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The genotoxic effect of microwave radiation on humans is one of the leading causes of some diseases like cancer. Despite many reported materials for microwave absorption, there is still a demand for a super‐thin and flexible microwave absorber. In the present work, we synthesized Fe3O4/graphene/polyaniline/nitrile butadiene rubber composites with a thickness of 0.7 mm using a melt mixing method. Then, we comprehensively studied the electromagnetic and microwave absorption properties of the composites from 8 to 12 GHz. The composite with 38 wt% Fe3O4 and 6 wt% graphene exhibited the highest microwave absorption of more than 8 dB in the entire range of 8–12 GHz, with a minimum reflection loss of −14 dB at 10.3 GHz. By increasing the weight content of Fe3O4 and graphene, the imaginary part of dielectric permeability and magnetic permeability initially went up and then declined, resulting in poor impedance matching. Hence, we precisely controlled the weight content of the fillers to reach the highest impedance matching and attenuation constant. Consequently, this work opened up a unique way for developing super‐thin, lightweight, flexible microwave‐absorbing materials. [ABSTRACT FROM AUTHOR]

In this study, Mg–Mn–Al ferrite with a chemical composition of Mg0.8Mn0.2Al0.1Fe1.9O4 was synthesized via the sol–gel auto-combustion method. The effects of the sintering time and temperature on the magnetic properties and transmission behaviors were investigated in detail. X-ray diffraction (XRD) results revealed that the powders in the as auto-combusted state were in an amorphous state. Moreover, based on the differential thermal analysis (DTA) curve, the calcination temperature was calculated to be ~900 °C. According to the Archimedes equation, the highest density was obtained for the specimen sintered at 1250 °C for 5 h (94% of the theoretical density). In addition, permagraph results revealed the average magnetic properties of the mentioned samples are as follows: Hc = 7.0 Oe and Ms = 1400 G. According to vector network analyzer (VNA) results, the samples with qualified transmission behaviors showed low scattering parameters in a wide range of frequencies. Highlights: Nanocrystalline Mg0.8Mn0.2Al0.1Fe1.9O4 was formed via a sol–gel auto-combustion method. Microstructural, magnetic, and transmission behaviors (TB) were investigated. The maximum density was obtained for the sample sintered at 1250 °C for 5 h (~4.08 g/cm3). The TB of the samples was improved by increasing Ms. The most favorable TB was obtained for the sample sintered at 1250 °C for 5 h. [ABSTRACT FROM AUTHOR]

The ongoing emergence of antibiotic‐resistant bacteria has become one of the biggest threats to global health and development today. Pseudomonas aeruginosa and methicillin‐resistant Staphylococcus aureus (MRSA) are important antibiotic‐resistant bacteria due to their increasing resistance to a broad array of antimicrobial agents. Herein, we developed a novel antibacterial nanocomposite based on chitosan and liquid silicone rubber filled zeolite‐A, Ag, and Cu nanoparticles with remarkable antibacterial activity against P. aeruginosa and MRSA. The antibacterial activity of the nanocomposite was studied by disc diffusion and broth culture methods. Besides, the mechanical properties, wetting behavior, and chemical structure of the present nanocomposite were also investigated. The results exhibited that the inhibition zone diameter of the nanocomposite for P. aeruginosa and MRSA were 40 and 27 mm, respectively. It also took approximately 1 h to inhibit the growth of the tested bacteria. The nanocomposite sample with a thickness of around 1 mm showed an elastic elongation of nearly 49% and a contact angle of roughly 120°. Thus, the present nanocomposite was found to be useful in killing and inhibiting the growth of P. aeruginosa and MRSA, and it could also be qualified as a superior elastic and hydrophobic material. [ABSTRACT FROM AUTHOR]

The possibility of synthesizing MnCo2O4 nanoparticles from MnCl2·4H2O and CoCl2·6H2O via mechanical alloying was investigated and sampled after 1, 2, 3, and 4 h of milling. X-ray diffraction (XRD) analysis showed that the initial materials were changed to MnCo2O4 after 1 h of milling and calcination. The broadening of the XRD lines showed that MnCo2O4 crystallites were on the order of nanometers. Fourier-transform infrared spectroscopy spectra of the MnCo2O4 samples indicated the cation distribution of Co-O (~ 567 cm−1) and Mn-O (~ 665 cm−1) in octahedral and tetrahedral sites, respectively. The morphology of the samples is spherical, according to field emission scanning electron microscopy results. Electrochemical measurements, including cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy, were performed to evaluate specific capacitance, cyclic stability, and charge transfer resistance, respectively. The highest capacitance of about 546 F/g and efficiency of 103% were obtained for the 3-h-milled MnCo2O4 sample. [ABSTRACT FROM AUTHOR]

