Real Metal Research Articles

Strength of structural elements with cracks

In almost every detail, despite careful control at all stages of production, there may be cracks. The reasons for their occurrence can be very different, including the shape and size of the part, the conditions and nature of loading, the nature of the environment, defects of a crystal lattice, the possible presence of non-metallic inclusions adverse forms, structure and grain size, depending on the technology upstream processing, fatigue, etc. The reliability of the equipment is determined by the correct choice of material and taking into account the operating conditions, including the level and nature of loading. The paper provides a comparative review of the main approaches for selecting strength criteria for structural elements with cracks. The energy and power strength criteria are considered. The energy criterion of A. A. Griffiths considered a perfectly brittle material without taking into account the plasticity reserve of real metal materials. The force criterion allows us to estimate the value of the stress taking into account the critical moment of loading, at which unstable destruction begins due to the reserve of elastic energy. It is shown that the transition of steel from a plastic state to a brittle one is influenced by the test temperature, the type and speed of deformation, and changes in the chemical composition and mode of heat treatment. Thus, when choosing a certain strength criterion, you should take into account the operating conditions and the degree of responsibility of the structure.

Destruction of real metal surface due to EM-field localization in fractal system of cracks

A new physical mechanism is proposed in order to elucidate how properties of a metal surface can differ from those of bulk metal. It is related with localization of an external electromagnetic field in the cracks on the surface. The localization decreases Van der Waals attraction between opposite sides of the cracks. This causes the appearance of new cracks. When the system of cracks has fractal structure, this self-sustaining process leads to the appearance of a finite volume interface between the metal sample and vacuum. This additional volume manifests itself as a swelling and destruction of the sample.

Thermal Analysis of Photoelectron Emission (PE) and X-ray Photoelectron Spectroscopy (XPS) Data for Iron Surfaces Scratched in Air, Water, and Liquid Organics

Little is known about the temperature dependence of electron transfer occurring at real metal surfaces. For iron surfaces scratched in seven environments, we report Arrhenius activation energies obtained from the data of photoelectron emission (PE) and X-ray photoelectron spectroscopy (XPS). The environments were air, benzene, cyclohexane, water, methanol, ethanol, and acetone. PE was measured using a modified Geiger counter during repeated temperature scans in the 25–339 °C range under 210-nm-wavelength light irradiation and during light wavelength scans in the range 300 to 200 nm at 25, 200, and 339 °C. The standard XPS measurement of Fe 2p, Fe 3p, O 1s, and C 1s spectra was conducted after wavelength scan. The total number of electrons counted in the XPS measurement of the core spectra, which was called XPS intensity, strongly depended on the environments. The PE quantum yields during the temperature scan increased with temperature, and its activation energies (ΔEaUp1) strongly depended on the environment, being in the range of 0.212 to 0.035 eV. The electron photoemission probability (αA) obtained from the PE during the wavelength scan increased with temperature, and its activation energies (ΔEαA) were almost independent of the environments, being in the range of 0.113–0.074 eV. The environment dependence of the PE behavior obtained from temperature and wavelength scans was closely related to that of the XPS characteristics, in particular, the XPS intensities of O 1s and the O2− component of the O 1s spectrum, the acid–base interaction between the environment molecule and Fe–OH, and the growth of non-stoichiometric FexO. Furthermore, the origin of the αA was attributed to the escape depth of hot electrons across the overlayer.

Dynamics and causality in distribution between spot and future precious metals: A copula approach

This paper examines the dependence structure and the Granger causality in distribution (GCD) between spot and future returns of precious metals (gold, silver, and platinum) via copula modelling. This study considers the evidence on real precious metals returns from Jan 2, 2002 to Jan 13, 2017. Throughout literature, the use of copula in precious metals markets is still limited. Indeed, unlike linear methods, using a copula-based approach has several attractive advantages. Our empirical findings show the following: (1) Using static and dynamic copulas, we find that the dependence between the spot and the future returns of precious metals is relatively strong and time varying with a strong tail dependence for all pairs (3) Using independence test based on the empirical copula, we detect a unidirectional GCD from future to spot precious metals market during normal times. This results means that past information from the future returns improve forecasts of spot returns. However, the causal relationship seems to be bidirectional in the case of gold and platinum during crisis periods.Our findings are important to investors for investigating hedging strategies since the efficacy of a hedging strategy is dependent on the price discovery mechanism. Hence, they should take the above findings into consideration to make optimal decisions, especially during periods of marked instability.

