Precipitation Of Ag Research Articles

EFFECTS OF HIGH MAGNETIC FIELD ON THE PRECIPITATE AND PROPERTY OF Cu--25%Ag ALLOY

在有无磁场条件下进行了Cu-25%Ag（质量分数）合金的凝固实验,研究了强磁场对Cu-25%Ag合金凝固组织中富Cu枝晶内部Ag析出相的影响,测试了合金的硬度和电导率.发现有无磁场条件下,在不同大小的富Cu枝晶内部,Ag析出相的形态和尺寸各不相同,大尺寸富Cu枝晶内部的Ag析出相呈连续的棒状结构,小尺寸富Cu枝晶内部的Ag析出相呈非连续的颗粒状结构.另外,无磁场条件下析出的Ag相数量较多,尺寸较细小;有磁场条件下析出的Ag相数量较少,尺寸较粗大.受到Ag析出相的影响,强磁场条件下合金的硬度降低,电导率升高.对强磁场下Ag析出相的影响机理进行了探讨,并分析了析出相对合金硬度和电导率的影响机制.

Enhancement of thermoelectric performance of NaxCo2O4 with Ag dispersion by precipitation from Ag+ aqueous solution

Thermoelectric NaxCo2O4/Ag composites were synthesized by citric acid complex (CAC) method and Ag precipitation from CH3COOAg aqueous solution on the NaxCo2O4 powders. Effects of the synthesis process on microstructure and thermoelectric performance of NaxCo2O4/Ag composites were investigated. When the NaxCo2O4 CAC powders were dipped in CH3COOAg aqueous solution and dried, fine Ag particles less than around 300 nm in size were precipitated on the surface of NaxCo2O4 powders. After the subsequent sintering process, the flaky Ag phase, the length and thickness of which were up to 5 and 1 μm, respectively, existed along interfaces between NaxCo2O4 grains. The sizes of Ag particles obtained in this study were found to be smaller than those of the conventionally prepared NaxCo2O4/Ag composites. The fine dispersion of Ag grains was effective for suppressing the increase in thermal conductivity due to the addition of metallic phase, Ag, and for improving the thermoelectric performance of NaxCo2O4/Ag composites, suggesting that the synthesis technique composed of the CAC method and Ag precipitation from CH3COOAg aqueous solution is significantly important process for thermoelectric NaxCo2O4/Ag composites.

アスコルビン酸水溶液を用いた還元逆抽出によるＡｇ（Ｉ）およびＣｕ（ＩＩ）担持ＶＡ１０からのＡｇおよびＣｕ微粒子の作製

The reduction stripping methods to generate Ag and Cu fine particles from Ag(I) and Cu(II) loaded VA 10 using aqueous ascorbic acid as a reductant were studied. Principal results obtained are as followed: (1) Since the pH for 50% extraction for Ag(I) and Cu(II) were 5.1 and 3.7, respectively, there is a possibility of selective extraction of those metal ions with VA 10. (2) In the stripping of Ag(I) or Cu(II) loaded VA 10, 100% reduction precipitation of fine Ag or Cu particulates can be obtained by choosing suitable stripping conditions, using an aqueous ascorbic acid as a reductant. (3) Complete reduction precipitation of Ag was achieved using an aqueous solution with a pH of 1.8-6.2 containing an amount of ascorbic acid equivalent to that of Ag(I). (4) To obtain fine Cu particles with 100% yield, we need to use 15 times ascorbic acid in a molar ratio at 333K for 24hrs. The average Cu particle size obtained under these conditions was 1.6 μm.

Separation of the no-carrier-added 109Cd from Ag, Cu and 65Zn by use of a precipitation and AG1-X8 resin

The 109Cd radionuclide was produced in the cyclotron via natAg(p,n)109Cd reaction. The radiochemical separation of 109Cd from silver and non-isotopic impurities comprised of two stages. The optimum conditions of the 109Cd separation methods were: Ag precipitation with 0.015 M HCl and Cu and 65Zn by use of 0.015 M HCl on AG1-X8 strong anion-exchange resin. Chemical and radionuclidic purity of 109Cd were measured by ICP-AES and gamma-ray spectrometry respectively. Recovery yield and radionuclidic purity were obtained 99.7% and 99%, respectively.

