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Enhancing the corona resistance of epoxy resin (EP) is crucial for ensuring the reliable operation of electrical equipment and power systems, and the incorporation of inorganic nanofillers into epoxy resin has shown significant potential in achieving this. In this study, functionalized graphene oxide (KHGO) was synthesized via a sol-gel method to enhance the corona resistance of EP with electrochemical impedance spectroscopy (EIS) used to assess the properties of KHGO/EP composites. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) verified the successful grafting of epoxy groups onto the GO surface. The thermal conductivity and stability of the KHGO/EP composite initially increased with KHGO content but declined when the content exceeded 1.2 wt.%. Positron annihilation lifetime spectroscopy (PALS) indicated that KHGO improved interfacial compatibility with EP compared to GO, with agglomeration occurring when KHGO content exceeded a threshold value (1.2 wt.%). EIS analysis revealed that the corona resistance of the KHGO/EP composite was optimal at a filler content of 0.9 wt.%. After corona treatment, the saturation water uptake of the 0.9 wt.% KHGO/EP composite decreased by 15% compared to pure EP with its porosity reduced to just 1/40th of that of pure EP. This study underscores that well-dispersed KHGO/EP composite exhibits excellent corona resistance property suggesting the potential for industrial applications in high-voltage equipment insulation. [ABSTRACT FROM AUTHOR]

The microstructure and chemical properties of the corona discharge process could provide an effective method for predicting the performance of high-voltage cable insulation materials. In this work, the depth profile of the microstructure and chemical characteristics of corona discharge-treated PE were extensively investigated using Doppler broadening of position annihilation spectroscopy accompanied with positron annihilation lifetime spectroscopy, attenuated total reflectance Fourier transform infrared spectra, Raman spectra and contact angle measurement. By increasing corona discharge duration, the oxygen-containing polar groups, including hydroxyl, carbonyl and ester groups, strongly contribute to the deterioration of hydrophobicity and the enhancement of hydrophilicity. And the mean free volume size, with a broadening distribution, decreases slightly. The line shape S parameter decreases because of the decrease in free volume elements and the appearance of oxygen-containing groups. Also, the thickness of the degradation layer, determined from the S parameter with positron injection depth, increases and diffuses into the PE matrix. A linear S-W plot within the degradation layer of different corona treatment duration samples indicates the defect type does not change. The S parameter decreases and the W parameter increases with an increasing corona duration. Using a slow positron beam, the nondestructive probe can be used to profile the microstructure and chemical environment across the corona discharge damage depth, which is beneficial for investigating the surface and interfacial insulation materials. [ABSTRACT FROM AUTHOR]

Ti3C2Tx, as a member of the two-dimensional (2D) MXene family, is subject to severe self-restacking due to van der Waals forces between the surfaces of the nanosheets, which limits its application in supercapacitors. In addition, Ti3C2Tx always stores electrical energy non-Faradaic, resulting in a low specific capacitance about 100 F g–1 in basic electrolytes. In this work, we report conductive bismuth-catecholate metal–organic frameworks (Bi-(HHTP)) with one-dimensional (1D) channels grown on the surfaces of 2D Ti3C2Tx nanosheets (Ti3C2Tx/Bi-(HHTP)) for supercapacitors. In the hybrid structure, conductive Bi-(HHTP) serves not only as the spacers to relieve the self-stacking of Ti3C2Tx nanosheets but also as the active component to provide battery-type capacitance. Meanwhile, Ti3C2Tx nanosheets provide skeletons for the conductive Bi-(HHTP), further enhancing the overall specific capacitance of Ti3C2Tx/Bi-(HHTP). By taking advantage of appropriate porosity, redox activity, and good properties of charge transport of Bi-(HHTP), the specific capacitance of Ti3C2Tx nanosheets is significantly increased. The Ti3C2Tx/Bi-(HHTP) electrode obtained exhibits an impressive specific capacitance of 326 F g–1 at 0.5 A g–1 and a good rate capacity of 52%. Additionally, an asymmetric device is assembled with a Ni-(OH)2 cathode and a Ti3C2Tx/Bi-(HHTP) anode, demonstrating remarkable performance with a maximum specific energy of 22.3 Wh kg–1 and a maximum specific power of 11.2 kW kg–1. This work presents a promising strategy for developing high-performance supercapacitor electrodes based on Ti3C2Tx, offering potential avenues for enhancing performance in energy storage applications. [ABSTRACT FROM AUTHOR]

In this work, nickel-catecholate (Ni-CAT) nanorods were in situ compounded on graphene oxide (GO) to form a composite Ni-CAT@GO (NCG) with a special "blanket-shape" structure, which was used as an electrode material for supercapacitors. The morphology of Ni-CATs in situ grown on GO was modulated by introducing various contents of GO. With increasing GO, the length of nanorods of Ni-CATs is obviously shortened, and the charge transfer resistance of NCG is significantly reduced as the GO content is relatively low while it increases with further addition of GO, because excessive GO in NCG results in smaller crystal sizes accompanied by smaller stacking pores. Both the over-long Ni-CAT nanorods and the smaller stacking pores can restrict the accessible surface areas for the electrolyte. Optimal nanorod sizes are crucial to achieve good electrochemical performance for electrode materials. Galvanostatic charge–discharge analysis of NCG electrodes shows that their capacity initially increases and then decreases with the addition of more and more GO, and Ni-CAT@GO-0.5 (NCG0.5) with minimal charge transfer resistance exhibits the best electrochemical performance. The results demonstrate that the NCG0.5 electrode with optimal morphology possesses an excellent capacitance of 563.8 F g−1 at 0.5 A g−1 and a good rate performance of 61.9% at 10 A g−1, indicating that Ni-CAT@GO is a new type of promising electrode material for supercapacitors based on conductive metal–organic frameworks. [ABSTRACT FROM AUTHOR]

