Fabrication of Layered SiC/C/Si/MeSi2/Me Ceramic-Metal Composites via Liquid Silicon Infiltration of Metal-Carbon Matrices

The growing demand for composite materials capable of enduring prolonged loads in high-temperature and aggressive environments presents pressing challenges for materials scientists. Ceramic materials composed of silicon carbide largely possess high mechanical strength at a relatively low density, even at elevated temperatures. However, they are inherently brittle in nature, leading to concerns about their ability to fracture. The primary objective of this study was to develop a novel technique for fabricating layered composite materials by incorporating SiC-based ceramics, refractory metals, and their silicides as integral constituents. These layered composites were produced through the liquid-phase siliconization method applied to metal-carbon blanks. Analysis of the microstructure of the resultant materials revealed that when a metal element interacts with molten silicon, it leads to the formation of a layer of metal silicide on the metal's surface. Furthermore, three-point bending tests exhibited an enhancement in the bending strength of the layered composite in comparison to the base silicon carbide ceramics. Additionally, the samples demonstrated a quasi-plastic nature during the process of destruction.

Investigation of the Effect of Supersonic Flow of Dissociated Nitrogen on ZrB2-HfB2-SiC Ceramics Doped with 10 vol.% Carbon Nanotubes

The method of fabricating dense ultra-high temperature ceramic materials ZrB2−HfB2−SiC−CCNT was developed using a combination of sol-gel synthesis and reaction hot pressing approaches at 1800 °C. It was found that the introduction of multilayer nanotubes (10 vol.%) led to an increase in the consolidation efficiency of ceramics (at temperatures > 1600 °C). The obtained ZrB2−HfB2−SiC and ZrB2−HfB2−SiC−CCNT materials were characterized by a complex of physical and chemical analysis methods. A study of the effects on the modified sample ZrB2−HfB2−SiC−CCNT composition speed flow of partially dissociated nitrogen, using a high-frequency plasmatron, showed that, despite the relatively low temperature established on the surface (≤1585 °C), there was a significant change in the chemical composition and surface microstructure: in the near-surface layer, zirconium−hafnium carbonitride, amorphous boron nitride, and carbon were present. The latter caused changes in crucial characteristics such as the emission coefficient and surface catalyticity.

Synthesis of MAX Phases in the Ti2AlC–V2AlC System as Precursors of Heterometallic MXenes Ti2 – xVxC

Abstract

A relatively low-temperature molten salt assisted synthesis is developed to prepare MAX phase solid solutions in the Ti2AlC–V2AlC system, to be used as precursors for the preparation of heterometallic MXenes Ti2 –xVxC. When the synthesis temperature is 1000°С, Ti1V1AlC, Ti0.5V1.5AlC, and Ti0.2V1.8AlC samples (despite the formation of a MAX phase and a systematic shift of reflection (002) in response to progressing vanadium-for-titanium substitution) typically feature appreciable amounts of impurity phases, namely Al2O3 and vanadium (their reflections are partially overlapping). An increase in synthetic temperature to 1100°С appreciably reduces the amount of impurities and, in a Ti1V1AlC sample, decreases the unit cell parameter a, which yet far exceeds the calculated and published values (while the parameter c corresponds with those values). Thermal analysis of Ti2AlC, Ti1V1AlC, and V2AlC samples in the range 20–1000°С shows that the oxidation resistance decreases in the progress of vanadium-for-titanium substitution in a MAX phase. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are used to study the microstructure of the prepared Ti2AlC and V2AlC phases.