Types Of Layered Materials Research Articles

Scalable synthesis of few-layered MoS2/C sandwiched nanocomposites via ionic crystal (NH4)2MoS4 assisted ball-milling method and their enhanced high-rate lithium storage property

Ball milling has been proven to be an efficient method for exfoliating and reassembling heterogeneous layered nanocomposites on a large scale. This study explores the use of ammonium tetrathiomolybdate (NH4)2MoS4, an ion crystal with an octahedral structure, as both a precursor of layered molybdenum disulfide (MoS2) and an intermediate during ball milling to assist in the exfoliation and fragilization of expandable graphite (EG). Due to its ion crystal structure and high hardness, (NH4)2MoS4 can efficiently transfer and magnify the impacting and shearing forces generated during the ball milling process, accelerating the exfoliation and fragmentation efficiency of EG. Moreover, (NH4)2MoS4 is nano-crystallized by the ball milling forces and uniformly distributed on the carbon nanosheets. Electrochemical performance tests indicate that the resulting nanocomposites, with a satisfactory heterogeneous structure, exhibit excellent Li-storage capacity, achieving 529 mA h g−1 after 150 cycles at a high current density of 500 mA g−1. The relationship between the microstructure and improved electrochemical performance, as well as the formation mechanism of the product, is discussed in detail. This study provides a new approach for conveniently constructing nanocomposites using two types of layered materials that offer satisfactory rate capability and cyclability, making them potentially suitable for application in Li-ion batteries.

Optical absorption in roughened silicon photovoltaic module

Photovoltaic current electric generation is directly related to the sunlight absorption in the active layers. The active layer material type and the optical losses remain the principal parameters, which have a greater effect on the amount of this absorption. This study focuses on improving the absorption in the silicon active layer of a silicon photovoltaic module by roughening the rear surface of the silicon layer. According to the Generalized Transfer Matrix Method, we derive the transmission from the incoherent multilayered module structure with a rough surface. We follow the optical model developed by Krauter and Hanitsch to derive the transmission into the silicon layer. Then the absorption is deduced from the difference between the transmission from the module and the transmission into the silicon. The effect of the incidence angles on the absorption is considered for different polarizations of light. The results of this study show a significant enhancement in the absorption in comparison to the absorption of the module with a polished rear surface. The short circuit current generated by the module with a rough rear surface silicon layer obtained is greater than that of the module with a polished rear surface.

THE SYNTHESIS METHODS AND APPLICATIONS OF LAYERED DOUBLE HYDROXIDES – A BRIEF REVIEW

Layered double hydroxides (LDHs) which are one type of layered material are promising materials due to some of their interesting properties, such as ease of synthesis, unique structure, uniform distribution of different metal cations in the brucite layer, surface hydroxyl groups, flexible tunability, intercalated anions with interlayer spaces, swelling properties, and high chemical and thermal stability, ability to intercalate different type of anions, and also high biocompatibility. This review article is focused on more information about synthesis methods of layered double hydroxides, and their applications in many fields. The most common synthesis methods for layered double hydroxides are co-precipitation, urea hydrolysis, hydrothermal synthesis, sol-gel, reconstruction, etc. are discussed. LDHs shows excellent performance as a multifunctional material for its promising applications in the fields of catalysts, water treatment, flame retardants, polymer additivies, adsorbents, nuclear industry, environmental protection, photocatalysts, and material science.

K0.54[Co0.5Mn0.5]O2: New Cathode with High Power Capability for Potassium-Ion Batteries

