Increasing Silver Content Research Articles

A ferric chloride hydrometallurgical process for recovery of silver from electronic scrap materials

A hydrometallurgical method for the recovery of silver from electronic scrap materials is suggested. Electronic scrap materials, containing silver with the accompanying brass and beryllium bronze, are leached at 80°C with ferric chloride. The leaching should be carried out with the concentration of ferric chloride and phase ratio chosen so that in the final phase of leaching the concentration ratio of Fe(III) to Fe(II) is not lower than 1. Under such conditions silver is found to be only slightly solubilized. This was confirmed by electrochemical studies. Potentiodynamic studies of the behaviour of silver in hydrochloric acid demonstrated that at the electrode potential value of 0.77 V, corresponding to the redox potential at 25°C of the solution where the concentration ratio [Fe(III)]/[Fe(II)] = 1, the silver surface is passivated not only by silver chloride but also by silver oxide. This prevents solubilization of silver in chloride solutions owing to the formation of AgCl 2 − and AgCl 3 2− complexes. The lowering of the solution oxidation potential resulting from consumption of Fe 3+ ions during the leaching process causes a sudden increase in silver concentration in solution.

Investigations on silica-supported platinum-silver alloy particles by infrared spectra of adsorbed CO and N 2

The surface properties of specially prepared, silica-supported platinum-silver alloy particles are studied by volumetric chemisorption of H 2, O 2, and NO and infrared spectra of adsorbed CO and N 2. The volumetric experiments show the surface compositions of the alloy particles after reduction and outgassing to be similar to the bulk compositions. Adsorption of CO on reduced pure Pt samples brings about an intense absorption band at 2085 cm −1. For the alloy particles the CO band shifts to 2023 cm −1 with increasing silver content, while a weak band at 2164 cm −1 is displayed. Mild oxidation (10 Torr O 2) of the alloy particles prior to CO adsorption leads to a drastic decrease of the intensity of the low-frequency band and a simultaneous growth of the high-frequency band, now positioned at 2173 cm −1. As the absorption bands around 2170 cm −1 are ascribed to CO bound to Ag + ions, these results point to a strong enrichment of the surface with silver due to adsorbed oxygen. Oxidation in 1 atm O 2 at elevated temperatures (300–400 °C) causes a redistribution of silver over the alloy particles without a considerable sintering of the entire particles, as can be inferred both from the volumetric and infrared experiments. Infrared spectra of N 2 adsorbed on reduced and thoroughly outgassed samples show the extent of adsorption to drop strongly with increasing silver content of the alloy. This behavior is tentatively ascribed to a strong influence of alloying on the surface structure of platinum particles.

Conductivity, Photoconductivity, and Luminescence Studies on Some Silversulfamides

Electrical conductivity, photoluminescence, and diffuse reflectance spectra have been measured for the following silversulfamides: ,, , and . They have been discussed in relation to their crystal structures. With increasing silver content the conductivity increases and the absorption edges of the reflectance spectra are red shifted. The luminescence data have been attributed to centers of the type , , and . Tetrasilversulfamide shows a conductivity increase of about between 365 and 396 K. For trisilversulfamide anisotropy effects have been detected in the photoconductivity measurements.

Determination of the AuCu superlattice formation region in gold-copper-silver ternary system.

The composition and temperature range of the AuCu-type superlattice formation in the Au-Cu-Ag ternary system was determined by X-ray powder diffraction. Four distinguishable phase transformations were detected, i.e., 1) alpha (disordered FCC phase) leads to AuCu I, 2) alpha leads to AuCu II, 3) alpha leads to alpha 1 (Cu-rich FCC phase) + alpha 2 (Ag-rich FCC phase). and 4) alpha leads to AuCu3. The stable temperature range of the AuCu I-type superlattice was restricted to a lower temperature range by adding silver to stoichiometric and off-stoichiometric Au-Cu alloys. Depending on the increase in silver content, the co-existing region of the AuCu II-type superlattice and the silver-rich alpha 2 phase extended to the lower temperature and over a wide composition range.

