Quality Сontrol of Metakaolin by the Method of Spectroscopy in the Near Infrared Region of the Spectrum
The express-method for control of kaolin calcination in terms of spectra of diffusion reflection in UV-VIS-NIR-field is proposed. The stages and temperature ranges of the heat treatmentwithin the range of 600-1000оC of the transformation of kaolinite to metakaolinite in terms of changes in the spectrum profile and the square of the characteristic bands of OH andAI-OH centers in the NIR field are determined. It is established that the greatest decrease in the absorption area of the OH center and the disappearance of structuring of OH and AI-OHcenters is connected with almost complete dehydroxylation of kaolinite. Structural disordering of metakaolinite is most clearly interconnected with the reduction of the band square ofAI-OH center. The advantage of measuring the spectra of diffusion reflection in the near infrared area comparing with infrared transmission spectra is shown: there is no need for samplepreparation, the measurement is performed in situ and in on-line regime.