Metal Substrate Research Articles

A unified strain energy-based fatigue life prediction methodology for composite and metal adhesive joints: Effects of adhesive, geometry and, environment

Ensuring the efficiency and safety of bonded structures across diverse engineering sectors requires a robust fatigue model for adhesive joints in both composite and metal substrates. This study presents a unified fatigue life prediction methodology for similar and dissimilar composite and metal adhesive joints. The proposed model integrates hydrostatic and deviatoric strain energy density components with the theory of critical distances. The model has been validated against diverse experimental data from different joint geometries, loading conditions, and different environments. The linear-elastic assumption is sufficient for toughened epoxies, whereas an elastoplastic model is necessary for ductile methacrylate adhesives. Calibration based on a single fatigue test yields the highest accuracy, while quasi-static test calibration is also satisfactory. The methodology addresses diverse loading conditions and environmental factors, showing a strong correlation with experimental results. It advances the performance, design, and reliability of similar and dissimilar composite to metal adhesive joints.

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

Effect of CaO deposit on the oxidation kinetics of CoCrAlY alumina forming alloys

MCrAlY (M = Ni and/or Co) alloys are commonly utilized as protective coatings for a variety of metallic substrates, including Ni- and Co-based superalloys due to their outstanding resistance to corrosion and oxidation in harsh environmental conditions. In such environments, external deposits have the potential to compromise the oxidation behavior of these alloys. This work assesses the oxidation kinetics of three different CoCrAlY alloys that can form alumina, with and without CaO deposits. Thermal gravimetric analysis experiments were carried out at 1100 °C for 50 h in dry-air conditions. It was observed that the presence of CaO deposits resulted in an accelerated oxidation rate and hindered the formation of alpha-alumina. Upon exposure to CaO, the examination of cross-sections revealed the formation of varying layers of calcium aluminates through the chemical reaction between Al2O3 and CaO. The characterized alloys exhibited a significant increase in oxidation rate during the initial stage, and therefore, an analysis at short oxidation times (9 min) is included in this study. These results indicate the formation of calcium chromate and suggest a potential link to the content of the gamma phase, which could be responsible for the accelerated oxidation during the early oxidation stages.

Reversible Sliding Motion by Hole-Injection in Ammonium-Linked Ferrocene, Electronically Decoupled from Noble Metal Substrate by Crown-Ether Template Layer.

Artificial molecular machines, especially when based on wheel-and-axle complexes, can generate mechanical motions in response to external stimuli. Ferrocene (Fc) is a key component, but it decomposes at 300 K on metal surfaces. Here, a novel method is presented to construct and control the molecular complex composed of ammonium-linked ferrocene (Fc-amm) and tetrabrominated crown ether (BrCR) on a Cu(111) surface. Fc-amm molecules are periodically arranged on a BrCR monolayer film and imaged using scanning tunneling microscopy and spectroscopy. A lateral motion of the Fc groups by ≈0.1nm is observed for pairs of "edge-on" Fc-amm molecules upon hole injection. This sliding motion is reversible and controlled by the applied voltage. Theoretical analysis indicates that the motion is caused by increased Coulomb repulsion of the hole-doped Fc-amm+ ions and accompanied by a weakening of CH-π interactions. These findings open new avenues for developing nanomolecular devices using on-surface bottom-up processes.

Effect of para-substituents on NC bonding of aryl isocyanide molecules adsorbed on metal surfaces studied by sum frequency generation (SFG) spectroscopy.

The effect of para-substituents on the NC bond of aryl isocyanide molecules adsorbed on Au, Ag, Pt, and Pd surfaces was examined by vibrational sum frequency generation (VSFG) spectroscopy. The frequency of NC stretching vibration, υNC, depended on the electronic property of the substituents. When the substituents were more electron-withdrawing and more electron-donating, υNC shifted to lower and higher frequencies, respectively. However, υNC shifted to lower frequency again when the substituents were too electron-donating. The strong dependence of υNC on metal substrates was also observed, reflecting the difference in metal d-band energies, which leads to the difference in the contributions of σ-donation and π back-donation of the NC-metal coupling.

