Showing papers in "Materials Science and Engineering B-advanced Functional Solid-state Materials in 2022"

Structural, mechanical, radiation shielding properties and albedo parameters of alumina borate glasses: Role of CeO2 and Er2O3

Abstract: In this study, the effect of CeO2 and Er2O3 on the physical, structural and mechanical properties of the B2O3-Na2O-Al2O3 glass composition, according to the formula [75-(x+y)]B2O3-20Na2O-5Al2O3-x(CeO2)+y(Er2O3) (where x+y=1, mol %) were investigated. The half-value layer (HVL), neutron removal cross-section (R), effective atomic numbers (Zeff), mean free path (MFP), mass attenuation coefficients (MAC), and radiation safety efficiency (RPE) of the prepared glass structure were experimentally tested and theoretically determined for radiation shielding properties. The MCNP5 code was also used to measure the mass attenuation coefficients of glasses. At 59.54 keV, the glass system's albedo number, energy, and dose were determined by examining Compton and coherent peaks in XRF spectra. The XRD analyses showed that CeO2 and Er2O3 doped alumina borate glasses had a completely amorphous structure. Optical band gap ( E opt ) values decreased according to pure glass because of the replacement of RO oxides in the glass matrix. Luminescence spectra had red emission correspond to 640–690 nm region through 4F9/2→6H11/2 transition. Good agreements were also observed between WinXCOM and Monte Carlo simulation results for MAC values. It was observed that doping 1 mol% of Er2O3 decreased the reflectivity of the gamma rays of the alumina borate glass by 30.9% compared to the doping 1 mol% of CeO2. In addition, the structural and mechanical properties of the CeO2 and Er2O3 doped borate glasses were examined, and comparisons were made.

Structural, mechanical, radiation shielding properties and albedo parameters of alumina borate glasses: Role of CeO2 and Er2O3

Abstract: In this study, the effect of CeO2 and Er2O3 on the physical, structural and mechanical properties of the B2O3-Na2O-Al2O3 glass composition, according to the formula [75-(x+y)]B2O3-20Na2O-5Al2O3-x(CeO2)+y(Er2O3) (where x+y=1, mol %) were investigated. The half-value layer (HVL), neutron removal cross-section (R), effective atomic numbers (Zeff), mean free path (MFP), mass attenuation coefficients (MAC), and radiation safety efficiency (RPE) of the prepared glass structure were experimentally tested and theoretically determined for radiation shielding properties. The MCNP5 code was also used to measure the mass attenuation coefficients of glasses. At 59.54 keV, the glass system's albedo number, energy, and dose were determined by examining Compton and coherent peaks in XRF spectra. The XRD analyses showed that CeO2 and Er2O3 doped alumina borate glasses had a completely amorphous structure. Optical band gap (Eopt) values decreased according to pure glass because of the replacement of RO oxides in the glass matrix. Luminescence spectra had red emission correspond to 640–690 nm region through 4F9/2→6H11/2 transition. Good agreements were also observed between WinXCOM and Monte Carlo simulation results for MAC values. It was observed that doping 1 mol% of Er2O3 decreased the reflectivity of the gamma rays of the alumina borate glass by 30.9% compared to the doping 1 mol% of CeO2. In addition, the structural and mechanical properties of the CeO2 and Er2O3 doped borate glasses were examined, and comparisons were made.

Influence of magnetization, variable viscosity and thermal conductivity on Von Karman swirling flow of H2O-FE3O4 and H2O-Mn-ZNFe2O4 ferromagnetic nanofluids from a spinning DISK: Smart spin coating simulation

Abstract: • Mathematical model developed for a Ferromagnetic nanofluids through rotating disk. • Features of Magnetization, variable viscosity and thermal conductivity are included. • Galerkin weighted residual method with Simpson’s 1/3rd rule utilized for solutions. • Rapidly convergent and accurate solutions are achieved with GWRM. Motivated by smart nano-ferromagnetic spin coating applications, A theoretical study is described for steady swirling Von Karman thermo-magnetic water-based flowing nanoliquids containing ferromagnetic nanoparticles from a rotating disk in Darcian permeable media. The governing mass, momentum and temperature equations are converted into nonlinear-coupled ordinary derivative momentum and energy equations via appropriate similarity transformations, resulting boundary value ordinary differential problem is solved by a Galerkin weighted residual method (GWRM) along with Simpson’s one-third rule. Verification of the GWRM solutions is achieved with numerical shooting quadrature (MAPLE) and very good correlation is demonstrated. Ferromagnetic Fe 3 O 4 nanofluid is observed to achieve superior thermal conductivity enhancement relative to ferromagnetic Mn-ZnFe 2 O 4 nanofluid. Increasing magnetic field intensity δ substantially modifies the viscosity and produces a consistent retardation in both axial and radial velocity whereas it weakly enhances the tangential velocity field. With greater ferromagnetic interaction number β axial velocity is enhanced strongly, and radial velocity is also boosted.

