scholarly journals Neutron Diffraction Study of the Martensitic Transformation of Ni2.07Mn0.93Ga Heusler Alloy

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1749
Author(s):  
Lara Righi
Keyword(s):  
Structural Analysis ◽  
Martensitic Transformation ◽  
Neutron Diffraction ◽  
Heusler Alloy ◽  
Neutron Diffraction Study ◽  
Martensitic Transition ◽  
Scanning Calorimetry ◽  
Limit Value ◽  
Different Temperatures ◽  
Scattering Lengths

The martensitic transition featuring the ternary Heusler alloy Ni2.09Mn0.91Ga was investigated by neutron diffraction. Differential scanning calorimetry indicated that structural transition starts at 230 K on cooling with a significant increase in the martensitic transformation onset compared to the classical Ni2MnGa. The low-temperature martensite presents the 5M type of modulated structure, and the structural analysis was performed by the application of the superspace approach. As already observed in Mn-rich modulated martensites, the periodical distortion corresponds to an incommensurate wave-like shift of the atomic layers. The symmetry of the modulated martensite at 220 K is orthorhombic with unit cell constants a = 4.2172(3) Å, b = 5.5482(2) Å, and c = 4.1899(2) Å; space group Immm(00γ)s00; and modulation vector q = γc* = 0.4226(5)c*. Considering the different neutron scattering lengths of the elements involved in this alloy, it was possible to ascertain that the chemical composition was Ni2.07Mn0.93Ga, close to the nominal formula. In order to characterize the martensitic transformation upon increasing the temperature, a series of neutron diffraction patterns was collected at different temperatures. The structural analysis indicated that the progressive change of the martensitic lattice is characterized by the exponential change of the c/a parameter approaching the limit value c/a = 1 of the cubic austenite.

scholarly journals Analysis of Sr3-xCa1+xMn2CoO9 combining electron, X-ray and neutron diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C929-C929
Author(s):  
Philippe Boullay ◽  
Olivier Pérez ◽  
Bernard Raveau ◽  
Seikh Motin ◽  
Caignaert Vincent
Keyword(s):  
Electron Diffraction ◽  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Structural Model ◽  
X Ray ◽  
Cell Parameters ◽  
Precession Electron Diffraction ◽  
Different Temperatures ◽  
Scattering Lengths

The AxBX3 hexagonal perovskite-type compounds exhibit interesting magnetic properties such as complex magnetism or random spin chain magnetism[1,2]. Their structures are built up from infinite [BO3] chains consisting of alternating octahedral and trigonal prismatic units, separated by A infinite chains. Sr3-xCa1+xMn2CoO9 are belonging to this family of materials. X-ray powder diffraction patterns are collected for different Sr3-xCa1+xMn2CoO9 samples with different x values. Pattern matching analysis with the SG P-3 and the following cell parameters a=b=9.490(1)Å c=3xc'=3x2.57=7.732(1)Å reveals problematic groups of reflections; these reflections are shifted from one pattern to another one and, moreover, have positions preventing their indexation. Owing to the lack of spatial resolution and peaks overlapping in the powder data, the understanding of the present problem is quite impossible. Electron Diffraction Tomography (EDT) combined with Precession Electron Diffraction (PED) has been used for exploring the reciprocal space of the Sr3-xCa1+xMn2CoO9, x=0 sample. The slight deviations observed from the rational 1/3 c'* value is in agreement with the existence of aperiodicities. The structure of this family of materials has been then described using the super space formalism as a composite structure. The structural model is determined from the PED data integrated with PETS[2]; the first and second sublattices are referring to (Mn,Co)O3 and (Ca,Sr) structural parts respectively. This model is confirmed by the refinement of the X-ray powder diffraction data. Powder neutron diffraction data were then collected at PSI for different temperatures and different Sr3-xCa1+xMn2CoO9 samples. Using the previously refined model, a Co/Mn ordering is revealed thanks to the neutron scattering lengths of these two elements (see fig1). Finally, the treatment of the antiferromagnetic behavior observed bellow 25K is performed in the 4d approach using Jana2006[3].

scholarly journals Field dependent neutron diffraction study in Ni50Mn38Sb12 Heusler alloy

2017 ◽  
Vol 110 (2) ◽  
pp. 021902 ◽  
Author(s):  
Roshnee Sahoo ◽  
Amitabh Das ◽  
Norbert Stuesser ◽  
K. G. Suresh
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Heusler Alloy ◽  
Neutron Diffraction Study ◽  
Field Dependent

scholarly journals Study of hydrogen storage materials by neutron powder diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C939-C939
Author(s):  
Jacques Huot ◽  
Catherine Gosselin ◽  
Thomas Bibienne ◽  
Roxana Flacau
Keyword(s):  
Neutron Diffraction ◽  
Hydrogen Storage ◽  
Room Temperature ◽  
Cast Alloy ◽  
Metal Hydrides ◽  
Structural Difference ◽  
Neutron Diffraction Study ◽  
Point Of View ◽  
Scattering Lengths ◽  
The One

