High Ag Content Research Articles

Distribution of indium in ores of some base metal and tin–sulfide deposits in Siberia and the Russian Far East

The study of base-metal massive sulfide and tin–sulfide deposits in Siberia and the Russian Far East has revealed that the indium content in ores exceeding the average statistical value at similar deposits worldwide could be economically important. Sphalerite and chalcopyrite and chalcopyrite, bornite, and sphalerite are the major indium carriers in the base-metal massive sulfide and tin–sulfide ores, respectively. In addition, base-metal massive sulfide ores have high Cd, Ag, and Te contents, whereas tin–sulfide ores have elevated Ge, Ga, and Nb contents. This has stimulated the investment attractiveness of these deposits.

Investigation of surface silver enrichment in ancient high silver alloys by PIXE, EDXRF, LA-ICP-MS and SEM-EDS

Surface elemental analysis presenting high silver (Ag) contents have been regarded as reliable for original bulk composition of silver coins which are accordingly referred as being produced from very pure Ag alloys. Also, the extent in which the surface elemental composition analytical results are influenced by surface Ag enrichment has been disregarded in coins alloys with Ag finenesses greater than the Ag content indexed to the maximum value of copper (Cu) solid solubility in Ag – 91.2wt.%. PIXE and EDXRF results obtained on Portuguese 11 dinheiros silver coins issued in the 16th century with a legal Ag fineness of 916.6 thousandths, show 4 to 7% higher Ag surface contents. As identified by LA-ICP-MS and μ-PIXE through coins thicknesses, the overestimation of the superficial measured Ag is associated to a Cu depletion gradient representing as much as 50% less Cu on surface than on the bulk of the coins. The subsurface microstructural characterization by SEM-EDS reveals the presence of an important superficial layer depleted of Cu-phase, with a thickness<70μm, resulting primarily from intergranular corrosion during the coin manufacturing process. These layers can only be accessed by destructive or invasive analysis, as thicknesses beyond the information emission depth obtained with EDXRF could not be identified by Ag Kα/Lα ratios. As showed by the combination of different methods of analysis, EDXRF, PIXE, SEM-EDS and LA-ICP-MS, the results obtained by surface analytical techniques may differ from the original bulk compositions for these high Ag content coins and should be taken cautiousness together with historical context and information.

Trace elements in pyrite from the Petropavlovsk gold–porphyry deposit (Polar Urals): Results of LA-ICP-MS analysis

The first study of the pyrite composition from gold deposit in the Urals by the LA-ICP-MS method has been carried out. In the pyrite high contents of Au (up to 49 ppm), Ag (105 ppm), and other micronutrients (As (417 ppm), Ag (105 ppm), Co (2825 ppm), Ni (75 ppm), Cu (1442 ppm), and Zn (19 ppm)) were detected. Furthermore, an increase in the concentrations of trace elements from early to later generations of pyrite (from Py-1 to Py-3) Au, Ag, Te, Sn, Te, and Bi and depletion of Co, As, and Ni have been revealed. Gold is mainly concentrated in the pyrite of the second generation (Py-2) and occurs mostly as an “invisible” form with prevalence of nano-sized particles of native Au, similar in composition to electrum AuAg, as well as Au- and Au–Ag tellurides. The presence in the pyrite of admixtures of Cu, Co, Ni, Pb, As, and Te, possibly favors the entrance of Au into it (up to 5–50 ppm), while in common pyrite, poor in the mentioned impurities, the gold content is <1 ppm.

