Continuous Metal Research Articles

Effect of deformation routes on torsion behavior via ACDR process

Plastic flow in continuous incremental bulk metal forming had aroused great interest. However, due to the observational difficulties of each section, the torsion-state plastic flow behavior during axial closed die rolling (ACDR) is usually ignored. Therefore, the flow line in main plastic deformation zone (PDZ) was chosen for detailed investigation in order to unveil the effect of deformation routes on the weight of the circumferential torsion during ACDR process. Then, the modified equation of the equivalent von Mises strain of ACDR process is provided to illustrate the local plastic flow behavior under different deformation routes and different conditions of stress. The results show that the overall strength of PDZ does not significantly change with the loading history, but local plastic flow is enhanced with the increasing deformation time. Severe deformation accumulation in PDZ brings about the increasing radial tension and weakened circumferential torsion axial compression.

Li–Ti Cation Mixing Enhanced Structural and Performance Stability of Li‐Rich Layered Oxide

AbstractLi‐rich layered metal oxides are one type of the most promising cathode materials in lithium‐ion batteries but suffer from severe voltage decay during cycling because of the continuous transition metal (TM) migration into the Li layers. A Li‐rich layered metal oxide Li1.2Ti0.26Ni0.18Co0.18Mn0.18O2 (LTR) is hereby designed, in which some of the Ti4+ cations are intrinsically present in the Li layers. The native Li–Ti cation mixing structure enhances the tolerance for structural distortion and inhibits the migration of the TM ions in the TMO2 slabs during (de)lithiation. Consequently, LTR exhibits a remarkable cycling stability of 97% capacity retention after 182 cycles, and the average discharge potential drops only 90 mV in 100 cycles. In‐depth studies by electron energy loss spectroscopy and aberration‐corrected scanning transmission electron microscopy demonstrate the Li–Ti mixing structure. The charge compensation mechanism is uncovered with X‐ray absorption spectroscopy and explained with the density function theory calculations. These results show the superiority of introducing transition metal ions into the Li layers in reinforcing the structural stability of the Li‐rich layered metal oxides. These findings shed light on a possible path to the development of Li‐rich materials with better potential retention and a longer lifespan.

Measures towards roll forming at the physical limit of energy consumption

The optimization of energy efficiency of industrial processes is a desirable objective. Roll forming is a continuous sheet metal forming process gradually producing profile-shaped parts. Although cold forming processes are usually comparatively energy-efficient, in roll forming, an efficiency of deformation of 25% and less has been observed in previous studies. At the same time, a significant energy-saving potential has been identified by means of the evaluation of drive torques and the readjustment of tool velocities. However, the efficiency of deformation is still small in comparison to other cold forming processes. In this study, a new decision rule for optimizing the tool velocity in roll forming is proposed and tested experimentally and numerically. The objective of this decision rule is, firstly, to avoid decelerating drive torques that counteract the forming process and need to be compensated by additional drive torques in other process steps. Secondly, the accelerating drive torques should not exceed a certain limit in order to ensure an effective process with respect to wear and surface quality of the products. The results show that a reduction of the energy demand of 66% in comparison with a conventionally operated roll forming process is possible resulting in an efficiency of deformation of 89%. Furthermore, the mechanism of the optimization is validated experimentally using a novel sensor concept, a sensorial parallel key.

Airborne lead dust concentration in Townsville, Queensland is associated with port activity and may contribute to estuarine sediment contamination

