Thermal transformations of gamma alumina with phosphorus oxide surface nanostructures

Resumo

Differential scanning calorimetry, thermogravimetry, and X-ray diffraction analysis were used to study the fundamental aspects of structural-chemical transformations occurring under the action of temperature in the range 50–1530°C in the system constituted by alumina core and phosphorus oxide shell synthesized by the molecular-layering method. It was shown that, as the P/Al molar ratio in the system increases from 0.05 to 0.14, the stability range of low-temperature forms of alumina extends to higher temperatures because crystalline aluminum phosphate is formed on the surface. It was demonstrated that using an inorganic binder based on a silicate binding agent and alumina modified with an aluminum phosphate layer provides a ~3.5-fold increase in the mechanical strength of the material at a ~5-fold decrease in the internal stress as compared with the composition with the unmodified oxide.