Effect Of Ni Substitution Research Articles

Tuning the magnetocaloric properties of the Ni2+xMn1−xSn Heusler alloys

We report the effect of Ni substitution on the magnetic properties of polycrystalline Ni2+xMn1−xSn (x = 0, 0.05, and 0.1) Heusler alloys using the magnetization and neutron diffraction measurement techniques. The paramagnetic to ferromagnetic transition temperature (Curie temperature, TC) has been tuned with the substitution of Ni at the Mn sites (TC≈ 349, 337, and 317 K for x = 0, 0.05, and 0.1 samples, respectively) without a significant reduction in the magnetic entropy change −ΔSM. For a magnetic field change from 0 to 5 T, −ΔSM of 2.9, 2.5, and 2.2 J kg−1 K−1 have been observed for x = 0, 0.05, and 0.1 samples, respectively. From the neutron diffraction study, it has been found that with increasing x, the Mn site ordered moment decreases. −ΔSM as a function of changing magnetic field and Curie temperature follows the molecular mean field model. The studied Ni2+xMn1−xSn alloys, with their nontoxic constituent elements and low-cost, can be used for magnetic cooling over a wide temperature range of 278–379 K covering room temperature.

Structural, magnetic and x-ray absorption studies of NdCo1−xNixO3 (0 ≤ x ≤ 0.5)

We have systematically investigated the effect of Ni substitution on the structural and magnetic properties of NdCoO3. Single phase nature and orthorhombic Pbnm structure is confirmed by the Reitveld refinement of X-ray diffraction data in all samples. X-ray absorption near edge spectroscopy of Co and Ni K-edges reveals the presence of trivalent state of Ni and Co ions in all samples. Composition dependent crossover from canted antiferromagnetic (AFM) (for x < 0.3) to spin glass behavior (for x ≥ 0.3) is observed in magnetic measurements. Low temperature ferromagnetic (FM) component in doped samples is attributed to the stabilization of Co+3 ions in intermediate-spin (IS) state t52ge1g with S = 1 The FM and AFM are observed to coexist as confirmed by M-H hysteresis. Nd sublattice seems to inhibit the magnetic contribution from Co ions, and we ruled out the possibility of charge disproportion induced by Ni substitution leading to FM interactions in these systems as proposed in different reports.

Effect of Ni substitution for Ga on the polycrystalline Ni–Mn–Ga–Gd high-temperature shape memory alloys

Ni53+xMn25Ga21.9−xGd0.1 (at.%) (x=0–5) alloys had been obtained by substituting Ga for Ni to increase transformation temperature. The microstructure and phase transformation of polycrystalline Ni53+xMn25Ga21.9−xGd0.1 alloys had been investigated by XRD, SEM, TEM and DSC. The results showed that the matrix of Ni53+xMn25Ga21.9−xGd0.1 alloys were tetragonal martensite phase, and the face-centered cubic γ phase was formed in Ni58Mn25Ga16.9Gd0.1 alloy. The transformation temperatures rose gradually with the increase of Ni content. The compressive fracture strength and strain firstly increased then decreased with the increase of Gd content when Ni content was less than 57at.%. The generation of ductile γ phase improved the compressive fracture strength and strain of Ni58Mn25Ga16.9Gd0.1 alloy up to 2327MPa and 51.7%, respectively. The complete recovery was obtained in Ni53+xMn25Ga21.9−xGd0.1 (x=0–3) alloys when the pre-strain was 10%.

Effect of Ni-substitution on glass forming ability, mechanical, and magnetic properties of FeBNbY bulk metallic glasses

