Compact Ag Research Articles

Adjusting Ion Diffusion Kinetics of Li Deposition Enabled by an Elastic Porous Melamine Sponge Host for Stable Lithium Metal Anodes.

Lithium (Li) dendritic growth and huge volume expansion seriously hamper Li-metal anode development. Herein, we design a lightweight 3D Li-ion-affinity host enabled by silver (Ag) nanoparticles fully decorating a porous melamine sponge (Ag@PMS) for dendrite-free and high-areal-capacity Li anodes. The compact Ag nanoparticles provide abundant preferred nucleation sites and give the host strong conductivity. Moreover, the high specific surface area and polar groups of the elastic, porous melamine sponge enhance the Li-ion diffusion kinetics, prompting homogeneity of Li deposition and stripping. As expected, the integrated 3D Ag@PMS-Li anode delivered a remarkable electrochemical performance, with a Coulombic efficiency (CE) of 97.14% after 450 cycles at 1 mA cm-2. The symmetric cell showed an ultralong lifespan of 3400 h at 1 mA cm-2 for 1 mAh cm-2. This study provides a facile and cost-effective strategy to design an advanced 3D framework for the preparation of a stable dendrite-free Li metal anode.

Chemical and electrochemical synergistic weaving stable interface enabling longevous zinc plating/stripping process

Dendrites growth and hydrogen evolution reaction of Zn anode greatly hinder the practical application of aqueous zinc ion batteries. Interface engineering strategies have attracted immense interest in addressing these challenges. Herein, a chemical and electrochemical method is proposed to synergistically weave a stable interface by introducing AgNO3 additive in conventional aqueous ZnSO4 electrolyte. The formed compact Ag layer acts as zincophilic sites, which is beneficial for zinc ion nucleation and growth. Consequently, the cell cycled in 2 M ZnSO4 with 3 mM AgNO3 electrolyte exhibits much more stable electrochemical properties than its counterpart. To be specific, the Zn || Zn half cell using the electrolyte with 3 mM AgNO3 shows reversible Zn plating/stripping behavior over 1350 h at 5.0 mA cm−2 with an ultra-low potential hysteresis. Moreover, Zn || V2O5 full cell using the electrolyte with 3 mM AgNO3 exhibits glorious rate capability and more stable cycling performance, attributing to the inhibited zinc dendrites growth by the weaved interfacial layer. This work sheds new light on improving the electrochemical performance of rechargeable batteries.

Zirconia-high entropy alloys joints for biomedical applications: The role of Ag-based fillers on interfacial reactivity

Metal-ceramic joints represent an important choice for biomedical devices, in orthopaedic field or as micro-stimulators. ZrO 2 -Ag-HEA joint is here proposed to replace the currently used Ti6Al4V by new Ti-based refractory HEAs. To evaluate the system reactivity, wettability of ZrO 2 by different Ag-based alloys at 1000 °C and their interfacial layers were studied, for the first time. Interpretation and discussion of systems reactivity were supported by thermodynamic calculations, according to the CALPHAD approach and the ad-hoc Ag-Ti-Zr-O thermodynamic database, implemented in this work. A good wettability was reached at 1000 °C adding Ti to Ag: Ag-4Ti and Ag-8Ti reached contact angles of 81–85°. Ag-4Ti-2Zr showed the best wettability (77°) and the most complex interfacial microstructure. A continuous hcp (Ti,O), ~ 20 µm thick, promoted the wettability of Ag-4Ti and Ag-8Ti. In both cases, AgTi was the only intermetallic compound found in the bulk. Ag-4Ti-2Zr formed a thicker interfacial layer of hcp-(Ti,Zr,O) + bcc-(Ti,Zr) + a less compact Ag(Ti,Zr) 2 layer. Here, a low amount of Ag(Ti,Zr) and Ag(Ti,Zr) 2 was found in the Ag matrix. Since Ag resulted a promising filler to braze Ti-rich substrates to ZrO 2 at 1000 °C, preliminary HEA-Ag-ZrO 2 joints were characterized. A sound and defects-free interface was observed, with a first layer, mainly formed by Ag, Ti and Zr (HV ~ 600), and a Ag-based interface (HV ~ 250), extending until the HEA. Further works envisage mechanical and electrochemical evaluations of the system to pave the way for the production of novel HEA-Ag-ZrO 2 joints to be used in biomedical applications. • Ti addition to Ag promoted ZrO 2 wettability at 1000 °C forming hcp-(Ti,O) at the interface. • Ag-4Ti-2Zr tested on ZrO 2 at 1000 °C showed the best wettability (ϑ<80°). • An ad-hoc Ag-O-Ti-Zr database was assembled and used to support reactivity discussion. • Ag-4Ti-2Zr showed an hcp-(Ti,O)+bcc-(Ti,Zr)+Ag(Ti,Zr) 2 interfacial layer formed at 1000 °C. • Ti 1.5 ZrTa 0.5 Hf 0.5 Nb 0.5 HEA was successfully brazed to ZrO 2 by using a Ag filler at 1000 °C.