Design of multipeak one-way light absorber based on one-dimensional magnetophotonic crystal

The study of magnetophotonic crystals is usually based on its reflection and transmission of light waves, but its absorption properties are rarely studied. Considering the current high absorptivity of one-way absorbers has one absorption peak, and the optical constants of magnetophotonic crystals are all ideal approximation, we introduce the practical optical constants of silicon carbide (SiC) into the magnetophotonic crystals model. The optical properties are investigated in visible wavelength based on the transformation matrix method, and some parameter effects are also discussed in detail, such as the incidence angle and the thickness of defect layer. The one-dimensional (1-D) magnetophotonic crystal structure was systematically optimized. Then a multipeak one-way light absorber composed of real semiconductor and metal based on 1-D magnetophotonic crystal is further proposed, which makes the channel position of perfect nonreciprocal absorption controllable and the number increased; the influence of incident conditions on the absorption efficiency is greatly weakened and the universality and flexibility of one-way absorber in practice are greatly enhanced. The achievement provides new ideas for the study of nonreciprocal absorbers.

Universal slow plasmons and giant field enhancement in atomically thin quasi-two-dimensional metals

Plasmons depend strongly on dimensionality: while plasmons in three-dimensional systems start with finite energy at wavevector q = 0, plasmons in traditional two-dimensional (2D) electron gas disperse as omega _p sim sqrt q. However, besides graphene, plasmons in real, atomically thin quasi-2D materials were heretofore not well understood. Here we show that the plasmons in real quasi-2D metals are qualitatively different, being virtually dispersionless for wavevectors of typical experimental interest. This stems from a broken continuous translational symmetry which leads to interband screening; so, dispersionless plasmons are a universal intrinsic phenomenon in quasi-2D metals. Moreover, our ab initio calculations reveal that plasmons of monolayer metallic transition metal dichalcogenides are tunable, long lived, able to sustain field intensity enhancement exceeding 107, and localizable in real space (within ~20 nm) with little spreading over practical measurement time. This opens the possibility of tracking plasmon wave packets in real time for novel imaging techniques in atomically thin materials.

General framework for testing Poisson‐Voronoi assumption for real microstructures

AbstractModeling microstructures is an interesting problem not just in materials science, but also in mathematics and statistics. The most basic model for steel microstructure is the Poisson‐Voronoi diagram. It has mathematically attractive properties and it has been used in the approximation of single‐phase steel microstructures. The aim of this article is to develop methods that can be used to test whether a real steel microstructure can be approximated by such a model. Therefore, a general framework for testing the Poisson‐Voronoi assumption based on images of two‐dimension sections of real metals is set out. Following two different approaches, according to the use or not of periodic boundary conditions, three different model tests are proposed. The first two are based on the coefficient of variation and the cumulative distribution function of the cells area. The third exploits tools from to topological data analysis, such as persistence landscapes.

High-Throughput Computational Screening of 12,351 Real Metal–Organic Framework Structures for Separation of Hexane Isomers: A Quest for a Yet Better Adsorbent

Adsorption-based separation of hexane isomers have been investigated widely by researchers across the globe employing variety of adsorbent materials including zeolites and metal–organic frameworks ...

Resonant Transmission Through a Single Subwavelength Slit for Varied Metallic Permittivities and Its Modal Orthogonality

This article investigates resonant transmission phenomena through a single metallic subwavelength slit when the permittivity of a real metal varies. The single metallic slit is utilized as a metal–insulator–metal waveguide, and a mode-matching technique is employed to obtain the transmitted power. The periodic resonant transmission phenomena (in terms of the metallic plate thickness) are solved, and the resonances can be understood by their guide wavelengths. Even when the permittivity of the real metal includes imaginary parts (i.e., metal with loss), the resonant transmittances are obtained. However, the peaks of the transmittances decrease, as the plate thickness increases. The orthogonal relationship of an incomplete orthogonal set is maintained despite metallic loss (given a relatively small amount of loss), due to the complex permittivity of the real metal.

ГЕОДЕЗИЧЕСКИЙ МОНИТОРИНГ БОЛЬШЕПРОЛЕТНЫХ СООРУЖЕНИЙ С ПРОСТРАНСТВЕННОЙ МЕТАЛЛИЧЕСКОЙ КОНСТРУКЦИЕЙ

The article draws the estimation of geodetic measurement results and conclusions, obtained at observation of deformations during the construction and exploitation of large span structure with bridging of space shell type, located on the territory with hazardous natural and seismic processes and hot climate. On the basis of measurement results of the vertical and horizontal deformation constituents the analysis of actual behavior of the constructions in these conditions was performed. Estimating the deformations on different stages and environmental parameters one can set critical parameters and tolerance for the behavior of a real spatial metal structure. The article draws the data of three observation cycles carried out during the construction process and three ones performed after the start of operation. The observations allowed making a conclusion that the structure undergoes little appropriate deformations, which correspond to the designed ones.

