A Brief Overview on Ferrite (Fe3O4) Based Polymeric Nanocomposites: Recent Developments and Challenges

In this article, we have mainly discussed about ferrite (Fe3O4) and its polymer based nanocomposites. Ferrite particles have become an important research material because of their vast applications in the field of biotechnology, magnetic resonance imaging (MRI), and data storage. It has been observed that ferrite Fe3O4 particles show best performance for size less than 10-30 nm. This happens due to the super paramagnetic nature of such particles. In super paramagnetic range these particles exhibit zero remanence or coercivity. Therefore, various properties of ferrite (Fe3O4) nanoparticles and its polymer nanocomposites are very much dependent on the size, and distribution of the particles in the polymeric matrix. Moreover, it has been also observed that the shape of the nanocrystals plays important role in the determination of their fundamental properties. These particles show instability over longer times due to the formation of agglomerates generated by high surface energies. Therefore, protection strategies such as grafting and coatings with silica/carbon or polymers have been developed to stabilize them chemically. Recently, silylation technique is mainly used for the modification of nanoparticles. Experimentally, it has been observed that nanocomposites composed of polymer matrices and ferrite showed substantial improvements in stiffness, fracture toughness, sensing ability (magnetic as well as electric), impact energy absorption, and electro-catalytic activities to bio-species

Nanocomposites of polymer and inorganic nanoparticles for optical and magnetic applications

This article provides an up-to-date review on nanocomposites composed of inorganic nanoparticles and the polymer matrix for optical and magnetic applications. Optical or magnetic characteristics can change upon the decrease of particle sizes to very small dimensions, which are, in general, of major interest in the area of nanocomposite materials. The use of inorganic nanoparticles into the polymer matrix can provide high-performance novel materials that find applications in many industrial fields. With this respect, frequently considered features are optical properties such as light absorption (UV and color), and the extent of light scattering or, in the case of metal particles, photoluminescence, dichroism, and so on, and magnetic properties such as superparamagnetism, electromagnetic wave absorption, and electromagnetic interference shielding. A general introduction, definition, and historical development of polymer–inorganic nanocomposites as well as a comprehensive review of synthetic techniques for polymer–inorganic nanocomposites will be given. Future possibilities for the development of nanocomposites for optical and magnetic applications are also introduced. It is expected that the use of new functional inorganic nano-fillers will lead to new polymer–inorganic nanocomposites with unique combinations of material properties. By careful selection of synthetic techniques and understanding/exploiting the unique physics of the polymeric nanocomposites in such materials, novel functional polymer–inorganic nanocomposites can be designed and fabricated for new interesting applications such as optoelectronic and magneto-optic applications

High performance magnetoelectric nanocomposite morphologies for advanced applications

