Thickness Of Surface Layer Research Articles

Development of surface-sulfonated graft anion-exchange membranes with monovalent ion selectivity and antifouling properties for electromembrane processes

This communication describes the development of anion-exchange membrane (AEM) with a modified surface possessing monovalent ion selectivity and antifouling properties. Modified AEMs series was obtained by the formation of an oppositely-charged thin layer utilizing the surface sulfonation of the grafted AEMs. The creation of the interface layer leads to a significant increase in the Cl/SO4 selectivity and the appearance of humic acid sorption resistance. The best surface-sulfonated anion-exchange membrane (s-AEM) has a high ionic conductivity of 11.2 mS cm−1 and high Cl/SO4 selectivity up to 6.4 in electrodialysis. The sulfonated layer was characterized by IR spectroscopy and electron microscopy. The relationship between the structure and thickness of the cation-exchange surface layer and the observed changes in membrane transport properties such as diffusion permeability, ionic conductivity, potentiometric transport numbers, and current-voltage characteristics are discussed. It was shown that the Cl/SO4 selectivity of s-AEM in the desalination process depends on the current density. The obtained data were successfully interpreted using a mathematical model based on the concept of the bipolar structure of the s-AEM surface layer and diffusion control of anion transport through it.

A physically unclonable function using NV diamond magnetometry and micromagnet arrays

A physically unclonable function (PUF) is an embedded hardware security measure that provides protection against counterfeiting. Here, we present our work on using an array of randomly magnetized micrometer-sized ferromagnetic bars (micromagnets) as a PUF. We employ a 4μm thick surface layer of nitrogen-vacancy (NV) centers in diamond to image the magnetic field from each micromagnet in the array, after which we extract the magnetic polarity of each micromagnet using image analysis techniques. After evaluating the randomness of the micromagnet array PUF and the sensitivity of the NV readout, we conclude by discussing the possible future enhancements for improved security and magnetic readout.

Morphological comparison of blocks in chaos terrains on Pluto, Europa, and Mars

Chaotic terrains are characterized by disruption of preexisting surfaces into irregularly arranged mountain blocks with a “chaotic” appearance. Several models for chaos formation have been proposed, but the formation and evolution of this enigmatic terrain type has not yet been fully constrained. We provide extensive mapping of the individual blocks that make up different chaos landscapes, and present a morphological comparison of chaotic terrains found on Pluto, Jupiter's Moon Europa, and Mars, using measurements of diameter, height, and axial ratio of chaotic mountain blocks. Additionally, we compare mountain blocks in chaotic terrain and fretted terrain on Mars. We find a positive linear relationship between the size and height of chaos blocks on Pluto and Mars, whereas blocks on Europa exhibit a flat trend as block height does not generally increase with increasing block size. Block heights on Pluto are used to estimate the block root depths if they were floating icebergs. Block heights on Europa are used to infer the total thickness of the icy layer from which the blocks formed. Finally, block heights on Mars are compared to potential layer thicknesses of near-surface material. We propose that the heights of chaotic mountain blocks on Pluto, Europa, and Mars can be used to infer information about crustal lithology and surface layer thickness.

Verification of physical parameters of insity p-type HPGe detector by scan method using collimated low energy photon beam and MCNP simulation

In this work, the physical dimensions and the actual position of germanium crystal within a detector housing, the homogeneity of the crystal surface and outer dead layer thickness for a p-type HPGe detector were confirmed by the scan method using the collimated low energy photon beams combined with Monte Carlo simulation. The length and the diameter of the crystal were found to match with the values supplied by the manufacturer in discrepancy of about 3%. Only one mounting strap (Typical) for holding the crystal inside the mounting cup instead of two which is indicated in the detector drawing supplied by manufacturer was revealed by scanning along the lateral face of detector. Scanning on the front surface and around the lateral face of detector by the collimated 59.5 keV photon beam verified the outer dead layer thicknesses at the front surface and lateral face of the crystal averagely increases about 6.5% and 12% respectively. Adjusting the detector parameters for MCNP simulation by these verified values, the simulated peak efficiencies for different photon energies become being in accordance with the experimental peak efficiencies.