To study the influence of multi-factors, such as long sunshine, sand erosion, and so on, in southern Xinjiang, we selected two kinds of composite insulators for the transmission lines in southern Xinjiang to study the aging characteristics of the umbrella skirt surface. The results of scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) show that the surface roughness of the umbrella skirt is high and there are a large number of micron inorganic particles. The skirt has the characteristics of low C/O element ratio and high Al element content. The results of thermogravimetric analysis and micro infrared test show that the aging depth of the Myli Line skirt after 19 years of operation is 160~190 µm and that of Yuhe Line 1 after 14 years of operation is greater than 180 µm. The plasma discharge method was used to simulate the corona discharge in the actual operation to accelerate the aging of the surface of the umbrella skirt and the hydrophobic recovery of the umbrella skirt was investigated. The results show that the temperature has a great influence on the surface hydrophobic recovery performance after plasma treatment. These results may provide some theoretical guidance and technical support for the selection, operation, and maintenance of composite insulators in Xinjiang. [ABSTRACT FROM AUTHOR]

The combination of metal oxides and 2D nanomaterials demonstrated remarkable enhancement in gas sensing performance. In this work, a heterojunction composite of 2D Bi2Se3 nanosheets and 1D MoO3 nanobelts was first synthesized by a simple and low-cost strategy. Significantly, the Bi2Se3/MoO3-2 composite with a mass ratio of 2 : 1 for MoO3 to Bi2Se3 exhibited a pronounced response of 151 to 10 ppm TEA at 240 °C, which was five times higher than that of MoO3. Moreover, the sensor showed excellent selectivity to triethylamine (TEA), long-term stability (96% response retention after 30 days), and a low detection limit of ∼5.5 ppb. The enhanced TEA sensing performance can be attributed to the formation of the n–n heterojunction between Bi2Se3 and MoO3, which provides more active sites for the reaction of TEA molecules and improves the electron carrier transfer from Bi2Se3 to MoO3. This work demonstrates the potential of the Bi2Se3 nanosheet and MoO3 nanobelt composite as an ultrasensitive sensor for TEA detection. [ABSTRACT FROM AUTHOR]

In the long-term working state, stains such as dust, oil, and charged particles in the environment are prone to deposit on the surface of the power equipment, which has great security risks. To achieve anti-stain performance, fluorocarbon composite coating with a low surface energy was prepared and studied. In this paper, SiO2 nanoparticles were used as inorganic fillers and fluorocarbon resin was used as the substrate to form anti-stain coatings. By adjusting and optimizing the ratio of fillers and organic resins, coatings with different static contact angles were constructed. The optimum composite coating has a contact angle of 151 ± 2° and a surface energy of 9.6 mJ/m2. After high-temperature treatment (up to 200 °C), immersion in corrosive solutions (pH 3–11), and sandpaper abrasion (after 5 abrasion cycles), the coating has been proven to show good thermal, chemical and mechanical stability. Our study provides significant research and market opportunities for the anti-stain application of the fluorocarbon composite coating on power equipment. [ABSTRACT FROM AUTHOR]

Fluorine-doped tin oxide (FTO) thin films were prepared by a radio frequency magnetron sputtering technique. The defects and charge carrier transport behavior in FTO thin films were evaluated during the transition process from amorphous to nanocrystalline structures. The stable lattice structure in FTO thin films was obtained as the annealing temperature reached 400 ° C. Positron annihilation results indicated that defect evolution in the FTO thin films was shown in two stages, formation and reduction of vacancies/vacancy clusters. The carrier mobility of the FTO thin films annealed at 600 ° C was enhanced twice the amount than that of the unannealed samples. The correlation between the results obtained from positron annihilation and the Hall effect revealed the importance of defect scattering in deciding the charge carrier mobility. A defect scattering mechanism was proposed to interpret the noticeable increment of carrier mobility in FTO thin films after thermal treatment. [ABSTRACT FROM AUTHOR]

