Hexagonal Surface Research Articles

Unconventional Hexagonal Close-Packed High-Entropy Alloy Surfaces Synergistically Accelerate Alkaline Hydrogen Evolution.

Accelerating the alkaline hydrogen evolution reaction (HER), which involves the slow cleavage of HO-H bonds and the adsorption/desorption of hydrogen (H*) and hydroxyl (OH*) intermediates, requires developing catalysts with optimal binding strengths for these intermediates. Here, the unconventional hexagonal close-packed (HCP) high-entropy alloy (HEA) atomic layers are prepared composed of five platinum-group metals to enhance the alkaline HER synergistically. The breakthrough is made by layer-by-layer heteroepitaxial deposition of subnanometer RuRhPdPtIr HEA layers on the HCP Ru seeds, despite the thermodynamic stability of Rh, Pd, Pt, and Ir in a face-centered cubic (FCC) structure except for Ru. The synchrotron X-ray absorption spectroscopy (XAS) confirms the atomic mixing and coordination environment of HCP RuRhPdPtIr HEA. Most importantly, they exhibit notable improvements in both electrocatalytic activity and durability for the HER in an alkaline environment, as compared to their FCC RuRhPdPtIr counterparts. Electrochemical measurements, operando XAS analysis, and density functional theory unveil that the binding strengths of H* and OH* intermediates on the active Pt and Ir sites can be weakened and strengthened to a moderate level, respectively, by mixing non-active Ru, Rh, and Pd atoms with Pt and Ir atoms within the HCP HEA with strong synergistic electronic effects.

Thermodynamic analysis of superhydrophobicity on three-dimensional hexagonal microcolumn surfaces

Thermodynamic analysis of superhydrophobicity on three-dimensional hexagonal microcolumn surfaces

A Comparative Analysis of the Impact of Circular, Square and Hexagonal Frequency Selective Surfaces on the Performance of a 10GHz Microstrip Patch Antenna

A Comparative Analysis of the Impact of Circular, Square and Hexagonal Frequency Selective Surfaces on the Performance of a 10GHz Microstrip Patch Antenna

Gas adsorption analysis for quantifying the edge sites of graphite

The edge plane exposed on the surface of carbon materials is the active site that determines their properties. When graphite is used as the negative electrode in lithium-ion batteries, the edge plane acts as an access point for lithium insertion/desorption. However, because of the low specific surface area and amorphous carbon coating of graphite particles, accurately estimating the number of edge planes is challenging. Therefore, we propose a technique for determining graphite edge planes based on the stepwise adsorption of Kr onto the hexagonal carbon network surface. Graphite particles with highly modified surface structures were prepared by controlling the particle size, heat treatment temperature, and amorphous carbon coating. Electrochemical evaluation revealed significant differences in charge-transfer resistance, an indicator of edge planes. The edge plane determination results obtained using conventional methods such as X-ray diffractometry and Raman spectroscopy did not correlate well with charge-transfer resistance. Meanwhile, Kr adsorption measurements revealed that the stepwise adsorption behavior, because of the interaction of Kr with the energetically homogenous surface, varied significantly depending on the surface properties of graphite particles. The number of edge planes estimated by gas adsorption strongly correlated with charge-transfer resistance. Consequently, we determined that the graphite edge plane tied to the electrochemical index can be derived using gas adsorption analysis. This edge plane determination technique would be applicable not only to graphite but also to highly crystalline carbon materials with an exposed hexagonal carbon network surface.

