Patent ID: 6528214
Filing Date: 2003-03-04
Classification: B01D,C04B

Abstract:
A method of manufacturing a semi-permeable ceramic membrane for use in an electrochemical cell having an anode chamber and a cathode chamber which are separated from each other by the membrane, the method comprising:providing a mixture of at least two non-metallic mineral components comprising fine particles having an effective particle size of up to 1 &mgr;m and coarse particles having an effective particle size of above 1 &mgr;m, respectively, the fine particles having a higher coefficient of thermal expansion than the coarse particles; suspending the mixture of fine and coarse particles in a liquid to form a slurry; applying the slurry to a porous mold so as to form a green intermediate product on a surface of the porous mold in which stratification occurs as the green intermediate product is being built up such that the further away from the surface of the porous mold the lesser the content of the coarse particles and the greater the content of sub-micron fine particles; baking or firing the green intermediate product; and allowing the baked or fired product to cool to form a finished ceramic membrane having a density distribution of the fine particles that increases in one direction, in use, across the finished ceramic membrane and a density distribution of the coarse particles that decreases in the same direction across the finished ceramic membrane and in which the stratification is retained so that a zone that is remote from the porous mold and has a higher content of sub-micron fine particles and a higher co-efficient of thermal expansion comprises one surface of the finished ceramic membrane, in use, and is subjected to a reduction in its dimensions by a larger magnitude during cooling than a zone which is adjacent the porous mold and having a higher content of coarse particles which, in use, comprises an oppositely facing surface of the finished ceramic membrane and which is in a state of compression.