Novel nanocomposite based on poly (xanthoneamide-triazole-ethercalix) and TiO2 nanoparticles: preparation,characterization, and investigation of nanocomposite capability in removal of cationic water pollutants

A new multifunctional nanocomposite based on poly (xanthoneamide-triazole-ethercalix) (PXTE) and TiO₂ nanoparticles (PXTE–TiO₂), which is a novel class of multiphase material containing nanosized inorganic material within polymer matrix, was prepared and characterized fully in this article. At first, PXTE was synthesized through click reaction, and then PXTE–TiO₂ nanocomposite was prepared by chemical immobilization of PXTE onto the modified TiO₂ nanoparticles. Nuclear magnetic resonance, Fourier transform infrared, X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, and thermal gravimetric analysis were applied for characterization of synthesized materials. Dye and ion removal capability of PXTE–TiO₂ nanocomposite were investigated by batch method for methylene blue and cadmium ion. The results showed that thermal stability and potential applicability of PXTE–TiO₂ nanocomposite make it as a good candidate for wastewater refinement.     

Characterization of composition,antioxidant potential and microbial organisms upon submerged <Emphasis Type="Italic">Cicer arietinum</Emphasis> fermentation

The aim of this work was to investigate the composition, antioxidant potential and microbial content of chickpea (Cicer arietinum) steep liquor (CSL) during a submerged fermentation. Chickpea seeds (250 g) were soaked in boiled distilled water (1:2, w/v) for 24 h at 37 °C then filtered and freeze-dried to obtain 8.2 g of CSL. Lysine was the main amino acid accounted for 77.0 % of total free amino acids followed by serine (6.49 %). The results of total amino acids found in CSL indicated that arginine was the main amino acid accounted for 24.0 % of total amino acids followed by tyrosine (20.0 %). Total carbohydrate in the freeze-dried CSL was 1.47 %, wherein reducing sugar was 1.25 % of total carbohydrates. Levels of nicotinic acid, pyridoxine, thiamin, riboflavin, folic acid, and vitamin B₁₂ were 14.3, 3.14, 24.2, 1.11, 0.59 and 24.5 mg/100 mg CSL, respectively. CSL exhibited antioxidant activity (AA) wherein AA was increased with increasing the fermentation time. After 24 h of fermentation, AA of CSL reached 77.0 % while tertiary butyl hydroquinone exhibited 82.0 %. Twenty-five Bacilli isolates were separated from freeze-dried CSL on nutrient broth medium. CSL might be used as an alternative to yeast extract for syngas fermentation because it is rich in nutrients and cheaper compared to yeast extract.     

Effect of Weather Conditions on Harmonic Performance of PV Inverters

Abstract

The effect of weather conditions on the generation of harmonics in PV systems is investigated. A PV model, including the inverting stage, is considered. The output of the equivalent PV model is fed to the load via an inverter and transformer. The analysis is conducted by using a dataset of weather conditions in a North American city. Two converter techniques, which form the basis for the majority of converters, are used to validate the proposed approach: a square-wave inverter with 60?Hz switching, and pulse width modulation (PWM). Probability density functions and probability distribution models with best fit are determined as aids for improving the quality of the power generated for different range of converter values and the best is selected in this article. The long-term effects of weather conditions on harmonics produced by PV inverters are considered. The results show the variability in amplitude of each harmonic component, the boundaries of each harmonic component, and which harmonic magnitudes occur more frequently. The classic PV DC-AC conversion system has been modeled using MATLAB. The work is validated by using different ranges of dataset for two different converters and the results improved the importance of the proposed work. Also, the results agree with previous studies that have been carried with a different method which could be considered as another way of validation for the proposed work. Based on the generated harmonic variation cases, the appropriate parameter values for dynamic adaptive circuit switching of the filtering system and determining the capacity of the storage system could be determined.     

