Research on corrosion performance of 6061 aluminum alloy in salt spray environment

Salt spray corrosion test was carried out on 6061 aluminum alloy, and quasi-static tensile test at room temperature was carried out on the sample with universal testing machine. The effect of salt spray corrosion on the mechanical properties of 6061 aluminum alloy was studied by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and electrochemistry. The corrosion rate of 6061 aluminum alloy was quantitatively characterized by different corrosion parameters. It was found that local corrosion of 6061 aluminum alloy occurred in salt spray environment, mainly pitting corrosion and intergranular corrosion. With the increase of corrosion time, the polarization resistance of 6061 aluminum alloy decreases, and the corrosion rate significantly increases. The average corrosion rate and the maximum corrosion rate of 6061 aluminum alloy were characterized by corrosion weight loss and corrosion pit depth. And they can be transformed into each other. The mechanical properties of 6061 aluminum alloy were mainly affected by the depth of corrosion pit. With the increase of corrosion time, the tensile strength and fracture strain decreased, resulting in poor plasticity of the sample. At the same time, the change of elongation of 6061 aluminum alloy can be accurately predicted by the depth of corrosion pit.     

Solidification microstructure characteristics of Ti–44Al–4Nb–2Cr–0.1B alloy under various cooling rates during mushy zone

Beta-solidifying TiAl alloy has great potential in the field of aero-industry as a cast alloy.In the present work,the influence of cooling rate during mushy zone on solidification behavior of Ti-44Al-4Nb-2Cr-0.1B alloy was investigated.A vacuum induction heating device combining with temperature control system was used.The Ti-44Al-4Nb-2Cr-0.1B alloy solidified from superheated was melted to β phase with the cooling rates of 10,50,100,200,400 and 700 K·min~(-1),respectively.Results show that with the increase in cooling rate from 10 to 700 K·min~(-1),the colony size of α_2/γ lamella decreases from 1513 to48 urn and the solidification segregation significantly decreases.Also the content of residual B2 phase within α_2/γlamellar colony decreases with the increase in cooling rate.In addition,the alloy in local interdendritic regions would solidify in a hypo-peritectic way,which can be attributed to the solute redistribution and enrichment of Al element in solidification.     

Mechanical properties and miscibility of polyethersulfone/phenoxy blends

The blends of polyethersulfone and phenoxy were prepared by melt mixing in a Brabenderlike apparatus. The specimens for measurements were made by compression molding and then were water-quenched at room temperature under pressure. The tensile strength, tensile modulus, elongation at break and yield, density, thermal analysis, and dynamic mechanical properties were each measured. The dependence of tensile strength, tensile modulus, elongation at break and yield, and density on composition was obtained. The relationship between tensile modulus and elongation at break and yield and speed of the crosshead at different weight ratios of the blends is shown. The effects of composition and miscibility on the mechanical properties are discussed. © 1996 John Wiley & Sons, Inc.     

海洋氨肽酶菌株的筛选鉴定及其酶学特性研究

从大连渤海海域海泥海水样品中分离出一株高产海洋氨肽酶(aminopeptidase)菌株YZ1-2,对其进行形态学、生理生化、分子生物学(16S rDNA)鉴定,确定该菌株为蜡样芽孢杆菌(Bacillus cereus)。并对其产海洋氨肽酶进行酶学特性研究,结果表明,最适作用温度为30 ℃;最适作用pH值为8.5;Co2+、Zn2+等能较强地激活氨肽酶的活性,Ni2+、Ca2+等对酶的抑制性较强;乙二胺四乙酸(EDTA)可以有效地抑制氨肽酶活性。     

分期实施地铁车站破墙接驳技术的工程实践

随着我国城市轨道交通建设的快速发展,车站分期实施的情况越来越多,既有车站与后期车站的合理对接,对确保既有车站的结构安全、运营安全至关重要。以北京地铁宋家庄枢纽站既有5号线与后期亦庄线车站接口实施方案为工程背景,研究了设计预留接口条件与设计未预留接口条件两种典型情况的工程处理原则和措施,总结了工程实施过程中的经验教训,其分析思路和采取的工程措施,对类似工程的设计和施工有一定的借鉴参考价值。     

Inverse Reconstruction of Fracture Splitting Connecting Rod and its Strength and Fatigue Life

Journal of Failure Analysis and Prevention - To investigate the strength and fatigue life of a fracture-split connecting rod, this study combines experiments on connecting rod fracture splitting,...     