Compact Ag nanoparticles anchored on the surface of glass fiber filter paper for SERS applications

Compact Ag nanoparticles anchored on the surface of glass fiber filter paper for SERS applications

Smooth Cu electrodeposition for Cu(In, Ga)Se2 thin-film solar cells: Dendritic clusters elimination by Ag buffer layer

Smooth and compact Cu(In, Ga)Se2 (CIGSe) thin film is critical to prepare high-quality solar cells. However, the ”dendritic” morphology of Cu tends to form on Mo leading to a nonuniform Cu distribution during the electrodeposition process, which affects the uniformity of CIGSe and device performance. In this work, Ag was used as the underlying buffer layer and Cu was electrodeposited on Ag film instead of Mo film. By adjusting deposition parameters, smooth and compact Ag layer was obtained on the Mo surface. With the Ag buffer layer, the ”dendritic” Cu on Mo was successfully eliminated. The electrodeposited Ag/Cu/In/Ga metal precursors were annealed in Se-containing atmosphere at 450 °C∼550 °C for 15min to prepare (Ag, Cu)(In, Ga)Se2 (ACIGSe) absorbers. Compared with the CIGSe absorber, the crystallinity of the ACIGSe absorber was improved. The VOC, JSC, FF and efficiency of ACIGSe solar cells were improved compared with CIGSe solar cells. Ultimately, an 11.73% efficiency of ACIGSe thin-film solar cells was obtained.

Facile synthesis of self-assembling silver spheres and evaluation of their catalytic properties in organic dyes degradation

Hierarchical self-assembly nanostructures have an important interest in nanoscience and nanotechnology. This research reports a facile method for self-assembly of silver spheres using the Hamelia patens plant extract as a reducing agent. Furthermore, the degradation of organic dyes assesses the catalytic properties of Ag nanostructures. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–Vis, and Fourier transform infrared techniques characterized the Ag spheres’ morphology and structure. SEM and TEM images revealed porous Ag assemblies with spherical morphologies of an average size of ~2 µm integrated by 20 nm thick petals. Also, more compact Ag spheres with an average size of around 3 µm, containing nanorods of around 100 nm on their surface, were obtained. Energy dispersive spectrometer and XRD techniques determined the chemical composition and crystal structure of the spheres. UV–Vis spectra show bands ranging from 400 to 500 nm, confirming quantum confinement in the material. Silver spheres with petals showed the best degradation performance of organic dyes such as methylene blue, methyl orange, and rhodamine B.

Electrodeposition of compact Ag–Ni films from concentrated chloride baths and their test in the reduction of nitrate in alkali

Compact Ag and Ag–Ni alloy layers have been electrodeposited from a concentrated chloride bath. The composition of the alloy can be controlled by regulation of the deposition current density jdep under conditions of accurate transport control like those ensured by the rotating disk electrode. XRD analyses suggest formation of Ag-rich crystalline phases in all samples and of Ni-rich crystalline phases only in samples with Ni fraction ≥50 at%. Test experiments of nitrate reduction in alkali show: almost exclusive reduction to nitrite on Ag; prevalent reduction to ammonia on Ni, with an important side evolution of hydrogen; predominant and more efficient reduction to ammonia on Ag–Ni, with lower hydrogen evolution and better current stability.

Electroless silver plating on modified fly ash particle surface

Ag-plated fly ash (FA) powders were prepared through modified electroless plating, which could be utilized for manufacturing conductive polymers for Electromagnetic interference (EMI) shielding applications. In order to improve the FA surface activity, alkali cleaning and coupling modification were employed. Extensive characterizations of Ag-plated FA particles were carried out by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The mechanism of electroless Ag plating was mainly studied by using XPS. The XPS results showed that the diammonia functional group from the coupling agent adsorbed silver ions to form the N-Ag coordination bond and produce pure Ag film. In addition, electrical conductivity and electromagnetic properties were studied by Four-probe resistance tester and vector network analyzer, respectively. The results indicated that uniform and compact Ag films were formed on FA particle surface strongly after alkali cleaning and coupling modification. The electrical conductivity of the as-prepared 0.6-FA-S-Ag particles with a coated thickness of 200 nm was about 8.2 × 10−5 Ω·cm. The electromagnetic parameters and calculated reflection loss indicate that Ag-plated FA powders have no magnetic conductivity and the main contribution of electromagnetic loss comes from dielectric loss.

