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The rising concentration of pollutants in the environment due to partially treated or untreated wastewater entering the surface waters has seriously challenged the integrity of the ecosystem and the quality of water for human health. Therefore, it is crucial to establish a productive and economical process to degrade recalcitrant pollutants from various water matrices owing to the ineffectual removal of these contaminants by conventional treatment methods. In this regard, advanced oxidation processes (AOPs), especially photocatalysis, have gained much attention due to their unique properties, such as low-cost, easy synthesis, and ability to produce reactive radicals under light irradiation with complete mineralization of recalcitrant pollutants. In this review, heterogenous photocatalysts, their fundamental properties, and their working mechanism have been described, along with their applications in the degradation of contaminants in water. Recent progress on pristine and modified nanomaterial-based photocatalysts for the degradation of various pollutants in water has been discussed. In particular, the removal of toxic heavy metals, pesticides, dyes, pathogens, pharmaceuticals, and other miscellaneous contaminants from water using a wide variety of nanomaterial-based heterogeneous photocatalysts has been summarized. The effect of temperature, solution pH, and loading of photocatalysts was found to be the most critical factors influencing the photocatalytic degradation of pollutants. Subsequently, the photocatalyst immobilization process using various support materials including carbon-based materials, glass, zeolites, and polymers in designing the efficient photocatalysts and future perspectives have been outlined.

This extensive review article critically overviews the newest research on the performance of a diverse array of EMI shielding materials by opening up an inventive flatland for designing next-generation high-performing EMI shielding materials.

The present study is focused on room-temperature synthesis carried out by reduction of an aqueous silver nitrate (AgNO3) and AgNO3/graphene oxide (GO) dispersion using a low-cost commercial Fehling B solution in one step to form silver quantum dots (Ag QDs) and their Ag/reduced graphene oxide (Ag/RGO) nanocomposites and their characterization. The crystallinity, surface chemistry, structural, and morphological studies indicated the formation of crystalline small-sized quasispherical-functionalized Ag particles distributed uniformly on the surface of RGO. The conductivity measurements further showed an improvement in the conductivity of Ag/RGO nanocomposites as compared to neat Ag QDs. Our findings showed that Ag/RGO nanocomposites prepared by using 0.055 wt % of GO exhibited a total enhanced electromagnetic interference (EMI)-shielding efficiency (SET) of ∼39.2-42.3 dB (2-8 GHz) with a maximum value of ∼43.8 dB at 7. 5 GHz due to conduction loss, an interconnected conducting network, and a synergistic effect, and it followed an absorption mechanism. Furthermore, this superior absorption-dominated shielding conferred reflection loss (RL) in the range of -79 to -82.5 dB with a RL minima of -88 dB at 7.5 GHz, considering an effective absorption bandwidth of ∼6 GHz with 99.9% absorptivity. It is anticipated that Ag/RGO nanocomposites prepared in one step at room temperature could find potential EMI-shielding applications.

Dyes are considered as recalcitrant compounds and are not easily removed through conventional water treatment processes. The present study demonstrated the fabrication of polyaniline hollow microsphere (PNHM)/MnO2/Fe3O4 composites by in situ deposition of MnO2 and Fe3O4 nanoparticles on the surface of PNHM. The physicochemical characteristics and adsorption behavior of the prepared PNHM/MnO2/Fe3O4 composites towards the removal of toxic methyl green (MG) and Congo red (CR) dyes have been investigated. The characterization study revealed the successful synthesis of the prepared PNHM/MnO2/Fe3O4 adsorbent with a high Brunauer-Emmett-Teller (BET) surface area of 191.79 m2/g. The batch adsorption study showed about 88 and 98% adsorption efficiencies for MG and CR dyes, respectively, at an optimum dose of 1 g/L of PNHM/MnO2/Fe3O4 at pH ∼6.75 at room temperature (303 ± 3 K). The adsorption phenomena of MG and CR dyes were well described by the Elovich and pseudo-second-order kinetics, respectively, and Freundlich isotherm model. The thermodynamics study shows that the adsorption reactions were endothermic and spontaneous in nature. The maximum adsorption capacity (Qmax) for MG and CR dyes was observed as 1142.13 and 599.49 mg/g, respectively. The responsible adsorption mechanisms involved in dye removal were electrostatic interaction, ion exchange, and the formation of the covalent bonds. The coexisting ion study revealed that the presence of phosphate co-ion considerably reduced the CR dye removal efficiency. However, the desorption-regeneration study demonstrated the successful reuse of the spent PNHM/MnO2/Fe3O4 material for the adsorption of MG and CR dyes for several cycles. Given the aforementioned findings, the PNHM/MnO2/Fe3O4 nanocomposites could be considered as a promising adsorbent for the remediation of dye-contaminated water.

