Vibrating Specimen Magnetometer Research Articles

Study on the Preparation and Optical Properties of Graphene Oxide@Fe3O4 Two-Dimensional Magnetically Oriented Nanocomposites.

In this work, graphene oxide@Fe3O4 (GO@Fe3O4) two-dimensional magnetically oriented nanocomposites were prepared through the co-precipitation approach using graphene oxide as the carrier and FeCl3·6H2O and FeSO4·7H2O as iron sources. The samples were characterized and tested by X-ray diffraction, a transmission electron microscope, Fourier-transform infrared spectroscopy, a vibrating-specimen magnetometer, a polarized optical microscope, an optical microscope, etc. The effects of material ratios and reaction conditions on the coating effects of Fe3O4 on the GO surface were investigated. The stable GO@Fe3O4 sol system was studied and constructed, and the optical properties of the GO@Fe3O4 sol were revealed. The results demonstrated the GO@Fe3O4 two-dimensional nanocomposites uniformly coated with Fe3O4 nanoparticles were successfully prepared. The GO@Fe3O4 two-dimensional nanocomposites exhibited superparamagnetic properties at room temperature, whose coercive force was 0. The stable GO@Fe3O4 sol system could be obtained by maintaining 1 < pH < 1.5. The GO@Fe3O4 sol showed magneto-orientation properties, liquid crystalline properties, and photonic crystal properties under the influence of the external magnetic field. The strength and direction of the magnetic field and the solid content of the GO@ Fe3O4 sol could regulate the aforementioned properties. The results suggest that GO@Fe3O4 two-dimensional magnetically oriented nanocomposites have potential applications in photonic switches, gas barriers, and display devices.

Adsorptive Remediation of Hazardous Crystal Violet Dye using Ni1‐xZnxFe2O4 Magnetic Nanocomposites

AbstractCrystal violet (CV) dye is one of the most poisonous colors primarily produced in the textile industry. In the current study, the co‐precipitation assisted ultrasonic radiation method was used to synthesized Ni1‐xZnxFe2O4 magnetic nanoparticles for the CV dye removal from aqueous solutions. The adsorbents were characterized by vibrating specimen magnetometer (VSM), X‐ray diffraction (XRD), High resolution transmission electron microscope (HRTEM), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), and nitrogen sorption analysis. XRD confirmed the successful synthesis of Ni1‐xZnxFe2O4 single phase with a characteristic diffraction (311) peak at 2θ=35.5°. XPS analysis proved the successful substitution of Ni2+ by Zn2+ ions in the spinel structure. N2 sorption revealed that, the prepared adsorbent exhibited a mesoporous structure of slit shaped and narrow entrances, especially at high annealing temperatures. Results revealed that the magnetic Ni0.1Zn0.9Fe2O4 nano adsorbent offered a maximum adsorption capacity of 473.9 mg g−1 at pH 10.0, which is significantly greater than that of the other noted for CV removal. In addition, ferromagnetic nature was observed by Ni0.5Zn0.5Fe2O4 with a saturation magnetization value of 60.1 emg/g. Equilibrium and kinetic studies demonstrated that, the adsorption is of chemical nature and controlled with pore and film diffusion. Finally, we concluded that Ni1‐xZnxFe2O4 can be utilized as a potential magnetic composite for the purification of CV contaminated water.

Effect of Annealing Temperature on the Soft Magnetic Properties of Fe&lt;sub&gt;70.43&lt;/sub&gt;Nb&lt;sub&gt;10.77&lt;/sub&gt;Si&lt;sub&gt;15.77&lt;/sub&gt;Cu&lt;sub&gt;2.34&lt;/sub&gt;B&lt;sub&gt;0.69&lt;/sub&gt; Amorphous Aanostrips at 20K, 300K

Since Fe-based amorphous alloys are widely used in magnetic separators, sensors and other fields, it is of practical significance to carry out research on amorphous strips used in this field.The effects of annealing temperature on the soft magnetic properties of Fe70.43Nb10.77Si15.77Cu2.34B0.69 amorphous nanostrips with 25 μm and 28 μm thickness prepared by the single roll cold method were investigated at 20 and 300K.Five specimens were annealed at472.12K, 672.12K, 772.12K, 822.12Kand 872.12K, respectively, and their microstructure and magnetic properties were tested viametallographic microscopy, X-ray diffraction, and vibrating specimen magnetometer. At cryogenic temperatureof 20K, specimens annealed at 672,12K exhibited the best magnetic properties, including the coercive forceof8.1265A/m, saturation magnetic induction intensity of1.4351T,and its residual value of 0.2462T. The comparative analysis of experimental results obtained strongly indicates that the soft magnetic properties of the amorphous alloy are significantly improved by the particular annealing treatment.

