Synthesis and characterization of novel waterborne polyurethane nanocomposites with magnetic and electrical properties

The novel nanocomposites derived from waterborne polyurethane and nano-Fe₃O₄ (WPU/Fe₃O₄) have been successfully synthesized by in situ polymerization progress. The nano-Fe₃O₄ particles prepared by co-precipitation method were modified by using oleic acid (OA) to improve their compatibility with monomers. The chemical structures, morphology, thermal behavior, mechanical properties, magnetic properties and electrical properties of the WPU/Fe₃O₄ nanocomposites were investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscope (AFM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMA), vibrating sample magnetometer (VSM) and high resistance meter respectively. The results indicated that the Fe₃O₄ nanoparticles modified by oleic acid could be homogeneously dispersed in the WPU and the introduction of ones was obviously improving the thermal properties, magnetic properties and electrical properties of WPU/Fe₃O₄ nanocomposites. The resulting WPU/Fe₃O₄ nanocomposites would be having the potential applications in microwave absorption.     

Aqueous ferrofluids as templates for magnetic hydroxyapatite nanocomposites

Poly (vinyl) alcohol stabilized aqueous ferrofluids (PVA-ff) were used as nanotemplates for the crystallization of calcium hydroxyapatite (HAp). Four sets of PVA-ff-HAp nanocomposites were synthesized using 20, 40, 60 and 80 ml of PVA-ff for the same initial constituents of HAp. Various physico-chemical analyses suggest that the HAp lattice structure accommodates PVA-ff to a certain extent, beyond which the magnetic intra-molecular interactions predominate and PVA-ff starts to be pushed out of the HAp matrix. The in situ incorporation of PVA-ff during HAp synthesis results in a novel magnetic biomaterial with potential applications as targeted delivery vehicles.     

Tuning of magnetic parameters in cobalt-polystyrene nanocomposites by reduction cycling

Cobalt nanoparticles were prepared by a reduction process inside polymer pores using CoSO₄·7H₂O and NaBH₄. A porous polymer network (sulphonated polystyrene) was chosen, as the template for the synthesis of elementary cobalt as high surface area cobalt nanoparticles are prone to oxidation. The preliminary studies reveal that the cobalt is first formed with an oxide protective layer outside and upon repeating the reduction cycles, inner pores of the polymers are opened which enhanced the yield of metallic cobalt. These high surface area cobalt nanoparticles embedded in a polymer are ideal for the synthesis of carbon nanotubes as cobalt can act as a catalyst for the nanotube synthesis. The concentration of cobalt can be tuned in this technique by repeating the cycling process.     

Effective enhancement of electric and magnetic properties of PMMA/LiFe5O8 nanocomposites via magnetic treatment

Journal of Materials Science: Materials in Electronics - The present study presents a facile effective method to enhance the electric as well as the magnetic properties of polymer/ferrite...     

Reduced graphene oxide enhanced magnetic nanocomposites for removal of carbamazepine

Ferrite, as a kind of common magnetic adsorbent, always tend to reuniting and lead to the poor performance for removing contaminant in aqueous. Meanwhile, reduced graphene oxide (rGO), a high-efficiency adsorbent used for water treatment, is hydrophobic and easy to stack because of the Van der Waals force, resulting in the low adsorption capacity. Herein, we prepare the magnetic CoFe₂O₄/rGO nanocomposites to solve the reuniting of CoFe₂O₄ and stacking of rGO simultaneously. The rGO nanosheets can improve the dispersion of CoFe₂O₄ nanoparticles. As sorbent, the adsorption behaviors of carbamazepine on the nanocomposites can be fitted well by the Langmuir and pseudo-second-order kinetic models. In addition, the CoFe₂O₄/rGO nanocomposites show enhanced adsorption performance than that of the pure CoFe₂O₄ nanoparticles, and the loading of rGO can affect their adsorption performance. The adsorption of carbamazepine on CoFe₂O₄/rGO is exothermic and mainly controlled by π–π interaction and hydrogen bond interaction. Furthermore, the CoFe₂O₄/rGO can be used to remove other organic pollutants simultaneously. Finally, the nanocomposites can be collected by external magnet, and the regenerated nanocomposites still showed a high adsorption capacity retention (90%) after five cycles.     

