Journal of Ultrafine Grained and Nanostructured Materials
Volume:55 Issue: 1, Jun 2022

In this study, to improve the corrosion performance, plasma electrolytic oxidation (PEO) coatings on AZ31B Mgalloy in a phosphate-based electrolyte containing hydroxyapatite nanoparticles were investigated. For this purpose,the corrosion behavior of coatings generated at different frequencies (100, 1000, and 2000 Hz) was studied. Theinfluence of coating frequency on the corrosion behavior of the coatings created as well as the microstructure of thecoating was investigated. Surface characteristics of the coatings were investigated using scanning electron microscopyand X-ray diffraction pattern. To investigate the corrosion behavior of coatings generated at different frequencies,polarization and impedance spectroscopy tests in simulated body fluid have been studied. The results showed that ata frequency of 1000 Hz, the created coating had a uniform surface with a lower porosity percentage. Also, the resultsof electrochemical tests showed that the corrosion resistance of the coating created at a frequency of 1000 Hz leadsto the lowest corrosion current density (5.83×10-8 A/cm2) in the coating and thus more became the most corrosionresistant

It is shown that the deformability of Ti49.2Ni50.8 and Ti50.0Ni50.0 alloys rolled with pulse electric current is considerably greater than that obtained by cold rolling. The influence of true strain and current density on features of the microstructure was investigated. It was demonstrated that severe grain refinement to size of 60-120 nm accompanies the electroplastic rolling process. At the same annealing temperature, the alloy with the initial martensitic structure has a larger grain size. These differences can probably be explained by the different recrystallization temperatures of deformed martensite and austenite. The intensity of strain hardening was compared for both alloys after electroplastic rolling (EPR). The reasons for the different behaviour in the EPR process are discussed.

Polysulfone (PSU) is one of the most frequently used polymers in membranes technology, and it can be electrospun to form nonwoven fibers. However, its hydrophilicity should be improved for water purification purposes. The fiber diameter in electrospun membranes can affect the physical properties of the product. The electrospinning parameters can largely control the average fiber diameter in electrospun membranes. In this study, PSU/SiO2/TiO2 nanocomposite membranes were fabricated via the electrospinning method, and the effect of the introduced nanoparticles on the properties of the primary solutions and hence the average fiber diameter has been investigated. Silica and Titania nanoparticles (0, 0.5, 1wt%) were added to 20 wt.% PSU solution and were electrospun at a constant voltage and feed rate of 15.5 kV and 2 ml/h, respectively. The conductivity of the prepared solutions and the surface tension was measured. In addition, the rheological behavior of the solutions was evaluated using rheometric measurements. Finally, scanning electron microscopy (SEM) was used to study the morphology of the membranes and estimate the average fiber diameter. The obtained results showed that increasing titania nanoparticles at a constant SiO2 content has decreased the average diameter from 959 to 712 nm, which can be attributed to the higher conductivity and lower surface tension of solutions with a higher TiO2 amount leading to facilitated fiber stretching during electrospinning. On the other hand, introducing silica nanoparticles to a certain extent can decrease the fiber diameter due to the predominant effect of improved conductivity. However, beyond this extent, the significant increase in the solution viscosity at 1wt.% caused the formation of thicker fibers with an average diameter of about 1160 nm. These findings emphasize the importance of solution properties for designing an efficient water membrane by controlling its fiber diameter and specific surface area.

In this work, the ZnO/CuO nanocomposite was synthesized with two different initial pH values in an acidic media through a simple one-step and cost-efficient chemical bath precipitation method. To alter the pH value of the solution, nitric acid was added dropwise and initial pH values were 1.5 and 4.5, respectively. The crystal phase structure of the samples was investigated by X-ray diffraction analysis (XRD), indicating the formation of wurtzite structure of ZnO and monoclinic structure of CuO. Additionally, the morphological structure of the as-formed nanocomposites was studied by field emission scanning electron microscopy (FESEM). It was demonstrated that at pH = 4.5 and 1.5, ZnO nanorods/CuO nanoflakes and ZnO nanoparticles/CuO nanosheets were formed, respectively. For optical characterizations, diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectra were performed. The band gap energy of the as-prepared samples was calculated at 3.08 and 2.9 eV with an initial pH of 1.5 and 4.5, respectively. Furthermore, PL data revealed that the sample synthesized in pH = 4.5 exhibits a significant decrease in electron/hole recombination rate compared with that of the sample fabricated in pH = 1.5. Accordingly, the photocatalytic activity of the as-prepared samples was studied employing methylene blue (MB) under visible-light irradiation. Overall, the prepared sample at pH = 4.5 and pH = 1.5 demonstrated ~76% and ~66% photo-degradation efficiency of MB after 150 min, respectively. Finally, the role of holes and hydroxyl radicals on the degradation of MB were proposed using charge carrier scavengers.

