U-O system

Phillips RJ, Golden TD, Shumsky MG, Bohannan EW, Switzer JA (1997) Electrodeposition of textured ceramic superlattices in the Pb-U-O system. Chem Mater 9 1670-1677... 

U—O system (Fig. 5 [65]) suggests an alternative explanation [77], viz. the constant rate is due to a constant oxygen pressure which is in equilibrium with the two solid phases, U409 and U308. This point of view will be extended further in Sect. 5. 

Fig. 10, Log X - log Foj diagram for U-O system prepared by Kofstad (193). Reproduced with permission.

Fig. 11. Logo-log diagram for U O system -----Matsui and Naito (29), (1) UjOg j,...

Thermodynamic data for a system (such as AS, AH, and AG) are obtained by preparing a chemical potential diagram as mentioned in Section A, and these data are useful as information contributing to better understanding of the defect structures of nonstoichiometric compounds. Several methods are available for preparing the chemical potential diagram (40), as described below, taking the U-O system as an example. 

The thermodynamical data 10, 64,247) of each phase in the U-O system are presented in Table III. Data reported by Hagemark and Broli 10) are presented for the region near stoichiometric composition, O/U = 2.00 2.03, where accurate thermodynamic data are difficult to obtain. 

Fig. 1 is a composite T-X phase diagram for the U-O system. The geologically significant portion of this system is probably below 1000°C and from UO2.0 to UOs.o- Uraninite in this region shows a solid solution the composition range of which is a function of temperature, but with an upper limit at low temperatures of around UO2.07. This composition probably represents the limit of natural uraninite. If a sample of stoichiometric UO2.00 is prepared in a reducing atmosphere, the resulting compound is brick red. When this material is exposed... 

Figure 1 Absorption spectra for system of excitons linear and locally coupled with strength S to nondispersive phonons with energy u>o calculated in NDCPA. B is excitonic bandwidth, and 7 is excitonic decay rate.

Another problem in high-temperature corrosion can be the effect of the formation of volatile metallic halides which can, in turn, disrupt the integrity of a protective surface oxide. Figure 7.73 shows that in the Ti-O-Cl system at very low oxygen potentials, volatile TiClj can be formed directly from TiO and Ti, whereas from Fig. 7.74 it is clear that in the system U-O-Cl at 450°C the volatile chloride cannot be formed directly from the oxides. 

The evaluation of the Integral In Eq. (23) differs from the corresponding Integral for the U/0 system because of the differences In the oxygen-potential models. In particular, the neglect of Pu6"1", but not U +, leads to the problem that In p((>2) for the Pu/O system becomes Infinite as x goes to zero. However, the Integral In Eq. (23) remains finite and has been evaluated (21). 

As noted before, the whole spectrum of particle sizes between 38 and 357 nm is encompassed with a AV of U.O ml or about 6% of the total column void volume. This low capacity of the HDC system is counterbalanced by its excellent resolution both of itself and in comparison to porous packing systems. The latter point is addressed in the next section. 

Edwards et al. (1997) demonstrate that for samples with similar " U(O), such as corals that grew in open marine water, and remained closed system since time of formation, isotopic data plot on or close to an ideal concordia in vs. °Th/ U... 

Progress Report by Fluid Systems Division of U.O.P. on Contract No. 14-30-0001-3303, to the Office of Water Research and Technology, U.S. Department of the Interior, July 1975. Progress Report by Fluid Systems Division of U.O.P. on Contract No. 14-34-0001-6516, to the Office of Water Research and Technology, U.S. Department of the Interior, March 1976. Special Report from the International Ozone Institute, Environ. Sci. Techno1. 11, 26 (1977). 

Phase analysis and texture of the metal particles. Iron powders are constituted of the a-Fe phase with a body-centered cubic (bcc) lattice, whereas Fe-Co powders appear as a mixture of three phases that are quite similar to those of pure metals (bcc for a-Fe and a mixture of hep and fee for cobalt) (6). In the Fe.Nil(m system, a single fee phase is observed over the whole available composition range U s 25) with a linear dependence of the lattice parameter versus z, which shows the existence of a fee solid solution as already evidenced for the Co.rNiu)o-. system (33). The XRD patterns of the Fe [CovNi(1()o -,v)] i - powders depend on the composition An fee phase is always observed either as a single phase or as the main phase a second hep phase with weak and broad lines appears for a cobalt content x > 35 a third body-centered cubic (hcc) phase can be evidenced when x > 80. 

Fig. 1. The autocorrelation function C(t) = (U (O)l I (i) is shown for a wavepacket initially prepared on the upper diabatic surface [7]. Panels (a) and (b) C(t) for the four core modes calculated by the standard MCTDH method for the model Hamiltonian Hy of Eq. (9), shown on different scales in the two panels. Panel (c) G-MCTDH calculation (bold line) as compared with standard MCTDH calculation (dotted line) for the composite system with four core modes (combined into two 2-dimensional particles

Two ternary compounds, USbOs and USb3O10 occur in the U—Sb—O system, as was shown by Aykan and Sleight [34] using various analysis techniques. ESR measurements revealed that, in both components, the formal... 

---