Preparation of Core-Shell ZrO₂@SiO₂ Nanoparticles and Its Effect on Properties of Composites

In this study, ZrO₂@SiO₂ nanoparticles with core-shell structure were prepared by Stöber method using tetraethyl orthosilicate (TEOS) as the silicon source. The core-shell structure of nanoparticles was characterized via transmission electron microscopy (TEM). The results showed that the surface of ZrO₂ could be uniformly coated with SiO₂ and the thickness of the SiO₂ shell was about 10 nm. The prepared ZrO₂@SiO₂ nanoparticles were modified with 3-methacryloxypropyltrimethoxysilane (γ-MPS) and the graft ratios were analyzed by FTIR and TGA. After modified with SiO₂ shell, the graft ratio of γ-MPS on ZrO₂@SiO₂ nanoparticles increased to 4.03%. Then the modified ZrO₂@SiO₂ nanoparticles were added into the quartz fibers (QFs) reinforced composites to prepare fiber posts with radiopacity. The effects of the nanoparticles on the mechanical properties of fiber posts were investigated by universal testing machine. The flexural strength of the composite material is reduced with the addition of ZrO₂. While with the modified ZrO₂@SiO₂ nanoparticles, the flexural strength can be improved even if the content of the inorganic nanoparticles is relatively high.