Dummy-surface molecularly imprinted polymers based on magnetic graphene oxide for selective extraction and quantification of pyrethroids pesticides in fruit juices

A highly binding dummy template molecularly imprinted polymers (Fe3O4-NH2@GO@MIPs) was synthesized used Fe3O4-NH2@GO as carrier by dummy surface molecular imprinting technique (DSMIT) for the first time. Fe3O4-NH2@GO@MIPs were characterized by fourier transform infrared (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), brunauer emmett teller (BET) and vibrating specimen magnetometer (VSM). Adsorption and selectivity experiments of Fe3O4-NH2@GO@MIPs and non-imprinted polymers (Fe3O4-NH2@GO@NIPs) verified that the Fe3O4-NH2@GO@MIPs had a better selectivity and adsorption properties for five pyrethroids pesticides. Adsorption test results revealed that the adsorption behaviors of pyrethroids onto Fe3O4-NH2@GO@MIPs followed Langmuir equation adsorption isotherm and pseudo-second-order kinetic models. Fe3O4-NH2@GO@MIPs were used as sorbent in magnetic solid phase extraction (MSPE) to extract five pyrethroids from fruit juice samples, following desorption with acidified ethyl acetate, the pyrethroids were quantified by gas chromatography with electron capture detection (GC-ECD). The developed method MSPE coupled with GC-ECD achieved satisfactory recovery (72.1–106.8%) with RSD less than 10.8%, and the detection limits (LOD) for fenpropathrin (FENP), lambda-cyhalothrin (LC), cyfluthrin (CYF), fenvalerate (FEN) and deltamethrin (DEL) ranged from 0.007 to 0.015 μg/L. Compared to other methods, the procedure MSPE-GC-ECD based on Fe3O4-NH2@GO@MIPs in this work demonstrated to be a more convenient and practical method for the separation, enrichment, and detection of pyrethroids pesticides from fruit juice samples.

Effect of Heating Rate on Pyrolysis Behavior and Kinetic Characteristics of Siderite

The pyrolysis characteristics of siderite at different heating rates under the neutral atmosphere were investigated using various tools, including comprehensive thermal analyzer, tube furnace, X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectrometry (EDS) and vibrating specimen magnetometer (VSM) measurements. The reaction of siderite pyrolysis followed the one-step reaction under the neutral atmosphere: FeCO3 → Fe3O4 + CO2 + CO. As the increasing of heating rate, the start and end pyrolysis temperatures and temperate where maximum weight loss rate occurred increased, while the total mass loss were essentially the same. Increasing heating rate within a certain range was in favor of shortening the time of each reaction stage, and the maximum conversion rate could be reached with a short time. The most probable mechanism function for non-isothermal pyrolysis of siderite at different heating rates was A1/2 reaction model (nucleation and growth reaction). With increasing heating rate, the corresponding activation energies and the pre-exponential factors increased, from 446.13 to 505.19 kJ∙mol−1, and from 6.67 × 10−18 to 2.40 × 10−21, respectively. All siderite was transformed into magnetite with a porous structure after pyrolysis, and some micro-cracks were formed into the particles. The magnetization intensity and specific susceptibility increased significantly, which created favorable conditions for the further effective concentration of iron ore.

