The above silica-based coreeshell nanoparticles were dissolved
in THF to form a homogenous solution. A mixture of epoxy, hardener,
and the nanoparticles solutionwas stirred. The weight ratio of
epoxy: hardener was fixed at 3.8:1. The amount of nanoparticles
was varied to obtain 0.5, 1.0 and 2.0 wt% of nanoparticles in the
whole resin mixture. After complete solvent removal and degasing
under vacuum at 75 C for 2 h, the mixture was poured into a glass
mold coated with releasing agent. The resin mixture was then
cured in an oven with nitrogen purge at 130 C for 1 h,160 C for 2 h
and 230 C for 4 h.