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Present work determined the phase relations of the SiC-AlO-NdO, SiC-NdO-SiO and SiC-AlO-NdO-SiO subsystems in the Si-Al-Nd-O-C system by XRD phase analysis of samples which were prepared via the solid-state reaction using SiC, AlO, NdO and SiO as the starting materials. The phase diagrams of the subsystems were presented. SiC was compatible with each of the two Nd-aluminates of NdAlO and NdAlO in the system. NdAlO was stable at temperatures >1720 °C and compatible with SiC. Six four-phase coexistent regions were established in the quaternary SiC-AlO-NdO-SiO system at 1250 °C. Possible effects of the SiO on sintering of the SiC ceramics were discussed. [ABSTRACT FROM AUTHOR]

β – SiC powder mixed with 10 wt.% Al 2 O 3 and Y 2 O 3 powder in a molar ratio of 2: 3 was consolidated by spark plasma sintering (SPS) at 1700–1900 °C. Three SPS routes were designed to contrast the effects of passing a strong direct current (DC) on the densification behavior of the SiC materials. The wetting of the Y – Al – Si – O liquid to the SiC particles was increased by the DC, hence better densification. The resultant SiC ceramic had a finer uniform microstructure and high flexural strength. [ABSTRACT FROM AUTHOR]

Abstract: TaC/SiC composites with 20vol.% SiC addition were densified by spark plasma sintering at 1600–1900°C for 5min under 40MPa. Effects of sintering temperatures on the densification, microstructures and mechanical properties of composites were investigated. The results showed the materials achieved >98% of theoretical density at a temperature as low as 1600°C. While the TaC grains grew slightly with the sintering temperature increasing, the SiC particles in materials decreased in size. Equiaxed to elongated grain morphology transformation was observed in the SiC phase in the 1900°C material to obtain a higher flexural strength and fracture toughness of 715MPa and 6.7MPam1/2, respectively. Lattice enlargement of the TaC phase in the 1900°C material suggested possible Si diffusion into TaC grains. Ta was also detected in SiC grains by energy dispersive spectroscopy. Glassy pockets present at multi-grain junctions explained the enhanced densification. [Copyright &y& Elsevier]

Abstract: Self-toughening α-SiAlON/6H-SiC composites containing both α-SiAlON and α-SiC elongated grains in the microstructures were previously fabricated by spark plasma sintering (SPS). In this study, the α-SiAlON/6H-SiC composites were heat treated at 1850°C for 3h. The effects of the heat treatment on the phase compositions, microstructures, and mechanical properties were investigated. The results showed M′ phases formed from crystallization of the intergranular glassy films. No polytype transformation for the SiC phase was observed. Both α-SiAlON and α-SiC grains grow anisotropic in the heat treatment, rather than converted into the brittle equiaxed morphologies. The flexural strength and fracture toughness of the post heat-treated composites were further increased and the 40wt% SiC composition reached 907MPa and 8.5MPam1/2, respectively. [Copyright &y& Elsevier]

Abstract: TaC/SiC composites with 5–40vol.% 6H–SiC were fabricated by spark plasma sintering at 1800°C for 5min. Effects of SiC concentrations on the densification, microstructure, and mechanical properties of the materials were investigated. The results showed the densification process of the TaC/SiC composites was composed of six sequent stages. SiC addition was effective in eliminating the closed porosities in the final stage to yield fully dense TaC/SiC composites at 20vol.% SiC concentrations and above. TaC grain sizes decreased with SiC concentration increase. The 40vol.% SiC composition had the highest flexure strength and fracture toughness up to 703MPa and 6.8MPam1/2 due to the reinforcement of the SiC agent. The TaC/SiC composites with 20 and 40vol.% SiC showed good flexural strength at 1400°C. [Copyright &y& Elsevier]

6 H- SiC powder mixed with Si3N4, Al2O3, Y2O3, and AlN was sintered in a spark plasma sintering ( SPS) equipment. The 6 H→3 C SiC transformation was concerned. Research results indicated the polytype transformation completed in less than 30 s by imposing a 14 458 W (6.2 V, 2332 A) transitory DC current at 1700°C upon cooling down from 2000°C. The fast transformation kinetic and the significant 3 C- SiC grain growth accompanying the phase transformation were suspected to be correlated with the pulsed SPS direct current. [ABSTRACT FROM AUTHOR]

Monolithic α-SiC particles and in situ β-Si3N4-reinforced barium aluminosilicate (BAS) glass ceramic matrix composites with good mechanical properties were obtained by spark plasma sintering. However, attempts at the synthesis of ternary phase composites in order to maximize the reinforcing effects by co-adding α-SiC and β-Si3N4 were only partly successful. β-Si3N4 grain growth was remarkably hindered by the coexistent α-SiC, thus the resultant composite suffered a loss of reinforcement efficiency. [Copyright &y& Elsevier]

