Unique Surface Morphology Research Articles

Temperature-Dependent Growth and Evolution of Silicene on Au Ultrathin Films-LEEM and LEED Studies.

The formation and evolution of silicene on ultrathin Au films have been investigated with low energy electron microscopy and diffraction. Careful control of the annealing rate and temperature of Au films epitaxially grown on the Si(111) surface allows for the preparation of a large scale, of the order of cm2, silicene sheets. Depending on the final temperature, three stages of silicene evolution can be distinguished: (i) the growth of the low buckled phase, (ii) the formation of a layered heterostructure of the low buckled and planar phases of silicene and (iii) the gradual destruction of the silicene. Each stage is characterized by its unique surface morphology and characteristic diffraction patterns. The present study gives an overview of structures formed on the surface of ultrathin Au films and morphology changes between room temperature and the temperature at which the formation of Au droplets on the Si(111) surface occurs.

Neodymium oxide doped neodymium phosphate as efficient electrocatalyst towards hydrogen evolution reaction in acidic medium

The development of an inexpensive, more stable and efficient electrocatalyst for hydrogen evolution reaction in water splitting has become more challenging task for researchers in present scenario. In the present study, different morphologies of two rare earth based nanomaterials Gd2O3:GdPO4 and Nd2O3:NdPO4 were successfully made via simple one-step hydrothermal method and used as catalyst for hydrogen evolution reaction in acidic medium (0.5 M H2SO4). The Nd2O3:NdPO4 exhibited comparable catalytic activity with standard Pt/C electrode material in 0.5 M H2SO4. The obtained overpotential to achieve current density of 10 mA cm−2 for Nd2O3:NdPO4 and standard Pt/C was 134 and 123.5 mV vs. RHE, respectively and their corresponding Tafel slopes were 55.6 and 52.5 mV.decade−1, respectively. The efficient catalytic activity of the prepared catalyst was due to its unique surface morphology and strong interaction between the present elements. The turnover frequency was found as 0.00008637 and 0.00171 s−1 for Gd2O3:GdPO4 and Nd2O3:NdPO4 nanomaterials, respectively and their corresponding BET surface area were 14.9663 and 78.2404 m2 g−1. Based on literature reports and best of our knowledge, Nd2O3:NdPO4 is an efficient novel catalyst and its electrocatalytic activity is not reported till date.

Polyacrylamide Gel Scaffold Immobilized with Silver Nanoparticles as SERS Substrates and Catalysts for H2 Generation via Methanolysis of NaBH4

This report discloses the preparation of a series of polyacrylamide materials with unique surface morphology. Polyacrylamide with N,N′-methylenebisacrylamide cross-linking provides reactive sites for the reduction of silver nitrate. The reaction refurbishes the relatively smooth polymer surface to clusters of submicron cubes impregnated with silver nanoparticles (AgNPs) and residual Ag(+1) ions. Subsequent treatment with NaBH4 grows additional silver structures from the AgNPs seeded in the polymer to give an overall morphology reminiscent of the famous great barrier reefs, the namesake of this material─the Great Barrier Gel (GBG). The GBG surface features a high content of active silver nanostructures. The use of GBG as a substrate for surface-enhanced Raman scattering (SERS) and a film catalyst for the methanolysis of NaBH4 demonstrates its versatility. The SERS sensitivity of this material is 10–10 M, or better, as assessed using 4-aminophenyl disulfide. It catalyzes the production of H2 by the methanolysis of NaBH4 without significant loss of activity in an exhaustion test. These methods create an enlarged surface area on the shape-adapting polymer material, chemically and productively, while generating a least amount of chemical waste.

