静电纺制备Fe3O4/PEK-C纳米复合膜及其吸波性能

静电纺丝技术是一种新颖、高效且简单的制备连续纳米纤维的方法,纳米复合纤维膜的优异特点赋予了纳米吸波剂新的吸波通道。本文采用静电纺丝工艺制备Fe3O4/PEK-C纳米复合纤维膜,利用SEM和TGA表征纳米复合纤维膜的微观形貌和热稳定性,用矢量网络分析仪测试样品在8.2~12.4 GHz的电磁参数与吸波性能。结果表明,Fe3O4/PEK-C纳米复合纤维膜呈现出超细纤维彼此交织构成的立体网络结构,其热稳定性、复介电常数和复磁导率均随着Fe3O4含量的增加而增加,介电损耗和磁损耗得到加强。当纳米复合纤维膜的厚度为1.8 mm时,其反射损耗在整个测试波段均处于-5 dB以下,-10 dB以下有效吸收频宽为2 GHz,频率在8.6 GHz处吸收强度达到最大值-15.4 dB。预期可作为隐身复合材料的吸波功能层。     

Preparation and characterization of magnetic nanofibrous composite membranes with catalytic activity

Magnetic nanofibrous composite membranes were electrospun from the mixtures of poly(acrylonitrile-co-acrylic acid) (PANCAA) and Fe₃O₄ nanoparticles. Field emission scanning electron microscopy (FESEM) and thermal gravimetric analysis (TGA) were used to characterize the composite membranes. TGA results indicate that the addition of Fe₃O₄ nanoparticles catalyzes the carbonization of PANCAA as well as dramatically increases the carbonization temperature. The intrinsic peroxidase-like activity of Fe₃O₄ nanoparticles was measured by the color reaction of phenol/4-amino antipyrine in the presence of H₂O₂. Under optimal conditions, the electrospun composite membranes show high peroxidase-like catalytic activity and reusability. Taking into account of the potentiality for separation, these as-prepared magnetic nanofibrous composite membranes will be applied in phenolic wastewater treatment.     

Crystallinity, magnetic and electrochemical studies of PVDF/Co3O4 polymer electrolyte

Organic-inorganic nanocomposites are gaining importance in the recent times as polymer electrolyte membranes. In the present work, composites were prepared by combining nano sized Co₃O₄ and poly(vinyledene fluoride) (PVDF), using spin coating technique. The surface of the PVDF/Co₃O₄ system characterized through field emission scanning electron microscopy (FESEM) revealed a porous structure of the films. The nanoparticles tend to aggregate on the surface and inside the pores, leading to a decrease in the porosity with an increase in Co₃O₄ content. Co₃O₄ nanoparticles prohibit crystallization of the polymer. Differential scanning calorimetry (DSC) studies revealed a decrease in crystallinity of PVDF/Co₃O₄ system with an increase in the oxide content. Magnetic property studies of the composite films revealed that with an increase in Co₃O₄ content, the saturation magnetization values of the nanocomposites increased linearly, showing successful incorporation of the nanoparticles in the polymer matrix. Further, ionic conductivity of the composite films was evaluated from electrochemical impedance spectroscopy. Addition of Co₃O₄ nanoparticles enhanced the conductivity of PVDF/Co₃O₄ system.     

Characteristic analysis of Fe3O4 nanoparticles modified by oleic acid and undecylenic acid

Carbonization of magnetic polymer microspheres is one of the methods for the preparation of magnetic carbon materials. Fe₃O₄ magnetic particle characteristics considerably influence the magnetic content and size distribution of magnetic polymer microspheres. The characteristics of Fe₃O₄ nanoparticles modified by oleic acid (OA) and undecylenic acid (UA) were analyzed by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, dynamic laser light scattering, thermogravimetry/differential thermogravimetry, vibrating sample magnetometer, and water contact angle. Fe₃O₄ nanoparticles modified by OA and UA are nearly spherical and exhibit superparamagnetism. Fe₃O₄ particle size and saturation magnetization are slightly influenced by the OA and UA composition. OA and UA both are chemically adsorbed onto Fe₃O₄ as bidentate chelates. OA shows easier adsorption onto Fe₃O₄ than UA. OA groups have an expanded arrangement on OA@Fe₃O₄, whereas UA groups have a condensed arrangement on UA@Fe₃O₄. Particle lipophilicity decreases and particle clustering increases with decreasing OA content and increasing UA content on OA-UA@Fe₃O₄ nanoparticles.     

Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

The assembly of superparamagnetic Fe₃O₄ nanoparticles on submicroscopic SiO₂ spheres have been prepared by an in situ reaction using different molar ratios of Fe³⁺/Fe²⁺ (50–200%). It has been observed that morphology of the assembly and properties of these hybrid materials composed of SiO₂ as core and Fe₃O₄ nanoparticles as shell depend on the molar ratio of Fe³⁺/Fe²⁺.     

Polyaniline/Fe3O4 nanocomposites synthesized under the direction of cationic surfactant

Polyaniline(PANi)/Fe₃O₄ nanocomposites have been prepared via in situ chemical oxidative polymerization directed with cationic surfactant cetyltrimethylammonium bromide (CTAB). The studies show that PANi can coat Fe₃O₄ nanoparticles. CTAB can produce insoluble substance with initiator of polyreaction, and plays a very important role for the coating of Fe₃O₄ nanoparticles by PANi. Many Fe₃O₄ nanoparticles are bald without being coated by PANi when CTAB is replaced by anionic surfactant, so anionic surfactant can not play the role of CTAB.     

Application of multi-functional chestnut shell in one-step preparing Fe3O4@C magnetic nanocomposite with high adsorption performance

Chestnut shell (CS) acts as a multi-functional material in the one-step preparation of Fe₃O₄@C nanocomposite via hydrothermal method by using Fe(NO₃)₃ as Fe source without adding any other additives. The characterized results show that under required hydrothermal conditions, a proper amount of CS can reduce a certain amount of adsorbed/enriched Fe³⁺ to Fe²⁺ to ensure the 2:1 molar ration of Fe³⁺ to Fe²⁺ and the in-situ formation of goal phase Fe₃O₄ on the surface of the CS. Meanwhile, CS is carbonized to C material similar to graphene oxide. In the preparation process of the composite of Fe₃O₄@C, CS plays multiple roles, such as promoter, reductive agent, C-source, and template, to endow a certain morphology of the nanocomposite Fe₃O₄@C. The composite material shows good magnetic separability and adsorption property for methylene blue (MB) solution. Furthermore, the adsorptive kinetic behavior of the Fe₃O₄@C is investigated. The method is simple, fast, low cost and green and really realizes the full use of wasteful resource CS.     

Au/Fe3O4磁性纳米粒子的合成及表征

报道了一种合成具有巯基官能团修饰的Au/Fe_3O_4磁性纳米粒子的新方法。采用共沉淀法制备Fe_3O_4磁性纳米颗粒,并在此基础上用聚(烯丙胺)溶液还原HAuCl4,制得Au/Fe_3O_4磁性核壳纳米颗粒,再用3-巯基-1-丙磺酸钠修饰Au/Fe_3O_4磁性纳米粒子,最后得到具有巯基官能团稳定的Au/Fe_3O_4磁性纳米粒子。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)、X射线光电子能谱(XPS)、振动样品磁强计(VSM)分别对产物的微观结构及磁性特征进行表征。     

Supercritical fluid mediated synthesis of poly(2-hydroxyethyl methacrylate)/Fe3O4 hybrid nanocomposite