Fe-Pd系合金磁石「Pallamagnet」の特性に対するAg添加の影響について

Magnetic properties of Fe-Pd-Ag alloys containing 17∼47 at%Pd and 1∼30 at%Ag have been measured. The coercive force of the alloys increases with increasing silver content to 12%. The 59 at%Fe, 29 at%Pd and 12 at%Ag alloy tempered after water-quenching has a coercive force of 95.5 kA·m−1, a residual magnetic flux density of 1.04T and a maximum energy product of 43.0 kJ·m−3. Another alloy containing 58 at%Fe, 32 at%Pd and 10 at%Ag wire-drawn has a higher coercive force of 115.4 kA·m−1, a residual magnetic flux density of 0.90T and a maximum energy product of 41 kJ·m−3.It is considered that the high coercivity of the alloy is due mainly to the high magneto-crystalline anisotropy of γ1 phase dispersed in α phase.

Fundamental aspects and technological implications of the solubility concept for the prediction of running properties

The first Goodzeit rule, which relates resistance to cold welding and seizure with mutual solubility of metal sliding couples, has been investigated. The sliding properties of Au-Ag and Pd-Ag alloys against SAE 1045 carbon steel were observed in ultrahigh vacuum and in argon. The abrupt change in friction and wear coinciding with the composition of the alloys at which the solubility of iron into the alloy vanishes found by De Gee was not confirmed. Instead a continuous decrease in friction coefficient and wear was observed with increasing silver content. Pure silver showed a very limited tendency to metal transfer, although in some cases the transferred layer was removed spontaneously after 200–300 cycles. Electrical conduction measurements made during sliding revealed a correlation between the momentary friction force and the electrical conductivity which indicated that variations in the friction force are synchronous with variations in the contact area. A model is proposed in which the conditions of friction and metal transfer are described in terms of one system and two material properties, i.e. the interfacial shear strength τ i , the shear strength τ ∗ and the strain hardening exponent n of the junction materials. The friction behaviour is described by a modified adhesion theory: instead of a contaminating layer it is the specific atomic interaction of the contacting metals acting over small regions of atomic contact which controls τ i . The junction growth mechanism is correlated with strain hardening. It is suggested that the first Goodzeit rule must be interpreted as a result of atomic interaction in the interface between the contacting metals. In this way prediction of the running behaviour of both metals and alloys would become possible.

Thermische Zersetzung nichtstöchiometrischer Cäsium-Silber-Gold(III)-Chloride und Darstellung von Mischkristallen zwischen Cs2AgAuCl6 und Cs2AuIAuIIICl6 / Thermal Decomposition of Nonstoichiometric Cesium-Silver-Gold(III)-Chloride and Preparation of Mixed Crystals of Cs2AgAuCl6 and Cs2Au<supI</supAuIIICl6

Abstract The thermal decomposition of cesium-silver-gold(III)-chloride Cs2Ag1-xAu1+x:/3Cl6 with 0 <x ≤ 0.63 at temperatures between 250 and 350 °C yields, under evolution of chlorine, mixed crystals of Cs2AgAuCl6 and Cs2AuIAuIIICl6. The composition of the latter can be described by the formula Cs2Ag1-y,Auy IAuIIICl6 with y = 2x;/ (3-x). Apart from the formation of the mixed crystals the reaction leads to CsCl as a further phase, and in the case of x < 0.35 also to some Cs2AgAuCl6. Mixed crystals with 0.23 ≤ y < 1, free from additional solid phases, can be obtained from strong hydrochloric acid solutions of Cs2AgAuCl6 and Cs2AuIAuIIICl6, which contain an excess of cesium ions. The mixed crystals are isostructural with Cs2AuIAuIIICl6 (space group I4/mmm). The variation of the lattice constants with increasing silver content confirms that the univalent silver, in contrast to the univalent gold, shows no tendency toward the formation of linear dichloro complexes. Our investigations show that the "tetragonal modification of Cs2AgAuCl6", described by Elliott and Pauling and obtained by them by heat treatment of cubic cesium-silver - gold(III)-chloride, is, in fact, CS2Ag1-y/Auy IAuIIICl6.