Preparation of carbon-coated Fe3O4 porous particles and their adsorption properties of iron (III) ion

Abstract Carbon-coated Fe3O4 porous particles were synthesized with phenolic resin as a carbon source using impregnating pyrolysis. The magnetic property, phase structure, pore structure, and surface morphology of the pyrolysis products were characterized by vibrating specimen magnetometer, X-ray diffraction, Brunauer–Emmett–Teller (BET), and scanning electron microscopy, respectively. Also, the adsorption properties of iron (III) ions on Fe3O4@C as well as pure carbon, including adsorption isothermal, kinetics, and pH effect, were investigated. The results showed that the size of synthesized Fe3O4@C particles ranged from 10 to 50 μm with micro-meso pores sized below 5 nm. The main phases of Fe3O4@C were magnetite, graphite and amorphous carbon. The adsorption kinetics of iron (III) ions on Fe3O4@C could be expressed by the pseudo-second-order kinetic model and the adsorption isotherm was fitted by a Freundlich model. Nano-Fe3O4 had synergism to porous carbon on the absorption of iron (III) ions.

Bifunctional ferromagnetic Eu-Gd-Bi-codoped hybrid organo-silica red emitting phosphors synthesized by a modified Pechini sol-gel method

Red phosphor, composed of Eu-Gd-Bi-codoped hybrid organo-silica glass, has been synthesized via a modified Pechini sol-gel process. The synthesized hybrid glass was analyzed with powder X-ray diffraction (XRD), differential thermal analysis coupled with thermogravimetry (DTA-TG) and Fourier transform infrared (FTIR) spectroscopy. XRD and DTA-TG confirmed its amorphous structure up to 1000 °C. Magnetic behavior of the produced phosphor was investigated using vibrating specimen magnetometer (VSM) and the obtained results revealed its unsaturated ferromagnetic behavior. Photoluminescence (PL) properties of the obtained phosphor have been investigated under near-UV excitation at 395 nm. The influence of calcination temperature on the PL intensity and its decay behavior as well as on the ferromagnetic characteristics has been studied to determine the optimal reaction temperature of the phosphor. The PL emission spectra show the characteristic emission bands of Eu3+ ions in the wavelength range from 580 to 700 nm. These emission spectra have been dominated by the electric dipole 5D0→7F2 transition of the Eu3+ peaked at 610–620 nm producing the red light emission of the phosphors. It was found that the phosphor performance, expressed by its PL intensity and life time, could be significantly improved by increasing of the heat treatment temperature up to 900 °C. Also, calcination at 900 °C for 6 h greatly increased both of the magnetization and retentivity, while decreased the coercivity value. The organic phenomenon of metal citrate-ethylene glycol chelation and its degradation by calcination were well followed by FTIR spectroscopy. The obtained results are promising and could afford a basis for designing of efficient red phosphors for displays, lighting and bifunctional biosensors for biomedical applications.

Deposition of luminescence YBO3:Eu3+,Gd3+ on ferromagnetic Fe@C nanoparticles

The magnetic and photoluminescent Fe@C@YBO3:Eu3+,Gd3+ nanocomposite with core–shell structure has been synthesized by a hydrothermal process. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to determine the structure and morphology of the nanocomposites. Vibrating specimen magnetometer (VSM) and photoluminescence spectroscopy (PL) were used to analyze magnetic and luminescence properties of the nanocomposite. In the nanocomposites, the amorphous carbon layer acts as coupling agent, and it can conduct the excited electrons between magnetic part and luminescent part. The luminescence properties of Fe@C@YBO3:Eu3+,Gd3+ nanocomposite are discussed under magnetic field. Under the external magnetic field for 2 h, the nanocomposite displayed the biggest luminescent intensity.

Novel magnetically separable AgCl/iron oxide composites with enhanced photocatalytic activity driven by visible light

In this work, AgCl/iron oxide composites were synthesized by a simple chemical precipitation method and calcining process. The composition of the material and magnetic and optical properties of the composites were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating specimen magnetometer (VSM) techniques, which confirms the high crystalline and magnetic behavior of the composites. UV-vis diffuse reflectance spectral (DRS) studies showed that the AgCl/iron oxide composites were of much higher absorption in longer wavelength region compared to bare iron oxide. The AgCl/iron oxide composites showed better performance in the photodegradation of organic dyes Rhodamin B (RhB) under the fluorescent lamp irradiation, which is remarkably superior to the N-TiO2. The degradation of microcystin-LR (MC-LR) and phenol was also found to be good owing to its effective electron-hole separation at AgCl/iron oxide interface. The separation of AgCl/iron oxide composites from the treated water was achieved by an external magnetic field as γ-Fe2O3 exhibits enough magnetic power to facilitate the separation.

