Electrical Bridging Research Articles

Preparation of grafted starch‐based cationic flocculants and its removal of reactive and disperse dyes

AbstractIn this paper, a starch‐based flocculant (ADSt) with medium and low temperature solubility and enhanced flocculation effect was synthesized using corn starch, acrylamide, and dimethyldiallyl ammonium chloride as main materials by the ethanol‐alkali method and grafting method. The main mechanism of ADSt's flocculation was electrical neutralization and bridging. The flocculation performance of ADSt was verified by using it along with polymeric aluminum chloride (PAC) as coagulant/flocculant, dispersible dye (dispersible yellow RGFL), and reactive dye (active trimeric blue KN‐G) to simulate dye wastewater. For the dispersed yellow water sample and active emerald blue water sample, the dosage of PAC was 40 and 35 mg/L respectively. When the dosage of ADSt was 10 mg/L with a dye content of 100 mg/L, the decolorization rates for both dyes reached up to 96.2% and 94.4% respectively. The properties of the flocs such as size and two‐dimensional fractal structure were described. The prepared ADSt maintained a good flocculation effect in the pH range of 5–9 due to its excellent water solubility achieved through the ethanol‐alkali preparation process, where its solubility reached 86.7% at 30°C. Overall, the preparation process for ADSt is simple, cost‐effective, while providing an effective solution for treating printing and dyeing wastewater.

Experimental study on toughening UV pre-curing adhesives for electrically conductive applications

Epoxy adhesives are not conductive materials, usually requiring the use of fillers to create electrical bridging between the joint's substrates. This work aims at the implementation of UV fixation, instead of clamping jigs, on doped joints to ensure enough contact bridging pressure during curing. As such, an UV pre-curable adhesive was mechanically characterised in terms of strength – bulk tensile test and TAST (shear) –, and fracture toughness – DCB (mode I) and ENF (mode II) tests –, in the neat state (reference). Afterwards, for the doped configurations – 5%v/v conductive spheres (Sph), 15%v/v aluminium (Al) and 10%v/v graphite (C) – only mode I and II tests were considered accessing the filler's toughening effect. The electrical conductivity of the real joints was assessed through electric discharge machining (EDM). In the end, the Sph's were deemed necessary for bond thickness control. And the Al (mode I +50 % and II +61 %) and C (mode I +25 % and II +42 %) powders presented improvements in toughening the adhesive. However, UV-fixation failed to provide enough clamping pressure, during curing, to maintain the electrical bridging necessary for EDM.

Electrical bridging effects of dual-carbon microsphere frameworks in Si-based composite anodes for high-performance Li-ion batteries

Herein, the successful fabrication of a high-performance Si-based composite Li-ion battery (LIB) anode, comprising a dual-carbon framework of reduced graphene oxide (r-GO) and oxidized single-walled carbon nanohorns (o-NHs), was demonstrated using a simple and scalable spray-drying process followed by heat treatment (h-s-GO/Si/NH). The r-GO nanosheets in the h-s-GO/Si/NH anode acted as a robust spherical framework that facilitated the mechanical and electrical connection between the carbon-coated Si (c-Si) nanoparticles, homogeneous dispersion of c-Si and o-NH nanoparticles, and suppression of the volume expansion and pulverization that occur during lithiation/delithiation. Additionally, the o-NH nanoparticles incorporated in the h-s-GO/Si/NH composite served as electrical bridges between the r-GO nanosheets, resulting in enhanced electrical conductivity and effortless Li-ion shuttling. The h-s-GO/Si/NH composite anode exhibited high electrochemical performance with a very high initial gravimetric charge capacity (2961 mAh g−1 at 0.1 A g−1), stable initial Coulombic efficiency (80.6% at 0.2 A g−1), and high cycling stability (983 mAh g−1 at 0.2 A g−1 after 50 cycles). This study highlights the importance of the effective design of electrically conductive three-dimensional frameworks in Si-based composite anodes, which may contribute to the development of high-performance LIB anode materials.

Synergistically Improved Thermoelectric Energy Harvesting of Edge-Oxidized-Graphene-Bridged N-Type Bismuth Telluride Thick Films.