Reactivity and Chemical Sintering of Carey Lea Silver Nanoparticles.

Carey Lea silver hydrosol is a rare example of very concentrated colloidal solutions produced with citrate as only protective ligands, and prospective for a wide range of applications, whose properties have been insufficiently studied up to now. Herein, the reactivity of the immobilized silver nanoparticles toward oxidation, sulfidation, and sintering upon their interaction with hydrogen peroxide, sulfide ions, and chlorocomplexes of Au(III), Pd(II), and Pt(IV) was investigated using SEM and X-ray photoelectron spectroscopy (XPS). The reactions decreased the number of carboxylic groups of the citrate-derived capping and promoted coalescence of 7 nm Ag NPs into about 40 nm ones, excluding the interaction with hydrogen peroxide. The increased nanoparticles form loose submicrometer aggregates in the case of sulfide treatment, raspberry-like micrometer porous particles in the media containing Pd(II) chloride, and densely sintered particles in the reaction with inert H2PtCl6 complexes, probably via the formation of surface Ag-Pt alloys. The exposure of Ag NPs to HAuCl4 solution produced compact Ag films along with nanocrystals of Au metal and minor Ag and AgCl. The results are promising for chemical ambient temperature sintering and rendering silver-based nanomaterials, for example, for flexible electronics, catalysis, and other applications.

Green synthesis and formation mechanism of Ag nanoflowers using l-cysteine and the assessment of Ag nanoflowers as SERS substrates

The synthesis and applications of anisotropic nanostructures have attracted much attention in modern nanotechnology. In this paper, based on our previous finding for the synthesis of well-defined and strikingly monomorphic Ag nanoflowers using l-cysteine (l-cys) molecules as both reducing agents and stabilizers, we further investigated the growth mechanism of the detailed structures of Ag nanoflowers. The formation process of the nanoflowers was studied by SEM and UV–vis spectroscopy, showing that there were three key stages in the growth of the Ag nanoflowers: 1) primary nanocrystals agglomerated to form multipod-like nanoparticles 2) the multipod-like nanoparticles aggregated into loose flower-like nanoparticles and 3) the nanoparticles ultimately grew into compact Ag nanoflowers through Ostwald ripening. The growth of Ag nanoflowers is highly sensitive to both the concentration of stabilizer and precursor. Moreover, their potential which is used as a surface enhanced Raman scattering (SERS) substrate was also investigated. The results demonstrate that the Ag nanoflowers exhibit excellent SERS enhancement ability relative to spherical nanoparticles.

Surface Thiolation of Al Microspheres to Deposite Thin and Compact Ag Shells for High Conductivity.

In this work, we have demonstrated a method for controllable thiolated functionalization coupled with electroless silver plating to achieve aluminum@silver (Al@Ag) core-shell composite particles with thin and compact layers. First, Al microspheres were functionalized by a well-known polymerizable silane coupling agent, i.e., 3-mercaptopropyltrimethoxysilane (MPTMS). Decreasing the ethanol-to-water volume ratio (F) in silane solution produces modification films with high content of thiol groups on Al microspheres, owing to the dehydration of silane molecules with hydroxyl groups on Al microspheres and self-polymerization of silane molecules. Then, ethanol was used as one of the solvents to play a major role in the uniform dispersion of silane coupling agent in the solution, resulting in uniformly distributing and covalently attaching thiol groups on Al microspheres. In electroless silver plating, thiol groups being densely grafted on the surface of Al microspheres favor the heterogeneous nucleation of Ag, since the thiol group can firmly bind with Ag(+) and enable the in situ reduction by the reducing reagent. In this manner, dense Ag nuclei tend to produce thin and compact silver shells on the Al microspheres surfaces. The as-obtained Al@Ag core-shell composite particles show a resistivity as low as (8.58 ± 0.07) × 10(-5) Ω·cm even when the Ag content is as low as 15.46 wt %. Therefore, the as-obtained Al@Ag core-shell composite particles have advantages of low weight, low silver content and high conductivity, which could make it a promising candidate for application in conductive and electromagnetic shielding composite materials.