The presence of microcapacitors near percolatrion threshold determines dielectric permittivity of a material. Motivated by this concept, we focused our work by preferentially allocating functionalized reduced graphene oxide (FRGO) in hard segment (disperse phase) of Thermoplastic polyurethane (TPU) by solution blending method and characterized. Morphological studies of TPU/FRGO nanocomposites established homogeneous dispersion of FRGO throughout the TPU matrix. It is noted that TPU/FRGO (1 phr) nanocomposites exhibit maximum increase in tensile strength (33%) and elongation at break (10%). Thermogravimetric analysis (TGA) showed maximum enhancement in onset of decomposition temperature (~6 °C) in 2 phr FRGO loaded TPU. Differential scanning calorimetry (DSC) analysis showed maximum reduction (~2 °C) in glass transition temperature (Tg) of soft segment of TPU followed by maximum improvements in melting temperature (~4 °C) as well as crystallization temperature (~22 °C) of hard segment compared to neat TPU. Further, a significantly high value of dielectric permittivity (401) is achieved in 1.5 phr loaded FRGO at 100 Hz due to the formation of significantly higher number of microcapacitors near the percolation threshold. It is anticipated that such thermally stable and mechanically strong high dielectric TPU/FRGO nanocomposites can find applications in the field of electronic devices.

The present work is focused on fabrication of reduced graphene oxide/iron(II/III) oxide/polyaniline (RGO/Fe3O4/PANI) ternary composite by a hydrothermal method, its characterization, and application in the development of a high microwave absorbing shielding material. The RGO/Fe3O4/PANI composite showed dramatic enhancement of dielectric loss and magnetic loss compared to Fe3O4/PANI and RGO/Fe3O4 binary composites. This is ascribed to the embedment of more heterostructure phases. As a result, RGO/Fe3O4/PANI showed remarkably high SET (∼28 dB) through the absorption dominant mechanism. Our findings also showed maximum RL of Fe3O4/PANI, RGO/Fe3O4, and RGO/Fe3O4/PANI in the range of 2–8 GHz corresponding to −25 to −35, −40 to −46, and approximately −64 dB, respectively. This is in all probability due to the good impedance matching between permittivity/permeability and dielectric/magnetic losses.

The present work reports on the fabrication of a lightweight microwave absorber comprising MnCo2O4 prepared from the urea complex of manganese (Mn)/cobalt (Co) and nitrogen-doped reduced graphite oxide (NRGO) by facile hydrothermal method followed by annealing process and characterized. The phase analysis, compositional, morphological, magnetic, and conductivity measurements indicated dispersion of paramagnetic MnCo2O4 spherical particles on the surface of NRGO. Our findings also showed that Mn, Co-urea complex, and GO in the weight ratio of 1:4 (NGMC3) exhibited maximum shielding efficiency in the range of 55-38 dB with absorption as an overall dominant shielding mechanism. The reflection loss of NGMC3 was found to be in the range of -90 to -77 dB with minima at -103 dB (at 2.9 GHz). Such outstanding electromagnetic wave absorption performance of NRGO/MnCo2O4 nanocomposite compared to several other metal cobaltates could be attributed to the formation of percolated network assisted electronic polarization, interfacial polarization and associated relaxation losses, conductance loss, dipole polarization and corresponding relaxation loss, impedance matching, and magnetic resonance to some extent.

The acute toxicity and mobility of hexavalent chromium [Cr(VI)] in water and wastewater pose a severe risk to the environment and human health. In view of this, the present work is focused on the fabrication and characterization of polypyrrole–polyaniline coated rice husk ash (termed as PPY–PANI@RHA) by in situ polymerization and its application as an adsorbent in the removal of Cr(VI) from the aqueous solution. Our findings have shown a Cr(VI) removal rate of ∼98% at room temperature (303 K) under optimum conditions with an adsorbent dose of 0.8 g L−1, an adsorbate concentration of 50 mg L−1, a solution pH of ∼2, and a contact time of 300 min. The adsorption of Cr(VI) followed the Elovich kinetics and is better described using the Freundlich isotherm with a maximum adsorption capacity of 769.15 mg g−1. The co-existing ion study result shows that the Cr(VI) removal efficiency is slightly decreased in the presence of high concentrations of Na+, Mg2+, Ca2+, Cl−, HCO3−, NO3−, SO42− and PO43− ions. Thermodynamic investigations have shown that the adsorption phenomenon of Cr(VI) on PPY–PANI@RHA is endothermic, feasible, and spontaneous in nature. Additionally, the reusability study of the spent PPY–PANI@RHA adsorbent indicated its high removal efficiency for several times. Finally, PPY–PANI@RHA was also successfully used to remove Cr(VI) ions from the highly polluted raw tannery wastewater sample. Our findings clearly demonstrated that PPY–PANI-coated rice hush ash could be an alternative as an effective bio adsorbent in the removal of Cr(VI) for wastewater treatment and benefit the industries in the future.