We present a method to identify bulk glass forming ability by partial substitution of Fe by Ni in FeBNbY based amorphous alloy ribbons and as a consequence obtain enhanced mechanical and soft magnetic properties of bulk glassy rods of diameter as large as 4.5 mm. A detailed investigation of thermal, mechanical, and magnetic properties of (Fe0.72−x NixB0.24Nb0.04)95.5Y4.5 alloys (with x ∼ 0.02, 0.04, 0.06, 0.08, 0.1) was carried out. The supercooled regime (ΔTx) and other glass forming parameters, e.g., reduced glass transition temperature (Trg), the gamma (γ) parameter, etc., were found to be enhanced due to the Ni substitution resulting in improvement of glass forming ability (GFA). The maximum values of such parameters (ΔTx ∼ 94 K, Trg ∼ 0.644, and γ ∼ 0.435) were obtained for the alloy with x ∼ 0.06, making it possible to cast cylindrical rods with 4.5 mm diameter for this composition. Nanoindentation studies on glassy rods also point out that (Fe0.66Ni0.06B0.24Nb0.04)95.5Y4.5 alloy exhibit the maximum value of hardness (H ∼ 12 GPa) as well as elastic modulus (E ∼ 193 GPa) among all of these samples. In addition to these, that particular sample shows the lowest room temperature coercivity (Hc ∼ 210 mOe). By annealing at 823 K, Hc can be further reduced to 60 mOe due to its structural relaxation. We attribute the improved soft magnetic and mechanical properties of as-quenched (Fe0.66Ni0.06B0.24Nb0.04)95.5Y4.5 alloy to higher packing density attained due to its large glass forming ability.

A Study of Ni-Substitution Effects on Heavy-Fermion CeCu2Si2–Similarities between Ni Substitution and High-Pressure Effects–

The effects of Ni substitution on Ce(Cu1-xNix)2Si2 have been studied by specific heat and electrical resistivity measurements. The specific heat measurement has revealed that the enhanced quantum fluctuations around an antiferromagnetic quantum critical point are markedly suppressed by Ni substitution, and that the Fermi liquid state recovers in the Nirich region (x > 0.12). The characteristic T-linear dependence of the resistivity has been observed at approximately x ~ 0.10 together with a sign of superconductivity. The variation of n in the form of rho - rho0 = aT^n against Tmax^1, at which the resistivity peaks, coincides with the case of high-pressure experiments on pure CeCu2Si2. The anomalous T-linear behavior appears to occur in the crossover region from the Kondo regime to the valence fluctuation regime rather than in the conventional antiferromagnetic quantum critical region.

Mechanical Properties of Bi1.6Pb0.4Sr1.8Ba0.2Ca2Cu3−x Ni x O10+δ Superconducting System

Samples of Bi1.6Pb0.4Sr1.8Ba0.2Ca2Cu3−xNixO10+δ were prepared by solid-state reaction methods. Mechanical properties (Vickers microhardness, Young modulus, yield strength, fracture toughness and surface energy) by Vickers microhardness measurements have been carried out to examine the effects of Ni substitution. The results showed a deterioration of the mechanical properties with the enhancement of Ni content.

Effects of Ni Substitution in Bi-2212 Superconductors

In this study the samples were synthesized from a 2234 stoichiometric composition in order to obtain a large amount of pure 2212-BSCCO. The effects of Ni substitution on the properties of Bi-based Bi2−xNixSr2Ca1Cu2Oy superconductor with x=0, 0.05, 0.1 and 0.2 were investigated by means of X-ray analysis (XRD), DC electrical resistivity and magnetic-hysteresis loop measurements. It has been found that the Tc (onset) transition temperature does not change independently of Ni content. In addition, Jc values of the samples were calculated from the hysteresis loop measurement by using Bean’s model, showing that Jc decreases with increasing Ni substitution.

Effect of Ni substitution on structural, morphological and magnetic properties of Zn1-xNixO nanorods

We report the preparation of Zn1-xNixO nanorods through a chemical route using microwave irradiation. The obtained Zn1-xNixO nanorods were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy and magnetization measurements. XRD and TEM results showed that the Zn1-xNixO nanorods have single phase nature with wurtzite structure and Ni was successfully incorporated at Zn site into the ZnO. The shape of the nanorods changed from hexagon (length ∼1.5 μm, diameter ∼200 nm) to pencil like tip (length ∼1 μm, diameter ∼80 nm) by only changing the Ni content from 1% to 3% in ZnO. Concerning the Raman scattering spectra, the modification in the intensity of E2high mode and sub-band edge emissions provides enough evidence for the existence of intrinsic defects associated with the O atoms. Magnetic measurement results revealed that Zn1-xNixO nanorods show the well-defined ferromagnetic features at room temperature and the value of Ms increased with the increase of Ni concentration.

