Different Number Of Layers Research Articles

Engineering a PVD-Based Graphene Synthesis Method

Graphene is an important nanomaterial with extraordinary properties. An established physical vapor deposition (PVD) based Graphene synthesis method is engineered in order to demonstrate the versatility of the growth method with respect to the quality and number of layers of synthesized Graphene. A statistical method known as factorial Design-of-Experiments (DoE) is demonstrated in this paper to determine key factors for synthesis of Graphene on Copper (Cu) using amorphous carbon (a-C) as the solid carbon source. Both qualitative and quantitative analysis are performed to determine a suitable recipe. Carbon source thickness (which is a-C) annealing temperature and annealing duration are varied to study their effect on the growth. Annealing temperature and a-C thickness are found to be significant factors for growth feasibility in a PVD-based growth, whereas annealing time is found to play a crucial role in growing different number of layers of Graphene with different quality. The quality and number of layers of Graphene are verified by Raman characterization.

Effects of fabric folding and thickness on the impact behaviour of multi-ply UHMWPE woven fabrics

This paper presents an experimental study on the dynamic response of multi-ply woven fabrics subjected to impact by a spherical steel projectile in a velocity regime ranging from 120 to 200 m/s. A plain weave fabric made of Spectra® 1000 fibres was used to fabricate test samples having different numbers of layers and fold patterns. The effect of fabric folding was investigated by comparing the impact performance of samples consisting of separate unfolded fabrics, continuous accordion-fold fabrics, and continuous roll-fold fabrics, respectively. It was found that the perforation resistance and energy absorption capacity were significantly improved by folding a fabric into multiple plies compared to the unfolded counterparts, and the roll-fold fabrics performed best in this study. Fabric folding seemed to have only a negligible effect on the back-face deflections of woven fabrics. The effect of thickness (or the number of layers) on energy absorption efficiency was different among the tested fabrics, due to the different inter-layer interactions depending on fold patterns.

Influence of multilayer deposition on characteristics of nanocrystalline SnO2 thin films produce by sol-gel technique for gas sensor application

Nanocrystalline SnO2 thin films have been prepared on glass substrates using sol-gel dip-coating technique. The deposited films were annealed in air at 500°C for one hour. Structural, optical, electrical, and sensing properties of the films were studied for different number of layers. X-ray diffraction spectra reveal the polycrystalline nature of the SnO2 films with tetragonal crystal structure, and have preferred growth direction along (110). The crystallite size of the thin films increased with increasing number of layers. AFM and SEM results indicated that the average grain size increased as number of layers increased. The optical band gap energy and transmittance of dip-coated films decreased as number of layers increased. The electrical properties of SnO2 films include DC electrical conductivity, showing that the films have two activation energies, namely, Ea1 and Ea2, which increase as number of layers increases. The films were further investigated in terms of their sensing abilities for carbon monoxide (CO) and nitrogen dioxide (NO2) gases at 50ppm by measuring their sensitivity to these gases at different times and temperatures. Our results demonstrated that dip-coated prepared films were highly sensitive to CO and NO2 at 200°C.

Modeling of composite plates with an arbitrary hole location using the variable separation method

In this paper, a method to compute explicit solutions for laminated plate with arbitrary hole position is presented using a variable separation method. The displacement field is approximated as a sum of separated functions of the in-plane coordinates x,y, the transverse coordinate z and the coordinates XT,YT of the hole position. As the parameterized problem involves the geometry, a mapping transformation is introduced to refer to a fixed reference configuration. This choice yields to an iterative process that consists of solving a 2D and three 1D problems successively at each iteration. In the thickness direction, a fourth-order expansion in each layer is considered. For the in-plane description, classical Finite Element Method is used. The functions of XT and YT are discretized with linear interpolations. Mechanical tests with different numbers of layers are performed to show the accuracy of the method and its capacity to capture local effects and 3D state of the stress near the curved free-edge.

Self‐Assembly of Solution‐Processable Polyindole via Langmuir‐Blodgett Technique: An Insight to Layer‐Dependent Charge Transport and Electronic Parameters

AbstractOrdering of polymer chains at molecular level using a suitable post‐synthesis fabrication technique is highly motivating towards enhancement in performance of organic electronic devices. Here, we report the formation of stable, large area self‐assembled Langmuir‐Blodgett (LB) films of unsubstituted polyindole (PIn) without aid of any surfactant. Pressure vs Area (π‐A) isotherm for PIn is studied prior to device fabrication. Investigation of film uniformity via atomic force microscopy and scanning electron microscopy justified 30 mN/m as optimum surface pressure for depositing large area PIn LB films. Self‐assembly in LB film is confirmed by absorption and Raman spectroscopy before device fabrication. A layer dependent charge transport of LB film of PIn is studied via current density (J)–voltage (V) characteristics and subsequently various device parameters are extracted using Schottky diode configuration of sandwiched structure Al/PIn LB film/ITO. A deviation in ideality factor, rectification ratio, current density and barrier height is observed for different number of layers. The electrical characteristics are also discussed taking into account the absorption spectra, Raman spectra, surface morphology, topography, barrier height. This study shows enormous potential for the fabrication of ordered PIn polymer on large area based electronic device application.

