Phase equilibria in Ag-Ga-S films and kinetics of AgGaS<Subscript>2</Subscript> crystallization

The phase compositions of films produced by coevaporation and sequential evaporation of Ag, Ga, and S have been determined. The phases identified in the films grown at room temperature are Ag₂S, GaS, Ga₂S₃, and AgGaS₂. The kinetics of phase transformations in thin amorphous AgGaS₂ films have been studied by dynamic electron diffraction. The dimensionality of growth during amorphous AgGaS₂ crystallization and the activation energies for nucleation and crystallite growth have been evaluated.     

Phase investigations in the silver-gallium-sulphur system

The binary join Ag₂SGa₂S₃ and some supplementary compositions in the ternary system AgGaS were examined by differential thermal analysis and X-ray diffraction. From the experimental results the phase diagram of the Ag₂SGa₂S₃ system was constructed. Besides the well-known chalcopyrite analog AgGaS₂ two additional compounds of composition Ag₉GaS₆ and Ag₂Ga₂₀S²₃₁ were established, both being dimorphic. Outside the binary section only one new phase, a Ag-containing rhombohedral modification of gallium sulphide, GaS:Ag(3R), could be found. Crystal data for all phases investigated are given. Ag₉GaS₆ is a representative of a group of possible superionic conductors with icosahedral structure.     

Influence of silver addition on microstructures and transport properties of La<Subscript>0.67</Subscript>Ca<Subscript>0.33</Subscript>MnO<Subscript>3</Subscript>:Ag<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> composites

In order to obtain high temperature coefficient of resistance (TCR) value of La_0.67Ca_0.33MnO₃:Ag _x (LCMO:Ag _x ) composites, samples with different Ag contents (x?=?0, 0.1, 0.2, 0.25, 0.3, and 0.5) were prepared by sol–gel method. X-ray diffraction analyses indicated that all samples had orthorhombic perovskite structures. As x increased, lattice parameters (a, b, c) and cell volumes underwent slight expansions. Interestingly, the addition of Ag dramatically affected TCR and magneto-resistance (MR) values. Elevated TCR value up to 53.46%·K^?1 at 277 K was observed for LCMO:Ag _x composites with added Ag at the composition of x?=?0.1. Meanwhile, MR value at 263 K reached 71% at the magnetic field of 1 T for samples with Ag composition of x?=?0.25. The increase in Mn⁴⁺/Mn³⁺ ratio and improvement in crystallization caused by added Ag was found responsible for the elevated values of TCR, MR, and T_p. These findings may have practical use in high-performance magneto-resistive manganites.     

Ag<Subscript>2</Subscript>S/Bi<Subscript>2</Subscript>S<Subscript>3</Subscript> co-sensitized TiO<Subscript>2</Subscript> nanorod arrays prepared on conductive glass as a photoanode for solar cells

TiO₂ nanorod arrays (TiO₂ NRAs) were synthesized through a hydrothermal method. Ag₂S and Bi₂S₃ were then grown on the surface of TiO₂ NRAs with successive ionic layer adsorption and reaction method. The pristine rutile TiO₂ NRAs, Ag₂S/TiO₂, Bi₂S₃/TiO₂, and Bi₂S₃/Ag₂S/TiO₂ electrodes were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible absorption spectroscopy, and electrochemical analysis. According to photoelectrochemical (PEC) measurement, an enhanced short circuit current density was obtained for the co-sensitized TiO₂ NRAs under simulated sunlight illumination, which was 10.7 times higher than that of the TiO₂ NRAs. Appropriate potential positions of conduction band and valence band of Bi₂S₃ that match well those of rutile TiO₂ NARs and Ag₂S lead to the improved PEC performance. In addition, the PEC property of the co-sensitized TiO₂ NRAs under visible light irradiation was also investigated and showed a dramatically enhanced photocurrent response.     

Phase separation and structural change accompanying the introduction of silver to arsenic trisulphide glass

Glass-glass phase separation has been observed when melts of compositions As₂S₃Ag_x (x=0.1, 0.25, 0.35, 0.4 or 0.5) were cooled slowly to 210° C and annealed at this temperature. The two glass phases produced were an Ag-rich one (approximate compositon for x=0.4, As₂S_3.4Ag_1.0) and an Ag-poor one (As₂S_2.7Ag_0.07). With increasing x value, Ag and S contents in the Ag-rich phase increased, and its composition approached that of trechmannite or smithite (AgAsS₂), whereas the Ag content of the Ag-poor phase changed little and only the S content decreased. A chemical-etching study of the phaseseparated glasses was also made.     

