Micro-sized Ag Particles Research Articles

Fast and Simple Ag/Cu Ion Exchange on Cu Foil for Anode-Free Lithium-Metal Batteries

Lithium-metal batteries with zero excess lithium on the anode side paired with a fully lithiated cathode are regarded as a form of the highest energy-density configuration. Unfortunately, the continuous lithium loss over cycling from a limited amount of the lithium reservoir significantly degrades the overall cell performance in the anode-free system. To mitigate the deterioration, modifying the current collector for enhanced lithium cycling is an indispensable route. Here, we apply a Ag/Cu ion exchange to precipitate micro-sized Ag particles on the Cu current collector to enhance the lithium reversibility via a (de)alloying process. We show a smoother morphology of lithium upon alloying, which leads to a lowered nucleation potential as well as increased average Coulombic efficiency in Li||Cu cells regardless of electrolyte formulation. The preferred lithium adsorption on Ag and AgLi over Cu is demonstrated using density functional theory calculations, which supports that Li forms a gamma-phase alloy in the last stage rather than being deposited beneath the alloy. Lastly, this simple Cu foil modification enhances lithium reversibility and reduces its nucleation barrier, thus mitigating the capacity fade of Cu||LiFePO4 with reduced polarization.

Sintered Joint Using Micro-Sized Ag Particles for High-Temperature Application

Sintered Joint Using Micro-Sized Ag Particles for High-Temperature Application

Silver Particles on the Thermal and Electrical Characteristics of ECAs

This study presents information on the thermal and electrical characteristics of silver (Ag) in range size of 2–3.5 μm and 80 nm in diameter. The present method demonstrates the thermal conductivity analysis and electrical resistivity influence by various particle content of Ag in Epoxy matrix for both micro and nano-sized. Furthermore, new technique of thermal properties and electrical resistivity observation is proposed by hybrid-sized analysis to characterize the effect of Ag size. The proposed hybrid-sized technique uses micro- and nano-sized particle ratios to generate the composite. The thermal and electrical resistivity characteristics of the epoxy composite-filled micro-, nano-, and hybrid-sized Ag particle are correlated with their morphology. The thermal conductivity of the electrically conductive adhesive sample is affected by Ag particle size. The micro-sized Ag particle is better filler than the nano-size Ag particle in increasing performance of the thermal conductivity in the matrix epoxy. The results of the electrical resistivity of micro- and nano-particles demonstrated similar characteristics that transition within insulator into conduction occurred at 6 vol%. While hybrid-sized systems shown decreasing in thermal conductivity performance when decreasing number micro-sized ratio. Other observation in hybrid-sized presented that the better performance of electrical conductivity has shown at 50:50 weight ratio.

Effect of polyol synthesis on sintering of microsized Ag particles

This study focuses on improving the sintering performance of microsized Ag pastes via in situ chemical synthesis. Ag particles of three different average sizes, 1.5, 2, and 5 μm, were used as the Ag fillers. Two kinds of Ag pastes were prepared: conventional Ag pastes and new Ag pastes via polyol synthesis by mixing ethylene glycol (EG) and AgNO3. The effect of the polyol synthesis on sintering was evaluated with respect to the microstructure and material properties, such as the electrical resistivity and shear strength. The conventional pastes showed a low sintering performance and poor necking, leading to low shear strengths of 8.8, 9.2, and 6.8 MPa at 300 °C for the 1.5, 2, and 5 μm Ag particles, respectively. The new pastes exhibited decreased electrical resistivity and shear strengths of 11.8, 15, and 13.0 MPa with a substantial coalescence of the Ag particles and thick necking. Moreover, the XRD and TG-DTA results indicated that the method can be applied to achieve pure metallic bonding with increased sintering performance. The increased sintering performance of the new pastes could be due to the membrane-like morphology from the synthesis process, which connects the Ag particles and may provide a diffusion layer between the Ag particles. The thermal aging test of the new paste with the 2.5 μm fillers indicated a high reliability, and the shear strength of the Ag joint was maintained.

