Search results for "Y alloy"

Smart composite films of nanometric thickness based on copper-iodine coordination polymers. Toward sensors.

2018

One-pot reactions between CuI and methyl or methyl 2-amino-isonicotinate give rise to the formation of two coordination polymers (CPs) based on double zig-zag Cu2I2 chains. The presence of a NH2 group in the isonicotinate ligand produces different supramolecular interactions affecting the Cu-Cu distances and symmetry of the Cu2I2 chains. These structural variations significantly modulate their physical properties. Thus, both CPs are semiconductors and also show reversible thermo/mechanoluminescence. X-ray diffraction studies carried out under different temperature and pressure conditions in combination with theoretical calculations have been used to rationalize the multi-stimuli-responsive …

Friction Stir Processing of NiTi Shape Memory Alloy: Microstructural Characterization

2010

Shape Memory Alloys (SMA) are metal materials that, after being strained, come back to their original shape at a designated temperature. Welding NiTi alloys is not simple because when the material is melted, due to the high reactivity of the alloy elements, the typical shape memory properties may disappear. The solid state welding process, such as friction stir welding, is thus attractive for SMA joining and it exhibits potentials for achieving welded joints affected by microstructural changes that preserve the shape memory properties. The present study investigates the feasibility of friction stir welding process to join NiTi shape memory alloys; in order to analyse the welding process, it…

Epitaxial films of the magnetic shape memory material

2007

Abstract By DC-sputtering from a stoichiometric target onto sapphire substrates we prepared epitaxial films of Ni 2 MnGa . X-ray diffraction in two circle geometry shows only the Ni 2 MnGa peaks corresponding to a (1 1 0) oriented growth on the (1 1 0) oriented sapphire substrate. Rocking curve scans shows that the out of plane orientation has a width of only 1 . 1 ∘ . By four circle X-ray diffraction we find an in-plane aligned growth. The Curie temperature as determined by SQUID magnetometry is 368 K. On cooling down the low field magnetization drops at around 260–280 K indicating the austenite to martensite transition. The presence of two different phases at high and low temperature also…

Influence of the mode of introduction of a reactive element on the high temperature oxidation behavior of an alumina-forming alloy. Part I: Isotherma…

2004

Several routes of yttrium introduction were applied to test the high temperature oxidation performance of a FeCrAl alloy. Isothermal oxidation tests were described in a previous paper (Part I of this paper in this journal, 2004, 55, 352). Cyclic oxidation tests were performed in air under atmospheric pressure on blank specimens, Y 2 O 3 sol-gel coated-, Y 2 O 3 metal-organic chemical vapor deposited (MOCVD)-, yttrium ion implanted-alloys, as well as on a steel containing 0.1 wt.% of yttrium as an alloying element. For the 20 hours cycles, all the samples, except FeCrAl-0.1Y, exhibit weight losses after a few cycles, indicating drastic spallation of the oxide scales. The MOCVD coated specime…

Structural and Magnetic Properties of Epitaxial Ni<sub>2</sub>MnGa Thin Films

2009

We report on the preparation and investigation of epitaxial thin films of the magnetic shape memory alloy Ni2MnGa. For samples close to the stoichiometric composition we find that the phase transformation temperature is affected by the crystallographic orientation. Changes in the crystal structure due to the transformation are observed using temperature-dependent X-ray diffraction. Films with higher manganese content are in the martensitic state at room temperature. Those samples on Al2O3(11-20) reveal the 7-layered orthorhombic structure that allows strains up to 10 %. To avoid blocking of magnetostrictive effects by the substrate, free-standing films are prepared using water-soluble NaCl(…

Microstructure of freestanding single-crystalline Ni2MnGa thin films

2011

Abstract The complex crystal structure and variant distribution of single-crystalline freestanding Ni–Mn–Ga films was studied in detail using X-ray diffraction in two- and four-circle geometry. Selective chemical etching of a chromium buffer layer facilitates the release of the rigid MgO substrate that would inhibit magnetically induced reorientation (MIR) of variants. The substrate-constrained as well as the freestanding films possess identical crystal structure featuring a seven-layered (pseudo-)orthorhombic modulation (7 M/14 M). Of the 12 different variants observed before and after releasing the film from the substrate, four are predominantly represented. These have the short c -axis a…

Preparation of Heusler thin films: The quaternary alloy CO2Fe0.5Mn0.5Si

2008

In this work the basic strategies for the preparation of CO2Mn0.5Fe0.5Si as an example for Heusler alloy thin films will be described. Texture and magnetic properties of these films will be discussed, especially with regard to different buffer layers and annealing temperatures. Finally, we will show the integration of Heusler thin films into magnetic tunnel junctions (MTJs) and calculate the effective spin polarization. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Development of high entropy tungsten-based alloys by powder metallurgy processes

2022

Although metallurgy is a very old research domain, many innovations are still being considered, such as the emergence of high-entropy alloys. These alloys, composed of at least three elements, are characterized by a chemical composition without a majority element and most of the time equimolar. Research in this field is very recent since the first studies concerning these alloys are from the early 2000s. The original chemical compositions of these alloys open the way to many possibilities to obtain unusual properties.In conjunction with these developments, powder metallurgy processes are expanding quickly because of the advantages they offer over more traditional techniques (foundry and for…

Nonlinear Analysis of Reinforced Concrete Frames: Safety Evaluation and Retrofitting Techniques

Correlation of quenched structural disorder and magnetism inTiFe2Laves-phase thin films

2002

In recent bandstructure calculations for the $C14$ Laves-phase intermetallic compound ${\mathrm{TiFe}}_{2}$ two energetically nearly degenerate magnetic ground states (antiferromagnetic and ferromagnetic) were predicted. As a consequence of this near-degeneracy in the $C14$ stability range of ${\mathrm{Ti}}_{x}{\mathrm{Fe}}_{1\ensuremath{-}x}$ $(x\ensuremath{\approx}1/3)$ the magnetic properties are strongly correlated with the sublattices' occupation by Ti and Fe. We analyzed the magnetic properties of a series of thin epitaxial films with varying composition in the $C14$ stability range. The temperature- and field-dependent magnetic properties of these samples were determined by dc superc…