Perpendicular Surface Research Articles

Controllable Graphene/MoS2 Heterointerfaces by Perpendicular Surface Functionalization.

Surface chemistry and interface interactions profoundly influence the properties of two-dimensional (2D) materials and heterostructures. Therefore, developing methods to precisely control surfaces and interfaces is crucial for harnessing the properties and functions of 2D materials and heterostructures. Here, we developed a facile approach to tuning the interface distance and properties of graphene/MoS2 heterostructures (G/MoS2) by varying the functional groups attached to the surface of graphene bottom layer. We systematically investigated how different functionalized graphene bottom layers affect the interlayer distance, coupling between the interlayers, and optical properties of resulting G/MoS2 heterostructures. Our findings indicate that both the size and electron-withdrawing/donating properties of functional groups are pivotal in regulating charge transport properties, with size playing a particularly decisive role. Our approach demonstrates an efficient and flexible pathway to regulate the interlayer spacing and charge transport, highlighting the potential of engineering interface chemistry in optimizing properties of van der Waals heterostructures.

Emergent biaxiality in chiral hybrid liquid crystals.

Biaxial nematic liquid crystals are fascinating systems sometimes referred to as the Higgs boson of soft matter because of experimental observation challenges. Here we describe unexpected states of matter that feature biaxial orientational order of colloidal supercritical fluids and gases formed by sparse rodlike particles. Colloidal rods with perpendicular surface boundary conditions exhibit a strong biaxial symmetry breaking when doped into conventional chiral nematic fluids. Minimization of free energy prompts these particles to orient perpendicular to the local molecular director and the helical axis, thereby imparting biaxiality on the hybrid molecular-colloidal system. The ensuing phase diagram features colloidal gas and liquid and supercritical colloidal fluid states with long-range biaxial orientational symmetry, as supported by analytical and numerical modeling at all hierarchical levels of ordering. Unlike for nonchiral hybrid systems, dispersions in chiral nematic hosts display biaxial orientational order at vanishing colloid volume fractions, promising both technological and fundamental research utility.

Einstellbare Graphen/MoS2 Grenzflächen durch vertikale Oberflächenfunktionalisierung

AbstractOberflächenchemie und Grenzflächeninteraktionen beeinflussen die Eigenschaften von zweidimensionalen (2D) Materialien und Heterostrukturen. Daher ist die Entwicklung von Methoden zur Kontrolle von Oberflächen‐ und Grenzflächeneigenschaften entscheidend, um die Funktionen von 2D‐Materialien und Heterostrukturen zu ermöglichen. In dieser Arbeit haben wir einen einfachen Ansatz entwickelt, um den Abstand von Grenzflächen in Graphen/MoS2‐Heterostrukturen (G/MoS2) durch Variation funktioneller Gruppen an der Oberfläche der Graphen‐Unterschicht einzustellen. Wir haben systematisch untersucht, wie der Abstand zwischen 2D‐Schichten in G/MoS2‐Heterostrukturen die optischen Eigenschaften beeinflusst. Unsere Ergebnisse deuten darauf hin, dass sowohl die Größe als auch die elektronischen Eigenschaften der funktionellen Gruppen zur Regulierung der Ladungstransporteigenschaften beitragen, wobei besonders die Größe funktioneller Gruppen entscheidend ist. Unser Ansatz zeigt einen effizienten und flexiblen Weg zum Einstellen der Schichtabstände in Heterostrukturen, wodurch die Elektronentransfer‐Eigenschaften beeinflusst werden. Die Grenzflächenchemie kann somit zur Optimierung der Eigenschaften von van‐der‐Waals‐Heterostrukturen herangezogen werden.

