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

Abstract

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.

Short-Term Oxidation of HfB2-SiC Based UHTC in Supersonic Flow of Carbon Dioxide Plasma

“…The HfB 2 -30vol.%SiC ceramic material was prepared using the reaction hot pressing method described in [30][31][32], as the use of the reaction sintering technique allows for a slightly lower consolidation temperature [22,[33][34][35][36]. Briefly, the synthesis of the initial HfB 2 -SiO 2 -C powder was carried out using sol-gel technology and its further hot pressing was performed using a hot press model HP20-3560-20 (Thermal Technology Inc., Minden, NV, USA) at a temperature of 1800 • C (heating rate 10 • /min) and a uniaxial pressure of 30 MPa in an argon atmosphere; the dwell time was 15 min.…”

“…This leads to the idea of using them in other gas environments, including the atmospheres of Mars, Venus, and Titan. However, there is a very small number of publications describing the behavior of such materials in non-air gas flows [20][21][22][23][24][25], mainly focusing on nitrogen atmospheres. Studies of UHTC's behavior in high-enthalpy carbon dioxide jets may be of interest for modeling the effects of Venus's atmosphere, which presents more demanding entry conditions than on Earth [26][27][28].…”

Oxidation of Ceramic Materials Based on HfB2-SiC under the Influence of Supersonic CO2 Jets and Additional Laser Heating

“…Studies of the behavior of ultra-high-temperature ceramics in non-air gas atmospheres are virtually non-existent in the literature. There are only single papers investigating the behavior of such materials in nitrogen [47][48][49][50] and argon-hydrogen plasma [51]. For ceramics based on the HfB 2 -SiC system, there are only two studies on the effects of highspeed flows of dissociated nitrogen [49,50].…”

“…There are only single papers investigating the behavior of such materials in nitrogen [47][48][49][50] and argon-hydrogen plasma [51]. For ceramics based on the HfB 2 -SiC system, there are only two studies on the effects of highspeed flows of dissociated nitrogen [49,50]. At the same time, it will be necessary to provide even higher oxidation resistance for sharp-edged materials to work in the atmospheres of the mentioned planets, since it is known that the atmosphere of both Mars and Venus is dominated by CO 2 (95-96% [52][53][54]), which should exert an even higher thermal load on parts due to the increased chemical component during high-speed motion [9].…”