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Ultra-permeable CNTs/PES membranes with a very low CNTs content and high H2/N2 and CH4/N2 selectivity for clean energy extraction applications

Polysulfone (PES) membranes are among the rare membranes that are capable of double filtration: a pre-filter layer captures agglomerates and a thin-dense layer is responsible for the main separation process. This work aims to enhance the permeability and H2/N2 and CH4/N2 of the dense layer of PES by mixing it with low concentrations of carbon nanotubes (CNTs: 0.01–0.03 wt.%) using solution casting and doctor blade techniques. The pore topology, microstructure, chemical, thermal, and mechanical properties of the synthesized CNTs/PES membranes were investigated using FTIR, XRD, TGA, and a universal testing machine, while permeability of single CO2, H2, N2, and CH4 permeability of the CNTs/PES membranes were tested under different temperatures (20–60 °C) and pressures (1–6 bar). Also, the effect of added CNTs, separation temperature, and pressure on the gas separation mechanism were investigated. The results showed that adding of CNTs contributed to increase in porosity from 81.7% (PES) to 88.4% (CNTs/PES) and decrease in pore sizes from 84 nm (PES) to 50 nm (CNTS/PES). Meanwhile, the thermal and mechanical analysis showed that CNTs/PES membranes had higher thermal stability and somewhat lower strength compared with neat membranes. Also, the permeability measurements showed a big increase when only 0.01 wt.% of CNTs had been added, where H2, CH4, N2, CO2 permeabilities were increased up to 28,553, 11,358, 7540, 6720 Barrer, respectively, vs 10.4, 4.6, 13.7, and 12.3 Barrer in case of PES membranes. In addition, CO2/N2, CH4/N2, and H2/N2 selectivity of CNTs/PES membranes were enhanced by 29%, 396%, and 426%, respectively, as a result of pores refining and increasing of free space in the prepared CNTs/PES membranes. According to these results, CNTs/PES membranes with small loading of CNTs have a tremendous ability to deal with separation of H2/N2 and CH4/N2, what make them promising candidates for clean energy extraction applications.

Experimental Study of the Leakage Flow in an Axial-Flow Fan at Variable Loading

The present paper reports a 2D-PIV (particle image velocimetry) study of the effect of the operating point on the leakage flow in a low-speed ring fan. First, the flow pattern has been studied at 12 operating points covering the whole characteristic curve. At very low loading, the leakage flow streams along the rotor ring and is directly reingested; then, a separation bubble attached to the ring forms that, approaching the design point, modifies in a flow streaming radially outward. As the loading further increases, a separated flow region appears in the blade tip region that finally merges with the leakage flow. A further, more detailed study has been performed at eight operating points in the neighborhood of the design one. Very small loading variations may yield the leakage flow pattern modification, but no intermittence is present during the transition, as instantaneous flow patterns of any intermediate type continuously alternate. These results provide a consistent explanation for the ones of previous acoustic measurements.

Cu2O‐CuO/Chitosan Composites as Heterogeneous Catalysts for Benzylic C−H Oxidation at Room Temperature

AbstractRecently, in catalysis, chitosan has been exploited as a macrochelating ligand for metal active species due to the presence of various functional groups in its structure. Moreover, copper‐based catalysts are classified as one of the most environmentally friendly catalytic systems and their use for the oxidation of alkylarene has not been established much. Therefore, in this work, the hydrothermal synthesis of copper oxide‐chitosan composites as heterogeneous catalysts for the benzylic C−H oxidation of alkylarene was investigated. Characterization results reveal mixed phases of CuO and Cu2O, inferring the ability of chitosan to act as a reducing sugar under the hydrothermal condition. The pre‐existing interaction between copper species and chitosan as well as the co‐existence of the Cu2O and CuO structures give rise to the efficient performance of the catalysts. The synthesized composites exhibit high activity for the oxidation of fluorene to 9‐fluorenone at room temperature and small catalyst loading (1 mol % of Cu, >90 % conversion and 100 % selectivity). Superior TOF was observed, and a good scope of substrates can be converted to corresponding ketones in 48–97 % yields with these copper oxide‐chitosan catalysts. In addition, the catalysts can be used for up to nine cycles without significant decrease of the activity.

