Ag-Cd Alloys Research Articles

The self-assembled AgCd nanoclusters: A novel plutonium separating material

• Novel alloy clusters, i.e. Ag 32 Cd 12 (SR) 36 and Ag 32 Cd 12 (SR) 36 are prepared. • The Ag 32 Cd 12 clusters show high efficiency and selectivity for Pu seperation. • The oxygen-rich environments by self-assembly of Ag 32 Cd 12 is pivotal. The selective sorption of plutonium from radioactive wastes is of high economic and strategic importance. Herein, the self-assembled Ag 32 Cd 12 (SPh 4− OMe) 36 (SPh 4− OMe = 4-methoxyphenylthiolate) have been developed as a powerful plutonium separating material. Compared to its non-assembled analogue of the trimetallic Au 4 Ag 28 Cd 12 (SPh 4− OMe) 36 cluster, the bimetallic AgCd alloy cluster shows excellent binding affinity and selectivity to 239 Pu(IV) over the other radionuclides (such as 237 Np(V), 241 Am(III), etc). The maximum value of the distribution coefficient (Kd) and separation factors reaches 3 × 10 4 mL g −1 and 7.52 × 10 3 at pH = 3. The significantly higher selectivity of the AgCd clusters than that of the reported solid-phase materials might originate from the regular, inter-cluster assembly via formation of the cyclic …Ag-S…Ag-S… interactions in the exterior AgS 3 motifs.

Determining the boundaries of second-type phase transitions in Ag–Mg–Cd alloys by means of diffusion couples

The interaction between elements in the transition zones of diffusion couples Mg + AgCd–alloy are studied. Isothermal sections of the Ag–Mg–Cd ternary system at 573 K are constructed. The existence of a Heusler phase based on H–Ag2MgCd compound is found in the field of the solid β′-solution. It is shown that the interdiffusion of components prevents the formation of ordered phases in the transition zones of bimetals, allowing us to determine the boundaries of second-type phase transitions in solid solutions.

Rudimentary simple, single step fabrication of nano-flakes like AgCd alloy electro-catalyst for oxygen reduction reaction in alkaline fuel cell

In this work, for the first time, we report rudimentary simple, single step fabrication of an electro-catalyst based on AgCd alloy nanoparticles with flakes like geometry which shows highly efficient activity towards oxygen reduction reaction (ORR). A simple potentiostatic deposition method has been employed for co-depositing AgCd alloy nanostructures with flakes like shapes along with dendrites on the surface of carbon fibre paper. The chemico-physical properties of the catalyst are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDXS). Electro-catalytic activity of AgCd alloy based electro-catalyst towards ORR is studied in alkaline medium by cyclic voltammetry and rotating ring disk electrode (RRDE) technique. Electrochemical in-situ FTIR measurements are also performed to identify the species generated during ORR process. Based on the results from electro-catalysis experiment, it is concluded that nano-alloyed AgCd electrodeposited on carbon paper shows excellent activity for ORR, following four electron pathways with H2O2 yield less than 15%. The combination of low cost of Ag and Cd, fast and facile method of its fabrication and higher activity towards ORR makes the AgCd electro-catalyst an attractive catalyst of choice for alkaline fuel cell.

Surface segregation of cadmium atoms at the interface of mechanically renewable Ag–Cd alloy electrode with surface-inactive electrolyte solution

The surface segregation of cadmium atoms at the interface of mechanically renewed electrodes of the Ag–Cd alloy (containing 1 at % Cd; the region of cadmium solid solutions in silver) with a surface-inactive electrolyte solution is studied in the potential range of ideal polarizability by means of impedance spectroscopy and cyclic voltammetry. It is shown that method of mechanic renewal makes it possible to obtain well reproducible data on the kinetics of electrode surface enrichment with atoms of cadmium which is the surface-active component of this alloy. As follows from the analysis of dependences of the electric double layer (EDL) capacitance on the potential (C vs. E curves) pertaining to different times after the electrode renewal, these dependences can be well described in terms of the model of capacitors connected in series (“the common dense layer”). Using this model, the dependences of the alloy surface coverage with cadmium atoms on the time of exposure of the freshly renewed electrode surface to the electrolyte solution are calculated. The mechanism of surface segregation of cadmium atoms is proposed. It allows the kinetics of relaxation processes that occur in the alloy surface layer to be consistently interpreted. The electrochemical data are supplemented and compared with the results of analysis of the surface composition and the data of the profile analysis over the depth of the same alloy at its interface with vacuum, performed by means of Auger electron spectroscopy.

