3D photocuring for circuit fabrication: optimization of UV penetration properties via the morphology of silver particles

The evaporation of particle‐free silver ink droplets on heated substrates directly impacts the morphology of the resultant silver particles and electrically conductive inkjet‐printed films. In this work, COMSOL Multiphysics simulations of the droplet evaporation process are used to help explain the fluidic processes responsible for the experimental observations. The results show that the silver particle morphology depends on its location within the evaporating droplet where large particles (3 to 5 µm) accumulate at the center and smaller ones (1 to 2 µm) in the area beyond the central region. The smallest particles (≈500 nm) are near the contact line. Without the fluoro‐surfactant FS‐31, an inner ring with 3 µm particles also appears within the evaporating droplet. The large particles at the central region originate from the fluid near the droplet's apex due to the accumulation of polyacrylamide in the concentrated ethylene glycol solvent near the flow‐abundant apex. Furthermore, the capillary flow along the fluid–air interface transports silver ions and particles throughout the droplet, causing the larger particles to fall onto the substrate at the central vortex, forming the inner ring. The simulations also demonstrate that the evaporating droplet heterogeneously accumulates ethylene glycol in a sandhill formation at the bottom center.

Photothermographic imaging systems based on silver halide and silver carboxylates have been utilized for a wide variety of imaging applications for many years. We have been investigating the morphology of silver particles formed in the image area of photothermographic imaging systems in order to understand the forces that affect their morphology. Because the size, shape, morphology and silver particle distribution within an image area affects the overall optical properties of the imaging material, control of these properties should lead to improved photographic responses of the materials. We have found in this investigation that there are multiple factors that influence the overall morphology of the silver particles, and show how morphological properties are changed by different conditions, e.g., the nature of the materials used, including the toners (succinimide, phthalimide, phthalazine), phenolic developers, and related components.

In this work, using chemical reduction method, we synthesized silver particles with different sizes and morphologies by simply changing the proportion of the associative reducing agents. More specifically, when the reducing agent is ascorbic acid, the morphologies of silver particles are quasi-spherical shapes, the diameter size of silver nanoparticles was in the range from 200 nm to 300 nm. When the reducing agent is hydrogen peroxide, the morphologies of silver particles are irregular bulks, the diameter size of silver nanoparticles was in the range from 1 um to 2 um. When the volume ratio of ascorbic acid (0.09M) and hydrogen peroxide (0.98M) is 1: 1, the morphologies of silver particles are unique, they are coral clusters reunited by long silver nanoplates.

A simple, low-cost, and high-efficient method is used for the fabrication of surface-enhanced Raman scattering (SERS) substrates. Silver particles deposited on porous silicon are prepared as a highly efficient SERS substrate by direct immersion of porous silicon in silver solution. The SERS measured with rhodamine 6G as a target molecule is affected by the morphology of silver particles on the top of porous silicon layer. The effect of solution concentration, dipping time, and thickness of porous layer on the morphology of silver particle is investigated. Highly efficient SERS spectra are observed for substrates with porous layer thickness of about 3 μm and incubated in the 50 mM AgNO3 solution for 3 minutes. The SEM images of the substrates show that there are many small Ag particles with the size of a few nanometers among large Ag particles with the size of several microns.

Silver particles with various morphologies including cubic, spherical, and rod-shaped have been synthesized by a facile solvothermal procedure using poly (vinyl pyrrolidone) (PVP) as an adsorption agent and architecture soft template. Preparation conditions such as the molar ratio and concentration of starting materials were optimized for studying the growth kinetics of silver particles. The amount of chloride ions and PVP plays an important role for the morphology of silver particles during synthesis. Chloride ions as a stabilizer against the aggregation of particles could sufficiently retard particle growth. The selected bounding of PVP molecules on the silver particle is a key for morphological controlling. The morphological evolution of the silver particle was investigated by adjusting systematically preparation parameters. Because of PVP molecules are easily bounded to the (100) facet of silver crystals, the growth of the silver particle occurred around (111) plane. Silver particles with a series of morphologies were created via such anisotropic growth.

Phase relation in Y211–Y123–Ag system and morphology of silver in Y123 crystal

In this paper, micro-size spherical silver particles were prepared by using a wet-chemical reduction method. The silver particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and a laser particle-size analyzer. The results indicate that different types and the content of surfactants can be used to prevent the accumulation, and control the morphology and particle size distribution, of silver particles. Moreover, the morphology of silver particles was changed from polyhedral to spherical when the pH was raised from 1 to 3. Under the optimal synthesis conditions (0.1 mol/L silver nitrate, 0.06 mol/L ascorbic acid, gelatin (5% by weight of silver nitrate), pH = 1), the micro-size spherical silver particles with diameter of 5–8 μm were obtained. In addition, the resistivity of conductive silver paste that prepared with the as-synthesized spherical silver particles was discussed in detail and the average resistivity of the conductive silver paste was 3.57 × 10−5 Ω·cm after sintering at 140 °C for 30 min.

