Further Increase In Zn Content Research Articles

Study of the magnetic properties of Zn doped Cobalt ferrite (CoZnxFe2-xO4)

Zinc substitution is proposed as an efficient way to improve the performance of the ferrite. In this work, Zinc doped cobalt ferrite with the generic formula CoZnxFe2-xO4, with x = 0.0, 0.1, 0.3 and 0.4 were prepared by conventional ceramic technique, sintered at 1000ο C for 4 hours in air. The effect of zinc concentration on the initial permeability, Curie temperature, saturation magnetization, magnetic moment, coercivity and magnetic susceptibility was investigated. Contrary to most of the work in this subject, here Co is maintained fixed and Fe is progressively varied along with Zn. Curie temperature is found to increase initially up to 459 0C for Zn content of x = 0.1 and then decreased to 1480C for further increase of Zn content (x = 0.4). Effect of Zn on the frequency dependent initial permeability, loss factor and relative quality factor was studied. The maximum value of saturation magnetization (51.37emu/gm) was found for the sample x = 0.1 and then decreases with the increase of Zn content. Morphological and magnetic properties of the samples were studied using scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) respectively. The Zn-doped cobalt-ferrite (x = 0.1) having a high strain derivative could be a potential material for stress sensor application.

Microstructure and mechanical properties of as-cast Mg-5Sn-2Ce-xZn alloys

The microstructure, mechanical properties and compression creep resistance of as-cast Mg-5Sn-2Ce-xZn (x=0, 2 wt.%, 4 wt.%) alloys were investigated in this paper. The results showed that the Ce-containing compounds were MgSnCe phase and an unknown phase, and they were the dominant intermetallics in as-cast Mg-5Sn-2Ce-xZn alloys. At x=0 wt.%, the Ce-containing compounds formed in interdendritic regions with the shape of rod. As the Zn content was increased to 2 wt.%, the Ce-containing compounds partly changed from rod-like to sheet-like. However, there were few further changes in the Ce-containing compounds with further increase in Zn content to 4 wt.%. Compared with Mg-5Sn-2Ce alloy, the tensile strength and elongation of the alloy containing 4 wt.% Zn increased by 39% and 112%, respectively, and the secondary creep rate (175 °C/55 MPa) decreased at least by an order of magnitude. These improvement could be attributed to the combined effects of the high content of Zn dissolving in α-Mg matrix and the modification of Ce-containing compounds by Zn addition.

Influence of Alloying Treatment and Rapid Solidification on the Degradation Behavior and Mechanical Properties of Mg

Magnesium (Mg) has drawn increasing attention as a tissue engineering material. However, there have been very few studies of laser-melted Mg-Zn alloys. In this study, four binary Mg-xZn (x = 2, 4, 6 and 8 wt. %) alloys were fabricated by laser melting. The influence of zinc (Zn) content and technique on the degradation behavior and mechanical properties of Mg were discussed. Results revealed that Mg-xZn alloys consisted of an α-Mg matrix and MgZn phases, which dispersed at the grain boundaries. In addition, the MgZn phase increased with the increase in Zn content. The laser-melted alloy had fine homogenous grains, with an average grain size of approximately 15 μm. Grain growth was effectively inhibited due to the precipitation of the MgZn phase and rapid solidification. Grain refinement consequently slowed down the degradation rate, with Zn content increasing to 6 wt. %. However, a further increase of Zn content accelerated the degradation rate due to the galvanic couple effect between α-Mg and MgZn. Moreover, the mechanical properties were improved due to the grain refinement and reinforcement of the MgZn phase.

