Metallic Side Research Articles

Molecular Simulation of Electrode-Solution Interfaces.

Many key industrial processes, from electricity production, conversion, and storage to electrocatalysis or electrochemistry in general, rely on physical mechanisms occurring at the interface between a metallic electrode and an electrolyte solution, summarized by the concept of an electric double layer, with the accumulation/depletion of electrons on the metal side and of ions on the liquid side. While electrostatic interactions play an essential role in the structure, thermodynamics, dynamics, and reactivity of electrode-electrolyte interfaces, these properties also crucially depend on the nature of the ions and solvent, as well as that of the metal itself. Such interfaces pose many challenges for modeling because they are a place where quantum chemistry meets statistical physics. In the present review, we explore the recent advances in the description and understanding of electrode-electrolyte interfaces with classical molecular simulations, with a focus on planar interfaces and solvent-based liquids, from pure solvent to water-in-salt electrolytes.

Asymmetric sheet-metal V-bending applying separate dies with different velocities for diversified bending shapes and operability

This paper presents a new bending method of sheet metal for forming diversified shapes and enhancing operability. The method, “asymmetric bending”, uses a punch and a pair of front and back dies. While the punch moves down for bending, the two dies move at different velocities so that the movement of the front side of the sheet metal can severely be restricted. The front side of the metal can be deformed with diversity in advance as it can escape from geometric interference with the bending tools. The method also improves operability and safety for operators due to the movement restriction.

Anchoring of a hydrophobic heptapeptide (AFILPTG) on silica facilitates peptide unfolding at the abiotic-biotic interface.

A hydrophobic heptapeptide, with sequence AFILPTG, as part of a phage capsid protein binds effectively to silica particles carrying negative charge. Here, we explore the silica binding activity of the sequence as a short polypeptide with polar N and C terminals. To describe the structural changes that occur on binding, we fit experimental infrared, Raman and circular dichroism data for a number of structures simulated in the full configuration space of the hepta-peptide using replica exchange molecular dynamics. Quantum chemistry was used to compute normal modes of infrared and Raman spectra and establish a relationship to structures from MD data. To interpret the circular dichroism data, instead of empirical factoring of optical activity into helical/sheet/random components, we exploit natural transition orbital theory and specify the contributions of backbone amide units, side chain functional groups, water, sodium ions and silica to the observed transitions. Computed optical responses suggest a less folded backbone and importance of the N-terminal when close to silica. We further discuss the thermodynamics of the interplay of charged and hydrophobic moieties of the polypeptide on association with the silica surface. The outcomes of this study may assist in the engineering of novel artificial bio-silica heterostructures.

Wetting and Bonding Behavior of SUS 304 Metal and Forsterite Ceramic with a PbO-Bi<sub>2</sub>O<sub>3</sub>-B<sub>2</sub>O<sub>3</sub>-ZnO Glass Frit

The joining behavior of metal to ceramic was investigated using glass frit media. Glass frit with a composition of 71.5PbO-24Bi2O3-2.5B2O3-1.5ZnO-0.5SiO2 in mol. % was designed to bond forsterite ceramic and SUS 304 metal. The glass frit demonstrated a glass transition temperature of 250°C and a thermal expansion coefficient of 15.9 x 10-6/°C, which isbetween the values of SUS 304 (17.8×10-6/°C) and forsterite (9.9×10-6/°C). The contact angle was smaller than 90° at a temperature of 460°C. Redox reaction at the interface between forsterite and SUS304 was found to appear when the electrons in the metal part moved toward the glass part and the oxygen ions in glass moved to the metal side. The decrease of the surface tension due to the PbO solubility on the forsterite side contributed to the better wetting behavior at low temperature. Due to the ionic bonding nature, the glass was able to chemically react with forsterite ceramic and form a rough boundary. The Fe metal in the SUS 304 was oxidized to form FeO ceramic. A thin FeO layer on the SUS 304 surface helped the glass frit to wet the SUS 304, and clear tight bonding between the glass and SUS 304 was achieved.

