Ni Ribbons Research Articles

Multilevel nonvolatile memory based on the hysteretic giant magnetoimpedance effect of heterogeneous magnetic laminate

This work investigates the asymmetric and hysteretic GMI effect of two-phase heterogeneous magnetic laminate consisting of Ni/Fe30Ni45Co18Si2B5/micro-planar coil/Fe30Ni45Co18Si2B5/Ni for nonvolatile memory application. Since the magnetostrictive Ni ribbon produces the remanent magnetoelastic and magnetostatic fields to the neighboring soft amorphous magnetic alloy (Fe30Ni45Co18Si2B5) when the external dc magnetic field is removed, the proposed laminate manifests multi-level remanent impedances depending on the previously applied magnetic field. And the maximum nonvolatile GMI ratio of 130% is obtained at 400 kHz frequency. Furthermore the laminate can function as multilevel nonvolatile memory, which consumes zero standby power without losing data.

Effect of Ni Addition on the Morphology and Microstructure of Both Conventional Cast and Melt-Spun of Al–Si–Fe–Nb (at wt%) Alloy

In this project the morphology and microstructure of both conventional cast and melt spun of Al–20Si–9Fe–1.2Nb and Al–20Si–9Fe–1.2Nb–6Ni (at wt%) alloys were investigated. Therefore, in order to study the effect of added Ni on the morphology characteristics of the above-mentioned alloy, the resulting conventional cast and ribbons of Al–20Si–9Fe–1.2Nb and Al–20Si–9Fe–1.2Nb–6Ni alloys were synthesized and analysed using OM optical microscopy, X-ray diffraction, SEM scanning electron microscopy together with EDS energy dispersive spectroscopy. Observations exhibit that, XRD patterns of Al–Si–Fe–Nb and Al–Si–Fe–Nb–Ni ribbons revealed the peaks of only α-Al phase. Therefore, after adding of 6 wt% Ni, peaks of α-Al were shifted to the relatively lower angles with a very weak intensity. Furthermore, 6 wt% Ni addition causes homogeneously scattered colonies (size range 5 –25 μm) which contain fine spherical (primary Si and δ-Al4(FeNiNb)Si2 phases) particles in the α-Al dendrite of rapidly solidified Al–20Si–9Fe–1.2Nb alloy, the size of spherical particles were found to be in the range of 100 nm–1 μm.

Methane partial oxidation over porous nickel monoliths: The effects of NiO-MgO loading on microstructural parameters and hot-spot temperature

Developments of highly efficient catalysts for hydrocarbon fuel conversion have a critical importance for the solid oxide fuel cell (SOFC) technology and hydrogen production. In this work, a series of catalytic monoliths made of porous Ni ribbons with various NiO-MgO loadings were prepared via impregnation with the metal acetates and calcination. The catalysts were tested for the partial oxidation of methane under adiabatic conditions without inlet flow preheating at air excess factors, O2/(2·CH4), varying in the range 0.3–0.4. When NiO-MgO loading increases, the inlet hot spot temperature was found to exhibit minima reflecting changes of the CH4 reforming rate-determining factors in the catalyst frontal layer. A model describing this unusual phenomenon in terms of the volumetric activity and gas permeability of the porous catalysts, was proposed. The model was validated using experimental results of the catalytic tests, high-resolution transmission electron microscopy and mercury porosimetry.

Improvement in Cycling Performance of Rechargeable Metal Hydride/Air Laminate Cell