Electrochemical synthesis of Cd–Ag bimetallic particles and the involved alloy formation

The formation of bimetallic Cd–Ag nanoparticles on vitreous carbon (VC) and the involved alloy formation have been studied by conventional electrochemical techniques and ex-situ atomic force microscopy (AFM). Both metals were deposited by sequential electrodeposition using single potentiostatic pulses. The AFM images of Ag deposits showed small differently sized Ag nanocrystallites uniformly distributed over the VC-substrate. This modified substrate was immersed in an electrolyte solution containing Cd2+ ions and bimetallic Cd–Ag particles were prepared by underpotential deposition (UPD) of Cd. The alloy formation phenomena observed previously during Cd UPD on massive Ag electrodes were found also in the case of Cd UPD on Ag nanoparticles. The desorption spectra in the system Cd/Ag (nanoparticles)/VC employing different polarization times, showed three desorption peaks associated with the dissolution of the Cd OPD and UPD deposits and an Ag–Cd alloy formed at low underpotentials, respectively. The electrochemical behavior of the bimetallic system was also studied applying other polarization routine designed for this purpose.

Fabricación y caracterización de materiales Ag-Cd/CdO producidos mediante incorporación de partículas de CdO en aleaciones Ag-Cd líquidas

In the present work it has been investigated the kinetic behavior of internal oxidation processes of strips of Ag-Cd/CdO materials fabricated by adding CdO particles (size of 5 and 20 μm) in liquid Ag-Cd alloys. It has been established the metallurgical mechanism that controls the formation of the thickness covered with CdO particles produced by internal oxidation of the Ag-Cd/CdO material. It has been developed, successfully, a metallographic preparation technique for characterizing the morphology, size and distribution of CdO particles produced by heat treatment of internal oxidation on the surface of each sample based on the distance from the original surface to the boundary of dispersed CdO particles. The material strips were sequentially roughed on its surface and the roughing thickness was measured in the cross section of each new surface to determine the number of particles per area and average particle size.

Analysis of Nonlinear Galvanostatic Oscillations in Ag-Cd Alloys Electrodeposition

Analysis of Nonlinear Galvanostatic Oscillations in Ag-Cd Alloys Electrodeposition

Synthesis and Electrochemical Study of Pd-Based Trimetallic Nanoparticles for Enhanced Hydrogen Storage

The success of acceptable hydrogen storage capacities on high surface area carbon materials at ambient temperature requires the combination of both physisorption and chemisorption. Despite the sole reliance on physisorption for hydrogen uptake in carbon, the dispersal of transition metal catalysts on carbon materials significantly enhances hydrogen uptake at ambient temperatures, via the process of hydrogen spillover. In the present study, hydrogen electrosorption onto activated carbon materials modified with different trimetallic dissociation catalysts (Pd–Ag–Cd) was investigated in an acidic medium using cyclic voltammetry and chronoamperometry. A significant synergistic effect on hydrogen storage was observed, which could be attributed to the electrochemical reduction of hydrogen ions initially at the Pd-based nanoparticles and the hydrogen surface diffusion subsequently to the activated carbon. Utilizing electrochemical methods, the optimized composition of the Pd–Ag–Cd alloys was determined to be Pd80Ag10Cd10, with the highest hydrogen sorption capacity at a hydrogen desorption charge of 18.49 C/cm2·mg. With increased kinetics and a decrease in the phase transition, the significant enhancement of hydrogen sorption, in comparison to the Pd–Ag and Pd–Cd bimetallic alloys, was further demonstrated, making Pd–Ag–Cd catalysts attractive for use as hydrogen dissociation catalysts for applications in both hydrogen purification and storage.

