Feng Yuan, Li Mao, Hou Wenyuan, Cheng Benjun, Wang Jiaoru, Li Hesong
School of Energy Science and Engineering, Central South University, Changsha 410083, China.
ACS Omega. 2021 Jan 25;6(5):3745-3751. doi: 10.1021/acsomega.0c05339. eCollection 2021 Feb 9.
A new method for the disposal of the spent refractory materials by adding them directly to electrolytic cells requires our better knowledge of the NaAlF-AlO-SiO melt system. The development of computational materials science offers us a new way to avoid the limitation of the experiment under a strong corrosive environment at high temperatures. First-principles simulation is applied to study the structure information, electronic properties, and transport properties of the system. The study reveals that the main Si and Al ions in the melt are complex ion groups such as [SiFO], [SiFO], [SiFO], [AlFO], [AlFO], and [AlFO]. Tangled structures like [SiAlOF] also exist in the melt. The average coordination number of Al-F and Si-F is 3.21 and 2.45, respectively. O ions mainly act as bridge ions in the melt. The bonding ability of Al with O ions is stronger than that of Si with O ions. Moreover, the Al-O bond is mainly covalent, while the Al-F bond is basically ionic characters. The order of diffusion ability of ions from large to small is Na, F, Al, Si, and O. Addition of SiO into the NaAlF-AlO molten salt causes an increase of the viscosity and a decrease of ionic conductivity.
一种通过将废旧耐火材料直接添加到电解槽中来处理它们的新方法，需要我们更好地了解NaAlF - AlO - SiO熔体系统。计算材料科学的发展为我们提供了一种新方法，以避免在高温强腐蚀环境下实验的局限性。应用第一性原理模拟来研究该系统的结构信息、电子性质和输运性质。研究表明，熔体中的主要Si和Al离子是诸如[SiFO]、[SiFO]、[SiFO]、[AlFO]、[AlFO]和[AlFO]等复合离子基团。熔体中也存在像[SiAlOF]这样的缠结结构。Al - F和Si - F的平均配位数分别为3.21和2.45。O离子在熔体中主要充当桥连离子。Al与O离子的键合能力强于Si与O离子的键合能力。此外，Al - O键主要是共价键，而Al - F键基本上具有离子特性。离子扩散能力从大到小的顺序是Na、F、Al、Si和O。向NaAlF - AlO熔盐中添加SiO会导致粘度增加和离子电导率降低。
