Ag Specimens Research Articles

Atomistic insight of deformation mechanisms and mechanical characteristics of nano-scale silver (100) using nanoindentation

This work aims to utilize the widely adopted nanoindentation technique to explore the deformation behavior and mechanical characteristics of nanocrystalline silver (Ag) materials. Molecular Dynamics simulations were conducted to understand the material behavior at the nanometer scale. In this simulation, the effect of indentation velocity and indentation depth on defect formation and hardness during nanoindentation of Ag specimens was analyzed and discussed in detail. The results show that the deformation behavior of the Ag specimen was affected by different indentation velocities. These phenomena were confirmed by analyzing the load-displacement curve, which indicates elastic deformation by the appearance of a linear load-displacement at low indentation velocities. In contrast, plastic deformation was found by the presence of intensified serration in the load-displacement relationship at higher indentation velocities. In these cases, the hardness showed little variation when the indenter velocity was increased from 5 m/s to 10 m/s, whereas a significant increase in hardness was observed when the indentation velocity was further increased to 20 m/s. Importantly, the progression of load-displacement curves during nanoindentation demonstrates the occurrence of minor and major load drops, corresponding to an increase in indentation depth from 0.5 nm to 2 nm respectively. These findings were elucidated through dislocation extraction analysis (DXA), which revealed that a minor load drop at low indentation depths is attributed to the nucleation of an amorphous structure, while a major load drop at higher indentation depths is associated with the expansion of dislocation nucleation. Consequently, the hardness increased significantly as the indentation depth increased. This research, provides insight into atomistic investigation and offers guidelines for designing materials with excellent mechanical properties using nanoindentation.

Microstructure evolution and mechanical properties of wire-arc-additively manufactured Al–Cu–Mg–Ag alloy

In this article, Al–Cu–Mg–Ag specimens were successfully wire-arc-additive-manufactured based on by gas metal arc process to investigate the evolution of microstructure and mechanical properties. The results showed that the grain morphology and pore size in the printed specimens varied in height direction. Under the influence of repeated thermal cycling, which affected the solid-state diffusion of the deviated elements at the grain boundaries, the distribution of the nanoscale second phase appeared significantly different in the height direction. The precipitation phase changes caused the microhardness of the printed specimens to decrease gradually from a peak of 125 HV and stabilise at around 100 HV. The changes in the printed specimens’ horizontal mechanical properties were insignificant mainly due to interlayer porosity.

Effect of Rinsing on Atmospheric Corrosion Environment of KT-1 Aircraft

Corrosion is difficult to predict and manage. Thus, understanding the characteristics of the atmospheric corrosion environment inside and outside the aircraft is necessary. A series of corrosion defects were found inside the KT-1 aircraft; hence, an atmospheric corrosion monitoring set was mounted inside the aircraft to measure the effect of external rinsing on the internal corrosion according to location (fuselage and wing). The effect of external rinsing was analyzed through surface analysis of the specimens and corrosion rate estimation using internal environmental parameters. Steel specimens within the monitoring set exhibited complete corrosion, while Ag specimens showed discoloration. External rinsing reduced the rate of chloride build-up inside the wing. Additionally, time of wetness (TOW) tended to increase with external rinsing regardless of location. Estimated and measured corrosion rates were positively correlated with TOW but negatively correlated with chloride accumulation rate. These results indicate the mixed effect of rinsing and require corrosion control for individual aircraft when deciding whether to apply cleaning for corrosion control.

Effect of drilling process parameters on bearing strength of glass fiber/aluminum mesh reinforced epoxy composites

The current study attempted to evaluate the impact of drilling parameters and delamination on the bearing strength of both neat GFRP (NG) and hybrid GFRP/aluminum (Al)-wire mesh with two various configurations, first with Al-mesh in the outer surface of specimen (AG) and the other with Al-mesh in the core of specimen (GA). Drilling procedure is carried out using varnothing 6 mm carbide twist drill with three different tip angles (90°, 120° and 135°), as well as Three different speeds and feeds (1000, 2000, and 3000 rpm) and (20, 40, and 60 mm/min), respectively. Taguchi and ANOVA analyses are used to analyze the influence of processing parameters. The findings showed that AG specimen experienced the least delamination damage. The maximum bearing strength refers to NG specimen, which is 9.6% and 8.7% more than AG and GA specimens, respectively. Drill point angle has the major effect on bearing strength for both AG and GA specimens, while for NG feed rate is of the major effect. The developed regression model displayed a high level of fitness with an average prediction error of less than 3%.

