Nanocrystalline structure and soft magnetic properties of nickel–molybdenum alloy thin films electrodeposited from acidic and alkaline aqueous solutions
“…It was shown that Ni-Mo alloys exhibit high activity and long-term stability as the hydrogen evolution reaction under alkaline conditions occurs either in the form of a catalyst coating [24] or as unsupported nanopowder [25,26]. Nanocrystalline electrodeposited Ni-Mo thin films are potentially applicable as novel catalytic materials with ferromagnetism [28]. The Ni-Mo substrates for superconducting coatings are produced by severe cryorolling and subsequent annealing resulting in an extremely sharp cube texture which is required for epitaxial coatings.…”
An investigation was conducted to examine the effect of molybdenum (Mo) content on the grain size, lattice defect structure and hardness of nickel (Ni) processed by severe plastic deformation (SPD). The SPD processing was applied to Ni samples with low (~0.3 at.%) and high (~5 at.%) Mo concentrations by a consecutive application of cryorolling and highpressure torsion (HPT). The grain size and the dislocation density were determined by scanning electron microscopy and X-ray line profile analysis, respectively. In addition, the hardness values in the centers, half-radius and peripheries of the HPT-processed disks was determined after ½, 5 and 20 turns. The results show the higher Mo content yields a dislocation density about two times larger and a grain size about 30% smaller. The smallest value of the grain size was ~125 nm and the highest measured dislocation density was ~60 × 10 14 m -2 for Ni-5% Mo. For the higher Mo concentration, the dislocation arrangement parameter was larger indicating a less clustered dislocation structure due to the hindering effect of Mo on the rearrangement of dislocations into low energy configurations. The resultsshow there is a good correlation between the dislocation density and the yield strength using the Taylor equation. The parameter in this equation is slightly lower for the higher Mo concentration in accordance with the less clustered dislocation structure.
“…It was shown that Ni-Mo alloys exhibit high activity and long-term stability as the hydrogen evolution reaction under alkaline conditions occurs either in the form of a catalyst coating [24] or as unsupported nanopowder [25,26]. Nanocrystalline electrodeposited Ni-Mo thin films are potentially applicable as novel catalytic materials with ferromagnetism [28]. The Ni-Mo substrates for superconducting coatings are produced by severe cryorolling and subsequent annealing resulting in an extremely sharp cube texture which is required for epitaxial coatings.…”
An investigation was conducted to examine the effect of molybdenum (Mo) content on the grain size, lattice defect structure and hardness of nickel (Ni) processed by severe plastic deformation (SPD). The SPD processing was applied to Ni samples with low (~0.3 at.%) and high (~5 at.%) Mo concentrations by a consecutive application of cryorolling and highpressure torsion (HPT). The grain size and the dislocation density were determined by scanning electron microscopy and X-ray line profile analysis, respectively. In addition, the hardness values in the centers, half-radius and peripheries of the HPT-processed disks was determined after ½, 5 and 20 turns. The results show the higher Mo content yields a dislocation density about two times larger and a grain size about 30% smaller. The smallest value of the grain size was ~125 nm and the highest measured dislocation density was ~60 × 10 14 m -2 for Ni-5% Mo. For the higher Mo concentration, the dislocation arrangement parameter was larger indicating a less clustered dislocation structure due to the hindering effect of Mo on the rearrangement of dislocations into low energy configurations. The resultsshow there is a good correlation between the dislocation density and the yield strength using the Taylor equation. The parameter in this equation is slightly lower for the higher Mo concentration in accordance with the less clustered dislocation structure.
“…Development of micromagnetic sensor using UV-LIGA process uses different magnetic materials. Ni and Ni-Fe are used in a variety of applications because of their soft magnetic effects, low-cost fabrication, and excellent mechanical properties, which are required for the development of micromagnetics MEMS devices [4,5]. The vibratory MEMS devices like gyroscope, magnetometers are fabricated using UV-LIGA process in which Ni or Ni-Fe are used as structural layer to achieve high aspect ratio [6,7].…”
This paper reports a new technique which is based on electroforming process for high permeability Ni and Ni-Fe alloy. The magnetic properties of Ni and Ni-Fe alloy are investigated as a function of plating current density via scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and vibrating sample magnetometer (VSM). Concentration-dependent kinetics is used to formulate the deposition rate and also the same is verified by using finite element analysis tool COMSOL Multiphysics. Several experiments are performed to derive the relation between electroplating parameters and magnetic properties. The process conditions are optimized to develop high permeability (∼16000) Ni-Fe alloy (85.71-14.29 %). The higher current density shows a monotonically increasing behavior of relative permeability (μ r ). In addition, the B-H curves indicate that the saturation magnetization (B sat ) increases and coercivity decreases with increasing plating current density. Our experimental data confirms that the higher current density increase the softness of Ni. The observed properties of Ni and Ni-Fe based on experimental results can be used to study the magnetic behavior of micromagnetic sensors and large force actuators.
“…This phenomenon was caused by the electrophoretic migration mechanism for metal cations in the pore. It is well known that the optimum deposition potential for growing nanowires can be determined by a cathodic polarization curve obtained in a wide cathode potential regime [17]. Usually, the optimum deposition potential should be selected to a potential region which is nobler than that controlled by electrophoretic migration.…”
Section: Resultsmentioning
confidence: 99%
“…When the potential shifts to − 1.5/− 1.8 V at t
on , recovered Fe 2+ concentration provides enough large cathodic (deposition) current as seen in Fig. 4 [17]. Fig.…”
Textured ferromagnetic Fe nanowire arrays were electrodeposited using a rectangular-pulsed potential deposition technique into anodized aluminum oxide nanochannels. During the electrodeposition of Fe nanowire arrays at a cathodic potential of − 1.2 V, the growth rate of the nanowires was ca. 200 nm s−1. The aspect ratio of Fe nanowires with a diameter of 30 ± 5 nm reached ca. 2000. The long axis of Fe nanowires corresponded with the <200> direction when a large overpotential during the on-time pulse was applied, whereas it orientated to the <110> direction under the potentiostatic condition with a small overpotential. By shifting the on-time cathode potential up to − 1.8 V, the texture coefficient for the (200) plane, TC200, reached up to 1.94. Perpendicular magnetization performance was observed in Fe nanowire arrays. With increasing TC200, the squareness of Fe nanowire arrays increased up to 0.95 with the coercivity maintained at 1.4 kOe at room temperature. This research result has opened a novel possibility of Fe nanowire arrays that can be applied for a new permanent magnetic material without rare-earth metals.
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