Significant Role of Al in Ternary Layered Double Hydroxides for Enhancing Electrochemical Performance of Flexible Asymmetric Supercapacitor

The Al effect on the electrochemical properties of layered double hydroxides (LDHs) is not properly probed, although it is demonstrated to notably promote the capacitive behavior of LDHs. Herein, ternary NiCo₂Al_x layered double hydroxides with varying levels of Al stoichiometry are purposely developed, grown directly on mechanically flexible and electrically conducting carbon cloth (CC@NiCo₂Al_x‐LDH). Al plays a significant role in determining the structure, morphology, and electrochemical behavior of NiCo₂Al_x‐LDHs. At an increasing level of Al in NiCo₂Al_x‐LDHs, there is a steady evolution from 1D nanowire to 2D nanosheets. The CC@NiCo₂Al‐LDH at an appropriate level of Al and with the nanowire–nanosheet mixed morphology exhibits both significantly enhanced electrochemical performance and excellent structural stability, with about a 2.3‐fold capacitance of NiCo₂‐OH. When applied as the anode in a flexible asymmetric supercapacitor (ASC), the CC@NiCo₂Al‐LDH gives rise to a remarkable energy density of 44 Wh kg^?1 at the power density of 462 W kg^?1, together with remarkable cyclic stability with 91.2% capacitance retention over 15 000 charge–discharge cycles. The present study demonstrates a new pathway to significantly improve the electrochemical performance and stability of transition metal LDHs, which are otherwise unstable in structure and poorly performing in both rate and cycling capability.     

The steric effect of exfoliation agent for fabrication of layer niobium oxide nanosheet

In this research, the steric effect of an exfoliation agent between n-ethylamine and triethylamine for the fabrication of Ca₂Nb₃O₁₀⁻ nanosheet was investigated. The experimental results revealed that the different structures of the exfoliation agent have affected to fabrication of Ca₂Nb₃O₁₀⁻ nanosheet. The use of n-ethylamine as an exfoliation agent gave a maximum exfoliation efficiency of 10 wt.% while the maximum exfoliation efficiency of triethylamine was 90 wt.%. The result showed that the difference in exfoliation efficiency was caused by the steric effect of exfoliation agents. The image of transmission electron microscopy exhibited Ca₂Nb₃O₁₀⁻ nanosheets which were formed by exfoliation of HCa₂Nb₃O₁₀. Furthermore, the reaction time for liquid exfoliation was studied in this work. The reaction time at 4 h gave a maximum of exfoliation efficiency. The Ca₂Nb₃O₁₀⁻ suspension was tested capability to remove hazardous ions. After the experiment, we found the white precipitate which was the formation of CsCa₂Nb₃O₁₀. The result showed that the Ca₂Nb₃O₁₀⁻ nanosheet was efficient for the removal of Cs⁺ ions in the wastewater.     

10kV配电站计算机监控系统的电气设计

以某公司10 kV配电站设计为例,介绍了10 kV配电站计算机监控系统的选型、继电保护、操作电源的设计,以及测量回路、信号回路、控制回路、中央信号系统、计算机网络的设计方法和应具备的功能.实践证明,设计方案可行,运行稳定.     

基于Kriging统计的移动曲面拟合

通过方位取点法选取采样点,移动拟合出二次曲面来逼近实际地形。对采样点处的逼近误差进行Kriging统计,获得待定点处高程逼近误差的最优估值。进行了基于Kriging统计的移动曲面拟合综合模型的模拟计算,通过单一曲面模型和Kriging统计模型的逼近误差及精度的比较,验证了综合内插模型的优越性。