Layered Properties Research Articles

Exploration of the deep-ultraviolet nonlinear optical materials in the derivatives of KBe<sub>2</sub>BO<sub>3</sub>F<sub>2</sub>

The use of nonlinear optical crystal materials to extend the limited range of laser sources to the deep-ultraviolet (deep-UV, λ < 200 nm) regions by various frequency conversion techniques, has become an attractive field for generating deep-UV light. However, the lack of nonlinear optics (NLO) crystal materials capable of frequency conversion in the deep-UV light range, limits the development and application of deep-UV all-solid-state lasers. Therefore, scientists all over the world are actively exploring the new generation of deep-UV NLO crystal materials. At present, only the KBe<sub>2</sub>BO<sub>3</sub>F<sub>2</sub> (KBBF) crystal is capable of generating deep-UV light through the direct sixth harmonic generation of the Nd:YAG laser. The infinite <sub>∞</sub>[Be<sub>2</sub>BO<sub>3</sub>F<sub>2</sub>]<sup>−</sup> single layers, as the brilliant building blocks in the crystal structures of KBBF family, provide a relatively large second harmonic generation coefficient (<i>d</i><sub>11</sub> = 0.47 pm/V) and a sufficient birefringence (Δ<i>n</i> = 0.07@1064 nm). However, the KBBF crystals have insurmountable intrinsic defects, such as the usage of high toxic beryllium oxide, and the serious layer growth habit, which greatly restrict its commercialization process. Since the layered structure of the KBBF crystal is still one of the most brilliant structures for generating deep-UV laser, an effective strategy is to change the interlayer connection mode and develop new NLO materials based on KBBF with less layering growth habit. In this paper, by reviewing the development history of borate deep-UV NLO crystals and the derivatives of KBBF, the relationship between layered structure and optical properties of different interlaminar connections of crystal materials is systematically analyzed. We discuss the main contradictions and solutions of the development of deep-UV NLO crystal materials which are similar to the KBBF structure. In order to provide a reference for the innovative exploration of new materials in the future, several design strategies are also proposed.

SIS/Aligned Fibre Scaffold Designed to Meet Layered Oesophageal Tissue Complexity and Properties

With donor organs not readily available the need for a tissue engineered oesophagus remains high particularly for congenial childhood conditions such as atresia. Previous attempts have not been very successful and challenges remain to be overcome. Small intestine submucosa (SIS) is an a cellular matrix material with good biological properties though, as with these materials, demonstrably poor mechanical properties. In this work electrospinning was used to mechanically reinforce a unique tubular SIS with PLGA nanofibers. It was hypothesised that if attachment could be achieved between the two materials than this would (i) improve the SIS's mechanical properties, (ii) facilitate smooth muscle cell alignment to support directional growth of muscle cells and potentially restore contractility and (iii) allow for the delivery of bioactive molecules (VEGF in this instance). Through a multistage process adhesion between the layers was achieved without chemically altering the SIS. It was also found that altering mandrel rotational speed affected the alignment of the PLGA nanofibers.SIS-PLGA scaffolds performed mechanically better than SIS alone; yield stress improvement was 200% and 400% along the longitudinal and circumferential direction, respectively (greatest with highly aligned fibres produced at 5000 rpm). Smooth muscle cells cultured on the aligned fibres showed resultant unidirectional alignment. In vivo the SIS-PLGA scaffolds demonstrated relatively limited foreign body reaction judged by the type and proportion of immune cells present and lack of fibrous encapsulation. The scaffolds remained intact at 4 weeks which is required for a structural tissue engineering matrix and obtained good cellular infiltration. The incorporation of VEGF within SIS-PLGA scaffolds increased the blood vessel density of the surrounding tissues, highlighting the possible stimulation of endothelialisation by angiogenic factor delivery. Overall, the designed SIS-PLGA-VEGF hybrid scaffolds might be used as a potential matrix platform for oesophageal tissue engineering. In addition to this, achieving improved attachment between layers of a cellular matrix materials and electrospun fibres layers does possess the potential to be applied to other applications.

