Surface modification with cobalt oxide nanocluster for enhanced surface oxygen exchange reactions of GDC-LSCF membrane: fabrication,electrochemical kinetic properties,and stability

Journal of Applied Electrochemistry - Surface oxygen exchange is a critical reaction process involved in ceramic devices for energy conversion and storage such as gas separation membranes and solid...     

Hybrid CuO-Co3O4 nanosphere/RGO sandwiched composites as anode materials for lithium-ion batteries

Hybrid CuO-Co₃O₄ nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional (3D) hybrid architecture (CuO-Co₃O₄-RGO), which are successfully applied as enhanced anodes for lithium-ion batteries (LIBs). The CuO-Co₃O₄-RGO sandwiched nanostructures exhibit a reversible capacity of~847 mA·h·g^-1 after 200 cycles' cycling at 100 mA·g^-1 with a capacity retention of 79%. The CuO-Co₃O₄-RGO compounds show superior electrochemical properties than the comparative CuO-Co₃O₄, Co₃O₄ and CuO anodes, which may be ascribed to the following reasons:the hybridizing multicomponent can probably give the complementary advantages; the mutual benefit of uniformly distributing nanospheres across the layered RGO nanosheets can avoid the agglomeration of both the RGO nanosheets and the CuO-Co₃O₄ nanospheres; the 3D storage structure as well as the graphene wrapped composite could enhance the electrical conductivity and reduce volume expansion effect associated with the discharge-charge process.     

生物质与烟煤混合燃烧特性及动力学分析研究

使用非等温热分析方法研究了生物质(麦秆)和烟煤混合燃烧的反应特性。结果表明,生物质的添加可以降低混合样品的燃烧着火温度和燃烬温度,且混合样品燃烧反应性能随着生物质混合比例的增加而提升;生物质添加质量分数为20%时,煤和生物质混合燃烧协同作用最明显。使用Coats-Redfern(CR)、Flynn-Wall-Ozawa(FWO)和Kissinger-Akahira-Sunose(KAS)动力学模型对混合样品燃烧活化能进行计算,其值在挥发分燃烧阶段随着生物质混合比例的增加而增加,在焦炭燃烧阶段呈现下降趋势;通过对FWO和KAS动力学模型有效性进行分析发现,FWO和KAS模型在描述混合样品燃烧动力学时存在一定的局限性,而采用适宜机理函数的CR模型更适用于描述混合样品的燃烧反应动力学,对燃烧机理的分析也印证了动力学的分析结果。     

纳米材料在抗高温钻井液中的应用进展

纳米材料具有尺寸较小、热稳定性强等性质,使其可作为钻井液处理剂来提高钻井液的抗高温性能。抗高温钻井液用纳米材料一般采用将材料纳米化或将纳米材料与聚合物复合制得,大致可分为无机纳米材料、聚合物纳米球和纳米复合材料三类。此外,对纳米材料进行结构优化可提高其热稳定性和分散性,用于封堵岩层中纳米孔隙、降低钻井液滤失量、改善钻井液流变性和提高钻井液抗温能力。本文简要阐述高温对钻井液性能的影响,分析纳米材料在钻井液中的作用,重点介绍不同类型纳米材料在抗高温（≥150℃）钻井液中的应用,尤其是对钻井液流变性能和降滤失效果的影响。最后指出纳米材料作为钻井液处理剂未来发展应向着环保、合成工艺简化和室内与现场研究相结合等方向突破。     

Synthesis of tubular silica fiber via all-aqueous microfluidics for geopolymer regulation

Lightweight hollow ceramic microfibers/microparticles hold promising prospects in numerous applications. To date, it remains a challenge to develop a fabrication strategy that well balances product quality and efficiency. In this article, an all-aqueous microfluidic method was proposed to prepare tubular polymeric fiber as the preceramic template. The relevant dimensional parameters could be promptly regulated via simple flow rate control. This approach could serve as a general technical route to preparing different kinds of ceramics by switching the types of nanoparticles. Here, silica nanoparticles were introduced and the ceramic microfiber could be got via calcination. Afterward, the tubular silica microfiber was employed to synthesize geopolymer composite by mold casting. The chemically formed interfacial bonding between the silica microfiber and geopolymer matrix was confirmed by elemental analysis. The addition of 10% volume fraction silica microfiber could not only increase the flexural modulus of geopolymer composite by 3.5 times but also effectively inhibited crack propagation under thermal circumstances.     

