Ag Phase Research Articles

Design and Properties of New Lead-Free Solder Joints Using Sn-3.5Ag-Cu Solder

This article aims to reduce the melting temperature of lead-free solder alloy and promote its mechanical properties. Eutectic tin-silver lead-free solder has a high melting temperature 221 ∘C used for electronic component soldering. This melting temperature, higher than that of lead–tin conventional eutectic solder, is about 183 ∘C. The effect of the melt spinning process and copper additions into eutectic Sn-Ag solder enhances the crystallite size to about 47.92 nm which leads to a decrease in the melting point to about 214.70 ∘C, where the reflow process for low heat-resistant components on print circuit boards needs lower melting point solder. The results showed the presence of intermetallic compound Ag3Sn formed in nano-scale at the Sn-3.5Ag alloy due to short time solidification. The presence of new intermetallic compound, IMC from Ag0.8Sn0.2 and Ag phase improves the mechanical properties, and then enhances the micro-creep resistance especially at Sn-3.5Ag-0.7Cu. The higher Young’s modulus of Sn-3.5Ag-0.5Cu alloy 55.356 GPa could be attributed to uniform distribution of eutectic phases. Disappearance of tin whiskers in most of the lead-free melt-spun alloys indicates reduction of the internal stresses. The stress exponent (n) values for all prepared alloys were from 4.6 to 5.9, this indicates to climb deformation mechanism. We recommend that the Sn95.7-Ag3.5-Cu0.7 alloy has suitable mechanical properties, low internal friction 0.069, low pasty range 21.7 ∘C and low melting point 214.70 ∘C suitable for step soldering applications.

Synthesis and Characterization of Ag/TiO<sub>2</sub> Thin Film via Sol-Gel Method

Ag/TiO2thin films were prepared via sol-gel spin coating method. Structural, surface morphology and optical properties were investigated with the addition of two different amount of silver (Ag). X-ray diffraction pattern shows the sample with pure TiO2, the only phase presence was brookite TiO2. When the Ag content added into the solution, the phase existed for the samples with TiO2doped 0.5g Ag and TiO2doped 1.0g Ag were anatase TiO2with no peak corresponds to Ag phase. The surface morphology of film was characterized by scanning electron microscopy (SEM). The films were annealed at 450 °C and it shows non-uniform films. The films have a large flaky and cracks film which was attributed to surface tension between the film and the air during the drying process. When the solution of sol was added with Ag content, it shows the porous structure with flaky-crack films. With the increasing of the Ag content from 0.5g to 1.0g, the structure is more porous and it is good for the photocatalytic activity. The UV-Vis spectra shows that the film exhibits a low absorbance which was due to the substrate is inhomogeneously covered by the flaky-crack films.

Microstructure and Mechanical Properties of Stainless Steel/Brass Joints Brazed by Sn-Electroplated Ag Brazing Filler Metals

To develop a high-Sn-content AgCuZnSn brazing filler metal, the BAg50CuZn was used as the base filler metal and a Sn layer was electroplated upon it. Then, the 304 stainless steel and the H62 brass were induction-brazed with the Sn-plated brazing filler metals. The microstructures of the joints were examined with an optical microscope, a scanning electron microscope and an x-ray diffractometer. The corresponding mechanical properties were obtained with a universal tensile testing machine. The results indicated that the induction brazed joints consisted of the Ag phase, the Cu phase and the CuZn phase. When the content of Sn in the Sn-plated Ag brazing filler metal was 6.0 or 7.2 wt.%, the Cu5Zn8, the Cu41Sn11 and the Ag3Sn phases appeared in the brazed joint. The tensile strength of the joints brazed with the Sn-plated filler metal was higher compared to the joints with the base filler metal. When the content of Sn was 6.0 wt.%, the highest tensile strength of the joint reached to 395 MPa. The joint fractures presented a brittle mode, mixed with a low amount of ductile fracture, when the content of Sn exceeded 6.0 wt.%.

An investigation on shear banding and crystallographic texture of Ag–Cu alloys deformed by high-pressure torsion

Ag–Cu alloys of two different initial microstructures—a cast eutectic alloy (AgCu-E) and an equivolume Ag–Cu powder mixture (AgCu-P)—were deformed by high-pressure torsion. The codeformation of Ag and Cu grains led to uniform refinement and a nanolamellar microstructure for both alloys. However, the lamellar structure in AgCu-P alloys was broken at intermediate shear strains (γ > 150) by extensive shear banding. On the other hand, no shear banding was observed for AgCu-E alloy at similar microstructural refinement. At higher strains deformation induced intermixing of Ag and Cu atoms was observed. Further, three-dimensional diffraction analysis of AgCu-E alloy showed that in contrast to conventional single phase alloys, the Ag and Cu phases develop similar crystallographic texture.

