Zn Particles Research Articles

Core@Double-Shell Engineering of Zn Particles toward Elevated Dielectric Properties: Multiple Polarization Mechanisms in Zn@Znch@PS/PVDF Composites.

Flexible dielectrics with large dielectric constant (ε') coupled with low loss are highly pursued in many applications. To bolster the ε' of raw Zn (zinc)/poly(vinylidene fluoride, PVDF) while maintaining pimping dielectric loss, in this study, the core@double-shell structured Zn@zinc carbonate (ZnCH)@polystyrene (PS) particles are first synthesized through a suspension polymerization of styrene, and then composited with PVDF to elevate the ε' and keep low loss of the composites. By optimizing the PS shells' thickness and tailoring the electrical resistivity of Zn@ZnCH@PS particles, both the slow inter-particle polarization and fast intra-particle polarization in the composites can be decoupled and synergistically tuned, thus, the Zn@ZnCH@PS/PVDF achieves a much higher ε' and lower dielectric loss, simultaneously, which far exceed the unmodified Zn/PVDF. Both experiment and theoretic calculation reveal that the double-shell ZnCH@PS not only induces and promotes multiple polarizations enhancing the composites' ε', especially at the optimized PS's thickness, but also maintains suppressed loss and conductivity thanks to their obvious barrier effect on long-range charge migration. The core@double-shell filler design strategy facilitates the development of polymer composites with desirable dielectric properties for applications in electronic and electrical power systems.

Effect of process parameters on friction stir welding of aluminium alloy AA6082–T6 with an interlayer using response surface methodology

In the present study, the effects of variation of process parameters on the mechanical properties of friction stir welded A6082–T6 aluminium alloy joints with Zinc (Zn) interlayer are experimentally investigated. Four process parameters, viz. rotational speed, welding speed, interlayer thickness and tool pin diameter are selected to fabricate the Friction Stir Welding (FSW) joints. After filling the Zn particles into the gap maintained between the plates, FSW is performed using different process parameters. Thereafter, tensile and impact strength tests are performed to evaluate the performance of the joints. It is analyzed that the tensile and impact strength of the joints vary from 121 to 197 MPa and 6 to 17 J, respectively. Subsequently, mathematical models are developed using Response Surface Methodology (RSM) to predict the effect of FSW process parameters on the tensile and impact strength of joints. Analysis of Variance (ANOVA) is used to check the level and degree of direct effect of process variables on the tensile and impact strength of the joints. It is observed from the results that tool rotational speed is the most influential process parameter, which enhances the mechanical properties of FSW joints, whereas an increase in welding speed reduces the mechanical properties of the joints.

Nucleation-promoting effect of mixed Zn and ZnO particles on tetra-n-butylammonium bromide hydrate

Tetra-n-butylammonium bromide (TBAB) hydrate is an ionic semi-clathrate hydrate, and it can be used as an energy-storage and gas-separation medium. Nucleation of TBAB hydrate is unlikely to occur and this characteristic causes problems in the refrigeration system due to the need for excessive cooling and delays in gas separation due to the slow formation. Therefore, a technique for rapid formation of TBAB hydrate is required. In a previous study, it was found that addition of mixed and ground Zn and ZnO particles (Zn–ZnO) to TBAB aqueous solution significantly promoted nucleation of TBAB hydrate. Since the nucleation of TBAB hydrates was effectively promoted by the very simple addition of Zn–ZnO, this technique can be easily applied to conventional systems. However, the nucleation-promoting mechanism have not been clarified. The clarification of the nucleation-promoting effect of Zn–ZnO on TBAB hydrates is important to elucidate the nucleation-promoting mechanism of clathrate hydrates by the addition of substances. Therefore, the objective of the present study was to investigate the nucleation-promoting mechanism of Zn–ZnO on TBAB hydrate. Experimental results showed that immersion of Zn–ZnO in TBAB aqueous solution reduced the nucleation-promoting effect, but a decrease in the nucleation-promoting effect was not observed when Zn–ZnO was immersed in water. Microscopy observation confirmed that immersion of Zn–ZnO in TBAB aqueous solution had little effect on its surface morphology, but X-ray diffraction and X-ray photoelectron spectroscopy indicated formation of solid TBAB on Zn–ZnO. Zn–ZnO did not show a significant nucleation-promoting effect on tetrahydrofuran hydrate, which is a non-ionic clathrate hydrate. This suggest that Zn–ZnO has properties that attract tetra-n-butylammonium and Br ions, and that the proximity of these ions may promote formation of TBAB hydrate. It was also suggested that the mechanism of nucleation promotion by the addition of substances is different for ionic clathrate hydrates and non-ionic clathrate hydrates.