The Upshots of Dufour and Soret in Stretching Porous Flow of Convective Maxwell Nanofluid with Nonlinear Thermal Emission

In this paper, the combined upshot of Soret and Dufoue of a convective Maxwell nanofluid on a porous perpendicular surface with nonlinear thermal emission was investigated. In the present work, the impact of permeable stretching sheet, nonlinear thermal emission, heat sour sink, Dufour and Soret effect, chemical reaction, Brownian motion and thermophoresis in a convective Maxwell nanofluid flow is widely discussed. The governing equations derived for the problem are highly nonlinear coupled partial differential equations. The governing equations were transformed into ordinary differential equations using Lie symmetry group alterations. The BVP4C MATLAB solver was employed to solve the ordinary differential equations numerically after validating the convergence of the method with existing results in the literature. The numerical results were established and discussed using tables and graphs. It was found that variations in porosity parameter (K), Dufour (Du) and Soret (Sr) improves velocity, temperature and concentration profiles respectively and the present of nonlinear thermal radiation and heat source emit more heat for the flow. Also, it is exciting to report that both porosity (K) and Dufour (Du) parameters has a strong impact on the flow of skin frictions, Nusselt number and Sherwood number. However, the current results may present applications in the areas of petroleum reservoir, heat exchangers, steel industries, cooling applications, nuclear waste disposal and so on.

Effects of Process-Induced Defects on the Corrosion of Additively Manufactured Stainless Steel 304L

This study investigates the impact of process-induced defects such as gas pores, lack of fusions, and surface roughness on corrosion behavior of stainless steel 304L (SS304L) fabricated by laser powder bed fusion additive manufacturing. Specimens are printed with optimized process parameters but selected from different locations on the build plate. Parallel and perpendicular surfaces to the build direction are investigated and compared with corrosion properties of wrought SS304L in 5 wt% NaCl. The results reveal significant difference in corrosion behavior among specimens due to variations in their defect features. Pitting potential, pit initiation, and growth rates are found to be influenced by specimen location on the build plate. The specimen located in downstream of the shielding gas flow shows the least corrosion resistance. While no clear trends are observed between some corrosion properties and defect features, other properties show strong correlations. For example, no trend is observed for the corrosion properties in relation to pore average area fraction. However, strong correlations are observed for the corrosion properties as functions of defects maximum area. Corrosion properties linearly deteriorate as the defects maximum area increases. Roughness shows a mixed relationship with pitting potential. Comprehensive discussions on all these effects are presented.

First-principles calculation of self-interstitial atom-impurity atom interactions in ferritic steel

In this study, the interactions between self-interstitial atoms (SIA) and impurity atoms (Cu and P) in the body-centered cubic (bcc)-Fe matrix have been investigated using the first principles approach. The results show that Cu and P atoms are more prone to segregation on perpendicular and parallel surfaces containing dumbbell atoms, respectively. Next, by combining the charge density difference and considering the electronic structure and lattice distortion, the origin of the binding energy of complexes formed between SIA and impurity atoms was discussed. The results show that as the number of impurity atoms increases, the atomic bonds formed by the interactions between the impurity atoms decrease the binding energy between single impurity atoms and the matrix and reduce the strain field around them, resulting in an increase in the stability of the complexes. Comparison with previous experimental results revealed the reasons for the changes in atomic occupancy during the segregation of Cu and P atoms. The results provide insights into the behavior of impurity atoms in irradiated materials and provide a deeper understanding of the electron level of impurity atomization.

Temperature dependence of electrochemical characteristics on the growth surface and isomorphous perpendicular surface of DD6

Electrochemical machining (ECM) is a highly effective method for processing nickel-based single crystal (NBSC) superalloys. However, the influence of temperature on the electrochemical corrosion of NBSC remains underexplored. This study investigates the temperature dependence of the corrosion characteristics on the growth surface and its isomorphous perpendicular surface of NBSC DD6 were investigated. Results indicate that temperature significantly impacts the passivation and dissolution processes of the material: at low temperatures, the passivation effect weakens, and the differences in self-corrosion potential between phases decrease, leading to smaller variations in corrosion. Additionally, a mechanism is proposed to elucidate the temperature-dependent corrosion behaviors on different surfaces.