RETRACTED ARTICLE: Relationship between water content, shear deformation, and elastic wave velocity through unsaturated soil slope

This study aims to determine the relationship between water content, shear deformation, and elastic wave velocity of unsaturated soil slope. The individual influence of volumetric water content and tilt angle on the normalized wave velocity through unsaturated soil was investigated through a series of adjustable slope model tests. The relationship function between volumetric water content, tilt angle, and normalized wave velocity was established. To verify the proposed relationship function, fixed slope model tests were carried out. The relationship functions could be used to estimate the behaviors of wave velocity in rainfall-induced slope failure model tests. The applicability of proposed relationship function for wave velocity behaviors is also presented. It is found that the relationship function is highly consistent with the measurements for wave velocity behaviors through unsaturated soil slope. In addition, the effects of rainfall duration/initial water content, density, slope angle, and surface layer thickness seem to be small on the decrease rate of normalized wave velocity with volumetric water content and tilt angle.

Thermodynamic inconsistency of the conventional theory of superconductivity

A type I superconductor expels a magnetic field from its interior to a surface layer of thickness [Formula: see text], the London penetration depth. [Formula: see text] is a function of temperature, becoming smaller as the temperature decreases. Here we analyze the process of cooling (or heating) a type I superconductor in a magnetic field, with the system remaining always in the superconducting state. The conventional theory predicts that Joule heat is generated in this process, the amount of which depends on the rate at which the temperature changes. Assuming the final state of the superconductor is independent of history, as the conventional theory assumes, we show that this process violates the first and second laws of thermodynamics. We conclude that the conventional theory of superconductivity is internally inconsistent. Instead, we suggest that the alternative theory of hole superconductivity may be able to resolve this problem.

Design of Ultrawide Bandwidth Electromagnetic Wave Absorbers with Square Patch Frequency Selective Surfaces with Different Geometries

A reliable and efficient numerical method is presented for the design of broadband absorbers, fabricated by layering two square patch-frequency selective surfaces (SP-FSS) with different geometries on a grounded dielectric substrate. The circuit parameters of the inductance and capacitance of the SP-FSS were retrieved using the strip wire conductor model. Due to the high capacitance and low inductance of the SPFSS, a nearly constant resonance frequency (<i>f</i><sub>0</sub> = 37 GHz) is observed, irrespective of patch size at a given unit cell periodicity of 7.5 mm. For the SP-FSS, the circuit is capacitive below <i>f</i><sub>0</sub> and inductive above <i>f</i><sub>0</sub>. For a grounded substrate with a quarter wavelength thickness, however, the input impedance is inductive below <i>f</i><sub>0</sub>, resulting in impedance matching over a wide frequency range, with the controlled FSS resistance matched to the free-space impedance. The double-layer absorber was designed by optimizing the surface resistance and layer thickness of two SP-FSSs with different geometries, and demonstrated a 10 dB absorption bandwidth of 6.1−41.4 GHz with a total thickness of 5 mm, which is equal to the theoretical limit. A test sample was prepared by screen printing method, and the free space measurement demonstrated a wide-bandwidth absorption result (4.7−40.0 GHz for −10 dB reflection loss) with a small total thickness (5.4 mm). The simulation and experimental results strongly validated the SP-FSS for the design of wide bandwidth electromagnetic wave absorbers.

Improving Stability and Kinetics of Alkaline HOR Catalysts – Towards Reduced System Cost

Anion exchange membrane fuel cells (AEMFCs) show great promise in overcoming high cost of currently state of the art proton exchange membrane fuel cells, that rely on expensive Pt catalysts for both the hydrogen oxidation reaction (HOR) as well as the oxygen reduction reaction (ORR). With recent advancements in demonstrating high ORR activity and stability of Fe-N-C catalysts in alkaline environments,1 the HOR suddenly became the bottleneck reaction towards high power density platinum group metal (PGM) -low or -free AEMFCs. While application of PGM-free ORR catalysts is an eventual goal, current state of the art NiM nanoparticles show relatively poor performance in terms of both activity and irreversible oxidation and dissolution.2 Hence, at least for some time, one will need to rely on PGM catalysts for alkaline HOR, where the biggest challenge will be lowering the loading and meanwhile increasing the stability in an alkaline environment. To this end, fundamental understanding of surface processes is required.In this work we investigate model CeOx covered Pt and Pd electrocatalysts as benchmark materials for the HOR reaction3 , 4. To prepare such model electrodes, we use physical vapor deposition for the formation of PGM and atomic layer deposition subsequently, to yield CeOx surface layers of variable thickness. Activity and stability of the CeOx@Pt and CeOx@Pd electrodes are studied in common rotating disk electrode and on-line inductively coupled plasma mass spectrometry setups, respectively. External analytics, e.g. X-ray photoelectron spectroscopy, are used to further characterize the electrodes before and after degradation studies. We show that stability of the electrodes at the higher anodic potentials can be greatly improved by tuning the thickness of the CeOx layer. Interestingly, this can be achieved without sacrificing and even with a significant enhancement in the HOR activity. This unique performance is explained by assuming that the deposited CeOx films form an ion selective semipermeable passivation layer on the surface of Pd and Pt. We anticipate that, as a next logical step, such layers can be used to stabilize PGM-free Ni alloys and reach the goal of having completely PGM-free AEMFCs.