The size and morphology of silver in the YBa 2Cu 3O 6+ x crystal

Mastery over the microscopic shape and size of a nanoparticle enables accurate control of its properties for some strict application. The mechanism of shape-controlled synthesis was discussed by investigating the formation of silver nanospheres prepared by chemical reduction method using Ag(NH3)2 + as metal source, ascorbic acid as reducing agent and polyvinylpyrrolidone (K-30) as dispersant. The effects of temperature, PVP/AgNO3 mass ratio, pH value and the interaction between PVP and silver on the shape and particle size were studied by XRD and SEM. The results show that the morphology of silver particles could transform from branched to spherical and the particle size gradually decrease with the increase of PVP/AgNO3 mass ratio. The particles size can also be significantly influenced by pH value and temperature. The key point for preparing high dispersity spherical silver powder is that the growth rate of each plane of the particle must be uniform and synchronous. Silver powders with spherical particles with mean size of 0.2 μm were synthesized under the optimum conditions (PVP/AgNO3 mass ratio 0.6, pH 7, reaction temperature of 40°C).

The catalytic properties of silver nanoparticles supported on silica and the relation between catalytic activity of silver particles and the support (silica) size are investigated in the present article. The silver nanoparticles with 4 nm diameters were synthesized and were attached to silica spheres with sizes of 40, 78, 105 nm, respectively. The reduction of Rhodamine 6G (R6G) by NaBH4 was designed by using the SiO2/Ag core-shell nanocomposites as catalysts. The experimental results demonstrated that the catalytic activity of silica/silver nanoparticles depends on not only the concentration of catalysts (silver) but also the support silica size. Silver particles supported on small SiO2 spheres (approximately 40 nm) show high catalytic activity. Moreover, by making a comparison between the UV-vis spectra of the catalyst before and after the catalytic reaction, we found that the position of surface plasma resonance (SPR) peak of Ag nanoparticles changes little. The above results suggested that the size and morphology of silver particles were probably kept unchanged after the reduction of R6G and also implied that the catalytic activity of silver particles was hardly lost during the catalytic reaction.

ABSTRACTThe rheological properties of silver thick film paste are influenced by the particle size, morphology of silver particles and by the nature of the filler. Rheological properties in-turn influence the multilayer processing parameters and properties. Silver particles, synthesised with gum Arabic (Ag/GA) as the dispersant resulted in agglomerated particles with irregular morphology. Ag/GA-based thick film paste exhibited thixotropic characteristics. Silver powder synthesised with polyvinyl alcohol (Ag/PVA) as the dispersant resulted in well-dispersed, spherical, free-flowing powder with narrow particle size distribution and exhibited pseudoplastic behaviour. The rheological characteristics of Ag/GA-based thick film paste are not influenced by the filler addition. Influence of filler addition is distinctly noted in the rheological characteristics of Ag/PVA-based thick film paste. The homogeneous mixing of Ag/PVA particles with filler and reproducible rheological characteristics of the corresponding thick film paste resulted in excellent printability with good edge-definition and repeatable properties.

Synthesis and characterization of spherical and mono-disperse micro-silver powder used for silicon solar cell electronic paste

The aim of this work was to study the influence of severe plastic deformation (SPD) on the dissolution of silver particles in Cu–8wt.%Ag alloys. In order to obtain different morphologies of silver particles, samples were annealed at 400, 500 and 600 °C. Subsequently, the material was subjected to high pressure torsion (HPT) at room temperature. By means of scanning and transmission electron microscopy, as well as X-ray diffraction techniques, it was found that during SPD, the dissolution of second phase was strongly affected by the morphology and volume fraction of the precipitates in the initial state. Small, heterogeneous precipitates of irregular shape dissolved more easily than those of large size, round-shaped and uniform composition. It was also found that HPT led to the increase of solubility limit of silver in the copper matrix as the result of dissolution of the second phase. This unusual phase transition is discussed with respect to diffusion activation energy and mixing enthalpy of the alloying elements.

The development of printing electronics technology promotes the application of conductive ink, and nano-silver conductive ink is a hot research. Sliver particles are the main conductive component in conductive ink, so nano-silver particles are very important for the ink conductivity. In this paper, silver nanoparticles were reduced from silver nitrate solution by liquid chemical reduction method, with Sodium hypophosphite as reductant, PVP as surface-protection reagent, and sodium hexametaphosphate as dispersant. Orthogonal test with 4 factors and 3 levels is designed in which the effect of reducing agent dosage, protective agent dosage, dispersant content and reaction temperature on the nano-particle size and morphology of silver is investigated. The size distribution of nano-silver powder is measured by nano-size potential analyzer, and the morphology of silver particles is characterized with the SEM. The experiment results showed that the minimum average size of sliver particles can reach 23.87nm, and the dispersed spherical nano-particles with the average size is about 60nm can be obtained.

Phytochemical screening and silver nanoparticle synthesis of extract of 3 local weeds from Sakon Nakhon Province, namely, Chromolaena odorata L., Amaranthus virdis L., and Cyperus Rotudus L., were carried out. The preliminary testing of chemical constituents revealed secondary metabolites with pharmacological activity. The weed extracts possessed bioactive compounds and were potent for silver nanoparticle synthesis. The weed extracts demonstrated a lower inhibition percentage (DPPH inhibition) than ascorbic acid, with significant differences at p<0.05. Reducing agent analysis revealed that the weed extracts contained reducing compounds such as phenol and carboxylic acid suitable for AgNPs. The XRD patterns of silver nanoparticles synthesized from the extracts demonstrated the efficacy of the weed extract for medical applications (the production of AgNPs). In the future, the size and morphology of silver particles should be investigated. The current results are expected to be a guideline for further applications of local weeds.