Magnetic entropy change of ErAl2 magnetocaloric wires fabricated by a powder-in-tube method
Takafumi D. Yamamoto, Hiroyuki Takeya, Suguru Iwasaki, Kensei Terashima, Pedro Baptista de Castro, Takenori Numazawa, Yoshihiko Takano
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This is the version of the article before peer review or editing, as submitted by an author to {insert name of Journal}. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at {https://dx.doi.org/10.1088/1361-6463/ab5c71}
We report the fabrication of ErAl2 magnetocaloric wires by a powder-in-tube method (PIT) and the evaluation of magnetic entropy change through magnetization measurements. The magnetic entropy change of ErAl2 PIT wires exhibits similar behavior to the bulk counterpart, while its magnitude is reduced by the decrease in the volume fraction of ErAl2 due to the surrounding non-magnetic sheaths. We find that another effect reduces the magnetic entropy change of the ErAl2 PIT wires around the Curie temperature, and discuss its possible origin in terms of a correlation between magnetic properties of ErAl2 and mechanical properties of sheath material.
We report the adiabatic temperature change in ErAl2 magnetocaloric wires fabricated by a powder-in-tube (PIT) process. The adiabatic temperature change of the PIT wires is found to be determined by not only the volume fraction of ErAl2 core but also the magnitude relationship between the specific heat of the ErAl2 core and the metal sheath. We propose a quantitative analysis method for calculating the temperature and core volume fraction dependence of adiabatic temperature change in the PIT wire, whose formula is applicable to also various magnetocaloric composites, useful to estimate the magn…
New approaches for the design of alloy systems with multiprincipal elements is recently researched in refractory materials field. However, most research aimed at arc melting process with weakness of coarsening of grains and inhomogeneous microstructure of segregation of elements during the cooling. This study aims to design and fabricate high-entropy alloy with powder metallurgy. In this study, a refractory high entropy alloys with composition near AlMo0.5NbTa0.5TiZr were produced by powder metallurgy. The alloy consists of two body-centered cubic (BCC) phases. One phase was disordered BCC enr…
Metal powders with hierarchical nanostructures are always designed and fabricated by dealloying with or without combination of other manufacturing processes. However, they are mainly nanoporous metal powder and its derivations, and their monotonous nanostructures restrict their applications, so metal powders with novel nanostructures should be explored further for various applications. Herein, high energy mechanical milling and dealloying can be combined together for fabricating mass-produced metal powders with controllable nanostructures. As an example, a nanograins-attached and ultrathin Cu …
The crystal and magnetic structure of the magnetocaloric compound FeMnP0.5Si0.5 have been studied by means of neutron and X-ray powder diffraction. Single phase samples of nominal composition FeMnP0.5Si0.5 have been prepared by the drop synthesis method. The compound crystallizes in the Fe2P-type structure (P-62m) with the magnetic moments aligned along the aaxis. It is found that the Fe atoms are mainly situated in the tetrahedral 3g site while the Mn atoms prefer the pyramidal 3f position. The material is ferromagnetic (TC = 382 K) and at 296 K the total magnetic moment is 4.4 μB/f.u. It is …
We report on the structural, magnetic, and magnetocaloric properties of polycrystalline (La0.5Pr0.5)0.6Ba0.4MnO3 (LPBMO), which was fabricated by a conventional solid-state reaction method. LPBMO undergoes a second-order paramagnetic to ferromagnetic (PM-FM) phase transition around a Curie temperature TC ~ 277 K. The maximum magnetic entropy change is ~ 3.22 J kg-1 K-1 for a magnetic field change of 5 T. Based on the modified-Arrott plot and the iterative Kouvel Fisher methods, a set of critical exponents (beta = 0.514, gamma = 1.164, and delta = 3.265) are determined. These values are close t…
A detailed study on the crystal structure and bulk magnetic properties of Cr substituted Ising type lanthanide gallium garnets $Ln_3\text{CrGa}_4\text{O}_{12}$ ($Ln$ = Tb, Dy, Ho) has been carried out using room temperature powder X-Ray and neutron diffraction, magnetic susceptibility, isothermal magnetisation and heat capacity measurements. The magnetocaloric effect (MCE) in $Ln_3\text{CrGa}_4\text{O}_{12}$ is compared to that of $Ln_3\text{Ga}_5\text{O}_{12}$. In lower magnetic fields attainable by a permanent magnet ($\leq$ 2 T), Cr substitution greatly enhances the MCE by 20% for $Ln$ = Dy…
Bi_{4}Ti_{3}O_{12}-PVC composites were fabricated. Ceramics powders of bismuth titanate were prepared by the sol-gel method using bismuth nitrate pentahydrate Bi(NO_{3})_{3} \cdot 5H_{2}O and tetrabutyl titanate Ti(CH_{3}(CH_{2})_{3}O)_{4} as precursors. The Bi_{4}Ti_{3}O_{12}-PVC composites were fabricated from ceramics powders and polymer powders by hot-pressing method.
