Fabrication of glassy membrane filters and characterization of its hydrophilic nature by thin layer wicking approach

Contact angle measurement of porous ceramics is difficult by goniometry application and it is impossible to determine where the water drops are immediately absorbed by the filter pores if the porous sample is of capillary type. The dynamic wicking approach is a potential technique for the contact angle measurement of capillary materials. In this study, different microstructures of glassy membrane filters were prepared and the water contact angle was determined by using thin layer wicking approach. The success of wicking results was examined. The glassy filters were shaped by two techniques (slip casting and pressing) and they were sintered at different temperatures (900, 950, 1000 and 1050 °C). Results indicated that both the shaping techniques and sintering temperature produced different microstructures and the contact angles obtained by the wicking approach were consistent with the hydrophilic nature of the filter materials. Low temperature sintering did not produce a sufficiently good glassy dispersion and high temperature led to crystallization. The best glassy filter was obtained at moderate temperatures: the sintering temperature being at 900 °C and 1000 °C for the material shaped by pressing and slip casting, respectively. At these temperatures, the glassy pore wall microstructure without crystallization could be obtained. The wicking results have been correlated with the hydrophilic nature of the filters so that the measured water contact angle was equal to or lower than 11°. Normally, the crystallization of the glassy material decreases the hydrophilic nature of the filters and the obtained wicking results are consistent with the phenomena and indicated higher contact angles.