Abstract
Monodisperse hollow silica nanospheres (HSNSs) with an outer diameter of ∼300 nm and shell thickness of ∼50 nm were prepared via a spontaneous dissolution–regrowth process of solid silica nanospheres (SSNSs) in NaBH4 aqueous solution. Experimental results indicated that the as-prepared HSNSs have a reduced thermal conductivity of about 0.0519±0.0007 W/(m·K), compared to ∼0.082±0.005 W/(m·K) of the corresponding SSNSs. Moreover, a small shell thickness and a small inner pore diameter are, in general, required to achieve HSNSs with low thermal conductivities. A comparison between HSNSs and SSNSs enables calculating the intrinsic solid thermal conductivity of SSNSs, which is about 0.042 W/(m·K) for SSNSs with a mean diameter of 200 nm.