Tuning the bandgap of 2D metallic Zn nanostructures

The semiconducting behavior of two-dimensional (2D) metal nanostructures has recently attracted much interest for their possible applications in optoelectronics and others. In particular, tuning the bandgap of such nanostructures can open up a new avenue for fabricating functional nano-devices. In the present article, we report the synthesis of 2D metallic Zn nanosheets at room temperature using a ball mill, which is capable of producing large-scale materials in a single run. Initially, nanoplates were formed for ball milling the octahedral-shaped Zn nanoparticles for the time of milling of 6 h. Subsequent ball milling for another 6 h leads these nanoplates to nearly uniform nanosheets. The thickness of these 2D nanostructures was found to decrease with an increase in the time of milling. Visible photoluminescence (PL) emissions centered at ∼3, ∼2.9, and ∼2.75 eV were observed from all the Zn particles showing semiconductor behavior. The origin of such semiconductor behavior was explained based on the radiative transition of electrons from the sp band to the upper states of the 3d band. This argument was confirmed through the studies of photoelectron spectroscopy and the first principle calculations employing density functional theory (DFT). Furthermore, excitation-dependent PL studies indicated that the bandgap of the 2D Zn nanostructures decreased with the increase in the ball milling time. Therefore, a redshift in the bandgap was observed with the increase in the ball milling time. Such changes in the bandgap with the thickness of 2D Zn nanostructures were also verified from the studies of DFT. Thus, the present study demonstrated that the bandgap of 2D metallic Zn nanostructures could be effectively tuned by reducing the thickness.

Microstructure and Corrosion Behavior of Zinc/Hydroxyapatite Multi-Layer Coating Prepared by Combining Cold Spraying and High-Velocity Suspension Flame Spraying.

The study aims to enhance the corrosion resistance and bioactivity of Mg alloy substrates through the development of a zinc/hydroxyapatite multi-layer (Zn/HA-ML) coating. The Zn/HA-ML coating was prepared by depositing a cold-sprayed (CS) Zn underlayer and a high-velocity suspension flame sprayed (HVSFS) Zn/HA multi-layer and was compared with the CS Zn coating and the Zn/HA dual-layer (Zn/HA-DL) coating. Phase, microstructure, and bonding strength were examined, respectively, by X-ray diffraction, scanning electron microscopy, and tensile bonding testing. Corrosion behavior and bioactivity were investigated using potentiodynamic polarization, electrochemical impedance spectroscopy, and immersion testing. Results show that the HVSFS Zn/HA composite layers were mainly composed of Zn, HA, and ZnO and were well bonded to the substrate. The HVSFS HA upper layer on the CS Zn underlayer in the Zn/HA-DL coating exhibited microcracks due to their mismatched thermal expansion coefficient (CTE). The Zn/HA-ML coating exhibited good bonding within different layers and showed a higher bonding strength of 27.3 ± 2.3 MPa than the Zn/HA-DL coating of 20.4 ± 2.7 MPa. The CS Zn coating, Zn/HA-DL coating, and Zn/HA-ML coating decreased the corrosion current density of the Mg alloy substrate by around two-fourfold from 3.12 ± 0.75 mA/cm2 to 1.41 ± 0.82mA/cm2, 1.06 ± 0.31 mA/cm2, and 0.88 ± 0.27 mA/cm2, respectively. The Zn/HA-ML coating showed a sixfold decrease in the corrosion current density and more improvements in the corrosion resistance by twofold after an immersion time of 14 days, which was mainly attributed to newly formed apatite and corrosion by-products of Zn particles. The Zn/HA-ML coating effectively combined the advantages of the corrosion resistance of CS Zn underlayer and the bioactivity of HVSFS Zn/HA multi-layers, which proposed a low-temperature strategy for improving corrosion resistance and bioactivity for implant metals.

