Decreasing Layer Thickness Research Articles

Identifying Optical Coherence Tomography Markers for Multiple Sclerosis Diagnosis and Management.

Multiple sclerosis (MS) is a common neurological disease affecting the optic nerve, directly or indirectly, through transsynaptic axonal degeneration along the visual pathway. New ophthalmological tools, arguably the most important being optical coherence tomography (OCT), could prove paramount in redefining MS diagnoses and shaping their follow-up protocols, even when the optic nerve is not involved. A prospective clinical study was conducted. In total, 158 eyes from patients previously diagnosed with relapsing remitting MS (RRMS)-with or without optic neuritis (ON), clinically isolated syndrome (CIS) with or without ON, and healthy controls were included. Each patient underwent an ophthalmologic exam and OCT evaluation for both eyes (a posterior pole analysis (PPA) and the optic nerve head radial circle protocol (ONH-RC)). The macular retinal thickness (the 4 × 4, respectively, 2 × 2 grid) and thickness of the peripapillary retinal nerve fiber layer (pRNFL) were investigated. Various layers of the retina were also compared. Our study observed significant pRNFL thinning in the RRMS eyes compared to the control group, the pRNFL atrophy being more severe in the RRMS-ON eyes than the RRMS-NON eyes. In the ON group, the macular analysis showed statistically significant changes in the RRMS-ON eyes when compared only to the CIS-ON eyes, regarding decreases in the inner plexiform layer (IPL) thickness and inner nuclear layer (INL) on the central 2 × 2 macular grid. The neurodegenerative process affected both the inner retina and pRNFL, with clinical damage appearing for the latter in the following order: CIS-NON, CIS-ON, RRMS-NON, and RRMS-ON. In the presence of optic neuritis, SMRR patients presented an increase in their outer retina thickness compared to CIS patients. To differentiate the MS patients from the CIS patients, in the absence of optic neuritis, OCT Posterior Pole Analysis could be a useful tool when using a central 2 × 2 sectors macular grid. Retinal changes in MS seem to start from the fovea and spread to the posterior pole. Finally, MS could lead to alterations in both the inner and outer retina, along with pRNFL.

In situ fragmentation of Al/Al2O3 multilayers on flexible substrates in biaxial tension

A unique deposition approach combining atomic layer deposition (ALD) and magnetron sputtering was used to fabricate a series of thin film multilayer structures of Al (50 nm) and Al2O3 (ALD, 2.4–9.4 nm) on flexible polymer substrates without breaking vacuum. The multilayers together with 50 nm and 150 nm Al reference films were analyzed by cross-sectional TEM analysis and experimentally strained in biaxial tension to investigate their deformation behavior. Al film stresses and peak widths, measured in situ with Synchrotron X-ray diffraction, are in good agreement with post-mortem surface SEM and through-thickness FIB analysis of the multilayers. It was revealed that brittle cracking of the multilayer can be avoided, and that the lateral and through-thickness crack resistance improve as a function of decreasing oxide layer thickness. An attempt to model the full biaxial yield surface of the multilayers, which remains experimentally challenging, appears to be valid up to 2.4 nm oxide thickness. Model predictions are further compared to compression data, obtained from the unloading segments of the tensile tests. Describing the mechanical behaviour under multiaxial stress conditions is of utmost importance for a diverse understanding of these multilayers across a variety of potential carrier systems and loading cases.