In a high-moisture environment where dust and coastal saltwater are prevalent, the stability of power equipment can be adversely affected. This issue can result in equipment downtime, particularly for transformers, severely disrupting the continuous operation of DC transmission systems. To address this challenge, a superhydrophobic modified fluorosilicone coating was developed, incorporating anti-stain properties. To tackle this issue comprehensively, an orthogonal experiment was conducted, involving six factors and three levels. The study focused particularly on assessing the impact of water-repellent recovery agents, nanofillers, antistatic agents, anti-mold agents, leveling agents, as well as wetting and dispersing agents on the coating's surface tension. The results demonstrate that selecting an appropriate base resin and incorporating well-matched functional additives played a central role in effectively reducing the surface tension of the coating. Consequently, optimized coatings exhibited exceptional resistance to stains and displayed strong corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, the aging process of a surface-functional titanium dioxide nanosheet (f-TNS) composited room-temperature-vulcanized silicone rubber (RTV) composite coating was simulated in a NO2 generation device, and then the electrochemical impedance spectroscopy (EIS) of the aged composite coating was tested in a 3.5% NaCl solution. The water permeation process was analyzed by the changes in the impedance modulus, porosity, and breakpoint frequency of the composite coating. The experimental results show that the water permeability of aged RTV decreases first and then increases with the increase in the composite proportion of f-TNS. When the composite proportion of TNS was 0.3 wt.%, the composite sample had the minimum water permeability and the best resistance to NO2 corrosion. The effect of TNS on the NO2 aging resistance of RTV composites and its mechanism were studied by SEM, FT-IR, and XPS. The impedance modulus and porosity of the aged 0.3% f-TNS/RTV, respectively, were 1.82 × 107 Ω cm2 and 0.91 × 10−4%, which increased by 2.23 times and decreased by 0.37 times, respectively, compared with the values of aged pure RTV sample. In addition, the breakpoint frequency of the aged 0.3% f-TNS/RTV also significantly reduced to 11.3 Hz, whereas it was 35 Hz in aged pure RTV. [ABSTRACT FROM AUTHOR]

The ion permeation through graphene oxide (GO) membranes irradiated by electrons was studied in this paper. The effect of irradiation on the microstructure of GO membranes was investigated using various techniques, such as scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectrum. FTIR results confirmed that no new chemical groups were formed during the electron beam irradiation process. XRD results indicated that the interlayer spacing shrunk with the irradiation dose. The ions permeation through the GO membrane was evaluated by electrochemical impedance spectroscopy. It was found that the inductive effect can be enhanced when the irradiation dose increased from 0 to 80 kGy and weakened at a higher irradiation dose. The machine learning method was further employed to explore the optimum parameters. The predicted data are highly consistent with the experimental data (results), which were verified by the testing phase in machine learning. The electron beam irradiation can be potentially applied to adjust the inhibition of ion permeation through the GO membrane. [ABSTRACT FROM AUTHOR]

The development of photocatalysts with a wide spectral response and effective carrier separation capability is essential for the green degradation of tetracycline hydrochloride. In this study, a magnetic recyclable Z-scheme ZnO/ZnFe2O4 heterojunction (ZZF) was successfully constructed via the solid phase method, using MIL-88A(Fe)@Zn as the precursor. An appropriate band gap width and Z-scheme charge transfer mechanism provide ZZF with excellent visible light absorption performance, efficient charge separation, and a strong redox ability. Under visible light irradiation, the degradation efficiency of tetracycline hydrochloride for the optimal sample can reach 86.3% within 75 min in deionized water and 92.9% within 60 min in tap water, exhibiting superior stability and reusability after five cycles. Moreover, the catalyst in the water can be conveniently recovered by magnetic force. After visible light irradiation for 70 min, the temperature of the reaction system increased by 21.9 °C. Its degradation constant (35.53 × 10−3 min−1) increased to 5.1 times that at room temperature (6.95 × 10−3 min−1). Using thermal energy enhances the kinetic driving force of the reactants and facilitates carrier migration, meaning that more charge is available for the production of •O2− and •OH. This study provides a potential candidate for the efficient degradation of tetracycline hydrochloride by combining thermal catalysis with a photocatalytic heterojunction. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have attracted increasing research interest in various fields. Unfortunately, the poor conductivity of most traditional MOFs considerably hinders their application in energy storage. Benefiting from the full charge delocalization in the atomic plane, two-dimensional conductive coordination frameworks achieve good electrochemical performance. In this work, π–π coupling conductive bismuth-catecholate nanobelts with tunable lengths, Bi(HHTP) (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene), are synthesized by a simple hydrothermal reaction and their length-dependent electrochemical properties are also investigated. The Bi(HHTP) nanobelts (about 10 μm in length) possess appropriate porosity, numerous redox active sites and good electrical conductivity. Being a negative electrode for supercapacitors, Bi(HHTP) nanobelts display a high specific capacitance of 234.0 F g−1 and good cycling stability of 72% after 1000 cycles. Furthermore, the mechanism of charge storage is interpreted for both battery-type and surface-capacitive behavior. It is believed that the results of this work will help to develop battery-type negative electrode materials with promising electrochemical performance using some newly designed π–π coupling conductive coordination frameworks. [ABSTRACT FROM AUTHOR]

In this study, functional graphene oxide (f-GO) nanosheets were prepared to enhance the NO2 resistibility of room-temperature-vulcanized (RTV) silicone rubber. A nitrogen dioxide (NO2) accelerated aging experiment was designed to simulate the aging process of nitrogen oxide produced by corona discharge on a silicone rubber composite coating, and then electrochemical impedance spectroscopy (EIS) was used to test the process of conductive medium penetration into silicone rubber. After exposure to the same concentration (115 mg·L−1) of NO2 for 24 h, at an optimal filler content of 0.3 wt.%, the impedance modulus of the composite silicone rubber sample was 1.8 × 107 Ω·cm2, which is an order of magnitude higher than that of pure RTV. In addition, with an increase in filler content, the porosity of the coating decreases. When the content of the nanosheet increases to 0.3 wt.%; the porosity reaches a minimum value 0.97 × 10−4%, which is 1/4 of the porosity of the pure RTV coating, indicating that this composite silicone rubber sample has the best resistance to NO2 aging. [ABSTRACT FROM AUTHOR]

