Search results for "Magnesium"
showing 10 items of 490 documents
Low-temperature studies of Cr 3+ ions in natural and neutron-irradiated g-Al spinel
2020
This study was supported by a grant from Latvian Council of Science (agreement No. LZP-2018/1-0214).
Nanoconfined mixed Li and Mg borohydrides as materials for solid state hydrogen storage
2012
Abstract Several mixtures of LiBH4 and Mg(BH4)2 borohydrides in different stoichiometric ratios (1:0, 2:1, 1:1, 1:2, 0:1), prepared by high energy ball milling, have been investigated with X-ray powder diffraction and thermal programmed desorption (TPD) volumetric analysis to test the dehydrogenation kinetics in correlation with the physical mixture composition. Afterwards mixed and unmixed borohydrides were dispersed on high specific surface area ball milled graphite by means of the solvent infiltration technique. BET and statistical thickness methods were used to characterize the support surface properties, and SEM micrographs gave a better understanding of the preparation techniques. It …
Oxidation of magnesia-supported Pd-clusters leads to the ultimate limit of epitaxy with a catalytic function
2005
Oxide-supported transition-metal clusters and nanoparticles have attracted significant attention owing to their important role as components of model catalysts, sensors, solar cells and magnetic recording devices. For small clusters, functionality and structure are closely interrelated. However, knowledge of the structure of the bare cluster is insufficient as the interaction with the chemical environment might cause drastic structural changes. Here we show by ab initio simulations based on the density functional theory that the reaction with molecular oxygen transforms small, non-crystalline, magnesia-supported Pd-clusters to crystalline Pd(x)O(y) nano-oxide clusters that are in epitaxy wi…
Metallic evolution of small magnesium clusters
2001
Structural and electronic properties of small magnesium clusters (N≤13) are studied using a first-principles simulation method in conjunction with the density functional theory and generalized gradient correction approximation for the exchange-correlation energy functional. It is observed that the onset of metallization of magnesium clusters is hard to assign since both the s-p hybridization and the energy gap between the valence and conduction bands do not evolve rapidly towards the known bulk properties. Instead these quantities show a slow and nonmonotonic evolution.
Experimental Research of the Formability of Lightweight Metallic Materials Used in Automotive Industry
2015
This paper aims to study the plastic deformation behaviour of lightweight metallic materials in order to reduce the total weight of the vehicles without affecting their performances. For the theoretical and experimental researches presented here, among these materials the AZ31B magnesium alloy has been chosen, a representative alloy for the magnesium-zinc-aluminium alloy system. The results of the theoretical researches, made on finite elements models, were validated by means of experimental researches consisting of tensile tests, forming limit curves determination tests and AZ31B magnesium alloy drawing, respectively.
Experimental and Numerical Analysis on FSWed Magnesium Alloy Thin Sheets Obtained Using “Pin” and “Pinless” Tool
2012
The present investigation aims at studying the effect of different tool geometries and process parameters on FSW of thin sheets in AZ31 magnesium alloy. In particular two properly designed tools, with shoulder diameters equal to 8 and 19 mm, were used; each of them was manufactured both in pin and pinless configurations. The effect of the different tool configurations and sizes, and welding parameters on mechanical properties of FSWed joints were analyzed in detail. The results were compared with those obtained on the base material. It was shown that FSWed joints are characterized by strength and ductility values lower than those of base material. Furthermore, the pin tool configuration, wi…
Friction Stir Welding as an Effective Alternative Technique for Light Structural Alloys Mixed Joints
2014
Abstract The increasing use of structural light alloys in the aeronautical, automotive and transportation industry is pushing researchers to find new solutions for the production of innovative components. Mixed joints made out dissimilar alloys represent a challenge for engineers to the difficulties arising in welding materials characterized by significantly different mechanical, thermal and chemical properties. In the paper, an overview of the most used process to produce dissimilar joints of aluminum, magnesium and titanium is given. Both fusion based and solid state welding processes can be used. Although the joining of these materials is possible, particular attention must be taken to t…
Methods for Enhancing the Thermal Durability of High-Temperature Thermoelectric Materials
2013
Author's version of an article in the journal: Journal of Electronic Materials. Also available from the publisher at: http://dx.doi.org/10.1007/s11664-013-2917-0 Thermoelectric materials, for example skutterudites and magnesium silicides, are being investigated as promising materials for medium-to-high-temperature waste heat recovery in transport and in industry. A crucial aspect of the success of a thermoelectric material is its stability over time when exposed to rapid heating and cooling. In this work different aspects of the degradation of these thermoelectric materials at high temperature were examined. Initial thermal durability was studied, and several candidate coatings were evaluat…
Prediction of alkaline earth elements in bone remains by near infrared spectroscopy.
2016
An innovative methodological approach has been developed for the prediction of the mineral element composition of bone remains. It is based on the use of Fourier Transform Near Infrared (FT-NIR) diffuse reflectance measurements. The method permits a fast, cheap and green analytical way, to understand post-mortem degradation of bones caused by the environment conditions on different skeletal parts and to select the best preserved bone samples. Samples, from the Late Roman Necropolis of Virgen de la Misericordia street and En Gil street located in Valencia (Spain), were employed to test the proposed approach being determined calcium, magnesium and strontium in bone remains and sediments. Coef…
Electrochemical reactivity of magnesium porphine : functionalization, oligo-polymerization and application to the synthesis of porphyrins and multi-p…
2012
This work deals with the redox reactivity of magnesium porphine, the study of its electropolymerization and resulting materials, of its functionalization by nucleophiles as well as the mechanistic investigation of the C-C oxidative coupling on a tris-meso-substituted porphyrin model.The electrochemical oxidation of magnesium porphine to its cation radical leads to oligomers in solution and polymers on the electrode, which molecular structure depends on the imposed potential. The reactivity of the cation radical has also been exploited by adding sufficient amount of nucleophiles (pyridine and triphenylphosphine) in the reactional in order to inhibit the oligomerization/polymerization process…