A study of water sorption effects on the microwave dielectric properties of calcium chloride/silica gel composites

The water sorption behavior of a two-phase system of calcium chloride/silica gel composite based on mesoporous and microporous silica gels as host matrices and calcium chloride as a hygroscopic salt was studied. The dielectric properties at microwave frequencies of the composites with different adsorbed water contents were also tested. It is found that the composite exhibits excellent water sorption efficiency. Water sorption increases rapidly with decreasing temperature from 100 1C to 40 1C. The dielectric constant at microwave frequencies can be predicted approximately by using the mixing model developed by Dobson. When the number of bound water molecules is less than 6, the measured data are in good agreement with the calculated results using the constant shape factor a1⁄40.5. However, when the number of bound water molecules is far more than 6, the measured data are close to the calculated results using a1⁄40.65. & 2013 Published by Elsevier B.V.