Poly(2-hydroxyethyl methacrylate) (PHEMA) and magnetic nanoparticle (Fe₃O₄) hybrid nanocomposite was synthesized by dispersion polymerization in supercritical carbon dioxide (scCO₂) using a copolymeric stabilizer, poly[(2-dimethylamino)ethyl methacrylate-co-1H,1H-perfluorooctyl methacrylate] (PDMAEMA-co-PFOMA). Fe₃O₄ nanoparticles were first surface-modified with a silane coupling agent methacryloxypropyltrimethoxysilane (MPTMS), which provides a reactive CC bond and can copolymerize with 2-hydroxyethyl methacrylate (HEMA). After immobilization of the silane coupling agent, polymer chains were successfully grafted onto the surface of Fe₃O₄, resulting in the formation of core-shell nanostructure. FE-TEM pictures showed that the nanoparticles were well dispersed in the polymer matrix. The incorporation of Fe₃O₄ in the nanocomposite was confirmed by FT-IR, XRD and XPS. Thermal stability and magnetic property increase with the increasing amount of Fe₃O₄ nanoparticles in the composite. This new environmentally benign green synthetic route may offer advantages of easy separation and solvent removal.     

A true nanocomposite: Single crystalline Au nanoparticles on single crystalline Fe3O4 nanoparticles

An Au/Fe₃O₄ nanocomposite catalyst was fabricated through a simple deposition-precipitation method. The Au/Fe₃O₄ nanocomposite is a true nanocomposite that has single crystalline Au nanoparticles supported on single crystalline Fe₃O₄ nanoparticles. Lattice fringes from both Au and Fe₃O₄ single nanoparticles were simultaneously observed by transmission electron microscope (TEM). This nanocomposite catalyst showed much high activity in low temperature CO oxidation reaction. The Au/Fe₃O₄ nanocomposite catalyst reaches 100% CO conversion at 40 °C. In comparison, Au/commercial Fe₃O₄ catalyst needs 375 °C to convert CO. This Au/Fe₃O₄ nanocomposite is an ideal sample to study synergetic effect between the catalyst and the support at nanoscale.     

Fabrication of nanocomposite membranes from nanofibers and nanoparticles for protection against chemical warfare stimulants

Nanoparticles of MgO were synthesized by Aero gel method. These MgO nanoparticles were then mixed with various polymer solutions (poly(vinyl chloride) (PVC), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF copolymer), polysulfone (PSU)) and then subjected to electrospinning to produce nanocomposite membranes. The hydrolysis of paraoxon, a never agent stimulant, in presence of these membranes was studied using UV. The order of the reactivity of the membranes are found to be PVC-MgO < PVDF < PSU < PVDF-MgO < PSU-MgO. After selecting PSU as the supportive candidate, relative rates of hydrolysis were compared for nanoparticles or charcoal with nanocomposite membranes. The order is as follows; Charcoal (1) < PSU-Al₂O₃ (1.5) < PSU-MgO (2.1) < Al₂O₃ nanoparticles (2.8) < MgO nanoparticles (5.4). The amount of hydrolysis of PSU-MgO composite membrane was 60% less when compared to MgO nanoparticles as such usage. The loading percentage of MgO into nanofiber is 35 %. The fabricated composite membrane (containing 5% MgO) was tested for chemical warfare agent stimulant, paraoxon, and found to be about 2 times more reactive than currently used charcoal.     

Enhanced photocatalytic activity of Fe3O4-WO3-APTES for azo dye removal from aqueous solutions in the presence of visible irradiation

Development of highly active photocatalysts for treatment of dye-laden wastewaters is vital. The photocatalytic removal of azo dye Reactive Black 5 was investigated by Fe₃O₄-WO₃-3-aminopropyltriethoxysilane (APTES) nanoparticles in the presence of visible light. The Fe₃O₄-WO₃-APTES nanoparticles were synthesized via a facile coprecipitation method. The photocatalyst was characterized by XRD, FT-IR, SEM, EDX, VSM, UV–Vis, and pH_PZC techniques. The effects of some operational parameters such as solution pH, nanophotocatalyst dosage, initial RB5 concentration, H₂O₂ concentration, different purging gases, and type of organic compounds on the removal efficiency were studied by the Fe₃O₄-WO₃-APTES nanoparticles as a photocatalyst. Maximum phtocatalytic activity was obtained at pH 3. The photocatalytic removal of RB5 increased with increasing H₂O₂ concentration up to 5?mM. The removal efficiency declined in the presence of different purging gases and all types of organic compounds. First-order rate constant (k_obs) decreased from 0.027 to 0.0022?min^?1 and electrical energy per order (E_Eo) increased from 21.33 to 261.82 (kWh/m³) with increasing RB5 concentration from 10 to 100?mg/L, respectively. The efficiency of LED/Fe₃O₄-WO₃-APTES process for RB5 removal was approximately 89.9%, which was more effective than the LED/Fe₃O₄-WO₃ process (60.72%). Also, photocatalytic activity decreased after five successive cycles.     