Influence of recrystallization annealing regime on the formation of a fine-grained structure in structural steels

The analysis of the main factors affecting the reliability and safety of welded metal structures in long-term operation is carried out. The features of obtaining a fine-grained structure due to recrystallization annealing and the main factors affecting the degree of dispersion of the formed microstructure are considered. For low-carbon steel 08ps and low-alloy steel 09G2S, optimal recrystallization annealing regimes have been developed with the aim of obtaining final structures with a given degree of dispersion, typical for real building metal structures. It was found that the degree of dispersion of the obtained microstructures depends on the heating temperature, the initial structure, and the chemical composition of the steels.

Multifunctional Silanization Interface for High‐Energy and Low‐Gassing Lithium Metal Pouch Cells

AbstractLithium (Li) metal has attracted unprecedented attention as the ultimate anode material for future rechargeable batteries, but the electrochemical behavior (such as Li dendrites and gassing problems) in real Li metal pouch cells has received little attention. To achieve realistic high‐energy Li metal batteries, the designed solid electrolyte interface to suppress both Li dendrites and catastrophic gassing problems is urgently needed at cell level. Here, an efficient multifunctional silanization interface (MSI) is proposed for high‐energy Li metal pouch cells. Such an MSI not only guides uniform nucleation and growth of Li metal but also suppresses interfacial parasitic reactions between Li metal and electrolyte. As a result, under harsh conditions (negative to positive electrode capacity ratio of 2.96 and electrolyte weight to cathode capacity ratio of 2.7 g Ah−1), a long‐running lifespan (over 160 cycles with a capacity retention of 96% at 1 C), and low‐gassing behavior of realistic high‐energy Li metal pouch cell (1 Ah, 300 Wh kg−1) is achieved. This work opens a promising avenue toward the commercial applications of high‐energy Li metal batteries.

Effect of helical micro-fins on two-phase flow behavior of R410A evaporating in horizontal round tubes obtained through visualization

This paper presents a new approach in visualization of the evaporation mechanism and the two phase flow. The visualization test section is a transparent micro-fin tube made by 3D printing. The 3D printing technology helps reproduce the real geometry in commercial metal micro-fin tubes. Even though the wall material is different from the real metal, this new method provides a more complete understanding of the mechanisms of flow boiling and the heat transfer enhancement due to micro-fin geometry. To investigate the effect of micro-fin geometries on two-phase flow behavior, R410A flow boiling experiments are conducted at 10 °C saturation temperature and visualized through a clear smooth tube and micro-fin tubes of 0°, 10° and 18° helix angles. The results showed that the annular flow pattern in the helical micro-fin tube occurred at a lower vapor quality than the smooth and axial micro-fin tubes. Helix angle affects the transition boundary of stratified wavy flow to wavy annular flow, which shifts downward (to lower mass flux and vapor quality conditions) as the helix angle increases. Other transitions are not significantly affected by the helix angle. Helical micro-fin tubes with different groove directions were made to understand the flow behavior on the upward side and downward side of the tube.

The Influence of Mechanical Stresses in a D16 Aluminum-Alloy Plate on the Generation of Acoustic Waves under Laser Irradiation

Laser generation of ultrasound in metals with internal mechanical stresses has been analyzed. The characteristics of a photoacoustic signal in the vicinity of a hole in a D16 alloy plate under the action of mechanical stresses have been studied. The discrepancy between the experimental results and predictions of the thermodynamic model for the dependence of the thermal expansion coefficient on mechanical stresses was found. For proper description of the signal characteristics in real metals, we have proposed to take into account the influence of the electron subsystem on laser generation of acoustic waves.

An improved background segmentation algorithm for fringe projection profilometry based on Otsu method

In fringe projection profilometry, there always exist background and shadow areas in the captured fringe images. To improve the data quality, these areas should be recognized and deleted before the point cloud is reconstructed. For the existing algorithms, it is a nontrivial task to obtain a reasonable threshold to recognize the background and shadow areas from the fringe images. An inappropriate threshold usually leads to a misclassification of the object and background/shadow areas. In this paper, an improved adaptive thresholding method is built to address this problem. Instead of the gray level histogram, the modulation level histogram is utilized to compute the threshold. The modulation image is computed from all the captured images in the projection sequence. A novel objective function with a Gaussian weighted factor is proposed to improve Otsu’s method. With this weighted factor, the between-class variance between the object and background/shadow is intensified. The new built objective function also makes the objective function plot much smoother, which makes the proposed method more suitable for noise image segmentation. Additionally, the weighted factor changes adaptively with the input images. Experiment results illustrate that the proposed scheme performs better than existing methods. The scan for an area on a car body rear demonstrates the effectiveness and feasibility of the proposed method in structured light measurement of real metal components.