Plastic inhomogeneity, particularly localised strain, is one of the main mechanisms responsible for failures in engineering alloys. This work studied the spatial arrangement and distribution of microstructure and their influence in the plastic inhomogeneity of Inconel 718 fabricated by additive manufacturing (AM). In particular, the density and spatial distribution of geometrically necessary dislocations (GNDs) and the crystallographic texture components were examined in relation to the spatial plastic deformation. In-situ tensile testing coupled with microscopy and EBSD was performed to under…
Open-porous scaffolds of WE43 Mg alloy with a body-center cubic cell pattern were manufactured by laser powder bed fusion with different strut diameters. The geometry of the unit cells was adequately reproduced during additive manufacturing and the porosity within the struts was minimized. The microstructure of the scaffolds was modified by means of thermal solution and ageing heat treatments and was analysed in detail by means of X-ray microtomography, optical, scanning and transmission electron microscopy. Moreover, the corrosion rates and the mechanical properties of the scaffolds were meas…
The polycrystalline Mn1.26Fe0.60P0.48Si0.52 microwires were successfully fabricated for the first time by the melt-extraction technique, and their magnetic and magnetocaloric properties were investigated systematically. The structural analysis shows that the microwires possess a hexagonal phase with Fe2P type, with a homogeneous composition distribution. Magnetometry measurements show that the microwires undergo a weak first-order magnetic phase transition at a temperature of 142 K. The maximum magnetic entropy change of the microwires reaches 4.64 Jkg-1K-1 for a field change of 5 T. These low…
La0.4Pr0.3Ca0.1Sr0.2MnO3 has been investigated as a potential candidate for room temperature magnetic refrigeration. Results from X-ray powder diffraction reveal an orthorhombic structure with Pnma space group. The electronic and chemical properties have been confirmed by X-ray photoelectron spectroscopy and ion-beam analysis. A second-order paramagnetic to ferromagnetic transition was observed near room temperature (289 K), with a mean-field like critical behaviour at low field and a tricritical mean-field like behaviour at high field. The field induced crossover in critical behaviour is a co…
The CrMnFeCoNi high-entropy alloy is highly printable and holds great potential for structural applications. However, no significant discussions on cyclic plasticity and fatigue damage in previous studies. This study provides significant insights into the link between print processes, solidification microstructure, cyclic plasticity and fatigue damage evolution in the alloy fabricated by laser powder bed fusion. Thermodynamics-based predictions (validated by scanning transmission electron microscopy (STEM) energy dispersive X-ray spectroscopy (EDX)) showed that Cr, Co and Fe partition to the c…
The implementation of processed magnetic materials onto thermoplastics can be an approach for practical application of brittle intermetallic materials with the advantage of enlarging the range of applications. In the present work, we evaluate the effect of blending magnetocaloric Gd$_5$Si$_{2.4}$Ge$_{1.6}$ micrometric particles with 3.4 $μ$m in different weight fractions onto a flexible, transparent and non-magnetic poly(methyl methacrylate) (PMMA). A close to homogeneous grain distribution along the polymer surface were achiever by using a simple solvent casting method for evaluation of their…
Effective post-heat treatment is critical to achieve desired microstructure for high-performance in additively manufactured (AM) components. In this work, the influence of homogenization on microstructure-property relationship in 17-4PH steels has been investigated. Precipitation of NbC, oxides, and ε-Cu were observed in the as-built 17-4PH steels. To design an optimum post-heat treatment, homogenization was performed at 1050oC for different times followed by aging at 482oC for 1 hour. It was identified that homogenization for 1 hour followed by aging leads to the best combination of strength …
For the first time, cyclic re-austenitization is carried out for additively manufactured high-strength low-alloy (HSLA) steels in order to refine the microstructure by reducing the prior austenite grain (PAG) size. In this work, HSLA-100 steels processed using laser powder bed fusion (LPBF) technique are subjected to several cycles of re-austenitization using quenching dilatometry. Microstructure characterization for every cycle revealed the presence of bainite, martensite and martensite/austenite (M/A) islands. From the analysis of the dilatometry curves and extensive microstructure character…
Frustrated lanthanide oxides with dense magnetic lattices are of fundamental interest for their potential in cryogenic refrigeration due to a large ground state entropy and suppressed ordering temperatures, but can often be limited by short-range correlations. Here, we present examples of frustrated fcc oxides, Ba$_2$GdSbO$_6$ and Sr$_2$GdSbO$_6$ and the new site-disordered analog Ca$_2$GdSbO$_6$ ([CaGd]$_A$[CaSb]$_B$O$_6$), in which the magnetocaloric effect is influenced by minimal superexchange ($J_1 \sim 10$ mK). We report on the crystal structures using powder x-ray diffraction and the bu…