Understanding the gas adsorption kinetics of Langmuir-Schaefer porphyrin films using two comparative sensing systems

This study investigated Langmuir-Schaefer (LS) films of a free base porphyrin 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-21H,23H-porphine (EHO) as sensors to detect acetic acid and methylamine. Such films are known to adsorb VOCs, resulting in a color change and a swelling of the film resulting in a thickness increase for the film. The adsorption kinetics of this process were studied using two different techniques, namely UV–vis absorbance spectroscopy and surface plasmon resonance (SPR), to investigate the color change and film thickness change respectively when exposed to acetic acid and methylamine vapors. These two techniques were used to allow a comparative study to be made of the color change and film swelling in order to enhance understanding of the interaction between the thin films and both acidic and basic vapor molecules.The transfer process of the LS thin films was performed using the constant transfer pressure of 5mNm−1. EHO films with different numbers of layers were fabricated and exposed to 855ppm acetic acid and 900ppm methylamine vapor. Sensor responses were recorded using both UV–vis and surface plasmon resonance techniques. The EHO films exhibited high sensitivity and fast responses using both techniques. Using two different detection systems permitted the investigation of the interaction mechanism with a quantitative, comparative study with the aim of obtaining an enhanced understanding of the nature of the interaction of the organic vapors with the sensor. The interaction between EHO and the analytes can be considered in terms of three processes which are surface adsorption, diffusion and desorption process. Although both the optical techniques have distinct sensing principles, similar vapor interaction characteristics can be distinguished in both sets of experiments. For both techniques the response to the acid was stronger than the response to methylamine. However, apart from this difference in the magnitude of the responses the interaction with the acid and base were remarkably similar. The sensitivity of the sensor is largely independent of the measurement system.

Comparative study on the thickness dependent output energy for (Bi,Sc)O 3 -(Pb,Ti)O 3 multilayered structure

Multilayered (Bi,Sc)O3-(Pb,Ti)O3 piezoelectric ceramic harvesters with the same volume size and with different numbers of layers were prepared as energy harvesters to maximize the generated output energy. Multilayered (Bi,Sc)O3-(Pb,Ti)O3 piezoelectric ceramic harvesters were also prepared with the same volume size with different layer thicknesses to extract and compare the acquired energy from the harvesters. Four different types of multilayered piezoelectric ceramic harvesters were prepared and analyzed in this experiment: 24 layers of 0.5 mm thick layered actuators, 12 layers of 1 mm thick layered actuators, 6 layers of 2 mm thick layered actuators, and 4 layers of 3 mm thick layered actuators. The generated output energy was measured through the 100 kΩ resistors. By measuring the output energy of the multilayered (Bi,Sc)O3-(Pb,Ti)O3 piezoelectric ceramic harvesters, the maximum output energy per volume of 12 layers with 1 mm thickness was 8.01 × 10−6 J/mm3. From an investigation of the maximum output energy of the energy harvester due to the high piezoelectric coefficient, Curie temperature, and high output energy, it was determined that multilayered (Bi,Sc)O3-(Pb,Ti)O3 piezoelectric ceramic harvesters are the best candidate for energy harvester applications.

The size-dependent analysis of multilayered microbridge systems under a moving load/mass based on the modified couple stress theory

In this study, the dynamical behavior of mutlilayered microbeam systems with respect to a moving load/mass is investigated. The Winkler elastic foundation beam is used to model the coupling between layers and small-scale effects are modeled by modified couple stress theory. Equations of motion are achieved using Hamilton's principle and the solution process is proposed for a different number of layers. For double- and three-layered microbridge systems, an analytical solution is presented using Laplace transform and moreover, for higher-layered MMBS, a state space method is employed. A comprehensive parametric study is presented to clarify the effects of various parameters such as small-scale effect, coupling, the moving velocity, number of layers, etc. It is shown that material variation and scale effects changes the behavior of microbridge systems and have a significant effect on the dynamic deformation under a moving nanoparticle which could be used in understanding and designing more efficient nanostructures. Accordingly, with the brand new discussions on moving atoms, molecules, cells, nanocars, nanotrims, point loads on different nanosctructures using scanning tunneling microscopes (STM) and atomic force microscopes (AFM), this study could be a step forward in understanding, predicting and controlling such kind of behaviors.

