高能超声波处理对细化过共晶Al-20%Si合金中硅相的影响

采用高能超声波对过共晶Al-20%Si合金进行熔体处理,研究超声波对Al-20%Si合金微观组织的细化效果和作用规律。结果表明,在Al-20%Si合金凝固过程中对其进行超声波处理,可以破碎组织中粗大板片状初晶硅,使晶粒尺寸变小,圆整度提高、分布均匀;提高超声波功率,可以增强对铝硅合金微观组织的细化效果并使熔体中组织细化的区域扩大;实验结果还表明,在熔体中不同位置导入超声波进行处理,对整体组织的作用效果有较大区别,在熔体中心位置较浅深度导入超声波时,所获得的组织细化区域较大,并且组织分布均匀。     

Oxidation of refractory metallic coatings on carbon fibers heated up to 1850 °C

A method for testing high refractory metallic coatings at high temperature (up to 1850 °C) in controlled atmosphere (inert or oxidizing), at low pressure (around 4 kPa) and with an exposure time of 5 s maximum is developed here. Metallic coatings on carbon fibers are deposited using the PVD (physical vapor deposition) process. The sample is then heated by Joule effect (electrical resistivity). Cooling is not controlled, so the material undergoes quenching and keeps the microstructure and chemical composition produced at very high temperature under controlled atmosphere. PVD coatings on carbon fibers are sufficiently continuous and thick to be used as protective coatings during the oxidation tests at high temperature. This test allows studying the diffusion of carbon at the fiber/coating interface and of oxygen at the interface of external environment/coating at high temperatures. The aim of this study is to highlight the effect of a modification of composition on the carburization and on the oxidation mechanism, from the testing at high temperatures on these metallic coatings. Pure Hf and Hf-Ta metal alloys are considered.     

Characterization of water transport in gas diffusion media

An in-depth insight in the role of gas diffusion layers (GDLs) and its impact on the water management is a key issue for the optimization of fuel cells. A new ex situ test method is developed to investigate the water transport in gas diffusion media for polymer electrolyte membrane fuel cells (PEMFCs). This research is focused on properties of GDLs, which influence the water removal and water retention in the cell.     

Research on the oxidation kinetics curve of 1Cr11Ni2W2MoV steel hot-dipped Al

In this paper, 1Cr11Ni2W2MoV steel that is aerial engine blade materials was hot dipped Al-6,Si-4,RE in order to improve its application temperature. According to GB/T13303 - 91 standard, samples with coating and without coating were oxidated at 700℃ from 5 h to 600 h. Two oxidation kinetics curves were drawn in terms of data of tests. The results showed that oxidation resistance of 1Cr11Ni2W2MoV steel hot-dipped Al-6, Si-4,RE is better than one without coating. From SEM and EMPA, the surface of coating formed dense and uninterrupted α-Al2O3, which is the bars of oxidation resistance. In addition, according to one crossing point of the two curves, it was suggested that hot dipped aluminum steel should be annealed before used.     

53 t 12%Cr超超临界转子电渣锭研制

利用自主研发的130 t电渣炉,结合对12%Cr材料的认识和巨型高品质电渣锭的生产经验,制定了技术方案,生产了53 t 12%Cr超超临界转子电渣锭,在氩气保护、渣系和脱氧制度等关键技术方面积累了经验。     

同纬度严寒地区建筑节能75%可行性研究

通过分析总结已出台75%居住建筑节能标准的同纬度地区的节能规范,在辽宁省现行标准的基础上大量测算阜新地区及新疆等地具有代表性的居住建筑的耗热量指标,并反复推敲各围护结构的限值,综合考虑锅炉效率和室外管网输送效率,最终制定出适用于阜新地区的居住建筑节能75%的相应标准。初步探讨现有节能技术的节能潜力以及如何提升建筑节能应用水平,从而从设计源头降低建筑物的能耗需求,扩大严寒地区建筑节能标准在同纬度地区的应用范围。     

Effect of Ni layer thickness and soldering time on intermetallic compound formation at the interface between molten Sn-3.5Ag and Ni/Cu substrate