High temperature thermodynamics of dilute solutions of hydrogen in palladium–copper alloys

The thermodynamic properties of dilute solutions of hydrogen and deuterium in palladium-copper alloys with copper contents of 10, 25, and 40 at.% have been determined by a calorimetric-equilibrium method at 555 K. The results are compared (a) with corresponding data for hydrogen in palladium–silver at the same temperature and (b) with equilibrium data for palladium–copper measured near room temperature. (1) The partial excess entropies of hydrogen in dilute solutions in palladium–copper alloys are reduced significantly compared to pure palladium. In palladium–copper this effect is only about one-half that in palladium-silver. Even so, it is believed to reflect in both systems a nonrandom distribution of the hydrogen atoms among the available interstitial sites. (2) It is shown that to a first approximation the dissolved hydrogen atoms may be considered to be isotropic, three-dimensional Einstein oscillators. In this approximation the observed differences between hydrogen and deuterium may be used to calculate the vibrational frequency of hydrogen. For palladium–copper these differences do not vary with copper content within experimental error. This points towards ?H being essentially independent of alloy composition. This behavior contrasts with that of hydrogen in palladium–silver, for which Picard et al. [J. Chem. Phys. 70, 2710 (1979)] recently found increasing values of ?H with increasing silver content. It is suggested that the different behavior of ?H in large measure may account for the observed difference between the concentration dependence of the excess entropy of hydrogen in palladium–copper and in palladium–silver.

High temperature thermodynamics of the solutions of hydrogen in palladium-silver alloys

The thermodynamic properties of solutions of hydrogen in palladium-silver alloys with silver contents ranging from 25 to 50% have been determined by a calorimetric-equilibrium method at 555 and 700 K. The results are compared with corresponding data recently reported for hydrogen in Pd and in Pd0.9Ag0.1. (1) For the alloy Pd0.75Ag0.25 the thermodynamic measurements give no evidence for an order–disorder transition in the considered temperature range. (2) Comparisons between the solutions of hydrogen and deuterium in the same alloy and at the same temperature allow calculations to be made of the vibrational frequencies of hydrogen. The calculated values of ?H show a very significant increase with increasing silver content. (3) The partial excess entropies of hydrogen in dilute solutions in palladium-silver alloys are reduced significantly compared to the values in pure palladium. It is probable that these changes, in large measure, are caused by a nonrandom distribution of the hydrogen atoms among the available interstitial sites. However, other possible interpretations also are discussed.

The tetrahedrite-freibergite series, with reference to the Mount Isa Pb-Zn-Ag orebody

Twenty eight electron microprobe analyses of freibergite from the Mount Isa (Queensland) Pb-Zn-Ag stratiform orebody, range in silver content from 18.4 to 42.5 wt. % Ag. These values significantly extend the tetrahedrite-freibergite series. The compositional range based on twenty-one complete analyses is indicated by the formula (Ag,Cu)9.21–11.44(Fe,Zn)1.59–2.31(Sb,As)3.87–4.43S13.0. As far as could be determined, Mount Isa freibergite is homogeneous and no marked compositional changes were detected either across individual grains, or in different grains of the same electron microprobe sample. The linear, atom for atom, replacement of copper by silver reported for lower silver bearing tetrahedrites continues in Mount Isa freibergite. A maximum silver content of about 51 wt. % Ag is predicted. X-ray investigations indicate however that in contrast to the structural expansion with increasing silver content reported for argentian tetrahedrite, Mount Isa freibergite contracts with increase in silver. The extrapolated lattice parameter for the theoretical freibergite (Ag10(Fe,Zn)2Sb4S13) end member is of the same order as tetrahedrite.

The behaviour of zinc and zinc-silver alloys in the presence of some inhibitors

The effect of potassium dichromate and sodium silicate on the corrosion of zinc and three zinc-silver alloys containing about 8, 30 and 92% silver respectively in N NaOH was studied. It was found that both potassium dichromate and sodium silicate (higher concentrations) are efficient inhibitors for zinc and alloy I. The efficiency of the dichromate decreased with the increase in silver content of the alloy while sodium silicate was found to be a poor inhibitor for alloys II and III. The lower concentrations of the silicate stimulated the corrosion of zinc and the three alloys in this medium.

Porosity in silver-tin amalgams.