Synthesis, structural and dielectric properties of Mg/Zn ferrites -PVA nanocomposites

Abstract: • Reinforcement of polyvinyl alcohol (PVA) nanocomposites blend using Mg 0.5 Zn 0.5 Fe 2 O 4 nanoparticles. • The interaction of PVA and nanoparticles in nanocomposites samples was confirmed by FTIR, which showed shifting bands in FTIR spectra. • Loss factor and dielectric constant show a decreasing trend, with variable amounts of nanoparticles and constant polymer concentration. Significant progress has been done in the synthesis of polymer nanocomposites owing to their great application in various fields like in devices, limiting diodes, photodetectors, solar cells, and spin-coating. The present study deals with the incorporation of polyvinyl alcohol (PVA) nanocomposites blend using Mg 0.5 Zn 0.5 Fe 2 O 4 nanoparticles. The Micro-emulsion method has been utilized to synthesis Mg 0.5 Zn 0.5 Fe 2 O 4 nanoparticles and after that implanted into PVA network via ultrasound-assisted liquid-phase approach. This method can be used to solve problems with nanoparticles dispersion and stabilization in the PVA matrix. Under ultrasonication, the aggregation of nanoparticles was found to be reduced. Transmission electron microscopy (TEM) revealed that PVA chains have encircled the Mg 0.5 Zn 0.5 Fe 2 O 4 nanoparticles, which is further verified by Fourier-transform infrared spectroscopy (FTIR) peak shifting values. The X-ray diffraction (XRD) patterns demonstrated that the composite crystalline structure is single-phase cubic. The crystallite size for the largest peak (1 1 1) increases gradually from 31.49 to 43.79 nm by increasing the concentration (0.1–0.5 g) of nanoparticles with PVA. The interaction of PVA and nanoparticles in nanocomposites samples was confirmed by FTIR, which showed shifting bands in FTIR spectra. Loss factor and dielectric constant show a decreasing trend, with variable amounts of nanoparticles and constant polymer concentration. The dielectric properties of with variation of nanoparticles revealed that these materials might be considered a good candidate for modern devices like memristors, and Random access memories (RAM).

A review on template assisted synthesis of multi-functional metal oxide nanostructures: Status and prospects

Abstract: The current review article deliberates the emerging template-assisted synthetic approach for the preparation of promising metal oxide nanostructures. The template-assisted synthesis offers promising greener protocols as compared with traditional synthetic techniques such as sol–gel, hydrothermal synthesis, etc to furnish the product with desired properties and application. The controlled morphology with tunable properties of MOx nanostructures can be achieved from the incorporation of hard and soft templates owing to template structural and characteristics features. The porous template surface act as surface directing agent for the fabrication of micro to nano-sized mesoporous material by restraining the crystal growth and crystal nucleation. Herein, we comprehensively review the research efforts of the worldwide laboratories on exemplary template materials to fabricate aimed MOx nanostructures. Furthermore, the critical analysis of various aspects to achieve desired response using template materials and correlation of template structure with metal oxide properties for the targeted applications have been discussed.

Cobalt-based full Heusler compounds Co2FeZ (Z = Al, Si, and Ga): A comprehensive study of competition between XA and L21atomic ordering with ab initio calculation

Abstract: To study the structural properties of Co2FeZ (Z = Al, Si, Ga) (CFZ) alloys, we will use the approximation method GGA-PBE based on the method of plane waves increased by linear waves at full potential using the theory of functional density in both the Hg2CuTi and Cu2MnAl-type structures. From the most stable state we determine the other properties such as the magnetic, elastic and thermoelectric properties. The band structure calculation reveals indirect band gap in spin down channel and zero band gap in spin up channel of valence and conduction bands confirming the spin gapless semiconducting nature of these compounds. Calculated Seebeck coefficient in spin up and spin down channel reveals that the CFZ behaves as both n and p type thermoelectric materials with better output efficiency. The transport properties of these materials are discussed on the basis of Seebeck coefficient, electrical conductivity coefficient, thermal conductivity and figure-of-merit coefficient. By analyzing the nature of the bonding between the different atoms that form CFZ that each of them has a strong covalent character.

Band gap shifting of halide perovskite CsCaBr3 from ultra-violet to visible region under pressure for photovoltaic applications

Abstract: • Pressure impact is used for the first time on cubic halide perovskite CsCaBr 3 . • The lattice parameters decreased under pressure as the interatomic distance is reduced. • The transition of band gap nature from indirect to direct is occurred at 40 GPa. • As the pressure rises, the optical spectra shift toward lower energy. • According to the mechanical stability criteria, CsCaBr 3 is stable over the whole range of applied pressure (0–80) GPa. • Pressure makes the CsCaBr 3 compound more ductile and anisotropic. Throughout this study, the effects of hydrostatic pressure on the physical properties of halide perovskite CsCaBr 3 are explored using the density functional theory. The calculated lattice parameters nicely agree with the previous experimental and theoretical reports, but being decreased under pressure as the interatomic distance is reduced. The electronic band gap is significantly reduced from ultra-violet to visible region under pressure, which makes easier to transport electron from valance band to conduction band responsible for enhancing photovoltaic device efficiency. In addition, the transition of band gap nature from indirect to direct is occurred at 40 GPa, which is more suitable for a material to be used in optoelectronic applications. Deep optical analysis suggests the potential applications of titled perovskite in microelectronics, integrated circuits, QLED, OLED, solar cell, waveguides, solar heat reducing materials, and surgical instruments. The elastic constants nicely pursue the Born stability conditions confirming the mechanical stability of CsCaBr 3 under entire range of applied pressure, which justify the thermodynamic stability obtained by the negative values of formation enthalpy. The mechanical properties are also significantly affected by external pressure, which make this compound more ductile and anisotropic.