Scanning electron microscopy and light microscopy of tongue, fingers, toes, nuptial pad, and humeral gland in Sylvirana nigrovittata (Anura: Ranidae)

The micromorphology and histology of anuran skin, particularly in Thai species, remain relatively understudied. Anurans use their tongues for prey capture and their hands and feet for adhesion and mating, suggesting a close relationship between micro-surface features and histological structure. Information on Sylvirana nigrovittata is particularly limited. This study provides a detailed examination of the micro-surface and histological characteristics of the tongue, fingers, toes, nuptial pad, and humeral gland in S. nigrovittata. Specimens collected from Phu Luang Wildlife Sanctuary in Loei province, northeastern Thailand, were studied using scanning electron microscopy (SEM) for micro-surface features and H&E staining for histological details. SEM micrographs revealed that the tongue was cordate-shaped, with about 75% of its surface covered by filiform papillae and 25% by fungiform papillae housing taste buds. Filiform papillae were trapezoidal, averaging 23.88±5.68 µm in width and 38.83±6.57 µm in length, while fungiform papillae were disc-like, averaging 52.95±14.64 µm in width and 66.70±15.88 µm in length. Digital pads on fingers and toes presented prismatic cells, with fingertip cells averaging 7.09±0.97 µm in width and 11.81±1.24 µm in length, and toe cells averaging 8.40±1.37 µm in width and 11.28±1.63 µm in length. Subdigital surfaces were smoother, containing squamous cells with dimensions of 10.65±3.21 µm in width and 21.29±4.35 µm in length. Subarticular tubercles were composed of prismatic cells with hexagonal or pentagonal surfaces, averaging 10.02±2.85 µm in width and 13.08±1.94 µm in length. Nuptial pad displayed cylindrical structures with dome-like tips, averaging 24.01±3.96 µm in width and 21.16±4.37 µm in length, and feature mucous openings. They consisted of a thick keratinized stratified squamous epithelium and a dense dermis with specialized mucous glands. Humeral gland exhibited rough surfaces with squamous cells and microridges, showing both small and large mucous openings, with average cell dimensions of 16.23±1.70 µm in width and 19.11±2.05 µm in length. Histological analysis confirmed that these structures were predominantly composed of keratinized stratified squamous epithelium, with variations in dermal collagen density and mucous gland distribution. This study enhances our understanding of the skin and gland morphology in S. nigrovittata, highlighting on its anatomical and functional adaptations.

Solar-driven purification: Removing pharmaceutical contaminants from water using carbon-doped NASICON photocatalyst

Pharmaceutical contaminants in water pose significant risks to aquatic ecosystems and human health. This work synthesized a novel NASICON@C composite (sodium super ionic conductor embedded with carbon) as a visible-light-driven photocatalyst for eliminating paracetamol from water. Characterization confirmed a well-dispersed composite with hexagonal morphology, surface porosity, and strong visible light absorption. The carbon phase enabled visible light harvesting while the NASICON facilitated charge transfer and redox reactions. Photocatalytic testing showed dramatic paracetamol degradation within 30 min under visible irradiation using NASICON@C. 99.7 % of the initial 100 mg L−1 paracetamol was eliminated in neutral pH conditions. The ion-conducting NASICON framework promoted efficient charge carrier separation and transfer to enable the oxidation reactions. The NASICON@C catalyst displayed excellent stability over five reuse cycles. The synergistic integration of carbon and NASICON phases in this composite photocatalyst makes it a promising and sustainable platform for visible light-driven pharmaceutical contaminant removal from water sources.

Hole-Carrier-Dominant Transport in 2D Single-Crystal Copper.

In 2D noble metals like copper, the carrier scattering at grain boundaries has obscured the intrinsic nature of electronic transport. However, it is demonstrated that the intrinsic nature of transport by hole carriers in 2D copper can be revealed by growing thin films without grain boundaries. As even a slight deviation from the twin boundary is perceived as grain boundaries by electrons, it is only through the thorough elimination of grain boundaries that the hidden hole-like attribute of 2D single-crystal copper can be unmasked. Two types of Fermi surfaces, a large hexagonal Fermi surface centered at the zone center and the triangular Fermi surface around the zone corner, tightly matching to the calculated Fermi surface topology, confirmed by angle-resolved photoemission spectroscopy (ARPES) measurements and vivid nonlinear Hall effects of the 2D single-crystal copper account for the presence of hole carriers experimentally. This breakthrough suggests the potential to manipulate the majority carrier polarity in metals by means of grain boundary engineering in a 2D geometry.

