Reactivity with hydrogen of pure iron oxide and of iron oxides doped with oxides of Mn, Co, Ni and Cu

Using dynamic TG in H2, X-ray powder diffraction and Mössbauer Spectroscopy the reactivities fot hydrogen reduction of Fe2O3 prepared at different temperatures, Fe2O3 doped with oxides of Mn, Co, Ni and Cu prepared at 300DaggerC from nitrate precursors and intermediate spinels derived from above samples during reduction have been explored. The reactivity is higher for finely divided Fe2O3 prepared at 250DaggerC. The reduction is retarded by Mn, marginally affected by Co and accelerated by Ni and Cu, especially at higher (5 at.%) dopant concentration. These reactivities confirmed also by isothermal experiments, are ascribed to the nature of disorder in the metastable intermediate spinels and to hydrogen rsquospill overrsquo effects.

The contribution of polarons, bipolarons and intersite tunneling to low temperature conductivity in doped polypyrrole

The conductivity of highly doped polypyrrole is less than that of intermediately doped samples, by two orders of magnitude, at 4.2 K. This may be due to more number of bipolarons in highly doped samples. Bipolarons require four times more activation energy than single polarons to hop by thermally induced virtual transitions to intermediate dissociated polaron states than by the nondissociated process. The conduction process in these polyconjugated systems involve ionization from deep trapped states, having a View the MathML source dependence, hopping from localised states, having View the MathML source dependence, and intersite tunnel percolation, having T−1 dependence. The interplay of these factors leads to a better fit by View the MathML source. The mechanism for this exponential behaviour need not be same as that of Motts variable range hopping. Conduction by percolation is possible, if an infinite cluster of chains can be connected by impurity centers created by dopant ions. The tendency for the saturation of conductivity at very low temperatures is due to the possibility of intersite tunnel percolation is disordered polaronic systems.

Metal-insulator transitions in Cr-doped V2O3 by x-ray and ultraviolet photoelectron spectroscopy

X-ray and ultraviolet photoelectron spectroscopy have been employed to investigate the high temperature metal-insulator transitions in V2O3 and (V0.99Cr0.01)2O3. The high temperature transitions are associated with more gradual changes in the 3d bands compared to the low-temperature transitions

Rapid synthesis of room temperature ferromagnetic Ag-doped LaMnO3 perovskite phases by the solution combustion method

We report the rapid solution combustion synthesis and characterization of Ag-substituted LaMnO3 phases at relatively low temperature using oxalyl dihydrazide, as fuel. Structural parameters were refined by the Rietveld method using powder X-ray diffraction data. While the parent LaMnO3 crystallizes in the orthorhombic structure, the Ag-substituted compounds crystallize in the rhombohedral symmetry. On increasing Ag-content, unit cell volume and Mn-O-Mn bond angle decreases. The Fourier transform infra red spectrum shows two absorption bands corresponding to Mn-O stretching vibration (v(s) mode) and Mn-O-Mn deformation vibration (v(b) mode) around 600 cm(-1) and 400 cm(-1) for the compositions x = 0.0, 0.05 and 0.10, respectively. Electrical resistivity measurements reveal that composition-controlled metal to insulator transition, with the maximum metal to insulator being 280 K for the composition La0.75Ag0.25MnO3. Increase in magnetic moment was observed with increase in Ag-content. The maximum magnetic moment of 35 emu/g was observed for the composition La0.80Ag0.20MnO3. (C) 2010 Elsevier Ltd. All rights reserved.

Photocatalytic treatment of municipal wastewater using modified neodymium doped TiO2 hybrid nanoparticles

Photocatalytic degradation of municipal wastewater was investigated using reagent grade TiO2 and modified neodymium doped TiO2 hybrid nanoparticles. For the first time, surface modification of Nd3+ doped TiO2 hybrid nanoparticles were carried out with n-butylamine as surface modifier under mild hydrothermal conditions. The modified nanoparticles obtained were characterized by Powder XRD, FTIR, DLS, TEM, BET surface area, zeta potential and UV-Vis Spectroscopy. The characterization results indicated better morphology, particle size distribution and low agglomeration of the nanoparticles synthesized. It was found that photodegradation of wastewater using surface modified neodymium doped TiO2 nanoparticles was more compared to pure TiO2, which can be attributed to the doping and modification with n-butylamine.

Critical resistivity in impurity doped binary liquid mixtures

The electrical resistance of the critical binary liquid system C6H12+(CH3CO)2O is measured both in the pure form and when the system is doped with small amounts (≈ 100 ppm) of H2O impurities. Near Tc, the resistance varies as dR/dT = A1+A2 (T-Tc)-b with b ≈ 0.35. Neither the critical exponent b nor the amplitude ratio A1/A2 are affected by the impurities. A sign reversal of dR/dT is noticed at high temperatures T much greater-than Tc.

Thermal expansion of doped lanthanum gallates

Thermal expansion of several compositions of Sr and Mg-doped LaGaO3 including an A-site deficient composition (La0.9Sr0.1)(0.98)(Ga0.8Mg0.2)O-2.821 were measured in the temperature range from 298 to 1273 K. The effect of doping on thermal expansion was studied by varying the composition at one site of the perovskite structure (either A or B), while keeping the composition at the other site invariant. Thermal expansion varied nonlinearly with temperature and exhibited an inflexion between 550 and 620 K, probably related to the change in crystal structure from orthorhombic to rhombohedral. The dependence of average thermal expansion coefficient (alpha (av)) on the dopant concentration on either A or B site of the perovskite structure was found to be linear, when the composition at the other site was kept constant. Mg doping on the B-site had a greater effect on the average thermal expansion coefficient than Sr doping on the A-site. Cation deficiency at the A-site decreases thermal expansion when compositions at both sites are held constant.

