الفهرس 
Introduction & Literature reviewOnly 14 pages are availabe for public view
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Abstract
Global demand for bone implants is continuously growing, lacking available organs and tissues suitable for transplantation forcing researchers to find new biological sources. Synthetic biomaterials especially those extracted from biogenic sources, are biocompatible, bioactive, economic and ecological with the environment. Sea shells are considered one of the promising bio sources that can be used in bioceramics rich with calcium and other valuable trace elements production. So, recycled biowaste materials act as a calcium precursor to synthesize hydroxyapatite (HAp) with a stochiometric Ca/P ratio of 1.67.
The clinical applications of HAp are limited due to its brittleness, poor mechanical properties and low biodegradation. Therefore, HAp incorporation with other materials can enhance mechanical resistance, osteoconductivity and biodegradability. For this aim, this thesis discusses the fabrication and characterization of some bioceramics based on hydroxyapatite and calcium magnesium silicate, especially akermanite. The thesis is divided into three main chapters: the introduction and literature survey, the experimental part and the results and discussion.
Chapter one: Introduction
The introduction includes the main objective of the study, highlighting the bone microstructure structure and its chemical composition, bone grafting, properties of biomaterials, bioceramics materials especially hydroxyapatite and its preparation methods. Biogenic hydroxyapatite sources gained the most attention, hydroxyapatite-based ceramics composites like calcium magnesium silicate especially akermanite are also discussed.
Literature survey:
This part dealt with published research in this field, especially recent ones, for its utilization for discussing the results obtained. Therefore, the extraction of hydroxyapatite from sea shells, and preparation of dense hydroxyapatite bodies were discussed. The properties of akermanite were mentioned and discussed as well as, its composites with biogenic hydroxyapatite.
Chapter 2: Experimental part
This chapter includes the synthesis of hydroxyapatite nanoparticles (HAp, Ca10 (PO4)6(OH)2) by co-precipitation method via adding a solution of 0.5 M of calcium hydroxide (prepared from trough clamshells) and 0.3 M of phosphoric acid with a molar ratio of 1.67, stirring well at room temperature for an hour, adjusting the pH to 10-11 with ammonium hydroxide and the separation and drying of the product.
The prepared HAp powder was characterized by X-ray diffraction analysis (XRD), Fourier-transform infrared (FTIR) and transmission electron microscopy (TEM) to investigate the phase composition, the functional groups and the particle size of the formed HAp, respectively.
The produced HAp powder was used for the preparation of hydroxyapatite bodies, which were shaped by uniaxially pressing and sintered at different sintering temperatures ranging between 1200 to 1300°C to obtain the optimum sintering temperature, which achieves low apparent porosity and high bulk density.
Akermanite (AK, Ca2MgSi2O7) powder was prepared by sol-gel method and characterized by different techniques such as transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) to study the particle size and the thermal stability, respectively. The dense akermanite/ hydroxyapatite (AK/HAp) composites were prepared by adding different concentrations of akermanite (10, 20, 30 and 40 wt.%) to hydroxyapatite, and sintered at various sintering temperatures from 1200 to 1300°C to study its optimum sintering temperature.
X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to study the phase composition and microstructure of the fabricated dense HAp and AK/HAp bodies. The physical properties (apparent porosity and bulk density) and mechanical properties (bending strength and Vickers hardness) were measured. In addition, the biological properties (bioactivity and biodegradation) were studied to evaluate the prepared bodies’ bioactivity.
Chapter 3: Results and discussion
Part I:
1. The powder produced from clamshells using the indirect approach is composed completely of pure hydroxyapatite, possessing a particle size ranging between 38.51 and 99.92 nm.
2. The samples obtained from nano HAp powder were sintered at 1275°C for 2h to create sintered bodies with high density and low apparent porosity.
3. HAp bodies’ apparent porosity increases and their bulk density drops as the sintering temperature rises to 1300°C. It is due to the HAp’s partial dissociation and the creation of the β-TCP phase.
4. The HAp bodies sintered at 1275°C for 2h possess bending strengths of 38.73 ± 1.42 MPa and Vickers hardness of 856.35±36.42 MPa.
5. Based on bioactivity measurements and the in vitro tests, an apatite layer was developed on the surface of sintered HAp bodies after 28 days of immersion in 1.5xSBF.
6. The biodegradability tests for sintered HAp samples displayed that it was possessing low biodegradability.
Part II:
1. The XRD patterns of AK/HAp composite bodies sintered at 1275°C for 2h revealed the presence of strong β-TCP peaks together with calcium magnesium phosphate and whitlockite, resulting from the interaction between HAp and AK.
2. Adding AK to HAp increases the apparent porosity and decreases the bulk density due to the decomposition of HAp to the β-TCP phase.
3. The optimum sintering temperature of the AK/HAp composite is 1275°C.
4. Compared to other composites, the 10 AK/HAp composite bodies sintered at 1275°C have the best bending strength (25.01 MPa) and Vickers hardness (747.66 MPa).
5. SEM results for 10 AK/HAp composite dense bodies sintered at 1275°C for 2h showed an apatite layer formation on the sample surface and the weight loss reached 33.43% during the soaking time up to 28 days.