The rapid increase in toxic dye wastewater generated from various industries remains a severe public health issue and prime environmental protection concern, posing a major challenge to existing conventional water treatment systems. Consequently, various physicochemical and biological treatment processes have been studied, which exhibit varying removal abilities depending on their experimental constraints. Among them, adsorption is considered to be the most efficient due to its high removal efficiency, easy operation, cost-effectiveness, and recyclability of the adsorbents. Considering this, the present review article focused on presenting a comprehensive summary of the various types of adsorbents such as commercial activated carbon, metal oxide-based, carbon-based, metal–organic framework, and polymer-based adsorbents used in dye remediation of contaminated water. The effects of several critical factors such as initial dye concentration, solution pH, temperature, and adsorbent dose on the dye adsorption performance are also described. In addition, the adsorption mechanisms responsible for dye removal are explained based on electrostatic attraction, ion exchange, surface complexation, and π–π interactions. Finally, critiques, future perspectives, and a summary of the present article are given. Various adsorbents such as carbon-based materials, metal oxides, bio-adsorbents, and polymer-based materials, have been shown to be efficient for the removal of dye pollutants from wastewater. Thus, it is anticipated that dye removal by adsorption can provide a feasible solution for the treatment of dye-laden water.

Microbial infections originating from medical care facilities are raising serious concerns across the globe. Therefore, nanotechnology-derived nanostructures have been investigated and explored due to their promising characteristics. In view of this, silver-based antimicrobial hydrogels as an alternative to antibiotic-based creams could play a crucial role in combating such infections. Toward this goal, we report a simple method for the synthesis and assembly of silver nanoparticles in a biopolymer physical gel derived from Abroma augusta plant in imparting antimicrobial properties against nosocomial pathogens. Synthesized silver nanoparticles (diameter, 30 ± 10 nm) were uniformly distributed inside the hydrogel. Such synthesized hydrogel assembly of silver nanoparticles dispersed in the biopolymer matrix exhibited hemocompatibility and antimicrobial and antibiofilm characteristics against nosocomial pathogens. The developed hydrogel as a surface coating offers reduced hardness and modulus value, thereby minimizing the brittleness tendency of the gel in the dried state. Hence, we believe that the hierarchical assembly of our hydrogel owing to its functional activity, host toxicity, and stability could possibly be used as an antimicrobial ointment for bacterial infection control.

The present work is focused on room-temperature reduction by subjecting reduction of an aqueous KMnO4 and KMnO4/graphene oxide (GO) dispersion by Fehling solution B in one step to form δ-MnO2, exhi...

Tuning of morphology and the electronic structure through substitution in the crystal lattice can enhance the performance of electrocatalysts. In view of this, the present work is focused on one-st...

Fe3O4@SiO2@PPy core-shell nanocomposites were fabricated by the coating of SiO2 on Fe3O4 through base catalyzed hydrolysis of tetraethyl orthosilicate followed by encapsulation of polypyrrole (PPy). Subsequently, these trilaminar composites have been characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller, superconducting quantum interference devices, and measurement of the total shielding efficiency in the frequency range of 2-8 GHz. Our findings showed the highest total shielding efficiency (∼32 dB) of Fe3O4@SiO2@PPy (Fe3O4@SiO2/pyrrole wt/wt = 1:9) and followed reflection as the dominant shielding mechanism. Such performance was attributed to poor impedance matching between the PPy (conducting)/SiO2 (insulating) and high electrical conductivity of Fe3O4@SiO2@PPy. Alternatively, electromagnetic (EM) waves incident on the SiO2@PPy interface could also account for enhancing the total shielding efficiency of Fe3O4@SiO2@PPy because of multireflection/refraction. Our earlier work also showed excellent total shielding efficiency of Fe3O4@C@PANI nanocomposites, through absorption as the dominant shielding mechanism. These findings clearly suggest that EM interference shielding in Fe3O4@SiO2@PPy and Fe3O4@C@PANI trilaminar core@shell nanocomposites is controlled by tuning of the shells through switching of the mechanism.

