Conversion of Tetranary Borate Glasses to Phosphate Compounds in Aqueous Phosphate Solution
In our earlier work, it was found that particles of a ternary alkali-borate glass, containing either CaO or BaO, converted completely to a crystalline phosphate of calcium or barium when reacted in an aqueous phosphate solution at 371C. The present work is an extension of our earlier work to investigate the conversion of tetranary borate glass with the composition 10Li2O. 10CaO. 10(AeO or T2O3) . 60B2O3 (weight percent), where Ae is the alkai-earth metal Mg or Ba, and T is the transition metal La, Sm, or Dy. In the experiments, particles of each glass (150-300 lm) were reacted in 0.25M K2HPO4 solution with a starting pH of B9.0 at 371C. Weight loss and pH measurements indicated that the reaction was complete after 30-50 h, yielding an amorphous product. X-ray fluorescence showed that the as-formed product consisted of a calcium phosphate phase that contained the alkali-earth metal or transition metal present in the starting glass. Heating the as-formed material for 8 h at 6001-7001C produced a mixture of two crystalline phosphates: calcium phosphate and an alkali-earth or transition metal phosphate. The kinetics and mechanism of converting tetranary borate glass to phosphate materials are discussed and compared with data from earlier work for the conversion of ternary borate glass.
W. Huang et al., "Conversion of Tetranary Borate Glasses to Phosphate Compounds in Aqueous Phosphate Solution," Journal of the American Ceramic Society, John Wiley & Sons, Apr 2008.
The definitive version is available at http://dx.doi.org/10.1111/j.1551-2916.2008.02354.x
Materials Science and Engineering
Keywords and Phrases
Barium; Boron Deposits; Calcium; Glass; Lithium; Tellurium Compounds
Article - Journal
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