Multi-application fennel-based composites for the adsorption of Cr(VI) ions from water and control of Escherichia coli and Staphylococcus aureus

Ubiquitous toxic metal ions and pathogenic microbes in contaminated water affects the lives of millions of people globally. The synthesis of multifunction composites that can uptake metal ion from contaminated water and simultaneously inhibit the growth of microbes is a novel concept. This study developed composite substances from fennel seeds impregnated with binary nanoparticles of CuO-ZnO. These composites were used to remove Cr(VI) from water and inhibit the growth of Escherichia coli and Staphylococcus aureus. SEM analysis of the surface of the starting material showed various sizes and shapes of pores. In contrast, the composites showed unique surface morphology cavity features and a rough texture. FTIR spectra indicated that peaks for (–OH), (–C=O) and (–COOH) shifted in the composites. The Freundlich model and PSO described the uptake process. The highest adsorption capacity recorded at pH 2 and 308 K were 75.96 and 84.77 mg/g for FS/CuO-ZnO[1:2] and FS/CuO-ZnO[2:1], respectively. Cr(VI) uptake was due to different adsorption processes such as electrostatic attraction, weak hydrogen bond and Cr(VI)–π complexation. The values of ΔGo became more negative when the solution temperature was increased. Data for ΔHo revealed that adsorption was controlled by chemisorption. The antibacterial assays indicated that the materials are effective in preventing the growth of microbes. The incorporation of CuO-ZnO onto the fennel seeds improved their antimicrobial activity. PFS were ineffective against E. coli but effective (MIC- 50 μg/mL) against S. aureus. Furthermore, composites were more effective against S.aureus (MIC- 25 μg/mL) than E.coli (MIC- 50 μg/mL).

Co/Zn bimetal organic framework elliptical nanosheets on flexible conductive fabric for energy harvesting and environmental monitoring via triboelectricity

Flexible and portable power sources are imperative chunks of wearable electronic devices. Fabric-based triboelectric nanogenerators (TENGs) have become most promising energy sources for wearable electronic devices as they can generate electrical energy from biomechanical movements with great flexibility. In this study, a highly flexible Co/Zn bimetal organic framework based TENG (BMOF TENG) is fabricated. Facilely prepared Co/Zn BMOF nanosheets are coated on flexible conductive fabric (BMOF/FCF) and utilized as the tribo-positive material against PTFE/Al based tribo-negative material for the fabrication of the BMOF TENG. The content of Zn is varied from 0% to 50% to achieve superior electrical output and observed that the 15% of Zn is appropriate for superior electrical output. The open circuit voltage, the short circuit current, and the charge density of the BMOF TENG are increased from 11 V to 47 V, from 1.06 µA to 7 µA, and from 4 nC/cm 2 to ~17 nC/cm 2 , respectively when the Zn content is increased from 0% to 15%. Thus, the optimized content of Zn in Co/Zn BMOF helped to enhance the electrical output of the BMOF TENG by nearly 450%. The output power of the BMOF TENG is found to be 1.1 mW/m 2 at a load resistance of 2 MΩ. As the phenomenon of gas sensing is largely associated to the surface of the material, the advantage of unique surface features of the BMOF/FCF is utilized in sensing hazardous gases. The device has shown variations in its electrical output in the presence of air and targeted gas and the good selectivity towards ammonia at room temperature. Ultimately, the BMOF TENG proposed in this study can convert mechanical energy into electrical energy and can be employed as an ammonia sensor in environmental monitoring and food quality assessment. • For the first time, Co/Zn bimetal organic framework (BMOF) nanosheet coated fabric is used for TENG. • At the optimized content of Zn (15%) in Co/Zn BMOF, the BMOF TENG is generated enhanced electrical output. • Fabric based flexible BMOF TENG is successfully employed as a room temperature ammonia sensor. • The unique surface morphology of BMOF has helped to evince good sensing behavior of the device. • Proposed BMOF TENG is able to serve as an energy harvesting as well as environmental monitoring device.

Study of wear and corrosion behavior of cathodic plasma electrolytic deposition of zirconia– hydroxyapatite on titanium and 316L stainless steel in Ringer’s solution

Abstract The wear resistance and corrosion behavior of titanium and 316L stainless steel were studied after depositing a composite coating of zirconia and hydroxyapatite using the cathodic plasma electrolytic deposition technique. No sign of adhesive wear was observed on coated samples due to the unique surface morphology of the treated samples, after a pin on disk wear test in Ringer’s solution. The average values of friction coefficient for treated titanium and steel samples were observed to be 0.2 which exhibited a decrease of about 4 fold for titanium and 7 fold for steel with respect to the substrates. As a result of potentiostatic cyclic tests in Ringer’s solution the corrosion current density of coated steel (2.47 × 10–10 A cm–2) was found to be much lower than for the steel substrate (1.87 × 10–7 A cm–2), treated and untreated Ti (6.60 × 10–6, 4.17 × 10–7 A cm–2), indicated the increase in corrosion resistance of steel and decrease of it for titanium after coating.

