Synthesis of Self-Supporting ZnO Nanowire Array Film and its Optical Property and Room Temperature Ferromagnetism

X-ray diffractometer, field emission scanning electron microscope (SEM, Hitachi S-4800), laser confocal micro-region Raman spectrometer and vibration sample magnetometer were used to systematically study the effects of polyethyleneimine concentrations and exposure time on the morphology and size of ZnO nanowire arrays. The photoelectric property and the relationship between the morphology of nanowire arrays and ferromagnetism at room temperature were also analyzed. Under 15 min exposure time, when the polyethyleneimine concentration is 2.25 g / L, the obtained ZnO nanowire array film exhibits the smallest size, the optimal density and vertical orientation. According to the study of luminescence and room temperature magnetism, it is shown that the optical and ferromagnetic property are related to the variation tendency of oxygen defects and surface defects of the ZnO nanowires.

Synthesis of Polymer-Based Magnetic Nanocomposite for Multi-Pollutants Removal from Water

A magnetic polymer-based nanocomposite was fabricated by the modification of an Fe3O4/SiO2 magnetic composite with polypyrrole (PPy) via co-precipitation polymerization to form PPy/Fe3O4/SiO2 for the removal of Congo red dye (CR) and hexavalent chromium Cr(VI) ions from water. The nanocomposite was characterized using various techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), vibration sample magnetometer, and thermogravimetric analysis (TGA). The results confirm the successful fabrication of the nanocomposite in the size of nanometers. The effect of different conditions such as the contact time, adsorbent dosage, solution pH, and initial concentration on the adsorption process was investigated. The adsorption isotherm suggested monolayer adsorption of both contaminants over the PPy/Fe3O4/SiO2 nanocomposite following a Langmuir isotherm, with maximum adsorption of 361 and 298 mg.g−1 for CR dye and Cr(VI), respectively. Furthermore, the effect of water type on the adsorption process was examined, indicating the applicability of the PPy/Fe3O4/SiO2 nanocomposite for real sample treatment. Interestingly, the reusability of the nanocomposite for the removal of the studied contaminants was investigated with good results even after six successive cycles. All results make this nanocomposite a promising material for water treatment.

Coexistence of Weak Ferromagnetism and Paramagnetism in T’-Pr2-xCexCuO4+α-δ Nanoparticles

The coexistence of ferromagnetism and paramagnetism of T’-Pr2-xCexCuO4+α-δ (T’-PCCO) nanoparticles with x = 0, and 0.10 have been studied intensively in the normal state. All samples were synthesized by a chemically dissolved method using HNO3 as a dissolving agent. The calcination process was performed at 1000°C for 15 h in air and followed by reduction annealing at 700°C in argon atmosphere for 10 h. All samples were first characterized by an x-ray diffraction (XRD) measureemnts followed by Rietveld and Maximum Entropy Method (MEM) analyseis. The result confirms the Ce-dependence and reduction annealing effect on the electron density at around the Cu site. The magnetic characterization was performed by using vibration sample magnetometer (VSM) indicating weak ferromagnetic properties at x = 0 and dominant paramagnetic properties at x = 0.10 at room temperature. Moreover, the weak ferromagnetic feature seems to remain after the annealing process. This signifies the coexist of weak ferromagnetism and paramagnetism at the normal state due to a number of oxygen vacancies in the crystal structure.

A facile approach for obtaining NiFe­2O4/C nanocomposites and their magnetic properties assessment

NiFe2O4/C nanocomposites were prepared using the two-step process, including reverse microemulsion followed by thermochemical vapour deposition (TCVD). Micelles made in the first step worked well and NiFe2O4 nanoparticles owing sizes smaller than 10 nanometer with narrow size distribution were obtained. Acetylene gas was used as a carbon source for deposition on the surface of NiFe2O4 nanoparticles. Coating applied for 1 and 2 h at 700°C and resulted in an enhancement of NiFe2O4 nanoparticle size to a level of 30 nanometer. Powder X-ray diffraction (PXRD) patterns revealed the spiel formation for all samples; however, the crystallinity of them has been increased as much as temperature rose to a level of coating. Fourier transform infrared spectroscopy (FT-IR) verified the metal-oxygen bonding linked to the octahedral and tetrahedral vibrations. Micro-Raman spectra for the coated samples were recorded as well, and the results confirmed the existence of ordered and disordered carbon-based materials in nanocomposites. It is noteworthy to mention that, in the sample with 2 h coating time, the defect densities were lower than the sample with an hour coating time. The vibration sample magnetometer (VSM) was also used to investigate the magnetic properties. The as-prepared sample behaves like a superparamagnetic matter; however, the coated ones behave like ferromagnetic materials. The saturation magnetization and coercivity of coated samples were lower than their bulk counterparts which was due to their smaller size.

