Thin Layer Of Material Research Articles

A Comparative Thermodynamic Study of AlF3, ScF3, Al0.5Sc0.5F3, and In0.5Sc0.5F3 for Optical Coatings: A Computational Study

Optical coatings are thin layers of materials applied to optical components in order to modify the transmission, reflection, or polarization properties of light. The common materials used for optical coatings include magnesium fluoride (MgF2), scandium trifluoride (ScF3), and aluminum trifluoride (AlF3), owing to their desirable optical properties, spectral range, and compatibility with substrates. However, each of these materials has its own drawbacks. For instance, AlF3 has been found to exhibit limited resistance to attack by chemicals, as well as poor thermal stability, while MgF2 has low durability, as well as being hygroscopic. In this study, we undertook ab initio calculations in order to compare the thermal properties of AlF3, ScF3, Al0.5Sc0.5F3, and In0.5Sc0.5F3 in order to obtain the best material for optical coatings. MgF2 was also included in the study as a reference. The calculations used PBE pseudopotentials and the extended generalized gradient approximation within the quantum espresso algorithm. The study demonstrated that the computed results agree with the information found in the literature. ScF3 exhibited a negative coefficient of thermal expansion, unlike the other four. Moreover, AlF3 was found to be the best candidate for optical coatings that are used in high-power laser systems with high thermal dissipation, due to its superior thermal expansion coefficient as well as its better response to thermal stress. The large variation between the cp and cv of ScF3 is not desirable. Moreover, due to its negative thermal expansion coefficient, ScF3 is not thermally stable. The highest thermal stability was exhibited by In0.5Sc0.5F3. Since Al0.5Sc0.5F3 and In0.5Sc0.5F3 have been modeled in this study for the first time, experimental determination of their crystal structures needs to be investigated.

Mathematical study of viscoelastic polymer during roll-over-web coating

Roll-coating, also known as roll-to-roll coating or web coating is a continuous and high-speed method used in various industrial applications to apply a thin and uniform layer of material onto a substrate. This process is commonly employed in industries such as electronics, photovoltaic, printing, packaging, and other fields where precise and consistent coating is essential. Here we present an asymptotic analysis of forward roll coating over a rigid substrate for low Weissenberg number viscoelastic fluids. The analysis uses lubrication theory coupled with regular perturbation theory assuming a simplified Phan-Thien-Tanner (SPPT) constitutive equation and small values of the extensibility parameter ε. The analytical expressions of velocity fields, pressure gradient and pressure fields are obtained while the load carrying force, and power input are estimated by numerical solutions (4th order Runge-Kutta). Increases in both Wi and ε increases the pressure gradient in the nip region and increases in viscoelasticity reduce the overall force on the roll. Further, SPTT model predicts 14% lower pressure for [Formula: see text] in the nip region when compared to Newtonian model.

Retinal Pigment Epithelial Detachments Devoid of Retinal Pigment Epithelium.

To describe two patients with chronic central serous chorioretinopathy (CSC) showing what appeared to be retinal pigment epithelium detachments (PED) lacking imaging findings consistent with retinal pigment epithelium (RPE) over the elevation. The patients underwent comprehensive ophthalmic examination, including multicolor fundus photography, fundus autofluorescence (FAF), and spectral-domain optical coherence tomography (SD-OCT). A 70-year-old male and a 58-year-old male, both diagnosed with chronic CSC, showed PED-like lesions that were hypoautofluorescent, suggesting an absence of RPE. SD-OCT B-scans showed serous, dome-shaped elevations composed of a narrow, mildly hyperreflective band (9-10 μm thick) that demonstrated hypertransmission of light. The material that constituted the elevation was contiguous with the outer portion of the RPE band at the lesion borders. Based on the multimodal imaging findings we hypothesize that these elevations of the retina have lost their overlying RPE. A thin layer of material that could represent a residual layer of basal laminar deposit produced by the RPE remains overlying the detachments, possibly accounting for their dome shape and structural stability.

