Optimized structure and electrochemical properties of sulfonated carbon nanotubes/Co–Ni bimetallic layered hydroxide composites for high-performance supercapacitors

Technical development in electronic devices is frequently stifled by their insufficient capacity and cyclic stability of energy-storage devices. The nano-structured materials have sensational importance for providing novel and optimized combination to overcome exiting boundaries and provide efficient energy storage systems. Metal hydroxide materials with high capacity for pseudo-capacitance properties have grabbed special attention. Lately, the blend of nickel and cobalt hydroxides has been considered as a favorable class of metallic hydroxide materials owing to their comparatively high capacitance and exceptional redox reversibility. The sulfonated carbon nanotube fluid (SCNTF) was prepared by the ion exchange method to be utilized as the exceptional templates due to astonishing specific surface area, ensuring the maximum utilization of the active material. The CoNi-layered double hydroxides (LDHs)/SCNTF core-shell nanocomposite was prepared by the simple solvothermal method. Structural analysis showed that the composite material had the high conductance of carbon materials, the pseudo-capacitance characteristics of metal hydroxides, and porous structure, which facilitates the ion shuttle when the electrolyte reacts with the active material. Electrochemical analysis results showed that CoNi-LDHs/SCNTF had excellent rate performance, reversible charge-discharge properties and cycle stability. It exhibited an extreme specific capacity of 1190.5 F g^?1 at a current density of 1 A g^?1; whereas specific capacity remained 953.7 F g^?1 at the current density was 10 A g^?1. In addition, the capacity retention rate after 5000 charge-discharge cycles at a current density of 20 A g^?1 was 81.0%. The results indicated that the CoNi-LDHs/SCNTF core-shell nanocomposite material is cost efficient and an effective substitute in energy storage applications.     

ZnO·2.7Al2O3 nanocomposite with high optical transparency

Here we report a transparent dual-phase ZnO·2.7Al₂O₃ ceramic. The composite is pore-free and consists of thin nanosheets with a spinel phase and a hexagonal phase, while the two phases match closely in both lattice and refractive index. Such features result in excellent optical transmittance (maximum value >80% in the visible spectrum) at comparable phase volume. This work may provide a new thought for the rational structural design of optical nanocomposites.     

大豆蛋白纳米纤维对铁纳米颗粒的稳态化作用

为明确大豆蛋白纳米纤维的结构形成和扩宽铁强化剂的食品工业应用，以大豆分离蛋白（soy protein isolate，SPI）为原料，通过5 h的酸热处理制备纳米纤维（soy protein isolate fibrils，Fib SPI），系统研究纤维形成前后蛋白结构的变化，并进一步制备铁纳米颗粒（iron nanoparticles，Fe NPs），探究Fib SPI对铁的稳态化作用。研究结果表明：在酸热处理过程中，SPI产生大量的β-折叠结构，其与硫磺素T结合，显示出增强的荧光强度；此外，7S组分先发生降解，利于纤维成核形成，随后11S逐渐被水解，促进纤维生长；同时水解产生大量的小肽组分，提高了产物的还原力。研究进一步利用Fib SPI递送铁纳米颗粒（Fe NPs），发现与原始SPI相比，铁纳米颗粒可在Fib SPI原位形成胶体稳定的铁-大豆蛋白纳米纤维复合物（Fe FibSPI），并以Fe（II）形式存在，其对乳液体系色泽及稳定性的影响较硫酸亚铁或氯化铁小。该研究可为构建新型植物基铁强化剂递送体系提供理论和方法指导。     

Effect of lattice structure evolution and stacking fault energy on the properties of Cu–ZrO2/GNP nanocomposites

