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Combinatorial analysis of Ag–Pd alloy thin films shows the formation of a solid solution with the face‐centered cubic structure for all investigated alloy compositions. Using mixed matter theory and the high field model, oxide growth upon applying an anodic potential is indicated. Electrochemical impedance spectroscopy supports the idea of oxide formation based on a change in behavior correlated to a sharp increase in oxide formation as indicated by cyclic voltammetry measurements. After polarization at 4 V, a stable total impedance and increasingly less‐pronounced phase shift are detected in the frequency range of 100 mHz to 10 kHz, which encompasses the common range of application of active implantable medical devices (AIMD). Upon fitting the measured impedance data with the Randles circuit, capacitances are determined in the nF cm−2 range for the investigated alloys and attributed to the formed mixed oxide layer. Charge transfer resistances are found to be in the kΩ cm−2 range. No correlation between alloy composition and capacitance or resistance can be detected so far. These findings indicate a fundamental applicability of Ag–Pd alloys for use in AIMD. [ABSTRACT FROM AUTHOR]

Accurately acquiring crucial data on tube furnaces and real-time temperature monitoring of different temperature zones is vital for material synthesis technology in production. However, it is difficult to achieve real-time monitoring of the temperature field of tube furnaces with existing technology. Here, we proposed a method to fabricate silver (Ag) resistance temperature detectors (RTDs) based on a blade-coating process directly on the surface of a quartz ring, which enables precise positioning and real-time temperature monitoring of tube furnaces within 100–600 °C range. The Ag RTDs exhibited outstanding electrical properties, featuring a temperature coefficient of resistance (TCR) of 2854 ppm/°C, an accuracy of 1.8% FS (full scale), and a resistance drift rate of 0.05%/h over 6 h at 600 °C. These features ensured accurate and stable temperature measurement at high temperatures. For demonstration purposes, an array comprising four Ag RTDs was installed in a tube furnace. The measured average temperature gradient in the central region of the tube furnace was 5.7 °C/mm. Furthermore, successful real-time monitoring of temperature during the alloy sintering process revealed approximately a 20-fold difference in resistivity for silver-palladium alloys sintered at various positions within the tubular furnace. The proposed strategy offers a promising approach for real-time temperature monitoring of tube furnaces. [ABSTRACT FROM AUTHOR]

The electrocatalytic activity of electrode materials synthesized by anodic selective dissolution of Ag–Pd alloys based on silver (4 and 8 at % Pd) was studied. Kinetic regularities of formic acid electrooxidation on palladium and anodically modified Ag–Pd alloys in an acidic sulfate solution have been established. The process includes the diffusion of HCOOH, its dissociative chemisorption, and irreversible ionization of atomic hydrogen. The conditions for formic acid anodic oxidation on Pd and Ag–Pd alloys were determined depending on the composition of the electrode system and the mode of preliminary electrochemical modification (selective dissolution) of the alloy using transient electrochemical measurements. The role of the surface development of an alloy in the kinetics of anodic degradation of formic acid was revealed. It was shown that the selective dissolution of Ag–Pd alloys contributes to a noticeable increase in the rate of the kinetic stage of atomic hydrogen ionization. A necessary condition for the activation of the anodically modified alloy in relation to the electrooxidation of HCOOH is the excess of both critical parameters (charge and potential) corresponding to the onset of morphological development and phase transformations in the surface layer of the Ag–Pd systems. [ABSTRACT FROM AUTHOR]

Selected results of investigations focused on the changes to some mechanical properties of palladium and several palladium-based alloys caused by exposure to hydrogen have been collected and presented. The findings indicate that the mechanical properties of pure palladium are highly susceptible to alteration upon exposure to hydrogen. In the cases of alloying palladium with silver and copper, the alloys, as compared to palladium, appear to resist changes to mechanical properties. In the case of alloying palladium with manganese, the interesting order–disorder phenomenon plays an important role on the effects of hydrogen exposure on their mechanical properties. [ABSTRACT FROM AUTHOR]

Silver (Ag), palladium (Pd), and bimetallic silver-palladium (Ag-Pd) coatings were deposited on a mild steel surface by the co-sputtering method. The aim was to investigate and compare the corrosion behavior of Ag-Pd nano-coatings as well as the effect of increasing the weight ratio of Ag in the Ag-Pd alloy in the 3.5% NaCl solution. The corrosion protection performance and barrier protection properties were monitored using electrochemical impedance spectroscopy and potentiodynamic polarization. The surface of the coatings was characterized by scanning electron microscopy, atomic force microscopy, energy-dispersive x-ray spectroscopy, and field-emission scanning electron microscopy. The results of corrosion measurements revealed a relationship between silver wt.% and corrosion resistance. Also, all the coatings had protective effects and barrier properties on the mild steel in the corrosive solution. The best efficiency was observed in silver monometallic coating with 54 nm thickness. [ABSTRACT FROM AUTHOR]

