Cu对热挤压Al-Mg-Si合金力学性能及导电率的影响

为了满足铝合金架空输电导线的使用需求,以热挤压法制备的Al-Mg-Si合金电工铝杆为研究对象,通过调节Cu元素的添加量,研究了Cu对Al-Mg-Si合金的力学性能及导电率的影响.结果表明,向Al-0.35Si-0.45Mg-0.13Fe合金中添入微量Cu元素后,Mg2Si析出相得到细化且时效强度提高.随着Cu元素含量的增加,峰时效时间缩短,合金抗拉强度不断提高,但伸长率逐渐降低.当Cu含量为0.06%时,合金抗拉强度达到最大值145.7 MPa.合金导电率随着Cu元素含量的增加先升后降,当Cu含量为0.03%时达到最大值60.18%IACS.     

Electrical conductivity of Cu-Li alloys

1　INTRODUCTIONCopperandcopperalloysarewidelyusedinelectricindustryduetotheirexcellentelectricalcon ductivity .ButtheimpuritiesandtraceelementsinCudecreasetheirelectricalconductivity ,especiallynon metalimpuritiessuchasoxygenandsulfurwhichaf fecttheirmechanicalproperties[14 ] .P ,MnandBecanbeusedasdeoxidant ,buttheresiduainCude creasetheelectricalconductivitydramatically[57] .ItwasreportedthatLicanrefinetheimpuritiesinCuandincreasethetensilestrengthofCuwithouttheelectricalconductivityd…     

纳米石墨/聚乙烯复合材料电导特性模拟仿真

为研究各因素对纳米石墨/聚乙烯复合材料电导特性的影响,在仿真计算的基础上绘制了具有不同微结构的纳米石墨/聚乙烯复合材料的电导率与外施电场强度关系曲线.通过改变纳米石墨的添加量、径厚比和取向程度设计了不同结构的纳米石墨/聚乙烯复合材料仿真模型,在其上下表面间施加直流电场后,利用COMSOL仿真软件基于有限元法模拟计算各模型内的电流密度分布,进而得到电流密度和电导率.研究结果表明:在纳米石墨的体积分数相同时,随着其径厚比和增加,在相同电场强度下复合材料的电导率显著增加;随纳米石墨沿外施电场方向取向程度的增大,复合材料的导电性明显提高.通过改变纳米石墨/聚乙烯复合材料的微结构可有效调控其电导特性.     

Electrical conductivity of Cu/（10NiO-NiFe2O4） cermet inert anode for aluminum electrolysis

Cu/(10NiO-NiFe2O4) cermets containing mass fractions of Cu of 5%, 10%, 15% and 20% were prepared, and their electrical conductivities were measured at different temperatures. The effects of temperature and content of metal Cu on the electrical conductivity were investigated especially. The results indicate that the metallic phase Cu distributes evenly in 10NiO-NiFe2O4 ceramic matrix. The mechanism of electrical conductivity of Cu/(10NiO-NiFe2O4) cermets obeys the rule of electrical mechanism of semiconductor, the electrical conductivity for cermet containing 5% Cu increases from 2.70 to 20.41 S/cm with temperature increasing from 200 to 900 ℃. The change trend of electrical conductivity with temperature is similar with each other and it increases with increasing temperature and content of metal Cu. At 960 ℃, the electrical conductivity of cermet increases from 2.88 to 82.65 S/cm with the content of metal Cu increasing from 0 to 20%.     

纳米Fe3O4及其复合体系的微波吸收特性研究

研究了纳米Fe3O4及其复合体系的微波吸收特性,并分析了吸收机制以及复合组分对吸波性能的影响。结果表明,在Fe3O4/BaTiO3复合体系中,通过调节材料组分可调节吸收峰的位置,复合体系的有效吸收频带较单一材料拓宽。当样品的厚度为2 mm,Fe3O4与BaTiO3的质量比为3:2时,反射率为-10 dB的有效频宽达2.7 GHz,Fe3O4与BaTiO3的质量比为2:3时,反射率为-10 dB的有效频宽可达4 GHz。在Fe3O4/PANI复合体系中,当Fe3O4在复合体系中的质量比为35%左右时,微波吸收率最高,吸收峰值为-21 dB,-10 dB频宽大于4GHz。     

稀土对纤维相Cu-12%Ag合金组织性能的影响

为研究稀土微合金化在纳米纤维强化Cu-Ag合金中的作用，制备了纤维相增强Cu-12%Ag和Cu-12%Ag-0.3%RE合金．采用冷拉拔结合中间热处理方法制备该类合金，观察并测定了不同变形程度下稀土元素对合金显微组织、力学性能和电学性能.实验结果表明，随变形程度增大，合金硬度和强度上升，相对电导率下降.稀土元素可增加原始组织枝晶轴间距、共晶体数量及共晶体中Ag的质量分数，提高合金的硬度，但对合金抗拉强度没有明显影响.在较低的变形程度范围内，稀土元素使合金导电性能略有降低.在大变形范围内，稀土元素可在一定程度上改善导电性能.     

