AGS Volume Research Articles

Exploring the process-microstructure-thermal properties relationship of resin-reinforced Ag sintering material for high-power applications via 3D FIB-SEM nanotomography

Resin-reinforced Ag sintering materials represent a promising solution for die-attach applications in high-power devices requiring enhanced reliability and heat dissipation. However, the presence of resin and intricate microstructure poses challenges to its thermal performance, and improvement strategies remain unclear. This work utilizes 3D FIB-SEM nanotomography to reconstruct the microstructure of this material under various process conditions. The analysis reveals that, even with an Ag volume fraction as low as 47.3%, Ag particles form a robust 3D network. Geometric tortuosity quantifies the effect of different sintering conditions on the Ag particle network in all spatial directions. Effective thermal conductivity is simulated based on realistic microstructure models. Results show a significant negative correlation between tortuosity and effective thermal conductivity. Increasing sintering temperature in Model B notably reduces tortuosity and enhances effective thermal conductivity. Sensitivity analysis underscores the dominant role of Ag volume fraction in regulating effective thermal conductivity. Finally, transient thermal impedance measurement of this material as a thin die-attach layer in actual high-power devices demonstrated its application potential. This article strives to explore the relationship between process, microstructure, and thermal properties of this material to provide a reference for further development.

Preparing Silver–Copper pastes in accordance with percolation theory for die attach bonding

The Si die and Cu substrate were successfully bonded with self-developed Ag–Cu pastes through two processes: tube furnace annealing at 250 °C for 30 min in an Ar atmosphere and hot pressing at 250 °C and 5 MPa for 30 min in air. The microstructures, mechanical properties, thermal conductivity, and resistivity of the bonded samples were analyzed and then compared with those of commercial Ag paste. For the samples subjected to tube furnace annealing, the critical Ag volume of the Ag–Cu paste was 35%, shear strength was 5.17 MPa, and resistivity was 9.22 μΩ-cm according to percolation theory. For the samples subjected to hot pressing, the critical Ag volume of the Ag–Cu paste was 75%, shear strength was 8.88 MPa, and resistivity was 12.88 μΩ-cm. The critical Ag volume could not be evaluated on the basis of percolation theory because the thermal conductivity increased gradually with the Ag content, and no saturation trend was observed. The thermal conductivity of the 75 vol% Ag–Cu paste produced through hot pressing was 241 W/mK, which was considerably higher than the commercial Ag paste (thermal conductivity: 48.417 W/mK; electrical resistivity: 400 μΩ-cm), and the cost of 25 vol% Ag particles was successfully reduced.

AGS volume 160 issue 6 Cover and Front matter

AGS volume 160 issue 6 Cover and Front matter

AGS volume 160 issue 5 Cover and Front matter

AGS volume 160 issue 5 Cover and Front matter

Ag-Pd bimetallic hollow nanostructures with tunable compositions and structures for the reduction of 4-nitrophenol

Bimetallic hollow nanostructures are of interest for high-performance nanocatalysis and achieving a higher utilization efficiency of noble metals. This paper reports the synthesis of Ag-Pd bimetallic hollow nano-hexagon with outer sizes of about 27 nm and wall thicknesses of 3–5 nm by galvanic replacement reaction (GRR) coupled with a co-reduction method using Ag nanospheres as sacrificial templates. Cetyltrimethylammonium bromide (CTAB) exhibited a double effect on controlling morphologies. First, it acted as the capping agent to mediate the rate of dissolution and deposition on different planes by selectively absorption, and second, it provided Br- ion with ability to promote the GRR. The compositions and structures of Ag-Pd bimetals could be finely tuned by changing the amount of palladium chloride acid (H2PdCl4) while maintaining the volume of Ag seed templates unaltered. By comparing the TOF rate of 4-nitrophenol reduction reaction over different samples of Ag-Pd bimetals as the catalyst, we conclude that hollow bimetallic nano-hexagons with the composition of AgPd0.61 exhibited the highest catalytic activity due to the high surface areas, synergy effect between the two metals, and {100} exposure facets.

Metal(loid) Deportment in Sulfides from the High-Grade Core of the Bingham Canyon Porphyry Cu-Mo-Au Deposit, Utah