Metal hydrides are interesting materials from a fundamental as well as practical point of view. Hydrogen storage applications have been the main driving force of research on these materials but lately uses such as thermal storage are considered. In this presentation we will review the use of neutron diffraction for the development of new metal hydrides. Two systems will be presented: BCC solid solution alloys and FeTi alloy. Ti-based BCC solid solutions are promising material for hydrogen storage applications which need high volumetric capacity and room temperature operation. One system that has been considered is Ti-V-Cr. Using only X-ray diffraction for structural identification does not provide information about hydrogen localization. Therefore, neutron diffraction is essential for complete determination of this class of hydrides. We will present examples of Ti-V-Cr compounds doped with Zr-Ni alloy. The peculiarity of this type of alloy is that, for neutron diffraction, the scattering lengths of the elements almost cancel. Therefore, the neutron pattern of as-cast alloy shows very small Bragg peaks but the advantage is that the hydride for is very easy to see and analyze. Another good candidate for hydrogen storage applications is the intermetallic compound TiFe which operates at around room temperature (RT) under mild pressure conditions. However one disadvantage of TiFe alloy synthesized by conventional metallurgical method is its poor activation characteristics. The alloy reacts with hydrogen only after complicated activation procedure involving exposure to high temperature (~4000C) and high pressure for several days. Recently we found that by doping this alloy with Zr and Zr7Ni10 the activation could be easily done at room temperature. We present here a neutron diffraction study of these compounds that shows the structural difference between the activated compound and the one cycled under hydrogen.

Neutron Diffraction Study of a CuAlBe Shape Memory Alloy

2011 ◽  
Vol 172-174 ◽  
pp. 178-183 ◽  
Author(s):  
Matthieu Dubois ◽  
Marie Hélène Mathon ◽  
Vincent Klosek ◽  
Gilles Andre ◽  
Alain Lodini
Keyword(s):  
Neutron Diffraction ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Texture Evolution ◽  
Neutron Diffraction Study ◽  
Raw Material ◽  
Martensitic Transition ◽  
Transition Temperatures ◽  
Austenitic Phase ◽  
Rolling Rate

This work presents the texture evolution of the austenitic phase of a copper based shape memory alloy by neutron diffraction. The Cu-11%Al-0.62%Be (in mass %) alloy was subjected to cold and hot rolling processes. The texture of the rolled samples at reduction rates of 5%, 10% and 15% respectively were compared to those of the raw material. A <001> partial fiber is observed for the raw material and cold rolled samples whereas the texture of the hot rolled sample is mainly characterized by a <111> fiber. The influence of these mechanical treatments on the transition temperatures and the hysteresis evolution was also analysed by following the integrated intensity of the {220} reflection of the austenitic phase. A shift towards low temperatures of martensitic transition temperatures is observed with the increasing of the rolling rate.

Neutron Diffraction Study of a Non-Stoichiometric Ni-Mn-Ga MSM Alloy

2013 ◽  
Vol 738-739 ◽  
pp. 103-107 ◽  
Author(s):  
Pnina Ari-Gur ◽  
V. Ovidiu Garlea ◽  
Ashley Coke ◽  
Yan Ling Ge ◽  
Ilkka Aaltio ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Diffraction Pattern ◽  
Lattice Constant ◽  
Heusler Alloy ◽  
Stoichiometric Composition ◽  
Site Occupancy ◽  
Neutron Diffraction Study ◽  
Critical Importance ◽  
Chemical Order

Abstract. The structure and chemical order of a Heusler alloy of non-stoichiometric composition Ni-Mn-Ga were studied using constant-wavelength (1.538 Å) neutron diffraction at 363K and the diffraction pattern was refined using the FullProf software. At this temperature the structure is austenite (cubic) with Fm space group and lattice constant of a = 5.83913(4) [Å]. The chemical order is of critical importance in these alloys, as Mn becomes antiferromagnetic when the atoms are closer than the radius of the 3d shell. In the studied alloy the refinement of the site occupancy showed that the 4b (Ga site) contained as much as 22% Mn; that significantly alters the distances between the Mn atoms in the crystal and, as a result, also the exchange energy between some of the Mn atoms. Based on the refinement, the composition was determined to be Ni1.91Mn1.29Ga0.8

Magnetic Field and Annealing Influence on the Martensitic Transition in Ni45.8Mn42.6In11.6 Shape Memory Alloy Ribbons

2012 ◽  
Vol 190 ◽  
pp. 307-310 ◽  
Author(s):  
Lorena González ◽  
J. García ◽  
M. Nazmunnahar ◽  
W.O. Rosa ◽  
L. Escoda ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Martensitic Transformation ◽  
Low Temperature ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
High Magnetic Field ◽  
Heusler Alloy ◽  
Vacuum Annealing ◽  
Martensitic Transition ◽  
Two Peaks

We report the effect of shorttime vacuum annealing, during 10 minutes at 923 K, 973 K, 1023 K and 1073 K, on magnetostructural properties of as-quenched ribbons of Ni45.5Mn43In11.5 Heusler alloy. The martensitic transformation is strongly sensitive to annealing treatments. The martensitic phase starting temperature is significantly shifted from 239 K towards higher temperatures around 370 K. It suffers a break down in two peaks when a field equal or higher than 500 Oe is applied to the as-quenched sample. This effect is not detected in the transformation of annealed ribbons but its signature can be observed at low temperature. Moreover, under high magnetic field up to 30 kOe temperatures associated with both martensitic and reverse transitions do not change for annealed samples, meanwhile the magnetization difference between austenite and martensite increases with the field. Nevertheless, it almost remains unchanged in the as-quenched ribbon.

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