Preparation and characterization of bio-functionalized iron oxide nanoparticles for biomedical application

Amine modified iron oxide (Fe₃O₄) nanoparticles were synthesized by thermal decomposition method and were further used to bio-functionalize by grafting of N-hydroxysuccinimide (NHS) ester of folate and ethylenediaminetetraacetate (EDTA). Fe₃O₄ nanoparticles of ~ 22 nm were confirmed from X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. FT-IR studies indicated two bands at 1515 cm^− 1and 1646 cm^− 1, which can be attributed to carboxylic group and the amide linkage respectively, revealing the conjugation of folate with Fe₃O₄. The conjugation of the chelating agent showed strong C=O stretch and Fe-O vibrations at 1647 and 588 cm^− 1 respectively. The value of saturation magnetization for Fe₃O₄ nanoparticles was found to be 88 emu/g, which further reduced to 18 and 32% upon functionalization with EDTA and NHS ester folate, respectively. These amine modified Fe₃O₄ nanoparticles can also be functionalized with other bifunctional chelators, such as amino acids based diethylene triamine pentaacetic acid (DTPA), and thus find potential applications in radio-labeling, biosensors and cancer detection, etc.     

Dispersion of Fe3O4 suspensions using sodium dodecylbenzene sulphonate as dispersant

Dispersion of Fe₃O₄-water suspension is enhanced with appropriate decision of solution pH and the amount of dispersant, sodium dodecylbenzene sulphonate. Active adsorption of dispersant onto Fe₃O₄ takes place only at pH levels below the isoelectric point. The median diameter is reduced with an increase in the adsorption amount of dispersant at first, and then it increases remarkably with higher adsorption. Change in Fe₃O₄ particle size according to the adsorption amount of dispersant is explained on the basis of contact angle measurements which relate to hydrophobicity or hydrophilicity of Fe₃O₄ particles.     

Synthesis and Magnetic Properties of Fe3O4 Nanoparticles

Magnetic Fe₃O₄ nanoparticles with size below 10 nm have been prepared by the aqueous phase coprecipitation method. The Fe₃O₄ nanoparticles show typical superparamagnetism. Comparison is made between the dispersed sample and the powder sample, and the results are discussed.     

An easy fabrication of monodisperse oleic acid-coated Fe3O4 nanoparticles

An easy route is described for the synthesis of monodisperse oleic acid-coated Fe₃O₄ nanoparticles with uniform size and shape via a thermal decomposition of Fe(acac)₃ in the presence of oleic acid (OA). The prepared Fe₃O₄ samples are characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectrometry, and vibrating sample magnetometer. The results show that the resulting OA-coated Fe₃O₄ nanoparticles have an average diameter of about 24 nm and an OA layer, around 3 nm in thickness. The magnetic saturation value of the prepared OA-coated Fe₃O₄ nanoparticles is determined to be 78.68 emu/g, indicating a well-established superparamagnetic property.     

Dechlorination of 3,3′,4,4′-tetrachlorobiphenyl in aqueous solution by hybrid Fe0/Fe3O4 nanoparticle system

