Layer Lattice Research Articles

A 3D-printed integrated MXene-based evaporator with a vertical array structure for salt-resistant solar desalination

A 3D integrated MXene-based evaporator, combining polyimide/MXene (PIM) aerogel arrays as the upper layer and polyimide (PI) aerogel lattices as the bottom layer, can achieve efficient photo-to-heat conversion and excellent salt-resistance in the same system.

Features of amplitude frequency characteristics of ABS plastic 3D printed metamaterial sample

In this study, we investigated the acoustical properties of custom-designed phononic crystal-like acoustic metamaterials 3D printed from ABS plastic. The elastic properties of these metamaterials were studied experimentally and numerically. The metamaterial consisted of a set of plane parallel lattices the number of which could vary in different samples. Each lattice in the sample consisted of 16 parallel square rods. The amplitude-frequency characteristics (AFC) of the fabricated metamaterial sample were measured in the frequency range (35-100) kHz using longitudinal acoustic waves both in air and water. The propagation velocities of longitudinal and shear acoustic waves of ABS plastic itself were measured prior to the experiment. The band gaps (stop bands) were detected and investigated while measuring AFC of the metamaterials. We have found that the increase in the number of lattice layers in the sample led to the band gap acoustic wave attenuation coefficient increase along with the band gap narrowing, while the central frequency of the band gap remained the same. The numerical simulation of the sample frequency response was carried out in COMSOL. The results of experimental studies and numerical simulations were in satisfactory agreement. We have also investigated the ultrasound scattering diffraction pattern of the sample. The obtained results can be used in solid-state physics and material science, to create materials with controlled frequency-dependent acoustic properties.

Quantum spin-liquid states in an organic magnetic layer and molecular rotor hybrid

The exotic properties of quantum spin liquids (QSLs) have continually been of interest since Anderson's 1973 ground-breaking idea. Geometrical frustration, quantum fluctuations, and low dimensionality are the most often evoked material's characteristics that favor the long-range fluctuating spin state without freezing into an ordered magnet or a spin glass at low temperatures. Among the few known QSL candidates, organic crystals have the advantage of having rich chemistry capable of finely tuning their microscopic parameters. Here, we demonstrate the emergence of a QSL state in [EDT-TTF-CONH2]2 +[[Formula: see text]] (EDT-BCO), where the EDT molecules with spin-1/2 on a triangular lattice form layers which are separated by a sublattice of BCO molecular rotors. By several magnetic measurements, we show that the subtle random potential of frozen BCO Brownian rotors suppresses magnetic order down to the lowest temperatures. Our study identifies the relevance of disorder in the stabilization of QSLs.

Effect of Patch Area and Interaction Length on Clusters and Structures Formed by One-Patch Particles in Thin Systems.

Assuming that the interaction between particles is given by the Kern–Frenkel potential, Monte Carlo simulations are performed to study the clusters and structures formed by one-patch particles in a thin space between two parallel walls. In isothermal–isochoric systems with a short interaction length, tetrahedral tetramers, octahedral hexamers, and pentagonal dipyramidal heptamers are created with increasing patch area. In isothermal–isobaric systems, the double layers of a triangular lattice, which is the (111) face of the face-centered cubic (fcc) lattice, form when the pressure is high. For a long interaction length, a different type of cluster, trigonal prismatic hexamers, is created. The structures in the double layers also changed as follows: a simple hexagonal lattice or square lattice, which is the (100) face of the fcc structure, is created in isothermal–isobaric systems.

Independent sets in the middle two layers of Boolean lattice

For an odd integer n=2d−1, let B(n,d) be the subgraph of the hypercube Qn induced by the two largest layers. In this paper, we describe the typical structure of independent sets in B(n,d) and give precise asymptotics on the number of them. The proofs use Sapozhenko's graph container method and a recently developed method of Jenssen and Perkins, which combines Sapozhenko's graph container lemma with the cluster expansion for polymer models from statistical physics.

Self-Lubricating PVD Hard Coatings through Tribological Activation

PVD (physical vapor deposition) hard coatings are widely used and common in manufacturing technologies, for the use as wear and oxidation protection of tools and components. Therefore, many specialized hard coatings systems have been developed until now. Nevertheless, there is a demand to improve the functionality of PVD hard coatings, i.e. due to a self-lubricating effect through tribological activation. According to the current state of research, solid lubricants with lattice layer structure and oxidic solid lubricants are particularly suitable for this purpose. This work gives an overview on the functional mechanisms as well as required environmental conditions and activation mechanisms of transition metal dichalcogenides (TMD) and Magnéli-phases.