Laser fabrication of Ag-HA nanocomposites on Ti6Al4V implant for enhancing bioactivity and antibacterial capability

For titanium alloy implants, both surface bioactivity and antibacterial infection are the two critical factors in determining the success of clinical implantation of these metallic implants. In the present work, a novel nanocomposite layer of nano-silver-containing hydroxyapatite (Ag-HA) was prepared on the surface of biomedical Ti6Al4V by laser processing. Analysis using SEM, EDS and XRD shows the formation of an Ag-HA layer of about 200μm fusion bonded to the substrate. Mineralization tests in simulated body fluid (SBF) showed that laser fabricated Ag-HA nanocomposite layer favors the deposition of apatite on the surface of the implants. Antibacterial tests confirmed that all Ag-HA nanocomposite layers can kill bacteria while a higher Ag content would lower the cytocompatibility of these coatings. Cell viability decreases when the Ag content reaches 5% in these coatings, due to the larger amount of Ag leached out, as confirmed by ion release evaluation. Our results reveal that laser fabricated Ag-HA nanocomposite coatings containing 2% Ag show both excellent cytocompatibility and antibacterial capability.

Antibacterial ability and osteogenic activity of porous Sr/Ag-containing TiO2 coatings

Implant-associated infection and poor osseointegration remains a major clinical challenge in Ti-based implant materials. A versatile strategy to endow Ti-based implants with long-term antibacterial ability as well as better osteogenic activity is highly desirable for high quality implantation. Strontium (Sr) has been shown to be a significant element to favor bone growth by promoting new bone formation and inhibiting bone resorption. In this study, a novel duplex-treatment technique encompassing magnetron sputtering with micro-arc oxidation is utilized to fabricate porous Sr/Ag-containing TiO2 coatings loaded with different concentrations of Ag and Sr. All coatings are porous with pore size less than 5 µm. Ag is primarily distributed homogeneously inside the pores, and the concentrations of Ag in Sr/Ag-containing TiO2 coatings with low and high Ag contents are 0.40 at.% and 0.83 at.% respectively. We have demonstrated that this kind of coating displays long-lasting antibacterial ability even up to 28 d due to the incorporation of Ag. Further, Sr/Ag-containing TiO2 coatings with optimum Ag and Sr contents revealed good cytocompatibility, enhanced osteoblast spreading and osseointegration, which stemmed primarily from the synergistic effect exerted by the porous surface topography and the bioactive element Sr. However, this study has also identified, for the first time, that proper addition of Ag would further facilitate osteogenic effects. Besides, Sr may be able to alleviate the potential cytotoxic effect of excessive Ag. Thus, integration of optimum functional elements Ag and Sr into Ti-based implant materials would be expected to expedite osseointegration while simultaneously sustaining long-term antibacterial activity, which would provide new insights for relevant fundamental investigations and biomedical applications.

The Role of Electrolyte Composition on Codeposited Ag and Cu

The eutectic Ag-Cu composition is a common brazing alloy. A complex ion bath containing KAg(CN)2, CuCN, KCN and K4P2O7 was used to codeposit Ag and Cu. The effects of KAg(CN)2, KCN and K4P2O7 concentrations on the composition and morphology of electrodeposited Ag-Cu films was investigated in this study. A constant CuCN concentration of 0.1 M was used. The increase in KCN and KAg(CN)2 concentrations caused major increases in Ag contents, but increase in K4P2O7 concentration caused a minor decrease in Ag content of the film. The deposits were found to be globular clusters when high KAg(CN)2 concentrations were used. Finer microstructures and higher Ag contents were observed in deposits produced in electrolytes containing higher KCN concentrations.

Microstructural influences on thermomechanical fatigue behaviour of third generation high Ag content Pb-Free solder alloys

New third generation lead free alloys are being targeted for use in harsh environments requiring resistance to both thermal and mechanical loading. In applications such as the engine compartment of motor vehicles where extreme thermal cycles and long dwell are common, it has been necessary to look for strengthening mechanisms that better survive extremes of temperature and strain. Alloys are being designed to improve toughness of interfacial intermetallic layers and provide solid solution strengthening to compensate for the loss of strength once the Ag3Sn particles coarsen. Results show that while solid solution-strengthening by additions of Sb is effective, it is not sufficient, and other strengthening options through the introduction of additional precipitates and solid solution strengthening using Bi is most desirable. The role of Ni is difficult to discern but it is most concentrated in the Cu6Sn5 intermetallic phase located at the interface between the solder and the copper substrate. This presumably has a toughening effect on the intermetallic thereby inhibiting crack formation and growth.

