Double Surface Research Articles

Wear and Deformation Performance of W/Ta Multilayer Coatings on Pure Cu Prepared by Double Glow Plasma Alloying Technique

In this study, a multilayered hard coating with a tungsten matrix and a transition layer was deposited on pure copper by double glow plasma surface alloying technology, which aimed to provide the coating superior binding force and favorable matching of mechanical properties. The micro-hardness tester was adopted to measure the surface and cross-sectional hardness of the coatings. The nanoindentation test was used to measure the elasticity modulus of the coatings. Sliding wear tests under different conditions were performed on the W/Ta multilayer coating as well as the Cu substrate and W coating. The fairly low specific wear rate of the multilayer coating proved its excellent wear-resisting property, and the wear mechanism of the multilayer coating was mainly abrasive wear. In addition, a scratch test was executed to evaluate the deformation mechanism of the coating. Compared to the W coating, the persistence of the changing elastic–plastic deformation in the W/Ta multilayer coating improved the adhesion and resistance to plastic deformation. Moreover, the changing elastic–plastic deformation region is a benefit to the wear process, and the mechanical properties of the transition layer present a linear gradient descent instead of a vertical gradient, which makes a significant contribution in the wear stage. Further, the exploration of deformation mechanisms has a significant contribution to the design for multilayered hard coatings.

Simultaneous measurement of double surfaces of transparent lenses with phase measuring deflectometry

The phase measuring deflectometry is a promising method for the high precision measurement of optical freeform surfaces. However, it fails to measure the double surfaces of transparent lenses, because the fringes reflected from both the upper and the lower surfaces are superimposed in the captured images. An effective method is proposed to solve this problem by displaying a set of fringe patterns with different frequencies and retrieving the fringe phases associated with both surfaces. The form of the lower surface is reconstructed using a hybrid reflection-refraction model. Experimental results demonstrate that the proposed method can reliably reconstruct both surfaces of a lens, making deflectometry capable of measuring transparent optics with high accuracy.

A modification on 3S criterion and simplified elastic-plastic ratcheting analysis in ASME VIII-2

Ratcheting is a common and important failure mode in pressure vessels. ASME VIII-2 2019 edition provides two kinds of ratcheting assessment methods——the elastic stress ratcheting assessment (paragraph 5.5.6) applied to the design by elastic stress analysis and the elastic-plastic ratcheting assessment (paragraph 5.5.7) applied to the design by elastic-plastic stress analysis. This paper focuses on the elastic stress ratcheting assessment, which includes again two methods——the elastic ratcheting analysis (paragraph 5.5.6.1), i.e. the 3S criterion, and the thermal stress ratcheting assessment (paragraph 5.5.6.3). This article reviews the development history of 3S criterion and discusses its applicable scope. The study found that the 3S criterion is not a complete elastic ratcheting assessment criterion, when the primary membrane stress range exceeds two-thirds of the cyclic yield stress, i.e. (2/3)Sy, the ratcheting assessment based on 3S criterion is unsafe for some situations. When the general primary membrane stress Pm and the local primary membrane stress PL, which allowable limit exceeds (2/3)Sy, are applied simultaneously, there is still the possibility of ratcheting failure in the structure even if the 3S criterion is met. As an extension of the 3S criterion, a complete and safe criterion on three-dimensional elastic ratcheting assessment is proposed in this paper. In order to avoid the inconvenience of partition assessment, a simplified thermal stress ratcheting assessment method based on double checking surfaces is proposed. It is a simple and conservative assessment method. Finally, elastic ratcheting analysis, thermal stress ratcheting assessment and simplified elastic-plastic analysis in ASME VIII-2 are integrated, a universal elastic stress ratcheting assessment is proposed.

Preparation of single-layer graphene based on a wet chemical synthesis route and the effect on electrochemical properties by double layering surface functional groups to modify graphene oxide

In this paper, we reported the effect of secondary intercalation by introducing a hydroxyl group (–oxide by hydroxyl (OH)) on the surface of graphene (GO) to prepare a large quantities of low-layer graphene. The (Scanning Electron Microscope) SEM,(Transmission Electron Microscope) TEM and (Atomic Force Microscope) AFM analyses showed that the graphene distribution was uniform with an atomic thickness of approximately 1–2 layers. The standardless standard quantitative analysis indicated that the O content was only 3.53% and the impurity element content was only 0.29%, which indicated that the graphene was reduced. (X-ray photoelectron spectroscopy) XPS and FT-IR analyses demonstrated that most oxygen-containing functional groups between the graphene sheets were converted and removed. When tested as a supercapacitor electrode, RGO-C2 exhibited significant electrochemical enhancement and better cycle stability than an electrode produced by a conventional modified Hummers’ method. The specific capacity, energy density and power density of RGO-C2 are respectively 278.91 F g−1, 38.74 W h kg−1, and 50 W kg−1. This experimental study can provide research guidance for the design of modification of oxygen-containing functional groups on the surface of GO.

