Sublayer Thickness Research Articles

Microstructure and properties of DLC/CNx films with different CNx sublayer thicknesses

The DLC/CNx multilayer films with different CNx sublayer thicknesses were deposited on Si wafer by using magnetron sputtering technique. The microstructure and properties of the films were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, scratch tests and a ball-on-disc tribometer. All the DLC/CNx films were amorphous and compact with low internal stresses and strong reinforcement effects. The content of sp3 bonds in CNx sublayer, the hardness and adhesion of the overall films decreased while the wear rate of the multilayer films increased with increasing the CNx sublayer thickness. The friction states of the multilayer films in vacuum and air were very stable. The friction coefficients of the DLC/CNx films were ~0.16 in vacuum and ~0.20 in air, and they were independent of CNx sublayer thickness. The multilayer film with CNx sublayer thickness of 0.5 nm was of a hardness of 36.9 GPa and interface adhesion of 27 N, which exhibited excellent tribological properties in vacuum and in air.

Investigation of the Boundary Layer Flow Under Engine-Like Conditions Using Particle Image Velocimetry

The turbulent boundary layer flow in internal combustion (IC) engines has a significant effect on the in-cylinder flow and the wall heat transfer. A detailed analysis of the in-cylinder near-wall flow was carried out on an optical steady flow test bench by using high-resolution particle image velocimetry (PIV) in order to characterize the in-cylinder boundary layer flow in this study. The difference between the in-cylinder boundary layer and the canonical turbulent boundary layer was analyzed. The experimental results show that small-scale vortices with a length scale of about 1–2 mm in the instantaneous flow fields appeared in the wall jet region due to the entrainment of the free jet in the outer region of the wall jet. The viscous sublayer thickness decreased from 0.5 mm to 0.3 mm as the valve lift increased from 2.32 mm to 7.975 mm and the pressure drop from 0.5 kPa to 1 kPa. The dimensionless velocity profile is in good agreement with the law of the wall in the viscous sublayer. However, no obvious logarithmic law distribution region was observed in the logarithmic layer. The distribution of the Reynolds stress and the turbulent kinetic energy is similar to that of the canonical turbulent boundary layer. But the Reynolds stress had a much larger magnitude because the turbulent velocity measured in this boundary layer included not only the turbulence generated by wall shear but also the large-scale turbulent vortices caused by the wall jet.

Visual Acuity in Pathological Myopia Is Correlated With the Photoreceptor Myoid and Ellipsoid Zone Thickness and Affected by Choroid Thickness.

To quantify the thickness of the outer retinal sublayers and choroid in pathological myopia and examine associations between these factors and best-corrected visual acuity (BCVA). The cohort was composed of 21 eyes with emmetropia and 70 eyes with high myopia (49 simple high myopia; 21 pathological myopia). Optical coherence tomography images were segmented to determine macular thicknesses of the choroid and the following outer retinal sublayers: outer plexiform layer (OPL), Henle fiber layer and outer nuclear layer (HFL + ONL), myoid and ellipsoid zone (MEZ), outer segment of photoreceptors (OS), and interdigitation zone and RPE/Bruch complex (IZ + RPE). Correlations between BCVA and thickness of the outer retinal sublayers and choroid were determined. In pathological myopia, the choroid, HFL + ONL, MEZ, and IZ + RPE were thinner than in emmetropia and simple high myopia (P < 0.05). Simple and multiple regression models showed that MEZ thickness was correlated with BCVA (both P < 0.001). The relationship between MEZ thickness and BCVA varied with choroidal thickness (P = 0.006). For a constant MEZ thickness, thinner choroids were associated with worse vision. In the final multiple regression predictive model, MEZ thickness, choroidal thickness, and interaction between MEZ and choroidal thickness (all P < 0.001) were predictors of BCVA. Outer retinal alterations, especially thinning of the MEZ, occurred in pathological myopia. The MEZ thickness was associated with BCVA, and this relationship was affected by choroidal thickness.