The Relation between the Surface Tension and the Bulk Properties of Diluted Silver Based Melts

The wettability of graphite by the Ag-M based (M: Cd, In Sn, Sb) liquid alloys was measured using the sessile drop method at a temperature interval of 1273 1473 K. Except the Ag-Cd alloys, the investigated systems exhibit worse wettability than that of Ag (host metal) melt, within the investigated temperature range. The compositional and concentration dependence of contact angle (Θ) exhibits similar trends, than the residual resistivity change measured in the same alloys in solid state. Nevertheless, the measured segregation effects during the solidification are not significant.

Oscillations and spatio-temporal structures during electrodeposition of AgCd alloys

During electrodeposition of cadmium both potentiostatic and galvanostatic oscillations are registered. Experiments under different hydrodynamic conditions show the possibility of formation/destruction of passive layers on the electrode surface, which besides the hydrogen evolution under limiting current density conditions could be an additional promoter of the oscillation behavior of the system. The duration of the observed galvanostatic potential oscillations decreases with increased current density, due to massive hydrogen evolution. XPS investigations confirm the existence of passive films at potentials corresponding to the onset of oscillations. Potential oscillations are observed again during electrodeposition Ag–Cd alloys at high current densities. They appear when the cadmium content in the deposits is more than 45wt.% and they have possibly the same origin as the oscillations during cadmium electrodeposition. The period and regularity of the oscillations depend on the current density, respectively on the cadmium content.At high cadmium content during alloy deposition, the formation of periodical structures consisting of different phases of the alloy is registered. The cadmium content of the different morphological areas of the patterns is almost identical. The XRD spectra of the obtained structured coatings suggest the existence of two textured phases, with a very strong preferred orientations of the crystallites in the direction 〈101〉 for the pure cadmium phase.

Microstructure and Hardness Property of Internally Oxided AgCdO Alloy

Microstructure and hardness property of AgCd alloy internally oxided at 973K for 1 h - 24 h with O2 atmosphere of 3 atm was investigated. Band typed CdO phase was formed at grain boundaries, and particle typed CdO phase was formed at grain interior. In this alloy, it was found that oxygen adsorpted at surface diffuses to interior through grain boundaries, and it subsequently diffuses into grain interior during internal oxidation. No Ag exduation was found in this alloy. The thickness of oxidized layer increased with increasing holding time at given temperature. Hardness of the oxidation zone was 125 ± 5 Hv, which value is higher two times than that of the oxidation free zone. The higher hardness of oxided region than the oxidation free zone was attributed to the dispersion strengthening by CdO particles.

Phase identification in electrodeposited Ag–Cd alloys by anodic linear sweep voltammetry and X-ray diffraction techniques

During electrodeposition of Ag–Cd alloy coatings phenomena of self-organization and formation of spatio-temporal structures can be observed. The difficulties in the determination of the local phase composition in the observed structures are mostly connected with the strong heterogeneity of the coatings consisting of several alloy phases. The results obtained with electrochemical techniques, such as anodic linear sweep voltammetry (ALSV) are compared with results obtained by X-ray analysis and SEM. In the proposed electrolyte for dissolution of Ag–Cd alloy coatings (12 M LiCl + 0.1 M HCl) the dissolution peaks of the pure metals, Ag and Cd, have a potential difference of about 700 mV. The peaks, corresponding to the alloy phases, are situated between the dissolution potentials of Ag and Cd, their height depending on the deposition current density, i.e. on the percentage content of the alloy. Different phases (Ag, Ag 3Cd, AgCd, AgCd 3 and pure Cd) are observed in the coatings deposited at different cathodic potentials. A good correlation between the XRD spectra of the Ag–Cd alloy coatings and the ALSV data obtained during their dissolution is established.

Alloy formation during the electrochemical growth of a Ag–Cd ultrathin film on Au(1 1 1)

The electrodeposition of a Ag/Cd ultrathin film on a Au(1 1 1) surface and the formation of a surface alloy during this process have been studied using classical electrochemical techniques and in situ Scanning Tunneling Microscopy (STM). The films were obtained from separate electrolytes containing Ag + or Cd 2+ ions and from a multicomponent solution containing both ions. First, the polarization conditions were adjusted in order to form a Ag film by overpotential deposition. Afterwards, a Cd monolayer was formed onto this Au(1 1 1)/Ag modified surface by underpotential deposition. The voltammetric behavior of the Cd UPD and the in situ STM images indicated that the ultrathin Ag films were uniformly deposited and epitaxially oriented with respect to the Au(1 1 1) surface. Long time polarization experiments showed that a significant Ag–Cd surface alloying accompanied the formation of the Cd monolayer on the Au(1 1 1)/Ag modified surface, independent of the Ag film thickness. In the case of an extremely thin Ag layer (1 Ag ML) the STM images and long time polarization experiments revealed a solid state diffusion process of Cd, Ag, and Au atoms which can be responsible for the formation of different Ag–Cd or Au–Ag–Cd alloy phases.