Power generation through the thermoelectric (TE) effect in small-sized devices requires a submillimeter-thick film that is beneficial to effectively maintain ΔT compared with a micron-scale thin film. However, most TE thick films, which are fabricated using printing technologies, suffer from low electrical conductivity due to the porous structures formed after sintering of the organic binder-mixed TE ink. In this study, we report an n-type TE thick film fabricated through bar-coating of the edge-oxidized-graphene (EOG)-dispersed Bi2.0Te2.7Se0.3 (BTS) paste with copper dopants. We have found that EOG provides the conducting pathway for carriers through electrical bridging between the separated BTS grains in porous TE thick films. The simultaneous enhancement in electrical conductivity and the Seebeck coefficient of the EOG-bridged TE film result in a maximum power factor of 1.54 mW·m-1·K-2 with the addition of 0.01 wt % EOG. Furthermore, the single element made of an n-type EOG-bridged BTS exhibits a superior output power of 1.65 μW at ΔT = 80 K. These values are 5 times higher than those of bare BTS films. Our results clearly indicate that the utilization of EOG with a metal dopant exerts a synergistic effect for enhancing the electrical output performance of n-type TE thick films for thermal energy harvesters.

3-D Printing Structural Electronics With Conductive Filaments

Integrating electronics into the body of complex structural parts through 3-D printing is one of the most promising new technologies in additive manufacturing, giving the potential of lighter weight and smaller electronic systems. Although fused filament fabrication (FFF) is one of the cheapest and most widely available 3-D printing approaches available, FFF has lagged behind alternatives, such as direct write printing for incorporating electronics into 3-D printed parts. In this article, complex structural electronics are demonstrated using FFF. Numerous surface-mount components are integrated into the printing process for 3-D structures, and electrical contact is made using conductive thermoplastic filament with and without copper electroplating for improved conductivity. The electrical contact characteristics and bridging behavior of several commercially available filaments are investigated. A circuit demonstrator, a 555-timer oscillator circuit, is then printed using the process.

On the Synergy between Elemental Carbon and Inorganic Ions in the Determination of the Electrical Conductance Properties of Deposited Aerosols: Implications for Energy Applications

The role of the elemental carbon (EC), in synergy with hygroscopic ionic species, was investigated to study the formation of electrical bridging phenomena once the aerosol deliquescence is achieved. Ambient aerosol samples were collected on hydrophobic surfaces in urban and rural sites in Northern Italy; their conductance was measured in an Aerosol Exposure Chamber (AEC) while varying the relative humidity. An electric signal was detected on 64% of the collected samples with conductance values (11.20 ± 7.43 μS) above the failure threshold (1 μS) of printed circuit boards. The ionic content was higher for non-electrically conductive samples (43.7 ± 5.6%) than for electrically conductive ones (37.1 ± 5.6%). Conversely, EC was two times higher for electrically conductive samples (26.4 ± 4.1 μg cm−2; 8.4 ± 1.7%) than for non-electrical ones (12.0 ± 4.1 μg cm−2; 5.2 ± 1.9%) suggesting that the synergy between the ionic and carbonaceous fractions is necessary to promote a bridging phenomenon. Synthetic aerosols (EC only, saline only, mixed saline and EC) were generated in laboratory and their conductance was measured in the AEC to verify the ambient results. Only in case of a contemporary presence of both EC and ionic components the bridging phenomenon occurred in keeping with the theoretical deliquescence values of each salt (R2 = 0.996).

Synthesis of lignosulfonate‐acrylamide‐dimethyldiallylammonium chloride copolymer and its flocculation performance

ABSTRACTIn this work, lignosulfonate‐acrylamide‐dimethyldiallylammonium chloride (LAD) terpolymer was designed and synthesized by microwave‐assisted graft polymerization. The optimal synthetic process was obtained as follows: the monomer ratio was 1:4:4, the amount of initiator was 0.9% (w/w), the monomer solid content was 21 wt %, and the reaction time was 14 min with the microwave power of 280 W. Furthermore, the flocculation performance of LAD was verified by removing acid black‐172 dye wastewater. At the LAD dosage of 350 mg L−1, the maximum color removal ratio reached 99.8% in 100 mg L−1 of dye wastewater. The dynamics of dye removal reached higher than 90% after 20 s. The flocculant can maintain color removal ratio more than 98% in a wide flocculant dosage and environmental pH. The flocculation mechanism was mainly electrical neutralization and bridging effect. In general, it is a promising candidate in wastewater treatment in terms of cost, synthetic method, and effectiveness. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48560.