A hybrid nanocomposite comprising nanosized ZrO₂ and graphene nanoplatelet (GNP)-reinforced Cu matrix was synthesised via powder metallurgy. The influence of sintering temperature and GNP content on the electrical and mechanical behaviour of the Cu–ZrO₂/GNP nanocomposite was investigated. The ZrO₂ concentration was fixed at 10% for all the composites. Upon increasing the GNP concentration up to 0.5%, a significant improvement was observed in the compressive strength, microhardness, and electrical conductivity of the composite. Furthermore, the properties were significantly improved by increasing the sintering temperature from 900 to 1000 °C. The compressive strength, hardness, and electrical conductivity of Cu–10%ZrO₂/0.5%GNP were higher than those of the Cu–ZrO₂ nanocomposite by 60, 21, and 23.8%, respectively. This improvement in the mechanical properties is because of the decrease in the crystallite size and dislocation spacing, which increases the dislocation density, thereby increasing the impedance towards dislocation movement. The lower stacking fault energy of the hybrid nanocomposites enables easier electron transfer within and between the Cu grains, resulting in an improved electrical conductivity. The enhancement in strength and electrical conductivity were aided by the GNPs and ZrO₂ nanoparticles that were dispersed widely in the Cu matrix.     

Molecular interactions arising in polyethylene-bentonite nanocomposites

High density polyethylene (HDPE), linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) are blended, and compared against a similar mixture but functionalized LDPE with maleic anhydride (MAh), HDPE-LLDPE-LDPE-g-MAh. In order to obtain nanocomposites from these polymer blends, a modified bentonite was added by incorporating l -lysine into the bentonite galleries by melt extrusion. The resulting nanocomposites presented improved mechanical properties linked to strong polymer-bentonite interactions and exfoliated structures as verified by transmission electron microscopy and rheometry. A detailed analysis of the feasible polymer-bentonite interactions was conducted, of particular concern between the polar MAh groups and the intercalated l -lysine. To gain further insights into the type of molecular interactions (i.e. polymer-bentonite), a model nanocomposite was synthesized in solution to carry out further assessments through NMR, infrared spectroscopy and rheology analysis. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46920.     

Polyetherimide-LaNi5 composite films for hydrogen storage applications

This study investigates the preparation of polyetherimide (PEI) – LaNi₅ composites films for hydrogen storage. Prior to the polymer addition, LaNi₅ was ball-milled at different conditions (250, 350, and 450 RPM) and annealed at 500 °C for 1 h under vacuum. The composites were produced with BM-LaNi₅-350 (PEI/LaNi₅-350) and annealed BM-LaNi₅-350 (PEI/LaNi₅-350-TT). Membranes were successfully produced through solvent casting assisted by an ultrasonic bath. The particles dispersion and the film morphology did not change after hydrogenation cycles. In the H₂ sorption experiments at 43 °C and 20 bar, the films stored H₂ without incubation time; both samples reached a capacity of ~0.6 wt%. The H₂ sorption kinetics of PEI/LaNi₅-350 was comparable to that of BM-LaNi₅-350, whereas PEI/LaNi₅-350-TT presented significantly slower kinetics. LaNi₅ oxidation was hindered by PEI, showing that it can be explored to improve metal hydrides air resistance. The results demonstrated that PEI films filled with LaNi₅ are promising materials for hydrogen storage.     

Enhanced dielectric and piezoelectric properties in potassium sodium niobate/polyvinylidene fluoride composites using nano-silicon carbide as an additive

Piezoelectric materials are an indispensable part of modern life. Yet the existing environmental issues with conventional lead-based piezoelectrics has motivated scientist to develop novel substitutes including lead-free piezoelectric polymer composites. Following this path, the present research has focused on the fabrication of ternary composites of Polyvinylidene fluoride (PVDF)/Potassium Sodium Niobate (KNN)/nano-Silicon carbide (SiC) via hot compression molding and studying the effect of additives on the PVDF structure and the electrical properties of the composite. The obtained scanning electron micrographs and density measurements showed that the fabrication method provided dense samples. The activated polarization phenomena in the prepared samples enhanced dielectric permittivity and dielectric loss at a constant frequency with increasing KNN and SiC contents. Besides the expected dipole polarization, the presence of interfaces in the composites gave rise to the Maxwell–Wagner–Sillars effect and its corresponding polarization phenomenon. The semiconductive nature of SiC also promoted space charge polarization. However, these properties were frequency-dependent because the first two polarization mechanisms are deactivated at high frequencies. XRD patterns showed that SiC addition can alter the primary crystalline structure of PVDF and promote β-phase formation in the poled samples. Piezoelectric measurements confirmed the significant role of SiC addition to PVDF-KNN composites. The most significant increase in the piezoelectric properties was observed in PVDF-60KNN-1SiC, with a 183% increase in d₃₃ value. The PVDF-80KNN-1SiC had the highest d₃₃ value of 30.5 pC/N. It also had the best piezoelectric voltage coefficient and hence the highest figure of merit. Higher SiC contents restrict the efficiency of poling by forming a conductive path across the sample which would deteriorate the piezoelectric performance of the material. The present findings show that PVDF-KNN-SiC composites can be considered as a potential flexible piezoelectric material for future applications.     