The kinetics and efficiency of 3,3′,4,4′-tetrachlorobiphenyl (PCB77) degradation in aqueous solution by hybrid Fe⁰/Fe₃O₄ nanoparticle system were investigated. The results showed that nano-sized Fe⁰ and Fe₃O₄ could efficiently degrade PCB77, and the residual rate of PCB77 by nano-sized Fe⁰ and Fe₃O₄ were 67.70% ± 0.42% and 82.26% ± 2.96%, respectively after 240 min of reaction (for 5 mg·L^?1 PCB77 and 5 g·L^?1 nanoparticles). The combined use of nanoscale Fe⁰ and Fe₃O₄ could enhance the degradation of PCB77. The dose ratios of nano-sized Fe⁰ and Fe₃O₄ significantly affected the PCB77 degradation rate. At Fe⁰/Fe₃O₄ ratios of 1:0.1, 1:0.2 and 1:1, the residual rates of PCB77 were 6.46%, 10.23% and 38.20%, respectively. The PCB77 degradation efficiency was also greatly affected by solution pH, and was maximised at pH 6.8. The degradation of PCB77 by Fe⁰/Fe₃O₄ nanoparticle was a dechlorination process, and the chlorion concentration increased with the decreasing residual rate of PCB77 accordingly. Fe₃O₄ provided Fe²⁺ and Fe³⁺ for enhancing the PCB77 degradation by nanoscale Fe⁰, suggesting a synergy between Fe⁰ and Fe₃O₄.     

Evaluation of magnetic nanoparticles performance as photocatalyst for the catalytic treatment of direct red 28 dye in synthetic and real water effluents

Integrated water resources management practice is gaining popularity as an alternative water source due to the limited supply of freshwater. The present study was carried out on the photocatalytic degradation of Direct red 28 (DR-28) dye using magnetic nanoparticles (MNPs; Fe₃O₄) as a photocatalyst. The study was conducted on the photocatalytic degradation of DR-28 dye in synthetic dye effluent water, to understand the effects of different photoreaction parameters on the degradation kinetics. The influence of different parameters such as time, amount of photocatalyst, concentration of H₂O₂ and pH was investigated. At the optimum dosage of MNPs (0.6?g/L) with 4?mmol/L of H₂O₂, significant photocatalytic degradation of DR-28 dye (93.2%) was observed. The kinetic study revealed that the photocatalytic degradation followed pseudo-first-order kinetics. The degradation performance of Fe₃O₄ nanoparticles as a photocatalyst for DR-28 dye was compared with titanium dioxide (TiO₂) and it was found that the performance of Fe₃O₄ as a photocatalyst is superior to TiO₂ photocatalyst. The real dye effluent was also degraded at optimum conditions and promising results were achieved.     

Structural and morphological properties of Fe2O3/TiO2 nanocrystals in silica matrix

We report on structural, morphological and ordering properties of Fe₂O₃/TiO₂ nanoparticles embedded in SiO₂-based multilayers. We investigated the structure of these systems by X-ray diffraction and grazing incidence small angle X-ray scattering after post-growth annealing. We found that the presence of TiO₂ promotes the growth and crystallization of the nanocrystals of Fe₂O₃. In multilayers containing both Fe₂O₃ and TiO₂, crystalline nanoparticles create partially ordered three-dimensional arrays.     

Preparation and characterisation of PPy/NanoGs/Fe3O4 conductive and magnetic nanocomposites

Nanocomposites composed of polypyrrole (PPy), graphite nanosheets (NanoGs), magnetite (Fe₃O₄) nanoparticles, have been successfully synthesised with a two-step process. First, we prepared NanoGs/Fe₃O₄ powder via wet chemical co-precipitation method. Next, pyrrole was polymerised in the suspension of NanoGs/Fe₃O₄ and then PPy/NanoGs/Fe₃O₄ nanocomposites were produced. The products were characterised by Fourier-transform infrared spectroscopy, Transmission electron microscopy, Thermogravimetric, conductivity and magnetisation analysis. The result showed that the conductivity of the PPy/NanoGs/Fe₃O₄ composites, compared with pure PPy, increased dramatically. And the saturation magnetisation of nanocomposites increased with the increase of the volume fraction of the Fe₃O₄ particles. In addition, according to the thermal gravimetric analysis, compared with PPy, nanocomposites exhibited enhanced thermal stability due to the introduction of NanoGs/Fe₃O_4. The PPy/NanoGs/Fe₃O₄ composites show potential applications in electric–magnetic shield materials.