Number Of Stacked Layers Research Articles

Vibration Simulation of Multilayer Stacking Packages through Symbol-Numerical Method

Abstract Distribution packages are commonly stacked as unit loads, and vibration is the main hazard that causes product damage in the logistics stage. A simulation method that considers the vibration of multilayer stacking distribution packages is proposed in this study. First, a dynamic model of a single-layer package is investigated to clarify the vibration mechanism. Second, a simulation model is built to clarify the vibration of a single-layer package. Third, a multilayer vibration model is proposed on the basis of the single-layer model, and the calculation method of the simulation parameters is analyzed using a mathematical model. Verification experiments are also performed in a self-designed typical box. Furthermore, a correction method is investigated for the simulation errors. The correcting effect is clarified by comparing the power spectral density between experimental and simulation results. The relationship between the spring constants of a multi- and a single layer and the stacking layer number is also analyzed. Finally, two types of equations are proposed for the multilayer stacking model of distribution packages.

Construction of an epoxy composite with excellent thermal/mechanical properties using graphene oxide nanosheets reduced/functionalized by Tamarindus indiaca extract/zinc ions; detailed experimental and DFT-D computer modeling explorations

Few-layered graphene oxide (GO) nanosheets were obtained through the chemical reduction of the GO sheets via nature-based reagents, i.e., Tamarind (Tamarindus indiaca extract, TIE). The obtained rGO-TIE particles were then modified by zinc ions. The outcomes of the Raman spectroscopy, FT-IR, and X-ray diffraction analysis (XRD) revealed about 53% reduction in CO/CC ratio, 40% reduction in the 2ϴ corresponded to the (002) plane of GO, and a 60% increment of I2D/IG intensity (from Raman test results), indicating that the GO was successfully reduced and the interlayer d-spacing and the number of stacked layers decreased. The thermo-mechanical properties of the epoxy ester composite coatings containing 0.15 wt% of GO, rGO-TIE, and rGO-TIE-Zn particles were assessed by TGA-DTG, tensile, and DMTA analysis. From the DMTA outcomes, it was revealed that in the presence of rGO-TIE-Zn particles, the storage modulus (at 25 °C) and cross-linking density of the epoxy film were enhanced by 50% and 57%, respectively, compared to the unfilled coating. Tensile test results depicted about 58% and 41% degree of improvements in the energy at break and tensile strength of the epoxy film reinforced with rGO-TIE-Zn particles. FE-SEM analysis revealed that the better rGO-ESR-Zn(II) particles' dispersion/exfoliation level in the polymer matrix, as well as stronger polymer/particle interfacial bonding than GO, resulted in the higher thermo-mechanical properties. TGA results evidenced about 106 °C improvement in the T80% and 41% improvement in the thermal stability of the epoxy coating in the presence of rGO-ESE-Zn particles.

Influence of different biomass ash additive on anthracite pyrolysis process and char gasification reactivity

Catalytic coal gasification technology shows prominent advantages in enhancing coal gasification reactivity and is restrained by the cost of catalyst. Two typical biomass ash additions, corn stalk ash (CSA, high K–Na and low Si) and poplar sawdust ash (PSA, high K–Ca and high Si), were employed to study the influence of biomass ash on pyrolysis process and char gasification reactivity of the typical anthracite. Microstructure characteristics of the char samples were examined by X-ray diffraction (XRD). Based on isothermal char-CO2 gasification experiments, the influence of biomass ash on reactivity of anthracite char was determined using thermogravimetric analyzer. Furthermore, structural parameters were correlated with different reactivity parameters to illustrate the crucial factor on the gasification reactivity varied with char reaction stages. The results indicate that both CSA and PSA additives hinder the growth of adjacent basic structural units in a vertical direction of the carbon structure, and then slow down the graphitization process of the anthracite during pyrolysis. The inhibition effect is more prominent with the increasing of biomass ash. In addition, the gasification reactivity of anthracite char is significantly promoted, which could be mainly attributed to the abundant active AAEM (especially K and Na) contents of biomass ash and a lower graphitization degree of mixed chars. Higher K and Na contents illustrate that the CSA has more remarkable promotion effect on char gasification reactivity than PSA, in accordance with the inhibition effect on the order degree of anthracite char. The stacking layer number could reasonably act as a rough indicator for evaluating the gasification reactivity of the char samples.