Vertical-cavity surface-emitting phase shifter.

This study proposes a novel technique for a 2D beam steering system using hybrid plasmonic phase shifters with a cylindrical configuration in a 2D periodic array suitable for LIDAR applications. A nanoscale VCSEP design facilitates a sub-wavelength spacing between individual phase shifters, yielding an expanded field of view and side lobes suppression. The proposed design includes a highly doped sub-micron silicon pillar covered by a thin layer of nonlinear material and an additional conductive metal layer. Characterization of a single VCSEP demonstrated a Free Spectral Range (FSR) of 53.28 ± 2.5 nm and a transmission variation of 3 dB, with VπL equal to 0.075 V-mm.

Fabrication of Amorphous Silicon-Carbon Hybrid Films Using Single-Source Precursors.

The aim of this study was the preparation of different amorphous silicon-carbon hybrid thin-layer materials according to the liquid phase deposition (LPD) process using single-source precursors. In our study, 2-methyl-2-silyltrisilane (methylisotetrasilane; 2), 1,1,1-trimethyl-2,2-disilyltrisilane (trimethylsilylisotetrasilane; 3), 2-phenyl-2-silyltrisilane (phenylisotetrasilane; 4), and 1,1,2,2,4,4,5,5-octamethyl-3,3,6,6-tetrasilylcyclohexasilane (cyclohexasilane; 5) were utilized as precursor materials and compared with the parent compound 2,2-disilyltrisilane (neopentasilane; 1). Compounds 2-5 were successfully oligomerized at λ = 365 nm with catalytic amounts of the neopentasilane oligomer (NPO). These oligomeric mixtures (NPO and 6-9) were used for the preparation of thin-layer materials. Optimum solution and spin coating conditions were investigated, and amorphous silicon-carbon films were obtained. All thin-layer materials were characterized via UV/vis spectroscopy, light microscopy, spectroscopic ellipsometry, XPS, SEM, and SEM/EDX. Our results show that the carbon content and especially the bandgap can be easily tuned using these single-source precursors via LPD.

Creation of Molecular Gel Materials Using Polyrotaxane-Derived Polymeric Organogelator.

Molecular gels, which are soft and flexible materials, are candidates for healthcare, cosmetic base, and electronic applications as new materials. In this study, a new polymeric organogelator bearing a polyrotaxane (PR) structure was developed and could induce the gelation of N',N″-dimethylformamide (DMF), a known solvent for dissolving polymeric materials and salts. Furthermore, the resulting DMF molecular gels exhibited thixotropic properties, observed by the inversion method using vials, which are essential for gel spreading. The scanning electron microscopy of the xerogels suggested that the gel-forming ability and thixotropic property of gels were imparted by the network of the laminated aggregates of thin layer material similar to those of other gels made of clay materials. This thin layer material would be formed by the aggregation of polymeric organogelators. The dynamic viscoelasticity measurements of the obtained gels revealed the stability and pseudo-thixotropic behaviors of the obtained gels, as well as a specific concentration effect on the mechanical behavior of the gels attributed to the introduction of the PR structure. Additionally, the preparation of the polymer organogelator/polymer composites was investigated to improve the mechanical properties via the filler effect induced by the agglomerates of organogelator. Moreover, the tensile tests confirmed that the introduction of the gelator enhanced the mechanical properties of the composites.

Comparative numerical and analytical computations for magnetized pseudoplastic materialwith roll-coating applications

The phenomenon of wire coating occurs in various applications in manufacturing systems, cables, drawing of sheets, polymer industries etc. The current investigation deals with the study of the reverse coating phenomenon of magnetized non-Newtonian fluid. A pseudoplastic material with applications of magnetic force is considered and the rheological impact based on the non-Newtonian model is investigated. The thin layer of pseudoplastic material is coated when it travels due to the small gap conveying by two reverse coating rollers. The formulation of problem is based on lubrication approximation theory. Both analytical and numerical simulations are performed, and the corresponding results are compared. The numerical assessment is based on the shooting technique while analytical outcomes are obtained using perturbation technique. The effects of the governing parameters on the flow profiles are depicted. The main parameters influence the flow are the Weissenberg number and velocity ratio parameter.