SrFe<Subscript>12</Subscript>O<Subscript>19</Subscript> ferrites and hard magnetic PVA nanocomposite: investigation of magnetization,coecivity and remanence

In this work, various morphologies of SrFe₁₂O₁₉ (SrFe) nanostructures were synthesized via a simple sol–gel method. The effect of concentration, temperature and various surfactants on the morphology and particle size of the magnetic seeds was investigated. The prepared magnetic products were characterized by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy techniques. Alternating gradient force magnetometry reveals that the samples exhibit hard magnetic property with the coercivity up to 5300 Oe. Strontium ferrite was added to poly vinyl alcohol to prepare the magnetic polymeric matrix thin film nanocomposites. The saturation magnetization and coercivity decreased due to agglomeration of magnetic nanoparticles in polymer matrix.     

Catalytically Active Bacterial Nanocellulose‐Based Ultrafiltration Membrane

Large quantities of highly toxic organic dyes in industrial wastewater is a persistent challenge in wastewater treatment processes. Here, for highly efficient wastewater treatment, a novel membrane based on bacterial nanocellulose (BNC) loaded with graphene oxide (GO) and palladium (Pd) nanoparticles is demonstrated. This Pd/GO/BNC membrane is realized through the in situ incorporation of GO flakes into BNC matrix during its growth followed by the in situ formation of palladium nanoparticles. The Pd/GO/BNC membrane exhibits highly efficient methylene orange (MO) degradation during filtration (up to 99.3% over a wide range of MO concentrations, pH, and multiple cycles of reuse). Multiple contaminants (a cocktail of 4‐nitrophenol, methylene blue, and rhodamine 6G) can also be effectively treated by Pd/GO/BNC membrane simultaneously during filtration. Furthermore, the Pd/GO/BNC membrane demonstrates stable flux (33.1 L m^?2 h^?1) under 58 psi over long duration. The novel and robust membrane demonstrated here is highly scalable and holds a great promise for wastewater treatment.     

Effect of Gap Parameter on Electronic Heat Capacity and Magnetic Susceptibility of Graphene in the Presence of Holstein Phonons

Thermodynamic properties of gapped graphene-like structures by considering the effects of interaction between electrons and Holstein phonons have been studied. Particularly, we study the heat capacity and paramagnetic susceptibility of structures as a function of temperature within the Green’s function method with the help of Holstein model. The paramagnetic susceptibility and heat capacity can be derived by using density of states based on the Kubo formula. We have found the energy dependence of density of states for various values of gap in the presence of Holstein phonons. Finally, the temperature behaviors of specific heat and spin susceptibility of gapped graphene structure due to electron-phonon coupling have been investigated. Our results show the electron-phonon interaction leads to the appearance of a double van Hov singularity for each value of gap parameter. Also, electron-phonon coupling affects the value of heat capacity and magnetic susceptibility at low temperatures.     

On the Magnetic and Structural Properties of Neodymium Iron Boron Nanoparticles

Neodymium iron boron nanoparticles were synthesized by means of sol–gel method. Correlation between magnetic properties and structural features were evaluated. The Nd–Fe–B gel was formed in hydrogen atmosphere. The gel was subsequently annealed under vacuum condition to obtain Nd–Fe–B oxide phases. The oxides powders were reduced at different temperatures of 750, 775, 800, 825, 850, and 875 ^°C for 3 h in a mixture of Ar and H₂ atmosphere to prepare Nd₂Fe₁₄B nanoparticles. The role of reduction temperature on phase, morphologies, microstructure, and magnetic properties of the final powders was investigated by employing X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), and vibrating sample magnetometer (VSM), respectively. The results show that Nd₂Fe₁₄B phase was formed successfully at temperatures of 750–875 ^°C. Maximum coercivity of 1757 Oe was obtained at 875 ^°C. The variation of coercivity was described by considering the particle size and magnetocrystalline anisotropy constant.     