Ag-rich phase precipitation in the Cu-9 mass% Al alloy with Ag additions

The Ag-rich phase precipitation in the Cu-9 mass% Al was studied using differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results indicated that Ag additions did not interfere on the metastable transitions sequence of the Cu-mass% Al alloy but Ag precipitation disturbs the β phase formation reaction and the martensitic phase decomposition reaction.

Investigations of rotamers in diaxial Sn(IV)porphyrin phenolates—towards a molecular timepiece

An approach to the formation of molecular timepieces is outlined based on differentiating between rotamers in diaxial Sn(IV) porphyrin phenolates. Two models are explored in detail. The first explores how the rates of rotation of the diaxial ligands is discriminated based on steric hindrance of the two porphyrin macrocycle faces at low temperature. The second model explores a ‘stopwatch’ function based on the ligation of Ag(I) ions to a 5,15-dipyridylporphyrinato tin(IV) complex bearing 3-hydroxypyridine ligands. The complexation inhibits rotation of the axial ligand, a result, which can be reversed by precipitation of Ag(I) using tetraethylammonium bromide. X-ray crystallography has also been used to characterize two Ag(I) 5,15-dipyridylporphyrinato tin(IV)complexes. The two isoforms differ in their supramolecular organization. One structure is formed through a cofacial stack linking each porphyrin by Ag(I) coordination. The other displays a sheet-like coordination polymer structure.

Reação de precipitação de Ag na liga Cu-8%Al-6%Ag

A reação de precipitação de prata na liga Cu-8%Al-6%Ag foi estudada usando medidas devariação da microdureza com a temperatura e o tempo de envelhecimento, difratometria de raios X(DRX), calorimetria exploratória diferencial (DSC), microscopia eletrônica de varredura (MEV). Osresultados obtidos indicaram que o mecanismo da reação de precipitação da prata é um processo controlado pela difusão da prata e a velocidade desta reação atinge um máximo em torno de 500°C.

Synthesis of Thermoelectric Fe<SUB>0.98</SUB>Co<SUB>0.02</SUB>Si<SUB>2</SUB> with Fine Ag Dispersion by Mechanical Milling with AgO Powder

Synthesis of n-type Fe0:98Co0:02Si2 thermoelectric materials with dispersion of fine Ag particles was tried by mechanical milling of Fe-Si powder with AgO powder and subsequent hot pressing. The AgO phase was reduced by Si, resulting in precipitation of Ag particles, SiO2 phase and -FeSi phase. Most of the Ag particles were quite small; less than 100 nm in size. The precipitation of Ag and phase significantly decreased both the Seebeck coefficient and the electrical resistivity of Fe0:98Co0:02Si2, in spite of the SiO2 formation. On the other hand, the dispersion of fine Ag particles effectively enhanced phonon scattering, resulting in the reduction in the thermal conductivity in spite of the precipitation of metallic phases. However, the dimensionless figure of merit could not be improved by AgO addition because of the significant deterioration of the Seebeck coefficient. The Si powder addition with AgO powder was found to be effective on recovering the reduction in the Seebeck coefficient. [doi:10.2320/matertrans.E-MRA2008808]

Diffusion and interface controlled reactions in α-(Cu–Al–Ag) alloys

The isothermal kinetics of Ag precipitation was studied in Cu–Al–Ag alloys with concentrations ranging from 2 to 8 wt.%Al and 2 to 12 wt.%Ag, using scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDX) and microhardness measurements. The results indicated a change in the precipitates growing mechanism from diffusion to interface controlled process, probably due to a change in the nature of the interface with the Ag and Al enrichment of the precipitates.

Ag precipitation and dissolution reactions in the Cu–3 wt.% Al–4 wt.% Ag alloy

The Ag precipitation and dissolution reactions in the Cu–3 wt.% Al–4 wt.% Ag alloy were studied using isothermal and non-isothermal analyses. The activation energy values, obtained for the Ag precipitation reaction indicated that, when the Kissinger, Ozawa and Johnson–Mehl–Avrami methods are compared, the Kissinger method is the most appropriate. Although the Johnson–Mehl–Avrami equation often does not fit precipitation data, the n values obtained for Ag precipitation kinetics are in agreement with what was experimentally observed. For the dissolution reaction of Ag precipitates the activation energy values obtained from the Kissinger and Ozawa methods are higher than that found in the literature for the Ag dissolution in Cu. This discrepancy seems to be related to the fact that the activation energy is influenced by the heating rate.