Transport and retention of biogenic selenium nanoparticles in biofilm-coated quartz sand porous media and consequence for elemental mercury immobilization

Bacterial biofilms are structured cell communities embedded in a matrix of extracellular polymeric substances (EPS) and a ubiquitous growth form of bacteria in the environment. A wide range of interactions between biofilms and nanoparticles have been reported. In the present study, the influence of a mixed bacterial biofilm on retention of biogenic selenium nanoparticles (BioSeNPs) and consequences for immobilization of elemental mercury (Hg0) in a porous quartz sand system were examined. BioSeNPs were significantly retained in the presence of a biofilm through electrical double layer effects, hydrogen bonding, and hydrophobic, steric and bridging interactions. Moreover, enhanced surface roughness, pore clogging, sieving and entrapment effects mediated by the biofilm also contributed to deposition of BioSeNPs. Whereas, thiol groups associated with the biofilm is a little helpful for the capture of Hg0. It is proposed that oxidative complexation between Hg0 and thiol compounds or S containing organic matter in the biofilm may result in the formation of Hg2+-thiolate complexes and HgS during the binding of Hg0 with BioSeNPs. The formation of mercury selenide was also involved in Hg0 immobilization in the porous quartz sand system.

Rapid removal of bound water from dredged sediments using novel hybrid coagulants

Abstract Dredging operations produce sediment masses that require chemical conditioning and dewatering before disposing of dredged sediments. Conventional chemical conditioners have difficulty removing the bound water parceled in extracellular polymeric substances (EPS), and the removal of bound water determines the dewatering ratio and the rate of sedimentation. In this study, the conventional conditioners FeCl3, Al2(SO4)3, and cationic polyacrylamide (CPAM) and a new covalently-bound hybrid coagulant (CBHyC) were investigated for dewatering sediments in laboratory conditions that simulated real-world conditions. The water content of dewatered cakes was 61.4–68.3% for sediment conditioned with FeCl3, Al2(SO4)3, and CPAM, while the water content was 52.6% with CBHyC. CBHyC achieved a setting rate that was 66–359% faster than conventional conditioners, decreased specific resistance to filtration (SRF) by 72–86% compared with conventional conditioners. CBHyC achieved the best sediment dewaterability due to its structure, which consists of hydrophobic group of a long carbon chain and hydrophilic groups of Fe-O-Si complexes and quaternary ammonium. This structure increases electrical neutralization ability and bridging effects, allowing formation of large dense flocs in sediments. Moreover, CBHyC also functioned as a surfactant, dissolving EPS (approximately 59.7%), especially proteins (approximately 59.9%) and humic substances (approximately 25.4%), from the sediment into water. The result was approximately 37.1% bound water parceled in EPS was transformed into free water. Lastly, the sediment conditioned with CBHyC exhibited a discontinuous and porous structure; thus, the water was more likely to flow quickly outward from interior locations. These results demonstrate the potential application of CBHyC for high efficiency and rapid dewatering of dredged sediments.

Electrical Double-Layer and Ion Bridging Forces between Symmetric and Asymmetric Charged Surfaces in the Presence of Mono- and Divalent Ions.

An atomic force microscope, employing the colloidal probe technique, was used to study the interactions between six different combinations of silane-functionalized silica surfaces in NaCl and CaCl2 solutions. The surfaces consisted of monolayers of the apolar trimethoxy(octyl)silane, the positively charged (3-aminopropyl)trimethoxysilane, and the negatively charged (3-mercaptopropyl)trimethoxysilane. The interactions between the three symmetric systems, as well as between the three asymmetric combinations of surfaces, were measured and compared to calculated electrical double-layer forces. The results demonstrated that the long-range interactions between the surfaces in all cases were dominated by double-layer forces, while short-range interactions, including adhesion, were dominated by ion bridging forces in the cases where both interaction surfaces favored adsorption of calcium ions. The study thus also demonstrates how surface force studies in mono- and divalent salt solutions can be used as an analytical tool for probing specific functional groups on heterogeneous surfaces.

Laser-induced Forward Transfer of Ag Nanopaste

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip.

Laser-induced Forward Transfer of Ag Nanopaste.

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip.

Detailed electromagnetic numerical evaluation of eddy currents induced by toroidal and poloidal magnetic field variation and halo currents

A detailed evaluation of the EM loads in the ITER divertor during plasma disruptions is mandatory for the correct dimensioning of the divertor component. The EM loads during plasma disruptions are mainly produced by: (1) toroidal flux variation (TFV) during the thermal quench (TQ) and current quench (CQ); (2) halo currents (HC); and (3) poloidal flux variation (PFV) during TQ and CQ phase. The new ITER reference disruption and the last changes in the divertor design have been considered in the EM models created to calculate all the EM loads due to TFV, HC and PFV. All the analyses have been performed for the three different main design options of the divertor plasma facing units (PFU). The effects of PFV have been analyzed using an EM-zooming procedure that has allowed a good detail of the component model, while new numerical approaches have been developed for the evaluation of the effects due to TFV and HC maintaining the same detail for the divertor model. Separate models have been developed to evaluate the equivalent electrical resistivities of the various PFU options; this allows in the full 3D model a strong simplification of a geometry which would otherwise be very complex. The effect of an electrical surface bridging of the PFU castellation has also been taken into account.

