Study on Properties of Conductive Adhesive Prepared with Silver Nanoparticles Modified by Silane Coupling Agent

采用经硅烷偶联剂KH-560表面改性的纳米银粉作为填料,环氧树脂为基体在180℃固化得到银导电胶。借助透射电子显微镜(TEM)、红外光谱(FTIR)、差示扫描量热法(DSC)等测试手段,对改性后纳米银粉和导电胶进行了表征。研究了银粉含量、固化时间对导电胶性能的影响。结果表明:KH-560改性后的纳米银粉平均粒径为20 nm,分散均匀;KH-560以化学键合的方式吸附在纳米银颗粒的表面。银粉含量、固化时间等均会影响导电胶的性能。当银粉含量为55%,固化时间为15 min时,导电胶的体积电阻率达最小值为2.5×10-3Ω·cm。与未做任何表面处理的纳米银粉填充的导电胶相比, KH-560改性后纳米银粉所得导电胶的电导率提高了3-5倍。     

High Electrical and Thermal Conductivity of Nano-Ag Paste for Power Electronic Applications

The nano-Ag paste consisted of Ag nanoparticles and organic solvents. These organics would be removed by evaporation or decomposition during sintering. When the sintering temperature was 300 °C, the resistivity of sintered bulk was 8.35×10^-6 Ω cm, and its thermal conductivity was 247 W m^-1 K^-1. The Si/SiC chips and direct bonding copper (DBC) substrates could be bonded by this nano-Ag paste at low temperature. The bonding interface, sintered microstructure and shear strength of Si/SiC chip attachment were investigated by scanning electron microscopy, transmission electron microscopy and shear tests. Results showed that the sintered Ag layer was porous structure and tightly adhered to the electroless nickel immersion gold surface of DBC substrate and formed the continuous Ag-Au interdiffusion layer. The shear strength of Si and SiC chip attachments was higher than 35 MPa when the sintering pressure was 10 MPa. The fracture occurred inside the sintered Ag layer, and the fracture surface had obvious plastic deformation.     

Preparation of oligoaniline derivative/polyvinylpyrrolidone nanofibers containing silver nanoparticles

Oligoaniline derivative/polyvinylpyrrolidone nanofibers containing silver nanoparticles have been successfully prepared by electrospinning technique. Silver nanoparticles were prepared through reduction of Ag⁺ by oligoaniline derivative, and the process of redox was monitored by UV–vis spectra. The morphology of Ag-polymer blends nanocomposites and the distribution of Ag nanoparticles were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical analysis of nanocomposites was checked by cyclic voltammetry (CV) in the 0.5 M H₂SO₄. In addition, the presence of Ag nanoparticles was indicated by X-ray diffractometer (XRD).     

Preparation of silver nanostructure from silver(I) coordination polymer and fabrication of nano silver(I) bromide by reverse micelles technique

A new one-dimensional silver(I) coordination polymer, [Ag(μ-bpfb)(NO₃)]_n (1); bpfb = N,N′-bis(4-pyridylformamide)-1,4-benzene, has been synthesized and characterized by IR, ¹H NMR and ¹³C NMR spectroscopy. The single crystal X-ray data show that the silver(I) 1D coordination polymer grows into a three-dimensional network by hydrogen bonding and π–π stacking interactions. Compound 1 with nanorod morphology was also prepared by sonochemical method. The cetyltrimethylammonium bromide (CTAB) as a cationic surfactant was used in reverse micelles technique to obtain spongy silver(I) bromide nanoparticles from compound 1. Also, different silver nanoparticles have been prepared via direct calcination at 673 K and thermal decomposition in oleic acid from compound 1. The nanostructures of [Ag(μ-bpfb)(NO₃)]_n (1), silver and silver(I) bromide were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDAX) analysis. Thermal stability of compound 1 in both bulk and nano-sized form was studied by thermal gravimetric (TG) and differential thermal (DT) analyses.     

金基电刷材料再结晶过程组织性能变化的研究

金银镍铜合金是一种优良的电刷材料,采用真空感应熔炼方法制备金银镍铜铸锭,通过轧制并配以中间热处理,使铸锭发生塑性变形,通过硬度检测、电阻率检测、扫描电镜对微观组织进行观察,研究金银镍铜合金在不同热处理条件、不同变形量下的力学性能变化。结果表明,金银镍铜合金塑性变形过程加工硬化现象明显,可通过加大变形量提高强度及电阻率。     