Hole quality assessment in drilling process of basalt/epoxy composite laminate subjected to the magnetic field

Drilling is one of the most important machining processes which are currently carried out on fiber-reinforced composites. These composites possess a layered structure and different properties through their thickness. When drilling such structures, internal defects like delamination occur, caused by the drilling forces and their uneven distribution among the plies. The current study investigates the effect of magnetic field on drilling process of basalt/epoxy composite laminate in order to reduce delamination and the thrust force and improve some hole quality parameters i.e. roughness and cylindricity. A comparison is made between the responses for both normal drilling and drilling with applying a magnetic field. For this purpose, after finding the best combinations of normal drilling parameters, magnetic field is applied to the different configurations of solenoids on the setup of the drilling process. The results highlighted that using different magnet solenoids on the top and the bottom of drilling zone reduces the delamination and can obtain better roughness and cylindricity with lower damage.

Torsional vibration of a large-diameter pipe pile embedded in inhomogeneous soil

An analytical solution is proposed to investigate the torsional dynamic response of a large-diameter pipe pile embedded in inhomogeneous soil. First, both the outer and inner soils are discretized into many annular vertical zones, and their radial inhomogeneity caused by the construction disturbance effect is considered by the gradual variedness of soil parameters in the radial direction. Meanwhile, the layered properties of the soil in the vertical direction are simulated by the distributed Winkler model. Then, the analytical solution for the torsional dynamic response at the pile head is obtained by solving the pile–soil dynamic governing equations and its reliability is verified by comparing with the existing solutions. Finally, selected results for the complex impedance and velocity admittance are presented to examine the influence of the pile–soil parameters and the radial inhomogeneity of the soil on the torsional dynamic characteristics of the large-diameter pipe pile.

Recovery of layered tissue optical properties from spatial frequency-domain spectroscopy and a deterministic radiative transport solver.

.We present a method to recover absorption and reduced scattering spectra for each layer of a two-layer turbid media from spatial frequency-domain spectroscopy data. We focus on systems in which the thickness of the top layer is less than the transport mean free path . We utilize an analytic forward solver, based upon the ’th-order spherical harmonic expansion with Fourier decomposition method in conjunction with a multistage inverse solver. We test our method with data obtained using spatial frequency-domain spectroscopy with 32 evenly spaced wavelengths within to 1000 nm on six-layered tissue phantoms with distinct optical properties. We demonstrate that this approach can recover absorption and reduced scattering coefficient spectra for both layers with accuracy comparable with current Monte Carlo methods but with lower computational cost and potential flexibility to easily handle variations in parameters such as the scattering phase function or material refractive index. To our knowledge, this approach utilizes the most accurate deterministic forward solver used in such problems and can successfully recover properties from a two-layer media with superficial layer thicknesses.

Kirigami-Inspired Highly Stretchable Nanoscale Devices Using Multidimensional Deformation of Monolayer MoS2

Two-dimensional (2D) layered materials, such as MoS2, are greatly attractive for flexible devices due to their unique layered structures, novel physical and electronic properties, and high mechanical strength. However, their limited mechanical strains (<2%) can hardly meet the demands of loading conditions for most flexible and stretchable device applications. In this Article, inspired from Kirigami, the ancient Japanese art of paper cutting, we design and fabricate nanoscale Kirigami architectures of 2D layered MoS2 on a soft substrate of polydimethylsiloxane (PDMS) using a top-down fabrication process. Results show that the Kirigami structures significantly improve the reversible stretchability of flexible 2D MoS2 electronic devices, which is increased from 0.75% to ∼15%. This increase in flexibility is originated from a combination of multidimensional deformation capabilities from the nanoscale Kirigami architectures consisting of in-plane stretching and out-of-plane deformation. We further discover a ...

Van der Waals Materials for Atomically-Thin Photovoltaics: Promise and Outlook

Two-dimensional (2D) semiconductors provide a unique opportunity for optoelectronics due to their layered atomic structure, electronic and optical properties. To date, a majority of the application-oriented research in this field has been focused on field-effect electronics as well as photodetectors and light emitting diodes. Here we present a perspective on the use of 2D semiconductors for photovoltaic applications. We discuss photonic device designs that enable light trapping in nanometer-thickness absorber layers, and we also outline schemes for efficient carrier transport and collection. We further provide theoretical estimates of efficiency indicating that 2D semiconductors can indeed be competitive with and complementary to conventional photovoltaics, based on favorable energy bandgap, absorption, external radiative efficiency, along with recent experimental demonstrations. Photonic and electronic design of 2D semiconductor photovoltaics represents a new direction for realizing ultrathin, efficient solar cells with applications ranging from conventional power generation to portable and ultralight solar power.