Lattice structures composed of periodic solid frames and pores can be utilized in energy absorption applications due to their high specific strength and large deformation. However, these structures typically suffer from post-yield softenings originating from the limited plasticity of available material choices. This study aims to resolve such an issue by fabricating lattice structures made of ductile pure copper (Cu). For the first time, Cu lattice structures are fabricated through laser-powder bed fusion (L-PBF) with green laser (λ = 515 nm). Structural and microstructural analysis confirm th…
Neutron powder diffraction studies of the crystal and magnetic structures of the magnetocaloric compound Mn1.1Fe0.9(P0.8Ge0.2) have been carried out as a function of temperature, applied magnetic field, and pressure. The data reveal that there is only one transition observed over the entire range of variables explored, which is a combined magnetic and structural transformation between the paramagnetic to ferromagnetic phases (Tc~255 K for this composition). The structural part of the transition is associated with an expansion of the hexagonal unit cell in the direction of the a- and b-axes and…
Double magnetic transition, complex field-induced phases, and large magnetocaloric effect in the frustrated garnet compound Mn$_{3}$Cr$_{2}$Ge$_{3}$O$_{12}$
The irreversibility of the martensite transition in magnetic shape memory alloys (MSMAs) with respect to external magnetic field is one of the biggest challenges that limits their application as giant caloric materials. This transition is a magneto-structural transition that is accompanied with a steep drop in magnetization (i.e., 'delta M') around the martensite start temperature (Ms) due to the lower magnetization of the martensite phase. In this communication, we show that 'delta M' around Ms in Mn rich Ni-Mn based MSMAs gets suppressed by two orders of magnitude in crushed powders due to t…
Ti and Ti-Based alloys have unique properties such as high strength, low density and excellent corrosion resistance. These properties are essential for the manufacture of lightweight and high strength components for biomedical applications. In this paper, Ti properties such as metallurgy, mechanical properties, surface modification, corrosion resistance, biocompatibility and osseointegration in biomedical applications have been discussed. This paper also analyses the advantages and disadvantages of various Ti manufacturing processes for biomedical applications such as casting, powder metallurg…
Additive manufacturing of Ni-Mn-Sn shape memory Heusler alloy -- Microstructure and magnetic properties from powder to printed parts
Technical University of Darmstadt（达姆施塔特工业大学）；University of Kassel（卡塞尔大学）；Fraunhofer Institution for Material Cycles and Resource Strategies IWKS（弗劳恩霍夫材料循环与资源策略研究所 IWKS）；TU Bergakademie Freiberg（弗莱贝格矿业技术大学）
Silver-doped ZnO nanoparticles were successfully fabricated at $400\,^{\circ}\mathrm{C}$ via a simple and rapid method based on short time solid state milling and calcination of precursor powders. The effect of Ag dilute doping on the structural, optical, and photocatalytic properties of ZnO nanoparticles was investigated by X-ray diffraction (XRD), UV-vis spectrophotometer and photoluminescence (PL) spectroscopy.~X-ray analysis revealed that Ag doped ZnO solidified in hexagonal wurtzite structure.~ The intensity of deep level emission was reduced with increasing silver doping in PL measuremen…
We report the structural, magnetic, and magnetocaloric properties of Co$_2$Cr$_{1-x}$Ti$_x$Al ($x=$ 0--0.5) Heusler alloys for spintronic and magnetic refrigerator applications. Room temperature X-ray diffraction and neutron diffraction patterns along with Rietveld refinements confirm that the samples are of single phase and possess a cubic structure. Interestingly, magnetic susceptibly measurements indicate a second order phase transition from paramagnetic to ferromagnetic where the Curie temperature (T$_{\rm C}$) of Co$_2$CrAl increases from 330~K to 445~K with Ti substitution. Neutron powde…
We use neutron powder diffraction to investigate the magnetic and crystalline structure of Cr$_2$GaN. A magnetic phase transition is identified at $T \approx 170$ K, whereas no trace of structural transition is observed down to 6 K. Combining Rietveld refinement with irreducible representations, the spin configuration of Cr ions in Cr$_2$GaN is depicted as an incommensurate sinusoidal modulated structure characterized by a propagating vector ${k}$=(0.365, 0.365, 0). Upon warming up to the paramagnetic state, the magnetic order parameter closely resembles to the temperature dependence of $c$-ax…
This study examines the lanthanide calcium oxyborates Ca$_4$LnO(BO$_3$)$_3$ (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb). The reported monoclinic structure (space group $Cm$) was confirmed using powder X-ray diffraction. The magnetic Ln$^{3+}$ ions are situated in well-separated chains parallel to the c axis in a quasi-one-dimensional array. Here we report the first bulk magnetic characterisation of Ca$_4$LnO(BO$_3$)$_3$ using magnetic susceptibility $χ$(T) and isothermal magnetisation M(H) measurements at T $\geq$ 2 K. With the sole exception of Ca$_4$TbO(BO$_3$)$_3$, which displays a…
By using solid-state reactions, we successfully synthesize new oxyselenides CsV$_2$Se$_{2-x}$O (x = 0, 0.5). These compounds containing V$_2$O planar layers with a square lattice crystallize in the CeCr$_2$Si$_2$C structure with the space group of $P4/mmm$. Another new compound V$_2$Se$_2$O which crystallizes in space group $I4/mmm$ is fabricated by topochemical deintercalation of cesium from CsV$_2$Se$_2$O powder with iodine in tetrahydrofuran(THF). Resistivity measurements show a semiconducting behavior for CsV$_2$Se$_2$O, while a metallic behavior for CsV$_2$Se$_{1.5}$O, and an insulating f…