108 m3聚合釜引发剂用量及加入技术对树脂质量的影响

引发剂是调节氯乙烯悬浮聚合反应速率,并影响聚合放热、聚合周期和聚合釜生产能力的重要助剂。引发剂对氯乙烯悬浮聚合动力学的影响主要与引发剂的活性、用量有关。引发剂用量、加入方式和前后期使用比例等对树脂质量也有明显的影响。     

Synthesis of Al2O3-SiC powder from electroceramics waste and its application in low-carbon MgO-C refractories

Composite additives are an efficient means to improve the high-temperature stability and slag resistance of low-carbon MgO-C refractories. In this work, Al₂O₃-SiC powder was firstly synthesized from electroceramics waste by carbon embedded method at 1500°C, 1550°C, and 1600°C for 4 h, and then the as-synthesized Al₂O₃-SiC powder was used as an additive to low-carbon MgO-C refractories. The effects of its addition amounts of 0, 2.5 wt.%, 5.0 wt.%, and 7.5 wt.% on the properties of the refractories were investigated in detail. It was found that increasing the heat treatment temperature is beneficial to the phase conversion of mullite and quartz to alumina and silicon carbide in the electroceramics waste. Furthermore, the addition of Al₂O₃-SiC powder effectively improves the performance of low-carbon MgO-C samples, and the formation of spinel dense layer and high-viscosity isolation layer is the internal reason for the improvement of the oxidation resistance and slag resistance of low-carbon MgO-C samples. This work provides ideas for the reuse of electroceramics waste and presents an alternative strategy for the performance optimization of low-carbon MgO-C refractories.     

Sintering behavior and morphology control of porous Al2O3-SiO2 ceramics for radome applications

Ceramics from porous Si₃N₄ and its derivatives SiAlON and Si₂N₂O were once considered the most promising high-temperature wave-transmitting materials. However, their large-scale application in the field of radomes is greatly restricted due to their poor oxidation resistance, high preparation costs, and expensive raw materials. Therefore, the development of low-cost porous oxide ceramics remains of significant interest to the field of high-temperature wave transmission. Surprisingly, mullite ceramics, which are representative of the Al₂O₃-SiO₂-system of ceramics, are ultra-low-cost materials with the potential to replace ceramics from Si₃N₄ and its derivatives. In this paper, integrated porous Al₂O₃-SiO₂-system ceramics were successfully prepared for load-bearing/wave-transmitting applications, using inexpensive calcined kaolin and alumina powder as the main raw materials. Calcined kaolin can provide seeds for the growth and development of mullite crystals in the ceramic system. High-strength and high-porosity ceramics were obtained with the mullite morphology controlled through the molar ratio of Al₂O₃ to SiO₂ and the resulting content of mullite seeds. With increasing of mullite seed content, the length and radial width of mullite whiskers with “interlocking structure” gradually change from rod-shaped “long and thick” to needle-like “short and thin.” The prepared porous Al₂O₃-SiO₂ ceramics have high flexural strength, fracture toughness, and good dielectric properties.     

Hierarchical porous metal-organic frameworks/polymer microparticles for enhanced catalytic degradation of organic contaminants

This work reports on a simple microfluidic strategy to controllably fabricate uniform polymeric microparticles containing hierarchical porous structures integrated with highly accessible catalytic metal organic frameworks for efficient degradation of organic contaminants. Monodisperse (W1/O)/W2 emulsion droplets generated from microfluidics are used as templates for the microparticle synthesis. The emulsion droplets contain tiny water microdroplets from homogenization and water nanodroplets from diffusion-induced swollen micelles as the dual pore-forming templates, and Fe-based metal-organic framework nanorods as the nanocatalysts. The obtained microparticles possess interconnected hierarchical porous structures decorated with highly accessible Fe-based metal-organic framework nanorods for enhanced degradation of organic contaminants via a heterogeneous Fenton-like reaction. Such a degradation performance is highlighted by using these microparticles for efficient degradation of rhodamine B in hydrogen peroxide solution. This work provides a simple and general strategy to flexibly combine hierarchical porous structures and catalytic metal-organic frameworks to engineer advanced microparticles for water decontamination.     

Room-temperature hydrogenation of halogenated nitrobenzenes over metal–organic-framework-derived ultra-dispersed Ni stabilized by N-doped carbon nanoneedles

Ultra-dispersed Ni nanoparticles (7.5 nm) on nitrogen-doped carbon nanoneedles (Ni@NCNs) were prepared by simple pyrolysis of Ni-based metal–organic-framework for selective hydrogenation of halogenated nitrobenzenes to corresponding anilines. Two different crystallization methods (stirring and static) were compared and the optimal pyrolysis temperature was explored. Ni@NCNs were systematically characterized by wide analytical techniques. In the hydrogenation of p-chloronitrobenzene, Ni@NCNs-600 (pyrolyzed at 600 °C) exhibited extraordinarily high performance with 77.9 h^–1 catalytic productivity and > 99% p-chloroaniline selectivity at full p-chloronitrobenzene conversion under mild conditions (90 °C, 1.5 MPa H₂), showing obvious superiority compared with reported Ni-based catalysts. Notably, the reaction smoothly proceeded at room temperature with full conversion and > 99% selectivity. Moreover, Ni@NCNs-600 afforded good tolerance to various nitroarenes substituted by sensitive groups (halogen, nitrile, keto, carboxylic, etc.), and could be easily recycled by magnetic separation and reused for 5 times without deactivation. The adsorption tests showed that the preferential adsorption of –NO₂ on the catalyst can restrain the dehalogenation of p-chloronitrobenzene, thus achieving high p-chloroaniline selectivity. While the high activity can be attributed to high Ni dispersion, special morphology, and rich pore structure of the catalyst.