Processing and Characterization of Ag-Cu-Sn Brazing Alloy Prepared by a Mechanical Alloying Method

Mechanical alloying was used to prepare an Ag-Cu-Sn brazing alloy with the low amounts of intermetallic compounds. X-ray diffraction and differential scanning calorimetry were carried out to investigate the phase transformation of the as-milled samples. It seemed that the intermetallic compounds experienced the stage of synthesis-decomposition-resynthesis in the ball milling process. By controlling the ball milling time and tin contents, the solid solution phases of Ag (Cu, Sn) and Ag (Cu) were achieved in the 60Ag30Cu10Sn sample after milling for 40 h. Although the intermetallic compound will be generated during the brazing process, the improvement of their distributed morphology is beneficial for the good bonding interface of the joint with stainless steel substrate.

Complex Oxides Based on Silver, Bismuth, and Tungsten: Syntheses, Characterization, and Photoelectrochemical Behavior

Silver-containing complex oxides present interesting light absorption and electronic properties pointing to their applicability for solar fuel generation and environmental remediation. In this vein, the syntheses, characterization, and photoelectrochemical properties of the Aurivillius oxide, AgBiW2O8, and a triphasic material, AgBiW2O8/Bi2WO6/Ag, are described herein. From UV–vis diffuse reflectance analysis, both oxides’ nanoparticles exhibited intense absorption at wavelengths <455 nm, with an additional band centered at ∼500 nm for the triphasic material, attributed to surface plasmon resonance of the metallic Ag phase. The triphasic material was further characterized by a variety of structural and spectroscopic probes, indicating a defect-rich crystalline structure. Voltammetric measurements were performed in the dark and under simulated solar irradiation with polarization at potentials more negative than the rest potential. Thin film electrodes of both materials showed p-type semiconductor behavior,...

Influence of Ag additions on the structure, mechanical properties and oxidation behaviour of Cr-O coatings deposited by HiPIMS

Here, we investigate the influence of Ag additions on the properties of Cr-O coatings deposited by magnetron sputtering. The deposition rate of Cr-O coating is 1.6 times higher than a single Cr coating, taken as reference, deposited with identical conditions. Incorporation of Ag in the Cr-O coating increases the deposition rate. Transition from a dominant columnar to a very compact morphology, as well as from crystalline to amorphous structure, was observed with the O addition. However, no morphological changes were observed with Ag additions. Annealing at temperature ≥ 500 °C promotes the crystallization of Cr-O and Cr-O-Ag coatings, i.e. the formation of a crystalline composite structure, formed by: Cr, Cr2O3 and Ag phases, the later in the case of Cr-O-Ag coatings. The increase of coatings crystallinity improved the mechanical properties. Thermogravimetric analysis showed that O and Ag additions to Cr have no influence on the onset point of oxidation. The oxidation kinetics of the Cr-based coatings is controlled by the outward diffusion of Cr ions through a top Cr2O3 layer. A dual oxide layer was formed for Cr-O and Cr-O-Ag coatings, when exposed to a continuous increase of the temperature up to 1200 °C. A compact layer of Cr2O3 grows on top of the coating, due to the Cr ions outwards diffusion, leaving behind a porous layer formed by Cr2O3 grains resulting from the recrystallization process, together with Ag agglomerates inside the empty porous zones.

Structural, Mechanical and Tribological Properties of NbCN-Ag Nanocomposite Films Deposited by Reactive Magnetron Sputtering

In this study, reactive magnetron sputtering was applied for preparing NbCN-Ag films with different Ag additions. Ag contents in the as-deposited NbCN-Ag films were achieved by adjusting Ag target power. The composition, microstructure, mechanical properties, and tribological properties were characterized using energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HRTEM), Raman spectrometry, nano-indentation, and high-temperature sliding wear tests. Results indicated that face-centered cubic (fcc) NbN, hexagonal close-packed (hcp) NbN and fcc Ag, amorphous C and amorphous CNx phase co-existed in the as-deposited NbCN-Ag films. After doping with 2.0 at.% Ag, the hardness and elastic modulus reached a maximum value of 33 GPa and 340 GPa, respectively. Tribological properties were enhanced by adding Ag in NbCN-Ag films at room temperature. When the test temperature rose from 300 to 500 °C, the addition of Ag was found beneficial for the friction properties, showing a lowest friction coefficient of ~0.35 for NbCN-12.9 at.% Ag films at 500 °C. This was mainly attributed to the existence of AgOx, NbOx, and AgNbOx lubrication phases that acted as solid lubricants to modify the wear mechanism.

