Design of experiment (doe) study of hydroxyapatite (ha) for load bearing application via 2k factorial design
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Date
2013-08-01
Authors
Nurul Shafyra Mohd Sabri
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Abstract
The present study aims to fabricate hydroxyapatite (HA)/alumina (Al2O3) biocomposite via dry mixing process, in order to evaluate the experimental factors and their effects (main effects and interaction effects) on the response or final biocomposite characteristics (hardness, density, and porosity). These effects were quantified using Design of Experiments (DOE) to develop mathematical models. This study covered two parts where the part I deals with the sample preparation procedures which was started with the characterization of raw materials in term of physical, structural (phases) and chemical properties. This procedure was followed by the fabrication of HA/Al2O3 biocomposite with different parameter setting (sintering temperature; 1100 ºC and 1250 ºC, mixing time; 3 hours and 9 hours and Al2O3 composition; 0wt% and 30 wt%). The experiment was run by following the run order suggested by DOE software (Minitab 16) through randomization stage. Next, the physical properties was characterized using density and porosity testing while the morphology of the sample was studied using Scanning Electron Microscopy (SEM). For phase analysis, the sample was characterized through X-ray Diffraction analysis and Vickers hardness testing was employed to study its hardness. In part II, two-level (2k) factorial method of DOE was employed to determine the suitable or significant factors in producing high strength HA/Al2O3 biocomposite. The experimental factors were analyzed and the significant factors were
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determined through regression model and Analysis of Variance (ANOVA). The model was then validated through ANOVA in order to study how fit is the model with the experimentally obtained data. Experimental errors and interactions between factors were investigated to verify the significant between predicted and experimental data. Results shows that Al2O3 composition and sintering temperature has given a significant effects on the responses while mixing time has given no influence. For hardness response, it shows that, in order to obtained a high hardness, the sintering temperature must be set above 1240 ºC with Al2O3 composition lower than 3 wt%. The same requirement goes to porosity response where sintering temperature must be above 1188 oC with Al2O3 composition below 7 wt% in order to obtained 5-10 % porosity. For density response, acceptable density that mimicking the natural dense male and female bone density (3.88 g/cm3 for male; 2.90 g/cm3 for female) can be obtained by setting the sintering temperature above 1180 oC and Al2O3 composition below 30 wt% or sintering temperature above 1200 oC and Al2O3 composition above 10wt % respectively. The most significant parameters that effecting all the response are Al2O3 composition and sintering temperature.