The Temperature Stability of Nanometric Multilayers of Copper and Chromium\u2013Nickel Steel (Cu/310S)

Multilayers consisted of Cu and AISI 310S steel fabricated on a Si(100) monocrystalline silicon substrate by the magnetron sputtering method were investigated. The multilayers were differentiated by the number of periods (50, 100 and 150) and by the thickness of 310S steel sublayer (2 nm and 4 nm), while maintaining a constant thickness of the Cu (2 nm). The temperature stability tests were performed in an air atmosphere by isothermal annealing in the temperature range from 23 °C to 400 °C. It was found that the temperature stability of Cu/310S steel multilayers depends on their thickness. The thickest multilayers show stability up to a temperature of 375 °C. Thinner multilayers exhibit stability up to a higher temperature of 400 °C, in spite of their thermal expansion coefficients being greater.

Blue Electroluminescent Al₂O₃/Tm₂O₃ Nanolaminate Films Fabricated by Atomic Layer Deposition on Silicon.

Realization of a silicon-based light source is of significant importance for the future development of optoelectronics and telecommunications. Here, nanolaminate Al2O3/Tm2O3 films are fabricated on silicon utilizing atomic layer deposition, and intense blue electroluminescence (EL) from Tm3+ ions is achieved in the metal-oxide-semiconductor structured luminescent devices based on them. Precise control of the nanolaminates enables the study on the influence of the Tm dopant layers and the distance between every Tm2O3 layer on the EL performance. The 456 nm blue EL from Tm3+ ions shows a maximum power density of 0.15 mW/cm2. The EL intensities and decay lifetime decrease with excessive Tm dopant cycles due to the reduction of optically active Tm3+ ions. Cross-relaxation among adjacent Tm2O3 dopant layers reduces the blue EL intensity and the decay lifetime, which strongly depends on the Al2O3 sublayer thickness, with a critical value of ~3 nm. The EL is attributed to the impact excitation of the Tm3+ ions by hot electrons in Al2O3 matrix via Poole–Frenkel mechanism.

Leakage currents in Al2O3/HfO2 multilayer high-k stacks and their modification by post-deposition annealing steps

Leakage currents of Al2O3/HfO2 multilayer stacks deposited by atomic layer deposition in the low voltage region (0 ÷ ±4V) are investigated in dependence on Al2O3 sublayers thickness and the post-deposition annealing in two ambients (O2, N2,). The stacks with 5cy of Al2O3 show highest current, compared to structures with lower (2cy) and higher (10cy) Al2O3 content. Oxygen treatment does not affect significantly the leakage current at low voltages, while annealing in nitrogen definitely increases it. The current follows power law dependence, Vn, with n varying in the interval of about 0.6 to ∼1. The application of ±12V pulses shift the leakage curves towards higher or lower current values depending on the polarity of the pulse. Leakage curves after the pulse stress are described either with Vn or (V-Vt)n relations depending on both pulse and measurement bias polarity. The results are found consistent with a model similar to the collective transport in array of small metal dots model in which the current is limited by the available sites for charge carriers to move on.

Two-layer nanocomposite WC/a-C coatings produced by a combination of pulsed arc evaporation and electro-spark deposition in vacuum

New cost-efficient technology combining pulsed arc evaporation (PAE) and electro-spark deposition (ESD) in vacuum was developed and implemented to coat Ti with two-layer WC/a-C coating in a single technological run using the same WC-6%Co electrode. A thick bottom ESD layer (70–90 μm) was composed of β-Ti (~70%), β-(W,Ti)C1-x and a small amount of α-Ti. A thin upper PAE layer had two sublayers (3.2 and 1.6 μm thick) sequentially deposited in an Ar and C2H4 atmosphere. Both sublayers had a nanocomposite, nearly amorphous structure, in which small disordered β-WC1-x crystallites were dispersed in a-C matrix. A superior tribological performance of the PAE/ESD coatings was attributed to gradual changes in phase composition and grain size, as well as a combination of tailored mechanical properties (hardness gradually increased from 3.6 GPa (Ti substrate) to 20 GPa (PAE layer)), enhanced toughness and high thickness of the ESD sublayer, which prevented the substrate from plastic deformation, and low friction coefficient of the top PAE layer due to its nearly amorphous WC/a-C structure with a large amount of a-C phase acting as a solid lubricant. In-situ mechanical TEM tests demonstrated superior adhesion strength of the PAE/ESD interface able to withstand high stresses of 560 MPa.