Partially compacted polypropylene glass fiber non-woven composite: Influence of processing, porosity and fiber length on mechanical properties and modeling

Non-woven materials feature unique properties that allow them to be used in different applications. In this study, polypropylene and glass fibers were commingled and pressed to obtain partially compacted composites. Fiber content, fiber length and processing parameters were modified to investigate their influence on the final properties of the composites. These were characterized by scanning electron microscopy (SEM), tensile and porosity measurements as well as fiber content and length distribution analysis. The stiffness of the composites increase linearly with increasing glass fiber content, from 1.6 GPa to 4.8 GPa. Longer fibers can be found in the composites with higher fiber contents. Applied pressure and number of stacked layers were found significant factors for the limitation of void content. Fiber-matrix interactions were improved with the addition of maleic anhydride grafted polypropylene, increasing the tensile properties in the low porosity range. A suitable model was found for the prediction of mechanical properties.

First Principle Investigation of Interlayer Interaction, Stacking Order and Layer Number Dependent Structural and Electronic Properties of Multi-Layered Boron Nitride (BN)

Layered Boron-Nitride (BN) consist of covalent in-plane bonding with van der Waals (vdW) interlayer interactions between layers. In this study, stacking order, interlayer-interaction and layer number dependent structural and electronic properties of multi-layered BN were studied using Density Functional Theory (DFT). The lattice constant, equilibrium interlayer distance and energy band structures for different interlayer distances and the number of layers were computed. The calculated result indicates that interlayer interaction and stacking order in a multi-layer limit could impact on its structural and electronic properties. In addition to this, the calculated energy band structure for the increasing number of layers indicates that as the number of layers increases the bandgap decreases. However, the nature of the bandgap remains direct. Moreover, the Partial Density of State (PDOS) analysis reveals that many contributions of states in the vicinity of Fermi level derived from Boron p-orbital followed by nitrogen p-orbital. The findings are bases for experimentalist to control structural and electronic properties of layered materials by manipulating its stacking patterns and layer numbers.

Preparation of Transparent and Thick CNF/Epoxy Composites by Controlling the Properties of Cellulose Nanofibrils.

Cellulose nanofibrils (CNFs) have been used as reinforcing elements in optically transparent composites by combination with polymer matrices. In this study, strong, optically transparent, and thick CNF/epoxy composites were prepared by immersing two or four layers of CNF sheets in epoxy resin. The morphology of the CNF, the preparation conditions of the CNF sheet, and the grammage and layer numbers of the CNF sheets were controlled. The solvent-exchanged CNF sheets resulted in the production of a composite with high transparency and low haze. The CNF with smaller width and less aggregated fibrils, which are achieved by carboxymethylation, and a high number of grinding passes are beneficial in the production of optically transparent CNF/epoxy composites. Both the grammage and number of stacked layers of sheets in a composite affected the optical and mechanical properties of the composite. A composite with a thickness of 450–800 μm was prepared by stacking two or four layers of CNF sheets in epoxy resin. As the number of stacked sheets increased, light transmittance was reduced and the haze increased. The CNF/epoxy composites with two layers of low grammage (20 g/m2) sheets exhibited high light transmittance (>90%) and low haze (<5%). In addition, the composites with the low grammage sheet had higher tensile strength and elastic modulus compared with neat epoxy and those with high grammage sheets.

Metal-to-insulator transition in Ruddlesden-Popper-type Srn+1VnO3n+1 (n = 1, 2) epitaxial thin films as a function of strain and VO2 stacking layer number

A series of Ruddlesden-Popper-type Srn+1VnO3n+1 (n = 1, 2) (001) epitaxial thin films was grown on LaAlO3 and LaSrGaO4 substrates with tensile and compressive epitaxial strains, respectively. The decrease in VO2 stacking layer number n and the increase in the interlayer distance between the (VO2)n layers resulted in metal-to-insulator transition. The sheet conductance of a single (VO2)n layer in Srn+1VnO3n+1 (n = 1, 2) was close to the well-known Ioffe–Regel limit, which suggests their two-dimensional electrical conduction. From resistivity and magnetoconductance measurements, it is found that renormalized electron–electron interaction and/or the Kondo effect were enhanced with the decrease in n, and possible quantum interference effects like weak localization were induced with the increase in the interlayer distance.