Improvement of structures seismic response based on pendulum systems with double sliding surface

The seismic isolation of the construction structures is of particular importance because the optimum stability premises of the structures during the seismic events are ensured. There are different isolation methods but based on the structure base isolation principle, the friction pendulum bearing systems (FPBS) have been used with good results in equipping new structures and also in rehabilitating of the old buildings that had to be consolidated. The double surface friction Pendulum (DSFP) bearing is an improved version of the well-known single concave friction pendulum bearing (FPBS). The principal benefit of the DSFP bearing is represented by its capacity to accommodate substantially larger displacements compared to a traditional FPBS of identical plan dimensions. Moreover, there is the capability to use sliding surfaces with different radius of curvature and friction coefficients, offering the designer greater flexibility to optimize the protective system performance. Through these systems good seismic isolation results are achieved for the building structures where mounted interposed between the foundation and the superstructure realizing the disconnection between the two structural elements. The disconnection is important because the insulated structure vibration period is modified in the sense of its significant increase, also with the increase of structure lateral flexibility, ultimately reducing the ground acceleration and avoiding the efforts vertical transmission to the isolated structure upper levels. The double surface friction pendulum system ensures an important modification of the isolated structure behavior materialized through the seismic response mitigation. This paper describes the double surface friction bearing (DSFP) constructive details with operation principles and also presents some numerical analysis results related to force–displacement relation considering different values of curvature radius and friction coefficients of the two friction surfaces used

A constitutive model for crushable sands involving compression and shear induced particle breakage

Properly modelling the particle breakage characteristics is important for crushable soils such as carbonate sands, rockfills and rail ballasts. According to the generation mechanism, particle breakage was decomposed into two parts: compression-induced particle breakage associated with the increase of mean effective stress and shear-induced particle breakage related to the change of shear stress ratio. The accumulation rate of the compression-induced particle breakage can be well correlated to the current stress state; while the accumulative rate of the shear-induced particle breakage depends on both the current stress state and the accumulated amount of particle breakage during past loading histories. Within the framework of the critical state plasticity, a double yield surfaces constitutive model incorporating the two particle breakage components was developed. By employing a breakage critical state surface with particle breakage being an extra dimension, the effect of particle breakage on the critical state, dilatancy, strength and modulus were involved. The drained and undrained triaxial test results of two carbonate sands and one silica sand of different densities were selected to validate the proposed model. It was shown that the proposed model is capable to reproduce well the stress-strain behavior of the crushable soils.

On the use of the supporting quadric method in the problem of designing double freeform surfaces for collimated beam shaping.

We propose a version of the supporting quadric method for calculating a refractive optical element with two working surfaces for collimated beam shaping. Using optimal mass transportation theory and generalized Voronoi cells, we show that the proposed method can be regarded as a gradient method of maximizing a concave function, which is a discrete analogue of the Lagrange functional in the corresponding mass transportation problem. It is demonstrated that any maximum of this function provides a solution to the problem of collimated beam shaping. Therefore, the proposed method does not suffer from "trapping" at a local extremum, which is typical for gradient methods. We present design examples of refractive optical elements illustrating high performance of the method.

TRIBOLOGICAL AND CORROSION BEHAVIOR OF SiC/TaXC BILAYER COATINGS PREPARED ON STAINLESS STEEL SURFACE BY DOUBLE GLOW PLASMA SURFACE ALLOYING TECHNIQUE

In this work, SiC/TaxC bilayer coatings were prepared on stainless steel surface by double glow plasma surface alloying technique to improve the wear and corrosion resistance of the substrate. The effect of reaction temperature during the growth of SiC on the microstructure and property of the coating was investigated. The results showed that the surface topography of the coating could be regulated by the reaction temperature during the growth of SiC. Interactional flower-shaped rings, reticulate patterns, nanoparticles and microparticles were observed on the samples prepared at 750∘C, 800∘C, 850∘C and 900∘C, respectively. Tribological performance tests showed that the friction coefficient and specific wear rate of all the coated specimens were significantly decreased than the uncoated ones, indicating that the wear resistance of stainless steel was improved by the SiC/TaxC coating. The construction of the bilayer coating enhanced the corrosion resistance of stainless steel in terms of electrochemical tests. With an increase of the reaction temperature, the wear and corrosion resistance increased at first and then gradually decreased. SiC/TaxC coating prepared at 800∘C exhibited the best overall performance.

