Study On The Preparation And Properties Of Ultra-fine ZrW₂O₈/AlN/epoxy Composites

This article reported the preparations of ZrW₂O₈/epoxy composites and AlN/ epoxy composites and ZrW₂O₈/AlN/epoxy composites using E-51 epoxy resin as the matrix. However, the new discovered ZrW₂O₈ powders with negative thermal expansion and the A1N powders with high thermal conductivity were used as reinforcing materials. The composites' mechanical properties and thermal properties and electric properties were studied.The XRD pattern analysis indicated that the ZrW₂O₈ powders synthesized by solid-state fractional-steps reaction were of high purity and the samples's SEM imaging showed that the powders' particle diameters were about 0.5-1μm. The high-low temperature XRD diffraction and the Powder X software calculation showed that the average linear expansion coefficient of ZrW₂O₈ particles was approximately-5.33×10^-6/K.The test results showed that, for both ZrW₂O₈/epoxy composites and AlN/epoxy composites, either their impact toughness values or their tensile strengths increased due to the ZrW₂O₈ or A1N powders as reinforcing materials and both of the composites' linear expansion coefficient reduced as the powders' adding amount increased. ZrW₂O₈/epoxy composites had the most excellent mechanical properties whenω(ZrW₂O₈)ω(E-51) was 16:100 and their impact toughness and tensile strength were respectively 16.13kJ/m² and 55.86Mpa; whenω(ZrW₂O₈) :ω(E-51) was 20:100, the composite' linear expansion coefficient was 3.5971×10^-5/K. And for the AlN/epoxy composites, they had the best synthetic mechanical properties whenω(AlN) :ω(E-51) was 15:100 and their impact toughness and tensile strength were respectively 13.47kJ/m² and 50.64Mpa; The composites' linear expansion coefficient was 3.6336×10^-5/K whenω(AlN):ω(E-51) was 20:100. Each reinforced material had little effect on its composites' Rockwell hardness.The ZrW₂O₈/epoxy composites' glass transition temperatures were within 124℃-129℃and their dielectric constants together with their dielectric loss were both lower than the neat cured resin; whenω(ZrW₂O₈) :ω(E-51) was 12:100, the composite had the lowest water absorption. Meanwhile, the AlN/epoxy composites had the highest glass transition temperature whenω(AlN) :ω(E-51) was 3:100, which was 137.4℃; as the A1N powders' adding amount increased, the composites' dielectric constants waved from 5.2015 to 5.7973. And compared to the neat cured resin, the composites' dielectric losses was greatly reduced. However, the AlN/epoxy composites had a good insulating property under their glass transition temperature and whenω(AlN) :ω(E-51) was 20:100, the composite's water absorption was the lowest.The optimal total content of ZrW₂O₈ and AlN powders was selected as 15wt%. The ZrW₂O₈/AlN/epoxy composites were prepared with the changing ratios of ZrW₂O₈ and AlN powders. As the ratio increased, the composites' impact toughness increased and the tensile strength was within 50-56Mpa and the linear expansion coefficient showed a decreasing tendency with the lowest 3.4999×l0^-5/K. Whenω(ZrW₂O₈) :ω(AlN) was 12:3, the ZrW₂O₈/AlN/epoxy composites' impact toughness and tensile strength were both the highest, which were 15.44kJ/m² and 55.3Mpa separately. As the ratio increased, the composites' dielectric constants also increased and the dielectric loss was less than 0.01 and the resistivities were greater than 8.7×10⁷Ω·m at room temperature. Compared with the neat cured resin, the addition of ZrW₂O₈ and AlN powders made the composites' thermal conductivity slightly increase. Yet the composites' thermal conductivity was effected by the resin matrix and both of the powders' content.