Microstructure Of Ag Research Articles

The Improved Age Hardening Response of Mg-11Al Alloys with Ag, Sc Addition and Corresponding Microstructure Characterization

The Improved Age Hardening Response of Mg-11Al Alloys with Ag, Sc Addition and Corresponding Microstructure Characterization

Chemical Activation Boosted Interface Interaction between Poly(tetrafluoroethylene-co-hexafluoropropylene) Film and Silver Coating.

To enhance the interfacial adhesion between poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) film and functional coatings, such as silver (Ag) coating, among others, the surface activation of FEP film has to be performed. Among various activation strategies, chemical activation, such as using naphthalene sodium system, is one of the most efficient methods. However, the effect of chemical activation on the interface interaction between the activated FEP and functional coating is rarely investigated. Herein, the FEP film was activated by naphthalene sodium solution under different conditions, and then the Ag layer was coated onto its surface by vacuum Ag deposition. Based on experimental results and density function theory (DFT) calculation, it is indicated that oxygen-containing functional groups (such as C=O and C-OH groups), introduced onto the surface of FEP by the chemical activation, play a key role in boosting the interface interaction, which is due to the strong interaction between the oxygen-containing functional groups and Ag atoms. In addition, the concentration of naphthalene sodium solution, activation time, and winding speed of Ag- deposition can have a significant impact on the microstructures of Ag coating and the interfacial adhesion between the activated FEP and Ag coating. Under the conditions of high concentration (0.9 M), medium activation time (15 min), and high winding speed (0.8 m min-1), there is the best interface adhesion.

Enhanced Durability and Antireflective Performance of Ag-Based Transparent Conductors Achieved via Controlled N-Doping.

Ag-based transparent conductors (TCs) are often proposed as an alternative to ITO coatings. However, while their performance has been widely demonstrated, their environmental durability is frequently overlooked or addressed with the use of highly specific encapsulating layers. In this work, the durability and antireflective performance of Ag-based TCs are simultaneously enhanced. To do so, a transfer matrix modeling approach is used to determine the general requirements for high performance antireflective properties as a function of Ag thickness and dielectric refractive indices, offering more widely applicable insight into stack optimization. Coating durability is investigated as a function of the Ag microstructure, which is modified by altering the N2 concentration used for doping of the Ag layer and the selection of the seed layer. Increasing N2 concentration during Ag deposition was found to decrease grain size and durability of Ag coatings deposited on Si3N4 whereas all coatings on ZnO(Al) showed higher stability. Significantly higher durability is found when specifically combining intermediate N2 concentrations in the sputtering gas mixture (Ag(N):5%, compared to 0% and 50%) and a ZnO(Al) seed layer, and a mechanism accounting for this increased durability is proposed. The addition of NiCrNx protective coatings increases the system durability without altering these trends. These findings are combined to fabricate a highly performant Ag-based TC (TV = 89.2%, RVFS = 0.23%, 21.4 Ω), which shows minimal property changes following corrosion testing by immersion in a heated and highly concentrated aqueous NaCl solution (200 g/L, 50 °C).

Abnormal evolution of resistivity and microstructure of annealed Ag nanoparticles/Ag–Mo films

Abstract Ag–Mo films with different thicknesses were prepared on polyimide substrate by magnetron sputtering and annealed at different temperatures. The effects of film thickness and annealing temperatures on the resistivity and microstructure of Ag–Mo alloys were investigated. Results show that many Ag nanoparticles were self-formed on Ag–Mo films’ surface. As the thickness of the Ag–Mo film increased from 163 to 409 nm, there was a significant decrease in its resistivity, dropping from 485.44 to 237.12 μΩ cm. Resistivity of the Ag–Mo film is dependent on the annealing temperature. When temperature rises from room temperature to 180℃, the resistivity decreases from 390.62 to 339.37 μΩ cm, with little change. After annealing above 270℃, a sudden increase of resistivity of the Ag–Mo film was attributed to the growth of Ag particles on the film surface contributing to the increase in surface roughness, which hindered electron transport and caused severe surface scattering. High-resistivity Ag–Mo films are expected to be candidates for high-resistivity thin-film devices.