AbstractPorosity has been determined metallographically for a series of spherical silvertin amalgams. The alloy consisted of separate size fractions of five compositions. Porosity was found to increase with increasing silver content and particle size, and was reduced by blending of large and small particle sizes. In blended alloys the porosity showed close correlation to the observed setting expansion.

Electrical Properties of Silver Doped As-Se Glasses

The electrical properties of silver doped As-Se glasses up to 1.0 atomic % have been studied. The d.c. conductivity of the doped glasses is represented by a single activation energy which is smaller than that of the parent glass. The d.c. conductivity at room temperature increases with increase of silver content. However the glass containing smaller amount of silver is less conductive than that of the parent glass above a certain temperature. Pressure dependence of the conductivity shows electronic and ionic characteristics. A dielectric relaxation which is closely related to the d.c. conduction is found. Above results can be related to the formation of defects which contain silver.

Structure and properties of silver phosphate glasses — Infrared and visible spectra

The infrared and visible spectra of glasses in the Ag 2OP 2O 5 glass-forming system were obtained. The infrared data were interpreted as indicating the presence of polymeric chains in these glasses. The partial covalent nature of the AgOP bond was discussed. A mixed NaPO 3AgPO 3 glass showed no unexpected bands in the infrared spectrum, again showing that silver is behaving in a manner similar to alkali metal ions in phosphate glasses. The shift in the absorption edge in the visible spectra of glasses of different Ag/P ratio was shown to arise from either an increase in the concentration of nonbridging oxygens with increasing silver content, or the presence of colloidal silver metal particles.

シアン化銀メッキの均一電着性

The throwing power of cyanide baths for silver plating was studied with respect to composition and conductance of the baths and current density-cathode potential curves; and the range of appropriate current density was studied by Hull Cell Test.The results obtained were as follows.The increase in silver concentration or decrease in free potassium cyanide made cathode potential more base for the deposition of silver. This fact would be due to the behavior for keeping low silver concentration by inhibiting the dissociation of complex ions. However, when the concentration of silver was 30g/l or lower, the current density was beyond the range of fine crystal deposition so that the deposit was powdered.The addition of potassium carbonate made bath conductance higher and also made throwing power higher. However, when its concentration was 90g/l or higher, the range of appropriate current density was made narrower by the appearance of burnt deposits.The range of bath composition for high throwing power and appropriate current density was as follows:Ag 30-50g/lFree KCN 40-70lK2CO3 30-60l

The investigation of the geographical and vertical distribution of several trace elements in sea water using neutron activation analysis

Methods for the determination of 18 trace elements in sea water by neutron activation analysis have been developed. Of these elements sufficient analyses have been completed for gold, selenium, antimony, silver, cobalt and nickel to permit a discussion of their distributions in the world ocean. The distributions of gold, selenium and antimony are more uniform than those of silver, cobalt and nickel, so little can be said regarding the processes important to their supply to and removal from the world ocean. The variations observed for silver, cobalt and nickel, however, make possible the evaluation of several factors which influence their concentrations in the ocean: The Atlantic Ocean north of 10°S receives 60 per cent of the total dissolved material supplied to the ocean by streams, but is lower in silver, cobalt and nickel than is the remainder of the world ocean indicating that continental run-off is not important in the deep-sea economy of these elements. Relatively high concentrations of cobalt and nickel are found in water of the central Pacific Ocean in areas where the cobalt/manganese and nickel/manganese ratios in manganese nodules are high. The evidence that the nodule material in these areas is of volcanic origin may also imply a volcanic origin for the cobalt and nickel in the overlying water. No such source is indicated for silver. Unweathered rock material supplied directly to the ocean by Antarctic glaciers seems to be sufficient to affect the silica economy of the ocean and may in part affect the economy of other trace elements such as cobalt and nickel. The data are not sufficient, however, to permit an unambiguous interpretation. Cobalt and nickel are relatively low in Long Island Sound compared to the North Atlantic indicating near-shore removal of these elements from sea water. In the deep sea much of the cobalt and nickel may be removed by co-precipitation with manganese oxide, but no mechanism seems singularly important in the removal of silver. Increase in concentration of silver, cobalt and nickel with depth in areas of high organic productivity indicates alteration of trace element concentration by organic reactions. In areas where upwelling currents oppose the downward movement of organic material a relatively high steady state concentration may be produced.

