Bond characteristics, mechanical properties, and high‐temperature thermal conductivity of (Hf_1−xTa_x)C composites

Abstract

Bond characteristics, mechanical properties, and high‐temperature thermal conductivity of ultrahigh‐temperature ceramics (UHTCs), hafnium carbide (HfC), tantalum carbide (TaC), and their solid solution composites, were investigated using first‐principles calculations. Mulliken analyses revealed that Ta formed stronger covalent bonds with C than did Hf. Bond overlap analyses indicated that the Hf–C bond possessed mixed covalent and ionic bond characteristics, compared with the more covalent character of the Ta–C bond. Consequently, the overall elastic properties were enhanced with increasing number of Ta–C bonds in the composites. The overall metallicity of the composites also increased with increasing TaC content; thus, the mechanical properties did not improve monotonically. Our results indicate that adding a small amount of TaC to HfC or vice versa to produce a composite would create a new UHTC with greatly improved elastic and mechanical properties as well as high‐temperature thermal conductivity.

Corrosion Protection Oxide Scale Formed on Surface of Fe-Ni-M (M = Al, Cr, Cu) Inert Anode for Molten Salt Electrolysis

“…where K B is the Boltzmann constant, ρ is the density, E is the Young's modulus, N A is the Avogadro number, M is the molar mass, m is the total number of atoms per formula, and M a is the average mass per atom. The thermal conductivity of solid materials varies with temperature and pressure because the phonon means that the free paths and vibration properties of the material depend on the temperature and pressure [62]. At high temperatures, solid materials converge to the minimum value of thermal conductivity, as suggested by Clarke.…”

Evolution of a metastable thin film with high‐hardness wear resistance for advanced cutting tool application

“…The volumes of the wurtzite solid solutions decrease with increasing Al content; however, there is nonlinear behavior at x = 0.625–0.75, reflecting the mixed effects of lattice parameter variations on the a ‐ and c ‐axis. This is not a common behavior in general ternary solid solutions, although the system is metastable 40,41 . To verify the reliability of the results, we performed several calculations for the equilibrium structures of the wurtzite solid solutions using both randomly substituted supercell and SQS models with different apparent crystal symmetries and sizes.…”

“…This is not a common behavior in general ternary solid solutions, although the system is metastable. 40,41 To verify the reliability of the results, we performed several calculations for the equilibrium structures of the wurtzite solid solutions using both randomly substituted supercell and SQS models with different apparent crystal symmetries and sizes. This nonlinear behavior was observed in most of the calculations.…”

Structure, Mechanical, and Micro-Scratch Behavior of Ta-Hf-C Solid Solution Coating Deposited by Non-Reactive Magnetron Sputtering

“…A recovery of around 70% is achieved for Ta-Hf-C solid solution coatin In contrast, the recovery of HfC and TaC coatings were about 50% and 58%, respectivel The introduction of Ta in the Ta-Hf-C would lead to the reduction of cohesive energ which is the total energy required to break all bonds in a solid. The reduction of cohesiv energy suggests the enhanced elastic properties [22].…”

“…The introduction of Ta in the Ta-Hf-C would lead to the reduction of cohesive energy, which is the total energy required to break all bonds in a solid. The reduction of cohesive energy suggests the enhanced elastic properties [22].…”