Two-Dimensional Designer Nanochannels for Controllable Ion Transport in Graphene Oxide Nanomembranes with Tunable Sheet Dimensions.

Graphene is a distinct two-dimensional (2D) material that provides a wide range of opportunities for membrane applications owing to its ultimate thinness, flexibility, chemical stability, and mechanical strength. In particular, chemically functionalized graphene oxide (GO) sheets containing amine and carboxylic acid groups facilitate solution-based processing and the formation of various internal structures depending on their properties such as the lateral dimension, defect density, and number of stacked layers. In this study, we designed and fabricated a multilayered GO membrane via the layer-by-layer assembly of two oppositely charged GO nanosheets and investigated the effects of the (1) lateral dimension of the GO nanosheet and (2) membrane thickness of the 2D nanochannels of the GO membrane on the ion permeation behavior. The correlations between the structural parameters of the GO membranes and ion diffusion kinetics were evaluated using the Nielsen model. The functional groups were selectively ionized by exposure to pH-adjusted water, which creates positive or negative net charges, resulting in an ion-selective permeability. The unique properties of the GO nanosheets play important roles in determining the trade-off between the membrane permeability and selectivity, leading to new applications of GO nanosheets as functional membranes.

Investigation of tensile properties of sprayed aluminium based PLA composites fabricated by FDM technology

Fused Deposition Modeling (FDM) has gained widespread popularity among researchers working in area of material science, medical implants and new product development. FDM is used by many industries for prototyping and end-use components due to lower cost and its versatility of material usage. Researchers have used variety of reinforcements for enhancement of mechanical properties of feedstock filament used for FDM. A novel technique has been developed to manufacture FDM composites using alternate layers of sprayed aluminium and Poly Lactic Acid (PLA) filament utilizing open source FDM printer. This study investigates the tensile properties of metal sprayed thermoplastic components and their possible interaction with other process parameters i.e. infill density and bed temperature of FDM printer using Taguchi and ANOVA techniques. Higher tensile strength of composites has been experienced as compared to both virgin PLA components and aluminium spray coated FDM parts. The study demonstrates that the tensile properties are significantly impacted by infill density and number of stacked layers of metal spray; peak strength is directly proportional to infill density while inversely proportional to number of layers.

Exfoliated CrPS4 with Promising Photoconductivity.

Layered semiconductors have attracted significant attention due to their diverse physical properties controlled by composition and the number of stacked layers. Herein, large crystals of the ternary layered semiconductor chromium thiophosphate (CrPS4 ) are prepared by a vapor transport synthesis. Optical properties are determined using photoconduction, absorption, photoreflectance, and photoacoustic spectroscopy exposing the semiconducting properties of the material. A simple, one-step protocol for mechanical exfoliation onto a transmission electron microscope grid is developed, and multiple layers are characterized by advanced electron microscopy methods, including atomic resolution elemental mapping confirming the structure by directly showing the positions of the columns of different elements' atoms. CrPS4 is also liquid exfoliated, and in combination with colloidal graphene, an ink-jet-printed photodetector is created. This all-printed graphene/CrPS4 /graphene heterostructure detector demonstrates a specific detectivity of 8.3 × 108 (D*). This study shows a potential application of both bulk crystal and individual flakes of CrPS4 as active components in light detection, when introduced as ink-printable moieties with a large benefit for manufacturing.

Multilayer silicene: Structure, electronics, and mechanical property

Abstract Herein, we performed first-principle calculations and classical molecular dynamics simulations to study geometry optimizations, band structures, and mechanical properties of differently stacked multilayer silicenes. Several local energy minima have been identified as metastable conformations with different stacking modes and layer numbers. Bandstructure of the low buckled AA bilayer silicene optimized with SCAN + rvv10 presents semiconducting behavior with a bandgap of 0.4419 eV. Young’s modulus of multilayer silicene shows low dependence on layer number or stacking mode. Whereas, fracture stress and strain are sensitive to the number of layers, specific stacking modes, and chiralities. Furthermore, bending moduli of multilayer silicenes (e.g., 0.44 eV for monolayer silicene) are even lower than that of graphene, which may attribute to the flexibility of bond angle.

