Sharif Digital Repository

In this study, a novel idea was utilized for designing high performance bilayer absorber for X-band frequency. The microwave dissipation features of the bilayer structure absorbers with one-layer bare resin epoxy and the other epoxy resin filled with [CaTiO3/ZnFe2O4]@C nanocomposite as lossy filler were simulated with CST studio suite within 2–18 GHz. The lossy filler was successfully developed via chemical method. In the first step two distinct single layer absorbers of bare resin epoxy and resin epoxy filled with [CaTiO3/ZnFe2O4]@C nanocomposite ([CT/ZF]@C) were prepared and in the second step the measured electromagnetic parameters were considered as input data of CST studio suite for... 

In this study, ternary MWCNTs/CoFe2O4/FeCo nanocomposite coated with conductive PEDOT-polyaniline (PA@MW/F/C) co-polymers were synthesized by microwave-assisted sol-gel followed in-situ polymerization methods. The phases, crystal structures, morphologies, magnetic and electromagnetic features of the as-prepared samples were identified via XRD, SEM, XPS, VSM, and VNA respectively. Absorption characteristics were investigated in the frequency (12–18 GHz) Ku band. XRD, VSM and SEM analysis confirmed the partial reduction process of CoFe2O4 and successfully decorated magneto-dielectric particles with co-polymers. By measuring electromagnetic features of the samples, it was found that coating... 

Herein, two distinct nanocomposites of CaTiO3 micro-cubes and polygonal SrFe12O19, both decorated with NiO nanoparticles, were successfully synthesized using hydrothermal method. The physico-chemical features of as-prepared samples were evaluated via XRD, FTIR, UV–vis, BET, XPS, FESEM and EDS analysis. Microwave attenuation features of as-prepared single layer absorbers were determined by VNA analysis in 2–18 GHz. Simulation confirmation was checked by preparing a bi-layer samples and evaluating it using VNA analysis after finding the appropriate thickness of each layer. The reflection loss from each single layer samples containing 20 wt% of each CaTiO3/NiO and SrFe12O19/NiO nanocomposites... 

In this study, a novel double-layer microwave absorber was designed based on the MWCNTs/La0.6Sr0.4Mn0.5Fe0.5O4 (C/LSMFO) and PEDOT-coated (P@[C/LSMFO]) nanocomposites. Co-precipitation and in-situ polymerization methods were utilized to synthesize the C/LSMFO and P@[C/LSMFO] nanocomposites, respectively. XRD, FESEM, VSM, and VNA analysis were used to determine the structural, morphological, magnetic, and electromagnetic properties of the nanocomposites. Single-layer absorbers with thicknesses of 1, 1.5, and 2 mm were fabricated, and electromagnetic parameters were evaluated via VNA in the X-band frequency. Moreover, the microwave absorbing features of the double-layer absorber with various... 

Oxidative cyanation of sp3C–H bonds at the α position of amines was achieved using CoCuFe2O4 as a catalyst and NaCN as an inexpensive cyanide source at room temperature. CoCuFe2O4 was found to be an active catalyst for Csp [3]-Csp coupling, efficiently delivering valuable α-aminonitriles from tertiary/secondary amines in good yields. The corresponding products were obtained with high selectivity toward α position. In addition, functional group tolerance offered the opportunity for application in late-stage functionalization of biologically active molecules. This transformation proceeds convenient on a gram-scale, and the catalyst can be reused for several runs with consistent catalytic... 

In this work, cycling-induced aging occurring in 18650-type LiFePO4/graphite full cells at different C-rates is studied extensively. The mechanism of performance degradation is investigated using a combination of electrochemical and microstructural analyses. Half-cell studies are carried out after dismantling the full cells, using fresh and cycled LiFePO4 cathode and graphite anode to independently study them. The results show that the capacity of LiFePO4 electrodes is significantly recovered. The rate of capacity fading in the discharge state considered as irreversible capacity in the graphite is higher than LiFePO4 half cells, indicating a greater degradation in the performance of this... 