Fabrication of 3D popcorn-like Ag microstructures film array substrate: SERS and catalytic property

Surface-enhanced Raman scattering (SERS) has tremendous significance in the fields of ultrasensitive detection and real-time in situ monitoring in catalysis. However, it remains a challenge to simultaneously achieve higher-quality SERS and excellent plasmonic catalytic properties in a nano/microstructure substrate under random excitation light. Here, we propose the design of a three-dimensional (3D) popcorn-like silver (Ag) microstructure (MS) with diameter of 1.2 ± 0.1 µm and a unique rough surface topography, realize a wide surface plasmon resonance (SPR) band ranging from 300 nm to 1100 nm, approximating a full spectrum. The popcorn-like Ag MSs with full-spectrum property effectively broaden the spectral overlap between the SPR band and wavelength of excitation light or absorption of probe molecules. Moreover, the 3D popcorn-like Ag MSs were used to construct a monolayer film array substrate on silicon wafer with a good homogeneity over large areas by an interfacial self-assembly method. The monolayer Ag MSs film array substrate can provide abundant “hot spots” and present excellent SERS performance for sensitive detection of Rhodamine 6G (Rh6G) with a low detection limit of 10−9 M. The single-layer Ag MSs film array with superior SERS activity is utilized for in situ monitoring the plasmonic catalytic kinetics of 4-nitrothiophenol (4-NTP) dimerized into 4, 4′-dimercaptoazobenzene (DMAB) under 532 nm and 785 nm excitation, respectively. The mechanism on plasmonic catalytic reaction of the popcorn-like Ag MSs substrate is systemically investigated by experimental and theoretical simulations aspects. The Ag MSs film array substrate will offer a new strategy to further explore applications of SERS in sensors, photocatalysis, and bio/chemical analysis.

Investigating on the microstructure and optical properties of Au, Ag and Cu implanted TiN thin films: The effects of surface oxidation and ion-induced defects

In the present paper, the effects of metal ion implantation on the structural and optical properties of TiN thin films have been investigated. TiN films of 170 nm thickness were grown by d.c. reactive sputtering on Si (100) wafers and then irradiated at 5 × 1016 ions/cm2 with either Au, Ag, or Cu ions by using two different energies per each implanted metal. The results showed that as deposited TiN crystallizes in the form of a fcc cubic structure, with the crystallites preferentially oriented along the (111) plane. For all implanted layers, the cubic structure was preserved, but compared to as deposited TiN the crystallites were smaller and the lattice was contracted. These changes were correlated with the depth distribution of Au, Ag and Cu ions and assigned to implantation-induced damage that was larger when higher ion energies were used. High-resolution XPS spectra of the surface of as deposited sample showed the coexistence of TiN, TiO2 and TiOxNy phases and this was related to the surface oxidation of the films due to the exposure to air. After implantation, the results were almost similar for all metals, showing an increase in TiO2 contribution and the formation of pure metallic Au and Ag phases, while copper is in the Cu2+ state, which is attributed to Cu(II)-oxide and Cu(OH)2. The microstructural characteristics including defect formation, changes in crystallite size and lattice contraction, and also growth of different metallic phases during implantations were correlated with the findings of the optical characterization of the implanted films. For the as deposited film we found an energy gap of 2.91 eV, which was lower than the value typical for TiN. After implantation the gap was shifted to higher energies, while at the visible part of the region, the existence of additional energy levels, at photon energies below 2.9 eV was observed. Besides, all implanted films showed degraded photocatalytic activity compared to as deposited TiN, among which Cu-implanted samples exhibited the best photocatalytic performances. The lower photocatalytic activity of Au and Ag implanted films compared to Cu implantations was ascribed to larger structural defects and the formation of less favorable electronic states.