Electrohydrodynamic jet printed bioinspired piezoelectric hair-like sensor for high-sensitivity air-flow detection

Inspired by the highly sensitive hairs of creatures in nature, this work proposes a high-aspect-ratio piezoelectric sensor that is processed using electrohydrodynamic jet (E-jet) printing technology. A thin layer of piezoelectric material is directly written on the surface of tungsten steel microwire by E-jet printing. The piezoelectric material was crystallized by high-temperature annealing and fully bonded to the microwire. The annealed piezoelectric thin film was then sputtered with copper electrodes which forms a piezoelectric hair-like sensor with a diameter of 120 μm and an aspect ratio of 300. It was observed that the piezoelectric hair-like sensor generates 18 mV with a displacement of 100 μm. The output signal increases linearly with the increase of lateral displacement and velocity. It was examined that the piezoelectric hair-like sensor can detect airflow velocity as low as 0.01 m s−1, which shows a lower detection threshold compared to piezoelectric hair-like airflow sensors processed in other ways. In addition, the piezoelectric hair-like sensor allows for the detection of an airflow velocity of 10 m s−1 and a response time of 70 ms. The experimental results show that the piezoelectric hair-like sensor has high sensitivity, a wide detection range and rapid detection response, which is expected to be a high-performance sensor for biosensing and airflow monitoring.

Properties of Mn3O4 thin film electrodes prepared using spray pyrolysis for supercapacitor application

Film electrodes are made by depositing a thin layer of an electroactive material onto a conductive substrate. The performance of thin film electrodes in energy storage devices is significantly governed by their preparative conditions, particularly the molar concentration of the initial precursor. In the current study, the preparation of Mn3O4 thin film electrodes utilizing the chemical spray pyrolysis technique is discussed. The effect of molar concentration on the structural, morphological, and electrochemical properties of the thin film electrodes was thoroughly investigated using techniques including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) studies. Additionally, X-ray photoelectron spectroscopy (XPS) was employed to gain more insight into the oxidation states of the sample with the best electrochemical performance. Findings suggested that the molar concentration considerably affects the crystallite size, surface area, surface roughness, and wettability, which would directly impact the functionality of the electrode. It was concluded that the electrode deposited using the molar concentration of 0.06 M showed significantly improved performance according to the electrochemical measurements. The areal capacitance of up to 105.3 mF/cm2 in the aqueous electrolyte was recorded from CV measurements at a scan rate of 5 mVs−1. These electrodes could be an option for low-cost, environmentally friendly electrochemical capacitors if prepared under optimal deposition conditions.

Solution of filtration problems of construction geotechnology in thin water layers

Filtration problems of construction geotechnics during water movement in thin permeable layers of soils and artificial materials are considered. Under such conditions, traditional approaches borrowed from classical hydrogeology give errors. This is due to the fact that under normal conditions of underground aquifers of a sufficiently large depth, in hydrogeological practice, the hydraulic theory of filtration is used, in which the velocities of filtration currents are averaged along the vertical coordinate. The original nonlinear differential equations of filtration flows are subjected to forced linearization by one or another known method. In this case, the method of linearization by introducing the average power (depth) of the filtration flow is widely used. This method was originally developed for aquifers of great depth. In the presented work, an attempt was made to abandon such a linearization and solve some of the problems of unsteady filtration flows in thin aquifers, which are characteristic of building geotechnics, with obtaining analytical solutions of the final form without introducing artificial simplifications. A methodology is proposed for combining analytical and numerical methods in the process of finding solutions to filtration problems of construction geotechnics with obtaining self-similar dependencies. This approach will make it possible to avoid linearization errors and carry out filtration calculations in thin permeable layers of soils and artificial materials more accurately. A review of domestic and foreign scientific publications on the topic of research has shown some stagnation in this direction. The comparison revealed that in thin permeable layers of soils and artificial materials, preference can be given to filtration calculations using the presented method, since it more accurately describes the non-stationary movement of water in construction geotechnics.

