铈对Cu-Zr合金热变形激活能和性能的影响

在Gleeble-1500D热模拟机上对Cu-1%Zr和Cu-1%Zr-0.15%Ce两种合金在变形温度分别为550,650,750,850和900℃,应变速率分别为0.001,0.010,0.100,1.000和10.000 s~(-1)条件下进行等温热压缩实验,分析了Ce对Cu-1%Zr合金热变形激活能的影响。通过透射电子显微镜,研究了合金在时效过程中的析出相和位错组态。结果表明:Cu-1%Zr和Cu-1%Zr-0.15%Ce两种合金具有相似的热压缩变形特征。高Zr和微量Ce的添加使Cu-Zr合金的热变形激活能显著提高。与Cu-1%Zr合金相比,添加0.15%Ce使合金的热变形激活能提高了约34%。添加Ce,使导电率下降了约5%IACS,显微硬度略有提高。通过导电率的变化,计算出时效过程中析出相体积分数,求得550℃时合金的析出动力学方程和导电率方程。     

微量元素铈对Cu0.9%Cr合金组织与性能的影响

采用石墨型铸造Cu0. 9%Cr,Cu0. 9%Cr0. 05Ce两种合金,并对合金固溶后在450℃进行不同时间的时效,利用光学显微镜、扫描电镜、导电率测量仪、电子拉伸试验机以及往复摩擦磨损试验机,研究微量Ce对Cu0. 9%Cr合金微观组织、强度、导电率和摩擦磨损的影响。结果表明:在时效前期,微量Ce的加入使Cu0. 9%Cr合金组织细化、Cr析出相增且更均匀分布,经450℃时效+4 h可达到抗拉强度峰值590 MPa,导电率达到83%IACS,且具有优异的耐磨性能;在时效后期,微量Ce的添加主要起到抑制过时效的作用,抗拉强度值下降缓慢、导电率平稳变化。     

稀土对管线钢中碳化物溶解与析出行为的影响

以X80管线钢为研究对象,研究了稀土对含铌钢奥氏体化与析出行为的影响。利用热力学固溶度积公式,计算了铌碳化物的溶解温度;借助显微组织观察与硬度测试,对比分析了稀土对高温下奥氏体晶粒粗化及不同温度淬火回火后硬度的影响;通过热模拟实验并利用透射电镜,研究了稀土对实验钢在热变形过程中铌碳氮化物析出行为的作用机制。结果表明:稀土元素的加入降低了碳氮化物的固溶温度,促进了Nb(C,N)等第二相粒子的固溶,稀土能够促进热变形过程中Nb(C,N)的析出,从而提高铌元素的析出强化效果。     

钇和铈对AM50镁合金显微组织和力学性能的影响

为了开发低成本、高强度和耐高温的新型镁合金，研究了微量Y，Ce复合对AM50镁合金显微组织和力学性能的影响。结果表明：Y和Ce复合加入AM50镁合金，能明显细化晶粒，由于显微组织的改善，合金的室温和高温力学性能得到明显提高，当稀土加入量为0．6％Ce-0．3％Y（质量分数）时，合金晶粒细化效果较好，其室温和高温（150℃）力学性能比较理想。     

稀土对LC4超硬铝组织性能的影响

系统地研究了La、Ce、Nd、Y和混合稀土对LC4超硬铝组织性能和时效行为的影响。结果表明,五种稀土均能不同程度地改善铸锭组织、提高再结晶温度和抗蚀性,其中只有镧能明显提高时效硬化效应并稍微提高强度,铈的作用恰好相反,其它稀土的作用不明显。     

热处理对Mg-11Gd-2Y-5Sm-0.5Zr合金组织和力学性能的影响

采用光学显微镜、扫描电镜、X射线衍射仪、显微硬度计和万能力学试验机等研究了Mg-11Gd-2Y-5Sm-0.5Zr合金在不同热处理工艺下显微组织和力学性能的变化规律。结果表明:合金的最佳固溶时效热处理工艺为525℃×8 h+225℃×12 h;Mg-11Gd-2Y-5Sm-0.5Zr合金铸态组织主要由α-Mg基体和沿晶界网状分布的Mg_5Gd,Mg_(41)Sm_5相组成,经固溶时效热处理后析出相主要为均匀分布于晶内和晶界的点状或粒状的Mg_5Gd,Mg_(24)Y_5以及Mg_(41)Sm_5相;经该工艺处理后,合金在室温下的硬度和抗拉强度分别为145.6HV和261.4 MPa;固溶时效态合金的主要强化机制为固溶强化和析出相弥散强化。     