Performance of gravity-driven membrane filtration for treatment of low-temperature and low-turbidity water: Effect of coagulation pretreatment

As a promising technology for decentralized drinking water treatment, performance of gravity-driven membrane (GDM) filtration for low-temperature and low-turbidity water purification and effects of coagulation pretreatment were investigated in this study. Flux development and permeate water quality of three GDM systems, i.e., control GDM without pretreatment, GDM with in-line coagulation (IC) pretreatment (IC-GDM), GDM with coagulation-sedimentation (CS) pretreatment (CS-GDM), were compared. Moreover, composition and morphology of bio-cake layer were characterized to explain underlying mechanisms for performance improvement by coagulation pretreatment. Results suggested that permeate flux of control GDM stabilized at ∼4.0 L/(m2·h) for raw water with relatively low temperature (8.1– 10.8 °C) and turbidity (1.15– 2.47 NTU). IC pretreatment increased stable flux by 65 %, although the bio-cake layer thickness in IC-GDM was increased by 71.7 %, probably due to a significant reduction (57.1 %) in extracellular polymeric substances (EPS) in the bio-cake layer. Meanwhile, CS pretreatment increased stable flux by 87.5 %, which can be attributed to 63.3 % reduction in EPS and 47.0 % decrease in bio-cake layer thickness. As for permeate water quality, dissolved organic matter (DOM) was significantly reduced by both IC and CS pretreatments, mainly due to transformation from dissolved state to particulates. Compared with control GDM, both IC and CS pretreatments resulted in decrease in microbial abundance and activity and changes in microbial community, probably due to decrease in bioavailable phosphate and DOM. This study suggested that both IC and CS pretreatments can be integrated with GDM filtration for efficient purification of low-temperature and low-turbidity water.

Assessment of the Efficacy of Cryolipolysis on Abdominal Fat Deposits: A Prospective Study.

Cryolipolysis is a non-invasive and efficacious procedure for body contouring. The effectiveness of cryolipolysis has been demonstrated on multiple areas of the body, but on a limited number of subjects. The aim of this study is to demonstrate the effectiveness and the safety of cryolipolysis in the lower abdomen adipose tissue thickness reduction. A prospective study on 60 healthy women was carried out using CryoSlim Hybrid device. Each patient underwent two cryolipolysis sessions centered on the abdominal area. The primary endpoint was to decrease the thickness of the abdominal fat deposits. The change in the abdominal circumference and the thickness of the subcutaneous fat layer were assessed. Patient satisfaction and tolerance of the procedure were also taken into account. A significant reduction of the abdominal circumference and subcutaneous fat layer thickness was observed. The mean decrease in abdominal circumference was 2.10 cm (3.1%) 3 months after the procedure and 4.03 cm (5.8%) 6 months after the procedure. The mean decrease in fat layer thickness was 1.25 cm (43.81%) 3 months after the procedure and 1.61 cm (41.73%) 6 months after the procedure. No major adverse events were noted. All patients were very satisfied, and minimal pain was reported. Cryolipolysis is an effective technique to treat abdominal localized fat deposits. No major adverse events have been described for this procedure. Our promising results should encourage further studies aimed at optimizing the efficacy of the procedure without a considerable increase in the risks. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266 .

Influence of bimetal interface confinement on the Hall-petch slope of multiscale Cu/Nb multilayer composites

Heterostructured materials afford a new way to improve the mechanical properties, which has become vital in both materials science and engineering applications. In the present research, Cu/Nb multilayer composites with layer thicknesses from the micrometer to nanometer were fabricated by accumulative roll bonding and the microstructure and mechanical properties of the Cu/Nb multilayer composites were then investigated. The yield strength and ultimate tensile strength of these composites increase with decreasing layer thickness. Moreover, the relationship between yield strength and (layer thickness)−1/2 approximately accords with the conventional Hall-Petch equation but with a decrease in the Hall-Petch slope when the layer thickness decreases from the micrometer to nanometer scales. The deformation microstructure of these Cu/Nb multilayer composites clearly exhibit dislocations glide in the layers, which reduces the stacking of dislocations at the Cu–Nb interface and thereby weakens the strengthening effect of the interface.