Investigation of Spray and Roll to Roll Coated Gas Diffusion Electrode Surface & Bulk Properties Using Microscopy and Spectroscopy

Further development of large-scale manufacturing capabilities for the most critical component in polymer electrolyte membrane fuel cells (PEMFC), the membrane electrode assembly (MEA) is needed. Advances in MEA manufacturing capabilities could reduce one of the major cost factors associated with MEA production, the platinum group metal (PGM) catalysts currently used at the cathode electrode for PEMFCs. While spray coating methods have been prevalently used at lab-scale for MEA fabrication, it is desirable to move towards roll-to-roll (R2R) techniques to enable scalable production. Gas diffusion electrode (GDE) based MEAs are easier to manufacture in a R2R fashion than catalyst coated membrane (CCM) based MEAs, since the catalyst layer is deposited directly on the gas diffusion media (GDM) without inducing the PEM swelling observed via other fabrication routes.1 Understanding interfacial properties of these electrodes is important for optimization of electrochemical performance and fabrication procedures employed for wide-scale manufacturing of PEM electrodes.Key surface properties such as surface morphology and surface chemistry, as well as the bulk electrode nanostructure and composition were analyzed for a variety of GDEs with catalyst layers (CLs) prepared by R2R and spray coating methods using X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Energy Dispersive Spectroscopy (EDS). The R2R-coated GDEs were fabricated using the slot die and microgravure coating methods on the same GDM substrate (Freudenberg H23C8) and they were made with both alcohol- and water-rich ink solvent ratios. The ultra-sonic spray coated GDEs were fabricated using both SGL 29BC and H23C8 GDM. In some cases, the spray coated GDEs had an additional amount of ionomer added, referred to as ionomer overlayer.2,3 The water-rich slot die R2R-coated GDE and the spray-coated GDE with an additional ionomer overlayer achieved the highest performance from this set of GDEs. Additionally, these GDEs showed the highest ionomer content measured by both XPS and SEM-EDS and shared a similar level of low surface roughness, implying the differences in composition and performance result from the different coating processes. Interestingly, STEM-EDS didn’t reveal a higher ionomer concentration in these samples, suggesting that these fabrication methods enrich the top surface layer without a significant impact on the bulk electrode. It was also found that the different microporous layer (MPL) surface properties inherent to a specific GDM influence the electrode morphological properties such as surface roughness as well as surface chemistry. The differences in MPL porosity lead to a unique surface ionomer enrichment degree and morphology at the CL surface that will interface with the membrane. These CL surface properties that are in contact with the membrane are hypothesized to be the reason for the improved performance metrics despite fabricating the GDE based MEAs under the same conditions. This work improved the knowledge of how a change in just one material component, or varying the fabrication process, can lead in some cases to vast differences and in others to subtle changes in initial performance, while also demonstrating the effectiveness of multiple characterization techniques towards identifying processing-property-performance trends. Mauger, S. A., Neyerlin, K. C., Yang-Neyerlin, A. C., More, K. L. & Ulsh, M. Gravure Coating for Roll-to-Roll Manufacturing of Proton-Exchange-Membrane Fuel Cell Catalyst Layers. Journal of The Electrochemical Society 165, F1012–F1018 (2018).Wang, M. et al. Impact of Microporous Layer Roughness on Gas-Diffusion-Electrode-Based Polymer Electrolyte Membrane Fuel Cell Performance. ACS Applied Energy Materials 2, 7757–7761 (2019).Mauger, S. A. et al. Fabrication of high-performance gas-diffusion-electrode based membrane-electrode assemblies. Journal of Power Sources 450, (2020).