A New Experimental Method for Determining the Thickness of Thin Surface Layers of Intensive Plastic Deformation Using Electron Backscatter Diffraction Data

It is, in general, essential to investigate correlations between the microstructure and properties of materials. Plastic deformation often localizes within thin layers. As a result, many material properties within such layers are very different from the properties in bulk. The present paper proposes a new method for determining the thickness of a thin surface layer of intensive plastic deformation in metallic materials. For various types of materials, such layers are often generated near frictional interfaces. The method is based on data obtained by Electron Backscatter Diffraction. The results obtained are compared with those obtained by an alternative method based on microhardness measurements. The new method allows for determining the layer thickness of several microns in specimens after grinding. In contrast, the measurement of microhardness does not reveal the presence of this layer. The grain-based and kernel-based types of algorithms are also adopted for determining the thickness of the layer. Data processed by the strain contouring and kernel average misorientation algorithms are given to illustrate this method. It is shown that these algorithms do not clearly detect the boundary between the layer of intensive plastic deformation and the bulk. As a result, these algorithms are unable to determine the thickness of the layer with high accuracy.

Experiment-Based Process Modeling and Optimization for High-Quality and Resource-Efficient FFF 3D Printing

This article reports on the investigation of the effects of process parameters and their interactions on as-built part quality and resource-efficiency of the fused filament fabrication 3D printing process. In particular, the influence of five process parameters: infill percentage, layer thickness, printing speed, printing temperature, and surface inclination angle on dimensional accuracy, surface roughness of the built part, energy consumption, and productivity of the process was examined using Taguchi orthogonal array (L50) design of experiment. The experimental results were analyzed using ANOVA and statistical analysis, and the parameters for optimal responses were identified. Regression models were developed to predict different process responses in terms of the five process parameters experimentally examined in this study. It was found that dimensional accuracy is negatively influenced by high values of layer thickness and printing speed, since thick layers of printed material tend to spread out and high printing speeds hinder accurate deposition of the printed material. In addition, the printing temperature, which regulates the viscosity of the used material, plays a significant role and helps to minimize the dimensional error caused by thick layers and high printing speeds, whereas the surface roughness depends very much on surface inclination angle and layer thickness, which together determine the influence of the staircase effect. Energy consumption and productivity are primarily affected by printing speed and layer thickness, due to their high correlation with build time.

Ultra-rapid cooling of aluminum: Homogeneous solidification to anisotropic nanocrystals

Aluminum fcc-crystal surfaces (110) are irradiated by series of ≈15 ns-long pulses of laser light. Each pulse is calculated to produce an ≈2 µm thick surface layer of liquid and quasi-liquid whose temperature decays rapidly, becomes supercooled liquid until ≈168 K below the nominal melting temperature, and then freezes homogeneously into fcc nanocrystals and amorphous atoms. The cooling rate is ≈1.2 × 109 K s−1 in the undercooled solidification region, which we call ultra-rapid because it is faster than that in experiments involving splat-cooling or melt-spinning. However, it is slower than those in a molecular-dynamics simulation with a million aluminum atoms, which was described by Mahata et al. [Model. Simul. Mater. Sci. Eng. 26, 025007 (2018)]. Standard θ/2θ x-ray diffraction is applied to the resulting solid. The magnitude and location of the diffraction peaks yield estimates of the anisotropy and the sizes of the nanocrystals. The sizes, between about 4 nm and 50 nm, are on the order of “critical” as defined in classical nucleation theory. The anisotropy is caused by a difference in growth rates among various crystal faces, which is in qualitative agreement with theoretical predictions. For example, the loosely packed (311) face grows much faster than that of the close packed (111).

Impact of losses on Love wave propagation in multilayered composite structures loaded with a Newtonian liquid

In this study, we analyze theoretically and numerically the properties of Love surface waves propagating in lossy multilayered composite waveguides, loaded on the upper surface with a Newtonian liquid. The propagation of Love surface waves was formulated in terms of a direct Sturm–Liouville problem. An analytical form of the complex dispersion equation of the Love surface wave was derived using the Thomson–Haskell transfer matrix method. By separating the complex dispersion equation into its real and imaginary parts, we obtained a set of two nonlinear algebraic equations, which were subsequently solved numerically. The effect of various physical parameters of the lossy viscoelastic waveguide on the velocity and attenuation of the Love surface wave was then analyzed numerically. It was found that because of the presence of losses in the analyzed waveguide, Love surface waves displayed a number of new original phenomena, such as resonant-like maxima in attenuation as a function of thicknesses of the first viscoelastic surface layer and thickness of the second elastic surface layer. These phenomena are completely absent in lossless waveguides.

