In Situ Crystallographic Probing on Ameliorating Effect of Sulfide Additives and Carbon Grafting in Iron Electrodes

Beneficial effects of carbon grafting into the iron active material for rechargeable alkaline-iron-electrodes with and without Bi2S3 additive is probed by in situ X-ray diffraction in conjunction with Extended X-ray Absorption Fine Structure (EXAFS) and electrochemistry. EXAFS data unravel that the composition of pristine active material (PAM) for iron electrodes comprises 87% of magnetite and 13% of alpha-iron while carbon-grafted active material comprises 60% of magnetite and 40% of alpha-iron. In situ XRD patterns are recorded using a specially designed electrochemical cell. XRD data reflect that magnetite present in PAM iron electrode, without bismuth sulfide additive, is not reduced during charging while PAM iron electrode with bismuth sulfide additive is partially reduced to alpha-Fe/Fe(OH)(2). Interestingly, carbon-grafted-iron electrodes with bismuth sulfide exhibit complete conversion of active material to alpha-Fe/Fe(OH)2. The ameliorating effect of carbon grafting is substantiated by kinetic parameters obtained from steady-state potentiostatic polarization and Tafel plots. The mechanism for iron-electrode charge - discharge reactions are discussed in the light of the potential - pH diagrams for Fe - H2O, S - H2O and FeSads - H2O systems and it is surmised that carbon grafting into iron active material promotes its electrochemical utilization. (C) The Author(s) 2015. Published by ECS. All rights reserved.

Die Filling Behaviour of Semi Solid A356 Al Alloy Slurry During Rheo Pressure Die Casting

The present work discusses the findings obtained from simulations of semi solid die filling of a steering knuckle, prior to actual component development using in-house developed rheo pressure die casting system. Die filling capability of A356 Al alloy at semi-solid state has been investigated using commercial software Flow-3Dcast to optimise the pouring temperature of semi-solid slurry into the die cavity, while all other variables such as gating design, die preheat temperature and injection velocity are kept constant based on the prior knowledge obtained from trial numerical simulations and experimentation. Efforts have been made to nullify the essence of costly, time consuming experiments towards obtaining high-quality castings out of the findings obtained from numerical simulations. The optimum pouring temperature identified in the present study is 610 A degrees C, which facilitates smoother slurry flow, minimum surface defect concentration, uniform temperature field and solid fraction distribution within the component cavity.

Noble metal ions in CeO2 and TiO2: synthesis, structure and catalytic properties

In the past four decades, CeO2 has been recognized as an attractive material in the area of auto exhaust catalysis because of its unique redox properties. In the presence of CeO2, the catalytic activity of noble metals supported on Al2O3 is enhanced due to higher dispersion of noble metals in their ionic form. In the last few years, we have been exploring an entirely new approach of dispersing noble metal ions on CeO2 and TiO2 matrices for redox catalysis. In this study, the dispersion of noble metal ions by solution combustion as well as other methods over CeO2 and TiO2 resulting mainly in Ce1-xMxO2-delta, Ce1-x-yTixMyO2-delta, Ce1-x-ySnxMyO2-delta, Ce1-x-yFexMyO2-delta, Ce1-x-yZrxMyO2-delta and Ti1-xMxO2-delta (M = Pd, Pt, Rh and Ru) catalysts, the structure of these materials, their catalytic properties toward different types of catalysis, structure-property relationships and mechanisms of catalytic reactions are reviewed. In these catalysts, noble metal ions are incorporated into a substrate matrix to a certain limit in a solid solution form. Lower valent noble metal-ion substitution in CeO2 and TiO2 creates noble metal ionic sites and oxide ion vacancies that act as adsorption sites for redox catalysis. It has been demonstrated that these new generation noble metal ionic catalysts (NMIC) have been found to be catalytically more active than conventional nanocrystalline noble metal catalysts dispersed on oxide supports.

Ultrafast Chemical Dynamics in Time Domain Through Fluorescence Spectroscopy

While absorption and emission spectroscopy have always been used to detect and characterize molecules and molecular complexes, the availability of ultrashort laser pulses and associated computer-aided optical detection techniques allowed study of chemical processes directly in the time domain at unprecedented time scales, through appearance and disappearance of fluorescence from participating chemical species. Application of such techniques to chemical dynamics in liquids, where many processes occur with picosecond and femtosecond time scales lead to the discovery of a host of new phenomena that in turn led to the development of many new theories. Experiment and theory together provided new and valuable insight into many fundamental chemical processes, like isomerization dynamics, electron and proton transfer reactions, vibrational energy and phase relaxation, photosynthesis, to name just a few. In this article, we shall review a few of such discoveries in attempt to provide a glimpse of the fascinating research employing fluorescence spectroscopy that changed the field of chemical dynamics forever.