Intercalation of calcein into layered silicate magadiite and their optical properties.

Calcein–Ca (II), Zn (II) and Al (III) complexes were successfully intercalated into interlayer surfaces of layered silicate magadiite and fluorescence properties of organic metal-chelates in the confined spaces were investigated. Structures, compositions and morphologies of the intercalated magadiites were adequately studied by tests, including X-ray diffraction, energy-dispersive X-ray spectrometer, elemental mapping, X-ray photoelectron spectroscopy, inductively coupled plasma atomic emission spectroscopy, Fourier-transform infrared spectra, ultraviolet–visible spectroscopy, thermo-gravimetric analysis, differential thermal analysis and scanning electron microscopy. Results confirmed that metal–organic chelate species were immobilized onto the silicate sheets via solid-state interaction. Basal spacings between silicate layers decreased by exchanged metal ions and increased after intercalation of calcein into the interlayer spaces of cation-exchanged magadiites. The encapsulation was obtained by a flexible solid–solid reaction, and the present reaction and products had a potential of application to industrial uses. A speculative mechanism was proposed for reaction by solid-state intercalation. Furthermore, it was found that the complexes in the interlayer space also exhibited special fluorescence properties. The significance of this current work was that it provided a possible route for synthesizing metal–organic complexes that encapsulated in phyllosilicate.

A Rigorous Hydraulic-Fracture Equilibrium-Height Model for Multilayer Formations

Summary Fracture height is a critical input parameter for 2D hydraulic-fracturing-design models, and also an important output result of 3D models. Although many factors may influence fracture-height evolution in multilayer formations, the consensus is that the so-called “equilibrium height belonging to a certain treating pressure” provides an upper limit. However, because of the complexity of the algebra involved, published height models are overly simplified and do not provide reliable results. We revisited the equilibrium-height problem, started from the definition of the fracture stress-intensity factor (SIF), considered variation of layered formation properties and effects of hydrostatic pressure, and developed a multilayer fracture-equilibrium-height (MFEH) model by use of the programming software Mathematica (2017). The detailed derivation of SIF and work flow of MFEH model are provided. The model is compared with existing models and software, under the same ideal geology condition. Generally, MShale (2013) calculated smaller height, and FracPro (2015) larger height, than the MFEH model. Most of the difference is attributable to the different interpretation of the “net pressure,” and the solving of the nonlinear equations of SIF as well. In the normally stressed case, they are both acceptable, although MShale is more reliable. The discrepancy is much larger when there is abnormally high or low stress in the adjacent layers of the perforated interval. The effects of formation rock and fluid properties on the fracture-height growth were investigated. Tip jump is caused by low in-situ stress, whereas tip stability is imposed by large fracture toughness and/or large in-situ stress. If the fluid density is ignored, the result regarding which tip will grow into infinity could be totally different. Second and even third and fourth solutions for a three-layer problem were found by Excel experiments and this model, and proved unrealistic; however, they can be avoided in our MFEH model. The full-height map with very-large top- and bottom-formation thicknesses shows the ultimate trend of height-growth map (i.e., when the fracture tip will grow to infinity) and suggests the maximum pressure to be used. To assess the potential effects of reservoir-parameter uncertainties on the height map, two three-layer pseudoproblems were constructed by use of a multilayer formation to create an outer- and inner-height envelope. The improved MFEH model fully characterizes height evolution amid various formation and fluid properties (fracture toughness, in-situ stress, thickness, and fluid density), and for the first time, rigorously and rapidly solves the equilibrium height. The equilibrium height can be used to provide input data for the 2D model, improve the 3D-model governing equations, determine the net pressure needed to achieve a certain height growth, and suggest the maximum net pressure ensuring no fracture propagation into aquifers. This model may be incorporated into current hydraulic-fracture-propagation simulators to yield more-accurate and -cost-effective hydraulic-fracturing designs.

