الفهرس 
COVEROnly 14 pages are availabe for public view
 |  | from | 180 |  |  |
| | | from | 180 | | |
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.
Summary
II
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.
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 PO4
3-
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.