Abstract Porphyry deposits supply the bulk of the world’s Cu and Mo and significant amounts of Au, as well as other minor and trace metal(loid)s, including Ag, Re, Te, Pd, Se, Bi, Zn, and Pb. Porphyry deposits are gaining in importance as a source of critical raw materials with the increasing global demand for these commodities. To date, minor and trace metal(loid)s are still commonly recovered as by-products from porphyry ores without prior characterization of their host mineralogy that could inform more efficient processing and improved recoveries. We report a comprehensive metal(loid) deportment study on a complete vein paragenetic series in samples from the northwestern high-grade zone of the Bingham Canyon Cu-Mo-Au porphyry deposit, Utah. The polyphase Bingham stock comprises an early premineralization equigranular monzonite phase that was intruded by a series of five successive, ore-related porphyry intrusions. Veins with hypogene Cu-(Fe) sulfide assemblages from all five porphyry intrusions were characterized for their trace metal(loid) contents by laser ablation-inductively coupled-mass spectrometry (LA-ICP-MS). It was found that bornite and digenite contain elevated Bi, Ag, Te, and Se relative to chalcopyrite, whereas the latter contains elevated concentrations of Co, Ga, and In. A stepwise decline in sulfide abundance occurs over the porphyry intrusion sequence and is more pronounced in digenite and bornite than in chalcopyrite. The related diminishing concentration per rock volume (inventory) of Bi, Ag, Te, and Se in the youngest porphyry dikes could have been caused in part by a geochemical change in the mineralizing fluid supply across successive intrusive-hydrothermal cycles. Element mapping of exsolved digenite within bornite revealed characterstic partitioning of metal(loid)s between bornite and digenite; most notably Ag, but also Te and Au are enriched in digenite relative to enclosing bornite. Bornite domains within these composite grains reveal complex zonation of Sn, In, and Bi, which are attributed to stress-induced diffusion within bornite, resulting from the digenite exsolution process. The selective partitioning of metal(loid)s between bornite and digenite is likely a common feature in many porphyry Cu deposits, given the fundamental mineralogical characteristics of these two sulfides. Our results contribute to an improved understanding of the distribution (from mineral to deposit scale) of critical trace metal(loid)s in porphyry deposits, particularly those containing exsolved digenite. This knowledge can be applied to determine more accurately the value of ore resources, to improve geometallurgical models and by-product recoveries, and to help limit the environmental effects of metal(loid) dispersion.

Fabrication of Ta-Ag composite deposits via cold spray: Investigation of bonding mechanism and deposition behavior

Cold spray is a solid-state deposition technology that can achieve deposition of pure metal, alloys, and composites with high efficiency. By taking the advantage of cold spray method, in this work, Ta and Ag were successfully used to fabricate Ta-Ag composite deposits for the first time, despite their significantly different properties. It was found that mechanical bonding was the major deposition mechanism between Ta and Ag. The Ag volume in the mechanically mixed powder influence the deposition between Ag and Ta particles. Deposition of Ta-Ag powder was same as pure Ta powder when Ag volume was low, and the small volume of deposited Ag inhibit the deposition of Ta particles. Higher Ag volume in powder promoted the deposition of Ta particles via mechanical interlocking due to the formation of large Ag agglomerates.

AGS volume 160 issue 3-4 Cover and Front matter

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AGS volume 160 issue 1-2 Cover and Front matter

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Hall and ion slip effects on the MHD flow of Casson hybrid nanofluid past an infinite exponentially accelerated vertical porous surface

In the present investigation, the radiative MHD flow of an incompressible viscous electrically conducting non-Newtonian Casson hybrid nanofluidover an exponentially accelerated vertical porous surface has been considered. Under the influence of slip velocity in a rotating frame, it takes Hall and ion slip impacts into account. Water and ethylene glycol mixture is considered a base Casson fluid. A steady uniform magnetic field is applied under the postulation of a low magnetic Reynolds number. The ramped temperature and time-altering concentration at the surface are considered. First-order consistent chemical reaction and heat absorption are also regarded. Silver and Titania nanoparticles are disseminated in base fluid water and ethylene glycol combination should be formed by a hybrid nanofluid. The Laplace transformation technique is employed on the non-dimensional governing equations to ensure closed-form analytical solutions. The graphical representations scrutinize the effects of physical parameters on the significant flow characteristics. The expression for non-dimensional shear stress, heat transfer rate and mass transfer are also evaluated. They are tabulated with different variations in implanted parameters. For uniform and ramped wall temperatures, the resultant velocity grows by an increase in Hall and ion slip parameters. The resultant velocity increases by an increase in volume fractions of nanoparticles with uniform wall temperature, and a reverse effect is observed with ramped wall temperature. The temperature of Casson hybrid Ag-TiO2/WEG nanofluid is relatively superior to that of Casson Ag-WEG nanofluid. Species concentration of Casson hybrid Ag-TiO2/WEG nanofluid decreases with an increase in Schmidt number and chemical reaction parameters. The heat absorption increases the Nusselt number near the surface, while Ag and TiO2 nanoparticle volume fractions tend to lessen it.

AGS volume 159 issue 9-10 Cover and Front matter

AGS volume 159 issue 9-10 Cover and Front matter

AGS volume 159 issue 7-8 Cover and Front matter

AGS volume 159 issue 7-8 Cover and Front matter

AGS volume 159 issue 5-6 Cover and Front matter

AGS volume 159 issue 5-6 Cover and Front matter

AGS volume 159 issue 3-4 Cover and Front matter

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The ultrahigh pressure stability of silver: An experimental and theoretical study

We measured the atomic volume of Ag in a toroidal diamond anvil cell to a maximum pressure of 416 GPa and calculated the atomic volume and elastic constants of Ag up to 750 and 460 GPa, respectively. Our density functional theory calculations at 0 K utilize an all-electron fully relativistic method and agree well with our volume measurements, particularly at pressures above ∼75 GPa. We corrected our experimental results for non-hydrostaticity using a line shift analysis, and the resulting Vinet equation of state (EOS) parameters are reported. We find that the uniaxial stress sustained by Ag increases linearly up to 4.5 GPa at a pressure of 416 GPa. Our experimental results indicate that the fcc structure of Ag remains stable to at least 416 GPa at room temperature. Our theoretical results show that C44 increases as pressure increases and reaches a maximum at ∼100 GPa above which it begins to decrease, a sign that the fcc structure of Ag is becoming unstable, and at V/V0 = 0.30, the bcc structure is lower in energy than fcc.

