Competing magnetic interactions in a dinuclear Ni(II) complex: Antiferromagnetic O-H center dot center dot center dot O moiety and ferromagnetic N-3(-) ligand

Synthesis, structural characteristics, magnetic studies and DFT calculations in Ni(II) dinuclear complexes containing two bridging N-3(-) and an O-(HO)-O-... linkage reveal the existence of ferromagnetic interactions between Ni(II) centers via N-3(-) ligands and antiferromagnetic interactions through the H-bonded moiety. The overall magnetic behavior of the system depends on the delicate balance between these two competing interactions.

Characterization of Alloy-Spinel-Corundum Equilibrium in the System Fe-Ni-Al-O

The three phase equilibrium between alloy, spinel solid solution and α-alumina in the Fe-Ni-Al-O system has been fully characterized at 1823K as a function of alloy composition using both experimental and computational methods. The oxygen potential was measured using a solid state cell incorporating yttria-doped thoria as the electrolyte and Cr+ Cr2O3 as the reference electrode. Oxygen concentration of the alloy was determined by an inert gas fusion technique. The composition of the spinel solid solution, formed at the interface between the alloy and an alumina crucible, was determined by EPMA. The variation of the oxygen concentration and potential and composition of the spinel solid solution with mole fraction of nickel in the alloy have been computed using activities in binary Fe-Ni system, free energies of formation of end member spinels FeO•(1+x)Al2O3 and NiO•(1+x)Al2O3 and free energies of solution of oxygen in liquid iron and nickel, available in the literature. Activities in the spinel solid solution were computed using a cation distribution model. The variation of the activity coefficient of oxygen with alloy composition in Fe-Ni-O system was calculated using both the quasichemical model of Jacob and Alcock and the Wagner's model, with the correlation of Chiang and Chang. The computed results for the oxygen potential and the composition of the spinel solid solution are in good agreement with the measurements. The measured oxygen concentration lies between the values computed using models of Wagner and Jacob and Alcock. The results of the study indicate that the deoxidation hyper-surface in multicomponent systems can be computed with useful accuracy using data for end member systems and thermodynamic models.

An in situ EXAFS investigation of bimetallic Cu---Ni/γ-Al2O3 catalysts

In situ EXAFS investigations have been carried out on Ni/γ-Al2O3 and Cu---Ni/γ-Al2O3 catalysts with different metal loadings, and prepared by different procedures. As-prepared Ni/γ-Al2O3 on calcination gives NiO and NiAl2O4-like phases on the surface, the proportion of the latter increasing with the increase in calcination temperature; the proportion of the NiO-like phase, on the other hand, increases with the metal loading. The reducibility of Ni/γ-Al2O3 to give metallic Ni on the surface directly depends on the proportion of the NiO-like phase present before reduction. Co-impregnating with Cu suppresses the formation of the surface aluminate and thereby favours the reduction to metallic Ni. This conclusion is clearly substantiated by our studies of bimetallic catalysts containing varying Cu/Ni ratios and also those prepared by the two-stage impregnation procedure.

Preparation, characterization, spectral and thermal analyses of (N2H5)2MCl4·2H2O (M = Fe, Co, Ni and Cu); crystal structure of the iron complex

Hydrazinium metal chlorides, (N2H5)2MCl4·2H2O (where M = Fe, Co, Ni and Cu), have been prepared from the aqueous solutions of the respective metal chlorides and hydrazine hydrochloride (N2H4·HCl or N2H4·2HCl) and investigated by spectral and thermal analyses. The crystal structure of the iron complex has been determined by direct methods and refined by full-matrix least-squares to an R of 0.023 and Rw of 0.031 for 1495 independent reflections. The structure shows ferrous ion in an octahedral environment bonded by two hydrazinium cations, two chloride anions and two water molecules. In the complex cation [Fe(N2H5)2(H2O)2Cl2]2+, the coordinated groups are in trans positions.

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.

A formate bridged Ni(II) sheet and its 3D analogue in presence of a linear organic linker: Synthesis, crystal structure and magnetic properties

Reaction of formamide with Ni(NO3)(2)center dot 6H(2)O under hydrothermal condition in a mixture of MeOH/H2O forms a two-dimensional formate bridged sheet Ni(HCOO)(2)(MeOH)(2) (1). X-ray structure analysis reveals the conversion of formamide to formate which acts as a bridging ligand in complex 1 where the axial sites of Ni(II) are occupied by methanol used as a solvent. An analogous reaction in presence of 4,4'-bipyridyl (4,4'-bipy) yielded a three-dimensional structure Ni(HCOO)(2)(4,4'-bpy) (2). DC magnetic measurements as a function of temperature and field established the presence of spontaneous magnetization with T-c (Curie temperature) = 17 and 20.8 K in 1 and 2, respectively, which can be attributed due to spin-canting. DFT calculations were performed to corroborate the magnetic results of 1 and 2. (C) 2010 Elsevier Ltd. All rights reserved.

Enhancement of fatigue life of Ni-Ti-Fe shape memory alloys by thermal cycling

The effect of thermal cycling on the load-controlled tension-tension fatigue behavior of a Ni-Ti-Fe shape memory alloy (SMA) at room temperature was studied. Considerable strain accumulation was observed to occur in this alloy under both quasi-static and cyclic loading conditions. Though, in all cases, steady-state is reached within the first 50-100 cycles, the accumulated steady-state strain, epsilon(p.ss), is much smaller in thermally cycled alloy. As a result, the fatigue performance of them was found to be significantly enhanced vis-a-vis the as-solutionized alloy. Furthermore, under load-controlled conditions, the fatigue life of Ni-Ti-Fe alloys was found to be exclusively dependent on epsilon(p.ss). Observations made by profilometry and differential scanning calorimetry (DSC) indicate that the 200-500% enhancement in fatigue life of thermally cycled alloy is due to the homogeneous distribution of the accumulated fatigue strain. (C) 2010 Elsevier B.V. All rights reserved.