Enhanced performance of polyimide hybrid membranes for benzene separation by incorporating three-dimensional silver–graphene oxide

Graphene oxide-Ag nanoparticle composites were prepared through impregnation reduction using different reactants. Transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy analyses were performed to characterize differences in the morphologies of three different Ag–GO composites. Scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry analyses were also applied to evaluate the morphology and thermal stability of the hybrid membranes. Swelling–sorption and pervaporation experiments of benzene and cyclohexane were conducted to evaluate the separation performance of hybrid membranes containing different Ag–GO composites. Results demonstrated that small Ag nanoparticles generated through impregnation reduction using Ag(NH3)2+ and PEG were homogeneously distributed in the hybrid membranes because of moderate reduction rate. The polymide (PI) hybrid membrane exhibited high separation performance. Increase in Ag content in the Ag–GO samples led to the formation of Ag particles on the GO surface; these particles enhanced the separation performance of the hybrid membranes. When Ag-GO samples with 15 mass percent added, the hybrid membrane showed the highest separation performance and its maximum separation factor in the pervaporation experiments reached 35. It is more than three times higher than that of the GO/PI hybrid membrane. Moreover, large Ag particles were formed and aggregated during the preparation and polymerization of Ag–GO samples with high Ag contents; these particles reduced the separation performance of the hybrid membranes.

Investigations of electrical, magnetic, and optical properties of Ag/Co0.05Ti0.95O2 random nanocomposites

A heterogeneous medium consisting of randomly oriented silver nanorods embedded in Co0.05Ti0.95O2 (CTO) matrix was prepared using the sol–gel method. In this work, negative permittivity properties and magnetic behavior of composites with different contents of Ag nanorods embedded in Co0.05Ti0.95O2 matrix are investigated. The impedance analyses indicate that with increasing Ag content (~35%) the composite shows an inductive behavior and the permittivity spectra show negative values, which is called electrically negative metamaterial. The silver networks possess diamagnetic behaviors due to Eddy current that is combined with the magnetic behavior of Co0.05Ti0.95O2 matrix. The permeability spectra of the composites reveal that the permeability of these samples decreases continuously with the increase in frequency. Additionally, the permeability spectra show negative susceptibility in the sample with high Ag content (35%) at high frequency.

The effect of vacuum atomic oxygen and ultraviolet radiations on Ag/a-C:H nanocomposite film

Ag/a-C:H nanocomposite film with nanosized Ag particles (about 2–5nm) embedded in a-C:H matrix is deposited by the medium frequency unbalanced magnetron sputtering. The effects of vacuum atomic oxygen and ultraviolet radiations on the composition, microstructure, morphology and vacuum tribological properties of the Ag/a-C:H nanocomposite film have been investigated. Results show that the radiations can induce the oxidation and decomposition of carbon matrix, which lead the high Ag content nearby surface, the increased sp2 carbon content, as well as the reconstruction of microstructure. As a result, the diffusion rate of Ag atoms increases while the connectivity and rigid of the carbon network decrease. The composite film exhibits low friction and high wear performance after radiations.

Structural investigation and laser plasma diagnostics of borate glasses containing silver nanoparticles

Non-equilibrium plasmas have been produced in vacuum by irradiating thin targets of Ag2O doped borate glasses by pulsed laser. Morphological and optical measurements have shown that in these glasses at high Ag content the metallic cations exist as nanoparticle and can induce effects of resonant absorption in laser-generated plasmas. Furthermore, preliminary time-of-flight measurements have been carried out by means of an infrared laser having a maximum intensity of the order of 1010 W/cm2 evidencing that the ions energy and yield increase with the silver concentrations and depend on the glass structure. This study has shown that concentrations of Ag2O up to 25% enhance the kinetic energies and the yields of the accelerated ions, whereas a higher content of silver oxide gives rise to high laser absorption thus modifying the properties of the plasma. The obtained characterization indicates that the targets may be irradiated by higher repetitive laser intensities in order to enhance the ion acceleration and current.

