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, On-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 On-TiB2, On-TiB2–epoxy (EP) resin composites with high dielectric constant and very low dielectric loss are developed. The influences of the structure and content of On-TiB2 on the electric and dielectric properties of On-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 On-TiB2–EP composites are greatly dependent on the oxidation time for preparing On-TiB2 and the content of On-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.