Effect of Yttria-doping on Mechanical Properties of Bovine Hydroxyapatite (BHA)

Abstract

Sintered bodies of hydroxyapatite, derived from calcinated bovine bone (BHA) and doped with 0.5 and 1 wt% Y2O3, were prepared. Measurements of density, compression strength, and microhardness, along with scanning electron microscopy (SEM) and X-ray diffraction (XRD) were carried out. The experimental results showed that BHA doping with yttria favors formation of glassy phase, which advances sintering and results in a dense and reinforced BHA matrix. The best mechanical properties were achieved after sintering at 1200°C for compressive strength (82MPa) and 1300°C for microhardness (672HV). These results are better than pure BHA or composites of hydroxyapatite with Y2O3-stablized zirconia, qualifying yttria (as dopant of BHA) for further in vitro and in vivo experimentation.

Synthesis, characterization, and biological properties of composites of hydroxyapatite and hexagonal boron nitride

“…The microhardness of sintered pure HA with biological (bovine) origin (BHA) was measured in our earlier study as 145 HV for samples sintered at 1300°C, which is considerably lower than the values found in this study. Many researchers have tried to reinforce HA.…”

“…The peaks of β‐TCP (beta tricalcium phosphate) are also observed in the X‐ray diffractograms at 1300°C, attributed to the partial decomposition of HA to β‐TCP, which usually occurs in synthetic HA at temperatures above 1200°C . The resistance of HA to extensively transform to β‐TCP even at 1300°C in this study is attributed to the biological origin of HA, which has been observed many times in our previous studies . However, it is worthy of noting that this thermal resistance was not annulled by the presence of h‐BN in the matrix of HA.…”

“…More specifically, the microstructure of the well‐sintered samples (Fig. b,d,f) is seemingly better than that developed in sintered samples of pure HA, which were produced by the authors and reported in our previous studies . The microstructure of the samples with 1.5% h‐BN sintered at 1300°C is apparently more homogeneous (in the size and the shape of the grains) than the samples sintered at the same temperature with lower amount in h‐BN.…”

“…19 The resistance of HA to extensively transform to b-TCP even at 13008C in this study is attributed to the biological origin of HA, which has been observed many times in our previous studies. 7,15,16 However, it is worthy of noting that this thermal resistance was not annulled by the presence of h-BN in the matrix of HA. Moreover, biphasic HA/b-TCP materials are, undoubtedly, bioceramics which are in increased demand (these days).…”

“…2b,d,f) is seemingly better than that developed in sintered samples of pure HA, which were produced by the authors and reported in our previous studies. 15,16 The microstructure of the samples with 1.5% h-BN sintered at 13008C is apparently more homogeneous (in the size and the shape of the grains) than the samples sintered at the same temperature with lower amount in h-BN. Earlier studies reported that the presence of BNNTs favors grain enhancement in Al 2 O 3 , Si 3 N 4 , HA, and Al-based composites.…”