Aluminosilicates aluminosilicate melt

The model of Richet and Bottinga (1985) considers the heat capacity of the melt to be variable with T and allows better reproducibility of experimental evidence in composi-tionally simple systems. The Stebbins-Carmichael model seems to reproduce the experimental observations on aluminosilicate melts better (Berman and Brown, 1987). Application of both models to natural melts gives substantially identical results (i.e., differences of about 1%, within the range of data uncertainty cf Berman and Brown, 1987). 

Sierralta M., Nowak M., and Keppler H. (2002) The influence of bulk composition on the diffusivity of carbon dioxide in Na aluminosilicate melts. Am. Mineral. 87, 1710-1716. 

Burnham C. W. (1981) The Nature of multicomponent aluminosilicate melts. Phys. Chem. Earth 13, 197-229. 

The Ca0-Ah0j,-Si02 system. The coordination of Al(III) atoms in aluminosilicate melts is one of the most important research directions in the structure of the melts containing alumina. This interest is associated with an extensive utilization of these melts in different sections of the silicate industry, such as glass, cement, porcelain production, etc. 

Conclusions on the structure of aluminosilicate melts are mainly based on the interpretation of physico-chemical properties, such as density and viscosity, in terms of composition, particularly of the x(Ca0)/x(Al203) ratio. The basic idea was the concept that in melts with the ratio x(Ca0)/x(Al203) > 1, all the Al(III) atoms are in tetrahedral coordination and that the octahedral coordination of Al(III) atoms occurs only at ratios x(Ca)/x(Al203) < 1, i.e. at the excess of alumina with respect to CaO. 

Extensive measurements were carried out to determine the mixing properties of different aluminosilicate melts. Two groups, Rammensee and Fraser [410] as well as Rogez et al. [411], studied the pseudobinary join NaA18i308-KAlSi30g... 

Viscosity studies have been carried out on a very large number of other silicate systems. The highest viscosities are found for compositions which are free of traditional modifier oxides, e.g., rare earth aluminosilicate melts, and for compositions containing large concentrations of Nb205 or Ta205. Low viscosities are usually found for melts containing PbO, or a limited concentration of fluorine or other halides. 

B. Cote, D. Massiot, F. Tantelle and J. P. Coutures, 27AI NMR spectroscopy of aluminosilicate melts and glasses. Chemical Geology, 96,367-370 (1992). 

Cot6 B, Massiot D, TauleUe F, Coutures J-P (1992) Al NMR spectroscopy of aluminosilicate melts and glasses. Chem Geol 96(3-4) 367-370... 

L.R. Corrales, J. Du, Characterization of Ion Distributions Near the Surface of Sodium-Containing and Sodium-Depleted Calcium Aluminosilicate Melts (Blackwell Publishing Inc, Beijing, 2006), pp. 36-41... 

The structure and thermodynamics of naturally occurring silicate melts is one of the unsolved problems in petrology. Clearly, calorimetric study of silicate and aluminosilicate melts along the lines described above would be very useful. However, the temperatures at which these mixtures are molten and have relatively low viscosities (ll00-1300OC) are at the upper limit of calorimetric capability. Recently, both Hong and Kleppa (197 ) and Warner,... 

They introduced a solvent coefficient (Henry s law constant) for each Eu species to account for the energy difference between the ideal gas and the particular liquid in question. They found, for a particular choice of major cation (i.e., Ca or Mg) in the solvent, 2EuO to be more soluble than EU2O3 in going from the ortho-or metasilicate end member of the mixture to the aluminosilicate end member. This result was not expected because the aluminosilicate end member has a higher fraction of its oxygen bound into polymer chains. This would be expected to decrease the activity of free oxide ion in the aluminosilicate melts, which according to eq. (21.4) would favor formation of Eu(III) at the expense of Eu(II), just opposite to what was observed. 

The viscosity calculated by the confined shear simulation is 1.11 Pa s at lOSO C. This agrees very well with the value measured previously for this composition within the (NNL). It also seems to have accounted for the mixed alkali effect, which could not be modeled using the simpler analytical methods. Comparisons at other temperatures and with other silicate, borosilicate, and aluminosilicate melts showed similar agreement. 

FIGURE 14.40 The aluminosilicate mica cleaves into thin transparent sheets with high melting points. These properties allow it to be used for windows in furnaces. 

Concentrated solutions of orthophosphoric acid, often containing metal salts, are used to form cements with metal oxides and aluminosilicate glasses. Orthophosphoric acid, often referred to simply as phosphoric acid, is a white crystalline solid (m.p. 42-35 °C) and there is a crystalline hemihydrate, 2H3PO4.H2O, which melts at 29-35 °C. The acid is tribasic and in aqueous solution has three ionization constants (pA J 2-15,7-1 and 12-4. 

Cooper R.F., Fanselow J.B., Weber J.K.R., Merkley D.R., and Poker D.B. (1996b) Dynamics of oxidation of a Fe -bearing aluminosilicate (basaltic) melt. Science 274, 1173-1176. 

Aluminosilicate ash (Class F) Quart/ and unburm carbon Melt, mullite. Ie4),. Fed), Glass-in-glass phase separation secondary mullite... 

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