Atomic Distribution in Molten Silver-Tin Alloy

Molten silver-tin alloys have been studied by x-ray diffraction technique, using a focusing Θ--Θ diffractometer with Mo-Ka radiation (quartz crystal monochromator in the diffracted beam). The scattered intensities Icoh eu in electron units and the interference function I (K)=Icoh eu/ƒ2 being the scattering factor) have been measured in the range of K=4 π sin Θ/λ = 1.4 Å-1 to K = 15 Å~-1 for 6 different alloy compositions at temperatures 100 °C above the liquidus line. Four alloys (from 62% to 82% Ag) were measured at 825 ℃. The positions of the first maximum of Ieu or I(K) shift considerably with increasing silver content from K=2.25 Å-1 for pure Sn to K=2.64 Å-1 for pure Ag. The radial distribution function 4 π r2ϱ (r) and the probability function W (r) = ϱ (r)/ϱ0, where ϱ (r) and ϱ0 are the atomic and average atomic densities respectively, were obtained by FOURIER transform of I(K). The positions of the first maximum of 4 π r2ϱ (r), (i. e., r1) and of W(r), (i.e., r1 1) are a measure of the interatomic distances, and vary from r1 1 = 3.18 Å for Sn to r1 1= 2.86 Å for Ag. The plot of r1 1 vs. composition of the alloys shows a negative deviation from a linear law. A discontinuity appears in the curve in the range of 50-60% Ag. The coordination number Z increases rapidly on addition of Ag to Sn (Z = 8.5 for Sn) and reaches a value of about 11 beyond 60% Ag.

Luminescence of pure and silver-activated alkali-halides

Synopsis A brief account is given of the luminescent properties of pure alkali-halide crystals grown from the melt. It could be shown that the so called “pure” crystals were mostly contaminated with oxygen. Oxygen ions accompanied by anion vacancies in the lattice are responsible for the blue or yellow emission when the crystals are excited with ultra-violet light. A study is also made of the luminescent behaviour of irradiated silver-activated alkali-halides. The radiophotoluminescence is maximum at 120°C and shifts to shorter wavelength as the silver content increases.

半導体に関する研究（第5報）亜酸化銅整流板の特性におよぼす銅素材中の金属性不純物の影響

The rectifying characteristics, their temperature dependence, the change of forward current at 0.8 V and the reverse current at 6 V of copper disks containing various kinds of impurities were studied and the following results have been obtained: (1) The rectifying characteristics of cuprous oxide rectifier increases with the purity of copper. (2) With the increase of silver content from 0.001% to 1%, the resistance in the reverse direction increases, but scarcely varies in the forward derection. The copper disks containing 0.1∼1% Ag show higher creeping tendency than the others. (3) When copper contains 0.001% Zn, the rectifier shows the highest efficiency. (4) As tin content increases from 0.001% to 1%, the rectifying resistance increases in the forward direction, while decreases in the reverse direction. (5) As nickel content increases from 0.001% to 1%, the resistance increases in both directions. (6) When copper contains 1% Ni or 1% Sn, it is difficult to prepare rectifying disks, mainly because of nonadherence of the oxide layer. (7) The forward current in running test increases in the first few minutes, but afterwards it remains almost constant.

Magnetic Susceptibilities of Palladium–Rhodium Alloys from 20° to 300° K.

THE rapid, yet accurate, method of measurement and the results thereby obtained for the magnetic susceptibilities of platinum, rhodium and palladium between liquid hydrogen and room temperatures have been previously described by two of us1. The same measurement techniques were afterwards applied to a series of polycrystalline palladium–silver alloys; the specific heats of these alloys have also been investigated (both sets of results yet unpublished). The results, when interpreted through the collective electron theory, make possible an estimate of the size and shape of the normally unfilled portion of the d electronic energy-band of metallic palladium, on the assumption that the addition of small amounts of silver to palladium cause a reduction of the number of holes in the d-band without significantly modifying its shape. With the filling of the band, it would be expected that the magnetic susceptibility and its variation with temperature would be affected. It was actually found experimentally that both decreased monotonically with increased silver content.