Thick Metal Research Articles

Impact of topography on extraordinary magnetoresistive devices

Abstract The extraordinary magnetoresistance (EMR) effect is a form of geometric magnetoresistance that occurs when the current redistribution inside a hybrid metal-semiconductor device changes when subjected to an external out-of-plane magnetic field. While the influence of material and geometrical properties on sensor performance has been extensively studied, the topography of EMR devices has not yet received much attention. Typically, flat, 2D topographies are assumed when optimizing EMR devices, which does not reflect the significant topography present in actual devices. This study fills this gap by numerically investigating concentric circular EMR devices with different topographies using a 3D finite element model. We show that EMR devices with metal top contacts, which are more straightforward to fabricate, behave similarly to conventional EMR devices where the metal shunt of the same thickness is embedded into the devices. For InSb/Au devices, both types of devices produce a magnetoresistance of 4.9×105 % at 1 T. Our results also reveal that the magnetoresistance increases with the thickness for a large range of metal thicknesses. In addition, we also explore sidewall dimensions and show that it is desirable to have a thicker shunt with thinner sidewalls, compared to the opposite case.

Enhanced two-temperature model and its application in comprehensive analysis of femtosecond laser melting of gold, copper and their alloys.

Extensive research on ultrashort laser-induced melting of noble metals like Au, Ag and Cu is available. However, studies on laser energy deposition and thermal damage of their alloys, which are currently attracting interest for energy harvesting and storage devices, are limited. This study investigates the melting damage threshold (DT) of three intermetallic alloys of Au and Cu (Au3Cu, AuCu and AuCu3) subjected to single-pulse femtosecond laser irradiation, comparing them with their constituent metals. This is accomplished by extending an earlier-developed two-temperature model (TTM)-based code with several improvements, including precise modeling of temperature-dependent optical properties and ballistic electron transport. The dynamic optical model inclusive of ballistic effects is demonstrated to reproduce the experimental DT of pure metals with minimal variation and is therefore adopted for further investigation. Our simulations reveal that the alloy films have significantly lower incipient and complete melting thresholds compared to the pure metals due to their low thermal conductivity and high electron-phonon coupling strength. Theoretical studies on varying the thickness of metal and alloy films unveil the usual trend of a rapid increase in DT up to a certain thickness, followed by a saturation region. This universal DT profile is elucidated by proposing a first-of-its-kind analytical function. Excellent agreement between the coefficients of the function with optical and electron diffusion parameters derived from the comprehensive theory proposed here reinforces the robustness of the model. The novelty of this study also lies in introducing the concept of a critical film thickness for which the entire film attains the melting temperature at its complete melting threshold.

Contactless manufacturing of TERS-active AFM tips by bipolar electrodeposition.

Tip-enhanced Raman spectroscopy (TERS) is a powerful technique for nanoscale chemical imaging. However, its worldwide expansion is still limited by the challenging fabrication of cheap, robust and efficient TERS tips as optical nanosources to amplify the Raman signal. An original method based on bipolar electrodeposition is described here to prepare gold-coated AFM cantilevers used as TERS tips. This wireless method is simple to implement, cost-effective, and allows for the parallel fabrication of several TERS tips with good reproducibility of the metal thickness and a relatively long lifetime. The TERS activity was confirmed by imaging graphene oxide flakes with high spatial resolution (below 10 nm). A promising yield of 64% was achieved for the fabrication of active TERS tips. Therefore, this method could pave the way for the development of new chemical routes for the preparation of TERS tips and other plasmonic nanostructures.

Back Mirror‐Free Selective Light Absorbers for Thermoelectric Applications

AbstractImproving light absorption is essential for the development of solar thermoelectric generators. Most efficient light absorbers require a back mirror (a thick metal film) to reduce the reflectivity by promoting the interference between the incident and the reflected light. However, the presence of thick a continuous metal film supposes a limitation for thermoelectric applications, as it behaves like a shortcut of the Seebeck voltage. In this work, a back mirror‐free selective light absorber is presented, designed for the fabrication of thermoelectric devices. The combination of a high and a low refractive index material covered by a semi‐transparent electrode is optimized. As a difference to the back mirror, the semi‐transparent electrode can be patterned to prevent the quenching of the Seebeck voltage. Thanks to this, the low refractive index material can be replaced by a transparent thermoelectric, enabling efficient heat‐to‐energy conversion with negligible loss of absorption performance.

