Diffusion Coefficient Of Silver Research Articles

Insights on the effect of process conditions on the optical properties of silver ion exchanged soda-lime silicate glass

The effects of ion exchange time and temperature on the optical properties and plasmonic response of silver ion exchanged soda-lime silicate glass were investigated using scanning electron microscopy (SEM) in energy dispersive spectrometry (EDS) configuration, m-lines spectroscopy, photoluminescence (PL) spectroscopy, and UV–visible absorption spectroscopy. SEM analyses in EDS mode provided profiles of silver oxide molar concentration. These profiles were directly correlated to the silver diffusion coefficient using an adjustment procedure. The effective indices of ion exchanged glasses measured by the standard prism coupling technique (m-lines) allowed access to refractive index distributions in ion exchange regions. These ion-exchanged glasses underwent evaluation to determine their potential suitability for use in multimode planar systems. The PL results acquired after ion exchange demonstrated that the creation of Ag0 atoms from Ag+ ions was responsible for the decline and quenching of PL intensity at ion exchange times and temperatures increase. Silver nanoparticles were generated in the samples subjected to ion exchange at 480 °C without the need for post-exchange treatments. The emergence of the surface plasmon resonance band around 427 nm in the optical absorption spectra confirmed the formation of Ag nanoparticles in annealed glasses. Estimates of the UV–visible absorption spectra indicated an average size of silver nanoparticles ranging from 1.8 to 2.4 nm.

Mechanistic calculation of the effective silver diffusion coefficient in polycrystalline silicon carbide: Application to silver release in AGR-1 TRISO particles

The silicon carbide (SiC) layer in tristructural isotropic (TRISO) fuel particles serves as a barrier to prevent the escape of fission products produced and not retained in the fuel kernel. The release of silver (Ag) is a concern due to the long half-life of the 110mAg isotope. However, accurately determining the fission gas release rate requires knowing the diffusion coefficient through the SiC layer. In this study, we leverage atomistic calculations of Ag diffusivity in SiC bulk and grain boundaries (GBs) to develop a mesoscale effective Ag diffusion coefficient (Deff) in SiC. Since GBs serve as pathways for Ag diffusion, Deff is defined as a function of temperature and microstructure variables. In particular, the size of SiC grains in the direction perpendicular to diffusion is shown to significantly affect Ag diffusion. The prediction of the mechanistic, mesoscale approach falls within one order of magnitude of empirical values. The temperature and microstructure-dependent effective Ag diffusivity in SiC is implemented in the fuel performance code Bison with a correction factor to predict Ag release from AGR-1 TRISO fuel particles. We hereby quantify the impact of SiC grain size on Ag release and improve Bison’s predictions.

A first-principles study of the temperature-dependent diffusion coefficients of silver in the thermoelectric compound PbTe

PbTe-based compounds establish an important class of thermoelectric (TE) materials due to their relatively high thermal-to-electrical energy conversion efficiency at the mid-temperature range (600 – 800 K). The Pb-Te-Ag system is of prime interest due to its potential of forming Ag-rich precipitates dispersed in the PbTe-matrix. Investigation of the microstructure evolution of this system enables us to predict the applicability regime of this system in service temperatures, and this involves both thermodynamic and kinetic aspects. Herein, we apply first-principles calculations to evaluate the diffusion coefficients of Ag in a PbTe matrix. Based on unique combination between calculations of point defect formation energies, electronic density of states (DOS), and electron localization function (ELF), we conclude that diffusion of Ag in PbTe in the interstitial mechanism is preferable compared to the vacancy or substitutional mechanism. We determine both the activation energy for diffusion and the pre-exponential diffusion coefficient for an interstitial mechanism, applying the transition state theory (TST), to be 1.08 × 10−5 cm2·s−1 and 52.9 kJ·mole−1, respectively. This study provides us with practical tools to evaluate the kinetics of phase transformations in these compounds by improving our ability to control nucleation and growth of Ag-rich precipitates in PbTe. This, eventually, provides us with predictive information on the thermal stability of PbTe-based compounds.