Plasmon-Induced Energy Transfer and Photoluminescence Manipulation in MoS2 with a Different Number of Layers

Monolayer or few-layer molybdenum disulfide (MoS2) with intriguing physical properties enables a wide range of applications such as photocatalysis and photodetection. The controllable light–matter interaction in MoS2 nanoflakes with different numbers of layers is critical for developing new optoelectronic functionalities. Recently, plasmonic nanostructures have been used to obtain strong near-field enhancement for the effective photoluminescence (PL) manipulation of MoS2. However, it is still unclear whether the PL manipulation is dominated by electron injection processes or the strong field induced Purcell effect so far. Here, we investigate the PL manipulation of MoS2 nanoflakes with different numbers of layers using Au nanoparticles with different aggregate states. Combining the measured PL and scattering spectra, the Kelvin probe force microscopy images at the single-particle level, and the numerical simulations, we figure out how the electron injection and strong field enhancement contribute to the PL manipulation and why PL quenching occurs in few-layer flakes but PL enhancement occurs in thicker flakes. These findings would give us a greater understanding of the interaction between two-dimensional materials and plasmonic nanostructures.

Microstructural and component evolution of self-assembled nanoperiod multilayered carbon-copper films with deposition pressure

Here, we report a facile synthesis method for the fabrication of various nanoperiod multilayers in carbon-copper films only by conveniently changing the deposition pressure from the reactive magnetron sputter process. To obtain the nano-multilayered structure with different number of layers, only one single sputtering target of copper is used at gas pressure varied from 0.4 Pa to 1.2 Pa by flowing gas mixture of argon and methane, while 600W DC input power is applied to a copper target. The influence of deposition pressure on the microstructure and constitution of the films are investigated by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The results show that carbon-rich layers and copper-rich layers are alternately arranged to self-organize the multilayered structure in the carbon-copper films, both of the carbon-rich layer and copper-rich layer constitute a period. The amount of layers in the multilayered structure is found to decrease with the deposition pressure, the film deposited with 0.4 Pa has the maximum layers and the highest copper content compared with the other deposition pressure. Effects of the growth condition on the growth rate, the number of the layers and the energy of plasmas during deposition process are discussed. Based on the (a) influence of the effect of carbon absorbed on the copper target leading to target poisoning, (b) influence of deposition pressure on the energy of etching ions and (c) the energetic ions bombardment enhanced inter diffusion of deposition ions, the mechanism of self-organized formation of nano-multilayer in the carbon-copper films with various number of layer is proposed.

Multiple Adhesive Layering Influence on Dentin Bonding and Permeability.

The aim was to evaluate the effect of the number of layers on the microtensile bond strength (μTBS), permeability and nanoleakage of an etch-and-rinse adhesive (Adper Single Bond 2). Different numbers of layers (1, 2 and 4) were applied on dentin susbstrate. Specimens were obtained and tested for μTBS. Stick-shaped samples were analysed by scanning electron microscope, to observe silver nitrate penetration. One-way ANOVA and Tukey tests were applied (α=0.05) for μTBS values. The fracture mode was evaluated under a stereomicroscope and a scanning electron microscope (SEM). Groups with two and four layers of bond showed higher μTBS to dentin and they also showed lower adhesive permeability than ONE layer. The silver nitrate uptake occurred in the hybrid layer in practically all groups. Fracture occurred predominantly at the mixed interface. The authors recommend the application of more than one layer of Adper Single Bond 2, because a single layer showed lower μTBS and higher permeability values.

Electrical conductivity of carbon nanotube/polypropylene composites prepared through microlayer extrusion technology

Abstract The morphological distribution of carbon nanotubes (CNTs) in polymer matrix has a crucial impact on the performance of CNT-filled polymer composites. A novel microlayer extrusion technology used in the dispersion and orientation of CNTs was proposed, and polypropylene (PP)/multiwalled CNT (MWCNT) composites with different numbers of layers were prepared with it. The MWCNT dispersion was investigated by scanning electron microscopy and Raman mapping method, and the MWCNT orientation was quantified by Raman spectroscopy. The influences of the dispersion and orientation of MWCNTs on the electrical conductivity and crystallization behavior of the composites were investigated. The results showed that the anisotropic conducting properties of the multilayered composites varied distinguishably with the increase of layer numbers and rotation speed. Furthermore, the degree of crystallinity of PP increased when the layer number increased from 1 to 729. All of these results suggest that with the increase of the layer numbers and the rotation speed, the dispersion and orientation of MWCNTs in PP matrix improve greatly. Overall, we provide an efficient and practical approach to control the dispersion and orientation of CNT in polymer matrix, which has a promising application prospect in the field of plastic processing.

