Characterization and Evaluation of Ceramic Properties with Spherical and Prismatic Samples of Clay Used in Red Ceramics

The Brazilian red ceramic industry monthly consumes about 10.3 million tons of clay, its main raw material. In most potteries, characterization of the clay is made empirically, which can result in roof tiles and blocks not according to standards. In this sense, this paper aims to characterize clays used in the manufacturing of red ceramic products in a factory located in Colatina-ES, which appears as a ceramic pole with about twenty small and midsize industries. The clays were characterized by: X-ray fluorescence, X-ray diffraction, thermal analysis (DSC/TG), granulometry, Atterberg limits and content of organic matter. Specimens of clay and mixture containing four clays were shaped. Specimens were shaped, dried at 110°C, and burned at 850ºC in an industrial furnace-type tunnel for 24 hours. The ceramics and mechanical properties evaluated were: mechanic strength, water absorption, apparent porosity, apparent specific mass and shrinkage by drying and firing. The characterization showed that kaolinitic clay presents high plasticity, but high porosity. The mixture formed by the four clays does not meet the requirements of the Brazilian standard clays for red ceramic. It is possible to confirm the use of the methodology of the spheres in potteries for analysis of ceramics raw materials.巴西红色陶瓷产业每月消耗约1030万吨黏土作为其核心原材料。多数陶瓷生产厂对黏土的性能表征均采用经验式方法，这可能导致所生产的瓦件与砌块不符合相关标准要求。基于此背景，本文旨在对位于圣埃斯皮里图州科拉蒂纳市（当地为聚集约20家中小型企业的陶瓷产业集群）的一家工厂内，用于制造红色陶瓷制品的黏土开展性能表征研究。本次研究采用以下手段对黏土进行表征：X射线荧光光谱（X-ray fluorescence）、X射线衍射（X-ray diffraction）、热分析（差示扫描量热法/热重法，DSC/TG）、粒度分析、阿特伯格极限（Atterberg limits）以及有机质含量测定。分别制备单一黏土试样与四种黏土混合试样并完成成型，将成型后的试样置于110℃环境下干燥，随后在隧道式工业窑炉中以850℃煅烧24小时。本次研究评估的陶瓷性能与力学性能包括：力学强度、吸水率、显气孔率、表观比质量，以及干燥与煅烧收缩率。表征结果显示，高岭石质黏土具备较高的塑性，但同时孔隙率亦偏高；由四种黏土混合而成的混合料不符合巴西红色陶瓷用黏土的相关标准要求；本研究可证实，陶瓷生产领域中用于陶瓷原料分析的球团分析法具备可行性。