Core-shell nanostructured magnetic Fe3O4@SiO2 with particle size ranging from 3 nm to 40 nm has been synthesized via a facile precipitation method. Tetraethyl orthosilicate was employed as surfactant to prepare core-shell structures from Fe3O4 nanoparticles synthesized from pomegranate peel extract using a green method. X-ray diffraction analysis, Fourier-transform infrared and ultraviolet-visible (UV-Vis) spectroscopies, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopy were employed to characterize the samples. The prepared Fe3O4 nanoparticles were approximately 12 nm in size, and the thickness of the SiO2 shell was ~ 4 nm. Evaluation of the magnetic properties indicated lower saturation magnetization for Fe3O4@SiO2 powder (~ 11.26 emu/g) compared with Fe3O4 powder (~ 13.30 emu/g), supporting successful wrapping of the Fe3O4 nanoparticles by SiO2. As-prepared powders were deposited on carbon fibers (CFs) using electrophoretic deposition and their electrochemical behavior investigated. The rectangular-shaped cyclic voltagrams of Fe3O4@CF and Fe3O4@C@CF samples indicated electrochemical double-layer capacitor (EDLC) behavior. The higher specific capacitance of 477 F/g for Fe3O4@C@CF (at scan rate of 0.05 V/s in the potential range of − 1.13 to 0.45 V) compared with 205 F/g for Fe3O4@CF (at the same scan rate in the potential range of ~ − 1.04 to 0.24 V) makes the former a superior candidate for use in energy storage applications. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles such as Fe3O4 and γ-Fe2O3 are extensively used in medical application, i.e. drug delivery, MRI, etc. Chemical toxicity and side-effect behaviors always play an important role in such applications. Thus, synthesis of such less-toxic compounds with green technology is privilege. In this study, the extract prepared from mango leaves was used for the preparation of iron oxide nanoparticles (γ-Fe2O3) using FeSO4 as iron source with the green-assisted route. The X-ray diffraction pattern indicated single-phase formation with the average crystallite size of 7 ± 2 nm. HRTEM micrographs indicated a dot-cloud-surrounded like particles ranging from 1 to 12 nm. Fourier Transform Infrared (FT-IR) spectroscopy showed two absorption bands at 457 and 634 cm−1, which are attributed to octahedral and tetrahedral sites of Fe-O band, respectively. A vibrating sample magnetometer (VSM) indicated a saturation magnetization (Ms) value about 53 emu/g with negligible coercivity (Hc), suggesting superparamagnetic behavior of the synthesized nanoparticles. The cytotoxicity was evaluated by exposing the breast cancer cell type (MCF7) to different concentrations of the γ-Fe2O3 nanoparticles. MTT assay results revealed that the growth and survival of MCF7 cells directly depend on the concentration of synthesized iron oxide nanoparticles. It was found that up to concentration of 200 µg/mL, cell survival has not yet reached 50%, which indicates the safety of nanoparticles and lack of toxicity. [ABSTRACT FROM AUTHOR]

Sr-Ca hexaferrite nanopowders with a nominal chemical composition of SrCaFeO, SrCaFeCrO and SrCaLaFeCrO with x = 0, 0.1, 0.3, and 0.5, were synthesized via sol-gel auto combustion method. Structural and phase formation of the samples were evaluated through X-ray diffraction (XRD). The XRD results indicated the Sr-Ca hexaferrites formation with the presence of α-FeO as second phase, after subsequent heat treatment of the synthesized samples at 1030 °C for 2.5 h. By increasing the amount of Ca from x = 0 to x = 0.5, the intensity of second phase (α-FeO) increased. Furthermore, the hexaferrite lattice constant 'c' decreased while the 'a' remained almost constant. Field emission scanning electron microscopy results indicated that the grains shape becomes more needle and spherical like with increasing the X content. By doping Cr at x = 0.5, the grains would vary from needle-like shape to platelet hexagonal. The magnetic behavior of the Sr-Ca hexaferrite samples with and without adding La and Cr ions were studied. The best result was achieved for the nanopowders with a chemical composition of SrCaLaFeCrO with coercivity (H) = 5474.28 Oe, saturation magnetization (M) = 61.16 emu/g and remnant magnetization (M) = 42.57 emu/g. [ABSTRACT FROM AUTHOR]

Soft magnetic materials are widely used in electrical and electronic industries due to their desirable electromagnetic features, i.e. relatively high electrical resistivity and low eddy current loss at high frequencies. From industrial point of view, once the size of grains is reduced to micron scale regimes, their performance is only narrowed to a few megahertz frequencies, due to their higher conductivity and domain wall resonance. Thus, one way to resolve this issue and utilize these materials at high frequency applications, is to reduce the size of grains from micron to sub or nanoscale before they are being compacted for sintering. In this aspect, however, several methods are employed to synthesize these nanoparticles, a mechanical alloying is found to be a proven route to produce a vast variety of materials with both non-equilibrium and equilibrium phases in a controlled size and shape of powder particles at desired tonnages. Mechanical alloying (MA) is a solid-state powder metallurgy route which involves a repeated action of fracturing and re-welding of powder particles in a high-energy ball mill. The final products characteristics are strongly dependent on the variable parameters of the process, i.e. milling time, ball-to-powder weight ratio, rotation speed, grinding media and milling atmosphere. Thus, this work reviews the key role of these parameters on the structure and magnetic behaviors of soft magnetic materials. Eventually, the mechanism of mechanical alloying and effect of diffusivity are also highlighted. [ABSTRACT FROM AUTHOR]

