Enhanced dielectric and thermal properties of SrTiO3/polyolefin composite substrate with dopamine-modified BNNS for microwave applications

The performance of microwave devices is significantly influenced by the substrates employed. In this study, we introduce a novel microwave composite substrate material exhibiting high dielectric constant and exceptional thermal conductivity, comprising dopamine-modified boron nitride nanosheets (BNNS@PDA) and SrTiO3/polyolefin. With an 8 wt% BNNS@PDA filler content, the composite material achieves a high dielectric constant of 17.7 (@10 GHz) and remarkable thermal conductivity of 1.604 W/(m·K), representing enhancements of 34% and 104% compared to SrTiO3/polyolefin, respectively. Additionally, a low dielectric loss of 2.95 × 10−3 and minimal water absorption of 0.15% are attained. The incorporation of BNNS@PDA augments the compatibility between the ceramic particles and resin matrix, contributing to increased dielectric constant, superior density and improved mechanical properties of composite materials. As an interval within the thermal conductive pathway, the PDA coating diminishes the system's thermal conductivity. And its interplay with polymer matrix influences the resin's curing process, subtly reducing the composite's thermal stability. In summary, BNNS@PDA/SrTiO3/polyolefin represents a promising microwave dielectric substrate material, offering high dielectric constant and excellent thermal conductivity.