Chapters authored
Limestone Clays for Ceramic Industry
Limestone clays are used in the ceramic segment in the manufacture of bricks, ceramic tiles, and in the production of cement, among others. Limestone can be present in soils in pure form or as a contaminant, but always from marine environments. The limestone after burning can present a high loss of mass (35–45%), which can cause serious problems with the sintering of ceramic products such as bricks, tiles. The calcium or magnesium carbonate once dissociated forms calcium oxide (CaO) and releases carbon dioxide (CO2). CaO in contact with water subsequently experiences very high expansions that can cause cracks in the materials. Researchers have studied procedures to inhibit limestone action on clays as well as to set the correct temperature for firing. In this chapter, examples of clays with different percentages of calcium carbonate (CaCO3) that are used in the ceramic segment and their characteristics will be given.
Part of the book: Clay Science and Technology
Chemical, Mineralogical, and Rheological Characterization of Regional Clays for Potential Use in Cosmetics and Pharmaceutical Products
Four clay samples from different deposits in the state of Sergipe, Brazil, were fractionated by dispersion and centrifugation for comparative tests with a standard commercial clay used for cosmetic and pharmaceutical purposes. For this, they were characterized by X-ray diffraction, X-ray fluorescence spectroscopy, measurements of cation exchange capacity, oil absorption and viscosity, in addition to particle sizes and plasticity indexes. The objective was to determine the physical and chemical properties of raw clays and the consequent granulometric fractions to evaluate their potential use in products with high added value. After fractionation, the samples showed significant amounts of smectite and kaolinite, which combined with the size, particle distribution, chemical composition, and high adsorption capacity, especially in the PDL and PV samples, make them potentially interesting for applications in pharmaceutical and cosmetic products, they can also be used in spas and esthetic centers for therapeutic purposes based on their softness and cation exchange capacity.
Part of the book: Clay and Clay Minerals