The Influence of Deep Drawing Parameters on Stresses and Strains in Drawing Tools in the Context of their Durability and Process Load

This publication presents the influence of selected parameters in the deep drawing process on the energy consumption of the entire process. It was analysed how die clearance and the radius of the rounded working edge of the die affect drawing force and work. Modifying these parameters does not directly affect the geometry of the finished stamped product. In addition, it was analysed how modifying the clearance and the radius of the rounding of the working edge of the die affects the magnitudes of stresses and strains in the tools, i.e. the punch and the die. The study was carried out numerically using Ansys Ls-Dyna software. An elastic-plastic model with isotropic hardening was used to model the tools without considering strain rate. This approach makes it possible to assess how a given process will affect the abrasive wear of the working surfaces of the die and punches when the yield stress in the tool material is exceeded. A significant increase in tool life was observed through a reduction in plastic deformation when using clearances greater than the thickness of the sheet metal. Using a larger die edge rounding radius also positively affected tool life, maximum drawing force, and total work.

Искажение геометрии, окисление кромки, структурные изменения и морфология поверхности реза листового проката толщиной 100 мм из алюминиевых, медных и титановых сплавов при плазменной резке на токе обратной полярности

The introduction describes the feasibility of using reverse polarity plasma cutting to produce large-sized non-ferrous metal blanks up to 100 mm thick. Data on the use of plasma cutting with direct and reverse polarity currents for thick sheet metal and the main technological problems associated with its implementation are presented. The purpose of the work is to study the organization of the structure and properties of the near-surface zone, changes in the chemical and phase composition when cutting aluminum, copper and titanium alloys. The research methods are optical and scanning electron microscopy, microhardness measurement, X-ray diffraction and energy-dispersive analysis. Plasma cutting was carried out using air as a plasma-forming and shielding gas, simultaneously with water injection into the discharge chamber and the formation of a “water fog” around the plasma column. Results and discussion. It is shown that both the arc stability and the shape of the plasma column are of great importance in reverse polarity plasma cutting of rolled sheets. The distortion of the cutting geometry during normal operation is greatest in the central part, and with insufficient heat input it shifts to the lower part and increases significantly. The operation of the plasma torch in air does not lead to significant changes in the composition of the cutting surface of aluminum and copper alloys. A decrease in the magnesium content near the edge is typical for the aluminum alloy in the surface layers. Cutting of the titanium alloy is accompanied by intense oxidation of the surface, especially in areas of difficult metal displacement from the cutting cavity. The formation of titanium oxides, mainly rutile Ti2O, sharply increases the microhardness values in the surface layers, which negatively affects the machinability of the cutting edge and requires shot blasting to remove the oxide layer. The conclusion describes the main patterns of implementing reverse polarity plasma cutting of sheet metal from aluminum, copper and titanium alloys with a thickness of 100 mm.

An advanced deep learning-driven Terahertz metamaterial sensor for distinguishing different red wines

Terahertz time-domain spectroscopy (THz-TDS) encounters two issues in the detection field, which refer to the detection target for solid samples caused by the strong absorption of water and the large content target substance led by the low sensitivity. Fortunately, terahertz metamaterial (THz-MM) that can carry liquid samples and amplify signals solves the above problems well. In addition, the THz-MM can achieve the detection of trace substances through the resonance peak shift generated by designing suitable structures. However, since most researchers focus on designing complex structures rather than analyzing data, deep learning (DL) that can mine new features from original features and construct decision models is used to research the rich information in THz-MM sensor data. In the current research, a flexible transmissive THz-MM in the shape of a circle (‘O’ shape) was designed by depositing the gold on the polyimide substrate. Firstly, the structures referring to substrate thickness (ST), metal thickness (MT) and ring width (RW) were optimized, and the performances referring to principle, stability and sensitivity were evaluated. Next, the best THz-MM (ST: 16 µm, MT: 0.2 µm, RW: 6 µm) was prepared and characterized from morphology, thickness and consistency. Then, different concentrations of anthocyanins (R2: 0.9982) and tannic acid (R2: 0.9736) were successfully predicted by combining the resonance peak shifts. Finally, resonance peak descriptors were constructed and combined with DL referring to a fully connected neural network (FCNN) model to successfully identify different varieties of red wines (Precision: 91.11 %; Recall: 90.74 %, F1-score: 90.83 %; Accuracy: 90.74 %). Overall, the current research presents an advanced DL-driven THz-MM sensor, which promotes the process of THz-TDS technology in the food detection field