Solidification behavior and microstructure of Ag–Cu eutectic alloy at different sub-rapid cooling rates

The microstructures of rapidly solidified Ag-39.9 at. % Cu eutectic alloys have been widely studied, while the research between microstructures and sub-rapid cooling rates is still lacking. Ag-39.9 at. % Cu eutectic alloy was solidified in quartz crucibles under different conditions. The alloy that was melted and in-situ cooled in a quartz crucible to room temperature solidified into eutectic dendrites composed of regular lamellae. The alloy that was melted and injection cast into a quartz crucible solidified into equiaxed eutectic colonies with primary α-Ag phase embedded. If the quartz crucible was further immersed in a gallium-indium liquid, a new spherical eutectic colony structure was found, with anomalous eutectic or primary α-Ag phase at the central part and a “ring” of coarse lamellar eutectic structure separating the eutectic colony into two parts. It is demonstrated that the cooling rate influences not only the primary phase selection and eutectic lamellar spacing, but also the eutectic nucleation and growth mode.

Thermodynamic modeling and solidified microstructure of Ag—Sn—Zr ternary system

The phase equilibria of the Ag—Sn—Zr ternary system were investigated over the whole composition via thermodynamic modeling coupled with key experiments. Twenty-two equilibrated alloys were prepared to determine the isothermal sections of the Ag—Sn—Zr system at 500, 700 and 900 °C by means of X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), and eight as-cast alloys were prepared to study the solidification behavior of the alloys. The solubilities of Zr, Sn and Ag in binary compounds of the Ag—Sn, Ag—Zr and Sn—Zr systems were measured. No ternary compound was found. Based on the thermodynamic descriptions of three constitutive binary systems as well as the experimental phase equilibria data obtained from the present work, thermodynamic assessment of the Ag—Sn—Zr system was carried out by the CALPHAD (Calculation of phase diagrams) approach. A set of thermodynamic parameters of the Ag—Sn—Zr system were obtained. The calculated isothermal sections are in good agreement with most of the reliable experimental data. The liquidus projection and reaction scheme of the Ag—Sn—Zr system over the whole composition were also presented. The solidification behaviors of as-cast alloys were simulated under Gulliver—Scheil non-equilibrium condition. The simulated and experimental results are consistent with each other.

Enhancing the tribological performance of Cu-WS2 composites with Ag-shell/Cu-core structure

The interface reaction between Cu and WS2 is an essential factor affecting the tribological properties of Cu-WS2 composites, and it is urgent to avoid and reduce the interface reaction. In this study, Ag-shell/Cu-core powder was fabricated by electroless plating, which was used to produce the (Ag shell/Cu core)-WS2 composites. For comparison, Cu-WS2 composites were prepared with pure Cu powder. The microstructure and tribological behaviors of (Ag shell/Cu core)-WS2 and Cu-WS2 composites were carefully investigated. Results revealed that the friction coefficient and wear rate of (Ag shell/Cu core)-WS2 were 0.21 and 15.4 × 10−6 mm3/(N·m) under 5 N, which were 66% and 79% lower than those of Cu-WS2 composites, respectively. The superior tribological performance of (Ag shell/Cu core)-WS2 composites stemmed from Ag-shell/Cu-core structure, which prevented the interfacial reaction during hot-pressing (HP) sintering. The WS2 could be well retained and form a low-shear transfer film with a coverage of more than 86.5%.

Effect of Magnetic Stirring on Microstructures and Properties of Ag-1.5Cu-1.0Y Alloy.

The microstructure of alloys is an important factor that affects their application. In this work, the Ag–1.5Cu–1.0Y alloys were prepared by the permanent magnet stirring method at different rates. The secondary dendrite arm spacing, dendritic segregation, density, microhardness, electrical resistivity, and sulfuration corrosion resistance were analyzed to investigate the effects of different rotation speeds on the microstructures and properties of the Ag–1.5Cu–1.0Y alloy. The results showed that the primary dendrite was refined and the secondary dendrite arm spacing decreased with the increase in the stirring rate of the permanent magnets. The Ag–1.5Cu–1.0Y alloys prepared with a 900 r/min stirring rate had the largest microhardness, relatively high density, and the best sulfuration corrosion resistance. However, the stirring rate had little effect on the electrical resistivity of the Ag–1.5Cu–1.0Y alloys. To sum up, the Ag–1.5Cu–1.0Y alloy had the best comprehensive properties when the permanent magnet stirring rate was 900 r/min, including the most refined dendrites, relatively high density, the largest microhardness, and the best sulfuration corrosion resistance. The study of the effects of permanent magnet stirring speed on the microstructures and properties of the Ag–1.5Cu–1.0Y alloy provides an experimental basis for future alloy casting optimization and property improvement of silver-based alloys.