Structural, morphological, optical, magnetic and dielectric properties of Ni1−xZnxFe2O4 (x = 0 − 1) nanoparticles

Ni1−xZnxFe2O4 (x = 0.0, 0.25, 0.5, 0.75, 1.0) nanoparticles (NPs) are prepared by solution combustion method. The presence of zinc ions causes considerable changes in the structural and magnetic properties of the NiFe2O4. The structural, morphological and magnetic properties of the samples are characterized by X-ray diffraction (XRD), Scanning Electron Microscopy, and Vibrating sample magnetometer. The average particle size of the powder is determined from XRD. It confirms the nanosized dimension of the NPs in the size range of 60–70 nm. The Zn2+ content has a significant influence on the dielectric properties of sintered Ni1−xZnxFe2O4 samples, such as dielectric constant (k) and dielectric loss tangent (δ). These values decrease with increasing zinc content. The saturation magnetization and the experimental magnetic moment are observed to initially increase (up to x = 0.25), and then continuously decrease with further increase in Zn content x. This decreasing trend obeys the three-sub lattice model suggested by Yafet–Kittel (Y–K). The Y–K angle for the NiFe2O4 NPs increases gradually with increasing Zn concentration.

A study of the microstructure, thermal properties and wetting kinetics of Sn–3Ag–xZn lead-free solders

Microstructure, thermal properties and wetting kinetics of Sn–3Ag–xZn solders (x = 0.4, 0.6, 0.8, 1, 2 and 4 wt%) were systematically investigated. The results indicate that a small amount of Zn (Zn wt% ≤ 1 wt%) has a rather moderate effect on the microstructure morphology of the Sn–3Ag–xZn solders. The microstructures are composed of a β-Sn phase and the mixture of Ag3Sn and ζ-AgZn particles. However, the β-Sn phase reduces its volume fraction in the entire microstructure and the intermetallic compounds population increases with the increasing of Zn content. The microstructure is dramatically changed with a further increase in the Zn content. The γ-AgZn phase is formed in a Sn–3Ag–2Zn solder. The e-AgZn phase is formed in a Sn–3Ag–4Zn solder. The melting temperature and the undercooling of the Sn–3Ag–xZn solder alloys decrease with the increase in Zn content, reach to a minimum value when the content of Zn is 1 wt%, and then increase with further increase in Zn content. The Sn–3Ag–1Zn demonstrates the minimum value of 228.13 °C in the melting temperature and 13.87 °C in undercooling. The wetting kinetics of the main spreading stage features the power law of Rn ~ t (n = 1), which is controlled by chemical reactions at the triple line.

Dielectric and transport properties of Zn-substituted cobalt ferrites

Effect of Zn content on the dielectric and transport properties of CoZnxFe2-xO4 (x = 0.0, 0.1, 0.2, 0.3 and 0.4), prepared by standard double sintering ceramic technique, sintered at 1000°C for 4 hours were investigated. The X-ray diffraction (XRD) pattern of the prepared samples showed single phase inverse-spinel structure without any detectable impurity. Lattice constant of the samples increased with the increasing Zn concentration which follows Vegard’s law. The theoretical densities of these samples remained almost constant whereas the bulk density decreased with Zn content up to x = 0.2. But with further increase of Zn content the bulk density increased. The porosity of the prepared samples showed the opposite trend. The dielectric constant (??) measurement showed the normal dielectric behavior of the prepared ferrite. The DC electrical resistivity of the prepared samples decrease with increasing temperature which indicates the semiconducting behavior of the prepared ferrites. The Zn concentration showed pronounced effect on the resistivity at room temperature. Possible explanation for the observed features of densities, porosity, dielectric constant and resistivity of the studied samples are discussed. DOI: http://dx.doi.org/10.3329/jbas.v37i1.15683 Journal of Bangladesh Academy of Sciences, Vol. 37, No. 1, 73-82, 2013

Yafet–Kittel-type magnetic order in Zn-substituted cobalt ferrite nanoparticles with uniaxial anisotropy