Influences of alloying elements and dendritic spacing on the corrosion behavior of Al–Si–Ag alloys

The most important commercial casting alloys are those based on Al–Si. Their technical characteristics are highly connected to their as-cast microstructure, which is translated by the secondary dendrite arm spacing (SDAS). The alloy microstructure has been demonstrated to be changed by the adding of certain alloying elements, in the sense of boosting the desired properties and features. Search has been intensified to provide a positive balance of several properties, such as: high yield strength, high electrical conductivity, and high corrosion resistance, besides maintaining the ability for the alloy to be conventionally solidified. Under such context, both addition of Ag and the control of the fineness of the dendritic structure can be alternatives seeking better properties for Al–Si alloys. In addition to the possibility of application in current studies contributing to the growing development needs as engine materials, Al–Si–Ag alloys can emerge as an alternative to the manufacture of parts for electric vehicles, such as rotors and inverters, where high mechanical strength, corrosion resistance and electrical conductivity are required. Corrosion findings of Al–Si–Ag specimens having quite different SDAS of five alloys are presented here: Al-5wt.% Si, Al-5wt.% Si-0.1wt.% Ag, Al-10wt.% Si-0.1wt.% Ag, Al-5wt.% Si-2wt.% Ag, Al-10wt.%Si-2wt.%Ag alloys. A complete set of characterization with potentiodynamic polarization, electrochemical impedance spectroscopy, immersion tests, optical microscopy and scanning electron microscopy (SEM) was developed for these alloys. It has been demonstrated that increase in the alloy Si content diminishes corrosion resistance, and that increase in Ag content, considering Al-10% Si alloys, reduces corrosion resistance as well, despite creating thicker passive films. Furthermore, the alloys with the lowest Ag content (0.1 wt.%) had the greatest corrosion performance among the Ag-containing alloys, while the microstructure refinement tends to enhance the nobility of the samples.

Quantitative Analysis Methods of Chloride Deposition on Silver for Atmospheric Corrosion Monitoring in South Korea

The chloride deposition rate is one of critical factors affecting the atmospheric corrosion of metals, which can be monitored by exposing Ag specimens and analyzing their surfaces using various ways. Although a coulometric reduction method can provide an absolute chloride deposition rate, new and alternative methods can be pursued, i.e., methods using typical surface analysis tools (scanning electron microscopy-energy dispersive x-ray spectroscopy [SEM-EDS], x-ray diffraction [XRD], and x-ray photoelectron spectroscopy [XPS]). As the surface analysis tools can only provide relative values, a correlation between the coulometric reduction and surface analyses should be developed. To develop the correlation between them, Ag specimens were prepared by exposing them to the atmosphere at 12 locations in South Korea for one year. Surface analysis of retrieved Ag specimens yielded correlations for the chloride deposition rates between the coulometric reduction method and typical surface analysis tools. Each correlation showed a fairly linear relationship, especially ones obtained from SEM-EDS and XPS. The developed correlations can be used when estimating the chloride deposition rate by using surface analysis tools as an alternative to the coulometric reduction method.

Cold Sintering of Ni–Ag Nanocomposite Particles Produced by Electric Explosion of Wires

77 Ni–23 Ag nanocomposite powder as well as nanopowders of Ni and Ag were produced by electric explosion of wires, and compacted specimens were made with the help of a cold sintering method at a high pressure. It is shown that electric explosion results in formation of mainly janus-nanoparticles of immiscible Ni and Ag metals with retention of nanostructure in consolidated bulk specimens. Microstructure and mechanical properties of cold sintered specimens prepared from as prepared and heat treated in hydrogen flow have been studied. It is ascertained that treatment of 70% dense compacts in hydrogen flow results in higher density and higher ductility of cold sintered specimens. Density of cold sintered at 3 GPa pressure 77 Ni–23 Ag and Ni specimens was reached about 95% from theoretical value whereas the density of Ag specimens is close to 100% of that. High strength was obtained under three-point bending tests and in compression tests.

Effect of transverse compression on superconducting properties of high-temperature superconducting wires

We designed a transverse loading device that can apply a more uniform compressive force perpendicular to superconducting tape than previously designed equipment. The effective compressive length and width reached up to 100 and 20 mm, respectively. The critical current (IC) and/or transport AC losses of the superconducting tape during transverse compression could be measured using this equipment. We used YBa2Cu3O7−x-coated conductor (YBCO CC) specimens with copper stabilizing layers of different thickness to investigate the characteristics of the critical current and transport AC losses under transverse compression loading. For comparison, several Bi-2223/Ag samples were also tested. A critical stress was observed for the compression process (the same as that for axial tension), and beyond this stress, IC degraded irreversibly. For the transport AC losses behavior of the YBCO CC and Bi-2223/Ag specimens, below the critical stress value, the AC losses remained almost unchanged with the increase of the compressive stress at the same current; while above the critical stress value, at increasing compressive stress, the AC losses increased rapidly and the normalized AC losses for normalized current decreased.

