用格点法研究银或银金合金表面上氧的吸附规律

对混合式格点法作了进一步的改进，并用这一改进方法研究了氧在银或银合金表面上的吸附．结果表明：氧分子在银表面上发生吸附的阈值约为６．５ｋＪ．ｍｏｌ－１；氧分子动量大于４５ａｕ或合金中金的质量分数大于０．３时，都不发生分子氧的吸附．另外，处在振动激发态的氧分子比在振动基态的更容易发生吸附．

微量钆对Ag-Au合金再结晶行为的影响

采用示差扫描量热、金相、透射电子显微镜及硬度测量等方法研究了微量Ｇｄ对互溶的ＡｇＡｕ系合金再结晶行为的影响。结果表明，在ＡｇＡｕ合金中加入微量（ｗＧｄ＝０２％）Ｇｄ后，在合金内形成含Ｇｄ的第二相颗粒，弥散分布于基体中，显著提高合金的再结晶温度，并使晶粒细化。随变形量增加，合金再结晶温度也随之提高。

铂基三元合金的可控制备与表征

采用共还原法制备了金-银二元合金纳米胶体,然后以制备得到的金-银二元合金Ag4Au纳米胶体为前驱体,加入氯铂酸,利用银和铂离子之间的置换反应制备出一系列铂含量不同的铂-银-金三元合金纳米胶体。紫外吸收光谱测试结果表明,铂-银-金三元合金纳米胶体的最大吸收峰波长介于Ag4Au(414nm)和PtAu(436nm)的最大吸收峰之间,而且这些合金都有且仅有1个吸收峰,表明产物为均相三元合金。同时铂-银-金三元合金最大吸收峰波长与Pt/(Pt+Au)物质的量比呈线性关系,随铂含量增加最大吸收峰波长向长波方向移动。TEM结果表明合金产物胶体颗粒分布均匀,基本无团聚现象,平均粒径在8～10nm之间。HRTEM结果中出现的晶面间距0.232nm和0.204nm分别与合金的(111)和(200)晶面对应。

Bi-2223带材制备的高温超导电流引线

为了降低沿电流引线的漏热,用于制备高温超导电流引线的B i-2223带材要求具有较低的热导率。文中介绍了低热导率银金合金B i-2223高温超导带材;给出了其热导率的测试结果;并采用该带材制造了高温超导电流引线样机。液氮条件下测试该段高温超导引线的临界电流为332A。

Microstructure and mechanical properties of powder metallurgy Ti-Al-Mo-V-Ag alloy

The Ti-Al-Mo-V-Ag α＋β alloys were processed by powder metallurgy（PM） using the blended elemental（BE） technique.The effects of Ag addition and sintering temperature on microstructure and properties of the Ti-5Al-4Mo-4V alloys were investigated using X-ray diffraction,optical microscope,scanning electron microscope and mechanical properties tests.The results show that adding Ag element increases the relative density and improves the mechanical properties of PM Ti-5Al-4Mo-4V alloy.After sintering at 1 250 ℃ for 4 h,the relative density and compression strength of Ti-5Al-4Mo-4V-5Ag alloy are 96.3% and 1 656 MPa,respectively.

Controlled synthesis of one-dimensional Au-Ag porous nanostructures

The fabrication of a new type of one-dimensional Au-Ag porous nanotube（NPT） structure was presented based on a facile combination of nanocrystal growth and surface modification.Ag nanowires with various diameters were firstly served as the chemical plating templates via a polyol-process.Then,one-dimensional（1D） Au-Ag porous nanostructures with tailored structural features could be prepared by controlling the individual steps involved in this process,such as nanowire growth,surface modification,thermal diffusion,and dealloying.Structural characterizations reveal these Au-Ag porous nanotubes,non-porous nanotubes and porous nanowires possess novel nano-architectures with multimodal open porosity and excellent structural continuity and integrity,which make them particularly desirable as novel 1D nanocarriers for biomedical,drug delivery and sensing applications.

