The bonding properties of solderable anisotropic polymer composites (SAPCs) containing only low-melting-point alloy (LMPA) fillers need improvement. In this study, a new composite containing LMPA and high-melting-point alloy (HMPA) fillers, named LH-SAPC, was proposed, and the establishment of the conduction path and bonding properties of LH-SAPC were investigated for different LMPA/HMPA mixing proportions. Six types of LH-SAPC filled with different LMPA/HMPA mixing proportions (100:0, 80:20, 50:50, 20:80, 10:90, and 0:100) were formulated, and bonding tests were performed using the quad flat package. The LH-SAPCs containing less than 50 vol

Stratified films offer high performance and multifunctionality, yet achieving fully stratified films remains a challenge. The layer-by-layer method, involving the sequential deposition of each layer, has been commonly utilized for stratified film fabrication. However, this approach is time-consuming, labor-intensive, and prone to leaving defects within the film. Alternatively, the self-stratification process exploiting a drying binary colloidal mixture is intensively developed recently, but it relies on strict operating conditions, typically yielding a heterogeneous interlayer. In this study, an active interfacial stratification process for creating completely stratified nanoparticle (NP) films is introduced. The technique leverages NPs with varying interfacial activity at the air-water interface. With the help of depletion pressure, the lateral compression of NP mixtures at the interface induces individual desorption of less interfacial active NPs into the subphase, while more interfacial active NPs remain at the interface. This simple compression leads to nearly perfect stratified NP films with controllability, universality, and scalability. Combined with a solvent annealing process, the active stratification process enables the fabrication of stratified films comprising a polymeric layer atop a NP layer. This work provides insightful implications for designing drug encapsulation and controlled release, as well as manufacturing transparent and flexible electrodes. Colloidal mixtures are stratified at the air-water interface depending on their interfacial activity, forming asymmetric multilayers. With the help of depletion pressure, lateral compression induces individual desorption of less interfacial active nanoparticles (NPs) into the subphase, while more interfacial active NPs remain at the interface. This active stratification process leads to nearly perfect stratified NP films with controllability, universality, and scalability. image

Sn58Bi-Cu composite solder, in which copper (Cu) particles were applied as a reinforcement material, was synthesized to address the material limitations and improve the bonding properties of Sn-58Bi eutectic solder. To evaluate the impact of Cu particle concentration on the solderability and mechanical properties of Sn58Bi-Cu composite solder, fi ve variants with different Cu particle concentrations (0, 3, 5, 10, and 15 vol%) were synthesized. Wetting, ball shear, and microhardness tests were then performed. The wetting test revealed that the Sn58Bi-Cu composite solder containing Cu particles up to 10 vol% exhibited satisfactory wetting morphology and a wetting angle of approximately 30 degrees, indicating appropriate wetting behavior. In contrast, the Sn58Bi-Cu composite solder containing excessive amounts of Cu particles (15 vol%) demonstrated weak wetting angle and solderability due to increased viscosity from the intensified chemical reaction between the molten solder and Cu particles. The solder ball shear and microhardness test results for the Sn58Bi-Cu composite solder containing Cu particles up to 10 vol% showed that the mechanical properties of the solder joint improved with increasing Cu particle concentrations. This improvement in mechanical properties was attributed to the grain refinement of the joint and the reinforcement effect of Cu particles.

In this papers, to enhance the mechanical bonding properties of solderable anisotropic polymer composites (SAPCs) containing low-melting-point solder filler only, a new low-melting-point solder and high-melting-point solder mixed filler filled SAPCs (LH-SAPCs) was proposed, and the influence of the high-melting-point solder filler on the conduction path formation and mechanical bonding properties of the LH-SAPC were investigated. Two types of LH-SAPC were synthesized by adding high-melting-point solder within the low-melting-point solder/high-melting-point solder mixed filler at mixing ratios of 0 and 50 vol% (the volume fraction of low-melting-point solder/high-melting-point solder mixed filler in the polymer composite was 20%), and a bonding test was conducted using QFP. The results exhibited that the LH-SAPC containing high-melting-point solder formed a wide and stable conduction path due to the proper selective conduction path formation behavior by the interaction between molten low-melting-point solder and solid-state high-melting-point solder fillers within the polymer composite with low viscosity condition. Furthermore, the mechanical bonding properties of the LH-SAPC joints containing high-melting-point solder were enhanced compared to that of LH-SAPC containing low-melting-point solder only owing to the precipitation hardening and dispersion strengthening effects due to the increase of fine Bi-rich, Cu6Sn5, and Ag3Sn intermetallic compound particles inside the conduction path.

