Novel High-Temperature-Resistant Phosphates: Thermal Ablation Behavior of La–Al System Phosphates at 2000 °C

Abstract

The saturation-free and directionless cross-linking and interpenetration processes between La 3+ and [(H 2 PO 4 )2Al(HPO 4 )]-plasma in La−Al phosphate by mixing Al(OH) 3 , CrO 3 , and H 2 O 2 dissolved in H 3 PO 4 and La 2 O 3 as a curing accelerator, as well as the thermal stability of the La−Al phosphate bulk materials and the evolutions of the phase composition and morphology at different temperatures were studied using thermogravimetric/differential scanning calorimetry under different temperatures in a muffle furnace. The La−Al phosphates showed good thermal stability, and the thermal weight loss rate of the materials decreased from 18% before heat treatment to ∼2% after heat treatment. In addition, the La−Al phosphate bulk material showed excellent resistance to ablation when subjected to ablation by an oxyacetylene flame at 2000 °C for 30 s. It evolved into a dense LaPO 4 and AlPO 4 high-temperature phase layer on the sample surface, which prevented further ablation damage to the sample and significantly improved the temperature resistance of the La−Al phosphate bulk material.