Microwave-assisted synthesis of graphene-supported Pd1Pt3 nanostructures and their electrocatalytic activity for methanol oxidation

This work reports the development of a facile, one-step microwave heating method for the synthesis of graphene-supported Pd₁Pt₃ (Pd core/Pt shell) electrocatalysts. The structure and composition of the synthesized nanocomposites were characterized via transmission electron microscopy and atomic force microscopy as well as energy-dispersive X-ray, X-ray powder diffraction, FTIR, and Raman spectroscopies. Using voltammetry, the electrocatalytic characteristics of the graphene-supported Pd₁Pt₃ nanostructures were evaluated for the oxidation of methanol as a model reaction. The results show that the introduction of graphene increases the electrochemically active surface area of the Pd₁Pt₃ nanostructures. As compared to the unsupported Pd₁Pt₃ electrocatalyst, the graphene-supported Pd₁Pt₃ electrocatalyst exhibited 80% enhancement of the electrocatalytic specific mass current for the oxidation of methanol. This method may serve as a general, facile approach for the synthesis of graphene-supported bimetallic PtM electrocatalysts with increased utilization of the Pt metal, which is expected to have promising applications in fuel cells.     

常温磷化液改进工艺研究

研究了40℃温度下实验所得磷化液。结果表明磷化液每升含氧化锌15g、磷酸二氢锌12g、磷酸25mL、氟化钠0.6g、氯酸钾0.3g、柠檬酸0.2g、乌洛托品0.25g、钼酸钠0.18g、十二烷基苯磺酸钠0.18g、磷酸锌3.5g、50%硝酸锰3.5g时,CuSO4点滴平均时间78s、磷化液酸比平均值23.8。实验所得磷化液优化配方,较其它磷化工艺温度有所降低,并且大大降低了锰离子的使用量,是一条经济节约、绿色环保的工艺路线。     

Growth of carbon nanotubes on natural organic precursors by chemical vapor deposition

Some plant tissues are rich in transition metal Fe. So, we explored the use of black jew’s-ear fungus and black sesame seeds as catalyst precursors to prepare carbon nanotubes by chemical vapor deposition. Each catalyst particle arises from the metal content of a single cell of the precursor, hence the distribution of catalyst particles is uniform. Their size and composition are almost identical. Carbon nanotube arrays can grow when black sesame seeds are used as catalyst precursors. Carbon nanotubes with diameters 80 nm and length greater than 100 μm can grow when black jew’s-ear fungus are used.     

Dual-template synthesis of magnetically-separable hierarchically-ordered porous carbons by catalytic graphitization

Magnetically-separable hierarchically-ordered porous carbons with graphitic structures (HPC-G) have been directly synthesized by one-pot dual-templating with evaporation-induced self-assembly at calcination temperatures ranging between 600 and 1000 °C. Polystyrene latex spheres and triblock copolymer F127 were used as macro- and meso-porous structure-directing agents, while phenol–formaldehyde resins and Ni species were added as the carbon source and graphitization catalyst, respectively. The microstructures in terms of morphology, surface area, pore texture, thermal stability, degree of graphitization and magnetic properties were characterized by scanning and transmission electron microscopy, small angle X-ray scattering, X-ray powder diffraction, surface area analysis, Raman spectroscopy, thermogravimetric analysis, and superconducting quantum interference device magnetometry. Addition of nickel species catalyzes the graphitization of HPC-G at relatively low carbonization temperatures under different atmospheres (N₂ or H₂/N₂). The HPC-G exhibits well-crystallized graphitic domains, excellent magnetic properties, uniform and interconnected porous structures, and high surface area. The magnetically-separable HPC-G shows a high adsorption capacity for methylene blue and improved electrocatalytic activity towards and I₂ reductions in dye-sensitized solar cells. Results obtained in this study allow us to develop an environmentally friendly technique for fabrication of HPC with well-crystallized graphitic carbon and magnetically-separable properties for novel applications.     