Non-similar analysis of bioconvective stagnation-point flow toward a stretching surface in the presence of buoyancy force, viscous dissipation, and thermal radiation

Aim of this analysis is to investigate, bioconvective stagnation flow of an incompressible fluid across an expanding perpendicular surface in the existence of buoyancy force, viscous dissipation, and thermal radiation. The physical model is described in terms of nonlinear coupled partial differential equations (PDEs). The dimensional PDEs are transformed into dimensionless PDEs by using appropriate non-similar transformations. Local nonlinearity method (LNS) is used to generate high accuracy truncated ordinary differential equations (ODEs) that are used to approximate dimensionless PDEs. Using well-known techniques like finite-difference-based bvp4c, the ODEs are numerically formulated. This research also investigates how several physical, nondimensional parameters affect the profiles of velocity, temperature, and concentration, for both assisted and opposed flow cases. The comparison and range tables describe the validity and range of the presented results, respectively. The tabulated results indicate that enhancement in radiation parameter increases the local Nusselt number, Sherwood number, and the surface drag force.

Mixed convection simulation of TMPHN by Eringen’s micropolar rules, Tiwari–Das nanofluid model, and mass-based hybridity algorithm

In this study, a combination of the Tiwari–Das nanofluid model, the mass-based hybridity algorithm, and the Eringen micropolar rules are applied to inquire about the mixed convective flow of a thermo-micropolar hybrid nanofluid (TMPHN) over a shrinking perpendicular surface. The working fluid of the TMPHN includes two nanoparticles (alumina and copper) suspended in an aqua-base fluid. The applied methodology considers the masses of base fluid and nanoparticles as an alternative to the first and second nanoparticle volume fractions, which is named the mass-based hybridity algorithm. The transformed ODEs are solved numerically by the shooting-based bvp4c method with MATLAB software. It is significant to mention that the nonlinearity of the pertinent governing equations and the nature of the pertinent boundary conditions both contribute to the duality of similar solutions. The effects of various controlling factors on the velocity, the angular velocity, and temperature, as well as the shear stress, the gradient of micro-rotation, and heat transfer, are graphically depicted. With great confidence, the current algorithm for the modeling of thermo-micropolar hybrid nanofluid can be applied to a variety of issues. Moreover, the numerical outputs reveal that the shrinking parameter range for the occurrence of solution duality increases with the alumina mass and the Richardson number. The findings, in a comprehensive and detailed form, have been presented in the article’s body.

Two distinct mechanisms of tonal sound production in supersonic jet impingement

The interaction of high-speed jets with a perpendicular surface produces not only broadband sound, but “impingement tones,” that can be more than 30 dB above the broadband noise. It is well recognized that these tones are the result of an aeroacoustic resonance, driven by a feedback loop between the jet nozzle and the plate. However, the exact mechanism by which the tones are produced remains a topic of some dispute; some researchers locate the source within the core of the impinging jet, others in the wall jet generated after impingement with the plate. In this work, we demonstrate that both camps have correctly identified sources; there are two distinct mechanisms, with two distinct locations. The relative strength of these sources depends on the geometry of the problem, but we show that they can actually coexist at a single condition. Decomposition of high-speed schlieren data directly visualizes the location of these sources as a function of jet operating condition.

Evaluation of Index-Based Methods for Impervious Surface Mapping from Landsat-8 to Cities in Dry Climates; A Case Study of Buraydah City, KSA

The natural landscape is fast turning into impervious surfaces with the increase in urban density and the spatial extent of urbanized areas. Remote sensing data are crucial for mapping impervious surface area (ISA), and several methods for ISA extraction have been developed and implemented successfully. However, the heterogeneity of the ISA spectra and the high similarity of the ISA spectra to those of bare soil in dry climates were not adequately addressed. The objective of this study is to determine which spectral impervious surface index best represents impervious surfaces in arid climates using two seasonal Landsat-8 images. We attempted to compare the performance of various impervious surface spectral Index for ISA extraction in dry climates using two seasonal Landsat-8 data. Specifically, nine indices, i.e., band ratio for the built-up area (BRBA), built-up area extraction method (BAEM), visible red near infrared built-up index (VrNIR-BI), normalized ratio urban index (NRUI), enhanced normalized difference impervious surfaces index (ENDISI), dry built-up index (DBI), built-up land features extraction index (BLFEI), perpendicular impervious surface index (PISI), combinational biophysical composition index (CBCI), and two impervious surface binary methods (manual method and ISODATA unsupervised classification). According to the results, PISI and CBCI combined with the manual method had the best accuracy with 88.5% and 88.5% overall accuracy (OA) and 0.76 and 0.81 kappa coefficients, respectively, while DBI combined with the manual method had the lowest accuracy with 75.37% OA and 0.56 kappa coefficients. PISI is comparatively more stable than the other approaches in terms of seasonal sensitivity. The ability of PISI to discriminate ISA from soil and vegetation accounts for much of its good performance. In addition, spring is the ideal time of the year for mapping ISA from Landsat-8 images because the impervious surface is generally less likely to be confused with bare soil and sand at this time of year. Therefore, this study can be used to determine spectral indices for studying ISA extraction in drylands in conjunction with binary approaches and seasonal effects.