This paper reports a study on the effect of silicon carbide nanoparticles on the adhesion strength of steel–glass/epoxy composite joints bonded with two-part structural acrylic adhesives. The introduction of nanosilicon carbide in the two-part acrylic adhesive led to a remarkable enhancement in the shear and tensile strength of the composite joints. The shear and tensile strengths of the adhesive joints increased with adding the filler content up to 1.5 wt%, after which decreased with adding more filler content. Also, addition of nanoparticles caused a reduction in the peel strength of the joints. DSC analysis revealed thatTgvalues of the adhesives rose with increase in the nanofiller content. The equilibrium water contact angle was decreased for adhesives containing nanoparticles. SEM micrographs revealed that addition of nanoparticles altered the fracture morphology from smooth to rough fracture surfaces. [ABSTRACT FROM AUTHOR]

This paper reports a study on the effect of Al2O3nanoparticles on the adhesion strength of steel-glass/epoxy composite joints bonded by a two-component structural acrylic adhesive. The addition of Al2O3nanoparticles to the two-component acrylic adhesive led to a remarkable enhancement in the shear and tensile strength of the composite joints. The shear and tensile strength of the adhesive joints increased by addition of Al2O3up to 1.5 wt%, which decreased by further addition of the nanofiller. Introduction of the nanoparticles caused a reduction in the peel strength of the joints. DSC analysis revealed that the glass transition temperature (Tg) of the adhesives rose by increasing the nanofiller content. The advancing water contact angle was decreased for adhesives containing nanoparticles. SEM micrographs indicated good dispersions of the Al2O3nanoparticles within the acrylic matrix in the specimens with up to 1.5 wt% Al2O3and revealed that addition of nanoparticles altered the fracture morphology from smooth to rough fracture surfaces. [ABSTRACT FROM AUTHOR]

This article reports a study on the effect of TiO2nanoparticles on the adhesion strength of steel–glass/epoxy composite joints bonded with two-part structural acrylic adhesives. The introduction of nano-TiO2in the two-part acrylic adhesive led to a remarkable enhancement in the shear and tensile strength of the composite joints. The shear and tensile strengths of the adhesive joints increased with adding the filler content up to 3 wt.%, after which it decreased with adding more filler content. Also, addition of nanoparticles caused a reduction in the peel strength of the joints. Differential scanning calorimeter analysis revealed that glass transition temperature (Tg) values of the adhesives rose with increasing the nano-filler content. The equilibrium water contact angle decreased for adhesives containing nanoparticles. Scanning electron microscope micrographs revealed that addition of nanoparticles altered the fracture morphology from smooth to rough fracture surfaces. [ABSTRACT FROM PUBLISHER]

This paper reports a study on the effect of silica nanoparticles on the adhesion strength of steel–glass/epoxy composite joints bonded with two-part structural acrylic adhesives. The introduction of nano-silica in the two-part acrylic adhesive led to a remarkable enhancement in the shear and tensile strength of the composite joints. The shear and tensile strengths of the adhesive joints increased with addition of the filler content up to 1.5 wt%, after which decreased with addition of more filler content. Also, addition of nanoparticles caused a reduction in the peel strength of the joints. Differential scanning calorimeter analysis revealed thatTgvalues of the adhesives rose with increasing the nanofiller content. The equilibrium water contact angle was decreased for adhesives containing nanoparticles. Scanning electron microscope micrographs revealed that addition of nanoparticles altered the fracture morphology from smooth to rough fracture surfaces. [ABSTRACT FROM PUBLISHER]

In the present study, central composite algorithm was used in order to model and optimize the mechanical behavior of "glass fiber reinforced epoxy composite - structural steel "connections. Initial tests showed that the polymer curing variables play a significant role as key process parameters in producing strong and reliable connections. After conducting Thermal Gravimetric Analysis on polymer, by selecting curing time and curing temperature as input variables, the parameters were coded and each of them was studied in five levels. In order to estimate the desirable response and provide appropriate models, thirteen tests were conducted systematically. In order to assess the accuracy and to validate the proposed model, analysis of variance was performed successfully. The effect of curing time and curing temperature on the connection's strength quality was studied utilizing two-dimensional graphs. Utilizing this approach the optimal bonding process variables was achieved at 40°C and 180 min for curing temperature and curing time respectively. Finally, the results obtained from micro structural characterization and fractography analyses of joints by Optical and Scanning Electron Microscope were in good agreement with the results achieved by the developed model. [ABSTRACT FROM AUTHOR]