Papers by Keyword: SiC-Al₂O₃ Laminate

Abstract: This paper reports the significant effects of addition of 30 nm SiC, polytitanocarbosilane and SiC fabric to enhance the mechanical reliability of SiC. The flexural strengths of dense SiC hot-pressed with 800 nm particles (average strength 565 MPa for Y2O3-Al2O3 additives and 640 MPa for Yb2O3-Al2O3 additives) were enhanced to average strength 735-820 MPa by the addition of 30 nm SiC particles (25 vol%). Addition of polytitanocarbosilane (3 vol%, precursor of SiC fiber) to the bimodal SiC powder compact with Y2O3-Al2O3 additives provided more excellent mechanical properties of average strength 910 MPa, fracture toughness 5.2 MPa·m1/2 and Weibull modulus 11.3. SiC fabric and SiC (60 vol%) - Al2O3 (40 vol%) sheet of 60 micrometer thick were alternatively laminated and bonded to the surfaces of dense SiC under the pressure of 5 MPa. The SiC fabric prevented the propagation of the cracks formed by Vickers indentor and showed a significant nonlinear stress-strain curve. As a result, no change in the strength was measured before and after the introduction of cracks.

Abstract: SiC fabric including SiC (60 vol%)-Al2O3 (40 vol%) mixed powders and SiC (60 vol%)-Al2O3 (40 vol%) sheet of 60 μm thick were alternatively laminated and hot-pressed to 79 - 83 % of theoretical density under a pressure of 39 MPa in an Ar atmosphere at 1600 °C. Four cracks were formed on the polished laminates with 30 ± 3 and 43 ± 2 vol% SiC fabric along the center line perpendicular to the direction of length by Vickers indentor at the load of 98 N and healed in air at 1100 °C for 24 h. The strength (253 MPa) of the as-hot-pressed laminate without SiC fabric decreased to 119 MPa after the introduction of the cracks but was recovered to 336 MPa after the healing. The crack size decreased because of the oxidation of SiC particles during the healing. However, the laminates with SiC fabric had a high damage tolerance and gave no change in the strength (~100 MPa) after the introduction of the cracks. The SiC fabric prevented the propagation of the cracks. After the healing, the porosity of the laminates decreased owing to the volume increase during the oxidation of SiC particles and SiC fabric. The strength of the healed laminates was comparable to that of as-hot-pressed laminates.