A New Technique for Impervious Surface Mapping and Its Spatio-Temporal Changes from Landsat and Sentinel-2 Images

Accurately mapping and monitoring the urban impervious surface area (ISA) is crucial for understanding the impact of urbanization on heat islands and sustainable development. However, less is known about ISA spectra heterogeneity and their similarity to bare land, wetland, and high-rise-building shadows. This study proposes a feature-based approach using decision tree classification (FDTC) to map ISAs and their spatio-temporal changes in a coastal city in southeast China using Landsat 5 TM, Landsat 8 OLI/TIRS, and Sentinel-2 images from 2009 to 2021. Atmospheric correction using simplified dark object subtraction (DOS) was applied to Landsat imagery, which enabled faster computation. FDTC’s performance was evaluated with three sensors with different spectral and spatial resolutions, with parameter thresholds held constant across remote-sensing images. FDTC produces a high average overall accuracy (OA) of 94.53%, a kappa coefficient (KC) of 0.855, and a map-level image classification efficacy (MICE) of 0.851 for ISA mapping over the studied period. In comparison with other indices such as BCI (biophysical composition index), PISI (automated built-up extraction index), and ABEI (perpendicular impervious surface index), the FDTC demonstrated higher accuracy and separability for extracting ISA and bare land as well as wetland and high-rise buildings. The results of FDTC were also consistent with those of two open-source ISA products and other remote sensing indices. The study found that the ISA in Xiamen City increased from 16.33% to 26.17% over the past 13 years due to vegetation occupation, encroachment onto bare land, and reclamation of coastal areas. While the expansion significantly reduced urban vegetation in rapidly urbanizing areas of Xiamen, ambitious park greening programs and massive redevelopment of urban villages resulted in a modest but continuous increase in urban green space.

Time courses of strains that induce necking and fracturing in high-density polyethylene

High-density polyethylene is widely used in pressure pipe applications, but its necking and pre-cut effects are still poorly understood. Herein, we analyze the spatial distributions of the time courses of strains to highlight the strain field evolution to necking and the effect of pre-cutting on the strain field evolution in a high-density polyethylene material deformed under tension. Digital image correlation was used to measure the strain fields on two perpendicular surfaces of a specimen. Necking and its propagation in the tension direction dominate the failure behavior of an intact specimen. However, in the pre-cut specimen, crack propagation prevents neck propagation in the tension direction. Energy release outside the crack zone is observed as a decrease in strain at approximately the failure time. This leads to a macroscopic stress-strain curve that deviates from that of the intact specimen. These findings provide novel insights that are significant in the theoretical modelling and simulations of advanced polymeric materials and structures.

Self-assembly of cellulose nanocrystals confined to square capillaries.

Biological systems exploit restricted degrees of freedom to drive self-assembly of nano- and microarchitectures. Simplified systems, such as colloidal nanoparticles that behave as lyotropic liquid crystalline mesophases in confined geometric spaces, may be used to mimic biological structures. Cellulose nanocrystals (CNCs) are colloidally stable nanoparticles that self-assemble into chiral nematic (ChN) liquid crystalline mesophases. To date, the self-assembly of ChN mesophases of CNCs has been studied under confinement conditions within curved surfaces or under drying conditions that impose curvatures that can be exploited to control ChN ordering; however, their self-assembly has not been investigated in geometries with square cross-sections under static conditions. Here, we show that because of surface anchoring on perpendicular surfaces, the ChN CNC phase is unable to bend with the 90° angle of the square capillary under increasing confinement. Instead, the ChN phase forms radial layers in the shape of concentric squircle shells. With increasing layer distance from the capillary wall, the squircles transition into concentric cylinder shells. In larger capillaries, the radial shell layers appear as a continuous spiral pattern that engulfs fragmented ChN pseudolayers, a defect to accommodate the cylindrical confinement of the mesophase. These results are useful for understanding the fundamentals of self-assembling systems and development of new technologies.

