Medium range structure and dynamics of glass and molten glass

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In this study, structural analysis of glass melts at high temperatures (〜1600℃) by means of X-ray diffraction has been dealt with. First, the principle and procedures of X-ray radial distribution function (RDF) analysis are described in detail. Second, the advantages of a pair function method and a molecular dynamics (MD) calculation method are also mentioned in detail, when they are used to interpret the obtained experimental RDF data. The X-ray diffraction apparatus used in this work is stated especially emphasizing that the photon counter with a high energy resolution such as Si(Li) solid state detector (SSD) should be used in order to obtain highly resolved RDF curves.The results obtained are as follows. First, the common computer programs written in C-language which made it possible to process the raw data and to calculate the RDF curves were developed using a Sun Ultra 5 workstation which is a UNIX machine. These programs are available on demand to anyone who wants to use them. S … More econd, structure analysis has been performed on SLS(16Na_2O 10CaO 74SiO_2) glass which is a model glass of commercial green glass pane in order to check the programs developed in this work. A well-resolved RDF curve was obtained for the room-temperature glass. Each peak was assigned to corresponding atomic pairs : Si-O at 0.164 nm, Na-O, Ca-O around 0.23 nm, O-O at 0.27 nm, Si-O-Si at 0.31〜0.32 nm and so on. It has been confirmed that they work perfectly. Then, the structure of SLS glass melt placed on a ZrO_2-dispersed Pt-10%Rh ribbon-heater(FKS16, Furuya Metals Co.) was analyzed at 1500℃ using a high temperature furnace in a similar way to that of the same glass at room temperature. Both the X-ray RDF analysis and MD calculation revealed that there is no distinct structural difference between the glass and melt, in other words, the network structure consisting of SiO_4 tetrahedra remains basically unchanged on melting. In this respect, the present soda-lime silicate glass can be classified into the "strong glass". It is also found from the MD calculation that the peaks due to the Na-O and Ca-O pairs become very broad and expand to the longer distance on melting, while the Si-O bondlength and the Si-O-Si bond angle remain almost unchanged. This result clearly indicates that the thermal motion of Na^+ and Ca^<2+> ions becomes remarkable at higher temperatures, leading to the thermal expansion. We can say that the thermal expansion of soda-lime silicate glasses is mainly governed by the thermal motion of Na^+ ions. Less