Tese de Doutoramento em Engenharia de MateriaisThe magnetoelectric (ME) effect is characterized by the variation of the electrical polarization of a material with an applied magnetic field and the variation of the magnetization of a material with an applied electric field. Single-phase materials with intrinsic ME effect are not generally used for practical applications since they typically show weak ME coupling at room temperatures. Such problem has been overcome by the development of ME composites. Strong ME effect at room temperature has been obtained, particularly in those composed by a piezoelectric and a magnetostrictive phase. In such materials, a strain is induced on the magnetostrictive phase once a magnetic field is applied to the composite. This strain is transmitted to the piezoelectric constituent, which undergoes a change in the electrical polarization. In an analogous way, the reverse effect can occur. The main objective of the thesis was the development of high performance polymer-based ME materials, that were characterized, optimized and their potential applications evaluated. Particulate ME composites were produced from materials with strong piezoelectric - poly(vinylidene fluoride) (P(VDF)) - and magnetostrictive - Cobalt iron oxide (CoFe2O4 - CFO) - responses in the form of film, membrane, fibers, and spheres. Related piezoelectric materials, such as the copolymer of P(VDF), poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), and magnetic nanoparticles, such as magnetite (Fe3O4), goethite (δ-FeO(OH)) and CoFeO(OH), were also used. All developed morphologies show the presence of the ME effect. The studies on film morphology addressed the relevance of the magnetostrictive filler dispersion on ME composite response, suggesting that the use of surfactants or ultrasounds to improve the dispersion leads to the same ME response. The filler size and shape shows an important role on the ME measurements. Studies with Fe3O4 nanoparticle with sizes of 9, 30 and 50 nm within a P(VDF-TrFE) matrix show that the largest α31 = 0.97 mV.cm-1Oe-1 is obtained for the lowest nanoparticle size. The shape of the same filler was studied and the results shows that a rod shape, comparing with a spherical, nucleate the β-phase of P(VDF), due to the high interface interaction between the polymer and the filler. Anisotropic nanosheet fillers of δ-FeO(OH) and CoFeO(OH) were synthetized and evaluated for the preparation of ME composites. Thus, δ-FeO(OH) /P(VDF-TrFE) composites lead to a maximum ME response of 0.4 mV.cm-1.Oe-1, which depends on filler content, alignment state as well as on both incident magnetic field direction and magnitude. A new ME effect is proposed based on the magnetic rotation of the nanosheets inside the piezoelectric polymer matrix. New CoFeO(OH) highly magnetostrictive (λ = 507 ppm) and anisotropic nanostructures were synthesized by a coprecipitation method using a modified gas-slugs microfluidic system. CoFeO(OH) /P(VDF-TrFE) composites reveal an interfacial ME coupling strongly dependent on the angle between HDC and filler length direction, with a maximum α31 = 5.10 mV.cm-1.Oe-1. ME membranes were also produced in CFO/P(VDF-TrFE) composites. The porous morphology and ME response were evaluated. The porous composite shows piezoelectricity with an effective piezoelectric coefficient (d33) of -22 pC.N-1, a maximum magnetization of 12 emu.g-1 and a maximum ME coefficient of 9 mV.cm-1.Oe-1. ME nanofibers and microspheres of CFO/P(VDF) produced by electrospinning and electrospray technique, respectively, were studied and evaluated. The average diameter of the nanofibers is ≈325 nm, independently of filler content, and the amount of crystalline polar β-phase was strongly enhanced when compared to pure P(VDF) polymer fibers, due to the introduction of the magnetostrictive fillers. The piezoelectric response of these electroactive nanofibers was modified by an applied magnetic field, thus evidencing the ME character of the CFO/P(VDF) composites. The CFO nanoparticles content in the ME microspheres (3-7 µm diameter) reached values up to 27 wt.%, despite their concentration in the starting solution reaching values up to 70 wt.