Effects of nanoparticles on the thermal, microstructural and mechanical properties of novel Sn3.5Ag0.5Zn composite solders

The effects of added nanoparticles (i.e., Al2O3 and TiO2) on the thermal, microstructural and mechanical properties of Sn3.5Ag0.5Zn nanocomposite solders have been investigated. Adding nanoparticles to the Sn3.5Ag0.5Zn solder increases the melting temperature by only 2.1–4.6 °C. It was also confirmed that the nanoparticles affect the microstructural and mechanical properties. The UTS, 0.2 YS, and microhardness of the Sn3.5Ag0.5Zn nanocomposite solder improved, which could be attributed to the refinement of the β-Sn grain size, the precipitation of Ag3(Sn, Zn) grains, and the second phase dispersion strengthening mechanism. The fracture mechanism of Sn3.5Ag0.5Zn nanocomposite solders was confirmed to be the ductile fracture mode. The cracks were initiated at the interfaces between β-Sn(Zn) grains and Ag(Zn, Sn) phases.

&lt;i&gt;Conocarpus erectus&lt;/i&gt; Leaf Extract for Green Synthesis of Silver Nanoparticles

Silver nanoparticles (SNPs) were synthesized by a green method using Conocarpus erectus leaves extract. Leaves were cleaned and used freshly then the extract was obtained by heating leaves in water for 15 min. Silver nitrate used as SNPs precursor and 5 mL of extract were added to silver ion solution at 80 °C and the growth of nanoparticle was monitored by electronic spectra at plasmon resonance absorption of SNPs, where the growth obeys sigmoidal kinetics. SNPs were characterized by SEM, XRD, FTIR, UV-vis absorption and fluorescence, and particle size was estimated. SEM reveals that the SNPs had spherical shape and particle size less than 100 nm. XRD analysis showed that only Ag phase was present and the estimated particle size was 20 nm. FTIR spectra analysis showed similarity of extract and SNPs, indicating the adsorption of active components of the extract on the high surface area of SNPs. Electronic absorption and fluorescence spectroscopy showed that plasmon absorption and fluorescence in the visible region were a characteristic feature of SNPs. Antibacterial activity examined against Escherichia coli and Staphylococcus aureus indicated that the inhibition zones were equal to 24 and 19 mm, respectively.

Wetting and solidification of silver alloys in the presence of tungsten carbide

The wettability of pure Ag and Ag alloys (with Ni and Cu) on WC was investigated as a function of temperature by means of sessile drop experiments. Ni was found to preferentially segregate at the Ag/WC interface resulting in a decreased contact angle as compared to Cu. The influence of the Ni content and WC particle size on the solidification behavior of Ag in infiltrated Ag-WC-Ni (40 wt% WC and 0.07/5 wt% Ni) composites was assessed, revealing the pushing of WC particles by the solidification front, especially in the materials with a finer WC particle size. Addition of Ni decreased the grain size of the Ag phase by promoting heterogeneous nucleation. Complete coherency between the Ag and Ni phases was confirmed by electron backscattered diffraction analysis.

The influence of Ag contents on the microstructure, mechanical and tribological properties of ZrN-Ag films

A series of ZrN-Ag films with various Ag contents (Ag/(Zr + Ag), at.%) were deposited by reactive magnetron sputtering and their microstructure, mechanical and tribological properties at various testing temperatures were investigated by the energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), nanoindenter and high temperature tribometer. The results showed that face-centered cubic (fcc) ZrN and fcc-Ag coexisted in the ZrN-Ag films. The hardness of the films, which was influenced by the fine-grain strengthening and the contents of soft Ag, initially increased gradually and reached a summit, then decreased with the increase of the Ag contents in the films and the maximum value was about 29 GPa at 0.3 at.% Ag. At room temperature, the average friction coefficient of the films first decreased and then almost remained stable with the increase of the Ag contents and the minimum value was 0.62 at 26.6 at.% Ag. The wear rate of the films first decreased slightly and reached a summit, then decreased with the increase of the Ag contents and the minimum value was 1.1 × 10−8mm3·N−1mm−1 at 0.3 at.% Ag. With the rise of the testing temperature from 200 °C to 600 °C, the combination of Ag into ZrN matrix could decrease the average friction coefficient of the films significantly and led to a relatively steady tendency of the average friction coefficient at the wide testing temperatures. However, the wear rate decreased with the increase of Ag content at the same temperature. Average friction coefficient and wear rate of the films regardless of the testing temperature were influenced by the soft lubricant Ag phase significantly.