ICP-MS measurement of silver diffusion coefficient in graphite IG-110 between 1048K and 1284K

Silver-110m has been shown to permeate intact silicon carbide and pyrolytic carbon coating layers of the TRISO fuel particles during normal High Temperature Gas-Cooled Reactor (HTGR) operational conditions. The diffusion coefficients for silver in graphite IG-110 measured using a release method designed to simulate HTGR conditions of high temperature and flowing helium in the temperature range 1048–1253 K are reported. The measurements were made using spheres milled from IG-110 graphite that were infused with silver using a pressure vessel technique. The Ag diffusion was measured using a time release technique with an ICP-MS instrument for detection. The results of this work are:DAg,IG−110=(6.6×10−4m2s)exp(−1.74×105JmolRT)The measured activation energy of 174 kJ/mol compares well with the range of values [154–193 kJ/mol] reported in the literature for LTI pyrocarbon. The measured pre-exponential D0 value of 6.60 × 10−4 m2/s is similar to the value of 5.3 × 10−4 m2/s reported for Russian LTI pyrocarbon.

Quantitatively in Situ Imaging Silver Nanowire Hollowing Kinetics.

We report the in situ investigation of the morphological evolution of silver nanowires to hollow silver oxide nanotubes using transmission X-ray microscopy (TXM). Complex silver diffusion kinetics and hollowing process via the Kirkendall effect have been captured in real time. Further quantitative X-ray absorption analysis reveals the difference between the longitudinal and radial diffusions. The diffusion coefficient of silver in its oxide nanoshell is, for the first time, calculated to be 1.2 × 10-13 cm2/s from the geometrical parameters extracted from the TXM images.

Silver diffusivity measurement in ZrC with SIMS to study the release behavior of 110mAg for nuclear fuel applications

Recently, the diffusion coefficient of silver (Ag) in zirconium carbide (ZrC) at 1500 °C was determined to help elucidate the diffusive behavior of radioactive 110mAg in the ZrC coating of the tri-structural isotropic (TRISO) nuclear fuel particle. This study was conducted using a recently developed diffusion experimental technique, known as the encapsulating source method. To verify the validity of this experimental method, modifications to the original experimental design have been made within the domain of this method. Primarily, the ability to retrieve the ZrC disk made it possible to create depth profiles using secondary ion mass spectrometry (SIMS) for more precise depth profiling of Ag concentration in ZrC. Applying this improved experimental design, a sample was fabricated and diffusion annealed at 1500 °C for 2 h. Finally, silver concentrations on the ZrC disk were measured using SIMS. Consequently, the diffusion coefficient of Ag in ZrC0.95 at 1500 °C was experimentally determined to be about 1.7 × 10−17 m2/s, remarkably consistent with the previously reported value of 2.8 × 10−17 m2/s, also obtained by means of the encapsulating source method. This proves that the encapsulating source method is a reliable experimental technique to determine the Ag diffusivity in ZrC.

Chemical sensors for determination of thallium ions with membranes based on TlI–Ag2S–As2S3: Radiotracer, solid-state, and analytical studies

A series of chalcogenide glasses of various compositions, based on the TlI–Ag2S–As2S3 system, were prepared. The conductivity parameters and diffusion coefficients of silver and thallium radiotracers in the glass samples were determined. Chemical sensors with membranes of four glass compositions were prepared, and their analytical characteristics (sensitivity, selectivity, detection limit) were studied. Correlation between the ionic conductivity parameters of the ion-sensitive membranes and the analytical characteristics of chemical sensors for thallium ions in solutions was found.

Suppression of Silver Diffusion in Borosilicate Glass‐Based Low‐Temperature Cofired Ceramics by Copper Oxide Addition

The silver diffusion behavior in the low‐temperature cofired ceramic (LTCC) comprising of borosilicate glass and alumina was investigated in this work. Transmission electron microscope (TEM) analysis revealed that silver ions diffused into LTCC materials through the glass phase. The addition of copper oxide in the LTCC materials can suppress the silver diffusion during the sintering process because of the enhanced crystallization of borosilicate glass, which leads to the quick increase in glass viscosity and retards the silver diffusion. Thermal dynamic analysis confirmed that the diffusion coefficient of silver in the copper‐oxide‐modified LTCC materials was largely reduced.

