Low-cost and facile fabrication of titanium dioxide coated oxidized titanium diboride–epoxy resin composites with high dielectric constant and extremely low dielectric loss

Abstract

A series of titanium dioxide (TiO₂) coated titanium diboride (TiB₂) particles, O_n-TiB₂, were facilely prepared using an oxidation process; interestingly, the surface morphology of TiO₂ on TiB₂ can be controlled from some unconnected TiO₂ particles to a full coating of TiO₂ by simply adjusting the oxidation time. Based on the synthesis of O_n-TiB₂, O_n-TiB₂–epoxy (EP) resin composites with high dielectric constant and very low dielectric loss are developed. The influences of the structure and content of O_n-TiB₂ on the electric and dielectric properties of O_n-TiB₂–EP composites were intensively studied, and the corresponding study on TiB₂–EP composites was also carried out for comparison. Results show that the dielectric properties of O_n-TiB₂–EP composites are greatly dependent on the oxidation time for preparing O_n-TiB₂ and the content of O_n-TiB₂ used. 20 min is proved to be the optimum oxidation time, the structure of the resultant fillers (O₂₀-TiB₂) shows that lots of TiO₂ particles exist on the surface of TiB₂ but do not form a full coating. For the composite with 25 vol% O₂₀-TiB₂, the dielectric constant is as high as 407 (at 1 Hz), about 1.8 times of the maximum value that can be reached by the TiB₂–EP composites; meanwhile, the dielectric loss of the O₂₀-TiB₂–EP composite is as low as 1.5 (at 1 Hz), only about 0.06 times of the corresponding value of the TiB₂–EP composite. Two different equivalent circuit models are setup for O₂₀-TiB₂–EP and TiB₂–EP composites to evaluate the nature behind these attractive results.