Titanium (IV) oxide phase stability in alkaline sodium phosphate solutions at elevated temperatures

Journal Article · Sat May 01 00:00:00 EDT 1993 · Chemistry of Materials; (United States)

DOI:https://doi.org/10.1021/cm00029a019· OSTI ID:6148463

Ziemniak, S E; Opalka, E P ^[1]

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1. Knolls Atomic Power Laboratory, Schenectady, NY (United States)

Titanium (IV) oxide is shown to transform to a sodium titanium hydroxyphosphate compound in concentrated sodium phosphate solutions at elevated temperatures via TiO[sub 2](s) + 4Na[sup +] + 2HPO[sub 4][sup 2-] [r reversible] Na[sub 4]Ti(OH)[sub 2](PO[sub 4])[sub 2](s). The thermodynamic equilibrium for this reaction was investigated in the system TiO[sub 2]-Na[sub 2]O-P[sub 2]O[sub 5]-H[sub 2]O for Na/P atom ratios between 2 and 3. On the basis of observed reaction threshold values for sodium phosphate concentration and temperature, the respective standard entropy and free energy of formation for Na[sub 4]Ti(OH)[sub 2](PO[sub 4])[sub 2] were calculated to be 823.1 J/(mol K) and -4025.1 kJ/mol at 298 K. 21 refs., 4 figs., 5 tabs.

• OSTI ID: 6148463
• Journal Information: Chemistry of Materials; (United States), Journal Name: Chemistry of Materials; (United States) Vol. 5:5; ISSN CMATEX; ISSN 0897-4756
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
AQUEOUS SOLUTIONS
CHALCOGENIDES
DISPERSIONS
ENERGY
EQUILIBRIUM
FORMATION FREE ENERGY
FORMATION FREE ENTHALPY
FREE ENERGY
FREE ENTHALPY
MIXTURES
OXIDES
OXYGEN COMPOUNDS
PHASE STABILITY
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHYSICAL PROPERTIES
SOLUTIONS
STABILITY
THERMODYNAMIC PROPERTIES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TITANIUM PHOSPHATES
TRANSITION ELEMENT COMPOUNDS