Desalination through reverse osmosis (RO) membrane is one of the most popular ways. However, conventional RO membranes meet a trade-off between salt rejection and water flux which limit their comprehensive performance. In this work, sulfonated zirconium (IV)-carboxylate metal–organic framework (MOF) material UiO-66-SO3H was successfully synthesized, and thin-film nanocomposite (TFN) with UiO-66-SO3H-incorporated polyamide (PA) layer was fabricated. Angstrom-sized UiO-66-X ion transport channels with different functional groups in TFN membranes change the membrane morphology and chemistry and accelerate the penetration of water molecules while maintaining the high ion screening effect. As a result, compared to the pristine TFC membrane, the optimized TFN-UiO-66-SO3H membrane exhibited an increase in water molecules permeability to 347% and still maintained a salt rejection with ~ 94.7% under 2000 ppm NaCl solution with reverse osmosis (RO) mode, leading to a great improvement of intrinsic separation properties. The improved performance was owing to the size exclusion effect and hydrophilic nature of UiO-66-SO3H particles. What is more, the additional water migration channels through the incorporated UiO-66-SO3H nanoparticles lead to a boosting water permeation and show optimized performance for desalination. [ABSTRACT FROM AUTHOR]

Fluorine doped tin oxide (FTO) thin films were deposited on glass substrates by e-beam evaporation. Much higher carrier concentration, broader optical band gap, and average transmittance over 80% were obtained with SnF2 doped SnO2 thin films. Positron annihilation results showed that there are two kinds of vacancy clusters with different sizes existing in the annealed FTO thin films, and the concentration of the larger vacancy clusters of VSnO in the thin films increases with increasing SnF2 contents. Meanwhile, photoluminescence spectra results indicated that the better electrical and optical properties of the FTO thin films are attributed to FO substitutions and oxygen vacancies with higher concentration, which are supported by positron annihilation Doppler broadening results and confirmed by X-ray photoelectron spectroscopy. The results showed that widening of the optical band gap of the FTO thin films strongly depends on the carrier concentration, which is interpreted for the Burstein-Moss effect and is associated with the formation of FO and oxygen vacancies with increasing SnF2 content. [ABSTRACT FROM AUTHOR]

A novel method for measuring temperature and conducting tensile tests of metallic wires at elevated temperatures is presented. Ohmic heating is used to elevate the sample temperature with a uniform distribution, which could vary from room temperature to its melting point. The temperatures of the wires in steady states are determined by using a heat transfer model without measuring directly by thermometers, which reduces the error introduced by contact temperature measurement or optical pyrometers. This technique for temperature measurement can be applied to measuring temperature-dependent electrical resistivity and conducting temperature-dependent tensile tests of metallic materials. A low-cost instrument was designed to conduct the tensile tests. In this work, temperature-dependent Young's modulus, tensile strength at break, and the steady-state creep rate of 99.994%-pure Pb wires were further determined as applications of the tensile tests. The results show that the proposed method is valid and very useful for conducting temperature-dependent tensile tests of metallic materials. [ABSTRACT FROM AUTHOR]

Uniform polyaniline (PANI) nanotubes were synthesized by a self-assembly method under relatively dilute hydrochloric acid (HCl) solution. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and UV-Vis-NIR spectroscopy were employed to characterize the morphology and molecular structure of the PANI products. SEM images show that the PANI nanotubes have uniform morphology and form compact coating on the substrate surface. For comparison, aggregated PANI was also synthesized by conventional polymerization method. The performance of the PANI products on carbon steel was studied using eletrochemical measurement and immersion corrosion experiment in 3.5 wt% NaCl aqueous solution. The corrosion potentials of carbon steel samples increase by 0.196 V and 0.060 V after coated with PANI nanotubes and aggregated PANI, respectively, and the corrosion currents density decrease by about 76.32% and 36.64%, respectively. The 6-day immersion experiment showed that the carbon steel samples coated by PANI nanotubes showed more excellent anticorrosion performance, because the more compact coating formed by PANI nanotubes may inhibit the corrosion process between the anodic and cathodic. [ABSTRACT FROM AUTHOR]

Nafion composite membranes with various amounts of sulfonated multi-walled carbon nanotubes (Su-CNTs) were prepared either in or without a strong magnetic field. Interestingly, it is found that being recast in a strong magnetic field, the tensile strength at break and proton conductivity of Su-CNTs/Nafion composite membranes parallel to the magnetic field direction were higher than those perpendicular to magnetic field. Remarkably, such anisotropic mechanical property and proton conductivity of Su-CNTs/Nafion composite membranes strongly depend on water uptake and temperature, in particular the content of Su-CNTs. Quite a different dependence of the proton conductivity of the composite membranes on Su-CNT content, relative humidities and temperatures is well explained for the anisotropic proton conductivity of the Su-CNTs/Nafion membrane recast in a strong magnetic field, which is attributed to the preferential proton transporting along ionic water channels mainly coalesced by the orientated Su-CNTs at a specific water uptake. For Nafion composite membranes with 5 wt.% Su-CNTs, the proton conductivity along the direction of treating magnetic field approaches to 0.216 S/cm, which is ∼ 46% higher than that perpendicular to the magnetic field at 95 ∘ C. The present work provides a deep insight of the humidity and temperature dependence of proton conductivity of Su-CNTs/Nafion composite membranes and a new strategy for fabrication proton exchange membranes with high proton conductivity as well as good mechanical property. [ABSTRACT FROM AUTHOR]