Microcrystalline Characterization and Morphological Structure of Tectonic Anthracite Using XRD, Liquid Nitrogen Adsorption, Mercury Porosimetry, and Micro-CT

Tectonic deformation acts as an indispensable factor affecting the crystalline structure, but its relationship with the evolution mechanism of the morphological structure is seldom considered. In this work, the characterization of microcrystalline and morphological structures in tectonic coal was comprehensively explored using X-ray diffraction (XRD), pore structure analyzers (liquid nitrogen and mercury intrusion methods), and micro-computed tomography (micro-CT). The XRD results indicate that a transformation of the chemical composition was observed in the coal body after continuous tectonic deformation. Meanwhile, the variation in microcrystalline parameters, such as the interlayer spacing (d), stacking height (L), effective stacking layer number (N), aromaticity (f), and graphitization degree (g), reveal that the microcrystalline structure of tectonic coal has experienced a positive evolution with graphitization and aromatization. Pore morphological analyses demonstrate that pore volume distributions of micropores, mesopores, and macropores were totally enhanced by tectonism while the pore shape potentially changes slightly. Simultaneously, the incremental noneffective pores of tectonic coal may promote gas accumulation and storage in the pore space. Fracture morphological analyses utilizing micro-CT lay emphasis on the orderly distributed cleats with a uniform scale in original coal, whereas the reconstruction of microstructures in tectonic coal illustrates a scattered distribution with good connectivity. In addition, the evolution of the macromolecular structure has an influence on the growth of nanoscale pores since the lattice defects may generate from the interlayer of the aromatic ring or the internal space. This research is of an enlightening significance for understanding the influence of tectonic stress on the chemical structure evolution of coals and its relationship with the nanoscale morphological structure development in tectonic coal.

Decay of Trapped Magnetic Field in Stacks of YBCO Coated Conductors Subjected to Traveling Magnetic Waves

High temperature superconducting stacks of tapes can also trap high magnetic fields which makes them a promising candidate for a multitude of electrical applications. In this paper, we aim to replace the traditional permanent magnet in linear synchronous motors by magnetized tape stacks. To study the characteristics of how traveling magnetic fields cause trapped fields to decay, stacked tape configurations comprised of two parallel columns were assembled, tested, and modeled computationally. The decay characteristics of the trapped magnetic field at different stator current amplitudes and different frequencies were measured by a homemade measurement system. A two-dimensional model including stator and stacks of YBCO coated conductors was constructed to investigate the related electromagnetic properties. The mechanisms linking the magnetic ac losses to the trapped magnetic field decay is discussed. Lastly, we present three effective methods to reduce trapped field decay which include: placing superconducting shielding layers at the sides; inserting Permalloy pieces in between; and increasing the number of stacked layers.

Study of the influence of mechanical pressure on the performance and aging of Lithium-ion battery cells

The influence of an applied mechanical pressure on the electrochemical performance and the aging of 1.4 Ah graphite/NMC622 stacked Lithium-ion battery cells (LiBs) is investigated comprehensively on the electrode and the full cell level. Pressure dependent ionic pore resistance measurements reveal an increase of the ionic pore resistance in both, the anode and the cathode of 6% and 2.9%, respectively at a pressure of 0.84 MPa. Compressibility measurements expose an interesting nonlinearity of the compressibility and the number of layers in an electrode stack, which must be considered for the cell application. The applied pressure improves the electrical contact in the cell. However, by the increase of both, the ionic pore resistance and the charge transfer resistance, the reversible capacity loss is strongly dependent on the applied C-rate during the cycling. For C-rates above 0.8C the polarization losses of the compressed cells are around 7.3% in comparison to 2.1% for the uncompressed cells. Contrariwise, for C-rates below 0.8C the compression of the cells is beneficial and leads to a capacity increase of 2.0% compared to the uncompressed cells. The subsequent post-mortem analysis demonstrates the negative influence of the absence of a homogeneous pressure distribution within the uncompressed cells.

