质子交换膜燃料电池催化剂研究

质子交换膜燃料电池(PEMFC)的有效电催化剂仍以铂为主.由于铂价格昂贵,资源匮乏,使得PEMFC成本高,限制了其广泛应用,所以降低贵金属催化剂用量,寻找廉价催化剂,提高电极催化剂性能成为电极催化剂研究的主要目标.采用铂/碳催化剂,将铂催化剂担载在高活性碳材料上,可以将铂的担载量从4 mg/cm2降低到0.7 mg/cm2～1.0 mg/cm2,甚至到0.05 mg/cm2～0.2 mg/cm2,有效提高了铂的利用率.铂合金电催化剂以Pt-Ru为主,通过Pt和Ru的协同作用,大大减少了铂的用量(Pt与Ru的质量比为0.05:1),提高了催化剂抗CO性能.多元复合催化剂和非铂系催化剂也是目前的研究热点.     

Pt-Ru-Eu／C电催化氧化甲醇的性能研究

采用脉冲电沉积法制备Pt—Ru．Eu／C电催化剂，循环伏安法（cv）测定催化剂的甲醇电氧化活性，用XRD，EDS和XPS表征电极及催化剂的物性结构、表面元素组成和价态形式。结果表明，电催化剂中Pt-Ru-Eu以合金的形式存在，在合金表面存在EuOx；合金微粒比表面积为55．8m^2．g^-1，粒径为4．6nm；掺杂适量稀土金属Eu对Pt．Ru合金活性有一定的促进效应，其中原子比为Pt：Ru：Eu=1：1：0．2时电催化活性较高。原子比过高则Pt-Ru-Eu活性低于Pt-Ru；在掺杂少量Eu时，Pt—Ru—Eu与Pt—Ru的Tafel常数b相近，常数a以Pt：Ru：Eu=1：1：0．2最小；甲醇反应级数为0．12级，反应活化能为28.3kJ·mol^-1。     

燃料电池膜电极中铂担载量测试方法研究

膜电极(MEA)作为质子交换膜燃料电池(PEMFC)的能量转换单元，在催化剂作用下将化学能转化为电能。铂基催化剂目前仍是商用PEMFC不可替代的催化剂，其中膜电极中铂担载量已成为PEMFC性能评价的一项重要指标。通过对现有PEMFC膜电极铂担载量测试国标方法进行了改进，并研究了PEMFC膜电极铂担载量测试的微波消解前处理方法。与国标方法相比，微波消解-ICP-MS法测定结果的准确性与标准方法相当，测试效率明显提高。     

化学还原法制备铂及铂合金催化剂及其性能

采用混合水溶液浸渍,硼氢化钠还原的方法制备了微型直接甲醇燃料电池用电催化剂,包括碳载铂、碳载铂基合金电催化剂.XRD、SEM、EDX测试结果表明催化剂的粒度达纳米级,且分散性好、原子摩尔配比合理.将Pt/C、Pt合金/C分别作为电池的阴极和阳极电催化剂,通过电池的极化曲线和功率密度曲线筛选出最佳的催化剂组成.在室温下,甲醇浓度为2mol/L时,阴极采用30wt%Pt的Pt/C,阳极采用n(Pt)∶n(Ru)∶n(Ir)∶n(Mo) = 2∶1∶2∶3的PtRuIrMo/C电催化剂,其电池的性能最好.     

n-TiO2阴极电沉积纳米金属铂及其电化学特性

用两步法对钛基材进行阳极氧化，然后用阴极电沉积方法制备出纳米级铂镀层Ti／TiO2．Pt阳极，用场发射电子扫描显微镜（SE-SEM）分析了Pt沉积前后的表面形貌，并测试了其晶粒度。结果表明，Pt晶粒度大小为80nm～130nm，阳极不仅具有与铂阳极相似的电化学行为特征，而且通过Pt掺杂明显改善月．TiO2电极的电催化活性，并随着沉积Pt时间的增加，其电催化活性提高。     

我国CCM型膜电极研究取得重大进展

膜电极是质子交换膜燃料电池(PEMFC)的核心部件,直接影响电池输出性能和反应效率,开发低铂(Pt)担量、高反应效率的CCM(催化剂制备到膜上)型薄催化层膜电极是目前质子交换膜燃料电池开发的一个重要技术方向。在863计划电动汽车重大项目支持下,大连化物所承担的"下一代燃料电池系统研究与开发"课题目前取得重大突破和阶段性成果。     

