Electrophoretic deposition of kaolin: effects of Al/(Al + Si) ratio, surface charge, mineral, structural and morphological properties

Aluminosilicate compounds such as zeolite and kaolin and their coatings can be useful as a support of sensors and absorbers. In this study, electrophoretic deposition (EPD) of four types of kaolin has been reported. Various types of kaolin differ from each other in Al/(Al + Si) ratio, mineral compositions, surface charge and size of kaolinite flakes. EPD in aqueous and non-aqueous (ethanol) suspensions were compared. Quality of deposition and yield of non-aqueous suspension was higher due to the higher current density which can be resulted from lower polarity index of ethanol. It was found that the kaolin sample with the highest ability of ion extracts, higher zeta potential in the wide range of pH (−20 to −60 mV) and larger diameter of basal surfaces with respect to edge size of kaolinite flakes were essential factors to obtain completely coverage of aluminum substrate below 15 min. This kaolin coating can be useful in sensors and catalysts, because of high surface area in contact with gas molecules.