Strontium aluminosilicate

On heat treatment, both hexacelsian and monoclinic celsian phases crystallize in BAS glass [23-25]. Also, hot pressing of barium aluminosilicate (BAS) glass or its composites reinforced with large diameter silicon carbide SCS-6 monofilaments or small diameter multifilament Nicalon or Hi-Nicalon fibers resulted in the crystallization of both hexacelsian andmonoclinic celsian phases [12]. On doping BAS with 5 wt.% monoclinic celsian seeds or 10 wt.% strontium aluminosilicate (SAS), only the celsian phase was formed in hot pressed... 

N. P. Bansal, Method of Producing a Silicon Carbide Fiber Reinforced Strontium Aluminosilicate Glass-Ceramic Matrix Composite, U. S. Patent 5,389,321 February 14, 1995. 

N. P. Bansal, CVD SiC (SCS-0) Fiber-Reinforced Strontium Aluminosilicate Glass-Ceramic Composites, J. Mater. Res., 12 [3] 745-753 (1997). 

M.J. Hyatt, N.P. Bansal, Crystallization kinetics ofbarium and strontium aluminosilicate glasses offeldspar composition, NASA Technical Memorandum, No. 106624, 1994... 

Researchers at NASA Lewis Research Centre have used SiC monofilaments for the reinforcement of glass-ceramic matrices of refractory compositions, including strontium aluminosilicate (SAS) [82] and barium aluminosilicate (BAS) [83], with temperature capability of up to 1600°C. 

Barrer, R. M. and Marshall, D. J. 1964. Hydrothermal chemistry of silicates. Part XII Synthetic strontium aluminosilicates. J. Chemical Society (A) 485-97. 

A previous examination of a synthetic calcium mordenite 15) revealed an orthorhombic cell. A synthetic strontium mordenite 16) had a C-centered orthorhombic cell although Kerr 12) reported that a few crystals giving electron diffraction patterns corresponding approximately to the body-centered structure Immm) have been synthesized hydro-thermally from aluminosilicate gels containing strontium similar to those gels which yielded a strontium-mordenite. ... 

Table I lists the binding energies for the major constituent elements present on the mineral surfaces, both before and after reaction. These values are, in general, in good agreement with literature values for aluminosilicates (5). The value for Cs corresponds to that for ionic Cs salts. No large shifts are expected in these numbers, since there is no oxidation state difference between reactants and products. A detailed XPS study of the interaction of cesium (and strontium) with feldspar surfaces is in progress, and will be the subject of a future paper ...

The dominance of carbonate hydrolysis, carbo-nation, and sulfide oxidation in subglacial weathering reactions on aluminosilicate/silicate bedrock is also found on carbonate bedrock. However, the balance between carbonate dissolution and sulfide oxidation depends on the spatial distribution of sulfides in the bedrock and basal debris (Fairchild et al., 1999). Noncongruent dissolution of strontium and magnesium from carbonate is also observed in high rock water weathering environments, such as the distributed drainage systems, in which water flow is also low (Fairchild et al., 1999). 

Ion-exchange models are commonly used to describe radionuclide sorption onto the fixed-charged sites of materials like clays. Ion exchange will be strongly affected by competition with monovalent and divalent ions such as Na" " and Ca, whereas it will be less dependent on pH over the compositional ranges common for natural waters. Many studies of strontium and caesium sorption by aluminosilicates (e.g., Wahlberg and Fishman, 1962 Tamura, 1972) have been carried out within the framework of ion-exchange theory. Early mechanistic smdies... 

Radioactive Strontium. Profound hematological effects were observed in beagle dogs that were exposed once by inhalation to either soluble aerosols containing 90SrCl2, or 90Sr fused to aluminosilicate particles that produced extremely large radiation dose rates and doses in the affected tissues sufficient to induce acute radiation syndrome. 

ICRP (1995) considers the experimental data on strontium carbonate and chloride and sulfate to support classification of these compounds as Type F. Data on strontium particulates released from irradiated fuel support their classification as either Type F or M. Data on strontium in fused aluminosilicate particles support a classification as Type S. ICRP (1995) recommends assigning all strontium aerosols to Type M in the absence of specific information supporting an alternative classification. 

T.T. Bobrova, V.V. Moiseev, T.V. Permyakova and G.E. Sheshukova, Interaction of Alkaline Aluminosilicate Glasses with Molten Calcium, Strontium and Barium Nitrates, Izv. AN SSSR, Neorg. Mater. 9 (1973) 1416-1419. 

Strontium oxide-aluminosilicate powder sources were used to introduce the diffusant, and Rutherford back-scattering spectroscopy was used to measure diffusion profiles. For latm experiments, Arrhenius relationships were obtained ... 

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