The influence of indium on the properties of Cu0.5Zn0.5Fe2O4 nano ferrites synthesized by sol–gel auto-combustion technique was studied. X-ray diffraction (XRD) analysis demonstrated that pure and substituted ferrites possessed cubic spinel structure. The lattice parameter increases with the inclusion of In3+ for x ≤ 0.16 and decreases subsequently. A linear decrease in crystallite size was found as concentration of indium increased. X-ray density, strain, and dislocation density were increased as indium content increases. Hopping lengths as well as radii of A and B sites revealed increasing behavior up to x = 0.16 and decreased thereafter. The spectral bands indicated the formation of... 

It's still a significant difficulty to find microwave absorbers that have outstanding microwave dissipation performance in hostile environments. Herein, the core–shell structure of polyindole-PANI co-polymer@BiFeO3 nanocomposite is successfully prepared via in-situ polymerization method. The introduction of a co-polymer shell on the surface of magnetic BiFeO3 nanoparticles considerably tuned the attenuation constant and impedance matching characteristics. The electromagnetic characteristics and microwave absorption feature of the polyindole-PANI co-polymer@BiFeO3 nanocomposites may be found to be influenced by filler loading content regulation. The sample containing 40 wt% of polyindole-PANI... 

Hydrothermal and in-situ polymerization methods were used to successfully fabricate a pompon flower-like CoGd0.5Fe1.5O4 (CG) as a magnetic component and a cauliflower-like poly(indole-co-Py) (PP) co-polymer as a dielectric component for microwave absorption. The physico-chemical properties of CG/PP samples were determined via XPS, XRD, FTIR, BET, UV–vis, EDS, and FESEM analysis. VNA and VSM were used to evaluate the dielectric and electromagnetic properties of the CG and PP samples. The results of the absorption capability tests revealed that bi-layer samples outperformed single layer samples in terms of microwave dissipation capability. The thickness and arrangement of each layer in bilayer... 

The influence of indium on the properties of Cu0.5Zn0.5Fe2O4 nano ferrites synthesized by sol–gel auto-combustion technique was studied. X-ray diffraction (XRD) analysis demonstrated that pure and substituted ferrites possessed cubic spinel structure. The lattice parameter increases with the inclusion of In3+ for x ≤ 0.16 and decreases subsequently. A linear decrease in crystallite size was found as concentration of indium increased. X-ray density, strain, and dislocation density were increased as indium content increases. Hopping lengths as well as radii of A and B sites revealed increasing behavior up to x = 0.16 and decreased thereafter. The spectral bands indicated the formation of... 

The effect of bisulfite (HSO3–) in nCaO2/Fe(III)/HSO3– system on improving HO• generation and trichloroethene (TCE) removal was innovatively reported. The enhancement mechanism of HSO3– for TCE removal in nCaO2/Fe(III)/HSO3– system was caused not only by the complexing and reducing effects on promoting the conversion of Fe(III) to Fe(II), but also due to the reaction with O2 in water to produce SO4–• for accelerating TCE degradation. A double effect of nCaO2 as an oxidant source to generate HO• and as a O2 source to promote SO4–• generation was revealed. A pseudo-second-order kinetic model of TCE removal was determined and 94.6% TCE degradation was achieved within 60 min at the... 

The crystal and electronic structures of normal phase of Ba1-xKxFe2As2 for x = 0.0, 0.5 and 1.0 have been studied by using pseudopotential Quantum Espresso code based on ab-initio density functional theory. Effects of K doping on the crystal structure and lattice parameters have been calculated and compared with the experimental and computational reported data for similar compounds. The metal-metal bonding scenario was used to explain the changes of lattice parameters by K doping. The electronic structure of this system including of density of states and band structure have been calculated and investigated by K doping. One of the interesting results is that a larger peak is appeared near the... 

In this study, electrolytic plasma processing (EPP) was employed for surface nitrocarburizing of AISI 1020 steel in a urea electrolyte, where the substrate samples were connected cathodically to a high-voltage DC current power supply. The structural, mechanical, wear and corrosion properties of the samples treated for 3-5 min were investigated. The results show that the surface layers formed on the samples by this treatment at 220 V have a ferritic nitrocarburizing characteristic which consists of a compound layer and diffusion zone. The surface layers of the treated samples at 240 V consisted of a compound layer, martensitic layer and diffusion zone, respectively, which is a marker of... 

