ИСТИНА

Graphite-based low-dense carbon materials are widely used in the production of sealing materials and oil adsorbents. Traditional procedure technique of these materials consists of several steps. First step is expandable graphite obtaining included natural graphite intercalation by nitric or sulfuric acids and following hydrolysis. After that expandable graphite is subjected to momentary heat at 900-1000 oC that leads to formation of exfoliated graphite with bulk density of 2-5 g/l. There is much research on Bronsted acids intercalation into graphite. However destruction of expandable graphite by thermal shocking, in which many harmful gases evolves, is not still investigated. Our work is devoted to the study of this stage. New technique of gas determination in thermal destruction of expandable graphite produced from graphite nitrate II-IV stages has been offered. Its correctness was confirmed by thermogravimetry and infrared spectroscopy. Static and dynamic modes were chosen to thermal destruction of expandable graphite. Static mode was carried out in three types of atmospheres: oxidizing, inert and reducing. Systematic analysis of the gases evolved during the thermal decomposition of expandable graphite is presented. The composition of these gases was found to depend on initial graphite nitrate stage number and atmosphere in which it was expanded. Dynamic mode was realized in argon atmosphere. Two-steps of gas evolution with increase of temperature were registered in dynamic mode. The same two-steps effect was observed on thermogravimetry curves and infrared spectra. Dynamic mode allows determining of chemical reactions carrying out in thermal destruction.