The crashworthiness performance of thin-walled ultralight braided lattice composite columns: Experimental and finite element study

We studied the crashworthiness performance of thin-walled ultralight braided lattice composites (UBLCs) under quasi-static compressive loading experimentally and numerically. The lattice structures were initially preformed on mandrels with various cross-sectional geometries, including circular, octagonal, hexagonal, and rectangular. The effects of cross-section type and perimeter were also investigated. Our results showed that the square-shaped sample exhibited the highest specific absorbed energy (SAE) and absorbed energy per length. We also investigated the effect of the number of lattice layers. The concentric multi-layer samples absorbed more energy than single-layer samples due to interactions between the embedded layers. Furthermore, the crushing force efficiency (CFE) was improved by the use of multi-layer samples. Finite element (FE) modeling was used to predict and analyze the energy absorption behavior of UBLC samples. Both structure buckling and material failure were included in the simulations. The results of the FE simulation were in good agreement with our experimental results. The SAEs of single-layer and multi-layer UBLCs are significantly higher than those of expanded metal tubes. Considering SAE and CFE simultaneously, we can conclude that the energy absorption behavior of UBLC structures is more promising than that of similar tubular lattice structures.

Improving Electrochemical Properties by Sodium Doping for Lithium-Rich Layered Oxides

Li-rich manganese base oxides with a high specific capacity of nearly 300 mA h g–1 are acting as the most superior cathode material for high-energy density lithium-ion batteries. However, voltage decaying and poor rate capability critically restrict their applications. In order to solve this problem, the Na ion was used to dope into the lattice of the Li-rich manganese base oxides through solid-state reactions. All prepared samples are highly crystalline, and Na+ is uniformly distributed. The doping of Na+ does not adversely affect the parallel crystal plane structure. The charge–discharge capacities can be effectively increased by doping of Na ions. The rate performance of Li1.2Na0.03[Ni0.2464Mn0.462Co0.0616]O2 (LNa0.03NMC) is improved significantly, and the discharge capacities are 248, 234, 209, 190, 172, and 138 mA h·g–1 at 0.1, 0.2, 0.5, 1, 2, and 5 C, respectively. After 110 cycles of Li1.2Na0.03[Ni0.2464Mn0.462Co0.0616]O2 at 1 C, the reversible capacity only reduced from the initial 194.4–188.9 mA h·g–1 and only attenuates from 3.710 to 3.622 V of average discharge voltage. This work demonstrates that doping of Na ions not only stabilizes lattice layers of lithium-rich layered cathode but also facilitates the diffusion of Li ions in the crystal lattice.

Ensemble Monte Carlo Electron Transport Simulation for GaN n+–n–n+ Diode

Ensemble Monte Carlo simulator is used for solution of Boltzmann transport equation coupling with Poisson equation. We study the electron transport in cubic GaN n+–n–n+ for voltages range from 0.5 to 4 V. In this simulation technique, spatial motion of electron is treated semi-classically and scattering mechanisms included are those due to phonons scattering and ionized impurities scattering. Profile of the electron density, average velocity, kinetic energy, electrostatic potential and electric field are computed. Results are reported for different lattice temperature and various active layer lengths.

Ferromagnetic epitaxial Cr2O3 thin films grown on oxide substrates by Pulsed Laser Deposition

Single-phase and single-oriented epitaxial Cr2O3 thin film has been grown on SrTiO3 (111) substrate for the first time. The morphology, epitaxial growth mode and oxygen stoichiometry of the obtained film have been investigated by AFM, XRR, XRD and XPS, and compared to thin film grown on α-Al2O3 under equivalent conditions. The Cr2O3/SrTiO3 system presents a non-coincidence growth based on in–plane rotation of 30° of the Cr2O3 layer respect to the underlying SrTiO3 (111) substrate, while a coincidence growth based on axis-on-axis coupling is present for Cr2O3/α-Al2O3. However, in both cases an in-plane compression occurs in order to match the layer and substrate lattices. The formation of punctual defects in the form of oxygen vacancies have been observed by XPS for the layer grown on α-Al2O3, being the main mechanism for strain alleviation (−4%). However, the 18 nm thick layer grown on SrTiO3 presents stoichiometric oxygen content maintaining an epitaxial strain (−1.6%) accumulated on the lattice. Both epitaxial Cr2O3 layers show soft ferromagnetic response with coercive fields of 60 Oe and 90 Oe for the layer grown on SrTiO3 and α-Al2O3, respectively.

