STRUCTURE OF ZIRCONIUM-PHOSPHATE GELS PRODUCED BY THE SOL-GEL METHOD

Several zirconium phosphate (ZrP) gels of various water contents produ ced by a sol-gel method were investigated. They were found to be the p olymer-class gels using the method of small-angle neutron scattering. X-ray diffraction analysis revealed that their solid-phase framework w as formed from branched fragments (layers and blocks) of alpha-ZrP cry stal structure. These gels are strongly fluctuating systems when they are on the scale of r < xi. Their fluctuation character is shown to be described by two parameters: a correlation radius xi and a fractal di mension D. It was found that xi approximate to 2.5 nm and almost did n ot depend on the water content and that D increased from 1.4 +/- 0.25 to 2.6 +/- 0.20 when the water content decreased from 50% to 0% as the gels were dried to a temperature of 105 degrees C. Simultaneously, su bstantial shrinkage of granules, a decrease in porosity and ion-exchan ge capability, and formation of blocks from alpha-phosphate layers occ urred with alpha decrease in the water of the hydrogel as it dried. A probable description of the evolution of the ZrP-gel structure with va riation in the water content during drying is suggested on the basis o f the data obtained.