Sublayer Thickness Research Articles

Significantly improved high k dielectric performance: Rare earth oxide as a passivation layer laminated with TiO2 film

In order to achieve a super gate dielectric performance, rare earth oxides featuring for large band gap, good thermodynamic stability and relatively high k value were selected to be laminated with TiO2 film to prepare bilayer dielectric films. As an example, the microstructure, morphology, band gap structure and electrical performance of TiO2–Y2O3 bilayer films were systematically investigated. Results show that stacking sequence of TiO2 and Y2O3 sublayers has a significant impact on the dielectric performance and Y2O3 film as a passivation layer can effectively improve electrical properties. Besides, the electrical behaviors analysis of TiO2–Y2O3, Y2O3–TiO2, Y2O3 and TiO2 samples was carried out by impedance spectra and equivalent circuit. The result shows that TiO2–Y2O3/Si sample holds the largest internal resistance of 74665 Ω among four samples. Moreover, the most outstanding properties of Pt/TiO2–Y2O3/Si capacitor are achieved by varying the thickness of sublayers and annealing temperature. 500 °C-annealed bilayer film with 17 nm-TiO2 and 3-nm Y2O3 displays a k value of 28.24, which is more than 1.4 times that of current commercial HfO2. Further, Schottky emission was determined to be leakage current transport mechanism for TiO2–Y2O3 bilayer films. Inspired by this result, the electrical performance of more general Pt/TiO2-REOs/Si MOS capacitors (RE = Sc, La, Ce, Gd and Pr) was measured. The combination of TiO2 film and REOs passivation layer with the satisfying performance provides promising candidates for future Si-based integrated circuit (IC).

An optimized strategy toward multilayer ablation coating for SiC-coated carbon/carbon composites based on experiment and simulation

Carbon/carbon (C/C) composites are widely used as thermal protection systems for atmospheric re-entry, where they are subjected to strong oxidation and mechanical denudation. Sublayer thickness of multilayer coating has considerable influence on its stress, which further governs their service life in critical environments. In this study, a multilayer coating with different sublayer thicknesses was fabricated on SiC-coated C/C composites using plasma spraying. Prior to the fabrication, finite element analysis (FEA) was firstly established to investigate the relationship between sublayer thickness and thermal stress. Thereafter, the coatings with typical sublayer thickness were verified through practical experiments. Raman spectra and ablated appearances showed well coincidence with the FEA results, pointing out close relationship among sublayer thickness, residual stress and ablation behavior. After testing for 90 s, the sample with optimized thickness owned the least stress (294 MPa) and lowest ablation rates (−0.467 µm/s and −0.343 mg/s) as compared to other coated ones.

Measurement and Scaling of Lake Surface Skin Temperatures

AbstractWater temperature microprofiles at the air‐water interface of a stratified lake were measured concurrently with moderate wind speeds of 0.8–8.2 ms−1 above the lake surface. The day‐time measurements revealed the cool skin effect of water surface temperatures that triggers the cooling of the lake surface and the occurrence of natural convection. Natural convection velocity scale mediates the thickness of the diffusive thermal sublayer and the corresponding net heat flux at the interface. The diffusive thermal sublayer thickness ranged from 0.7 to 3.6 mm. The temperature microprofiles and proposed parameterization of skin‐to‐bulk temperatures enable similarity scaling of temperature microprofiles over the diffusive thermal sublayer thickness. The proposed parameterizations allow for the estimation of diffusive thermal sublayer thickness and skin‐to‐bulk temperature difference in the presence of natural convection. Our results have the potential to facilitate the validation and integration of satellite‐derived lake surface temperatures.

Maxwell-Wagner Relaxation-Driven High Dielectric Constant in Al2O3/TiO2 Nanolaminates Grown by Pulsed Laser Deposition.

Multilayer nanolaminates (NLs) of alternate ultrathin sublayers of Al2O3 and TiO2 (ATA) with the thickness ranging ∼2 to 0.5 nm were fabricated by optimized pulsed laser deposition (PLD). Maxwell-Wagner (M-W) relaxation-induced interfacial polarization was realized and engineered by precisely controlling the sublayer thicknesses and the number of interfaces. X-ray reflectivity and cross-sectional transmission electron microscopy measurements of ATA NLs revealed an artificial periodicity with well-defined uniformly thick amorphous sublayers with chemically and physically distinct interfaces down to a sublayer thickness of ∼0.8 nm. The dielectric constants and loss of ATA NLs were found to increase from ∼60 to 670 and decrease from ∼0.9 to 0.16, respectively, as sublayer thicknesses reduced from ∼2 to 0.8 nm. However, for a sublayer thickness below 0.8 nm, the trend was reversed. Furthermore, temperature-dependent impedance spectroscopy studies revealed two distinct thermally activated relaxation processes, corresponding to TiO2 and Al2O3 sublayers, corroborating the M-W relaxation. The conductivity contrast between the sublayers of ATA NLs enhanced with reducing sublayer thickness and plateaued at a sublayer thickness of ∼0.8 nm, resulting in dominant M-W interfacial polarization and a high cut-off frequency of ∼50 kHz. These results demonstrate that ATA NLs grown by PLD may find application as potential high-k materials for next-generation nanoelectronic devices.

