[Infrared spectroscopic study of Changbaishan diatomite]

Changbaishan diatomite was treated under the conditions of temperature from 100 to 1330 degrees C, and examined by infrared spectroscopy applying the KBr-technique. In the range from 250 to 1500 cm(-1), the spectra of the samples at 100 to 1100 degrees C show the same three characteristic broad bands at 1100, 801 and 471 cm(-1), which are similar to amorphous silica. Besides the above three broad bands, the spectra of 1200 and 1330 degrees C treated samples exhibit three new bands at 618, 386 and 301 cm(-1), which indicate that the diatornite transforms into cristobalite. While all of the eleven samples show an asymmetric broad band at 3440 cm(-1) in the range from 3000 to 4000 cm(-1), the spectrum of 500 degrees C treated sample begins to exhibit a 3745 cm(-1) band assigning to isolated Si-OH group stretching vibration. The 3745 cm(-1) band shows the highest intensity at 900 degrees C, and disappears at 1200 degrees C. According to the absorbance of the 3745 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.