EIGEN-OSCILLATIONS OF A TRANSVERSELY ISOTROPIC ELASTIC LAYER ATTACHED TO AN ISOTROPIC HALF-SPACE

Layered media have waveguide properties - waves can propagate without sources in such structures. For the most part, such media are anisotropic ones. The simplest case of anisotropy is a transversely isotropic medium. The properties of such media are characterized by the fact that its elastic modules are the same in a plane perpendicular to the axis of symmetry, but they are different from the modules in the direction of the axis. As studies show, many sedimentary rocks are transversely isotropic. Besides, such structures are used in the production of composites. For example, if fibers parallel to each other are used as a reinforcing material, then the composite has a unidirectional structure and is transversely isotropic material in the planes perpendicular to the direction of reinforcement. Sheet metals are often non-isotropic ones, and have normal (transversal) anisotropy. Reinforced concrete is also considered as transversely isotropic after the appearance of cracks. Similar structures appear during the production of glued wood. Waveguide structures formed by a transversely isotropic layer conjugated to an isotropic half-plane are considered. Two waveguides are studied: one with a fixed wall, the other one with a free surface. The characteristic equations are constructed for them. The discrete and continuous spectra of these waveguide structures are singled out.

Layered structures mechanical properties assessment by dynamic tests

An effective method of the layered structures mechanical properties determination is presented. The method is based on the non-stationary analysis of the structure response that is acted by impact load on the surface of multi-layered structure. The assessment of the design parameters using a genetic algorithm is performed. During the solving procedure there are several methods for breeding and selection processes are used, that demonstrated different results. The most appropriate parameters for described algorithms are selected and analysed.

Inversion of soil electrical conductivity data to estimate layered soil properties

Bulk apparent soil electrical conductivity (ECa) sensors respond to multiple soil properties, including clay content, water content, and salt content (i.e. salinity). They provide a single sensor value for an entire soil profile down to a sensor-dependent measurement depth, weighted by a nonlinear response function. Because of this, it is generally difficult to elucidate strong relationships between ECa and the measured properties of individual soil layers. This research investigated inversion of the equations that govern the ECa-depth response relationship to reconstruct the soil conductivity in profile layers using data collected in multiple fields in the Midwest US. Layer conductivities obtained by inversion were first validated by comparison with true conductivities measured as a function of depth with an ECa-sensing penetrometer. Then, the validated layer conductivities were related to laboratory- measured soil properties. Inversion worked well but sometimes required iterative adjustment of initial conditions and other input parameters to obtain best results. Strong linear relationships (r2≥0.76) were obtained between inversion-estimated and measured layer conductivity data in all cases, sometimes with a truncated depth range. Layer conductivity data was successfully used to estimate soil texture fractions in the two alluvial fields examined. This was not the case for a claypan soil field, where there appeared to be parameters other than texture strongly affecting the EC response. Further examination of this approach is warranted to potentially provide improved ways to estimate depth-variable soil properties using ECa.

Two-dimensional transition metal sulfides for electrical applications

In recent years, due to its unique layered structure and electrical properties, Graphene has attracted tremendous research attention. So far, the rapid pace of progress in graphene and the methodology developed in preparing ultrathin layers has led to exploration of other 2D materials, such as transition-metal sulfides (TMSs). Similar to their well-known cousin, graphene, TMSs exhibit many excellent properties, including the superior mechanical flexibility, impressive thermal stability, absence of dangling bonds and compatibility to silicon CMOS processes. More importantly, field-effect transistors (FETs) made from graphene cannot be effectively switched off and have low on/off switching ratios because graphene lacks a bandgap. In a distinct contrast to the bandgap issue of graphene, some of TMSs are semiconducting with a satisfied thickness-dependent bandgap, which can enable lots of fascinating device applications in FETs. This paper describes the basic structural properties, band structure and electrical properties of TMSs. Here, we focus on MoS2 as a typical example to introduce its applications in FETs, logic circuit, sensors and so on. Finally, the prospects for future advances in TMSs are briefly discussed.