Multi-channel wide-angle nonreciprocal thermal radiator with planar heterostructure

From the perspective of application at mid-infrared frequencies, omnidirectional nonreciprocal thermal radiation represents a critical need for effective thermal energy harvesting. In this study, we propose a nonreciprocal thermal radiator (NTR) which can be fabricated with a lithography-free approach. The structure is composed by germanium(Ge)-aluminum nitride(AlN)-Weyl semimetal (WSM) stacks and terminated with a metallic substrate. The results indicate that both the magnitude and the sign of the contrast between emission (e) and absorption (α) can be manipulated. This design achieves multi-channel nonreciprocal stability for transverse magnetic (TM) polarized incident wave over an exceptionally wide angular range. Additionally, the electromagnetic field distributions at the resonance wavelengths have been analyzed to elucidate the underlying principles. Multi-band nonreciprocity under transverse electric (TE) polarized incident wave has also been obtained. The capability of our proposal offers a relatively straightforward method to realize high-performance NTR. This advancement holds potential implications for the development of efficient energy harvesting and conversion devices.

High strength lignocellulose derived epoxy adhesive with heat and acid-base resistance

In this work, we developed a high-performance two-component epoxy adhesive from two biobased triple-functional and hexa-functional epoxy monomer from lignin-derived monomer eugenol, and a cellulose-derived furfuryl diamine for metal substrates. Through a tight cross-linked network and rich electronegative structure, the adhesives showed excellent adhesive performance to various metal substrates, especially for Fe. It demonstrated a high lap shear strength up to 19.8 MPa to Fe substrate, surpassing most reported epoxy adhesives. Moreover, these adhesives exhibited excellent long-term adhesion properties in high-temperature and acidic/base aqueous environments. It can maintain more than 95% of the adhesive strength to Fe substrate after soaking in different acid-base environments for 7 days, and achieved a maximum adhesion strength of 16.46 MPa to Fe substrates at 200 °C only 14.2% decrease when compared to that at room temperature. Molecular simulations revealed that these two adhesives could rapidly achieve dynamic equilibrium with Fe (110) surface in 15 and 22 ps which was much shorter than that to Cu and Al, suggesting a stronger binding energy between these adhesive and Fe surfaces and was consistent with the adhesion performance. This work widens the way for high-performance bio-based epoxy adhesives to be used in more demanding environments.

Electron delocalization in a 2D Mott insulator

The prominent role of electron-electron interactions in two-dimensional (2D) materials is at the origin of a great variety of fermionic correlated states reported in the literature. Artificial van der Waals heterostructures comprising single layers of highly correlated insulators allow one to explore the effect of the subtle interlayer interaction in the way electrons interact. We study the temperature dependence of the electronic properties of a van der Waals heterostructure composed of a single-layer Mott insulator lying on a metallic substrate by performing quasi-particle interference (QPI) maps. We show the emergence of a Fermi contour in the 2D Mott insulator at temperatures below 11K, which we attribute to the delocalization of the Mott electrons associated with the formation of a quantum coherent Kondo lattice. The comparison between experiments and Density Functional Theory calculations provides a complete picture of the delocalization of the highly correlated electrons from the 2D Mott insulator.