Polyaniline hollow microsphere (PNHM)/Fe3O4 magnetic nanocomposites have been synthesized by a novel strategy and characterized. Subsequently, PNHM/Fe3O4-40 (Fe3O4 content: 40 wt.%) was used as an adsorbent for the removal of arsenic (As) from the contaminated water. Our investigations showed 98–99% removal of As(III) and As(V) in the presence of PNHM/Fe3O4-40 following pseudo-second-order kinetics (R2 > 0.97) and equilibrium isotherm data fitting well with Freundlich isotherm (R2 > 0.98). The maximum adsorption capacity of As(III) and As(V) correspond to 28.27 and 83.08 mg g−1, respectively. A probable adsorption mechanism based on X-ray photoelectron spectroscopy analysis was also proposed involving monodentate-mononuclear/bidentate-binuclear As-Fe complex formation via legend exchange. In contrast to NO3− and SO42− ions, the presence of PO43− and CO32− co-ions in contaminated water showed decrease in the adsorption capacity of As(III) due to the competitive adsorption. The regeneration and reusability studies of spent PNHM/Fe3O4-40 adsorbent showed ~83% of As(III) removal in the third adsorption cycle. PNHM/Fe3O4-40 was also found to be very effective in the removal of arsenic (−1) from naturally arsenic-contaminated groundwater sample.

Dyes are considered as recalcitrant compounds and are not easily removed through conventional water treatment processes. The present study demonstrated the fabrication of polyaniline hollow microsphere (PNHM)/MnO

Though investigations have been made on several metal chalcogenides in hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs), antimony sulfide (Sb2S3) has not generated much attention. In this direction, the present work reports on the synthesis of N, Ru codoped pellet drum bundle-like antimony sulfide (Sb2S3) via a simple reflux method. Subsequent HER and HOR electrocatalytic investigations in 1 M KOH revealed their suitability as an efficient and inexpensive alternative to platinum, as is evident from the overpotential (72 mV at a current density of 10 mA cm-2), Tafel slope (193 mV/decade), exchange current density (1.42 mA/cm2), and breakdown potential at ∼0.6 V vs RHE, respectively. Such remarkable HER and HOR performance of N, Ru codoped Sb2S3 could be ascribed to the presence of relatively larger active sites compared to Sb2S3 and N-doped Sb2S3 individually due to synergistic effects arising from N and Ru dopants. Further, N, Ru codoped Sb2S3 demonstrated high intrinsic catalytic activity as indicated by its turnover frequency (2.03 s-1) and current loss, corresponding to 35% after 10 h of continuous amperometric i-t operation. Alternatively, such excellent catalytic performance of N, Ru codoped Sb2S3 arises due to geometric lattice defects with surface oxygen vacancy, and the availability of abundant edges and its pellet drum-like morphology also cannot be overruled.

The present work is focused on the synthesis of bismuth sulfide (Bi2S3) nanorod/reduced graphene oxide (RGO) composites via a one-step hydrothermal method using GO and bismuth nitrate in 5 : 1, 3 : 1 and 2 : 1 weight ratios and their characterization. The morphological studies revealed the formation of homogeneously dispersed Bi2S3 nanorods on RGO sheets along with occasional wrapping in the Bi2S3 nanorod/RGO (3 : 1) composite. XRD, FTIR, Raman and XPS studies suggested the incorporation of Bi2S3 in RGO sheets. The galvanostatic charge–discharge measurements showed that the Bi2S3 nanorod/RGO (3 : 1) composite exhibited the highest specific capacitance (1932 F g−1) at 1 A g−1 in the presence of 2 M aqueous KOH in a three-electrode cell. This is ascribed to the enhanced contact area between metal sulfide nanoparticles and RGO, increased conductivity and synergistic effect of Bi2S3 and RGO. The optimized Bi2S3 nanorod/RGO (3 : 1) composite also maintained an excellent cycling stability with ∼100% capacitance retention after 700 cycles. It is noted that the supercapacitor performance of the Bi2S3 nanorod/RGO (3 : 1) composite was better than group V and VI metal chalcogenides and their nanocomposites reported in several previous studies.

The electromagnetic interference shielding effectiveness (EMI SE) of amorphous and annealed melt-spun ribbons having typical composition of Co72.5Si12.5B15, (Fe0.65Co0.35)83Si1.3B11.7Nb3Cu1, Fe80Si8B12 and Fe83Si2B13Nb2 were studied in the 0.2–8.5 GHz microwave range. The amorphous nature of the as-quenched ribbons was confirmed by X-ray diffraction patterns and differential scanning calorimetry (DSC). The flexible electromagnetic wave absorber ribbons of CoSiB, FeSiB, and FeCoSiBNbCu based alloys exhibit ∼99.99% attenuation of electromagnetic waves in the entire 0.2–8.5 GHz (L, S and C-band) range. Both as-quenched and annealed amorphous ribbons of Co72.5Si12.5B15 and Fe80Si8B12 are electromagnetically active and total electromagnetic shielding effectiveness (SET) of ribbons found to be ∼36 dB, ∼34 dB throughout the test range. The EMI shielding properties deteriorates for FeCoSiBNbCu and FeSiBNb based nanocomposite ribbons achieved by in-situ crystallization annealing. The electromagnetic shielding of magnetic ribbons is effected mainly by absorption mechanism due to high electrical resistivity and magnetic permeability. The CoSiB and FeSiB melt-spun ribbons can be a potential magnetic filler for military and stealth applications in L, S and C-band range.