Similarity between Ni and Zn impurity effects on the superconductivity and Cu-spin correlation in La2−xSrxCu1−yNiyO4high-Tccuprates: A comparison based on the hole trapping by Ni

Ni-substitution effects on the superconductivity and Cu-spin correlation have been investigated in La2-xSrxCu1-yNiyO4 from the electrical resistivity and muon spin relaxation measurements, taking into account the hole trapping by Ni recently suggested. It has been found that the Ni-substitution suppresses the superconductivity, induces the localization of holes and develops the Cu-spin correlation to the same degree as the Zn substitution. These suggest that Ni with a trapped hole tends to give rise to potential scattering of holes in the CuO2 plane to the same degree as Zn, being discussed in relation to the so-called dynamical stripe correlations of spins and holes.

Resistivity, thermopower, and thermal conductivity of nickel doped compounds Cr1−xNixSb2 at low temperatures

Substitutional compounds Cr1−xNixSb2 (0≤x≤0.1) were synthesized, and the effect of Ni substitution on transport and thermoelectric properties of Cr1−xNixSb2 were investigated at the temperatures from 7 to 310K. The results indicated that the magnitudes of the resistivity and thermopower of Cr1−xNixSb2 decreased greatly with increasing Ni content at low temperatures, owing to an increase in electron concentration caused by Ni substitution for Cr. Experiments also showed that the low-temperature lattice thermal conductivity of Cr1−xNixSb2 decreased substantially with increasing Ni content due to an enhancement of phonon scattering by the increased number of Ni atoms. As a result, the figure of merit, ZT, of lightly doped Cr0.99Ni0.01Sb2 was improved at T>∼230K. Specifically, the ZT of Cr0.99Ni0.01Sb2 at 310K was approximately ∼29% larger than that of CrSb2, indicating that thermoelectric properties of CrSb2 can be improved by an appropriate substitution of Ni for Cr.

Structure and hydrogen storage properties of Mg 2Cu 1− xNi x ( x = 0–1) alloys

The effect of Ni-substitution on the structure and hydrogen storage properties of Mg 2Cu 1− x Ni x ( x = 0, 0.2, 0.4, 0.6, 0.8, 1) alloys prepared by a method combining electric resistance melting with isothermal evaporation casting process (IECP) has been studied. The X-ray single-crystal diffraction analysis results showed that the cell volume decreases with increasing Ni concentration, and crystal structure transforms Mg 2Cu with face-centered orthorhombic into Ni-containing alloys with hexagonal structure. The Ni-substitution effects on the hydriding reaction indicated that absorption kinetics and hydrogen storage capacity increase in proportion to the concentration of the substitutional Ni. The activated Mg 2Cu and Mg 2Ni alloys absorbed 2.54 and 3.58 wt% H, respectively, at 573 K under 50 bar H 2. After a combined high temperature and pressure activation cycle, the charged samples were composed of MgH 2, MgCu 2 and Mg 2NiH 4 while the discharged samples contained ternary alloys of Mg–Cu–Ni system with the helpful effect of rising the desorption plateau pressures compared with binary Mg–Cu and Mg–Ni alloys. With increasing nickel content, the effect of Ni is actually effective in MgH 2 and Mg 2NiH 4 destabilization, leading to a decrease of the desorption temperature of these two phases.

Effect of Ni substitution on electrical and thermoelectric properties of LaCoO 3 ceramics

LaCo 1− x Ni x O 3 (0 ≤ x ≤ 0.2) ceramics were prepared by solid state reaction and their thermoelectric properties were investigated from room temperature (RT) to 400 °C. In the range from RT to 180 °C, LaCoO 3 showed a large negative Seebeck coefficient, but it changed to a positive value above 180 °C. However, the Seebeck coefficient became positive in the whole investigated temperature span due to Ni substitution for Co even for a tiny amount, but its absolute value decreased significantly with increasing Ni content. The LaCo 0.9Ni 0.1O 3 composition showed an enhanced power factor with a maximum value of 1.41 × 10 −4 W m −1 K −2 at room temperature, which is about 3.5 times higher than that of un-doped LaCoO 3. Because the power factor decreased and the thermal conductivity increased apparently with temperature, the ZT values were not increased at elevated temperatures, in spite of a relatively large ZT value of 0.031 at a low temperature (50 °C) obtained in the composition LaCo 0.9Ni 0.1O 3.