Particulate structure of FePt thin films enhanced by Au and Ag alloying

The additions of Au and Ag to FePt thin film change the film structure from an interconnected network to a completely isolated island structure. In particular, the Ag addition led to an isolated particulate structure smaller than 100nm, which increased the coercivity from 5.4to20.5kOe. Energy filtered elemental mapping did not show evidence for the precipitation or segregation of Au and Ag.

Structure and properties of Ag embedded aluminum doped ZnO nanocomposite thin films prepared through a sol–gel process

Aluminum doped zinc oxide transparent conducting thin films with embedded silver nanoparticles were prepared by a sol–gel method. Silver doping was found to enhance the crystallization of the aluminum doped zinc oxide phase. However, the precipitation of Ag inhibits the grain growth of aluminum doped zinc oxide. The Ag particle size was increased from 30 to 70 nm as Ag concentration increased from 0.01 to 0.2 M after firing at 650 °C. The interconnected network of Ag phases provides effective conducting paths that reduced the electrical resistivity of the films to 4.2×10−4 Ω cm. The optical transmission of the films are greater than 80% in visible wavelength and shows an absorption band towards a longer wavelength at a higher Ag concentration.

Effect of Ag additions on the reverse martensitic transformation in the Cu-10 mass% al alloy

The effect of Ag additions on the reverse martensitic transformation in the Cu-10 mass% Al alloy was studied using differential thermal analysis (DTA), optical (OM) and scanning electron microscopies (SEM) and X-ray diffractometry. The results indicated that Ag additions to the Cu-10 mass% Al alloy shift the equilibrium concentration to higher Al contents, allow to obtain both β'1 and β' martensitic phases in equilibrium and that Ag precipitation is a process associated with the perlitic phase formation.

高分解能ラザフォード後方散乱分析（ＲＢＳ）による銀負イオン注入熱酸化薄膜における銀の熱拡散分布の測定と拡散障壁による単層銀ナノ粒子の形成

Thermal diffusion of implanted Ag atoms in 25-nm-SiO2/Si and nanoparticle formation after annealing at various temperatures were investigated by a high-resolution RBS and cross-sectional TEM. Ag atoms were implanted into the thermal grown thin oxide layer on silicon substrate by negative-ion implantation at 10 keV with 5×1015 ions/cm2. The samples were then thermally annealed at 500, 700 and 800°C for 1 h. In the HRBS measurement with 400 keV He+ beam, Ag atoms in the as-implanted sample were found to have almost the same depth profile as a predicted one by TRIM-DYN calculation, although some Ag atoms diffused to the surface due to local heating during implantation. After annealing at 500°C, a main fraction of Ag atoms appeared at a depth of 12 nm as same as that of the as-implanted sample, and two small precipitations of Ag atoms appeared at depths of 7 and 22 nm. After annealing at 700°, the only one fraction peak of Ag atoms appeared at a depth of 20 nm with a relatively narrow FWHM. At this temperature, the XTEM observation revealed the Ag precipitation at 700°C was contributed from the mono-layered Ag nanoparticles. The both of small and remarkable precipitations of Ag atoms observed at a depth around 22 nm just near the SiO2/Si interface after annealing at the temperature less than 700°C, suggested the existence of a diffusion barrier against Ag atoms in the thermally grown SiO2 on Si. This is considered to be due to compressive stress in the transition layer in SiO2 just near the crystalline Si surface. However, after annealing at 800°C, the Ag atoms diffused to the SiO2/Si interface at 25 nm.

Strain-induced charge separation in the photocatalytic single crystalline anatase TiO 2 film

A single crystalline anatase TiO 2 film was grown on a LaAlO 3 substrate. Photocatalytic reduction of Ag ions resulted in Ag precipitation on the surface of the film. The density and the morphology of the Ag precipitation varied at the twin boundaries of the substrate. The anatase film should suffer from the strain caused by this twinning and the strain distribution should be different in each twin domains. Hence, this twin-domain dependent Ag precipitation is a possible clue for the electron–hole charge separation centers induced by the stress concentration in the anatase film which act as active sites for photocatalytic reaction.