Shielding effect of Ag<Subscript>3</Subscript>Sn on growth of intermetallic compounds in isothermal heating and cooling during multiple reflows

In this research, the shielding effect of Ag₃Sn particles on Cu₆Sn₅ grain boundaries in isothermal heating and cooling of multiple reflows was investigated in Sn/Cu and Sn3.5Ag/Cu solder bumps by utilizing the real-time imaging technology of Shanghai Synchrotron Radiation Facility as well as scanning electron microscope. Results show that controlled by volume diffusion growth mechanism, the value of time exponent n for Sn is much closer to 1/2 with increasing reflow cycle than for Sn3.5Ag that governed by both grain boundary and volume diffusion mechanisms in isothermal heating. Consequently, IMC increment in Sn3.5Ag is larger than in Sn due to the Cu supplement effect of J^*_in?b in cooling during multiple reflows. The reason for the phenomena may be the shielding effect of Ag₃Sn nano particles on grain boundaries in Sn3.5Ag during multiple reflow process.     

Ag2SeGa2Se3 pseudobinary phase diagram

The pseudobinary Ag₂Se-Ga₂Se₃ phase diagram has been redetermined by differential thermal analysis, x-ray diffraction, and crystal growth studies. A new ternary phase, Ag₉GaSe₆, has been observed, and the phase boundaries of the solid solutions based on AgGaSe₂ and Ga₂Se₃ have been measured. The optical scattering observed in slow-cooled crystals of AgGaSe₂ is due to precipitates of a Ga₂Se₃-based solid solution, which has the approximate composition AgGa₇Se₁₁. The new Ag₂Se-Ga₂Se₃ diagram differs significantly from the one given by Palatnik and Belova but is qualitatively similar to the Ag₂S-Ga₂S₃ diagram recently reported by Brandt and Krämer.     

Optical and photo catalytic characteristics of Ag<Subscript>2</Subscript>S/TiO<Subscript>2</Subscript> nanocomposite films prepared by electrochemical anodizing and SILAR approach

Ag₂S decorated titanium oxide nanotubes (Ag₂S/NTs) were prepared by electrochemical anodizing and successive ionic layer adsorption and reaction (SILAR) approach. The prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy coupled with energy dispersive X-ray analysis and diffuse reflectance spectroscopy. SEM results indicate titanium oxide nanotubes (NTs) with 90–220 nm in diameter and 15–30 nm in wall thickness were prepared by one-step anodizing method on the surface of titanium foils. Characterization of the Ag₂S/NTs samples indicated that the number of SILAR cycles influenced the morphology of fabricated films. The degradation of rhodamine B was used as a model reaction to evaluate the photo catalytic activity of the obtained samples. Results showed that the photo catalytic activity of Ag₂S/NTs nanocomposite samples is higher than that with bare NTs sample. The incorporation of Ag₂S on NTs improves the photo catalytic activity due to the synergetic effect. Ag₂S/NTs nanocomposite sample prepared by SILAR deposition with 2 cycles gives the highest degrading rate, which can be attributed to appropriate Ag₂S content and high surface area of this sample. Ag₂S/NTs nanocomposites are easy to be recycled and have good stability for repeated use. With the improved visible light degradation performance, Ag₂S/NTs samples would be expected to be used in water purification. Since these prepared electrodes can be easily removed and replaced after the photo catalytic reaction, avoiding the filtration step after photoreaction or the immobilizing process required for photo catalyst particles, the operation in the photo-reactor becomes much easier from an engineering point of view.     

Formation of Li<Superscript>+</Superscript> superionic crystals from the Li<Subscript>2</Subscript>S–P<Subscript>2</Subscript>S<Subscript>5</Subscript> melt-quenched glasses

The 70Li₂S·30P₂S₅ (mol%) glass was prepared by the melt quenching method and the glass–ceramic electrolytes were obtained by heating the prepared glass over crystallization temperatures. The superionic metastable Li₇P₃S₁₁ crystal was formed by heating the glass in the temperature range from 280 and 360 °C. The conductivity of the glass–ceramics was enhanced by the precipitation and growth of the Li₇P₃S₁₁ crystal, and the highest conductivity of 4.1 × 10⁻³ S cm⁻¹ at room temperature was achieved in the glass–ceramic heated at 360 °C for 1 h. The Li₇P₃S₁₁ crystal changed into the thermodynamically stable phase such as the Li₄P₂S₆ crystal with further increasing heat treatment temperature and holding time, resulting in lowering conductivities of the glass–ceramics.     

Verres d'oxysulfures de terres rares conducteurs ioniques

Glass formation in the ternary system La₂O₂S-Ag₂S-Ga₂S₃. Preparation. Extent of the glassy region in the ternary diagram. Thermal behaviour and electrical properties of the glasses. The electrical conductivity is essentially depending on the Ag content.     

