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Group II Tris(glycolato)silicates as Precursors to Silicate Glasses and Ceramics
Author(s) -
Kansal Pallavi,
Laine Richard M.
Publication year - 1995
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1995.tb08210.x
Subject(s) - silicate , hexacoordinate , materials science , amorphous solid , crystallization , aluminosilicate , differential thermal analysis , raman spectroscopy , ceramic , sodalite , fourier transform infrared spectroscopy , alkoxy group , mineralogy , inorganic chemistry , chemical engineering , chemistry , organic chemistry , alkyl , zeolite , silicon , physics , diffraction , optics , metallurgy , composite material , engineering , catalysis
Group II tris(glycolato)silicates, MSi(OCH 2 CH 2 O) 3 (where M = Ba, Ca, Mg), can be synthesized directly by reaction of silica with ethylene glycol and alkaline‐earth (group II) oxides at 200°C. These hexa‐alkoxy silicates serve as precursors to silicate glass and ceramic powders. They are readily modified by exchange with longer‐chain diols into processable polymer precursors. These Theologically useful precursors may provide access to silicate or aluminosilicate powders, thin fllms, fibers, and coatings. Thus, we have examined the utility of hexacoordinate glycolatosilicates as model precursors. Pyrolysis of the compounds, MSi(OCH 2 ‐CH 2 O) 3 , in air transforms them to their anticipated ceramic products, MO‐SiO 2 . The phase transformations and chemical changes that occur during pyrolysis were characterized using X‐ray powder diffractometry (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), thermal gravimetric analysis (TGA), differential thermal analysis (DTA), and scanning electron microscopy (SEM). The hexacoordinate glycolatosilicates oxidatively decompose at ∼300°C to form amorphous materials. Moderate to significant quantities of the group II carbonates, MCO 3 (15–50 wt%), form coincidentally as the amorphous intermediates trap CO 2 generated by ligand oxidation. At ∼900°C, the amorphous materials crystallize into the expected, phase‐pure, MO‐SiO 2 .