A metal hydride (MH)/air secondary battery is one of the next generation energy storage devices, since a high energy density and a high power density are expected from its unique property that the active mass of the positive electrode is oxygen in air. We have developed this type of battery and demonstrated that a non-packaged cell fabricated using PTFE container has about 900 Wh/L [1] and a laminate cell using polyethylene film about 772 Wh/L [2], which are beyond the energy density of lithium ion secondary batteries. However, the laminate cell also indicated some issues on the structure and components of the cell, causing the electrolyte’s leakage and a poor cycleability. This work was done to improve the charge-discharge performance of the MH/air laminate cell, especially the cycling performance, and evaluated the charge-discharge behaviors of the cell obtained with some modification in the process and materials. The laminate cell consisted of an MH electrode (23 mm x 23 mm), an air electrode (23 x 23 mm), and a separator with 6 mol/L KOH solution between the electrodes, which were thermally sealed and packed in polyethylene (PE) film having an open area (13 x 13 mm) on the air electrode. All the components were the same as those used in our previous work [1]. We examined the design, size, and thickness of PE film to improve the adhesion to the electrode and between PE films and to inhibit the leakage of the alkaline solution. A water repellent film attached to the air electrode to prevent the flooding of the solution was also modified to suppress the increase in internal pressure by oxygen generated during charge. The cell was operated with constant current (0.05 C) at room temperature in a desiccator, and the cell voltages during charge and discharge were measured, in which charge was limited for 2 hours and the cut-off voltage of discharge was 0.5 V. Some modifications in the structure and components of the laminate cell, e.g., the change in the electrode’s tab from Ni ribbon to Ni mesh and the optimization on the thickness of PE film and the thermal bonding conditions such as heating temperature and time, resulted in no leakage of the electrolyte during charge-discharge cycles and no expansion of the laminate package by oxygen, and the cycling performance was significantly enhanced compared to our previous cell [2]. The cell presented very stable charge and discharge voltages for 20 cycles and the current efficiency was more than 90 %. More detailed results will be shown in this paper. This work was financially supported by “Advanced Low Carbon Technology Research and Development Program (ALCA)” of Japan Science and Technology Agency (JST). The authors acknowledge FDK Corporation for supplying the MH negative electrode. Reference [1] T. Gejo, K. Kawaguchi, M. Morimitsu, 2017 TMS Annual Meeting & Exhibition, Pan American Materials Congress, San Diego, USA (2017). [2] S. Kino, M. Morimitsu, The 232th ECS Meeting, Abs#104870, Washington, D. C., USA (2015).

Kinetics of order-disorder transformation of L12 FeNi3 in the Fe-Ni system

The Fe-Ni system has seen a resurgence of interest for the development of high magnetocrystalline anisotropy alloys. The kinetics of the chemical order-disorder phase transformation of the ferromagnetic test-bed compound L12 FeNi3 were quantified using differential scanning calorimetry data obtained from annealed meltspun Fe-75 at% Ni ribbons. The isothermal transformation kinetics are found to be well described by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation with a determined Avrami exponent of unity, consistent with one-dimensional growth of the chemically-disordered A1 phase from the chemically-ordered L12 FeNi3 parent phase. The determined activation energy for the transformation from the chemically-ordered L12 structure to the disordered A1 structure in FeNi3, 3.1 ± 0.1 eV, is equal to that reported for the L10-to-A1 order-disorder phase transformation of the FeNi phase that is found in meteoritic specimens. These results confirm that the L12 phase of FeNi3 is a suitable model phase for investigation of formation aspects of the tetragonal L10-type FeNi phase, also known as tetrataenite, which exhibits extremely sluggish formation kinetics but possesses appreciable magnetocrystalline anisotropy and excellent saturation magnetization that is of interest for sustainable permanent magnet applications.

Microstructural Evolution and Performance of In-situ Ag-Ni Composite after Solidification under Electromagnetic Stirring and Deformation

The effect of electromagnetic stirring (EMS) on microstructure and performance of Ag-8 mass% Ni composite was investigated under both solidified and deformed conditions. Without EMS, the Ag matrix formed short, thick dendrites in the ingot; whereas with EMS, dendrites were long and slim. Ni phase mainly formed particles or ribbons, distributed along boundaries between dendrite arms. Cold drawing of the solidified Ag-Ni ingots, both with and without EMS, produced high strength in-situ metal-matrix composite (MMC) consisting of Ag matrix reinforced by Ni ribbons. EMS improved the ductility of the composite, consequently enhancing its drawability and strength. EMS also increased the electrical conductivity in both solidified ingots and deformed in-situ composite wires. In both cases, hardness and tensile strength remained high. A model based on a combination of the modified linear rule of mixtures and the Hall-Petch relationship was used to rationalize the tensile strength and hardness with respect to its fabrication parameters and the microstructure of Ag-Ni in-situ composite.

Effect of Spun Velocities and Composition on the R‒phase and Thermomechanical Behavior in Ti‒Ni Ribbons Electrically Heated

This work deals with structural, electrical and mechanical characterization of Ti‒50.13Ni and Ti‒49.62Ni (at.%) shape memory alloys (SMAs) fabricated at different circumferential wheel velocities. The effect of wheel velocity, chemical composition and heat treatments are investigated. The characterization of crystallographic phases of the Ti‒Ni ribbons was carried out using X-ray diffraction. Electrical resistance variations as function of temperature (∆R/R %) were analyzed using a non-commercial technique, which consists in a thermal-adjustable bath apparatus revealing the temperatures of B2→R→B19´ two stage transformation, whereby the presence of R‒phase can be definitively confirmed. The Stress-Assisted Two-Way Memory Effect was measured by an own designed apparatus with an Linear Variable Differential Transformer captor and a current controlled heating, and results indicate that the as-spun condition, promotes the Stress-Assisted Two-Way Memory Effect. On the other hand, increments in Ni content tend to decrease transformation temperatures and high wheel velocities help to the R‒phase formation.