Modeling and optimization of CZTS kesterite solar cells using TiO2 as efficient electron transport layer

Abstract: In this paper, a numerical simulation study via AMPS 1D simulator is carried out to investigate the degradation mechanisms occurred in hybrid Cu2(Zn,Sn)Se4 (CZTS) solar cells that use a nonporous n-type-TiO2 material as a window. The advantageous Spike-like conformation against recombination at the TiO2/CZTS interface, which is ensured by the band-engineering offset established using TiO2 material, is discussed. The influence of the geometrical and physical parameters on the device fundamental figures of merit is assessed. Besides, the degradation effect linked to both deep and tail states situated in the gap of the materials, and the effective working temperature, are taken into account. The results reveal that the actual defect type (donor or neutral) at the Cu2ZnSnS4 layer has a harsh influence on the device performance. This is attributed to the raised Shockley–Read–Hall (SRH) recombination highlighted by investigating the variation of the carrier density along the absorber layer. A low barrier height at the back contact (ϕbl = 0.1 eV) and a suitable doping level and thickness of both the window (ND = 4 × 1017 cm−3, WTiO2 = 0.02 µm) and the absorber (NA = 6.5 × 1016 cm−3, WCZTS = 3.2 µm) layers could efficiently improve the device performance.

Axisymmetric radiative titanium dioxide magnetic nanofluid flow on a stretching cylinder with homogeneous/heterogeneous reactions in Darcy-Forchheimer porous media: Intelligent nanocoating simulation

Abstract: • A novel mathematical model is developed for dual catalytic reactive species diffusion in axisymmetric coating enrobing forced convection boundary layer flow. • Homogeneous and heterogeneous reactions, heat source (e.g. laser source) and non-linear radiative transfer are included. • The non-linear conservation equations proposed here with species diffusion (species A and B) are transformed via an appropriate stream function and scaling variables into a set of non-linear united multi-degree ODEs. • The rising nonlinear ordinary differential boundary value problem is solved with four-point Gauss-Lobotto formulae in the MATLAB bvp5c routine. • Validation is conducted with an Adams-Moulton predictor–corrector numerical scheme (AM2 coded in Unix). Modern nanomaterials coating processes feature high temperature environments and complex chemical reactions required for the precise synthesis of bespoke designs. Such flow processes are extremely complex and feature both heat and mass transfer in addition to viscous behaviour. Intelligent nano-coatings exploit magnetic nanoparticles and can be manipulated by external magnetic fields. Mathematical models provide an inexpensive insight into the inherent characteristics of such coating dynamics processes. Motivated by this, in the current work, a novel mathematical model is developed for dual catalytic reactive species diffusion in axisymmetric coating enrobing forced convection boundary layer flow from a linearly axially stretching horizontal cylinder immersed in a homogenous non-Darcy porous medium saturated withmagnetic nanofluid. Homogeneous and heterogeneous reactions, heat source (e.g. laser source) and non-linear radiative transfer are included. The Tiwari-Das nanoscale model is deployed. A Darcy-Forchheimerdrag force formulation is utilized to simulate both bulk porous drag and second order inertial drag of the porous medium fibres. The magnetic nanofluid is an aqueous electroconductive polymer comprising base fluid water and magnetic TiO 2 nanoparticles. The TiO 2 nanoparticles are one chemically reacting species (A) and a second species (B) is also present (e.g. oxygen) which also reacts chemically. Viscous heating and Ohmic dissipation are also included to produce a more physically realistic thermal analysis. The non-linear conservation equations proposed here with species diffusion (species A and B) are transformed via an appropriate stream function and scaling variables into a set of non-linear united multi-degree ODEs. The rising nonlinear ordinary differential boundary value problem is solved with four-point Gauss-Lobotto formulae in the MATLAB bvp5c routine. Validation is conducted with an Adams-Moulton predictor–corrector numerical scheme (AM2 coded in Unix). The widespread visualization of velocity, temperature, species A concentration, species B concentration, skin friction, local Nusselt number and species A and B local Sherwood numbers is included. For the higher Schmidt number the momentum diffusion rate exceeds the species diffusion rate and this will produce a depression in concentration values. Further, increasing Darcian parameter retards the local Nusselt number magnitudes since higher permeability corresponds to sparsity in the solid fibres, reduction in thermal conduction and a concomitant cooling of the cylinder surface.

Infrared stealth and microwave absorption properties of reduced graphene oxide functionalized with Fe3O4

Abstract: In this study, we synthesized three-dimensional porous-network composites containing reduced graphene oxide (rGO) and Fe3O4 nanoparticles (rGO/Fe3O4) via hydrothermal and freeze-drying processes. These were then introduced into a smoke canister, and colloidal silicone rubber (RTV-615) was used as an infrared (IR) and microwave (MW) absorber. The infrared shielding effectiveness was investigated by measuring the thermal extinction in the smoke canister for dynamic testing using a thermal imager in the 8–12 μm range. The microwave-absorbing properties were investigated by measuring the reflection loss in the 2–18 GHz range with a network analyzer using the free space method. For the rGO/Fe3O4 composite with concentrations of 1–3 mg/cm3 and 1 mg/cm3, the thermal extinction reached 30–43 °C and 26–35 °C in static testing and dynamic testing, respectively. The rGO/Fe3O4(1:2) composite exhibited a maximum absorption value of −31.3 dB at 15.3 GHz at a thickness of 2.0 mm.