%. No relevant effect on β-phase content (≈60 %), crystallinity (40 %) and onset degradation temperature (460-465 °C) of the polymer matrix was observed. The ME microspheres show a maximum|d33|≈30 pC.N-1, leading to a ME response of ∆|d33|≈5 pC.N-1 obtained when a 220 mT DC magnetic field was applied. Its also shown that the interface between CFO and P(VDF) (0-55 %) has a strong influence on the ME response of the microspheres. The simplicity and the scalability of the processing methods used in the present work as well as the excellent ME response in a large variety of composite morphologies suggest a large application potential of the developed polymer-based ME composites in areas such as sensors and actuators and tissue engineering, among others.O efeito magnetoelétrico (ME) é caraterizado pela variação da polarização elétrica do material na presença de um campo magnético e pela variação da magnetização do material quando um campo elétrico é aplicado. Os materiais de fase única com o efeito ME intrínseco não são usualmente utilizados em aplicações uma vez que possuem fraco acoplamento ME à temperatura ambiente. Este problema é então ultrapassado com o desenvolvimento de compósitos MEs. Nestes, verifica-se um forte efeito ME obtido à temperatura ambiente, particularmente quando constituídos por uma fase piezoelétrica e outra magnetostritiva. Nestes materiais, a deformação é induzida na fase magnetostritiva quando um campo magnético é aplicado ao compósito. Essa deformação é transmitida ao constituinte piezoelétrico que provoca uma mudança na polarização elétrica do material. O efeito contrário pode ser também observado. O objetivo principal desta tese foi o desenvolvimento de materiais ME de base polimérica com alta performance, caracterização, otimização e avaliação para potencial aplicação. Foram produzidos compósitos ME particulados a partir de materiais com uma forte resposta piezoelétrica – poli(fluoreto de vinilideno) (P(VDF)) – e magnetostritiva – CoFe2O4 (CFO) – em forma de filme, membrana, fibras e esferas. O polímero piezoelétrico como o copolimero do P(VDF), poli(fluoreto de vinilideno-trifluoretileno) (P(VDF-TrFE)), e nanopartículas como Fe3O4, δ-FeO(OH) e CoFeO(OH) foram também estudados. Todos as morfologias desenvolvidas mostram a presença do efeito ME. Os estudos realizados na morfologia de filmes mostram a relevância da dispersão do material de reforço nos compósitos ME. Estes sugerem que tanto o uso de surfactantes como do ultrassons, para dispersar, têm a mesma influência nas medidas ME dos compósitos. O tamanho e a forma do material de reforço têm um papel importante nas medidas ME. Estudos com nanopartículas de Fe3O4 com tamanhos de 9, 30 e 50 nm no interior da matriz polimérica de P(VDF-TrFE), mostram que o maior α31 (0.97 mV.cm-1Oe-1) é obtido para a nanopartícula de menor tamanho. A influência da forma do material de reforço foi estudada e os resultados mostram que a forma de bastão, comparada com a esférica, nucleiam a fase β do P(VDF) devido à alta interação na interface entre o polímero e o material de reforço. Foram também sintetizadas e avaliadas as nanofolhas anisotrópicas de δ-FeO(OH) e CoFeO(OH) para a preparação de compósitos ME. Compósitos de δ-FeO(OH)/P(VDF-TrFE) com um máximo de ≈0.4 mV.cm-1.Oe-1, variam consoante a concentração do material de reforço, alinhamento e a direção e intensidade dos dois campos magnéticos incidentes. Um novo efeito ME é proposto baseado na rotação magnética das nanofolhas no interior da matriz polímérica. Sintetizou-se uma nova nanoestrutura anisotrópica de CoFeO(OH) com alta magnetostrição (λ = 507 ppm), pelo método de coprecipitação, com uma modificação no sistema microfluídico “gas-slugs”. Nanocompósitos de CoFeO(OH) /P(VDF-TrFE) revelam um acoplamento ME fortemente dependente do ângulo entre o HDC e o comprimento do CoFeO(OH), com um máximo α31 de 5.10 mV.cm-1.Oe-1. Membranas ME foram igualmente produzidas em compósitos CFO/P(VDF-TrFE). A morfologia porosa e a resposta ME foram avaliadas. O compósito poroso apresenta uma resposta piezoelétrica com um coeficiente piezoelétrico efetivo (d33) de -22 pC.N-1, uma magnetização máxima de 12 emu.g-1 e um coeficiente ME máximo de 9 mV.cm-1.Oe-1. Foram estudadas e avaliadas nanofibras e microesferas de CFO/P(VDF) produzidas por electrospinning e electrospray, respetivamente. O diâmetro médio das nanofibras foi de ≈325 nm, independentemente da quantidade de material de reforço e da quantidade da fase polar β, que é fortemente aumentada com a introdução do material de reforço magnetoestritivo quando comparada com as fibras puras de P(VDF). A resposta piezoelétrica das nanofibras eletroativas é modificada com a aplicação de um campo magnético, evidenciando assim o carácter ME do compósito CFO/P(VDF). Microesferas ME (3-7 µm de diâmetro) com nanopartículas de CFO foram preparadas com concentrações que chegam aos 27 % em peso, apesar de a solução inicial ter 70 %. Não foram verificadas alterações de fase β (≈60 %), cristalinidade (40 %) e temperatura de degradação onset (460-465 °C) do polímero. As microesferas ME apresentam um máximo |d33|≈30 pC.N-1, com a uma resposta ME de ∆|d33|≈5 pC.N-1 quando um campo magnético DC (220 mT) é aplicado. Verificou-se que a interface entre as nanopartículas de CFO e o P(VDF) (0-55 %) tem uma forte influência na resposta ME das microesferas. A simplicidade e a escalabilidade dos métodos de processamento apresentados neste trabalho, assim como a distinta resposta ME numa ampla variedade de morfologias, sugerem uma potencial aplicabilidade dos compósitos ME de base polimérica, em áreas como sensores e atuadores, engenharia de tecidos, entre outros