A novel bonding system for a solderable epoxy composite (SEC) containing a mixed low-melting-point solder (LMS) and high-melting-point solder (HMS) filler (LH-SEC) was proposed to overcome the thermal and mechanical limitations of SECs with LMS fillers. To evaluate the influence of the LMS/HMS mixing ratio on the wetting properties (i.e., the wettability and selective patterning) of the resulting LH-SEC, six types of LH-SEC with different LMS/HMS mixing ratios (100:0, 80:20, 50:50, 20:80, 10:90, and 0:100) were synthesized, and planar and line pattern wetting tests were conducted. The LH-SEC with only the HMS filler exhibited very weak wetting properties because of the excessive curing of the epoxy composite before the HMS melted. In contrast, two wetting modes were observed for the LH-SECs that contained both LMS and HMS. In the LH-SEC with less HMS than LMS, conduction paths were established via the internal flow, integration, and wetting behaviors of the molten LMS containing solid-state HMS within the melting temperature (T-m) range of the LMS filler. For the LH-SECs with more HMS than LMS, conduction paths were formed via the wetting behavior of the molten HMS filler at a temperature range lower than the typical T-m range of the HMS filler because of the decreased T-m of HMS due to the wetting of the molten LMS to the HMS and the diffusion of Bi atoms into the interior of the HMS filler.

A Sn-58Bi (SB)/Sn-3Ag-0.5Cu (SAC) composite solder was developed to overcome the challenges, e.g., the low ductility, deterioration of bonding properties and joint reliability, associated with SB eutectic solder and enhance its mechanical bonding properties. Specifically, four types of SB/SAC composite solder samples with different SB/SAC mixing ratios (100:0, 50:50, 20:80, and 0:100) were formulated. Two types of mechanical property investigations, i.e., ball shear and microhardness tests, were conducted to explore the influence of the SB/SAC mixing ratios on the mechanical properties of SB/SAC composite solder joints. The results indicated that the mechanical properties of the joint that containing both SB and SAC were superior to that with only SB or SAC. Furthermore, the mechanical properties of SB/SAC composite solder joint increased linearly with increasing SAC content. This improvement was attributable to the precipitation hardening and dispersion strengthening induced by the presence of fine intermetallic compounds and Bi-rich phase particles dispersed in the SB/SAC composite solder joint. [doi:10.2320/matertrans.MT-M2023115]

We demonstrate the morphology control of pre-aligned hydrophilic channels of ultrathin (∼30 nm) perfluorinated sulfonic acid membranes leading to enhancement of ion-selectivity and vanadium redox flow battery cell performance.

Perfluorosulfonic acid (PFSA) membranes, such as Nafion, are widely used in vanadium redox flow batteries (VRFBs) because of their high proton conduction through the ion channels and excellent chemical stability. However, the high vanadium permeability of PFSA membranes induced by the randomly interconnected channels limits efficient cell operation. In this work, we demonstrate a sub-20 nm ultrathin PFSA-grafted graphene oxide/PFSA (PFSA-g-GO/PFSA) composite membrane with highly aligned ion channel morphology, which results in a 100-fold improvement in proton/vanadium ion selectivity compared to 25 mu m-thick Nafion 211. In addition, the PFSA-g-GO nanosheets physically reinforce the ultrathin membrane while enabling the proton transport through the grafted PFSA ionomers, leading to stable cell operation at overall current densities from 40 to 200 mA cm-2. Especially, at a high current density of 200 mA cm-2, the PFSA-g-GO/PFSA composite membrane shows an energy efficiency (EE) of 78%, which is higher than that of Nafion 211, indicating its potential as an ion-selective membrane for VRFB.

This study developed Cu particle-filled solderable isotropic polymer composites (Cu-SIPCs) to improve the bonding properties of SIPCs with low-melting-point solder (LMPS) fillers. To examine the influence of Cu particle concentration on the bonding properties of Cu-SIPC joints, Cu-SIPCs comprising different Cu particle concentrations in the conductive fillers were formulated, and a bonding test using a quad flat package was conducted. The bonding properties of these joints were measured and compared. The Cu-SIPCs with a Cu particle content of below 10 vol% formed a wide and reliable metallurgical conduction path, with uniformly dispersed Cu particles, due to the proper internal flow and wetting behavior exhibited by molten LMPS fillers. The mechanical bonding strength of the Cu-SIPC joints increased linearly with an increase in the Cu particle content due to the mechanical enhancement effect offered by the Cu particles within the conduction path. However, Cu-SIPCs with excessively high Cu particle concentrations formed weakly shaped conduction paths because of the partly raised viscosity of molten LMPSs and the local agglomeration of Cu particles, which diminished the fluidity of molten LMPSs.