Hydrogen storage properties of Ti1.4V0.6Ni + x Mg (x = 1–3, wt.%) alloys

We prepared Ti1.4V0.6Ni ribbons by arc-melting and subsequent melt-spinning techniques. Ti1.4V0.6Ni + x Mg (x = 1, 1.5, 2, 2.5 and 3, wt.%) composite alloys were obtained by the mechanical ball-milling method. The structures and hydrogen storage properties of alloys were investigated. Ti1.4V0.6Ni + x Mg composite alloys contained icosahedral quasicrystalline phase, Ti2Ni-type phase, β-Ti solid-solution phase and metallic Mg. The electrochemical and gaseous hydrogen storage properties of alloys were improved with Mg addition. Ti1.4V0.6Ni + 2 Mg alloy showed maximum electrochemical discharge capacity of 282.5 mAh g−1 as well as copacetic high-rate discharge ability of 82.3% at the discharge current density of 240 mA g−1 compared with that of 30 mA g−1, and the cycling life achieved above 200 mAh g−1 after 50 consecutive cycles of charging and discharging. The hydrogen absorption/desorption properties of Ti1.4V0.6Ni + x Mg (x = 1, 2 and 3, wt.%) alloys were better than Ti1.4V0.6Ni. Ti1.4V0.6Ni + 3 Mg alloy also exhibited a favorable hydrogen absorption capacity of 1.53 wt.%. The improvement in the hydrogen storage characteristics caused by adding Mg may be ascribed to better hydrogen diffusion and anti-corrosion ability.

Electrochemical hydrogen storage characteristics of TiVNi-quasicrystalline composite materials

The Ti1.4V0.6Ni ribbon alloy and VTZN (V5Ti9Zr26.7Ni38Cr5Mn16Sn0.3) alloy ingot are prepared by melt–spinning technique and induction levitation melting technique, respectively. The Ti1.4V0.6Ni + 20 wt.% VTZN mixture powders are synthesised by ball–milling the above prepared alloy ingots, and their structures and the electrochemical hydrogen storage properties are investigated. It is found that the icosahedral quasicrystal, FCC and BCC structural solid solution phase are all presented in the composite material. The maximum electrochemical discharge capacity of the composite electrode is 308.2 mAh/g at the discharge current density of 30 mA/g and 303 K. In addition, the electrode made of Ti1.4V0.6Ni and AB3 composite holds better high–rate discharge ability than that of Ti1.4V0.6Ni.

Influence of heat treatment on electrochemical properties of Ti1.4V0.6Ni alloy electrode containing icosahedral quasicrystalline phase

The structures and electrochemical properties of the Ti1.4V0.6Ni ribbon before and after heat treatment are investigated systematically. The structure of the sample is characterized by X-ray powder diffraction analysis. Electrochemical properties including the discharge capacity, the cyclic stability and the high-rate discharge ability are tested. X-ray powder diffraction analysis shows that after heat treatment at 590 °C for 30 min, all samples mainly consist of the icosahedral quasicrystal phase (I-phase), Ti2Ni phase (FCC), V-based solid solution phase (BCC) and C14 Laves phase (hexagonal). Electrochemical measurements show that the maximum discharge capacity of the alloy electrode after heat treatment is 330.9 mA·h/g under the conditions that the discharge current density is 30 mA/g and the temperature is 30 °C. The result indicates that the cyclic stability and the high-rate discharge ability are all improved. In addition, the electrochemical kinetics of the alloy electrode is also studied by electrochemical impedance spectroscopy (EIS) and hydrogen diffusion coefficient (D).

