Microstructure Of Ag Research Articles

The microstructure, liquidus projection and thermodynamic modeling of thermoelectric Ag–Pb–Te system

Ag–Pb–Te is an important system in thermoelectric applications. Various Ag–Pb–Te alloys are prepared and their microstructures are examined. The liquidus projection of ternary Ag–Pb–Te system is determined both by experimental investigations and Calphad calculations, and the results are in good agreement. There are eight primary solidification phases, Ag, γ-Ag2Te, β-Ag2Te, Ag1.9Te, Ag5Te3, Te, PbTe and Pb, including a miscibility gap extended from the Ag–Te side. A ternary-eutectic reaction, L = PbTe + Te + Ag5Te3, was determined with a liquid composition of Ag-4.3at%Pb-62.6at%Te at 337 °C. A nanoscale microstructure containing a dotted PbTe and a lamellar matrix of Ag5Te3 and Te phases results from the ternary eutectic reaction. The solidification paths of selective ternary Ag–Pb–Te alloys are calculated using the Scheil model with the optimized interaction parameters obtained in this study, and the results are consistent with the experimental observations.

Sn含量对银钎料焊接性的影响

通过往Ag-Cu-Zn系钎料内添加适量的Sn和Ni元素，利用OM、SEM、XRD研究了钎料内Sn含量对钎料组织与焊接性能的影响。结果表明：Ag-Cu-Zn系钎料内主要成分为：Ag基固溶体；Cu基固溶体；CuZn化合物；当Sn含量达到4 wt%时，出现少量的Ag2Cu2O化合物。在本研究设计的成分范围内，钎料内并未出现Cu-Sn金属间化合物。差热分析表明：随着Sn含量的增加，钎料的固液相线温度均出现不同程度的下降。润湿试验表明：相同的加热温度下，不同Sn含量的银钎料均可对不锈钢形成良好的润湿。此外，采用该系列钎料手工火焰钎焊了不锈钢与不锈钢，得到的接头内母材/钎料界面处形成了致密的连接，无缺陷存在；当Sn含量为3.0 wt%时，得到接头的最高拉伸强度达到了450 MPa；当Sn含量超过3.0 wt%时，由于钎料内少量氧化物的存在使接头性能出现大幅度下降。 Sn and Ni element were introduced into Ag-Cu-Zn filler alloy, and the effect of Sn content on microstructure and brazing properties of Ag based filler alloy was analyzed by OM, SEM and XRD. The results indicated that the Ag-Cu-Zn filler alloy was mainly comprised of Ag based solid solution, Cu based solid solution and CuZn compounds. A trace amount of Ag2Cu2O occurred in the filler alloy while the content of Sn exceeded 4 wt% in the filler. However, the Cu-Sn intermetallics were not detected in the range of composition in the research. By using DSC analysis, the melting temperature of the filler alloy was decreased with increasing Sn content. The wettability test showed that the stainless steel could be wetted by the Ag-Cu-Zn based filler alloy with different Sn content. Besides, this kind of filler alloy was used to join stainless steel by torch brazing, and a compact bonding could be obtained at the substrates/filler alloy interface. The maximum joint strength could reach 450 MPa while the filler contained 3.0 wt% Sn element. While the content of Sn exceeded 3.0 wt% in the filler, the joint strength decreased sharply due to the existence of few oxides.

Effects of calcination temperature on the piezoelectric properties of lead-free Ag doped (Na,K)NbO3–LiTaO3 piezoelectric ceramics

The effects of calcinations temperature on the piezoelectric properties were investigated by employing the lead free piezoelectric Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 ceramics. Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 ceramics were prepared by employing the conventional mixed oxide method. The crystal structures and microstructure of Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 lead-free piezoelectric ceramics were examined by varying the calcination temperature from 750 to 950°C by X-ray diffraction analysis and scanning electron microscopy measurement. The effects of calcination temperature on the microstructure, piezoelectric and ferroelectric properties were systematically investigated. The dielectric and electrical properties of Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 ceramics were measured from 1kHz to 1MHz at various calcination temperatures. We expect that an optimized calcination condition can improve the piezoelectric and ferroelectric properties of Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 lead-free piezoelectric ceramics.