Holographic investigation of silver electromigration in nano-sized As2S3 films**This work is dedicated to the 90th anniversary of the birth of Academician Jordan Malinowski.

Holographic gratings with a diffraction efficiency (DE) greater than 8% and a spatial resolution of 2237 mm−1 are recorded in very thin As2S3 films with a thickness of 100 nm. Silver photo-diffusion is observed during the holographic recording process while applying a corona discharge. We use the method of holographic grating relaxation spectroscopy (forced Rayleigh scattering) based on the evanescent waves to determine that the silver diffusion coefficient in the thin As2S3 film is in the range of (0.9–10.3) × 10−13 cm2 s−1 depending on the corona charge polarity.

Solid-state field-assisted silver diffusion in (TeO2)0.6(WO3)0.25(La2O3)0.05(Na2O)0.1 glass

Silver-doped layers have been produced in (TeO2)0.6(WO3)0.25(La2O3)0.05(Na2O)0.1 (TWLN) glass by solid-state field-assisted diffusion. The silver concentration profile in the glass has been determined by secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectrometry (RBS). The Matano-Boltzmann method applied to thermally activated diffusion indicates that the silver diffusion coefficient in the glass is a weak function of silver concentration. We carried out modeling of silver concentration profiles in the doped layer of the TWLN glass after solid-state field-assisted diffusion. Good agreement of the theoretical fit and experimental data suggests that the model chosen can be used to describe solid-state field-assisted diffusion of silver ions in TWLN glasses. Using RBS data, we have quantitatively estimated the surface density of silver atoms after field-assisted diffusion. Combining SIMS and RBS, we were able to assess the absolute silver concentration depth profile. Our results demonstrate that field-assisted diffusion, a simple and effective procedure for doping optical glasses, can be used to produce planar waveguide structures based on the tellurite glass studied here.

Graded index waveguide elaboration by silver–sodium or silver–lithium ionic exchange for various glass compositions

The synthesis of planar optical component has a particular interest in the manufacturing of complex waveguides as multiplexer, coupling unit or optical fiber connector. Most important criteria of choice of these components are the network losses and the Δ n value of the refractive index variation between the treated glass and the non treated part and the operating life. In this way ionic exchange is a very efficient method to achieve the realization of planar waveguides. Thus, it is the optical index changing between the silver doped glass and the matrix which determines the allowed trapped mode. The choice of substrate composition (glass) which will contain silver ions and the ionic exchange conditions are fundamental criteria in the manufacturing of these components. In this paper, we present three characterization methods allowing the understanding of the exchange mechanisms according to the silicate glass composition selected: Scanning Electron Microscopy measurement (SEM) allows the evaluating of the silver concentration profile and the determination of the silver diffusion coefficient after a fitting procedure, UV/Visible Absorption gives the absorption spectra after the ionic exchange and the identification of a potential Surface Plasmon Resonance (SPR) linked to silver nanoparticle formation which would entail linear losses and infrared spectroscopy gives refractive index thanks to the permittivity value obtained above 1250 cm −1 (below 8 μm) in the glass electronic transition domain. Finally, we show the effect of the alkaline rate and other glass compounds about the optical properties for obtaining waveguide.

Solid state field-assisted diffusion of silver in multi-component tellurite glasses

In this work, we have prepared Ag-doped multi-component tellurite glasses by solid state electric field-assisted (SSFA) diffusion. The silver concentration profiles after SSFA diffusion were measured by secondary ion mass spectrometry (SIMS). It is found that the SIMS depth profiles can be well fitted by a classical erfc-like function. And the concentration dependence of silver diffusion coefficient has been investigated by using the Boltzmann–Matano analysis. The refractive index after SSFA diffusion is increased by ∆n=0.025 (λ=1550nm) without the glass surface being contaminated. Our results demonstrate that SSFA diffusion is a well controllable, non-destructive method to fabricate planar waveguides based on our newly developed tellurite glasses.