Effect of Na Doping on Electrochemical Properties of Cobalt-Free Li-Rich Mn-Based Cathode Materials

Na doping is introduced to improve the electrochemical properties of Li1.2Mn0.6Ni0.2O2 cathode material, which is synthesized by sol–gel method. The effect of Na doping on the morphological, structural and electrochemical properties was systematically studied and analyzed. These results illustrate that lattice layer spacing is enlarged by Na doping, which is beneficial for the diffusion of Li-ion, and the voltage fading is successfully suppressed. The best electrochemical properties were obtained when Na doping amount is approximately 1%, which is attributed to the stronger structural stability and better reversibility of Li+ during the initial charge and discharge process.

The role of kaolin and kaolin/ZnO nanoadsorbents in adsorption studies for tannery wastewater treatment

In the present study, comparative studies of kaolin and kaolin/ZnO nanocomposites for the adsorption of Cr(VI), Fe(III), COD, BOD, and chloride from tannery wastewater were investigated. ZnO nanoparticles and kaolin/ZnO nanocomposites were prepared by sol–gel followed by wet-impregnation methods. The prepared adsorbents were characterized using different analytical tools such as X-ray diffraction, Fourier transforms infrared, high-resolution transmission electron microscopy, energy dispersive spectroscopy, selective area electron diffraction and Brunauer Emmett–Teller (BET) and X-ray Photoelectron Spectroscopy (XPS). The HRSEM/EDS/XPS analysis confirmed successful immobilization of clay structural network on the lattice layers of zincite hexagonal structure of ZnO nanoparticles. BET measurement showed an increase in the surface area of kaolin/ZnO nanocomposites (31.8 m2/g) when compared to kaolin (17 m2/g). Batch adsorption studies were carried out by varying the parameters such as contact time, adsorbent dosage and temperature. The maximum removal of Cr(VI) (100%), Fe(III) (98%), COD (95%), BOD (94%) and Chloride (78%) was obtained at 15 min by kaolin/ZnO composites. While 78% Cr(VI), 91% Fe(III), 91% COD, 89% BOD and 73% Chloride were removed by kaolin under the same conditions. The kaolin/ZnO nanocomposites exhibited better adsorption performance than kaolin due to higher surface area of the former than the latter. It was found that the Jovanovic isotherm model fitted the adsorption experimental data most with the highest correlation (R2 > 0.99) for both nanoadsorbents and indicate the occurrence of adsorption on monolayer and heterogeneous surfaces. The mechanism for the adsorption of metal ions in tannery wastewater onto the nano-adsorbents was examined using Weber Morris intra-particle diffusion model and Boyd plot which showed that the adsorption process was both intra-particle and film diffusion controlled. The thermodynamic parameters such as enthalpy change showed that that adsorption of metal ions and other parameters was feasible, spontaneous and endothermic. The ZnO/clay nanocomposites exhibited excellent recyclable and re-useable properties even after six repeated applications and can, therefore, be applied in wastewater treatment for removal of heavy metals and other physicochemical parameters.

Static and dynamic spin properties in the quantum triangular lattice antiferromagnet Ag2CoO2