Fumed silica (FS)-filled polydimethylsiloxane (PDMS) composite is widely used as the external insulating material in power grid. The function of PDMS composite is to keep the core of an insulation device being dry by preventing the permeation of outside water. To study water diffusion in PDMS composite helps to shed light upon the failure mechanism of the insulation devices. In this paper, positron annihilation lifetime spectroscopy (PALS) and electrochemical impedance spectroscopy (EIS) were applied to study the FS/PDMS interface structure and water diffusion in PDMS composite. It is found that the FS has two basic existing states in PDMS matrix: dispersed state and percolated state, and the percolation threshold of FS is fitted to be 6.0 wt.%. In the dispersed state, the FS particles are randomly dispersed in PDMS matrix. The values of τ 3 remain stable, being approximately 1.0 ns, indicating no overlaps of the FS/PDMS interfaces. Moreover, water cannot diffuse through the sample after corona aging. In the percolated state, the FS particles are tightly packed in the PDMS matrix. The values of τ 3 decrease with the weight fraction of FS, suggesting the overlapping of the FS/PDMS interfaces. As the FS percolates in sample bulk, these overlapped FS/PDMS interfaces provide continuous diffusion tunnels for water, thus resulting in failure of the composite after corona aging. It is found that polarization and discharge of the electrons at FS/PDMS interface under corona discharge is the main mechanism that leads to the failure of the composite bulk. [ABSTRACT FROM AUTHOR]

The cell culture density of Haematococcus pluvialis has an important influence on the high content of astaxanthin. A single factor experiment was conducted to investigate the influence of carbon source sodium acetate, pH value, inoculum amount and other factors; the four factors of fermentation process culture time, carbon source sodium acetate content, initial pH value and inoculum amount were adopted L 9 (3 4 ) positive The cross method was optimized; the four plant hormones 3-indolebutyric acid (3-IBA) and 2,4dichlorophenoxyacetic acid (2,4-dichlorophenoxyacetic acid, 2, 4-D), 1-naphthylacetic acid (NAA), and 6benzyl aminopurine (6-BA) were added for optimization experiments. The test results showed that the optimized fermentation process was culture time 11 days, inoculation amount 30%, initial pH 7.5, sodium acetate addition amount 10 mmol/L, adding plant hormones can increase cell density, hormones 3-IBA, 2, 4 The optimal addition amounts of -D, NAA, and 6-BA are 0.5, 0.1, 0.01, and 0.1 mg/L, respectively. After optimization, the cell density of Haematococcus pluvialis can reach 1.17×10 6 cells/mL, which is 28 times higher than before optimization. [ABSTRACT FROM AUTHOR]

Silicone rubber is widely used in power grids, electronics and aerospace, because of its hydrophobicity, high flexibility, etc. However, it is susceptible to some environmental chemical factors, such as NO2 and ozone, which can induce chain scission, the generation of defects and the ingress of water. In this work, we systematically studied the microstructure variations and water diffusion behavior of high-temperature vulcanized (HTV) silicone rubber after NO2-induced oxidative damage. Microstructure evolution in silicone rubber was investigated by positron annihilation lifetime spectroscopy (PALS). The results show that the oxidation of NO2 significantly degrades organic matrices, which induces the decrease of crosslinking degree and the formation of defects compared to virgin samples. The water transportation was evaluated by electrochemical impedance spectroscopy (EIS), which showed that the diffusion coefficient, under the NO2 concentration of 28.75 mg L−1, is 106 times that of virgin sample with a water uptake of 31%. Particularly, when the concentration reaches the critical value around 17.25 mg L−1, the diffusion coefficient and water uptake increase sharply, and the calculated average porosity of samples also dramatically increases by 4 orders of magnitude. These indicate the formation of more nano- and micron holes, serving as a pointer for percolation of defects in silicone rubber bulk. The study of microstructure variations and water transportation can help us to understand the aging mechanism, design reasonable composite polymer materials and prevent the damage of chemical contact. [ABSTRACT FROM AUTHOR]

In this paper, Bi2O3 samples were prepared by a hydrothermal way. The effects of microstructure on the electrochemical properties of Bi2O3 samples were studied by adjusting hydrothermal time of synthesization (2, 6, 10, 14, and 18 h) to control the microstructure. The structure, morphology, specific surface, and chemical environment of Bi2O3 were characterized by XRD, SEM, BET, and XPS. XRD patterns revealed that all diffraction peaks intensity increased with the increase of reaction time and it indicates that a higher crystallization had taken place. However, continuous improvements in electrochemical properties of the samples were not found with enhancement of the crystallinity. The specific capacitance decreases with the increase of crystalline grain size. From the SEM results, as the hydrothermal time increases, it is obvious that the sample particles agglomerate to flakes and then to flowers. The sample of Bi2O3 with a hydrothermal time of 10 h exhibited a high specific capacitance (980 F g−1 at 1 A g−1), excellent capacity retention (86.9% from 1 to 20 A g−1), and a good cycle stability (85.2% at 5 A g−1 after 1000 cycles). The significance of this work is that it is possible to boost the electrochemical properties of the samples by controlling the microstructures, including reducing the crystalline grain size and maintaining a proper morphology of Bi2O3 particles. [ABSTRACT FROM AUTHOR]

