Phase Stability Of Composites Research Articles

Phase Stability in Hydroxyapatite / Barium Titanate Piezo Bioceramics

It has been reported in the biocompatibility researches performed in-vivo and in-vitro that the electric signals produced by piezoelectric implants may induce accelerated healing of the injured tissue after implantation. Barium titanate (BaTiO3; BTO), as a well known piezoelectric ceramic, is a suitable candidate to be used in these kind of biomedical researches about the effect of the electrical polarity and piezoelectricity on tissues. The excellent biocompatibility and faster bone adaptation characteristics of hydroxylapatite (HA) have been well documented in the literature. Therefore, HA / BTO composites may be a suitable bioceramic material introducing both the piezo effect and biocompatibility at the same time. However, the main point to process such composites should be to keep HA and BTO phases as stable as possible not to loose the biocompatibility of HA and the piezoelectricity of BTO ceramics. In this research HA / BTO, piezo-composites were prepared with powder mixing method in various mixing ratios and sintered at the temperatures between 500 and 1300 oC. Sintering was carried out under different atmospheres to evaluate the effect of atmosphere on the phase stability of composites. Then composites are characterized with XRD, DTA, density measurements and d33 piezoelectricty coefficient measurements.

Critical issues in applications of self-assembled monolayers

Molecular self-assembly of supported monolayers can produce a variety of structures with different types of surface functional groups and with varied topography. Such structural flexibility promises many applications. In addition, strategies for precision chemical patterning have evolved which expand the possibilities. Real applications of these monolayers will require precise control of structural features which in turn depends critically upon improved understanding of such factors as formation mechanisms and mixed composition phase stability. Recent advances show that such an understanding should evolve in the future.