Fabrication and characterization of boron nitride bulk foam from borazine

•The BN foams exhibit controlled bulk densities varying from 0.08 to 0.25 g cm−3.•The specific compressive strength of BN foams vary from 35 to 55.•The low dielectric constant and low loss tangent with little variation.•The as-obtained BN foams provide excellent thermal insulation.•The BN foams are useful for high-temperature radomes and thermal insulation.