Hydrogen, deuterium, and helium gases were separately cycled through a Johnson-Matthey purifier containing coiled palladium silver alloy tubing: Pd25Ag (75 wt% Pd and 25 wt% Ag). During the cycling of D 2 gas, evidence of anomalous heat production was observed. However, during the cycling of H 2 and He, very little (H 2) or no (He) unusual heat events were observed. After cycling the D 2 gas through the coiled tubing for several months, Pd25Ag samples showed an increase in Cu and Fe compared with the amounts in unexposed Pd25Ag. Chromium, manganese, and zinc were detected in gas-cycled Pd25Ag samples, whereas they were not detected in unexposed Pd25Ag samples. In particular, Zn was present in the gas-cycled Pd25Ag material in larger quantities than either Cr or Mn. Although a small amount of Cu was present in the Pd25Ag coil before the D 2 gas cycling, 7 times more was present after the cycling. Multiple material characterization techniques were used to obtain both pre-test and post-test elemental composition. The results indicate that novel post-test elements, primarily on the surface, were created by unknown nuclear mechanisms at low energy. • Surface transmutations occurred in deuterium gas cycling experiments of PdAg tubes. • Zn and Cr not present in PdAg before experiments were observed on PdAg afterwards. [ABSTRACT FROM AUTHOR]

We introduce the class of discrete silver(I)-palladium(II)-oxo nanoclusters with the preparation of {Ag4Pd13} and {Ag5Pd15}. Both polyanions represent the first examples of noble metal-capped polyoxo-noble-metalates in a fully inorganic assembly, featuring an unprecedented host-guest mode containing hetero- and homometallic Ag-Pd and Ag-Ag bonding interactions. Comprehensive theoretical calculations suggest that the Ag-Pd metallic bonds originate partially from surface confinement of AgI guest ions onto the anionic polyoxopalladate host that is induced by strong electrostatic forces. This work opens the field of fully inorganic silver-palladium-oxo nanoclusters, which can be considered as discrete mixed noble metal precursors for the formation of monodisperse core-shell nanoparticles, with high relevance for catalysis. [ABSTRACT FROM AUTHOR]

Highly dispersed bimetallic AgPd nanoparticles with different composition have been successfully deposited on the metal-organic frameworks (ZIF-8) by using a simple liquid impregnation method. The resultant catalysts are composition dependent toward dehydrogenation of formic acid, while Ag 18 Pd 82 @ZIF-8 exhibits exceedingly high catalytic activity, with the turnover frequency (TOF) value of 580 h −1 , and 100% hydrogen selectivity at 80 °C. [ABSTRACT FROM AUTHOR]

Silver-palladium alloys have various industrial applications, such as in hydrogen permeation and hydrogen storage materials. The objective of the present study is to determine experimentally the thermodynamic properties of solid state silver-palladium alloys in low temperatures. Thermodynamic measurements of silver-palladium alloys have been performed over a temperature range of 450-750 K by the electromotive force method with superionic conductor AgI as the solid electrolyte. The activity and partial molar Gibbs energy of silver were obtained for Ag-Pd alloys over the whole composition range, and the thermodynamic properties of palladium were calculated using the Gibbs-Duhem equation. The results show that activities of silver exhibit fairly large negative deviations over most of the composition range, and the activities of palladium are characterized by both negative and positive deviations from the ideal Raoultian behavior. The results also show the minimum integral enthalpy of mixing of Ag-Pd alloys to locate at around 60 at.% Ag. [ABSTRACT FROM AUTHOR]

Abstract: An Ag-controlled co-plating method was developed for the preparation of palladium/silver alloy membranes on porous tubular alumina supports. By controlling the feed rate of Ag to the Pd bath, the concentration of the silver in the plating bath was restricted during the course of plating. As a result, preferential deposition of silver at the beginning was suppressed and uniform dispersion of silver inside the membrane with silver composition in the desired range was achieved. Ultrathin (∼2.5 μm) PdAg alloy membranes with uniform silver composition of ∼25% were successfully obtained. The membrane showed a hydrogen permeance of 0.88 mol m−2 s−1 and pure-gas H2/N2 selectivity of 2140 at 823 K with ΔP = 100 kPa. Only one hydride phase existed in the studied temperature range from 373 to 823 K with . Direct comparisons with the conventional simply-mixed co-plating method showed that membranes made by the novel Ag-controlled co-plating method had much more uniform silver distribution, smoother surface, denser membrane structure, higher utilization rate of metal sources, and shorter alloying time. [Copyright &y& Elsevier]