Fabrication of Graphene/Cu Composite by Chemical Vapor Deposition and Effects of Graphene Layers on Resultant Electrical Conductivity

Graphene(Gr)has unique properties including high electrical conductivity;Thus,graphene/copper(Gr/Cu)composites have attracted increasing attention to replace traditional Cu for electrical applications. However,the problem of how to control graphene to form desired Gr/Cu composite is not well solved. This paper aims at exploring the best parameters for preparing graphene with different layers on Cu foil by chemical vapor deposition(CVD)method and studying the effects of different layers graphene ...     

Effect of Synthesis Process on CuO Segregation and Dielectric Properties of CaCu_3Ti_4O_(12) Ceramic

The CaCu_3Ti_4O_(12)(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and electrical properties were investigated. The phase composition was determined by X-ray diffraction and the microstructure was examined by SEM. The dielectric constant, dielectric loss, and resistance of the ceramic were also determined by a precision impedance tester. The results show that, as the synthesis temperature increases, the CCTO ceramic grain size decreases and the stoichiometric ratio of Cu/Ca at the grain boundary increases, the dielectric constant increases and the dielectric loss decreases(40 f 10 kHz). In addition, when the synthesis time is shorter than 12 h, the Cu/Ca ratio of CCTO decreases and the dielectric constant increases with time increase. However, when the synthesis time exceeds 12 h, this trend is just the opposite. It is further proved that Cu at the grain boundary is not conducive to the dielectric constant of CCTO.     

Mn3(Cu0.6Si0.15Ge0.25)N/Ag复合材料的负热膨胀与物理性能

采用机械球磨加固相烧结法合成Mn3(Cu0.6Si0.15Ge0.25)N/Ag复合材料。在77K-300K温度范围内,分别研究了Mn3(Cu0.6Si0.15Ge0.25)N/Ag复合材料的热膨胀性能,电导性能和热导性能。当含Ag量分别为1,5,10和20 wt%时,所有样品在有效的温度区间205K-275K表现出负热膨胀。随着Ag含量的增加,有效温度区间向室温方向移动。另外,和Mn3(Cu0.6Si0.15Ge0.25)N材料相比,Mn3(Cu0.6Si0.15Ge0.25)N/Ag复合材料具有更高的电导率1?0-6（Ohm.m）-1和热导率10.5W/(mK)。     

基于金属氢化物的单级氢压缩机的性能模拟

基于金属氢化物的氢压缩机是金属氢化物最有前途的应用之一。它具有从低温位热源中回收动力、对环境友好、安全可靠等优点。以LaNi5合金为氢压缩机的工质,建立了考虑壁面对流换热系数、合金导热系数、热源温度等因素的能量分析模型,应用有限容积法对描述反应床与储氢罐间的动态平衡过程进行了离散求解,综合分析了其操作工况的改变,对单级氢压缩机性能的影响,并提出了系统的优化措施。给定氢压缩机的压力比,氢压缩机存在最低热源温度;效率随热源温度的增加先增后减,冷源温度大约控制在285 K;给定冷、热源温度,合金导热系数与对流换热系数值亦存在最合适值;在给定工况及反应床尺寸下,储氢罐容积对压缩机性能有较大的影响。     

悬沙矿物组分对盐度测量的影响

选用石英砂、高岭土及两者的混合物模拟悬沙矿物,利用温盐深剖面仪CTD75M测定不同初始盐度和悬沙浓度下的水体盐度. 试验结果表明,测量盐度随初始盐度的减小、悬沙浓度的增大以及矿物组分密度的减小而减小. 运用有效介质渗透模型和Maxwell电导率模型分析含沙盐水的电导率;试验数据与电导率理论公式拟合良好,显示悬沙所占体积是影响相对电导率的主要因素. 对已有文献的试验数据进行分析,结果表明：基于悬沙浓度的经验盐度修正公式在悬沙密度不同的沿海海域并不适用,具有区域局限性. 为此提出基于悬沙体积分数的理论盐度修正公式,提高公式的适用范围.     