Deformation and structural densification in Al2O3-Y2O3 glass

In this article, we examine the unusual plastic deformation under uniaxial compression of an Al2O3-15 mol % Y2O3 (A15Y) glass synthesized by a wet chemical route At a low temperature of 650-725 degrees C, plastic deformation of this glass is largely non-viscous through shear instabilities In contrast deformation near the crystallization temperature (850 degrees C) occurs homogeneously with work hardening and with a monotonic increase in the true density of the glass by 10-12% accompanied by an increase in hardness (H) and elastic modulus (E) of up to 100% We hypothesize a phenomenon of molecular densification of the amorphous structure through a hierarchy of multiple phases, analogous to density- or entropy-driven amorphous to-amorphous phase transitions (polyamorphism) These results suggest that the present method of preparation and the unusual behavior can trigger a search for many more systems that display such behavior (C) 2010 Acta Materialia Inc Published by Elsevier Ltd All rights reserved

Q-band beam waveguide

A report of the design, development ana periom~ance characteristics of a Q-band (8 nim) confoal. mned, aielectric lens beam waveguide is presented.

Looking-Glass Reflections : Norms in translating Lewis Carroll

This thesis in the field of translation studies focusses on the role of norms in the work of a literary translator. Norms are seen as guidelines for the translator; they also reflect the way the target audience either accepts or rejects the translation. Thus they are of an intersubjective nature. The theoretical background of the study is based on the views on norms of Andrew Chesterman and Gideon Toury. The writer makes use of her own editing and publishing experience, as well as her experience in translating Lewis Carroll, considering these in respect to theoretical views of norms and vice versa. The aim is also to bring to light some of the tacit knowledge related to translating, editing and publishing in Finland. The study has three angles. First, the writer introduces the norms of Finnish literary translation as gathered from her own working experience. The sources from which these norms arise and which affect them are briefly described. Six central translation norms emerge; they are described and exemplified through cases of Carroll translation. Secondly, a small-scale questionnaire study is presented. This was carried out in order to sound the normative views of other translators and to limit the role of subjectivity. The views of the informants largely support the set of norms presented by the writer, although the norms of quotability and harmony between translation and illustration do not arise. Instead, the answers give rise to a seventh, ethical norm, which is labelled the norm of integrity. Thirdly, there is a brief presentation of Lewis Carroll, his Alice books and their translation history in Finland. The retranslation hypothesis and the motives of retranslation are considered in the light of the work of Outi Paloposki and Kaisa Koskinen. The final part of the thesis plunges into actual translation work. It includes one and a half chapters of Through the Looking-Glass (Alicen seikkailut peilintakamaassa) as translated into Finnish by the writer. The translation commentary first discusses a number of recurring and general translation points; the running commentary then analyses 77 individual translation solutions and their justifications. The writer uses introspection as a way of reflecting on her own translation process, its decisive points and the role of norms therein. Keywords: Translation studies, Carroll, norms

A molecular dynamics study of a PbO.SiO2 glass and melt

The structures of a PbO.SiO2 glass and melt have been studied using molecular dynamics simulation employing Born-Mayer-Huggins pair potentials. Various pair distribution functions are presented and discussed. Pb-Pb correlations persist in the melt, in agreement with experimental observations. The calculated and experimental radial distribution functions are compared.

Role of alumina in flexure of glass/epoxy composites

The influence of particulate additions of alumina on the flexural properties of glass-fabric/epoxy composites was studied. The additions improved translaminar flexural strength, while decreasing interlaminar strength. The translaminar bending modulus showed an increasing trend whereas its interlaminar value showed a decrease, up to additions of 3 vol%. The mechanisms of deformation and the fracture features have been discussed with the aid of scanning electron microscopy.

Magnetic properties of pure, Sr- and Ca-Doped La2NiO4+δ ceramics: Onset of high-Tc superconductivity

We present the results for the temperature and field dependence of the magnetic for ceramic materials of the composition La2−xMxNiO4, with M=Sr or Ca and 0≤x≤0.4. The onset of a strong diamagnetism has been observed at temperatures between 8 and 70 K, depending on sample composition, annealing conditions. and thermal cycling procedures. The results are similar to those obtained earlier for monocrystalline samples and are likewise interpreted as due to the onset of superconductivity in a minority phase. A comparison with the results for superconducting La1.8Sr0.2Cu0.9Ni0.1O4 ceramics is also made; this illustrates some unique features of the nickelate systems, such as the high values of the critical fields Hc1 and Hc2. The differences between monocrystalline and ceramic systems are also discussed.

Electronic states in a disordered metal: Magnetotransport in doped germanium

We observe a sharp feature in the ultra-low-temperature magnetoconductivity of degenerately doped Ge:Sb at H∼25 kOe, which is robust up to at least three times the critical density for the insulator-metal transition. This field corresponds to a low-energy scale characteristic of the special nature of antimony donors in germanium. Its presence and sensitivity to uniaxial stress confirm the notion of metallic impurity bands in doped germanium.

AC impedance spectroscopic characterization of 10 mol% MgO doped ZnO varistors

The performance parameters e.g. non-linear coefficient (α) and breakdown electric field (Eb1mA/cm2) of ZnO based ceramic varistors were found to improve after the addition of 10 mol% MgO. The improvement in the varistor properties is examined by ac impedance spectroscopy technique in the frequency range (1 Hz–10 MHz) between temperature 25–250°C and understood in terms of differing contributions from the equivalent electrical circuit elements.