Modelling and Simulation using Finite Element Method of Surface Acoustic Wave Biosensor for Gas Detection Application

A surface acoustic wave (SAW) sensor detects changes in physical properties such as mass and density on its surface. Compared to other types of sensors, SAW sensor have a good stability, high selectivity and sensitivity, fast response, and low-cost. On the other hand, to design and optimize a SAW biosensor requires a long process including time and cost using conventional methods. Therefore, numerical simulation and computational modelling are useful and efficiently conduct analysis for the SAW biosensor. In this paper, a numerical simulation technique is used to analyse the SAW device sensitivity for the application of gas detection. The SAW biosensor can detect very small mass loading by changing its sensor resonance frequency. The two-dimensional (2D) device model is based on a two-port SAW resonator with a gas sensing layer. We made two design of SAW biosensor device with frequency of 872 MHz and 1.74 GHz. A gas with vary concentration from 1 to 100 ppm were used to determine the change of the device resonance frequency. As a result, the high frequency (1.74 GHz) device, shows that the resonance frequency is shifted larger than to the low frequency (872 MHz) device. In addition, the high frequency device offers five times more sensitivity than the low frequency device. By changing the sensor design, the sensor characteristics such as sensitivity can be altered to meet certain sensing requirements. Numerical simulation provides advantages for sensor optimization and useful for nearly representing the real condition.

Enhancing Nb2O5 activity for CO2 photoreduction through Cu nanoparticles cocatalyst deposited by DC-magnetron sputtering

Herein we demonstrate that the deposition of a small loading of Cu nanoparticles (0.51 wt %) by DC-magnetron sputtering over niobium oxide (Nb2O5) increases its photocatalytic activity for the reduction of carbon dioxide (CO2) into methane (CH4), methanol (CH3OH), acetone (CH3COCH3), acetic acid (CH3COOH), isopropanol (CH3CH(OH)CH3) and formate (HCOO−). The improvement in the CO2 photoreduction of the Nb2O5/Cu can be attributed mainly to a reduction in the recombination rate of the electron-holes pairs photogenerated due to the electron trapping by Cu species as observed by the photoluminescence analysis, high dispersion of Cu, and high specific surface area of material even after addition Cu.

Swelling pressure of compacted bentonite acting on constraining material with deformability

In order to better understand the physical interactions between compacted bentonite and the host rock, the swelling pressure acting on a constraining material with slight deformability and the volume change of the compacted bentonite caused by unloading without consolidation history were investigated. A swelling test apparatus equipped with controls for applying a small strain and loading pressure was developed to mechanically simulate the elastic strain of a soft and a hard rock and large deformation of the constraining materials. After the equilibrium swelling pressure had been measured, the vertical pressure was unloaded. It was found that the slight deformation of the compacted bentonite decreased the swelling pressure. Furthermore, upon unloading, for the Na-bentonite with no consolidation history, after the equilibrium swelling pressure had been measured by a sufficiently confined condition, the slope angle of the unloading curve approximately equalled that of the normal consolidation line, although a slight non-linearity of the curve was observed in highly compacted bentonite. Based on the Mohr–Coulomb yield criterion, this indicated a mechanism whereby the shear strain in the saturation and one-dimensional swelling deformation processes effects an isotropy of swelling pressure and a non-linearity of the unloading curve.