ДОСЛІДЖЕННЯ ВПЛИВУ НАПОВНЮВАЧІВ РІЗНОГО ПОХОДЖЕННЯ НА ВЛАСТИВОСТІ АСФАЛЬТОБЕТОНІВ

Introduction. The properties of a bituminous material are determined by the peculiarities of the bonds that arise between individual mineral grains and depend on the properties of bitumen, the thickness of the bitumen layer covering the mineral grains, as well as on the processes of interaction between mineral materials and bitumen on their common interface. To ensure a strong and stable bond between the grains, bitumen should evenly cover the surface of the mineral materials with a thin layer. To increase the strength of the pavement constructed from bituminous material, it is necessary that the maximum amount of bitumen is adsorbed by the mineral material, and the content of free bitumen is reduced to a minimum value. Problem Ыtatement. Depending on the nature of the mineral material and the chemical composition of the bitumen, the properties of its thin layers change in different ways. The strength of bitumen in a thin layer on an active mineral surface increases with decreasing thickness, while on an inactive surface the strength of bitumen changes little with decreasing layer thickness. Objective. The present study was devoted to determining the effect of aggregates of different origins on the volumetric properties of asphalt concrete and the mechanical properties of asphalt concrete, as well as on their weather resistance. Materials and methods. Mineral filler from limestone, granite, quartzite, and fly ash was used for the study. Results. The results of the research showed that the type of aggregate has virtually no effect on changes in the volumetric and mechanical properties of asphalt concrete. However, at the same time, asphalt concrete with different aggregates differs significantly in water and frost resistance.

Numerical study on the scale effect of tip vortex cavitation induced by incoming velocities and scale ratios

Large eddy simulations of tip vortex cavitation (TVC) around an elliptical hydrofoil is performed to study its scale effect. A satisfying agreement is obtained between the numerical and experimental data. It indicates that the scale effect of TVC is remarkable. With the increase of scale ratio or incoming velocity, the intensity of TVC significantly increases. Based on our results, two mechanisms for the scale effect of TVC are proposed, i.e., the roll-up of boundary layer and the interaction between tip vortex (TV), secondary vortex and trailing vortex. As incoming velocity increases, the fusion of TV and secondary vortex enhances and the boundary layer thickness decreases, which lead to larger circulation and smaller vortex core radius, tending to intensify TV. As scale ratio increases, the fusion of TV and secondary vortex enhances and the boundary layer thickness increases slightly, which lead to much higher circulation and slight increase of vortex core radius, promoting the occurrence of TVC in general. In addition, with equal cavitation number and Reynolds number, TVC in the large scale is stronger than that in the small scale, indicating that it seems not so reasonable to equate the velocity-induced scale effect with the scale-ratio-induced one.

Multifunctional Additive Manufacturing and Multiphysics Numerical Investigations of Carbon Fiber Structural Battery Composite using a Drop-on-Demand method with In-situ Consolidation

Lightweight carbon fiber structural battery composite has great potential in increasing structural energy storage efficiency for multifunctional applications. However, it is still challenging to design carbon fiber multifunctional composite due to lack of proper manufacturing methods. In this study, an integrated multifunctional design and fabrication approach is developed by combining a drop-on-demand additive manufacturing method with a multiphysics numerical model to guide the development of the new multifunctional composite. Through deposition with in-situ consolidation, the function and thickness of each carbon fiber layer as well as its fiber volume fraction are accurately controlled. Decreasing layer thickness improves flexural properties. The discharge capacity and energy density are initially improved by 47% and 39%, respectively, but then significantly reduced due to limited lithium transport within closely packed carbon fibers at higher volume fraction. An optimal fiber volume fraction of 35 vol% exists for carbon fiber structural battery composite. A good agreement is found between prediction results and experimental measurements. Further investigations of lithium-ion concentration and stress distribution by the validated multiphysics model find that electrolyte conductivity more significantly affects discharge process than discharge rate. The multifunctional design and fabrication approach provides insights for future development of high-performance carbon fiber structural battery composite.