La2O3掺杂AgSnO2电接触材料的制备及性能研究

以Ag、Sn、La₂O₃粉为原料,采用机械合金法制备复合粉体。结合氧化法与粉末冶金工艺,对复合粉体进行氧化、压制、烧结。采用扫描电镜(SEM)和能谱仪、硬度计、金相显微镜、金属电导率测量仪等对复合粉体氧化前后的形貌以及电接触材料烧结前后的性能进行表征。结果表明：烧结后,电接触材料硬度较于烧结前明显下降。同时电接触材料随Sn含量增大,电阻率升高,密度反而下降。在一定的La₂O₃(0wt.%、0.75wt.%、1.5wt.%、2.25wt.%、3wt.%)含量范围内,La₂O₃掺杂量越高,密度越低。同时电接触材料经烧结后,随La₂O₃含量增加,其电阻率先降后升,在La₂O₃含量为0.75wt.%时,电接触材料的电阻率最低。     

Using nanoparticles as direct-injection printing ink to fabricate conductive silver features on a transparent flexible PET substrate at room temperature

Conductive metallic features that are flexible could have application in integrated circuits, ranging from large-area electronics to low-end applications. This paper shows the creation of conductive silver thin film and wire on the transparent flexible polyethylene terephthalate (PET) substrate by a room-temperature chemical reduction process. One-step synthesis and spectroscopic characterizations of size-controlled silver nanoparticles are also described. Transmission electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric-mass analysis, X-ray photoelectron spectroscopy and synchrotron radiation X-ray diffraction were used to characterize the dodecanoate-protected silver nanoparticles. Silver metal film and wire were produced by soaking the dodecanoate-protected silver nanoparticle film and wire, which were prepared, respectively, by spin-coating and by directly drawing with a commercial Epson T50 inkjet printer onto the flexible PET substrate using Ag nanoparticles suspended in cyclohexane (10 wt.%) as the ink, in an aqueous solution containing 80% N₂H₄. The resistivities of the Ag films are actually lower compared with the Ag thin films prepared by other conventional chemical routes, such as using silver salts as metallo-organic precursors. It is suggested that the use of nanoparticles as a precursor may be an explanation for the lower resistivity.     

Preparation and dispersive properties of Ag colloid by electrical explosion of wire

In this work, Ag colloid was prepared by electrical explosion of wire in deionized water with 0.2 mm and 0.3 mm wire diameter. The temperature of water used for medium of explosion process was change from 20 °C to 80 °C. Morphology and particle size of nanoparticles was observed by transmission electron microscope. The particle size and size distribution of nanoparticles was found to shift to a smaller size with a decrease of temperature and smaller wire diameter. Surface plasmon resonance of the silver colloids was studied by UV–vis spectroscopy. Stability of silver colloids was investigated by zeta-potential and Turbiscan techniques. The results indicated that temperature of medium during explosion affects much on the stability of Ag colloid. The silver colloidal stability prepared at lower temperature and smaller wire diameter was more stable.     

Effect of Heat Treatment on Microstructure and Mechanical Properties of ZM6 Alloy Prepared by Solid Recycling Process

ZM6 magnesium alloy was prepared by solid recycling process. Effect of heat treatment on microstructure and mechanical properties of the alloy was investigated. Cold pressing was employed to prepare extrusion billets of ZM6 chips, then the billets were hot extruded at 773 K with an extrusion ratio of 25:1. During hot extrusion, the grains refined and the particles were broken. The peak-aging materials showed fine plate-shaped β′ precipitates. The ultimate tensile strength and elongation to failure of as-extruded rods was 232.2 MPa and 23%, respectively. After T5 and T6 heat-treatment, obvious improvement of the tensile strength was obtained because of dispersive particles or fine precipitates. The morphology of the fracture surfaces was examined by employing scanning electron microscope.     

Effects of solid lubricants on friction and wear behaviors of the phenolic coating under different friction conditions

The phenolic coating filled with micro-MoS₂ or micro-graphite was prepared by spraying the coating precursors. The friction and wear behaviors of the unfilled and filled phenolic composite coating sliding against the steel ring were evaluated on an MHK-500 friction and wear tester under dry friction and under water lubrication conditions. The worn surfaces of the unfilled and filled phenolic coating and the transfer films formed on the surface of the steel ring were investigated using a scanning electron microscope (SEM) and an optical microscope (OM), respectively. FTIR analysis was performed to detect the chemical changes of the composite coating under different lubrication conditions. It was found that addition of graphite was effective in enhancing the wear life of the phenolic coating. Especially, the anti-wear ability of the phenolic coating was best when the content of graphite is 10 wt.%. However, the MoS₂ as filler was harmful to the friction and wear behaviors of the phenolic coating. The character of the fillers varied with the types of the solid lubricants and the transfer films of varied features formed on the counterpart steel ring, largely accounted for the different friction and wear behaviors of the unfilled and filled phenolic composite coating. Compared with under dry sliding, the phenolic composite coating filled with 10 wt.% MoS₂ or 10 wt.% graphite had lower friction coefficients and lower wear life under water lubrication. Since water hindered the formation of transferred films, and might penetrate and corrode the filler-matrix interface, the anti-wear ability of the phenolic composite coating reinforced with MoS₂ or graphite deteriorated under water lubrication.     