铈、钇在AZ91D镁合金中的存在形式及其作用

在AZ91D镁合金中添加稀土元素Ce和Y,研究了Ce,Y元素在铸态AZ91D镁合金中的存在形式以及对合金组织和性能的影响。结果表明,铸态AZ91D镁合金中加入的Ce,Y大部分形成Al4Ce和Al2Y化合物,少量剩余的Ce,Y部分取代Mg元素的位置,以代位固溶的形式固溶在α-Mg固溶体和β-Mg17Al12金属间化合物中;Ce,Y能够细化镁合金铸态组织的晶粒,使Mg17Al12相发生"断网"并减少其在组织中的相对比例;适量添加Ce,Y能够提高AZ91D镁合金铸态机械性能,其主要原因是Ce,Y的细晶作用、固溶强化作用、Al-RE相的第二相强化作用以及对Mg17Al12相强化作用的改善。     

稀土对Al2O3陶瓷烧结温度、显微组织和力学性能的影响

研究了Y2O3, La2O3 等稀土氧化物对Al2O3陶瓷烧结温度、力学性能和显微组织的影响. 结果表明, 添加稀土氧化物可以降低Al2O3陶瓷的烧结温度, 改善显微组织, 提高力学性能. 添加复合稀土氧化物(Y2O3+La2O3)后, Al2O3陶瓷的抗弯强度和断裂韧性分别提高1.8倍和2.08倍. 其性能提高的主要原因是稀土氧化物对细晶强化、净化界面、固溶强化、自增韧补强等作用的贡献.     

稀土对ZA-27合金高温性能的影响

研究了ｃＣｅ≥４５％（ｗｔ）的混合稀土对ＺＡ－２７合金显微组织及高温机械性能的影响。结果表明，在锌铝合金中，稀土元素可与Ａｌ、Ｚｎ、Ｃｕ等形成多种复杂成分化合物，其硬度高，热硬性好，分散于晶界或枝晶间，细化了组织，且有效地阻碍了高温时基体的变形和晶界移动。添加适量的稀土，可使ＺＡ－２７合金在１５０℃时的抗拉强度提高３０％，硬度提高２５％，延伸率虽有所下降，但冲击韧性却得以改善。同时发现，室温强度变化不大，唯塑性、韧性略有下降。     

La, Ce在钛镍合金中的作用

以近等原子比钛镍形状记忆合金为研究对象，通过向其分别添加微量第三元素稀土La，Ce，利用示差扫描热分析法、X射线衍射法分析研究了稀土元素La和Ce对Ti-Ni形状记忆合金相变类型、相变温度、物相组成的影响，利用透射电子显微镜观察和分析了马氏体相的形貌1和结构。加入微量稀土元素能提高Ti-Ni合金相变程度，但是合金的物相组成无明显变化，仍为B2母相和畸变单斜马氏体相B19。结果表明，可以通过添加第三元素La，Ce得到一定工作条件下性能优良的Ti-Ni形状记忆合金，提高Ti-Ni合金在实际中的应用价值。     

Electrical relaxation in in situ dried acid-form nafion

Electrical relaxation studies have been carried out on dried, acid-form Nafion 117 (copolymer of tetrafluoroethylene and perfluoro 3,6-dioxa-4-methyl-7-octenesulfonic acid and which has an equivalent weight of 1100). Significant electrical conductivity is found and the data are found to be non-Arrhenius. The results are converted to the electrical modulus representation and a conductivity relaxation is observed. A stretched exponential is best-fit to the conductivity relaxation and again, non-Arrhenius behavior is observed for the peak position. Finally, at low temperatures, a new dielectric relaxation peak is found which has an activation enthalpy of about 0.57 eV (13 kcal/mol). This relaxation is analogous to the γ-relaxation observed in mechanical relaxation studies. © 1994 John Wiley & Sons, Inc.     

Distribution of Electrical Field Energy for Conversion of Methane to C2 Hydrocarbons via Dissymmetrical Electric Field Enhanced Plasma

Direct conversion of methane into C2 hydrocarbons through alternating current electric field enhanced plasma was studied under room temperature, atmospheric pressure and low power conditions. The distribution of electrical field intensity and distribution of energy were calculated with software that was developed by us according to the charge simulation method. The results indicated that the energy of tip of electrode was 0.36 J/mm3 and it was higher than the methane dissociation energy (0.0553 J/mm3). The methane located at this area can be activated easily. The higher-energy particles produced by dissociation collided with molecules around them and initiated consecutive reactions between free radicals and molecules. The method was proved to be valided and could be taken as a basis for the electrical field study concerned.     

