Silver Crystallite Research Articles

The Influence of Ag Addition and Different SiO2 Precursors on the Structure of Silica Thin Films Synthesized by the Sol-Gel Method.

In this work, the structure of silica thin films synthesized with three different SiO2 precursors and obtained by the sol-gel method and dip coating technique was studied. Additionally, the influence of Ag addition on the obtained silica sols and then gel structure was investigated. Silica coatings show antireflective properties and high thermal resistance, as well as hydrophobic or hydrophilic properties. Three different silica precursors, TEOS (tetraethylorthosilicate), DDS (dimethyldietoxysilane) and AerosilTM, were selected for the synthesis. DDS added to silica sol act as a pore size modifier, while Ag atoms are known for their antibacterial activity. Coatings were deposited on two different substrates: steel and titanium, dried and annealed at 500 °C in air (steel substrate) and in argon (titanium substrate). For all synthesized films, IR (infrared) spectroscopic studies were performed together with GID and XRD (Grazing Incidence Diffraction, X-ray Diffraction) measurements. The topography and morphology of the surface were traced by SEM and AFM microscopic methods, providing information on the samples' roughness, particle sizes and thickness of the particular layers. The wetting angle values were also measured. GID and XRD measurements pointed to the distinct contribution of an amorphous phase in the samples, allowing us to recognize the crystalline phases and calculate the silver crystallite sizes. The FTIR spectra gave information on the first coordination sphere of the studied samples.

Effect of sintering temperature on ratcheting-fatigue behavior of nanosilver sintered lap shear joint

Purpose The paper aims to study the effect of sintering temperature on the microstructure, shear strength and ratcheting fatigue life of nanosilver sintered lap shear joint. In addition, the Gerber model is used to predict the ratcheting fatigue lives of nanosilver sintered lap shear joints at different sintering temperatures. Design/methodology/approach In this paper, the nanosilver sintered lap shear joints were prepared at three sintering temperatures of 250 °C, 280 °C and 310 °C. The bonding quality was characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscope and shear tests, and the long-term reliability was studied by conducting ratcheting fatigue tests. In addition, three modified models based on Basquin equation were used to predict the ratcheting fatigue life of nanosilver sintered lap shear joint and their accuracies were evaluated. Findings When the sintering temperature is 250°C, the nanosilver sintered lap shear joint shows the porosity of 22.9 ± 1.6 %, and the shear strength of 22.3 ± 2.4 MPa. Raising the sintering temperature enhances silver crystallite size, strengthens sintering necks, thus improves shear strength and ratcheting fatigue life in joints. In addition, the ratcheting fatigue lives of the joints sintered at different temperatures are effectively predicted by three equivalent force models, and the Gerber model shows the highest life prediction accuracy. Research limitations/implications The sintered silver bondline is suffering a complex stress state. The study only takes the shear stress into consideration. The tensile stress and the combination of shear stress and tensile stress can to be considered in the future study. Practical implications The paper provides the experimental and theoretical support for robust bonding and long-term reliability of sintered silver structure. Social implications The introduced model can predict the ratcheting fatigue lives of the joints sintered at different temperatures, which shows a potential in engineering applications. Originality/value The study revealed the relationship between the sintering temperature and the microstructure, the shear strength and the ratcheting fatigue life of the joint. In addition, the Gerber model can predict the ratcheting fatigue life accurately at different sintering temperatures.

GO: Ag Composites Materials for Dynamic Humidity Sensing Applications

Silver crystallite-graphene oxide (Ag-Nps/GO) composites are widely used for various applications and are an attractive material for next-generation nano-electronic devices, and we demonstrate their use in humidity sensors. Silver crystallite (Ag-Nps) is prepared through a single step by reduction method at room temperature. The resulting crystallite is a pure phase as confirmed through X-ray diffraction (XRD) without any traces of oxides or secondary impurities. The crystallite size is around 1 μm. These crystallites are blended with synthesized graphene oxide in a different weight ratio to make the composite. Various characterization techniques like scanning electron microscopy (SEM), UV spectroscopy, and XRD are used to understand structures and surface morphology. The composite is dropped on Al printed sensor (IDE). The humidity is varied from 5% to 55%, the conductivity decreases with an increase in humidity. The sensor has a fast response/recovery time reproducible. In conclusion, the present work describes a low-cost, novel strategy for synthesizing humidity sensor applications. The sensors can be used in applications like biomedical, food processing, agriculture, pharmaceutical, and microelectronics.