Effect of heat treatment on structure and magnetic properties of FeCoNi/CNTs nanocomposites

Fe₄₆Co₃₅Ni₁₉/CNTs nanocomposites have been prepared by an easy two-step route including adsorption and heat treatment processes. We investigated the effect of heat treatment conditions on structure, morphology, nanoparticle sizes and magnetic properties of the Fe₄₆Co₃₅Ni₁₉ alloy nanoparticles attached on the carbon nanotubes by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-disperse X-ray spectroscopy (EDS) and vibrating sample magnetometer (VSM). When the reducing temperature changes from 300–450°C, a transition of the crystalline structure from bcc phase to fcc-bcc dual phase and an increase in particle size of Fe₄₆Co₃₅Ni₁₉ nanoparticles together with a local maximum at 350°C are observed. Meanwhile, the saturation magnetization (M _s) for Fe₄₆Co₃₅Ni₁₉ nanoparticles increases with the increase of reducing temperature and the coercivity (H _c) decreases rapidly with a local minimum at 350°C. When the reducing time (tr) changes from 2–5 h, bcc phase is predominant in the Fe₄₆Co₃₅Ni₁₉ alloy particles. Both the particle size and M _s have a maximum at tr = 3 h, and the H _c reaches a maximum at tr = 4 h.     

Optical head tracking for functional magnetic resonance imaging using structured light

An accurate motion-tracking technique is needed to compensate for subject motion during functional magnetic resonance imaging (fMRI) procedures. Here, a novel approach to motion metrology is discussed. A structured light pattern specifically coded for digital signal processing is positioned onto a fiduciary of the patient. As the patient undergoes spatial transformations in 6 DoF (degrees of freedom), a high-resolution CCD camera captures successive images for analysis on a computing platform. A high-speed image processing algorithm is used to calculate spatial transformations in a time frame commensurate with patient movements (10-100 ms) and with a precision of at least 0.5 microm for translations and 0.1 deg for rotations.     

Systematic investigation and in vitro biocompatibility studies on implantable magnetic nanocomposites for hyperthermia treatment of osteoarthritic knee joints

The inefficacy of the currently used treatment modalities for osteoarthritis has elicited considerable research interest in the exploration of alternative methods. Hyperthermia treatment, generally used in the case of lesions, maybe considered as a viable solution owing to the economic and ergonomic factors involved. In the present study, Cr-doped Fe₂O₃ embedded in PVDF matrix is proposed as the biocompatible magnetic-dielectric composite to provide thermo-regulated prolonged treatment. A systematic study was carried out to characterize the physical properties of the prepared formulation. Further, cellular uptake studies were done to ensure bioviability. Finite element method studies using COMSOL were used to simulate the hyperthermia treatment of osteoarthritic knee joint. The approach proposed here may be used further to develop a novel class of therapeutic devices for the treatment of osteoarthritis.     

Tumour cell toxicity of intracellular hyperthermia mediated by magnetic nanoparticles

Intracellular hyperthermia is a process by which malignant cells can be selectively killed by heat generated by nanomediators located inside the cell. Here we show that maghemite anionic nanoparticles are efficiently captured by human prostatic tumor cells (PC3) and concentrate within intracellular vesicles. When submitted to an alternative magnetic field, maghemite nanocrystals generate heat from the cell inside, inducing a temperature elevation of eight degree in a loose pellet of 20 million magnetically labeled cells. We demonstrate that this heating modality was as lethal as external waterbath heating. A one hour AC magnetic field (700 kHz-31 mT) exposure of the magnetically labeled cells killed 44% of the cells. Interestingly, more than 80% of the cells were killed after being submitted twice to the magnetic field. Finally, when magnetic cells coexist with non magnetic ones, the same proportions of cells were damaged for both populations, after magnetic field exposure. These findings pave the way for an efficient cell killing mediated by intracellular magnetic hyperthermia.     

Hierarchically structured polymer blends based on silsesquioxane hybrid nanocomposites with quaternary ammonium units for antimicrobial coatings

The paper reports the first study on hierarchical assemblies (nanofibrillar micelles confined within semi-cylindrical shells) with silsesquioxane and quaternary ammonium units obtained through polymer blending intended for antimicrobial/antifungal stone coatings. The formation of hierarchical structures on solid surfaces is due to the multiple intermolecular ionic interactions, intermolecular Van der Waals and hydrophobic interactions acting among the component molecules. Their antimicrobial/antifungal properties toward the Gram-negative bacteria, Escherichia coli, Gram-positive bacteria, Staphylococcus aureus, and Candida albicans fungus were determined in aqueous solution and were found to be strongly dependent of the topographical features of the coating.     