Mechanical Properties and Assessment of PLA Mixed with Carbon by Using Additive Manufacturing

Abstract: Three-dimensional (3D) printing is an additive manufacturing process that creates a physical object from a digital design. The process works by laying down thin layers of material in the form of liquid or powered plastic, metal or cement, and then fusing the layers together. Fused deposition modelling has gained much attention in recent years, as it revolutionizes the rapid manufacturing of customized polymer-based composite components. To facilitate the engineering applications of these fused deposition modelling printed components, understanding their basic mechanical behaviours is necessary. In this project, the mechanical characteristics, including tensile, hardness and impact properties of samples fabricated by fused deposition modelling with different additives, i.e. wood, ceramic, copper, aluminium and carbon fibres, based polylactic acid composites are comprehensively investigated. The effects of different polylactic composites, build orientations and raster angles on mechanical responses are compared and analysed in detail. In this study, We investigate the mechanical properties such as Tensile strength, Impact strength, and Hardness of three dimensional (3D) Carbon mixed with PLA (polylactic acid) filament. The specimen are made using FDM method. The blend ratio of PLA and the carbon additive is chosen as 8:2 in this Project, which is believed to have the effectively modified mechanical properties compared to the pure PLA. For each printing orientation, two kinds of printing paths are designed with parameter of raster angles , Infill Density , Speed .

Self-powered broadband photodetector based on Bi2Se3/GaN pn mixed-dimensional heterojunction with boosted responsivity

Self-powered broadband photodetectors (SPBDs) have received considerable attention because of their significance in optoelectronic applications. However, limited by problems inherent to the material, such as high dislocation density, complex heteroepitaxy processing of bulk materials, and the small photoabsorption cross section in atomically thin layers of two-dimensional materials, SPBD photodetectors with both a wide detection range and attractive response characteristics are difficult to fabricate. To address this difficulty, herein the synthesis of n-Bi2Se3/p-GaN mixed-dimensional heterojunctions by the transfer method and their assembly into SPBD photodetectors are described. This photodetector offers both a wide spectral response range (ultraviolet to mid-infrared) and excellent response characteristics. The high responsivity (24554 A/W, 3V), remarkable Ion/Ioff (223.8), and rapid rise and decay times (τr = 0.063 s and τd = 0.043 s) benefit from both the built-in electric field of the pn junction and the fast electron transport on the surface of topological insulator Bi2Se3. The results of this research should facilitate the use of this emerging material for the design and fabrication of high-performance SPBD photodetectors.

Accelerated measurement of electrical resistivity and Seebeck coefficient for thin-layer thermoelectric materials

Compared to the diffusion couple and thin film material library, the thin-layer (also known as thick film) material library with discrete compositions is more suitable for the screening of high performance thermoelectric (TE) materials. However, there are few apparatuses for high throughput characterizing TE properties of thin-layer material library. In this work, a tool with high reliability for effectively and quickly measuring electrical resistivity and Seebeck coefficient has been successfully developed via using a combination of van der Pauw and quasi-steady state method. The relative measurement errors of the electrical resistivity and Seebeck coefficient are less than 10%, comparable to commercial ZEM-3 equipment. The time to measure the electrical resistivity and Seebeck coefficient at a single temperature point is 4 min, saving up to 61.8% of the time compared to ZEM-3. This will contribute to the screening of novel TE materials from the thin-layer TE material libraries in the future.