Electroless deposition of a Ag matrix on semiconducting one-dimensional nanostructures

Composite materials consisting of one-dimensional semiconducting nanostructures embedded in a Ag matrix were produced. The regarded nanostructures are hydrothermally grown TiO2 nanorods and SnO2 nanowires obtained by chemical vapor deposition with a vapor–liquid–solid growth process. The Ag was deposited by means of electroless plating, for which AgNO3 was employed as the Ag+ source and a glucose-based aqueous solution as the reducing agent. Cross-section micrographs obtained through scanning electron microscopy show homogeneous and compact Ag coatings, which penetrated down to the substrate level filling the space between the oxide structures. Additionally, the SnO2 composite was analyzed by focused ion beam nanotomography with a measured porosity of 0.1%. The obtained materials are potential candidates for electrical contacts applications.

Pump energy reduction for a high gain Ag X-ray laser using one long and two short pump pulses

A pump scheme with one long and two short pump pulses is proposed, in a grazing incidence pumping x-ray laser (XRL) configuration. A 360 ps long pulse, prepares a plasma in a low charge state. Then, an initial short pulse ionizes the plasma to an optimal charge state, while the second short pulse induces strong collisional excitation in the gain region. With only 200 mJ of pump energy on target, a compact Ag XRL at 13.9 nm with a gain coefficient of 55 cm(-1) was achieved.

A New Route To Fabricate Large-Area, Compact Ag Metal Mesh Films with Ordered Pores

Ordered Si nanowire (SiNW) arrays can be fabricated by metal-assisted chemical etching. The metal mesh films (MMFs) are extremely important for achieving a high quality of the SiNWs. We have developed a two-step chemical deposition method to obtain compact porous Ag MMFs. By the separation of the nucleation and growth stages of the metal in the two-step deposition processes, the overgrowth of the metals to form randomly aggregated irregular metal particles can be overcome. Hexagonally arranged polystyrene (PS) latex microspheres have been employed as a template for the deposition of porous Ag MMFs. The spacing of the pores in the Ag MMFs is determined by the diameter of PS microspheres, and the pore size can also be tuned by changing Ar plasma etching time. One of the main advantages of the two-step deposition method lies in that Ag MMFs can be produced with PS microspheres that are not limited to a single layer, which dramatically simplifies the tedious processes of producing a monolayered PS template. The two-step chemical deposition method shows great potential in metal-assisted chemical etching.

The peculiarities of the kinetics of silver chemical deposition on dielectrics with various technologies of the surface activation

The chemical reduction of single-charged ions of metal (Ar+) under the conditions of a hydrodynamic mode on a rotating cylindrical dielectric (D) specimen is first studied. The partial manifestation of the effect of the hydrodynamical rate limitation (HDRL) of silver deposition has been determined. It has been established that the complete manifestation of the HDRL (VAg = 0) effect is blocked by the development of the process of the concentration increasing of the electro-active particles in the reactionary zone due to the increase of the amount of collisions of the noncompact silver deposit (growing in the reactor volume) and the oxidation products of the reducer (inverted sugar) with a surface of a compact Ag layer on the D specimen. The results of this research confirm the conceptions concerning the mechanism of the HDRL phenomenondue to the repulsion of electro-active particles of silver from the reactionary layer at high speeds of rotation.

Capping antibacterial Ag nanorods aligned on Ti interlayer by mesoporous TiO 2 layer

In this work, aligned and compact Ag nanorods capped by sol–gel mesoporous TiO 2 layer were grown on Ti/Si(100) in order to be applied in antibacterial applications. The Ag nanorods with a high effective surface were grown by applying an electric field perpendicular to the surface of the Ag/Ti/Si thin film while it was being heat-treated at 700 °C in an Ar + H 2 ambient. The grown silver nanorods had widths and lengths of 20–50 and 250–500 nm with an abundance in {100} facet, respectively. The TiO 2 cap layer also had the specific surface area, the total pore volume and the pore diameter of 474 m 2/g, 0.49 cm 3/g and 8.0 nm, respectively. Antibacterial activities of the TiO 2-capped Ag nanorods against E. coli bacteria were examined in the dark and under UV irradiation, and then compared to the corresponding activities of the TiO 2-capped Ag thin film and the TiO 2-capped Ag nanoparticles grown on the Ti layer. The Ag + ion release measurements showed that the mesoporous and aqueous TiO 2 cap layer can control the silver release process by inter-diffusion of water and silvers thorough its capillary structures, completely different from the ion release behavior of the silver nanorods not capped by the TiO 2 layer. The results showed a strong and lasting antibacterial activity for the TiO 2-capped Ag nanorods with 2.34 h − 1 for the relative rate of reduction of the number of viable bacteria.

