Synthesis, characterization and stability of amorphous alloys

In this paper the results of chemical and electrochemical synthesis of Fe-P, Fe-W and Fe-Ni amorphous powders, investigations of their structural characteristics, stability and processes of their relaxation and stabilization during heating in the temperature range of 20-1000oC are presented.

Hydrogen Energy - Challenges and Perspectives

Hydrogen economy represents the future of human civilization. Limited resources of our planet are compelling us to turn to renewable clean energy resources and hydrogen figures prominently as the energy carrier of a future sustainable energy system. There are significant challenges to be overcome in order to make hydrogen viable, in production, storage and power generation, while safety of operation is an ever-present factor that determines success or failure of a proposed solution. Recent developments in all of these aspects are reviewed in this book, along with some latest research in the field of hydrogen energy and use

Influence of the changes of free electron density on electrical and magnetic properties of the CO70Fe5Si10B15 amorphous alloy

In this study we present the results on structural relaxation of the Co70Fe5Si10B15 amorphous alloy investigated by measuring the thermo-electromotive force (TEMF) during isothermal annealing (for 600 s). A mechanical junction of the investigated alloy and a copper conductor has been constructed for measuring the thermo-electromotive force (ε). Annealing was performed at temperatures T1 = 430˚C, T2=460˚C and T3=480˚C which are about 50 to 100˚C lower than the crystallization temperature. At these temperatures structural relaxation occurred only in the amorphous alloy. The activation energy E=224 kJ/mol and rate constants k1=6.66·10-5 s-1 k2=33·10-5 s-1 and k3=76·10-5 s-1 at temperatures T1, T2 and T3 respectively, have been determined for the process. Each isothermal annealing has been followed by determination of the relative change of the electronic state density at the Fermi level as Dn1/n=2.36%, Dn2/n =3.21% and Dn3/n= 9.80%, respectively.

Thermal stability and kinetic studies of new cobalt(III) complexes with a tetraazamacrocyclic and dithiocarbamate ligands

The thermal properties of four cobalt(III) complexes with cyclam (1,4,8,11-tetraazacyclotetradecane) and the heterocyclic dithiocarbamates Rdtc(-) [2-, 3-, 4-methylpiperidine (2-, 3-, 4-Mepipdtc(-)) or 4-thiomorpholine (Timdtc(-)) dithiocarbamates], of the general formula [Co(Rdtc)cyclam](ClO4)(2), have been investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). The thermal decomposition pathways of these complexes were also proposed. The following thermal stability order can be recognized for the examined complexes. depending on the position of the methyl group on the piperidine ring coordinating dithiocarbamates 2- GT 3- GT 4 -Mepipdtc(-). Generally, the same order was found to affect the decrease in kinetic and activation parameters.Trends in Advanced Materials and Processes, 3rd Yugoslov-Materials-Research-Society Conference, Sep 20-24, 1999, Herceg Novi, Yugoslavi

Electrochemical oscillations during copper electrodissolution/passivation in trifluoroacetic acid induced by current interrupt method

Complex oscillatory behavior of electric current and electrode potential were observed during potentiodynamic anodic polarization of Cu in 1 M TFA, applying the current interrupt method for IR drop compensation. This oscillatory behavior was found to give an electrochemical response in the form of a polarization curve with continuous loop. The results presented show that the current interrupt method is capable of eliminating the entire IR drop. Under such conditions, oscillations of the applied potential are in fact those of the double-layer potential. Theoretically predicted interplay between oscillatory behavior of the double-layer potential and the electric current is experimentally demonstrated. (C) 2014 Elsevier Ltd. All rights reserved

Influence of MgO addition on the synthesis and electrical properties of sintered zinc-titanate ceramics

Starting mixtures of ZnO, TiO(2) and MgO (0, 1.25 and 2.5 wt.% MgO) powders were mechanically activated for 15 min in a planetary ball mill. The powders obtained were sintered non-isothermally to temperatures between 800 and 1100 degrees C and then held at those temperatures for 120 min. Analysis of the influence of MgO addition on the synthesis of zinc-titanate ceramics showed that its addition increased slightly the temperature at which the reaction process started, accelerated the reaction and resulted in higher sample densities. These results were correlated with the results of structural characterization using X-ray powder diffraction method and SEM analysis. Also, the results of electric resistivity, capacitance and loss tangent of the sintered samples were obtained. (C) 2008 Elsevier B.V. All rights reserved

Morphology and Microstructure of Annealed Ni-Co Alloy Powders Electrodeposited on Copper Substrates

Kein Abstract verfügba