Results and Discussion We propose P3-K0.54[Co0.5Mn0.5]O2, which is rationally designed as a promising cathode material for high-performance potassium-ion batteries (KIBs). Its composition adopts the use of the valence state of Mn above 3.5+ to minimize the disruptive effect of Jahn–Teller distortion in the MnO6 octahedra during the electrochemical reaction. Unlike other types of layered materials that suffer from the sluggish diffusion of large potassium ions accompanying multi-step voltage profiles, P3-K0.54[Co0.5Mn0.5]O2 delivers a high specific discharge capacity of 120.4 mAh (g-oxide)-1 with smooth charge and discharge curves. First-principles calculations predict an activation barrier energy of ~260 meV for a large K+ diffusion, which is comparable to those observed in conventional layered cathode materials for lithium-ion batteries. As a result, even at 500 mA g-1, P3-K0.54[Co0.5Mn0.5]O2 is able to deliver a high discharge capacity of 78 mAh g-1, which is a retention of 65% versus the capacity obtained at 20 mA g-1. Combination studies using operando X-ray diffraction, the ex-situ X-ray absorption near-edge structure, and first-principles calculations elucidate the nature of the excellent potassium storage mechanism of K0.54[Co0.5Mn0.5]O2. This work provides a new insight for the development of efficient cathode materials for KIBs. Experimental The P3-K0.54[Co0.5Mn0.5]O2 powder was synthesized using a typical combustion method. An aqueous solution was stoichiometrically prepared by dissolving KNO3, Co(NO3)6H2O, Mn(NO3)26H2O, and citric acid as a chelating agent in distilled water. The starting solution was evaporated overnight on a hot plate at 110 °C under constant stirring. Then, the dried powders were further heated to 200 °C for the auto-combustion of the citric acid. The as-received powders were calcined at 500 °C for 3 h to decompose the nitrates, and then re-calcined at 800 °C for 5 h under an air atmosphere at a heating rate of 2 °C min-1. This was followed by slow cooling at a cooling rate of 1 °C min-1. The X-ray diffraction (XRD) with Cu kα radiation were conducted and structural crystallinity analyzed by Rietveld refinement. The particle morphologies and surface of the powders were observed using SEM and TEM. Galvanostatic charge/discharge test was performed using a R2032-type coin cell. The K-storage mechanisms in the charge and discharge processes were examined by means of ex-situ XRD, in operando XRD, and ex-situ X-ray absorption spectroscopy (XAS). Also, the structural variation of P3-K x [Co0.5Mn0.5]O2 was predicted as a function of the K+ content in the structure based on the first-principles calculation. Figure 1

Mitigating early fracture of amorphous metallic thin films on flexible substrates by tuning substrate roughness and buffer layer properties

Ductility mismatch between brittle amorphous thin films and flexible polymer substrate often leads to limited elongation and early failure of the system. A combined experimental and computational study was carried out to investigate the roles of buffer layer material type, thickness, and substrate roughness on the fracture toughness of the amorphous thin film/polymer system. Experimentally, about 1 μm thick amorphous aluminum-manganese thin films were deposited on polyimide substrates and tested in tension. The reliability of such systems was found to be strongly influenced by the film/substrate interface adhesion. Several strategies to improve the adhesion of the interface were conducted, including roughening the surface of the substrate, and adding a buffer layer with a desired mechanical properties and thickness. Computationally, finite element simulations of the same system were carried out under tension. It was found that by introducing substrate roughness and adding a Cr buffer layer of 75 nm, the interface toughness of the film/substrate can be increased by almost twenty times. The results of the present work may shed light on the interfacial engineering strategies for improving reliability of future flexible electronics.

Enhance the solar cell efficiency by reduction of reflection losses

The enhancement of the solar cell efficiency field has been achieved in many methods due to the different factors and conditions that led to loss the solar energy. This work deals with the increasing of the efficiency of solar cell that made of single crystalline silicon. This increment achieved by the reduction of biggest type of losses of the conversion efficiency named reflection. by using two methods first; forming grooves on the surface using pulse Nd:YAG laser with max energy 1J and pulse width 10ns, using the fast and accurate movement of the 3D optical galvo mirror scanning system to form the grooves, the second method was by deposition nanomaterials as Silver (Ag) and Cadmium telluride (CdTe) to constitute an antireflection layer for the incident solar spectrum. The effect of antireflection layer material type and the effect of incident light angle on the reflection had been studied in this work. The reflectance had been measured by a system designed and built to give the reflection for angles ranged 0 – 180 degree controlled by Microcontroller. The result inducate that increase in conversion efficiency was 28.3% for Ag/Si, and 32.9% for CdTe/Si than the original efficiency of Si solar cell.

K0.54[Co0.5Mn0.5]O2: New cathode with high power capability for potassium-ion batteries

We propose P3-K0.54[Co0.5Mn0.5]O2, which is rationally designed as a promising cathode material for high-performance potassium-ion batteries (KIBs). Its composition adopts the use of the valence state of Mn above 3.5 + to minimize the disruptive effect of Jahn–Teller distortion in the MnO6 octahedra during the electrochemical reaction. Unlike other types of layered materials that suffer from the sluggish diffusion of large potassium ions accompanying multi-step voltage profiles, P3-K0.54[Co0.5Mn0.5]O2 delivers a high specific discharge capacity of 120.4 mAh (g-oxide)−1 with smooth charge and discharge curves. First-principles calculations predict an activation barrier energy of ∼260 meV for a large K+ diffusion, which is comparable to those observed in conventional layered cathode materials for lithium-ion batteries. As a result, even at 500 mA g−1, P3-K0.54[Co0.5Mn0.5]O2 is able to deliver a high discharge capacity of 78 mAh g−1, which is a retention of 65% versus the capacity obtained at 20 mA g−1. Combination studies using operando X-ray diffraction, the ex-situ X-ray absorption near-edge structure, and first-principles calculations elucidate the nature of the excellent potassium storage mechanism of K0.54[Co0.5Mn0.5]O2. This work provides a new insight for the development of efficient cathode materials for KIBs.

