Novel nitrogen-doped hafnium carbides for advanced ablation resistance up to 3273 K

Investigation of the Effect of Molybdenum Silicide Addition on the Oxidation Behavior of Hafnium Carbonitride

“…For effective protection against high-intensity thermal loads (T > 2000 • C), materials with high erosion and oxidation resistance, high mechanical properties, as well as high thermal conductivity, are required to remove heat from the most heat-loaded units to the "cold" load-bearing assemblies of an aircraft. The most suitable compounds for high-temperature applications are ultra-high temperature ceramics (UHTC) [1][2][3], in particular, transition metal carbonitrides [4][5][6][7] due to their high thermal stability. Numerous publications [8][9][10][11] suggest that the introduction of nitrogen atoms into the carbide sublattice promotes an increase in the melting temperature, mechanical, and thermophysical properties, as well as oxidative resistance, due to the hybridization of electron orbitals upon substitution of atoms in the metallic and nonmetallic sublattices and due to the phenomenon of solid solution hardening.…”

“…Furthermore, hafnium carbonitride HfC 0.5 N 0.35 , obtained by a combination of mechanical activation, combustion synthesis, and spark plasma sintering, exhibited high hardness and crack resistance. However, like most UHTCs, Hf(C,N) is actively oxidized in air with the formation of a highly porous cracking layer consisting of monoclinic HfO 2 (k p = 10 -7 g 2 •cm 4 •s -1 [13]).…”

“…Si-containing additives, such as SiC and MoSi 2 , are usually added to UHTC, which contributes to the formation of a protective MeSiO 4 orthosilicate with a low oxygen diffusion rate (k p = 10 -11 g 2 •cm 4 •s -1 ) [13]. The introduction of silicon carbide into Hf(C,N) has already been proven to be an effective method of protecting against oxidation due to the formation of a complex oxide layer.…”

Crystallographic Study of Product Phases of Carbothermic Reduction and Nitridation of Hafnium Dioxide

“…The high thermal stability of HfN makes it a good candidate in metal oxide semiconductor device applications. , Not only HfN but also hafnium carbonitride Hf­(C, N) has shown improved mechanical properties leading to its use as a hard coating material . It has also been predicted for HfC 0.75 N 0.22 to have highest known melting temperature based on ab initio calculations. , A similar composition (HfC 0.76 N 0.24 ) of Hf­(C, N) has shown great resistant to ablation (3000 °C) making it an interesting material for vehicles for space explorations …”

“…18,19 A similar composition (HfC 0.76 N 0.24 ) of Hf(C, N) has shown great resistant to ablation (3000 °C) making it an interesting material for vehicles for space explorations. 20 Several methods for synthesizing HfN are reported in the literature. Metal sheets of hafnium react with nitrogen over a 876−1034 °C temperature range under pressure with a reported activation energy of 238.5 ± 12.6 kJ/mol.…”