Hot corrosion behavior of Lu2SiO5 and La2SiO5 in a molten Na2SO4 environment: A first-principles corrosion resistance investigation. Issue 12 (15th August 2019) - Jiang, Fengrui
Abstract: The hot corrosion behavior of Lu2 SiO5 and La2 SiO5 (RE2 SiO5, RE: rare earth) under Na2 SO4 attack was investigated at temperatures ranging from 900 to 1100 °C. First-principles quantum mechanical calculations based on the density functional theory (DFT) were used to obtain the electronic structures of RE2 SiO5 . The results indicated that the hot corrosion behavior of these compounds depended on their crystal structure and the structural stability of various corrosion products. First-principles results revealed that the RE–O bond was easier to break than the Si–O bond under molten Na2 SO4 corrosion environment. In this process, Na + cations partly substitute RE 3+ cations to form NaRE silicates. Once NaRESiO4 was initially formed, cyclosilicate and apatite phases were produced sequentially as the temperature and extent of corrosion increased. In addition, Lu2 SiO5 exhibited higher corrosion stability than La2 SiO5 because of the lower distortion of the RE–O coordinated polyhedral. The Lu–O bonds showed higher bonding strengths than the La–O bonds as revealed by the density of state (DOS) and Mulliken population analyses. Furthermore, the stability of the formed NaRESiO4 increased upon decreasing the size of the RE 3+ cation. Therefore, Lu2 SiO5 was more readily formed than NaLuSiO4, and La2 SiO5 was prone to form oxyapatite NaLa9 Si6 O26 after undergoing corrosion with Na2 SO4 . Overall, Lu2 SiO5 showed better corrosion resistance to Na2 SO4 than La2 SiO5 .