Australia has a history of overlooking heavy metal contamination in towns and water bodies that can impact on human and environmental health. Airborne lead pollution in many regional Australian towns is often related to mining, smelting and transport of minerals. Recent studies in Townsville have shown inner city soil and playgrounds, creek and nearby off-shore sediment to have heavy metal concentrations that exceed Australian standards; this contamination is suspected to originate from the port. To assess the port as a current source of lead dust, we evaluated one year of data in 2015-2016 on lead concentration in air from the Department of Environment and Heritage Protection continuous metals monitoring station. The analysis shows that when the wind direction is from the port, and ships are present at the berth where the lead and zinc concentrates are loaded, there is a significant increase in lead concentration. This suggests that shipping activity at the port continues to be the source of lead-laden dust in inner Townsville and in estuarine and coastal marine sediments. The sediments have the highest concentration of lead in Ross Creek, southwest of the port. The geographical relationship between the port, metal analyser and the creek relative to the northeast winds, the latter being directly downwind, suggest that the Ross creek and metal monitoring station have the same source of lead contamination. Our results indicate lead testing in people and wildlife in the area may be warranted to directly assess risks, and that remedial action should continue to focus on reducing escape of lead dust from the port.

Metal matrix composite material reinforced with metal wire and produced with gas metal arc welding

In the search for high-performance parts and structures, especially for the aviation and aerospace industry, metal matrix composites appear with prominence. However, despite exhibiting high levels of mechanical properties and low densities, these materials are still very expensive, mainly due to complex production. Thus, this work aims to present and evaluate a novel way of manufacturing metal matrix composites, with relative low cost and complexity: by using low-energy fusion welding to deposit the matrix material on top of continuous metal wire reinforcement. For proof of concept, Al alloy was used as matrix material, a single Ti alloy wire as reinforcement, and gas metal arc welding CMT-Pulse® as the process for material deposition. The simplified Al–Ti composite was evaluated in terms of impact resistance and tensile strength and stiffness. Overall, the mechanical performance of the composite was around 23% higher than that of the matrix material itself (Al), this with only about 2% of reinforcement volume and just over 3% of increase in weight. Analyses of the Al–Ti composite fractures and cross-sections and of chemical composition and hardness of the matrix–reinforcement transition interface indicated the preservation (no melting) of the Ti wire and the existence of a fine contour of bonding between matrix and reinforcement. At the end, a brief discussion on the dynamics of the wire reinforcement preservation is carried out based on high-speed filming.

A Ka-Band Cylindrical Paneled Reflectarray Antenna

Cylindrical parabolic reflectors have been widely used in those applications requiring high gain antennas. Their design is dictated by the geometric relation of the parabola, which relate the feed location, f, to the radiating aperture, D. In this work, the use of reflectarrays is proposed to increase D without changing the feed location. In the proposed approach, the reflecting surface is loaded with dielectric panels where the phase of the reflected field is controlled using continuous metal strips of variable widths. This solution is enabled by the cylindrical symmetry and, with respect to rectangular patches or to other discrete antennas, it provides increased gain. The proposed concept has been evaluated by designing a Ka-band antenna operating in the Rx SatCom band (19–21 GHz). A prototype has been designed and the results compared with the ones of a parabolic cylindrical reflector using the same feed architecture. Simulated results have shown how this type of antenna can provide higher gain in comparison to the parabolic counterpart, reaching a radiation efficiency of 65%.

Measures of Harm from Heavy Metal Pollution in Battery Technicians’ Workshop within Ilorin Metropolis, Kwara State, Nigeria

