Synthesis of high-surface-area complex zirconium phosphates via mechanochemical activation route

摘要

High-power ball mill activation of the mixture of hydrated zirconium and lanthanum salts (oxonitrates. oxochlorides) with ammonium phosphate followed by hydrothermal treatment at temperatures not exceeding 200 DEG.C and a nearly neutral PH was found to yield crys- talline dispersed phase of a cubic NH4Zr2(PO4.)3 type along with admixtures of disordered orthorhombic com- pounds of a zirconium orthophosphate type. In the same conditions and at the same Zr/P ratio, hydrothermal treatment of gels obtained by reacting mixed zirconium and lanthanum nitrates solutions with ammonium phos- phates yields no crystalline products, and only treatment in acid media generates a phase of the alpha-ZrPO4(OH) type coexisting with the NH4Zr2(PO4)3 phase if polyeth- ylene oxide is present. X-ray powder diffraction, trans- mission electron microscopy, 31MAS-NMR, FTIRS and thermal analysis were applied to elucidate factors affect- ing crystallization of complex zirconium phosphates in the hydrothermal conditions. The most essential factor appears to be generation of some nuclei of zirconium phosphates under high pressures developed in the course