Interfacial microstructure and mechanical properties of tungsten carbide brazed joints using Ag-Cu-Zn + Ni/Mn filler alloy

WC-Co hard metal was furnace brazed by Ag-Cu-Zn+Ni/Mn filler alloy using a tube furnace under high-purity argon at730°C.The influence of brazing time and gap size of joints was studied.The results revealed the maximum shear strength of(156±7)MPa for samples with150μm gap size at a holding time15min.The characterization and microstructure of the brazed joints were characterized by SEM,EDS and XRD.The results showed that increasing the time from5to15min could provide a better chance for the liquid interlayer to flow towards the base metal.However,the formation of some metallic phases such as Mn3W3C at brazing time longer than15min resulted in decreased shear strength of the joint.

Modeling of whole process of ageing precipitation and strengthening in Al-Cu-Mg-Ag alloys with high Cu-to-Mg mass ratio

A physically based numerical model to predict the microstructure evolution and yield strength of high Cu-to-Mg mass ratio Al-Cu-Mg-Ag alloys during the whole ageing process was developed.A thermodynamically-based precipitation model,employing the classical nucleation and growth theories,was adapted to deal with the precipitation kinetics (evolution of radius and volume fraction of precipitates for Ω phase) of aged Al-Cu-Mg-Ag alloys.The model gives an estimation of the precipitation kinetics (evolution of radius and density of precipitates for both θ' and Ω phases) of the alloy.The strengthening model based on Orowan mechanism was deduced.The microstructural development and strength predictions of the model are generally in good agreement with the experimental data.

Theoretical research on vacuum separation of Au-Ag alloy

To provide an accurate prediction of the product component dependence of temperature and pressure in vacuum distillation and give convenient and efficient guidance for the designing of the process parameters of industrial production, according to the molecular interaction volume model(MIVM), the separation coefficient(β) and vapor-liquid equilibrium composition of Au-Ag alloy at different temperatures are calculated. Combined with the vapor-liquid equilibrium(VLE) theory, the VLE phase diagrams, including the temperature-composition(T-x) and pressure-composition(p-x) diagrams of Au-Ag alloy in vacuum distillation are plotted. The triple points and condensation temperatures of gold and silver vapors are calculated as well. The results show that the β decreases and the contents of gold in vapor phase increase with the distillation temperature increasing. Low pressures have positive effect on the separation of Ag and Au. The difference between the condensation temperatures of gold and silver is about 450 K in the pressure range of 1-10 Pa.

Behavior of silver and lead in selective chlorination leaching process of gold-antimony alloy

The behavior of silver and lead in the selective chlorination leaching process of gold-antimony alloy was analyzed in detail and appropriate recovery methods were developed.A reduction method by adding gold-antimony alloy powder was adopted to recover silver according to the thermodynamics calculation.The reducing rate of silver can exceed 99%at 80℃for 1.5 h when the dosage of gold-antimony alloy powder is 10%.The dissolution equilibrium curved surfaces of PbSO4 and PbCl2 under different conditions were drawn.The experimental results are well consistent with theoretical analysis that indicate lead may be precipitated in the form of lead chloride.The grade of gold in the residue can be further concentrated to 94.5%after being washed with hot water. These two methods have been applied successfully in the practice.

An examination of active sites on Au-Ag bimetallic catalysts based on CO oxidation over Au/Ag_2O and a comparison to Ag-contaminated Au powder

