Study of carbonitriding reactions of bentonites

Natural aluminosilicates can be treated by means of carbonitriding reactions (i.e., reduction with carbon and simultaneous nitriding). Phases of the SiAlON system are obtained from clay minerals, andalusite, diatomite, etc. Especially β′-sialons are important due to their technological applications. The products obtained depend on the raw materials were studied. The reaction was carried out this paper carbonitriding reactions of three bentonites were studied. The reaction was carried out in the range 1320–1480°C using carbon black as reducing agent in a N2 atmosphere. Evolved phases and mechanisms were studied using XRD and SEM. Predominant products depend on the carbon/mineral ratio, composition, temperature and reaction time. Low carbon/mineral ratio mainly generates, β′-sialons. More reduced compounds as SiC and A1N appeared at high ratios. SiC is an intermediate compound. The mechanism involved is a carbonitriding reaction of a glassy phase resulting from the thermal decomposition of bentonite.