Synthesis of hydroxyapatite powders via mechanical activation technique
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Date
2007
Authors
Omar, Zarina
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Abstract
A preliminary experiment on low-speed ball-milling was carried out using calcium
pyrophosphate and calcium carbonate (Ca2P2O7 – CaCO3) as starting materials with an
addition of some amount of distilled water to produce hydroxyapatite (HA),
Ca10(PO4)6(OH)2. The mixtures were milled for 8 hours using two equipment i.e. millingmixer
and roll-mill. The milled mixtures were subsequently calcined at 1100 °C and was
found that both methods successfully formed a single-phase HA. A more detailed study of
the same mixtures but with mechanical activation being effected using a high-speed
planetary ball-mill for different milling durations, calcination temperatures and milling cycles.
The phase changes after each milling condition were analysed by x-ray diffraction (XRD)
before and after calcination. Thermogravimetry and differential scanning calorimetry
(TG/DSC) were conducted on the as-milled samples to determine the thermal behavior
upon heating. Other analysis was also carried out such as particle size analysis, x-ray
fluorescence (XRF) and fourier transformation - infra red (FT-IR) spectroscopy. Phase
transformations were found to take place upon milling to produce a few intermediate
phases other than the starting materials, which were finally transformed to a single-phase
or mixed HA upon calcination. It was found that the optimum calcination temperature is
influenced by the milling duration as well as the milling cycle. The lowest calcination
temperature obtained in this work to form a single-phase hydroxyapatite (HA) is 900 oC
after 6 hours milling using a cycle of 30 minutes milling and 2 minutes pause. This is
obviously a significant improvement to the current status in forming a single-phase HA,
which requires a calcination temperature of 1100 oC after 8 hours of milling.
Description
Master
Keywords
Materials and Mineral Resources Engineering , Hydroxyapatite powders , Mechanical activation technique