Zn-substituted cobalt ferrite (Zn x Co1−x Fe2O4 with 0.0 ≤ x ≤ 1.0) nanoparticles coated with triethylene glycol (TREG) were prepared by the hydrothermal technique. The effect of Zn substitution on temperature-dependent magnetic properties of the TREG-coated Zn x Co1−x Fe2O4 nanoparticles has been investigated in the temperature range of 10–400 K and in magnetic fields up to 9 T. The structural, morphological, and magnetic properties of TREG-coated Zn x Co1−x Fe2O4 NPs were examined using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). The average crystallite size estimated from X-ray line profile fitting was found to be in the range of 7.0–10 nm. The lattice constant determined using the Nelson–Riley extrapolation method continuously increases with the increase in Zn2+ content, obeying Vegard’s law. TEM analysis revealed that the synthesized particles were nearly monodisperse, roughly spherical shaped nanoparticles in the size range of 9.0–15 nm. FT-IR spectra confirm that TREG is successfully coated on the surface of nanoparticles (NPs). The substitution of non-magnetic Zn2+ ions for magnetic Co2+ ions substantially changes the magnetic properties of the TREG-coated Zn x Co1−x Fe2O4 NPs. The saturation magnetization and the experimental magnetic moment are observed to initially increase (up to x = 0.2), which is explained by Neel’s collinear two-sublattice model, and then continuously decrease with further increase in Zn content x. This decrease obeys the three-sublattice model suggested by Yafet–Kittel (Y–K). While the Y–K angle is zero for the CoFe2O4 NPs coated with TREG, it increases gradually with increasing Zn concentrations and extrapolates to 82.36° for ZnFe2O4 NPs coated with TREG. The increase in spin canting angles (Y–K angles) suggests the existence of triangular (or canted) spin arrangements in all the samples (except for the samples with x = 0.0) under consideration in this work. From the computation of Y–K angles for the TREG-coated Zn x Co1−x Fe2O4 NPs, it can be concluded that all the zinc-doped cobalt ferrite nanoparticles (for x > 0.0) have a Y–K-type magnetic order, while the pure cobalt ferrite nanoparticles (x = 0.0) have a Neel-type magnetic order. Zero field cooled (ZFC) and field cooled (FC) measurement results further verify that the samples with 0.6 ≤ x ≤ 1.0 have superparamagnetic behavior at room temperature, which shows weak interaction between magnetic particles. The blocking temperatures obtained from ZFC–FC curves decrease as a function of Zn concentration. It was found that the effective magnetic anisotropy, the coercivity, and remanence magnetization continuously decrease with increasing Zn concentration. Lower reduced remanent magnetization (M r/M s) values (<0.5) suggest that all the samples have uniaxial anisotropy. Ferromagnetic resonance (FMR) measurement shows that the FMR spectra of all the samples have broad linewidth because of the magnetic nanoparticles with randomly distributed anisotropy axes, and the decrease in the internal field conversely leads to the increase in the resonance field with respect to increasing Zn concentration.

Effects of Zn on microstructure, mechanical properties and corrosion behavior of Mg–Zn alloys

In this study, binary Mg–Zn alloys were fabricated with high-purity raw materials and by a clean melting process. The effects of Zn on the microstructure, mechanical property and corrosion behavior of the as-cast Mg–Zn alloys were studied using direct observations, tensile testing, immersion tests and electrochemical evaluations. Results indicate that the microstructure of Mg–Zn alloys typically consists of primary α-Mg matrix and MgZn intermetallic phase mainly distributed along grain boundary. The improvement in mechanical performances for Mg–Zn alloys with Zn content until 5% of weight is corresponding to fine grain strengthening, solid solution strengthening and second phase strengthening. Polarization test has shown the beneficial effect of Zn element on the formation of a protective film on the surface of alloys. Mg–5Zn alloy exhibits the best anti-corrosion property. However, further increase of Zn content until 7% of weight deteriorates the corrosion rate which is driven by galvanic couple effect.