Application of Optical Coherence Tomography (OCT) to Analyze Membrane Fouling under Intermittent Operation

There is increasing interest in membrane systems powered by renewable energy sources, including solar and wind, that are suitable for decentralized water supply in islands and remote regions. These membrane systems are often operated intermittently with extended shutdown periods to minimize the capacity of the energy storage devices. However, relatively little information is available on the effect of intermittent operation on membrane fouling. In this work, the fouling of pressurized membranes under intermittent operation was investigated using an approach based on optical coherence tomography (OCT), which allows non-destructive and non-invasive examination of membrane fouling. In reverse osmosis (RO), intermittently operated membranes were investigated by OCT-based characterization. Several model foulants such as NaCl and humic acids were used, as well as real seawater. The cross-sectional OCT images of the fouling were visualized as a three-dimensional volume using Image J. The OCT images were used to quantitatively measure the thickness of foulants on the membrane surfaces under different operating conditions. The results showed that intermittent operation retarded the flux decrease due to fouling compared to continuous operation. The OCT analysis showed that the foulant thickness was significantly reduced by the intermittent operation. The decrease in foulant layer thickness was found to occur when the RO process was restarted in intermittent operation.

Цифровая осциллография полимерных мембран с протонной проводимостью

Polyvinyl alcohol-based cast membranes have promising application in creating commonly available fuel cells and fuel synthesizers, as well as inexpensive water sources and microelectromechanical systems. In order to control the properties of such membranes a deep understanding of the charge transfer mechanisms and their relationship with the structure formed at a certain composition and manufacturing technology is required. A method for studying the structure of the proton-conductive polymer membranes using digital oscillography of ion currents excited by the low-frequency rectangular pulses with the amplitudes below the threshold voltage of the ionic conductivity in a dehydrated membrane, and for the analysis of the resulting ion current pulses (spikes) in the frames of the model of a proton pump acting in each layer of the membrane is proposed in this paper. Fast Fourier transform of these oscillograms reveals from 2 to 4 branches or spike sequences corresponding to the phases with different ionic conductivity and makes it possible to determine the thicknesses of both high-conductivity phase layers (7–30 µm) and low-conductivity phase interlayers (1–7 µm) formed in the process of polymerization. The reason of spike merging into bursts is described in terms of successively induced increase in the excited proton density over a threshold value in highly conductive layers. The resonance observed in dry proton membranes at the frequencies of about 2.2 to 3.0 kHz is interpreted as the burst merge point with the further increase in impedance due to proton lagging and respective decrease in the effective thickness of active layers. The effective charge carrier concentrations (as small as 1012 to 1013 cm−3) and the velocity (from 5 to 18 cm/s for the highly conductive phases which turned out to be much higher than those observed in solutions) are estimated. The asymmetry of the cast membranes, which becomes apparent at low frequencies and causes the generation of a direct ion current in response to excitation by a purely alternating current, is studied. It is found that the apparent conductivity determining contribution to the total ohmic resistance is made by a thin interlayer with a very low ion velocity, presumably surface layer, rather than the main layers. The conclusion on the optimization of the production technology and the composition of the proton membranes for various applications is made.

Variability of Visual Recovery with Time in Epiretinal Membrane Surgery: A Predictive Analysis Based on Retinal Layer OCT Thickness Changes.

To correlate postoperative optical coherence tomography (OCT) thickness changes of each retinal layer with different patterns of visual recovery after idiopathic epiretinal membrane (ERM) surgery in a cohort of patients showing no known risk factors for poor visual recovery at preoperative imaging. Best corrected visual acuity (BCVA) and OCT images were acquired preoperatively and 1 month, 3 months and 6 months postoperatively. Patients were divided into four groups according to postoperative BCVA improvement: improvement < 15 ETDRS letters (GROUP 1), immediate improvement of BCVA without further improvements at later follow-ups (GROUP 2), immediate improvement of BCVA with further improvements at later follow-ups (GROUP 3) and delayed improvement of BCVA (GROUP 4). Eighty-five patients were included. GROUP1 was the only one characterized by retinal nerve fiber layer (RNFL) thickness increase and ganglion cell layer/central macular thickness (GCL/CMT) ratio decrease at 1 month and outer nuclear layer (ONL) thickness decrease at 3 and 6 months. GROUP 2 was the only one showing a decrease in GCL/inner plexiform layer (GCL/IPL) ratio at 1 month. GROUP 3 and 4 showed higher preoperative RNFL thickness compared to the other, and GROUP 4 manifested a late increase in RNFL thickness at 6 months. Different patterns of VA recovery are associated with specific layer thickness changes. If further confirmed, this would help detect those cases characterized by poor or delayed visual recovery despite the absence of other known imaging risk factors.

