الفهرس 
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Abstract
Highly porous alumina and ZTA bone scaffolds were fabricated from bioorganic nonwoven cellulosic fabric by sol-gel infiltration technique. Biommetic process were used to grow a bone-like calcium phosphate layer on the ceramic surface using SBF and dicalcium phosphate solutions. The scaffolds with and without coatings were characterized by FTIR, X-ray diffraction analysis (XRD), Scanning electron microscope (SEM) with energy dispersion spectroscopy (EDS) and inductively coupled plasma emission spectroscopy (ICP) measurements.
The XRD examination revealed that the main phase of alumina substrate is corundum. Aluminum titanate is present also, as a minor phase. On the other hand ZTA substrates are composed mainly of corundum, aluminum titanate and tetragonal zirconia phases.
Fired substrates physical properties showed that alumina and ZTA substrates possess high open porosity of 81.27 and 94.30 % respectively. The bending strength results of alumina and ZTA samples showed relatively low figures due to the bodies’ high open porosity.
The microstructure of the studied substrates revealed that they maintaining the microstructure features of the original template. Aluminum titanate grains are embedded mainly in the alumina grains. ZTA substrates microstructure revealed a good distribution of the zirconia grains in the alumina matrix. Zirconia particles are found to be intragranular, situated at either grain boundaries or triple points, and intergranular within alumina grains.
Changes in element concentrations of SBF due to the immersion of Al2O3 and ZTA indicate the formation of apatite on the samples surface. Once apatite nuclei are formed, they grow spontaneously by consuming the calcium and phosphorous ions from SBF.
Coating of alumina and ZTA substrates with dicalcium phosphate increases the substrates bulk density and decreases their apparent porosity. It was observed that dicalcium phosphate is transformed to tetra-calcium phosphate, as indicated by XRD examination.
Microstructure of alumina and ZTA substrates immersed in DCP depicted the evolution of the characteristic morphology of plate-like CDHA. A dense layer of CDHA consists of globules of homogeneous size and plate-like sheets was formed on the alumina substrates.
CONCLUSION
1- Porous alumina and ZTA bodies that had a porosity of 81.27 and 94.30 respectively were prepared based on rapid fluid infiltration into textile template structure.
2- The initial textile architecture may allow the fabrication of cellular ceramics with tailored pore structure.
3- It was demonstrated that the prepared bodies did ont suffer from drying or firing cracks.
4- SEM showed the fibrillar microstructure of the prepared ceramic bodies, which was supposed to offer a high potential for optimization of thermomechanical properties by tailoring the fiber microstructure and architecture in the body.
5- The bending strength varied between 4.00 and 2.75 Mpa for alumina and ZTA bodies respectively. The higher strength magnitude obtained for alumina bodies are due to less porosity and higher density.
6- The surface of the bioinert alumina and ZTA substrates can be modified by the formation of a bioactive calcium phosphate layer after soaking in SBF solution. Ca2+ and PO43- ions which are incorporated into the surface induce the nucleation of HA. The biomimetically formed CP coatings are expected to accelerate the in vivo ingrowth of bone.
7- The amount and the morphologies of the deposited calcium phosphate and CDHA were influenced by the immersion time.
8- The formation of a bioactive DCP and HA layer on the surface of alumina and ZTA substrates can be achieved by immersing the substrates in a dicalcium phosphate solution for 6 days and then firing at 1100˚C.
9- The thickness of the bioactive layer deposited on the alumina substrate was thick and dense, while that on ZTA substrate was relatively thin and contained pores.
10- The characteristics of the prepared scaffolds, such as the relatively high bending strength in comparison to HA, and homoeneous microstructure of their phases, combined with the bioactive surface produced by biomimetic coatings; which give these composites their bioactive nature; qualify them for use as implant material able to withstand mechanical stresses.