Morphology and Properties of the Laser-Irradiated Composition “Chrome Coating — Copper Substrate”

Introduction. During pulsed laser processing and modification of the surface of non-ferrous alloys and coatings based on them, several still unresolved issues arise. In particular, the extreme thermal deformation conditions of laser processing are not linked to the peculiarities of structure formation and formation of properties in irradiated “coating — copper substrate” compositions. A metal physical analysis of the possibility and reasons for increasing the adhesion strength of coatings to a metal (copper) substrate during high-speed laser processing is insufficiently substantiated and evidence-based. To make a reasonable choice of technological parameters for the surface hardening mode of non-ferrous alloy products, as well as for obtaining high-quality workable composite layers on their surface, it is necessary to solve the above issues and tasks. The aim of this article is to determine the possibility and conditions for increasing the adhesion strength of a chrome coating to a copper substrate under laser irradiation of the composition.Materials and Methods. Metal physical studies in the work were carried out on samples of non-ferrous alloys of the Cu–Zn system with a chrome electrochemical coating with a thickness of 20 μm. The “copper substrate — chrome coating” composition was irradiated at a Kvant-16 installation with a radiation power density of 70–250 MW/m2. Metallographic structural analysis, scanning probe microscopy, and durometric studies were used in the work.Results. It has been calculated that the dynamic and thermal stresses arising in the laser-irradiated compositions “chrome coating — copper substrate” were about 320 MPa. Metal physical studies revealed that, in extreme thermal deformation conditions of laser treatment, the effect of contact melting was manifested at the boundary of the coating with the copper base. Dynamic recrystallization occurred in the surface layers of the irradiated L62 copper alloy, resulting in the formation of grains with a size of 4.5–5.0 μm on the surface of the alloy with an initial grain size of 25 μm.Discussion and Conclusion. It has been found that the adhesion strength of a chrome coating to a copper alloy substrate increased laser irradiation at a radiation power density of 150 MW/m2. This was due to the formation of a transition region 2–4 μm deep in the contact zone with a structure consisting of sections of mutually insoluble solid solutions based on chromium and copper. Based on the analysis of the copper —chromium state diagram and the model of the temperature field under laser irradiation of the chromium coating, it was suggested that contact melting occurred in the transition zone from the coating to the copper substrate. It was shown that thermostrictive stresses, the calculated quantitative values of which were about 320 MPa, had an initiating effect on the observed processes of structure formation in the laser irradiation zones. It was found that such a level of stresses arising in copper alloys under laser irradiation was sufficient for plastic deformation and dynamic recrystallization of the metal and contributed to the formation of a fine-grained structure (4.5–5.0 μm) with an initial grain size of 25 μm. An analysis of the results of studies of irradiated compositions "coating — copper substrate" allowed us to conclude that they expanded the technological capabilities of the laser method of hardening materials and ensure guaranteed high performance of irradiated products with coatings

Interfacial Coupling Induced Discrete Orientation of Epitaxial Graphene on High‐Index Cu Substrates

AbstractControlled and precise synthesis of materials has been a central pursuit in academia and industry. With the rise of twistronics research, there is growing demand for synthesizing orientation‐controlled 2D materials with atomic precision. Previous theories for 2D materials can predict graphene (Gr) growth on low‐index metal substrates but fail to explain the discrete orientations on most high‐index substrates, inconsistent with experimental data. Using density functional theory (DFT) and ab‐initio molecular dynamics (AIMD), this study explores graphene growth on high‐index substrates, showing that atomic steps do not dominate in trapping C atoms or driving preferential graphene nucleation at high temperatures. Thus, the possibility of intrinsic atomic steps in inducing graphene orientation on high‐index substrates is ruled out. Interfacial coupling strength between graphene and substrates is quantified using a close contact index (CCI), linking atomic structure and electronic states. The coupling between graphene and high‐index Cu surfaces is generally weak, reducing substrate anchoring and increasing graphene orientation dispersion. The extension of this theory to bilayer graphene (BLG) reveals competition between Gr/Cu interfacial coupling and Gr/Gr interlayer coupling, offering insights for controlling twist angles. This theory explains the discrete orientations on high‐index substrates, providing a theoretical basis for synthesizing orientation‐controlled graphene.

