(中南大學(xué) 冶金科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 研究磷酸改性對氫氧化鋁物相、形貌、表面基團及熱穩(wěn)定性的影響，并從動力學(xué)與熱力學(xué)角度分析磷酸改善氫氧化鋁熱穩(wěn)定性的機理。采用磷酸改性處理可提高氫氧化鋁粉體的熱穩(wěn)定性，其直接的原因是改性后粉體表面形成耐熱鋁鹽包覆層；改性氫氧化鋁熱穩(wěn)定性提高的動力學(xué)原因是，顆粒受熱分解產(chǎn)生的水蒸氣在向外擴散時，除需克服分解產(chǎn)物層的擴散阻力外，還要克服其在包覆層中的動力學(xué)阻礙；改性氫氧化鋁熱穩(wěn)定性提高的熱力學(xué)原因是，包覆層使氫氧化鋁內(nèi)核表面的水分子濃度提高，使得氫氧化鋁分解反應(yīng)的平衡水蒸氣分壓增大，從而相應(yīng)提高分解溫度。
關(guān)鍵字: 氫氧化鋁；磷酸改性；包覆層；熱穩(wěn)定性；機理
phosphoric acid
（School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of modification by phosphoric acid on phases, morphologies, surface groups and thermal stability of aluminum hydrate (AH) were investigated, and the mechanism of phosphoric acid improving thermal stability of AH was analyzed from views of kinetics and thermodynamics. The modification by phosphoric acid can improve thermal stability of AH, which attributes to the formation of heat resistant aluminum salt coating on the surface of AH particles caused by the inter-reaction between phosphoric acid and AH particles. The mechanism of improving thermal stability of modified AH is that, according to kinetics of the water vapor produced by decomposing modified AH diffuses, it has to get over not only the diffusion resistance of decomposed product, but also the kinetics resistance of coating layer. According to thermodynamics, AH decomposing the water vapor on the surface of AH kernel increases the equilibrium press of water vapor, thus, the decomposing temperature rises.
Key words: aluminum hydrate; phosphoric acid modification; coating; thermal stability; mechanism