Thermodynamic properties and homogeneity regions of Tl<Subscript>6</Subscript>SCl<Subscript>4</Subscript> and Tl<Subscript>5</Subscript>Se<Subscript>2</Subscript>Cl

In this activity system Tl-Tl₂X-X (X = S, Se)are studied using emf measurements of concentration chains relative thallic electrode. The solid phase diagrams of these systems are clarified, homogeneity areas of the compounds Tl₆SCl₄ and Tl₅Se₂Cl are determined. On the basis of emf measurement results, relative partial molar functions of thallium in alloys and standard integral thermodynamic functions (ΔG ⁰(298 K), ΔH ⁰ (298 K), ΔS ⁰ (298 K)) of the ternary compounds Tl₆SCl₄ and Tl₅Se₂ Cl and phases of variable composition based on the latter are calculated.     

Evaluation of the toxicities of silver and silver sulfide nanoparticles against Gram‐positive and Gram‐negative bacteria

In this study, the endogenous lipid signalling molecules, N ‐myristoylethanolamine, were explored as a capping agent to synthesise stable silver nanoparticles (AgNPs) and Ag sulphide NPs (Ag₂ S NPs). Sulphidation of the AgNPs abolishes the surface plasmon resonance (SPR) maximum of AgNPs at 415 nm with concomitant changes in the SPR, indicating the formation of Ag₂ S NPs. Transmission electron microscopy revealed that the AgNPs and Ag₂ S NPs are spherical in shape with a size of 5–30 and 8–30 nm, respectively. AgNPs and Ag₂ S NPs exhibit antimicrobial activity against Gram‐positive and Gram‐negative bacteria. The minimum inhibitory concentrations (MIC) of 25 and 50 μM for AgNPs and Ag₂ S NPs, respectively, were determined from resazurin microtitre plate assay. At or above MIC, both AgNPs and Ag₂ S NPs decrease the cell viability through the mechanism of membrane damage and generation of excess reactive oxygen species.Inspec keywords: cellular biophysics, biomembranes, transmission electron microscopy, nanomedicine, microorganisms, molecular biophysics, antibacterial activity, nanofabrication, silver, biomedical materials, surface plasmon resonance, nanoparticles, materials preparation, silver compounds, lipid bilayersOther keywords: Gram‐negative bacteria, Gram‐positive bacteria, endogenous lipid signalling molecules, N‐myristoylethanolamine, capping agent, silver nanoparticles, Ag sulphide NPs, sulphidation, surface plasmon resonance, concomitant changes, transmission electron microscopy, minimum inhibitory concentrations, resazurin microtitre plate assay, cell viability, membrane damage, reactive oxygen species, Ag toxicities, Ag, Ag₂ S     

Strengthening mechanism of nano-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> particles reinforced Sn3.5Ag0.5Cu lead-free solder

To improve the properties of the eutectic Sn3.5Ag0.5Cu lead-free solder, various amounts of mixed nano-Al₂O₃ particles were added. The microstructure, thermal analysis, density, thermal expansion coefficient (CTE), and mechanical behavior were studied. The results of differential scanning calorimetry (DSC) indicate that the melting point of the composite solder doped with nano-Al₂O₃ particles is slightly higher that of the Sn3.5Ag0.5Cu lead-free solder and has a eutectic peak. The Sn3.5Ag0.5Cu composite solders exhibited lower density values and thermal expansion coefficient (CTE) values than did the unreinforced solder matrix. Compared to solder without the addition of nano-Al₂O₃ particles, the formation of dendritic β-Sn grains, the Ag₃Sn phase average size, and the spacing of lamellae decreased significantly in the composite solder matrix. The mechanical properties also improved with increasing weight percentages of nano-Al₂O₃ particles. However, the ductility of the Sn3.5Ag0.5Cu composite solder decreased. For the addition of 1 wt% nano-Al₂O₃ particles, microporosity was observed both at and along the grain boundary regions, coupled with the presence of second-phase particles (i.e. nano-Al₂O₃ and Ag₃Sn).     

Phase relations in the Ag<Subscript>8</Subscript>SnS<Subscript>6</Subscript>-Ag<Subscript>2</Subscript>SnS<Subscript>3</Subscript>-AgBr system and crystal structure of Ag<Subscript>6</Subscript>SnS<Subscript>4</Subscript>Br<Subscript>2</Subscript>

The T-x phase diagram of the Ag-Sn-S-Br system has been studied in the composition region Ag₈SnS₆-Ag₂SnS₃-AgBr, and a compound of composition Ag₆SnS₄Br₂ has been identified. Ag₆SnS₄Br₂ has a new structure, closely related to that of Ag₆GeS₄Br₂: sp. gr. Pnma, a = 6.67050(10), b = 7.82095(9), c = 23.1404(3) Å, Z = 4, R _B = 0.0519, R _wp = 0.0782, χ² = 1.36.     