To understand the effect of nitrogen doping in hard carbon as anode for sodium ion battery, experimental and theoretical study have been done. To also see the size effect along with nitrogen doping, four varieties of carbon spheres are synthesized of two different size ranges viz. micron and nano-sized. Two of these spheres are nitrogen-doped, while the other two are un-doped. Nitrogen doping enhances the electrochemical performance of carbon spheres and increases the active storage sites by enhancing the number of defects and porosity. It further improves electrochemical performance by increasing electrical conductivity and controlling volume expansion. The density functional theory (DFT) study shows significant reduction in expansion associated with sodiation, i.e., from 21.7% to 7.9% because of nitrogen doping. After nitrogen doping, micron and nano-sized carbon spheres show an increase in capacity by 38.6% and 39.5%, respectively. Among these four electrodes, nitrogen-doped nano carbon spheres (NNCS) give the best performance. NNCS shows first reversible capacity of 286 mAh g−1, retains 85% of the capacity till 200 cycles at a current density of 30 mAg−1. This increase in electrical conductivity, defects, porosity, and reduction in volume expansion in nitrogen-doped carbon samples makes them an excellent material for sodium ion batteries.

Herein, Fe3O4 nano-particles are anchored over nitrogen doped reduced graphene oxide (Fe3O4@N-rGO) structure to accommodate electric and magnetic components, so that it could match both the conduction and polarization loss to augment the attenuation of electromagnetic radiation. The formation of condensed heteroaromatic structure and decoration of Fe3O4 particles on r-GO structure are confirmed by photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD). The Fe3O4@N-rGO hybrid is subsequently dispersed in epoxy matrix, which result in significantly higher electrical conductivity (1.31 s/m) and electromagnetic interference (EMI) shielding efficiency (−26 dB at 1 mm thickness). It was assumed that presence of electric-magnetic integrated Fe3O4@N-rGO hybrid in epoxy matrix significantly improved the interfacial polarization and anisotropy energy, which was reflected in absorption loss value of −27 dB. The composites also exhibited enhanced mechanical and thermo-mechanical properties coupled with improved thermal stability.

ZrO2/MWCNT nanocomposites have been prepared by simple refluxing method and characterized by X-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FTIR), and Raman analysis suggests chemical interactions present between zirconia and Multiwalled carbon nanotube (MWCNT) in the as prepared nanocomposites. Electromagnetic inteference shielding efficiencies (EMI SE) for the nanocomposites were found to increase with increasing amount of MWCNT loading. Highest EMI SE value of 29.1–30.5 dB was obtained for nanocomposite containing 15 wt% loading of MWCNT in the microwave frequency range of 2–8 GHz. This optimum performance is due to several factors like highest percentage of intermolecular H-bonding, highly defective, interconnected network structure, high conductivity and dielectric permittivities of the nanocomposites.

The evolution of high electromagnetic absorption materials is essential in the fast growing electronic industry in overcoming electromagnetic pollution. In view of this, a series of Ni nanoparticle-decorated functionalized graphene sheets (FG/Ni) are synthesized by a solvothermal method using different ratios of FG/Ni precursors. Subsequently, FG/Ni is subjected to in situ polymerization of aniline to form FG/Ni/PANI ternary composites and characterized. The total electromagnetic interference shielding efficiency (SET) measurements on FG/Ni/PANI with an optimized FG/Ni ratio (50 mg:600 mg NiCl2·6H2O) exhibit enhanced performance, i.e., ∼47-65 dB (2-3.8 GHz) and ∼65-45 dB (3.8-8 GHz), following absorption as the dominant mechanism due to the matching of dielectric loss and magnetic loss. It is anticipated that such excellent performance of robust FG/Ni/PANI ternary composites at a very low thickness (0.5 mm) has great potential in the application of microwave-absorbing materials.

The present work is focused on the fabrication of manganese dioxide/carbon dots (MnO2/CDs) nanocomposites at room temperature in situ co-participation method in an aqueous medium and characterized. Our study showed that the concentration of CDs controls the morphology of MnO2/CDs nanocomposite and also acted as a reducing agent to convert potassium permanganate (KMnO4) to MnO2. Subsequently, nanoflowers, quasi-spherical particles, broken, and interconnected chain type of morphology was observed by adding dispersion of 0.5, 1.0, 1.5, and 2.0 ml CDs in acetone to 1 mmol KMnO4 aqueous solution in the corresponding MnO2/CDs-0.5, MnO2/CDs-1.0, MnO2/CDs-1.5, and MnO2/CDs-2.0 composites, respectively. A plausible mechanism on the transformation of morphology of MnO2/CDs with CDs concentration is also provided. Further, the present work also focused for the first time on the application in the electromagnetic interference (EMI) shielding of MnO2/CD nanocomposites due to the high dielectric and conductivity. Interestingly, MnO2/CDs-2.0 (nanochains) exhibited the highest total EMI shielding efficiency (SET) of ~39.4 dB following reflection as dominant shielding mechanism due to the high aspect ratio, highest conductivity, high dielectric loss, and impendence mismatch.