Contact Formation of Silver Paste and Atmospheric Pressure Chemical Vapor Deposition (n) Poly‐Silicon Passivating Contacts on Planar and Textured Surfaces

One of the main challenges for the industrialization of the passivating contact approach for Si solar cells is the metallization with screen‐printed paste while maintaining the low saturation current density. Using a non‐commercial Ag paste to metallize atmospheric pressure chemical vapor deposition (APCVD) (n) poly‐Si, the metal contact formation for passivating contacts on planar and textured substrates is investigated. The paste creates deep imprints caused by silver crystallite formation at the pyramid tips of textured silicon wafers. In contrast, on planar wafers, the silver crystallite growth stops at the interface between poly‐Si and the Si wafer. Similar contact resistivities are determined by comparing textured and planar Si samples. On planar samples, a contact resistivity of 4.6(14) mΩcm2 and a saturation current density of only 141(10) fA cm−2 for the metallized contact area are demonstrated. Textured samples with a contact resistivity of 2.7(17) mΩcm2 show a higher saturation current of 480(40) fA cm−2. This etching behavior is investigated by structural and elemental analyses using scanning electron microscopy.

A comprehensive investigation of the potential of metal assisted chemical etched (MACE) nano-textures over conventional micron-sized iso-textures for industrial silicon solar cell applications

We present a comprehensive comparative analysis of acid textured and MACE (Metal Assisted Chemical Etching) nano-textured multi crystalline silicon (mc-Si) solar cells processed in an industrial cell line in terms of performance parameters. The batch average open circuit voltage of nano-textured solar cells was marginally lower and the measures for improving the same are discussed. Batch average short circuit current (JSC) and fill factor (FF) were respectively 0.65 mA-cm−2 and 0.7% (absolute) higher for MACE nano-textured solar cells. Significantly lower surface reflectance in MACE nano-textured cells in the blue and near infrared regions are found to be the reason for the enhancement in JSC. The main component of FF gain is identified as the lower series resistance in MACE cells. The contact formation mechanism in screen printed mc-Si solar cells, investigated using scanning electron microscopy, revealed that the elevated portions at the boundaries of the textures act as favorable sites for silver crystallite precipitation. A larger areal density of such sites is observed on the MACE nano-textured surface than in case of acid textured solar cells, leading to a much lower series resistance. The results suggest the potential for the application of MACE in the more popular mono-crystalline silicon cell technology for further reduction of contact resistance. Alternatively, MACE may be used to obtain similar contact resistance with lower amount of silver paste, compared to iso- and pyramid textured solar cells.

Influence of the specific surface area and silver crystallite size of mesoporous Ag/SrTiO3 on the selectivity enhancement of ethylene oxide production

ABSTRACTBackgroundEthylene oxide, which is industrially produced by ethylene epoxidation, is an important versatile chemical intermediate, thus its selectivity enhancement can bring substantial economic profits. In this work, the effects of two important, but still debatable, factors, i.e. catalyst specific surface area and active phase crystallite size, on the catalyst selectivity enhancement were investigated. Surfactant assisted sol–gel method with good control ability on the pores structure was selected to produce mesoporous strontium titanate (SrTiO3) nanocrystals with various specific surface area. The SrTiO3 nanocrystals were used as the supports of silver (Ag) for ethylene epoxidation.ResultsThe Ag/SrTiO3 catalysts with various surface areas were obtained by changing the surfactant‐alkoxide ratio and the calcination time. The ethylene oxide selectivity of the prepared catalysts was examined in a laboratory‐scale fixed bed reactor. The best performance was observed at the lowest surfactant–alkoxide ratio of 0.2 and calcination time of 4 h, with the surface area of 1.7 m2/g and Ag crystallite size of 15 nm.ConclusionThe best catalyst selectivity was observed at the lowest surface area and the highest average Ag crystallite size. In this condition, the selectivity of the Ag/SrTiO3 catalyst without any modifier was superior to a commercial Ag/Al2O3 catalyst with 3.7m2/g surface area and alkaline earth metal modifiers. © 2019 Society of Chemical Industry

Studies of Cobalt(III) and Chromium(III) Complexes as Mediators in the Silver Nanoparticle Electrosynthesis in Aqueous Media