The role of Ag precipitates in Cu–12 wt% Ag

The Cu–12wt% Ag was prepared to investigate the role of Ag precipitates on the properties of the alloy. Two kinds of heat treatment procedures were adopted to produce different amount of Ag precipitates in the Cu–12wt% Ag. The microstructure of Ag precipitates was systematically observed by optical microscopy and electron microscopy. The Cu–12wt% Ag with more Ag precipitates exhibits higher strength and lower electrical conductivity. More Ag precipitates results in more phase interface and less Ag atoms dissolved in Cu matrix. By comparing the strengthening effect and electron scattering effect of phase interface and dissolved Ag atoms, it is conclude that the interface between Cu matrix and Ag precipitates could significantly block dislocation movement and enhance electron scattering in Cu–Ag alloys.

The microstructure and properties of Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 ceramic system

The microstructure and dielectric properties of Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 (x=0, 0.04, 0.08, 0.12, 0.16) ceramic system were investigated. The Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 ceramics were prepared by the traditional solid-state reaction method and were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM) and Raman spectrometer. The sintering ability and dielectric properties of Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 were found to be improved with the doping of Mn4+ and W6+ ions. The densification temperature of Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 ceramics decreased from 1 080 °C to 1 000 °C when x increased from 0 to 0.16. Ag(Nb0.8Ta0.2)1−x (Mn0.5W0.5) x O3 ceramic was found to have the best dielectric properties when x=0.08, larger permittivity (ɛ=547) and smaller dielectric loss (tanδ=0.00156).

Effects of a site substitution of bivalent ions on Ag(Nb0.8Ta0.2)O3 ceramics

Bivalent ions equivalent substitution and equimolar substitution for Ag+ in silver niobate tantalate ceramic were studied, which will result in Ag0.98A0.01(Nb0.8Ta0.2)O3 and Ag0.98A0.02 (Nb0.8Ta0.2)O3 respectively, where A2+ = Mg2+, Ca2+, Sr2+, Ba2+, Cu2+, Pb2+. The samples were synthesized by traditional solid method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of a little Ag+ (in mol ratio 2 %) on the dielectric properties in Mg2+, Ca2+, Sr2+, Ba2+, Cu2+, Pb2+ substituted samples, and the influences of radius and ionic electronegativity on the dielectric properties were discussed. The results showed that the substitution of most bivalent ions except large Ba2+ ions for a little Ag+ (in mol ratio 2 %) showed no obvious change on the perovskite structure and microstructure of Ag(Nb0.8Ta0.2)O3 ceramics. Basically, the dielectric properties of equivalent substituted samples were better than that of equimolar equimolar substituted samples, Ca2+ equivalent substituted samples showed lower dielectric loss, and Cu2+ equivalent substituted samples showed higher dielectric constant.

Improved piezoelectric properties of Ag doped 0.94(K0.5–βNa0.5–δ)NbO3–0.06Li1–γNbO3 ceramics by templated grain growth method

In this work, Ag doped 0.94(K0.5–βNa0.5–δ)NbO3–0.06Li1–γNbO3 lead-free piezoelectric ceramics have been prepared by templated grain growth (TGG) using cubic (K,Na)NbO3 single crystal seeds as templates. Specimens were prepared by the conventional mixed method and sintered in controlled atmosphere. TGG method was well known, because that this method can improve piezoelectric properties by increasing the grain size during the sintering process. Sintering caused densification and grain growth of ceramics by the expense of matrix particles. Densification prior to grain growth was found to be necessary to obtain highly textured ceramics. Crystalline properties were analyzed by the XRD method. The effects of TGG on phase structure, microstructure, piezoelectric and dielectric properties of Ag doped 0.94(K0.5–βNa0.5–δ)NbO3–0.06Li1–γNbO3 ceramics were investigated.

자기펄스 압축성형법으로 성형된 Ag-SnO2접점소재의 미세조직 및 특성

In this study, we reported the microstructure and properties of Ag- contact materials fabricated by a controlled milling process with subsequent consolidation. The milled powders were consolidated to bulk samples using a magnetic pulsed compaction process. The nano-scale phases were distributed homogeneously in the Ag matrix after the consolidation. The relative density and hardness of the Ag- contact materials were 95~96% and 89~131 Hv, respectively.