Influence of the deposition interruption on the texture degree of barium hexaferrite BaFe12O19 films

BaFe 12 O 19 films on Al 2 O 3 (001) substrates were synthesized by ion beam deposition with post-annealing. Three deposition regimes were applied, resulting in unique surface morphology and X-ray diffraction patterns of obtained samples. In the first case, the deposition process was interrupted several times and the sample was subjected to ex situ annealing at 900 °C after each interruption. As a result, a film with high texture degree (about 97 %) was obtained. In the second case, the deposition process was interrupted the same number of times, but during each pause the film remained in the vacuum chamber for 10 min at 300 °C. This approach resulted in a medium texture degree of the sample (about 72 %). In the third case, there were no breaks in the deposition process and the texture of the resulting film was extremely poor. An explanation for the observed differences is proposed. To improve the texture of the films, a second annealing at 1280 °C for 10 h was applied, but as a result strong interdiffusion and misorientation of the grains occurred. • Interruptions of the deposition of BaFe 12 O 19 led to an improvement in films texture. • Annealing at 1280 °C led to noticeable interdiffusion between BaFe 12 O 19 and Al 2 O 3 . • Highly textured films were obtained by repeated deposition and annealing technique.

Exploiting eutectic formation and phase separation to produce plasmonic metamaterials

Novel Au mesostructures with a polyhedron shape, henceforth referred to as pyramids, are produced by annealing in vacuo an Au thin film on a Si(100) substrate. Gold diffusion and incorporation into pyramids is a function of the thickness of the Au film, the annealing temperature, and the vacuum pressure. The Au pyramids have unique surface morphologies due to the presence of channels and plateaus, where channels are cut into the surface of the pyramids and plateaus are the surfaces between adjacent channels. The bulk of the pyramids consists of Au with cavities that are devoid of Au or Si. Normalized energy dispersive spectroscopy of intact regions of the surface are 98.1 wt. % Au and 1.9 wt. % Si, while the bottom of the channels are 85.7 wt. % Au and 14.3 wt. % Si. Therefore, one step in the growth process is the formation of an Au–Si eutectic. The low concentration of Si in the solid regions of the pyramid and its high concentration in the walls of the cavities are indicative of phase separation of the Au–Si eutectic. The pyramids are oriented in the same direction relative to one another and are a consequence of eutectic formation-induced etching of the Si(100) surface. The scattering spectrum (non-specular reflectivity) of the Au pyramids consists of two very strong surface plasmon polariton states that correspond to excitation from the Au d-bands to the sp conduction bands. The surface morphology produces linearly polarized reflected light.

Hierarchical structured PVA-PLA nanofibrous membrane with "water-chestnut-like" surface morphology for water harvesting

In order to solve the problem that there is no clean water to drink in many parts of the world, researchers are trying to explore some unconventional strategies to take water from nature, such as fog collection. Herein, we constructed a hydrophilic/hydrophobic composite membrane with unique surface morphology by electrospinning as a new collection system. The surface layer is composed of water chestnut-like PVA particles, and the bottom layer is composed of directional polylactic acid fibers. The force acting on the droplets moving between the needle and the collector is studied in detail to explain the formation mechanism of water chestnut-like PVA particles. The small droplets formed by low concentration PVA solution are mainly affected by gravity electric field force. Due to the gradual volatilization of solvent, the decrease of concentration easily leads to the generation of beads. Due to the poor volatility of water, droplets continue to flow downward under the action of gravity and form water chestnut-like particles. When collecting fog, the area of water chestnut particles is larger than that of fibers, which make water droplets condense faster, and directional polylactic acid then conveys the collected fog water. Taking advantage of the synergistic cooperation of two regions, the surface can collect water with the collecting efficiency as high as 57 mg cm −2 h −1 . There is no doubt that these functional composite membranes will provide a new idea for developing a new way to solve the global water shortage problem. • Hierarchical structured PVA-PLA fiber membrane was prepared with unique morphology. • The formation mechanism of water-chestnut-like PVA particles was proposed. • Membrane with water-chestnut-like morphology provides a rapid accumulation of water.