A series of MIL-101-SO3H/Nafion composite membranes was synthesized. They show an improved proton conductivity, due to the abundance of SO3H groups, which fosters proton conduction by binding the water molecules and enabling a larger number of conducting sites. Gas (including water vapor, hydrogen, and oxygen) permeability, crystallinity, and free volumes of the MIL-101-SO3H/Nafion composite membranes were investigated, as well as their correlation. By increasing the MIL-101-SO3H content, the gas permeability of the membranes significantly decreases, since the crystalline region is larger and the water-bearing MIL-101-SO3H particles are efficient barriers for the gas molecules. The gas permeation in the composite membranes is a very complex process and the results indicate no simple linear relation between the gas permeability and the free volume size (VFV), or between the gas permeability and the crystallinity. Moreover, it is very interesting to observe that the influence of VFV on the gas permeability is closely related to the size of the particular gas molecules: the larger the size of the gas molecules, the larger the free volume needed to achieve their rapid diffusion in the membrane. The results suggest the presence of a threshold value for VFV, which depends on the size of the gas molecules: when VFV is lower than this value, the gas molecules cannot easily jump through neighboring free volumes to a neighboring site, and, as a result, the permeability drops quickly. [ABSTRACT FROM AUTHOR]

An enhanced positronium (Ps) formation in low-temperature polymers has been widely observed. The additional positronium formation is due to shallow trapped electrons in them. Positron annihilation lifetime spectroscopy was applied to investigate the Ps formation in a series of polymers, such as low-density polyethylene, ethylene-methyl methacrylate copolymers with various methyl methacrylate contents, and pure poly(methyl methacrylate) at low temperature. An analysis of the experimental data based on simple kinetic equations enables one to understand the Ps formation mechanism in polymers during low-temperature positron annihilation experiments as functions of the temperature and elapsed time. Good fittings of the experimental data were obtained. The fitting parameters seemed to show clear physical meanings. [ABSTRACT FROM AUTHOR]

Polyamide thin film composite reverse osmosis membranes on porous polysulfone support were prepared using m-phenylenediamine, trimesoyl chloride and dimethyl sulfoxide (DMSO) with various contents as precursors via an interfacial polymerization. The membrane with heterogeneous multilayer structure was depth-profiled by positron annihilation lifetime spectroscopy based on a pulsed slow positron beam and the thickness of the polyamide active layer can be estimated through fitting the results of depth dependence of o-Ps intensity. The free volume characteristics in the polyamide selective layer of the membranes were evaluated and were correlated with the permeation properties. With increasing DMSO content, mean free volume size (VFV) was enlarged, which was responsible for the enhanced water and sodium chloride permeation. However, the salt rejection was significantly decreased with a slight increase in the VFV around a critical value of 88.0 Å3, which was the average size of hydrated sodium and chloride ions. It was well interpreted for that the broadened free volume distribution enables an amount of larger free volumes to be involved in the salt permeation, although little change in VFV was found. [ABSTRACT FROM AUTHOR]

Silicone rubber is widely used as the housing material of composite insulator for outdoor high-voltage insulation. However, corona-induced aging in silicone rubber contributes to the ingress of water or moisture, which finally leads to fracture of a composite insulator. To investigate water transportation in silicone rubber helps to shed light upon the insulator fracture mechanism. In this work, water transportation behaviors in silicone rubber treated by different applied voltages of corona discharge were systematically studied using electrochemical impedance spectroscopy (EIS). Low voltages (3, 4 kV) of corona treatments result in growing value of fθmin in Bode phase angle, indicative of severer degree of surface delamination. After 5 kV of corona treatment, water can finally diffuse through the silicone rubber, and then induces double-layer capacitance (Cdl) and the charge transfer resistance (Rct) in EIS spectra. For high-voltage (≥6kV) corona-exposed samples, great number of surface cracks are observed, and then Warburg impedance appears in EIS spectra on initial period of immersion, suggesting a direct water transportation process. The polar groups generated in silicone rubber during corona exposure also facilitate this water diffusion process. Calculated water diffusion coefficients show a sharp increase between 5 and 6 kV, which serves as an indicator for percolation of cracks or defects in bulk of silicone rubber. [ABSTRACT FROM AUTHOR]

In this paper, the variations in surface structure of polydimethylsiloxane elastomers before and after argon plasma treatments have been investigated by X‐ray photoelectron spectroscopy, slow positron beam, and scanning electron microscope. An inorganic silica‐like layer was probed by X‐ray photoelectron spectroscopy after 3 minutes or longer time of treatments, and the sample surface turned into totally hydrophilic. Short time (1 and 2 min) plasma exposure mainly removed preexisting low molecular weighted (LMW) siloxanes on sample surface. By using slow positron beam, the thicknesses of silica‐like layer for 3‐, 5‐, and 10‐minute–treated samples were estimated to be around 30, 66, and 91 nm, respectively. Beneath the silica‐like layer, a loose polymeric structure was also detected, which was ascribed to the accumulation of LMW siloxanes. Scanning electron microscope images showed that the silica‐like layer cracked after 10 minutes of plasma treatment, which provided direct diffusion pathways for LMW siloxanes. Hence, 10‐minute–treated sample showed rather low organic composition near surface. Slow positron beam provides valuable depth profile information for evaluating the surface aging condition of polydimethylsiloxane composite. [ABSTRACT FROM AUTHOR]