Three-terminal Weyl complex with double surface arcs in a cubic lattice

Exploring unconventional topological quasiparticles and their associated exotic physical properties has become a hot topic in condensed matter physics, thus stimulating extensive interest in recent years. Here, in contrast to the double-Weyl phonons (the topological chiral charge +2) in the trigonal and hexagonal crystal systems, we propose that the unconventional double-Weyl without counterparts in high-energy physics can emerge in the phonons of cubic structures, i.e., SrSi2. Employing a two-band k ⋅ p Hamiltonian, we prove that the quadratic double-Weyl nodes are protected by the fourfold screw rotational symmetry {tilde{C}}_{4}. Strikingly, we find that the surface arcs are terminated with the Weyl nodes that possess unequal topological charges with opposite sign (i.e., +2 and −1), leading to unique three-terminal Weyl complex (one quadratic double-Weyl and two linear single-Weyl) with double surface arcs in SrSi2. In addition, we apply a uniaxial tensile strain along z-axis to examine the evolution of the three-terminal Weyl complex when the corresponding symmetries are broken. Our work not only provides an ideal candidate for the realization of the quadratic double-Weyl and the corresponding unique surface arc states, but also broadens the understanding of topological Weyl physics.

Flexible Humidity and Pressure Sensors Realized by Molding and Inkjet Printing Processes with Sandwich Structure

AbstractFlexible and wearable devices are important parts toward the realization of artificial intelligence and have an irreplaceable advantage over traditional rigid sensors. In this work, a film with double surface structure is prepared by using sandpaper and the leather with a rhombic structure as a mold, thereby obtaining a sandwich structure resistive type pressure sensor, which has high sensitivity (77.78 kPa−1, 24 Pa minimum detection) and wide detection range (0.024–230 kPa). The sensors have fast response time (30 ms) and high reliability over 5000 repetitive cycles. The humidity sensor is printed on the top layer of the sensor by using screen printing and inkjet printing technique, and the sandwich structure humidity and pressure sensor is obtained. The humidity sensors show the sensitivities of 0.137/%, 1.57/%, and 11.145/% in the relative humidity range from 25 to 55%, 55 to 70%, and 70 to 80%, respectively. Such sensors not only have excellent capabilities in pressure and humidity detection, but also avoid the complex process of multiple single‐function devices stacked on each other. The applications of sensors in monitoring artery pulse waves, detecting spatial pressure distribution, and sweat is demonstrated.

Extraction of water from atmospheric air using double slope condensation surface

In this study, extraction of water from atmospheric air using double slope condensation surface is investigated. Solar energy as a heat source and Calcium Chloride (CaCl2) as the desiccant are used. The experimental apparatus involves two parts. The first part, which functions as absorber has nine channels containing mixture of Calcium Chloride (CaCl2) and sand while the second part, which functions as transparent and condensation surface has a prism shape. At night, the absorber is exposed to atmospheric air where Calcium Chloride (CaCl2) absorbs moisture from atmospheric air. At sunrise, the absorber is covered tightly with the transparent and condensation surface that allows the transmission of sun rays to the absorber. Condensate is collected in sloping channels that fixed at the bottom inner surface of transparent cover. The temperature of transparent surface, air-vapor mixture and absorber surface, solar radiations intensity and amount of collected water are recorded during the experiments at various operating days. Experimental measurements indicate that the condensed water productivity changes with ambient conditions. It is found that the maximum yield for Aug.19th,2015 was 735 gm /m2.day for accumulative solar radiation of about 7806 W.hr/m2.day. A mathematical model is developed to estimate the solar radiation intensity and amount of collected water. Its results are compared with the experimental data and a reasonable agreement between theoretical results and experimental measurements is attained

Fracture Toughness and Surface Energy Density of Kerogen by Molecular Dynamics Simulations in Tensile Failure

Fracture toughness and surface energy density are critical parameters in the simulation of hydraulic fracturing in shale formations. In this study, a microscopic insight into the mechanisms of tensile failure in kerogen is advanced by molecular dynamics simulations for the first time. The elastic properties, critical stress, surface energy density, and fracture toughness of kerogen are analyzed systematically. Our work reveals that kerogen is potentially a weak component in shale, which may serve as a region of fracture initiation and preferential fracture propagation path. The critical energy release rate Gc is higher than the doubled surface energy density γs (Gc ≥ 2γs), which indicates that there may be pronounced plastic deformation in kerogen in the tensile failure. This work sets the stage for the determination of various shale mechanical properties and surface energy density to examine fracturing effectiveness in shale media from the molecular scale.