Electro-magnetic Responsive Ni0.5Zn0.5Fe2O4 Nano-particle Composite

The purpose of this study is to simulate and synthesize a Radar (or Radiation) Absorbent Material (RAM) by using polymers and nickel zinc ferrite (Ni0.5Zn0.5Fe2O4) magnetic nanoparticles. There is an ardent desire in military, space and electronics for lighter, faster, cheaper and widespread bandwidth providing RAM materials. Electromagnetic property such as magnetic permeability and electric permittivity play a major in controlling the radiation. The appropriate combination of permeability and permittivity properties is acquired for the synthesis of RAM providing wide-ranging bandwidth. The apt property is achieved by rule of mixture, mixing of particular composition of epoxy polymer having low permeability and permittivity with the nickel zinc ferrite magnetic nanoparticle having high permeability and permittivity. In this investigation, we studied the effective relative permeability and permittivity of Ni0.5Zn0.5Fe2O4 nanoparticles encapsulated within the epoxy polymer resin through Finite Element Analysis (FEA) and several various analytical experiments to verify and match both the simulation and experimental results. The FEA model was explored in two different aspect. First, shape of the nanoparticle is assumed to be spherical, cubic and bar structure. Secondly, the distribution of nanoparticle in the epoxy polymer matrix is assumed to be Simple Cubic (SC), Body Center Cubic (BCC), Face Center Cubic (FCC) and Random distributed unit cell. The result is compared with analytic approaches (Maxwell-Garnett (M-G) theory, Bruggeman theory) and Vibrating Sample Magnetometer (VSM) experimental data

Synthesis and Characterization of Ferrous Nanoparticles and Polymer-Grafted Ferrous Nanoparticles with an Examination of Thermal and Magnetic Properties

Energy harvesting using ferrofluid in OHP. Characterization of as-synthesized (bare) and surface-modified ferrofluid samples was performed using Fourier transform infrared spectroscopy, dynamic light scattering, X-ray powder diffraction, transmission electron microscopy, and atomic force microscopy. These ferrofluids were tested in a novel oscillating heat pipe set-up was utilized to harvest electricity, demonstrating the concept of ferrofluidic induction. Cobalterrite nanoparticles surface-modified with citric acid demonstrated good magnetic strengths and generated voltages close to those of the as-synthesized ferrofluids while maintaining dispersion. Surface modification of ferrous nanoparticles with SRP. Thermo responsive polymer poly(N-isopropylacrylamide) was successfully grown from the surface of cobalt-zinc ferrite nanoparticles. A dual responsive block copolymer, pH and thermo responsive comprised of poly(itaconic) acid and poly(N-isopropylacrylamide) was successfully polymerized from the surface of ferrous oxide nanoparticles. These composite having magnetic properties along with stimulus can be used in applications such as controlled drug delivery and similar biomedical applications