Organic-inorganic halide perovskites (OIHP) are an emerging family of semiconductor materials widely used in the fabrication of optoelectric devices, including solar cells, due to their superior optical and electrical properties. Poor long-term stability of OIHPs is the main hindrance to the commercialization of perovskite solar cells. Using 2D Ruddelsden-Popper perovskites is a common approach to improve perovskite solar cell stability. However, their 2D structure restricts the transport of charges, thus reduces the photovoltaic performance of perovskite solar cells. Out-of-plane growth of 2D perovskite film can significantly improve carrier transport and consequently reduces the rate of non-radiative recombination. One of the main factors that affects the preferential growth of 2D perovskites is the type of spacer cation that exists in the 2D perovskites structure. Herein, butylammonium (BA+) and phenetylammonium (PEA+) spacer cations, as well as their combination, are employed in 2D perovskite thin film, and their effects on preferential growth and phase segregation have been investigated. X-ray diffraction (XRD) data shows that the BA-based 2D perovskite has a more desirable (220) preferential direction, but the preferred peaks of PEA-based 2D perovskite have higher intensity and narrower full width at half maximum (FWHM) than the BA-based counterparts, which is due to the rigid nature of the PEA+ compared to the BA+ molecule. It is also observed that the replacement of BA+ instead of PEA+ significantly reduces phase segregation. This phenomenon is probably related to the phenyl ring of the PEA+ molecule, which is entirely solvophobic and slows down the formation of DMF.PEAI complex during the crystallization step, which in turn leads to the formation of small n 2D perovskite nucleus causing phase segregation. SEM images also represent that the BA, PEA-based film has a smoother surface and lower pinholes than the PEA and BA-based 2D perovskite.

In the energy storage field, lithium-ion batteries were known to be the most important approach for mitigating the environmental impacts of fossil fuels. Cathode materials are the crucial part of a lithium-ion battery, and LiFePO4 (LFP) cathode material was selected for its high voltage (3.45 V vs. Li+/Li), high theoretical capacity (170 mAh.g-1), significant cyclic stability, and environmental friendliness. On the contrary, the main downside of LFP materials is their one-dimensional lithium-ion diffusion channel at the crystallographic direction of [010]. These channels can be blocked by antisite defects, plunging the specific capacity of LFP materials. Thus, in order to reduce such impacts, having sheet-like morphologies with a significant crystallographic plane of (010) is essential. A great deal of research has been performed using a solvothermal method for the synthesis of LFP materials, and factors - as precursors, pH of the solution, temperature, time, and additives - were known to have significant roles in the structural as well as electrochemical properties of LFP materials. In this study, different amounts of the amino acids, namely glycine, and glutamic acid, were introduced in the solvothermal synthesis of LFP materials, and their respective roles in morphology and electrochemical characteristics were investigated. The self-assembled morphology of LFP particles using glycine was discussed by the formation of peptide bonds. Additionally, having another carboxylic acid group in the molecular structure of glutamic acid sustained a low pH in the solvothermal solution; therefore, the formation of self-assembled morphology could not occur during the synthesis process. Additionally, the specific capacity of the LFP/C materials after the heat treatment was discussed by Rietveld refinement investigations for determining the antisite defects.

Tin oxide (SnO2) has gained much attention in various fields such as optoelectronic industries and gas sensors. SnO2 thin films have been extensively used as electron transport layers (ETL) in planar perovskite solar cells due to their high stability, good processability, and appropriate band alignment. However, it suffers from relatively low charge mobility. Although there were some successful attempts to improve the charge mobility of SnO2 thin films by incorporating carbon nanotubes (CNT) or graphene in its structure, simultaneous addition of these 1D/2D mixed nanostructures in SnO2, which can lead to far better optoelectronic properties has never been reported. 1D/2D mixed nanocomposite thin films based on SnO2/CNT/graphene are successfully synthesized in this research, and the structural, morphological, and optoelectrical properties of the films are investigated. For this purpose, SnO2 sols were prepared by dissolving and refluxing SnCl2.2H2O in 1-propanol at 87 °C for 2 h. In order to synthesize nanocomposite samples, various amounts of CNT and/or graphene were added to the solution prior to refluxing. The films were deposited by dip coating and subsequently calcined at 180 °C. The thin films were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and UV-Vis spectroscopy. The XRD results confirm the formation of the SnO2 phase. FESEM images thoroughly demonstrate the presence of CNTs and graphene beside SnO2 nanoparticles. The absorbance of the films as well as their band gaps are remained almost constant after CNT/graphene addition.

The present work aimed to develop the anodic electrophoretic deposition (EPD) of sodium alginate/nano-Bioglass® (Na-Alg/nBG) bioactive nanocomposite coatings on Mg-Zn-Ca alloy without any previous surface pre-treatment (other than polishing). In comparison with other alloys, such as stainless steel or titanium, the density and elastic modulus of magnesium are similar to those of natural bone, and corrosion products of Mg-Zn-Ca alloy are not harmful to the patient body. Alginate is an anionic natural polysaccharide which, due to its low toxicity and biocompatibility, has been studied for different biomedical applications. Through the presence of Bioglass® particles in the coatings, mechanical properties are advanced by increasing adhesion to the substrate and also increases the formation of hydroxyapatite after immersion in simulated body fluid (SBF). A stable water/ethanol EPD suspension was used to produce composite nBG/Alg coating for potential biomedical applications. nBG contents (3 g/L) were studied for a constant concentration of sodium alginate (10 g/L); DC voltage and deposition times varied between 3-20 V and 10-60 seconds, respectively. It has been revealed how electrophoretic deposition (EPD) occurs on the magnesium alloy surface. The coatings composition was analyzed by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) and the surface of the coatings was studied with field emission scanning electron microscopy (FESEM). For investigating corrosion protection of bioactive coatings, polarization and electrochemical impedance spectroscopy (EIS) tests were used; samples were immersed in simulated body fluid (SBF) at 37°C and results were compared with the bare uncoated Mg-Zn-Ca alloy. The present work confirmed that electrophoretic deposition is a practical method for the co-deposition of Bioglass® nanoparticles and Na-Alg that can be used to produce a wide range of magnesium alloy coatings with tailored microstructures and surfaces with biomedical applications.