Effects of different extraction methods on the structure, antioxidant activity, α‐amylase, and α‐glucosidase inhibitory activity of polysaccharides from Potentilla discolor Bunge

Three different methods, namely hot water extraction (HWE), ultrasound-assisted extraction (UAE), and microwave-assisted extraction (MAE), were used to extract Potentilla discolor Bunge polysaccharides (PDBP). The effects of different extraction methods on the yield, chemical structure, antioxidant, α-amylase, and α-glucosidase activities of PDBP were investigated in this study. The results showed that MAE led to the highest PDBP yield (4.56%), the highest percentage of high molecular weight fraction, the highest galacturonic acid content, the highest antioxidant scavenging activity, and the highest α-glucosidase inhibitory activity. Besides, PDBP extracted by MAE have a unique surface morphology and better thermal stability. These findings suggest that MAE might be a potential technique that can be used in industry to extract PDBP with high bioactivities. Novelty impact statement Three different extraction methods were used to extract Potentilla discolor Bunge polysaccharides (PDBP). Different extraction methods affected the structure and activity of PDBP. PDBP by microwave-assisted extraction (MAE) has higher antioxidant ability and α-glucosidase inhibitory activity than other extraction methods.

Slippery-Liquid-Infused Electrostatic Flocking Surfaces for Marine Antifouling Application.

Most marine antifouling coatings rely on the release of toxic biocides to prevent fouling organisms from attaching, causing environmental pollution. This work proposes a biocide-free environmentally friendly marine antifouling strategy. Slippery-liquid-infused electrostatic flocking surfaces (S-EFSs) were prepared by combining electrostatic flocking and slippery liquid infusion. They exhibited complete mussel resistance after comparing adhesion to the surface of different materials in the laboratory. In addition, the unique surface morphology including lubricant was found to be crucial to their antifouling performance. Real-time polymerase chain reaction showed that different surfaces significantly affected the gene-expression levels of the mussels' foot proteins, where higher levels on S-EFSs meant that the mussels tried to secrete more proteins but they failed to adhere. Moreover, a 148-day field test showed that S-EFSs can resist not only mussels but also tubeworms, tunicates, and barnacles, and the total fouling area decreased by more than 50% compared to control samples. Notably, the maturity of electrostatic flocking technology and the simplicity of the modification steps used endow this strategy with the potential to significantly reduce the economic loss caused by marine biofouling in practical applications.

PHYSICAL PROPERTIES OF NOVEL α-Fe2O3/NiO HETEROSTRUCTURES THROUGH IMMERSION/ SOL–GEL SPIN COATING METHOD: DIFFERENT DEPOSITION NUMBERS OF NiO LAYER

The novel hematite (α-Fe2O3)/nickel oxide (NiO) heterostructures were grown on fluorine-doped tin oxide (FTO) coated glass substrates at various deposited NiO of 3, 5, and 7 layers. The heterostructures were successfully synthesized using the immersion and sol–gel spin coating methods for α-Fe2O3 and NiO films, respectively. The field emission scanning electron microscopy analysis showed that each sample of α-Fe2O3/NiO heterostructures has a unique surface morphology when deposited with different NiO layers. The X-ray diffraction pattern shows that the number of NiO layers affected the diffraction peaks. The NiO diffraction peak intensity at (111) plane increased when the deposition number of NiO layer was increased. The crystallite sizes of NiO were 35.4, 33.6, and 38.0 nm for 3-, 5-, and 7-layer NiO, respectively. The interplanar spacing, lattice parameter, and unit cell volume indicate NiO with 3-layer as the highest, while 5- and 7-layer had the same values. Meanwhile, the strain and stress values show the compressive strain and tensile stress, respectively. The optical properties reveal that the highest transmittance and the lowest absorbance percentages were recorded for a 3-layer NiO sample. In contrast, the lowest transmittance and the highest absorbance percentages were obtained for the sample with 5-layer NiO. Different thicknesses and morphologies of heterostructures explained these situations. In addition, each unique heterostructure of α-Fe2O3/NiO with high visible light absorption nature is perceived to reduce the bandgap energy and has the potential to be used in sensor and solar cell applications.

Tailoring silicon for dew water harvesting panels

SummaryDew water, mostly ignored until now, can provide clean freshwater resources, just by extracting the atmospheric vapor available in surrounding air. Inspired by silicon-based solar panels, the vapor can be harvested by a concept of water condensing panels. Efficient water harvesting requires not only a considerable yield but also a timely water removal from the surface since the very beginning of condensation to avoid the huge evaporation losses. This translates into strict surface properties, which are difficult to simultaneously realize. Herein, we study various functionalized silicon surfaces, including the so-called Black Silicon, which supports two droplet motion modes—out-of-plane jumping and in-plane sweeping, due to its unique surface morphology, synergistically leading to a pioneering combination of above two required characteristics. According to silicon material's scalability, the proposed silicon-based water panels would benefit from existing infrastructures toward dual functions of energy harvesting in daytime and water harvesting in nighttime.

