Zirconium thermodynamic data

The anticipated content of impurities in the refined metal may be calculated a priori by assuming thermodynamic equilibrium at both metal/gas interfaces, and using the relevant stabilities of tire gaseous iodides. Adequate thermodynamic data could provide the activities of the impurities widr that of zirconium close to unity, but tire calculation of tire impurity transport obviously requires a knowledge of activity coefficients in the original impure material, which are not sufficiently well known. 

Thermodynamic data in the area of transition metal chemistry is available, but additional studies would be desirable. One of the early indications that C—Ti bonds are not notoriously weak was obtained from the heats of combustion of Cp2Ti(CH3)2 and Cp2Ti(C6H5)2 with subsequent estimation of the a-bond dissociation energies (250 kJ/mol-1 and 350 kJ/mol 1, respectively)49. From heats of alcoholysis of a number of titanium, zirconium and hafnium compounds, and heats of solution of the products as well as subsidiary data, Lappert estimated heats of formation (AHf°) and thermochemical mean bond energy terms (EM X) of metal—X bondsso> (Table 2). 

The existence of the zirconium selenides ZrSe(cr), ZrSe 5(cr), ZrSe2(cr), and ZrSc3(cr) have been reported. No experimental thermodynamic data are available except for ZrSesCcr) for which the heat capacity has been measured in the temperature range 8 to 200 K [86PRO/AYA]. These temperatures are too low for a derivation of thermodynamic quantities at 298.15 K. Mills [74MIL] has estimated some thermodynamic values by comparison with the corresponding sulphides and tellurides. 

Recent experimental work has indicated that the existing thermodynamic data on fluoride and chloride salts of zirconium and hafnium in a molten salt environment are unreliable. These data are required for the evaluation of non-aqueous processes for the separation of the two metals. ... 

GAM/BUG] and [2005OLI/NOL]), and their use is recommended by this review. Zirconium forms compounds with many of the elements of the Periodic Table. The sources of auxiliary data mentioned do not eontain all data that were needed. Additional auxiliary data were obtained from the literature and, when used, the source has been indicated in Chapter VI. Recalculation of data is presented in Appendix A and, where necessary, the re-evaluation has involved new auxiliary data when needed. Care has been taken that all the selected thermodynamic data at standard conditions are internally consistent. For this purpose, special software has been developed at the NEA Data Bank that is operated in conjunction with the NEA-TDB data base system, cf. Section II.6. To maintain consistency in the application of the values selected by this review, it is essential to use these auxiliary data. 

Chapter III contains a table of selected thermodynamic data for individual compounds and complexes of zirconium (Table lll-l), a table of selected reaction data (Table 111-2) for reactions concerning zirconium species and a table containing selected thennal functions of the heat capacities of individual species of zirconium (Table I1I-3). The selection of these data is diseussed in Chapter V. 

Chapter IV contains, for auxiliary compounds and complexes that do not contain zirconium, a table of the thermodynamic data for individual species (Table IV-1) and a table of reaction data (Table lV-2). Most of these values are the CODATA Key Values [89COX/WAG], The selection of the remaining auxiliary data is discussed in [92GRE/FUG], and other preeeding volumes of this series. 

This chapter presents the chemical thermodynamic data set for zirconium species which has been selected in this review. Table lll-l contains the recommended thermodynamic data of the zirconium compounds and species, Table 111-2 the recommended thermodynamic data of chemical equilibrium reactions by which the zirconium compounds and complexes are formed, and Table 111-3 the temperature coefficients of the heat capacity data of Table 111-1 where available. 

Table III-l Seleeted thermodynamic data for zirconium compounds and complexes. All ionic species listed in this table are aqueous species. Unless noted otherwise, all data refer to the reference temperature of 298.15 K and to the standard state, i.e., a pressure of 0.1 MPa and, for aqueous species, infinite dilution (/ = 0). The uncertainties listed below each value represent total uncertainties and correspond in principle to the statistically defined 95% confidence interval. Values obtained from internal calculation, cf. footnotes (a) and (b), are rounded at the third digit after the decimal point and may therefore not be exactly Identical to those given in Part V. Systematically, all the values are presented with three digits after the decimal point, regardless of the significance of these digits. The data presented in this table are available on computer media from the OECD Nuclear Energy Agency.

This chapter presents the chemical thermodynamic data for auxiliary compounds and complexes which are used within the NEA-TDB project. Most of these auxiliary species are used in the evaluation of the recommended zirconium data in Table lll-l, Table IIT 2, and Table 111-3. It is therefore essential to always use these auxiliary data in conjunction with the selected data for zirconium. The use of other auxiliary data can lead to Inconsistencies and erroneous results. 

The only zirconium selenite compound for which reliable chemical thermodynamic data are available is Zr(Se03)2(cr). Nesterenko et al. [73NES/PINJ investigated the dissociation of zirconium selenite via the reaction ... 

No other thermodynamic data have been reported for zirconium phosphide eompounds. 

No thermodynamic data relevant to the formation of aqueous zirconium phosphate species was found. 

The enthalpy change of Zr, Zr02, ZrN, ZrSi04 and ZrC were measured at elevated temperatures 390 to 1371, 397 to 1841, 371 to 1672, 385 to 11823 and 336 to 567 K, respectively. Over the temperature range studied, both zirconium metal and Zr02 were found to change state. The transition was found to occur at 1135 K for Zr and 1478 K for Zr02- Thermodynamic data were obtained for both states of both phases. The heat content was measured as the difference between the heat content at a particular tempera-... 

A study by means of ion exchange yields thermodynamic data for zirconium sulphate complexes. The study confirmed the finding of [49CON/MCV] that no hydrolysis and polymerisation occur at log, [Zr] < - 4 in 2 M HCIO4. 

SIL] Silva, R. J., Yucca Mountain site charactherization project. Thermodynamic data review for nickel and zirconium. Review of zirconium (IV) thermodynamic data. Hydroxide complexes. Report, (1998). Cited on page 341. 

This volume is the eighth of the series Chemieal Thermodynamies edited by the OECD Nuclear Energy Agency (NEA). It is a critical review of the Thermodynamic Data Base of zirconium and its compounds initiated by the Management Board of the NEA Thermochemical Database Project Phase II (NEA TDB II). 

Table 111-1 Selected thermodynamic data for zirconium compounds and complexes 48...

Table III-2 Selected thermodynamic data for reactions involving zirconium compounds and complexes.54...

Table 10.4 Thermodynamic data for zirconium species at 25 °C determined in the present review together with data available in the literature.

The thermodynamic data for baddeleyite, Zr02(s), have been given by Brown, Curti and Grambow (2005) as they have for zirconium metal. The data are listed in Table 10.8. The Gibbs energy for baddeleyite was used to determine the Gibbs energy value for Zr listed in Table 10.4. 

I W Titanium(IV), Zirconium, Hafnium and Thorium Table 10.8 Literature thermodynamic data for baddeleyite and Zr(s) at 25 °C. 

This type of side-on bending, which has been established by X-ray crystallographic methods for the related acyl complexes (r 5-C5H5)2Zr(COMe)Me (38) and (T>5-C5H5)2Ti(COMe)Cl (39), could overcome the thermodynamic objection, previously discussed, against the formation of a normal, linearly bonded formyl by CO insertion into a metal-hydride bond. Thermochemical data obtained from alcoholysis of zirconium tetralkyl species show that the mean bond energy of Zr—O is 50 kcal/mole greater than that of Zr—C (40). 

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