Statistical machine learning methods applied in the study of web accessibility: a literature review

Technological development in solid-state chemistry, nanotechnology, and new materials is advancing at an accelerated pace; studies of methods to generate thin films of conductive and semiconductor materials are of great interest; however, current methods tend to be very expensive and inaccessible to developing countries. This work seeks to present viable and economical alternatives for teaching laboratories to investigate chemical deposition processes in aqueous solutions and produce thin layers of materials of interest in solid-state chemistry and new materials. The metals studied were copper, cobalt and, nickel in different salts and reducing agents, hydrazine hydrochloride, phenylhydrazine and, sodium borohydride. The main results show that it is possible to use cheaper chemicals to study depositions in an aqueous solution, a viable alternative for laboratories.

On the Origin of Raman Activity in Anatase TiO2 (Nano)Materials: An Ab Initio Investigation of Surface and Size Effects.

Titania-based materials are abundant in technological applications, as well as everyday products; however, many of its structure-property relationships are still unclear. In particular, its surface reactivity on the nanoscale has important consequences for fields such as nanotoxicity or (photo)catalysis. Raman spectroscopy has been used to characterize titania-based (nano)material surfaces, mainly based on empirical peak assignments. In the present work, we address the structural features responsible for the Raman spectra of pure, stoichiometric TiO2 materials from a theoretical characterization. We determine a computational protocol to obtain accurate Raman response in a series of anatase TiO2 models, namely, the bulk and three low-index terminations by periodic ab initio approaches. The origin of the Raman peaks is thoroughly analyzed and the structure-Raman mapping is performed to account for structural distortions, laser and temperature effects, surface orientation, and size. We address the appropriateness of previous experimental use of Raman to quantify the presence of distinct TiO2 terminations, and provide guidelines to exploit the Raman spectrum based on accurate rooted calculations that could be used to characterize a variety of titania systems (e.g., single crystals, commercial catalysts, thin layered materials, facetted nanoparticles, etc.).

Evaluation of reduction reactions in aqueous solution: economical alternatives for laboratory

Technological development in solid-state chemistry, nanotechnology, and new materials is advancing at an accelerated pace, studies of methods to generate thin films of conductive and semiconductor materials are of great interest, however, current methods tend to be very expensive and inaccessible to developing countries. The present work seeks to present viable and economical alternatives for teaching laboratories to investigate chemical deposition processes in aqueous solutions and produce thin layers of materials of interest in solid-state chemistry and new materials. The metals studied were copper, cobalt and, nickel in different types of salts and reducing agents, hydrazine hydrochloride, phenylhydrazine and, sodium borohydride. The main results show that it is possible to use cheaper chemicals to study depositions in an aqueous solution, a viable alternative for laboratories.

Towards fully epoxy-based thin film composite membranes for solvent-resistant and solvent-tolerant nanofiltration

Epoxy curing is a versatile chemistry that can be applied in membrane preparation, both via phase inversion and interfacial polymerization. Here, fully epoxy-based TFC membranes are demonstrated for the first time and tested for solvent-tolerant nanofiltration (STNF) applications. First, UF membranes with a retention for bovine serum albumin (BSA, ∼66000 g mol−1) of ∼40% and a water permeance of 171 L m−2 h−1 bar−1 were prepared via phase inversion by pre-curing epoxide resins (EPON™ resin 1009F and EPON™ resin SU-8) with 1,6-hexanediamine (HDA) prior to phase inversion in water. Subsequently, selective top layers were synthesized on these supports layers via interfacial polymerization (IP) or interfacial initiation of polymerization (IIP) of the same epoxy resins, resulting in a thin selective top layer of the same material. By using different amines, different epoxide ring-opening polymerizations (ROP) could be targeted. These TFC membranes were then tested for use in water-solvent mixtures and achieved a 92.8% methyl orange (MO, 327 g mol−1) retention and a permeance of 0.21 L m−2 h−1 bar−1 in a 20/80 DMF/water feed solution. Cured epoxy chemistry is known for its excellent chemical stability, making these membranes suitable for a wide variety of solvent-resistant NF (SRNF) and STNF applications.