Interactive Effect of Grain Orientation and Grain Size on Magnetic Properties of Fe–78 wt% Ni Ribbons

Fe–78 wt% Ni ribbons were prepared by the melt spinning technique and the interactive contribution of the grain size and grain orientation on the magnetic properties was examined. Heat treatment at 673 K for 1 h followed by furnace cooling was performed to show the annealing impact. At three wheel speeds of 10, 20, and 30 m/s, the saturation magnetization nearly does not change. High wheel speed and heat treatment are inclined to promote the growth of grains. Although the orientation is not the easy axis of magnetization, the improvement of the texture in this direction makes the coercivity decrease, which counteracts the inverse effect of the grain size at high wheel speed. It indicates that for preparing soft magnetic ribbons, the interactive contribution of grain orientation variation and the grain size should be considered.

Investigation on Physical Properties of Ti-Based Quasicrystalline

The Ti1.4V0.6Ni ribbon alloy containing icosahedral quasicrystal is prepared by melt-spinning technique, and the Ti40.33Zr40.33Ni18.34 icosahedral quasicrystal powders are prepared by mechanical alloying. Both samples are annealing in a vacuum furnace. DSC trace obtained during continuous heating to 1300°C show a distinctly broad exothermic peak between 100°C and 1000°C for the Ti1.4V0.6Ni alloy, two sharp exothermic peaks between 100°C and 700°C for the Ti40.33Zr40.33Ni18.34, respectively. The magnetic behavior results demonstrated the Ti1.4V0.6Ni ribbon alloy exhibited higher ferromagnetic properties than those of Ti40.33Zr40.33Ni18.34 powders both at 15 K and 300 K. The specific heat capacity of two the sample increase when the temperature increase from 400 to 650°C.

Electrochemical performance of TiVNi-Quasicrystal and AB 3-Type hydrogen storage alloy composite materials

The Ti 1.4V 0.6Ni ribbon alloy and AB 3-type (La 0.65Nd 0.12Mg 0.23Ni 2.9Al 0.1) alloy ingot are prepared by melt-spinning technique and induction levitation melting technique, respectively. The Ti 1.4V 0.6Ni + 20 wt.% AB 3 mixture powders are synthesized by ball-milling the above prepared alloy ingots, and their structures and the electrochemical hydrogen storage properties are investigated. It is found that the icosahedral quasicrystal, Ti 2Ni, BCC structural solid solution and AB 3-type phases are all presented in the composite material. The maximum electrochemical discharge capacity of the composite electrode is 294.7 mAh/g at the discharge current density of 30 mA/g and 303 K. In addition, the electrode made of Ti 1.4V 0.6Ni and AB 3 composite holds better high-rate discharge ability than that of Ti 1.4V 0.6Ni.

Transmission electron microscopy and X-ray diffraction study of microstructural evolution in magnetoresistive Cu–Fe–Ni ribbons

The evolution of the microstructure of a granular Cu80Fe10Ni10 (at%) melt-spun ribbon is studied by transmission electron microscopy (TEM), energy-filtered transmission electron microscopy (EFTEM) and X-ray diffraction. This system is interesting as large giant magnetoresistance (GMR) values have been measured for this composition. We have shown the presence of two face-centred cubic phases, an (Fe,Ni)-rich phase and a Cu-rich phase. The lattice parameters of these two phases are close and no diffraction or elastic contrast is involved in displaying the two phases in TEM bright-field mode. With EFTEM imaging, we have shown the presence of a fine-scale (Fe,Ni)-rich precipitation inside the Cu-rich fcc matrix. The precipitates are 2–4 nm in the as-spun state and 4–6 nm after annealing for 2 h at 400°C. The lattice parameter of the Cu-rich phase in the as-spun sample is 0.3608 nm and 0.3610 nm for the (Fe,Ni)-rich phase. After a 24-h annealing treatment at 600°C, the mean diameter of the particle is 20 nm and the lattice parameter of the (Fe,Ni)-rich phase has decreased to 0.3600 nm, while that of the Cu-rich phase has increased to 0.3613 nm, which is consistent with a segregation of Fe and Ni in the precipitates. The composition and volume fraction of the two phases measured for this annealed sample are in good agreement with the Thermocalc® predictions.

Peculiarities of structural state and hydrogen storage properties of Ti–Zr–Ni based intermetallic compounds

Structural states of the Ti–Zr–Ni based melt-spun ribbons have been investigated by means of the X-ray diffraction analysis. The ribbon structural state was found to be strongly affected by the production conditions. A small amount of Si (0.2–0.3 at.%) in the Ti–Zr–Ni alloy leads to the formation of an amorphous or a mixed amorphous-quasicrystalline state in the ribbons produced at the different hardening rates. The amorphous-quasicrystalline structural state of the ribbons is stable during annealing up to temperatures of 400 ° C but some changes in its parameters take place. The uncoated by Pd amorphous and amorphous-quasicrystalline Ti–Zr–Ni ribbons have the property of absorbing a large amount of hydrogen. Changes in the amorphous and quasicrystalline subsystems have a reversible character: the structural states of the ribbons after natural dehydrogenation practically fully returns to the initial one.