MAGNETIC PROPERTIES AND DOMAIN STRUCTURE OF CoFeB/Pd MULTILAYERS WITH PERPENDICULAR MAGNETIC ANISOTROPY

The magnetic properties and domain structure of (CoFeB/Pd)n (n = 2 – 10) multilayers with perpendicular magnetic anisotropy have been investigated systematically. The study has been carried out by using vibration sample magnetometer (VSM) and magneto-optical Kerr effect (MOKE) microscope. The results show clear changes of magnetic hysteresis and domain structure when increasing the number of bilayer (n) from 2 to 10. With increasing the number of bilayer, the multilayers’ hysteresis loops change from square-shaped to slanted, while domain structures change from circular-like to maze.

EFFECT OF ANNEALING ON MAGNETIC AND STRUCTURAL PROPERTIES OF THE NANOCRYSTALLINE Fe-Mn-Al ALLOYS

<p>In this work, the formations of Fe₅₅Mn₁₀Al₃₅ nanocrystalline alloys were made by using mechanical alloying (MA) technique with the milling time of 24 hrs and then annealed at 300, 500, and 700^oC. The sizes and the morphology of the particles were checked by using a Scanning Electron Microscope (SEM). The magnetic properties were characterized by using a Vibration Sample Magnetometer (VSM), and it give results both of the magnetic saturation (<em>Ms</em>) and Coercivity (<em>Hc</em>) are decreased respect to annealing temperatures. Last one; the structures were characterized by using an Extended X-ray Absorption Fine Structure (EXAFS) and X-Ray Diffraction (XRD). It give results that the structures were single phase at 24 hrs milled and 300^oC annealed, then the structure to be changed at 500 and 700^oC. </p>

Effect of Polyvinyl Pyrrolidone Dosage on Barium Ferrite Fibers via Electrospinning

Barium ferrite micro/nanofibers were successfully prepared via the electrospinning by using dimethyl formamide (DMF) as the solvent, poly vinyl pyrrolidone (PVP) as the spinning auxiliaries and iron nitrate and barium nitrate as raw materials. The effect of poly vinyl pyrrolidone on the structure, morphology, magnetic and microwave absorbing properties were investigated by scanning electron microscope (SEM), X-ray diffraction analysis (XRD), vibration sample magnetometer (VSM) and vector network analyzer (VNA). XRD patterns of the samples confirmed that when the additive content of PVP was up to 10%, (wt%) pure barium ferrite fibers formed under the condition of the same heat treatment. Also, the FE-SEM images showed that the morphology of the fibers improved with the increase of PVP content. Moreover, the VSM results demonstrated that the saturation magnetization can reach 54.7 emu/g when the PVP dosage is 14% (wt%) in the precursor solution.

Structural and Magnetic Properties of Mn-Zn Ferrites Synthesized by Microwave-Hydrothermal Process

Nanocrystalline Mn1-xZnxFe2O4 (x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) ferrites have been successfully synthesised using microwave–hydrothermal method for high frequency applications. The nanopowders were characterised using X-ray diffraction (XRD) and sintered using microwave furnace at 900°C and the total time taken for sintering is 30 min. The frequency dependence of real and imaginary part of permeability were measured in the range 1 MHz to 1.8 GHz. The saturation magnetisation and coercive force were obtained using a vibration sample magnetometer (VSM) in the field of 1.5 T. The temperature dependence of initial permeability (μi) was measured in the temperature range of 300K to 600K at 10 kHz. The high values of permeability and saturation magnetization enables these materials to be the potential candidates for a number of applications, for example, in transformers, choke coils, noise filters and recording heads.

Annealing effect on the microstructural and magnetic properties of Er2.5Y0.5Fe5O12 films prepared by sol-gel method

The effect of annealing on the microstructural and magnetic properties of Er2.5Y0.5Fe5O12 sol-gel films were studied at different temperatures using X-ray diffraction (XRD), field emission scanning electron microscopic (FESEM) and vibration sample magnetometer (VSM).The results show that the XRD pattern of the samples have a single phase garnet structure with reduction in the lattice parameter of Er:YIG films due to the smaller ionic radii of Er3+ compare to Y3+. The sizes of the particles are in the range of 50 to 90 nm. The saturation magnetization (Ms) increase and then decreases as the temperature increased.

Size Controlled Synthesis of Magnetite Nanoparticles Using Microwave Irradiation Method

The experimental conditions play an important role in particle size and in their properties in multifunctional magnetic nanoparticle synthesis. In the present study, magnetite nanoparticles of various sizes were synthesized by microwave irradiation method. The synthesized powder samples were characterized using XRD and SEM which substantiated the formation of magnetic nanoparticle in cubic phase. The particle sizes obtained were 40 nm, 31 nm and 27 nm from TEM micrographs. The FTIR studies confirmed the characteristic band of Fe-O within the range of 574 - 580 cm-1. The magnetic properties of the samples were measured by vibration sample magnetometer that confirmed ferrimagnetic behavior of magnetite nanoparticles at room temperature. From the present study, it is observed that the microwave irradiation method is a convenient method to produce a wide range of magnetite nanoparticles of desired size for a variety of novel biomedical applications.