Static and Fatigue Properties of Rotary Friction Welded Dissimilar AA7075/AA5083 Aluminium Alloy Joints at Various Rotational Speeds

In the present study, dissimilar rotary friction welding of AA7075/AA5083 aluminium alloy rods having diameter of 15 mm was conducted at various rotational speeds in the range of 370 to 2500 rpm. The aim of this research is to gain the best weld mechanical properties in particular weld tensile strength and fatigue performance. Several experiments were carried out including macro and microstructural examinations, microhardness measurements, tensile tests and fatigue tests combined with residual stress measurements. Results show that at higher rotational speeds, typically 540 rpm or above, the dissimilar AA7075/AA5083 rotary friction weld joints reveal static fracture in the AA5083 base metal side indicating the joint efficiency is more than 100%. It seems that the best weld joint is achieved at the rotational speed of 1200 rpm in which the friction heat is sufficient to form metallurgical bonding without causing excessive flash and burn-off shortening. In such a condition, the fatigue strength of the weld joint is slightly higher than its AA5083 base metal but it is lower compared to another AA7075 base metal. It is confirmed that the crack origin is observed at the interface followed by fatigue crack growth towards AA5083 side and the growth of crack seems to be controlled by microstructure and residual stress.

Behaviour of the conductivity in metallic 70 Ge:Ga close to the metal-insulator transition

The electrical transport properties in sample 1 of impurity concentration n=xx of the 70Ge: Ga system are studied in the absence of a magnetic field and at low temperature in the range 0.53 to 0.017 K. It is noted that the electrical conductivity of sample 1 exhibits a metallic behavior. We found that the exponent S is equal to 0.5 (σ=σ(T=0)+mTs). This result is in agreement with the theory of weak localization (WL) at 3D and the theory of electronelectron interactions (EEI). We also found that sample 1 is located near the metal-insulator transition (MIT) of the metallic side.

Metal-insulator Transition in \({}^{70}\)Ge: Ga Semiconductor by Applying the Scaling Laws

In this article, we focus on the scaling theory of Abraham et al. without and with a magnetic field on the metallic side of the Metal-Insulator Transition (MIT) for the three-dimensional system \({}^{70}\)Ge: Ga, at very low temperatures. In particular, we have determined the zero temperature conductivity critical exponent when the MIT transition occurs with the variation of the impurity concentration \((\upsilon=0.503)\) and with the application of a magnetic field \((\upsilon=1.06)\). We have also estimated the critical magnetic field \(B_C\) that separates the metallic behavior \((B<B_C)\) from the variable-range hopping regime \((B>B_C)\). The data are for a \({}^{70}\)Ge: Ga sample prepared and reported by Itoh et al., Physical Review Letters 77 (1996), 4058 and Watanabe et al., Physical Review B 60 (1999), 15817.

Characterization of composite laminate with copper and AISI304 made by a diffusion bonding process

The composite laminate assembly was made by stacking alternate layers of AISI304 and copper foils. The copper and AISI304 foils of 0.1 mm thick were placed one above the other and during diffusion bonding experiments. The bonding parameter temperature was varied as 850, 900 and 925 ⁰C, constant pressure of 4 MPa, and bonding time of 60 min was maintained for all the experiments. The laminated joints were characterized by optical, scanning electron microscopy for grain size measurement and phase identification. Electron microprobe analysis (EPMA) was performed at the joint region for elemental analysis across the interface and into the base metals. At the AISI304 base metal side a maximum hardness of 342.6 VHN and at the copper base metal side, it was 152.5 VHN. For the sample bonded at 925 ⁰C, the shear strength was a maximum of 72.8 MPa. X-Ray Diffraction Analysis (XRD) revealed the presence of phases γ-Fe and γ-Cu, and intermetallic compounds such as FeCu 4 , Cu 2 CrNi, sigma (σ)-phase and oxide CuO.