Investigation on morphology measurement and evaluation of TiO2 nanoparticles synthesized by SANSS

The article investigates the morphology of TiO₂ nanoparticles synthesized by a physical fabrication process, namely the submerged arc spray nanoparticle synthesis system (SANSS). An in-process sample preparation and an on-line nanoparticle sizing system using photon correlation spectroscopy (PCS) were developed to analyze the geometric (shape and size) properties of the TiO₂ nanoparticles. To evaluate the measurement results, the prepared particles were measured to quantify the nanoparticle geometric characteristics by employing a group of three different microscopes, including a transmission electron microscope (TEM), a scanning electron microscope and an atomic force microscope. More than 100 particle measurement for each experiment was performed to ensure data accuracy within 95% confidence level. The experimental results revealed that the averaged sphericity of the prepared nanoparticles was 5% of the particle size. It was found that the particle sphericity was deteriorated from 3.8% to 5.6% when the averaged particle diameter was decreased from 600 nm to 50 nm.     

Spherical granular structures of Ag/Co nanoparticles: Synthesis, characterization and magnetic properties

Ag/Co bimetallic nanoparticles in the form of hierarchical spherical structures were prepared by the polyol process using oleic acid and oleylamine as surfactants. The Ag/Co nanoparticles so obtained were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), UV-vis spectroscopy (UV-Vis), small angle X-ray scattering (SAXS), vibrating sample magnetometer (VSM) and super-conducting quantum interference device (SQUID). The XRD results in complement with the UV-vis studies indicated the absence of Ag-Co alloy formation during the synthesis. The FESEM observations depicted dense and uniform spherical granular structures for the Ag/Co nanoparticles; while the TEM studies apparently revealed a bimodal distribution of nanoparticles exist in the Ag/Co samples. The SAXS analysis on the Ag/Co colloids further validated the TEM results. The VSM studies showed typical ferromagnetic characteristics for the Ag/Co nanoparticles at room temperature; whereas the SQUID measurements demonstrated superparamagnetic nature for these nanoclusters with a blocking temperature close to 250 K. The synthetic route presented in this work represents a simple means of producing bimetallic composite superstructures of Ag/Co nanoparticles in the form of spherical granules on a large scale. These spherical aggregates have the potential to be important building blocks for more complex nanostructures and would be interesting for magnetic studies and catalytic applications.     

海绵钛电极块压制模具的结构优化

采用纳米银薄膜作为研究对象,在250℃下施加5~10 MPa的烧结压力,获得低孔隙率(1.2%~1.4%)的高质量烧结接头。随着烧结压力由5 MPa增大至10 MPa,接头抗剪切强度显著提升。借助深腐蚀技术对烧结接头及块体银的微观组织结构进行对比分析。结果表明,烧结接头的深腐蚀形貌与块体银存在明显差异。烧结接头在深腐蚀条件下呈现大量微米尺度的多边形银晶粒,当烧结压力由5 MPa增大至10 MPa时,多边形晶粒的尺寸与晶粒间的连接面积发生明显变化。这一现象是影响纳米银压力烧结连接接头性能的主控因素。     

Morphology of conductive blend fibers of polyaniline and polyamide-11

Polyaniline (PANI), a member of the intrinsically conducting polymer (ICPs) family, was blended with polyamide-11 (poly-ω-aminoundecanoyle) in concentrated sulfuric acid. The above solution was used to spin conductive PANI/polyamide-11 fibers by wet-spinning technology. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to study the two-phase morphology of the conductive PANI/polyamide-11 fibers. The micrographs of the cross-section, the axial section and the surface of the monofilament demonstrated that the two blend components were incompatible. The morphology of PANI in the fibers was of fibrillar form, which was valuable for producing conducting channels. The electrical conductivity of the fibers was from 10⁻⁶ to 10⁻¹ S/cm with the different PANI fraction and the percolation threshold was about 5 wt.%. By comparing the two blend systems of PANI/Polyamide-11 fibers and carbon black filled poly(ethylene terephthalate) (PET) fibers, it was shown that the morphology of the conductive component had an influence on electrical conductivity. The former had higher conductivity and lower percolation threshold than the latter.     

