Microstructural mechanical and optical characterisation of polymer infiltrated (Al/Ti/Zr) oxide-reinforced nano-SiO 2 dual networks

Abstract

In the present work, the silica blocks with a ceramic-polymer dual network in nanoscale were obtained by sintering of the silica nanopowder doped with 1.0 wt% of Al₂O₃, ZrSiO₄ or TiO₂ nanoparticles. Polymer infiltrated ceramic network samples were fabricated by infiltration of the methyl methacrylate monomer into the silica porous structure, followed by polymerisation at an elevated temperature. The porous structure of the sintered blocks were analysed using different models including the BET, BJH, t-plot, a_s-plot, Horvath–Kawazoe and excess surface work. The results showed that the pores formed in the blocks are interconnected in a slit-like form that are necessary for the formation of the dual network structure. The results of the excess surface work model showed that due to the doping, the change of the chemical potential of the surface (Δμ₀) and consequently the excess surface work (φ) decrease due to the increase of the polar functional groups (OH groups) attached to the surface of the nano-SiO₂. The significant increase of the surface functional groups was also confirmed by IR spectroscopy. XRD patterns revealed that the addition of 1.0 wt% of an Al₂O₃ dopant to the nano-SiO₂ and its sintering did not produce a crystalline phase and finally resulted in the formation of the transparent polymer infiltrated ceramic network. It was also found that the Vickers hardness of the polymer infiltrated ceramic network samples reinforced with Al₂O₃ or ZrSiO₄ with a polymer content of 41 and 39 wt% was in the range of 2.5–3.4 and 3.9–4.1 Gpa, respectively, which were comparable to the human tooth enamel.