Nickel-cobalt (oxy)hydroxide battery-type supercapacitor electrode with high mass loading

Transition metal hydroxides have shown high capacity performances when at a small mass loading of active material, while it is still a great challenge to obtain a high capacity performance when the mass loading is high. To maximize the capacity at high mass loading, the microstructure of the electrode should be rationally designed. Herein, we report a nickel–cobalt (oxy)hydroxide composite with three-dimensional hierarchical porous architecture realized by an in-situ electrochemical activation method to trigger the active sites and structural rearrangement. By systematically tuning the pore sizes in the hierarchical structure, an optimal composite delivers a record high areal capacity (34.8 mAh cm−2) and energy density (19.1 mWh cm−2) at the mass loading up to 230 mg cm−2. It gives new insights for preparing high performance electrode materials by a facile method and provides a blueprint for the design of high mass-loading supercapacitors.

Negative Thermal Expansion HfV2O7 Nanostructures for Alleviation of Thermal Stress in Nanocomposite Coatings.

A primary mode of failure of thin-film coatings is the mismatch in thermal expansion coefficients of the substrate and the coating, which results in accumulation of interfacial stresses and ultimately in film delamination. While much attention has been devoted to modulation of interfacial bonding to mitigate delamination, current strategies are constrained in their generalizability and have had limited success in imbuing resistance to prolonged thermal cycling. We demonstrate here the incorporation of rigid thermal expansion compensators within polymeric films as a generalizable strategy for minimizing thermal mismatch with the substrate. Nanostructures of the isotropic negative thermal expansion (NTE) material HfV2O7 have been prepared based on the reaction of nanoparticulate precursors. The NTE behavior, derived from transverse oxygen displacement within the cubic structure, has been examined using temperature-variant powder X-ray diffraction, Raman spectroscopy, electron microscopy, and selected-area electron diffraction measurements. HfV2O7 initially crystallizes in a 3 × 3 × 3 superlattice but undergoes phase transformations to stabilize a cubic structure that exhibits strong and isotropic NTE with a coefficient of thermal expansion (CTE) = -6.7 × 10-6 °C-1 across an extended temperature range of 130-700 °C. Incorporation of HfV2O7 in a high-temperature thermoset polybenzimidazole enables the reduction of compressive stress by 67.3% for a relatively small loading of 26.6 vol % HfV2O7. Based on a composite model, we demonstrate that HfV2O7 can reduce the thermal expansion coefficient of polymer nanocomposite films, even at low volume fractions, as a result of its substantially higher elastic modulus compared to the continuous polymer matrix. By changing the volume fraction of HfV2O7, the overall coefficients of thermal expansion of the film can be tuned to match a range of substrates, thereby mitigating thermal stresses and resolving a fundamental challenge for high-temperature composites and nanocomposite coatings.

Ternary NiO/Ag/reduced graphene oxide nanocomposites as, a sensitive electrochemical sensor for nanomolarity detection of sunset yellow in soft drinks

NiO nanoparticles (NPs) with small Ag NPs loading supported on reduced graphene oxide nanosheets (ternary NiO/Ag/RGO nanocomposites) were synthesized via a hydrothermal process followed by high-temperature calcination, extending the synergistic effects among noble metal, metal oxide and carbon materials. Based on ternary NiO/Ag/RGO nanocomposites, a new electrochemical sensor was fabricated for the detection of sunset yellow (SY) in soft drinks through cyclic voltammetry, Tafel plot and differential pulse voltammetry. The experimental conditions were optimized and kinetic parameters studied. Due to the synergistic effect of the ternary components, the prepared sensor exhibited superior electroanalytical performance toward SY detection, including wide linear range from 0.1 to 50 μM and from 50 to 450 μM, low detection limit of 13 nM, excellent specificity against various interfering colorants, good reproducibility and stability. Importantly, the electrochemical sensors was successfully employed for quantitative SY analysis in soft drinks with satisfactory recoveries, where the analyzed results were also in agreement with LC/MS analysis.