Effect of SiO2 Etching Inhibitor to H3PO4 for the Selective Si3N4 Wet Etching of 3D NAND

As the number of stacked layers of the 3D NAND structure increases, the memory density of 3D NAND flash memory device increases [1]. In the fabrication of 3D NAND device, it is essential to selectively etch Si3N4 by an etchant flowing along a narrow slit followed by metal deposition. However, as the number of Si3N4/SiO2 multi-stack increases, selective etching of Si3N4 becomes difficult. In order to increase the Si3N4-to-SiO2 etch selectivity, SiO2 etching inhibitor should be added to H3PO4. Unfortunately, most of SiO2 etching inhibitors added to H3PO4 generate oxide regrowth around SiO2 layer on the Si3N4/SiO2 multi-stack structure. In this study, the mechanism of oxide regrowth occurred on the 3D NAND structure was investigated. Patterned Si3N4/SiO2 multi-stack structures were prepared. Etching experiments were performed using coupon wafers in 85% H3PO4 or etching inhibitor-added H3PO4 at 160 °C. The Si3N4 and SiO2 etching rates and Si3N4-to-SiO2 etch selectivity were measured using spectroscopic ellipsometry and oxide regrowth on the Si3N4/SiO2 multi-stack structure was analyzed using FE-SEM and HR-TEM. When the Si3N4/SiO2 multi-stack structure was etched in the SiO2 etching inhibitor-added H3PO4, oxide regrowth was observed on the SiO2 layered trenches on the Si3N4/SiO2 multi-stack structure, as shown in Fig. 1. The oxide regrowth occurred intensively at the corner of SiO2 layered trench and oxide regrowth occurred heavily at the bottom of Si3N4/SiO2 multi-stack structure as compared to the top. The overall amount of oxide regrowth on the SiO2 layered trench increased as the concentration of SiO2 etching inhibitor added to H3PO4 increased. In addition, it is shown that generation rate of etching product is an important factor to occur oxide regrowth. Based on the results, it is suggested that etching inhibitor addition and high generation rate of etching product and mass transfer limitation are responsible for the oxide regrowth. Through their optimization, selective Si3N4 etching on the Si3N4/SiO2 multi-stack structure without oxide thinning and regrowth could be obtained, as shown in Fig. 2.

Large-Area and Strain-Reduced Two-Dimensional Molybdenum Disulfide Monolayer Emitters on a Three-Dimensional Substrate.

Atomically thin membranes of two-dimensional (2-D) transition-metal dichalcogenides (TMDCs) have distinct emission properties, which can be utilized for realizing ultrathin optoelectronic integrated systems in the future. Growing a large-area and strain-reduced monolayer 2-D material on a three-dimensional (3-D) substrate with microstructures or nanostructures is a crucial technique because the electronic band structure of TMDC atomic layers is strongly affected by the number of stacked layers and strain. In this study, a large-area and strain-reduced MoS2 monolayer was fabricated on a 3-D substrate through a two-step growth procedure. The material characteristics and optical properties of monolayer TMDCs fabricated on the nonplanar substrate were examined. The growth of monolayer MoS2 on a cone-shaped sapphire substrate effectively reduced the tensile strain induced by the substrate by decreasing the thermal expansion mismatch between the 2-D material and the substrate. Monolayer MoS2 grown on the nonplanar substrate exhibited uniform strain reduction and luminescence intensity. The fabrication of monolayer MoS2 on a nonplanar substrate increased the light extraction efficiency. In the future, large-area and strain-reduced 2-D TMDC materials grown on a nonplanar substrate can be employed as novel light-emitting devices for applications in lighting, communication, and displays for the development of ultrathin optoelectronic integrated systems.