Computer simulation of ionic transport in silver iodide within carbon nanotubes

Filling of carbon single-wall nanotubes (SWNTs), of diameter d = 11.5–15 Å, by silver iodide from the melt is modeled by molecular dynamics. Formation of AgI inorganic nanotube (INT) structures in the SWNTs on cooling, and ion diffusion in AgI within the tubes (AgI@SWNT) at 500–1200 K are studied. Dependence of AgI@SWNT structure on carbon SWNT geometry is examined. For d ≤ 14.2 Å, a single-wall AgI INT is formed within the carbon tube, with structure (geometry) depending on d; in wider tubes, there are extra silver and iodine ions in the central region. The calculated diffusion coefficients of silver and iodine ions and their diffusion activation energies depend on the nanotube geometry. Ion mobilities within carbon SWNTs are significantly lower, and diffusion activation energies, higher than in the bulk phase of AgI, especially in narrow tubes. In the (11,11) carbon SWNT, the widest among those simulated, the activation energy for silver ion diffusion becomes close to the “bulk” value, while for iodine ions, larger in size, the difference remains.

Diffusion coefficient, activation energy and the effect of Ag-doping on some physical properties of silver doped Bi 1.8Pb 0.4Ca 2.2Sr 2Cu 3O x

The aim of the present study is to investigate the effect of diffusion-doped silver on some physical properties of Bi 1.8Pb 0.4Ca 2.2Sr 2Cu 3O x superconducting samples and to calculate the diffusion coefficient and the activation energy of silver. The present work consists of three parts: (a) optimization of annealing temperature, (b) the effect of Ag diffusion-doped on microstructure and superconducting properties of Bi(Pb)CaSrCuO, and (c) calculation of diffusion coefficient of silver. First, to investigate the optimum annealing temperature we prepared Bi 1.8Pb 0.4Ca 2.2Sr 2Cu 3O x ceramic superconductors annealed at 830, 835, 840, 845, and 850 °C using the solid state reaction method. The investigations consist of XRD, SEM, dc resistivity, and transport critical current density measurements. The highest T c and J c values were observed for the sample annealed at 840 °C for 48 h (B840). Large grain size, denser surface, and high volume fraction of the high- T c phase were obtained for the sample B840. The diffusion doping of Bi 1.8Pb 0.4Ca 2.2Sr 2Cu 3O x by silver increased the critical current density from 123 to 696 A/cm 2 and the transition critical temperature by about 3 K compared with the undoped sample. Ag-doping increased the amount of high- T c phase and improved the surface morphology. It also caused an increase of the lattice parameter c by an amount of 0.15%. The temperature dependence of the silver diffusion coefficient in the range 600–800 °C is described by D=2.9×10 −4exp(−1.05 eV/ k B T). Possible reasons for the observed improvement in the structural and superconducting properties of the samples due to silver diffusion are discussed.

Silver Self-Diffusion in Al<sub>2</sub>O<sub>3</sub>/QE22 Magnesium Alloy Matrix Composite

Self-diffusion of 110mAg has been investigated in fiber reinforced QE22 magnesium alloy matrix composite. Short Saffil fibers (97% -Al2O3 + 3% SiO2) were used as reinforcement. The diffusion measurements were carried out in the temperature interval 648 – 728 K by serial sectioning method. The volume diffusion coefficients Dv (alloy without reinforcement) and the effective diffusion coefficients Deff (alloy with reinforcement) were obtained by analysis of the penetration curves. The silver diffusion coefficient in the interface boundary matrix/Saffil Di was also estimated. The temperature dependence of volume diffusion coefficients Dv was compared with previous data measured using 65Zn in the same alloy and with literature data for Zn impurity diffusion in Mg single crystal. It was observed, that the temperature dependence of both Deff and Di was significantly non-linear in the measured temperature interval. This behavior supports previous observations with zinc diffusion in the same alloy.