Crossover between ballistic and diffusive regime in 2D SiGe quantum well

In this manuscript, we report a theoretical investigation of the magneto-conductivity (σ(B,T)) in the metallic side (where dσ/dt<0) of a low densities 2D hole system in SiGe at very low temperature (below 2K). We have reanalyzed the experimental data already prepared and published by Drichko et al. in [23]. The purpose of this study is to determine the dominant electronic transport regime by confronting the experience with current theories. Based on the Fermi-liquid approach and the ZNA theory, we have able to determine the régimes of electronic transport in 2D p-SiGe quantum well. Indeed, the careful analysis of the results shows the coexistence of the two electronic transport regimes: ballistic and diffusive and, above all, a transition from one regime to the other. At low magnetic field (less than 6T), the Fermi liquid parameter values are found negative and positive for the highest values of the parallel magnetic field. The results are consistent with recent works on graphene sample and other similar samples.

Modeling Unconventional Superconductivity at the Crossover between Strong and Weak Electronic Interactions.

High-temperature superconductivity emerges in many different quantum materials, often in regions of the phase diagram where the electronic kinetic energy is comparable to the electron-electron repulsion. Describing such intermediate-coupling regimes has proven challenging as standard perturbative approaches are inapplicable. Here, we employ quantum MonteCarlo methods to solve a multiband Hubbard model that does not suffer from the sign problem and in which only repulsive interband interactions are present. In contrast to previous sign-problem-free studies, we treat magnetic, superconducting, and charge degrees of freedom on an equal footing. We find an antiferromagnetic dome accompanied by a metal-to-insulator crossover line in the intermediate-coupling regime, with a smaller superconducting dome appearing in the metallic region. Across the antiferromagnetic dome, the magnetic fluctuations change from overdamped in the metallic region to propagating in the insulating region. Our findings shed new light on the intertwining between superconductivity, magnetism, and charge correlations in quantum materials.

Study of Transport Phenomenon in Amorphous RexSi1 – x Thin Films on the Both Sides of the Metal–Insulator Transition at Very Low Temperatures

In this work, we study the electrical conductivity behaviors on the both sides of the metal-insulator transition (MIT) in RexSi1 – x amorphous thin films at very low temperature. In fact, our investigation re-analyzed the experimental measurements of RexSi1 – x obtained by K.G. Lisunov et al. On the insulating side of the MIT, the electrical conductivity can be interpreted by the existence of the variable range-hopping regime. However, on the metallic side of the MIT, the electrical conductivity is mainly due to electron–electron interactions and low localization effects.

Observation of Interfacial Degradation of Solid Electrolytes Against Lithium Metal and Layered Transition Metal Oxides Via in Situ Electrochemical Raman Microscopy

Solid state batteries, utilizing ceramic solid-state electrolytes, are attracting intensive research for their improved safety and possible higher energy density. Solid-state electrolytes can have comparable ionic conductivities to the liquid carbonate electrolytes, for example, Li10GeP2S12 with an ionic conductivity at 1.2 × 10-2 S cm-1 at room temperature. However, the performance of solid state batteries requires improvement to enable long term cycling. The interface instability between the solid electrolytes and electrodes is one of the limiting factors for the utilization of solid state batteries. Traditionally, mostly ex situ surface characterisation techniques such as Raman or x-ray photoelectron spectroscopy can be used to study the buried interfaces within all-solid-state batteries. Raman microscopy, in particular, is a powerful surface characterisation technique and has been used to detect structural and chemical information on electrode interfaces primarily in liquid electrolyte cells. The ability to do in situ observation of the solid electrolyte – electrode interface is paramount for understanding the performance and design interfacial strategies for solid state batteries.In this study, in situ Raman microscopy and ex situ Raman imaging were adopted to study the interfacial evolution during cycling covering β-Li3PS4, Li10GeP2S12, and Li6PS5Cl electrolytes against Li metal and LiCoO2 or LiNi0.6Mn0.2Co0.2O2. Degradation products at both Li metal side and cathode side were detected. For example, the degradation products of the interface Li6PS5Cl at both Li metal side and LiCoO2 side were resolved [1]. Li2S was formed by Li deposition onto Li6PS5Cl and there were polysulfides, and P2Sx species formation between Li6PS5Cl and LiCoO2 interface. In situ Raman results were correlated with ex situ Raman microscopy from cycled cells. The ex situ Raman imaging also directly visualised the distribution of degradation products. We will demonstrate that in situ Raman microscopy as a powerful tool in the study of electrode/electrolyte interfaces within the solid-state cell. The technique can be translated to alternative solid electrolyte – cathode combinations to understand the operando interfacial evolutions for designing improved all-solid-state batteries. Y Zhou, C Doerrer, J Kasemchainan, P.G. Bruce, M. Pasta, L.J. Hardwick, Batteries & Supercaps 3(2020)1-7.