Water-Etched Porous Ti: Surface Manipulation of Ti Foam Fabricated by Liquid Metal Dealloying Technique.

The liquid metal dealloying (LMD) process enables the fabrication of porous metals with various chemical compositions. Despite its advantages, LMD still faces key challenges such as maintaining the high-temperature molten metal bath for a prolonged time, avoiding the use of toxic etchants, and so on. To overcome these challenges, the study develops a water-leachable and oxidation-resistant alloy melt (AM) in Ca-Mg binary system. Specifically, Ca72Mg28 eutectic AM is designed, which exhibits higher oxidation resistance and lower melting temperature compared to pure Mg, allowing LMD to be conducted in atmospheric conditions as well as temperatures >200K lower. The AM also enables an innovative process to fabricate Ti foams with a hexagonal faceted surface structure by carefully manipulating the etching rate during the water etching process. This approach allows for the creation of foam with a surface area over 13% larger than that of foams with smooth surfaces via normal acid etching, potentially enhancing efficiency in applications such as electrodes for electrochemical systems or biomedical materials where increased cell adhesion can be beneficial. This study paves the way for efficiently manipulating the LMD process to fabricate metal foams with customized compositions and enhanced surface properties.

Characterization and Adsorption Capacity Evaluation of ZnCl2 Impregnated Cassava Peel Carbon for Removal of Fe, Ca, Mg and Zn ions in Wastewater from Cassava processing Industry

The objective of this paper was to prepare, characterize and evaluate the adsorption capacity of cassava peel carbon (CPC) impregnation with ZnCl2 salt for the removal of Fe, Ca, Mg and Zn ions in wastewater derived from cassava processing which has been noted to be problematic in terms of management. CPC and cassava peel activated carbon (CPAC) at 1:3, 2:3, and 1:1 impregnation levels were placed in fixed bed adsorption columns to determine metal ion adsorption capacities of the carbon materials after 120, 240, 360 and 480-minute contact times. Langmuir and Freundlich isotherm models were used in assessment of adsorption of the carbon materials, while pseudo-first and second order models were used to validate the adsorption kinetics of Fe, Ca, Mg and Zn. Pore space development was also monitored using scanning electron microscope (SEM) imagery. Results SEM images revealed hexagonal honeycomb surface structure at 2:3 impregnation level and spongy configuration at 1:1 ZnCl2 impregnation level. The correlation coefficient of Langmuir isotherm was observed to be between 0.86 to 1, indicating that the adsorbent is very good in adsorption of the metals, however, Freundlich isotherm is found to be unfavorable in describing CPAC’s capacity in adsorbing zinc ion contaminant. The pH of the carbon materials was observed to have increased while the bulk density reduced with increasing level of impregnation. Conclusively, CPC and CPAC materials are well suited to Langmuir isotherm as well as pseudo-second order model, implying that adsorption occurs well in a monolayer form on the surface material surface.

Probing structural superlubricity of two-dimensional water transport with atomic resolution.

Low-dimensional water transport can be drastically enhanced under atomic-scale confinement. However, its microscopic origin is still under debate. In this work, we directly imaged the atomic structure and transport of two-dimensional water islands on graphene and hexagonal boron nitride surfaces using qPlus-based atomic force microscopy. The lattice of the water island was incommensurate with the graphene surface but commensurate with the boron nitride surface owing to different surface electrostatics. The area-normalized static friction on the graphene diminished as the island area was increased by a power of ~-0.58, suggesting superlubricity behavior. By contrast, the friction on the boron nitride appeared insensitive to the area. Molecular dynamic simulations further showed that the friction coefficient of the water islands on the graphene could reduce to <0.01.