Electrodeposition of silver–tin alloys from pyrophosphate-cyanide electrolytes

Using cyclic-voltammetric techniques, a pyrophosphate-cyanide electrolyte for the electrodeposition of compact Ag–Sn alloy coatings is investigated. This electrolyte is suited to further investigations on the alloy composition, structure and properties. The electrodeposition of coatings with up to 40 wt% Sn is possible from the investigated complex electrolytes. The alloy surpasses the saturation limit of the silver lattice with Sn and allows the formation of coatings with phase heterogeneity. At high tin content an ordered spatial distribution of different alloy phases on the cathodic surface can be observed. The pattern formation in this system looks very similar to the phenomena and structures observed during electrodeposition of other silver alloys, such as Ag–Sb, Ag–Bi and Ag–In.

Diffusion studies in a nonequilibrium system with repulsive interactions

The diffusion behavior of silver islands on charged silicone oil surfaces has been studied. Compact Ag islands with an average diameter of $1.2 \ensuremath{\mu}\mathrm{m}$ form after thermal deposition of silver on a charged silicone oil surface. In contrast to the behavior of the uncharged oil surface, no aggregation of the Ag islands is observed. Instead the average distance of the islands increases as the islands diffuse toward the edge of the oil substrate. This process is driven by the repulsive Coulomb interaction. An exponential decay of the island density n with time t results everywhere on the oil surface, and the corresponding time constant ${O}_{f}$ ranges between $1.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and $2.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4} {\mathrm{s}}^{\ensuremath{-}1}.$ In the central area of the substrate, the relative speed V between two islands increases linearly with their distance L according to ${V}_{\mathrm{fit}}=HL,$ where ${V}_{\mathrm{fit}}$ is the linear fit speed of V. The slope H is of the order of $2.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}--3.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4} {\mathrm{s}}^{\ensuremath{-}1}$ after the deposition, and decreases with time. Our theoretical analysis indicates that ${O}_{f}\ensuremath{\approx}H,$ in agreement with the experimental finding. The experiment also shows that this nonequilibrium expansive diffusion already starts at the early stage of deposition. During their motion, the islands must carry a small fraction of the electron charge on the oil surface. After the islands reach the sample edge, they form a band-shaped silver film along the border. This results in the accumulation of charge, which slows down the speed of the remaining islands, which diffuse toward the edge.

He scattering from random adsorbates, disordered compact islands, and fractal submonolayers: Intensity manifestations of surface disorder

A theoretical study is made on He scattering from three basic classes of disordered adlayers: (a) translationally random adsorbates, (b) disordered compact islands, and (c) fractal submonolayers. The implications of the results to experimental studies of He scattering from disordered surfaces are discussed, and a combined experimental-theoretical study is made for Ag submonolayers on Pt(111). Some of the main theoretical findings are: (1) The scattering intensities from the three disorder classes differ significantly, and can be used to distinguish between them. (2) Structural aspects of the calculated intensities from translationally random clusters were found to be strongly correlated with those of individual clusters. (3) For fractal islands, just as for all surfaces considered here, the off-specular intensity depends on the parameters of the He/Ag interaction, and does not follow a universal power law as previously proposed in the literature. In the experimental-theoretical study of Ag on Pt(111), we use experimental He scattering data from low-coverage (single adsorbate) systems to determine an empirical He/Ag–Pt potential of good quality. Then, we carry out He scattering calculations for high coverage and compare with experiments for these systems. The conclusion is that the actual experimental phase corresponds to small compact Ag clusters of narrow size distribution, with partial translational disorder.

Application of time-resolved EQCM to the study of the mechanism of silver(I) oxide formation on a polycrystalline silver electrode in alkaline solution

The time-resolved EQCM was used to investigate the mechanism of the electrochemical formation of silver(I) oxide on a polycrystalline silver electrode in 0.1 M NaOH. The mass change was monitored in a series of potentiodynamic experiments. The first stage of the oxidation can be unambiguously attributed to the formation of a monolayer of Ag 2O. In the second stage of the oxidation, a very small amount of Ag or its oxide dissolves into the solution and the Ag 2O layer thickens gradually. No species other than Ag 2O was detected during the whole oxidation process. The structure of the Ag 2O layers formed is different at different stages of the oxidation. Compact Ag 2O layers are formed in the first two stages, while Ag 2O formed at more positive potentials is porous. The roughening of the electrode during the formation and reduction of the oxide is also discussed on the basis of the mass changes.