Spin-wave study of magnetic perpendicular surface anisotropy in single crystalline MgO/Fe/MgO films

The authors report an experimental separation of the two perpendicular surface anisotropies present in MgO/Fe/MgO epitaxial films through a careful study of inhomogeneous magnetization dynamics. This is achieved by combining the strengths of two experimental techniques: the frequency broadband capabilities of ferromagnetic resonance and the precise determination of non-reciprocal propagation via propagating spin wave spectroscopy. This new experimental approach allows to separate the top and bottom perpendicular surface anisotropies often measured together in thin films, and it provides new light into the technologically-relevant ferromagnet/MgO interfaces and their effect on spin waves.

Numerical investigation on steady natural convective flow past a perpendicular wavy surface with heat absorption/generation

The controlling of heat transport procedures through external energy source effects is one of the mainly significant problems in modern applied physical sciences. Major strong research in thermal sciences, mechanical engineering and including energy modeling, planning and energy supervisions, energy conservations, energy efficiencies, biomass and bio-energy, renewable energy, energy storage, energy in buildings. In the current existing paper, the consequences of thermal conductivity on temperature, this is inversely proportionally by the linear function of temperature on free convective movement of an incompressible viscous fluid through the heated uniform and vertical wavy surface is examined. Associated with boundary conditions, the governing boundary layer equations be translated into the non-dimensional structure for phenomenon by utilizing an appropriate transformation. In the domain of vertical plate that is flat, the resulting method of nonlinear partial differentiated equations are mapped and then numerically by applying the implicit finite difference technique with Keller-box technique. The rate of heat transfer, the skin friction coefficient, the isotherms and streamlines throughout the boundary layer are exhibited graphically.

Characterizing the anisotropic response of similar and dissimilar FSW joints by DIC-based simultaneous strain measurements on two orthogonal surfaces

In friction stir welding (FSW), various zones with microstructural heterogeneity are formed with a difference in local constitute properties. To define anisotropy ratio through strain measurement in thickness and width direction simultaneously, utilizing a standard contact-type extensometer is challenging, or assuming volume constancy to calculate strain in the thickness direction may not be applicable for FSW joints. The present work proposes an approach where strain is measured concurrently on two mutually perpendicular (width and thickness) surfaces of a deforming tensile specimen by digital image correlation. Strain localization and local anisotropy ratio are calculated over the specimen gauge length, and the average anisotropy ratio is specified for the similar and dissimilar FSW joints of AA6061 and AA7075. For AA6061 similar FSW joints, tensile specimens with longitudinal axis along (θ = 0°) or close to weld line that contains solely stir zone (SZ) material and/or minimal presence heat affected zone (HAZ) exhibit uniform strain accumulation and failure from SZ. However, beyond that, the presence and orientation of HAZ influence the strain localization, anisotropy and subsequent failure. For dissimilar AA6061-AA7075 FSW joints, the anisotropic nature is largely governed by the strain localization at the softer material rather than the orientation of various zones within the specimen gauge length.

Chemical reaction impacts the unsteady MHD convective flow of an incompressible viscous fluid past an infinite vertical porous plate

AbstractWe studied the radiation magnetohydrodynamic flow of an incompressible viscous electrically conducting fluid past an exponentially accelerated perpendicular surface under the influence of slip velocity in the revolving structure. A steady homogeneous magnetic strength is applied under the assumption of low magnetic Reynolds quantity. The ramped heat and time‐altering concentration near the plate are taken into consideration. First‐order consistent chemical reactions and thermal absorption were also studied. The Laplace transformation technique is used for the non‐dimensional governing equations to get the closed‐form solutions. Supporting these results, the phases for nondimensional shear stress, rate of thermal as well as accumulation transport are also found. Graphical profiles are represented to examine the impact of physical parameters on the important physical flow features. The computational quantities of shear stress and rate of thermal and mass transportation near the surface are tabulated with a variety of implanted parameters. The resulting velocity is growing with an increase in heat and solutal buoyancy forces, while revolution and slip parameters have reverse effects on this. The resulting velocity is falling due to an increase in the Hartmann quantity, while the penetrability parameters have the opposite impacts on this. The species concentration of fluid is reduced by an increase in Schmidt number and chemical reacting parameter.