Small-sized monodisperse Pd-Ag alloy nanocrystals (NCs) are synthesized via a solid-liquid and solid-solid phase chemical route, i.e., sequential reduction of Pd(NO3)2 and AgNO3 solid precursors in the liquid mixture of dodecylamine and 1-octadecene, followed by fusion of formed Pd and Ag NCs at 250 °C. By controlling the addition sequence and molar ratio of the metallic precursors, a series of Pd-Ag alloy NCs, including Pd5Ag, Pd2Ag, PdAg, PdAg2, and PdAg5, is obtained. The alloy NCs are highly crystallized and exhibit a strong atomic ensemble in addition to component-dependent electronic effects. Pd2Ag NCs have unique structure and electronic properties, showing a much faster electron transfer process at a modified glassy carbon electrode interface compared with that of other alloys. Therefore, the Pd2Ag NCs are chosen as the electrocatalyst to evaluate the performance of Pd-Ag nanoalloy and a novel non-enzymatic glucose biosensor is fabricated. The biosensor exhibits an acceptable reproducibility, a good stability and low interferences, which can be used to examine glucose in clinic blood serum samples. This work provides a simple multiphasic reaction system to synthesize binary alloy NCs with well-controlled componential ratio and opens the avenue to utilize them in biosensing or other advanced technological fields. [ABSTRACT FROM AUTHOR]

Abstract: The mechanism of the oxidation of glycerol to dihydroxyacetone over Pd–Ag catalysts was discussed. Characterization results suggest that the metal composition of the surface of the crystalline Pd–Ag alloy particles is almost the same as the bulk composition. The synergetic effects of Pd and Ag appear on the oxidation of the secondary OH group of vic-diols. The reaction order with respect to glycerol concentration over Pd–Ag/C was zero, suggesting the strong interaction between glycerol and the catalyst surface. The reaction order with respect to O2 pressure was 0.4, suggesting that the rate-determining step is the reaction involving oxygen species. These reaction trends and characterization results support the mechanism where the terminal OH group of glycerol is adsorbed on the Ag site and the neighboring secondary OH group (CH–OH) is attacked by the oxygen species dissociatively adsorbed on the Pd site. [Copyright &y& Elsevier]

Abstract: Thin PdAg alloy membranes with 20–25% Ag are being developed for hydrogen separation technology. Despite many investigations on such membranes as well as representative experimental and theoretical model systems, unresolved issues remain concerning the effect of the alloy surface structure and composition on adsorption and vice versa. Therefore, the interaction between hydrogen, carbon monoxide or oxygen with the surface of a PdAg model alloy was studied using periodic self-consistent density functional theory (DFT-GGA) calculations. In particular, the adsorption structure, coverage dependence and possible adsorption-induced segregation phenomena were addressed using Pd3Ag(111) model surfaces with varying degrees of surface segregation. In agreement with previous experimental and theoretical investigations, we predict Ag surface termination to be energetically favorable in vacuum. The segregation of Ag is then reversed upon adsorption of H, CO or O. For these adsorbates, the binding is strongest on Pd three-fold hollow sites, and hence complete Pd termination is favored at high coverage of H or CO, while 25% Ag may remain under oxygen because of the lower O-saturation coverage. CO adsorption provides a somewhat stronger driving force for Pd segregation when compared to H, and this may have implications with respect to permeation properties of PdAg alloy surfaces. Our predictions for high coverage are particularly relevant in underlining the importance of segregation phenomena to the hydrogen transport properties of thin PdAg alloy membranes. [Copyright &y& Elsevier]

Abstract: The existing assessment of thermodynamic and phase equilibrium data in the Ag–Pd system was revised on the basis of calorimetric data for liquid Ag–Pd alloys published recently in the literature and on new determination of liquidus and solidus temperatures and activity data for Ag in liquid phase, using differential scanning calorimetry (DSC) coupled with Knudsen cell mass spectrometry (KC/MS). A substantially narrower liquid/fcc two-phase field in phase diagram as well as new non-ideal activity data were revealed. [ABSTRACT FROM AUTHOR]

To achieve cost reduction in multi-layer ceramic capacitors and actuators, which use a silver-palladium alloy as internal electrode, the trend is to use alloys with the highest silver content possible. This requires ceramic materials which must be sintered at a relative low temperature. Goal is to avoid much diffusion of silver into the ceramics. Analysis of the composition of the electrode in multilayer components is a good tool to investigate the diffusion of silver during sintering. Analysis of various multi-layer components with different silver-palladium alloys shows that the diffusion of silver during sintering is dependent on the difference between the sintering temperature of the multilayer component and the melting point of the silver-palladium alloy used. Diffusion of silver into the ceramics during sintering is negligible when this difference is at least 100 °C. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that silver segregates to the surface of pure and ideal Pd–Ag alloy surfaces. By first-principles band-structure calculations it is shown in this paper how this may be changed when hydrogen is adsorbed on a Pd–Ag(111) surface. Due to hydrogen binding more strongly to palladium than to silver, there is a clear energy gain from a reversal of the surface segregation. Hydrogen-induced segregation may provide a fundamental explanation for the hydrogen or reducing treatments that are required to activate hydrogen-selective membrane or catalyst performance. [Copyright &y& Elsevier]

We have used IR spectroscopy of adsorbed CO to study the effect of the method for preparation of silver-palladium catalysts on a TiO2 substrate and exposure to an oxidizing or reducing gaseous atmosphere on the state of Ag and Pd centers. We have shown that as a result of the metal-support interaction, the reducibility of the Ag and Pd particles is increased, which leads to a change in their adsorption and catalytic properties. [ABSTRACT FROM AUTHOR]