Soil pollution with Heavy Metals (HMs) has been of much interests lately and is one of the major issues to be faced globally and requires attention because heavy metals above their normal ranges are extremely threatened to both biotic and abiotic life. It was therefore of interest to conduct study to assess the extent of heavy-metal contamination of soils within battery technicians’ workshops within Ilorin metropolis, Kwara State, Nigeria. A total of twenty-five composite soil samples were collected from six selected battery charger workshop within Ilorin metropolis and analyzed for the presence of heavy metals using atomic absorption spectrophotometer. Result reveals significant positive relationship between Mn and Fe (r=0.511**, p<0.001), Mn and Cu (r=0.565**, p<0.001), Fe and Cr (r=0.895**, p<0.001), Fe and Cu (r=0.823**, p<0.001) and between Cr and Cu (r=830**, p<0.001). Result also shows significant negative relationship between Mn and Cr (r=-0.679**, p<0.001), Pb and Cu (r=-0.468*, p<0.05) respectively. The pollution status of heavy metals in soils was evaluated using quantitative indices (pollution index–PI). The result shows that Zn was moderately contaminated while other heavy metals (Pb, Cd, Cr and Cu) had very slight contamination (pollution index<0.1). The Ilorin metropolis soils of Kwara State were found to have a moderate to very slight contamination respectively. Large variations in PI values of Zn revealed that soil in those areas of the city, which are influenced by anthropogenic activities, have moderate concentrations of Zn resulting in “considerable risk”. The findings of this study recommend comprehensive continuous annual monitoring and auditing and further studies on the level of these heavy metals in the near future to ascertain long-term effects of anthropogenic impact is forestalled to protect the men and the environment. This should also involve larger coverage with studies on ground water around such locations. Furthermore, continuous metals speciation should be carried out so that the form and extent of metal bioavailability can be evaluated further.

Van der Waals solid phase epitaxy to grow large-area manganese-doped MoSe2 few-layers on SiO2/Si

Large-area growth of continuous transition metal dichalcogenides (TMDCs) layers is a prerequisite to transfer their exceptional electronic and optical properties into practical devices. It still represents an open issue nowadays. Electric and magnetic doping of TMDC layers to develop basic devices such as p-n junctions or diluted magnetic semiconductors for spintronic applications are also an important field of investigation. Here, we have developed two different techniques to grow MoSe2 mono- and multi-layers on SiO2/Si substrates over large areas. First, we co-deposited Mo and Se atoms on SiO2/Si by molecular beam epitaxy in the van der Waals regime to obtain continuous MoSe2 monolayers over 1 cm2. To grow MoSe2 multilayers, we then used the van der Waals solid phase epitaxy which consists in depositing an amorphous Se/Mo bilayer on top of a co-deposited MoSe2 monolayer which serves as a van der Waals growth template. By annealing, we obtained continuous MoSe2 multilayers over 1 cm2. Moreover, by inserting a thin layer of Mn in the stack, we could demonstrate the incorporation of up to 10% of Mn in MoSe2 bilayers.

Electroless Metal Deposition Using Multivalent Metal Ions As Reducing Agents

The possibility and conditions to use lower oxidation state metal ions as reducing agents for autocatalytic electroless metal deposition are discussed. The theoretical background of such kind reactions is presented in the view of thermodynamics. Kinetic data on electroless silver, copper, palladium and platinum deposition using Co(II)/Co(III) redox systems with different ligands are presented and discussed. Ti(III)/Ti(IV) redox systems with different ligands were shown also to be suitable reducing agents for reducing of Pt(IV), Pd(II), Ni(II) and Co(II) to metallic state and formation of continuous metal layer on the surface to be plated. The morphology of metal layers deposited using above-mentioned reducing agents was characterized by means of Field Emission Scanning Electron Microscopy (FESEM). Kinetics of metal deposition rate was investigated by means of the gravimetry or Electrochemical Quartz Crystal Microgravimetry (EQCM).