Metal complexes [Cr(bipy)3]3+, [Co(bipy)3]3+, and [Co(sep)]3+ in aqueous media at the potentials of M(III)/M(II) redox couple are shown playing a role of mediators in the electrosynthesis of silver nanoparticles, stabilized in a polyvinylpyrrolidone shell, by means of Ag(I) reduction. [Cr(bipy)3]3+ is consumed under the conditions of long-term preparative electrolysis, the reduction process is accompanied by cathode passivation, therefore, the Ag+ ions complete conversion to the Ag-nanoparticles is unattainable. The two other metal complexes are fully remained unimpaired; the mediated electrosynthesis of the Ag-nanoparticles is carried out well effectively: the Ag-nanoparticles are produced in the solution bulk with a nearly quantitative yield, a theoretical charge being consumed. the [Co(bipy)3]3+-mediated reduction of the Ag+ ions, generated by a silver anode in situ dissolution in the course of single compartment cell electrolysis, is accompanied by the anode metal dispersion and results in the formation of polydisperse Ag-nanoparticles. The summary Ag-nanoparticle current efficiency in the solution bulk comes to 128%. Thus formed Ag-nanoparticles are characterized by using dynamic light scattering, scanning and transmission electron microscopy, and X-ray powder diffraction. The Ag-nanoparticles are spherical, with a mean size of 83 ± 53 nm, or have a form of nanowires, with a length of l = 1216 ± 664 nm and diameter of d = 94 ± 17 nm. The [Co(sep)]3+-mediated AgCl reduction gives ellipsoidal Ag-nanoparticles sized l = 46 ± 19 nm, d = 27 ± 7 nm; the silver crystallite mean size is 20(1)–34.4(9) nm.

Impact of Extended Contact Cofiring on Multicrystalline Silicon Solar Cell Parameters

During the temperature spike of the contact cofiring step in a solar cell process, it has been shown that the concentration of lifetime-killer dissolved metallic impurities increases, while adding an annealing after the spike getters most of the dissolved impurities toward the phosphorus emitter, where they are less detrimental. The contact cofiring temperature profile, including the after-spike annealing, has been called extended contact cofiring, and it has also been proposed as a means to decrease the emitter saturation current density of highly doped emitters, thus benefiting a wide range of materials in terms of detrimental impurity content. The aim of the present work is to determine the effect of performing this additional annealing on contact quality and solar cell performance, looking for an optimal temperature profile for reduction of bulk and emitter recombination without affecting contact quality. It presents the effect of the extended cofiring step on fill factor, series resistance, and contact resistance of solar cells manufactured with different extended cofiring temperature profiles. Fill factor decreases when extended cofiring is performed. Series resistance and contact resistance increase during annealing, and this happens more dramatically when the temperature peak is decreased. Scanning electron microscopic images show silver crystallites in contact with silver bulk before the annealing that allow a direct current path, and silver crystallites totally surrounded by glass layer ( $>$ 100 nm thick) after annealing. Glass layer redistribution and thickening at low temperatures at the semiconductor–metal interface can be related to the series resistance increase. Degradation of series resistance during the temperature spike, when it is below the optimum one, can also be attributed to an incomplete silicon nitride etching and silver crystallite formation. To make full use of the beneficial effects of annealing, screen-printing metallic paste development supporting lower temperatures without a thick glass layer growth is needed.

Removal of methyl mercaptan with highly-mobile silver on graphitic carbon-nitride (g-C3N4) photocatalyst

Modification of graphitic carbon nitride (g-C3N4) with silver metal significantly improved the adsorption capacity and the photocatalytic degradation activity for methyl mercaptan, which is a typical sulfurous compound, under visible light. These improvements were easily obtained by the shear mixing method. The ultrafine crystallites of metallic silver were formed on surface of carbon nitride by shear mixing of HT-g-C3N4 (Hydrothermal treated g-C3N4) in aqueous solution of silver acetate. One atom of the silver captured ca. 0.6 molecule of methyl mercaptan on average, while a silver atom deposited on TiO2 captured only 0.03 molecule. The migration of silver crystallites over the g-C3N4 surface and the formation of silver thin-layer during the adsorption of methyl mercaptan were observed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The silver crystallite on g-C3N4 seemed to have higher mobility than that on TiO2 to form the coordination suitable for the adsorption of methyl mercaptan. This coordination of Ag also enhanced the photocatalytic degradation of methyl mercaptan to dimethyl disulfide.