Here, we report the synthesis and physical properties of Co2FeGe (CFG) Heusler alloy (HA) nanoparticles (NPs). The NPs of size 23 nm are prepared using the co-precipitation method. X-ray and selected area electron diffraction patterns have confirmed the cubic Heusler phase of the NPs with the A2-disorder. These NPs are soft ferromagnetic, and exhibit a high saturation magnetization (Ms) along with a very high Curie temperature (Tc) of 1060 K. The observed Tc value matches closely with the theoretically calculated one following a model provided by Wurmehl et al. [1]. The high Ms and Tc make the present system a potential candidate for magnetically activated nano-devices working at high temperatures. The near-integral value 5.9 mehoB/f.u. of Ms at low temperatures indicates that the half-metallic ferromagnetism is preserved even in the particles even on the 20 nm length scale. Additionally, we have facilitated the existing HA-NP preparation method, which can be used in synthesizing other HA-NPs. The first-principles density functional theory computations complement the experimental results., 26 pages, 8 figures, 3 tables

The present work reports on the fabrication of a lightweight microwave absorber comprising MnCo

The lightweight high-performing materials are high in demand in protecting electronic circuits from the electromagnetic (EM) radiation/mechanical damage. In view of this, present article reviews’ research focuses on general importance of electromagnetic interference (EMI) shielding, different mechanism and various theoretical aspects related to the measurement of EMI shielding. The modification of textile (woven and nonwoven) fabrics materials with intrinsically conductive polymers (ICPs) and metallic electro-conductive textiles are reportedly used in EMI shielding and accordingly reviewed in this chapter. In addition, performance of different shielding materials fabricated by combining ICPs with metals and alloys are also reviewed. Finally, recent developments on nanocomposites of ICP and magnetic/dielectric/conducting materials used as shielding materials are also provided.

Spherical nanoparticles (NPs) of size 14 nm, made of intermetallic Fe2CoAl (FCA) Heusler alloy, are synthesized via the co-precipitation and thermal deoxidization method. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns confirm that the present nanoalloy is crystallized in A2-disordered cubic Heusler structure. Magnetic field (H) and temperature (T) dependent magnetization (M) results reveal that the NPs are soft ferromagnetic (FM) with high saturation magnetization (Ms) and Curie temperature (Tc). Fe2CoAl nanoalloy does not follow the Slater Pauling (SP) rule, possibly because of the disorder present in the system. We also investigate its magnetic phase transition (MPT) and magnetocaloric (MC) properties. The peak value of the magnetic entropy change vs T curve at a magnetic field change of 20 kOe corresponds to about 2.65 J/kg-K, and the observed value of refrigeration capacity (RCP) is as large as 44 J/kg, suggesting a large heat conversion in magnetic refrigeration cycle. The Arrott plot and the nature of the universal curve accomplish that the FM to paramagnetic (PM) phase transition in Fe2CoAl nanoalloy is of second-order. The present study suggests that the Fe2CoAl nanoscale system is proficient, useful and a good candidate for the spintronics application and opens up a window for further research on full-Heusler based magnetic refrigerants., Comment: 25 pages, 9 figures, 2 tables

This study is focused on the preparation of the CuS/RGO nanocomposite via the hydrothermal method using GO and Cu-DTO complex as precursors. X-ray diffraction, Fourier-transform infrared spectroscopy, and Raman and X-ray photoelectron spectroscopy study revealed the formation of the CuS/RGO nanocomposite with improved crystallinity, defective nanostructure, and the presence of the residual functional group in the RGO sheet. The morphological study displayed the transformation of CuS from nanowire to quantum dots with the incorporation of RGO. The galvanostatic charge/discharge curve showed that the CuS/RGO nanocomposite (12 wt % Cu-DTO complex) has tremendous and outperforming specific capacitance of 3058 F g-1 at 1 A g-1 current density with moderate cycling stability (∼60.3% after 1000 cycles at 10 A g-1). The as-prepared nanocomposite revealed excellent improvement in specific capacitance, cycling stability, Warburg impedance, and interfacial charge transfer resistance compared to neat CuS. The fabricated nanocomposites were also investigated for their bulk DC electrical conductivity and EMI shielding ability. It was observed that the CuS/RGO nanocomposite (9 wt % Cu-DTO) exhibited a total electromagnetic shielding efficiency of 64 dB at 2.3 GHz following absorption as a dominant shielding mechanism. Such a performance is ascribed to the presence of interconnected networks and synergistic effects.