Cost and Environmental Impacts of a Mixed Fleet of Vehicles

Urban parcel delivery is increasingly restricted by regulations limiting access to certain heavy or high emitting vehicles to reduce emissions and noise pollution in cities. Cargo bikes represent an alternative solution that enables deliveries with low environmental impact, but they may represent a higher economic cost and come with constraints like battery autonomy or small loading capacity. As a transport scheme relying on bikes for the last miles with fewer externalities, it is regarded as an environmentally friendly choice, and economic sustainability is assessed. This paper aims to present the environmental and economic aspects of different delivery means of transport in European urban areas. Life cycle assessment (LCA) methodology is selected to analyse the environmental impact of several vehicles, allowing us to quantify the emissions according to the loading factor. The electricity mix is an important parameter and makes the results vary according to the country studied. For the economic aspect, the cost price allows us to quantify the operational cost of each means of transport. A trade-off can thus be made between the two.

Preparation and characterization of quinoa starch nanoparticles as quercetin carriers

Quinoa starch nanoparticles (QSNPs) prepared by nanoprecipitation method under the optimal condition was developed as a carrier for quercetin. The QSNPs prepared under the optimal condition (90 DMSO/H2O ratio, 10 ethanol/solvent ratio, and ultrasonic oscillation dispersion mode) had the smallest particle size and polymer dispersity index through full factorial design. Compared with maize starch nanoparticles (MSNPs), QSNPs exhibited a smaller particle size of 166.25 nm and a higher loading capacity of 26.62%. Starch nanoparticles (SNPs) interacted with quercetin through hydrogen bonding. V-type crystal structures of SNPs were disappeared and their crystallinity increased after loading with quercetin. QSNPs was more effective in protecting and prolonging quercetin bioactivity because of their small particle sizes and high loading capacities. This study will be useful for preparing starch-based carrier used to load sensitive bioactive compounds.

Mechanical Stirring Synthesis of 1D Electrode Materials and Designing of Pyramid/Inverted Pyramid Interlocking for Highly Flexible and Foldable Li-Ion Batteries with High Mass Loading.

Flexible and foldable Li-ion batteries (LIBs) are presently attracting immense research interest for their potential use in wearable electronics but are still limited to electrodes with very small mass loading, low bending/folding endurance, and poor electrochemical stability during repeated bending and folding movements. Moreover, one-dimensional (1D) structured electrode materials have shown excellent electrochemical performance but are still restricted by the high cost and complicated fabrication process. Here, we present a very simple yet novel approach for fabricating extra-long Li4Ti5O12 (LTO) and LiCoO2 (LCO) nanofiber precursors by directly stirring the reagents in an atmospheric vessel. In addition, we present multilayer pyramid/inverted pyramid interlocking inside the LTO and LCO nanofiber films as well as between films and current collectors, which can create strengthened interfacial bonding like a zipper and tangentially disperse the strains generated during folding through the pyramidal planes and edges, leading to the realization of thick-film electrodes with outstanding electrochemical stability during folding movements. The foldable LIBs that are assembled with LTO and LCO nanofiber electrodes at a practical level of mass loading (14.9-19.4 mg cm-2) can maintain 102% of the initial capacity after 15 000 times of fully folding (180°) motions.

Effect of Alkyl Structures on the Anti‐stacking and Anchoring of Pd/Diamine‐Functionalized Graphene Nanoparticles in Application in Suzuki Reaction

Main observation and conclusionThree diamines (1,8‐diaminooctane/p‐phenylenediamine/biphenylenediamine) with different alkyl groups were used to synthesize the functionalized graphene networks. Pd as the common metal catalyst was used to explore the effects of alkyl types of diamines on anti‐stacking, metal anchoring ability of functional graphene and hence the catalytic performance. The results were discussed by characterization of the material and its catalytic properties. All catalysts showed excellent catalytic performance on the Suzuki cross‐coupling reaction with a high yield of up to 100%. The p‐phenylenediamine and biphenylenediamine functionalized graphene with larger specific surface area was beneficial to improve the stability of the graphene catalyst and maintain good catalytic activity after 5 cycles. The Pd nanoparticles in 1,8‐octanediamine materials have smaller size and a smaller loading with the same or even better catalytic performance than p‐phenylenediamine, biphenylenediamine materials, due to the stronger electron donating ability of N of octanediamine than that of p‐phenylenediamine.