Mesoporous carbon/titanium dioxide composite as an electrode for symmetric/asymmetric solid‐state supercapacitors

Abstract: This paper reports the successful synthesis of mesoporous carbon/titanium dioxide (MC/TiO2) composite electrodes via the hydrothermal method for supercapacitor (SC) applications. The morphology and structural properties of MC/TiO2 composites were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectra (FTIR). The electrochemical properties were recorded by cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) with an electrolyte (6 M KOH) in symmetric/asymmetric configuration. The specific capacitance (Cs) evaluated by CV is about 280F/g for composite electrode (95 % capacitance retention after 1000 cycles) and pristine has 150F/g @ 10 mV/s. Enhancement in capacitance is owing to faster charge dynamics within electrode material. The fabricated asymmetric device demonstrates high energy density (30.31 Wh/kg), than the symmetric configuration (∼27 Wh/kg). Finally, both symmetric/asymmetric supercapacitors have illuminated a red LED, and strengthens the candidature of composite electrode for energy storage technology.

Effect of stress on the magnetic Barkhausen noise energy cycles: A route for stress evaluation in ferromagnetic materials

Abstract: The analysis of the magnetic Barkhausen noise energy hysteresis cycles, MBNenergy(H), is a promising non-destructive testing method for evaluating internal mechanical stresses in ferromagnetic structural steels. This study applies this method to two ferromagnetic materials with significantly different behaviors subjected to uniaxial tensile stress. Coercivity is shown to be the most sensitive tensile stress indicator. A multiscale model is then developed to simulate the stress-dependent MBNenergy(H) anhysteretic behavior. Combined with a hysteresis contribution, it successfully reproduces the whole cycle. 2D simulation predictions reveal that the identification of uniaxial tensile stress is more efficient when the magnetic field is applied with an angle between 30° and 75° from the stress direction. The proposed modeling approach allows the prior determination of the most favorable configurations for the sensor orientation depending on the material tested and all available a priori knowledge of the stress configuration.

Computational approach and ultrasound Probe–Assisted synthesis of magnetic molecularly imprinted polymer for the electrochemical detection of bisphenol A

Abstract: A new theoretical approach based on density functional theory was developed to find the most suitable monomer and porogen solvent to design a specific molecularly imprinted polymer (MIP) for bisphenol-A (BPA). Various theoretical investigations were carried out including HOMO and LUMO calculation, molecular electrostatic potential of the BPA-monomer interactions, and selection of the optimal monomer and porogen solvent using binding energies of BPA-monomer. Besides, counterpoise correction was used to avoid the problem of basis set superposition error. The theoretical results demonstrated that among virtual monomers, methacrylic acid and acrylamide showed good affinity towards BPA. The optimization of solvents was done using the polarizable continuum model and it was found that acetone was the most appropriate solvent. According to the obtained theoretical approach results, magnetic MIP (magMIP) was prepared using a high-power ultrasound probe. Scanning/transmission electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction were used to characterize the as-prepared magMIP. Adsorption behavior was explained by Sips and pseudo-second-order models for isotherm and kinetic studies, respectively. Furthermore, magMIP showed favorable adsorption selectivity for BPA over other phenolic compounds. Finally, the developed magMIP was successfully used as a sorbent in solid-phase extraction combined with an electrochemical sensor for the detection of BPA. The obtained limit of detection was 66 nM and the recovery values in tap water sample were 104 and 105.5% for 2 and 10 µM, respectively, with RSD values lower than 5 % (n = 3).

Flexible and self-standing polyimide/lignin-derived carbon nanofibers for high-performance supercapacitor electrode material applications

Abstract: For attaining flexible and self-standing electrode materials for advanced energy storage devices, we herein report the fabrication and electrochemical properties of carbon nanofibers (CNFs) derived from polyimide (PI) and lignin precursors with different mass ratios (10/0, 9/1, 8/2, and 7/3) via electrospinning and carbonization at 1000 °C. The electron microscopic and photographic images exhibit that the average diameter and flexibility of PI/lignin-derived CNFs decreases and increases, respectively, with increasing the lignin mass ratio in the precursors. The EDS, XRD and Raman analyses confirm that PI/lignin-derived CNFs possess a partially ordered graphitic structure with oxygen self-doping. The electrical conductivity of the CNFs increases from 1.5 S/cm to 2.8 S/cm with the increment of the lignin mass ratio in the precursors. Accordingly, PI/lignin (7/3)-derived CNF is found to have the most excellent electrochemical properties from the analyses using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) test, and electrochemical impedance spectroscopy (EIS). For a symmetric two-electrode supercapacitor based on PI/lignin (7/3)-derived CNFs, high specific capacitance of 83.6 F/g at 1 A/g, power density of 5000 W/kg, energy density of 13.3 Wh/kg, and capacitance retention of ∼100% after 1000 GCD cycle are attained.

Dislocations and crystallite size distribution of cadmium oxide thin films synthesized by spray pyrolysis technique

Abstract: • Spray pyrolysis technique is employed to grow CdO. • The XRD is analyzed using modified Williamson–Hall and modified Warren–Averbach methods. • The size parameters, lattice strain, dislocation arrangement parameter, effective outer cut-off radii, dislocation density and size distribution functions are investigated. Cadmium oxide (CdO) thin films have been successfully deposited on amorphous glass substrates by spray pyrolysis technique at a temperature, 573 °K using aqueous solution of cadmium nitrate 4-Hydrate powder with a concentration of 0.1 M. The X-ray diffraction (XRD) studies have revealed that the films exhibit cubic crystal structure. The modified Williamson–Hall and Warren–Averbach methods are used successfully for analyzing the XRD line profile for determining the crystallite size, dislocation densities and crystallite size distribution in CdO thin films. The crystallite size (D) and integral breadths (d) ( D = 44.139 nm and d = 32.237 nm) are obtained by the modified Williamson Hall, while the area-weighted average grain sizes and volume-weighted obtained of modified Warren–Averbach method are x vol = 46 , 06 n m and x area = 29 , 7 n m , respectively. The size parameter ( L o ), dislocation density ( ρ ), effective outer cut-off radii ( R e ) and dislocation arrangement parameter ( μ ) gotten of Warren–Averbach are 35.53 nm, 2.0 × 10 15 m −2 , 7 nm and 0.31 nm, respectively. The particle size distribution ( x ) derived of XRD and estimated of size parameter is the size distribution function f ( x ) of log-normal .