Influence of Silver on Photocatalytic Activity of Nanosized ZnO Doped with Iron Group Metals

Zinc oxide nanoparticles doped with 0.2–1.5 mol% of Fe, Ni or Co and co-doped with 1 mol% of Ag were prepared by co-precipitation method and their photocatalytic activity in degradation of MB (methylene blue) water solution under ultraviolet irradiation was determined. X-ray diffraction analysis of the samples containing up to 0.5 mol% of iron group metals showed only ZnO and Ag phases. Crystallite size of doped ZnO nanoparticles was in the range of 27–31.6 nm depending on the sample composition and additional calcination at 400 °C. The photocatalytic activity of ZnO doped with iron group metals depended on the content of metals. The highest activity was observed for ZnO doped with 0.2 mol% of nickel. The co-doped with silver samples showed enhanced photocatalytic activity and higher reaction rate constant.

Study of structural phase transitions in quinary TiNi(MoFeAg)-based alloys

The structural phase transitions of quinary Ti50Ni49.5−XMo0.3Fe0.2AgX (X = 0, 0.1, 0.2, 0.5, 1.0, and 1.5 at%) alloys prepared by vacuum-induction melting were studied by means of the four-point-probe, x-ray diffraction (XRD), and optical microscopy methods after thermal cycling. The two-stage B2 ↔ R ↔ B19′ reversible martensitic transformation (MT) took place in all the investigated samples. It is found that the substitution of Ag for Ni in the studied alloy when CAg = 0–0.5 at%, reduces the TR, Ms, and Mf characteristic points by 20–30 K, whereas they increase by 15–35 K when the Ag content was varied from 1.0 to 1.5 at% and the B2 ↔ R ↔ B19′ MT was realized in the high-temperature area. XRD patterns of the studied alloys recorded at the ambient temperature detected the pure Ag phase as well as Ti2Ni precipitate with a small volume fraction (up to 5%) alongside with structural lines of B2, R, and B19′ phases.

Highly efficient catalysts of Mn1 − xAgxCo2O4 spinel oxide for soot combustion

A series of Mn1−xAgxCo2O4 spinel-type catalysts that can promote soot removal were prepared by a sol-gel method along with the characterization of physical and chemical properties. The results show that the selected catalysts feature a spinel-type structure, and Ag phase for Ag-substituted Mn1−xAgxCo2O4 with Ag molar ratio higher than 0.1, and the introduced Ag+ can also tailor the distribution of oxygen species, as such, enhance the formation of the adsorbed oxygen species. Mn0.6Ag0.4Co2O4 demonstrates a superior activity with a T50 of 325°C, with a reduction of 122°C compared to MnCo2O4, and CO2 selectivity of 97%, which is strongly relevant to the substituted Ag+ ions.

Study on a novel Sn-electroplated silver brazing filler metal

Novel Sn-electroplated Ag brazing filler metal with a high tin content was prepared by combining the plating and thermal diffusion method. The BAg45CuZn alloy was used as a base filler metal, and a Sn layer was electroplated on it. Then the H62 brass was brazed with the Sn-plated brazing filler metal containing 6.2 wt% of Sn. The results showed that the microstructure of the brazed joints with the Sn-plated filler mainly consisted of the Ag phase, Cu phase, CuZn phase and Cu5Zn8 phase. The tensile strength of the joints brazed with the Sn-plated filler metal was 326 MPa, which was higher than that of the joints with the base filler metal. Fracture analysis showed that the fractures of the joints brazed by the Sn-plated filler metal was mainly ductile fracture mixed with a small quantity of brittle fracture.

