Richard P. Burns

Thermodynamic study of Al2O3 using a mass spectrometer

The evaporation of alumina under nearly neutral conditions in tungsten and molybdenum Knudsen cells has been investigated by mass spectrometric methods. The atomization energies of the gaseous molecules are D0o(AlO) = 115±5 kcal/mole; D0o(Al2O) = 245±7 kcal/mole; D0o(Al2O2) = 365±7 kcal/mole.

Mass spectrometric study of gaseous molybdenum, tungsten, and uranium oxides

Partial pressures of the gaseous oxides MoO, MoO2, MoO3, WO, WO2, WO3, UO, UO2, and UO3 in the systems Mo–Al2O3 and U–Al2O3 have been measured by mass spectrometric methods. The vapor pressure of uranium has also been determined. The reaction enthalpies derived from these measurements are: Reaction         ΔH0ο kcal/moleMoO(g)→Mo(g)+O(g)         116±15MoO2(g)→Mo(g)+2O(g)         262±10MoO3(g)→Mo(g)+3O(g)         411±7WO(g)→W(g)+O(g)         154±10WO2(g)→W(g)+2O(g)         296±7WO3(g)→W(g)+3O(g)         443±7UO(g)→U(g)+O(g)         179±7UO2(g)→U(g)+2O(g)         340±7UO3(g)→U(g)+3O(g)         493±7U(s)→U(g)         126±5.

Thermodynamics of the vaporization of Cr2O3: Dissociation energies of CrO, CrO2, and CrO3

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.

Systematics of the Evaporation Coefficient Al2O3, Ga2O3, In2O3

The rate of evaporation from surfaces of Al2O3, Ga2O3, and In2O3 has been studied through a combination of thermal‐imaging and mass‐spectrometric techniques.A discontinuity is observed in the rate of evaporation of Al2O3 and Ga2O3 at the melting point TM. The evaporation coefficient αv of the solid at the melting point is equal to 0.3±0.05 for all gaseous species over Al2O3, Ga2O3, and In2O3. The rate of evaporation from the surface of the liquid at the melting point is the equilibrium rate (αv=1) for all gaseous species. The evaporation coefficient αv over the solid is very nearly temperature independent for monatomic vapor species but depends strongly on temperature for polyatomic species.It is shown that the data for the different systems can be directly correlated when they are plotted as logαv vs TM/T, where TM is the melting temperature. This correlation also applies to other systems and appears to be useful in predicting evaporation behavior in related systems.The equilibrium rates of evaporation a...

Mass Spectrometric Investigation of the Sublimation of Molybdenum Dioxide

A mass spectrometric investigation of the vapor in thermodynamic equilibrium with powdered molybdenum dioxide has shown the vapor phase to consist, in decreasing order of importance, of the species MoO3, (MoO3)2, MoO2, and (MoO3)3. The heats, entropies, and free energies of reaction have been determined for the reactions (T=1600°K): 32x MoO2(s)→(MoO3)x(g)+12x Mo(s)         where x=1, 2, 3MoO2(s)→MoO2(g)         ΔHT=134.4±7 kcal/mole2MoO3(g)→(MoO3)2(g)         ΔHT=−110.2±8 kcal/mole3MoO3(g)→(MoO3)3(g)         ΔHT=−222.8±13 kcal/mole For the case x=1, 2, 3 the ΔHTs are 121.8±3, 133.4±7, and 142.6±13 kcal/mole, respectively. Entropies of the gaseous molecules MoO3, (MoO3)2, (MoO3)3, and MoO2 at T=1600°K are 96.6, 151.0, 201.2, and 85.5 eu, respectively. In addition, the atomization energies (ΔH0o) for the reaction MoOx(g)→Mo(g)+xO(g) were calculated to be 277.4±7 and 419.7±10 kcal/mole for x=2 and 3, respectively.

Thermodynamics of the Vaporization of Nickel Oxide

A mass spectrometric investigation of the vapor species in equilibrium with nickel oxide has shown the vapor phase to consist of Ni, O2, NiO, and O, whereas the solid phase consists of a NiO solid solution and Ni(s). The dissociation energy of NiO(g) was found to be 86.5±5 kcal/mole.

Mass‐Spectrometric Study of the Vaporization of Cobalt Oxide

A mass‐spectrometric investigation of the vapor species in equilibrium with the Co–O system has shown the vapor phase to consist of Co, O2, and small amounts of CoO. The dissociation energy, D0°, of CoO(g) was found to be 86.4 kcal/mole and the heat of sublimation of CoO(s), ΔH0°sub, is 130.3 kcal/mole.