Crystallographic and Low Frequency Conductivity Studies of the Spinel Systems CuFe_2O_4 and Cu_（1-x）Zn_xGa_（0.1）Fe_（1.9）O_4

Spinel solid solutions of CuFe2O4 and Cu1-xZnxGa0.1Fe1.9O4 with (0.0≤x≤0.5) are synthesized. Crystallographic phase transformation from tetragonal-to-cubic occurred at x=0.2. The derived structural parameters manifest that Zn occupies the tetrahedral A-site while Cu and Ga occupy the octahedral B-site and Fe distributes among A- and B-sites. Electrical conductivity measurements of these materials as a function of temperature and frequency revealed semiconducting behavior except CuFe2O4 sample, which has a metallic behavior at low frequency and at high frequency, metallic -to- semiconductor transition occurred as temperature increases. The metallic behavior in this sample is attributed to cation-cation interactions at B-site while, the semiconductor behavior in Cu1-xZnxGa0.1Fe1.9O4 compounds is due to the cation- anion -cation interactions at the same site in the spinel lattice. All compositions exhibit transition with change in the slope of conductivity versus temperature curve. This transition temperature (Tc) decreases linearly with increasing Zn content x. The relation of the universal exponent s with temperature gives evidence that over large polaron OLP and correlated barrier hopping CBH conduction mechanisms are presented in CuFe2O4 and Cu1-xZnxGa0.1Fe1.9O4 compounds respectively.     

Epitaxial growth of Fe/Ag single crystal superlattices and their magnetic properties

Single crystal Fe/Ag(001) superlattices with various periodicities were fabricated using ultrahigh vacuum evaporation de-position.It was found that single crystal bcc Fe layers and single crystal fcc Ag layers can epitaxially grow on a single crystal Ag buffer layer alternately,which was deposited on NaCl single crystal chips by ion beam assisted deposition.The magnetic measure-ments of the superlattices reveal an oscillation coupling between ferromagnetism and antiferromagnetism as a function of the Ag layer thickness.The oscillation period,which is 1 nm (5 Ag layers),is in good agreement with the calculated values when the Ag thickness is greater than 1.5 nm.While the thickness of the Ag spacer layer decreases to 1 nm,the oscillation coupling varies from calculations,which can be attributed to the intermixing of the interlayers according to the annealing results.     

Medium-range order clusters in metal melts

Structures of molten metals Cu and Al, alloys Cu-Al, Al-Ni, Al-Fe and, Al-Si were investigated by using high temperature X-ray diffractometer. It has been found that there are not only short-range order structures (SRO) but also medium range order structures (MRO) in Cu-Al, Al-Ni, Al-Fe alloy melts. There are only short-range order structures in the pure metals Cu and Al and Al-Si alloy melts at different temperatures. It has also been found that the presence and the disappearance of the MRO structures in molten metals are a function of temperature. Moreover, the pre-peak in the structure factor is an indication of MRO in molten metals. There is a pre-peak in each structure factor S( Q) of Al-Fe alloy melt containing 14 wt% Fe, 16 wt% Fe and 19 wt% Fe at 1550℃, showing that there are the medium range order structures in these alloy melts. For Al-35wt% Ni alloy, the pre-peak exists in S(Q) when the temperature is lower than 1300?, and it is weakened drastically when the temperature surpasses 1300℃. The     

Theoretical analyses of the performance of a concentrating photovoltaic/thermal solar system with a mathematical and physical model,entropy generation minimization and entransy theory

In this paper, the performance of a concentrating photovoltaic/thermal solar system is numerically analyzed with a mathematical and physical model. The variations of the electrical efficiency and the thermal efficiency with the operation parameters are calculated. It is found that the electrical efficiency increases at first and then decreases with increasing concentration ratio of the sunlight, while the thermal efficiency acts in an opposite manner. When the velocity of the cooling water increases, the electrical efficiency increases. Considering the solar system, the surface of the sun, the atmosphere and the environment, we can get a coupled energy system, which is analyzed with the entropy generation minimization and the entransy theory. This is the first time that the entransy theory is used to analyze photovoltaic/thermal solar system. When the concentration ratio is fixed, it is found that both the minimum entropy generation rate and the maximum entransy loss rate lead to the maximum electrical output power, while both the minimum entropy generation numbers and the maximum entransy loss coefficient lead to the maximum electrical efficiency. When the concentrated sunlight is not fixed, it is shown that neither smaller entropy generation rate nor larger entransy loss rate corresponds to larger electrical output power. Smaller entropy generation numbers do not result in larger electrical efficiency, either. However, larger entransy loss coefficient still corresponds to larger electrical efficiency.     

