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Conversion of Tetranary Borate Glasses to Phosphate Compounds in Aqueous Phosphate Solution
Author(s) -
Huang Wenhai,
Day Delbert E.,
Rahaman Mohamed N.
Publication year - 2008
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.1551-2916.2008.02354.x
Subject(s) - aqueous solution , alkali metal , phosphate , boron , inorganic chemistry , alkaline earth metal , barium , chemistry , ternary operation , amorphous calcium phosphate , amorphous solid , glass transition , nuclear chemistry , materials science , organic chemistry , computer science , programming language , polymer
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 37°C. The present work is an extension of our earlier work to investigate the conversion of tetranary borate glass with the composition 10Li 2 O·10CaO·10(AeO or T 2 O 3 )·60B 2 O 3 (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 μm) were reacted in 0.25 M K 2 HPO 4 solution with a starting pH of ∼9.0 at 37°C. 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 600°–700°C 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.