Influence of surface near doping concentration on contact formation of silver thick film contacts

We investigate the properties of silver thick film contacts on phosphorus doped alkaline textured silicon surfaces with varying surface doping levels. Using scanning electron microscopy, we find that the surface near doping concentration influences the formation of silver crystallites especially those that are in direct contact with both the silicon surface and the contact finger. The observed correlation between direct silver crystallite imprint coverage and specific contact resistance allows for extracting the specific contact resistance of individual crystallites to be approximately 3.3µΩcm2, which agrees well with theoretical predictions. Furthermore we present a new approach that allows for a quantitative separation of direct and indirect current conduction channels. For our experimental conditions, the assumption of current conduction exclusively by transport through silver crystallites adequately describes the experimental data. Finally we fabricate bifacial n-type solar cells with peak efficiencies of 19.9%.

Glass frits coated with silver nanoparticles for silicon solar cells

Glass frits coated with silver nanoparticles were prepared by electroless plating. Gum Arabic (GA) was used as the activating agent of glass frits without the assistance of stannous chloride or palladium chloride. The silver-coated glass frits prepared with different GA dosages were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA). The characterization results indicated that silver-coated glass frits had the structures of both glass and silver. Spherical silver nanoparticles were distributed on the glass frits evenly. The density and particle size of silver nanoparticles on the glass frits can be controlled by adjusting the GA dosage. The silver-coated glass frits were applied to silver pastes to act as both the densification promoter and silver crystallite formation aid in the silver electrodes. The prepared silver-coated glass frits can improve the photovoltaic performances of solar cells.

Effect of the Pb–Te–B–O system glass frits in the front contact paste on the conversion efficiency of crystalline silicon solar cells

In the present paper, many monocrystal silicon (Si) solar cells are produced by screen printing a front contact paste prepared with crystalline silver particles, a series of glass frits with the different lead oxide (PbO) contents in Pb–Te–B–O system glass, and an organic medium. Under scanning electron microscopy, the selective etching of cells screen-printed by pastes containing the glass frits of different PbO contents from low to high (37.2–52.5 mol%) reveals the corrosion degree of antireflection coating and the growth of silver crystallite microstructures on Si substrate. When the PbO content is 42.7 mol% in glass frits, the silver crystallites of optimal size were formed to make the conversion efficiency of cells best. By comparing the cross-section microstructures of solar cells, the different transition temperatures (Tg = 283–546 °C) of glass frits are found to have a substantial impact on wetting behavior during the firing cycle. When the glass Tg is medium (Tg = 393 °C), the optimal glass layer will be obtained to derive photoelectrons smoothly.

Dependence of Ag Deposition Methods on the Photocatalytic Activity and Surface State of TiO2 with Twistlike Helix Structure

The 1% silver clusters containing twistlike helix titania nanoparticles have been synthesized and tested in photocatalytic applications. The special twistlike helix structures were obtained by controlling the hydrolysis of titanium tetrachloride, while variety of routes were investigated to deposit the silver nanoparticles, where impregnation, chemical deposition, and photodeposition methods are adopted to fabricate the Ag/TiO2 samples. The influence of the photocatalytic activity of the mesoporous helix materials and the preparation methods on the final structure of the samples was investigated, including the surface area, pore size, silver crystallite size, silver distribution, and silver surface content. The dispersion and particle size of Ag clusters or nanoparticles on Ag/TiO2 nanocatalysts were investigated by TEM analysis. The surface Ag nanoparticles contents were determined by XPS results. Diffuse reflectance and photoluminescence analysis were used to investigate the visible light adsorption abi...

Morphology Change of Silver Deposit from BMITFSI Ionic Liquid

The electrodeposition of silver was investigated with 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide containing Ag-TFSI at 150°C. The influence of current density on the morphology of the silver deposit was studied by cyclic voltammetry and scanning electron microscopy. The size of the silver crystallite became smaller and dendrite-like growth was suppressed with increasing current density.

