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51.
组件式设计常被用地人工髋关节,钴络钼合金(Co-Cr-Mo)与钛合金(Ti-6Al-4V)的压配最常用,本文应用电化学方法研究了静态条件下两种合金的电偶腐蚀行为,浸泡实验表明,钴络钼合金为阳极,但电偶电流与其维钝电流相近,并无明显加速度腐蚀效应,钛合金为阴极,受到保护,失重及金相观察结果显示,在45天的浸泡实验周期内,未发现腐蚀痕迹,混合电位理论和电位处于两种合金的钝化电位区,电偶电流为合金的维钝 相似文献
52.
N. Ibriş J. Mirza-Rosca A. Santana T. Vişan 《Journal of Solid State Electrochemistry》2002,6(2):119-125
The corrosion and passivation of Zn powder particles dispersed in a paste electrode immersed in 0.5 M Na2SO4 and 5×10–3 M Na2HPO4 solutions were studied mainly by electrochemical impedance spectroscopy. The role played by diffusion in the mechanism of
anodic oxidation of zinc powder particles has been shown. It was demonstrated that the anodic reactionof Zn powder in neutral
or near neutral media involves at least two adsorbed intermediates. By simulating the porous structure of the electrode, some
information about porous nature of zinc electrode could be extracted.
Electronic Publication 相似文献
53.
The influence of spent catalyst from catalytic cracking in fluidized bed on the hydration process of cement and the properties
of cement mortars were studied. The spent catalyst was used as an additive to cement in the mortars (10 and 20% of cement).
The samples of mortars kept in water for28 days, then they were placed in sulfate and chloride media for 2 months (the control
samples were kept in water for 3 months). After this time they were subjected to bending strength and compressive strength
determinations. Thermogravimetric and infrared absorption studies were performed and capillary elevation, capability of binding
heavy metals, and changes in mass and apparent density were determined too. The studies disclosed the pozzolana nature of
spent catalyst and its influence on cement mortars being in contact with corrosive media.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
54.
针对点阵夹层结构主动热防护问题,建立了夹层结构面板和芯体导热与冷却剂对流耦合的非稳态传热理论模型,利用有限体积法离散控制方程并在MATLAB中进行了迭代求解.模型首次考虑了面板与夹芯杆之间的收缩热阻,并利用分离变量法得到了收缩热阻的近似解析解.基于单胞模型和周期性边界条件,模拟得到了模型所需的表面对流传热系数h_(b)和h_(fin).最后,选取多单胞计算工况进行数值模拟和理论模型对比,并讨论了收缩热阻对模型预测精度的影响.结果表明:理论模型能够准确预测夹层结构及内部流体的温度变化,理论与仿真之间的最大误差不超过1%;随着外加热流密度不断增大,忽略收缩热阻使得计算结果造成的误差不断增大;与数值模拟相比,理论模型可显著地减少计算时间并节省计算资源,尤其适用于非均匀、非稳态复杂热载荷下点阵夹层结构的温度响应计算. 相似文献
55.
Normalized Dynamic Characterization and Application of Multiple Heat Storage Materials Based on Standard Thermal Resistance北大核心CSCD
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基于标准热阻和能量流法,推导出储热材料与换热流体的瞬态换热热阻,通过类比电路分析法,获得了储热-换热过程的瞬态热量流模型及动态响应时间常数。进一步引入节点温度,重新定义换热热阻,获得了储热与换热过程耦合的三阶电路瞬态热量流模型,求解得到了加热、储热和释热三类时间常数,可用于协同表征储热材料中储热与释热的快慢程度,从而实现了多类储热材料的归一化动态表征。通过数值模拟验证与应用对比分析,发现基于多时间常数的归一化动态模型用于表征储热材料的动态特性是可行的,可直接对不同换热、储热材料进行对比分析。案例分析发现与固体储热材料换热时,液态金属的动态换热能力优于熔融盐,而相比于水蒸气和CO2,空气与陶瓷材料换热能更快达到稳态。 相似文献
56.