Isothermal decomposition kinetics in the Cu–9%Al–4%Ag alloy

The influence of 4wt.%Ag addition on the isothermal decomposition kinetics of the β′ phase in the Cu–9wt.%Al alloy was studied by microhardness measurements, optical and scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, and X-ray diffractometry. The results showed that the presence of Ag decreases the β′→(α+γ1) decomposition reaction rate in the Cu–9%Al–4%Ag alloy, an effect that may be associated to the γ1 phase which catalyses the Ag precipitation, making it faster than the decomposition reaction, and thus, stabilizing the martensitic phase.

Ag and Cu Precipitaion in Multi-Layer Chip Inductors Prepared with V2O5-Doped NiCuZn Ferrites

The purpose of this study is to investigate the effect of <TEX>$V_2$</TEX><TEX>$O_{5}$</TEX> addition on the Ag and Cu precipitation in the NiCuZn ferrite layers of 7.7<TEX>${\times}$</TEX>4.5<TEX>${\times}$</TEX>1.0 mm sized multi-layer chip inductors prepared by the screen printing method using 0∼0.5 wt% <TEX>$V_2$</TEX><TEX>$O_{5}$</TEX> -doped ferrite pastes. With increasing the <TEX>$V_2$</TEX><TEX>$O_{5}$</TEX> content and sintering temperature, Ag and Cu oxide coprecipitated more and more at the polished surface of ferrite layers during re-annealing at <TEX>$840^{\circ}C$</TEX>. It was thought that during the sintering process, V dissolved in the NiCuZn ferrite lattice and the Ag-Cu liquid phase of low melting point was formed in the ferrite layers due to the Cu segregation from the ferrite lattice and Ag diffusion from the internal electrode. During re-annealing at <TEX>$840^{\circ}C$</TEX>, the Ag-Cu liquid phase came out the polished surface of ferrite layers, and was decomposed into the isolated Ag particles and the Cu oxide phase during the cooling process.

Aging kinetics in the Cu–8 wt.% Al alloy with Ag additions

The influence of additions of 2, 4, 6, 8, 10 and 12 wt.% Ag in the isothermal aging kinetics of the Cu–8 wt.% Al alloy was studied using microhardness measurements, differential scanning calorimetry, optical and scanning electron microscopy and X-ray diffractometry. The results indicate that the presence of silver is responsible for the shift of the equilibrium concentration to higher Al contents, allowing the formation of the γ 1 phase (Al 4Cu 9) in this alloy. For Ag additions up to 6% the dominant kinetic process is Ag precipitation and for additions from 8 to 12% Ag the nucleation of the perlitic phase dominates.

Trimodal distribution of CO2-bearing fluid inclusions in the gold — silver-bearing quartz veins of the Phuoc Thanh area, Central Vietnam: Its implication to the Au−Ag precipitation

CO2-rich fluid inclusions from quartz veins provide information about pressure-temperature conditions, as well as effervescence, in the gold-silver-bearing quartz veins in the Phuoc Thanh area, Central Vietnam. Homogenization temperatures of fluid inclusion are bimodal, and support textural evidence that mineralization occurred in two stages. 90% of the fluid inclusions in the quartz are CO2-bearing. The trimodal distribution of CO2 mole fraction of the inclusions are common in the area, which indicates the CO2 unmixing, resulting the separation of the high (type IIb) and low (type IIa1) XCO2 fluids from the parental fluid (type IIa2) with intermediate XCO2. The precipitation of associated sulfide and Au−Ag minerals is related to CO2 effervescence with a concomitant decrease in sulfur activity. The temperature of mineralization is estimated as the range from 300 to 380°C in stage I and from 230 to 300°C in stage II. Pressure of ore formation ranged from 350 to 500 bars during both stages.

Thickness effect on grain growth and precipitate coarsening of a copper-silver thin film in an advanced metallization process

Annealing of Cu(Ag)/SiO2/Si films was carried out to investigate the relationship between grain growth and precipitate coarsening. Ag in copper was selected as an immiscible dopant for diffusion and precipitation. Annealing effects were characterized in terms of resistivity, morphology, preferred orientation, grain growth, precipitation, and diffusional characteristics. The lowest observed resistivity was 2.06 μΩ cm in a 900 nm thick film annealed at 500 °C. The resistivity decrease was attributed to Ag precipitation and grain growth. A transition thickness exists at below 220 nm in the grain growth and the precipitate coarsening of the Cu(Ag) films. A relationship was established between grain growth and precipitate coarsening above the transition thickness that fits well to the experimental data. The grain size in the Cu(Ag) film can thus be predicted from the Ag precipitate size by using this relationship.