Search

Calcium copper titanate(CCTO)/polyurethane composite films with high dielectric constant, low dielectric loss and super flexibility were fabricated by incorporating CCTO ceramic powders into millable polyurethane elastomer (MPU) matrix using a rubber milling combined with hot compression molding method. The composite films show uniform microstructures and the dielectric constant is as high as 35.2 while the dielectric loss is only 0.041 when CCTO content reaches 40 vol% at 100 Hz and room temperature (RT). Moreover, it is important to note that this film has stable dielectric constant and dielectric loss in a relatively wide temperature range (from 0 °C to 70 °C), which is significantly import to the practice use of electronic devices based on CCTO composites. In addition, the flexibility of the film could be retained even when the CCTO content is up to 40 vol% and the elongation at break of this composite film is as high as 159.1%. Theoretical analysis indicates that the experimental data are in good conformity to the effective medium theory (EMT) model with a derived n = 0.21, suggesting more close association of the dielectric constant with the CCTO filler size and shape. [ABSTRACT FROM AUTHOR]

The high-temperature ablation properties of nano zirconia reinforced fused silica ceramics were tested using an ultra-high-temperature oxyacetylene ablation equipment. The results show that the linear recession rate and the mass loss rate of the composite ceramics containing 10 wt% zirconia are 0.087 mm/s and 0.016 g/s at 40 s ablation time, respectively, both much lower than that (0.106 mm/s and 0.028 g/s) of the pure fused silica ceramics, indicating superior ablation resistance properties of the composite ceramics. The depth of the melting area along with the flame direction of the composite ceramics is much shallower than that of the pure samples. Moreover, the composite ceramics show excellent heat shielding properties. [ABSTRACT FROM AUTHOR]

Abstract: Zirconia-toughened alumina (ZTA) ceramics were prepared using three different kinds of Al2O3 powders (marked PW-A average particle size: 7.53μm, marked PW-B average particle size: 1.76μm, marked PW-C average particle size: 0.61μm) by gelcasting. Effect of Al2O3 particle size on zeta potential, dispersant dosage and solid volume fractions of ZTA suspensions as well as the mechanical properties of ZTA green bodies and ceramics were investigated. The optimum dosages of dispersant for ZTA suspensions prepared by PW-A, PW-B and PW-C are 0.4wt%, 0.5wt% and 0.7wt%, respectively. The highest solid volume fractions of ZTA suspensions can reach 62vol% (SP-A), 60vol% (SP-B) and 52vol% (SP-C), respectively. The green bodies show a bending strength as high as 20MPa, which can meet the requirement of machining. The Al2O3 powder with fine particle size is beneficial to the improvement of mechanical properties. The ZTA ceramics prepared by PW-B Al2O3 powder show the highest bending strength (680MPa) and toughness (7.49MPam1/2). [Copyright &y& Elsevier]