Comprehensive analysis of advanced solar cell contacts consisting of printed fine‐line seed layers thickened by silver plating

AbstractThis work presents a detailed analysis of a new two‐layer process to contact industrial solar cells. However, most of the results seem to be transferable to standard screen print paste contacts. The seed layer was created by a pad or screen printer and thickened by light‐induced plating (LIP) of silver. These contact structures were investigated microscopically to gain a better understanding of the observed electrical parameters. A review of the present microscopic contact formation model for flat surfaces is presented. This model was extended and applied to surfaces textured with random pyramids. This analysis has revealed two new types of silver crystallites which can be described by a crystallographic model. The dependence of the silver crystallite density on the surface doping concentration was investigated. Next, the dependence of the contact resistance on the width of the seed layer was measured showing that the contact resistivity increases with a reduction of the seed layer width. These results have been further approved by an analysis of SEM images of wet‐chemically etched contacts examining the density of crystallites and the fraction of removed SiNx layer. Contact resistance RC measurements before and after LIP of silver showed surprisingly a positive influence of the plating process on RC. A detailed microscopical analysis revealed four new possible current flow paths due to the LIP of a conventional contact or a seed layer. The results led to an extension of the existing model for a screen‐printed contact. Copyright © 2008 John Wiley & Sons, Ltd.

Biomimetic synthesis silver crystallite by peptide AYSSGAPPMPPF immobilized on PET film in vitro

AG3 (AYSSGAPPMPPF) is an inorganic-binding peptide that specifically and selectively binds to silver demonstrated by phage display library according to the Stone group. In our experiment, synthesized silver-binding peptide AG3 was immobilized on the surface of protonated poly(ethylene terephthalate) (PET) film which was prepared for biomimetic synthesis silver particles in vitro. Silver crystallites formatted on the surface of AG3-PET film showed various shapes and was 1–4 μm in size. In addition to hexagonal and triangular crystallite, a silver crystallite presents a cubical shape that has seldom been reported in the literatures so far. With comparison of the control and silver nitrate salt, the surface energy of the silver particles on AG3-PET film surface XPS analysis suggested that Ag + was being reduced to Ag 0 in the reaction. Moreover, CD spectrum revealed that the secondary structure of AG3 peptide in solution had a little change before and after binding silver.

Copper- and Silver–Zirconia Aerogels: Preparation, Structural Properties and Catalytic Behavior in Methanol Synthesis from Carbon Dioxide

Copper- and silver-zirconia aerogels containing 10 at% IB metal were prepared from tetra-n-butoxy zirconium(IV) and IB metal acetates using the solution sol-gel method and ensuing high-temperature (HT) and low-temperature (LT) supercritical drying, respectively. The influence of preparation parameters and calcination on the structural and catalytic properties of the aerogels for the synthesis of methanol from carbon dioxide and hydrogen was investigated. After calcination in air at 573 K, the catalysts had BET surface areas in the range of 100–143 m2·g−1(Cu/ZrO2) and 77–125 m2·g−1(Ag/ZrO2), respectively. Due to the reductive alcoholic atmosphere during high-temperature supercritical drying, metallic copper and silver existed in all raw HT-aerogels. The mean size of the copper crystallites was 30 nm. The silver crystallite size for the HT-aerogel prepared with nitric acid was 10 nm, whereas for samples prepared with acetic acid it was 5–7 nm. Calcination in air at 573 K led to the formation of highly dispersed amorphous copper oxide and silver. Comparing the catalytic behavior of the calcined copper–zirconia aerogels with corresponding xerogels prepared by coprecipitation revealed highest activity for the LT-aerogel, whereas the HT-aerogels were least active. In contrast, similar catalytic behavior was observed for the differently dried silver-zirconia samples. Generally, CO2-conversion of the copper–zirconia aerogels was markedly higher than that of the corresponding silver–zirconia aerogels, whereas methanol selectivity was similar.

Influence of metal crystallite size and morphology on selectivity and activity of ethylene oxidation catalyzed by supported silver

The kinetic effects of total surface area, average silver crystallite size, and silver crystallite morphology of supported silver catalysts were investigated under ethylene oxidation conditions. Catalysts were prepared by impregnation of α-alumina with silver nitrate solution followed by drying, reduction, and calcination. They were characterized as to total surface area (0.02–3.03 m 2/g) by the BET method, average silver crystallite size (300–7400 Å) by selective oxygen chemisorption and X-ray diffraction line broadening, and silver crystallite morphology by scanning electron microscopy. The specific activity and selectivity of the catalysts were found to be strong functions of the total surface area. The specific rates to ethylene oxide and to carbon dioxide and water formation exhibited strong structure sensivity with minimum rates at silver crystallite sizes in the range of 500–700 Å. The changes in specific activity and selectivity appeared to be related to changes in the morphology as well as the size of the silver crystallites.