Accommodating a hexagonal [formula omitted]- phase Mn2N film on a cubic MgO (001) substrate

The thin films of c-plane dominated hexagonal ζ- phase Mn2N were successfully grown on a cubic MgO (001) substrate directly using plasma-assisted molecular beam epitaxy. The surface was comprehensively studied through experimental and theoretical approaches. Reflection high energy electron diffraction revealed two pseudo-cubic domains along [100]MgO and [110]MgO, and one hexagonal domain, which is 30° apart from the [100]MgO direction. Scanning tunneling microscopy was used to image and resolve the high quality surface, revealing a distorted hexagonal surface structure. Furthermore, atomic resolution of the hexagonal domain with a 2 × 2 reconstructed surface is presented. For the c-plane surface, theoretical investigations were carried out using first-principle studies to determine the surface formation energy for various reconstructed surfaces. The theoretical study shows that the nitrogen terminated 2 × 2 structure with a manganese adatom on the surface is the most stable reconstruction that reproduces the experimental results. A corresponding simulated scanning tunneling microscopy model is also presented, providing strong support for the experimentally observed in-plane lattice structures. The manganese:nitrogen stoichiometry within the bulk and surface is in good agreement with the expected ratio of 2:1.

An optimization study focused on lattice structured custom arm casts for fractured bones inspiring additive manufacturing

In case of fractures, cracks or damage to bone tissues, it is important to use casts, fixatives and protective equipment. Especially in cases where long-term use of casts is required, soft tissue wounds may occur in the human body due to their moisture and airtight structure. For this reason, the use of casts with custom designs, breathable materials, and high mechanical properties has become widespread in recent years. This study focuses on the design of custom arm casts using advanced additive manufacturing technologies and lightweight materials. By utilizing Voronoi lattice structures and hexagonal surface meshes, optimized designs adaptable to additive manufacturing were obtained from a standard arm cast. All cast geometries were investigated under 196 N and 380 N forces. Then, the impact of a 100 g and 1000 g concrete piece with a speed of 12.5 m/s on the arm cast was investigated. As a result of the analyzes, stress, impact plate velocities, deformation, strain and deformation energy were evaluated. The results showed that the designed arm casts have up to 60% better impact strength compared to conventional arm casts. Based on the findings of this study, the use of custom arm casts with optimized lattice structures designed for additive manufacturing will demonstrate high performance.

The influence of anthropogenic regulation and evaporite dissolution on earthquake-triggered ground failure

Remote sensing observations of Searles Lake following the 2019 moment magnitude 7.1 Ridgecrest, California, earthquake reveal an area where surface ejecta is arranged in a repeating hexagonal pattern that is collocated with a solution-mining operation. By analyzing geologic and geotechnical data, here we show that the hexagonal surface ejecta is likely not a result of liquefaction. Instead, we propose dissolution cavity collapse (DCC) as an alternative driving mechanism. We support this theory with pre-event Interferometric Synthetic Aperture Radar data, which reveals differential subsidence patterns and the creation of subsurface void space. We also find that DCC is likely triggered at a lower shaking threshold than classical liquefaction. This and other unknown mechanisms can masquerade as liquefaction, introducing bias into liquefaction prediction models that rely on liquefaction inventories. This paper also highlights the opportunities and drawbacks of using remote sensing data to disentangle the complex factors that influence earthquake-triggered ground failure.

Nonlocal Electrodynamics in Ultrapure PdCoO2

The motion of electrons in the vast majority of conductors is diffusive, obeying Ohm’s law. However, the recent discovery and growth of high-purity materials with extremely long electronic mean free paths has sparked interest in non-Ohmic alternatives, including viscous and ballistic flow. Although non-Ohmic transport regimes have been discovered across a range of materials—including two-dimensional electron gases, graphene, topological semimetals, and the delafossite metals—determining their nature has proved to be challenging. Here, we report on a new approach to the problem, employing broadband microwave spectroscopy of the delafossite metal PdCoO2 in three distinct sample geometries that would be identical for diffusive transport. The observed differences, which go as far as differing power laws, take advantage of the hexagonal symmetry of the conducting Pd planes of PdCoO2. This permits a particularly elegant symmetry-based diagnostic for nonlocal electrodynamics, with the result favoring predominantly ballistic over strictly hydrodynamic flow. Furthermore, it uncovers a new effect for ballistic electron flow, owing to the highly faceted shape of the hexagonal Fermi surface. We combine our extensive data set with an analysis of the Boltzmann equation to characterize the nonlocal regime in PdCoO2, and we include out-of-plane impurity scattering as a source of apparent momentum-conserving scattering at low temperatures. More broadly, our results highlight the potential of broadband microwave spectroscopy to play a central role in investigating exotic transport regimes in the new generation of ultrahigh-conductivity materials. Published by the American Physical Society 2024

