Abstract：Changbaishan diatomite was treated under the conditions of temperature from 100 to 1 330 ℃, and examined by infrared spectroscopy applying the KBr-technique. In the range from 250 to 1 500 cm-1, the spectra of the samples at 100 to 1 100 ℃ show the same three characteristic broad bands at 1 100, 801 and 471 cm-1, which are similar to amorphous silica. Besides the above three broad bands, the spectra of 1 200 and 1 330 ℃ treated samples eｘhibit three new bands at 618, 386 and 301 cm-1, which indicate that the diatomite transforms into cristobalite. While all of the eleven samples show an asymmetric broad band at 3 440 cm-1 in the range from 3 000 to 4 000 cm-1, the spectrum of 500 ℃ treated sample begins to eｘhibit a 3 745 cm-1 band assigning to isolated Si—OH group stretching vibration. The 3 745 cm-1 band shows the highest intensity at 900 ℃, and disappears at 1 200 ℃. According to the absorbance of the 3 745 cm-1 band of different temperature treated samples, the H2O content in the form of Si—OH group was calculated semi-quantitatively, which indicates that the Si—OH group exists at the internal structure defects in addition to eｘisting at the surface. The transform mechanism of diatomite into cristobalite was also discussed.