Fabrication and Characterization of Zn Particle Incorporated Fibrous Scaffolds for Potential Application in Tissue Healing and Regeneration.

Zinc (Zn) metal and its alloys have received a lot of interest in biomedical applications due to their biodegradability, biocompatibility, antimicrobial activity, and ability to stimulate tissue regeneration. Bulk Zn has been successfully utilized in a variety of implant applications, most notably as bioabsorbable cardiac stents and orthopedic fixation devices, where it provides adequate mechanical properties while also releasing helpful Zn ions (Zn2+) during degradation. Such beneficial ions are dose-dependent and, when released in excess, can induce cellular toxicity. In this study, we hypothesize that embedding Zn metal particles into a polymer nanofibrous scaffold will enable control of the degradation and time release of the Zn2+. We designed and fabricated two polymer scaffolds, polycaprolactone (PCL) and polycaprolactone-chitosan (PCL-CH). Each scaffold had an increasing amount of Zn. Several physicochemical properties such as fiber morphology, crystallinity, mechanical strength, hydrophilicity, degradation and release of Zn2+, thermal properties, chemical compositions, and so forth were characterized and compared with the PCL fibrous scaffold. The biological properties of the scaffolds were evaluated in vitro utilizing direct and indirect cytotoxicity assays and cell viability. All the data show that the addition of Zn changed various physical properties of the PCL and PCL-CH scaffolds except their chemical structure. Further investigation reveals that the PCL-CH scaffolds degrade the Zn particles relatively faster than the PCL because the presence of the hydrophilic CH influences the faster release of Zn2+ in cell culture conditions as compared to the PCL fibrous scaffold. The combined advantages of CH and Zn in the PCL scaffold enriched 3T3 fibroblast cells' survival and proliferation except the ones with the higher concentration of Zn particles. These new composite scaffolds are promising and can be further considered for tissue healing and regeneration applications.

Improving the anti-corrosive performance of epoxy/zinc composite coatings with N-doped 3D reduced graphene oxide

Three-dimensional reduced graphene oxide (3DRGO) doped with N heteroatoms was innovatively incorporated into a Zn-containing epoxy (EP/Zn) composite coating. Comprehensive investigations that introducing 3DRGO significantly improved the anti-corrosion performance of the coating, and the optimal 3DRGO content was only 0.05 wt%. The effects of both the spatial structure and chemical doping of graphene on the surface protection performance of their EP/Zn coating were revealed for the first time. Compared with the conventional 2-dimensional reduced GO (RGO) sheets and 3D graphene (3DG) with similar 3D structures, 3DRGO exhibited superior effect on promoting the corrosion resistance of its composite coating. This can be attributed to not only the unique 3D porous strut structure of 3DRGO, but also its N-doping, which plays important roles in increasing its interaction with the epoxy matrix, preventing 3DRGO agglomeration, improving the barrier property of the coating, facilitating the construction of an electrical conduction network between Zn particles, and exploiting the cathodic protection function of Zn more efficiently.

Characterizing Distribution and Morphology of ZnO Discharge Products in Commercial Alkaline Zn-MnO2 Batteries

During the discharge of alkaline Zn-MnO2 batteries, the dissolution of Zn particles in the anode saturate the electrolyte with zincate, prompting the formation of solid ZnO. Zincate is highly mobile in the electrolyte, giving rise to complex spatial distributions and morphologies of ZnO discharge products. The passivating behavior of ZnO is dependent on its distribution and morphology, as the active Zn particles within the anode must maintain a connection with the electronic network, while also having access to hydroxide ions from the electrolyte.1 Therefore, characterizing the factors that impact ZnO formation is critical to understanding how battery performance is impacted.2 Past attempts to model these batteries fail to adequately predict the behavior of Zn anodes under discharge conditions aimed at simulating real-world use cases.3 This work seeks to better characterize the behavior of Zn anodes in an effort to improve modeling capabilities based on experimental results.4 High resolution synchrotron CT was used to create in situ volumetric reconstructions of anodes from commercial AA and AAA batteries to determine ZnO morphology and radial distribution at various discharge conditions. Through a novel segmentation algorithm, quantitative data show a shift in ZnO radial distribution and microporosity depending on the rate and depth at which the anodes were discharged. High rate discharge leads to ZnO formation preferentially near the separator with a lower microporosity, increasing its passivating characteristics. Microporosity calculations show the discharge products form in two types, namely type I ZnO and ZnO hydrate. The latter type had only ever been reported on planar electrodes, yet it has a significant presence in commercial alkaline batteries discharged under certain conditions.4,5 In addition to a decreased microporosity, the morphology of ZnO also showed increased passivating characteristics when discharging using a continuous protocol. Shells of ZnO form around undischarged Zn cores during a continuous discharge, restricting hydroxide transport to the Zn surface and potentially isolating the core from the electronically conductive Zn network. When using a pulsed discharge protocol, ZnO formed distributed regions of microporous ZnO not adhered to undischarged Zn surfaces, leaving the remaining Zn in good contact with the electrolyte. Developing a more robust understanding of the factors that impact ZnO formation will enable more advanced models to be created. Acknowledgements This research was supported by funding from Energizer Holdings, Inc. We acknowledge collaborators Xiaotong Chadderdon, Matthew Wendling, Andrew Chihpin Chuang, and John Okasinski. This research also used resources of the Advanced Photon Source beamline 6-BM, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Comparison of microstructural, texture and mechanical properties of SiC and Zn particle reinforced FSW 6061-T6 aluminium alloy