Rapid Formation of Full Intermetallic Bondlines for Die Attachment in High-Temperature Power Devices Based on Micro-sized Sn-Coated Ag Particles

A new die attach material prepared by pressing micro-sized Sn-coated Ag powders as a preform is proposed for high-temperature power device packaging. The Sn-coated Ag powders were completely transformed into Ag3Sn with a melting point of 480°C after bonding at 250°C for 10 min, subsequently producing a bondline which can sustain a much higher temperature than the processing temperature. The detailed microstructural analysis indicates that a fine-grained full Ag3Sn bondline with high-density twin boundaries can be formed in a short reflow time, which contributes to the improved performance of the full Ag3Sn bondline, with an average shear strength of 37.5 MPa at 400°C. Nano-indentation testing showed that the average hardness and elasticity modulus of the prepared full Ag3Sn bondline were 3.1 ± 0.26 GPa and 84.56 ± 6.13 GPa, respectively. The electrical resistivity was measured to be 11.42 μΩ cm. The shear strength at 400°C was kept above 20 MPa after aging at 200°C for 200 h due to the thermostability of Ag3Sn microstructure in the bondlines.

Intense pulse light sintering of an Ag microparticle-based, highly stretchable, and conductive electrode

This study proposes a highly stretchable, conductive electrode based on micro-sized Ag particles and Ag flakes incorporated into a polyester binder. The use of the microparticles in fabricating the stretchable electrode has several advantages over the spherical nanoparticles, namely, affordable, easier to synthesize, slower oxidation, and higher aspect ratio. Intense pulsed light (IPL) was employed to sinter the stretchable composite electrode printed on a polyurethane substrate. IPL was found to be an effective and fast sintering technique that lasts within seconds for stretchable electrodes consisting of Ag microparticles. The electrical and electromechanical properties were examined with varying the IPL energy intensities. The optimum IPL energy intensity was found to be 2 J/cm2 without damaging the substrate. The stretchable electrodes exhibited superior stretchability of 170% strain and high mechanical stability of over 1000 stretching cycles under 50% strain. The stretchable electrodes exhibited excellent bendability, as they could be bent up to 1 mm and withstand 1000 repetitive bending cycles at a bending radius of 2 mm. The electrodes also showed a robust static bending endurance during the 240 h test and excellent adhesion strength. The electromechanical properties of the stretchable electrode could be further enhanced by minimizing the pores and voids inside the electrode during the synthesis and sintering process.

The growth of silver nanostructures on porous silicon for enhanced photoluminescence: The role of AgNO3 concentration and deposition time

Silver nanostructures were obtained by using the electrodeposition method on n-type porous silicon (PSi) under different deposition times and concentrations of AgNO3 solutions. The analyses of the structural and photoluminescence properties of PSi/Ag were studied by SEM, XRD and photoluminescence spectroscopy. SEM analysis showed that the shape and size of Ag nanostructures significantly depend on the deposition time and concentration. It was found that spherical nanoparticles and thin Ag dendrites were obtained in short deposition times at 1 and 5 mM AgNO3 concentrations, whereas, Ag complex dendrite nanostructures formed in long deposition times. It was also found that only micro-sized Ag particles were formed at 10 mM. XRD results revealed that the degree of crystallization increases with increasing concentration. Photoluminescence analysis showed that the deposition time and concentration of AgNO3 remarkably affect the PL intensity of PSi/Ag samples. We determined a PL enhancement of ∼2.7 for the PSi/Ag deposited at 120 s for 1 mM AgNO3. The improved PL intensity of PSi/Ag nanostructures can be explained by the combination of quantum confinement and surface states. PL analyses also indicated that with increasing deposition time and AgNO3 concentrations, the PL intensity of PSi/Ag structures significantly decreases due to the auto-extinction phenomenon.