Nucleation and growth of bubbles in He ion-implanted V/Ag multilayers

Microstructures of He ion-implanted pure Ag, pure V and polycrystalline V/Ag multilayers with individual layer thickness ranging from 1 nm to 50 nm were investigated by transmission electron microscopy (TEM). The bubbles in the Ag layer were faceted and larger than the non-faceted bubbles in the V layer under the same implantation conditions for both pure metals and multilayers. The substantially higher single defects surviving the spike phase and lower mobility of trapped He in bcc than those in fcc could account for this difference. For multilayers, the bubbles nucleate at interfaces but grow preferentially in Ag layers due to high mobility of trapped He in fcc Ag. In addition, the He concentration above which bubbles can be detected in defocused TEM images increases with decreasing layer thickness, from 0 for pure Ag to 4–5 at. % for 1 nm V/1 nm Ag multilayers. In contrast, the bubble size decreases with decreasing layer thickness, from approximately 4 nm in diameter in pure Ag to 1 nm in the 1 nm V/1 nm Ag multilayers. Elongated bubbles confined in the Ag layer by the V–Ag interfaces were observed in 1 nm multilayers. These observations show that bubble nucleation and growth can be suppressed to high He concentrations in nanoscale composites with interfaces that have high He solubility.

Interfacial Reactions and Joint Strengths of Sn-xZn Solders with Immersion Ag UBM

The solder joint microstructures of immersion Ag with Sn-xZn (x = 0 wt.%, 1 wt.%, 5 wt.%, and 9 wt.%) solders were analyzed and correlated with their drop impact reliability. Addition of 1 wt.% Zn to Sn did not change the interface microstructure and was only marginally effective. In comparison, the addition of 5 wt.% or 9 wt.% Zn formed layers of AgZn 3 /Ag 5 Zn 8 at the solder joint interface, which increased drop reliability significantly. Under extensive aging, Ag-Zn intermetallic compounds (IMCs) transformed into Cu 5 Zn 8 and Ag 3 Sn, and the drop impact resistance at the solder joints deteriorated up to a point. The beneficial role of Zn on immersion Ag pads was ascribed to the formation of Ag-Zn IMC layers, which were fairly resistant to the drop impact, and to the suppression of the brittle Cu 6 Sn 5 phase at the joint interface.

TRIBOLOGICAL PROPERTIES OF AG/BSCCO SELF-LUBRICATING COMPOSITES

The superconductors Bi 2 Sr 2 CaCu 2 O x ( Bi 2212 ) and Ag / Bi 2212 composites samples were prepared by the powder metallurgy method. The frictional behaviors of Bi 2212 pins in contact with stainless steel plate were examined from -196 to 20°C on friction and wear tester. When the temperature was lower than the superconducting transition temperature, the friction coefficient of Bi 2212 dropped sharply, and it kept 0.11 with increase of the test time. The microstructure and morphology of Ag / Bi 2212 composites were investigated by means of X-ray diffraction (XRD), transmission electronic microscope (TEM) and high resolution transmission electronic microscope (HRTEM). The elemental compositions of the worn surfaces of Ag / Bi 2212 composites were determined by using energy dispersive X-ray analysis (EDXA). The results showed that the superconducting structure of Bi 2212 was not changed and Ag was distributed in the Bi 2212 matrix. Ag doping improved the toughness of oxide ceramics Bi 2212. The friction test results of Ag / Bi 2212 composites showed the tribological properties were improved at room temperature. The friction coefficient of 10% Ag / Bi 2212 against stainless steel showed a lower value (0.2) and the wear rate of 15% Ag / Bi 2212 was minimum (9.5×10-5 mm3·(N·m)-1 ). The lubrication of soft metallic film and load of hard matrix were the mechanism of decreased friction and anti-wear of Ag / Bi 2212 composites.