Double Glow Plasma Surface Metallurgy Technology Fabricated Fe-Al-Cr Coatings with Excellent Corrosion Resistance

Double glow plasma surface metallurgy (DGPSM) technology was applied to obtain a Fe-Al-Cr coating on the surface of Q235 carbon steel. The influence of the sample temperature, gas pressure, the distance between the substrate, and the source electrode on the quality of the obtained Fe-Al-Cr coatings was systematically investigated. The results showed that the parameters for DGPSM have a significant effect on the uniformity, particle size, compactness, and thickness of the coating. Under the optimized parameters (sample temperature: 800 °C, gas pressure: 35 Pa, and electrode distance: 15 mm), the obtained Fe-Al-Cr coating contains Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) solid solution, Cr23C6, and α-Fe(Al), exhibiting excellent corrosion resistance in a 0.5 mol/L H2SO4 solution, which is even better than that of the 304 stainless steel.

Tribological behavior of borocarburized layer on low-carbon steel treated by double glow plasma surface alloying

In this paper, the borocarburized layer was fabricated on the surface of low-carbon steel via double glow treatment to enhance the wear resistance. Benefited by the gradient structure of an outermost boride layer and inner carburized layer, the bonding strength of the protective coating was improved. The novel design improved the mechanical properties at the coating-substrate interface and extended the service life of the coating. The microstructure and composition of borocarburized layer were analyzed by SEM, XRD, XPS. The tribological properties of substrate and borocarburized layer under dry sliding against ZrO2 ball were investigated. The results indicated that borocarburized layer consisted of a 38 μm boride layer with main phase of Fe2B and a 75 μm carburized layer with main phase of Fe5C3. The microhardness of borocarburized layer emerged in gradient distribution attributed to the double glow plasma surface alloying technique, and the maximum value was around 1700 HV. In addition, the major wear mechanisms of low carbon steel were fatigue and abrasive wear, which transformed to abrasive and adhesive wear with the load increased. The wear mechanisms of borocarburized layer were abrasive and adhesive wear. During wear process, borocarburized layer with high hardness against ZrO2 ball due to the decreased real contact areas. Therefore, the borocarburized layer fabricated on low carbon steel enhanced the wear resistance effectively.

Effect of Ta diffusion layer on the adhesion properties of diamond coating on WC-Co substrate

To enhance diamond nucleation and adhesion on cemented carbide substrates, the Ta diffusion layers with gradient structure were deposited by the combination with double glow plasma surface alloying technique (DGPSA) and the reverse-sputtering process. The effect of reverse-sputtering times on phase composition and morphology of the Ta surface layers was studied. It was found that both the thickness of the Ta deposition layer and the amount of Ta elements decreased during the removal of the Ta deposition layer. With the reverse-sputtering time increases from 0 to 60 min, the thickness of the Ta deposition layers decreased from 1.6 μm to 0 μm. When the reverse-sputtering time reached 30 min, the as-prepared sample surface exhibited the maximum micro-hardness (3496.3 HV1.96N). Rockwell C indentation tests were used to investigate the effect of the Ta diffusion layers on the adhesion between the WC-Co substrate and the diamond coating. The results show that diamond coating exhibits good adhesion performance on WC-Co substrate with the Ta diffusion layer after reverse-sputtering for 60 min, indicating that the barrier effect of cobalt diffusion is enhanced by introducing the Ta diffusion layer.

Revealing roaming on the double Morse potential energy surface with Lagrangian descriptors

In this paper, we analyse the phase space structure of the roaming dynamics in a 2 degree of freedom potential energy surface consisting of two identical planar Morse potentials separated by a distance. This potential energy surface was previously studied in Carpenter B K et al (2018 Regul. Chaotic Dyn. 23 60–79), and it has two potential wells surrounded by an unbounded flat region containing no critical points. We study the phase space mechanism for the transference between the wells using the method of Lagrangian descriptors.

