In-situ fabrication of hetero-structured fillers to significantly enhance thermal conductivities of silicone rubber composite films

With the method of precipitation followed by high temperature calcination, hetero-structured fillers boron nitride nanosheets@alumina (BNNS@Al2O3) were in-situ fabricated. Thereafter, thermally conductive & insulating BNNS@Al2O3/silicone rubber (SR) composite films were then prepared. The “point-surface” hetero-structured fillers BNNS@Al2O3 had more significant thermal conductivity coefficient (λ) improvement than single Al2O3, BNNS and directly blending BNNS/Al2O3 fillers. With the mass fraction of BNNS@Al2O3 to be 30 wt% (BNNS/Al2O3, 1:1, wt:wt), the in-plane λ (λ∥) and through-plane λ (λ⊥) of the BNNS@Al2O3/SR composite films attained 2.78 W/mK and 0.84 W/mK, 1.75 times higher than λ∥ (1.01 W/mK) and 3.0 times higher than λ⊥ (0.21 W/mK) of pure SR, also more excellent than BNNS/SR (λ∥ = 2.46 W/mK, λ⊥ = 0.76 W/mK), Al2O3/SR (λ∥ = 1.58 W/mK, λ⊥ = 0.50 W/mK) and directly blending (BNNS/Al2O3)/SR (λ∥ = 2.04 W/mK, λ⊥ = 0.62 W/mK) composite films under the same mass fraction of fillers. Also, BNNS@Al2O3/SR composite films presented wonderful mechanical, insulation as well as thermal properties.