Debenzylation by Ni-A1 alloy

Nickel-aluminum alloy in aqueous sodium hydroxide-ethanol medium brings about facile hydro-enolrsis of benzyl ether function in substrates carrying a vicinal methoxy group. Simplicity of the reaction conditions and cheapness of the reagent are some of the advanrages of the procedure. Additionally, carbonyl functions when present are untouched and alkaline medium of the reaction makes it compatible with the presence of acid-sensitite groups.

Tiedostumaton nykytaiteessa : Katse, ääni ja aika vuosituhannen taitteen suomalaisessa nykytaiteessa

Leevi Haapala explores moving image works, sculptures and installations from a psychoanalytic perspective in his study The Unconscious in Contemporary Art. The Gaze, Voice and Time in Finnish Contemporary Art at the Turn of the Millennium . The artists included in the study are Eija-Liisa Ahtila, Hans-Christian Berg, Markus Copper, Liisa Lounila and Salla Tykkä. The theoretical framework includes different psychoanalytic readings of the concepts of the gaze, voice and temporality. The installations are based on spatiality and temporality, and their detailed reading emphasizes the medium-specific features of the works as well as their fragmentary nature, heterogeneity and affectivity. The study is cross-disciplinary in that it connects perspectives from the visual culture, new art history and theory to the interpretation of contemporary art. The most important concepts from psychoanalysis, affect theory and trauma discourse used in the study include affect, object a (objet petit a) as articulated by Jacques Lacan, Sigmund Freud s uncanny (das Unheimliche) and trauma. Das Unheimliche has been translated as uncanny in art history under the influence of Rosalind Krauss. The object of the study, the unconscious in contemporary art, is approached through these concepts. The study focuses on Lacan s additions to the list of partial drives: the gaze and voice as scopic and invocative drives and their interpretations in the studies of the moving image. The texts by the American film theorist and art historian Kaja Silverman are in crucial role. The study locates contemporary art as part of trauma culture, which has a tendency to define individual and historical experiences through trauma. Some of the art works point towards trauma, which may appear as a theoretic or fictitious construction. The study presents a comprehensive collection of different kinds of trauma discourse in the field of art research through the texts of Hal Foster, Cathy Caruth, Ruth Leys and Shoshana Felman. The study connects trauma theory with the theoretical analysis of the interference and discontinuity of the moving image in the readings by Susan Buck-Morss, Mary Ann Doane and Peter Osborn among others. The analysis emphasizes different ways of seeing and multisensoriality in the reception of contemporary art. With their reflections and inverse projections, the surprising mechanisms of Hans-Christian Berg s sculptures are connected with Lacan s views on the early mirroring and imitation attempts of the individual s body image. Salla Tykkä s film trilogy Cave invites one to contemplate the Lacanian theory of the gaze in relation to the experiences of being seen. The three oceanic sculpture installations by Markus Copper are studied through the vocality they create, often through an aggressive way of acting, as well as from the point of view of the functioning of an invocative drive. The study compares the work of fiction and Freud s texts on paranoia and psychosis to Eija-Liisa Ahtila s manuscripts and moving image installations about the same topic. The cinematic time in Liisa Lounila s time-slice video installations is approached through the theoretical study of the unconscious temporal structure. The viewer of the moving image is inside the work in an in-between state: in a space produced by the contents of the work and its technology. The installations of the moving image enable us to inhabit different kinds of virtual bodies or spaces, which do not correspond with our everyday experiences. Nevertheless, the works of art often try to deconstruct the identification to what has been shown on screen. This way, the viewer s attention can be fixed on his own unconscious experiences in parallel with the work s deconstructed nature as representation. The study shows that contemporary art is a central cultural practice, which allows us to discuss the unconscious in a meaningful way. The study suggests that the agency that is discursively diffuse and consists of several different praxes should be called the unconscious. The emergence of the unconscious can happen in two areas: in contemporary art through different senses and discursive elements, and in the study of contemporary art, which, being a linguistic activity is sensitive to the movements of the unconscious. One of the missions of art research is to build different kinds of articulated constructs and to open an interpretative space for the nature of art as an event.

Phase relationships in the system Ni-W-O and thermodynamic properties of NiWO,

The phase diagram of the Ni-W-O system at 1200 K was established by metallographic and X-ray identification of the phases present after equilibration at controlled oxygen potentials. The oxygen partial pressures over the samples were fixed by metered streams of CO+CO2 gas mixtures. There was only one ternary oxide, nickel tungstate (NiWO4), in the Ni-W-O system at a total pressure of 1 atm, and this compound decomposed to a mixture of Ni+WO2.72 on lowering the oxygen potential. The Gibbs' free energy of formation of NiWO4 was determined from the measurement of the e.m.f. of the solid oxide galvanic cell, Pt, Ni+NiWO4+WO2.72/CaO-ZrO2/Ni+NiO, Pt and thermodynamic properties of tungsten and nickel oxides available in the literature. For the reaction, NiO(s)+WO3(s)rarrNiWO4(s) DeltaG°=–10500–0.708 T (±250) cal mol–1.