In ${\mathrm{Ag}}_{2}{\mathrm{CoO}}_{2}$, Co forms triangular lattice layers, which are separated by the metallic (${\mathrm{Ag}}_{2}$) block. The magnetic susceptibility and heat capacity measurements show that this material exhibits an antiferromagnetic transition at ${T}_{\mathrm{N}}=17.5$ K and the Weiss temperature (${T}_{\mathrm{\ensuremath{\Theta}}}$) and the effective moment are $\ensuremath{-}274$ K and $1.62\phantom{\rule{0.28em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$, respectively, indicating that the Co ion carries spin ($S$) 1/2 and has a strongly frustrated state with ${T}_{\mathrm{\ensuremath{\Theta}}}/{T}_{\mathrm{N}}=15.7$. A density functional theory calculation confirmed that the valence state of the Co ions is $2+$ and the low-spin state with $S=1/2$ is realized at reduced on-site Coulomb interaction on Co. We performed elastic and inelastic neutron scattering experiments in a powder sample of ${\mathrm{Ag}}_{2}{\mathrm{CoO}}_{2}$. Although no noticeable magnetic Bragg peaks were observed below ${T}_{\mathrm{N}}$, distinct magnetic excitations were observed in the inelastic neutron scattering experiments. The excitations are consistent with those expected for the $S=1/2$ Heisenberg triangular lattice antiferromagnet. These results suggest that the ordered moment is reduced due to the quantum effect, which explains the absence of the magnetic Bragg peaks. Our results thus suggest that ${\mathrm{Ag}}_{2}{\mathrm{CoO}}_{2}$ is a good candidate to realize a quantum Heisenberg triangular lattice antiferromagnet.

Stanene: A good platform for topological insulator and topological superconductor

Two dimensional (2D) topological insulators (TIs) and topological superconductors (TSCs) have been intensively studied for recent years due to its great potential for dissipationless electron transportation and fault-tolerant quantum computing, respectively. Here we focus on stanene, the tin analogue of graphene, to give a brief review of its development as a candidate for both 2D TI and TSC. Stanene is proposed to be a TI with a large gap of 0.3 eV, and its topological properties are sensitive to various factors, e.g., the lattice constants, chemical functionalization and layer thickness, which offer various methods for phase tunning. Experimentally, the inverted gap and edge states are observed recently, which are strong evidence for TI. In addition, stanene is also predicted to be a time reversal invariant TSC by breaking inversion symmetry, supporting helical Majorana edge modes. The layer-dependent superconductivity of stanene is recently confirmed by both transport and scanning tunneling microscopy measurements. This review gives a detailed introduction to stanene and its topological properties and some prospects are also discussed.

External quantum efficiency of a resonant tunneling diode photo detector: Structural parameters and wavelength dependencies

In this study, a resonant tunneling diode with AlAs/GaAs double barrier structure is simulated by using the non-equilibrium green’s function. A lattice mastched InGaAs absorption layer is added to the device for light sensing at the wavelength λ = 600 nm. The Photo current of the device and source photo current curves versus light intensity are compared. The quantum efficiency of the device and its dependences on structural parameters (absorption layer thickness, spacer thickness, collector and emitter width) and different wavelengths were simulated and their influences on operation of the device were investigated. The external quantum efficiency of 0.95 was obtained for the device at room temperature. The simulation results show that changing of external quantum efficiency upon absorption layer thickness is nonlinear. Electric field through the device and the absorption curve versus wavelength are presented. Also with increasing of spacer layer and collector thicknesses, external quantum efficiency also changes.

Paleogeographic, paleoclimatic and sea-level implications of glauconite deposits in Egypt: A review

Glauconite deposits are confined to the Western Desert in Egypt of four different sequences and ages from older to younger include, 1) Lower Cenomanian Bahariya Formation, 2) Lower-Middle Campanian Qusseir Formation, 3) Upper Campanian Duwi Formation, and 4) Lutetian-Bartonian Hamra Formation.Lower Cenomanian, Upper Campanian and Lutetian-Bartonian glauconites occur as pellets, while the Lower-Middle Campanian glauconite occurs as fine-grained particles of non-pelletal texture. Based on K2O contents, the Lower Cenomanian and Upper Campanian glauconites are classified as slightly evolved, while the Lower-Middle Campanian and Lutetian-Bartonian glauconite are categorized as evolved. Positive correlations between K2O and Fe2O3 in the Bahariya Formation, Qusseir Formation and Hamra Formation deposits suggest a layer lattice glauconitization mechanism for these deposits. On the other hand, the lack of correlation between Fe2O3 and K2O declines the layer lattice formational mechanism for the Duwi Formation glauconite. A neo-formation mechanism was suggested for this glauconite. Rare earth elements patterns are the same in the four deposits and resemble the shallow sweater pattern.The four glauconite deposits formed in shallow marine environments and might correspond to major eustatic transgressive and global warming events. Glauconite of the Bahariya Formation corresponds to the Early Cenomanian Tethys major transgression in Egypt and can be correlated to the Albian/Cenomanian global cycle boundary as well as the early Cenomanian “hot greenhouse”. The sequence boundary near the topmost part of the Qusseir Formation matches the global warming of the Middle Campanian Event (MCE). The upper Campanian glauconite of the Duwi Formation occurs as lowstand wedge and may correlate to the late Campanian climatic warm optimum. The stratigraphic position of the Hamra glauconite above the unconformity surface refers to transgressive phase that may match with latest Lutetian major sequence boundary (Lu4) and global warming event of the Middle Eocene Climatic Optimum (MECO).Paleogeographic maps show that the Western Desert of Egypt during Cenomanian and Lower Campanian covered by shallow marine setting, which match with the proposed setting for the glauconites in these ages. However, paleogeographic maps for the Upper Campanian and Middle Eocene were modified to fit with the suggested setting of glauconites of these epochs. The prevalence of shallow marine setting during these four ages interprets the restricted occurrences of glauconites at the Western Desert of Egypt during these epochs.

