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This journal is c the Owner Societies 2011 Phys. Chem. Chem. Phys. Cite this: DOI: 10.1039/c1cp22185j
 

Summary: This journal is c the Owner Societies 2011 Phys. Chem. Chem. Phys.
Cite this: DOI: 10.1039/c1cp22185j
Heat capacity and glass transition in P2O5­H2O solutions: support for
Mishima's conjecture on solvent water at low temperature
Horacio R. Corti,*ab
Federico J. Nores-Pondalwa
and C. Austen Angellc
Received 3rd July 2011, Accepted 19th August 2011
DOI: 10.1039/c1cp22185j
The P2O5­water system has the widest range of continuously glass-forming compositions known
for any glassformer + water binary system. Despite the great range of structures explored by the
glasses and liquids in this system, the glass transition temperature (Tg) itself varies in a simple
monotonic fashion. However the values of Tg reported in the literature show wide disagreement,
linked to the different methods of measurement employed. In this work we use differential
scanning calorimetry (DSC) to obtain both Tg itself and the jump in heat capacity that occurs as
the metastable equilibrium of the supercooled liquid relieves the non-ergodic glassy state. Our
study covers the molar ratio range of H2O/P2O5 from 1.5 to 14 (corresponding to the mass
fraction of P2O5 between 0.36 and 0.84), which includes the compositions corresponding to
pyrophosphoric acid (H4P2O7) and orthophosphoric acid (H3PO4). The theoretical model of
Couchman and Karasz predicts very well the glass transition temperatures of the P2O5­H2O

  

Source: Angell, C. Austen - Department of Chemistry and Biochemistry, Arizona State University

 

Collections: Materials Science; Chemistry