Large-amplitude dynamics of a functionally graded microcantilever with an intermediate spring-support and a point-mass

Numerical modelling and simulations are conducted on the large-amplitude dynamics of a functionally graded microcantilever with a tip-mass, additionally supported by an intermediate spring; the functionally graded microsystem is subject to a base excitation. Since one end of the microsystem is free to move, it undergoes large deformation; curvature-related nonlinearities play an important role. Taking into account this type of nonlinearity, using the Mori–Tanaka homogenisation scheme, as well as the modified couple stress theory, an energy technique is employed to derive the nonlinearly coupled equations for the longitudinal and transverse motions. An inextensibility assumption is applied for the functionally graded microcantilever, and hence, a nonlinear equation of motion for the transverse motion involving inertial (apart from stiffness) nonlinearity is obtained. For the functionally graded microsystem considered, effects of the length-scale parameter, the material gradient index, the tip-mass, and the stiffness of the spring-support on the nonlinear resonant responses are highlighted by means of a Houbolt’s finite difference scheme together with Newton–Raphson method.     

Sulfidation of 2D transition metals (Mo,W, Re,Nb, Ta): thermodynamics,processing, and characterization

Sulfidation of selected transition metal thin films (Mo, W, Re, Nb, Ta) was combined with thermodynamic calculations to study the synthesis of transition metal dichalcogenides (TMDCs) and understand variations among the metals as well as processing atmosphere. Metal seed layers were prepared by DC magnetron sputtering and sulfidized using sulfur vapor and H₂S. Surface chemistry, structure, and morphology of the films were investigated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and atomic force microscopy (AFM), respectively. XPS analysis revealed that after treatment with sulfur vapor (p (S₂) = 1–10 Torr), Mo, W, and Re films were transformed into MoS₂, WS₂, and ReS₂, respectively. However, Nb and Ta films changed little, and Nb₂O₅ and Ta₂O₅ remained the predominant components. Alternatively, conversion of Nb and Ta films to NbS₂ and TaS₂ was feasible under H₂S. Raman spectroscopy also revealed improved crystallinity for Mo, W, and Re sulfidized under H₂S. Isobaric and isothermal stability diagrams were calculated to identify feasible processing conditions (sulfur partial pressure and temperatures) for the sulfidation of all of the metals, and our findings were in good agreement with the XPS and Raman results. It was found that for Mo, W, and Re a p (S₂) = 10^?5 bar is sufficient for the metals to be converted to sulfide phases at 750 °C. On the other hand, due to very high stability of Nb₂O₅ and Ta₂O₅, even at very low p (O₂), a sulfur partial pressure of 10³–10⁴ bar is required to make NbS₂ and TaS₂, respectively. Nevertheless, thermodynamic calculations confirmed that Nb and Ta could be transformed to NbS₂ and TaS₂ under 760 Torr H₂S. AFM analysis revealed very smooth films for MoS₂, WS₂, and NbS₂ films, but dewetting of TaS₂, and ribbons for ReS₂. These results provide guidance for designing new processes for synthesizing 2D TMDCs.     

Numerical study on heat transfer and entropy generation of developing laminar nanofluid flow in helical tube using two-phase mixture model

Nanofluids and helical tubes are among the best methods for heat transfer enhancement. In the present study, laminar, developing nanofluid flow in helical tube at constant wall temperature is investigated. The numerical simulation of Al₂O₃-water nanofluid with temperature dependent properties is performed using the two-phase mixture model by control volume method in order to study convective heat transfer and entropy generation. The numerical results is compared with three test cases including nanofluid forced convection in straight tube, velocity profile in curved tube and Nusselt number in helical tubes that good agreement for all cases is observed. Heat transfer coefficient in developing region inside a straight tube using mixture model shows a better prediction compared to the homogenous model. The effect of Reynolds number and nanoparticle volume fraction on flow and temperature fields, local and overall heat transfer coefficient, local entropy generation due to viscous dissipation and heat transfer, and the Bejan number is discussed in detail and compared with the base fluid. The results show that the nanofluid and the base fluid have almost the same axial velocity profile, but their temperature profile has significant difference in developing and fully developed region. Entropy generation ratio by nanofluid to the base fluid in each axial location along the coil length showed that the entropy generation is reduced by using nanofluid in at most length of the helical tube. Also, better heat transfer enhancement and entropy generation reduction can be achieved at low Reynolds number.