Selective Laser Melting of Pure Ag and 925Ag Alloy and Their Thermal Conductivity

Due to the high reflectivity of Ag to infrared lasers, there is little research focused on the manufacturing of Ag and Ag alloys by selective laser melting (SLM) technique. In this paper, the manufacturing characteristics, microstructure, and thermal conductivity of SLMed Ag, 925Ag, and their heat-treated parts were studied. With the suitable processing parameters, Ag and 925Ag samples with relative densities of 91.06% and 96.56%, respectively, were obtained. Due to the existence of non-molten particles inside the samples and local high energy density of the laser during the processing, a large number of irregular pores and micropores were formed in the microstructures. XRD analysis shows that no phase transition occurred in the annealed Ag and solution-treated 925Ag parts, as compared to their as-built conditions. The SLMed Ag exhibited fine equiaxed grains, while both columnar grains and elongated lath grains existed in the SLMed 925Ag parts. The annealed Ag and solution-treated 925Ag exhibited large equiaxed grains. Due to the grain growth that occurred in the microstructure, the thermal conductivity of Ag increased by 11.35% after completing the annealing treatment. However, that of 925Ag decreased by 17.14% after completing the solid solution treatment, due to the precipitation of the strengthening phase at grain boundaries. A comparison of the thermal conductivities of Ag and 925Ag shows that the influence of the materials on the obtained thermal conductivities was more pronounced than that of the porosity.

Low concentration isopropanol gas sensing properties of Ag nanoparticles decorated In2O3 hollow spheres

In order to detect low concentrations of volatile organic compounds (VOCs) for the early diagnosis of lung cancer, sensors based on hollow spheres of In2O3 were prepared through the soft template method. Ag nanoparticle decorated In2O3 composites were synthesized via dipping and annealing. The microstructure, phase composition, element distribution, and state of Ag were analyzed by the scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The gas sensing tests showed that Ag-In2O3 sensors had the highest response to isopropanol at 300 °C. The best response of Ag-In2O3 composite sensor was 5.2, which had a significant improvement compared with only In2O3. Moreover, the response and recovery time of Ag-In2O3 composite sensor was significantly shortened. The improved sensing properties of Ag-In2O3 composite sensor could be attributed to the Schottky barrier created at Ag-In2O3 interface and catalytical effect of Ag.

Plastic deformation induced formation of supersaturated solid solution nanostructure in a dual-phase Cu-Ag alloy

A gradient nanostructured (GNS) surface layer was generated in a dual-phase Cu-Ag alloy by means of surface mechanical grinding treatment at liquid nitrogen temperature. With a decreasing depth in the surface layer, the coarse-grained microstructure of Cu matrix and Ag precipitates gradually converts into a nanolaminated structure of Ag- and Cu-rich phases with simultaneous chemical mixing, and finally forms a homogeneous single-phase supersaturated solid solution (SSS) nanostructure. Accordingly, a dislocation-mediated transportation mechanism was proposed to dominate the chemical mixing of Ag and Cu atoms, i.e., dislocations interacting with solution atoms penetrate the Cu/Ag interface and glide in the neighboring solvent-phase lamella.

Amelioration of boiling heat transfer by 3D deposition structure of graphene-silver hybrid nanoparticle