The effect of additional orange Pangkep (Citrus maxima) peel oil on characteristics and microbial inhibition of corn flour-based edible film

The edible film is a thin layer of hydrophilic materials made of proteins, carbohydrates, and fats that replaces plastic packaging. This study was carried out to determine the effect of adding the Pangkep orange peel (Citrus maxima) oil on edible films based on corn flour. Treatments applied in this research were concentration of corn flour (2%, 4%, and 6% (w/v)) and concentration of Pangkep orange peel (Citrus maxima) oil (1%, 1.5%, and 2% (v/v)). Measurement parameters were tensile strength, elongation, thickness, moisture content, and inhibition of Escherichia coli and Staphylococcus aureus. The results showed that the composition of Pangkep orange oil (Citrus maxima) and corn flour had a significant effect on the elongation, thickness, moisture, and inhibition of Escherichia coli and Staphylococcus aureus. The best formula treatment was obtained with a combination treatment containing 4% corn flour and 1% Pangkep orange peel oil (Citrus maxima).

Ultrasonic tomography imaging enhancement approach based on deep convolutional neural networks.

The containment liner plate (CLP) is a thin layer of carbon steel material applied as a base for concrete structures protecting nuclear material. The structural health monitoring of the CLP is critical to ensure the safety of nuclear power plants. Hidden defects in the CLP can be identified utilizing ultrasonic tomographic imaging techniques such as the reconstruction algorithm for the probabilistic inspection of damage (RAPID) methodology. However, Lamb waves have a multimodal dispersion feature, which makes the selection of a single mode more difficult. Thus, sensitivity analysis was utilized since it allows for the determination of each mode's level of sensitivity as a function of frequency; the S0 mode was chosen after examining the sensitivity. Even though proper Lamb wave mode was selected, the tomographic image had blurred zones. Blurring reduces the precision of an ultrasonic image and makes it more difficult to distinguish the dimensions of the flaw. To enhance the tomographic image of the CLP, deep learning architecture such as U-Net was utilized for the segmentation of the experimental ultrasonic tomographic image, which includes an encoder and decoder part for better visualization of the tomographic image. Nevertheless, collecting enough ultrasonic images to train the U-Net model was not economically feasible, and only a small number of the CLP specimens can be tested. Thus, it was necessary to utilize transfer learning and get the values of the parameters from a pre-trained model with a much larger dataset as a starting point for a new task, rather than training a new model from scratch. Through these deep learning approaches, we were able to eliminate the blurred section of the ultrasonic tomography, leading to images with clear edges of defects and no blurred zones.

Exchange-coupled Core/shell Structure CoFe2O4@NiFe2O4/CNFs Composites with Enhanced Microwave Absorption Performance

One strategy to solve the electromagnetic pollution is proposed to fabricate electromagnetic wave absorption materials. The CoFe2O4@NiFe2O4/CNFs composites with magnetic exchange-coupled core/shell structure were synthesized by a facial solvothermal method. The CoFe2O4@NiFe2O4 particles with core/shell structure was anchored on surface of carbon nanofibers. Compared with CoFe2O4 /CNFs whose the minimum reflection loss is −39.17 dB at 15.45 GHz and the effective absorbing band is 3.32 GHz at 1.5 mm, the composite exhibits excellent microwave absorption performance that the minimum reflection loss at 12.32 GHz reaches −51.46 dB when the mass ratio of CoFe2O4 to NiFe2O4 is 3:1 and the thickness is 1.80 mm and the effective absorbing bandwidth reaches 3.85 GHz at 1.5 mm. The results indicate that the exchange coupling effect could enhance the electromagnetic wave absorption. Also, the content of NiFe2O4 could influence the properties if its content is too heavy, the exchange coupling effect will decrease and the impedance will be mismatched. Therefore, CoFe2O4@NiFe2O4/CNFs particles can be used as thin layer materials with strong absorption of low frequency microwave. The study provides a novel way to improve electromagnetic wave absorption properties based on exchange-coupled core/shell structure and the composition control.