Thermodynamic/dynamic modeling of liquid immiscibility in silicates is seriously hindered due to lack of in situ investigation on the structural evolution of the melt.In this work,atomic-scale structural evolution of ...Thermodynamic/dynamic modeling of liquid immiscibility in silicates is seriously hindered due to lack of in situ investigation on the structural evolution of the melt.In this work,atomic-scale structural evolution of a classic binary silicate immiscible system,SiO2–TiO2,is tracked by in situ high energy X-ray diffraction(HE-XRD).It is found that both the configuration of[SiO]and the polymerization between them are closely coupled with embedment and extraction of the metallic cations(Ti^4+).[SiO]monomer goes through deficit-oxygen and excess-polymerization before liquid–liquid separation and enables self-healing after liquid–liquid separation,which challenges the traditional cognition that[SiO4]monomer is immutable.Ti4+cations with tetrahedral oxygen-coordination first participate in the network construction before liquid separation.The four-fold Ti–O bond is broken during liquid separation,which may facilitate the movement of Ti4+across the Si–O network to form TiO2-rich nodules.The structural features of nodules were also investigated and they were found highly analogous to that of molten TiO2,which implies a parallel crystallization behavior in the two circumstances.Our results shed light on the structural evolution scenario in liquid immiscibility at atomic scale,which will contribute to constructing a complete thermodynamic/dynamic framework describing the silicate liquid immiscibility systems beyond current models.展开更多
基金supported by the National Natural Science Foundation of China-Excellent Young Scholars(No.51922068)the National Key Research and Development Program(No.2017YFA0403800)+1 种基金the National Natural Science Foundation of China(Nos.51727802,51821001 and 51971138)Shanghai Pujiang Program(No.19PJ1404400)。
文摘Thermodynamic/dynamic modeling of liquid immiscibility in silicates is seriously hindered due to lack of in situ investigation on the structural evolution of the melt.In this work,atomic-scale structural evolution of a classic binary silicate immiscible system,SiO2–TiO2,is tracked by in situ high energy X-ray diffraction(HE-XRD).It is found that both the configuration of[SiO]and the polymerization between them are closely coupled with embedment and extraction of the metallic cations(Ti^4+).[SiO]monomer goes through deficit-oxygen and excess-polymerization before liquid–liquid separation and enables self-healing after liquid–liquid separation,which challenges the traditional cognition that[SiO4]monomer is immutable.Ti4+cations with tetrahedral oxygen-coordination first participate in the network construction before liquid separation.The four-fold Ti–O bond is broken during liquid separation,which may facilitate the movement of Ti4+across the Si–O network to form TiO2-rich nodules.The structural features of nodules were also investigated and they were found highly analogous to that of molten TiO2,which implies a parallel crystallization behavior in the two circumstances.Our results shed light on the structural evolution scenario in liquid immiscibility at atomic scale,which will contribute to constructing a complete thermodynamic/dynamic framework describing the silicate liquid immiscibility systems beyond current models.
