Microwave absorbers designed from PVDF/SAN blends containing multiwall carbon nanotubes anchored cobalt ferrite via a pyrene derivative (original) (raw)
Related papers
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.
Nanoscale ordering in a polymer blend structure is indispensable to obtain materials with tailored properties. It was established here that controlling the arrangement of nanoparticles, with different characteristics, in co-continuous PC/PVDF (polycarbonate/poly(vinylidene fluoride)) blends can result in outstanding microwave absorption (ca. 90%). An excellent reflection loss (R L) of ca. À71 dB was obtained for a model blend structure wherein the conducting (multiwall carbon nanotubes, MWNTs) and the magnetic inclusions (Fe 3 O 4) are localized in PVDF and the dielectric inclusion (barium titanate, BT) is in PC. The MWNTs were modified using polyaniline, which facilitates better charge transport in the blends. Furthermore, by introducing surface active groups on BT nanoparticles and changing the macroscopic processing conditions , the localization of BT nanoparticles can be tailored, otherwise BT nanoparticles would localize in the preferred phase (PVDF). In this study, we have shown that by ordered arrangement of nanoparticles, the incoming EM radiation can be attenuated. For instance, when PANI–MWNTs were localized in PVDF, the shielding was mainly through reflection. Now by localizing the conducting inclusion and the magnetic lossy materials in PVDF and the dielectric materials in PC, an outstanding shielding effectiveness of ca. À37 dB was achieved where shielding was mainly through absorption (ca. 90%). Thus, this study clearly demonstrates that lightweight microwave absorbers can be designed using polymer blends as a tool.
Tuning the microwave absorption through engineered nanostructures in co-continuous polymer blends
Herein, we report tailor-made properties by dispersing nanostructured materials in a co-continuous polymer blend (PVDF/ABS) that is capable of shielding electromagnetic (EM) radiation. To accomplish this, lossy materials were employed like multi-walled carbon nanotubes (MWNTs), and barium titanate (BT), (which exhibit relaxation losses in the microwave frequency domain) and ferrites (like Fe 3 O 4 ). To improve the state of dispersion, the MWNTs were non-covalently modified using 3,4,9,10-perylenetetracarboxylic dianhydride (PTCD) via π-π stacking, and for effective shielding the MWNTs were conjugated with either BT or Fe 3 O 4 nanoparticles through suitable modifications. The hybrid nanoparticles were selectively localized in the PVDF phase, governed by its polarity, and exhibited excellent microwave attenuation. In order to gain insight into the dielectric and magnetic attributes, the microwave parameters were assessed systematically. Taken together, our results uncover polymer blend as a promising candidate for designing lightweight, thermally stable microwave absorber materials.
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.
In order to obtain better materials, control over the precise location of nanoparticles is indispensable. It is shown here that ordered arrangements of nanoparticles, possessing different characteristics (electrical/ magnetic dipoles), in the blend structure can result in excellent microwave absorption. This is manifested from a high reflection loss of ca. −67 dB for the best blend structure designed here. To attenuate electromagnetic radiation, the key parameters of high electrical conductivity and large dielectric/magnetic loss are targeted here by including a conductive material [multiwall carbon nanotubes, MWNTs], ferroelectric nanostructured material with associated relaxations in the GHz frequency [barium titanate, BT] and lossy ferromagnetic nanoparticles [nickel ferrite, NF]. In this study, bi-continuous structures were designed using 50/50 (by wt) blends of polycarbonate (PC) and polyvinylidene fluoride (PVDF). The MWNTs were modified using an electron acceptor molecule, a derivative of perylenediimide, which facilitates π–π stacking with the nanotubes and stimulates efficient charge transport in the blends. The nanoscopic materials have specific affinity towards the PVDF phase. Hence, by introducing surface-active groups, an ordered arrangement can be tailored. To accomplish this, both BT and NF were first hydroxylated followed by the introduction of amine-terminal groups on the surface. The latter facilitated nucleophilic substitution reactions with PC and resulted in their precise location. In this study, we have shown for the first time that by a compartmentalized approach, superior EM attenuation can be achieved. For instance, when the nanoparticles were localized exclusively in the PVDF phase or in both the phases, the minimum reflection losses were ca. −18 dB (for the MWNT/BT mixture) and −29 dB (for the MWNT/NF mixture), and the shielding occurred primarily through reflection. Interestingly, by adopting the compartmentalized approach wherein the lossy materials were in the PC phase and the conductive materials (MWNT) were in the PVDF phase, outstanding reflection losses of ca. −57 dB (for the BT and MWNT combination) and −67 dB (for the NF and MWNT combination) were noted and the shielding occurred primarily through absorption. Thus, the approach demonstrates that nanoscopic structuring in the blends can be achieved under macroscopic processing conditions and this strategy can further be explored to design microwave absorbers.