In recent years, the potential of nanobubbles (NBs) for biological activation has been actively investigated. In this study, we investigated the proliferative effects of nitrogen NBs (N-NBs) on fibroblast cells using cell assays with image analysis and flow cytometry. A high concentration of N-NBs (more than 4 × 108 NBs/mL) was generated in Dulbecco’s modified Eagle’s medium (DMEM) using a gas–liquid mixing method. In image analysis, the cells were counted and compared, which showed an 11

The role of anionic surfactant in nanobubble (NB) generation behavior by ultrasonication was investigated in terms of zeta potential and concentration of NBs. NBs were generated by ultrasonication in deionized (DI) water and surfactant solutions with different concentrations of surfactant. In pure water, a low number of NBs was generated because the coalescence of bubbles generated by ultrasonication actively occurred and bubble growth was accelerated. On the contrary, as the surfactant concentrations in the solutions were increased, sporadic nucleation occurred because of the influence of surfactant molecules, which were adsorbed to the gas–liquid interface of the bubbles grown from nucleation. Thus, the solutions with surfactants exhibit a strong negative zeta potential characteristic. Such a strong surface electrical property of the generated bubbles strongly suppresses the coalescence behavior by ultrasonication. As a result, this tendency was dominant in the solutions, and the NB concentration considerably increased with increasing surfactant concentration.

The effects of liquid temperature on bulk nanobubbles (BNBs) generation using ultrasound was investigated. When liquid at different temperatures and relatively similar dissolved oxygen concentration (25 degrees C: 8.29 ppm; 50 degrees C: 8.11 ppm; and 75 degrees C: 7.78 ppm) were sonicated, a high number of negatively charged (-13 to -21 mV) BNBs were consistently generated within a few minutes. As the temperature of the liquid increased, it is expected that the concentration of BNBs considerably increased due to a lot of nucleation site and strong collapse of tiny bubbles. On the other hand, in a liquid with relatively low temperature, a high number of large bubbles were formed and the BNBs concentration considerably decreased. It is suggested that it has less nucleation sites compared to a liquid with higher temperature; thus, the bubble growth was accelerated by rectified diffusion and coalescence, owing to less nucleation sites versus dissolved gas concentration.

In this study, low-melting-point alloy (LMPA) and high-melting-point alloy (HMPA) filler-filled solderable polymer composite (LH-SPC) system was proposed to enhance the mechanical and thermal properties of SPC with LMPA fillers. To identify the conduction path formation characteristics of LH-SPC according to the mixing ratio of LMPA and HMPA, four types of LH-SPC with different mixing ratios of LMPA and HMPA fillers (100:0, 80:20, 30:70, and 0:100) were formulated. Furthermore, a chip resistor interconnection test was conducted. The results indicated that LH-SPC with only HMPA did not form a conduction path because of the excessively cured polymer composite before melting HMPA. Meanwhile, LH-SPC with LMPA and HMPA fillers showed different conduction path formation mechanisms according to the mixing ratio of LMPA and HMPA fillers. In LH-SPC filled with lower HMPA content than LMPA, the conduction path was formed by the flow, coalescence, and wetting behaviors of molten LMPA containing solid-state HMPA at the melting range of the LMPA filler. On the other hand, in LH-SPC containing higher HMPA content than LMPA, the conduction path was formed by the wetting behavior of the molten HMPA at a lower temperature range than the melting temperature of HMPA because of the decreased melting temperature of HMPA owing to the chemical composition change of HMPA by the diffusion of Bi into HMPA.

Abstract As the field of application of nanobubbles (NBs) expands, more in-depth research into NB generation techniques is required. In this study, the NB characteristics generated by gas–liquid mixing and an NB generation mechanism were investigated according to the different liquid volume fraction (LVF). In the gas–liquid mixing method, we confirmed that the important factors for NB generation are the shear force applied to the trapped bubbles and the amount of trapped bubbles in the liquid. Based on these factors, NBs were generated at more than 10×108 NBs/ml and remained in a stable state for seven days. This study proposes a more specific NB generation mechanism and a valuable methodology for high-concentration NB generation through the gas–liquid mixing method.