Silver Microstructure Control for Fluxless Bonding Success Using Ag-In System

A fluxless bonding process is successfully developed between silicon (Si) chips and copper (Cu) substrates using the silver-indium (Ag-In) binary system. This is a new design concept that utilizes thick Ag plated over the Cu substrate to deal with the large mismatch in coefficient of thermal expansion between semiconductors, such as Si (3 ppm/°C) and Cu (17 ppm/°C). The Ag layer actually becomes a part of the Ag-Cu substrate. Ag is chosen for the cladding because of its superior physical properties of ductility, high electrical conductivity, and high thermal conductivity. Following the thick Ag layer, 5 μm In and 0.1 μm Ag layers are plated. The thin outer Ag layer inhibits oxidation of inner In. After many bonding experiments, we realize that the success of producing a joint relates to the microstructure of the Ag layer. Ag with small grains results in rapid growth of solid Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> In intermetallic compounds through grain boundary diffusion. Thus, a joint is not obtained because of lack of molten phase (L). To coarsen Ag grains, an annealing step is added to the Ag-plated Cu substrate. This step makes Ag grains 200 times coarser compared to the as-plated Ag. The coarsened microstructure slows down the Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> In growth. Consequently, the (L) phase stays at the molten state with sufficient time to react with the Ag layer on the Si chip to produce a joint. Nearly perfect joints are produced on Ag-plated Cu substrates. The resulting joints consist of pure Ag, Ag-rich solid solution, Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> In, and Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> In. The melting temperature exceeds 650 °C. Using the present process, high temperature joints of high thermal conductivity are made between Si chips and Cu substrates at low bonding temperature (200°C). We foresee the Ag-In system as an important system to explore for various fluxless bonding applications in electronic packaging. This system provides the possibilities of producing joints of wide composition choices and wide melting temperature range. This paper provides preliminary but useful information on how the microstructure of Ag affects the bonding results.

Interface dominated high photocatalytic properties of electrostatic self-assembled Ag2O/TiO2 heterostructure

Electrostatic self-assembled Ag(2)O/TiO(2) nanobelts heterostructure was synthesized via simple physical mixing of Ag(2)O nanoparticles and TiO(2) nanobelts. The morphologies and microstructures of Ag(2)O/TiO(2) nanobelt heterostructure were characterized by high resolution transmission electron microscopy. The interface dominated high UV photocatalytic activity and degraded photoluminescence strength of composite catalyst confirmed the heterostructure effect between Ag(2)O nanoparticles and TiO(2) nanobelts. X-ray photoelectron spectroscope provided direct evidence of charge transfer on the heterostructures between them.

Microstructure characteristics of CBN/steel joints brazed with TiB2 modified active filler

The joint of cubic boron nitride (CBN) grits to 0·45%C steel were obtained by using TiB2 modified Ag–Cu–Ti active filler at the brazing temperature of 920°C for the holding time of 5 min. The microstructure characteristics of the brazing interface were detected by means of optical microscope, scanning electron microscope, energy dispersion spectrometer, X-ray diffraction and microhardness measuring equipment as well. It has been found that the microstructure of Ag–Cu–Ti filler layer is significantly refined by TiB2 particles. The almost well proportioned distribution of TiB2 particles in the filler layer is realised. Negative influence of TiB2 particles has not occurred on the chemical reaction of CBN particles and the filler at elevated temperatures. Reliable joining of CBN grits to 0·45%C steel is accomplished dependent on the resultant reaction products at the brazing interface.

Time of flight-photoemission electron microscope for ultrahigh spatiotemporal probing ofnanoplasmonic optical fields

Nanoplasmonic excitations as generated by few-cycle laser pulses on metal nanostructuresundergo ultrafast dynamics with timescales as short as a few hundred attoseconds (1 as = 10−18 s). So far, the spatiotemporal dynamics of optical fields localized on the nanoscale(nanoplasmonic field) have been hidden from direct access in the real space and timedomain. An approach which combines photoelectron emission microscopy and attosecondstreaking spectroscopy and which provides direct and non-invasive access to thenanoplasmonic field with nanometer-scale spatial resolution and temporal resolution of theorder of 100 as has been proposed (Stockman et al 2007 Nat. Photon. 1 539). To implementthis approach, a time of flight-photoemission electron microscope (TOF-PEEM) with∼25 nm spatialand ∼50 meV energy resolution, which has the potential to detect a nanoplasmonic field withnanometer spatial and attosecond temporal resolution, has been developed andcharacterized using a 400 nm/60 ps pulsed diode laser. The first experimental resultsobtained using this newly developed TOF-PEEM in a two-photon photoemission modewith a polycrystalline Cu sample and an Ag microstructure film show that the yield andthe kinetic energy of the emitted photoelectrons are strongly affected by the nanolocalizedplasmonic field.