Low-Temperature Sintering Behavior (≤ 400°C) of Micro-sized Silver Particles Decorated by Silver Nanoparticles Through Surface Iodination

This paper introduces a facile and effective route to decorate micro-sized silver particle surfaces with Ag/AgI nanoclusters through a wet chemical reaction at room temperature using iodine and ethanol as reactant and solvent, respectively. Photosensitivity of AgI is utilized in the route, and AgI decomposes into Ag upon contact with sunshine, forming Ag/AgI nanoclusters. The modified micro-sized Ag particles showed sinterability even at 200°C and formed rigid electrical conductive networks at 350°C. Moreover, sintered film containing the modified Ag particles reached the best conductivity, 9.35 mΩ/sq, after sintering at 350°C for 20 min, while the film with untreated control Ag particles obtained its best conductivity at 400°C. The excellent sinterability should be attributed to the nanoclusters which served as a sintering aid during the heating process. However, increase of sintering temperature and time destroyed densification and conductivity of the sintered film containing the modified particles.

Low temperature bonding with high shear strength using micro-sized Ag particle paste for power electronic packaging

Bonding technology using a Ag nanoparticle paste has been a promising substitute for high-Pb-containing solder joining. However, it has some drawbacks, such as high cost and low compatibility, due to its high sintering temperature. Recently, the bonding process using the micro-sized Ag particle paste has been studied for cost-effectiveness, but it is limited in terms of high applied pressure or relatively low joint strength. In this study, a low pressure of 0.4 MPa was applied during bonding by micro-sized Ag particle paste for lower bonding temperature and higher joint strength. The micro-sized Ag paste was composed of chestnut-burr-like and spherical particles. Under low applied pressure, the joint with a high shear strength of 54.6 MPa was achieved when the bonding temperature and time were 260 °C and 10 min, respectively. It was also possible to reduce the bonding temperature and time for the joints having similar strength to that of the pressureless process. The microstructure showed a linear relationship to the shear strength, regardless of the bonding conditions.

Effect of temperature and substrate on shear strength of the joints formed by sintering of micro-sized Ag particle paste without pressure

The production of joints using micro-sized Ag particle paste without applied pressure was investigated for replacing high lead containing solder in power electronic packaging. The micro-sized Ag paste used in this study was composed of chestnut-burr-like and spherical particles whose weight ratio was 5:5. Sintering was conducted at 250–400 °C for 60 min in a nitrogen atmosphere. Electroless nickel immersion gold (ENIG) finished Cu and bare Cu were used as the joint substrates. The experimental results showed that the microstructure at all sintering temperatures had an open porous system. The shear strength increased from 10.4 to 16.1 MPa with increasing sintering temperature from 250 to 300 °C, and there was no significant improvement above 300 °C. The Ag area ratio gradually increased with increasing sintering temperature, but the bonding ratio exhibited a similar trend to the shear strength. The ENIG finished Cu showed better bonding strength than bare Cu. The Ag area ratio of both substrates was almost similar but the bonding ratio on ENIG finished Cu (64.1%) was higher than that on bare Cu (40.9%).

Coexposure to silver nanoparticles and ultraviolet A synergistically enhances the phosphorylation of histone H2AX

