Influence of pH on dispersion stability of a ceramic glaze and its components

• Main Authors: Thongphrom S., Watanesk R., Keowkamnerd K., Watanesk S., Arquero O., Beckett R.
• Format: Article
• Language: English
• Published: 2014
• Online Access: http://www.scopus.com/inward/record.url?eid=2-s2.0-0038487671&partnerID=40&md5=781a1904dc532f5e9f976f53400d62f4; http://cmuir.cmu.ac.th/handle/6653943832/6086
• Institution: Chiang Mai University

The stabilities of dilute dispersions of a glaze and its components, kaolin, feldspar, quartz and calcium carbonate at pH 2...10 were investigated by monitoring their turbidities after settling. It was found that the turbidity of kaolin was high compared with the others across the whole pH range; especially at pH 10 where its turbidity reached a maximum value. Moreover, the turbidity of kaolin at pH 10 was almost unchanged after settling for 5 min, in contrast to the others whose turbidities decreased with settling time. The kaolin dispersion at pH 6, which is close to its point of zero charge, produced the lowest turbidity due to particle agglomeration and settling. The turbidities of feldspar and quartz were independent of pH. The stability of the calcium carbonate dispersion depended greatly on the pH as evidenced from the drastic increase in turbidity in basic media. In acidic solution, the calcium carbonate dissolved producing an almost clear solution. In addition, the stabilities of concentrated slurries of kaolin and the glaze mixture were also examined by monitoring their viscosities at various pH-values. The results indicated that the maximum viscosities of kaolin and glaze were obtained at pH levels of 6 and 7, respectively, which are also close to their point of zero charge. This is evidence for network aggregate occurring at this pH range.