{"title":"Structural behavior of F− in mould flux melt of CaO-SiO2-Al2 O3-Na2 O-CaF2 system","authors":"Qiang Gao , Yi Min , Cheng-jun Liu , Mao-fa Jiang","doi":"10.1016/S1006-706X(17)30167-X","DOIUrl":null,"url":null,"abstract":"<div><p>The influence of fluorine on the structure of CaO-SiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub>-Na<sub>2</sub>O-CaF<sub>2</sub> continuous-casting-type slag was measured by Raman spectroscopy, and the degree of polymerization of mould flux and the structural behavior of F<sup>−</sup> in the melt were investigated by classifying and quantifying the structural species of F<sup>−</sup> ions. The results exhibit that the main structural units of Si-O tetrahedra are Q<sup>0</sup>, Q<sup>1</sup> and Q<sup>2</sup> and the actual measured number of non-bridging oxygen ions in the [SiO<sub>4</sub>]-tetrahedra (denoted by NBO/T) increases from 2. 73 to 3. 44 with increasing the molar ratio of F to (F+O) (denoted by <em>X</em><sub>F</sub>/<em>X</em><sub>(F+O)</sub>) from 0. 06 to 0. 19. It means that the degree of polymerization of melt structure decreases with an increase in <em>X</em><sub>F</sub>/<em>X</em><sub>(F+O)</sub>. In addition, most of F<sup>−</sup> ions were distributed in Si-O tetrahedra and Al-O tetrahedra. With increasing <em>X</em><sub>F</sub>/<em>X</em><sub>(F+O)</sub>, the complex structural units Al-O tetrahedra are gradually replaced by discrete structural units AlF<sup>1–</sup> because of the breakage of Al-O bonds in Al-O tetrahedra by F<sup>−</sup> ions, and the Si-O (bridging oxygen) bonds of Si-O tetrahedra are broken to form [SiO<sub><em>n</em></sub>F<sub>1–<em>n</em></sub>]-tetrahedra by F<sup>−</sup> ions coordinating with Si<sup>4+</sup>.</p></div>","PeriodicalId":64470,"journal":{"name":"Journal of Iron and Steel Research(International)","volume":"24 11","pages":"Pages 1152-1158"},"PeriodicalIF":3.1000,"publicationDate":"2017-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/S1006-706X(17)30167-X","citationCount":"2","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Iron and Steel Research(International)","FirstCategoryId":"1087","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1006706X1730167X","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"METALLURGY & METALLURGICAL ENGINEERING","Score":null,"Total":0}
引用次数: 2
Abstract
The influence of fluorine on the structure of CaO-SiO2-Al2O3-Na2O-CaF2 continuous-casting-type slag was measured by Raman spectroscopy, and the degree of polymerization of mould flux and the structural behavior of F− in the melt were investigated by classifying and quantifying the structural species of F− ions. The results exhibit that the main structural units of Si-O tetrahedra are Q0, Q1 and Q2 and the actual measured number of non-bridging oxygen ions in the [SiO4]-tetrahedra (denoted by NBO/T) increases from 2. 73 to 3. 44 with increasing the molar ratio of F to (F+O) (denoted by XF/X(F+O)) from 0. 06 to 0. 19. It means that the degree of polymerization of melt structure decreases with an increase in XF/X(F+O). In addition, most of F− ions were distributed in Si-O tetrahedra and Al-O tetrahedra. With increasing XF/X(F+O), the complex structural units Al-O tetrahedra are gradually replaced by discrete structural units AlF1– because of the breakage of Al-O bonds in Al-O tetrahedra by F− ions, and the Si-O (bridging oxygen) bonds of Si-O tetrahedra are broken to form [SiOnF1–n]-tetrahedra by F− ions coordinating with Si4+.