Effect of microstructure on the mechanical properties of liquid-phase-sintered silicon carbide at pre-creep temperatures

Contact-mechanical properties at intermediate temperatures of ZrB2 ultra-high-temperature ceramics pressureless sintered with Mo, Ta, or Zr disilicides

“…Specifically, E exhibits a first linear fall that is in accordance with the theoretical expectation [47][48][49], and then a second accelerated fall between 400 and 600 • C that is attributable to the activation of reversible grain boundary sliding [47,48]. This two-stage decline in E is the usual trend observed in polycrystalline ceramics [36,[41][42][43][44][45][46]49]. It can also be seen that ZrB 2 + 20 vol%MoSi 2 is stiffer than ZrB 2 + 20 vol%ZrSi 2 and ZrB 2 + 20 vol%TaSi 2 , this last being the most compliant of the three UHTCs fabricated here.…”

“…6 shows the critical loads for the initiation of quasiplasticity (P Y ) and fracture (ring/cone (P C ) and radial (P R ) cracking) as a function of temperature in the three ZrB 2 + 20 vol%MeSi 2 (Me = Mo, Ta, or Zr) UHTCs. Clearly, all three, P Y , P C , and P R decrease with increasing temperature, which is the usual trend observed in other polycrystalline ceramics [36,42,[44][45][46]. It can also be seen that the first damage mode is always quasiplasticity, indicating that these UHTCs are "ductile" under highly-local contact stresses.…”

“…It can be seen in Fig. 3 that the Hertzian curves have the typical shape reported for other polycrystalline ceramics [36,[41][42][43][44][45][46], with a first linear stretch attributable to the elastic deformation regime and a second nonlinear stretch associated with the quasiplastic deformation regime. The particular details of the curves depend however on the test temperature and on the metal disilicide used as sintering additive.…”

“…It can also be seen that ZrB 2 + 20 vol%MoSi 2 is stiffer than ZrB 2 + 20 vol%ZrSi 2 and ZrB 2 + 20 vol%TaSi 2 , this last being the most compliant of the three UHTCs fabricated here. The decline in Y, which in liquid-phase-sintered ceramics dictates the onset of quasiplastic deformation in the form of shear faulting along the weak interfaces [45,46], is entirely consistent with the greater thermal energy available. Also, it can be seen that ZrB 2 + 20 vol%MoSi 2 is more resistant to quasiplastic damage, indicating that it has stronger interfaces than ZrB 2 + 20 vol%TaSi 2 and ZrB 2 + 20 vol%ZrSi 2 , most likely due to lower residual stresses.…”

Thermal plasma synthesis of Si/SiC nanoparticles from silicon and activated carbon powders

“…Therefore, nanomaterials are often more useful in many application as compared to bulk mainly due to their higher specific surface areas. For example, high density of nanosized SiC provides low-temperature sinterability in the consolidation processing and the improvement of mechanical properties [8]. However, low self-diffusion coefficient and covalent nature of Si-C bonding hinder the densification of SiC, and therefore additives are required for its densification [9,10].…”