Study on the pyrolysis characteristic of mild liquefaction solid product of Hami coal and CO2 gasification of its char

Efficient utilization of mild liquefaction solid product (MLS) of Hami coal is critical to improve energy efficiency of the whole process, which accounts for >30 wt% of raw coal. In this work, the structure features of MLS were characterized by the solid-stage 13C NMR (SS-NMR) and its pyrolysis behavior was measured by a thermogravimetric analyzer (TGA) coupled with a mass spectrometer (MS). Additionally, the chars of MLS were prepared in a quartz tube fixed-bed reactor at different temperatures. Then the physico-chemical structure and CO2 gasification reactivity of the MLS chars were measured by multiple methods, including Fourier Transform Infrared Spectrometer (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD) and TGA. According to the SS-NMR analysis, the aromaticity of MLS is relatively high even though it contains ca. 47.90% aliphatic carbon. The evaporation of hexane soluble fraction (HS) and cleavage of CalCal and CarCal bonds are dominant in the process of MLS pyrolysis according to the TGA-MS analysis. With the increase of final pyrolysis temperature, the yield of char and H/C atomic ratio gradually decrease from 69.4% to 54.9% and from 0.664 to 0.110, respectively. In addition, the side chains and functional groups of char gradually reduce, the char becomes dense and dim, and the degree of ordering of char increases. Well quantitative linear relationships (R2 > 0.95) between gasification reactivity, carbon crystalline stacking layer number (n) and H/C atomic ratio are established, which could be used to finely evaluate the CO2 gasification reactivity of MLS and pyrolysis chars.

A Behavioral Compact Model for Static Characteristics of 3D NAND Flash Memory

We present a behavioral compact model for static characteristics of 3D NAND flash memory for integrated circuits and system-level applications utilizing BSIM-CMG 110.0.0. This model is easy to implement, computationally efficient, fast, accurate, and effectively accounts for the different parasitic capacitance coupling effects applicable to the 3D geometry of the vertical channel Macaroni body charge-trap flash memory. The model parameter extraction methodology is simple and can be extended to reproduce the electrical behavior of different 3D NAND flash memory architectures (with different page size, dimension, or a number of stacked layers). We believe that the developed compact model would equip the circuit designers and system architects with an effective tool for design-exploration of 3D NAND flash memory devices for diverse unconventional analog applications.

Clarifying photoluminescence decay dynamics of self-assembled quantum dots

We studied the temperature-dependent photoluminescence (PL) and time-resolved PL spectra of multilayer CdTe/ZnTe quantum dots (QDs) to understand their carrier dynamics. We demonstrated a method of enhancing the confinement of carriers in CdTe QDs by modulating the number of stacked layers, leading to enhanced acoustic phonons up to 67 μeV and reducing the optical phonon coupling to 20 meV with an average phonon energy of 20 meV. The temperature-dependent decay time could be explained using a simple model of the thermal redistribution of carrier states. Thermal escape from hole states during multiphonon scattering occurred only at high temperatures, whereas blue shifts and enhanced PL intensity were expected to enhance the electron–phonon coupling and confinement-induced mixing among discrete state and continuum states with separation energies of 3.5–7.4 meV. Time-resolved PL measurements probed the electric field screening effect as a function of the strain distribution in QDs and was established to be 2.5 ± 0.2 MV/cm.

What Will Come After V‐NAND—Vertical Resistive Switching Memory?

AbstractThe NAND flash memory serves as the key enabler of the flourishing of portable handheld information devices, such as the cellular phone. The recent upsurge in the sales of vertical NAND flash memory (V‐NAND) entails a further increase in the available information capacity at the edge devices and the servers with higher performance and lower power consumption compared with the magnetic hard‐disc drives. Nonetheless, there will certainly be an upper limit for the number of stacked layers, which will be the point at which further memory density increase will stop. While V‐NAND is a supreme outcome of semiconductor memory technologies, it still relies on conventional Si‐based materials. The newly explored memory materials and concepts, such as the resistance‐based memories, can therefore be an appealing contender to or successor of V‐NAND. In this review, the current state of V‐NAND is first briefly looked into, and then the eventual limitation of memory density increase and performance boost are discussed. Most importantly, the possible strategies of integrating the resistance‐based memories into the vertical architecture are then discussed. Finally, the outlook for such resistance‐based vertical memories is presented.