Geometrically nonlinear finite element simulation of smart laminated shells using a modified first-order shear deformation theory

This article investigates geometrically nonlinear and linear analysis of multilayered shells with integrated piezoelectric materials. An efficient nonlinear shell element is developed to solve piezoelastic response of laminated structure with embedded piezoelectric actuators and sensors. A modified first-order shear deformation theory is introduced in the present method to remove the shear correction factor and improve the accuracy of transverse shear stresses. The electric potential is assumed to be a linear function through the thickness of each active sub-layer. Several numerical tests for different piezolaminated geometries are conducted to highlight the reliability and efficiency of the proposed implementation in linear and geometrically nonlinear finite element analysis.

Gradients of microstructure, stresses and mechanical properties in a multi-layered diamond thin film revealed by correlative cross-sectional nano-analytics

Thin diamond films deposited by chemical vapour deposition (CVD) usually feature cross-sectional gradients of microstructure, residual stress and mechanical properties, which decisively influence their functional properties. This work introduces a novel correlative cross-sectional nano-analytics approach, which is applied to a multi-layered CVD diamond film grown using microwave plasma-enhanced CVD and consisting of a ∼8 μm thick nanocrystalline (NCD) base and a ∼14.5 μm thick polycrystalline (PCD) top diamond sublayers. Complementary cross-sectional 30 nm beam synchrotron X-ray diffraction, depth-resolved micro-cantilever and hardness testing and electron microscopy analyses reveal correlations between microstructure, residual stress and mechanical properties. The NCD sublayer exhibits a 1.5 μm thick isotropic nucleation region with the highest stresses of ∼1.3 GPa and defect-rich nanocrystallites. With increasing sublayer thickness, a 110 fibre texture evolves gradually, accompanied by an increase in crystallite size and a decrease in stress. At the NCD/PCD sublayer interface, texture, stresses and crystallite size change abruptly and the PCD sublayer exhibits the presence of Zone T competitive grain growth microstructure. NCD and PCD sublayers differ in fracture stresses of ∼14 and ∼31 GPa, respectively, as well as in elastic moduli and hardness, which are correlated with their particular microstructures. In summary, the introduced nano-analytics approach provides complex correlations between microstructure, stresses, functional properties and deposition conditions.

In-Situ Polarized Neutron Reflectometry Study of the Passive Film Growth on Fe-20Cr Alloy

Metal dissolution and passivation of Fe-20Cr alloy in an alkaline solution were investigated using in-situ polarized neutron reflectometry. The dissolution of the alloy, the thickness of sub-layers in the passive film, the interfacial roughness between layers, and the scattering length density profile of the passive film were measured with sub-nanometer resolution. An anodization ratio for oxide growth of 3.4 ± 0.4 nm/V was determined. The oxide formation efficiency and the layer density at different applied potentials were also quantified.

Subretinal Implantation of aHuman Embryonic Stem Cell-Derived Retinal Pigment Epithelium Monolayer in aPorcine Model.