Specific Effect of Metal Cations on Stress Corrosion Cracking

The specific effect of certain cations on stress corrosion cracking (SCC) has been observed in many systems. In particular, Ag-Cd alloys are known to be susceptible to SCC in silver nitrate aqueous solutions, at the equilibrium potential of Ag. The aim of the present work was to find out if this is a more general phenomenon; and to this purpose, Ag-20Zn (at. pct) samples were tested in solutions containing Ag+ ions at the equilibrium potential of Ag. The SCC was found, and the crack propagation rate was a function of the Ag+ ion concentration.

급속응고한 Ag-Sn-In계 접점재료의 미세조직에 미치는 Te 의 영향

Contact material is widely used as electrical parts. Ag-CdO has a good wear resistance and stable contact resistance. But the disadvantages of Ag-Cd alloy are coarse Cd oxides and harmful metal, Cd. Then Ag-Sn alloy that has stable and fine Sn oxide at high temperature has been developed. In order to investigate the effect of Te additional that affects the formation of the oxide layer on the surface and the formation of oxide in matrix Ag, we studied the microstructures and properties of Ag-Sn-In(-Te) material fabricated by rapid solidification process. The experimental procedure were melting using high frequency induction, melt spinning, and internal oxidation. Specimens were examined and analyzed by Transmission electron microscopy(TEM), energy dispersive X-ray spectroscopy(EDS) and Vickers hardness. As a result, internal oxidation was completed even at <TEX>$600^{\circ}C$</TEX>. Te forms coarse <TEX>$In_{2}TeO_{6}$</TEX> phase and makes fine and well dispersed <TEX>$SnO_{2}$</TEX> Phase. 0.3 wt% Te shows favorable properties.

Stress corrosion cracking of copper and silver, specific effect of the metal cations

Based on stress corrosion cracking (SCC) studies on brass, and on Ag–Cd alloys (a model alloy used to reproduce the behaviour of brass), it was found that both pure copper and pure silver are susceptible to SCC in 1 M copper(II) nitrate and in 1 M silver nitrate aqueous solutions, at the equilibrium potentials for the reactions: Cu 2++2e −↔Cu and Ag ++e −↔Ag, respectively. The results were analysed under the light of recent developments in surface science. It was concluded that the same SCC mechanism that operates in brass and in Ag–Cd alloys should be operating during SCC of pure copper and pure silver, under equivalent experimental conditions.

Low temperature coefficient of resistivity Ag–Cd and Ag–Sn alloys—structure and transport

The microstructure vis-a-vis electrical transport behavior of Ag–Cd and Ag–Sn binary alloys in the temperature range 70–300 K has been studied. The 22.2 wt.% Cd and 29.4 wt.% Cd alloys were both found to have a single-phase structure made of solid solution of Ag. The lattice parameter however increased with increasing Cd content in the alloy. The microstructure of 17.7 wt.% Sn and 23.5 wt.% Sn alloys however is made of two phases Ag 4Sn and Ag 3Sn. The resistivity of Ag–Cd alloys increased with increasing Cd content and the temperature coefficient of resistivity (TCR) decreased to 1560 ppm K −1 for the 29.4 wt.% Cd alloy compared to 4100 ppm K −1 for pure Ag. The lowest TCR however was obtained for the 17.7 wt.% Sn alloy, 375 ppm K −1, which has a room temperature resistivity of 23.93 μΩ cm.

