Magnetic Ni Nanoparticles Research Articles

Assembly and magnetic properties of nickel nanoparticles on silicon nanowires

The directed assembly of magnetic Ni nanoparticles at the tips of silicon nanowires is reported. Using electrodeposition Ni shells of thickness from 10 to 200 nm were selectively deposited on Au catalytic seeds at the ends of nanowires. Magnetic characterization confirms a low coercivity (≈115 Oe) ferromagnetic behavior at 300 K. This approach to multifunctional magnetic-semiconducting nanostructure assembly could be extended to electrodeposition of other materials on the nanowire ends, opening up additional approaches to device integration. Such magnetically functionalized nanowires offer an approach to developing highly localized magnetic probes for high resolution magnetic resonance force microscopy.

A simple method to ordered mesoporous carbons containing nickel nanoparticles

A series of ordered mesoporous carbons containing magnetic Ni nanoparticles (Ni-OMCs) with a variety of Ni loadings was made by a simple one-pot synthetic procedure through carbonization of phenolic resin-Pluronic block copolymer composites containing various amount of nickel nitrate. Such composite materials were characterized by N2 sorption, XRD, and STEM. Ni-OMCs exhibited high BET surface area, uniform pore size, and large pore volume without obvious pore blockage with a Ni loading as high as 15 wt%. Ni nanoparticles were crystalline with a face-center-cubic phase and observed mainly in the carbon matrix and on the outer surface as well. The average particle size of Ni nanoparticles was dependent on the preparation (carbonization) temperature and Ni loading; the higher the temperature was used and the more the Ni was incorporated, the larger the Ni nanoparticles were observed. One of the applications of Ni-OMCs was demonstrated as magnetically separable adsorbents.

Self-assembly of magnetic Ni nanoparticles into 1D arrays with antiferromagneticorder

In this paper, we report on the magnetic properties of isolated nanoparticles andinteracting nanochains formed by the self-assembly of Ni nanoparticles. The magneticproperties were studied using superconducting quantum interference device (SQUID)magnetometry and magnetic force microscopy (MFM). We demonstrate that single-domainNi nanoparticles spontaneously form one-dimensional (1D) chains under the influence of anexternal magnetic field. Furthermore, such magnetic field-driven self-assembly inconjunction with surface templating produces regular arrays of 1D nanochains withantiferromagnetic intra-chain order. The antiferromagnetic order, which is in strikingcontrast to what is found for non-interacting nanoparticle assemblies within the chains, canbe evidenced from MFM and SQUID measurements.

Two-phase magnetoelectric nanopowder/polyurethane composites

This study deals with the observation of magnetoelectric (ME) effect in nanocomposite films constituted of semicrystalline polyurethane matrix filled with magnetic Fe3O4 (hard) or Ni (soft) nanoparticles. The measurement of the magnetic field-induced ground current of the so-called particulate composites enabled the precise determination of true ME current after extraction of the part corresponding to the inductively coupled (loop) current. Experimental ME current could be successfully simulated considering coexistence of both true linear and quadratic ME effects and by taking into account the nonlinear variation of applied dc bias and ac field magnitude due to the magnetization saturation of the magnetic field generator. Although linear ME coefficients of particulate composites are lower than those of laminate composites, they are of the same order of magnitude than that of reference ME material Cr2O3 (up to 18 mV/cm Oe). Besides, nanocomposites are simple to prepare, flexible, easily integrable, and sensitive to magnetic field anomaly at room temperature. At last, they present a linear ME coupling apparently not triggered by magnetostrictive phenomenon.

Magnetic nano-particles of Ni in MgO single crystals by ion implantation

Magnetic Ni nano-particles in the near surface regions of MgO single crystals have been synthesized by 64keV Ni ion implantation to 1×1017cm−2 followed by thermal annealing. Transmission electron microscopy (TEM) and magnetic properties measurement system (MPMS) equipped with a superconducting quantum interference device (SQUID) detector have been employed to characterize the microstructure and magnetic properties of the Ni nano-particles. The average particle size ranges 3–5nm in the as-implanted sample and 8–10nm in the annealed sample. The orientation of Ni particles is perfectly matched with that of the MgO matrix. The M–H hysteresis loop measured at 10K revealed the coercivity, Hc, ∼195Oe. The superparamagnetism of Ni particles was evident in as-implanted sample at the temperature above 35K but did not show in the annealed sample.

Synthesis and characterization of polymer encapsulated Cu–Ni magnetic nanoparticles for hyperthermia applications

Copper nickel alloy nanoparticles were synthesized by polyol reduction method and by physical melting process. The particles were further coated with a biodegradable polymer, polyethylene glycol. The particles have a curie temperature in the range of 43–46 °C and are designed to be used for hyperthermia applications. Morphology of these encapsulated particles was determined by electron microscopy. The curie temperature for alloy particles and encapsulated particles was also measured.

Formation of magnetic Ni nanoparticles in x-ray irradiated electroless solution

Magnetic nanostructures are attracting tremendous interest as regards application inhigh-density data storage devices and magnetic fluids. We have prepared magneticnanoparticles ( nm) by x-ray irradiation of electroless solutions and furthermore have investigatedtheir structural and magnetic properties. Interestingly, we find that the formationof these Ni nanoparticles occurs spontaneously, during the room temperatureprocess, dominantly at electrolyte pH of 8.2. The hydrated electrons producedduring the irradiation of electroless solution seem to play a decisive role in thespontaneous formation and growth of nanoparticles. The possible surface alloyingand/or coating over these pure Ni cores occurs only upon longer irradiation ofhigh-P-content solutions. This suggests a possible catalytic behaviour of these nano-Nisurfaces in relation to P counter-ions in the irradiated solutions. The magneticproperties of these ‘as-received’ particles have been studied using a vibrating samplemagnetometer. The saturation magnetic moment per gram for the Ni particles is9.38 emu g−1, which is 17% of the saturation moment of bulk ferromagnetic Ni at room temperature;this can be attributed due to the size effect of these magnetic domains. The symmetrichysteresis loop about the zero-field axis showing negligible loop shift (–10 Oe) suggests that Ni particles are free from oxide layers.

Microstructure and Magnetic Properties of Carbon‐Coated Nanoparticles

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and characterization of Ni magnetic nanoparticles in AlMCM41 host

Superparamagnetic nickel nanoparticles were prepared by incorporating nickel ion into AlMCM41 as a nanoreactor and then reduced with sodium borohydride or H 2 gas. Products were characterized by elemental analysis, transmission electron microscopy, X-ray powder diffraction, and magnetic susceptibility. The nickel particle size and blocking temperature depend on the reduction method.

Characterization of magnetic nanoparticles using energy-selected transmission electron microscopy.

Fe, Co, and Ni magnetic nanoparticles have been characterized using energy-selected imaging in a high-resolution transmission electron microscope. The samples comprised Fe/FeO x and Co/CoO x nanoparticles synthesized by inert gas evaporation and a Ni/C nano-composite prepared by a sonochemical method. All of the particles examined were found to be between 5 and 30 nm in size, with the Fe and Co crystals coated in 5-10 nm of metal oxide layer and the Ni metallic crystallites embedded in an amorphous carbon spherical matrix.