Formation of nanoclusters through silver reduction in glasses: The model

The system of equations describing the formation of silver nanoclusters through the reduction of ionic silver in the course of thermal processing of silver containing glasses in hydrogen is formulated and solved numerically. The processes of the clusterization of neutral silver within the glass and at the surface, and the growth of the nanoclusters are modeled with the account of different mobilities and concentrations of the participating species. The influence of the variation of diffusion coefficients of Ag 0 atoms, Ag + and H + ions as well as concentration of Ag + ions in the glass matrix. It is shown that concentration distribution of neutral hydrogen (H 0) strongly depends on the relationship between concentration of Ag + ions ( C Ag + ) and concentration of neutral hydrogen at the glass surface ( C 1), as well as between diffusion coefficients of silver and hydrogen ions. When D Ag + ≪ D H + and C Ag + ≫ C 1, the total hydrogen concentration profile ( C Htot = C H 0 + C H + ) is defined by silver ion diffusion coefficient D Ag + . Concentration of neutral silver, C Ag 0 , represents a bell-shaped depth distribution, whose maximum moves to the depth linearly with t 1/2 with the rate depending both on the diffusion coefficient of neutral silver, D Ag 0 , and neutral hydrogen, D H 0 . It is shown that the depth position of the maximum coincides with the frontier of the layer filled by clusters. The kinetics of the cluster radius growth in the bulk of the glass also depends both on D Ag 0 and D H 0 and essentially deviated from the kinetic law R 2 ∼ t predicted earlier in the assumption of time-independent oversaturation. The kinetics of Ag cluster growth on the glass surface turned out independent of the D Ag0 diffusion coefficient.

The effect of duration of diffusion on Ag diffusion coefficients in YBa 2Cu 3O 7

The Ag diffusion in superconducting YBa 2Cu 3O 7 (YBaCuO) ceramic has been studied over the duration of the diffusion range 5–24 h in the temperature range 700–850 °C by the energy-dispersive X-ray fluorescence (EDXRF) technique. For the excitation of silver atoms, an annular Am-241 radioisotope source (50 mCi) emitting 59.543 keV photons was used. The temperature dependences of silver diffusion coefficients in grains ( D 1) and over the grain boundaries in the range 700–850 °C ( D 2) are described by the relations D 1=1.4×10 −2 exp[−(1.18±0.10)/kT] and D 2=3.1×10 −4 exp[−(0.87±0.10)/kT].

Silver diffusion and defect formation in Si (1 1 1) substrate at elevated temperatures

Silver diffusion into Si (1 1 1) substrate at moderate temperatures (400–700 °C) has been studied by the use of secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), and optical etch pit observations. The diffusion coefficient of silver has been estimated. Silicon crystallographic defects start to form at the silicon surface when the annealing temperature is above 450 °C. This phenomenon is related to the silver diffusion. The activation energy of the defect formation is approximately 2.46±0.26 eV . It is higher than the reported activation energy (1.59 eV) for silver diffusion at higher temperature (1100–1300 °C). The possible mechanisms are discussed to account for the experimental results.

Silver and platinum diffusion in alumina single crystals

Silver and platinum diffusion in α-alumina single crystals have been investigated using SIMS technique in 800–1150°C and 900–1200°C temperature ranges. Previous radiotracer measurements yielded higher diffusion coefficients of silver than those presented here. This difference is attributed to the resolution differences between the SIMS and the radiotracer techniques. The former allows us to obtain the bulk diffusion coefficients while the latter the dislocation ones. Silver and platinum diffusion coefficients are one to two orders of magnitude higher than those of chromium and aluminium. It is suggested that such a difference can be related to the ability of low valency cations to occupy interstitial sites, allowing a proportion of the noble elements to dissolve in alumina through the self-compensating mode. Hence, a diffusion mechanism involving correlated jumps of interstitial and substitutional foreign atoms (Ag, Pt) is proposed.

Study of silver and copper diffusion in p-type Hg0.3Cd0.7Te and CdTe by capacitance measurements

A procedure to determine the diffusion coefficients of metallic impurities in p-type semiconductors is presented. This method, which rests on the analysis of the capacitance transient curve C(t) at various temperatures has been applied to the study of copper and silver diffusion in p-type Hg0.3Cd0.7Te and CdTe crystals. The as-found diffusion coefficients are in good agreement with existing results. The large activation energy of the silver diffusion coefficient, at low temperature, might come from the formation of a donor–acceptor complex.