Optical and electrochemical properties of pure and Ti-doped CdO nanoparticles for device applications

Abstract: Cadmium oxide (CdO) is one among the transparent conducting oxides which is famous for its various applications in optoelectronics, gas sensors, and electrochemical sensors, etc. The present work therefore reports the synthesis and structural, optical, and electrochemical properties of pure CdO and Ti doped CdO nanoparticles which were synthesized using simple sol–gel method. The structural analysis of the prepared samples was done by using x-ray diffraction (XRD) technique. The XRD peaks revealed the existence of crystalline structure of the samples. The average crystallite sizes of the samples were calculated by considering the intense peaks observed in the XRD spectrum and they were found to be 59.45 nm and 55.25 nm for pure CdO and Ti doped CdO nanoparticles respectively. The absorption and transmission spectra of synthesized nanoparticles were recorded in the UV–VIS-NIR region. Using the absorption and transmission spectra, the optical band gap of pure CdO and Ti doped CdO were estimated as 2.14 eV and 2.99 eV respectively, using Tauc plot method. The Urbach energies were calculated, and they were found to be 1059 meV and 679 meV for the pure and Ti doped CdO nanoparticles. The optical conductivity, real and imaginary part of dielectric constant, dielectric loss tangent were also investigated using UV–VIS-NIR spectral data for the possible application in opto-electronic devices. The electrochemical performance of the samples was investigated using cyclic voltammetry (CV) technique. The specific capacitance and diffusion coefficients were calculated using the recorded cyclic voltammogram. The results of CV data showed that the maximum specific capacitance was occurred to be 390F/g at the rate 25 mV/s and 219F/g at the rate 50 mV/s for the pure and Ti-doped CdO nanomaterials respectively. The outcome of the present study provided an useful information for the possibilities of these materials in the device applications.

Flexible and self-standing polyimide/lignin-derived carbon nanofibers for high-performance supercapacitor electrode material applications

Abstract: For attaining flexible and self-standing electrode materials for advanced energy storage devices, we herein report the fabrication and electrochemical properties of carbon nanofibers (CNFs) derived from polyimide (PI) and lignin precursors with different mass ratios (10/0, 9/1, 8/2, and 7/3) via electrospinning and carbonization at 1000 °C. The electron microscopic and photographic images exhibit that the average diameter and flexibility of PI/lignin-derived CNFs decreases and increases, respectively, with increasing the lignin mass ratio in the precursors. The EDS, XRD and Raman analyses confirm that PI/lignin-derived CNFs possess a partially ordered graphitic structure with oxygen self-doping. The electrical conductivity of the CNFs increases from 1.5 S/cm to 2.8 S/cm with the increment of the lignin mass ratio in the precursors. Accordingly, PI/lignin (7/3)-derived CNF is found to have the most excellent electrochemical properties from the analyses using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) test, and electrochemical impedance spectroscopy (EIS). For a symmetric two-electrode supercapacitor based on PI/lignin (7/3)-derived CNFs, high specific capacitance of 83.6 F/g at 1 A/g, power density of 5000 W/kg, energy density of 13.3 Wh/kg, and capacitance retention of ∼100% after 1000 GCD cycle are attained.

Influence of tool rotational speed on the microstructural characterization and mechanical properties of friction stir welded Al-Si10Mg parts produced by DMLS additive manufacturing process

Abstract: Present study investigate the joining of precipitation hardened AlSi10Mg alloy, developed using direct metal laser sintering technique of additive manufacturing using friction stir welding. Consequently, three, single-pass, square butt-welded joints were fabricated from 3 mm thick plates of this alloy, using friction stir welding process at different tool rotational speeds (low, medium and high). Each welded joint was fabricated at the same transverse speed of 50 mm/min, H13 tool steel possessing scrolled shoulder and 3° tilt angle. Microstructural observations show a significant grain refinement within the stir zone, which reduced with the increase in tool rotational speed. This variation was accredited to the significant dynamic recrystallization in the weldment, and change in the morphology and size of the Si-particles. The transverse tensile test results show a considerable drop in the joint efficiency of the welds from ≈48% to ≈42% with the increase in tool rotational speed from low to high.