Silver-Doped Calcium Phosphate Bone Cements with Antibacterial Properties.

Calcium phosphate bone cements (CPCs) with antibacterial properties are demanded for clinical applications. In this study, we demonstrated the use of a relatively simple processing route based on preparation of silver-doped CPCs (CPCs-Ag) through the preparation of solid dispersed active powder phase. Real-time monitoring of structural transformations and kinetics of several CPCs-Ag formulations (Ag = 0 wt %, 0.6 wt % and 1.0 wt %) was performed by the Energy Dispersive X-ray Diffraction technique. The partial conversion of β-tricalcium phosphate (TCP) phase into the dicalcium phosphate dihydrate (DCPD) took place in all the investigated cement systems. In the pristine cement powders, Ag in its metallic form was found, whereas for CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, CaAg(PO3)3 was detected and Ag (met.) was no longer present. The CPC-Ag 0 wt % cement exhibited a compressive strength of 6.5 ± 1.0 MPa, whereas for the doped cements (CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt %) the reduced values of the compressive strength 4.0 ± 1.0 and 1.5 ± 1.0 MPa, respectively, were detected. Silver-ion release from CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, measured by the Atomic Emission Spectroscopy, corresponds to the average values of 25 µg/L and 43 µg/L, respectively, rising a plateau after 15 days. The results of the antibacterial test proved the inhibitory effect towards pathogenic Escherichia coli for both CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, better performances being observed for the cement with a higher Ag-content.

Nano-galvanic coupling for enhanced Ag+ release in ZrCN-Ag films: Antibacterial application

The antibacterial properties of materials developed for medical devices with embedded silver nanoparticles are enhanced by controlling the release of silver ions. In this study, a simple experimental procedure for the augmentation of the silver ion release from ZrCN-Ag coatings is described. The silver nanoparticles are embedded in an amorphous carbon matrix within the ZrCN coatings, to create nano-galvanic couples between the silver and the carbon phases. The galvanic couple promotes the oxidation of silver, and consequently, increases the silver release. It is demonstrated that coatings with a lower silver content, but integrating amorphous carbon phases, can release similar or even a larger amount of Ag+ ions than those with higher Ag content having just ZrCN and Ag phases. The antibacterial tests demonstrate that coatings with silver nanoparticles encapsulated into amorphous phase reveal a larger bacterial zone of inhibition compared to samples with similar or lower silver content. However, it is shown that the antibacterial effect of the coatings not only depends on the ability for silver ion release, but also on the availability of silver nanoparticles on the surface. (C) 2016 Elsevier B.V. All rights reserved.

The Role of Electrolyte Composition on Codeposited Ag and Cu

The eutectic Ag-Cu composition is a common brazing alloy. A complex ion bath containing KAg(CN)2, CuCN, KCN and K4P2O7 was used to codeposit Ag and Cu. The effects of KAg(CN)2, KCN and K4P2O7 concentrations on the composition and morphology of electrodeposited Ag-Cu films was investigated in this study. A constant CuCN concentration of 0.1 M was used. The increase in KCN and KAg(CN)2 concentrations caused major increases in Ag contents, but increase in K4P2O7 concentration caused a minor decrease in Ag content of the film. The results are summarized in the figure. The deposits were found to be globular clusters when high KAg(CN)2 concentrations were used. Finer microstructures and higher Ag contents were obseerved in deposits produced in electrolytes containing higher KCN concentrations. Figure 1

Effects of Ag content on the interfacial reactions between liquid Sn–Ag–Cu solders and Cu substrates during soldering

