Effects of Y2O3 on mechanical, dielectric, and microwave- absorbing properties of short carbon- fiber/Al2O3 composites

Short carbon-fiber (C-sf) reinforced alumina ceramics with MgO-Y2O3 as additives were fabricated by pressureless sintering at 1500 degrees C for 2h. The mechanical, dielectric and microwave properties of the composites in the X band (8.2-12.4GHz) were evaluated. The flexure strength and HRA of the ceramic increased with increasing Y2O3 content and the maximum values of 293MPa and 98 were obtained by the addition of 1.0wt% Y2O3, which were about 33.2% and 12.6% higher than the composite without Y2O3, respectively. Both the real and imaginary parts of the complex permittivity increased with increasing Y2O3 content. The composite containing 0.5wt% Y2O3 showed that reflection loss exceeded -10dB in the frequency of 9.6-11.6GHz and the minimum value was -33dB at 10.38GHz. The results showed that the addition of Y2O3 allowed both mechanical and microwave absorbing properties of the composite to be enhanced and it indicates that the C-sf/Al2O3 ceramic prepared by pressureless sintering with a small quantity of Y2O3 is a promising microwave absorber with satisfactory mechanical properties.