Microwave absorption properties of NiCoFe2O4-graphite embedded poly(o-phenetidine) nanocomposites (original) (raw)
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ChemistrySelect, 2016
Microwave absorbers derived using poly(vinylidene fluoride) (PVDF), super paramagnetic nanocrystalline calcium ferrite (CaFe 2 O 4) and multiwall nanotubes (MWNTs) were developed in this study. Effect of in-situ modification of CaFe 2 O 4 and MWNTs with a conducting layer, (polyaniline, PANI) on different properties of the composite has been investigated systematically. Two approaches were investigated here to gain insight into the mechanism of microwave absorption. Firstly, coating PANI onto CaFe 2 O 4 and blending along with MWNTs; secondly, coating PANI onto MWNTs and blending along with CaFe 2 O 4. The electrical and magnetic properties of various composites containing hybrid particles were evaluated. Interestingly, the PVDF composites containing PANI coated CaFe 2 O 4 blended together with MWNTs showed excellent shielding effectiveness (-57 dB at 18 GHz) as compared to the second approach where PANI was coated onto MWNTs and blended along with CaFe 2 O 4. This was discussed here with respect to the relative permittivity and permeability in a wide range of frequency.
Microwave Absorbing by Conducting Hybrid Nanocomposites Based on Magnetite Nanoparticles
2012
Microwave absorbing properties of hybrid nanocomposites of Fe3O4 nanoparticles with carbon nanotubes and polyaniline (PANI) doped with dodecylbenzenesulfonic acid have been studied. It has been found that the the addition of nanostructured components increases the absorbtion of the nanocomposites. Moreover, CNTs affect the absorbtion in high frequency range, and Fe3O4 nanoparticles – in low frequency range. Introduction of conductive PANI into the matrix enhances the influence of nanomaterials on the absorbance of the films.
Microwave Absorption Characteristics of some Ferrite-Filled Polymer Composites
Advanced Materials Research, 2014
Prior to their use for microwave absorption, different compositions of NixZn1-xFe2O4 (x = 0.5, 0.6, 0.7 and 0.8) were prepared via mechanical alloying and sintering. X-ray diffractometry (XRD) was used to investigate the crystalline phase formation. Scanning transmission electron microscopy (STEM) and field emission electron microscopy (FeSEM) were used to investigate the particle size and surface morphology respectively. The complex-permeability components, μʹ and μʺ, were also measured using an Agilent 4291B material analyzer from 1 MHz to 1 GHz. From the XRD results it is shown that at 900oC the full phase of nickel zinc ferrite was formed. The μʺ values suggest that the ferrite sample can absorb well microwave energy for frequencies 1 MHz to 1 GHz and higher. This is proved by microwave absorption measurements carried out up to 12 GHz.Keywords: NiZn-ferrite, microwave absorption, magnetic materials
Microwave Absorption Behaviour of Polyaniline-MWCNT Composites Containing Nanoparticles of
Conducting polymer nanocomposites having both dielectric & magnetic properties were developed using polyaniline matrix containing multiwalled carbon nanotube (MWCNT) and a hybrid filler consisting of nanoparticles of γ-Fe 2 O 3 and BaTiO 3 . These nanocomposites were characterized by X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and Transmission electron microscopy (TEM). Electrical conductivity was measured by four-probe technique and magnetic behaviour was studied using vibrating sample magnetometer (VSM). Microwave absorption behaviour was studied using two port vector network analyser (VNA) in the Ku band (12.4 -18.0 GHz). It was observed that these nanocomposites show absorption dominated total shielding effectiveness in the range of ~ -65 dB, which can be attributed to the combined magnetic and dielectric losses in the shield.
Enhanced microwave absorption properties in polyaniline and nano-ferrite composite in X-band
Lancet, 2010
Highly conducting polyaniline (PANI) nanocomposite with Mn 0.2 Ni 0.4 Zn 0.4 Fe 2 O 4 ferrite was prepared by mechanical blending. The present work reports the EMI shielding characteristics of the ferrite-Pani nanocomposite with different thickness. The saturation magnetization (Ms) for pure MnNiZn ferrite (52 emu/g) and composite (41 emu/g) was measured by VSM at room temperature. The crystalline size of MnNiZn ferrite was found in the range of 25-30 nm as analyzed by TEM and XRD. The complex permittivity, permeability and shielding effectiveness of the composite for different thicknesses were measured in the 8-12 GHz (X-band) frequency range. The composite of 2.5 mm thickness has shown high shielding effectiveness (49.2 dB) due to absorption (SE A ). The high value of SE A suggests that this composite can be used as a promising absorbing material for X-band frequency range.