碳载铂纳米微粒修饰的玻碳电极对甲醇的电催化氧化

利用X射线粉末衍射、透射电镜和扫描电镜对商用Pt/C催化剂反应前后的变化进行了物化表征，同时应用电化学方法研究了甲醇在碳载铂纳米微粒修饰的玻碳电极上的电催化氧化性能。结果表明，修饰电极对甲醇氧化呈现较高的电催化活性。铂氧化物的电化学还原在Pt/c催化剂中受到了抑制，该现象可能是由于Pt与载体碳间的强烈作用所引起的。通过扫描电镜和循环伏安研究表明，该催化剂对甲醇的氧化可能存在着表面结构敏感效应。     

LiMn2-xCoxO4催化剂的溶胶-凝胶法合成

为了改善空气电极的电催化性能，提高锌空气电池的放电电流密度。采用溶胶．凝胶法制备了锌空气电池用催化剂LiMn2-xCoxO4。通过X射线衍射(XRD)、粒径分布、稳态电流．电压极化曲线等方法，研究了所得催化剂的结构及其电催化性能。并与高温固相反应法所得催化剂的结构与电催化性能作了对比。结果表明，当反应体系的pH值为7～8、温度为80℃时所得凝胶再经600℃下保温处理12h，可以得到具有最高催化活性的催化剂；溶胶．凝胶法合成催化剂的粒径较小，主要集中在1μm～4．5μm的范围内，粒度分布较窄，而高温固相反应法合成催化剂的粒径较大，主要集中在5μm～30μm的范围内。粒度分布较宽：2种方法所得的催化剂具有完全相同的晶态结构；溶胶．凝胶法和高温固相反应法催化剂的空气电极在-0．6V极化电位下的电流密度分别达到250mA／cm^2和210mA／cm^2，前者比后者的较高。     

等离子体质谱法测定地质样品中超痕量贵金属和铼

用等离子体质谱法同时测定地质样品中超痕量Au、Pt、Pd、Os、Ir、Ru、Rh和Re。试验了HCl／H2O2封闭溶样法，研究了ZPA4螯合树脂富集8元素的条件，并通过树脂灰化、HCl／H2O2封闭分解制备成试液，供ICP—MS测定。本法的检出限（ng/g）分别为0．21Au、0．12Pt、0．20Pd、0．024Os、0．016Ir、0．028Ru、0．022Rh、0．22Re，方法的相对标准偏差（RSD）为3．1％～14．8％。本法的特点是有效地降低了空白值，提高了仪器的检测能力。     

Fe掺杂对质子交换膜燃料电池Pt/C催化剂性能的影响

用铁作掺杂元素,通过液相均相沉淀-气/固高温还原两段反应方法制备了碳载Pt-Fe合金催化剂,比较了3种不同Fe含量催化剂的电催化性能.采用X射线衍射和X光电子能谱技术研究了Fe掺杂对Pt/C催化剂晶体结构及表面元素存在形态的影响.结果显示:Pt-Fe/C催化剂比单一Pt/C催化剂有更小的晶格参数,其中Fe元素可能的存在形态应为与铂结合的合金态,但不排除表面存在部分氧化态.单电池放电稳定性实验表明:在200 mA·cm-2电流密度下放电时电池电压基本稳定,其中Pt与Fe摩尔比为1∶1时电极催化效果相应较好,但大电流密度放电时电池电压下降比单一Pt/C催化剂电极的快,这说明Fe的加入能提高催化剂的电催化性能,但阴极表面氧原子浓度较大时,Fe可能发生氧化而使得电极稳定性受到影响.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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Antimony Induced Crystallization of Amorphous Silicon

Antimony induced crystallization of PVD (physics vapor deposition) amorphous silicon can be observed on sapphire substrates. Very large crystalline regions up to several tens of micrometers can be formed. The Si diffraction patterns of the area of crystallization can be observed with TEM (transmission electron microscopy). Only a few and much smaller crystals of the order of 1μm were formed when the antimony layer was deposited by MBE (molecular beam epitaxy) compared with a layer formed by thermal evaporation. The use of high vacuum is essential in order to observe any Sb induced crystallization at all. In addition it is necessary to take measures to limit the evaporation of the antimony.     

A CUMULATIVE FATIGUE DAMAGE RULE UNDER THE ALTERNATIVE OF CORROSION OR CYCLIC LOADING

Fatigue damage increases with the applied loading cycles in a cumulative manner and the material deteriorates with the corrosion time. A cumulative fatigue damage rule under the alternative of corrosion or cyclic loading was proposed. The specimens of aluminum alloy LY12-CZ soaked in corrosive liquid for different times were tested under the constant amplitude cyclic loading to obtain S-N curves. The test was carried out to verify the proposed cumulative fatigue damage rule under the different combinations among corrosion time, loading level, and the cycle numbers. It was shown that the predicted residual fatigue lives showed a good agreement with the experimental results and the proposed rule was simple and can be easily adopted.