Development of a new, fully automated system for electron backscatter diffraction (EBSD)-based large volume three-dimensional microstructure mapping using serial sectioning by mechanical polishing, and its application to the analysis of special boundaries in 316L stainless steel.

We report the development of a fully automatic large-volume 3D electron backscatter diffraction (EBSD) system (ELAVO 3D), consisting of a scanning electron microscope (ZEISS crossbeam XB 1540) with a dedicated sample holder, an adapted polishing automaton (Saphir X-change, QATM), a collaborative robotic arm (Universal Robots UR5), and several in-house built devices. The whole system is orchestrated by an in-house designed software, which is also able to track the process and report errors. Except for the case of error, the system runs without any user interference. For the measurement of removal thickness, the samples are featured with markers put on the perpendicular lateral surface, cut by plasma focused ion beam (PFIB) milling. The individual effects of both 1μm diamond suspension and oxide polishing suspension polishing were studied in detail. Coherent twin grain boundaries (GBs) were used as an internal standard to check the removal rates measured by the side markers. The two methods for Z-spacing measurements disagreed by about 10%, and the inaccurate calibration of the PFIB system was found to be the most probable reason for this discrepancy. The angular accuracy of the system was determined to be ∼2.5°, which can be significantly improved with more accurate Z-spacing measurements. When reconstructed grain boundary meshes are sufficiently smoothed, an angular resolution of ±4° is achieved. In a 3D EBSD dataset of a size of 587 × 476 × 72μm3, we focused on the investigation of coincidence site lattice ∑9 GBs. While bearing predominantly a pure tilt character, ∑9 GBs can be categorized into three groups based on correlative 3D morphologies and crystallography.

Circularly Polarized High Gain Leaky-Wave Antenna for CubeSat Communication

In this work, a novel planar leaky-wave antenna (LWA) and its array are proposed and presented for CubeSat communication applications. Using the substrate-integrated waveguide (SIW) technology, the proposed LWA is implemented by etching periodic fan-shaped slots on top of an SIW. These novel fan-shaped slots exhibit extraordinary circular polarization (CP) radiation in high efficiency over a wide frequency band. Moreover, by switching the excitation ports, both left-handed (LH) and right-handed (RH) CPs are achieved in a wide beam steering range backward or forward. An SIW LWA prototype has been designed and tested with validate LHCP/RHCP steering beams ranging from –51° to 0° or from 51° to 0° in the elevation when the frequency varies from 27.4 to 37.3 GHz. In the 30% frequency band, the axial ratios (ARs) on the main beams are all less than 3 dB demonstrating the broadband CP characteristic. In this 1-D LWA, the realized gain varies from 12.4 to 17.9 dBi. However, it requires higher gain and a fixed beam but narrow bandwidth (BW) in some applications like CubeSats. Hence, a conformal LWA array is further introduced by combining the CP radiation of two LWAs deployed in two perpendicular surfaces of a one cubic unit (1U) CubeSat. Fed by an elaborated vertical transition, the conformal array is designed at 28 GHz with a high directive sum beam along the diagonal direction, requiring each LWA to radiate at ± 45°. As a result, the total gain is enhanced from 14.4 to 16.6 dBi with an AR of 1.8 dB and a sidelobe level (SLL) of −17.1 dB. The proposed compact planar LWA and its array provide promising CP radiation in terms of ARs, BW, polarization flexibility, impedance matching, efficiency, and gain, which reveals great potential for applications in satellite communication systems that demanding low profile, lightweight, dual CPs, and high directivity.