Effect of Blockage on Heat Transfer Phenomena of Spheroid Particles at Moderate Reynolds and Prandtl Numbers

Effects of the confining wall or blockage on the heat transfer phenomena of spheroid particles were numerically investigated. The heated spheroid particles were maintained at constant temperature and allowed to sediment in cylindrical tubes filled with Newtonian liquids. In this flow configuration, the heat transfer took place from the heated spheroid particles to the surrounding Newtonian liquid. The governing conservation equations of the mass, momentum, and energy together with appropriate boundary conditions were numerically solved using commercial software based on computational fluid dynamics. A simple correlation for the average Nusselt number of the confined spheroid particles was developed which can be applied in new applications.     

Soybean‐Oil‐Based Thermosetting Resins with Methacrylated Vanillyl Alcohol as Bio‐Based,Low‐Viscosity Comonomer

A novel, bio‐based, aromatic monomer (methacrylated vanillyl alcohol, MVA) is synthesized using vanillyl alcohol and methacrylic anhydride in the absence of solvents. The resulting MVA is used as a sustainable comonomer to replace styrene in a maleinated acrylated epoxidized soybean‐oil (MAESO) resin to produce novel thermosets via free radical polymerization. The influence of MVA loading on the viscosity, gelation time, curing extent, thermomechanical properties, and tensile properties of the MAESO–MVA thermoset is investigated. The synthesized MVA exhibits very low volatility, which is beneficial for the development of construction material with low or zero emission. The viscosity of the MAESO–MVA system can be tailored to meet the commercial requirements. Increasing the MVA content accelerates the crosslinking reaction rate and improves thermal and mechanical properties of the MAESO–MVA system. The glass transition temperature increases with increasing MVA content. Soxhlet extraction experiments show that more than 90% of the components are incorporated into the crosslinking network. Overall, the developed MVA monomer shows promising properties to be used as an effective, green comonomer to replace styrene.     

Conversion of calcium aluminate cement hydrates at 60°C with and without water

There have been different hypotheses about the transformation mechanisms of calcium aluminate cement hydrates and this work aims to clarify the long‐running debate about the conversion approaches. In this work, CAH₁₀ and C₂AH₈ were produced from the pastes of calcium aluminate cement (CAC) cured for 24 hours at 10 and 20°C separately. And the cured pastes were continually cured at 60°C for 3 days with water and without water, respectively. The hydration of the pastes was halted by freeze‐drying, and the phases and microstructure of hydrates were investigated by XRD and SEM, respectively. The results indicate that CAH₁₀ and C₂AH₈ converted into C₃AH₆ and AH₃ in water presence at 60°C, but did not transform into C₃AH₆ and AH₃ without water. It is confirmed that the conversion of CAH₁₀ and C₂AH₈ to C₃AH₆ and AH₃ happens through preceding solution of CAH₁₀ and C₂AH₈ and subsequent precipitation of C₃AH₆ and AH₃.     

回流泵机械密封泄漏分析及处理

针对甲醛塔回流泵机械密封频繁泄漏的现象,通过检查发现是摩擦副端面间出现泄漏,同时发现波纹管和静环辅助密封圈损坏,处理后问题得到解决。     

500kV伊敏─冯屯串联补偿站设计原则的研究──特高压线路用串联补偿站的典型单元

本文结合东北地区伊敏－齐齐哈尔冯屯变电站５００ｋＶ输电工程提出了５００ｋＶ等级串联电容补偿站的通用设计。设计中的主要技术为“积木式”构思，即用典型单元装配成不同参数的串补站，便于通用、制造与维护。本设计中采用的扩大的典型单元使辅助设备减少了几乎一半。新一代的ＺｎＯ保护装置，提高了串补站的性能。双回线中串补站的新型主结线方式，可以使串补站的电容器容量减少一半，就伊敏－冯屯串补站而言，可节省基建投资近５０００万元。本文所述的典型单元除对地绝缘外也可用于任何电压等级（７５０～１２００ｋＶ）。     

微电子电路PC机辅助教育系统

文章介绍法中两国合作开发的微电子电路计算机辅助教育系统中的两部分，重点陈述其中的辅助测试虚拟仪器和专用实验芯片，期望对电子测试领域的教育工作者和科技工作者有所启发。