 2 phases, which are the initial components of the substrate and oxide composition, respectively.

The research aimed at the composition optimization for diamond-SiC-Si composites. The effect of a porous diamond workpiece was studied on the properties (porosity, density, modulus of elasticity, phase composition) of the product of its siliconization with molten silicon. The lowest porosity and highest modulus of elasticity were observed in the case of using mixed matrices with the maximum size of diamond grains of 250/200 μm for siliconization. The best results in terms of the sound speed (16,600 m/s) and elasticity modulus (860 GPa) were achieved by microwave processing of a composite containing detonation nanodiamonds.

The use of high-modulus ceramic materials under conditions simulating the screen protection of space objects from damage by fragments of space man-made debris is considered. The introduction of an aluminum jet at a speed of ~10 km/s into an aluminum barrier located behind brittle material screens was experimentally studied. A comparative analysis of the parameters of the residual cavity in the barrier made it possible to reveal the effect of the structural rearrangement of the ceramic material on the effectiveness of screen protection.