There are two theories regarding the origin of the remarkable synergistic effect observed in Au‐Ag bimetallic catalysts when applied to various oxidative reactions. One is based on the importance of the contact interfaces between AgOx regions and the surface of the bulk Au as active working sites, while the other holds that charge transfer from Ag to Au in a surface Au‐Ag alloy causes the catalytic activity. One key point in examining these theories and determining the origin of the synergy in‐volves determining whether or not Ag exists as an oxide or as a metallic alloy on the Au surface. To confirm that enhanced activity results from contact between Ag2O and Au nanoparticles （NPs）, a comparative study of catalytic CO oxidation over Au/Ag2O and Ag2O was performed in the present work, using a closed recirculation reaction system. A reaction mixture consisting of a stoichiometric composition of CO and O2 （CO/O2=2/1） was supplied to both catalysts and the resulting pressure decrease rates were tracked, from which the amounts of gas consumed as well as the quantity of CO2 produced were determined. The steady state reactions of both Au/Ag2O and Ag2O did not lead to any meaningful difference in the rate of pressure decrease during the oxidation. The pressure decrease over both catalysts was attributed to the reduction of surface lattice O on Ag2O by CO. The results obtained for Au/Ag2O are in good agreement with previous data resulting from the use of Ag‐contaminated Au powder （Ag/Au‐b） having an oxidized surfaces. This finding suggests that the perimeters between AgOx zones and the bulk Au surface may not function as active sites during CO oxidation. A review of previous results obtained with Ag/Au‐b specimens having so‐called steady state surfaces indicates that AgOx species in such materials are reduced to the 0 state to form a Ag‐Au alloy that provides the active sites.

Vacuum Brazing of TiAl Based Alloy with 40Cr Steel

The vacuum brazing of TiAl based alloy with 40Cr steel was investigated using Ag-Cu-Ti filler metal. The experimental results show that the Ag, Cu, Ti atoms in the filler metal and the base metal inter-diffuse toward each other during brazing and react at the interface to form an inter-metallic AlCu 2Ti compound which joins two parts to produce a brazing joint with higher strength.

Effective Management of Own Funds in Polish Cooperative Banks

Today cooperative banks belong to the most significant financial institution in the world. Moreover, they can compete with commercial banks. The own funds of the cooperative bank are important in their activity. The main goal of this paper is to investigate how much the level of the own funds of the Polish cooperative banks influenced their efficiency. The research pertained to operating cooperative banks in Poland. The following measures of the efficiency were used in the research： return on Equity （ROE）, net profit, index C/I, and financial margin. The results of the study indicate that banks from the Quartile III （highest aggregate own funds）, had the highest net profits, the highest ROE, the lowest C/I value, the lowest ROE, and the lowest financial markups. On this basis, it remains to be recommended that banks of highest aggregate own funds continue expansion of own funds which will increase lending capacity and subsequently contribute to higher effectiveness.

Dendritic growth and solute trapping in rapidly solidified Cu-based alloys

Rapid solidification of binary Cu-22%Sn peritectic alloys and Cu-5%Sn-5%Ni-5%Ag quaternary alloys was accomplished by glass fluxing, drop tube and melt spinning methods. The undercooled, by glass fluxing method, Cu-22%Sn peritectic alloy was composed of a（Cu） and δ（Cu41Snll） phases. If rapidly solidified in a drop tube, the alloy phase constitution changed from α（Cu） and δ（Cu41Sn11） phases into a single supersaturated （Cu） phase with the reducing of droplet diameter, and the maximum solubility of Sn in （Cu） phase extended to 22%. The Cu-5%Sn-5%Ni-5%Ag quaternary alloy was composed of （Cu） and （Ag） phases under the containerless processing condition in a drop tube, and the solute microsegregation of （Cu） phase was obvious. When the Cu-5%Sn-5%Ni-5%Ag quaternary alloy was solidified by melt spinning method, microsegregation was suppressed and solute trapping occurred. The experimental results show that the microstructures of primary （Cu） phase in the two alloys transfer from coarse dendrites into equiaxed grains with the increase of cooling rate and undercooling, which is accompanied by the grain refinement effect.

Fabrication of AgA u alloy-TiO_2 core-shell nanoparticles and their photocatalytic properties

In this paper, for improving the photocatalytic efficiency of titania(TiO2) nanoparticles(NPs), Ag Au alloy-TiO2 core-shell NPs are fabricated via a sol-gel(SG) process in the presence of Ag Au alloy NPs with block copolymer shells as templates. The photocatalytic activities of the Ag Au-TiO2 NPs on the photodecomposition of methylene blue(MB) are investigated. The Ag Au-TiO2 composite NPs coated with 5.0% titania related to block copolymers show higher photocatalytic activity than the other samples in which the titania contents are larger than 5.0%. The results indicate that the increase of the thickness of the TiO2 shell leads to the decrease of the photocatalytic activity.