Highly sulfonated poly ether ether ketone chelated with Cu2+ as a proton exchange membrane at sub-zero temperatures.

Improving the proton conductivity (σ) of proton exchange membranes at low temperatures is very important for expanding their application areas. Here, sulfonated poly ether ether ketone (SPEEK) membranes were prepared with different sulfonation degrees, and its maximum ion exchange capacity is 3.15 mmol/g for 10 h at 60 °C. Highly sulfonated SPEEK membrane exhibits ultra-high water uptake and excellent proton conductivity of 0.074 S/cm at -25 °C due to its abundant -SO3H. Nevertheless, its high swelling ratio and low mechanical strength are not conducive to the practical application of the membrane. Luckily, by employing the chelation of Cu2+ with -SO3- on the SPEEK chain, Cu2+-coordinated SPEEK membranes were prepared, and they not only retain high -SO3H content but also possess robust mechanical properties and good dimensional stability compared to pristine SPEEK membrane. Meanwhile, the σ of the SPEEK-Cu membrane reaches 0.054 S/cm at -25 °C, and its fuel cell maximum power (Wmax) reaches 0.42 W/cm2 at -10 °C, demonstrating superior low-temperature performance in comparison to other reported materials. Particularly, water states in the prepared membranes are quantified by low-temperature differential scanning calorimetry. Because much more water bound to the plentiful -SO3H and Cu2+ inside the membrane endows it with anti-freezing performance, the decay of the σ and the Wmax for the SPEEK-Cu membrane is retarded at sub-zero temperatures. It is envisioned that composite membranes comprising metal ions such as Cu2+-SPEEK have a high potential for sub-zero fuel cell applications.

Ultrasensitive triethylamine gas sensors with ZnSe nanospheres/nest-like Cr-doped MoO3.

Developing high-sensitivity TEA sensors has extremely important significance for human health. Design of three-dimensional (3D) nanostructures assembled from one-dimensional nanomaterials can effectively improve sensing performance. In this work, a nest-like structure assembled by Cr-doped MoO3 (Cr-MoO3) nanorods with relatively higher specific surface area was prepared. In order to improve the sensing performance, Cr-MoO3 skeleton was combined with ZnSe nanospheres of different mass ratios as sensing materials (ZnSe/Cr-MoO3), and the successful construction of the heterojunction structure was supported by various spectroscopies and charge density calculation. The prepared composite with an optimal moiety ratio showed very high response values of 371 and 1301 for 10 ppm and 50 ppm for TEA at 200 °C, respectively. Simultaneously, the composite sensor also exhibited a low detection limit (1.7 ppb). The improvement of the sensing performance of ZnSe/Cr-MoO3 was attributed to the formation of oxygen vacancies induced by Cr doping, the 3D nest-like structure provided an efficient network for charge transport/collection and the n-n heterojunctions between Cr-MoO3 nanorods and ZnSe nanospheres. The simulation analysis based on density functional theory (DFT) calculations indicated that the heterojunctions could effectively enhance the adsorption energy of TEA and the more charges transferring from TEA to the Cr-MoO3 nanorods.

Analysis of Aging Characteristics of Umbrella Skirts of Composite Insulators Operating under the Influence of a Wind and Sand Environment in South Xinjiang.

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.

Morphology regulation of conductive metal-organic frameworks in situ grown on graphene oxide for high-performance supercapacitors.

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.

Fabrication of a Fluorocarbon Low Surface Energy Coating for Anti-Stain Applications.

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.

The Influence of Titanium Dioxide Nanosheet on Water Permeability of Silicone Rubber after Nitrogen Dioxide Aging Treatment.

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.

Design and Synthesis of Low Surface Energy Coating with Functionalized Al2O3 Nanoparticles.

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.

MOF-Derived Spindle-Shaped Z-Scheme ZnO/ZnFe2O4 Heterojunction: A Magnetic Recovery Catalyst for Efficient Photothermal Degradation of Tetracycline Hydrochloride.

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.

Study on NO2 Barrier Properties of RTV Silicone Rubber by Incorporation of Functional Graphene Oxide.