Enhancing high-temperature tensile properties of Ni/Ni-W laminated composites for MEMS devices

There is an increasing demand for materials with excellent mechanical performance for Micro-Electro-Mechanical System (MEMS) devices serving at elevated temperatures. However, how to enhance the high-temperature strength of the materials without losing their plasticity is a pending problem. Here, the Ni/Ni-W laminated composites with different monolayer thicknesses and the same ratio of the constituent layer thicknesses were fabricated successfully by using the dual-bath electrodeposition technique. The microstructure stability and tensile properties of annealed Ni/Ni-W laminated composites with different monolayer thicknesses were investigated at 400 °C. The results show that the annealed Ni0.5/Ni-W0.05 laminated composites have both high yield strength (450 MPa) and excellent elongation to failure (25.1%) at 400 °C, being superior to that of the monotonic Ni (179 MPa and 17.7%). Such a high strength of the laminated composite at 400 °C results from the contribution of the intrinsically high strength of the Ni-W layers with excellent thermal stability, the thickness-constrained effect on grain growth of Ni layers and the interface coupling effect of heterogeneous structures. The good plasticity may be derived from the heterogeneous laminated structure and the decrease in the constituent layer thickness, providing a good co-deformation ability. Basic mechanisms for the high tensile strength and good plasticity of the Ni/Ni-W laminated composites at 400 °C were analyzed theoretically. The findings reveal a potential strategy to fabricate MEMS components with excellent high-temperature tensile properties through tailoring the microstructure thermal stability and the constituent layer scale.

On the Influence of Manufacturing Parameters on the Microstructure, Mechanical Properties and Corrosion Resistance of AISI 316L Steel Deposited by Laser Engineered Net Shaping (LENS®).

Samples of 316L SS were manufactured by Laser Engineered Net Shaping (LENS®) using different technological parameters. The deposited samples were investigated in terms of microstructure, mechanical properties, phase content and corrosion resistance (salt chamber and electrochemical corrosion). Parameters were chosen to obtain a proper sample built for layer thicknesses of 0.2, 0.4 and 0.7 mm by changing the laser feed rate while keeping the powder feed rate constant. After a comprehensive analysis of the results, it was found that the manufacturing parameters slightly affected the resulting microstructure and also had a minor impact (almost undetectable considering the uncertainty of the measurement) on the mechanical properties of samples. Decreases in resistance to electrochemical pitting corrosion and environmental corrosion with an increased feed rate and a decrease in layer thickness and grain size were observed; however, all additively manufactured samples were found to be less prone to corrosion than the reference material. In the investigated processing window, no influence of deposition parameters on the phase content of the final product was found-all the samples were found to possess austenitic microstructure with almost no detectable ferrite.

Variable fluid properties analysis for thermally laminated 3-dimensional magnetohydrodynamic non-Newtonian nanofluid over a stretching sheet

This article is mainly focused on the viscous flow of cu-water/Methanol suspended nanofluids towards a three-dimensional stretching sheet reformed by magnetohydrodynamic phenomenon. The viscous effect is considered as temperature dependent with water treated as a base fluid. Similarity conversions are employed to set forth the non-linear equations of this physical problem. An innovative model for 3D analysis for cu-water/Methanol nanofluid with an irregular viscosity is presented in the present study. Reynold’s model of viscosity is considered in the present study. Moreover, shooting technique is employed to elaborate the non-linear coupled governing equations with the relevant boundary conditions. The physical interpretation of these numerical calculations is presented through a graphical specimen of velocity, Nusselt number, temperature, and skin friction etc. The results of present model are showing quality harmony with the results of existing model. This model is being used for manipulating and designing the surfaces such as stretching/shrinking wrapping and panting devices in nanotechnology. The results also show the significant changes in flow characteristics with changing the value of stretching parameter. It is observed that with an increasing in nanoparticles volume fraction boundary layer thickness decreases. Further, it is also observed that with an increase in viscosity parameter, temperature increases because here we are considering temperature dependent viscosity.