This work investigates the microstructure, mechanical characteristics, and texture evolution of friction stir welding (FSW) of AA6061-T6 metal matrix composites (MMCs) reinforced with silicon carbide (SiC) and zinc (Zn) particles. The SZ region of the SiC and Zn particle-reinforced aluminium matrix (Al-matrix) composites has ultra-fine grain refinements of 4.79 and 4.18 μm, respectively, compared to base metal (BM) particle sizes of 44.97 μm. Ultra-fine grain refinement in the SZ zone produces dynamic recrystallization with particulate-driven nucleation, Zenner Hollomon, and homogeneous SiC/Zn particle distribution in the Al-matrix. Recrystallization texture components P {011} <112>, cube {001} <101>, rotating cube (H) {001} <110>, and F {111} <112>, along with primary shear texture components (B/B¯, and C), suggested DRX at the joint interface in the SiC-reinforced Al-matrix composite. However, the Zn-reinforced Al-matrix composite has a high plain strain, recrystallization, and deformation texture components of copper {112} <111>, Brass {011} <211>, cube {001} <101>, Goss {110}, and P 011 <112>, and major shear texture components (B/B¯ and C). SiC and Zn-reinforced Al-matrix composites have 110 ± 4 and 120 ± 5 HV0.2 average microhardness, respectively. Also, SiC and Zn-reinforced Al-matrix composites have 224 and 236 MPa tensile strengths, respectively.

Conducting Polymer Films on Zn Deposited Carbon Electrode

Zn plating on carbon steel (CS) was achieved applying current of 4 mA with galvanostatic technique in acidic medium. Zn particles had homogenous, smooth with spherical structure. It was shown that the Zn particles exhibited active behavior on CS substrate. Poly(aniline), poly(pyrrole), poly(N-methylpyrrole) and poly(o-anisidine) homopolymer films were obtained on CS/Zn electrode. Evaluation of anticorrosion performance of these homopolymer coatings in 3.5 % NaCl solution was investigated by using AC impedance spectroscopy (EIS) technique, anodic polarization and the Eocp-time curves. Homopolymer films exhibited significant physical barrier behavior on Zn plated carbon steel, in longer exposure time.

Nitrogen-doped carbon coated zinc as powder-based anode with PVA-gel electrolyte enhancing cycling performance for zinc-ion batteries

Zn-powder based anodes are considered as candidates for Zn-based batteries in practical industrial applications in terms of cost, large-scale processing, versatility and tunability. However, Zn-P-based anodes suffer from even more severe side effects including corrosion, passivation, and uncontrolled dendrite growth. Herein, we successfully fabricated nitrogen-doped carbon coating layer on Zn particles (Zn-NC) as anode material for more homogeneous Zn deposition by inducing more zincophilic site on N-doped carbon layers and enhanced electrical connection with carbon networks on Zn-NC particle surface. Nevertheless, metallic Zn deposited on Zn-NC surface still suffers from unavoidable side effects with continuous cycling, even though the dendrite growth was suppressed. It is worth mentioned that PVA-gel electrolyte greatly improves the cycling performance of Zn-NC with limited water content, which can alleviate side reactions. Experiments and simulations address the importance of NC layers with higher electricity, chemical stability, and zincophilic property, as well as the role that PVA-gel electrolyte plays for the further improved cycling performance. Zn-NC with PVA-gel electrolyte achieves ultra-long cycling hours with over 3500 h at 1 mA cm−2 and 850 h at 5 mA cm−2 in symmetrical cells. This study provides a promising pathway and in-depth mechanistic analysis for Zn-powder based anode in versatile applications especially for flexible energy-storage devices.

