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材料手册 5 陶瓷、耐火材料、玻璃、聚合物、弹性体 英文版_24.docx

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Raw Materials for Ceramics, Refractories and Glasses 607irreversibly. The rate of transformation into a-Al2O3depends on the residence time of the aluminumhydroxide at these temperatures. The transformation is usually complete after a few hours at morethan 1250°C. Calcined aluminas are prepared by calcination of aluminum hydroxide performed inrotary kilns, fluidized-bed kilns, or tunnel kilns. The a-Al20, crystallites give a polycrystallineproduct that becomes friable. Calcined aluminas are offered in a wide variety of technical gradesfrom those containing 100 wt.% a-Al2Oj to grades containing some sodium such as soda-alumina,also calledbeta alumina[NaAlHO17= Na2O-llAl2OJ, the remaining component being unreactedtransition alumina. Some halogenated compounds (e.g., BFp SCI,) called mineralizers are used tocatalyze the nucleation of the a-Al2O5crystallites. The mineralizers also form volatile sodiumchloride (NaCl), which removes the sodium. Calcined alumina consists of a-Al2O5crystallite
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Term
Spring
Professor
LeonorCeballos
Tags
Sodium, Aluminium, Sodium chloride, Sodium hydroxide, Tabular Alumina

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