Inductance Model of a Backside Integrated Power Inductor in 2.5D/3D Integration

Inductor integration is of vital importance for miniaturization of power supply on chips. In this paper, a backside integrated power inductor is presented. The inductor is placed at the backside of a silicon interposer and connected to the front side metal layers by through-silicon vias (TSVs) for area saving and simple fabrication. An inductance model is proposed to effectively capture the total inductance of the power inductor by an analytical method. The results obtained from the analytical model and finite element method exhibit good agreement with various design parameters and the error between the proposed model and measurement remains less than 7.91%, which indicates that the proposed model can predict the inductance suitably.

Mode coupling enhancement from dielectric to plasmonic waveguides

Efficient dielectric–plasmonic interconnect is significant in the design of future electronic–photonic integrated circuits that deal with large data transfer. We propose three designs and analysis of small-footprint couplers that are located at the interface between dielectric and plasmonic waveguides. To the best of our knowledge, our proposed couplers outperform all the works reported in the literature in several aspects including size and coupling efficiency (CE). Our results indicate that the optimum dimensions of the proposed couplers are determined based on whether the coupler is located in the metal side or dielectric side, or the coupler extends equally in both types of materials. The proposed couplers work over a broad frequency range achieving a CE above 88% at the optical communications wavelength 1550 nm. In addition, our results indicate that the CE can be further increased to above 93% by increasing the width of the dielectric waveguide before it is connected to the coupler. Moreover, our proposed designs provide a considerable alignment tolerance, which is needed when aligning the dielectric waveguide to the metal–dielectric–metal waveguide. Our proposed couplers have an impact on the design and miniaturization of nanoscale all-optical devices.

The Electronic and Physical Structure Evaluation of MoS2(1−x)Te2x Alloy Fabricated with Co-Sputtering and Post-Deposition Annealing in Chalcogen Ambient

In recent years, the fabrication of transition metal dichalcogenide (TMD) alloys is drawing attention due to their controllable bandgap. Fabrication of MoS2(1−x)Te2x is expected to be difficult due to its thermal instability although it shows wide tunable bandgap range. In this study, MoS2(1−x)Te2x fabrication is carried out by sputtering and post-deposition thermal treatment in chalcogen ambient. Films without phase separation were successfully fabricated. It was revealed that the band structure changes according to the chalcogen ratio. The valence band maximum shifted non-linearly showing bowing effect, while the conduction band minimum remained almost unchanged. It was considered that such bowing behavior of valence band minimum is attributed to the electronegativity difference between S and Te. The invariant nature of the conduction band was attributed to the fact that there is no such competition of electronegativity for the metal side whose electron orbitals mainly contribute to the conduction band formation. The maximum shift in the valence band maximum was as large as 0.5 eV. It was also revealed that suppressing the chalcogen deficiency may prevent phase separation. The wide tunability in the band structure and the possibility of realizing the uniform alloy promises the materials high applicability to different electronic devices.

Transient solution of temperature field of conjugate laminar forced convection heat transfer in functionally graded hollow cylinder

AbstractIn this study, the numerical analysis of conjugate heat transfer of laminar flow in a functionally graded hollow cylinder (FGHC) made of metal/ceramic for a two‐dimensional fluid and wall conduction subject to Newton boundary condition is considered. The fluid and FGHC energy equations are coupled through the continuity of temperature and heat flux at the inner wall‐fluid interface while the outer surface is subject to convective heat transfer. The continuity, momentum, and energy equations of the fluid are discretized using the finite volume approach. The effects of fluid and functionally graded material parameters, such as volume fraction index, volume composition, time history, wall‐to‐fluid thermal diffusivity ratio, wall‐to‐fluid thermal conductivity ratio, Biot number, Peclet number, and Prandtl number are investigated on the temperature field in the FGHC. The result shows that on account of the inhomogeneity of the material property, the volume fraction index has a significant effect on the other parameters and the temperature variation along the thickness. The lower the volume fraction index, the higher the inner wall (metal side) temperature, and the temperature gradient along the thickness. However, except for the variation in the wall‐to‐fluid thermal conductivity ratio, the lower the volumetric fraction, the lower the outer wall (ceramic side) temperature distribution.