The Adsorption of Bovine Serum Albumin onto Magnetic Chitosan Microspheres

Magnetic chitosan nanoparticles(Fe2O3-CS) were prepared in microemulsion by crosslinking method. The transmission electron microscopy (TEM),Fourier transform infrared spectrophotometry (FT-IR) and vibrating specimen magnetometer (VSM) were used to characterize the nanoparticles. The mean diameter of the particles was about 40 nm with good dispersibility and magnetic response. The bovine serum albumin (BSA) was connected onto the surface of the magnetic nanoparticles with carbodiimide hydrochloride (EDC) as the activator. The products were then characterized by atomic force microscope (AFM) and ultraviolet spectrometer (UV). The results showed that the nanoparticles had a good adsorbability of the BSA. The adsorption isotherm of the BSA on the magnetic chitosan microspheres basicly obeyed the Langmuir model,with a maximum adsorption capacity of 250 mg·g-1 and an adsorption equilibrium constant of 0.007 L·mg-1. The stability of the particles-BSA complex in phosphate buffer solution (PBS) with different pH was also studied. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that BSA was desorbed from magnetic particles under alkaline condition.

Structure and characteristics of large Fe–O/AlOx/Fe–O tunnel junctions

The Fe–O/AlOx/Fe–O tunnel junctions with an area of 1 cm2 were fabricated by reactive magnetron sputtering. The structure and properties of the junctions were studied by scanning electron microscopy, scanning Auger microprobe, x-ray diffraction (XRD), cross-sectional transmission electron diffraction (XTED), atomic force microscopy, vibrating specimen magnetometer, and I–V characteristic. The as-deposited and annealed Fe–O layers have disparate crystalline grain structure. Only bcc–Fe structure is observed in the Fe–O layers through XRD and XTED measurement. Most of the oxygen atoms exist as impurity in the films, and large compressive stress (σ≈−7.9×109 Pa) is induced in the Fe–O layers. The insulating AlOx layer formed by radio-frequency sputtering directly from the alumina target is dense and shows good insulating property.

Magneto-optical properties of four-element semimagnetic semiconductor CdMnCoTe films on quartz glass

Magneto-optical properties in the visible wavelength region have been studied with four-element semimagnetic semiconductor CdMnCoTe films deposited on quartz glass substrates by using MBE equipment. A Faraday rotation value of 0.3 deg/cmG in the (Cd 0.647Mn 0.34Co 0.013) 0.5Te 0.5 film has been observed at 570 nm. This is approximately two times larger than the Faraday rotation for (Cd 0.61Mn 0.39) 0.5Te 0.5 film on quartz glass. By using a vibrating-specimen magnetometer, it has been confirmed that the prepared (Cd 0.647Mn 0.34Co 0.013) 0.5Te 0.5 film is paramagnetic.

Anomalous paramagnetism in pressure quenched CdS

Very large “paramagnetic” on positive magnetization has been observed in “pressure quenched” samples of CdS. Pressure quenching is a formative process involving pressure release rates ≈10 6 bar s −1. The pressure quenched samples were prepared by pressure quenching at room temperature from above 30 kbar, i.e. from above the insulation-to-metal like transition. magnetization as a function of magnetic field was measured at 293 and 77 K using a vibrating specimen magnetometer. A linear M versus H behavior is observed in fields above a few hundred gauss, with values of χ = ( αM/ αH) ≈ 10 -4 cgs units. In some specimens saturation occurs, while in others the magnetization passes through a maximum. The maximum value of the magnetic moment M observed is of the order of tens of gauss.

Magnetic studies of oxidation processes and mechanisms

Measurements of saturation magnetization, using a vibrating specimen magnetometer, have been used to follow the course of the oxidation of iron, cobalt, and nickel. A linear decrease of the magnetization w.r.t. the volume of oxygen absorbed indicates the regular formation of NiO, and for cobalt the initial formation of CoO is followed by that of Co3O4. The results for iron are more complex. Alternate dosing with oxygen and hydrogen gives information on the mechanisms of oxidation and regeneration.