Measurement of Thermal Diffusivity at Low Temperatures Using an Optical Reflectivity Technique

An experimental arrangement has been developed for measuring the transient temperature responses and the thermal diffusivities of foil materials in the range of 10 to 300K by using the optical reflectivity technique. The cryogenic system with optical windows is designed to provide temperatures from 10 to 300 K. The front surface of a foil specimen is heated by a pulsed Nd:YAG laser. In situ measurement of the reflectivity of a continuous-wave He–Ne laser at the rear surface is conducted on the microsecond time scale. Using the temperature dependence of reflectivity, the transient temperature response is deduced. The thermal diffusivity is obtained by fitting Parker's formulae to the experimental data on temperature rise. Stainless-steel foils are chosen as samples and are studied in the region from 10 to 300 K. The accuracy is examined by comparing the present results with the theoretical temperature responses and thermal diffusivity data from the literature. Good agreement is observed.     

改进的活化方法制备钯/多孔不锈钢复合膜

提出了一种新的、适用于化学镀法制备钯/多孔不锈钢复合膜的活化方法,即利用Fe2 的还原性将活化液中的Pd2 还原为钯单质并沉积在载体表面,形成钯核.着重考察了该方法的活化条件对化学镀过程及钯膜表面形貌的影响.结果表明,活化时间及活化温度对载体表面钯核的分布情况及聚集状态有较大影响,而钯核的分布及聚集状态对制备的钯膜表面形貌又有较大影响.实验确定了适宜的活化条件:活化时间1min,活化温度60℃.在活化该条件下得到的钯膜比较致密,且化学镀过程的反应速率也比较平稳.     

Synthetic curli enables efficient microbial electrocatalysis with stainless-steel electrode

Microbial electrocatalysis systems (MES) provide a cutting-edge solution to global problems associated with the environment and energy, but practical applications are hindered by the expensive electrode materials. Although stainless steel (SS) has been proposed as a promising inexpensive candidate, poor cell/SS interaction results in a low performance for MES. Here, a new synthetic biology approach was established for reinforcing the cell/SS interaction. Hybridized curli nanofibers fused with a metal-binding domain were heterogeneously expressed onto the cell surface, which realized efficient cell binding with the SS electrode. Consequently, it enabled a ~420-fold improvement of the anodic power output and a substantial enhancement of the cathodic Coulombic efficiency (from 0.6 to 4% to over 80%) with an SS electrode. This work demonstrates low-cost MES with an SS electrode and introduces a new avenue to engineer the cell/electrode interaction, which is promising for future practical applications of MES.     

龙滩水轮机转轮的设计和制造评述

龙滩水电站安装9台700MW混流式机组,电站的运行条件十分苛刻：水头变幅大,从97m到179m,最大水头与最小头差值达82m,电站下游洪枯水位差值达40m,电站在系统中担任调频、调峰和事故备用,启动频繁。设计的水轮机转轮,必须具有良好的水头和负荷变化的适应性,稳定运行范围要宽广。龙滩水轮机转轮的设计和制造,在特大型机组中具有代表性,尤其是在工地制作700MW转轮,更居首次。转轮的设计和制造,由伏依特西门子水电设备公司负责,日前此项工作正在进行中,第一台转轮已组装焊接完毕,并进行了退火热处理。文章就龙滩水轮机转轮的水力设计、模型试验、转轮结构设计、转轮工地制造及转轮的最终验收,进行评述并提出一些建议。     

Effects of minor additions of ruthenium on the passivation of duplex stainless-steel corrosion in concentrated hydrochloric acid solutions

The effects of minor additions of ruthenium (0.14%, 0.22%, and 0.28%) on the passivation of duplex stainless-steel (DSS, Fe–22%Cr–9%Ni–3%Mo) corrosion in 2 M HCl solutions have been studied using open-circuit potential (OCP), potentiodynamic cyclic polarization, potentiostatic current–time, electrochemical impedance spectroscopy (EIS), and weight loss measurements. OCP measurements showed an increased shift in the corrosion potential to more positive values with increasing Ru content. Polarization and EIS experiments indicated that the presence of Ru and the increase of its content decrease the corrosion rate, critical and passive current density, and polarization resistance. Moreover, it shifts the corrosion and pitting potentials to more positive values. Current–time measurements at −100, −50, and 50 mV versus Ag/AgCl also confirmed that the severity of pitting corrosion decreases with an increasing Ru content. Weight-loss time data showed good agreement with the electrochemical measurements.     