Microstructure of rapidly solidified Cu–Al–Ni shape memory alloy ribbons

Cu–Al–Ni shape memory alloys (SMAs) are currently the only available high temperature SMAs, showing a good resistance against functional fatigue. In polycrystalline state, they are very brittle and exhibit, in general, only small reversible deformations. By melt spinning, thin Cu–Al–Ni ribbons can be manufactured directly from the melt. Appropriate casting parameters can ensure a single layer columnar structure with a fibre texture, which significantly increases the maximal reversible strain in longitudinal direction. Cu–Al–Ni ribbons, containing 13, 14 and 15 wt.% Al were cast by free jet melt spinning. Because of the alloys’ low thermal conductivity, the cooling rate was surprisingly low – considering the crystal grain size – significantly below 10 3 K/s. Therefore, wide ribbons having a single layer columnar and (except the ribbons containing 13 wt.% Al) completely martensitic structure could not be obtained. Regardless the chemical composition, the ribbons have a single layer columnar structure only if the thickness does not exceed approximately 50 μm, otherwise the structure consists of at least two layers of equiaxed grains. In as-cast condition, only ribbons containing 13 wt.% Al seem to be completely martensitic. Heat treatments at temperatures up to 900 °C improved the structure of 13 and 14 wt.% Al ribbons. All ribbons exhibit one-way shape memory effect in as-cast condition. Heat-treated ribbons containing 13 wt.% Al exhibited two-way shape memory effect already after one bending and heating cycle.

Effect of Ni-Content on Shape Memory Behavior of Ti-Rich Ti-Ni Melt-Spun Ribbons

The microstructure and shape memory behavior of Ti-rich Ti-Ni melt-spun ribbons with various Ni-contents were investigated. Ti-xNi(x=40~48at%) ribbons were fabricated by the melt-spinning method at the rotation speed of 5000rpm. They were heat-treated at 1073K for 3.6ks. It was found that the Ti-40at%Ni as-spun ribbon exhibited almost complete amorphous structure, while the specimen with more Ni-content, such as 48at%Ni ribbon exhibited the coexistence of amorphous and crystalline structures. It was also found that the maximum shape recovery strain increased with increasing Ni-content. The Ti-40at%Ni ribbon was very brittle because of many Ti2Ni precipitates formed.

Mechanical behaviour of amorphous Mg–23.5Ni ribbons

The tensile properties of amorphous Mg–23.5Ni (wt.%) ribbons in the temperature range 25–350 °C were studied. The mechanical behaviour of the alloy can be divided into four different intervals depending on the test temperature. In the 25–125 °C interval, the ribbons are brittle or exhibit small ductility. Between 138 and 150 °C, a substantial increase in the yield stress takes place due to the crystallization of a metastable magnesium-rich phase. In the 175–250 °C temperature range the material exhibits maximum elongations. In this interval the microstructure consists of a mixture of Mg, Mg 2Ni and the metastable magnesium-rich phase. Variations in the volume fraction of these phases determine the mechanical properties of the alloy within this interval. Above 250 °C, the equilibrium eutectic microstructure, consisting of Mg and Mg 2Ni phases, is developed prior to the tensile test.

Mechanical behaviour of amorphous Mg?23.5Ni ribbons

Mechanical behaviour of amorphous Mg?23.5Ni ribbons

Structural state of melt-spun Ti–Zr–Ni ribbons with a small amount of Si

A structural state of the melt spun Ti 37.1Zr 38.8Ni 23.9Si 0.2 ribbons produced at different cooling rates has been investigated. It was found by means of X-ray diffraction analysis that their structural states are affected very strongly by the ribbon production conditions. The small amount addition of Si (0.2–0.3 at.%) to the Ti–Zr–Ni alloy leads to the formation of an amorphous state on the both—contact and free—sides of the ribbons produced at the wheel surface velocity of 44 m/s. For the case of 30 m/s however we have detected an amorphous state for the contact side and a mixed amorphous–quasicrystalline state for the free side of the ribbon. Parameters of the amorphous state were calculated for the ribbons as prepared and annealed.