Magnetic Gel Composites for Hyperthermia Cancer Therapy

Hyperthermia therapy is a medical treatment based on the exposition of body tissue to slightly higher temperatures than physiological (i.e., between 41 and 46 °C) to damage and kill cancer cells or to make them more susceptible to the effects of radiation and anti-cancer drugs. Among several methods suitable for heating tumor areas, magnetic hyperthermia involves the introduction of magnetic micro/nanoparticles into the tumor tissue, followed by the application of an external magnetic field at fixed frequency and amplitude. A very interesting approach for magnetic hyperthermia is the use of biocompatible thermo-responsive magnetic gels made by the incorporation of the magnetic particles into cross-linked polymer gels. Mainly because of the hysteresis loss from the magnetic particles subjected to a magnetic field, the temperature of the system goes up and, once the temperature crosses the lower critical solution temperature, thermo-responsive gels undergo large volume changes and may deliver anti-cancer drug molecules that have been previously entrapped in their networks. This tutorial review describes the main properties and formulations of magnetic gel composites conceived for magnetic hyperthermia therapy.Financial from DFG (PRJ 9209720) and University of Regensburg are gratefully acknowledged. D.D.D. thanks DFG for the Heisenberg Professorship Award.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)Peer reviewe

Magnetically induced release of fluorescein isothiocyanate (FITC) from polymer nanoparticle composites (PNCs)

Magnetically induced drug release can be used as a site-specific, minimally invasive pharmaceutical treatment. Its purpose is to increase the efficacy of drug therapies to diseased or damaged tissue and to decrease the amount of unnecessary damage to healthy, surrounding tissue. To prove the concept of drug release by a magnetic field, this study focused on the release of a fluorescent molecule from magnetic polymeric nanoparticle composites (PNCs) via induction of an alternating current (AC) magnetic field. Fluorescent magnetic PNCs used were 250 ?m or less in size, and were made of poly(methyl methacrylate) (PMMA) containing either the magnetic material magnetite nanoparticles or cobalt nanoparticles, and the fluorescent dye fluorescein isothiocyanate (FITC). Characterization of the composites included transmission electron microscopy (TEM) and scanning electron microscopy (SEM) for size and morphology, fluorescent microscopy for fluorescent images, elemental analysis for iron and cobalt content, and superconducting quantum interference device (SQUID) magnetometer readings for saturation magnetization measurements and field profiles of each particle type. Magnetic release of FITC from the composites was induced by applying an AC magnetic field to the PNCs in phosphate buffered saline (PBS) at various frequencies in the range of 44-430 Hz at the corresponding voltage of 15-123 V, magnetic field strength of approximately 465 G and current of 11 A. The PNCs were exposed to the magnetic field for various amounts of time ranging from 5 minutes to 3 hours and at temperatures of 4°C, 22°C, and 43°C. For each experiment, a control sample that was not exposed to the magnetic field was also tested for release. Fluorescence released was measured using a fluorospectrometer following filtration and sample dilution. The investigations demonstrated that the release of FITC was not significantly dependent on the frequency of the magnetic field, the experimental duration, nor the presence of the AC magnetic field. The study demonstrated, however, that greater release of FITC was dependent on higher temperatures and that magnetite-PNCs released more FITC than cobalt-PNCs. This research potentially leads the way to the biological applications of in-vitro and in-vivo studies of magnetically induced, controlled drug release from magnetic polymeric structures

Magnetic Gel Composites for Hyperthermia Cancer Therapy

Hyperthermia therapy is a medical treatment based on the exposition of body tissue to slightly higher temperatures than physiological (i.e., between 41 and 46 °C) to damage and kill cancer cells or to make them more susceptible to the effects of radiation and anti-cancer drugs. Among several methods suitable for heating tumor areas, magnetic hyperthermia involves the introduction of magnetic micro/nanoparticles into the tumor tissue, followed by the application of an external magnetic field at fixed frequency and amplitude. A very interesting approach for magnetic hyperthermia is the use of biocompatible thermo-responsive magnetic gels made by the incorporation of the magnetic particles into cross-linked polymer gels. Mainly because of the hysteresis loss from the magnetic particles subjected to a magnetic field, the temperature of the system goes up and, once the temperature crosses the lower critical solution temperature, thermo-responsive gels undergo large volume changes and may deliver anti-cancer drug molecules that have been previously entrapped in their networks. This tutorial review describes the main properties and formulations of magnetic gel composites conceived for magnetic hyperthermia therapy