The free volumes and proton conductivities of Nafion membranes were investigated at different humidities by positron annihilation lifetime spectroscopy (PALS) and using an electrochemical workstation, respectively. The results showed that the variation in o-Ps lifetime τo-Ps was closely associated with the microstructure evolution and the development of hydrophilic ion clusters in Nafion membranes as a function of water uptake, regardless of metal oxide additives. In particular, with increasing relative humidity, the maximum value of τo-Ps in the Nafion membranes corresponded to the formation of numerous water channels for proton transportation. Numerous well-connected water channels in Nafion–TiO2 hybrid membranes could be formed at a much lower relative humidity (∼40% RH) than in the pristine one (∼75% RH), due to the better water retention ability of the Nafion–TiO2 membranes. Further, a percolation behavior of proton conductivity at high water uptake in Nafion membranes was observed, which showed that the percolation of ionic-water clusters occurred at the water uptake of ∼4.5 wt%, and ∼6 wt% was basically enough for the formation of a well-connected water channel network. [ABSTRACT FROM AUTHOR]

Atomic scale point defects play important roles in tuning the carrier concentration and ultimately influencing electrical and thermal properties. Herein, we fabricated the ternary SbTeSe alloys to study the intimate relationship of internal point defects and thermoelectric performance. The Se substitution of Te atoms in the SbTe lattice decreased the electrical conductivity from 2.2 × 10 S/m to 6.4 × 10 S/m owing to the reduced holes concentration. The declined point defects, including antisite defects and vacancies in materials, gave rise to the decrease in carrier concentration. The Seebeck coefficient of the ternary SbTeSe exhibited an increase with doping of Se atoms. Simultaneously, the thermal conductivity behaved a fallihg trend as well as increasing Se content. As a result, the ZT value reached the maximum from the corresponding SbTeSe pellet. Positron annihilation measurement revealed that the average positron lifetime showed a monotonic decrease with Se addition, demonstrating the reduced point defects, which was in agreement with the thermoelectric performance. [ABSTRACT FROM AUTHOR]

A correction is presented to the article "Vacancy defects and optoelectrical properties for fluorine tin oxide thin films with various SnF2 contents" which appeared in the previous issue of the periodical.

Autophagy is an intracellular catabolic mechanism that maintains the balance of proteins, lipids and aging organelles. 3-Methyladenine (3-MA) is a selective inhibitor of autophagy, whereas rapamycin, an antifungal agent, is a specific inducer of autophagy, inhibiting the protein mammalian target of rapamycin. In the present study, we examined the role of autophagy, inhibited by 3-MA and enhanced by rapamycin, in a model of acute spinal cord injury in rats. We found that rapamycin could significantly increase the expression of microtubule-associated protein 1 light chain 3 (LC3) and Beclin1 at the injury site. At the same time, the number of neurons and astrocytes with LC3 positive in the spinal cord was upregulated with time. In addition, administration of rapamycin produced an increase in the Basso, Beattie and Bresnahan scores of injured rats, indicating high recovery of locomotor function. Furthermore, expression of the proteins Bcl-2 and Bax was upregulated and downregulated, respectively. By contrast, the results for rats treated with 3-MA, which inhibits autophagy, were the opposite of those seen with the rapamycin-treated rats. These results show that induction of autophagy can produce neuroprotective effects in acute spinal cord injury in rats via inhibition of apoptosis. [ABSTRACT FROM AUTHOR]

Multifunctional (poly(diallyldimethyl ammonium chloride)/ sodium poly(4-styrene sulfonate))((PDDA/PSS)) thin films were fabricated by layer-by-layer assembled on the glass substrate. The monolayer silica nanoparticles were prepared on the (PDDA/PSS) films. The SiO-polyelectrolyte coatings exhibit antireflection properties with low refractive index (as low as 1.22). Interestingly, wavelengths of maximum transmittance could be well tailored by simply changing the particle size of SiO. A maximum transmittance of 97.03% in the visible spectral range is achieved for the particle size of 100 nm SiO films. The coatings also show excellent mechanical stability and good adhesion to substrates. The easy availability of the raw materials and simplicity of the fabrication method for such films might make them be potentially useful for various applications. [ABSTRACT FROM AUTHOR]

Formed in silica aerogels, positronium annihilation in oxygen and nitrogen mixture is studied by a simple and convenient method. The results show that ortho-positronium (o-Ps) lifetime is significantly shortened when some oxygen is introduced into nitrogen gas and that the o-Ps collisional quenching rate for an oxygen molecule is (28.0±0.4) μs·amagat (1 amagat = 2.69×10 m). It is found that the o-Ps annihilation rate in oxygen of 1atm at room temperature is (25.5±0.5) μs and that the effective number of electrons per oxygen molecule available for 2γ annihilation of positron in the o-Ps is (34.6±0.4). [ABSTRACT FROM AUTHOR]