SiC (containing) ceramics were prepared by pressureless sintering at 1400–1750 °C in an argon atmosphere using SiC, Al 2 O 3 , Yb 2 O 3 and SiO 2 as starting materials. Phase compositions of the as-sintered materials were investigated by X-ray diffraction. Subsolidus phase relations in the SiC–Yb 2 O 3 –Al 2 O 3 –SiO 2 quaternary system were investigated. The results confirmed the formation of oxide compounds of Yb 4 Al 2 O 9 (YbAM), Yb 3 Al 5 O 12 (YbAG), Yb 2 SiO 5 , Yb 2 Si 2 O 7 and mullite, and a solid solution of Yb 4 Al 2(1 −x ) Si 2 x O 9 −x (YbAMss) on the YbAM–Yb 2 SiO 5 tie line. SiC was compatible with each of these phases, as well as the oxides of Al 2 O 3 , Yb 2 O 3 and SiO 2 , whereas YbAG was compatible with Yb 2 Si 2 O 7 , Al 2 O 3 and SiC, but was not compatible with mullite. Based on these observations, six compatible four-phase regions were established in the SiC–Yb 2 O 3 –Al 2 O 3 –SiO 2 phase diagram. Effects of SiO 2 on liquid phase sintering and high-temperature mechanical properties of SiC ceramics were discussed. [ABSTRACT FROM AUTHOR]

SiC (containing) ceramics were fabricated by pressureless sintering or hot pressing using SiC, Al 2 O 3 , Gd 2 O 3 and SiO 2 as starting materials. Phase compositions of the ceramics were detected by X-ray diffraction (XRD). The results showed that SiC was compatible with Al 2 O 3 , SiO 2 and Gd 2 O 3 at <1700 °C. Six binary oxide compounds, i.e. Gd 4 Al 2 O 9 (GdAM), GdAlO 3 (GdAP), Gd 2 SiO 5 , Gd 2 Si 2 O 7 , Gd 9.33 (SiO 4 ) 6 O 2 (GdH) and mullite, and two solid solutions, i.e. Gd 4 Al 2(1− x ) Si 2 x O 9+ x (GdAMss) on the GdAM–Gd 2 SiO 5 tie-line and the Gd 9.33+2 x (Si 1− x Al x O 4 ) 6 O 2 (GdHss) on the Gd 9.33 (SiO 4 ) 6 O 2 –GdAM tie-line formed. The GdAP phase was compatible with each of GdH, Al 2 O 3 and SiC, but was incompatible with Gd 2 Si 2 O 7 or mullite. Based on this information, seven four-phase compatible regions were established in the subsolidus phase diagram of the Gd 2 O 3 –Al 2 O 3 –SiO 2 –SiC quaternary system. Effects of the presence of SiO 2 on liquid phase sintering and high-temperature strength of the SiC ceramics were clarified. [ABSTRACT FROM AUTHOR]

Abstract: Dense short silicon carbide (SiCsf) and carbon fibers (Csf) reinforced BaAl2Si2O8 (BAS) glass-ceramic composites with silicon nitride were fabricated by hot-pressing technique. The phase characterization, microstructure, mechanical properties and fracture behavior of the composites were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and three-point bending tests. The results showed that short silicon carbide and carbon fibers disperse homogeneously in BAS matrix, and had good chemical compatibility with the glass-ceramic matrix. The addition of Si3N4 could successfully eliminate the microcracks in the BAS matrix induced by the thermal mismatch between the fiber and matrix. Both the added short fibers could effectively reinforce the BAS glass-ceramic by the associated toughening mechanisms such as crack deflection, fiber bridging and pullout effects. [Copyright &y& Elsevier]

Abstract: Dense silicon carbide (SiC)-based ceramics were obtained by hot-pressing using BaAl2Si2O8 (BAS) as an additive. The results showed that BAS could serve as an effective liquid sintering aid to promote densification and facilitate the growth of SiC grains. The relative densities, flexural strength and fracture toughness of the composites increase with increasing the BAS content. The flexural strength and fracture toughness of 40wt%BAS/SiC composite could reach 510MPa and 7.0MPam1/2, respectively, The main toughening mechanisms are crack deflection, crack bridging and SiC grain pullout. The complete crystallization of BAS is beneficial to the high temperature mechanical properties and the obtained 40wt%BAS/SiC composite could maintain the room strength up to 1200°C. [Copyright &y& Elsevier]