Nanoarray Device for Detection of Gas Phase I2

We report on a nanoelectrode array sensor for the detection of I2 (iodine gas) at levels as low as near 0,02 ppm within tens of seconds of exposure. The sensor is constructed on a free-standing anodic aluminum oxide wafer with nanopores of 120 nm diameter and 50 um length. On each wafer surface, continuous metal films of tens of nm thickness are deposited: on one surface, a gold film is deposited such that it covers the nanopores, and, on the opposite surface, a platinum film is deposited such that the nanopores remain open and their volumes in contact with the environment. The gold film serves as the working electrode and the platinum film serves as the auxiliary and pseudo-reference electrode. The nanopores are filled with a pH 9 buffer aqueous solution to create an array of electrochemical cells in parallel, and ionic conductivity is maintained for environments with relative humidity levels greater than about 30%. The detection mechanism is the electrochemical oxidation of anionic species of I2 that form from the dissolution and subsequent hydrolysis of gas phase I2 in the pH 9 buffer electrolyte: the gas phase I2 dissolves in the buffer in proportion to Henry's Law constant and then the dissolved I2 is hydrolyzed to several species, including the anionic species iodide and tri-iodide. The detection of I2 is achieved by measuring oxidizing current during the cyclic voltammetry technique bounded between -0,2 and 0,5 V vs the Pt pseudoreference electrode. The hydrolysis mechanism of I2 in the pH 9 buffer enables the buffer to function as a concentrator for the anionic species of I2. When the sensor is exposed to a gas stream containing I2, practically continuous accumulation of the electrochemically detectable anionic species of I2 is possible, with a saturation point where the pH 9 buffer contains > 100 ppm iodide anion. For context, the sensor can detect iodide anions in pH 9 buffer at levels as low as 0,01 ppm. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Ultrathin and Ultrasmooth Gold Films on Monolayer MoS2

AbstractSub‐10 nm continuous metal films are promising candidates for flexible and transparent nanophotonics and optoelectronic applications. In this article, it is demonstrated that monolayer MoS2 is a perspective adhesion layer for the deposition of continuous conductive gold films with a thickness of only 3–4 nm. Optical properties of continuous ultrathin gold films deposited on 2D MoS2 grown by chemical vapor deposition are investigated by spectroscopic ellipsometry over a wide wavelength range (300–3300 nm). Results show that optical losses in ultrathin films increase with decreasing thickness due to the fine‐grained structure and the presence of a small number of voids, however, they exhibit metallic properties down to a thickness of 3–4 nm. The atomic‐scale MoS2 interfaces can be transferred to any substrate and thus open up new opportunities for the creation of metasurfaces and a new type of van der Waals heterostructures with atomically thin metal layers.

Tunable, polarized and deeply modulated photoluminescence based on gold nano-islands and liquid crystal

Tunable, polarized and strongly modulated photoluminescence from liquid crystal (LC)-based Fabry Perot (FP) cavity is reported. Reflectors of this cavity are a continuous metal thin film and a plasmonic gold nano-island (NI) layer. The NI layer is selectively reflective and transparent inside and outside of the plasmonic spectral region. The NI layer strongly enhances the quality of the cavity modes in a defined plasmonic spectral area, unlike what happens in thick metal layer. The defect free nature of LC layer in the cavity can excite the FP mode and work as a light emitter by doping a dye in LC layer. Photoluminescence (PL) of the cavity is anisotropic and polarized due to the alignment of molecular dipole moment of dye along the LC director. The role of the NI layer and the LC layer on the optical quality of the cavity is investigated theoretically and experimentally. This FP cavity could be applicable in tunable optoelectronics and lasing applications.

Method for manufacturing a fibre reflection interferometer based on a metal-dielectric diffraction structure

A new method for manufacturing a two-mirror reflection fibre interferometer in a single-mode fibre consisting of an input mirror with an asymmetric reflection coefficients and a highly reflective end mirror is presented and experimentally demonstrated. The input mirror is based on a metal-dielectric diffraction structure in the form of an aperture in an aluminium film and a dielectric multilayer coating, which provides asymmetry of the reflection coefficient. The method includes the calculation of the energy coefficients of the aluminium film with a hole, the determination of the optimal diameter of the hole, as well as making of the hole, the entrance mirror and the resonator with a short fibre base. A sample interferometer is demonstrated that has an increased (at least by two orders of magnitude) radiation resistance compared to variants based on a continuous metal film, namely, at least 100 mW of radiation in a single-mode SMF-28e fibre at a wavelength of 1550 nm.