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.

Negative electrodes for supercapacitors with good performance using conductive bismuth-catecholate metal-organic frameworks.

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.

Novel method and instrument for temperature-dependent tensile test of metallic materials without thermometers.

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.

Lodging resistance of rice plants studied from the perspective of culm mechanical properties, carbon framework, free volume, and chemical composition.

In this study, four varieties of rice were cultivated on the same farmland under same conditions and for same duration. However, their lodging resistance was found to be obviously different from each other. Herein, three key factors that highly influenced the lodging resistance were identified. First, in terms of morphological trait, in contrast to the generally believed theory that the overall thickness of the fresh culm wall governs the strength, the thickness of the depressed region of the dried basal culm wall largely determined the mechanical properties by acting as the weak link. This depressed region represents the vulnerable part with high syneresis rate. Second, the culm and its carbon framework exhibited sufficient strength and rigidity for both support and stability of the rice stem. The constraint of high lodging resistance of rice plants is attributed to the culm flexibility. Furthermore, the results of the positron annihilation lifetime spectroscopy corroborate that the most amorphous part and the highest-fraction free volume in the culm carbon framework were found for samples that exhibited high lodging resistance. This result confirmed the significant influence of the culm flexibility on lodging resistance. Third, a higher level of nitrogen element content in the basal culm can benefit its growth and development, which may contribute to an increase in lodging resistance of rice plants.

Preparation of One-Dimensional Polyaniline Nanotubes as Anticorrosion Coatings.

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.

Gas permeation and microstructure of reduced graphene oxide/polyethyleneimine multilayer films created via recast and layer-by-layer deposition processes.

Nowadays, graphene/polymer composite films with multilayer structure have attracted significant attention for gas barrier application. In this study, a series of reduced graphene oxide/polyethyleneimine (RGO/PEI) composite films were created via recast and layer-by-layer deposition processes. By using the recast process, the myriad PEI molecules in the precursor solution (the PEI : GO feeding ratio is 0.02 : 0.1, 0.05 : 0.1, 0.1 : 0.1, 0.3 : 0.1 and 0.5 : 0.1) ensure more effective reduction and surface modification of the graphene oxide (GO) sheets, while the undesirable free PEI molecules are eventually removed via a filtration process. Then, the RGO/PEI composite films were synthesized on PET substrate using a layer-by-layer assembly. The resulting films show a homogeneous and compact brick-wall structure with excellent gas barrier properties. Barriers against water vapor, nitrogen/oxygen, and carbon dioxide require different content of PEI in the composite film for optimal performance; the ideal values are 19.7, 23.8, and 24.1 wt%, respectively. These values are much lower compared with previously reported studies. Further, the permeability, free volumes, component ratio, morphology, and density of the RGO/PEI composite films have been carefully investigated and discussed. The results revealed that the mechanism behind the excellent gas barrier property of the RGO/PEI composite films is a synergistic effect created by the combination of the brick-wall structure, the small free volume holes, the suitable PEI content (ranging from 19.7 wt% to 24.1 wt%), the high density, and the hydrophobicity.

High piezocatalytic capability in CuS/MoS2 nanocomposites using mechanical energy for degrading pollutants.

Piezocatalysis, driven by mechanical energy and piezoelectric effect, is of great potential in addressing the environmental issues. In this work, a piezoelectric catalyst was fabricated by growing few-layer MoS2 nanosheets onto CuS, for the piezocatalytic degradation of Rhodamine B (RhB), methylene blue (MB) and hexavalent chromium (Cr (VI)). The excellent removal efficiency of Cr (VI) and RhB can be reached 100% within 180 s, through the piezocatalysis of CuS/MoS2-0.6 driven by mechanical stirring in the dark. Impressively, the piezoelectric current of CuS/MoS2-0.6 is 48 and 35.7 times higher than that of pure CuS and MoS2, respectively. The significantly enhanced piezocatalytic performance can be ascribed to the formation of CuS/MoS2 heterojunction and the piezoelectric field generated by MoS2 nanosheets, which promotes the efficient separation of electrons and holes. This study provides insights into strategies to improve catalytic performance through utilizing mechanical energy and opens a new horizon for environmental remediation.