The effects of Ag content on the interfacial reactions between Sn–Ag–Cu (SAC) solders and Cu substrates during soldering were studied based on an experiment in which the liquid solder is removed after a long exposure time. This removal of the solder allows for the capture and visualization of the interfacial IMCs formed during soldering and avoids the influence of Cu6Sn5 precipitated from the solder matrix during cooling. The results showed that a Cu6Sn5 scallop type layer with round grains having a strong texture was formed at the interface of the SAC solders/Cu systems. The addition of Ag decreased the IMC/liquid SAC solder interfacial energy and improved the wettability of the solder on the Cu. In addition to the reaction energy, the interfacial microstructure also affected the interfacial IMC growth extent. By changing the growth environment near the interface, Ag affected the orientation of Cu6Sn5 grains formed at the interface, leading to the evolution of a microstructure that generates more Cu6Sn5 grain boundaries at the interface. Consequently, under the same reflow conditions, SAC solders with a higher Ag content in contact with the Cu substrate form thicker IMCs interfacial layers.

Gold from the tomb of Scribe Beri: a comparative analytical approach to the New Kingdom gold grave goods from Riqqa (Egypt)

The gold necklace and penannular earrings from tomb 296 at Riqqa, containing the coffins of a female and of a male, the latter a scribe named Beri of the reign of Tuthmosis III (eighteenth Dynasty Egypt), were analysed by PIXE, XRF, and EDS, together with eight penannular earrings from other find-spots of the same period. Analysis of jewellery items from tomb 296 at Riqqa revealed the use of high-purity gold alloys and electrum alloys, while the other earrings investigated were found to be made of electrum with high Ag content. Two earrings conserved in different museums were shown to be originally a pair. PIXE mapping revealed the extensive use of a hard soldering technique for the joints, with the solders being obtained by the addition of Cu to the base alloy. The presence of PGE inclusions indicated the use of alluvial gold, but the variability of their composition could be ascribed to the recycling of gold from different origins, in the case of some objects.

Advanced glycation end products upregulate lysyl oxidase and endothelin-1 in human aortic endothelial cells via parallel activation of ERK1/2-NF-κB and JNK-AP-1 signaling pathways.

Endothelial dysfunction involves deregulation of the key extracellular matrix (ECM) enzyme lysyl oxidase (LOX) and the vasoconstrictor protein, endothelin-1 (ET-1), whose gene expression can be modulated by the transcriptional activators nuclear factor kappa B (NF-κB) and activator protein-1 (AP-1). Advanced glycation end products (AGEs) present an aggravating factor of endothelial dysfunction which upon engagement to their receptor RAGE induce upregulation of mitogen-activated protein kinases (MAPKs), leading to NF-κB and AP-1 potentiation. We hypothesized that AGEs could induce NF-κΒ- and AP-1-dependent regulation of LOX and ET-1 expression via the AGE/RAGE/MAPK signaling axis. Western blot, real-time qRT-PCR, FACS analysis and electrophoretic mobility-shift assays were employed in human aortic endothelial cells (HAECs) following treatment with AGE-bovine serum albumin (AGE-BSA) to investigate the signaling pathway towards this hypothesis. Furthermore, immunohistochemical analysis of AGEs, RAGE, LOX and ET-1 expression was conducted in aortic endothelium of a rat experimental model exposed to high- or low-AGE content diet. HAECs exposed to AGE-BSA for various time points exhibited upregulation of LOX and ET-1 mRNA levels in a dose- and time-dependent manner. Exposure of HAECs to AGE-BSA also showed specific elevation of phospho(p)-ERK1/2 and p-JNK levels in a dose- and time-dependent fashion. AGE administration significantly increased NF-κΒ- and AP-1-binding activity to both LOX and ET-1 cognate promoter regions. Moreover, LOX and ET-1 overexpression in rat aortic endothelium upon high-AGE content diet confirmed the functional interrelation of these molecules. Our findings demonstrate that AGEs trigger NF-κΒ- and AP-1-mediated upregulation of LOX and ET-1 via the AGE/RAGE/MAPK signaling cascade in human endothelial cells, thus contributing to distorted endothelial homeostasis by impairing endothelial barrier function, altering ECM biomechanical properties and cell proliferation.