Elemental composition of PM10 in indoor environments of a scientific research institution and risk assessment

ABSTRACT Synchronized indoor and outdoor sampling campaigns of PM10 were performed in two research laboratories and a mechanical workshop in Mexico City, during the dry cold season. The goals were to measure indoor and outdoor gravimetric mass and elemental concentrations, recognize the origin of particles, penetration toward the indoor environments, and assess inhalation, ingestion, and dermal absorption risks to human health. Concentrations of 18 elements were measured with X-ray Fluorescence; selected samples were studied with Scanning Electron Microscopy. Mass concentrations were higher outdoors than indoors and elemental concentrations were similar. Enrichment factors identified several geogenic elements. Cluster Analysis recognized common sources of elements and penetration of outdoor particles to indoor environments. Particles emitted indoors could be identified. Exposure to Mn, Fe, Ni, Cu, Zn, and Pb particles produced low health risks; Cr may only cause an ingestion risk. Only outdoor Mn and Ni Hazard Quotients are higher outdoors than indoors.

Characterization of CZO thin films prepared by Sol – Gel dip coating technique with varied concentrations and annealed at different temperatures

Zinc Oxide (ZnO) thin films doped with Cobalt (Co) is prepared on glass substratum by using Sol-Gel dip coating technique. Volume of Cobalt can be varied from 0% to 2% and annealed at various temperatures. The obtained films analyzed by availing the results of Energy Dispersive X-ray Spectroscopy (EDS), Scanning Electron Microscopy (SEM), X-ray Diffraction analysis (XRD) and Ultraviolet – Visible Spectroscopy (UV–Vis). The EDS result shows that Zn and Co particles are present in the thin films. The SEM result reveals that as concentration of the dopant increases subsequently the intermolecular space decreases and conductivity increases. The XRD pattern shows a dominant peak (002) and it confirms hexagonal wurtzite structure. The UV– Visible spectrum shows that the minimum range of absorbance occurs at the visible region. All these results show that the prepared films could be used as Transparent Conducting Oxides (TCO) in solar cells and other opto-electronic gadget applications.

Microstructural evolutions and mechanical characteristics of roll-bonding Mg/Al clad plate regulated by cold spraying micron particle interlayer

A new process of “cold spraying interlayer + roll-bonding” (CSIR) was put forward for the preparation of Mg/Al clad plates. First, the micron Ni and Al powders (including some Zn particles) were cold sprayed to form an ultrathin coating on Al or Mg substrate slabs. Then roll-bonding was performed at 400 °C. The influence of cold sprayed coating on slab surfaces, interfacial microstructures, texture evolutions, mechanical properties and the related mechanism were systematically investigated. The results show that the average shear strength of the as-rolled Mg/Al clad plate assisted by cold spraying Al and Ni micron powders interlayer on the substrate slabs was nearly twice (35.58 MPa) than that of conventional rolling under the same conditions (single pass, reduction ratio was 35%). For as-rolled Mg/Al clad plates, almost no reaction diffusion layers are generated, and the mechanical interlocking between cold sprayed coatings and substrate slabs is the main mechanism for improving the shear strength. The interface between the Al coating and the Ni coating is weakest of the as-rolled Mg/Al clad plates. As the reduction rate increases from 27.5% to 47.5%, the function of the mechanical interlocking of cold sprayed coatings will first increase and then weaken. After annealing at 400 °C for 1 h, the interface between the Al coating and the Mg substrate slab will form thick mixed brittle intermetallic compounds, including Al3Mg2, Mg17Al12, MgZn2 and AlMg4Zn11, and cause local gaps, holes, and cracks around the Zn-rich Ni coating. The fracture path after annealing starts from the vicinity of the defective Ni particles, and eventually enlarges along the mixed intermetallic compounds layer between the Al coating and the Mg substrate slab. The research indicates that the CSIR process has great potential in cooperating the metallurgical bonding with the mechanical interlocking of clad plates.