SN Applied Sciences
This research work describes the design and method of development of microwave absorber. This study was conducted for analysis of reflection loss performance with the magnetic modifications of Multi-Walled Carbon Nanotubes (MWC-NTs). Cobalt filled Multi-Walled Carbon Nanotubes composites were prepared by three step method. Composites were developed with varying weight percentage of Cobalt Sulphate and Multi-Walled Carbon Nanotubes. The morphology, elementary analysis and absorbing properties of Cobalt filled Multi-Walled Carbon Nanotubes composites were studied by FESEM, EDX and Vector Network Analyzer. The maximum reflection loss is observed for (50% MWCNT and 50% Cobalt Sulphate) is −30.22 dB at 11.8 GHz and the maximum bandwidth window is available for (40% MWCNT and 60% Cobalt Sulphate) is 3.9 GHz in the frequency range of 8-13 GHz with 3 mm thickness, which can be credited to synergistic effect of improved matched impedance and greater microwave attenuation properties of the absorber. The combined usage of dielectric loss and magnetic loss absorber design shows great diversity and can be a promising candidate for designing high performance microwave absorbing materials.
Microwave absorption properties of NiCoFe2O4-graphite embedded poly(o-phenetidine) nanocomposites
AIP Advances, 2011
Poly(o-phenetidine) nanocomposites (PNG) with NiCoFe 2 O 4 and exfoliated graphite have been synthesized via in-situ emulsion polymerization. Systematic investigations reveal that the NiCoFe 2 O 4 nanoparticles (30-40 nm) in the poly(o-phenetidine) matrix have phenomenal effect in determining the electrical, magnetic, and the microwave absorption properties of the nanocomposites. Shielding effectiveness due to absorption (SE A ) value of 32 dB (>99.9%) has been achieved for PNG composite for its use as broadband microwave absorbing material. The microwave absorption of these composites can be attributed to dielectric loss from graphite and poly(ophenetidine) matrix, and magnetic loss from NiCoFe 2 O 4 nanoparticles.
2021
Electrical characteristics of iron coated multi-walled carbon nanotubes (MWNTs) along with ferromagnetic properties are very interesting nanomaterial for microwave absorption. In this research work, surface morphology, compositions and microwave absorption properties of polymer containing iron coated MWNTs have been investigated. Iron coated multi-walled carbon nanotubes composite were prepared by two simple steps method. In addition, microstructure and microwave absorption properties under frequency range 8÷13 GHz by means of FESEM, EDX &Vector network analyzer had shown. The maximum reflection loss is observed for Fe-coated MWNTs/polymer sample B is –20.86 dB and –18.13 dB at frequency 8.1 and 10.75 GHz respectively. And the maximum bandwidth window is available for sample C is 3.25 GHz from frequency 8.45 to 11.7 GHz with 3 mm thickness, which can be attributed to synergistic effect of improved impedance matching characteristic and superior microwave attenuation characteristic of...
Highly conducting composites were derived by selectively localizing multiwall carbon nanotubes (MWNTs) in co-continuous PVDF/ABS (50/50, wt/wt) blends. The electrical percolation threshold was obtained between 0.5 and 1 wt% MWNTs as manifested by a dramatic increase in the electrical conductivity by about six orders of magnitude with respect to the neat blends. In order to further enhance the electrical conductivity of the blends, the MWNTs were modified with amine terminated ionic liquid (IL), which, besides enhancing the interfacial interaction with PVDF, facilitated the formation of a network like structure of MWNTs. This high electrical conductivity of the blends, at a relatively low fraction (1 wt%), was further explored to design materials that can attenuate electromagnetic (EM) radiation. More specifically, to attenuate the EM radiation by absorption, a ferroelectric phase was introduced. To accomplish this, barium titanate (BT) nanoparticles chemically stitched onto graphene oxide (GO) sheets were synthesized and mixed along with MWNTs in the blends. Intriguingly, the total EM shielding effectiveness (SE) was enhanced by ca. 10 dB with respect to the blends with only MWNTs. In addition, the effect of introducing a ferromagnetic phase (Fe 3 O 4) along with IL modified MWNTs was also investigated. This study opens new avenues in designing materials that can attenuate EM radiation by selecting either a ferroelectric (BT–GO) or a ferromagnetic phase (Fe 3 O 4) along with intrinsically conducting nanoparticles (MWNTs).
Microwave Absorption Properties Of Low Density Polyethelene-Cobalt Ferrite Nanocomposite
2015
Low density polyethylene (LDPE) nanocomposites with 3, 5 and 7 wt. % cobalt ferrite (CoFe2O4) nanopowder fabricated with extrusion mixing and followed up by hot press to reach compact samples. The transmission/reflection measurements were carried out with a network analyzer in the frequency range of 8-12 GHz. By increasing the percent of CoFe2O4 nanopowder, reflection loss (S11) increases, while transferring loss (S21) decreases. Reflectivity (R) calculations made using S11 and S21. Increase in percent of CoFe2O4 nanopowder up to 7 wt. % in composite leaded to higher reflectivity amount, and revealed that increasing the percent of CoFe2O4 nanopowder up to 7 wt. % leads to further microwave absorption in 8-12 GHz range.