Advances in deformation processed gold composites

Conventional metallic composites are comprised of a metal matrix with a ceramic second phase. In recent years, composites have been developed in which both the matrix and the reinforcing phase are ductile metals. In 1998 a 90 vol%Au – 10 vol% Ag metal-metal composite wire was produced and found to possess both high tensile strength (550 MPa) and low electrical resistivity (2.56 m ohm-cm). In that composite, the silver reinforcing phase consisted of sub-micron diameter filaments parallel to the wire axis. This article describes the microstructures, mechanical properties, and electrical resistivity of three gold matrix composites in which the reinforcing phases are 7 vol% Ag, 14 vol% Ag, and 7 vol%Pt. These composites were drawn to diameters as small as 60 microns. Results from wedge bonding trials with these composite wires are also reported.     

Growth and Morphology Modulation of Needle-like Silicon Nanowires for SERS Application

半导体纳米线作为一种潜在的表面增强拉曼光谱（SERS）基底材料正受到广泛的关注。本文采用金作为催化剂,通过等离子体增强化学气相沉积系统,以气-液-固生长机制制备一种直径可控的针尖状硅纳米线。基于合金液滴控制硅纳米线形貌的事实,通过设计调节合金催化剂的尺寸,制备了针尖状硅纳米线。所制备硅纳米线形貌通过SEM清晰可见,为针尖状。TEM和XRD分析表明,硅纳米线为同轴结构,单晶硅核包覆非晶SiO2壳层。作为SERS活性基底,通过伽伐尼置换在纳米线表面沉积活性Ag颗粒,同等条件下对R6G的检测显示,针尖状硅纳米线基底其增强因子是柱状硅纳米线的十多倍。由此预测,这种针尖状的硅纳米线可应用于新型传感器、环境监测、生物医疗诊断等领域。此外,这种针尖硅纳米线的制备方法也可以用作制备其他的针尖状纳米线,例如同族的锗针尖纳米线等等。     

过热处理时间对Zr-Cu基大块非晶合金力学性能的影响

在一定初始温度下经过不同时间的熔体过热处理,利用铜模吸铸法,制备纯非晶合金Zr_(48)Cu_(36)Ag_8Al_8棒状试样,通过X射线衍射仪(XRD)、差示扫描热分析仪(DSC)、万能力学试验机和场发射扫描电子显微镜(SEM)研究过热处理对其力学性能的影响。结果表明,在一定的处理时间范围内,随着处理时间的增长,Zr_(48)Cu_(36)Ag_8Al_8非晶合金原子排列的混乱度增加,非晶合金的平均自由体积增加,Zr_(48)Cu_(36)Ag_8Al_8非晶合金的变形局域化程度降低,变形能力随之增强,非晶合金的断裂强度和塑性得到了提高。     

Investigations of Solidification Structures of High Carbon Alloy Cast Steel Containing RE-V-Ti

The solidification microstructural characteristics of rare earth (RE) and vanadium and titanium-treated high carbon alloy cast steel, whose chemical compositions are 0.90 wt.% C, 3.0 wt.% Si, and 1.0 wt.% Mn, were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), electron probe microanalyzer (EPMA), and energy dispersive X-ray spectrometry (EDS). The alloys were prepared in an induction furnace. The results showed that compound additions of RE-V-Ti could obviously refine the solidification structures and decrease the diameter of grains. The average grain diameter of untreated high carbon alloy cast steel was 80 μm. The average grain diameter of high carbon alloy cast steel containing RE-V-Ti decreased to 40 μm. Finally, the reasons that RE-V-Ti refined the solidification structure were analyzed in detail.     

Effect of Fe on vacuum breakdown properties of CuW alloys

CuW alloys with different Fe additions were prepared by the infiltration method. The microstructures of the CuW alloys prepared were characterized by a transmission electron microscope (TEM). The effect of Fe content on the surface erosion morphology was observed by a scanning electron microscope (SEM). The distribution of cathode spots was analyzed by a digital high-speed video camera. The results show that Fe addition can improve the relative density and thermal conductivity of CuW alloy with less than 0.6 wt.% Fe. However, excessive Fe addition can deteriorate the relative density and thermal conductivity. TEM results show that Fe addition can promote the formation of CuW solution. The area and depth of the erosion pits on the surface of CuW alloy depend on the breakdown position. Fe addition can strengthen the interface bond of Cu and W, improve the arc stability and the division of the cathode spots and, thus, avoid the concentration erosion.     

Polypyrrole nanoparticles and dye absorption properties

Polypyrrole (PPy) nanoparticles were prepared by using microemulsion polymerization processes at 3 °C. Particle characterization was performed by using FTIR, elementary analysis, UV–vis spectra and scanning electron microscope (SEM). The size of the nanoparticles varied from about 50 to 100 to 100 to 200 nm with the change in concentration of surfactant from 0.8 to 0.44 M. Polypyrrole nanoparticles were dedoped by a 10% NaOH solution, followed by a redoping process using a nuclear fast red kernechtrot dye, which has a sulfonate group. Dedoping changed the optical absorption properties of the nanoparticles.