Transitory Embrittlement of Polycrystalline Silver by Liquid Gallium

The phenomenon of embrittlement of polycrystalline silver (Ag) by liquid gallium (Ga) is known as liquid metal embrittlement (LME). An investigation was performed to determine the effects of holding the solid metal in contact with liquid Ga on the embrittlement. Solid Ag specimens in contact with liquid Ga were placed in a furnace at 308­573K for different time periods before testing at 308K. The specimens undergo severe embrittlement when the holding time is short, whereas ductility is recovered when the holding time is long. The duration of brittleness decreases with increase in furnace temperature, and it is proportional to the amount of Ga on the surface. The brittle to ductile transition is considered to occur during the formation process of an intermetallic Ga and Ag compound. [doi:10.2320/matertrans.M2013394]

Structural characterization and mechanical properties of plasma sprayed nanostructured Cr2O3-Ag composite coatings

In the present study, nanostructured Cr2O3-Ag composite coatings were fabricated by plasma spraying technique and their surface characteristics and mechanical properties were evaluated as a means of improving the tribological performance. For this purpose, Cr2O3 and various amounts of silver nanoparticles (0%, 2%, 5%, and 10), as a solid lubricant phase, were agglomerated into appropriate feedstock powders and plasma spraying parameters were controlled to produce nanostructured composite coatings. The microstructure of coatings was examined by a scanning electron microscope (SEM), phase composition by X-ray diffraction (XRD) and distribution of chemical composition through the thickness by energy dispersive spectroscopy (EDS). The influence of nanostructure on mechanical properties, including hardness and toughness, was evaluated by indentation testing. Uniform distribution of Ag nanoparticles was obtained in Cr2O3-2% Ag and 5% Ag specimens, but accumulation of Ag nanoparticles was observed within interlamellar regions of Cr2O3-10% Ag coating. The presence of nanoparticle zones, comprising 15–18% of the surface area, was observed on the cross sections of the specimens; these zones caused a reduction in lamella thickness and increased the fracture toughness by arresting crack tips.

In vitro cytotoxicity evaluation of porous TiO2–Ag antibacterial coatings for human fetal osteoblasts

Implant-associated infections (IAIs) may be prevented by providing antibacterial properties to the implant surface prior to implantation. Using a plasma electrolytic oxidation (PEO) technique, we produced porous TiO2 coatings bearing various concentrations of Ag nanoparticles (Ag NPs) (designated as 0Ag, 0.3Ag and 3.0Ag) on a Ti–6Al–7Nb biomedical alloy. This study investigates the cytotoxicity of these coatings using a human osteoblastic cell line (SV-HFO) and evaluates their bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA). The release of Ag and the total amount of Ag in the coatings were determined using a graphite furnace atomic absorption spectrometry technique (GF-AAS) and flame-AAS, respectively. Cytotoxicity was evaluated using the AlamarBlue assay coupled with the scanning electron microscopy (SEM) observation of seeded cells and by fluorescence microscopy examination of the actin cytoskeleton and nuclei after 48h of incubation. Antibacterial activity was assessed quantitatively using a direct contact assay. AlamarBlue viability assay, SEM and fluorescence microscopy observation of the SV-HFO cells showed no toxicity for 0Ag and 0.3Ag specimens, after 2, 5 and 7days of culture, while 3.0Ag surfaces appeared to be extremely cytotoxic. All Ag-bearing surfaces had good antibacterial activity, whereas Ag-free coatings showed an increase in bacterial numbers. Our results show that the 0.3Ag coatings offer conditions for optimum cell growth next to antibacterial properties, which makes them extremely useful for the development of new antibacterial dental and orthopedic implants.

