Development of α-SiAlON-SiC ceramic composites by liquid phase sintering

Elongation of α‐SiC Particles in Spark Plasma Sintered α‐SiAlON/α‐SiC Composites

“…Both 20 and 40 wt% SiC compositions resulted in a uniform fine normal microstructure (see Figs. 3(c) and (d)) in contrast to the bimodal in the 0–5 wt% SiC compositions, in consistency with the previous reports 8–12 . In addition, as mentioned in the introduction section in those literatures both SiAlON and SiC grains lost anisotropic to form fine equiaxed microstructures, contrast to the maintenance of the self‐toughening microstructures formed by anisotropic grains in this study.…”

“…In the two‐phase α‐SiAlON/α‐SiC composites the α‐SiC remained the same 6H polytype as the starting powder, suggesting no interreactions between the α‐SiAlON and α‐6H. The chemical composition of the α‐SiAlON phase was estimated using the equation established in Shen et al 14 and remained the same ( m =1.09±0.03) despite detect uncertainties, regardless the difference in the SiC contents 9,10 . The larger m values than the designed m =1.0 was attributable to more Y 3+ incorporation into the α‐SiAlON lattice 13 …”

“…SPS may play a unique role in the microstructural development of the 0–40 wt% SiC compositions regarding the fast elongation of the α‐6H SiC in the 40 wt% SiC for the absence of the β→α‐SiC polytype transformation to grow the anisotropic SiC grains 4–7 . As evidence Santos and colleagues 8–12 tried unsuccessfully to grow either the elongated α‐SiAlON grains or SiC in the SiAlON/SiC composites by various sintering techniques such as pressureless sintering, gas pressure sintering, or hot pressing for hours at 1900°–2100°C. The rapid SPS heating presumably increased the driving force for mass transportation and anisotropically grew the selected α‐SiAlON and α‐6H SiC grains by avoiding server impinging until the final microstructure was obtained.…”

Role of carbon nanotube dispersion in fracture toughening of plasma sprayed aluminum oxide - carbon nanotube nanocomposite coating

“…A summary of strengthening and toughening mechanisms in non-oxide structural ceramics is presented in Table 2.1. It can be observed that most of the research work and commercial development of the non-oxide ceramics has been limited to SiC and Si 3 N 4 [45,48,50,56]. can be calculated by the semi-empirical formula given by Antis, equation 2.1 [59]:…”

“…for A-SD coating, whereas it increases to 3. It must be noted that porosity content, porosity size and porosity distribution can also alter the fracture toughness of the nanocomposites [10,45,56]. The dispersion of CNTs (in A4C-B, A4C-SD and A8C-SD) has shown contrasting change in the thermal exposure to inflight powders (Table 4.6), which consequently results in the variation in porosity in the plasma sprayed coatings, as seen in Fig.…”