Thermodynamics of the Gaseous Zirconium Iodides

1980

Auger electron spectroscopy was used to observe the relative coverage of iodine on the surface of a zirconium crystal exposed to a flux of iodine gas molecules. The zirconium was heated to temperatures of 1000–1300 K, and the iodine pressures corresponded to 10−4–10−6 Pa (10−9–10−11 atm). Iodine was found to chemisorb on the surface; the isotherms corresponded to the Temkin model. Isoteres derived from these isotherms showed a logarithmic dependence of pressure on reciprocal temperature. The slopes of the isoteres indicated an enthalpy of formation of the surface layer of about 60 kcal/mole. The thermodynamics of formation of an iodine adspecies on a zirconium surface were compared with the thermodynamics of formation of zirconium monoiodide, the lowest solid iodide of zirconium.

Section: Fig 3 Adsorption Isotherms For Iodine On Zirconiummentioning

confidence: 99%

Auger Electron Spectroscopy Study of the Chemisorption of Iodine on Zirconium

Krishnan

Wood

1980

“…Figure 2 summarizes the solid-phase boundaries and the vaporization thermodynamics we have derived from our assessment of the available data ZrI4 is given in Eq. [1]. The enthalpy changes corresponding to those reactions are also shown in Fig.…”

Section: (660~176 [4] Tmentioning

confidence: 92%

“…In the present investigation, the vaporization behavior of solids in part of the Zr-I system has been studied. The generalized reaction occurring can be represented as y u [1] The predominant gaseous iodide species in equilibrium with any condensed phase in the zirconium*iodine species below about 1000~ is ZrI4. Measurements (1) of the thermodynamics of the gaseous iodides showed that ZrI4 is the predominant gas species in equilibrium with Zr metal, for I pressures at which condensed iodides might form.…”

mentioning

confidence: 99%

“…The generalized reaction occurring can be represented as y u [1] The predominant gaseous iodide species in equilibrium with any condensed phase in the zirconium*iodine species below about 1000~ is ZrI4. Measurements (1) of the thermodynamics of the gaseous iodides showed that ZrI4 is the predominant gas species in equilibrium with Zr metal, for I pressures at which condensed iodides might form. Therefore, over the condensedphase iodides, for which the activity of Zr must be smaller than unity, the predominant gaseous sPecies must be ZrI4.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Thermodynamics of Vaporization of ZrI4 from Substoichiometric Solid Zirconium Iodides

Lau

1979

The pressures of gaseous ZrI4 for solid zirconium iodides in the composition range ZrI2.4‐ZrI1.0 were measured by a torsion‐effusion method. A univariant equilibrium region was found between the solids ZrI1.9 and ZrI1.3 for which the pressure of gaseous ZrI4 was given bylog10 P)(normalatm=−9308T+8.84A review of the literature concerning the solid phase in the Zr‐I system indicates that there are solid solution regions corresponding approximately to the tetra, tri, di, and monoiodide.

“…----7.53 -t-0.0051T + n(10.91 ~-0.00487T) [7] That equation is assumed to be applicable for n including nonintegral values, from 1 to 4 and over the temperature range 400-800 K.…”

mentioning

confidence: 99%

Estimated Thermodynamic Properties of the Solid Zirconium Iodides

Lamoreaux

1981

Literature values of ZrI4 pressures in equilibrium with solids of the zirconium‐iodine system have been used to calculate Zr and ZrI4 activities as functions of composition at 700 K. These activities, along with estimated heat capacities and free energy functions, were used to derive values of the activity of iodine and of the enthalpies of formation of solid stoichiometric normalZrI , ZrI2 , and ZrI3 . The estimated enthalpies of formation were: normalΔH2980false(normalZrI,normalsfalse)=−34.0±2.5 normalkcal/normalmole ; normalΔH2980false(ZrI2,normalsfalse)=−66.4±2.5 normalkcal/normalmole ; normalΔH2980false(ZrI3,normalsfalse)=−93.6±3.5 normalkcal/normalmole .