Aluminium nitride ceramics containing 15 -30 w/o of SiC whiskers can be sintered to full density (by hot pressing at 1800℃)using 2-3 w/o of Y2O3 additions. The whiskers increase the toughness and strength of the comp...Aluminium nitride ceramics containing 15 -30 w/o of SiC whiskers can be sintered to full density (by hot pressing at 1800℃)using 2-3 w/o of Y2O3 additions. The whiskers increase the toughness and strength of the composite, KIC increasing from 2. & to about 5.0 and flexural strength increasing by 30-50%. However, the whiskers must be well dispersed and if the dispersion is not satisfactory, toughness may increase but the strength decreases. The hot-pressing temperature can be reduced by up to 100℃ if Y(NO3)3 . 5H2O is used as the sintering additive instead of Y2O3, but some oxidation of the AIN occurs during heating. Isopropan-2-01 is a better dispersing agent than cyclohexane, but again some oxidation of the AIN does occur.The best sample prepared during this work contained 20 w/o of SiC whiskers and 2 w/o Y2O3 added as Y(NO3)3. 5H2O and mixed in isopropanol. This exhibited a mean strength of 453MPa (maximum 522MPa, measured by disc flexure) and a fracture toughness of5. 5MPam1/2.展开更多
文摘Aluminium nitride ceramics containing 15 -30 w/o of SiC whiskers can be sintered to full density (by hot pressing at 1800℃)using 2-3 w/o of Y2O3 additions. The whiskers increase the toughness and strength of the composite, KIC increasing from 2. & to about 5.0 and flexural strength increasing by 30-50%. However, the whiskers must be well dispersed and if the dispersion is not satisfactory, toughness may increase but the strength decreases. The hot-pressing temperature can be reduced by up to 100℃ if Y(NO3)3 . 5H2O is used as the sintering additive instead of Y2O3, but some oxidation of the AIN occurs during heating. Isopropan-2-01 is a better dispersing agent than cyclohexane, but again some oxidation of the AIN does occur.The best sample prepared during this work contained 20 w/o of SiC whiskers and 2 w/o Y2O3 added as Y(NO3)3. 5H2O and mixed in isopropanol. This exhibited a mean strength of 453MPa (maximum 522MPa, measured by disc flexure) and a fracture toughness of5. 5MPam1/2.