Bearing Fault Detection Using DWT and CNN

Bearing is a key component of satellite inertia actuators such as moment wheel assemblies (MWAs) and control moment gyros (CMGs), and its operating state is directly related to the performance and service life of satellites. However, because of the complexity of the vibration frequency components of satellite bearing assemblies and the small loading, normal running bearings normally present similar fault characteristics in long-term ground life experiments, which makes it difficult to judge the bearing fault status. There are various methods introduced for condition monitoring such as vibration analysis, temperature analysis, wear and debris analysis, image processing etc. Among this image analysis is found to be the most effective method for detection of machine faults. This paper proposes an automatic fault diagnosis method for bearings based on a DWT and CNN.

Fabrication and analysis of two-wheeler connecting rod for aluminium hybrid composites using finite element method

In this study, the powder metallurgy process is applied for the development of composite material Al/3 wt% Si3N4/4.5 wt% ZrO2 and a 3D model of the connecting rod, as per the engine specifications of TVS Apache 150 motor, is designed using Solidworks software. The model is then imported into ANSYS Workbench for the finite element method to analyse the von-mises stress, elastic strain and deformation on the connecting rod for the particular loading conditions. Moreover, a comparative study is done between the developed connecting rod and the existing Al7068/5 wt% Si3N4 composite results taken from the literature. From the results, it is revealed that the maximum von-mises stress for Al/3 wt% Si3N4/ 4.5 wt% ZrO2 composite reduced by 53.54% for big end loading conditions and 71.24% for small end loading conditions. The weight of the connecting rod was found to be 0.2412 kg.

Highly sensitive, reliable and flexible pressure sensor based on piezoelectric PVDF hybrid film using MXene nanosheet reinforcement

The rapid advances in intelligence terminal devices have raised expectations for highly sensitive, reliable and flexible pressure sensor. Herein, we present a highly sensitive flexible pressure sensor based on piezoelectric MXene/poly(vinylidene fluoride) (PVDF) hybrid film. Making use of MXene nanosheet reinforcement, one can efficiently promote the piezoelectric output and consequently sensitivity of PVDF. For instance, upon a small loading of 0.4 wt%, the piezoelectric coefficient d33 of MXene/PVDF hybrid film reaches the peak of 43 pC/N. Meanwhile, the incorporation of MXene nanosheet is advantageous to strengthen the mechanical performance of PVDF. With the excellent piezoelectric response and mechanical property, the MXene/PVDF hybrid film sensor demonstrates to perform superior voltage sensitivity up to 0.0480 V/N, which is double that of PVDF based sensor. Meanwhile, the novel hybrid film sensor also exhibits fast recovery time of 3.1 ms and stable operation capability under cyclic force, confirming their applicability as reliable pressure sensor.

Effects of Ferroelectric Fillers on Composite Dielectric Elastomer Actuator

Integrating nano- to micro-sized dielectric fillers to elastomer matrices to form dielectric composites is one of the commonly utilized methods to improve the performance of dielectric elastomer actuators (DEAs). Barium titanate (BaTiO3) is among the widely used ferroelectric fillers for this purpose; however, calcium copper titanate CaCu3Ti4O12 (CCTO) has the potential to outperform such conventional fillers. Despite their promising performance, CCTO-based dielectric composites for DEA application are studied to a relatively lower degree. Particularly, the composites are characterized for a comparably small particle loading range, while critical DEA properties such as breakdown strength and nonlinear elasticity are barely addressed in the literature. Thus, in this study, CCTO was paired with polydimethylsiloxane (CH3)3SiO[Si(CH3)2O]nSi(CH3)3 (PDMS), Sylgard 184, to gain a comprehensive understanding of the effects of particle loading and size on the dielectric composite properties important for DEA applications. The dielectric composites’ performance was described through the figures of merit (FOMs) that consider materials’ Young’s modulus, dielectric permittivity, and breakdown strength. The optimum amounts of the ferroelectric filler were determined through the FOMs to maximize composite DEA performance. Lastly, electromechanical testing of the pre-stretched CCTO-composite DEA validated the improved performance over the plain elastomer DEA, with deviations from prediction attributed to the studied composites’ nonlinearity.