Phase Coexistence of Mn Trimer Clusters and Antiferromagnetic Mn Islands on Ir(111).

Clusters supported by solid substrates are prime candidates for heterogeneous catalysis and can be prepared in various ways. While mass-selected soft-landing methods are often used for the generation of monodisperse particles, self-assembly typically leads to a range of different cluster sizes. Here we show by scanning tunneling microscopy measurements that in the initial stages of growth, Mn forms trimers on a close-packed hexagonal Ir surface, providing a route for self-organized monodisperse cluster formation on an isotropic metallic surface. For an increasing amount of Mn, first a phase with reconstructed monolayer islands is formed, until at full coverage a pseudomorphic Mn phase evolves, which is the most densely packed one of the three different observed Mn phases on Ir(111). The magnetic state of both the reconstructed islands and the pseudomorphic film is found to be the prototypical antiferromagnetic Néel state with a 120° spin rotation between all nearest neighbors in the hexagonal layer.

Effect of morphology of ZnO on colorimetric hydrogen sensitivity of PdO@ZnO hybrids

The PdO decorated ZnO (PdO@ZnO) colorimetric hydrogen sensor garners attention for visually detecting hydrogen leaks without relying on external electrical systems. While sensitivity optimization primarily focuses on PdO variations, the influence of the ZnO substrate effect remains less explored. PdO@ZnO hybrids with four different morphologies (sphere, rod, plate, hexagonal disk) are synthesized using an acid-base reaction. The morphology of ZnO influences PdO adsorption due to variations in surface area and oxygen defects. The chemical state of adsorbed palladium species is also affected by the ZnO charge. Among these hybrids, the PdO@ZnO hexagonal disk demonstrates the quickest response time (T90; 182.4s) and the highest color difference (ΔE; 16) under exposure to 4 vol% hydrogen gas. This superior performance is attributed to the hexagonal disk's larger surface area, appropriate zeta potential, and oxygen defect, all of which enhance PdO adsorption. These findings enhance our comprehension of how morphology impacts the colorimetric hydrogen sensitivity of PdO@ZnO hybrids.

Notice of Violation of IEEE Publication Principles: A thin broadband microwave absorber with hexagonal resistive frequency selective surface

Notice of Violation of IEEE Publication Principles A Thin Broadband Microwave Absorber with Hexagonal Resistive Frequency Selective Surface by Feifei Li, Chao Meng, Fan-guang Meng, Digang Fan, Ping Chen, and Rui-xin Wu in the IEEE Antennas and Wireless Propagation Letters (Early Access) April 2018 After careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE’s Publication Principles. This paper contains significant portions of work presented in the paper cited below. The original work was translated and copied without attribution (including appropriate references to the original author(s) and/or paper title) and without permission. Design of a Wide‐band Metamaterial Absorber Based on Resistance Films by Gu Chao, Qu Shao‐Bo, Pei Zhi‐Bin, Xu Zhuo, Lin Bao‐Qin, Zhou Hang, Bai Pen, Gu Wei, Peng Wei‐Dong, and Ma Hua in Acta Physica Sinica, Vol 60, No. 8, August 2011 We realized a thin, broadband absorber based on resistive frequency selective surface (FSS). By introducing a design parameter, p-factor, we successfully designed a microwave absorber, whose reflectivity below -10dB covers 6.4-24.9 GHz. The thickness of the absorber is only 0.087-L at the lowest operating frequency. We show that broadband absorption can be achieved by carefully balancing susceptances of resistive FSS and other parts of the absorber. Furthermore, we find that lossless dielectric slabs with lower dielectric constant are the best choices for broadband absorber. Experimentally, the samples were fabricated by using silk-screen printing technique and their absorbing performance was measured. Experimental results are in good agreement with simulated ones. Our work provides a method to realize broadband absorber in a simple way, which may be used for the absorbers working in THz, infrared or even optical band.