Synthesis, characterization and nonlinear optical properties of polylactide and PMMA based azophloxine nanocomposites for optical limiting applications

Abstract: The widespread usage of harmful pulsed laser sources emitting brief but intense radiations implies to search for appropriate and convenient forms of protection. Nonlinear optical nanomaterials can serve this purpose when properly embedded in a solid medium, resulting in nanocomposite passive optical limiting filters. This article focuses on the optical limiting behavior of a series of polymer-dye nonlinear nanocomposites, for which we combined azophloxine, a red azo dye, with two polymer hosts, namely polymethyl methacrylate (PMMA) and polylactide (PLA). In this work, optical filters were produced by chemical synthesis from the bulk. Their linear absorption and transmittance were measured by UV–VIS-NIR spectrophotometry and their thermal examination was done via TGA measurements. The optical limiting properties were characterized using an appropriate custom-made optical setup and the nonlinear absorption coefficients and refractive indices were measured by the Z-scan method. Optical measurements in the nonlinear regime were performed at the wavelength of 1064 nm with nanosecond pulses at a low pulse repetition rate. The nonlinear optical properties resulting from energy dependent transmittance assessments reveal that the dye concentration is of major relevance regarding the PMMA nanocomposites, and to a lesser extend for the PLA based systems. The PLA synthesis concept described in this study offers an easy way to directly attach the dye covalently to the polymer chain. The originality and novelty of this synthesis technique is to be pointed out since it has never been mentioned elsewhere to date. For the various types of nanocomposites investigated, significant differences in the optical limiting response were observed. For instance, it is averred that a significantly higher optical limiting effect results in the systems with the less azo dye concentration and the best optical limiting performance corresponding to a laser protection level of OD = 3.3 was measured for the PLA based system. Besides, the PMMA nanocomposite system exhibits an optical limiting level of OD = 1.9. A molecular model claiming for the dye aggregation in the PMMA nanocomposites is discussed. Two different absorption regimes responsible for the optical limiting action have been identified to be reverse saturable (RSA) – excited state absorption (ESA) on the one hand and multi-photons absorption (MPA) on the other hand. By means of transmittance investigations in an open Z-scan configuration, one could observe the sudden and remarkable changeover from a saturable absorption (SA) regime to a reverse saturable absorption one for high azo dye loads in PMMA. Such transition from SA to RSA has been basically revealed for materials and experimental conditions close to or centered on the resonance of absorption (i.e. around 532 nm). To the author’s knowledge, a study in off-resonant conditions (i.e. 1064 nm) was never reported elsewhere to date. Also tracked out by open Z-scan measurements, significantly higher nonlinear absorption coefficients βresulted for the PLA based systems. Similar experiments in a close aperture Z-scan scheme revealed nonlinear refractive indexes in the order of n 2 = - 2.0 X 10 - 15 cm 2 / W for the PMMA nanocomposites and n 2 = - 3.0 X 10 - 15 cm 2 / W for the PLA nanocomposites.

Nanobiomaterials in support of drug delivery related issues

Abstract: • A wide variety of materials have been utilized as drug delivery carriers for various diseases. • Nano biomaterial application as drug delivery systems has been rapidly evolving through the multidisciplinary field of nanotechnology due to its predominant opportunities related to therapy of life-threatening diseases. • Summarised the major challenges faced by drug delivery systems and the introduction of nanobiomaterials to overcome these challenges. • The importance of toxicity evaluation and risk assessment is also detailed. Nanobiomaterials have been widely accepted as potential drug delivery agents over the past decade. A wide variety of materials have been utilized as drug delivery carriers for various diseases like Cancer, Alzheimer's etc . Being the leading cause of death worldwide, effective drug delivery to cancer cells by using nanomaterials has become the most fascinating and dynamic regions of research. The decreased size of these materials increased permeability through physiological barriers, and increased cell to cell interactions are the properties that are highly suitable for drug delivery applications. Biocompatibility and biodegradability are added advantages of using nano biomaterials as drug delivery systems. However, to transfer the nanobiomaterials for advanced clinical applications, a detailed study should be established considering the interactions of these nanobiomaterials with the physiological environment. Moreover, the need for extensive toxicity studies will open up a new window for the effective translation of these materials into clinical drug delivery carriers. The integration of nanomedicine and drug delivery system framework is unquestionably the pattern that will stay in the field of innovative work for quite a long time. Herein, we highlight the challenges of nanobiomaterials related to drug delivery and the possible strategies utilized to overcome the drug delivery-related issues.

Advances in conducting polymer nanocomposite based chemical sensors: An overview

Abstract: Advances in conducting polymer-based nanocomposites (CPNCs) as sensing materials offer unique prospects to apprehend previously inaccessible sensing properties and applications. In this review article, the synthesis and properties of CPNCs are highlighted as pioneer transducers for designing advanced sensing devices. Synthetic strategies of CPNC are also discussed in the brief and classified into ex-situ and in-situ categories employing (1) chemical; (2) electrochemical; (3) photochemical; and (4) hybrid approach. The composite structure of conducting polymers (CPs), with inorganic and organic compounds, has enhanced surface adsorption, responsiveness, catalytic, and/or electron transport behavior for sensing applications. Thus, CPNCs are explored to sense atmospheric gases, humidity, explosives, water pollutants, and food adulterants. The literature reveals that sensor technology has been effectively improved in terms of sensitivity and selectivity due to progress in CPNCs. However, there are still several technical challenges that need to be solved for CPNCs based sensor technology. Herein, the key issues regarding the use of CPNC based materials in the development of state-of-the-art sensors are discussed. Furthermore, a perspective on the next-generation sensor technology concerning materials has been demonstrated with exclusive examples of conducting polymers based nano composite.

Heterostructure of CsPbBr3-CdS perovskite quantum dots for enhanced stability and charge transfer

Abstract: CsPbBr3 quantum dot (PQD) was interfaced with CdS quantum dot (QD), via modified hot injection method to form a heterostructure, across whose interface a significantly enhanced charge transfer is demonstrated. Formation of heterostructure (with retention of individual characteristics) was evidenced by various spectroscopy, microscopy and DFT tools. The heterostructure is observed to be much stable (one acting as pseudo protecting layer for the other) with enhanced electron lifetime and favorable band energy offset. CdS QDs reduce the strain within PQDs by holding them in a matrix kind of a structure, thus passivating the uncoordinated sites. It thus holds potential to be exploited for faster charge transfer in solar cell and other optoelectronic applications. Nature of PL quenching with growth of CdS QDs on PQDs, suggest energy transfer. The optimized formulation was also applied to liquid junction solar cells as sensitizers just to evidence the better electron transport, and charge separation properties.

