Catalytic Atom Recombination on ZrB2/SiC and HfB2/SiC Ultrahigh-Temperature Ceramic Composites

Thermochemical and Mechanical Stabilities of the Oxide Scale of ZrB2+SiC and Oxygen Transport Mechanisms

“…4 that disfavors the Deal-Grove mechanism: (a) the DFT calculations indicate that the O Ã s not only have entropy advantage, but also mobility advantages over O 2 Ã , (b) intense aerothermal heating environment may introduce a significant level of dissociated oxygen on the outer liquid surface, 14,33 which would favor O Ã diffusion from a nonequilibrium kinetics perspective, (c) as pO 2 drops from B10 4 Pa on the outer liquid surface to o 10 À5 Pa equivalent at the internal gas finger-liquid interface ( Fig. 2(b) The mobility advantage of the peroxyl linkage over O 2 Ã suggests that arc-jet testing, 13,33 which introduces a nonequilibrium distribution of dissociated oxygen atoms on the surface, will likely lead to faster oxidation than ordinary furnace testing at the same temperature.…”

“…SiO 2 ðlÞ þ COðgÞ (2) respectively. Intense research is ongoing to characterize and enhance this scale as a barrier against oxygen [11][12][13][14][15][16][17][18][19][20][21][22][23] (the scale microstructure can be seen in, for example, Fig. 4 of Opila et al 15 ), which apparently is superior to that of either monolithic diboride or SiC at the intended high temperatures (see Fig.…”

Stability of ultra-high-temperature ZrB2–SiC ceramics under simulated atmospheric re-entry conditions

“…Therefore the catalytic properties of the material, in respect to the recombination of oxygen atoms, may be larger at lower pressures, as found for instance in arc-jet experiments with ZrB 2 /SiC and HfB 2 /SiC ceramic materials. 2 It should also be emphasised that the co-existence of crystalline (i.e. zirconia) and amorphous (i.e.…”

“…[1][2][3][4] This emerging attention is driven by the demand of developing re-usable hot structures as thermal protection systems (TPS) of space vehicles able to re-enter from Low Earth Orbit (LEO) at relatively high speed (order of 8 km/s). In contrast to traditional blunt capsules or Shuttle-type vehicles, characterised by poor gliding capabilities and complex TPS, the future use of UHTCs opens new prospects for the development of space planes with slender fuselage noses and sharp wing leading edges.…”

Oxidation Behavior of a SPS Sintered ZrB2-SiC-MoSi2Ceramic at 1500 °C

“…In recent years, ZrB 2 -SiC ceramic have become one of the most attractive candidate materials for the thermal protection system of the next generation hypersonic vehicles due to its high melting points, high strength, high thermal conductivity and relatively low density [1,2,3,4]. During supersonic flight and re-entry process, ZrB 2 -SiC ceramic will serve in extremely harsh oxidative environment at high temperature.…”