Thermodynamics of the Vaporization of Cr2O3: Dissociation Energies of CrO, CrO2, and CrO3

Abstract

The vaporization of Cr2O3 under neutral and oxidizing conditions has been studied using mass spectrometric methods. The vaporization proceeds with the formation of Cr, CrO, CrO2, O, and O2 as the principal gaseous species. Under oxidizing conditions CrO3 was also observed. Dissociation energies of the gaseous molecules are D00(CrO)=101.1±7 kcal/mole, D00(CrO2)=227.1±15 kcal/mole, and D00(CrO3)=341±20 kcal/mole.

A Critical Appraisal of the Experimental Data on the Molecular Structure and Spectra of Halides, Oxides, and Hydrides of the s-, d-, and f-Block Elements

“…In certain cases the desired gaseous oxide may be obtained by passing oxygen over the metal or a lower oxide. Examples include Ag 2 O [75] , PtO 2 , [76] CrO 3 , [77] and OsO 3 . [78] Easily vaporized oxides often give polymeric vapors, and examples that demonstrate the tendency towards tetrahedral coordination include V 4 O 10 [79] and (MO 3 ) n (M Cr, [77] Mo, W).…”

“…Examples include Ag 2 O [75] , PtO 2 , [76] CrO 3 , [77] and OsO 3 . [78] Easily vaporized oxides often give polymeric vapors, and examples that demonstrate the tendency towards tetrahedral coordination include V 4 O 10 [79] and (MO 3 ) n (M Cr, [77] Mo, W). [80] Although matrix-isolation IR spectroscopy is particularly attractive for oxides because of the large relative mass change from 16 O to 18 O and the high frequency of most metal oxygen vibrations, generating gaseous oxides in a systematic fashion analogous to the work on the halides is difficult.…”

Catalytic inhibition of laminar flames by transition metal compounds

“…Often, this information is incomplete. Vapor pressures for some metal compounds can be found in [145][146][147][148][149]. Further, the kinetic rates of the formation of more stable oxides of the metal must be known to assess the contribution of those compounds to condensed-phase particles (since often, the vapor pressure of these oxides is very low; e.g., Fe 2 O 3 ).…”

Methods to Quantify Reactive Chromium Vaporization from Solid Oxide Fuel Cell Interconnects

“…44 Note that the vertical axis in Figure 7 [5] where X is the mole fraction of the designated gas species, and a Cr 2 O 3 is the activity of chromia (equal to one for pure chromia). The partial pressure of CrO 2 (OH) 2 p CrO 2 (OH) 2 = n CrO 2 (OH) 2 n tot P tot [6] is obtained from experiment by measuring the number of moles of collected Cr, n CrO 2 (OH) 2 , the total number of moles of gas, n tot , that passed through the transpiration apparatus; and the experimental pressure, P tot . Two criteria must be met to obtain reliable thermodynamic data using a transpiration experiment: flow rates must be governed such that they lie in the equilibrium flow regime, region B in Figure 4;…”

“…4 High temperature corrosion resistance exhibited by ferritic steel (containing over 15 wt% Cr) in oxidizing environments is attributed to the formation of a thin, passivating chromia (Cr 2 O 3 ) scale on the surface of the metal. 5,6 Under operating conditions of the SOFC cathode, chromia reacts with oxygen and water vapor producing gaseous Cr vapors, [5][6][7][8] depleting Cr in the alloy and, most importantly, poisoning the cell by depositing Cr around the cathode/electrolyte interface. [9][10][11][12][13][14] Many varieties of alloys, shown in Table I, and protective coatings have been developed to help mitigate Cr vaporization.…”