Incorporation of Magnesium and Zinc Metallic Particles in PLGA Bi-layered Membranes with Sequential Ion Release for Guided Bone Regeneration.

Guided bone regeneration (GBR) membranes are commonly used for periodontal tissue regeneration. Due to the complications of existing GBR membranes, the design of bioactive membranes is still relevant. GBR membranes with an asymmetric structure can accommodate the functional requirements of different interfacial tissues. Here, poly(lactic acid-glycolic acid) (PLGA) was selected as the matrix for preparing a bi-layered membrane with both dense and porous structure. The dense layer for blocking soft tissues was incorporated with zinc (Zn) particles, while the porous layer for promoting bone regeneration was co-incorporated with magnesium (Mg) and Zn particles. Mg/Zn-embedded PLGA membranes exhibited 166% higher mechanical strength in comparison with pure PLGA membranes and showed suitable degradation properties with a sequential ion release behavior of Mg2+ first and continuously Zn2+. More importantly, the release of Zn2+ from bi-layered PLGA endowed GBR membranes with excellent antibacterial activity (antibacterial rate > 69.3%) as well as good cytocompatibility with MC3T3-E1 (mouse calvaria pre-osteoblastic cells) and HGF-1 (human gingival fibroblast cells). Thus, the asymmetric bi-layered PLGA membranes embedded with Mg and Zn particles provide a simple and effective strategy to not only reinforce the PLGA membrane but also endow membranes with osteogenic and antibacterial activity due to the continuous ion release profile, which serves as a promising candidate for use in GBR therapy.

Determination of Flowing Electrolyte Parameters in a Zinc-Air Fuel Cell by the Taguchi Method

The flowing electrolyte in a zinc-air fuel cell (ZAFC) can reduce the problem of incomplete reaction caused by the concentration gradient of the electrolyte. In this study, we propose a self-developed ZAFC with a flowing electrolyte system and optimize control parameters. The anode of the ZAFC used Zn particles through which the electrolyte penetrates and combined with a negative pressure pump to allow the potassium hydroxide (KOH) electrolyte to have an effective chemical reaction with the Zn particles during the discharge process. However, the flow rate of the electrolyte is required to match other control parameters, such as operating temperature, KOH concentration, and cell size, to effectively improve the efficiency of ZAFC. Therefore, the Taguchi method is adopted to obtain the optimal reaction parameters and the key factors affecting the discharge efficiency of the cell. The best operation condition is the temperature at 50°C, the KOH concentration of 30% wt, and the electrolyte flow rate of 150ml/min; then, the maximum power obtained from the experimental results is 13.8 W, the maximum current density reaches 699.721 mA/cm2, and the maximum power density is 395.037 mW/cm2. This paper provides valuable insights for the upgrade of ZAFC for future practical applications.

A Modified Method for Increasing Radiochemical Purity of I-125 for Radiopharmaceuticals

Iodine-125 (125I) is one of the radioisotopes widely used in radiopharmaceuticals for diagnosis and therapy of various cancers. Recent reports indicate that there has been shortages in the world supply of this radioiodine isotope. One of the absolute requirements good radiopharmaceuticals must meet is radiochemical purity, which generally has to be above 95 %, with an efficiency of over 90 %. The previous investigation shows that the radiochemical purity is low and does not meet the radiochemical requirement. In this work, we aim at improving the previous method by modifying the Jones reductor-based method. The modified method includes reduction and uniformization of Zn particle sizes, Zn particle compaction, and the performance of reduction process in a closed process flow. The Jones reductor converted impurities into products; in this case, iodate (IO3-) and periodate (IO4-) impurities were converted into iodide (I-), so that 125I product fulfills the radiochemical purity requirements and yielded high efficiency. In this investigation, the 125I previous product was, for the first time, improved with a radiochemical purity of 99.24 % and an efficiency of 97.98 %.

Observation of Zn Dendrite Growth via Operando Digital Microscopy and Time-Lapse Tomography.

