Ultrasonic-assisted organic–inorganic multilayer thin film synthesis and enhanced visible-light phototropy based on PVP /PMoA

Novel organic–inorganic layer-by-layer (LbL) multilayers for visible-light phototropy, comprised of polyvinylpyrrolidone (PVP) and phosphomolybdic acid (PMoA), were fabricated via layer-by-layer (LbL) assembly with ultrasonic pretreatment. The characterizations revealed that the Keggin spatial geometry of the PMoA was still maintained in the final ultrasonic-assisted LbL thin films, which promoted halogenesis between the PVP and PMoA. Intriguingly, instead of destroying the PVP thin film, the ultrasonic pretreatment process successfully dispersed the PMoA in the PVP thin film with a median size of approximately 3.6 nm. Thanks to the dispersion of the PMoA particles, the photochromic capabilities of the ultrasonic-assisted PVP/PMoA LbL thin films gained remarkable improvement. Moreover, decreasing the size of the PMoA particles to quantum dots (10–3.4 nm) induces an up-conversion and dielectric confinement effect, which increases the intensity of the absorption peak (0.235 increased to 0.45) while narrowing the emission energy (2.51 eV narrowed to 2.23 eV). At the same time, the size reduction also extended the range of the absorption wavelength, increases the characteristic absorption intensity, and accelerates the coloration rate over the same illumination period.

     

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Iron-doped cobalt nitride nanoparticles (Fe–Co3N): An efficient electrocatalyst for water oxidation

The exploration of efficient, low-cost and earth-abundant oxygen-evolution reaction (OER) electrocatalysts and the understanding of the intrinsic mechanism are important to advance the clean energy conversion technique based on electrochemical water oxidation. In this work, Fe-doping Co₃N catalysts were successfully synthesized by a simple nitridation reaction of the Co_3-xFe_xO₄ precursor. This material exhibited a low overpotential of 294 mV at a current density of 10 mA cm^?2, and a small Tafel slope of 49 mV dec^?1 in 1 M KOH solution, superior to the performance of Co₃N and IrO₂. As revealed by the spectroscopic and electrochemical analyses, the enhanced OER performance mainly originates from the electronic modulation induced by the incorporation of Fe into Co₃N, benefitting the formation of CoOOH as active surface species and thus facilitating the OER process. These findings also demonstrate the introduction of heterogeneous element is a simple and effective strategy to regulate the OER property of the cobalt nitrides (Co₃N) catalysts.     

Visible-light-enhanced catalytic hydrolysis of ammonia borane using RuP2 quantum dots supported by graphitic carbon nitride

Hydrolytic dehydrogenation of ammonia borane (AB) driven by efficient catalysts has attracted considerable attention and is regarded as a promising strategy for hydrogen generation. Herein, RuP₂ quantum dots supported on graphitic carbon nitride (g-C₃N₄) were successfully prepared by in-situ phosphorization, yielding a highly efficient photocatalyst toward AB hydrolysis. The catalysts were characterized by field-emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction, x-ray photoelectron microscopy, inductively coupled plasma atomic emission spectroscopy, UV–visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. A conventional water-displacement method was employed to record the hydrogen volume as a function of reaction time. Owing to visible-light irradiation, the initial turnover frequency of the AB hydrolysis was significantly enhanced by 110% (i.e., 134 min^?1) at room temperature. Furthermore, the apparent activation energy decreased from 67.7 ± 0.9 to 47.6 ± 1.0 kJ mol^?1. The photocatalytic hydrolysis mechanism and catalyst reusability were also investigated.     