The binary eutectic Sn-3.5wt.%Ag alloy was soldered on the Ni/Cu plate at 250°C, the thickness of the Ni layer changing from 0 through 2 and 4 μm to infinity, and soldering time changing from 30 to 120 s at intervals of 30 s. The infinite thickness was equivalent to the bare Ni plate. The morphology, composition and phase identification of the intermetallic compound (IMC, hereafter) formed at the interface were examined. Depending on the initial Ni thickness, different IMC phases were observed at 30 s: Cu₆Sn₅ on bare Cu, metastable NiSn₃ + Ni₃Sn₄ on Ni(2 μm)/Cu, Ni₃Sn₄ on Ni(4 μm)/Cu, and Ni₃Sn + Ni₃Sn₄ on bare Ni. With increased soldering time, a Cu-Sn-based η-(Cu₆Sn₅)_1−xNi_x phase formed under the pre-formed Ni-Sn IMC layer both at 60 s in the Ni(2 μm)/Cu plate and at 90 s in the Ni(4 μm)/Cu plate. The two-layer IMC pattern remained thereafter. The wetting behavior of each joint was different and it may have resulted from the type of IMC formed on each plate. The thickness of the protective Ni layer over the Cu plate was found to be an important factor in determining the interfacial reaction and the wetting behavior.     

Decomposition of 2-chlorophenol using a tourmaline–photocatalytic system

10.0 wt.% tourmaline mineral was loaded onto amorphous TiO₂ and treated at 100–900 °C to obtain anatase and rutile structures, respectively, and were used for the photodecomposition of 2-chlorophenol. Tourmaline (10.0 wt.%)/TiO₂ (anatase) and pure TiO₂ (anatase) adsorbed 2-chlorophenol at 15 ppm and 8 ppm, respectively. 2-Chlorophenol was completely decomposed after 42 h in 10.0 wt.% tourmaline/TiO₂ (anatase), by a first-order rate equation. The decomposition rate increased with increasing catalyst amount and tourmaline concentration to give optimal conditions of 1.0 g/L and 12.5 wt.%, respectively. The decomposition of 2-chlorophenol was also affected by H₂O₂ addition and pH regulation. The decomposition rate reached 40.0 ppm/h when 10.0 mL/L of H₂O₂ was added to the feed solution, and 100 ppm of 2-chlorophenol was completely removed after 21 h at pH 11.0.     

An ecofriendly approach for corrosion control of 6061 Al-15％(v) SiC(p) composite and its base alloy

Corrosion inhibition characteristics of bio polymer dextran was studied for the corrosion control of 6061 Al-15%_((v)) SiC_((P)) composite and its base alloy in 1 mol·L~(-1) HCl. Standard electrochemical techniques such as potentiodynamic polarization(PDP) measurements and electrochemical impedance spectroscopy(EIS) method were adopted for corrosion rate measurement. Surface morphology was studied by scanning electron microscopy(SEM) and elemental mapping was done by energy dispersive X-ray(EDX) analysis. Suitable mechanism was proposed for corrosion and inhibition process. Results indicated that dextran acts as an excellent anticorrosive agent for the corrosion control of 6061 Al-15%_((v)) SiC_((P)) composite, with maximum inhibition efficiency of 91% for the concentration of 0.4 g·L~(-1) at 303 K. Dextran acted as a mixed type of inhibitor, and got physically adsorbed both on composite and base alloy by obeying Langmuir adsorption isotherm. Dextran is proved to be a green inhibitor with environmental and economic benefits.     

纳米石墨负载功能化石墨烯纳米带/EVA复合材料薄膜的性能及表征

采用十二烷基硫酸钠改善纳米石墨(CNPs)在水溶液中的分散性,使其均匀负载至功能化石墨烯纳米带(EGNRs)上,制得功能化石墨烯纳米带-纳米石墨复合体(EGNRs_(75%)-CNPs),随后利用溶液涂覆成膜工艺在涂膜机上制得EGNRs_(75%)-CNPs/乙烯-醋酸乙烯共聚物(EVA)复合材料薄膜。采用FTIR、XRD、XPS、TEM、FESEM、氧气透过仪、高阻计对不同EGNRs_(75%)-CNPs含量的EGNRs_(75%)-CNPs/EVA复合材料薄膜进行了结构和性能表征。研究表明:EGNRs_(75%)-CNPs以3D网络形式存在,能够抑制纳米带团聚,说明其与EVA基体相容性好。当EGNRs_(75%)-CNPs质量分数为1%时,EGNRs_(75%)-CNPs/EVA复合材料薄膜的氧气透过率降低了67.6%,阻隔性能提高明显;当质量分数为0.8%时,CNPs负载到EGNRs构建3D导电网络,协同发挥增强作用,EGNRs_(75%)-CNPs/EVA复合材料薄膜导电性能提升了约8个数量级,表现出了优良的室温导电性能。