Stability evaluation of alkali metal standard solutions by using precise ion chromatography

Mass fractions of alkali metal (Li, Na, K, Rb, Cs) standard solutions (1000 mg/kg) were measured with about 0.1% relative standard deviation by improving the method of injection in ion chromatography (IC). This technique was applied to stability testing of the standard solutions. After storage of each alkali metal standard solution for 18 months, an increase of the mass fraction was observed, for all the alkali metal ions, of approximately 0.15% per year at 25 °C and approximately 0.02% per year at 5 °C. The observed increase of the mass fraction can be explained by the weight loss of the solution during storage. The deviation between the mass fraction measured by IC and the preparation mass fraction after correcting the weight loss for solvent evaporation was within ±0.05% for every alkali metal ion. It is concluded that alkali metal standard solutions of 1000 mg/kg are basically stable for more than 18 months under these storage conditions and that correction for evaporation is effective if weight monitoring of each bottle is performed precisely. Presented at BERM-11, October 2007, Tsukuba, Japan.     

Thermodynamic assessment of the K-Na and Cr-V system

The assessment of the thermodynamic properties of K-Na and Cr-V molten alloys has been theoretically examined using a simple statistical mechanical model based on pairwise interaction to obtain higher-order conditional probabilities that describe the occupation of the neighbouring atoms in molten binary alloys. The optimised values of order energy ω obtained are used to describe a number of thermodynamic quantities computed for different concentrations in the alloys at 384 and 1550 K, respectively. The study shows that there is a tendency for homocoordination (like atoms pairing as nearest neighbour) in K-Na and the existence of heterocoordination in Cr-V at all concentrations. Thus, the consistency between calculated and reported experimental thermodynamic values enforces the legitimacy of the findings.     

Palladium-catalyzed cross-couplings of allylic phosphates

A range of palladium-catalyzed cross-coupling reactions can be performed using allylic phosphates as electrophiles. Both conventional heating and microwave irradiation can be used.     

Ab initio prediction of the low-temperature phase diagrams in the systems CsX–LiX (X = F, Cl, Br, I)

We have calculated the low-temperature phase diagrams for the ternary alkali halides CsX–LiX (X = F, Cl, Br, I) at an ab initio level without any recourse to experimental information. The starting point of our general approach is the global exploration of the enthalpy landscapes for many different compositions in these systems. Candidates for both ordered stoichiometric modifications and crystalline solid-solution phases are identified, and their free enthalpies are computed at an ab initio level. From this the low-temperature phase diagrams are derived. We find that in all systems under investigation only crystalline ordered phases should be present, in agreement with available experimental data. Furthermore, we predict several new thermodynamically stable and metastable phases in these systems.     

Improved determination of tributyl phosphate degradation products (mono- and dibutyl phosphates) by ion chromatography

Tributyl phosphate (TBP) is a very important compound in the nuclear industry, particularly in the area of nuclear fuel reprocessing. This compound is used in the PUREX (plutonium and uranium refining extraction) process which consists of the extraction of uranium and plutonium from an aqueous nitric acid phase, for the purpose of recycling. But TBP may be degraded to dibutyl phosphate (DBP) and monobutyl phosphate (MBP) by dealkylation of one or two butoxy groups, respectively. We have compared and evaluated the capacity of two resins manufactured by Dionex (AS11 and AS5A) in the separation and measurement of these two degradation products. AS11 generates two interferences: nitrite/DBP and carbonate/MBP. The first one is the most serious. So, we have developed a method for oxidising nitrite ions to nitrate ions which have no trouble over the measurement. The second resin tested, AS5A, allows a very efficient separation between DBP and NO₂⁻ ions and a good separation between MBP and CO₃²⁻ in comparison with the AS11. The detection limits for the AS5A column are 0.13 μM for MBP and 0.71 μM for DBP (injection LOOP=50 μl).     

Morphology of alkali halide thin films

Two alkali halide adsorbate-substrate systems were investigated by atomic force microscopy (AFM) working in contact mode. Adsorbate film orientation relative to the substrate was determined from the arrangement of the atomic steps of the substrate and the edges of the forming islands. In this work we present experimental results obtained for systems: NaCl/LiF(0 0 1) and LiF/NaCl(0 0 1), which exhibit a strong tendency of the self-assembly into regular structures.     

Photocatalytic Aerobic Phosphatation of Alkenes

A catalytic regime for the direct phosphatation of simple, non‐polarized alkenes has been devised that is based on using ordinary, non‐activated phosphoric acid diesters as the phosphate source and O₂ as the terminal oxidant. The title method enables the direct and highly economic construction of a diverse range of allylic phosphate esters. From a conceptual viewpoint, the aerobic phosphatation is entirely complementary to traditional methods for phosphate ester formation, which predominantly rely on the use of prefunctionalized or preactivated reactants, such as alcohols and phosphoryl halides. The title transformation is enabled by the interplay of a photoredox and a selenium π‐acid catalyst and involves a sequence of single‐electron‐transfer processes.     

Meet the Cerium(IV) Phosphate Sisters: CeIV(OH)PO4 and CeIV2O(PO4)2

Two new cerium(IV) phosphates were obtained: cerium(IV) hydroxidophosphate, Ce(OH)PO₄, and cerium(IV) oxidophosphate, Ce₂O(PO₄)₂, which were shown to complement the classes of isostructural compounds M(OH)PO₄ and R₂O(PO₄)₂, where M=Th, U and R=Th, U, Np, Zr. Ce₂O(PO₄)₂ oxidophosphate is formed by elimination of H₂O from the crystal structure of Ce(OH)PO₄ during its thermal decomposition. The structures of Ce(OH)PO₄ and Ce₂O(PO₄)₂ are related to each other with the same Cmce space group and similar unit cell parameters (a=6.9691(3) Å, b=9.0655(4) Å, c=12.2214(4) Å, V=772.13(8) ų, Z=8; a=7.0220(4) Å, b=8.9894(5) Å, c=12.544(1) Å, V=791.8(1) ų, Z=4, respectively).     

An Intrinsically Non‐flammable Electrolyte for High‐Performance Potassium Batteries

Potassium‐ion batteries are promising for low‐cost and large‐scale energy storage applications, but the major obstacle to their application is the lack of safe and effective electrolytes. A phosphate‐based fire retardant such as triethyl phosphate is now shown to work as a single solvent with potassium bis(fluorosulfonyl)imide at 0.9 m , in contrast to previous Li and Na systems where phosphates cannot work at low concentrations. This electrolyte is optimized at 2 m , where it exhibits the advantages of low cost, low viscosity, and high conductivity, as well as the formation of a uniform and robust salt‐derived solid‐electrolyte interphase layer, leading to non‐dendritic K‐metal plating/stripping with Coulombic efficiency of 99.6 % and a highly reversible graphite anode.     

Alkali activated fly ash: effect of admixtures on paste rheology

In this paper, an investigation related to the rheological behaviour of alkali-activated fly-ash pastes (AAFA) is described. Those pastes were prepared by mixing the fly ash with an alkaline dissolution containing 85% of a 12.5 M NaOH solution and 15% of waterglass and adding some commercial chemical admixtures usually used in the Portland cement concrete fabrication, like lignosulphonates, melamines (first and second generation products) and polycarboxylates (latest generation). The fly ash rheological data were determined by rotational viscometry measurements as well as by the use of the flow table test. Results indicate that chemicals admixtures used do not work the same in the Portland cement systems than in alkali-activated fly ash systems. As a general rule, it seems that the most efficient admixtures for these new cementitious pastes (AAFA) are those based in polycarboxylates.