Synthesis of silver nanostructure on gold nanoparticle using near field assisted second harmonic generation

By using gold (Au) nanoparticles (NPs) as an optical near-field source under far-field illumination in combination with a silver (Ag) ion solution containing a photoinitiator, we coated Ag on Au NPs using a near-field (NF)-assisted process. We evaluated the change in the size of the NPs using transmission electron microscopy. Evaluation of the synthesized Ag volume over illumination power confirmed the squared power dependence of the NP volume with illumination using 808 nm light, i.e., a wavelength longer than the absorption edge wavelength of the photoinitiator molecules. The rate of volume increase was much lower than the plasmonic field enhancement effect. Therefore, the squared power dependency of the volume increase using a wavelength longer than the absorption edge wavelength originated from NF-assisted second-harmonic generation and the resulting excitation.

AGS volume 159 issue 1-2 Cover and Front matter

AGS volume 159 issue 1-2 Cover and Front matter

Catalytic properties of the composite of La-doped ZnO nanorods and Ag2CrO4 nanoparticles

To study the application of ZnO in photocatalysis, a composite of La-doped ZnO nanorods and Ag2CrO4 nanoparticles was prepared by hydrothermal and precipitation methods. At a fixed concentration, the volume of Ag+ precursor has a significant effect on the composition and structure of the composite. With the increase in the Ag+ source volume, the amount of Ag2CrO4 nanoparticles generated in the composite increases. When the volume of the Ag+ source exceeds some critical value, although the amount of Ag2CrO4 nanoparticles in the composite continues to increase, the quality of the crystals is lower. Both the content and crystal quality of Ag2CrO4 nanoparticles affect the photocatalytic properties of the composite. The introduction of additional oxygen vacancy defects in nanorods leads to the formation of more, and larger, Ag2CrO4 nanoparticles in the composite without degradation of crystal quality. Then, two dyes (methyl orange and methylene blue) were selected to examine the photocatalytic properties of the samples. The improvement of photocatalytic performance of the composite samples is realized by the separation of electron–hole pairs in both ZnO and Ag2CrO4 crystals.

Synthesis of Nano-Flakes Ag•ZnO•Activated Carbon Composite from Rice Husk as A Photocatalyst under Solar Light

This study aimed to synthesize Ag•ZnO•Activated carbon (Ag•ZnO•AC ) composite from rice husk for degradation of dyes. The deposition of Ag and ZnO on AC led to decreasing the surface area and pore volume of Ag•ZnO•AC composite. In addition, when Ag and ZnO were dispersed on activated carbon, the Ag•ZnO flakes became denser and tighter, but the particle size of Ag became smaller from 5 to 7 nm. The photocatalytic ability of Ag•ZnO•AC composite was evaluated by degradation of Janus Green B (JGB) and compared with that of AC, ZnO, Ag•ZnO, and ZnO•AC samples. The effects of catalyst dosages, pH values, and initial dye concentrations on photocatalytic degradation were investigated in detail. The Ag•ZnO•AC composite had a high degradation efficiency of 100% in 60 min, showing the reaction rate of 0.120 min-1 and degradation capacity of 17.8 mg/g within 20 min. The photocatalytic performance of the Ag•ZnO•AC composite was also evaluated by cyclic test and the degradation of other persistent dyes such as Methylene Blue, Tartrazine, Congo Red, and organic compounds (Caffeine and Bisphenol A). Based on the experimental results, the possible destruction route of JGB by the as-synthesized Ag•ZnO•AC composite was suggested. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Enhanced figure of merit in La0.95Sr0.05CoO3/Ag nanocomposites

In this work, we present an experimental study of the influence of silver nanoparticles (AgNPs) addition over the thermoelectric properties of La0.95Sr0.05CoO3 (LSCO) in order to improve its thermoelectric efficiency. For this aim, ceramic samples of LSCO were obtained by solid-state reaction (SSR) and subsequent ball milling in order to reduce their grain size. Then, nano- and submicrometric LSCO/Ag composites were prepared for different Ag volume fractions and by using different sintering temperatures. We have evaluated the thermoelectric efficiency by means of the dimensionless figure of merit, ZT. The results do not follow a clear trend but confirm that the AgNPs addition enhances noteworthy the ZT value of La0.95Sr0.05CoO3. Therefore, it is concluded the validity of the nanocomposite approach on thermoelectric oxides to improve their thermoelectric efficiency.