The zinc-ion battery is one of the promising candidates for next-generation energy storage devices beyond lithium technology due to the earth's abundance of Zn materials and their high volumetric energy density (5855 mA h cm-3). To date, the formation of Zn dendrites during charge-discharge cycling still hinders the practical application of zinc-ion batteries. It is, therefore, crucial to understand the formation mechanism of the zinc dendritic structure before effectively suppressing its growth. Here, the application of operando digital optical microscopy and in situ lab-based X-ray computed tomography (X-ray CT) is demonstrated to probe and quantify the morphologies of zinc electrodeposition/dissolution under multiple galvanostatic plating/stripping conditions in symmetric Zn||Zn cells. With the combined microscopy approaches, we directly observed the dynamic nucleation and subsequent growth of Zn deposits, the heterogeneous transportation of charged clusters/particles, and the evolution of 'dead' Zn particles via partial dissolution. Zn electrodeposition at the early stage is mainly attributed to activation, while the subsequent dendrite growth is driven by diffusion. The high current not only facilitates the formation of sharp dendrites with a larger mean curvature at their tips but also leads to dendritic tip splitting and the creation of a hyper-branching morphology. This approach offers a direct opportunity to characterize dendrite formation in batteries with a metal anode in the laboratory.

Properties of Cu/Zn+15%SAC0307+15%Cu/Al joints by different ultrasonic-assisted degrees

PurposeThis paper aims to investigate the effects of different ultrasonic-assisted loading degrees on the microstructure, mechanical properties and the fracture morphology of Cu/Zn+15%SAC0307+15%Cu/Al solder joints.Design/methodology/approachA new method in which 45 μm Zn particles were mixed with 15% 500 nm Cu particles and 15% 500 nm SAC0307 particles as solders (SACZ) and five different ultrasonic loading degrees were applied for realizing the soldering between Cu and Al at 240 °C and 8 MPa. Then, SEM was used to observe and analyze the soldering seam, interface microstructure and fracture morphology; the structural composition was determined by EDS; the phase of the soldering seam was characterized by XRD; and a PTR-1102 bonding tester was adopted to test the average shear strength.FindingsThe results manifest that Al–Zn solid solution is formed on the Al side of the Cu/SACZ/Al joints, while the interface IMC (Cu5Zn8) is formed on the Cu side of the Cu/SACZ/Al joints. When single ultrasonic was used in soldering, the interface IMC (Cu5Zn8) gradually thickens with the increase of ultrasonic degree. It is observed that the proportion of Zn or ZnO areas in solders decreases, and the proportion of Cu–Zn compound areas increases with the variation of ultrasonic degree. The maximum shear strength of joint reaches 46.01 MPa when the dual ultrasonic degree is 60°. The fracture position of the joint gradually shifts from the Al side interface to the solders and then to the Cu side interface.Originality/valueThe mechanism of ultrasonic action on micro-nanoparticles is further studied. By using different ultrasonic loading degrees to realize Cu/Al soldering, it is believed that the understandings gained in this study may offer some new insights for the development of low-temperature soldering methodology for heterogeneous materials.

Aero-manufacture of nanobulges for an in-place anticoronaviral on air filters.

The interest in removing contagious viruses from indoor air using ventilation and filtration systems is increasing rapidly because people spend most of the day indoors. The development of an effective platform to regenerate the antiviral function of air filters during use and safe abrogation of used filters containing infectious viruses is a challenging task, because an on-demand safe-by-design manufacture system is essential for in-place antiviral coatings, but it has been rarely investigated. With these considerations, an electrically operable dispenser was prepared for decorating continuous ultrafine Fe-Zn, Fe-Ag, or Fe-Cu particles (<5nm) onto SiO2 nanobeads (ca. 130nm) to form nanobulges (i.e., nanoroughness for engaging coronavirus spikes) in the aerosol state for 3min direct deposition on the air filter surfaces. The resulting nanobulges were exposed to human coronaviruses (HCoV; surrogates of SARS-CoV-2) to assess antiviral function. The results were compared with similar-sized individual Zn, Ag, and Cu particles. The nanobulges exhibited comparable antiviral activity to Zn, Ag, and Cu particles while retaining biosafety in both in vitro and in vivo models because of the significantly smaller metallic fractions. This suggests that the bimetallic bulge structures generate reactive oxygen species and Fenton-mediated hydroxyl radicals for inactivating HCoV.