Experiments and numerical simulations on ceramic-metal composite targets penetrated by a 7.62 mm armour-piercing projectile

Abstract In order to explore the protective performance of ceramic-metal fibre composite target plate, a lightweight composite target plate consisting of aramid cloth, silicon carbide ceramic, TC4 titanium alloy, and ultra-high molecular weight polyethylene fibre plate was designed. The effects of adhesive type, stacking sequence and delamination on the protective performance of the target plate were researched through the ballistic impact test on the protective target plate with 7.62mm armour-piercing bullets. The effect of thickness variation of ceramic metal on the protective properties of target plate was investigated by LS-DYNA finite element software. It was found that the bonding effect of silicon carbide ceramics with TC4 was better than that of AB adhesive when the silica gel was used as the bonding adhesive. When the ceramic metal thickness dimension is certain, the ceramic delamination will weaken the protective structure performance, and the performance of the metal plate as the back support of the ceramic layer is better than that of the ceramic covered before and after the metal layer. The energy efficiency of the ceramic-metal structure is optimal when the ratio of the thickness of silicon carbide ceramic to TC4 is 4.84:1 for a certain surface density.

Investigating the Suitability of Printing Metal Current Collectors Directly Onto the GDMs of PEMFCs

Flexible electrochemical energy sources with unconventional cell materials and topologies are becoming more and more popular because they present novel design possibilities that are currently being investigated. Adopting electronics manufacturing techniques to manufacture flexible electrochemical devices can provide advantages such as conformability, high power density, high specific power, and lower costs. This study examines the feasibility of printing metal current collectors (CCs) directly onto Gas Diffusion Medium (GDM) typically used in Proton Exchange Membrane Fuel Cells (PEMFCs). In this work, we print the metal CCs directly onto the GDM using different techniques such as screen printing and ink jet printing. We also investigate the effect of varying the metal CCs geometry (square shape vs. hexagonal), opening ratio (30%, 40% and 50%) and metal thicknesses (10 µm to 50 µm thick) on the overall single cell performance and cell ohmic resistances. Techniques used to understand cell performance include I-V polarization curves, electrochemical impedance spectroscopy (EIS), and thermal imaging. The performance of the cells tested with the embedded GDM/Metal CCs is compared to the performance of a standard cell.

Using Thermal Crowding to Direct Pattern Formation on the Nanoscale.

Metal films and other metal geometries of nanoscale thickness deposited on an insulating substrate, when exposed to laser irradiation, melt and evolve as fluids as long as their temperature is sufficiently high. This evolution often leads to pattern formation, which may be influenced strongly by material parameters that are temperature dependent. In addition, the laser heat absorption itself depends on the time-dependent metal thickness. Self-consistent modeling of evolving metal films shows that, by controlling the amount and geometry of the deposited metal, one can control the instability development. In particular, we demonstrate the "thermal crowding" effect: additional metal leads to elevated temperatures, which strongly influence the metal evolution, even if the metal geometries are disjoint. We demonstrate that the communication of disjoint metal domains occurs via heat diffusion through the underlying substrate. Fully self-consistent modeling focusing on the dominant effects, as well as accurate time-dependent simulations, allow us to describe the main features of thermal crowding and provide a route to control fluid instabilities and pattern formation on the nanoscale.

Optimization of visible transmission and NIR reflection in multilayer via PSO: Simulation and experimental validation

Transparent heat reflective windows (THRW) effectively manage solar energy by reflecting near-infrared (NIR) heat while maintaining high visible (VIS) light transmittance, thus improving building energy efficiency. Conventional THRW designs using dielectric/metal/dielectric (D/M/D) structures often increase metal thickness for better NIR reflectance, which compromises VIS transmittance. In this work, we present a dielectric/metal/dielectric/metal/dielectric (D/M/D/M/D) multilayer structure, utilizing TiO2 as the dielectric and Ag as the metallic component. The film thicknesses were systematically optimized using the particle swarm optimization algorithm to achieve an optimal balance between high VIS transmittance ((T‾VIS = 87 %) and high NIR reflectance (R‾NIR = 95 %). Additionally, the structure shows only 15 % UV transmittance due to absorption by TiO2 and reflection by Ag. The multilayer films are fabricated using electron beam evaporator, with the experimental results show that the multilayers maintain good VIS transmittance as well as high NIR reflectance. This high-performance THRW design demonstrates significant potential for energy-saving applications in hot climates, offering a viable solution for enhancing building energy efficiency and occupant comfort in the future.