• The novel hybrid coating solves the thermal barrier problem of graphene. • Modification makes the coating have rich chemical bonds and complex microstructure. • The oxygen-containing functional groups promote the capillary effect of coating. • Concentration has little effect on structure and element content of hybrid coating. During the boiling process, the heating surface has a substantial influence on the growth of the bubbles, the wetting of dry spots, and the deposition of the particles. Therefore, improving the surface properties is one of the main ways to enhance heat transfer. In this study the heating coatings were prepared by boiling deposition using GNP nanofluids, GNP/Ag mixed nanofluids, and GNP-Ag hybrid nanofluids with different mass fractions (wt% = 0.001,0.002,0.003) as raw materials. The boiling heat transfer characteristics of DI water on the bare copper surface and heating coatings were studied, and the heat transfer mechanism was analyzed. The results show that GNP-Ag hybrid nanoparticle coating has the most outstanding enhanced heat transfer effect. DI water achieves the highest critical heat flux (CHF) of 163.65 W/cm 2 and heat transfer coefficient (HTC) of 9.69 W/cm 2 K on the coating, which are respectively 45.84% and 82.14% higher than the smooth copper surface. The wettability was analyzed by measuring the contact angle. Scanning electron microscope image was used to analyze the microstructure of the coating. The microstructure of Ag modified functionalized GNP nanoparticle has a great change compared with mixed nanoparticles. It was observed that the hybrid nanoparticle deposit into a large number of bulges and cavies, and the bulges accumulate in clusters and form self-assembled flower-shaped bulges. Combined with the energy spectrum test results of the heating coating, the coverage of the nanoparticles in the coating on the copper substrate and the variation trend of each deposited element with the concentration are analyzed. The novel heating coating enhances heat transfer under the combined action of nanoparticle functional groups, coating microstructure, and wettability. GNP-Ag hybrid nanoparticle coating was applied towards the heat dissipation of electronic devices. When the input power is 300 W, the maximum temperature of electronic devices is 108.52 °C, which is much lower than that of other coatings.

Influence of Co contents on the microstructure and SERS performance of self-formed Ag nanoparticles/Ag-Co alloy films on flexible substrates

Self-formed Ag nanoparticles/Ag-Co alloy films with various Co contents were fabricated by sputtering Ag-Co composite target. Effects of Co contents in Ag-Co films on the microstructure and SERS performance of nanoparticles/alloy films were thoroughly investigated through SEM, TEM and Raman spectrometer. Amorphous Co in Ag-Co films restricted the growth of Ag grains in the films and promoted the formation and growth of Ag nanoparticles on the film’s surface. The size and number of Ag nanoparticles grown on the surface were closely related to Co contents in Ag-Co films, Ag-Co film thicknesses and annealing temperatures. Ag nanoparticles/Ag-Co films covered with Ag layers performed ultra-sensitive Raman signals due to forming abundant active hot spots. This flexible SERS substrate could detect 10−12 mol/L Rhodamine 6G (R6G), which indicated that this novel type of Ag nanoparticles/Ag-Co alloy films could be used and applied as high-efficient SERS substrates.

Evolution of microstructure and properties of Ag and Si-doped AlMg alloys

Evolution of microstructure and properties of Ag and Si-doped AlMg alloys

The microstructural refinement and performance improvement of a nanoporous Ag/CeO2 catalyst for NaBH4 oxidation

In this paper, Cu and Ce were added to melt-spun Al–Ag precursor alloys to refine the microstructures of nanoporous Ag and Ag/CeO2 composite catalysts for NaBH4 oxidation. After the precursor alloys were dealloyed in 20% NaOH, calcined in air and corroded again in 50% NaOH, Ag2Al in the precursor alloys was completely removed, and refined nanoporous Ag could be obtained; from this process, the finest microstructures were exhibited by Al84Ag8Cu8. When more than 0.3% Ce was added to the Al84Ag8Cu8 ribbons, a refined nanoporous Ag material that consisted of CeO2 nanorods interspersed between Ag ligaments was obtained. Electrochemical measurements indicated that the catalytic properties were clearly increased due to the Cu addition to the Al–Ag alloy. After Ce was added to the Al84Ag8Cu8 ribbons, the catalytic properties of the resulting material were further improved. In regard to melt-spun Al84Ag8Cu8Ce0.5, the obtained nanoporous Ag/CeO2 presented the best properties, and its current density was 2.5 times that of Al84Ag8Cu8, 3.1 times that of Al90Ag8Cu2 and 2.3 times that of Ag/Ce from the Al79Ag15Ce6 precursor alloy without Cu. It was believed that the core–shell structure composed of Ag and Cu-rich phases formed during dealloying could limit the diffusion of Ag and prevent the coarsening of Ag ligaments. Thus, the refined microstructures could provide a large specific surface or additional active sites for the catalytic reaction. Strong interactions resulted from the many interfaces between the Ag ligaments and interspersed CeO2 nanorods, and the more effective utilization of Ag was due to the decomposition of Ag2Al; this result was the key reason for the clear improvement in catalytic performance.

