Inorganic phosphate cement fabricated with wollastonite, barium titanate, and phosphoric acid

Inorganic phosphate cement (PC) matrix composites with different wollastonite (CaSiO3) and barium titanate (BaTiO3) powder contents were manufactured in this research through a room temperature process. Wollastonite powder is used because of its low cost and good cementing properties when mixed with phosphoric acid (H3PO4). BaTiO3 was selected because of its good dielectric properties and high thermochemical stability. Samples were made by mixing an aqueous acidic formulation of phosphoric acid (H3PO4) and mineral wollastonite (CaSiO3) in a planetary mixing apparatus. Powder mean sizes for CaSiO3 and BaTiO3 were respectively 15 and 0.35 μm. The effect of the BaTiO3 concentration on the compressive strength, density, and dielectric properties is presented. Results obtained by scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed a composite with residual CaSiO3 and BaTiO3 powders as well as newly formed silica (SiO2), brushite (CaHPO4⋅2H2O), and monetite (CaHPO4). BaTiO3 additions improved the compressive strength (over 100 MPa). It is shown that as the BaTiO3 content increased, the porosity and dissipation factor decreased and the dielectric constant increased. As a control experiment, dielectric tests were conducted over the as-received wollastonite powders. The motivation of this research is to develop phosphate cements with tailored electronic properties for new applications.