The goal of this study was to quantitatively assess retinal thickness using spectral domain optical coherence tomography (SD-OCT) after subretinal implantation of human embryonic stem cell-derived retinal pigment epithelium in a porcine model. The implant is called CPCB-RPE1 for the California Project to Cure Blindness-Retinal Pigment Epithelium 1. Data were derived from previous experiments on 14 minipigs that received either subretinal implantation of CPCB-RPE1 (n=11) or subretinal bleb formation alone (sham; n=3) using previously described methods and procedures (Brant Fernandes et al. Ophthalmic Surg Lasers Imaging Retina 47:342-51, 2016; Martynova et al. (2016) Koss et al. Graefes Arch Clin Exp Ophthalmol 254:1553-65, 2016; Hu et al. Ophthalmic Res 48:186-91, 2016; Martynova et al. ARVO Abstract 2016. SD-OCT retinal thickness (RT) and sublayer thickness over the implant were compared with topographically similar preimplantation regions as described previously Martynova et al. ARVO Abstract 2016. Imaging results were compared to postmortem histology using hematoxylin-eosin staining. RT overlying the CPCB-RPE1 postimplantation was not significantly different from preimplantation (308±72μm vs 292±41μm; p=0.44). RT was not significantly different before and after implantation in any retinal sublayer at 1month. Histology demonstrated grossly normal retinal anatomy as well as photoreceptor interdigitation with RPE.

Heating Duration of Polyethylene Pipes for Unwinding from Bays during Construction and Installation Works at Low Temperatures

The present paper proposes a technique for determining duration of heating coiled polyethylene pipes with hot air for laying and installation operations in construction of gas pipelines in conditions of low temperatures. A mathematical model of the thermal process of heating polyethylene pipes with hot air is considered. Herewith, it is assumed that a turbulent flow of heated air courses inside the pipe along its entire length. A laminar sublayer is formed in the pipe wall through which heat is transferred by means of molecular thermal conductivity. The rest of the pipe section is filled with turbulent flowing air (turbulent core). Heat is transferred in a turbulent flow not only by thermal conductivity, but also by turbulent pulsations. The coefficient of turbulent thermal conductivity is determined on the basis of the temperature data of the full-scale experiment at a certain ambient air temperature. The thickness of the laminar sublayer, which is the thermal resistance, is regulated by the known formula. The results of a calculation study of duration of the heating of polyethylene pipe in the temperature range of the ambient air at a known air flow rate fed into the pipe are presented. The effectiveness of the proposed method for determining the duration of heating polyethylene pipes in coils is confirmed experimentally.

The Spectral-Domain Optical Coherence Tomography Findings Associated with the Morphological and Electrophysiological Changes in a Rat Model of Retinal Degeneration, Rhodopsin S334ter-4 Rats.

Purpose To characterize the spectral-domain optical coherence tomography (SD-OCT) findings of the rhodopsin S334ter transgenic rats (line 4) in relation to the morphologic and electroretinographic features. Materials and Methods Rhodopsin S334ter transgenic rats (line 4) were employed as a model of retinal degeneration. The Sprague-Dawley (SD) rats were used as a wild-type control. SD-OCT (Micron IV®; Phoenix Research Labs, Pleasanton, CA, USA) was performed on the S334ter rats (line 4) from postnatal days (P) 13−110. The longitudinal changes of the SD-OCT images were analyzed both qualitatively and quantitatively in comparison to those of SD rats. The SD-OCT images were also compared to the histological and electron microscopic findings from examination performed on P 22, 36, and 61. Full field combined rod and cone electroretinography (ERG) was performed and the relationship between the thickness of the retinal sublayers and the amplitudes of the a- and b-waves was further analyzed. Results The photoreceptor inner and outer segment layer became diffusely hyperreflective in the SD-OCT images of the S334ter rats; these findings were not observed in the SD rats. This hyperreflective change corresponded to the degenerated inner and outer segments and the accumulation of the extracellular vesicles in the interphotoreceptor matrix. Quantitatively, the retinal outer sublayer and the photoreceptor sublayer in the S334ter rats became progressively thinner in comparison to those in the SD rats; the difference was statistically significant. The amplitudes of both the a- and b-waves on ERG were severely deteriorated in the S334ter rats. Discussion The SD-OCT images in the S334ter rats noninvasively provided information regarding the pathological changes in the photoreceptors and the longitudinal changes of both qualitative and quantitative changes during retinal degeneration in the S334ter rats (line 4). The pathological features of the photoreceptor inner and outer segments can be detected on SD-OCT as diffuse hyperreflective changes in the photoreceptor layer.

