Clay minerals, thermal behavior

Brindley, G. W. and Kikkawa, S. (1980). Thermal behavior of hydrotalcite and of anion-exchanged forms of hydrotalcite. Clays Clay Miner. 28, 87. 

Like calcite, pyrite is quite reactive and its thermal behavior is influenced by the presence of clay minerals. The initial reaction temperature of pyrite alone or in the presence of calcite alone is to... 

One of the early fields of application of DTA was in the area of clays and minerals. These compounds, which gave birth to the theory and instrumentation of the technique, have been widely investigated. DTA was used to identify clays from various locations throughout the world and was widely used to determine the free quartz content of minerals. Numerous other applications were made of DTA DSC was little used due to the low-temperature capability of the latter. Most of the interesting thermal behavior of clays and minerals occur above 500°G and frequently above 1000°C. The applications of DTA to these materials is discussed by Mackenzie et al. (62, 186-188) and many others. 

The techniques of DTA, and to some extent TG, have long been used by geochemists and others to study the thermal behavior of clays and minerals. Since many simultaneous reactions occur in clays, as well as solid-state reactions that alter the decomposition reaction, the use of other methods such as EGA, X-ray, IR. and so on, are used to supplement conventional thermal analysis techniques. Consequently, there has recently been an unusual amount of interest in the use of EGA (MS) in the study of these compounds. 

Application of multiple thermal techniques to clay mineral identification and behavior is more advantageous than applying any single technique. 

A field of growing attention is the development of polymer-clay nanocomposites due to the significant technological applications of these materials. Therefore, composite systems produced by organic polymers and clay minerals prepared at the nanoscale level, which typically present a unique layered structure, rich intercalation chemistry and availability at low cost, have been used to develop plastic materials with superior mechanical properties, molecular barrier behavior, fire retardant abilities, enhanced thermal stability, among other properties, compared to the individual polymeric materials [3-5]. 

The performance of clay-based construction products, e.g., bricks and roofing tiles, can be monitored using thermal methods. The types of raw materials, viz., clay and accessory minerals, and their reactions that occur during the firing process and the durability of clay products can be examined through the application of DTA, TG, TMA, and dilatometric methods. This is particularly important for quality control as physical and chemical behaviors are dependent on the raw material characteristics, e.g., composition, particle size, and morphology. 

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