Effect of Ni-substitution on Ni 2MnGe Heusler alloys: Ab initio study

The effect of Ni-substitution on magnetic properties of Ni 2MnGe alloy has been investigated by first principles method FPLO, which is used in the CPA form. The theoretical lattice parameters obtained from the dependence of the total energy on the lattice parameter are comparable with experimental ones. A decreasing trend of total magnetic moment with Ni-substitution is found for Ni 2+ x Mn 1− x Ge for studied concentrations of x. The linear pressure-magnetization behaviour is obtained for Ni 2+ x Mn 1− x Ge for applied pressure from 0 to 9 GPa, and the pressure derivative of the total magnetic moment is calculated. The value of equilibrium bulk modulus of Ni 2+ x Mn 1− x Ge (for x = 0.1 – 0.9) obtained from Murnaghan equation of state (EOS) shows that the studied compounds are less compressible than Ni 2MnGe.

Minimizing of power loss in Li–Cd ferrite by nickel substitution for power applications

The effect of Ni substitution on the microstructure, dielectric, impedance, magnetic and power loss properties has been investigated on a series of Li 0.35–0.5 x Cd 0.3Ni x Fe 2.35–0.5 x O 4 (0.00≤ x≤0.08) ferrite prepared by citrate precursor method. Dielectric and impedance measurements have been determined in the frequency range 100 Hz–10 MHz. An enhancement in permittivity was observed with Ni concentration and exhibits the maximum value of ∼7×10 3 for x=0.02 sample. The impedance spectroscopy technique has been used to study the effect of grain and grain boundary on the electrical properties of all the samples. Power loss measurements have been carried out in the frequency range 50 kHz–5 MHz at induction condition of B=10 mT. Power loss has been found to be quite low, less than 100 kW/m 3 up to 500 kHz, with the substitution of Ni in Li 0.35–0.5 x Cd 0.3Ni x Fe 2.35–0.5 x O 4 ferrite, which is useful for technological aspects.

Structural, magnetic properties and magnetocaloric effect in Ni-doped antiperovskite compounds GaCMn 3− xNi x (0≤ x≤0.10)

The effects of Ni substitution on the structure, magnetic properties and magnetocaloric effect (MCE) of antipervoskite compounds GaCMn 3− x Ni x (0≤ x≤0.10) have been investigated systematically. As the doping level x increases, both the Curie temperature T C and the saturated magnetization M S at 200 K increase, while the antiferromagnetic ground state gradually decreases. The observed behavior could be well interpreted by considering the lattice shrinkage and band filling effects. The magnetic entropy change Δ S M with an applied field change of 48 kOe shows a plateau-like temperature dependent behavior for x=0.05, 0.07 and a caret-like behavior for x=0.10. Our results indicate that the magnetic properties and MCE of GaCMn 3 may be easily tunable by chemical doping in Mn site.

Enhancement of plasticity of Fe-based bulk metallic glass by Ni substitution for Fe

Bulk metallic glasses (BMGs) (Fe 1− x Ni x ) 71Mo 5P 12C 10B 2 ( x = 0, 0.1 and 0.2) with a diameter of 3 mm were synthesized by copper mold casting. The effect of Ni substitution for Fe on the structure, thermal and mechanical properties has been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and compressive testing. It was found that the substitution of Ni for Fe enhances the glass forming ability, and improves the plasticity of Fe 71Mo 5P 12C 10B 2 BMG as indicated by the increase in the plastic strain from 3.1% ( x = 0) to 5.2% ( x = 0.2). The improvement of the plasticity is discussed in term of the reduction of glass transition temperature and the supercooled liquid region due to the substitution of Ni for Fe.