Separating electrons and holes by monolayer increments in van der Waals heterostructures

Since the discovery of graphene and its outstanding chemical, optical, and mechanical properties, other layered materials have been fiercely hunted for throughout various techniques. Thanks to their van der Waals interaction, acting as weak glue, different types of layered materials with mismatched lattices can be stacked with high quality interfaces. The properties of the resulting multilayer structures can be tuned by choice of the materials, layer thicknesses, and sequence in which they are arranged. This opens the possibility for a large array of applications across many different fields. Here we present a systematic study with two-dimensional stacked layered materials, where their properties are tailored monolayer by monolayer. By arranging ${\mathrm{WSe}}_{2},{\mathrm{MoSe}}_{2},{\mathrm{WS}}_{2}$, and ${\mathrm{MoS}}_{2}$ monolayers in predetermined sequences, that are predicted to have a ladder band alignment in both the conduction and valence bands, we separate electrons and holes between the two utmost layers by monolayer increments. The samples studied are a ${\mathrm{WSe}}_{2}$ monolayer, a ${\mathrm{WSe}}_{2}\text{\ensuremath{-}}{\mathrm{MoSe}}_{2}$ bilayer, a ${\mathrm{WSe}}_{2}\text{\ensuremath{-}}{\mathrm{MoSe}}_{2}\text{\ensuremath{-}}{\mathrm{WS}}_{2}$ trilayer, and a ${\mathrm{WSe}}_{2}\text{\ensuremath{-}}{\mathrm{MoSe}}_{2}\text{\ensuremath{-}}{\mathrm{WS}}_{2}\text{\ensuremath{-}}{\mathrm{MoS}}_{2}$ four-layer. We observe an increase in absorbance, a decrease in photoluminescence, a variation in interlayer charge transfer, and photocarrier lifetimes that are extended up to a few nanoseconds as additional layers were added. With these results, we demonstrate that van der Waals stacked two-dimensional materials can form effective complex stacks and are promising platforms for fabricating ultrathin and flexible optoelectronics.

Modelling Delamination in Layered Anisotropic Material Structures

A quasi-static model for numerical solution of damage in layered anisotropic material structures has been developed. It invokes a cohesive type response of the interface interpreted as a thin layer of an adhesive. In the model, various types of layered materials can be proposed by using any type of anisotropic materials of the layers with different mechanical properties. The analysis calculates stress and strain quantities in the structure and at the damaged interface. The proposed mathematical approach is based on an energetic formulation looking for a kind of weak solution. The solution is approximated by a time stepping procedure, the Symmetric Galerkin Boundary Element Method (SGBEM), and it utilizes nonlinear programming algorithms.

First-Principles Prediction of Thermodynamically Stable Two-Dimensional Electrides.

Two-dimensional (2D) electrides, emerging as a new type of layered material whose electrons are confined in interlayer spaces instead of at atomic proximities, are receiving interest for their high performance in various (opto)electronics and catalytic applications. Experimentally, however, 2D electrides have been only found in a couple of layered nitrides and carbides. Here, we report new thermodynamically stable alkaline-earth based 2D electrides by using a first-principles global structure optimization method, phonon spectrum analysis, and molecular dynamics simulation. The method was applied to binary compounds consisting of alkaline-earth elements as cations and group VA, VIA, or VIIA nonmetal elements as anions. We revealed that the stability of a layered 2D electride structure is closely related to the cation/anion size ratio; stable 2D electrides possess a sufficiently large cation/anion size ratio to minimize electrostatic energy among cations, anions, and anionic electrons. Our work demonstrates a new avenue to the discovery of thermodynamically stable 2D electrides beyond experimental material databases and provides new insight into the principles of electride design.

Rapid thermal decomposition of confined graphene oxide films in air

The ability to scale up the production of chemically modified forms of graphene has led to intense interest in the manufacture and commercialization of graphene-based materials. Free-standing film-like materials comprised of stacked and overlapped platelets of graphene oxide (G-O) or thermally and electrically conductive reduced graphene oxide (rG-O) are potentially useful in various applications including filtration membranes, mechanical seals, protective layers, heating elements and components of batteries or supercapacitors as well as in electronics and optoelectronics. The advances in these applications require efficient and low-cost protocols for fabricating certain types of layered materials and, as such, protocols are urgently needed for the reduced forms of G-O. Here we report an efficient and straightforward method to thermally reduce thin films of stacked G-O platelets while still maintaining their structural integrity. By rapidly heating confined G-O films on a hot plate set to 400 °C under an atmosphere of air, G-O films were readily converted to intact, electrically conductive, reduced thin films. The structure and degree of reduction of the resulting free-standing rG-O films were found to be comparable to those obtained by slow annealing at the same temperature.