植钉挂贴饰面板施工技术应用研究

饰面板通过不锈钢沉头螺栓和结构胶直接挂贴于填充墙墙体基材上,作为一种饰面板新的施工技术与普通饰面板施工工艺比较,具有良好的效益;本文通过理论分析和一系列的试验研究,证明该技术的可行性,并对其施工技术特点、工艺及其质量控制要点进行论述。     

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 通过对不同厚度、不同抗拉强度的奥氏体不锈钢304箔材进行多种标距的拉伸试验,利用伸长率与比例系数进行回归拟合的方式,分析了影响304箔材[n]值的主要因素,总结了Olive公式在固溶态和冷变形304箔材中的应用规律,拓宽了Olive伸长率换算公式的应用范围。结果表明：试样适宜的[L0]取值范围为20～90 mm,试样厚度（宽厚比）与[n] 值间无明显的相关性。另外对于[Rm]≥750 MPa的冷变形304箔材,[n]值与抗拉强度间呈正相关。同时分3个抗拉强度范围给出了[n]值的预测值,当[Rm]≤750 MPa时,[n]＝0.130,与标准规定值完全吻合;760 MPa≤[Rm]≤960 MPa时,[n]＝0.160;1 050 MPa≤[Rm]≤1 270 MPa时,[n]＝0.378。     

光纤不锈钢松套管的制造工艺

简要介绍了光纤不锈钢松套管的两种结构以及相关制造工艺。对生产原理、关键技术进行了对比分析，对一些有争议的问题进行了探讨。     

增容作用对聚乳酸/高密度聚乙烯合金发泡行为的影响

以乙烯甲基丙烯酸缩水甘油酯共聚物（GEMA）为增容剂,采用熔融共混法制备了聚乳酸（PLA）/高密度聚乙烯（PE-HD）增容合金。以CO2为发泡剂进行釜压发泡,制备出PLA/PE-HD增容合金泡沫。结果表明,加入GEMA后,聚合物合金的结晶能力有所下降和流变性能略有提高;随着GEMA含量的增加,PE-HD分散相尺寸减小,数量增多,聚合物合金发泡样品的泡孔结构可以实现从复合泡孔到单一泡孔的转变。     

304不锈钢消音蜂窝钎焊工艺、组织及力学性能分析

采用镍基BNi2钎料钎焊制备了304不锈钢消音蜂窝,对蜂窝芯体与面板钎焊界面组织和蜂窝的力学性能进行了分析和测试,并研究了钎焊热循环次数对钎焊界面组织和蜂窝拉伸力学性能的影响,为实际工程应用确定未焊合缺陷补焊次数提供了依据。液态钎料的毛细作用使钎料沿蜂窝芯箔材表面铺展并与箔材发生显著的元素扩散反应,蜂窝芯与面板之间的钎缝由Ni、Cr、Si等互溶而成的Ni基固溶体组织组成,未生成脆性共晶组织或金属间化合物。钎料中的B和Si元素显著扩散于面板材料中,形成钎料-面板反应区,因B元素的沿晶界快速扩散效应,面板侧组织呈现晶界元素渗入特征。随着钎焊次数增加,钎料对母材的溶解和晶界渗透增加,钎焊界面组织发生显著变化。制备的304不锈钢消音蜂窝拉脱强度为7.21MPa,呈现板/芯界面附近蜂窝芯破坏特点,多次钎焊时蜂窝拉脱强度呈下降趋势。制备的304不锈钢消音蜂窝平压、侧压和弯曲力学性能测试过程均经历弹性变形、塑性变形和失稳三个阶段,强度值分别为5.67MPa、33.85MPa和105.87MPa,平压和弯曲失效模型为蜂窝失稳,侧压破坏除蜂窝失稳外,发生穿孔面板与蜂窝芯体剥离的现象。鉴于多次钎焊热循环对蜂窝拉脱强度的不利影响,建议304不锈钢蜂窝钎焊缺陷的最大补焊次数为一次。