New Aspects of Degradation in Silicone Rubber under UVA and UVB Irradiation: A Gas Chromatography-Mass Spectrometry Study.

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 D4-D9 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, D4 was generated and the lifetime of τ3 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 D4 was generated after UVB irradiation can be used to evaluate the UVB stability of silicone rubber in the future.

Open Porosity and Pore Size Distribution of Mesoporous Silica Films Investigated by Positron Annihilation Lifetime Spectroscopy and Ellipsometric Porosimetry.

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.

[Clinical observation of arthroscopic all-inside combined with outside-in "suture loop" repair for meniscus bucket-handle tear].

OBJECTIVE: To investigate the effectiveness of arthroscopic all-inside combined with outside-in "suture loop" repair for meniscus bucket-handle tear (BHT). METHODS: Between August 2016 and May 2019, 44 case of meniscus BHT were treated with arthroscopic all-inside combined outside-in "suture loop". There were 29 males and 15 females with an average age of 26.6 years (range, 18-42 years). The causes of injury included sports injury in 31 cases, falling injury in 7 cases, and sprain in 6 cases. There were 32 cases of medial meniscus posterior horn tears and 12 cases of lateral meniscus posterior horn tears. The disease duration ranged from 6 weeks to 3 months. Thirty-three cases were complicated with anterior cruciate ligament rupture. All patients had normal lower limb alignment. The preoperative Lysholm score was 42.1±9.1. According to the evaluation criteria of MRI and Barrett et al., the healing of meniscus was evaluated, and the effectiveness was evaluated by Lysholm score. RESULTS: All the 44 patients were followed up 8-36 months with an average of 16.8 months. At last follow-up, according to the evaluation criteria of Barrett et al., 39 cases were clinically healed, 5 cases were not healed, the clinical healing rate was 88.6%; according to MRI evaluation, 32 cases were completely healed, 7 cases were partially healed, and 5 cases were not healed, the total healing rate was 88.6%, and the complete healing rate was 72.7%. Lysholm score was 87.8±4.8, which was significantly different from that before operation ( t=31.060, P=0.000). CONCLUSION: Arthroscopic all-inside combined with outside-in "suture loop" repair is a reliable and effective method for the meniscus BHT, which can obtain good joint function.

Transcriptome analysis of Haematococcus pluvialis of multiple defensive systems against nitrogen starvation.

Haematococcus pluvialis could accumulate large amounts of triacylglycerol (TAG) and astaxanthin under various environmental stresses. To gain insights into the multiple defensive systems for carbon metabolism against nitrogen starvation, transcriptome analysis was performed. It was found that the genes related to carbon fixation, glycolysis, fatty acid and carotenoid biosynthesis pathways were up-regulated remarkably. Glyceraldehyde 3-phosphate (G3P) biosynthesis was accelerated with the enhanced C3 and C4 pathway. Meanwhile, the pyruvate kinase (PK) and pyruvate dehydrogenase E2 component (aceF) genes were significantly increased 12.9-fold and 13.9-fold, respectively, resulting more pyruvate and acetyl-CoA generation, which were beneficial to carotenoids and fatty acid biosynthesis. Methylerythritol 4-phosphate (MEP) pathway mediated carotenoid precursor isopentenyl diphosphate (IPP) synthesis, as the all eight related genes were up-regulated. The carbon flux toward astaxanthin biosynthesis with the increased astaxanthin pathway genes. The redistribution of carbon was also promoted for TAG accumulation. In addition, the up-regulation of diacylglycerol acyltransferase (DGAT) and phospholipid: diacylglycerol acyltransferase (PDAT) genes indicated that both acyl-CoA dependent and independent pathway regulated TAG accumulation. Therefore, this work reveals the multiple defensive mechanism for carbon metabolism in response to nitrogen starvation, which extended our understanding on the carotenoids, TAG and other important metabolites synthesis.