Photoelectron angular distributions of Cu, Ag, Pt and Au samples: experiments and simulations

AbstractAngular distributions of photoelectrons emitted from semi‐infinite Cu, Ag, Pt and Au specimens have been measured for off‐normal emission angles in the range between 20 and 70° with a Thermo Theta Probe electron spectrometer. Experimental peak intensities for peaks of atomic subshells observable in the spectra were compared with results of simulations using the NIST Database for the Simulation of Electron Spectra for Surface Analysis (SESSA) that takes into account the effects of (i) anisotropy of the photoelectric cross‐section; (ii) elastic scattering of the photoelectrons; and (iii) the finite solid angle of the detector. In addition, a separate correction was made to the simulated intensities for the effects of surface excitations. The combined influence of these effects was found to significantly affect the angular distributions. Furthermore, it was found that ratios of the calculated peak intensities of the observed subshells for a particular material to the measured intensities deviate from unity by typically less than 1% after corrections for multiple inelastic scattering and surface excitations. Copyright © 2010 John Wiley & Sons, Ltd.

NaCl水溶液中における歯科用Ti-Ag合金の耐食性

The purpose of this study was to evaluate the corrosion resistance of experimental dental Ti-Ag alloys in 0.9% NaCl solution. Open-circuit potential (OCP) measurement and elution tests of the alloys with 5-30% Ag were performed. The amounts of both Ti and Ag ions released from the alloys with Ag≤20% were below the detection limit. A very small amount of Ti ions was released from some of the 22.5% Ag specimens and some of the 25% Ag specimens. The time for the Ti-Ag alloys with 5-25% Ag to become the stable potential was earlier than that for titanium, and the OCP of the alloys was higher than that of titanium. These results indicated that the corrosion resistance of the alloys with 5-25% Ag was equivalent to that of titanium. On the other hand, it was suggested that the precipitation of TiAg deteriorated the corrosion resistance of Ti-Ag alloys because TiAg dissolved preferentially in the NaCl solution. Ti-Ag alloys with 5-25% Ag can be used not only as dental restorative materials but also as dental implant materials.

The microstructure and properties of the Sn-xBi-0.9Zn-0.3Ag lead-free solders

Low Ag content, Sn-Bi-Zn-Ag lead-free solders, have been studied. The microstructures of the Sn-xBi-0.9Zn-0.3Ag (x = 0, 1 and 3, in weight percent, hereafter) specimens are composed of β-Sn phase, AgZn3 intermetallic compounds (IMCs) and Zn-rich phase. Bi precipitates appear when the Bi content amounts to 3 wt%. The Sn-Bi-Zn-Ag alloys exhibit high performance on tensile properties, microhardness and melting temperature, owing to the existence of Bi precipitates. Moreover, the reactions upon heating and cooling of the investigated Sn-Bi-Zn-Ag lead-free solders are also systematically studied.

Corrosion Resistance of Dental Ti-Ag Alloys in NaCl Solution

The purpose of this study was to evaluate the corrosion resistance of experimental dental Ti-Ag alloys in 0.9% NaCl solution. Open-circuit potential (OCP) measurement and elution tests of the alloys with 5–30% Ag were performed. The amounts of both Ti and Ag ions released from the alloys with Ag � 20% were below the detection limit. A very small amount of Ti ions was released from some of the 22.5% Ag specimens and some of the 25% Ag specimens. The time for the Ti-Ag alloys with 5–25% Ag to become the stable potential was earlier than that for titanium, and the OCP of the alloys was higher than that of titanium. These results indicated that the corrosion resistance of the alloys with 5– 25% Ag was equivalent to that of titanium. On the other hand, it was suggested that the precipitation of TiAg deteriorated the corrosion resistance of Ti-Ag alloys because TiAg dissolved preferentially in the NaCl solution. Ti-Ag alloys with 5–25% Ag can be used not only as dental restorative materials but also as dental implant materials. [doi:10.2320/matertrans.M2009355]

Atmospheric corrosion of electro-electronics metals in urban desert simulated indoor environment

The corrosion of pure Ag, Cu, Ni, and Sn specimens exposed for 1 to 24 months in a simulated indoor environment, consisting of a rain sheltered atmospheric corrosion test chamber placed in an urban desert environment (Baja California) has been measured. The corrosion rates of the metals were determined by mass loss measurement and the environment was thus classified in the low to medium indoor corrosivity category (IC2–IC3) according to ISO. Silver and copper weight losses were found to be very similar, while the nickel and tin weight losses were several times lower. The silver surface was tarnished in a non-uniform manner, presenting Ag2S and AgCl corrosion products, while the copper specimens corrode uniformly, being covered with Cu2O corrosion product. Owing to the presence of chloride contamination, the nickel and tin oxide corrosion films show fracture and pitting corrosion, developed over the first few months of exposure.