Investigation of the impact of product thickness and strain on cold forging processes

This study investigates the impact of sheet metal thickness and strain generated on a cold forging process. A cold forging die was manufactured based on a numerically modelled product design that considered stress concentration die profiles. Experiments involved cold forging various sheet metals (lead, brass, aluminium, and steel) with thicknesses ranging from 2mm to 6mm to assess their influence on the thickness and strain. An assumption was formulated using Solidworks to determine the appropriate sheet metal thickness based on the material type. This assumption, based on volume considerations, showed practical applicability for selecting sheet metals with thicknesses close to those designed in the numerical modelling. The results revealed that softer materials, such as lead and aluminium, closely approximated the design thickness, particularly in the central region of the die profile, with error deviations of 1.14 % and 4.36 %, respectively. In contrast, harder materials demonstrated larger deviations from the design, with minimum errors of 4.94 % for brass and 5.73 % for steel. All sheet metals underwent compressive strain in the central region of the die profile due to the stamping operation. This work demonstrates a practical approach for selecting sheet metals based on material and thickness considerations, providing insights into the behaviour of different materials during the cold forging process.

Control of coherent phonon dynamics in CoFeB/heavy metal heterojunction structures for future hybrid phononic and spintronic devices

Abstract The heterojunction structure of CoFeB/heavy metal has shown significant potential for spintronics, where both electrons and magnons potentially can serve as information carriers. However, another promising information carrier, coherent phonons, has not been fully explored for hybrid phononic and spintronic devices. In this study, we used time-resolved pump–probe spectroscopy to investigate the dynamic behaviour of coherent phonons. We observed variations in reflectivity spectra, corresponding to changes in phonon frequency and relaxation times, with different thicknesses of the heavy metal and CoFeB layers. The experimental results demonstrated a decrease in coherent phonon oscillation frequency as the thickness of the CoFeB and heavy metal layers increased. These findings were further supported by first-principles calculations, which showed that the frequency of the optical modes is suppressed due to interface relaxation between the magnetic and heavy metal layers.

Designing TiB2/Cr multilayer coatings on Ti6Al4V substrate for optimized wear resistance

The difference in mechanical properties between the TiB2 coating and the Ti6Al4V substrate can deteriorate the wear resistance of the TiB2 coating. To enhance the TiB2-based coating’s ability to deform in coordination with the ductile Ti6Al4V substrate and improve its tribological performance, the TiB2/Cr multilayer coatings were designed and deposited on Ti6Al4V substrates by magnetron sputtering. Results reveal that the FEM stress distribution of the TiB2/Cr multilayer coatings was optimized by varying the ceramic–metal thickness ratio (Q). As Q decreased from 1.0 to 0.5, the fracture toughness and adhesion strength of the coatings improved. The multilayer coating with Q = 0.5 exhibited the best toughness, crack propagation resistance (CPRs), and the smallest equivalent stress area, leading to a threefold enhancement in wear resistance compared to the TiB2 monolayer coating. However, further reduction of Q to 0.3 diminished wear resistance due to low hardness and significant stress concentration. Thus, there is an optimal balance between hardness, toughness, and stress distribution for achieving improved wear resistance in the multilayer design. Moreover, a notable correlation was observed between CPRs and the wear resistance of TiB2/Cr multilayer coatings.

Experimental demonstration of coupling between cavity resonance and Tamm plasmons in photonic multilayers.

