Impurities in silicon carbide ceramics and their role during high temperature creep

Enhancement of high-temperature deformation in fine-grained silicon carbide with Al doping

“…Backhaus-Ricoult et al [3] studied the compression creep behavior of hot-pressed B, C-doped SiC with an average grain size of 3.5 m at 1500-1700 • C and at 100-1100 MPa, and reported the transition of the stress exponent with increasing stress. They showed that the controlling creep mechanism at the low-stress region (n = 1.5) was grain-boundary sliding accommodated mainly by grain-boundary diffusion; at high-stress region (n = 3.5), the controlling mechanism was dislocation motion.…”

“…Gu [2] reported that B, C-doped SiC had no intergranular amorphous phase, so that SiC could exhibit superplastic deformation without the help of intergranular liquid phase in a similar way to that of metals. The creep and superplasticity of SiC is significantly influenced by the grainboundary structure [3,4] and the segregation of impurities at grain boundaries. Shinoda [5] studied the effect of boron doping on compression deformation of SiC, and showed that the grain-boundary diffusion coefficient was increased with increasing amount of boron segregation at grain boundaries.…”

Compression Deformation Mechanism of Silicon Carbide: I, Fine‐Grained Boron‐ and Carbon‐Doped β‐Silicon Carbide Fabricated by Hot Isostatic Pressing

“…Backhaus-Ricoult et al 19 investigated B,C-SiC with an average grain size of 3.5 m at 1500°-1700°C and at 100 -1100 MPa, and revealed that the controlling creep mechanism at low stress range (n ϭ 1.5, Q d ϭ 364 -453 kJ/mol) was grain-boundary sliding compensated mainly by grain-boundary diffusion; at high stress range (n ϭ 3.5-4, Q d ϭ 629 kJ/mol), the controlling mechanism became dislocation motion. Although Lane et al 17 or Nixon and Davis 18 interpreted that the obstacle to dislocation motion was B 4 C precipitates, Backhaus-Ricoult et al suggested that the grain boundaries themselves acted as obstacles to dislocation glide.…”

Thermomechanical properties of a spark plasma sintered ZrC–SiC composite obtained by a precursor derived ceramic route

“…Backhaus-Ricoult et al [52] have studied the effect of impurities such as boron and carbon on the creep behaviour at temperatures of 1500-1700°C of α-SiC with mean grain size of 0.5 mm sintered by hot isostatic pressing. For additive-free α-SiC, they note a change in the power law creep behaviour: for applied stresses lower than 500 MPa, n¼1.5 and Q¼ 364-453 kJ/mol; for higher stresses, n¼3.5-4 and Q¼ 629730 kJ/mol.…”