Inverted polymer fullerene solar cells exceeding 10% efficiency with poly(2-ethyl-2-oxazoline) nanodots on electron-collecting buffer layers.

Polymer solar cells have been spotlighted due to their potential for low-cost manufacturing but their efficiency is still less than required for commercial application as lightweight/flexible modules. Forming a dipole layer at the electron-collecting interface has been suggested as one of the more attractive approaches for efficiency enhancement. However, only a few dipole layer material types have been reported so far, including only one non-ionic (charge neutral) polymer. Here we show that a further neutral polymer, namely poly(2-ethyl-2-oxazoline) (PEOz) can be successfully used as a dipole layer. Inclusion of a PEOz layer, in particular with a nanodot morphology, increases the effective work function at the electron-collecting interface within inverted solar cells and thermal annealing of PEOz layer leads to a state-of-the-art 10.74% efficiency for single-stack bulk heterojunction blend structures comprising poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] as donor and [6,6]-phenyl-C71-butyric acid methyl ester as acceptor.

Numerical evaluation of pavement design parameters for the fatigue cracking and rutting performance of asphalt pavements

Over recent years, significant research has been conducted to investigate ways to predict fatigue cracking and permanent deformation (rutting), which are two common distresses found in asphalt pavements. These distresses are affected by material properties, environmental conditions, and the pavement’s structure. This paper investigates common pavement design parameters, including surface mixture type, base layer thickness, base layer type, sub-base layer thickness, and an anti-frost layer, with regard to the asphalt pavement performance of the Korea Expressway Corporation (KEC) test road. Test roads are often regarded as the most realistic tools for evaluating the effects of various parameters because they are subjected to real traffic and environmental factors. The KEC test road is 7.7 km long and was constructed with the aim of developing a Korean mechanistic-empirical pavement design guide. According to the findings, the surface layer type, base layer thickness, and base layer material type were found to affect the fatigue cracking and rutting performance, whereas the sub-base thickness and anti-frost layer were found not to affect the amount of distress significantly. The newly developed ‘layered viscoelastic pavement analysis for critical distresses’ (LVECD) program was able to capture the effects of the changes in the aforementioned parameters on the amount of cracking and rut depths. Reasonable agreement was found between the LVECD predictions and the field distress measurements. However, it remains necessary to develop a laboratory-to-field transfer function in order to obtain more accurate field performance predictions.

Lighting Up Two-Dimensional Lanthanide Phosphonates: Tunable Structure–Property Relationships toward Visible and Near-Infrared Emitters

We report the solvothermal synthesis and characterization of the structure, morphology, and photoluminescence properties of a series of unprecedented layered, organic–inorganic lanthanide (LnIII) phosphonates based on tert-butyl- (But), 1-naphthalene (Naph)- and 4-biphenyl (Biphen)-phosphonic acid. Through systematic variation of the ligand and the LnIII, we discuss the key structure–property relationships that must be managed for the design of Ln-phosphonates with tailored functionality. Single crystal and X-ray powder diffraction studies revealed that the size and shape of the employed ligand affects the type of layered material that forms. In agreement with their molecular structures, two distinct crystal morphologies are observed, 1D nanorods and 2D platelets, demonstrating that the anisotropy in the crystal structure and the variable coordination behavior of the ligands is directly translated to the crystal growth. Judicious selection of the ligand enables us to switch-on Ln-centered photoluminescence in both the visible (EuIII, TbIII) and near-infrared (NdIII and YbIII) spectral regions. Notably, the presented Yb-phosphonates are rare examples of phosphonate-based near-infrared emitters. Furthermore, the EuIII spectral fingerprint provided unique insight into the coordination environment of the metal center, facilitating structural characterization where X-ray diffraction analysis was limited.