Synthesis and Magnetic Properties of Ba&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;Ni&amp;lt;sub&amp;gt;2–x&amp;lt;/sub&amp;gt;Zn&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;Fe&amp;lt;sub&amp;gt;12&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;22&amp;lt;/sub&amp;gt;

Y-type hexagonal ferrites with the nominal chemical composition Ba2Ni2-xZnxFe12O22 (0.0 ≤ x ≤ 0.6 with a step of 0.1) have been synthesized by the conventional solid state reaction method and sintered in the temperature range 1150℃-1250℃ to study their structural and magnetic properties. The aim of the present work is to increase the magnetic properties of Y-type hexaferrites by Zn substitution. X-ray diffraction analysis confirms the formation of the hexagonal phase. The effect of chemical composition on the lattice parameter, density and porosity is studied. The lattice parameter increases with Zn substitution. The density increases with Zn substitution up to a certain level and after that density decreases. The ac magnetic properties of the hexaferrites sintered at temperature 1200℃ are characterized within the frequency range 100 kHz -120 MHz. The real part (μi') of the complex initial permeability for different compositions indicates that μi' decreases with increase in frequency. The permeability increases with the increase in Zn content, reaches a maximum value and then decreases with further increase in Zn content. Magnetization has been measured using the Superconducting Quantum Interference Device (SQUID) magnetometer. The saturation magnetization is observed to be maximum at x = 0.1 and then decreases with Zn content for x > 0.1. From the M-H curve it is clear that at room temperature the polycrystalline Ba2Ni2-xZnxFe12O22 compositions are in ferrimagnetic state.

Effect of Zn on the microstructure and mechanical properties of Mg–Si alloy

Microstructure and mechanical properties of Mg–0.6Si– xZn alloys ( x = 0–1.6 wt%) were investigated to reveal the modification effect of Zn on the morphology of eutectic Mg 2Si. It was found 0.5–1.3 wt% Zn effectively modified the morphology of eutectic Mg 2Si from laminated structure to fine fiber, and in turn improved significantly the mechanical properties of Mg–Si alloy. Further increase in Zn content changed Mg 2Si from fine fiber to Chinese script shape. It was suggested that the Zn content should not exceed 1.5 wt% in Mg–Si–Zn alloy in order to get good mechanical properties.

Characterization and magnetic properties of electrospun Co1−x Zn x Fe2O4 nanofibers

By the electrospinning and calcination techniques, we have prepared uniform nanofibers of Co1−xZnxFe2O4 (0.0≤x≤0.5) ferrites with diameters of 110–130 nm. The Co1−xZnxFe2O4 nanofibers are single-phase spinels and the lattice constant with Zn content deviates from the Vegard’s law for these Co1−xZnxFe2O4 nanofibers. The Co1−xZnxFe2O4 nanocrystal grains by which are built nanofibers increase with calcination temperature. Variations of coercivity and saturation magnetization with calcination temperature can be explained in terms of the grain-size (D) effect. The coercivity (Hc) of Co0.5Zn0.5Fe2O4 nanofibers varies as D0.65 and basically follows the predicted D2/3 dependence based on the random anisotropy model in a D range below the single-domain size around 40 nm. The saturation magnetization of Co1−xZnxFe2O4 nanofibers initially increases with increasing Zn content, reaches a maximum value at x=0.3 and then decreases with further increase of Zn content, while the coercivity exhibits a continuous reduction with the increase of Zn content.

Effect of Zn on mechanical property and corrosion property of extruded Mg-Zn-Mn alloy

The effect of Zn on the microstructure, the mechanical property and the corrosion property in simulated body fluid(SBF) of an extruded Mg-Mn alloy was studied. The results indicate that the addition of Zn element can significantly refine the grain size of the extruded Mg-Mn alloy. When Zn content is increased from 0% to 3%, the grain size decreases from 12 μm to 4 μm. Meanwhile, the mechanical properties also increase remarkably with increasing Zn content. When Zn content is 3%, the ultimate tensile strength and the yield strength are increased by 54.7 MPa and 69.7 MPa, respectively. Zn can also improve the anti-corrosion property of the alloy. The best anti-corrosion property is obtained with 1% Zn. However, further increase of Zn content up to 3% deteriorates the corrosion property. Finally, the influence mechanism of Zn on the microstructure, the mechanical property and the corrosion property was discussed.