Exchange-coupled nanocomposites with novel microstructure and enhanced remanence by a new approach

Exchange-coupled nanocomposites with hard/soft magnetic phases are promising for the next generation of permanent magnets.Chemical methods have an advantage in controlling the nanoscale size of both phases.The nanocomposites obtained by the chemical method generally consist of a hard phase core and a soft phase shell.However,the soft-phase shell is easily oxidized leading to small enhancement of remanence.Here,a novel microstructure of Fe@FePt nanocomposites with Fe soft phase core and FePt hard phase shell has been synthesized by replacement reaction,in which the size of core and shell can be controlled below 10 nm by adjusting the ratio of Fe nanoparticles to PtCl4.Excellent exchange-coupling(single-phase-like demagnetization curves) between soft-hard phases was observed due to the precise size control of both phases,and substantial enhancements both in remanence (32 ％) and saturation magnetization (81％) were obtained in optimal nanocompistes.This work provides an alternative routine to prepare heterostructure materials with various applications.     

Oil-field wastewater purification by magnetic separation technique using a novel magnetic nanoparticle

In the present work, oil-field wastewater purification through superconducting magnetic separation technique using a novel magnetic nanoparticle was investigated. The magnetic nanoparticle, which has a multi-shell structure with ferroferric oxide as core, dense nonporous silica as inter layer and mesoporous silica as outer layer, was synthesized by co-precipitation method. To functionalize the magnetic nanoparticle, plasma polymerization technique was adopted and poly methyl acrylate (PMA) was formed on the surface of the nanoparticle. The multi-shell structure of the nanoparticle was confirmed by transmission electron microscope (TEM) and the characteristic is measurable by FTIR. It is found that most of the pollutants (85% by turbidity or 84% by COD value) in the oil-field wastewater are removed through the superconducting magnetic separation technique using this novel magnetic nanoparticle.     

A novel magnetic trap for spin-polarized hydrogen

A microwave trap for spin-polarized atomic hydrogen has the important advantage of trapping very cold atoms in the ground hyperfine states at the high densities necessary for BEC. By first cooling atoms in a static trap the shallow microwave trap can be loaded. We report the construction of such a hybrid trap in this article.     

聚吡咯/凹凸棒石水性导电涂料的制备

用吡咯单体(Py)在凹凸棒石(ATP)的表面发生原位聚合反应,制备出聚吡咯/凹凸棒石(PPy/ATP)纳米导电复合材料.通过Fourier红外光谱、X射线衍射、扫描电子显微镜对复合材料进行表征,结果表明聚吡咯的包覆没有破坏凹凸棒石的晶体结构,两者之间作用仅为物理作用.以PPy/ATP为填料制备的水性丙烯酸涂料导电性高于以PPy为填料制备的水性丙烯酸涂料,并通过SEM研究了涂层的导电机理,表明PPy/ATP在导电涂料中具有更为广阔的应用前景.     

A novel strategy for making poly(vinyl alcohol)/reduced graphite oxide nanocomposites by solvothermal reduction

Poly(vinyl alcohol) (PVA)/reduced graphite oxide (rGO) nanocomposites were synthesized by solvothermal reduction of graphite oxide (GO) in the presence of PVA. The solvent, the mixed dimethyl sulfoxide (DMSO)-dimethylformamide (DMF), could act not only as a reducing agent but also as a good stabilizer, which achieved effectively reduction of GO in the PVA matrix and avoided the agglomeration of rGO during reduction. A 53.0% increase in tensile strength and 52.6% improvement of Young’s modulus were achieved by addition of 3 wt% of rGO. Furthermore, a significant improvement of thermal stability was observed for the PVA/rGO nanocomposites.     