Revising of the Purcell effect in periodic metal-dielectric structures: the role of absorption

Periodic metal-dielectric structures attract substantial interest since it was previously proposed that the spontaneous emission amplification rates (the Purcell factor) in such structures can reach enormous values up to 105. However, the role of absorption in real metals has not been thoroughly considered. We provide a theoretical analysis showing that absorption leads to diminishing values of Purcell factor. We also suggest that using emitting organic compounds such as CBP (4,4-Bis(N-carbazolyl)-1,1-biphenyl) can lead to a moderate increase of about an order of magnitude in the Purcell factor. Defining the experimentally measured Purcell factor as a ratio between the excited state lifetimes in bare CBP and in periodic structure, this increase in the fabricated periodic structure is demonstrated through a 4–8 times decrease in excited state radiative lifetime compared to a bare organic material in a wide emission spectrum.

Versatile core/shell-like alginate@polyethylenimine composites for efficient removal of multiple heavy metal ions (Pb2+, Cu2+, CrO42-): Batch and fixed-bed studies

Versatile adsorptive materials that can efficiently capture anionic and cationic heavy metals are extremely significant in purification of complex wastewater systems. Herein, a new type of amine modified, biopolymer-derived core/shell-like adsorbents were employed in heavy metal anion and cation adsorption. The maximum adsorption capacities for Cr(VI), Pb(II), and Cu(II) were measured to be 497.1, 535.6, and 163.7 mg/g, respectively. The adsorbent also showed great performance in heavy metal cation adsorption in fixed bed column experiments. Additionally, removal efficiency and rapid adsorption kinetics on low concentration heavy metal pollutions for both anion and cations were well discussed to demonstrate the potential in real accidental heavy metal pollution. The prepared core/shell-like biopolymer adsorbents were demonstrated to be a kind of versatile adsorbent for both anionic and cationic heavy metal ions in aqueous solutions.

A Simple Model for Stretched Exponential Relaxation in Three‐Level Jumping Process

In this study, operator formalism is briefly introduced which is used to model Debye‐type relaxation with three‐level jumping based on Markovian framework. The author generalizes this formalism to the non‐Markovian process to model the non‐exponential relaxation and internal friction of real bcc metals or systems like Snoek‐type. By using this formalism, stretched exponential relaxation and the frequency and temperature dependence of internal friction depending upon β parameter are obtained. For β = 1, it is shown that the relaxation is exponential which obeys Debye law, and the frequency and temperature dependence of internal peak are represented by a single Debye peak. However, for 0 < β < 1 the author shows that relaxation is given by stretched exponential form, and the internal friction deviates from single Debye peak. It is concluded that β represents the memory, aging, and coupling effects of stochastic dynamics in complex materials.

Hybridized plasmonic modes and Fabry-Perot effect in nanoscale bowtie aperture waveguide

Based on Bethe's theory, light is hard to transmit through sub-wavelength apertures. However, a special designed sub-wavelength bowtie aperture is found to be able to transmit light with high efficiency. In this letter, modal analysis is used to study the hybridized plasmonic modes and Fabry-Perot effect of the nanoscale bowtie aperture waveguide. High frequency structure simulator (HFSS) simulations in perfect electrically conductor (PEC) and real metals are performed to calculate the fundamental mode, higher order mode, as well as their own cutoff wavelength. Mode analysis can give a better understanding of the intrinsic link between the plasmonic effects and Fabry-Perot effect. The TE10 and TE30 modes hybridize with channel plasmon polaritons (CPPs) modes and surface plasmon polaritons (SPPs) modes respectively. Experiments are carried out to verify the numerical results. These results are of great significance for understanding the internal mechanism of the bowtie aperture for coupling light to a sub-diffraction limited spot with high transmission efficiency.

Subwavelength topological edge states based on localized spoof surface plasmonic metaparticle arrays.

Plasmonic cluster arrays have demonstrated rich physics in topological photonics, but they are seriously affected by the material loss and limited by the requirement of high-precision machining. Here, we propose a kind of ultra-thin metaparticle arrays which can mimic the coupled localized plasmonic resonances at lower frequency ranges and so that can overcome the loss and fabrication problems in real metal plasmonic systems. The metaparticle is a metallic disk with circuitous grooves that can support both spoof electric and magnetic localized resonances, and these resonances can be pushed to a subwavelength region through tuning the geometric parameters. In virtue of the highly field confinement of these localized resonances, it is thought to be an ideal experimental platform to be an analogy with various near-field interactions in topological materials. As a first proof-of-concept study to show this feasibility, the subwavelength topological edge states at the zigzag metaparticle chain boundaries are numerically and experimentally demonstrated at microwave ranges. Moreover, the subwavelength topological edge states in this zigzag chain can be excited simply by the plane wave incidence, and the edge modes at two ends can be selectively excited by controlling the polarization direction. Therefore, this kind of metaparticle array not only provides an ideal platform to experimentally study various near-filed interaction dominated topological systems but may also find massive potential applications.