Inthe current work, we reported the in situ fabrication of a nickel vanadate (Ni3V2O8)-anchored N-doped reduced graphene oxide (NRGO) hybrid by a simple one-step reflux method. Subsequently, the electrocatalytic performance of the Ni3V2O8/NRGO hybrid was investigated in an alkaline medium (1.0 M KOH) for the hydrogen evolution reaction (HER). It was noted that the optimization of the NRGO content (∼5.6 wt%) highly influenced the homogeneous distribution of quasi-spherical Ni3V2O8 nanoparticles over NRGO sheets and enhanced the water reduction ability. This hybrid material exhibited a sufficiently high electrochemical active surface area (517.5 cm2) and remarkably low charge transfer resistance (∼1.6 Ω). Furthermore, the very low overpotential (∼43 mV) and the high exchange current density (∼1.24 mA cm−2) of Ni3V2O8/NRGO (5.6 wt%) demonstrated its promising HER performance. Additionally, superior long-term and accelerated stability compared to that of the benchmark Pt/C in a strong basic medium clearly signified that Ni3V2O8/NRGO (5.6 wt%) can act as an efficient, cost-effective, and durable electrocatalyst for water electrolyzers.

Tuning of the defect is critical for specific application of a material worth exploring and researching. In view of this, additional defects have been incorporated in single-walled carbon nanotubes...

Successful utilization of natural anionic clays like montmorillonite and hectorite for the homogeneous dispersion of multiwalled carbon nanotubes (MWCNTs) in ethylene-co-vinyl acetate (EVA), motivated us to investigate the role of magnesium aluminium layered double hydroxide (MgAl-LDH) in a similar role. MWCNT/MgAl-LDH 3D hybrid filler (HML) was prepared from the unmodified constituents in 1:1 wt. ratio by simple dry grinding method. The dispersion of this hybrid filler with extraordinary stability was subsequently used in the preparation of EVA/HML nanocomposites by solution intercalation method. Analysis shows MWCNTs to be homogeneously dispersed in the polymer matrix in presence of LDH layers. Reinforcing efficiency of HML in EVA matrix was evaluated through detailed studies of the nanocomposites. Mechanical, thermal and dielectric properties of neat EVA are substantially improved with HML content. Maximum improvement observed in tensile strength, elongation at break and toughness are 182%, 87%, and 300% respectively at 4 wt% HML. However, best dielectric response with ~400 and ~89 times enhancement in AC conductivity and dielectric constant are observed 1 wt% HML content. Comparison of HML with previously reported MWCNT/montmorillonite (MMT) and MWCNT/hectorite 3D hybrid fillers confirms superior reinforcing efficiency of the former. Improvements in properties are attributed to homogeneous dispersion of fillers and improved polymer-filler interaction on account of synergy between MWCNTs and LDH.

Clay-assisted dispersion of MWCNT has emerged as a novel alternative to its conventional modification. The report deals with preparation of MWCNT/hectorite hybrid (HMH) by dry grinding method and i...

Boron based solid fuels have remained attractive for solid fuel ducted rocket (SFDR) applications since long due to their potential to release high energy on combustion. However, boron's energetic potential has not been successfully harnessed even till date in any practical combustion system. In view of this, present investigation is focused on utilizing boron nanoparticles embedded in paraffin-wax in various proportions (5–20% by weight) as solid fuel. To evaluate its performance an opposed flow burner (OFB) is used in presence of gaseous oxygen (GOX) and the oxidizer mass flux (Gox) varies from 5 to 30 kg/m2 s to estimate its regression rates relative to paraffin-wax. Burning process of boron loaded samples was captured using a high-speed camera to understand the ejection trajectory of the particles/agglomerates. Further, different material characterization techniques were employed on the pre- and post-burnt samples to understand the chemical and morphological changes and interlink that with overall burning characteristics. The active boron content determined from thermogravimetric analysis of pre-burnt sample, ejected agglomerates and post-burnt residue were 78.8, 34 and 18.7% respectively which confirm the combustion of boron nanoparticles up to a significant extent in the present OFB configuration. The present study may be helpful in futuristic application of hybrid propellant-based gas generator for SFDR systems.

Tin oxide thin films were uniformly deposited by successive ionic layer adsorption reaction (SILAR) method on glass substrates using ethylene diamine as a complexing agent. The proper annealing treatment in air converts as-deposited amorphous films into crystalline and removes defects, reducing strain in the crystal lattice. The films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared (FTIR) spectroscopy. The film shows good optical transparency in the range of 200-1000 nm wavelength and electrical resistivity decreases upon annealing.