Effect of an Insulation Layer to Prevent Water Vapor Condensation along the Inside Surface of a Building Wall Using an Artificial Neural Network

AbstractA theoretical analysis was performed to study the attenuation of a heat wave through two composite walls. Each wall was made of three homogenous layers in addition to an insulation layer, all of which were made of local materials. One way to attenuate this heat wave was to apply insulation inside the wall. In this work, an artificial neural network (ANN) was developed to study the effect of insulation materials on a building wall through a four-layered wall. The layer material type, the layer thickness, and the inside and outside temperature were used in the input layer of the network, whereas the temperature distribution was in the output layer of the network. Data that were obtained from previous experiments were used to train the neural network. It was found that the algorithm used (Levenberg-Marquardt) was very much capable of estimating the temperature distribution within each of the four-layered walls with excellent accuracy.

Free vibration of antisymmetric angle-ply-laminated plates including transverse shear deformation: Spline method

A free vibration study of antisymmetric angle-ply composite plates including shear deformation and rotatory inertia using the point collocation method and applying spline function approximations is presented. The equations of motion for the plate are derived using the theory of Yang, Norris and Stavsky. The solution is assumed in a separable form to obtain a system of coupled differential equations in displacement and rotational functions and these functions were approximated by Bickley-type splines of order three. A generalized eigenvalue problem is obtained and solved numerically for an eigenfrequency parameter and an associated eigenvector of spline coefficients. The vibrations of two- and four-layered plates, made up of several types of layer materials and subjected to two types of boundary conditions are considered. Parametric studies were made of the variation of frequency parameters with respect to the aspect ratio, side-to-thickness ratio and ply angle. The numerical results are presented through diagrams and, in some cases, are compared with results obtained by FEM.

Axisymmetric vibrations of layered cylindrical shells of variable thickness using spline function approximation

Free axisymmetric vibrations of layered cylindrical shells of variable thickness are studied using spline function approximation techniques. Three different types of thickness variations are considered namely linear, exponential and sinusoidal. The equations of axisymmetric motion of layered cylindrical shells, on the longitudinal and transverse displacement components are obtained using Love?s first approximation theory. A system of coupled differential equations on displacement functions are obtained by assuming the displacements in a separable form. Then the displacements are approximated using Bickley-spline approximation. The vibrations of two-layered cylindrical shells, made up of several types of layered materials and different boundary conditions are considered. Parametric studies have been made on the variation of frequency parameter with respect to the relative layer thickness, length ratio and type of thickness variation parameter.

KUALITAS PAPAN KOMPOSIT YANG TERBUAT DARI LIMBAH KAYU SENGON DAN KARTON DAUR ULANG

The use of recycled carton as an alternative material for the layer of composite board may increase the board strength properties. The objective of this research was to find out the influence of face and back layer types on the quality of produced boards. Materials used in this study were wafer made from sengon wood (Paraserianthes falcataria L. Nielsen), water based polymer isocyanate adhesive, and several kinds of cartons such as duplex carton, recycled carton, and waste of corrugated board. The composite board was produced with the target density of 0.65 g/cm3 and the resin solid content of 6% based on oven dry weight of particle, face and back layers. The results are as follows : 1) Utilization of carton layers improved the dimensional stability and bending strength of board; 2) Composite board with recycled carton layer fullfilled the Japanese Industrial Standard (JIS) A-5908-1994 for wafer board type in terms of density, water content, and modulus of rupture (MOR) in lengthwise and widhtwise of board but, did not fullfill that for veneered particled board type; 3) The presence of those layer material types decreased internal bond of the board. Keywords : composite board, face and back layer types, recyled carton

Free vibration of layered truncated conical shell frusta of differently varying thickness by the method of collocation with cubic and quintic splines

Free vibrations of layered conical shell frusta of differently varying thickness are studied using the spline function approximation technique. The equations of motion for layered conical shells, in the longitudinal, circumferential and transverse displacement components, are derived using extension of Love’s first approximation theory. Assuming the displacement components in a separable form, a system of coupled equations on three displacement functions are obtained. Since no closed form solutions are generally possible, a numerical solution procedure is adopted in which the displacement functions are approximated by cubic and quintic splines. A generalized eigenvalue problem is obtained which is solved numerically for an eigenfrequency parameter and an associated eigenvector of spline coefficients. The vibrations of two-layered conical shells, made up of several types of layer materials and supported differently at the ends are considered. Linear, sinusoidal and exponential variations in thickness of layers are assumed. Parametric studies are made on the variation of frequency parameter with respect to the relative layer thickness, cone angle, length ratio, type of thickness variation and thickness variation parameter. The effect of neglecting the coupling between bending and stretching is also analysed.

Materiales laminares pilareados: preparación y propiedades

The structure of several types of layered materials will be described. These include clays, layered double hydroxides, group IV metal phosphates and other layered materials. The preparation of the pillared materials and pillaring agents will be presented along with a description of the properties and applications of the products.