Flexoelectric energy harvesters based on Timoshenko laminated beam theory

Different from piezoelectricity which is restricted to certain materials, flexoelectricity is a universal electromechanical coupling in all dielectrics. In this work, mechanical energy harvester models were developed based on Timoshenko laminated beam theory, in which the flexoelectric and piezoelectric mechanisms were discussed. For a three-layered energy harvester in parallel configuration, the mechanical vibration energy can be converted into electrical energy due to flexoelectricity, and for the three-layered energy harvester in series configuration, the energy conversion is enhanced by the flexoelectricity. Resonance frequency shifts were observed in the calculations due to flexoelectricity and external circuit resistance. It is found that the electromechanical coupling displayed from the electrical responses versus resonance frequency and resistance. The energy conversion for the three-layered energy harvester system was found to be increased with the decrease in the laminated beam thickness. The energy conversion calculated for different numbers of layers also indicates that laminated energy harvester systems excel single-layered energy harvesters. This work therefore might help in designing flexoelectricity-based energy harvesters.

A theoretical modeling of photocurrent generation and decay in layered MoS2 thin-film transistor photosensors

A model that universally describes the characteristics of photocurrent in molybdenum disulphide (MoS2) thin-film transistor (TFT) photosensors in both ‘light on’ and ‘light off’ conditions is presented for the first time. We considered possible material-property dependent carrier generation and recombination mechanisms in layered MoS2 channels with different numbers of layers. We propose that the recombination rates that are mainly composed of direct band-to-band recombination and interface trap-involved recombination change on changing the light condition and the number of layers. By comparing the experimental results, it is shown that the model performs well in describing the photocurrent behaviors of MoS2 TFT photosensors, including the photocurrent generation under illumination and a hugely long time persistent trend of the photocurrent decay in the dark condition, for a range of MoS2 layer numbers.

Numerical study on the bearing capacity of masonry platform with different number of layers

Numerical study on the bearing capacity of masonry platform with different number of layers

Effect of wire mesh on double-suppression of CH4/air mixture explosions in a spherical vessel connected to pipelines

Most inlets or outlets of tanks and reactors are linked vessels consisting of the tank or reactor itself and pipelines. In this study, a series of experiments was conducted to study the double-suppression effect of a multi-layer wire-mesh structure on methane-air mixture explosions in a spherical vessel connected to pipelines. The double-suppression effect was analyzed using explosion-suppression structures with different number of layers and meshes, and in particular, the effect was compared with the suppression of single-wire mesh. The results show that the explosion suppression effect primarily depends on both the number of layers and number of meshes. The number of layers plays a positive role in suppression when enough layers are used, and the number of meshes also has a significant effect on explosion suppression. It appears that the position of the wire mesh only has a slight effect on explosion suppression. The results provide a fundamental basis for actual explosion protection designs.

Surface functionalization of single-layer and multilayer graphene upon ultraviolet irradiation

The process of oxidation of single-layer and multilayer graphene films upon ultraviolet irradiation of the structure in water vapor was studied. The systematic features and distinctions between changes in the topographic and optical properties of graphene films composed of different numbers of layers were established. The possibility of surface functionalization accompanied by modification of the energy structure of graphene was shown. Differences between single-layer and multilayer graphene films in the mechanisms of oxidation on ultraviolet irradiation are discussed and analyzed. Correlation of the topographic imperfections of the properties of the graphene material with its structural defects observed in Raman spectra was shown.