Light Induced Metastable State of Silver Nitroprusside Probed by Raman Spectroscopy

Low temperature Raman spectroscopic measurements on silver nitroprusside (AgNP), Ag-2Fe(CN)(5)NO] powders display reversible features of a partially converted metastable state. The results are compared with similarly observed metastable state in case of sodium nitroprusside (NaNP) and the differences have been discussed in terms of possible resistance to metastable state formation offered by silver atoms on the basis of hard soft acid base (HSAB) theory.

Effect of Super-exchange Interaction on Ground state Magnetic Properties of Spin-dependent Falicov-Kimball Model on a Triangular Lattice

Ground state magnetic properties are studied by incorporating the super-exchange interaction (J(se)) in the spin-dependent Falicov-Kimball model (FKM) between localized (f-) electrons on a triangular lattice for half filled case. Numerical diagonalization and Monte-Carlo simulation are used to study the ground state magnetic properties. We have found that the magnetic moment of (d-) and (f-) electrons strongly depend on the value of Hund's exchange (J), super-exchange interaction (J(se)) and also depends on the number of (d-) electrons (N-d). The ground state changes from antiferromagnetic (AFM) to ferromagnetic (FM) state as we decrease (N-d). Also the density of d electrons at each site depends on the value of J and J(se).

Folding of Protein L with Implications for Collapse in the Denatured State Ensemble

A fundamental question in protein folding is whether the coil to globule collapse transition occurs during the initial stages of folding (burst phase) or simultaneously with the protein folding transition. Single molecule fluorescence resonance energy transfer (FRET) and small-angle X-ray scattering (SAXS) experiments disagree on whether Protein L collapse transition occurs during the burst phase of folding. We study Protein L folding using a coarse-grained model and molecular dynamics simulations. The collapse transition in Protein L is found to be concomitant with the folding transition. In the burst phase of folding, we find that FRET experiments overestimate radius of gyration, R-g, of the protein due to the application of Gaussian polymer chain end-to-end distribution to extract R-g from the FRET efficiency. FRET experiments estimate approximate to 6 angstrom decrease in R-g when the actual decrease is approximate to 3 angstrom on guanidinium chloride denaturant dilution from 7.5 to 1 M, thereby suggesting pronounced compaction in the protein dimensions in the burst phase. The approximate to 3 angstrom decrease is close to the statistical uncertainties of the R-g data measured from SAXS experiments, which suggest no compaction, leading to a disagreement with the FRET experiments. The transition-state ensemble (TSE) structures in Protein L folding are globular and extensive in agreement with the Psi-analysis experiments. The results support the hypothesis that the TSE of single domain proteins depends on protein topology and is not stabilized by local interactions alone.

Origin of the Spin-Orbital Liquid State in a Nearly J=0 Iridate Ba3ZnIr2O9

We show using detailed magnetic and thermodynamic studies and theoretical calculations that the ground state of Ba3ZnIr2O9 is a realization of a novel spin-orbital liquid state. Our results reveal that Ba3ZnIr2O9 with Ir5+ (5d(4)) ions and strong spin-orbit coupling (SOC) arrives very close to the elusive J = 0 state but each Ir ion still possesses a weak moment. Ab initio density functional calculations indicate that this moment is developed due to superexchange, mediated by a strong intradimer hopping mechanism. While the Ir spins within the structural Ir2O9 dimer are expected to form a spin-orbit singlet state (SOS) with no resultant moment, substantial frustration arising from interdimer exchange interactions induce quantum fluctuations in these possible SOS states favoring a spin-orbital liquid phase down to at least 100 mK.

Interpenetrated and Catenated Zinc Thiosulfates Frameworks with dia and qtz Nets: Synthesis, Structure, and Properties

Reactions between Zn(NO3)(2)center dot 6H(2)O, Na2S2O3, 4,4'-bipyridine (bpy), 1,2-bis(4-pyridyl)ethene (bpe), 1,2-bis (4-pyridyl) ethane (bpa), and 1,3-bis(4-pyridyl)propane (bpp) under solvothermal conditions resulted in four new zinc thiosulfate hybrid compounds. Compound I has four-membered zinc thiosulfate rings connected by the ligand, 1,3-bis(4-pyridyl)propane (bpp) forming a two-dimensional structure. Compounds II-IV have one-dimensional zinc thiosulfate chains connected by the ligands, bpy (II), bpe (III), and bpa (IV) giving rise to three-dimensional structures. All the four-structures exhibit 3-fold interpenetration. Proton conductivity studies indicate reasonable proton mobility at 34 degrees C and at 98% relative humidity. The compounds also exhibit Lewis acid character and good photocatalytic activity for the decomposition of cationic dyes.