Anomalous Zn- and Ni-substitution effects on superconductivity in the superconducting weak ferromagnets RuSr2RCu2O8 (R = Gd, Eu)

The effect of magnetic Ni and non-magnetic Zn impurities on superconducting transition temperature Tc in RuSr2R(Cu1−x(Ni,Zn)x)2O8 with R=Gd or Eu (Ni- and Zn-substituted Ru1212Gd(Eu)) was extensively studied. It is found that the suppression rate dTc/dx of RuSr2R(Cu1−x(Ni,Zn)x)2O8 is comparable to that of underdoped YBa2(Cu1−x(Ni,Zn)x)3O7−δ. The suppression of superconductivity in Ni-substituted Ru1212Eu samples is more significant than that in Zn-substituted ones, indicative of Ni being a more effective pair-breaker than Zn. In strong contrast, the magnetic Ni impurity atoms have a weaker effect on superconductivity than non-magnetic Zn atoms in Ru1212Gd, similar to what was observed in the high-Tc cuprates. These intriguing findings strongly suggest that the impurity-induced local disturbance of the 3d-spin correlation at Cu sites around Ni/Zn is distinctly different between Ru1212Gd and Ru1212Eu.

Hole-trapping and Kondo effect in Ni-substituted La2−xSrxCu1−yNiyO4 with x = 0.08–0.30

We have measured the specific heat in a wide range of hole-concentration in partially Ni-substituted La2−xSrxCu1−yNiyO4, in order to investigate Ni-substitution effects on the electronic state. For 10% Ni-substituted samples of y=0.10, it has been found that the electronic specific heat divided by temperature, Cel/T, decreases with decreasing temperature at low temperatures for x⩽0.20, which is concluded to be due to a decrease in the effective hole-concentration caused by strong hole-trapping by Ni2+ ions. For x>0.20, on the other hand, an increase in Cel/T with decreasing temperature has been observed, which is due to the Kondo effect. In fact, both a logarithmic temperature-dependence of the electrical resistivity and a negative magnetoresistance have been observed for x>0.20. It has been concluded that the ground state of non-superconducting La2−xSrxCu1−yNiyO4 changes upon hole doping from a magnetically ordered state to a metallic state and that the quantum phase transition is crossover-like due to the phase separation in the overdoped regime.

Effects of Ni substitution on the properties of Co 3O 4/graphite composites as anode of lithium ion batteries

Ni-substituted Co 3O 4/graphite composites were synthesized by precipitation of cobalt oxalate and nickel oxalate on the surface of graphite and pyrolysis of the precipitate. The effects of nickel content and calcination temperature on the properties of the composites were investigated. The samples were characterized by thermogravimetry and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV) and charge/discharge measurements. The composites consist of graphite and a face-centered cubic (fcc) Co 3O 4 phase of fd3m space group, and there is no diffraction peaks associated with nickel compounds. Mild nickel substitution can improve the reversible capacity of the Co 3O 4/graphite composite. With increasing the calcination temperature from 300 to 500 °C, the reversible capacity of the composites with 10% Ni substitution increases from 641 to 874 mA h g −1. The composite synthesized at 400 °C shows an initial reversible capacity of 690 mA h g −1 and excellent cycling stability.

Effect of Co, Ni, and Cu substitution on the electronic structure of hexagonal YMnO3 studied by x-ray absorption spectroscopy

X-ray absorption spectroscopy measurements have been performed to elucidate local electronic and atomic structures of orthorhombic 3d-transition metal-doped yttrium manganites (YMnO3) with chemical formulae YMn2/3Me1/3O3 (Me=Co, Ni, and Cu). The Mn L3- and K-edges x-ray absorption near-edge structure (XANES) demonstrate the direct substitution of Me2+ for Mn3+, so that the positive effective charge of Mn ions are increased. Me-doping is also found to induce substantial broadening of the Mn L3-edge feature, which suggests enhancement of the delocalization of Mn 3d eg subbands and conductivity. Local spin density approximation (LSDA)+U (Hubbard U parameter) calculations were used to understand their electronic structures.