Purpose. To analyze retrospectively the sonographic characteristics of the peripheral nerve injuries (PNIs) resulted from Wunchuan earthquake. Methods. The sonographic images of 38 patients with surgically proved PNIs were reviewed and compared with the surgical findings. Results. A total of 78 nerves in 38 patients were found injured in surgery, which included 16 median nerves in the forearm (20.5%), 6 ulnar nerves in the forearm or arm (7.7%), 8 radial nerves in upper limb (10.0%), 8 sciatic nerves (10.3%) in gluteal region, 17 tibial nerves in the leg (21.8%), and 23 peroneal nerves (29.5%). The most common injured nerve in the lower extremity was the peroneal nerve (29.5%) and in upper extremity was the median nerve (20.5%). Sonography correctly diagnosed 72 earthquake-related nerve injuries (92.3%), which included 5 complete disruption (6.4%), 4 partial disruption (5.1%), 63 nerve entrapment (88.5%, included 1 entrapment by bone calus, 38 entrapments by the scar tissue, 13 entrapments by the thickened muscle or tendinous arch, and 11 entrapment in the narrowed osteofibrous tunnels). Conclusions. Nerve entrapment injury was the common sonographic finding in earthquake-related PNI. © 2011 Wiley Periodicals, Inc. J Clin Ultrasound, 2011; [ABSTRACT FROM AUTHOR]

In this paper, gas chromatography–mass spectrometry (GC–MS) and positron annihilation lifetime spectroscopy (PALS) were used to probe the changes of oligomers and the polydimethylsiloxane (PDMS) network in silicone rubber, after different durations of UVA/UVB irradiation. At the early stage (<300 h) of UVA/UVB irradiation, the concentration of D 4 -D 9 decreases. The o-Ps intensity of the extracted silicone rubber increases in the stage after UVB irradiation. These results indicate the crosslinking of oligomers into the PDMS network. After a long duration (>300 h) of UVB irradiation, D 4 was generated and the lifetime of τ 3 also increased, indicating the rupture of the Si-O bond in the PDMS network. These two aging processes were termed the post curing process and the chain session process. The new finding was that UVA could only induce the post curing process; UVB causes the rupture of the chemical bond in silicone rubber. Photons of UVB could break the C-H bond, and then trigger the backbiting decomposition of PDMS, breaking the Si-O bond, while the photons of UVA cannot. The fact that D 4 was generated after UVB irradiation can be used to evaluate the UVB stability of silicone rubber in the future. [ABSTRACT FROM AUTHOR]

Tunable mesoporous silica films were prepared though a sol-gel process directed by the self-assembly of various triblock copolymers. Positron annihilation γ-ray energy spectroscopy and positron annihilation lifetime spectroscopy (PALS) based on intense pulsed slow positron beams as well as ellipsometric porosimetry (EP) combined with heptane adsorption were utilized to characterize the open porosity/interconnectivity and pore size distribution for the prepared films. The consistency between the open porosities was examined by the variations of orthopositronium (o-Ps) 3γ annihilation fractions and the total adsorbed volumes of heptane. The average pore sizes deduced by PALS from the longest-lived o-Ps lifetimes are in good agreement with those by EP on the basis of the Barrett–Joyner–Halenda model, as indicated by a well fitted line of slope k = 1. The results indicate that the EP combined with heptane adsorption is a useful method with high sensitivity for calibrating the mesopore size in highly interconnected mesoporous films, whereas PALS is a novel, complementary tool for characterizing both closed and open pores in them. [ABSTRACT FROM AUTHOR]

Lifetimes of ortho-positronium in mesoporous silica films were measured before and after surface trimethylsilylation of –OH groups. Variations of positronium lifetimes in the mesopores upon the surface modification indicate that the interaction between positronium and the pore surface is weakened in the pores, whose surface is covered with –CH3 groups, in comparison with those covered with –OH groups. This is consistent with the authors’ previous observation that positronium slowing down is less efficient in the pores covered with –CH3 groups. The present work demonstrates that in the porosimetric application of positron annihilation lifetime spectroscopy, the interaction between positronium and the pore surface has to be properly taken into consideration. [ABSTRACT FROM AUTHOR]

Silicone rubber is the outer dielectric material of the composite insulator used in high‐voltage transmission lines. A study of the microstructure evolution during corona discharge could provide a new understanding of catastrophic fracture in composite insulators. In this paper, the corona degradation process of silicone rubber is divided into three stages based on the data obtained by slow positron beam and electrochemical impedance spectroscopy. In stage I, the S parameter decreases slightly in the low‐energy range, suggesting a crosslinking process in the polymeric "skin," and the silicone rubber holds its high value of resistance, Rpore. In stage II, the organic sample surface is gradually transformed into an inorganic one. Further cracking of the surface layer contributes to a dramatic increase in the sample porosity. At the beginning of water immersion, the Bode phase angle remains approximately −50∘ at low frequency, and a diffusion‐dependent Warburg impedance is observed. In stage III, a massive number of polar groups and inorganic particles are generated and the sample fails to repel water. The increase in the sample porosity is the main factor that leads to an ingress of water and failure of the material, while the generated polar groups are the secondary factor. [ABSTRACT FROM AUTHOR]

Defects in undoped and antimony (Sb)-doped tin oxide thin films fabricated via a sol-gel method have been investigated using a slow positron beam by which an annihilation lineshape parameter is used to evaluate defects in the films. With increasing calcination temperature, the resistivity for undoped films increased because of removal of oxygen vacancies in them; however, the resistivity gradually declined for Sb-doped films upon annealing at higher temperatures, mainly due to weakened carrier scattering with fewer residual defects. The results show that defects as well as dopants play an important role in determining the resistivity of tin oxide films. [ABSTRACT FROM AUTHOR]