Graduation Semester and Year

2009

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Materials Science and Engineering

Department

Materials Science and Engineering

First Advisor

Pranesh B Aswath

Abstract

Hydroxyapatite is the most well known phosphate in the biologically active phosphate ceramic family by virtue of its similarity to natural bone mineral. Among all bioglass compositions Bioglass®45S5 is one of the most bioactive glasses. This study initially started by adding different amounts (1, 2.5, 5, 10, and 25 wt. %) of Bioglass®45S5 to synthetic hydroxyapatite in order to improve the bioactivity of these bioceramics.The chemistries formed by sintering and their effect on different material properties including bioactivity were identified by using various techniques, such as powder and thin film x-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, X-ray absorption near edge spectroscopy, compression test, and nano indentation. All the results demonstrated that 10 and 25 wt. % Bioglass®45S5 addition to hydroxyapatite and sintering at 1200ºC for 4 hours yield new compositions with main Ca5(PO4)2SiO4 and Na3Ca6(PO4)5 crystalline phases dispersed in silicate glassy matrices, respectively. In addition, in vitro bioactivity tests such as bone like apatite formation in simulated body fluid and bone marrow stromal cell culture have shown that the crystalline and amorphous phases have an important role on improving bioactivity of these bioceramic compositions. Besides, compression test and nano indentation has given important information on compression strength and nano structure properties of these newly composed bioceramic materials and the bone like apatite layers formed on them, respectively. Finally, the effect of silicate addition on both formation and bioactivity of Na3Ca6(PO4)5 bioceramics were shown. These findings and different techniques used assisted to develop a phenomenological approach to demonstrate how the novel bioceramic compositions were composed and aid improving bioactivity of known bioceramic materials.

Disciplines

Engineering | Materials Science and Engineering

Comments

Degree granted by The University of Texas at Arlington

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