A ternary compound additive for vacuum densification of β-silicon carbide at low temperature

Ultra‐Low‐Temperature Sintering of Nanostructured β‐SiC

“…Figure 2 shows XRD patterns of SiC sintered with Al 4 SiC 4 using SPS at the temperature range of 1400°–1650°C for 30 min under vacuum. All the sintered specimens were consisted of a 3C–SiC phase together with 2H, 4H, 6H–SiC, Al 4 SiC 4 , and C. The specimens sintered above 1400°C showed a significant β to α phase transformation because of the generation of Al gas above 1450°C 8 . The formation of 4H– and 6H–SiC was identified at 1450°C.…”

“…The intensity of X‐ray peaks of graphite in the sintered SiC increased slightly above 1500°C. The specimen sintered at 1650°C had strong graphite peaks due to the active decomposition of the additive and graphitization of free amorphous carbon 8 …”

“…From a crystallographic perspective, Al 4 SiC 4 is described as an Al 4 C 3 ‐type crystal with hexagonal α‐SiC‐type structural units alternatively stacked along the c ‐direction 17 . The decomposition of Al 4 SiC 4 originates from breaking the bonds of the Al 4 C 3 ‐type unit without the damage of α‐SiC‐type unit because the Al–C bonds are considerably weaker than the Si–C bonds 8,17 …”

“…Recently, a ternary compound (Al 4 SiC 4 ) has received attention because of outstanding oxidation and corrosion resistance induced by the formation of dual oxide layers with mullite at the inner layer and alumina at the outer area 7 . Moreover, we recently found that Al 4 SiC 4 was an effective additive for concurrently obtaining SiC densification and refinement by hot pressing at 1700°C 8 . The material did not strongly react with air when pulverized into fine powder, thus it is more appropriate for industrial application than the Al–B–C system.…”

Processing and mechanical characterisation of monolithic silicon carbide ceramic consolidated by spark plasma sintering (SPS)

“…As aconsequence, the mechanicalproper-ties of SiC ceramics prepared via the sinteringmethodsreferred to above are verylow [1]. Nadeau et al [11] fabricated SiC ceramic by hot-pressing withouta ny sintering additives, and the theoretical density couldo nly be achieved at 2773 Kw hile applying50MPa of pressure. Generally, conventional sinteringm ethodsf or SiC ceramicsh ave been carried out at temperatures higher than 2273 Kand with very long sinteringt imes.…”