Effect of iron content on the wear behavior and adhesion strength of TiC–Fe nanocomposite coatings on low carbon steel produced by air plasma spray

In this study, the effect of Fe content on the abrasion behavior of TiC–Fe nanocomposite coatings applied on the CK45 steel substrate by air plasma spray method was investigated. For this purpose, milled TiC powder was prepared at 1, 2, 3 and 4 h milled TiC powder for 4 h was selected as the suitable sample. In the next step, a suitable sample mixture with different iron powder concentrations of 5, 10, 15, 20 and 25% was prepared by mechanical milling. The granulated mixture was applied to the substrate using air plasma spray technique. Microstructural and phase analyzes were performed using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). According to the results of Williamson-Hall calculations, the TiC crystallites' size decreased by 49 nm–29 nm, and network strain reached 0.16% by increasing milling time from 1 h to 4 h. Studies have shown that the coatings contain titanium carbide, iron oxide, and titanium oxide, with the number of phases formed depending on the amount of iron in the chemical composition. Investigation of the tribological properties of the coating layer showed that with increased iron content in the coating, the wear resistance of the samples is reduced. Hardness tests on coatings indicate that adding iron to nanocomposite from 5 to 25% reduces hardness from 1025 to 699 Hv. It can be argued that a slight increase in the adhesion strength of the coating to the substrate is due to increased wettability because of the formation of molten iron in the coating.     

Pt-WC/Mnt三元纳米复合材料的制备及其电催化性能

以剥离后的蒙脱石(Mnt)片层为载体、六氯化钨(WCl6)为钨源,通过浸渍负载及原位还原碳化获得了碳化钨(WC)与蒙脱石(Mnt)纳米复合材料,然后将氯铂酸(H2PtCl6)通过浸渍负载于复合材料上,并在氢气(H2)中还原得到Pt-WC/Mnt三元纳米复合催化材料。采用X射线粉末衍射和透射电子显微镜对三元纳米复合催化材料的物相、形貌和结构进行表征,采用三电极体系和循环伏安法测试了样品的电催化性能。结果表明:样品物相主要为WO3和WC,蒙脱石片层结构明显,铂(Pt)纳米粒子均匀分布于WC/Mnt复合材料的外表面。Pt-WC/Mnt三元纳米复合材料对甲醇电催化氧化具有较高的催化活性,并且在酸碱体系中均具有良好的稳定性。     

Microstructure and mechanical properties of TiC nanoparticle-reinforced Mg−Zn−Ca matrix nanocomposites processed by combining multidirectional forging and extrusion

TiC nanoparticle-reinforced Mg−4Zn−0.5Ca matrix nanocomposites were processed by combining multidirectional forging (MDF) and extrusion (EX). The grain size of the nanocomposite after MDF+EX multi-step deformation was significantly decreased compared with that processed only by MDF. The average size of the recrystallized grains gradually increased after EX with increasing the number of MDF passes at 270 °C. However, the grain size significantly decreased by MDF processing at 310 °C. Both fine and coarse MgZn₂ phases appeared in the (MDF+EX)-processed nanocomposites, and their volume fractions gradually increased with increasing the number of MDF passes before EX. Ultrahigh tensile properties (yield strength of ~404 MPa, ultimate tensile strength of ~450.3 MPa and elongation of ~5.2 %) were obtained in the nanocomposite after three MDF passes at 310 °C followed by EX. This was attributed to the refinement of the recrystallized grains, together with the improved Orowan strengthening provided by the precipitated MgZn₂ particles that were generated by MDF+EX multi-step deformation.