A comparative analysis of the effect of post production treatments and layer thickness on tensile and impact properties of additively manufactured polymers

Abstract In recent years, additive manufacturing (AM) technologies have become greatly popular in the polymer, metal, and composite industries because of the capability for rapid prototyping, and appropriateness for the production of complex shapes. In this study, a comprehensive comparative analysis focusing on the influence of post-processing types (heat treatment and water absorption) on tensile and impact responses was carried out on 3D printed PETG, PLA, and ABS. In addition, layer thickness levels (0.2, 0.3, and 0.4 mm) were selected as a major production parameter and their effect on mechanical properties was combined with post-processing type for the first time. The results showed that both tensile and impact resistance of the printed polymers increased thanks to the heat treatment. The highest tensile strength was measured for heat-treated PLA, while the peak impact endurance level was reached for heat-treated PETG. Also, water absorption caused a mass increment in all samples and induced higher tensile elongation values. Decreasing layer thickness had a positive effect on tensile features, but impact strength values dropped. On the other hand, all samples were subjected to macro and micro failure analyses to understand the deformation mechanism. These inspections indicated that for impact samples straight crack lines converted to zigzag style separation lines after the heat treatment. As for the tensile samples, the exact location of the main damage zone altered with the production stability, the water absorption capacity of the polymer, and the thermal diffusion ability of the filament.

Surface integrity of NiTi-SMA during WEDM: effect of spark parameters

ABSTRACT The current study looks at surface integrity measures for example surface crack density, surface roughness, recast layer thickness, and foreign elements content in wire electric discharge machining (WEDM) of the Ni55.95Ti44.05 shape memory alloy (SMA) with purposefully varied spark parameters (spark frequency, spark energy density, and spark gap voltage). Surface roughness has a similar tend to surface crack density, which increases with an increase in spark energy density and decreases with an increase in spark gap voltage and spark frequency. As the spark energy density declines and the spark gap voltage and spark frequency rise, foreign elements content and recast layer thickness decrease. Scanning electron microscope (SEM) and optical profilometer observations of the surface topography of SMA following WEDM show the presence of lumps, voids, pockmarks, discharge craters, microcracks, and a layer of melted material that has resolidified. Energy dispersive spectroscopy (EDS) studies show that foreign elements are deposited on machined surfaces from wire electrode and dielectric fluid.

Biostimulants for Sustainable Management of Sport Turfgrass.

Research on the efficacy of innovative, ecofriendly biostimulants in sport turf management is scarce, with less information available from open-field experiments, and even less pertaining to thatch control-related problems. The objective was to investigate the open-field effectiveness of a commercial product, EM-1, and two newly developed products, ExpA and ExpB, in improving both rhizosphere and turfgrass, Agrostis stoloniferous L., characteristics on a golf green. ExpA and ExpB, identical in microbial composition, were equally effective in significantly increasing chlorophyll synthesis and visual turf quality, as well as in resistance to tearing out, compared to the untreated control 56 days after treatment (DAT). EM-1 showed intermediate trends between the control and novel biostimulants. The inclusion of humic acids and mycorrhizal fungi to the microbial composition in ExpB significantly improved some rhizosphere properties 56 DAT relative to the control. Results on ExpB evidenced a significant decrease in the thatch layer thickness and fresh leaf weight, associated with a significant increase in the humus thickness, organic matter decomposition and evapotranspiration efficiency. An increased dry leaf biomass was also shown. ExpA and EM-1 showed either marginal or intermediate improvements relative to the control. ExpB represents a promising alternative to alleviate negative environmental impacts associated with turf maintenance-related activities.