The Arctic Polar Vortex Response to Volcanic Forcing of Different Strengths

AbstractTropical volcanic eruptions injecting sulfur into the stratosphere are assumed to not only scatter radiation and cool Earth's surface but also alter atmospheric circulation and in particular to strengthen the stratospheric polar vortex in boreal winter. The exact impact is difficult to estimate because of the small number of well observed eruptions and the high internal variability of the vortex. We use large (100‐member) ensembles of simulations with an Earth system model for idealized volcanic aerosol distributions resulting from sulfur injections between 2.5 and 20 Tg. We suggest the existence of a threshold somewhere between 2.5 and 5 Tg(S) below which the vortex does not show a detectable response to the injection. This nonlinearity is introduced partly through the infrared aerosol optical density which increases much stronger than linear with increasing particle size occurring for increasing injection amount. Additionally, the dynamical mechanism causing the vortex strengthening seems not to set in for small aerosol loading. Furthermore, we add to the recent discussion concerning a possible downward propagation of the circulation response leading to a winter warming in Northern Eurasia. At latitudes northward of about 50°N, our simulations do show such an average warming pattern that is statistically significant for injections of 10 Tg(S) or more.

Changes of adhesion properties for negative electrode and positive electrode under wet conditions and different states of charge

Debonding often occurs in flexible batteries due to mechanical and electrochemical coupling during service. Debonding of electrode will seriously affect the capacity and life of the battery, and even cause a short circuit inside the battery, resulting in spontaneous combustion. Here, the adhesion performance between the electrode sheet and the active material are investigated under the electrolyte environment and different states of charge (SOCs). A small stretcher loading device is used to perform stripping experiments on positive electrodes and negative electrodes in a glove box filled with argon to obtain the peel strength. The binders used in the positive and negative electrodes in this paper are polyvinylidene fluoride (PVDF) and Styrene-Butadiene Rubber/Carboxymethyl Cellulose (SBR/CMC). Compared with the electrode sheet without electrolyte, the peel strength of the positive electrode and negative electrode is decreased by 89.7% and 46.3%, respectively. The significant reduction in peel strength is due to the swelling effect of the electrolyte on the binder. The scanning electron microscope observation shows that there is a large number of active material particles at the interface of the positive electrode and the negative electrode after peeling. Additionally, the peel strength of the positive electrode was increases slightly with the increase of SOC and the added value is 14.8%. But the peel strength of negative electrode decreased with the increase of SOC and the added value is 47.6%. These results play an essential role in evaluating the interface peel strength of the electrode sheet in the different environment and designing electrochemical performance for batteries.

Comparison of confirmatory factor analysis estimation methods on mixed-format data

Weighted least squares (WLS), weighted least squares mean-and-variance-adjusted (WLSMV), unweighted least squares mean-and-variance-adjusted (ULSMV), maximum likelihood (ML), robust maximum likelihood (MLR) and Bayesian estimation methods were compared in mixed item response type data via Monte Carlo simulation. The percentage of polytomous items, distribution of polytomous items, categories of polytomous items, average factor loading, sample size and test length conditions were manipulated. ULSMV and WLSMV were found to be the more accurate methods under all simulation conditions. All methods except WLS had acceptable relative bias and relative standard error bias. No method gives accurate results with small sample sizes and low factor loading, however, the ULSMV method can be recommended to researchers because it gives more appropriate results in all conditions.