Electrophysiological Modeling of Fibroblasts and their Interaction with Myocytes

Experimental studies have shown that cardiac fibroblasts are electrically inexcitable, but can contribute to electrophysiology of myocardium in various manners. The aim of this computational study was to give insights in the electrophysiological role of fibroblasts and their interaction with myocytes. We developed a mathematical model of fibroblasts based on data from whole-cell patch clamp and polymerase chain reaction (PCR) studies. The fibroblast model was applied together with models of ventricular myocytes to assess effects of heterogeneous intercellular electrical coupling. We investigated the modulation of action potentials of a single myocyte varying the number of coupled fibroblasts and intercellular resistance. Coupling to fibroblasts had only a minor impact on the myocyte's resting and peak transmembrane voltage, but led to significant changes of action potential duration and upstroke velocity. We examined the impact of fibroblasts on conduction in one-dimensional strands of myocytes. Coupled fibroblasts reduced conduction and upstroke velocity. We studied electrical bridging between ventricular myocytes via fibroblast insets for various coupling resistors. The simulations showed significant conduction delays up to 20.3 ms. In summary, the simulations support strongly the hypothesis that coupling of fibroblasts to myocytes modulates electrophysiology of cardiac cells and tissues.

Assessment of risk resulting from unattached tin whisker bridging

PurposeThis paper aims to present a methodology for estimating the risk of component level electrical bridging failures from unattached conductive (tin) whiskers.Design/methodology/approachBased on experimental data an algorithm was developed and assessed by further experiments. The risk estimate is based on whisker parameters, generated from experiments over a period of time. A bridging failure risk is defined as the probability of a conductive whisker landing between two isolated electrical conductors. A probabilistic estimate for electrical bridging failure risk is achieved by randomly sampling distributions of conductive whisker length, deposition angle, and density for a defined electrical structure. A fine pitch quad flat package attached to a printed wiring board is used as test vehicle to verify the risk estimate.FindingsThe estimated risk is found to be higher than planned in the experimental test. The lower experimentally determined risk was found to be the result of high contact resistance between the conductive whisker and the electrical conductors that form the unintended circuit. Contact resistance between the whisker and electrical conductors was found to mitigate the whisker shorting risk.Originality/valueThis is the first attempt to quantify the risk failure due to unattached conductive whiskers in electronic products. A methodology for estimating electrical bridging risk due to unattached conductive whiskers is provided. Contact resistance of conductive whiskers is found to be a critical issue that may be mitigate failure risks.

A population balance model for flocculation of colloidal suspensions by polymer bridging

A detailed population balance model for flocculation of colloidal suspensions by polymer bridging under quiescent flow conditions is presented. The collision efficiency factor is estimated as a function of interaction forces between polymer coated particles. The total interaction energy is computed as a sum of van der Waals attraction, electrical double layer repulsion and bridging attraction or steric repulsion due to adsorbed polymer. The scaling theory is used to compute the forces due to adsorbed polymer and the van der Waals attraction is modified to account for presence of polymer layer around a particle. The irregular structure of flocs is taken into account by incorporating the mass fractal dimension of flocs. When tested with experimental floc size distribution data published in the literature, the model predicts the experimental behavior adequately. This is the first attempt towards incorporating theories of polymer-induced surface forces into a flocculation model, and as such the model presented here is more general than those proposed previously.

A model for bridging and coupling in superconductors

A general treatment of the influence of metallurgical and electrical bridging and the associated interfilamentary coupling on the DC magnetic response of multifilamentary superconductors has been developed. Metallurgical bridging is emphasized, and is treated from the perspective of an anisotropic continuum; a comparison with the traditional d eff approach is made. Bridging-induced loss is seen to be determined by an intrinsic parameter γ 2, describing the amount of electrical connectivity perpendicular to the filamentary axis. Expressions for magnetization and penetration fields for samples as a function of twist pitch and sample length are given. Transfer lengths are calculated, and the effects of weak connectivity along the filament axis are also discussed. The applicability of, and deviations from, the anisotropic continuum approximation are addressed. The expressions developed are then applied to experimental results for multifilamentary Nb 3Sn and Bi:HTSC/Ag strands.