Effect of zinc oxide and zirconia on structure, degradability and in vitro bioactivity of wollastonite

Abstract

The partial substitution of ZnO or ZrO2 for CaO in CaO–SiO2 system was performed by sintering sol–gel derived precursor. The effects of ZnO and ZrO2 on structure, mechanical properties, in vitro bioactivity and degradability of the CaO–SiO2 ceramic were studied. Their pore size distribution was analyzed by the Barrett Joyner Halenda (BJH) method using Surface Area Analyzer (SAA). The bending strength and elastic modulus were determined by the three-point bending method. The degradability was evaluated in tris-(hydroxymethyl)-aminomethane and hydrochloric acid (Tris–HCl) buffer solution and the bioactivity by in vitro assays in simulated body fluid (SBF). Results indicate the main crystal phase to be wollastonite beta-CaSiO3. A new Ca2ZnSi2O7 phase appears in the sample doped with ZnO, and t-ZrO2 appears in the sample doped with ZrO2. The addition of ZnO or ZrO2 decreases the total pore volume of wollastonite, improves the bending strength of wollastonite. The elastic moduli of all produced ceramics match that of human body bone. After soaking in Tris–HCl solution, the samples doped with ZnO or ZrO2 present a lower weight loss. All samples have shown the ability of apatite induction in SBF solution.