PolyHIPE, a polymerized high internal phase emulsion, is considered a promising platform for producing porous polymers. In particular, photo-polymerized HIPE has recently been utilized in the 3D printing of porous materials and other applications due to its rapid curing. However, unlike polyHIPEs prepared by thermal polymerization, a systemic study for the structural control of photo-polymerized HIPE has not yet been reported. To achieve this, here, we examine the influence of various parameters, such as partition behavior of the photo-initiator, the intensity of light, and type of emulsifier, on the structure of photo-polymerized oil-in-water HIPE. As a result, we, for the first time, report the guidelines to effectively regulate morphology of photo-polymerized HIPEs, including void interconnectivity and shape.

A Cu powder-filled solderable epoxy composite (Cu-SEC), in which Cu powders were applied as reinforcement materials, was developed to enhance the mechanical properties of solderable epoxy composite (SEC) joints. To clarify the influence of the Cu powder content on the wettability and mechanical properties of SECs, four types of Cu-SECs with different Cu powder concentrations in the metal fillers (from 0 to 20 vol%) were synthesized, and two types of wetting tests (i.e., planar and line metallization wetting tests), and microhardness tests were conducted. The Cu-SECs for which the Cu powders content less than a certain value (10 vol%) exhibited proper wettability with a reasonable wetting angle and spreading shapes to the Cu metallization in a planar metallization wetting test, and showed excellent selective wetting properties with a uniform and stable selectively wetted conductive path morphologies in a line metallization wetting test. The microhardness of the Cu-SEC joints increased with the increasing Cu powder content due to the strengthening effect of the uniformly distributed Cu powders within the wetted low-melting-point solder (LMS) filler. However, the wettability and selective wetting properties of the molten LMS deteriorated as the Cu powder content increased to more than a certain value because of the partially increased viscosity and reduced fluidity of the fused LMS.

In recent years, minuscule gas bubbles called bulk nanobubbles (BNBs) have drawn increasing attention due to their unique properties and broad applicability in various technological fields, such as biomedical engineering, water treatment, and nanomaterials. However, questions remain regarding the stability and behavior of BNBs. In the present work, BNBs were generated in water using a gas–liquid mixing method. NB analysis was performed using a nanoparticle tracking analysis (NTA) method to investigate the coarsening behavior of BNBs in water over time. The diameters of the BNBs increased, and their cubic radii increased linearly (r 3 ~ t) over time. While the concentration of BNBs decreased, the total volume of BNBs remained the same. The size distribution of the BNBs broadened, and the concentration of larger BNBs increased over time. These results indicate that relatively small BNBs disappeared due to dissolution and larger BNBs grew through mass transfer between BNBs instead of coalescence. In other words, BNBs underwent Ostwald ripening: gas molecules from smaller BNBs diffused through the continuous phase to be absorbed into larger BNBs.

A novel Cu-powder contained solderable epoxy-solder composite (Cu-SESC) was introduced, and its interconnection mechanism was proposed as a means to improve the interconnection properties of the SESC joints. To identify the possibility and strengthening effect for the SESC joints by added Cu powder, two types of wetting tests using planar and line type metallization formed test boards, and a microhardness evaluation were performed. The Cu-SESC showed appropriate wetting and spreading properties. The Cu powders in the wetted low meltingpoint alloy (LMA) exhibited a uniform dispersion state, and a Cu-Sn intermetallic compound created on the surface of the Cu powders. The SESC that had Cu powders showed a superior microhardness value to that of the SESC without Cu powders because of the strengthening effect from the added Cu powder. Additionally, the selective conduction joint establishment properties obtained through the flowage. integration, and selective wetting behaviors of the fused LMA were not interrupted by the incorporated Cu powders.

In this study, highly concentrated hydrogen nanobubble water was utilized as the blending water for cement mortar to improve its compressive and flexural strengths. Highly concentrated nanobubbles can be obtained through osmosis. This concentration was maintained by sustaining the osmotic time. The mortar specimens were cured for 28 days, in which the nanobubble concentration was increased. This improved their flexural strength by 2.25–13.48% and compressive strength by 6.41–11.22%, as compared to those afforded by plain water. The nanobubbles were densified at high concentrations, which caused a decrease in their diameter. This increased the probability of collisions with the cement particles and accelerated the hydration and pozzolanic reactions, which facilitated an increase in the strength of cement. Thermogravimetric analysis and scanning electron microscopy were used to confirm the development of calcium silicate hydrate (C-S-H) and hydration products with an increase in the nanobubble concentration. Quantitative analysis of the hydration products and the degree of hydration were calculated by mineralogical analysis.