To improve the infrared emissivity and ablation resistance of HfB2/SiC/TaSi2 coatings for serving in heat flux 4400 kW/m2, with different contents high-emissivity Gd2O3 were prepared using atmospheric plasma spraying. The highest 3–5 μm can reach up to 0.92 at 1273 K when content is 10 vol.%. increase attributed additional electronic transitions induced by oxygen vacancies, which are generated ...

Hafnium diboride (HfB2) in aluminum matrix (Al) material was prepared by diffusion sintering of a mixture hafnium and micropowders. The effect the content on characteristics properties samples is presented. microwave activation powders has been established. behavior concluded. structure were defined.

Phase pure HfB2–SiC powders were efficiently synthesized via microwave/molten salt assisted boro/carbothermal reduction (MMS-BCTR) method by using HfO2, SiO2, activated carbon and B4C as raw materials, NaCl–KCl a molten medium. The effects of mass ratio to reactant (ms/mr), holding period, reaction temperature content on the phase composition microstructure investigated. results showed that opt...

ifThe technique of matrix isolation has been used to obtain the infrared spec ra of several high temperature molecules. A double boiler and reaction oven type Knudsen cell technique have been added to the general methods of matrix isolation result g in greater versatility of the method. Differentiation between monomer and polymer spectra appears to be entirely possible. The following molecules ...

The aim of this work is to optimize the oxidation resistance of ZrB2-SiC-based composites with different additives. Effect of nine factors including SiC, Cf, MoSi2, HfB2 and ZrC contents, milling time of Cf (M.t) and SPS parameters such as temperature, time and pressure on oxidation resistance in four levels was investigated. Taguchi design was applied to explore effective parameters for ...

A comprehensive ab initio analysis of the ultra high temperature ceramics ZrB2 and HfB2 is presented. Density functional theory (DFT) computations were performed for the electronic, mechanical, thermal, and point defect properties of these materials. Lattice constants and elastic constants were determined. Computations of the electronic density of states, band structure, electron localization f...

Transition metal diborides are ceramic materials with potential applications as hard protective thin films and electrical contact materials. We investigate the possibility to obtain age hardening through isostructural clustering, including spinodal decomposition, or ordering-induced precipitation in ternary diboride alloys. By means of first-principles mixing thermodynamics calculations, 45 ter...

Understanding the behavior of ultra-high temperature ceramics (UHTCs) against oxidation is particular importance in high-temperature applications. In this study, ZrB2–SiC–HfB2 UHTC composites were fabricated by spark plasma sintering (SPS) method at different temperatures, times, and pressures to investigate effects process variables on their resistance. Before tests, as-sintered samples contai...