Fracture mechanism of microporous Ag-sintered joint in a GaN power device with Ti/Ag and Ni/Ti/Ag metallization layer at different thermo-mechanical stresses

Ag sinter joining technology is emerging as a die attach material for next-generation power modules in high-temperature applications. Thermal shock test has revealed that the fracture characteristics and reliability of sintered Ag joint were influenced by thermo-mechanical stress. This was study conducted to understand the microstructure, vertical crack formation, and fracture behavior of sintered Ag joints which were designed with different metallization layers on a direct bonded aluminum (DBA) substrate, at different thermo-mechanical stresses during thermal shock tests. Two kinds of metallization layers were designed as Ti/Ag and Ni/Ti/Ag layers. A finite element model (FEM) simulation confirmed that the Ni layer prohibited Al hillock-like deformation and generates different thermo-mechanical stresses during the thermal shock test from − 50 °C to 250 °C. Depending on the degradation of the interfaces for both of the Ag-sintered joints, the sintered Ag grain necking thickness and microstructure characteristics including the Ag grain structures, which have a dominant influence on the bonding strength in terms of long-term reliability, are considerably different from the results by an electron back scatter diffraction (EBSD) analysis. This paper proposes a novel metallization technology that can induce joint fracture with complete recrystallization of sintered Ag joints by effectively suppressing interfacial degradation. The mechanism of this technology was systematically analyzed through experiments and FEM simulations.

Specific heat, thermal diffusivity, and thermal conductivity of Ag–Si alloys within a wide temperature range of 293–823 K

The laser flash method was employed to explore the heat transfer behaviors of Ag-x at.% Si (where x = 0, 5, 11, 25, 50, 75 and 100) alloys over a wide temperature range from 293 to 823 K. The temperature dependency of specific heat and thermal diffusivity were determined by a differential scanning calorimeter and laser flash equipment. Accordingly, the thermal conductivity of Ag–Si alloys was derived. It is found that the thermal conductivity decreases with increasing temperature. At a certain temperature, there is a sharp decline of thermal conductivity with the rising Si content before it reaches the eutectic composition. The decreasing rate of conductivity with rising Si content reduces when Si content is larger than 11%. The microstructures of Ag–Si alloys reveal that the abnormal thermal conductivity at eutectic composition may be caused by the large amount of phase boundaries.

Microstructure, anti-corrosion and biological performance of Ag, Zn Co-doped titania coating: The influence of Zn contents

Bio-medical materials with sufficient antibacterial performance and osteogenic activity are desirable for orthopaedic implantable devices. In the present work, titanium (Ti) surface was modified through micro-arc oxidation in an electrolyte containing Ag nanoparticles (NPs) and disodium zinc ethylenediaminetetraacetate tetrahydrate (Na2Zn-EDTA) to fabricate Ag, Zn co-doped titania coating, with the influence of Na2Zn-EDTA content on its microstructure, corrosion behaviour and biological performances investigated systematically. By increasing the amount of Na2Zn-EDTA from 5 g/L to 50 g/L, the coating exhibits a significantly reduced average pore size along with a decreased coating thickness. Further, unlike micro-sized dicalcium phosphate dehydrate (DCPD) crystals and Ag NP clusters for the coating produced by 5 g/L Na2Zn-EDTA, both Ag NPs of a reduced amount and nano-sized amorphous Ca and P-rich components were observed on the coating surface when the electrolyte containing 50 g/L Na2Zn-EDTA was used. The microstructural variation inevitably leads to the modification of its performances. The high amount of Na2Zn-EDTA results in a bio-ceramic characterized by higher corrosion resistance, enhanced antibacterial capability and improved osteogenic activity relative to that fabricated with the addition of a low amount of Na2Zn-EDTA. Therefore, this work provides a new strategy for the fabrication of bio-ceramics on Ti-based implants.