An Improved Model for Predicting Hydraulic-Fracture-Height Migration

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 173335, “An Improved Equilibrium-Height Model for Predicting Hydraulic- Fracture-Height Migration in Multilayer Formations,” by Songxia Liu, SPE, and Peter P. Valko, SPE, Texas A&amp;M University, prepared for the 2015 SPE Hydraulic Fracturing Technology Conference, The Woodlands, Texas, USA, 3–5 February. The paper has not been peer reviewed. While many factors may influence fracture-height evolution in multilayer formations, the consensus is that the so-called “equilibrium height belonging to a certain treating pressure” provides an upper limit, at least for nonnaturally fractured media. The authors have revisited the “equilibrium-height problem,” and their theoretical and numerical investigations led to a new model that fully characterizes height evolution amid various formation properties. Introduction Solutions for the equilibrium-height problem have been known since the 1970s, and several models have been developed for calculating hydraulic-fracture height. However, because of the complexity of the algebra involved, the equations used in these early models were overly simplified and gave unreliable results. The authors developed an improved, mathematically rigorous model that, for the first time, solves the equilibrium height under various formation-property conditions and fluid properties. The authors started from the definition of fracture toughness, incorporated the effects of hydrostatic pressure, and considered nonsymmetric variations of layered formation properties. The model was applied to the classic three-layer problem and then extended up to six layers. With the new model, the effects of fracture toughness, in-situ stress, fluid density, and their interactive effects on fracture-height growth were investigated. The full height profile with very large top and bottom formation thicknesses showed the ultimate trend of fracture-height migration. Two three-layer pseudo problems were constructed to create an outer and inner height envelope for any multilayer-formation problem, to assess the potential effects of reservoir-parameter uncertainties on height profile. The occurrence of a second solution pair and its analytical solutions were presented, to avoid misleading results in the 3D models.

Multi-Functional Surface Engineering for Li-Excess Layered Cathode Material Targeting Excellent Electrochemical and Thermal Safety Properties.

The Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2 cathode material is modified by a Li4M5O12-like heterostructure and a BiOF surface layer. The interfacial heterostructure triggers the layered-to-Li4M5O12 transformation of the material which is different from the layered-to-LiMn2O4 transformation of the pristine Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2. This Li4M5O12-like transformation helps the material to keep high working voltage, long cycle life and excellent rate capability. Mass spectrometry, in situ X-ray diffraction and transmission electron microscope show that the Li4M5O12-like phase prohibits oxygen release from the material bulk at elevated temperatures. In addition, the BiOF coating layer protects the material from harmful side reactions with the electrolyte. These advantages significantly improve the electrochemical performance of Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2. The material shows a discharge capacity of 292 mAh g(-1) at 0.2 C with capacity retention of 92% after 100 cycles. Moreover, a high discharge capacity of 78 mAh g(-1) could be obtained at 25 C. The exothermic temperature of the fully charged electrode is elevated from 203 to 261 °C with 50% reduction of the total thermal release, highlighting excellent thermal safety of the material.

Inferring the mesoscale structure of layered, edge-valued, and time-varying networks.

Many network systems are composed of interdependent but distinct types of interactions, which cannot be fully understood in isolation. These different types of interactions are often represented as layers, attributes on the edges, or as a time dependence of the network structure. Although they are crucial for a more comprehensive scientific understanding, these representations offer substantial challenges. Namely, it is an open problem how to precisely characterize the large or mesoscale structure of network systems in relation to these additional aspects. Furthermore, the direct incorporation of these features invariably increases the effective dimension of the network description, and hence aggravates the problem of overfitting, i.e., the use of overly complex characterizations that mistake purely random fluctuations for actual structure. In this work, we propose a robust and principled method to tackle these problems, by constructing generative models of modular network structure, incorporating layered, attributed and time-varying properties, as well as a nonparametric Bayesian methodology to infer the parameters from data and select the most appropriate model according to statistical evidence. We show that the method is capable of revealing hidden structure in layered, edge-valued, and time-varying networks, and that the most appropriate level of granularity with respect to the additional dimensions can be reliably identified. We illustrate our approach on a variety of empirical systems, including a social network of physicians, the voting correlations of deputies in the Brazilian national congress, the global airport network, and a proximity network of high-school students.

