High-Temperature Vaporization and Thermodynamics of the Titanium Oxides. VII. Mass Spectrometry and Dissociation Energies of TiO(g) and TiO2(g)

Abstract

Two experiments of the successive vaporization type, five mass spectrometric vaporization experiments, and two isomolecular exchange reaction experiments were undertaken to resolve discrepancies in the thermodynamics of the titanium—oxygen system. The first two types of experiments confirmed that Ti3O5(s) is the congruently vaporizing phase. The second type of experiment showed that the principal reaction accounting for the congruent vaporization is Ti3O5(S)=TiO(g)+2TiO2(g). In the third type of experiment, measurements on the isomolecular exchange reaction TiO(g)+Sc(g)=Ti(g)+ScO(g) showed that the dissociation energy of TiO(g) is smaller than that for ScO(g) and on the basis that D0o(ScO) is 160.4±2.0 kcal/mole, D0o(TiO) becomes 156.9±2.2 kcal/mole, or 6.80±0.10 eV. This result may be combined with earlier vapor pressure measurements on Ti3O5(s) and the congruency condition to yield D0o(TiO2)=311.7±1.8 kcal/mole, 13.52±0.08 eV, or very nearly twice D0o(TiO). One of the two previously discussed discrepancies in the thermodynamics of the titanium oxides appears to have been resolved, and the likely resolution of the other is discussed.

Vapor Pressures of TiO(g) in Equilibrium with Ti2O3(s) and Ti3O5(s, β); Dissociation Energy of TiO(g)

“…They also have studied isomolecular reactions in order to determine DoO[TiO(g)]. They principally used Reaction (3) and confirmed the previous results of Drowart et al 6 From the studies of Drowart et al 6 and of Hampson and Gilles 7 …”

“…Their vapor pressure measurements were interpreted using Reaction (2) 7 have performed extensive mass spectrometric studies. Through studies of several phases in this sytem they confirmed .the congruent vaporization of Th05(S, (3) from W effUSIon cells.…”

A Solid‐State Galvanic Cell Study of the Ti2 O 3 , Ti3 O 5 Equilibrium

“…3 were fit by unweighted least squares to obtain E(obs, mV) ----(303.6 • 5.0) --(0.1382 ___ 0.0040)T(K) [7] while the data corrected for the solubility of oxygen in niobium via Eq. 3 were fit by unweighted least squares to obtain E(obs, mV) ----(303.6 • 5.0) --(0.1382 ___ 0.0040)T(K) [7] while the data corrected for the solubility of oxygen in niobium via Eq.…”

Gaseous titanium molybdates and tungstates: Thermodynamic properties and structures

“…In order to obtain gaseous ternary titaniummolybdenumoxygen and titaniumtungstenoxygen species a mixture of titanium oxide Ti 3 O 5 and silicon dioxide was evaporated from molybdenum or tungsten effusion cells, respectively. Ti 3 O 5 was selected because it is known [26][27][28][29] that this oxide evaporates congruently. The SiO 2 oxide was taken as a source of oxygen, which oxidized the cell and produced gaseous XO 2 and XO 3 oxides.…”