Speciation of chromium aqua and chloro complexes in hydrochloric acid solutions at 298 K.

The distribution of metal aqua and chloro complexes is fundamental information for analysis of a chemical reaction involving these complexes. The present study investigated the speciation and structures of chromium aqua and chloro complexes using the thermodynamic model fitting analysis of UV-vis/X-ray absorption spectra. The existence of a negatively charged species was examined by adsorbability of chromium species on a strong base anion exchanger. In the results, a planar square [CrIII(H2O)4]3+, a planar square or distorted tetrahedral [CrIIICl(H2O)3]2+, a trigonal bipyramidal [CrIIICl3(H2O)2]0, and a distorted octahedral [CrIIICl4(H2O)2]- were confirmed and the thermodynamic parameters of complexation reactions were quantitatively determined. Investigation of the evolution of speciation of chromium aqua and chloro complexes in a pH 1 solution suggested the existence of [CrIIICl2(H2O) m ]+ (m = 2 or 3) during the hydration process, which diminished in the equilibrium state. The kinetic analysis deserves further investigation to understand the speciation process quantitatively.

Finding Degradation Trigger Sites of Structural Materials for Airplanes Using X-Ray Microscopy.

Macroscopic properties of carbon fiber-reinforced plastic (CFRP) and environmental barrier coating (EBC), widely used for airplanes, can be deteriorated by local cracks or degradation ("trigger sites"). We have tried to find these trigger sites using x-ray microscopy (XM), which can provide the 2D or 3D images of the chemical states and microstructures. Crack initiation in CFRP was observed in a non-destructive manner in multi-scales (nm-mm). 3D chemical-state mapping of Yb in EBC was achieved with high resolution (<50 nm). In addition to XM, in-situ observations at high temperatures were conducted for obtaining complementary information. X-ray absorption spectroscopy (XAS) and x-ray diffraction (XRD) analysis were performed simultaneously up to 1773 K. Dynamic XAS with short time-resolution (<10 ns) was conducted to investigate changes in the local structure of metal. These approaches can help us identify degradation trigger sites in the materials.

Deprotonation of a dinuclear copper complex of 3,5-diamino-1,2,4-triazole for high oxygen reduction activity.

A dinuclear copper(II) complex of 3,5-diamino-1,2,4-triazole is one of the highly active copper-based catalysts for the oxygen reduction reaction (ORR) in basic solutions. Our in situ X-ray absorption near edge structure measurements revealed that deprotonation of the triazole ligand might cause coordination geometrical changes, resulting in the enhancement of the ORR activity.

Preparation of a self-standing mesoporous carbon membrane with perpendicularly-ordered pore structures.

A self-standing mesoporous carbon membrane (sOMC) with perpendicularly-ordered pore structures was prepared through a simple synthetic method; the pores with a diameter of 8 nm were well ordered over a large area and perpendicularly-oriented to the surface without any external field; in the formation of this ordered structure, the drying process is key, and a porous alumina support is important to induce drying.

Effects of the water content on the growth rate of AgCl nanoparticles in a reversed micelle system.

The effects of water content on the growth rate and the final particle size of AgCl nanoparticles in a reversed micelle (RM) system of polyoxyethylene (6) nonylphenyl ether (NP-6)/water/cyclohexane were investigated using a double-jet technique, in which RM solutions of AgNO(3) and KCl were added concurrently to a RM solution containing the excess concentration of chloride ion. As a result, the particle growth rate and the final particle size at a constant Rw ( identical with[water]/[surfactant]) below 5 were found to be in excellent agreement with our theoretical prediction based on a dynamic Ostwald ripening mechanism governed by the overall solubility of the solid and the diffusivity of the reversed micelles, whereas the final particle size was far beyond the size of the water pool of a reversed micelle. Thus, the dramatic reduction of the particle size in the RM system can be explained by the drastic reduction of the overall solubility of the solid and the small diffusivity of the bulky reversed micelles as a carrier of silver ion, and not by the size of the water pool of a reversed micelle as conventionally explained. Some additional contribution of a coagulation process was also suggested in a high Rw range above 5. Significant coagulation of AgCl particles was observed in a RM system with AOT in place of NP-6 even under the standard conditions for the NP-6 system.