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Porcelain Insulators

Nature volume 150, pages 1920 (04 July 1942) | Download Citation



WRITING in the Electrical Review of June 12, 1942, on the design of electrical insulators in relation to manufacturing processes, Dr. E. Rosenthal points out that methods of shaping ceramic materials are based on the plastic quality of the china clay and ball clay in the case of porcelain, and of clay, talcum or bentonite in the case of certain ceramics. The plasticity of ceramic materials is caused by the adsorption of water at the surface of the kaolinite crystals forming the china and ball clays, this water surrounding the clay molecule. The forces which attract the water to the molecules and crystals are electrical in origin and impart to the clay molecules their colloidal and plastic nature. The hygroscopic water and the “water of formation” form the colloidal gels which give to the clay particles their plastic characteristics. All ceramic plastic materials also contain chemically combined water of crystallization. Although ceramic articles can easily be shaped as a result of the plasticity of their raw materials, the finished materials owe their physical and mechanical properties to the crystals and to the glass matrix formed during firing at high temperatures.

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