Strong coupling in photonic microstructures attracts broad attention due to its promising applications in spectral control, optical sensing, and light-matter interactions. Herein, we demonstrate the coupling effect in the photonic multilayer with a planar nanocavity on a one-dimensional (1D) photonic crystal (PC). The experiment results show that the spectral profile of the coupling effect can be effectively controlled by adjusting the thickness of the dielectric layer in the nanocavity, which is in good accordance with the calculations. The coupled-oscillator theoretical analysis reveals that the coupling response exhibits a Rabi splitting of 36 meV with a distinct anticrossing behavior, which stems from the strong coupling interaction between the nanocavity resonance and Tamm plasmons (TPs) between the metallic film and PC. The coupling strength can be effectively tuned by adjusting the thickness of the metallic film on the PC. We find that the coupling between the cavity and TP modes locates in the strong coupling regime when the metallic film thickness is less than 36 nm. This work will offer a new pathway for realizing optical coupling and spectral control in photonic microstructures.

Re-manufacturing of Pre-deformed Automotive Sheet Metal Stamping Scrap Without Melting

Abstract The recycling of aluminium sheet metal typically involves shredding and re-melting, processes which are both energy-intensive and challenged by the presence of metallic contaminants. To mitigate these issues, this study explores an alternative approach: the re-manufacturing of deep-drawn parts directly from scrap aluminium sheets, thus bypassing the melting step. We used 2 mm thick Al-Mg sheet metal in H111 temper to produce simulated stamping scrap (miniaturized bonnets). Blanks were cut from these bonnets and secondary parts in a cross-cup geometry were deep-drawn using two different forming processes: warm-forming at 200 °C and O-temper forming at room temperature. The resulting maximum draw depths were 20-22 mm for warm-forming and 25-30 mm for O-temper forming. While warm-forming resulted in lower draw depths, O-temper forming led to coarse recrystallized grain formation in some regions. Our approach could significantly reduce the energy consumption associated with aluminium recycling.

Enhanced Photocatalytic Paracetamol Degradation by NiCu-Modified TiO2 Nanotubes: Mechanistic Insights and Performance Evaluation.

Anodic TiO2 nanotube arrays decorated with Ni, Cu, and NiCu alloy thin films were investigated for the first time for the photocatalytic degradation of paracetamol in water solution under UV irradiation. Metallic co-catalysts were deposited on TiO2 nanotubes using magnetron sputtering. The influence of the metal layer composition and thickness on the photocatalytic activity was systematically studied. Photocatalytic experiments showed that only Cu-rich co-catalysts provide enhanced paracetamol degradation rates, whereas Ni-modified photocatalysts exhibit no improvement compared with unmodified TiO2. The best-performing material was obtained by sputtering a 20 nm thick film of 1:1 atomic ratio NiCu alloy: this material exhibits a reaction rate more than doubled compared with pristine TiO2, enabling the complete degradation of 10 mg L-1 of paracetamol in 8 h. The superior performance of NiCu-modified systems over pure Cu-based ones is ascribed to a Ni and Cu synergistic effect. Kinetic tests using selective holes and radical scavengers unveiled, unlike prior findings in the literature, that paracetamol undergoes direct oxidation at the photocatalyst surface via valence band holes. Finally, Chemical Oxygen Demand (COD) tests and High-Resolution Mass Spectrometry (HR-MS) analysis were conducted to assess the degree of mineralization and identify intermediates. In contrast with the existing literature, we demonstrated that the mechanistic pathway involves direct oxidation by valence band holes.

Study on the effects of electrode volume fraction and electrode particle radius on dynamic electrochemical-thermal-aging coupling characteristics of lithium cell based on cylindrical cell design method

Electrode volume fraction and electrode particle radius are important electrode parameters for the lithium cell design and deeply influence the electrochemical-physical processes inside lithium cell, which is still insufficiently clear. In order to obtain the effects of electrode parameters on lithium cell, a combine method of the dynamic electrochemical-thermal-aging coupling model and cylindrical cell design was proposed. Simulation was conducted at charge rate 1C. Cell temperature, current density and Solid-Electrolyte-Interface at ambient temperature 25 °C, and total strain energy density and lithium plating at ambient temperature −5 °C were analyzed. As electrode volume fraction or electrode particle radius increases, maximum temperature and maximum temperature difference of lithium cell increase. When electrode volume fraction increases from 0.3 to 0.7, maximum temperature of cell increases by 2.6 °C at least. Current density peak increases with the increase of the positive electrode volume fraction or electrode particle radius. When electrode volume fraction increases from 0.3 to 0.7, current density peak increases by 44 %∼74 %. As electrode volume fraction increases, total strain energy density Ws decreases in the early stage of charge, while increases in the late stage of charge. As the negative (or positive) electrode particle radius increases, Ws of the negative (or positive) electrode increase, while Ws of the positive (or negative) electrode decreases. Solid-Electrolyte-Interface thickness increases with the increase of the electrode volume fraction or electrode particle radius. The effect range of negative electrode volume on lithium plating is 0.5 ∼ 0.7. The lithium metal thickness increase with the increase of the positive electrode volume fraction. As the negative or positive electrode particle radius increases, the lithium metal thickness increase or decrease, respectively.