Benzimidazole functionalized waterborne polyurethane with excellent mechanical properties, UV and corrosion resistance

Waterborne polyurethane coatings represented a viable substitute for conventional solvent-based coatings, primarily due to their eco-friendliness and straightforward application process. However, these coatings still encounter various issues such as corrosion, aging, and cracking during their actual application. In this research, a range of waterborne polyurethanes (MWPU) was developed by utilizing 4,4′-dicyclohexylmethane diisocyanate (HMDI) for the hard segment and polytetrahydrofuran ether diol (PTMG) as the soft segment, UV absorber benzimidazole (CR-455) as the functional monomer, and 2-mercaptobenzimidazole (MBI) as a corrosion inhibitor. A comprehensive investigation was conducted to evaluate the impact of varying MBI content on the characteristics of MWPU emulsions and films. The findings demonstrated that incorporating MBI led to enhancements in the comprehensive properties of MWPU films. Specifically, when the MBI content reached 1 wt%, MWPU exhibited optimal comprehensive performance, tensile strength reached 26.0 MPa, adhesion reached 2.02 MPa, water absorption measured at 3.2 %. It demonstrated excellent UV resistance and the anti-corrosion performance was additionally impressive, with the impedance modulus reaching 4120 Ω/cm2 at a frequency of 10−2 Hz. This can be mainly attributed to the unique benzimidazole structure in MBI and its ability to form chemical bonds with metal substrates. This innovative approach proposed in this study has the potential to expand applications for waterborne polyurethane in functional coatings.

Electrochemical Corrosion Resistance of Al2O3–YSZ Coatings on Steel Substrates

Ceramic materials as coatings are known to have very good corrosion resistance properties compared to metallic or organic coatings, regardless of environmental conditions. The following samples were used for the experiments: an initial steel substrate and Al2O3 + YSZ (12.5%; 25% and 37.5% wt) atmospheric plasma spray-coated samples. The open circuit potential showed similar average values for all samples coated with ceramic layers, which were slightly higher than the potential of the original uncoated sample. The corrosion current densities (icorr) of all plasma jet sputter-coated systems were very similar and significantly lower than those of the original material. Corrosion rates were much lower in the coated systems due to the chemical inertness of the ceramic coatings, particularly alumina- and zirconia-based coatings. It was observed that ceramic layers improve the corrosion resistance of the metallic material, especially at higher percentages of YSZ in the plasma spray-deposited complex layer. The porosity of the sputter-deposited layers reduced their corrosion resistance due to the contact between the electrolyte solution and the metal substrate created by the interconnection of the pores. The complex equivalent electrical circuit chosen for the analysis of the values led to results in accordance with the experimental parameters.

Electrochemical synthesis and carbon doping of nanostructured iron fluorides from the selection of metal current collectors in lithium-ion batteries

The use of materials that rely on conversion reactions as electrodes in lithium-ion batteries is extensively investigated due to their potential for enhanced capacity compared to traditional electrode materials. Iron fluorides, in particular, present a promising alternative in terms of specific capacity. However, these materials often face challenges related to low intrinsic conductivity. This issue is typically addressed in the literature by doping the active material with carbon particles and reducing the particle size of the active material. This study explores the feasibility of directly integrating conductive carbon from the substrate into the fluoride-based active material during the synthesis process. The synthesis employs a simple anodic method conducted directly on the chosen metallic substrate, which then functions as the current collector in the devices. This approach simplifies the synthesis process, reduces processing time, and eliminates the need for additives and binders at the conventional active material-current collector interface. Two FeF3 layers were electrochemically synthesized on steel substrates with different carbon contents. These layers were evaluated as cathode-active materials for rechargeable lithium-ion batteries. The influence of carbon on the conductivity of the conversion layer was assessed using Electrochemical Impedance Spectroscopy (EIS) with a model based on conductive porous electrodes. Morphological and thickness analyses of the layers showed a strong correlation between increased pore size and layer thickness and the carbon content in the metallic substrate. The optimal performance was observed with the layer on the substrate with higher carbon content. The electrochemical performance of the active material was further evaluated using electrochemical impedance spectroscopy and galvanostatic tests in pouch cells. The conversion layers derived from carbon steel exhibited reduced resistivity and enhanced specific capacitance and cyclability compared to layers formed on pure iron.