Wide-range tuning of interfacial exchange coupling between ferromagnetic Au/Co and ferrimagnetic Tb/Fe(Co) multilayers

The ability to perform wide-range tuning of the magnetic field required to switch the magnetization of ferromagnetic layers with perpendicular magnetic anisotropy is of great importance for many applications. We show that, for (Au/Co)2(3) multilayers, this field can be changed from minus several kOe to plus several kOe because of changes to the coupling with a ferrimagnetic multilayer [either (Tb/Fe)6 or (Tb/Co)6] across a Au spacer (either homogeneous 1 nm thick or wedge-shaped). The adjustable parameters are the ratio of sublayer thicknesses of the ferrimagnet and the sequence of layers around the Au spacer. The change of the sequence from Co/Au/Co to Tb/Au/Co is accompanied by both the reduction of the interaction energy and the change of the magnetic field sign necessary to switch the magnetization of ferromagnetic multilayers. For a 1 nm thick Au spacer this fields change from positive (negative) to negative (positive) if the ferrimagnet is dominated by the transition metal (rare earth) as a result of its composition. The characteristic oscillatory behavior of RKKY-like coupling is demonstrated using a system with a wedge-shaped Au spacer.

Recubrimientos nanoestructurados de circonia estabilizada con itria (YSZ) depositados mediante termorrociado por plasma por suspensión

The outstanding properties of ytria stabilized zirconia (YSZ) coatings allow an excellent performance of these materials for many applications, ranging from dentistry to thermal barriers, including its use as solid electrolytes in fuel cells. In the present work, nanostructured coatings of 8YSZ with a maximum thickness of 75μm were deposited on a Haynes 230 superalloy substrate by means of a suspension plasma spraying (SPS) process. The deposited coatings act as a sub-layer between the smooth and unprepared substrate and a thicker microstructured YSZ coating. The effect of the deposited sub-layer thickness and the influence of subsequent heat treatments (TT) at 300̊C and 600̊C, on its tribological performance at room temperature and 650̊C, were studied. During sliding wear tests with a load of 2N versus alumina, it was determined that reducing the coating thickness from 75μm to 25 μm increases the wear resistance by approximately 5 times. Also, it was found that the heat treatment at 600̊C applied to the coating of 25μm thickness decreases its wear resistance 6 times with respect to the as-sprayed condition. Similarly, when the tests were performed at 650̊C, the tribological behavior was significantly deteriorated. These results have been related to the morphological changes that take place during the heat treatment process.

Multiple spin reorientation transitions and large in plane magnetic anisotropy in epitaxial Au/Co/Fe(1 1 0) films

Abstract We report on in-plane magnetic anisotropy in Au/Co/Fe(1 1 0) trilayers epitaxially grown on W(1 1 0). We observe single and double in-plane spin reorientation transitions that can be explained by the strongly non-monotonic dependence of magnetic anisotropy on the Co sublayer thickness. We point out the significant flexibility of the Au/Co/Fe(1 1 0) system for switching the in-plane easy axis of the magnetic anisotropy between the [ 1 1 ¯ 0 ] and [0 0 1] directions of the bcc(1 1 0) plane.

Determination of cleaning mechanisms by measuring particle size distributions

Knowledge of the dominant removal mechanism (diffusive vs. convective mass transport) is important for understanding, modelling and predicting cleaning behavior of food soils. The size of the detached particles is thereby a useful physical quantity, since small particles, which are fully immersed within the viscous sublayer of the flow, will rather be removed due to diffusion than caught from the flow itself. The dimensionless particle diameter relates the particle size to the thickness of the viscous sublayer and has therefore been chosen to identify whether the particles were removed rather by diffusive or convective mass transport.This contribution presents the online measurement of particle size distributions during cleaning of starch and egg yolk soils in an automated laboratory test rig. To achieve accurate results for the particle sizes, measurements with Fraunhofer and Mie theory were compared. Furthermore, the influence of the cleaning temperature on the dimensionless particle diameter was examined for both soils.

