Synthesis of Nanostructured Calcium Phosphate Bioceramics by Liquid Flame Spray Method

Abstract

The rapidly increasing demand for calcium phosphate (CaP) bioceramics, especially those with nanostructures, has generated strong interest in developing simple, convenient, adjustable, and scalable synthesis methods. However, significant opportunities still exist to improve strategies for producing nanostructured CaPs, because many CaP phases have not yet been synthesized through a continuous single-step process. Flame-based aerosol synthesis methods can provide a fast, simple, continuous, and single-step route, and they can be easily scaled up by employing multiple burners within a single industrial reactor. Moreover, increasing concerns about environmental sustainability have driven the development of nanostructured CaP synthesis methods with strong potential for environmentally friendly production. Therefore, the Liquid Flame Spray (LFS) method was advanced in this study to be utilized for producing nanostructured CaP bioceramics. LFS is a subcategory of liquid-fed aerosol flame synthesis methods that uses a hydrogen-oxygen flame and does not rely on combustible solvents. Thus, in the absence of surfactants, acids, and organic solvents, it can be considered an eco-friendly synthesis process, in addition to meeting the criteria mentioned above.

The LFS process parameters were systematically studied and optimized to enable the straightforward synthesis of various nanostructured CaPs, including the β-polymorph of calcium pyrophosphate (β-CPP), monetite, and hydroxyapatite. Several advanced characterization techniques were employed to evaluate the purity and nanostructural features of the LFS-synthesized CaPs, and in-situ aerosol measurements were conducted for a few samples to determine their particle size distributions and to validate the characterization results.

All in all, this dissertation demonstrates that the advanced LFS method can be a highly promising approach for the industrial production of nanostructured CaP materials, which are of interest across numerous application domains.