Effects of Electroless Plating with Cu Content on Thermoelectric and Mechanical Properties of p-type Bi<Subscript>0.5</Subscript>Sb<Subscript>1.5</Subscript>Te<Subscript>3</Subscript> Bulk Alloys

Bi_0.5Sb_1.5Te₃/Cu core/shell powders were prepared by electroless plating and hydrogen reduction, and then sintered into bulk by spark plasma sintering. After electroless plating, with increasing the Cu content, the electrical conductivity keeps enhancing significantly. The highest electrical conductivity reaches 3341S/cm at room temperature in Bi_0.5Sb_1.5Te₃ with 0.67wt% Cu bulk sample. Moreover, the lowest lattice thermal conductivity reaches 0.32 W/m·K at 572.2 K in Bi_0.5Sb_1.5Te₃ with 0.67wt% Cu bulk sample, which is caused by the scattering of the rich-copper particles with different dimensions and massive grain boundaries. According to the results, the ZT values of all Bi_0.5Sb_1.5Te₃/Cu bulk samples have improved in a high temperature range. In Bi_0.5Sb_1.5Te₃ with 0.15wt% Cu bulk sample, the highest ZT value at 573.4 K is 0.81. When the Cu content increases to 0.67wt%, the highest ZT value reaches 0.85 at 622.2 K. Meanwhile, the microhardness increases with increasing the Cu content.     

大气中SO_2对铜的腐蚀行为研究

利用三电极电化学电池和Cu/Fe双电极原电池对铜在含SO2大气中的腐蚀行为进行研究.通过电化学阻抗谱、极化曲线和电偶电流测定分析了金属铜在不同厚度液膜、不同SO2气体浓度条件下的初期腐蚀行为.结果显示:电极表面液膜越薄,金属铜的腐蚀电流密度越大;随着SO2浓度的增加,铜电极反应电阻减小,电极的去极化作用增强,Cu/Fe双电极原电池的电偶电流明显增大.     

不锈钢表面电镀Cu—Mn3O4复合涂层

铁素体不锈钢的热膨胀系数与固体氧化物燃料电池（SOFC）的组元相近,成本低廉,具有良好的抗氧化性,已被广泛用作SOFC电池堆的金属连接体材料．但是表面Cr2O3膜的挥发会导致SOFC阴极Cr中毒,缩短SOFC的服役寿命．为解决这一问题,本文利用电镀的方法在铁素体不锈钢（SUS430）连接体表面沉积cu—MnsO。复合涂层,研究了复合电镀Cu—Mn3O4涂层的电镀工艺,结果表明：复合电镀的适宜工艺参数为：溶液pH值为3,阴极电流密度为2．12A／dm^2,镀液温度为35℃,溶液中Mn3O4粉末添加量为20g／L,并研究了涂覆不锈钢在800℃空气中的氧化行为及氧化膜的导电性能．涂覆Cu—Mn3O4不锈钢氧化后表面生成CuO、（Mn,Ca）3O4和（Fe,Cu）3O4尖晶石氧化物,表面氧化物的导电性良好,并能有效阻止Cr向外迁移和扩散．     

多孔介质有效导热系数的实验与模拟

应用实验与数值模拟相结合的方法研究了多孔介质的有效导热系数.将分形理论与孔道网络模型相结合的分形孔道网络模型用于研究多孔介质的有效导热系数,为太阳池储热、地源热泵传热、食品干燥等方面打下了基础.模拟计算结果与实验结果吻合较好,证明了分形孔道网络模型适用于计算多孔介质的有效导热系数.研究了孔喉比、配位数、垂直热流方向喉道比例、喉道长度、孔隙率、固体骨架导热系数(K.)及流体导热系数(Kf)等多方面对多孔介质有效导热系数的影响.结果表明,垂直热流方向喉道会增大多孔介质的热阻,降低多孔介质的有效导热系数.当K8大于Kf时,随着孔喉比的增大以及喉道长度的减小,多孔介质的有效导热系数越大.当平行热流方向喉道数目相等时,多孔介质的有效导热系数随着配位数的减小而增大;当垂直热流方向喉道数目相等时,多孔介质的有效导热系数随着配位数的增大而增大.     

Synthesis and Thermoelectric Properties of Polyaniline

1　IntroductionConductingpolymerspossessseveralattractivefea turesforusesasthermoelectricmaterialscomparabletotheinorganicsemiconductor .Theyarecheap ,light weight,andflexible ,especiallyforpolyanilinewhichisairstableandeasytobesynthesized .However ,manyofresearchesonconductingpolymerssofarhavebeencarriedoutaim ingtoobtainahigherelectricalconductivity ,whichisnotthebeststateforthermoelectricapplication .Thereareonlyfewstudiesthathavereportedconductingpolymersusedasthermoelectricmaterials[1,2 ]…