Papers by Author: Witoon Thepsuwan

Abstract: This study aims to improve the strength of porous BCP samples by the addition of titanium dioxide (TiO₂), the well known biocompatible and strong ceramic. BCP powder with HA/TCP ratio of 70/30 (BCP7030) obtained by mixing a pure HA and β-TCP powder. TiO₂ powder with 2 (BCP_2Ti), 5 (BCP_5Ti) and 10 (BCP_10Ti) %wt were added into the BCP7030 powder, then ball milled in ethanol for 6 hrs. The porous samples were fabricated by the combination of the gel-casting and freeze drying techniques. All samples were sintered at 1100°C for 2 hrs. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were used to determine crystal structures and morphology of the sintered samples, respectively. Mechanical properties and porosity of samples were measured by using the universal testing machine and Archimedess principle, respectively. XRD results showed that the phases of the undoped sample can be indexed HA and β-TCP with the ratio of 70/30 as the major phases. In BCP_2Ti, CaTiO₃ was observed as a minor phase among the crystallization of HA and β-TCP with the proportion of 30:70. Meanwhile, in BCP_5Ti and BCP_10Ti, XRD patterns revealed a completely transformation of HA to β-TCP with minor phases of CaTiO₃ and TiO₂. The microstructure of sintered samples present highly porous structure which consisted of two-dimensional pore channels along the long axis and the short axis, which replicates the ice and pore orientation in the direction of freezing. Relatively, the porosity of the samples was increased with the amount of TiO₂. Surprisingly, an additions of the TiO₂ was not rather improved the mechanical strength of porous BCP7030 in this study. This might be a result of a high percentage of porosity (84%).

Abstract: Biphasic calcium phosphate (BCP) ceramic is commonly used in the biomedical applications particularly as a bone substitute due to its biocompatibility and directly bond to bones. However, the mechanical strength is quite poor. Therefore, well known biocompatible and strong ceramics such as SiO₂, ZrO₂ and TiO₂ were added to improve the strength of BCP. BCP powder with HA/TCP ratios of 70/30 (HAP7030) was obtained by controlling the calcining temperature of the mixture between a pure HA and TCP. SiO₂, ZrO₂ and TiO₂ powder with 2, 5 and 10 %wt were mixed with the HAP7030 powder by ball milling in ethanol. The mixtures were dried, pressed and sintered at 1100°C for 2 hrs. XRD and SEM were used to determine crystal structures and morphology of the sintered samples, respectively. Physical properties and flexural strength of samples were measured. Results showed that the bending strength of HAP7030 sample was rather improved by adding TiO₂ than the addition of SiO₂ or ZrO₂. With increasing TiO₂, HAP7030 strength was superior and HAP7030 with 10 %wt of TiO₂ obtained the optimum bending strength around 61 MPa. However, the addition of TiO₂ induced the thermal stability of HA/TCP, in which HA completely decomposed to β-TCP in this study.