Electromagnetic-pulse-induced acoustic testing for nondestructive testing of plastic composite/metal adhesive bonding

For the hydrogen tanks of type 2 and 3, the metal lining and composite wrapping are bonded together by adhesive. To ensure the safety of these tanks for long-term use, nondestructive testing (NDT) and nondestructive evaluation (NDE) of their plastic composite/metal adhesive bonds are required. However, up to now, there is no effective NDT method for the debonding detection of hydrogen tanks of type 2 and 3. In this study, we propose the use of electromagnetic-pulse-induced acoustic testing (EPAT) to generate guided waves in plastic composite/metal adhesive bonding to detect debonding in adhesive parts. The EPAT method can excite the electromagnetic force from outside of the plastic composite material without contact, thereby directly exciting sound waves on the metal contacting the plastic composite. Through reasonable design, the intensity of the pulsed magnetic field can pass through a very thick plastic composite material and directly induces guided waves in the inner side metal. Therefore, EPAT method has the potential to detect the debonding of plastic composite/metal adhesive bonding in hydrogen tanks of type 2 and type 3 at the site of use. EPAT testing of acrylic/aluminum, glass-fiber-reinforced plastic/aluminum, and carbon-fiber-reinforced plastic/aluminum specimens was performed. The testing signals were analyzed in the time domain and frequency domain. The results indicate that the time-domain signals exhibited guided wave dispersion characteristics. In addition, the guided wave signals showed significant differences between the specimen with debonding and that without debonding, which could be used for the detection of debonding. In addition, different frequency guided waves had different sensitivities to debonding defects.

Microstructure and Mechanical Properties of Laser Butt Welded Laser Powder Bed Fusion Manufactured and Sheet Metal 316L Parts

Laser weldability of dissimilar parts produced with different techniques from 316L material was studied in this paper. Butt joint welding was performed on pairs of sheet metal and parts produced with additive manufacturing by laser powder bed fusion. The effect of heat treatment was also considered and the stage in which it was applied. The experiments showed very good weldability and the results were verified with microstructural analysis and tensile testing with digital image correlation equipment. Microstructures of the welds revealed morphology consisting of equiaxed and columnar grains in somewhat random orientation. Tensile tests showed that the 75% higher yield strength of the printed material compared to sheet metal leads to uneven elongation of the dissimilar joint and the part breaks from the sheet metal side. Hardness measurements showed higher values for the printed side (225 HV) compared to sheet metal side (170 HV). All the welded specimens broke outside of the welds showing a good weldability independent of the heat treatment stage.

Electron transmission across normal metal-strained graphene–normal metal junctions

The transmission of the electron across the single normal metal–graphene (NG) and normal-metal–graphene–normal-metal (NGN) junctions has been investigated. For the single NG junction, the profile of the maximum transmission bears similarity to that of the conductance of the system and the minor effect of the incidence energy on transmission is found in conductance of the single NG junction. Concerning with NGN junction, the increase of strain strength always induces more resonance peaks at different angles in transmission and can therefore enhance the conductance. The increase of length of the middle graphene segment can accommodate more quasi-resonance states, leading to the more resonance peaks and richer structures in transmission. In both single NG and NGN junctions, the increase of the wavefunction period on metal side(s) can be observed due to the enhancement of strain strength, which can serve as the sensor for the detection of the strain strength in graphene.

Manifestation of strong correlations in transport in ultraclean SiGe/Si/SiGe quantum wells

We observe that in a strongly interacting two-dimensional electron system in ultra-clean SiGe/Si/SiGe quantum wells, the resistivity on the metallic side near the metal-insulator transition increases with decreasing temperature, reaches a maximum at some temperature, and then decreases by more than one order of magnitude. We scale the resistivity data in line with expectations for the transport of strongly correlated Fermi systems and find a nearly perfect agreement with theory over a wide range of electron densities.