Synthesis and properties of na nomagnetite for the preparation of biocomposites

Magnetite powder (FeO·Fe2O3 or Fe3O4) is obtained by the chemical precipitation method, using FeCl3·6H2O and FeCl2·4H2O as a starting materials in the presence of hydrazine N2H4 at a temperature of 80 °C. X-ray diffraction analysis, infrared spectroscopy, and scanning electron microscopy are used for the study of the phase composition and morphology of the synthesized powder. Its specific surface area and magnetic properties such as, in particular, the specific saturation magnetization, coercive force and residual induction are investigated. It is established that the composition of the synthesized powder is represented by magnetite as the main phase with a small admixture of hematite. It is shown that the particles of the obtained magnetite have sizes of 33-84 nm and tend to the agglomeration. The prepared powder has superparamagnetic properties (specific magnetization — 35 A · m2/kg, coercive force — 0.24 kA/m, residual induction — 0.009 T) and is promising for the biocomposite creation.

Synthesis and Application of Nanomagnetic Immobilized Phospholipase C

The nanomagnetic carrier (Fe3O4@SiO2@p(GMA)) was prepared by atom transfer radical polymerization, and then, the free phospholipase C (PLC) was immobilized on it proved by the results of FT-IR analysis. The enzyme loading was 135.64 mg/g, the enzyme activity was 8560.7 U/g, the average particle size was 99.86 ± 0.80 nm, and the specific saturation magnetization was 16.00 ± 0.20 emu/g. PLC-Fe3O4@SiO2@p(GMA) showed the highest activities at the pH of 7.5, and tolerance temperature raised to 65°C in soybean lecithin emulsion. Enzymatic degumming with PLC-Fe3O4@SiO2@p(GMA) under the conditions of the enzyme dosage of 110 mg/kg, reaction temperature of 65°C, pH of 7.5, and reaction time of 2.5 h resulted in residual phosphorus of 64.7 mg/kg, 1,2-diacylglycerol (1,2-DAG) contents of 1.07%, and oil yield of 98.1%. Moreover, PLC-Fe3O4@SiO2@p(GMA) still possessed more than 80% of its initial activity after 5 cycles.

Inductive Heating Property of Superparamagnetic Graphene Nanosheets-Fe3O4 Nanoparticles Hybrid in an AC Magnetic Field for Localized Hyperthermia

The superparamagnetic graphene nanosheets–Fe3O4 nanoparticles (GNs–Fe3O4) hybrid has been successfully prepared via an easy and scalable chemical precipitation method. The inductive heat property of GNs–Fe3O4 hybrid in an alternating current (AC) magnetic field was investigated. The potential of GNs–Fe3O4 hybrid was evaluated for localized hyperthermia treatment of cancers. The GNs–Fe3O4 hybrid exhibits a superparamagnetic behavior, its specific saturation magnetization, Ms is 66.963 emu g-1. After exposed in the AC magnetic field for 1140 sec, the temperature of physiological saline suspension containing GNS–Fe3O4 hybrid were 81 oC. The GNs–Fe3O4 hybrid will be useful as good thermoseeds for localized hyperthermia treatment of cancers.

Structural Analysis and Magnetic Properties of FeCo Alloys Obtained by Mechanical Alloying

A systematic study on the structural and magnetic properties of Fe100-xCox alloys (10<x<90, Δx=10 in wt. percent) obtained by mechanical alloying is presented. Elemental powders of Fe and Co mixed in an adequate weight ratio were milled at room temperature in a shaker mixer mill using vials and balls of hardened steel as milling media with a ball : powder weight ratio of 12 : 1. The mixtures were milled for 3 h. The results show that, after milling, for almost all the composition (up to x=60), solid solutions based on bcc structures were obtained. For Co-rich alloys (x≥70), different phases were found, revealing the formation of a metastable intermetallic phase (FeCo, wairauite) together with fcc-Co and hcp-Co phases. The specific saturation magnetization increases by increasing Co content, reaching a maximum value of 225 emu/g for hcp-Fe70Co30, and then it shows a diminution up to 154 emu/g for bcc-Fe30Co70. All studied alloys (Fe100-xCox) present low coercivity, in the range from 0 to 65 Oe, which is lower than reported. The coercivity increases with the increment in Co, reaching a maximum of 64.1 Oe for Fe40Co60. After that, the coercivity falls up to 24.5 Oe for Co-rich alloys, which make them a very low coercive material.