Electrical resistivity and thermoelectric power studies on Zn-substituted Li–Mg ferrites

The electrical resistivity and thermoelectric power measurements of Zn-substituted Li–Mg ferrites having the general formula LixMg0.4Zn0.6−2xFe2+x04 (where x=0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3) were carried out from room temperature to 600°C. The variation of logρ with reciprocal of temperature shows a discontinuity at Curie temperature. The activation energy in the ferrimagnetic region is found to be lower than that in paramagnetic region. The conduction mechanism is explained on the basis of hopping of electrons. The variation of room temperature resistivity with composition indicates that resistivity initially decreases with Zn content up to 0.3 and then it increases with further increase in Zn content. The Curie temperature is found to decrease linearly with addition of Zn. The variation of Seebeck coefficient with temperature indicates that all the samples show n-type conductivity.

Preparation and characterization of Zn substituted Li–Mg ferrites

Studies on preparation and characterization of Zn substituted Li–Mg ferrites having the general formula Li x Mg 0.4Zn 0.6−2 x Fe 2+ x O 4 (where x=0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) have been carried out. These polycrystalline ferrites were prepared by a standard ceramic technique. The single-phase formation was confirmed from X-ray diffractograms. The lattice parameter ‘ a’, bond lengths R A, R B and site radii r A, r B were found to increase linearly with increase in Zn content. IR absorption spectral studies show two fundamental absorption bands ν 1 and ν 2 in the frequency range 600–400 cm −1. The center frequency of ν 1 and ν 2 was found to shift towards low frequency side. The average grain diameter determined from SEM studies was found to increase with Zn content, it is maximum for Zn=0.3 and then it decreases with further increase in Zn content. The Curie temperature was found to decrease linearly with Zn content.

Microstructural and magnetic properties of Zn substituted Li–Mg ferrites

The microstructural and magnetic properties of Zn-substituted Li–Mg ferrites having the general formula Li x Mg 0.4Zn 0.6−2 x Fe 2+ x O 4 (where x = 0, 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3) have been investigated as a function of composition and temperature. The SEM studies show that the average grain diameter initially increases to 2.66 μm with Zn content up to 0.3 and then decreases beyond this limit. The magnetic moment ( μ B) initially increases up to Zn = 0.3 and then decreases with further increase in Zn content. The initial permeability in the same way increases but up to 0.4 and then decreases. The variation of normalized a.c. susceptibility with temperature indicates that the sample with Zn = 0 possess single domain (SD) type of magnetic particles whereas those with Zn = 0.1 to 0.5 and beyond Zn = 0.5 showed multidomian (MD) and superparamagnetic (SP) natures, respectively. The Curie temperatures obtained from μ i– T and χ– T curves indicate that T c goes on decreasing linearly with addition of Zn.

Determination of magnetic properties and Y–K angles in Cu–Zn–Fe–O system

The effects of compositional variation on magnetic susceptibility, saturation magnetization, Curie temperature and magnetic moments of Cu 1− x Zn x Fe 2O 4 ferrites, where x=0.0, 0.25, 0.50, 0.75, 1.00 are reported. The Curie temperatures have been evaluated by measuring AC magnetic susceptibility using a mutual inductance technique. On increasing Zn content from 0.0 to 0.75, the Curie temperature and the saturation magnetization increase. On further increase in Zn content, x>0.75, a decreasing trend is exhibited. This effect can partially be related to the low magnetic moments of Zn +2 ions. The Y–K angle increases gradually with increasing zinc content and extrapolates to 90° for ZnFe 2O 4. From the computation of Y–K angles for Zn substituted ferrites (0< x<0.75), it can be concluded that the mixed zinc ferrites exhibit a non-collinearity of the Y–K type while CuFe 2O 4 shows a Néel type of ordering.