The effect of temperature and initial pH on biomimetic apatite coating

Bone-like apatite coatings were prepared using a biomimetic method in a simulated body fluid (SBF). The effect of initial pH values and immersing temperatures on biomimetic apatite coating formation was studied. Three different temperatures were used in this study: 24 (room temperature), 40, and 60 degrees C. At each temperature, SBF solutions with three different initial pHs were chosen: low, medium, and high. The total inorganic carbon (TIC) content and pH-time profile of each coating system were recorded during the coating formation. The apatite coatings were characterized using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and Fourier transform infra-red (FTIR). It has been found that SBF temperature has a great effect on the bicarbonate decomposition rate. The bicarbonate ions tend to decompose faster as the temperature increases. The decomposition of bicarbonate ions results in a pH increase in the SBF. With different initial SBF pHs, the decomposition of different amounts of bicarbonate ions is required to reach the critical pH range of apatite formation. With different amounts of bicarbonate ions in the SBF, the surface morphology of the biomimetic apatite coating formed is different. Therefore, the initial pH of the SBF solution plays a vital role in controlling the surface morphology of the biomimetic apatite coating. Also, it was found that as the SBF temperature increased, the critical pH range at which biomimetic apatite coating forms decreased. The critical pH range for the SBF prepared at 24, 40, and 60 degrees C was 6.65-6.71, 6.55-6.65, and 6.24-6.42, respectively. (C) 2008 Wiley Periodicals, Inc.