Waste sugar solution polymer-derived N-doped carbon spheres with an ultrahigh specific surface area for superior performance supercapacitors

Waste sugar solution (WSS), a waste by-product of manufacturing vitamin C, contains abundant waste acids and organics. In this work, a N/O-enriched copolymer was synthesized via a facile polymerization via the hydrogen bonding of O-containing functional groups and melamine and the crosslinking of aldehyde groups. Subsequently, N-doped carbon spheres were prepared by a typical carbonation/activation method. Remarkably, benefiting from an ultrahigh specific surface area (3612 m²/g) and rich heteroatom content (4.3% for N, 8.8% for O), the carbon spheres deliver a high specific capacitance of 387 F/g at 50 mA/g and 283 F/g at 5 A/g with 6 M KOH in two-electrode system. The assembled symmetric electric double-layer capacitor exhibits high energy density of 10.83 Wh/kg at 11.10 W/kg. This research provides a facile method for preparing N/O-doped carbon spheres by WSS, and confirms the excellent electrochemical performance of WSS-derived carbons in energy storage applications.     

In-situ self-reconstruction of Ni–Fe–Al hybrid phosphides nanosheet arrays enables efficient oxygen evolution in alkaline

Developing efficient oxygen evolution reaction (OER) electrocatalysts with earth-abundant elements is very important for sustainable H₂ generation via electrochemical water splitting. Here we design a crystalline-amorphous Ni–Fe–Al hybrid phosphides nanosheet arrays grown on NiFe foam for efficient OER application. Dynamic surface reorganization of phosphides at anodic/cathodic polarizations is probed by in situ Raman spectroscopy. The reconstructed amorphous Ni(Fe)OOH species are determined as the active phases that facilitate the OER process. This unique electrode shows highly catalytic activity toward water oxidation, achieving the current densities of 10 and 100 mA cm^?2 at 181 and 214 mV in 1 M KOH, respectively. Meanwhile, it also exhibits excellent stability at a large current density of 100 mA cm^?2 for over 60 h. This work reveals the dynamic structural transformation of pre-catalyst in realistic conditions and highlights the important role of oxyhydroxides as real reactive species in OER process with high activity.     

某型燃机支承环故障诊断分析及改进措施

针对某型燃气轮机支承环在试验过程中发生断裂、掉块故障，分别进行了强度计算、振动模态分析、低循环疲劳寿命分析以及断口分析。综合分析结果表明：支承环故障属于高低周复合疲劳；焊缝和螺纹处应力集中导致应力过大而开裂；采取把周向焊缝取消，将月牙板和罩壳一体设计及降低应力集中等措施，排除故障。     

益生菌发酵对苹果汁主要营养成分及挥发性物质的影响

以红富士苹果汁为原料，研究益生菌混菌发酵对苹果汁挥发性物质及主要营养成分的影响。结果表明，苹果汁经混合益生菌发酵后，琥珀酸、苹果酸含量明显下降，而乳酸、柠檬酸、酒石酸、奎宁酸、莽草酸与丙酮酸的含量均明显上升；总酚含量呈先上升后下降趋势；儿茶素、表儿茶素、槲皮素、根皮苷和芦丁含量分别上升了5.57%、5.65%、5.83%、19.2%和4.52%，绿原酸含量下降了14.9%。发酵后的苹果汁共检出37种挥发性物质，与发酵前相比，增加了10种。其中，醇类增加5种、含量增加106.9%，酯类增加8种、含量增加84.5%；酮类种类不变，含量增加171.7%；醛类减少3种、含量降低了80.9%。     

SiO2基复合隔热材料制备及其性能研究

通过静电纺丝技术制备出柔性SiO2纳米纤维,将其与亲水型气相SiO2混合均匀后,采用半干法压制得到SiO2复合隔热材料.研究结果表明,柔性SiO2纤维为亲水型气相SiO2提供了空间网络骨架,在未明显提高其导热系数的基础上提高了其抗折强度.     

先开挖后施工预制工程桩工法在舟山软土基坑中的应用

依托工程实例,介绍了新型先开挖后施工预制工程桩工法在舟山地区软土基坑中的应用情况.通过采取关键技术措施,该工法可以解决软土基坑开挖对预制工程桩的影响问题.通过对现场实际开挖情况及现场实时监测数据的研究,证明该工法在软土地区具有可行性和使用价值,在一定条件下可选取该工法以降低工程桩费用.