Ruthenium thermodynamic propertie

Plutonium-noble metal compounds have both technological and theoretical importance. Modeling of nuclear fuel interactions with refractory containers and extension of alloy bonding theories to include actinides require accurate thermodynamic properties of these materials. Plutonium was shown to react with noble metals such as platinum, rhodium, iridium, ruthenium, and osmium to form highly stable intermetallics. 

Plutonium-noble metal compounds have both technological and theoretical importance. Modeling of nuclear fuel interactions with refractory containers and extension of alloy bonding theories to include actinides require accurate thermodynamic properties of these materials. Plutonium was shown to react with noble metals such as platinum, rhodium, iridium, ruthenium, and osmium to form highly stable intermetallics. Vapor pressures of phases in these systems were measured by the Knudsen effusion technique. Use of mass spectrometer-target collection apparatus to perform thermodynamic studies is discussed. The prominent sublimation reactions for these phases below 2000 K was shown to involve formation of elemental plutonium vapor. Thermodynamic properties determined in this study were correlated with corresponding values obtained from theoretical predictions and from previous measurements on analogous intermetallics. 

The classical compilations of binary phase diagrams, give no information at all on this system. Consequently, it has been supposed that there is a negligible mutual solid solubility of calcium and ruthenium in each other, and a wide miscibility gap in the liquid state, the mutual solubility increasing at high temperature. Thus, the assessed diagram is only qualitative and the solid and liquid solubilities are entirely estimated. No thermodynamic property is available for that system. The system was assessed by Chevalier and Fischer [1996Che]. 

That the above redox isomer is formed instead of the FenRuin one, can be demonstrated by careful analysis of the MLCT band of the product, as well as by the properties of the intervalence (IV) band. However, it is well known that the [Run(NH >)r,LV,+ ions are generally much more reactive that the [Fen(CN)5L]" analogues toward oxidation by peroxydisulfate (126,128), as required by the lower redox potential at the ruthenium center. A careful mechanistic analysis showed that, although the FeinRun isomer is the thermodynamically stable product, it is not the kinetically accessible one. Then, the reaction evolves as follows ... 

The redox properties of ruthenium(II) sarcophaginates are discussed in Refs. 324 and 327. The [Ru(sar)] + cation oxidized readily to the corresponding ruthenium (III) complex, which spontaneously disproportionated to the initial cation and a monodeprotonated intermediate ruthenium(IV) complex. This complex quickly produced the imine ruthenium(II) clathrochelate by both base- and acid-catalyzed pathways (Scheme 118). Intermediate di- and triimine species were also observed. The kinetic and thermodynamic data for the disproportionation process demonstrated that the secondary amino group in [Ru(sar)] + cation is quite acidic (pRTa = 5-r6) and that the ruthenium(IV) state is stabilized at more than 2000 mV. 

Ruthenium dioxide, RuO, displays interesting physical properties such as a low resistivity and high thermodynamic stability [63]. Additionally, the compound exhibits excellent diffusion barrier properties [64] and is used in resistor applications [65]. Precursors for the deposition of RUO2 include ruthenium acetylacetonate, Ru3(CO)i2 (12) and RuCp2 (11) [63, 64]. However, only RuCp produces high quality RUO2 films [63]. 

In principle, the theory of reversible electrodes can serve as the basis for developing the thermodynamic approach to the surface electrochemistry of oxide materials with metalhc conductivity (iridium, ruthenium, tin dioxides, and so on) [100]. In addition, the properties of these interfaces can be considered within the framework of three models the classical model of bound sites [101], which can be modified by considering several types of surface groups... 

Anion Retention. Transition metal chlorides are often favored as catalyst precursors because of their ready availability, high solubility, and their ease of reduction. However, residual chloride anions (from incomplete catalyst reduction) can have a very marked effect on the properties of the catalysts. While the platinum group metal chlorides are, from a thermodynamic standpoint, very easy to reduce (Pt > Ru > Ir > Rh), residual chloride ions on the metal surface can be tenaciously bonded. The severity necessary to remove all the surface chloride reflects the surface energy of the metal (Ru, Mo, Ir > Rh > Pt > Pd). In the case of ruthenium, although bulk reduction apparently occurs at around 470 K, extended reduction above 700 K can be necessary to remove all chloride anions. The presence... 

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