Brownfield Topsoil Vertical Heterogeneity: Implications for Germination and Soil Microbial Functioning.

Soil vertical heterogeneity refers to the variation in soil properties and composition with depth. In uncontaminated soils, properties including the organic matter content and nutrient concentrations typically change gradually with depth due to natural processes such as weathering, leaching, and organic matter decomposition. In contaminated soils, heavy metals and organic contaminants can migrate vertically through leaching or root uptake and translocation by plants and macrobiota, if present, leading to vertical heterogeneity in contaminant concentrations at different depths. Contaminants can alter soil properties, and we investigated the implications of soil vertical heterogeneity for germination and microbial functioning. We collected soil from an urban brownfield and created two conditions: structured soil samples collected with the soil core intact and mixed (unstructured) samples. When planted, the germination rate was significantly lower in the structured conditions (3.1 ± 1.7%) compared to mixed soils (17 ± 4.6%), suggesting that the vertical heterogeneity of contaminated soil influenced plant germination. To map the vertical distribution of contaminants and nutrient cycling rates in the structured soil samples, we collected 10 cm-deep soil cores from the barren site and a neighboring vegetated reference site and measured heavy metal concentrations, soil enzyme activities, and organic matter content in five 2 cm vertical layers. In the barren soil cores, metals were found concentrated in the top 2 cm layer, while in the vegetated soil cores, metals were uniformly distributed. No significant differences were observed for the organic matter content or moisture along depth. Published studies on vertical distribution of enzyme activities and metal concentrations have treated the top 10-20 cm as a single layer and thus would have not revealed the thin (<2 cm thick) metal cap on the surface of the barren soil core. Despite the metal cap, enzyme activities in the top layer were similar to those in the lower layers of the barren soil core, suggesting that high metal concentrations do not limit soil enzyme activity under all circumstances. Investigating vertical heterogeneity in postindustrial soils can inform efforts to convert industrial barrens to vegetated environments.

Simulation of quantum states in solid-state ferromagnetic nanostructures

Purpose of the article. Identification and analysis of mathematical expressions for the energy spectrum of charge carriers in nano-sized magnetic films of nickel and Ni-Cu (substrate), as well as NiO-Ni-Cu (substrate) structures.Methods. In this work, based on basic quantum mechanical concepts and taking into account the boundary conditions for coupled quantum wells, expressions for the energy spectrum of electrons are obtained. The ferrimagnetic properties of nickel are taken into account through the effective mass value. The solution of nonlinear equations that determine discrete energy levels was achieved by numerical methods using the Mathcad mathematical package.Results. Transcendental expressions for the energies of free charge carriers in quantum wells of ferromagnetic nickel films are obtained, and the influence of the position of nickel on the copper substrate is shown. It has been shown that the use of a copper substrate leads to an increase in the density of energy levels in the nickel nanofilm. The influence of the oxide layer on single-electron states in nanofilms of nickel and its oxide is considered within the framework of the Anderson model. Based on the numerical solution of the transcendental equations obtained in the work, the influence of the ratio of the thicknesses of a ferromagnetic metal and its oxide on the energy levels of electrons localized in the oxide layer is shown.Conclusions. The formulas presented in the work for the energy spectrum take into account the energy relief of a complex quantum well, the dimensions of the film, surface oxide, and the significant effective mass in the region of the ferromagnetic film. It has been shown that an increase in the effective mass in magnetic heterostructures leads to an increase in the electron density of states. It was found that the density of electronic states in the region of surface nickel oxide is practically independent of the thickness of the nickel film. The results and conclusions of the work can be used for theoretical prediction of the physical properties of magnetic nanostructures, in particular spintronic elements.