Sintering of Ti&lt;sub&gt;3&lt;/sub&gt;SiC&lt;sub&gt;2&lt;/sub&gt; Ceramics by Hot Press from Commercial Powders

Layered ternary compounds Ti3SiC2 combines attractive properties of both ceramics and metals, and has been suggested for potential engineering applications. Near-fully dense Ti3SiC2 bulks were sintered from commercial Ti3SiC2 powders by hot press at 1350°C-1600°C for 60-120min under Ar atmosphere in this paper. The phase compositions and morphology of the as-prepared samples were evaluated by X-Ray diffraction (XRD) and scanning electron microscopy (SEM). And the mechanical properties were measured by Three-Point bending method. It was found that the Ti3SiC2 had only a little of decomposition at sintering temperature above 1350°C. And effects of sintering temperature and holding time on the morphology of the bulk Ti3SiC2 are not obvious. Relative density of 98% and flexural strength of 480MPa were obtained for the Ti3SiC2 samples sintered at 30MPa and 1400°C for 90min.

High power diode laser cladding of Fe–Co–B–Si–C–Nb amorphous coating: Layered microstructure and properties

Fe–Co–B–Si–C–Nb amorphous composite coating about 0.6mm in thickness was fabricated by using a one-step laser cladding method. Microstructures and phases were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and electron probe microanalysis. Microhardness and wear resistance tests were conducted to evaluate the mechanical properties of this coating. Near the interface of coating/substrate, the region showed a layered microstructure, which could be generally categorized into three layers: layer I (columnar dendrites phase), layer II (equiaxed dendrites phase) and layer III (amorphous-particle composite phase). The main reason for this layered structure was due to the difference in chemical compositions of the three layers. With regard to mechanical properties, the microhardness and wear resistance of the Fe–Co–B–Si–C–Nb amorphous composite coating also exhibited layered characteristics. The mean value of the microhardness for layer I, layer II and layer III was 729, 680 and 1245HV, respectively. The friction coefficient of the transitional layer III was 0.28 times lower than that of the substrate under the same sliding friction condition.

Layered crystal structure, conformational and vibrational properties of 2,2,2-trichloroethoxysulfonamide: An experimental and theoretical study

The molecular structure of 2,2,2-trichloroethoxysulfonamide, CCl3CH2OSO2NH2, has been determined in the solid state by X-ray diffraction data and in the gas phase by ab initio (MP2) and DFT calculations. The substance crystallizes in the monoclinic P21/c space group with a=9.969(3)Å, b=22.914(6)Å, c=7.349(2)Å, β=91.06(3)°, and Z=8 molecules per unit cell. There are two independent, but closely related molecular conformers in the crystal asymmetric unit. They only differ in the angular orientation of the sulfonamide (SO2NH2) group. The conformers are arranged in the lattice as center-symmetric NH⋯O(sulf)-bonded dimers. Neighboring dimers are linked through further NH⋯O(sulf) bonds giving rise to a crystal layered structure. The solid state infrared and Raman spectra have been recorded and the observed bands assigned to the molecular vibration modes. Also, the thermal behavior of the substance was investigated by TG–DT analysis. The stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been analyzed using natural bond (NBO) analysis.

Broadband ultraviolet-visible optical property measurement in layered turbid media

The ability to accurately measure layered biological tissue optical properties (OPs) may improve understanding of spectroscopic device performance and facilitate early cancer detection. Towards these goals, we have performed theoretical and experimental evaluations of an approach for broadband measurement of absorption and reduced scattering coefficients at ultraviolet-visible wavelengths. Our technique is based on neural network (NN) inverse models trained with diffuse reflectance data from condensed Monte Carlo simulations. Experimental measurements were performed from 350 to 600 nm with a fiber-optic-based reflectance spectroscopy system. Two-layer phantoms incorporating OPs relevant to normal and dysplastic mucosal tissue and superficial layer thicknesses of 0.22 and 0.44 mm were used to assess prediction accuracy. Results showed mean OP estimation errors of 19% from the theoretical analysis and 27% from experiments. Two-step NN modeling and nonlinear spectral fitting approaches helped improve prediction accuracy. While limitations and challenges remain, the results of this study indicate that our technique can provide moderately accurate estimates of OPs in layered turbid media.