Owing to the wide application of silver nanoparticles (AgNPs), the assessment of health risks associated with their use is of great importance. In this study, we revealed that the potential genotoxicity of AgNPs was enhanced by ultraviolet A (UVA) exposure. Three cultured cell lines were treated with AgNPs, followed by exposure to UVA. AgNPs induced phosphorylation of histone H2AX (γ-H2AX) following the formation of DNA double-strand breaks (DSBs), which was synergistically enhanced by UVA exposure. Enhanced γ-H2AX was observed only in cell lines that positively took up AgNPs, and microsized Ag particles, which were difficult to incorporate into cells, showed no γ-H2AX. Incorporation of AgNPs was not increased by UVA exposure. AgNO3 treatment followed by UVA exposure also induced a marked increase in γ-H2AX, indicating that the enhanced γ-H2AX was attributed to Ag ions released from AgNPs. Ag ions reacted with the −SH group of antioxidant molecules, such as glutathione, and induced intracellular oxidative conditions. 8-Hydroxy-2′-deoxyguanosine was formed in the cells treated with AgNPs, which was augmented by UVA irradiation, suggesting that intracellular oxidation caused oxidative DNA damage, leading to the enhanced formation of DSBs and γ-H2AX. Ag has been considered a safe metal; however, our results provide important insights into the influence of sunlight on the genotoxic potency of AgNPs.

Shear strength of Cu-to-Cu joints using mixed Ag particle paste

The high-temperature joining process is a key technology for electronic components and assemblies of automotive and other high-temperature applications. Recently, focusing on a sintering behavior of metal particles, the joining process using metal particles has been proposed as a solder alternative to establish a new joining technology for high-temperature applications. In this study, mixed Ag particle pastes were experimentally applied and the effect of the addition of Ag nanoparticles into micro-sized Ag particles on the joint strength has been studied to improve joint strength using Ag particle paste. Then, the effect of joining atmosphere on the joint strength of Cu-to-Cu joint using mixed Ag particle paste has been investigated.

Bonding strength of Cu/Cu joints using micro-sized Ag particle paste for high-temperature application

High-temperature joining is a key technology for electronic component assembly and other high-temperature applications. Recently, focusing on the sintering behavior of metal particles, the joining process using a nanoparticle paste has been proposed as an alternative to establish a new joining technology for high-temperature applications. In this study, a feasibility study was conducted to determine whether chestnut-burr-like microscale Ag particles can be used for joint material, and the shear strength of the Cu-to-Cu joints was investigated. Then, the interfacial microstructure of the joints using the microscale particle paste was examined. As a result, joining using microscale Ag particles was successfully achieved and the shear strength of more than 20 MPa was obtained under nitrogen atmosphere.

Effects of Joining Conditions on Cu/Cu Joint Using Chestnut-burr-like Micro-sized Ag Particles

Effects of Joining Conditions on Cu/Cu Joint Using Chestnut-burr-like Micro-sized Ag Particles

Synergistic bactericidal effect by combined exposure to Ag nanoparticles and UVA

Broad and strong antimicrobial properties of silver (Ag) have been used for biomedical applications, water treatment, etc. In this study, a synergistic antibacterial effect between Ag nanoparticles (AgNPs) and ultraviolet (UV) light was examined. AgNPs (<0.1μm) with subsequent exposure to UVA (320–400nm) showed pronounced toxicity in Escherichia coli, but micro-sized Ag particles (>1μm) with UVA and AgNPs with UVB (280–325nm) did not. As significant bactericidal activity was also exhibited by hydrogen peroxide-treated AgNPs, the surface oxidation of AgNPs caused by UVA irradiation was considered to contribute to the enhanced antibacterial effect. Although no difference in NP-incorporation rates was observed with or without the surface oxidation of AgNPs, a particle size of less than 0.1μm was a factor for AgNPs uptake and an essential requirement for the antimicrobial function of Ag particles. Incorporated AgNPs oxidized by UVA irradiation released larger amounts of Ag ion inside cells than reduced AgNPs, which reacted with intercellular molecules having –SH groups such as glutathione. The synergistic use of AgNPs and UVA could become a powerful tool with broad antimicrobial applications.