Evaluation about Solder-IMC Crack of Fine Pitch BGA Package

FBGA is widely adopted as AP and memory package for mobile devices such as a smart phone and a smart watch. FBGA is attached to PCB assembly during SMT process. Double side SMT is preferred to increase the battery area for slim design and long life of mobile device. Solder-IMC crack is in-process reliability failure occurs during 2nd side SMT. The buried via is often used in double side SMT PCB is filled with filler material of CTE is highly mismatched to surrounding PCB laminates (FR-4). Tensile stress is applied to BGA pad by this CTE mismatch at high temperature and causes the solder-IMC crack. In this paper, we evaluate the factors of solder-IMC crack related to PCB and BGA. It is found that the length of buried via related to PCB thickness influences the solder-IMC crack. But if the location of buried via is not aligned to the location of BGA pad, solder-IMC crack does not occur. In the case of buried via and BGA pad are aligned each other, the failure rate of solder-IMC crack can be lowered by controlling O2 level that is less than 1000ppm and by applying solderball with high Ag content for SAC alloy. The temperature cracking solder-IMC interface is measured. The result shows that the solder-IMC crack occurs before solder joints are fully melted. The solder joint with low Ag content having broad melting temperature range is relatively weaker than high Ag having near eutectic point. It is recommended to design the PCB with buried via which avoids the location of the BGA pad and this is the good solution to reduce the failure rate of solder-IMC crack to near zero.

Synthesis and characterization of ZnO nanostructures on noble-metal coated substrates

In this work, ZnO nanostructures were fabricated on noble-metal (Au, Ag and Au–Ag alloys) coated silicon substrates by applying pulsed laser deposition. The samples were prepared at a substrate temperature of 550°C, an oxygen pressure of 5Pa, and a laser fluence of 2Jcm−2 – process parameters usually used for deposition of smooth and dense thin films. The metal layer's role is substantial for the preparation of nanostructures. Heating of the substrate changed the morphology of the metal layer and, subsequently, nanoparticles were formed. The use of different metal particles resulted in different morphologies and properties of the ZnO nanostructures synthesized. The morphology of the ZnO nanostructures was related to the Au–Ag alloy's content of the catalyst layer. It was found that the morphology of the ZnO nanostructures evolved from nanorods to nanobelts as the ratio of Au/Ag in the alloy catalyst was varied. The use of a small quantity of Ag in the Au–Ag catalyst (Au3Ag) layer resulted predominantly in the deposition of ZnO nanorods. A higher Ag content in the catalyst alloy (AuAg2) layer resulted in the growth of a dense structure of ZnO nanobelts.

The investigation of interfacial and crystallographic observation in the Ni(V)/SAC/OSP Cu solder joints with high and low silver content during thermal cycling test

This study investigated the microstructure and grain orientation of Ni(V)/SAC396/OSP Cu and Ni(V)/SAC105/OSP Cu solder joints during thermal cycling test (TCT). In general, adjusting Ag content in solders influenced the performance of thermal cycling (TC). Nevertheless, it is still crucial to find the optimal condition of Ag and related mechanisms of crack formation during TCT. This study applied FE-SEM to observe the crack propagation and the precipitation of Sn–Ag IMCs in the solders. Moreover, FE-EPMA and EBSD were used to detect the elemental distribution and grain orientation near the cracks, respectively. The locations of crack initiation are strongly related to the CTE mismatch between Si chip and solder alloy. Besides, the large number of Ag3Sn precipitations in the joint with high Ag content efficiently hinder the crack propagation due to the effects of precipitation hardening. It is revealed that the Ni(V)/SAC396/OSP Cu exhibits good thermal stability during thermal cycle test.