Effects of microstructure evolution on the oxidation behavior and high-temperature tribological properties of AlCrN/TiAlSiN multilayer coatings

AlCrN/TiAlSiN multilayer coatings have drown great attentions due to they combine both high hardness of TiAlSiN coating and outstanding oxidation resistance of AlCrN coating. In this study, AlCrN, TiAlSiN, and AlCrN/TiAlSiN multilayered coatings with two different multilayer designs: AlCrN/TiAlSiN-1 coating with fixed modulation period and ratio and AlCrN/TiAlSiN-2 coating with gradient increased AlCrN sub-layer thickness, were synthesized. The microstructure, mechanical property, thermal stability, oxidation behavior, and tribological performance of these coatings were comparably investigated. The variation of structure effects on the properties of the coatings were also discussed. The results indicated that the AlCrN/TiAlSiN multilayered coatings had superior performance than the monolayer AlCrN and TiAlSiN coatings. The AlCrN/TiAlSiN-2 coating also showed better thermal stability, oxidation resistance and high-temperature tribological properties compared to AlCrN/TiAlSiN-1 coatings, which can be attributed to the formation of a denser Al2O3 oxide layer on the surface of the coating.

Electrodeposition of Copper on Mild Steel: Peculiarities of the Process

The process of electrodeposition of copper coatings on a mild steel substrate was analyzed. The reasons for poor adhesion of the coatings from acid and alkaline cyanideless electrolytes were determined. It was shown that the problem of the direct copper coatings’ electrochemical plating on a steel substrate from cyanideless electrolytes results from the presence of the adjoint process of contact exchange in a copper ions–iron system. Good adhesion coatings can be developed only on termination of the contact exchange at the initial stage until the steel substrate under the sediment pores is not subjected to significant etching. In acid electrolytes, the adhesion is poor because of a large value of the contact exchange current. In alkaline cyanideless electrolytes iron is passivated, and adhesion of the coating is insufficient because of the presence of a separating passive film at the substrate–coating interface. In neutral electrolytes, it is possible to obtain a coating with a good adhesion to the substrate, but the results are not stable due to a low buffer capacity of the solution. During the deposition of a copper coating from acid electrolytes using a prenickel-plating, a thin nickel sublayer has pores through which the process of the contact exchange occurs. It is shown that, in order to develop coatings with a good adhesion, the minimum thickness of the nickel sublayer must be 3–5 μm.

Relationship between Retinal Thickness Profiles and Visual Outcomes in Young Adults Born Extremely Preterm: The EPICure@19 Study

To quantify inner and outer retinal layer thicknesses and understand their relevance to visual function among young adults born extremely preterm (EP). Prospective observational study with 19 years of follow-up. A total of 354 eyes (226 eyes of former EP infants and 128 age-matched full-term control eyes) from 177 young adults were evaluated. Among EP participants, 50% of eyes (112/226) were not previously diagnosed with neonatal retinopathy of prematurity (ROP), 38% of eyes (84) had ROP not deemed to require treatment in the neonatal period, and 13% of eyes (30) had neonatal cryotherapy or laser ablation for ROP. Subjects underwent eye examinations including best-corrected visual acuity (BCVA) and Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany) macular spectral-domain (SD) OCT imaging. Retinal layers were auto-segmented and thickness profiles were computed at the fovea by the instrument software. Correlation between retinal sublayer thickness and BCVA. Compared with control eyes, the inner and outer retinal layers of EP eyes were significantly thicker and BCVA was significantly reduced. Retinal layer thicknesses and BCVA were similar for untreated EP eyes and those without neonatal ROP. In contrast, treated eyes had increased inner and outer retinal layer thickness and decreased vision. Inner retinal layer thickness was moderately correlated with worse BCVA (r= 0.30, P < 0.001), but outer retinal layer thickness was not (r=-0.01, P= 0.80). Multivariate regression indicated ganglion cell layer thickness was a significant independent predictor of BCVA. Extremely premature birth influences maturation of the fovea and visual outcomes into early adult life. Increased ganglion cell layer thickness was associated with worse BCVA. Eyes requiring neonatal treatment for ROP had associated worse BCVA at the age of 19 years.