Atmospheric pressure plasma engineered superhydrophilic CuO surfaces with enhanced catalytic activities

Cupric oxide (CuO) thin film has found widespread application as a low-cost, earth-abundant material for electro and photo catalytic applications. High surface wettability is a key factor to achieve enhanced efficiency in these catalytic applications. Here, we report a fast and environment friendly route to fabricate super hydrophilic CuO thin films using a low power (5–10 W) atmospheric pressure plasma jet (APPJ). With APPJ treatment for 5 min, the CuO surface transforms from hydrophobic to super-hydrophilic with threefold increase in catalytic activity. The electrodes were extensively characterized using various bulk and surface-sensitive techniques. APPJ introduces anisotropy in the crystal structure and creates unique three-dimensional surface morphology with distinct surface chemical and electronic features. Interestingly, presence of oxygen in the plasma was found to be critical for the enhanced activities and the activity decreased when the functionalised with nitrogen plasma. Oxygen plasma functionalisation of CuO electrodes resulted in a 130 mV reduction in the onset potential for oxygen evolution reaction along with enhanced current density, 10 mA cm−2 against 3 mA cm−2 at 1 V vs Saturated Calomel Electrode in 0.1 M KOH without iR compensation. Importantly, without introducing any external dopants the work function could be decreased by 80 mV. Moreover, the treated films exhibited a higher rate of photo degradation (0.0283 min−1 compared to 0.0139 min−1) of Methylene Blue and phenol indicating efficient charge separation. This work presents the potential of APPJ functionalisation of CuO surface to boost the activity of other thin film catalyst materials and solutions processed systems.

High-performance supercapacitor based on MoS2@TiO2 composite for wide range temperature application

Transition metal sulphide and their composites gain attention as electrode material in energy storage devices due to their superior properties like excellent conductivity, high surface area, and porosity. We report an evaluation of the electrochemical performance of MoS2@TiO2 binary composite in symmetric supercapacitor assembly at different temperatures. A facile hydrothermal technique is used to prepare MoS2@TiO2 binary composite. Structural and morphological analysis reveals that highly crystalline composite comprising MoS2 assembled in flower-like flake configuration, whereas, TiO2 in nanorods form are prepared. Among all three electrodes, MoS2@15%TiO2 demonstrates maximum specific capacitance 210 F/g at 10 mV/s with excellent cycling stability (98%, 2000 cycles) at ambient temperature. It may be concluded that the mono-phased, mesoporous structure is a key feature behind the improved performance over the other electrodes. Further, improvement in charge-discharge characteristics has been observed by a factor of 200% at 60 °C attributing to low activation energy and faster ion dynamics at elevated temperatures. The impedance spectroscopic analysis reveals a significant reduction in interfacial impedances that leads to a superior capacitance effect compounded with favourable electrolytic charge dynamics. The highest energy density is reported to be 21 Wh/kg with a power density of 1300 W/kg in symmetric configuration. Synergistic effect of the binary system along with unique surface morphology and charge storage followed by intercalation and capacitive mechanism results in enhanced performance of supercapacitor with MoS2@15%TiO2. Thus, binary MoS2@TiO2 composite seems to be an exceptional candidate for the energy storage device operating at a wide temperature range (25–60 °C).

