Formation mechanism and crystal simulation of Na₂O-doped calcium aluminate compounds

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• 作者：Yong-pan TIAN ; Xiao-lin PAN ; ^{panxl@smm.neu.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Hai-yan YU ; Gan-feng TU
• 关键词：calcium aluminate ; Na2O-doping ; formation mechanism ; crystal structure ; sintering ; computer simulation
• 刊名：Transactions of Nonferrous Metals Society of China
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：26
• 期：3
• 页码：849-858
• 全文大小：2720 K

文摘

Calcium aluminate clinkers doped with Na₂O were synthesized using analytically pure reagents CaCO₃, Al₂O₃, SiO₂ and Na₂CO₃. The effects of Na₂O-doping on the formation mechanism of calcium aluminate compounds and the crystal property of 12CaO·7Al₂O₃ (C₁₂A₇) cell were studied. The results show that the minerals containing Na₂O mainly include 2Na₂O·3CaO·5Al₂O₃ and Na₂O·Al₂O₃, when the Na₂O content in clinkers is less than 4.26% (mass fraction). The rest of Na₂O is mainly doped in 12CaO·7Al₂O₃, which results in the decrease of the crystallinity of 12CaO·7Al₂O₃. The crystallinity of 2Na₂O·3CaO·5Al₂O₃ is also inversely proportional to the Na₂O content in clinkers. The formation processes of 2Na₂O·3CaO·5Al₂O₃ and 12CaO·7Al₂O₃ can be divided into two ways, which are the direct reactions of raw materials and the transformation of CaO·Al₂O₃, respectively. The simulation shows that the covalency of O—Na bond in Na₂O-doped 12CaO·7Al₂O₃ cell is weaker than those of O—Ca and O—Al bonds. The free energy of the unit cell increases because of Na₂O doping, which results in the improvement of chemical activity of 12CaO·7Al₂O₃. The leaching efficiency of Al₂O₃ in clinker is improved from 34.81% to 88.17% when the Na₂O content in clinkers increases from 0 to 4.26%.