Currently, transition metal disulfides are used as promising non-noble metal-based electrocatalysts for the hydrogen evolution reaction (HER) from water splitting in quest for alternative renewable and clean energy sources. In view of this, the present study reports the fabrication of N and P co-doped exfoliated tungsten disulphide (PNEWS2) as a superior electrocatalyst for HER. The high performance of PNEWS2 imparts a significantly low potential (59 mV), which corresponds to a geometrical current density of 10 mA cm−2 and Tafel slope of 35 mV per decade. This could be attributed to the presence of highly active sites in the exfoliated single-layered porous 1T-WS2 network and synergistic effect of N and P doping. Furthermore, evaluation of durability tests suggested excellent stability of the PNEWS2 catalyst. Our multifaceted strategy for the formation of a flake-like 1T (metallic) phase with expanded interlayer spacings in the PNEWS2 catalyst compared with that in WS2 results in an increase in S active edges and presence of sulphur vacancies, facilitating extremely high electrochemically active surface area (Cdl = 37.1 mF cm−2) and high turnover frequency (0.791 s−1). Furthermore, the downshift in the d band, high lifetime (0.239 ms) and low Gibbs free energy (−0.26 eV) of PNEWS2 account for its excellent mass transport properties. We also established that the electrochemical performance of PNEWS2 is not associated with the dissolution/redeposition of platinum from the counter electrode (Pt). In summary, the superior performance of the nonprecious, promising N–P-co-doped WS2 provides an alternative substitute for Pt-based electrocatalysts.

Fabrication of rubber blends (EPDM, NBR, and NR) with the polystyrene (PS)-polyaniline (PANI) core-shell (PS@PANI) approach are reported for the first time, and their performance is compared with similar blends prepared by simple individual mixing of PS, PANI, and rubber under identical conditions. It is noted that the unique core-shell morphology accounted for its high surface to volume ratio, leading to the homogeneous dispersion of polyaniline shell and the slow release of polystyrene core into rubber matrix as established by high-resolution transmission electron microscopy. Fourier transform infrared studies show that property enhancement of rubber blends is not significantly affected by the interaction between respective blend components. Conductivity of core-shell rubber blends is found to be relatively higher due to the presence of the interconnected conducting network of PS@PANI within the rubber matrix. These rubber blends also exhibit superior mechanical and thermal properties due to dispersion and slow release of polystyrene core from the polyaniline shell. Electromagnetic interference (EMI) shielding analysis indicated the high shielding efficiency of rubber/PS@PANI blends (∼30 dB: 1–8 GHz) compared to the blends prepared individually from PS, PANI, and rubber (∼18 dB: 1–8 GHz). Such high performance of rubber blends is attributed to the trapping of electromagnetic waves through enhanced internal reflection due to the typical core-shell morphology of PS@PANI. It is anticipated that such low cost, light weight, corrosion resistant and environmentally stable sheets of PS@PANI rubber blends could provide an effective alternative as EMI shielding material for commercial application purposes.

The present work reports fabrication of trilaminar core–shell composites of Fe3O4@C@PANI as efficient lightweight electromagnetic wave absorber by facile hydrothermal method and subsequent high-temperature calcination followed by its encapsulation through oxidative polymerization of aniline. The prepared composite structure was characterized by FTIR, XRD, XPS, TEM, HRTEM, and SQUID. The measurement of reflection loss, complex permittivity, complex permeability, and total shielding efficiency of the composites has been carried out in the frequency range of 2–8 GHz. Our findings showed lowest reflection loss (∼33 dB) in composite comprised of Fe3O4@C:aniline (1:9 wt/wt) corresponding to shielding efficiency predominantly due to absorption (∼47 dB) than reflection (∼15 dB). Such high value of shielding efficiency could be ascribed to the presence of dual interfaces and dielectric–magnetic integration in Fe3O4@C@PANI. In all probability, higher dielectric loss through interface polarization and relaxation eff...

Additional defects inclusion in the form of rehybridization, twisted kinks, and fragmentation has been achieved in MWCNTs fabricated through a unique camphor mediated combustion and sublimation approach. The significant defects induced in MWCNTs through combustion of camphor are unambiguously evidenced by their superior fluorescence quenching efficiency.

We report a study on the competition between soft ferromagnetism (FM) and enhanced Pauli paramagnetism (PM) in Ce(Fe 1− x Ni x ) 2 ( x =0.0, 0.5, 0.8) compounds under doping. We provide convincing experimental evidence for the occurrence of a ferromagnetic (FM) phase and a paramagnetic (PM) phase at different concentrations. The quality of the samples was established by X-ray diffraction and X-ray photoelectron spectroscopy. Quantification of f - d hybridization was made from high-resolution X-ray photoelectron spectroscopy. A proportionality was found between ‘ x ' dependencies of fall of f - d hybridization strength and magnetic order. A prediction that a quantum critical point may exist at a nickel concentration x close to 0.69 can be made from the extrapolation of x dependent Curie temperature (T c ) plot.