Effect of transition metal cations on the local structure and lithium transport in disordered rock-salt oxides.

Lithium-excess oxides LiTiMnO and LiNbMnO with a disordered rock-salt structure and Mn/Mn as a redox couple were compared to analyze the effect of different d metal ions on the local structure and Li ion migration. These cathode materials were obtained by mechanochemically assisted solid-state synthesis. Using XRD, Li NMR and EPR spectroscopy and transmission electron microscopy it was shown that the Mn ions are prone to form clusters, while d metal ions are evenly distributed in the crystal lattice.

Chitosan Cross-Linking with Acetaldehyde Acetals.

Here we demonstrate the possibility of using acyclic diethylacetal of acetaldehyde (ADA) with low cytotoxicity for the fabrication of hydrogels via Schiff bases formation between chitosan and acetaldehyde generated in situ from acetals in chitosan acetate solution. This approach is more convenient than a direct reaction between chitosan and acetaldehyde due to the better commercial availability and higher boiling point of the acetals. Rheological data confirmed the formation of intermolecular bonds in chitosan solution after the addition of acetaldehyde diethyl acetal at an equimolar NH: acetal ratio.

Effect of the Resorcinol/Formaldehyde Ratio and the Temperature of the Resorcinol-Formaldehyde Gel Solidification on the Chemical Stability and Sorption Characteristics of Ion-Exchange Resins.

A series of resorcinol-formaldehyde resins (RFR) samples for Cs-137 removal from liquid alkaline media have been synthesized. It has been demonstrated that the chemical stability as well as sorption characteristics are determined by the resorcinol/formaldehyde molar ratio and the solidification temperature. It has been also demonstrated that the sample synthesized at the resorcinol/formaldehyde molar ratio of 1.

Carboxyalkylchitosan-based hydrogels with "imine clip": Enhanced stability and amino acids-induced disassembly under physiological conditions.

Here we report on the properties of hydrogels of carboxyalkylchitosans-salicylimines depending on the salicylaldehyde (SA) grafting density, type of carboxyalkyl substitution, pH, and presence of amino acids. The mechanism of SA grafting has been investigated using C NMR and FT-IR spectroscopy and elemental analysis. We have found that, despite lower SA grafting density to carboxyalkylchitosans, gelation in these solutions occurred at much lower SA:polymer molar ratios than for chitosan-salicylimines, being the highest for a N-carboxyethylchitosan with a medium substitution degree.

Fluxional seven-coordinated fluorido- and oxofluoridotantalates.

Seven-coordinated (NH)TaF, RbTaF and RbTaOF were synthesized in single-crystal form and their structures were determined. A monocapped trigonal prism (CTP) or a pentagonal bipyramid (PB) of the TaF anion are stereochemically nonrigid and coexist in the first two compounds as a result of strong intraspheric dynamics. Upon cooling, tetragonal RbTaF undergoes a first-order phase transition at 145 K and the seven-coordinated polyhedron transforms into a regular CTP.

SPS technique for ionizing radiation source fabrication based on dense cesium-containing core.

The work presents a novel method for fabrication of the high-quality ionizing radiation source (IRS), which is promising to replace unsafe commercial products based on CsCl prohibited by IAEA. Spark plasma sintering (SPS) technique has been applied to produce dense ceramic and glass-ceramic matrixes from Cs-containing (˜13.5 wt.

Cryogels of carboxyalkylchitosans as a universal platform for the fabrication of composite materials.

Here we report a new simple method for fabrication of supermacroporous beads and monoliths via cross-linking of carboxyalkylated chitosan derivatives with hexamethylene diisocyanate in aqueous solution at subzero temperature. These materials provide high filtration rate and good mass-transfer that in combination with high binding capacity toward metal ions allows their application as a universal platform for fabrication of composite catalysts, sorbents, and metal-affine chromatography stationary phases. Using N-(2-carboxyethyl)chitosan (CEC), we have demonstrated that optimum chitosan carboxylation degree for cryogels synthesis is close to 1.

Chitosan Gels and Cryogels Cross-Linked with Diglycidyl Ethers of Ethylene Glycol and Polyethylene Glycol in Acidic Media.

Here we show that the efficacy of the chitosan interaction with diglycidyl ethers of glycols significantly depends on pH and the nature of acid used to dissolve chitosan. In solutions of hydrochloric acid, cross-linking with diglycidyl ethers of ethylene glycol (EGDGE) and polyethylene glycol (PEGDGE) at room and subzero temperatures yields mechanically stable chitosan gels and cryogels, while in acetic acid solutions only weak chitosan gels can be formed under the same conditions. A combination of elemental analysis, FT-IR spectroscopy, and solid state C and N NMR spectroscopy was used to elucidate possible differences in the mechanism of chitosan cross-linking in alkaline and acidic media at room and subzero temperatures.

Bonding and structure of oxofluoroniobate-based glasses.

Glasses based on the oxofluoroniobate anion have been characterized by vibrational and solid-state NMR spectroscopy. The mechanism of glass formation in the systems K2NbOF5-MF3 (M = Al, In) has been suggested. A glass network is built from the chains of corner-sharing octahedra through -Nb-F(O)-M- and -Nb-F-Nb- bridges.