모넬(Monel)-Clad 파이프의 오버레이 용접 적층수가 용접성에 미치는 영향에 관한 실험적 연구

오버레이 용접은 희석율에 의해 적층 두께에 따라 화학성분 함량과 용접부의 경도에 영향을 미치며 이는 파이프 제품의 표면성질을 결정한다. 이로 인해 오버레이 용접은 적층의 수를 고려하여야 한다. 본 연구에서는 탄소강 모재에 내부식성 소재인 모넬 소재를 오버레이 용접하여 적층수에 따른 Fe함량, 모재와 모넬 소재와의 용접성, 부위별 경도와 표면 평탄도를 실험적으로 연구하였다. 각각의 평가는 평판의 모재와 파이프 모재에 3개의 층으로 오버레이 용접 후 실시하였다. Fe함량은 각 층별 시료를 채취하여 성분 분석을 통해 평가하였으며, 3Layer에서 만족하는 함량을 나타내었다. 또한 적층별 시편을 밴딩 시험하여 용접성을 평가하였다. 적층별 경도와 비드 평탄도는 Micro Vickers와 3차원 측정을 통해 평가하였다. 경도는 1Layer에서 발생하는 HAZ부에 의해 가장 높은 경도 값을 보였으며, 적층이 증가할수록 경도가 감소하였다. 비드 평탄도의 경우 적층수 증가에 따라 편차가 급격한 차이가 발생하였으며, 이는 경도와 함께 사용 목적의 측면에서 주의 깊게 고려해야 한다. 이러한 실험적 결과는 목적에 따른 용접 파이프 적층수의 결정 방법을 나타내었다. Overlay welding affects the chemical components and weld hardness by dilution of the lamination layer thickness, which determines the surface properties. This study experimentally investigates different numbers of layers for overlay welding monel materials, which are anti-corrosion materials. The Fe content, weldability of the base metal and monel materials, hardness, and surface flatness were examined. Each evaluation was carried out after overlay welding with three layers on the base material and pipe base material of the plate. The Fe content was evaluated by analyzing the constituents of each layer. The Fe content was satisfactory in the three layers. The weldability of the laminate specimens was evaluated by a bending test. The hardness and bead flatness of the laminate specimens were evaluated by micro Vickers and 3D measurements. The hardness was highest in the heat-affected zone with one layer, and it decreased with increasing lamination. In the case of bead flatness, there is a sharp difference in the deviation with increasing numbers of laminations, which should be considered carefully.

Novel Superdielectric Materials: Aqueous Salt Solution Saturated Fabric.

The dielectric constants of nylon fabrics saturated with aqueous NaCl solutions, Fabric-Superdielectric Materials (F-SDM), were measured to be >105 even at the shortest discharge times (>0.001 s) for which reliable data could be obtained using the constant current method, thus demonstrating the existence of a third class of SDM. Hence, the present results support the general theoretical SDM hypothesis, which is also supported by earlier experimental work with powder and anodized foil matrices: Any material composed of liquid containing dissolved, mobile ions, confined in an electrically insulating matrix, will have a very high dielectric constant. Five capacitors, each composed of a different number of layers of salt solution saturated nylon fabric, were studied, using a galvanostat operated in constant current mode. Capacitance, dielectric constant, energy density and power density as a function of discharge time, for discharge times from ~100 s to nearly 0.001 s were recorded. The roll-off rate of the first three parameters was found to be nearly identical for all five capacitors tested. The power density increased in all cases with decreasing discharge time, but again the observed frequency response was nearly identical for all five capacitors. Operational limitations found for F-SDM are the same as those for other aqueous solution SDM, particularly a low maximum operating voltage (~2.3 V), and dielectric “constants” that are a function of voltage, decreasing for voltages higher than ~0.8 V. Extrapolations of the present data set suggest F-SDM could be the key to inexpensive, high energy density (>75 J/cm3) capacitors.

Influence of 100 MeV Au+ 8 ion on photovoltaic response of BiFeO3/BaTiO3 multilayer structures

This work presents the swift heavy ion (SHI) irradiation induced possible modifications in structural strain and surface morphology of (BiFeO3)BFO/(BaTiO3)BTO multilayer structures prepared by chemical solution deposition technique. Furthermore, the role of structural defects (induced due to irradiation) on the ferroelectric property and photovoltaic response of BFO/BTO multilayer structures having different number of layers has been studied. Significant modifications in the morphological and ferroelectric properties of BFO/BTO (two, four and six layers) multilayer structures due to induced structural defects were observed after SHI irradiation performed using 100MeV Au+8 ion with ion fluence of ~1×1012, 1×1013 and 3×1013ions/cm2. Ferroelectric photovoltaic response decreases with increase in ion fluence from 1×1012 to 1×1013ions/cm2 along with change in open circuit voltage from 0.41V to 0.23V, short circuit current density from 5.177μA/cm2 to 1.71μA/cm2 and Ion/Ioff ratio from 33.02 to 13.02. This study on effect of SHI irradiation on multilayer ferroelectric photovoltaic cell is important to understand the possible application of BFO/BTO multilayer photovoltaic cells in the regions susceptible to radiations. Furthermore, the study of perovskite solar cell performance in the presence of SHI radiation, is essentially required for the development of durable solar energy harvesters.