Banana peels based zinc oxide doped silver nanoparticles for enhanced photocatalytic degradation of paracetamol

Paracetamol (PCM) is a common drug for daily use in each household and considering PCM’s availability and huge production, traces of waste PCM present in water sources are concerned. Photocatalysis technology shows promising results with the utilization of semiconductor materials and light energy to degrade and remove organic pollutants. In this study, zinc oxide/silver nanoparticles (ZnO/Ag NPs) photocatalyst were synthesized via sol-gel and co-precipitation technique with the aid of banana peels extract (BPE) for photodegradation of PCM. The produced photocatalysts were characterized by UltravioletVisible Spectroscopy (UV-Vis), X-ray Diffraction (XRD), surface area and pore analysis and Field Emission Scanning Electron Microscope (FESEM). Results shows that a blue shift phenomenon occurs between ZnO NPs and ZnO/Ag NPs while XRD analysis suggested that all samples exhibit hexagonal wurtzite structure. ZnO/Ag NPs portrayed a spherical and hexagonal surface morphology with average particles size of 25.68 nm and mesoporous structure. ZnO/Ag NPs shows the highest photodegradation of PCM with 96 % with five repeated cycles compared to pristine ZnO NPs. The main species responsible for PCM degradation via ZnO/Ag are hydroxyl radical and electron. The prepared BPE based ZnO/Ag has a high potential as advanced materials for pharmaceutical wastewater treatment.

Oxidation Tuned Cu 1.94 S Nanostructures for Ultrafast Charge and Discharge

Morphological control is an effective approach to enhance the rate performance of nanostructured electrode materials, offering a promising solution for alleviating energy concerns. We have utilized a seed-mediated growth method to synthesize hexagonal djurleite (Cu 1.94 S) nanoplates and nanoflowers under N 2 and air, respectively. The influence of the morphology on the ion interaction has been investigated in the storage process through half-cell electrochemical energy storage. Cu 1.94 S nanoplates performed a higher specific capacity of 193 mAh g −1 at a high rate of 8 A g −1 than nanoflowers and showed excellent cycle stability over 4,000 cycles with capacity retention of 80.8%. The relationship between morphology and electrochemical performance was explored through further electrochemical characterization. It is found that the stacking of hexagonal surfaces of nanoplates increases the contact area of the electrode material and reduced resistance, leading to faster ion migration and a more complete redox process, ultimately contributing to a higher specific capacity. Our study has enhanced the understanding of structure–property relationships for electrode material, providing an insightful approach for the preparation of electrode materials suitable for ultrafast charge and discharge.

Sharp zero-phonon lines of single organic molecules on a hexagonal boron-nitride surface

Single fluorescent molecules embedded in the bulk of host crystals have proven to be sensitive probes of the dynamics in their nano environment, thanks to their narrow (about 30–50 MHz or 0.1–0.2 μeV) optical linewidth of the 0-0 zero-phonon line (0-0 ZPL) at cryogenic temperatures. However, the optical linewidths of the 0-0 ZPL have been found to increase dramatically as the single molecules are located closer to a surface or interface, while no 0-0 ZPL has been detected for single molecules on any surface. Here we study single terrylene molecules adsorbed on the surface of hexagonal boron-nitride (hBN) substrates. Our low-temperature results show that it is possible to observe the 0-0 ZPL of fluorescent molecules on a surface. We compare our results for molecules deposited on the surfaces of annealed and non-annealed hBN flakes and we see a marked improvement in the spectral stability of the emitters after annealing.