A novel approach to plasma channel radius determination and numerical modeling of electrical discharge machining process

In this investigation, a single discharge of electrical discharge machining (EDM) has been simulated using finite element method (FEM) to obtain the temperature distribution on the workpiece surface. The dimensions of discharge crater on workpiece surface were calculated using temperature distribution profile, and a FEM model for material removal rate was developed for EDM process. Also, the plasma channel radius was obtained by a newly developed mathematical model and used at simulation stage. Considering the maximum error of 8.2%, between the recast layer thickness obtained by numerical and experimental approaches, the numerical results were used to study the influences of pulse current and pulse duration as input parameters on plasma efficiency in ejection of the molten materials from molten puddles on machined surface and recast layer thickness. The results showed that enhancement of pulse current leads to increasing plasma flushing efficiency and increasing pulse duration decreases plasma flushing efficiency and enhances recast layer thickness.

Effect of phase in surface layers on rotating-bending fatigue strength of SCM415 steel after austenitic nitriding

The rotating bending fatigue strength of JIS-SCM415 steels after austenitic nitriding was evaluated to find the surface phase that gave the highest strength. Nitriding was performed at 903 K under conditions of KN = 0.15, 0.25 and 0.35 atm-1/2. In addition, specimens which were tempered at 523 K for 7.2 ks after nitridings with KN = 0.15 and 0.25 atm-1/2 were prepared. A specimen prepared by nitrocarburizing at 853 K was also evaluated as a comparison. Specimens nitrided at 903 K at KN = 0.15 atm-1/2 showed the highest fatigue limit because the 10 μm thick surface layer was a dual phase of austenite and martensite that might have a fine microstructure which inhibited initial crack generation and growth. Specimens nitrided at 903 K at KN = 0.35 atm-1/2 showed the second highest fatigue limit because the ε compound layer that was 20 μm thick had a high compressive residual stress. Specimens nitrides at 903 K at KN = 0.25 atm-1/2 showed the third highest fatigue limit because of the formation of a 6 μm thick compound layer which was a dual phase of ε and γ’ that had few voids and a high toughness (low hardness) in addition to its compressive residual stress. Tempered specimens showed a lower fatigue limit than that of non-tempered specimens. This was because the surface layer became brittle in tempered specimens. Specimens other than the tempered specimen in KN = 0.25 atm-1/2showed a fatigue strength higher than that of a sample nitrocarburized at 853 K.

THE INFLUENCE OF HYDRO BLASTING ON THE EN-DURANCE LIMIT OF SPECIMENS WITH A CUT UNDER BENDING AND STRETCHING-COMPRESSION

The hydro blasting influence on an endurance limit of cylindrical specimens with circular cuts of a semicircular profile of 0,3 mm radius under bending and stretching-compression in a case of symmetric cycle has been examined. Specimens of 10 mm diameter for fatigue tests were made of steels 30ХГСА, 12Х18Н10Т, ЭИ961,45 and aluminum alloys В93, Д16Т.The influence of surface hardening on an endurance limit of specimens with cuts was valuated by two criteria: residual stresses on the concentrator surface and the average integral residual stresses calculated through the parts dangerous section surface layer thickness equal the critical depth of a non-propagating fatigue crack. 
 On results of residual stresses and specimens with cuts endurance limits determination its been stated that coefficients of surface hardening influence on an endurance limit increase under bending and stretching-compression by two criteria are approximately equal. Besides, the coefficient of the influence by the average integral residual stresses criterion changes within essentially lesser limits than the coefficient of the influence by the residual stresses on the concentrator surface criterion. So the average integral residual stresses criterion should be used for the evaluation of a surface hardening influence on an endurance limit of parts with concentrators.
 On an example of specimens within and without peening in a dangerous section its been shown that peening doesnt influence the endurance limit of a surface hardened part. The compressive residual stresses only influence the endurance limit of these parts.

Optical Characteristics of Parallel-Sided Quartz Plates at Brewster Angles Determined by Spectral Ellipsometry

A method is proposed for determining the optical characteristics of glass plates after physicochemical surface treatment by measuring spectra of ellipsometric angles at incidence angles equal to Brewster’s angle. The dispersion dependence of the refractive index could be determined and the surface layer thickness during the plate manufacturing process could be estimated using the coordinates of the ellipsometric-angle spectral minima. Refractive-index spectra calculated by the Brewster formula for KU-1 optical quartz plates in the non-absorbing region were in satisfactory agreement with spectra determined by numerical methods in the DeltaPsi2 software of a UVISEL 2 spectral ellipsometer (Horiba). The relative error of a refractive-index determination of the quartz plates by the proposed method was ≤0.1%.