Controlling the Selectivity of Reaction Products by Transmetalation on a Ag(111) Substrate.

On-surface synthesis has shown great promise in the precise bottom-up preparation of molecular nanostructures. Apart from the direct C-C coupling reaction pathway, an alternative strategy is to exploit the metal-organic interactions provided by integrated metals for preassembly, which exhibit high reversibility and can anchor specific conformations of molecular precursors, thus allowing the precise construction of nanostructures with improved reaction selectivity. Previous studies have mainly been devoted to the construction of target reaction products through the incorporation of metal atoms, ranging from intrinsic to extrinsic atoms on metal substrates and, more recently, to their cooperative effects. However, the formation of different covalent nanostructures by competitive interactions between intrinsic and extrinsic adatoms remains elusive. Herein, we controlled the selectivity of covalent reaction products from isomerically specific trans-chains to cis-rings, resulting from the transmetalation of intrinsic Ag adatoms to extrinsic Na atoms on a Ag(111) substrate. Our results exhibit the competitive interactions between intrinsic and extrinsic metal atoms in real space and demonstrate their influence on the selectivity of reaction products, which should broaden the regulatory strategies for on-surface synthesis that shed light on the controllable and selective synthesis of target covalent nanostructures.

THE EROSIVE WEAR OF GRAPHENE OXIDE REINFORCEDEPOXY POWDER COATINGS

Powder coatings are organic coatings that protect the metal substrate against corrosion and wear, and playa decorative role. The doping of paints with nanoparticles is intended to create a barrier to corrosive andchemical agents and to increase abrasion resistance. This work tested the erosion resistance of epoxy powdercoating with graphene oxide flakes and polyethylene wax covered with a layer of micro diamonds. Twomethods of testing resistance to abrasive wear were used, in which the conditions are similar to operatingconditions: solid particle impingement (sandblasting) and barrel finisher with ceramic shapes. Mass loss dueto erosion in a sandblaster using glass beads with a diameter of 200 μm for the paint with graphene was muchlower than for the reference sample. The mass loss of the samples was tested after 15, 30, and 60 seconds ofabrasive jet operation. The surface texture was analyzed during the process and after the test. The test in thebarrel finisher was carried out twice for different times: for the first series weight loss was measured after 30,90, and 210 minutes, for the second Vickers hardness at 40 g load after 90 and 210 minutes. The tests showedthat the epoxy coating with the addition of graphene oxide has a much higher resistance to erosion under theinfluence of an abrasive stream than the reference paint, and a similar resistance to erosion in a containersmoother. It was found that the paints showed a higher Vickers hardness after the wear test.

Effects of plasma modification of hybrid Kevlar/PTFE fabric surface on adhesive and tribological properties

A study on surface modification with Ar and N2 plasma of hybrid PTFE/Kevlar fabrics was conducted. The chemical and molecular structure changes of the PTFE and Kevlar fibers were analyzed as well as their surface properties i.e. roughness, morphology, wettability, and surface energy. The results show that the treatment caused etching and defluorination on the PTFE fiber surface improving its hydrophilicity, surface energy, and adhesion of the Kevlar fiber without weakening its mechanical strength. The plasma treatment contributed to improving the interfacial strength of the composite, enhancing its adhesion to the metal substrate. The long-term friction and wear behaviors were also investigated to obtain a better understanding of the tribological properties of the hybrid Kevlar/PTFE-epoxy/phenolic composites. The results illustrate that the treated fabric composite showed better wear resistance and self-lubrication performance due to the improved wettability and adhesive properties of the fabrics. The modification effect of the sample treated with Ar plasma is better; however, N2 is economical, and the effect is also significant.

Theoretical Design of Smart Bionic Skins with Self-Adaptive Temperature Regulation.