Simulation-Assisted Process Design and Experimental Verification of Laterally Confined Oxide Areas Generated with Continuous Electrolytic Free Jet on EN AW-7075 Aluminum Alloy

Local anodization with a free electrolyte jet is a suitable solution for locally confined surface functionalization without additionally required preparation of the parts. However, the geometrical formation of the anodic oxide layer in jet-based anodization is not yet sufficiently understood. In this study, numerical calculations based on physical descriptions are used to describe the lateral and vertical oxide formation on aluminum alloy EN AW-7075. The required electrical resistance and capacitance were determined by immersion-based anodization and implemented into the numerical simulation model to evaluate the electrical conductivity of the porous layer. The simulation results showed an electrical conductivity of 2.6 × 10-6 S/m for the porous layer. Subsequently, a model for jet-based anodization was developed and the previous results were implemented to calculate the oxide formation. The simulation results showed decreasing oxide layer thickness at increasing radial distance from the center of the jet, which corresponds to experimental results. The simulation model was validated by varying the current efficiency from 5% to 90%, where similar developments of the anodic oxide layer thickness compared with experimental results were determined at 5%.

Thickness-dependent semimetal-to-semiconductor transition in two-dimensional GaGeTe

Two-dimensional GaGeTe flakes with different thicknesses from 80 to 2.2 nm (bilayer) were exfoliated and transferred to a SiO2/Si substrate. A series of samples with different thicknesses were prepared and identified by optical microscopy, atomic force microscopy, and Raman spectrum. Raman modes strongly dependent on the layer thickness and characteristic Raman-active modes for few-layer (FL) GaGeTe flakes are demonstrated. These vibration modes of FL GaGeTe show a linear red-shift phenomenon with increasing temperature and their full width at half maximum of the Raman mode exhibits a weak temperature dependence below 200 K, and then, a linear increase with temperature. The electrical conductivity is 96.48 S/cm for 74 nm flakes and drops exponentially to 2.27 × 10−7 S/cm for 7 nm ones because of the bandgap widening with the decrease of layer thickness, which is evidenced by the work function increase from 4.4 to 4.96 eV, when the thickness decreases from 80 to 2.2 nm. Moreover, the electrical conductivity performs two different temperature dependence behaviors on the thickness, indicating a transition from semimetal for bulk to semiconductor for FL GaGeTe, which agrees well with that of the theoretical calculation.

Prenos mase na rotirajući disk adsorpcionom i elektrohemijskom metodom

One of the ways to intensify the process is the use of rotating elements, which increase the mass transfer coefficients many times over. In this study, the mass transfer coefficient was determined by adsorption and electrochemical methods, using a rotating disk (RD) to study the effect of rotation on the mass transfer intensity. For adsorption method, a dilute solution of methylene blue was used, and silica gel foils on rotation disk were used as adsorbents. The measurements were performed under diffusion-controlled conditions, and the color intensity of the surface was determined using SIGMA Scan Pro. The study of mass transfer by electrochemical method was performed in batch systems with a volume of 20 dm3 and 0.8 dm3 , using a solution of sulfuric acid and copper sulfate, and potassium ferricyanide (III), potassium ferricyanide (II), and potassium chloride. Disks with diameters of 0.8 cm, 1 cm, 2 cm, 5.6 cm, and 20 cm were used in the rotation range up to 800 rpm. After determining the operating voltage, the current intensity was measured at different rpm and the mass transfer coefficients were calculated. It was found that the mass transfer coefficient increases as the rotation speed of the RD increases, and that is does not depend on the diameter of RD. It is shown that the current density increases with the increase of the RD speed, while the diffusion layer thickness decreases. A comparative analysis of the results obtained by the adsorption and electrochemical methods was made and the results were compared with literature correlations.