Polypropylene (PP)/Carbon-Nanotube (CNT) nanocomposites and PP/CNT/Glass fiber (GF) hybrids were foamed using supercritical carbon dioxide (CO2) through a batch foaming process. Uniform nanofiller dispersion was assessed by field emission scanning electron microscopy (FE-SEM). By incorporating CNTs in the matrix, the average cell size was reduced to less than one-second that of neat foam (from 49 to 22.5 µm), and cell density increased. As a matter of fact, high electrical conductivity is crucial to achieving a great electromagnetic interference (EMI) shielding performance. Hence, CNTs were loaded up to 3 wt%. By incorporation of CNTs, electrical conductivity increased from ~10-16 to ~10-4 and ~10-5 S/cm for unfoamed and foamed PP/CNT3 samples, respectively, and EMI shielding effectiveness increased to 11 dB and 9.5 dB for unfoamed and foamed PP/CNT3 samples, respectively. After evaluating the microstructural and electrical properties of the nanocomposites and their foams, as well as elucidating the foaming process's role in the EMI shielding performance of the hybrids and foams, there was a great need to investigate the mechanical properties of hybrid systems and the effect of fiber concentration. Tensile properties revealed that by increasing the fiber content, young modulus and tensile strength increased for unfoamed samples and decreased for foams. The compression test of hybrid foams showed that by loading nanotubes and glass fibers, compressive mechanical properties increased. Also, by adding CNTs and glass fibers, impact properties increased and decreased, respectively, for solid and foamed hybrids. Moreover, by loading both additives impact properties enhanced.

Nanotechnology has a widespread application in textile fields, especially in technical textiles, finishing, and dyeing processes. Accordingly, in this research, we investigated the effect of nanogold as a mordant for woolen textile dyeing. The purpose of this research was to produce a multifunctional woolen textile by applying nanogold particles as a novel mordant. Therefore, after the yarn purification and neutralization, the yarns were pre-treated with nanogold (60ppm) in boiling water for 1 hour and then were dyed using the onchrome method. Nanoparticles and dyed yarns were subsequently assessed through DLS, EDS, FESEM, SEM, washing fastness, light fastness, and antibacterial properties. The obtained results indicated that nanogold was absorbed by the wool and the washing fastness was enhanced without affecting softness and causing stains whereas light fastness remains constant. Furthermore, the yarns showed excellent antibacterial properties against Gram-positive and Gram-negative bacteria, namely Escherichia Coli and Staphylococcus Aureus.

In this study, the Al-BN nanocomposite powders were prepared using two different methods of i) ultrasonic mixing, and ii) planetary ball milling. The Al-BN bulk nanocomposite samples were fabricated by hot extrusion. Morphology of powders through the preparation process and fracture surface were characterized using scanning electron microscopy and the microstructure of optimized bulk nanocomposite sample was investigated by a transmission electron microscopy and electron back scattered diffraction technique (EBSD). The mechanical properties of composite samples were examined by uniaxial tension test. With the use of planetary high energy ball milling and hot extrusion, the ultimate tensile strength of fabricated milled and unmilled pure Al samples reached to 104 MPa and 212 MPa, respectively. The ultimate tensile strength of extruded milled nanocomposite increased to 297, 330, 333MPa by adding 1, 2 and 4 wt. % BN, respectively. In the process of composite powders mixing and hot extrusion, the mechanical properties of samples were significantly decreased. By increasing the BN content within range of 0-6 wt. %, the tensile strength of mixing and extruded composite samples was not changed. On the other hand, the ductility is reduced from 24 % for pure Al to 5 % for Al-6 wt. % BN.

Biosynthesis of Sm2O3 NPs using Sm(NO3)3.6H2O and double bloom purple Rose of Sharon in ethanol, produced an efficient catalyst for the synthesis of some nitrogen-containing heterocycles such as morpholine and piperidine derivatives. Sm2O3 nanoparticles have been confirmed by FT-IR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Energy-dispersive X-ray spectroscopy (EDX). The products were obtained in moderate to good yields under mild reaction conditions and identified by CHN analysis, NMR, and FT-IR spectra. The catalyst could be easily separated from the reaction mixture by centrifugation, washed, dried, and re-entered to a fresh reaction mixture 4 times without considerable loss of activity.