Effects of silver and cerium dioxide micro- and nano-sized particles on Daphnia magna

Acute (96 h) and chronic (21 d) exposures of Daphnia magna neonates were carried out with nano- and micro-sized Ag and CeO(2) particles to assess the influence of both material and size of particles on mortality and moulting. Mortality rates for silver in the acute exposures were: AgNP, 56.7 ± 23.3% at 0.1 mg L(-1) and 100 ± 20% at 1 mg L(-1), and micro-Ag, 13.3 ± 6.7% at 0.1 mg L(-1) and 80 ± 20% at 1 mg L(-1). CeO(2) was not acutely toxic at concentrations up to 10 mg L(-1). Mortality for Ag over 21d at concentrations of up to 0.05 mg L(-1) was low, while mortality of 30% was observed for 0.001 mg L(-1) of nano-Ag. CeO(2), with the exception of the 10 mg L(-1) of nano-CeO(2) (100% mortality by day 7), was non-toxic. Inhibition of moulting and growth in the acute study occurred at toxic concentrations (Ag particles), and at 10 mg L(-1) of nano-CeO(2). The chronic study revealed reduced moulting at 0.001 mg L(-1) of nano-Ag and 0.01 and 0.05 mg L(-1) of both sizes of Ag, but there was no impact on D. magna size, and no effects of CeO(2). The toxicity of nano-CeO(2) may be attributed to reduced feeding and physical interference with the daphnids' carapace, resulting in reduced swimming ability. Our results suggest that Ag NPs in particular have the potential to be harmful to aquatic invertebrates after release into the environment, whereas CeO(2) particles appear to cause little adverse effects, and only at environmentally irrelevant concentrations.

Creep Properties of Composite Solders Reinforced with Nano- and Microsized Particles

In the present work the creep properties of Sn37Pb- and Sn0.7Cu-based composite solders reinforced with metallic nano- and microsized Cu and Ag particles have been studied. First, a series of volume percentages of reinforcements were selected to optimize the content of reinforcing particles. Then, the composite solder with optimum volume fraction of reinforcement particles, corresponding to the maximum creep rupture lifetime, was selected to investigate the effect of applied stress and temperature on the creep rupture lifetime of the composite solder joints. In the creep rupture lifetime test, small single-lap tensile-shear joints were adopted. The results indicate that composite solders reinforced with microsized particles exhibit better creep strengthening than composite solders reinforced with nanosized particles, although the mechanical tensile shear strength of composite solder joints reinforced with nanosized particles may be higher than those reinforced with microsized particles. Moreover, the creep strengthening action of the reinforcement particles is more obvious under conditions of lower applied stress or lower test temperature. Strengthening by metallic Cu or Ag reinforcement particles decreases with increasing temperature or applied stress. The Sn0.7Cu-based composite solder reinforced with microsized Ag particles is a low-cost lead-free solder that is easy to process and may have good market potential.

Properties investigation on isotropical conductive adhesives filled with silver coated carbon nanotubes

In this study, chemical plating method was used to prepare silver coated carbon nanotubes (SCCNT). Fundamental materials characterizations including X-ray diffraction and transmission electro microscopy (TEM) were conducted on these nanotubes. Two kinds of isotropical conductive adhesives (ICA) were developed by using multi-walled carbon nanotubes (CNT), SCCNT as conductive fillers, respectively. The electrical, mechanical and aging properties of above ICAs were investigated and compared with that of conventional ICA filled with 1 μm average-sized Ag particles. The results indicated that the percolation threshold of bulk resistivity reaches 2.4 × 10 −3 Ω cm for ICA filled with 31% CNT and the shear strength reaches the maximum value for ICA filled with 23% CNT. At the same filler volume content of 28%, the ICAs filled with SCCNT shows the lowest conductive resistivity of 2.2 × 10 −4 Ω cm and the ICAs filled with both CNT and SCCNT exhibit higher shear strength (19.6 MPa). The testing results of aging properties under conditions of 85 °C, RH85% for 1000 h showed that the shifts of both bulk resistivity and shear strength did not exceed 15% for the ICAs filled with both CNT and SCCNT, while the shifts of conductive resistivity and shear strength were 200% and 35%, respectively, for ICA filled with micro-sized Ag particles.