Effect of Shock Sintering Temperature and Carbon Content of the WC–Co Hardmetal Anode on the Mass Transfer in Electrospark Deposition

The paper examines how the shock sintering temperature and carbon content of the VK25 hardmetal and the process time and discharge energy in the electrospark deposition of the hardmetal onto steel 45 samples influence the mass transfer, thickness, and microhardness of the resultant surface layers. The experiments were performed employing an Elitron-24 unit providing a discharge energy of 0.34–1.1 J. The VK25 hardmetal was produced by shock sintering in the range 1150–1300°C using WC with different carbon contents. For the maximum mass transfer, the hardmetal sintering temperature should be 100–150°C lower than the temperature at which samples with the highest strength were produced. The maximum mass transfer was observed when the hardmetal was depleted of carbon (3.9 instead of estimated 4.59 wt.%). A protective layer 100–200 μm thick, with a hardness of 8.0–13.7 GPa, was produced on the steel samples.

The Effect of Heating Time and Heating Temperatures to Layer Thickness and the Glossiness Level of a Surface in Blackening Coating Process

Metal coating without electrical energy using usually could be the conversion coating technique. One method of the conversion coatings that are widely used in the industrial field is blackening or black oxide coating. Blackening or black oxide coating technique is a chemical conversion process that is formed from the chemical reaction between the iron in ferrous metals by an oxidizing salt to form a layer of magnetite (Fe3O4) thin metal substrates. The metal coating process has a lot of choices to improve the quality of materials from metallic and nonmetallic. This study aims to investigate the effect of the time and the temperature of the heating process of the steel AISI 1015 on the thickness and the value of the glossiness level by the blackening processing technique. The research variables are used various heating process time: 30; 60; and 90 minutes, temperature: 100 °C; 150 ºC and 200 ºC, and other variables are controlled constantly. The workpieces made from a steel metal plate AISI 1015 has a dimension size = 200 x 30 x 3 mm3 in 27 pieces. The experimental method was designed by formation 3 x 3 x 3. It could be revealed the longer the healing process time could increase the thickness of the layer of the workpiece surface. A higher heating temperature could decrease the value of the glossiness level of a metal surface. The surface layer thickness level is found the best in the plating process time about 90 minutes and a temperature of 200ºC with a coating thickness values of 20,27μm. The highest value of the glossiness level is obtained at the highest coating time of 30 minutes at a temperature of 100ºC with the value of the shiny level of about 68.50 GU.

Asymmetric Surface Engineering for Janus Membranes

AbstractJanus membranes show great promise toward various applications and are undergoing a fast‐paced development in materials science. The asymmetric surface engineering on surface wettability, layer thickness, and pore structure enables Janus membranes with superiority in mass transport over conventional membranes. This review aims to provide an overview on the role of asymmetric surface engineering in membrane fabrication, structure control, and property tuning. The relationship between asymmetric surface engineering and performance optimization of Janus membranes is then elucidated based on an understanding of the underlying mass transport mechanism for target applications. Finally, current challenges in this field are highlighted, hopefully inspiring more researches to address the controllability and tunability of surface engineering for Janus membranes in future.

Effects of suspended particulate matter, surface oil layer thickness and surfactants on the formation and transport of oil-sediment aggregates (OSA)

This study illustrated the significant effects of oil surface layer thickness, the presence of suspended particulate matter (i.e. sediment resuspension) and surfactants (chemical oil dispersants and a bio-surfactant) on the formation and transport of oil-sediment aggregates (OSA). Oil spill thickness on surface waters influenced the weathering rates of residual oil. Thin oil slicks on the water surface were more readily dispersed by physical processes. This study provided evidence for the dispersion of thin oil slicks by the bursting of air bubbles. The OSA formation within the water column by interaction of oil with suspended particulate materials promoted the sedimentation of oil. The addition of a chemical dispersant (i.e., GM-2) and biosurfactant (i.e., rhamnolipid) to a surface oil slick increased the dissolved and aggregated oil concentrations in the aqueous phase and subsequent oil biodegradation rates. These findings provide a deeper understanding on the processes influencing vertical distribution and environmental persistence of a crude oil spilled on the ocean surface both in the presence and absence of surfactant additions.