Se, As, Mo, Ag, Cd, In, Sb, Pt, Au, Tl, Re traces in biogenic and abiogenic sulfides from Black Shales (Selwyn Basin, Yukon territories, Canada): A nuclear microprobe study

Black shales can be an important source of rare metals such as Cu, Ag, As, Mo, Se, Tl, Cd, platinum group elements (PGE) and gold (Pasava et al., Econ. Geol. 91 (1996) 63). However, especially in the case of noble metals, carriers such as discrete minerals could not be identified. This nuclear microprobe study brings new data on the partition of rare metals in Fe-, Fe (Ni)-, Ni- (Fe)-, Ni- and Zn-sulfides from the Ni-Zn-Mo-PGE mineralized marin black shales (Selwyn Basin, Yukon Territories). Sulfides are present as mineralized vestimentiferan tube-worms which are pyritized. Fluid-mineral interaction led to transformation of these biogenic Fe-sulfides successively to Fe–Ni- and Ni–Fe-sulfides which is indicated by increasing Se contents. Ni-sulfides which are interstital to the tube worms represent remobilized material, they are richest in Se. Several tens to thousands ppm of Cu, Zn, As, Se, Mo were located in the biomineralized and transformed tube worms. Antimony was located in Fe–Ni and Ni-, and Zn sulfides and Ag was present in Fe–Ni and Ni–Fe-sulfides. Pt and Au can also be related to submicron-sized inclusions in Fe–Ni sulfides. Hydrothermal fluids (at least 250 °C) precipitated silica around tube worms, intercalating submicron-sized sphalerites. Larger Zn-sulfides contain about 5000 ppm Cd and locally about 60 ppm In. Ba-rich K-feldspar contains Cl-rich Ag–Cd alloys.

The massive transformation in titanium aluminides: Initial stages of nucleation and growth

Rapid solidification by twin-anvil splat quenching captures the initial nucleation and growth of the α → γm massive transformation in titanium aluminides. Splat quenching Ti52Al48 and Ti50Al48Cr2 from the liquid at slightly below the melting point produces an equiaxed α solidification structure. Solid-state cooling rates that approach 106 K/s arrest the α → γm massive transformation with 1- to 5-µm-sized γm nuclei, especially in the Ti50Al48Cr2 alloy. Classical massive-transformation heterogenous nucleation occurs at α:α grain boundaries with an orientation relationship of [111]γ//[0001]α and \(\{ 110\} _\gamma //\{ 11\bar 20\} _\alpha \). The γm nucleus then grows into the adjacent α grain without the orientation relationship by forming an incoherent α:γ interface with {111}γ facets. Orthogonal variants of the tetragonal c-axis in the γm product suggest that the massive transformation initially produces an fcc structure which subsequently orders into the L10 phase. Nucleation of γm is not only observed at α:α grain boundaries and triple points, but also within the α grains. The intragranular γm nucleation, which is believed to be heterogeneous, occurs with the same orientation relationship as for the intergranular nuclei. However, the intragrain nuclei do not form {111}γ facets and retain a curved α:γm interface. Although analysis of the {111}γ faceted growth using weak-beam dark-field (WBDF) imaging shows no evidence for any type of misfit-compensating dislocations, lattice imaging of the {111}γ facets with high resolution transmission electron microscopy (HRTEM) reveals that the planar interface exhibits a slight curvature, produced by atomic steps of (111) planes. These experimental data have been used to estimate a ratio of ledge spacing (λ) to ledge height (h) for the {111}γ facets as λ/h=41, which is similar to calculated values for a ledge growth mechanism of massive transformations in Cu-Zn and Ag-Cd alloys.

Underpotential deposition of cadmium onto (111) face of silver from chloride containing solution

The underpotential deposition (UPD) of cadmium and Ag–Cd alloy formation on the (111) face of silver in chloride containing solutions were investigated by cyclic voltammetry and the potentiostatic pulse technique. It was shown that the UPD of cadmium commences at about −400 mV versus SCE (300 mV vs. Cd 2+/Cd) with the formation of ordered structure of the type ( 3 x 3 ) R30°. Chloride adatoms, which are adsorbed on the silver substrate when UPD of Cd starts, do not desorb. They become replaced by Cd adatoms and remain adsorbed and discharged on top of a Cd layer. At potentials close to the reversible potential of Cd alloying of Ag with Cd takes place, being expressed by two sharp cathodic peaks on the voltammograms.