Alkaline beta-alumina mfr. from alumina and sodium carbonate - suitable for mfg. solid electrolyte tubes used in sodium-sulphur batteries

摘要

The alkaline beta-alumina (ABA) is made by heating a mixt. of alumina and Na2CO3 powders to obtain a prescribed ratio (R) of Al2O3/Na2O; heating is in an open crucible and after cooling, the mixt. is milled and moulded to the required shape. The mouldings are sintered inside a casing made at least partly of a refractory contg. three materials: (a) a beta alumina chamotte obtd. by melting and crushing to grains of ca. 0.5 mm; (b) a cement or binder of beta alumina obtd. by reaction at 1200 degrees C of a mixt. of alpha alumina and Na2CO3, and with size 10 mu m; and (c) a sodium salt. The proportions (a:b:c) create an atmos. rich in sodium during the sintering of the mouldings. The pref. refractory (abc) contains 75% (a); 20% (b); 5% (c); and may form the casing or a lining in a concrete outer casing. The mixt. (abc) is pref. mixed with water; moulded to make casing elements; set at 80 degrees C and baked at 1200 degrees C. It is essential to avoid the loss of Na from eg. moulded ABA tubes during the sintering of the tubes.