Optical properties and microstructures of Pd-free Ag–Au–Pt–Cu dental alloys

Nine experimental Pd-free Ag–Au–Pt–Cu dental alloys containing 10 at.% Pt and 10–35 at.% Au were prepared and their optical properties and microstructures were investigated by means of spectrophotometric colorimetry, optical microscopy, and electron probe microanalysis. All the alloys were annealed at 850 °C and mirror-polished to observe their reflectance curves in the visible spectrum and three-dimensional color coordinates. All the alloys were composed of a major phase of Ag–Au-rich matrix and a minor and almost colorless Pt–Cu-rich phase. It was found that the color of the alloys was substantially controlled by the Ag–Au-rich matrix and that with increasing Au/Ag atomic ratio from 0.130 to 0.996, the yellow-blue chromaticity index b* increased from 8.0 to 14.4, giving a pale yellow color. This systematic increase in yellowness was caused by a continuous shift of the absorption edge of reflectance curve toward longer wavelengths with increasing Au/Ag atomic ratio.

Molecular dynamics simulation for cooling rate dependence of solidification microstructures of silver

A molecular dynamics simulation study has been performed to investigate the solid microstructures of Ag at room temperature resulted from rapid solidification with six cooling rates by using Quantum Sutton–Chen (QSC) many body potential. Several structural analysis methods have been employed to characterize and analyze the atomic configurations in the system. The results reveal that as the cooling rate γ ⩾ 1.0 × 10 13 K/s, an amorphous structure can be obtained; as the cooling rates in the range of γ = 5.0 × 10 12 ∼ 1.38 × 10 11 K/s, the coexistence structures of the meta-stable hcp with stable fcc configurations can be formed with phase separating or layering structures. Moreover, by using the 3D graphics technology, the arrangement of atoms in the system reveals that the phase separating occurs before the layering structures can be formed following the cooling rate decreasing. And an interesting layering structures have been found, in which the central atoms of fcc and hcp basic clusters are arranged by alternate close-packed-layers with a new repeating sequence ABCB.

Electrical properties and microstructure of glassy-crystalline Ag +-ion conducting composites synthesized by a high-pressure method

Rigid, mechanically reinforced, composite Ag +-ion conductors based on xAgI·(100- x) (0.67Ag 2O·0.33B 2O 3), 40 ≤ x ≤ 60, glasses and hard insulating powders of α-Al 2O 3 (2 µm) or ZrO 2 (1 µm) were prepared by a high-pressure method. Microstructure of the composites, depended on the content of AgI in the glasses and the temperature of the high-pressure stage of the synthesis. In all cases, however, it consisted of the evenly distributed phases (conductive and insulating), which did not interpenetrate at a nanometer length scale. It was found that the high electrical conductivity of the composites, though somewhat lower than that of the glasses, generally followed the temperature- and composition dependencies of the latter. An important advantage of the composites over the corresponding glasses was their higher microhardness and non-brittleness, which, contrary to the glasses, enabled their post-synthesis machining, cutting or polishing.

Formation of silver nanostructures (spheres, wires and islands) on pulsed laser deposited hexagonal and cubic MgxZn1−xO thin films by thermal reduction method

In this study, we present the formation of silver (Ag) nanowires, nanoshells and nanorods by the thermal reduction of an aqueous silver nitrate solution on the surface of magnesium zinc oxide (MgxZn1−xO) multiphase alloy thin films. MgZnO thin films were grown by the pulsed laser deposition method. The Ag nanowires are characterized by scanning electron microscopy and selective area electron diffraction methods. The microstructure of Ag is found to depend on the crystalline nature and phase of the MgZnO thin films.

Effect of sodium dodecylsulfate on improving microstructural properties of electroplated silver–oxygen–tungsten thin films

An electrodeposition process using cyclic voltammetry (CV) for preparing silver films containing tungsten (Ag–O–W) on p-type silicon (100) wafers is described. The electrochemical behaviors and microstructural properties of Ag–O–W deposits were compared in the absence and presence of sodium dodecylsulfate (SDS). It was found that SDS functioned as precipitation action to silver ions and promoted strongly the microstructure of Ag–O–W films as its concentration amounted to 5 wt.%. X-ray electron spectroscopy (XPS) investigation demonstrated that the concentration of tungsten was 3.4% and the O/W atom ratio was about 3.0 for Ag–O–W deposits. XPS and X-ray diffraction (XRD) measurements certified that the silver coating was not corroded at temperatures up to 350 °C in air. Finally, the resistivity of the films with the CV cycle number was analyzed.