Development of continuous metal patterns using two-dimensional atmospheric-pressure plasma-jet: on application to fabricate electrode on a flexible surface for film touch sensor

A two-dimensional atmospheric-pressure plasma jet (2D-APPJ) was developed for photoresist residual layer removal, which is essential for the continuous and uniform fabrication of large-area micro/nanoelectronics via continuous-imprinting lithography. To verify the feasibility of the developed method, the electrode structure for a capacitive-type film touch sensor was continuously fabricated using a combination of the developed 2D-APPJ and a roll-to-roll imprinting method. As a result of applying the process conditions confirmed through system design, fabrication, and parametric study, photoresist removal up to 4917 Å with a uniformity of 7.8% was achieved in the APPJ sample scanning at a scan speed of 1 mm s−1. Using the developed APPJ process, a double-layer electrode consisting of Cu and indium tin oxide with a minimum line width of 10 μm was successfully patterned by employing the auto-alignment process using a double-step etch barrier.

Enhanced pseudocapacitance of amorphous oxy-hydroxides epitaxially grown on intermetallics nanofoam

Transition metal oxide based pseudocapacitors possess the merits of high theoretical specific capacitance and high energy density. However, the poor rate performance especially for thick electrodes, originating from the poor conductivity of most transition metal oxides, is still a hindrance for their practical applications. To resolve the conundrum, increasing the conductivity of metal oxides and developing new electrode constructions with high electron/ion conductivity are effective alternatives to acquire high-rate performance and high specific capacitance. In this study, we report a facile approach to fabricate low-cost transition metal based amorphous oxy-hydroxide epitaxially grown on intermetallics nanofoam by electrochemical polarization in an alkaline solution. The enhanced electron/ion conductivity, generated from the continuous metal substance and pore channel networks in the whole electrode, as well as amorphous structure induced transportation channels of oxy-hydroxide, contributes to the ultrahigh specific capacitance (1058 F/cm3 at a current density of 1 A/cm3) and excellent rate performance (74.2% retention when the current density increases from 1 A/cm3 to 10 A/cm3). Combined with their excellent cyclic stability and low cost, the 3D amorphous oxy-hydroxide/metal architectures demonstrate great potentials for applications in next generation supercapacitors.

Continuous Metal–Organic Framework Biomineralization on Cellulose Nanocrystals: Extrusion of Functional Composite Filaments

Growing metal–organic frameworks (MOFs) around biomolecules has recently emerged as a promising method to combine natural and synthetic materials. In parallel, cellulose nanocrystals (CNCs) have fo...

Wrinkled Graphene Cages as Hosts for High-Capacity Li Metal Anodes Shown by Cryogenic Electron Microscopy.

Lithium (Li) metal has long been considered the "holy grail" of battery anode chemistry but is plagued by low efficiency and poor safety due to its high chemical reactivity and large volume fluctuation, respectively. Here we introduce a new host of wrinkled graphene cage (WGC) for Li metal. Different from recently reported amorphous carbon spheres, WGC show highly improved mechanical stability, better Li ion conductivity, and excellent solid electrolyte interphase (SEI) for continuous robust Li metal protection. At low areal capacities, Li metal is preferentially deposited inside the graphene cage. Cryogenic electron microscopy characterization shows that a uniform and stable SEI forms on the WGC surface that can shield the Li metal from direct exposure to electrolyte. With increased areal capacities, Li metal is plated densely and homogeneously into the outer pore spaces between graphene cages with no dendrite growth or volume change. As a result, a high Coulombic efficiency (CE) of ∼98.0% was achieved under 0.5 mA/cm2 and 1-10 mAh/cm2 in commercial carbonate electrolytes, and a CE of 99.1% was realized with high-concentration electrolytes under 0.5 mA/cm2 and 3 mAh/cm2. Full cells using WGC electrodes with prestored Li paired with Li iron phosphate showed greatly improved cycle lifetime. With 10 mAh/cm2 Li metal deposition, the WGC/Li compositeanodewas able to provide a high specific capacity of ∼2785 mAh/g. With its roll-to-roll compatible fabrication procedure, WGC serves as a highly promising material for the practical realization of Li metal anodes in next-generation high energy density secondary batteries.