(Bio)degradable biochar composites – Studies on degradation and electrostatic properties

Abstract: In this work, biochar was introduced as a filler into the aliphatic-aromatic copolyester and polylactide blend. Properties and the changes during degradation of obtained materials were evaluated. A new application path was also determined by lowering the surface resistivity by increasing the biochar content. Measurements of electrostatic properties showed that surface resistivity of the poly(1,4-butylene adipate-co-1,4-butylene terephthalate)/polylactide/biochar composites is strongly dependent on the biochar content. Six-fold reduction of the surface resistivity after introduction of the 30 wt% of carbon to the reference specimen was observed. Degradation tests were conducted under abiotic and composting conditions. Visual evaluation indicated that the increase of biochar content had caused cracks to increase on the sample surfaces. The values of thermal properties after degradation do not indicated on the biochar influence on polymer matrix degradation mechanism. Nuclear magnetic resonance analysis revealed that after 42 days of hydrolytic degradation amount of polylactide was 0–2%.

ALD and PEALD deposition of HfO2 and its effects on the nature of oxygen vacancies

Abstract: The high-k materials are essential in thin-film transistors. A well-controlled thin film deposition that produces less electronic defects induced by charged vacancies is highly desirable for avoiding high leakage current and and providing an exceptional dielectric strength. This work addresses the use of atomic layer deposition (ALD), plasma-enhanced ALD (PEALD), and its variants to produce low-defective HfO2. The X-ray photoelectron spectroscopy (XPS) and Capacitance-Voltage (C-V) analysis revealed that the thermal ALD (TALD) samples produce electron emissions of ∼ 1 eV above the valence band maximum, negative flat band voltage shift of 1.51 V, and low dielectric breakdown strength (4.37 MV/cm). These properties confirm the high density of positive oxygen vacancies (1.2 × 1013 cm−2) acting as shallow traps, despite its O/Hf ratio (1.84) being higher than the Direct Plasma ALD (DPALD) sample. On the other hand, PEALD induces the formation of neutral vacancies promoted by the electric field of the plasma sheath. These defects are less detrimental to the capacitor performance as their flat band shifts are −0.25 and 1.01 V for remote plasma ALD (RPALD) and DPALD samples. Their dielectric breakdown strength increases by ∼ 1 MV/cm, and a reduced current density by 3 orders of magnitude less than TALD samples. The O/Hf ratio in DPALD samples is 1.80, confirming the benefits of using PEALD approaches.

Role of deposition temperature on physical and electrochemical performance of manganese oxide electrode material for supercapacitor application

Abstract: In the present work, Manganese dioxide (MnO2) with a nanothorn surface architecture was synthesized with a simple, industry scalable, and chemical approach, namely a one-step hydrothermal method. The structural, morphological, and surface area properties of the as-synthesized MnO2 nanostructures electrodes deposited at different deposition temperatures have been systematically characterized by using different characterization The supercapacitive properties of MnO2 electrodes were studied by using cyclic voltammetry, galvonastic charge-discharge, long-term cyclic stability, and electrochemical impedance techniques in 1 M Na2SO4 as electrolyte. The SEM micrographs show different morphologies like nanoflakes, nanoflowers, and nanothorn at concerning deposition temperature. Among all the electrodes of MnO2 nanostructures prepared, nanothorn-like MnO2 nanostructures deposited at 160 °C for 6 h delivered the highest specific capacitance value of 432.52 F/g at a scan rate of 5 mV/s and good cycling stability after 2000 cycles. The excellent large surface area and optimized charge transfer pathway mark the MnO2 and make it potential electrode material for energy storage applications.

Synthesis of ultrasonic assisted co-precipitated Ag/ZnO nanorods and their profound anti-liver cancer and antibacterial properties

Abstract: The current cancer Survey reports liver cancer is the second leading cause of cancer related death worldwide. Active liver cancer research is underway as several new therapies are emerging to treat it, with more showing promise. Our present study aims at preparation of silver/zinc oxide nanocomposites for potential applications in antibacterial, anti-inflammatory, anti-cancerous, against human liver cancer cells (hepG2). Silver ions added Zinc oxide (Ag/ZnO) have been synthesized by ultrasonic assisted co-precipitation method. It is found that 3% of silver ions added ZnO were precipitated as nanoplates. And interestingly the observation shows when the concentration of the silver ions increased to 5%, it reduced as nanorods. X-Ray diffraction, SAED patterns and Fourier Transform Infrared Spectrum confirms that silver ions are well attached in ZnO lattice. Ag/ZnO possesses good absorption in the UV region. The reduction in average particle size due to the increase of silver ion concentration in ZnO lattice was confirmed by dynamic light scattering (DLS). SEM and TEM studies witnessed the micro structural transformation from nanoplates (3% Ag) to the rod-like structure on (5% Ag). Ag/ZnO displayed strong antibacterial activity against different pathogens. The obtained results are comparable with standard antibiotics against pathogenic bacteria. Anti-inflammatory study reveals that Ag/ZnO prevents inflammation. Dose dependent response of Ag/ZnO against human liver cancer cells (HepG2) indicates its greater efficacy in killing cancer cells. The selective silver ion concentration (5%) in ZnO have reduced its cross-sectional area with respect to volume. This property helps the silver ion/ZnO nanorods to penetrate efficiently into the affected cells and fight against bacteria, suppress cell inflammation, eradicate the growth of liver cancer cells; which shows feasibility of this composites in further research for therapeutic applications.