Preparation and Characterization of Amorphous Fe-B-P Ultrafine Particles

Soft magnetic Fe-B-P ultrafine particles with amorphous structure were prepared by aqueous reduction method with variable pH values. The microstructure, compositions and the soft magnetic properties of Fe-B-P submicron particles were investigated by using field emission scanning electron microscope (FE-SEM), X-Ray Diffraction (XRD), mössbauer spectrum (MS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), vibrating sample magnetometer (VSM). The results showed that a series of Fe-B-P amorphous particles with the average particle size of 0.26~0.42 μm were obtained depending on the pH value of solution. As pH value increased, the contents of B and P increased, and the specific saturation magnetization of the Fe-B-P submicron particles decreased. Some electrons, transferred from p-shell of B atoms and P atoms to 3d-shell of Fe atom, resulted in the decrease of the number of unpaired electron, which in turn led to reduction of the average hyperfine magnetic field of the Fe-B-P particles and the decrease of the magnetic torque of Fe atoms. The relation between hyperfine magnetic field (Hhf) and the specific saturation magnetization was in accord with the Marshall’s equation. At the same time, the enhancement of the shielding effect on 4s electron orbital, i.e., the density of 4s electron reduced, leading to the increase of Isomer Shift.

Investigation of Ultradispersed Powders FexOy Obtained in the Electric Discharge Plasma

The paper shows the iron oxide powder production in the hypersonic jet of electro discharge plasma generated by a coaxial magnetoplasma accelerator with steel electrodes. The influence of gaseous atmosphere parameters has been investigated by carrying out experiments in normal atmospheric conditions and with the introduction of additional oxidant into the plasma discharge. Studies of the structure of synthesized powders and their magnetic properties have been carried out. It has been found that by introducing of additional oxidant it is possible to regulate the phase composition in the direction of increasing the yield of magnetite phase. Specific saturation magnetization decreases with decreasing of the magnetic nanoparticle sizes.

Transformations of Titanium(IV) Butoxide on Magnetite Surface in the Presence of Pluronic P-123

The technique of producing magnetically operated nanocomposites Fe3O4/TiO2 with high specific surface area (to 320 m2/g) was developed. A copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic-123) was used as a template. The processes of converting n-butylortotytanatu (BOT) in TiO2 on the surface of magnetite in the presence of PL when heated, and the structure, magnetic and adsorption properties of nanocomposites Fe3O4/TiO2 were investigated. It is shown that the maximum temperature of the heat treatment of nanocomposites is 500 ºC. It was established that the specific saturation magnetization (σs) of nanocomposites Fe3O4/TiO2 by varying the content of PL ranges from 3.75 to 3.96 μT·m3/kg, while coercive force Hc – 1.47-1.61 kA/m. Adsorption complexes such as Fe3O4/TiO2/DNA were obtained.

Effect of La-Zn Doping on Magnetic Properties of SrFe12O19

La-Zn doped strontium ferrite, Sr1-xZnxFe12(1-x) La12xO19, was prepared by chemical co-precipitation method. The samples were characterized by XRD, SEM and VSM and the results reveal that La-Zn ions are dispersed completely into the strontium ferrite lattice at 900°C. The VSM analysis shows that Hcj increases to 240.1 KA/m, almost double the value of the original sample. And the specific saturation magnetization increases from 48.78 A • m2/Kg to 63.11A• m2/Kg.

Calibration of a Measuring Device to Determine Specific Saturation Magnetization by A Special Coil

Specific saturation magnetization σS is an important parameter of ferromagnetic materials. It is in principle independent of the structure and shape of the sample. There are two ways to calibrate devices for determining σS: the standard method, using a calibrated magnetic moment standard, or an alternative method, using a special moment coil. This paper presents a calibration method used at Czech Metrology Institute for calibration of Koerzimat 1.096 using a special moment coil. Special attention is given to a description of the special moment coils used for Koerzimat 1.096 calibration, and to analysis of sources of uncertainty. Calibration expanded uncertainty of 0.4 up to 0.6 % can be achieved using this method.

Preparation and Superparamagnetic Properties of Graphene/Fe3O4 Nanocomposite

The superparamagnetic graphene/Fe3O4nanocomposite has been successfully prepared via an easy and scalable chemical precipitation method. High quality graphene sheets were prepared from natural flake graphite by oxidation, rapid expansion and ultrasonic treatment. The structure of graphene and graphene/Fe3O4nanocomposite was investigated by transmission electron microscopy, Xray diffraction and Fourier transform infrared spectroscopy. The graphene sheets possess a curled morphology consisting of a thin wrinkled paper-like structure. The graphene/Fe3O4nanocomposite exhibits a superparamagnetic behavior, its specific saturation magnetization,Msis 38.92 emu g-1.