Positively charged nanofiltration membranes mediated by a facile polyethyleneimine-Noria interlayer deposition strategy

The development of the positively charged nanofiltration (NF) membrane is of great importance for water softening. The relative low water permeance restricts its widespread application. Up to now, numerous efforts on the interlayer technologies have been implemented to manipulate the interfacial polymerization (IP) process of the negatively charged NF membrane. However, there are few reports on the interlayer-mediated positively charged NF membrane. Herein, an interlayer-mediated positively charged NF membrane is fabricated via an IP process between polyethyleneimine (PEI) and trimesoyl chloride. A facile interlayer is deposited based on the interaction of a macrocycle polyphenol of Noria and PEI. The fabricated NF membrane possesses a unique surface morphology, less intrusion of the polyamide layer, a low lateral mass transfer resistance and adequate separation layer thickness. Consequently, the interlayer-mediated NF membrane exhibits a high water permeance of 110.4 L·m−2·h−1·MPa−1, which is ~2.6 times over the control group of 41.6 L·m−2·h−1·MPa−1, while preserves a considerable rejection of 95.4% towards MgCl2 solution. More importantly, the water permeance is enhanced not at the expense of membrane thickness, which is conducive to the long-term running stability. This study paves a new way to fabricate a high performance positively charged NF membrane through an interlayer manipulation strategy.

Controlled-synthesis of hierarchical NiCo2O4 anchored on carbon nanofibers mat for free-standing and highly-performance supercapacitors

In this work, a versatile one-step hydrothermal technique was used to produce a hybrid standalone electrode of NiCo2O4 hierarchical nanostructures anchored on CNFs mat for highly-performance and substrate-free supercapacitors. The CNFs mat was working as a conductive and a three-dimensional template for the deposition of the hierarchical NiCo2O4 nanostructures at the same time. The morphological and structural data analysis revealed a pure spinel NiCo2O4 nanostructures with a unique surface morphology comprising interconnected ultrathin nanoneedles and nanoflowers were successfully anchored to the CNFs mat. Real supercapacitors consist of two-symmetrical hybrid electrodes with different NiCo2O4 loading ratios were assembled and tested. The electrochemical performances of the assembled devices in terms of specific capacitance, energy, and power densities were systematically evaluated. Increasing the NiCo2O4 loading on the CNFs mat had shown a positive impact on improving the overall electrochemical performance of the assembled supercapacitors. A hybrid electrode loaded with NiCo2O4 twice as much as CNFs possess a specific capacitance value of 540 F g−1 along with an energy density of 30 Wh kg−1 at a power density of 515.6 W kg−1. In addition, the device showed excellent cycling stability and high capacitance retention against 6000 charge–discharge cycles at a charging current of 1.0 A g−1.

Influence of stitching on the fracture of stitched sandwich composites

Sandwich composites consist of two rigid outer facesheets that are bonded to a lightweight internal core. Although they have a high stiffness-to-weight ratio, these structures have low interlaminar strengths, which may lead to core-to-facesheet separation when subjected to out-of-plane stresses. In this study, sandwich composites with carbon/epoxy facesheets and a 110 kg/m3 foam core, were manufactured with through-the-thickness reinforcements, or stitches, using a vacuum-assisted resin transfer molding process. A design of experiments approach was used to investigate the influence of stitch parameters (stitch density, linear thread density, and facesheet thickness) on fracture energy. Single cantilevered beam tests were performed to obtain the mode I dominant fracture energy for each treatment combination. This study reveals and discusses the unique fracture surface morphologies associated with stitch processing parameters for a sandwich composite. For increased fracture toughness, the optimum stitch parameters for different linear thread densities are captured in the response surface model.

Improving mechanical properties and electrode life for joining aluminum alloys with innovatively designated Newton ring electrode

Abstract Aluminum alloys are critical lightweight materials in the automotive industry, which can significantly reduce vehicle weight and improve vehicle fuel efficiency. However, resistance spot welding, as one of key joining approaches, faces the challenges of short electrode life and unstable weld quality when welding aluminum alloy. A novel electrode named as Newton Ring (NTR) electrode was developed to address these issues. The mechanical property, nugget evolution and electrode degradation during continuous welding of aluminum alloy with NTR electrode were investigated and compared with the typical spherical electrode. Results indicate that the mechanical property, electrode life and surface quality of the weld fabricated by NTR electrode were much better than typical one. The improvement in the weld quality with NTR electrode stems from its unique surface morphology, which changes the current density distribution during welding and creates a ring-shaped nucleation process of the nugget. Therefore, the shape and size of the nugget are more stable, and the nugget does not cause serious offset in the continuous welding test. Additionally, the wear of the NTR electrode gradually grows from concentric rings to the base ring, avoiding the random and rapid wear on the electrode weld face, thus improving the surface quality of the weld.