ATR-FTIR spectra of the CSP-sintere

ATR-FTIR spectra of the CSP-sintered samples were collected to evaluate how CSP affected local chemical environment of calcium phosphate. Broad, superimposed absorption bands that are characteristic to amorphous materials were observed in IR spectrum of the starting ACP powder and in the spectra of the CSP-sintered samples that were produced from the dry starting ACP powder at room temperature, 100 and 120 ◦C (Fig. 2A). Absorption bands around 550 and 1000 cm−1 were assigned to ν3 and ν1 PO43- group vibrations, while the bands in the range of 1420–1490 and 871 cm-1 to carbonate vibrations. In addition, the bands at 1640 cm-1 and in the range of 2700 – 3500 cm−1 were attributed to H–O–H bending and O–H stretching modes, respectively. All these bands become sharper and some of them were shifted to higher wavenumbers in the IR spectra of the sample sintered at 150 ◦C. Furthermore, additional absorption bands around 470 and 600 cm-1 appeared in this sample spectrum. From the CSP-sintered samples that were produced from the moistened ACP powder, only the sample sintered at room temperature had similar IR spectra to the starting ACP powder (Fig. 2B). IR spectra of the samples that were sintered at higher temperatures resembled spectrum of the sample that was made from the dry ACP powder at 150 ◦C (Fig. 2A). Intensity of absorption bands around 470 and 600 cm-1 increased with increased sintering temperature of these samples.