Michael Popall Jürgen Kappel Monika Pilz Jochen Schulz Gusty Feyder 《Journal of Sol-Gel Science and Technology》1994,2(1-3):157-160
Inorganic-organic polymers with barrier properties against water vapor, excellent electrical data (3, 2, R
D>1016 cm, E
D up to 400 V/µm) and good adhesion to various substrate materials have been developed. Tailored modifications of these materials provide an excellent protective coating for thin film capacitors. Several mm thick, expensive, encapsulations could be replaced by thin coatings (up to 10 µm). The polymer coating allows the use of thin film chip capacitors in surface-mount technology. As a measure for the efficiency of the coating, the capacitance decrease under controlled humidity has been used. The influence of the material composition, the type of catalyst during sol-gel processing and the curing conditions have been studied. Adhesion and water vapor permeation properties of the polymers and rheological properties of the coating solutions have been investigated. A protective coating is developed, which increases the withstandness of capacitors against humid conditions (90°C, 100% rel. humidity) by a factor of about 30 (compared to uncoated capacitors) and shows no crack formation during thermal cycling. 相似文献
57.
58.
非晶态镍磷—镍钨磷双层组合镀层的耐蚀性能研究 总被引:2,自引:0,他引:2
本文对比研究了镍磷镀层、镍钨磷镀层及非晶态镍磷和镍钨磷双层组合镀层的耐蚀性能,分别进行了各种镀层的浸渍腐蚀实验,镀层的X射线衍射图象、镀层的扫描电镜图象、以及在工厂实际的腐蚀环境里进行的腐蚀实验。实验结果表明镍磷及镍钨磷双层组合镀层的耐 性优于镍磷镀层、镍钨磷镀层的耐蚀性。 相似文献
59.
Two amino acid analog resistant mutants of the cyanobacteriumAnabaena sp 287 were isolated after MNNG mutagenesis.Anabaena ST 16, a mutant resistant to the alanine analog D-α-aminobutyric acid andAnabaena ST 25, another mutant resistant to the histidine analog l,2,4-triazole-3-alanine, released alanine and histidine, respectively,
into the medium upon immobilization in alginic acid during diazotrophic growth in fluidized bed reactors. The rates of amino
acid production by the mutants were 4.3 μmol mg chl-1 h-1 of D-alanine byAnabaena ST 16 and 16.6 μnol mg chl-1 h-1 of L-histidine byAnabaena ST 25. Nitrogen fixation by the mutants was not affected by the extracellular amino acid concentration. While the radioactive
carbon flow was followed, the parent strain retained 93% of fixed14C and released only 7% into the medium. On the other hand,Anabaena ST 16 released 13% andAnabaena ST 25 released 29% into the medium. These mutants are beneficial in the production of radioactive amino acids using diazotrophic
photobiotechnology. 相似文献
60.
A low-cost lead-acid battery with high specific-energy 总被引:1,自引:0,他引:1
S. K. Martha B. Hariprakash S. A. Gaffoor D. C. Trivedi A. K. Shukla 《Journal of Chemical Sciences》2006,118(1):93-98
Lightweight grids for lead-acid battery grids have been prepared from acrylonitrile butadiene styrene (ABS) copolymer followed
by coating with lead. Subsequently, the grids have been electrochemically coated with a conductive and corrosion-resistant
layer of polyaniline. These grids are about 75% lighter than those employed in conventional lead-acid batteries. Commercial-grade
6V/3.5Ah (C20-rate) lead-acid batteries have been assembled and characterized employing positive and negative plates constituting these
grids. The specific energy of such a lead-acid battery is about 50 Wh/kg. The batteries can withstand fast charge-discharge
duty cycles.
Dedicated to Prof J Gopalakrishnan on his 62nd birthday. 相似文献