T-x phase diagram of the Cu<Subscript>2</Subscript>S-Al<Subscript>2</Subscript>S<Subscript>3</Subscript> quasibinary System

The T-x phase diagram of the Cu₂S-Al₂S₃ system was achieved experimentally from 35 different mixtures of the binary compounds. The results of powder X-ray diffraction (XRPD), differential thermal analysis (DTA) and microprobe analysis (EPMA) are presented. The ternary phases CuAlS₂ and CuAl₅S₈ were found and their homogeneity regions were established.     

Solar photocatalytic generation of hydrogen under ultraviolet-visible light irradiation on (CdS/ZnS)/Ag<Subscript>2</Subscript>S + (RuO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript>) photocatalysts

In order to efficiently use the UV-vis light in the photocatalytic reaction, a novel (CdS/ZnS)/Ag₂S + RuO₂/TiO₂ was synthesized by chemical coprecipitation and metal ion implantation. The composition and structure of this composite were characterized by BET, UV-vis spectroscopy, SEM, XRD and EDX. This composite exhibited much higher photocatalytic activity for the generation of hydrogen (H₂).     

Phase equilibria in the Ag<Subscript>2</Subscript>Se-AgAsSe<Subscript>2</Subscript>-AgBiSe<Subscript>2</Subscript> system

Phase equilibria in the pseudoternary system Ag₂Se-AgAsSe₂-AgBiSe₂ have been studied using differential thermal analysis, X-ray diffraction, microhardness tests, and emf measurements on silver concentration cells with Ag₄RbI₅ as solid electrolyte. The results are used to construct the 300-, 600-, and 800-K isothermal sections, a number of partial phase diagrams, and the liquidus projection. Several in- and univariant peritectic and eutectic equilibria and a broad region of AgBiSe₂-based solid solutions are identified. The homogeneity range of the high-temperature phase of AgBiSe₂ reaches −50 mol % in width (650 K), and that of the low-temperature phase is 20 mol % in width (300 K) along the AgAsSe₂-AgBiSe₂ constituent binary. The melting points, lattice parameters, and microhardness of the solid solutions are determined.     

Metal-nonmetal transition and the electronic transport behavior in disordered PbO<Subscript>2</Subscript>-Ag<Subscript>2</Subscript>O-xCsystem synthesized by ball milling

The electronic transport properties as a function of temperature and the graphite content have been investigated for disordered PbO₂-Ag₂O-xC (0 x 3) composite materials. The components of the system change from (1) lead-silver oxides of Ag₅Pb_2.5O₆ and/or Ag₂PbO₂ to (2) PbCO₃ + 2PbCO₃PbO + Ag and (3) PbCO₃ + Ag + Pb with increasing the graphite content. Ag₅Pb₂O₆ is synthesized directly by mechanical milling with a simple solid-state reaction of Ag₂O and PbO₂. The structure, thermal and electric properties of silver-lead oxides are characterized by means of X-ray diffraction, scanning electron microscope, a differential scanning calorimeter analysis and DC resistivity measurements. Strengthening the degree of disorder through mechanical milling and/or doping the lead oxide into Ag₅Pb₂O₆ causes the conductivity transition from metallic to semiconducting behavior, while decreasing the degree of disorder by annealing and the segregation of the lead oxide from the solid solution leads to a reverse transition.     

Phase equilibria in the Ag<Subscript>2</Subscript>Se-As<Subscript>2</Subscript>Se<Subscript>3</Subscript>-Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> system

We have studied phase equilibria in the pseudoternary system Ag₂Se-As₂Se₃-Bi₂Se₃ and constructed the 300-, 600-, and 800-K isothermal sections, a number of partial phase diagrams, and the liquidus projection of this system. The AgAsSe₂-AgBiSe₂ and As₂Se₃-AgBiSe₂ joins are shown to be pseudobinary, and the Ag₃AsSe₃-AgBiSe₂ and AgAs₃Se₅-AgAsSe₂ joins are pseudobinary below the liquidus. Several in- and univariant peritectic, eutectic, and eutectoid equilibria and a broad region of AgBiSe₂-based solid solutions are identified. The homogeneity region of the AgBiSe₂-based phase has the largest extent along the AgAsSe₂-AgBiSe₂ join: 40 mol % (650 K) for the high-temperature form of AgBiSe₂ and 20 mol % (300 K) for its low-temperature form.     

Verres formes par les oxysulfures de terres rares Ln2O2S

Glass formation in the Ln₂O₂S-Ga₂S₃ systems (Ln = La to Nd). Preparations. Extent of the glassy regions as a fonction of the R.E. content and of the nature of the R.E. : Vitreous transition temperatures and crystallization temperatures. Microhardness. Optical properties.