(Bio)degradable biochar composites – Studies on degradation and electrostatic properties

Abstract: In this work, biochar was introduced as a filler into the aliphatic-aromatic copolyester and polylactide blend. Properties and the changes during degradation of obtained materials were evaluated. A new application path was also determined by lowering the surface resistivity by increasing the biochar content. Measurements of electrostatic properties showed that surface resistivity of the poly(1,4-butylene adipate-co-1,4-butylene terephthalate)/polylactide/biochar composites is strongly dependent on the biochar content. Six-fold reduction of the surface resistivity after introduction of the 30 wt% of carbon to the reference specimen was observed. Degradation tests were conducted under abiotic and composting conditions. Visual evaluation indicated that the increase of biochar content had caused cracks to increase on the sample surfaces. The values of thermal properties after degradation do not indicated on the biochar influence on polymer matrix degradation mechanism. Nuclear magnetic resonance analysis revealed that after 42 days of hydrolytic degradation amount of polylactide was 0–2%.

Cool white light emission from Dy3+-doped SiO2 – Bi2O3 – Ga2O3 – B2O3 -GeO2- TeO2 glasses: Structural and spectroscopic properties

Abstract: The authors aim to study multi former oxide glasses doped with different concentrations of Dy3+ (0.00, 0.5, 1.0, 1.5, and 2 mol%) for white light-emitting application. All samples characterized by XRD, FTIR, and optical properties (absorption, excitation, and emission). The optical band gap calculated by a differential method. FTIR spectra confirm the network composed of GaO4, GeO4, TeO4, and BO4 tetrahedra, BO3 triangles, B-O-B linkages, and SiO4 tetrahedra with one NBO. In addition to the TeO3, BiO3, TeO6, and BiO6 vibration groups. Oscillator strengths and Judd–Ofelt parameters (Ω2, Ω4, Ω6) calculated and found that the glass samples had a variable trend from Ω2 > Ω4 > Ω6 to Ω2 > Ω6 > Ω4, at a Dy2O3 content >1 mol%. Furthermore, radiative emission transition probability (AR), branching ratio (βR), and radiative lifetime (τR) estimated for Dy3+ ion in various excited states using J–O parameters. Upon 454 nm excitation, 4F9/2 → 6H15/2 [483 nm (blue)], 4F9/2 → 6H13/2 [575 nm (yellow)], and 4F9/2 → 6H11/2 [680 nm (red)] emission. Among them, it noticed that the transition 4F9/2 → 6H13/2 shows the highest intensity. The CIE chromaticity coordinates, correlated color temperature (CCT), and color purity (CP) indicate a generally neutral white light emission from all samples, which meant their suitability for optical applications. Determination of the white light coordinated from the CIE program, which verifies the values of samples are close to the pure white light. And sample containing 2 mol% Dy3+ close to the standard CIE D65 glow.

Dielectric spectroscopy and ferroelectric studies of multiferroic bismuth ferrite modified barium titanate ceramics for energy storage capacitor applications

Abstract: This study reports a single-phase solid-solution of barium titanate- bismuth ferrite (1-x) BaTiO3-xBiFeO3 (x = 0.0, 0.1, 0.2 and 0.3, abbreviated as BTO, BTBF1, BTBF2 and BTBF3) composition fabricated via conventional solid-state reaction technique. The BFO modified BTO ceramics exhibit a single perovskite structure with pseudo-cubic (x ≥ 0.1) symmetry, and the c/a ratio decreases with an increase in BFO content. Dielectric studies suggest that the ferroelectric-paraelectric phase transition around 150 °C for BTBF1 ceramic increases to 180 °C for BTBF3 ceramic, attributed to the higher transition temperature of BFO ceramic. The temperature-dependent impedance studies suggest non-Debye type relaxation and NTCR (negative temperature coefficient of resistance) behavior of the composition. Among the prepared ceramics, BTBF1 ceramic showed an improved energy density of 39.91 mJ/cm3 and energy efficiency of 60.92%. Thus, prepared ceramics can be considered a potential candidate for energy storage applications.

Characterization of intrinsic low-polyimide films studied by positron annihilation

Abstract: Four kinds of polyimide (PI) films were prepared by polycondensation reaction using the pyromellitic dianhydride (PMDA) and 4, 4′-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA）as the dianhydride monomer, the p-phenylenediamine (PDA), 4-4′-diaminodiphenyl ether (ODA) and 4,4′-(Hexafluoroisopropylidene) bis(p-phenyleneoxy) dianiline (HFBDA) as the diamine monomer respectively. The incorporation of trifluoromethyl groups can effectively inhibit the formation of intermolecular and intramolecular charge-transfer complex (CTC), improve the energy gap and increase the free volume in PI, which leads to an improvement in the optical and dielectric properties in different degree for three fluorinated PI films compared with the Kapton film. The maximum transmittance in visible region reaches 90.5% and the dielectric constant at 104Hz is close to 2.0 for PI6FDA-HFPBDA film. The breakdown strength weakens because of the increase of free volume. The correlation between the dielectric and breakdown characteristics and their free volume has been explained with the help of positron lifetime spectra.