Adaptive density-guided approach to double incremental potential energy surface construction

We present a combination of the recently developed double incremental expansion of potential energy surfaces with the well-established adaptive density-guided approach to grid construction. This unique methodology is based on the use of an incremental expansion for potential energy surfaces, known as n-mode expansion; an incremental many-body representation of the electronic energy; and an efficient vibrational density-guided approach to automated determination of grid dimensions and granularity. The reliability of the method is validated calculating potential energy surfaces and obtaining fundamental excitation energies for three moderate-size chain-like molecular systems. The use of our methodology leads to considerable computational savings for potential energy surface construction compared to standard approaches while maintaining a high level of accuracy in the resulting potential energy surfaces. Additional investigations indicate that our method can be applied to covalently bound and strongly interacting molecular systems, even though these cases are known to be very unfavorable for fragmentation schemes. We therefore conclude that the presented methodology is a robust and flexible approach to potential energy surface construction, which introduces considerable computational savings without compromising the accuracy of vibrational spectra calculations.

Enhanced color sensitivity by coupling of surface plasmon and fabry-perot resonances for spectrometer-free and label-free biosensing

Plasmonic sensors have received much attention in recent years since they are highly sensitive to the refractive index changes of surrounding dielectric and can be applied to spectrometer-free biosensing. In particular, the sensing based on the color factors and the imaging is considered as a powerful method due to its simplified sensing process as well as high sensitivity with high spatial resolution. Herein, we report on improvement in the color sensitivity to the refractive index changes by employing an aluminum-silicon dioxide-aluminum (AOA) structure consisted of the Fabry-Perot (FP) cavity sandwiched between double surface plasmonic (SP) layers. The coupling of SP and FP resonances in aluminum nanohole arrays and silicon dioxide cavity lead to the synergistic or attenuated change in transmission spectra and colors. Therefore, as optimizing the coupling of the resonances to increase the color change, it is possible to obtain enhanced color sensitivity and more accurate refractive index prediction. Color sensitivities up to 122.29 (L*), 169.58 (a*), and 174.72 (b*) RIU−1 of the CIELAB color space are achieved through imaging process and statistical analysis. Uniform and sensitive sensing factors of AOA sensors can distinguish the concentration difference of bovine serum albumin (BSA) with a limit of detection of 9 × 10-4 RIU. Moreover, this approach confirms the possibility of being used for in vivo detection by observing the intracellular structure of HEK-293 cells. Our AOA sensor suggests a great potential to be utilized as a spectrometer-free, label-free, and functionalization-free detection of the refractive index and the transparent biomaterials.

First-Principles Calculation of Optimizing the Performance of Germanene-Based Supercapacitors by Vacancies and Metal Atoms

Germanene with folded atomic layers has double surfaces and high surface/volume ratio, similar to carbon nanomaterials, and is expected to be used in supercapacitors and field effect transistors. B...

Manipulation tribological behavior of Ti6Al4V alloy via a duplex treatment of double glow plasma surface molybdenizing-laser surface texturing (LST)

In this work, Ti6Al4V alloy was treated by a duplex treatment of double glow plasma surface molybdenizing-laser surface texturing (LST) aiming to realize surface strengthening and manipulate its tribological behavior. The double glow plasma surface alloying (DGPSA) with molybdenum (Mo) was firstly conducted on the Ti6Al4V alloy and followed by LST to prepare round dimple-shape texture with a density of 5%, 7%, 11%. The results showed that Mo and Mo/Ti solid solution phases were detected in the Mo-layer by X-ray diffraction (XRD), the received Mo-layer with a thickness of about 13μm was uniform and compact. Double glow plasma surface molybdenizing significantly improved the surface hardness and elastic modulus of Ti6Al4V alloy by nanoindentation test. The gradient distributed Mo-layer was tightly adhered to the Ti6Al4V alloy matrix through scratching and indentation tests. Duplex treated Ti6Al4V alloy with a 5% texture density suggested better wear resistance in comparison to the untreated Ti6Al4V alloy, which was confirmed by a 48.7% lower specific wear rate than that of Ti6Al4V alloy. Taking advantages of DGPSA and LST, duplex treatment of double glow plasma surface molybdenizing-laser surface texturing was established to create on the working surface of Ti6Al4V alloy with promisingly improved tribological behavior.