Preparation and characterization of nickel nanoparticles in different carbon matrices (original) (raw)
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Magnetism as indirect tool for carbon content assessment in nickel nanoparticles
Journal of Applied Physics, 2017
We report a combined experimental and theoretical study to ascertain carbon solubility in nickel nanoparticles embedded into a carbon matrix via the one-pot method. This original approach is based on the experimental characterization of the magnetic properties of Ni at room temperature and Monte Carlo simulations used to calculate the magnetization as a function of C content in Ni nanoparticles. Other commonly used experimental methods fail to accurately determine the chemical analysis of these types of nanoparticles. Thus, we could assess the C content within Ni nanoparticles and it decreases from 8 to around 4 at. % with increasing temperature during the synthesis. This behavior could be related to the catalytic transformation of dissolved C in the Ni particles into graphite layers surrounding the particles at high temperature. The proposed approach is original and easy to implement experimentally since only magnetization measurements at room temperature are needed. Moreover, it c...
Two kinds of nickel nanoparticlesÐcarbon encapsulated Ni nanoparticles Ni(C) and pure Ni nanoparticles coated with NiO layers Ni(O) are successfully prepared. Structural characterizations (HR-TEM, SAED, and XRD) reveal their distinct morphological properties. Magnetization measurements for the assemblies of two kinds of Ni nanoparticles show a larger coercivity and remanence by a deviation between the zero-®eld-cooled and the ®eldcooled magnetization below the irreversibility temperature, T irr , for the assemblies of Ni(O) particles. This deviation may be explained as a typical nanocluster±glass behavior (collective behavior) due to ferromagnetic dipole±dipole interaction effects among the assemblies of Ni(O) particles. However, Ni(C) particles exhibit modi®ed superparamagnetic properties above the average blocking temperature of T B , which is determined to be around 115 K at 1000 Oe. Moreover, a gradual decrease in saturation magnetization is observed, which is attributed to the nanocrystalline nature of the encapsulated particles, coupled with possible carbon solution in Ni nanocrystals. #
Materials Chemistry and Physics
A method for synthesis of nickel nanoparticles in a magnetic nickel phthalocyanine anions matrix has been developed. The method is based on intercalation of potassium atoms to the nickel phthalocyanine (NiPc) polycrystalline powder at 300°C. The structure of (K 2 NiPc) was investigated by using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) spectroscopes. Magnetic properties were studied by SQUID magnetometry and magnetic resonances methods. It is revealed that the resultant compound contains of 1 wt% Ni nanoparticles with the average size of 15 nm. The measured values of the magnetization and absorption of the ferromagnetic resonance considerably exceed the magnetism which can be attributed to metallic Ni nanoparticles. The obtained results indicate the presence of room temperature molecular ferromagnetism caused by anionic molecules of NiPc.
Technical Physics, 2017
Data for the vapor-phase doping (300°C) of nickel phthalocyanine (NiPc) by sodium taken in different concentrations (x), as well as structural analysis data for Na x = 0.2 NiPc, Na x = 1 NiPc, and Na x = 3 NiPc samples, have been reported. The structure of the samples and their atomic configuration versus the doping level have been studied by transmission electron microscopy, Raman scattering, X-ray diffraction, X-ray absorption spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The structural parameters of Ni-N, Ni-C, and Ni-Ni bonds have been determined, and it has been found that, at a low level of doping by sodium, local structural distortions are observed in some molecules of the NiPc matrix near nickel atoms. The fraction of these molecules grows as the doping level rises from x = 0.2 to x = 1.0. It has been shown that doping changes the oscillation mode of light atoms, which indicates a rise in the electron concentration on five-and six-membered rings. At a high level of sodium doping (x = 3.0), nickel nanoparticles with a mean size of 20 nm and molecule decomposition products have been observed in the NiPc matrix. It has been found that the fraction of nickel atoms in the Na x = 3 NiPc nanoparticles as estimated from EXAFS data is sufficient for the room-temperature magnetic properties of the samples to persist for a long time.
Journal of Alloys and Compounds, 2006
Magnetic nanoparticles of nickel ferrite (NiFe 2 O 4 ) have been synthesized by co-precipitation route using stable ferric and nickel salts with sodium hydroxide as the precipitating agent and oleic acid as the surfactant. X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses confirmed the formation of single-phase nickel ferrite nanoparticles in the range 8-28 nm depending upon the annealing temperature of the samples during the synthesis. The size of the particles (d) was observed to be increasing linearly with annealing temperature of the sample while the coercivity with particle size goes through a maximum, peaking at 11nmandthendecreasesforlargerparticles.Typicalblockingeffectswereobservedbelow11 nm and then decreases for larger particles. Typical blocking effects were observed below 11nmandthendecreasesforlargerparticles.Typicalblockingeffectswereobservedbelow225 K for all the prepared samples. The superparamagnetic blocking temperature (T B ) was found to be increasing with increasing particle size that has been attributed to the increased effective anisotropy energy of the nanoparticles. The saturation moment of all the samples was found much below the bulk value of nickel ferrite that has been attributed to the disordered surface spins or dead/inert layer in these nanoparticles.
Synthesis and Characterization of Ferromagnetic Nickel Nanoparticles
Journal of Superconductivity and Novel Magnetism
Nickel nanoparticles on mass production scale have been prepared using a modified polyol process with Ni(CH3COO)2⋅4H2O, NaOH, 1,2 propandiol and hydrazinium hydroxide (N2H4∗H2O). A mixture of face centered cubic (fcc) metallic nickel nanoparticles with 12 nm diameter were obtained. We have experimentally studied the structure of nanoparticle by X-ray and Scanning Electron Microscopy (SEM, EDS). The magnetic properties of the prepared Ni film have been studied by Ferromagnetic Resonance (FMR) technique, Vibrating Sample Magnetometer (VSM) and Vector Network Analyzer (VNA). The effective g-factor and magnetic anisotropy constant were determined as g eff=2.25 and K eff=85 Oe, respectively.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000
In the present work, experiments aim at the encapsulation of foreign materials within hollow graphitic cage have been carried out for iron group metals (Fe, Co, Ni) using a modified arc-discharge (carbon arc) reactor. HRTEM (high resolution transmission electron miscroscope), and XRD (X-ray diffractometer) studies, for three carbon encapsulated materials, showing nanoparticles of both a metallic phase (a-Fe, g-Fe; hcp-Co, fcc-Co; fcc-Ni) and also a carbide phase (M 3 C, M =Fe, Co, Ni) are encapsulated in graphitic carbon. The magnetic measurement for the three as-made nanoparticles, indicating that the values of saturation magnetic moment of three nanoparticle are 37.6, 55.5 and 15.7% of the bulk ferromagnetic elements counterparts, respectively. The different comparison values (M r /M s ) of remanent magnetization (M r ) and saturation magnetization (M s ) suggest, the encapsulated Fe and Co nanoparticles are shown to be ferromagnetic with a ratio of remnant to saturation magnetization M r /M s 0.3; whereas, the encapsulated Ni nanoparticles exhibits superparamagnetic behavior at room temperature.
Nickel nanoparticles arrays, growth into hydro-genated amorphous carbon, were prepared by means of RF-plasma enhanced chemical vapor deposition and RF-sputtering co-deposition from acetylene and a nickel target. The resulting nanocomposite films were characterized by X-ray diffraction and atomic force microscopy, and their magnetic responses and magnetoresistance behavior were investigated as a function of the exciting magnetic field and the Ni nanoparticles content, which was conveniently controlled by adjusting the deposition time. These physical properties were explained by a combination of hopping and tunneling effects.