Effects of primers containing sulfur and phosphate monomers on bonding type IV gold alloy

Objective The purpose of the present study was to evaluate the effect of five primers (two sulfur, one phosphate, and two sulfur–phosphate dual-function primers) on the bond strength between a self-curing luting agent and gold–copper–silver (Au–Cu–Ag) alloy. Methods The primers used were two sulfur primers (V-Primer and Metaltite), one phosphate primer (Epricord), and two primers which contained a sulfur monomer and a phosphate monomer (Alloy Primer and Metaltite/Epricord). The surface of Au–Cu–Ag specimens were blasted with alumina, and then bonded with acrylic rods using a tri- n-butylborane-initiated self-curing luting agent. Shear bond strengths were determined after 5000 thermocycles. An additional alumina-blasted Au–Cu–Ag alloy specimen was subjected to X-ray photoelectron spectroscopy (XPS) analysis. Results The maximum shear bond strengths were obtained with Metaltite/Epricord (29.6 ± 2.3 MPa) and Alloy Primer (23.0 ± 1.6 MPa), followed by Metaltite (10.3 ± 4.2 MPa), V-Primer (8.9 ± 0.6 MPa), Epricord (6.4 ± 1.5 MPa), and No primer control (2.0 ± 0.5 MPa). The XPS analysis detected six chemical elements (Au, Cu, Ag, Al, O, and C) on the Au–Cu–Ag alloy. In addition to pure Au element, the metal oxide-states of Ag 2O, AgO, Cu 2O, and CuO were suggested. Conclusion The combined use of a sulfur monomer and a phosphate monomer significantly improved the bond strength of resin to Au–Cu–Ag alloy which should be especially significant to clinicians.

A novel process for fabricating electrical contact SnO2/Ag composites by reciprocating extrusion

Reciprocating extrusion combined with simple powder compaction was used to produce electrical contact SnO2/Ag composites from Ag and SnO2 powders with improved properties. The SnO2 particles were uniformly dispersed in the Ag matrix after 20 passes of extrusion. The hardness of the composites increased with extrusion passes and leveled off after ten passes, whereas the electrical conductivity decreased slowly after five passes. The variation of the coefficient of thermal expansion with temperature revealed that SnO2/Ag interface strength increased with extrusion passes and was greatest after 20 passes. The SnO2/Ag composites with 20 passes showed the best electrical contact properties in which there was no mass loss through mass transfer from cathode to anode during the make-break erosion test at both low and high current conditions. On the other hand, SnO2/Ag composites with one pass and commercial SnO2-In2O3/Ag specimens had an apparent mass loss under the same condition. Electrical contact composites produced by the present method are promising in electrical contact applications in consideration of cost and performance.

Nanocluster formation during ion irradiation of SiO 2/Ag/SiO 2 multilayers

Nanocluster formation during heavy ion bombardment of a thin contiguous Ag layer sandwiched between two continuous SiO 2 layers has been observed using in situ transmission electron microscopy (TEM). During ion bombardment, irradiation-induced plastic flow of the Ag film enlarges pre-existing pin holes and separates the film at grain boundaries transforming the as-deposited thin Ag film into three-dimensional microcrystals having diameters greater than 30 nm. This plastic flow process is similar to that observed in free-standing Ag specimens during heavy ion irradiation. In addition to plastic flow, ballistic recoils inject Ag atoms into the SiO 2 where they precipitate into nanoclusters. Both effects are greatly enhanced by simultaneous electron and ion irradiation.

The dependence of normal and abnormal grain growth in silver on annealing temperature and atmosphere

When polycrystalline pure Ag specimens are compressed to 40 pct and annealed, there is no noticeable texture in the recrystallized structure, and normal or abnormal grain growth occurs during annealing. When annealed further in low vacuum (10−3 to 10−4 Torr) after the completion of recrystallization, normal grain growth occurs at 920 °C and 800 °C, but abnormal grain growth (AGG) occurs at 700 °C, 600 °C, and 500 °C. When annealed in O2 atmosphere, normal grain growth occurs at 920 °C and AGG at 800 °C, 700 °C, 600 °C, and 500 °C. At temperatures close to the melting point (960.5 °C), the grain boundaries are expected to be rough at atomic scales and hence have nearly isotropic boundary energy. The normal growth of the grains with such atomically rough boundary structures is consistent with some theoretical analysis and simulation. At low temperatures, the grain boundaries can be faceted with probably singular structures. Because these grain boundaries apparently migrate by the movement of boundary steps, AGG occurs. The observations with optical microscopy indeed indicate that some grain boundaries are faceted at low temperatures and all of them are smoothly curved indicating an atomically rough structure at high temperatures close to the melting point. Although the results are not conclusive, they support the hypothesis that AGG occurs because the faceted singular grain boundaries migrate by the step mechanism.