Properties of calcium phosphate bioceramic prepared by solid state and chemical route / Natasha Ahmad Nawawi
In this research, a simple solid state sintering was successfully employed to synthesize highly crystalline, high purity and single phase nanostructured hydroxyapatite powder using waste eggshells (HA-Es). The process involved mixing calcined eggshell powder and dicalcium hydrogen phosphate di-hy...
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| Format: | Thesis |
| Published: |
2017
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| Online Access: | http://studentsrepo.um.edu.my/9941/2/Natasha_Ahmad_Nawawi.pdf http://studentsrepo.um.edu.my/9941/1/Natasha_Ahmad_Nawawi_%E2%80%93_Thesis.pdf http://studentsrepo.um.edu.my/9941/ |
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| Institution: | Universiti Malaya |
| Summary: | In this research, a simple solid state sintering was successfully employed to
synthesize highly crystalline, high purity and single phase nanostructured
hydroxyapatite powder using waste eggshells (HA-Es). The process involved mixing
calcined eggshell powder and dicalcium hydrogen phosphate di-hydrate followed by a
heat treatment at 800 °C. The resultant flower-like morphology of HA-Es powder
exhibited excellent sintering characteristics. Besides that, pure HA was also synthesized
using commercial chemical as Ca precursors through two chemical methods that are wet
chemical precipitation (HA-Wp) and sol-gel (HA-Sg) for comparison study.
In conventional pressureless sintering, HA-Es was able to retain the single HA phase
stability until 1250 °C. The optimum sintering temperature for HA-Es was 1250 °C with
the overall best combination of properties being recorded: relative bulk density of 97.7
%, Vickers hardness of 5.62 GPa, excellent fracture toughness of 1.51 MPam1/2 and
average grain size was below 1 μm (0.950 μm). In contrast, the optimum sintering
temperature of HA-Wp was 1200 °C with a bulk density of 97.9 %, Vickers hardness of
4.8 GPa, fracture toughness of 1.29 MPam1/2 and average grain size of 1.62 μm. In
addition, the overall structural characterization and relative density of HA-Wp were
significantly better than that of the HA-Sg.
In microwave sintering, HA-Es was able to retain the HA phase stability up to
1200 °C and this is regarded as the optimum sintering temperature with the following
properties: relative bulk density of 96.0 %, Vickers hardness of 3.65 GPa, fracture
toughness of 1.05 MPam1/2 and average grain size of 2.08 μm. Meanwhile for HA-Wp,
the optimum sintering temperature was 1100 °C with a bulk density of 96.9 %, Vickers
hardness of 3.82 GPa, fracture toughness of 0.86 MPam1/2 and average grain size of
0.85 μm. Overall, these result revealed that the sinterability and mechanical properties of the
HA-Es produced by the conventional sintering method were significantly better than
HA-Es produced by microwave sintering method. Basically, the hardness and fracture
toughness of all HA samples were initially influenced by the increase in relative density
with sintering temperature until they reached a maximum value at a critical grain size
limit (dc). Above this critical limit, grain growth acts as the controlling parameter.
Therefore, the properties then decreased with increasing grain size despite exhibiting
high bulk density.
Both in vitro dissolution study in PBS and cell culture investigations confirmed that
conventionally sintered eggshell derived HA exhibited excellent biological
performance. In this work, sintered HA-Es at 1250 °C was found to have the best cell
response and also improved mechanical properties.
It can be suggested that the mechanical properties and the efficiency of HA in cell
response are grain size dependent activities. Smaller grain size will induce an increase
in grain boundary at the surface and therefore facilitates the cells to proliferate.
Thus, this research proved that HA synthesized from waste eggshell through solid state
method could be a potential bioceramic for use in the clinical application.
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