Lightweight and flexible electromagnetic shielding materials were designed by selectively localizing multiwall carbon nanotubes (MWNTs) anchored magnetic nanoparticles in melt mixed co-continuous blends of polyvinylidene fluoride (PVDF) and poly(styrene-co-acrylonitrile) (SAN). In order to facilitate better dispersion, the MWNTs were modified using pyrenebutyric acid (PBA) via p–p stacking. While one of the two-targeted properties, i.e., high electrical conductivity, was achieved by PBA modified MWNTs, high magnetic loss was accomplished by introducing nickel (NF) or cobalt ferrites (CF). Moreover, the attenuation by absorption can be tuned either by using NF (58% absorption) or CF (64% absorption) in combination with PBA-MWNTs. More interestingly, when CF was anchored on to MWNTs via the pyrene derivative, the minimum reflection loss attained was À55 dB in the Ku band (12–18 GHz) frequency and with a large bandwidth. In addition, the EM waves were blocked mostly by absorption (70%). This study opens new avenues in designing flexible and lightweight microwave absorbers.
Polymer microwave absorber with nanosized ferrite and carbon fillers
27th International Spring Seminar on Electronics Technology: Meeting the Challenges of Electronics Technology Progress, 2004., 2005
The paper presents studies on the microwave properties of two types of polymer composites based on acrylic resin and polyurethane with nanosized magneticmagnetite and dielectriccarbon fillers. The microwave (MW) absorption was measured at 9.4 GHz, while the dielectric and magnetic properties were investigated in the frequency range I + 18 GHz. Promising MW absorption properties were observed for nanostructured filler applications in comparison with the traditional MW absorbers.
The present paper deals with the synthesis of conducting ferrimagnetic polyaniline nanocomposite embedded with ␥-Fe 2 O 3 (9-12 nm) and titanium dioxide (70-90 nm) nanoparticles via a micro-emulsion polymerization. The microwave absorption properties of nanocomposite in 12.4-18 GHz (Ku-band) frequency range shows shielding effectiveness due to absorption (SE A ) value of −45 dB, which is much higher than polyaniline composite with iron oxide and polyaniline-TiO 2 composites. The higher EMI shielding is mainly arising due to combined effect of ␥-Fe 2 O 3 and TiO 2 that leads to more dielectric and magnetic losses which consequently contributed to higher values of shielding effectiveness. XRD analysis of the nanocomposite reveals the incorporation of nanoparticles in the conducting polymer matrix while the thermal gravimetric analysis (TGA) demonstrates that the nanocomposite is stable up to 250 • C.
Fabrication and characterisation of selected microwave absorbing ferrite-polymer composites
2012
Although absorbing materials are a useful part of modern-day defence systems, very little published knowledge exists on the fabrication of such materials especially microwave absorbing materials. The present research attempts to fabricate absorbing material compositions suitable for microwave absorption from 8 to 18 GHz. Various compositions of composite ferrites were prepared using mechanical alloying and sintering. The starting metal oxide raw materials were weighed according to the targeted proportion and milled for 10 hours using a SPEX8000D mill to get nanosized particles. The resulting mixture was poured into a PVA solution as a binder and stirred while drying it using an ultraviolet lamp until the powder contained ~1 wt% PVA. It was then pressed into pellet/toroid-shaped samples and sintered at temperature 900 °C for 10 hours. Then, a composite of ferrite powder with polymer paint as matrix was prepared. The composite paint produced was applied on the surface of a metal sheet of specified surface dimensions. Physical characteristics of the as-prepared filler samples were studied using X-ray diffraction (XRD), scanning transmission electron microscopy 65 5.3.1 Microstructural properties 65 5.3.2 Complex Permeability Component μ" and μ" 72 5.4 Composition materials in X-band (8-12 GHz) and Kuband (12-18 GHz) frequency range 77 5.4.1 The effect on reflection loss and absorption of ferrite in polymer matrix composites with metal back 5.4.1.1 The influence of physical thickness 5.4.1.2 The influence of materials with different composition 77 78 84 5.4.2 Microwave absorption characteristics of the prepared polymer matrix composites on metal plate