Thermal management presents a significant challenge in electric design, particularly in densely packed electronic systems. This study proposes a theoretical model for radiative bionic skin that emulates human skin, enabling the self-adaptive modulation of the thermal exhaustion rate to maintain homeostasis for objects covered by the skin in fluctuating thermal environments. The proposed artificial skin consists of phase change material (VO2) nanoparticles embedded in a low-loss matrix situated on a metallic substrate with a minimal thickness of several micrometers. The findings from our theoretical analyses indicate that substantial alterations in thermal radiation power around the phase transition temperature of 340 K enable a silicone substrate to sustain a relatively stable temperature, with variations confined to ±6 K, despite external heat fluxes ranging from 150 to 450 W/m2. Furthermore, to improve the spectral resemblance to natural skin, a plasmonic surface composed of self-assembled silver nanocubes is incorporated, allowing for modifications to the visible light properties of the bionic skin while maintaining its infrared characteristics. This theoretical investigation offers a cost-effective and conformal approach to the design of ultra-compact, fully passive, and versatile thermal management solutions for robotic systems and related technologies.

Hybrid package integration strategy for silicon ICs operating beyond 200 GHz

Abstract This paper proposes an innovative hybrid package integration strategy compatible with silicon-based technologies. It is evaluated beyond 200 GHz by the integration of a WR3 back-to-back waveguide-to-suspended stripline transition designed in BiCMOS technology, relying on metallic split-block package and organic laminate substrate. Simulated insertion loss below 3 dB is observed in the 220–320 GHz frequency band, competing with reported traditional solutions using III–V substrates. The achieved performances lead to promising perspectives for low-cost silicon packaging solutions beyond 200 GHz.

Design and Verification of Multiphase Multilevel Traction Inverter

The paper presents the practical design and implementation of a three-level neutral point clamped (TNPC) six-phase inverter rated at 100 kVA. The study initiates with prior work review, whereby most research work done earlier was mainly simulation-based. Based on the simulation results, this paper focuses on the practical aspects of inverter design, such as the development of a power board on an Insulated Metal Substrate, a gate driver board, an interconnect board, and the main control board. An inverter physical prototype has been built and tested at 500 V and 20 kW of output power. The SiC semiconductor technology is the base of the inverter, which represents the main merit of the work. Finally, high power density, compact design, and high efficiency are shown, which are major contributions of the paper. Tests performed proved that the designed converter was operating reliably and efficiently. While a simple Sinusoidal Pulse Width Modulation (SPWM) control algorithm has been implemented, the overall performance of the inverter showed great promise for higher-power applications. Compact and high-efficiency TNPC converters are developed for meeting increasing demands of advanced energy, automotive, and industrial applications.

Achieving precise graphenization of diamond coatings below the interfacial thermal stress threshold

Abstract Diamond coatings possess numerous excellent properties, making them desirable materials for high-performance surface applications. However, without a revolutionary surface modification method, the surface roughness and friction behavior of diamond coatings can impede their ability to meet the demanding requirements of advanced engineering surfaces. This study proposed the thermal stress control at coating interfaces and demonstrated a novel process of precise graphenization on conventional diamond coatings surface through laser induction and mechanical cleavage, without causing damage to the metal substrate. Through experiments and simulations, the influence mechanism of surface graphitization and interfacial thermal stress was elucidated, ultimately enabling rapid conversion of the diamond coating surface to graphene while controlling the coating’s thickness and roughness. Compared to the original diamond coatings, the obtained surfaces exhibited a 63%–72% reduction in friction coefficients, all of which were below 0.1, with a minimum of 0.06, and a 59%–67% decrease in specific wear rates. Moreover, adhesive wear in the friction counterpart was significantly inhibited, resulting in a reduction in wear by 49%–83%. This demonstrated a significant improvement in lubrication and inhibition of mechanochemical wear properties. This study provides an effective and cost-efficient avenue to overcome the application bottleneck of engineered diamond surfaces, with the potential to significantly enhance the performance and expand the application range of diamond-coated components.