Effect of Na Doping or Substitution on the Structural and Electrochemical Properties of Cobalt-Free Li-Rich Mn-Based Cathode Materials

Cobalt-free Li-rich Mn-based cathode materials are considered to be the next generation of Li-ion batteries due to low cost, high discharge capacities and high safety feature. However, there are still several serious issues that need to be solved urgently, such as low initial coulombic efficiency, low rate capability, poor cycling performance and voltage fading. Na doping or substitution is introduced to improve the electrochemical performance of Li1.2Mn0.6Ni0.2O2 cathode material, which is synthesized by sol-gel method. The effect of Na doping or substitution on the morphological, structural and electrochemical properties was systematically studied and analyzed by scanning electron microscope (SEM), X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cell test system and electrochemical workstation. These results illustrate that lattice layer spacing is enlarged by Na doping or substitution, which is beneficial for the diffusion of Li-ion, and the voltage fading is successfully suppressed. The best electrochemical properties were obtained when Na doping, which is attributed to the stronger structural stability and better reversibility of Li+ during the initial charge and discharge process.

Atomistic Perspective of Long Lifetimes of Small Skyrmions at Room Temperature.

The current development to employ magnetic skyrmions in novel spintronic device designs has led to a demand for room-temperature-stable skyrmions of ever smaller size. We present extensive studies on skyrmion stability in atomistic magnetic systems in two- and three-dimensional geometries. We show that for materials described by the same micromagnetic parameters, the variation of the atomistic exchange between different neighbors, the stacking order, and the number of layers of the atomic lattice can significantly influence the rate of the thermally activated decay of a skyrmion. These factors alone are important considerations, but we show that their combination can open up novel avenues of materials design in the search for sub-10nm skyrmions, as their lifetime can be extended by several orders of magnitude.

Thermal Characteristics of Expandable Graphite-Wood Particle Composites.

According to the Fire Statistics Yearbook of the National Fire Agency of the Republic of Korea, the total number of fires in 2018 was 42,338, which resulted in 2500 victims and amounted to property damages of approximately 560 billion KRW. The number of fires in buildings where wood was used as a finishing material was 28,013 (66%) in that period. To minimize human and property damage, composite materials were prepared by mixing wood particles with expandable graphite. The physical and thermal properties of the composite materials were investigated. It was observed that the expansion rate increased by 341.7% according to the expandable graphite content. Additionally, the total heat released and the thermal conductivity decreased from 38.63 to 2.5 MJ/m2 and from 24.62 to 7.8 W/m·K. The time to inactivity of white mouse in the smoke toxicity test was 14.9 min and exceeded the toxicity standard for flame retardant performance. The expandable graphite added to composite materials adopted worm-like shapes as a result of combustion, and it formed a fine lattice layer structure with 16–22 μm gaps that could reduce thermal conductivity. In addition, we can minimize the damage to people and property in the event of a fire.

Solvable Models of Supercooled Liquids in Three Dimensions.

We introduce a supercooled liquid model and obtain parameter-free quantitative predictions that are in excellent agreement with numerical simulations, notably in the hard low-temperature region characterized by strong deviations from mode-coupling-theory behavior. The model is the Fredrickson-Andersen kinetically constrained model on the three-dimensional M-layer lattice. The agreement has implications beyond the specific model considered because the theory is potentially valid for many more systems, including realistic models and actual supercooled liquids.