Biomaterials-Hydroxyapatite and Titania


Nanocrystalline hydroxyapatite (HAp) powder of size 10-20 nm was synthesized applying microwave radiation using calcium nitrate tetrahydrate and sodium phosphate dibasic anhydrous as the starting materials. Microwave power of 600 W and Ca/P ratio of 1.66 in the starting chemicals served as the major factors in the synthesis of nanocrystalline HAp powder. Phase composition and evolution were studied using X-ray diffraction (XRD) technique. Morphology, agglomeration and particle-size of the synthesized powder were studied using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques. Energy Dispersive Spectrum (EDS) was used to determine the elemental composition of the powder. Thermal properties were investigated using Thermogravimetric (TG) and Differential Thermal Analysis (DTA) and, Fourier Transform Infrared Spectroscopy (FTIR). As-synthesized HAP and TiO2 powder was uniaxially compacted into cylindrical pellets at a pressure of 78.69 MPa and sintered at high temperature to examine the effects of sintering on nano powder particles, densification behavior, phase evolution and mechanical properties. Phase evolution was studied using XRD whereas microstructure evolution was studied by SEM. To determine the mechanical properties Vickers hardness and biaxial flexural strength tests were performed. Biodegradability and biomechanical strength of nano-HAp and TiO2 samples sintered at high temperature was assessed in Simulated Body Fluid (SBF) having ionic concentration as that of human plasma. Biodegradation and change in mechanical properties of the sintered samples when kept in SBF and maintained in a dynamic condition were studied in terms of weight loss, change in Vickers hardness and biaxial flexural strength as a function of time. Highly crystalline HAp powder was achieved after microwave synthesis with average particle size in the range of 10-20 nm which was further confirmed by HR-TEM and SEM. Calcination of the synthesized powder at 500[degrees]C for 2 h increased the average particle size to 21 nm. EDS confirmed the elemental composition of the powder. FTIR analysis showed the presence of phosphate band which confirmed the presence of HAp at high temperature. TG analysis showed 23% weight-loss upon heating up to 1200[degrees]C, contributed by the removal of adsorbed and possible lattice water, decarboxylation of HAp or condensation of HPO42- releasing water. HAp along with [Beta]NaCaPO4 and Na3Ca6(PO4)5 was observed at 950[degrees]C, 1100[degrees]C and 1200[degrees]C. Density of HAp samples continued increasing with the increase in temperature from 1100[degrees]C to 1250[degrees]C and sintered density of 2.88 g/cc was obtained at 1250[degrees]C. Hardness and Biaxial strength of the HAp samples increased with temperature and maximum hardness value of 249.53 [plus or minus] 3.98 HV and biaxial flexural strength of 52.07 [plus or minus] 4.96 MPa were observed for samples sintered at 1250[degrees]C. Biaxial strength and hardness of TiO2 samples increased with temperature. Maximum biaxial flexural strength of 125.5 [plus or minus] 11.07 MPa and maximum hardness of 643.27 [plus or minus] 7.96 HV were observed for the TiO2 sample sintered at 1500[degrees]C which was much more than that of sintered HAp samples. Decrease in mass, hardness and biaxial strength of HAp samples sintered at 1250[degrees]C and TiO2 samples sintered at 1400[degrees]C showed biodegradation in SBF, maintained in a dynamic state, as a function of time. Increase in mass was observed for the HAp samples in SBF during the fourth week.


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Graduation Date





Kalita, Samar


Master of Science in Materials Science and Engineering (M.S.M.S.E.)


College of Engineering and Computer Science


Mechanical, Materials, and Aerospace Engineering

Degree Program

Materials Science and Engineering








Release Date

December 2007

Length of Campus-only Access


Access Status

Masters Thesis (Open Access)