A spent processing catalyst from an Iranian oil refinery was initially characterized physically and chemically. Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were used to mobilize Al, Co, Mo and Ni from the spent catalysts under optimized conditions in batch cultures. The characteristics of the bioleach solution (pH, Eh, cell concentration and Fe(II)/Fe(III) concentration) were determined along with the concentration of metal values extracted from the catalyst. The results showed that after bioleaching using A. ferrooxidans in the presence of ferrous sulfate, maximum extractions of 63% Al, 96% Co, 84% Mo and 99% Ni were achieved after 30 days at pH 1.8-2.0. However, the... 

In-situ aluminum matrix composites were fabricated by 1-3 passes of friction stir process (FSP) using iron (Fe) particles with initial size of 10. μm. Although the initial reinforcing particles were relatively large in size and also agglomerated particles were formed in the obtained composites, all of the processed specimens fractured from the base metal during transverse tensile test. Longitudinal tensile tests revealed that the ultimate tensile strength (UTS) of the composites was up to 43% higher than that of the base metal; however, the strain to fracture of the composites reached to about 0.2. Al-Fe intermetallic compounds (IMCs) formed at the interface of the aluminum matrix and Fe... 

Density functional theory generalized gradient approximation has been used to calculate the electronic and structural properties of BaFe2As2 compound up to 56 GPa by using Quantum Espresso code. Structural properties like bulk modulus, Fe-As bond length, and As-Fe-As bond angles have been investigated by pressure especially near the tetragonal to collapsed tetragonal (T-cT) structural phase transition. This study shows considerable changes of these parameters in the cT phase, which happens near our calculated critical pressure, Pc = 24 ± 2 GPa. Electronic band structure and its orbital-resolved, total and partial density of states and Fermi surfaces have been... 

The equilibrium crystal structure and electronic structure of BaFe2-x Cox As2 (x = 0,1, 2) superconductor have been investigated by using the pseudopotential Quantum Espresso code based on the ab initio density functional theory in the generalized gradient approximation. The equilibrium crystal structure for x = 1.0 has been determined by considering five different Fe/Co configurations. This study shows that the spin calculation is essential to obtain the experimental values at x = 0.0. The total and partial density of states, band structure, and Fermi surfaces of the three compounds has been calculated. Density of states calculation indicates the important... 

We substitute indium present in the CuInS2 ternary compound by iron and zinc using a facile one-pot synthesis method. The quaternary compound of CuIn1-xMxS2 (M = Fe and Zn) was synthesized by dissolving CuCl, InCl3, FeCl3, Zn(ac)2 and SC(NH2)2 as precursors in 1-octadecene, oleylamine and oleic acid as non-coordinating, coordinating and capping agent solvents, respectively. Oleic acid, oleylamine and thiourea were used respectively as a hard Lewis base, borderline Lewis base (in comparison with oleic acid) and soft Lewis base to form appropriate complexes. The complex formation, structure, and... 

Magnetite nanoparticles with a size distribution of 15-21 nm were synthesized and decorated onto surface of graphene oxide by ultrasound assisted precipitation. Size and size distribution of the obtained M-GO hybrid were appreciably finer than the hybrids prepared by stirring method. M-GO is a superparamagnetic material with saturation magnetization of 31 emu g-1. The Langevin equation was successfully applied for estimation of size of Fe3O4 nanoparticles in M-GO hybrid, with maximum error of 17.5%. The study put forward a formation mechanism for M-GO, based on instrumental analyses. Adsorption isotherms of Sr2+ and Co2+ ions, which were fitted by Langmuir monolayer... 

A molybdenum complex, [MoO2Cl2(DMSO)2], was immobilized on amino propyl and Schiff base modified magnetic Fe3O4@SiO2 nanoparticles by covalent linkage. The resulting nanoparticles were used as efficient and recyclable catalysts for the selective oxidation of sulfides to sulfoxides using urea hydrogen peroxide as the oxidant. The complete characterization of catalysts was carried out by means of thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), elemental analysis, FT-IR and Raman microprobe...