Empowering Electroless Plating to Produce Silver Nanoparticle Films for DNA Biosensing Using Localized Surface Plasmon Resonance Spectroscopy.

To facilitate the implementation of biosensors based on the localized surface plasmon resonance (LSPR) of metal nanostructures, there is a great need for cost-efficient, flexible, and tunable methods for producing plasmonic coatings. Due to its simplicity and excellent conformity, electroless plating (EP) is well suited for this task. However, it is traditionally optimized to produce continuous metal films, which cannot be employed in LSPR sensors. Here, we outline the development of an EP strategy for depositing island-like silver nanoparticle (NP) films on glass with distinct LSPR bands. The fully wet-chemical process only employs standard chemicals and proceeds within minutes at room temperature. The key step for producing spread-out NP films is an accelerated ripening of the silver seed layer in diluted hydrochloric acid, which reduces the nucleation density during plating. The reaction kinetics and mechanisms are investigated with scanning (transmission) electron microscopy (SEM/STEM), X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy, with the latter enabling a convenient live monitoring of the deposition, allowing its termination at a stage of desired optical properties. The sensing capabilities of chemically deposited NP films as LSPR transducers are exemplified in DNA biosensing. To this end, a sensing interface is prepared using layer-by-layer (LbL) buildup of polyelectrolytes (PE), followed by adsorption and covalent immobilization of ssDNA. The obtained LSPR transducers demonstrate robustness and selectivity in sensing experiments with binding complementary and unrelated DNA strands.

Manufacture of Continuous Metal Matrix Composite Strip Reinforced by Particulate Materials from the Semisolid Processing

Strip casting is a new method of producing metal matrix composites. Two-roll melt dragged processing (TRMD-ing) and single-roll melt dragged processing (SRMD-ing) methods were used to study the manufacture of 2-mm-thick composite strips by using PbSn (≈ 11.3 g/cm3) eutectic alloy matrix reinforced with iron (≈ 7.86 g/cm3) powder (≈ 70 μm) at a rate of 0.3 m/s. The metallic powder stored in the feed hopper (≈ 90 g) was pushed during the pouring operation of the cast alloy (≈ 4 kg) at 260 oC on the cooling slope to produce a mixture of metallic slurry and particles to feed the nozzle to be dragged by the lower roll. Various surface defects occurred during processing, such as the failure of the powder particle to be embedded in the matrix by SRMD-ing with and without stirrer into the nozzle, and the rolling up of the strip into the nozzle by TRMD-ing. Graphite nanoparticles formed inside the α-Pb grain revealed a complicate eutectic structure in both the processing methods. The colloidal graphite used to coat the crucible, cooling slope, and nozzle could act as a nucleation agent for preferential centre segregation in the α-Pb grain. This suggests that the graphite nanoparticles functioned as nucleation points in the lead-rich α phase. Thus, another type of composite was formed in the presence of graphite nanoparticles within the lead-rich α-phase surrounded by β-Sn. An electron probe microanalysis and scanning electronic microscopy were used to investigate the composition and distribution and identify the different phases. Several types of particulate reinforcements may be added to the matrix to obtain composites for mechanical, electronic, and magnetic applications using these technologies.

Versatile route to core-shell reinforced network nanostructures.

In this work we present the generation of new core-shell network nanostructures of macroscopic dimensionality by a two-step process analogous to the seeded-growth method in colloidal nanoparticle modification. The nanoparticle-based core network is assembled first and in a separate second step it is coated with a continuous metal oxide shell by sol-gel methods. The interparticle contact of the nanoparticles comprising the core network is kept intact throughout the process. By analyzing the local elemental distribution, the shells can be shown to be homogeneous over the macroscopic network monolith. The shell network can be used to considerably reinforce the mechanical strength of the final core-shell network structure.