Insights into post-annealing and silver doping effects on the internal microstructure of ZnO nanoparticles through X-ray diffraction probe

ZnO nanoparticles were synthesized via Pechini method at various post-annealing temperatures (400°, 500°, and 600 °C) and silver doping concentrations (Zn:Ag molar ratios of 30, 20, and 10). Multifarious microstructural features including crystallite size, size-strain based broadening, residual stress, preferential orientation, crystallinity degree, lattice parameters, unit cell variation, and stacking fault probability were surveyed through phase analysis, Williamson-Hall plot, texture coefficient and unit cell calculations. X-ray probing verified good crystallinity with a hexagonal close pack Wurtzite morphology. Williamson-Hall analysis exhibited distributions of crystallite size and microstrain as well as their contributions on the line broadening of the host ZnO and guest Ag phases upon annealing-doping treatments. Textural analysis revealed the alteration in anisotropic crystallinity of the host phase and transformation of the preferred directions, (100) and (101), as function of annealing-doping processes. Besides, while guest Ag phase was shown to be polycrystalline with randomly orientated crystals at moderate concentration with respect to thermal treatment, preferential orientation went through a major change, (220) to (111), with increment in Ag loadings. Under identical synthetic conditions, the distinction in the lattice constants and unit cell variation between pure and doped ZnO nanoparticles was enforced and results verified major impressionability via annealing and doping factors.

Ag‐decorated SnO 2 nanorods: microwave‐assisted green synthesis and enhanced ethanol gas sensing properties

The green synthesis of gas-sensing materials, which monitor volatile organic compounds, avoid synthesis-induced pollution, and thus is a major challenge faced by scientific researchers. Herein, we report a microwave-assisted green synthesis of Ag-decorated SnO 2 nanorods with water being used as solvent and comparatively non-toxic chemicals being used as reactant. The as-prepared product was characterised by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed one-dimensional Ag-decorated SnO 2 nanorods constituted of tetragonal rutile phase of SnO 2 and cubic phase of Ag were successfully prepared. Ethanol was used as a model system for measuring gas-sensing properties and an enhanced gas-sensing property was found due to Ag decoration. Moreover, a linear dependence of the sensitivity on the ethanol concentration was observed.

Structural and thermal performance of Ag, Ni, and Ag/Ni thin films as thermal interface material for light-emitting diode application

Silver (Ag), Nickel (Ni), and their stack (Ag/Ni) were prepared at various thicknesses on Al substrates by sputtering process and used as thermal interface material (TIM). The structural and thermal properties of prepared thin films were studied by XRD and transient method, respectively. XRD spectra confirmed the presence of cubic phase of both Ag and Ni. Phase changes from hexagonal to cubic were also noticed with Ni thin film in Ag/Ni stack. From transient analysis, low total thermal resistance (Rth) and low rise in junction temperature (Tj) of LED were observed with Ag (50 nm) thin film interface measured at >350 mA and recorded difference in Tj (ΔTj) was high as 11.28 °C as compared with bare Al boundary condition. Overall, the performance of Ag thin film with low thickness was good on reducing Rth and Tj of device under test and can be used as thin film thermal interface material in electronic packaging.

Joining of SiO2f/SiO2 composite to Ti-6Al-4V using Ag-Cu-In-Ti brazing fillers, the joint strengths, and microstructures

Three novel Ag-Cu-In-Ti brazing fillers were designed for joining of SiO2f/SiO2 composite to Ti-6Al-4V. The wettability of the three brazing fillers on the composite was studied with the sessile drop method at 1073 K for 30 min. The results showed that the three brazing fillers exhibited contact angles of 27°, 33°, and 35°, respectively. The joints brazed with Ag-(22~26)Cu-(8~12)In-(4.5~6.0)Ti at 1073 K for 10 min presented the maximum average shear strength of 19.6 MPa, whereas the strength of the joints brazed with Ag-(22~26)Cu-(8~12)In-(3.2~3.8)Ti was only 10.5 MPa. During the brazing process, the active element Ti diffused significantly from the Ag-Cu-In-Ti alloy to the surface of the SiO2f/SiO2 composite and a thin reaction layer was formed close to SiO2f/SiO2 composite. Sound interfacial bonding was also achieved at the Ti-6Al-4V side. According to micro-analysis results, Ag, Ni3Ti3O, Cu4Ti3, Cu3Ti, and TiSi2 phases were identified at the fracture surface of SiO2f/SiO2/Ag-(22~26)Cu-(8~12)In-(4.5~6.0)Ti/Ti-6Al-4V by the XRD method. The interface structure of the joint brazed with Ag-(22~26)Cu-(8~12)In-(4.5~6.0)Ti alloy can be described as the following sequence: SiO2f/SiO2 → Cu-Ti-O + Ti-Si phases → Ag-based solid solution + Cu-Ti + Ti-In phases → Ti-6Al-4V.