双酞菁镥电学性能的研究

测量了(Pc_2Lu)H的电阻温度特性曲线、伏安特性曲线和交流电导。室温时电阻率(ρ)为1.2×10~5Ωcm,激活能△E为0.21eV,不受气氛的影响。伏安特性曲线上转折点电场强度约为7×10~2V/cm。当频率达10~7Hz时,ρ才到达平衡,从这里估算出,迁移率约在0.1cm~2/V.sec左右。由于(Pc_zLu)H的夹心结构和分子间的氢键,非常有利于载流子的输运。其导电机理为非本征定域化的跳跃电导。     

孔状Co_3O_4纳米片和纳米棒的选择性合成和表征(英文)

利用两步实验选择性合成孔状Co3O4纳米片和纳米棒:首先,以Co(NO3)2·6H2O,NaOH和不同量的NH4F为原料在120℃水热6h的条件下合成了Co(OH)2-Co3O4纳米片(S1)和Co(OH)F-Co3O4纳米棒(S2);然后将所得纳米片和纳米棒在400℃时加热2h即得到多孔的Co3O4纳米片和纳米棒。所得产物用X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)和透射电子显微镜(TEM)进行了表征。此外电化学测试表明Co3O4纳米棒的电容量比Co3O4纳米片的更大。     

Temperature dependences of electrical and electrochemical properties of titanium disulfide

The electrical conductivity and thermoelectric power of titanium disulfide were measured at temperatures ranging from 77 to 300 K on samples exhibiting different deviations from stoichiometry. It was found that Ti_1+yS₂ has metallic properties at the temperatures studied, the effective mass of the carriers varying with the deviation from stoichiometry. It was shown that the character of the discharge curve for the Li/Li⁺/Li_xTi_1+yS₂ cell was correlated with the electronic structure of titanium disulfide.The author is grateful to Prof. S. Mrowec and Dr. A. Stoklosa for helpful discussions.     

Accounting for the Adsorption of Anions When Interpreting the Mechanism of Electrodeposition of Metals from Complex Electrolytes: The Reaction Order by the Electrochemically Active Ion

The relationship between the current and the bulk concentration of complex ions during concurrent specific adsorption of an electrochemically active complex ion and a complexing ligand is considered. The effect of parameters that characterize adsorption of such ions and the structure of the electrical double layer on this relationship is analyzed.__________Translated from Elektrokhimiya, Vol. 41, No. 7, 2005, pp. 817–822.Original Russian Text Copyright © 2005 by Rogozhnikov.     

Electrical breakdown in high‐density polyethylene/graphite nanosheets conductive composites

The electrical breakdown is investigated in high‐density polyethylene/graphite nanosheets (HDPE/GNs) conductive composites. A sample suffers electrical breakdown when the applied field exceeds the critical electrical breakdown field below which the sample reaches a stable state. It is found that the ratio of the critical electrical breakdown resistance to the linear resistance assumes a fixed value Y, which is found to be about 1.30 in HDPE/GNs conductive composites. The value Y is independent of GNs' content, sample size, breakdown cycle, but depends on the property of GNs. The critical breakdown field E_b scales with the resistance R₀ as with the exponent y_b = 0.46 ± 0.02, which is close to the value predicted in mean‐field theory but higher than the value given by the singly connected bonds networks. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 576–582, 2009     

Mechanism of metals’ electrodeposition from complex electrolytes allowing for the anions’ adsorption: Effect of the position of ligands and complex ions in the compact layer on the reaction orders

Effect of the relative position in the compact layer of specifically adsorbed electroactive complex ion and complexing ligand on the magnitude of current is considered. Effect of parameters that characterize the adsorption of such ions and the electrical double layer structure on the dependence of current on the solution composition and effective reaction orders is analyzed.     

Electrical conductivity measurements of hyaluronic acid and collagen

Electrical properties of hyaluronic acid (HYA) and collagen in the temperature range from –90°C (resp. –50°C for collagen) to 40°C are described. The value and type of electrical conductivity, temperature stability, and processes arising in the investigated samples during continual stress heating are determined by the measurements of temperature dependence of the electrical conductivity (both d.c. and a.c.).     

Electrical transport properties of an organic semiconductor on polyaniline doped by boric acid

The electrical conductivity, thermoelectric power, and dielectric properties of polyaniline doped by boric acid (PANI‐B) have been investigated. The room temperature electrical conductivity of PANI‐B was found to be 1.02 × 10^?4 S cm^?1. The thermoelectric power factor for the polymer was found to be 0.64 µW m^?1 K^?2. The optical band gap of the PANI‐B was determined by optical absorption method, and the PANI‐B has a direct optical band gap of 3.71 eV. The alternating charge transport mechanism of the polymer is based on the correlated barrier hopping (CBH) model. The imaginary part of the dielectric modulus for the PANI‐B suggests a temperature dependent dielectric relaxation mechanism. Electrical conductivity and thermoelectric power results indicate that the PANI‐B is an organic semiconductor with thermally activated conduction mechanism. Copyright © 2008 John Wiley & Sons, Ltd.