In view of their immensely intriguing properties, 2D materials are being intensely researched in search of novel phenomena and diverse application interests; however, studies on the realization of 2D/2D nanocomposites in the application-worthy thin film platform are rare. Here we have grown MoS2-hBN 2D/2D composite thin films on different substrates by the pulsed laser deposition (PLD) technique and made comparative studies with the pristine MoS2 and hBN films. The Raman and x-ray photoelectron spectroscopy (XPS) techniques as well as high-resolution transmission electron microscopy (HRTEM) confirm the concomitant presence of both the 1T (conducting) and 2H (semiconducting) polymorphs of MoS2 in the composite film. Interestingly, a peculiar reentrant semiconductor-metal-insulator transition is seen in the MoS2-hBN 2D/2D composite film which is absent in the MoS2 film, and it correlates well with the signatures of phonon softening seen in temperature dependent Raman spectroscopy. Furthermore, electrostatic force microscopy (EFM) reveals the presence of three distinct regions (metallic, semiconducting and insulating) in the MoS2-hBN composite film with differing contact potentials and enhanced propensity for charge transfer with respect to pristine MoS2. A triboelectric nanogenerator (TENG)device containing biphasic MoS2-hBN composite film as an electron acceptor exhibits more than two-fold (six-fold) enhancement in peak-to-peak output voltage as compared to the pristine MoS2 2 (hBN) film. These observations bring out the potential of 2D/2D nanocomposite thin films for unfolding emergent phenomena and technological applications.
Research on electromagnetic interference (EMI) shielding materials has become very important as one looks for polymer composites as EMI shielding paints and coatings. EMI Shielding is mainly dependent on absorption and reflection losses, which in turn depend on conductivity, permittivity and permeability of the material. In the present work, we have tried to use the properties of graphene to improve EMI shielding and absorbing properties of the polymer composite. The work is focussed on two aspects of the materials; firstly, to developed an EMI shielding paint which can be used as coating and secondly, development of such paint which has absorption as the dominant mechanism of shielding. Reduced graphene oxide(rGO) has been conjugated with ferromagnetic nanostructures. Absorption of up to ∼12 dB for composite of rGOFe 3 O 4 and ∼18 dB for the composite of rGONi was observed, which is more than 99% of the total radiation and hence, can be useful for commercial applications.
To improve electromagnetic (EM) wave
attenuation and its absorption
properties, herein, for the first time, we grow needle-like magnetic
NiCo2O4 nanoparticles in situ on lightweight
open cell reticulated vitreous carbon (RVC) foam by the hydrothermal
method, leading to hierarchically nanostructured foam. The foam was
synthesized by the carbonization of flexible polyurethane foam followed
by acid treatment. The coating structure, stability, and performance
were systematically investigated by various complementary techniques
using XRD, XPS, Raman, and FTIR spectroscopies, compression test,
and ultrasonication. The foam coated for 12 h exhibited considerably
improved shielding effectiveness (SE), i.e., ∼36 dB from ∼23
dB for the bare RVC foam in the X-band, leading to ∼99.97%
shielding efficiency. Although the foams mainly showed reflection-dominated
properties regardless of the coating, the EM absorption improved with
coating. The shielding mechanism is explained by means of reflection
and absorption coefficients and dielectric and magnetic losses manifested
by NiCo2O4 coating and interfacial polarization.
Composite materials made of polymers and carbon‐based ferromagnetic filler are attractive for electromagnetic interference shielding through a combination of reflection and microwave absorption. It is possible to enhance their shielding properties by controlling electrical conductivity, dielectric, and magnetic properties. In this work, the aforementioned properties are tailored to achieve optically transparent films with microwave absorbing properties. Nanocarbon materials, namely carbon nanotubes, graphene nanoribbons (GNR) and their ferromagnetic nanocomposites with Fe3O4 and cobalt in PVA‐PEDOT:PSS matrix were made and tested in X‐band. The highest shielding effectiveness for PVA films with nanocarbon filler was observed for 0.5 wt% GNR − Fe3O4 at 16.36 dB (9.7 GHz) with 79.8% transmittance.
The magnetic properties of the metal nanoparticles (NPs) can play remarkable role in electromagnetic interference shielding (EMI Shielding) of many defence and commercial electronic devices. In the present work, coconut oil and PVA capped magnetic cobalt/cobalt oxide nanoparticles (Co/Co3O4
NPs) were synthesized by chemical reduction method and impregnated in polymer matrix to verify their EMI shielding behaviour. The coconut oil capped Co/Co3O4 NPs with presence of hcp and fcc phases were prepared in the size domain of 7–10 nm and the effect of surfactant
(the oil) on size and oxidation state was studied by varying the ratios. The shielding efficiencies of Co/Co3O4 NPs PVA nanocomposites were analysed by using vector network analyser (VNA) in X- and Ku-band ranging from 8 GHz–18 GHz. The VNA results showed
increased shielding efficiency with increasing concentration of NPs.
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