Mechanical properties of NBR/clay nanocomposites by using a novel testing system

NBR/clay nanocomposites are prepared by two different filler types: clay microparticles and clay nanoparticles. The morphology properties of all specimens are explored by XRD and SEM. The mechanical properties are characterized by means of a novel video-controlled method under uniaxial tension. Apart a limited increase in tensile stress at small strains, the ultimate stress at rupture of nanocomposites is much higher than microcomposites. The most dramatic phenomenon is the development of volume strain while the materials are stretched. The nucleation of voids is much more active in composites containing the filler with higher specific surface when the cavitation occurs at the poor interface between the clay platelets and the rubber matrix. In turn, the existence of very diffuse voids hinders the propagation of cracks and retards the rupture process. DMA results reveal that the interfacial action of NBR molecules with layered silicates increases with the degree of intercalation.     

Core-shell structured Mn-Zn-Fe ferrite/Fe-Si-Cr particles for magnetic composite cores with low loss

A Mn-Zn-Fe ferrite layer, several hundred nanometers thick, was deposited on the surface of Fe-3.5Si-4.5Cr (mass%) powder particles as an insulating material by an ultrasonic enhanced ferrite plating method. The compositions of the Mn-Zn-Fe ferrite layer were Mn_0.18Zn_0.27Fe_2.55O₄, Mn_0.38Zn_0.25Fe_2.37O₄, and Mn_0.54Zn_0.24Fe_2.22O₄. The core loss (P_cv) performances of the compacted cores and magnetic properties of the core-shell structured powders were evaluated. All the ferrite-coated cores exhibited a saturation flux density (B_s) in the range of 1.54–1.56?T derived from their soft magnetic metal and ferrite composition. All ferrite-coated cores annealed at 773?K exhibited a constant permeability µ′ in the frequency range up to 50?MHz owing to the insulating effect of the ferrite layer, and the Mn_0.54Zn_0.24Fe_2.22O₄ ferrite-coated core exhibited the highest real permeability µ′ of 56 at 50?MHz. The core loss of the Mn-Zn-Fe ferrite-coated Fe-3.5Si-4.5Cr cores was 604–738?kW/m³ at 100?kHz and 50?mT, which was much smaller than that obtained for the Fe-3.5Si-4.5Cr core without a ferrite layer (3617?kW/m³). The eddy-current loss (P_e) of the Mn-Zn-Fe ferrite-coated Fe-3.5Si-4.5Cr cores considerably decreased compared with those of the non-coated Fe-3.5Si-4.5Cr core owing to the insulating properties of the ferrite layer.     

用于磁传感器的新结构磁电复合材料

研究了可用于磁场传感器的磁电复合材料, 对传统的磁电复合材料进行了结构创新, 采用条状PZT和 Terfenol-D 的材料体系, 用热固树脂进行粘合, Terfenol-D 沿长度方向磁化且PZT条沿厚度方向极化。与传统的1-3型复合不同的是: 每根PZT的输出极被串联起来。在同样的磁场激励下, 新型复合材料的输出电压为相同体积的同种结构复合材料的2.2倍, 增强了材料对磁场的灵敏度和抗噪声性能。      

Modification of montmorillonite by novel geminal benzimidazolium surfactant and its use for the preparation of polymer organoclay nanocomposites

A new benzimidazolium derivative, the benzimidazolium-N,N′-hexadecane-2-hydroxy-ethyl bromide (Bz) featuring two geminal hexadecyl hydrophobic buttress has been synthesized and used for the functionalization of sodium montmorillonite (MMT-Na) via cationic exchange process. The resulting benzimidazolium-modified MMT (MMT-Bz) exhibits a large d-spacing of 3 nm between silicate layers and shows a high thermal stability compared to the commonly used clay modified alkyl ammonium salts (cloisite 20A and cloisite 20B). MMT-Bz was incorporated in high density polyethylene (HDPE) matrix via melt mixing method to produce HDPE/MMT-Bz nanocomposites. The microstructure and the morphology of these nanocomposites were studied by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The dispersion state of the organoclay within HDPE was monitored by UV–Vis spectroscopy and melt rheology. A more homogeneous dispersion or a greater content of the MMT-Bz in the matrix produced stronger solid-like and non-terminal behavior in the nanocomposites. Tensile properties and thermal stability were evaluated and discussed on the basis of the amount of clay incorporated within the nanocomposites. The intercalated structure in the nanocomposites, resulting from both the better dispersion/distribution of clay nano-platelets and their strong interaction with the polymer chains, provides the driving force to significantly enhance the HDPE properties.