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theses

Materials that are used for biomedical or clinical applications are known as biomaterials. These materials are made in different forms according to their functionality and the body part they will repair. Biocompatibility, biofunctionality, and bioavailability are three significant factors in selecting these materials, as they might be bioinert, resorbable, or bioactive like hydroxyapatite.
Hydroxyapatite (HAp), chemical formula Ca10(PO4)6(OH)2, having a calcium to phosphorus ratio of 1.667, has received special interest in the field of biomaterials as it is well known to be an inorganic bioactive material capable of forming chemical bonds with bones and teeth, besides promoting tissue engineering and bone growth for the treatment of infected or damaged organs. It is chemically and crystallographically similar to the main minerals in bones, dentin, and enamel where no toxicity or inflammation of a foreign body response has occurred. Affinities of biopolymers, and the high osteogenic potential of promoting bone in-growth and osteoconduction, are common reasons for synthetic HAp to dominate the field of biomaterials.
HAp ceramics are mostly limited to applications of low mechanical loads. In use, this may mean that the HAp is used in conjunction with a polymer in a composite. Consideration is given to using HAp powders in 3D printing. By using 3D printing, it is possible to control the pore size and pore distribution of composite scaffolds. Since the characteristics of the HAp powders influence the ability to print bone scaffolds, it is interesting to compare their properties.
There are numerous synthesis methods and approaches to produce HAp. In this study, hydroxyapatite is prepared by the sol-gel method, where precursors are subjected to high temperatures treatment after a gel-like network is formed. These powders are compared to HAp prepared by the hydrothermal method, where the precursors react in an aqueous solution under high temperature and pressure to synthesize HAp crystals. Both materials have been studied in comparison to a commercial HAp powder obtained from a manufacturer (FLUIDINOVA, S.A). This study focuses on the differences of preparation methodology, the resulting microstructures, phase composition, particle size and crystallinity.
The sol-gel method provided a homogeneous molecular mixing at a low processing temperature (<95°C). The resulting apatite structure mainly depended on the choice of the precursors and the sintering temperature. For comparison, the hydrothermal technique produced crystalline HAp in one step without requiring post heat treatment to crystallize. HAp formed directly from the aqueous solution in a sealed vessel at high pressure and temperature of 150°C.
Phase identification by X-ray diffraction analysis, microstructure analysis (FESEM), nitrogen surface area (BET), particle size, differential thermal analysis was performed on the samples of the HAp powders. Higher crystallinity, higher surface area, high pore volume, a narrow range of particle sizes, and a needle-like morphology point to the fact that hydrothermal HAp powder is a preferred choice for 3D printing applications.

ETD_9434

Ph.D.

Includes bibliographical references

by Ahmed Ahmed Sarhan

doi:10.7282/t3-ar15-jp86

ETD doctoral

The author owns the copyright to this work.