Depth profiling of very thin HfO2/Al2O3 stacks by ellipsometry

Ellipsometry (VASE and MAIE) with appropriate algorithms for experimental data interpretation was applied for quantitative characterization of thin Al2O3/HfO2 multilayers formed by atomic layer deposition (ALD) applicable to the fabrication of charge-trapping nonvolatile memories. A substantial benefit of the algorithms is the depth profiling of the stacks. In this work, the depth profiles were retrieved of the HfO2 constituent in very thin (Al2O3:HfO2) stacks embedded in thin Al2O3 surrounding layers. The peculiarities in the achieved depth profiles are used to determine the bi-layer blocks and their sub-layer thicknesses. The influence of a rapid thermal annealing in O2 on the depth profile and the sub-layer thicknesses is studied; substantial changes are thus revealed in the thickness and composition of the stacks. This information could be used in optimizing the dielectric and electrical properties of the stacks and multilayers.

Microstructural and micro-mechanical investigation of cathodic arc evaporated ZrN/TiN multilayer coatings with varying bilayer thickness

Modifying the architecture of multilayer hard coatings allows to adjust the mechanical properties of these materials for a given application. Within this work, the effect of the bilayer thickness (Λ) and the individual sublayer thickness ratio on the microstructure and mechanical properties of ZrN/TiN multilayer coatings was investigated. Multilayer coatings with Λ of 570, 320 and 35 nm were deposited by cathodic arc evaporation and compared to TiN and ZrN single-layer coatings. The microstructure was investigated by X-ray diffraction (XRD) and scanning electron microscopy. All coatings exhibit a single phase face-centred cubic structure and a predominant (111) texture. A columnar structure was observed for all coatings and grain growth extending beyond the ZrN/TiN interfaces was evident in all multilayers. For all coatings, compressive residual stresses were determined by XRD using the sin 2 ψ method, where the multilayer sample with the largest Λ exhibited the highest compressive residual stress of −1.7 ± 0.2 GPa. Lower compressive residual stresses could be correlated with decreasing Λ and decreasing ZrN:TiN thickness ratio. Nanoindentation experiments as well as micro-mechanical bending tests were conducted to assess the mechanical properties of the coatings. The ZrN/TiN multilayer sample with Λ of 35 nm showed the highest hardness of 28.0 ± 1.1 GPa. This value is similar to the TiN single-layer and higher compared to the ZrN single-layer, which exhibited a hardness of 27.9 ± 1.4 GPa and 25.8 ± 1.3 GPa, respectively. While the ZrN single-layer showed the highest fracture toughness, the ZrN/TiN multilayer samples were identified as the mechanically stiffest and strongest of the investigated coatings, since they exhibited a higher fracture stress compared to the single-layer coatings. The obtained results allow to optimise the architecture of ZrN/TiN multilayer coatings yielding the desired coating properties for application in the cutting industry. • Arc evaporated ZrN/TiN multilayer coatings with varying bilayer thickness Λ • Smaller Λ leads to grain refinement and more pronounced (111) texture. • Multilayer coating with lowest Λ exhibits the highest hardness. • Highest fracture toughness for ZrN single-layer coating • Improved fracture stress for multilayers compared to single-layers

Travertine crystal growth ripples record the hydraulic history of ancient Rome\u2019s Anio Novus aqueduct

Travertine crystal growth ripples are used to reconstruct the early hydraulic history of the Anio Novus aqueduct of ancient Rome. These crystalline morphologies deposited within the aqueduct channel record the hydraulic history of gravity-driven turbulent flow at the time of Roman operation. The wavelength, amplitude, and steepness of these travertine crystal growth ripples indicate that large-scale sustained aqueduct flows scaled directly with the thickness of the aqueous viscous sublayer. Resulting critical shear Reynolds numbers are comparable with those reconstructed from heat/mass transfer crystalline ripples formed in other natural and engineered environments. This includes sediment transport in rivers, lakes, and oceans, chemical precipitation and dissolution in caves, and melting and freezing in ice. Where flow depth and perimeter could be reconstructed from the distribution and stratigraphy of the travertine within the Anio Novus aqueduct, flow velocity and rate have been quantified by deriving roughness-flow relationships that are independent of water temperature. More generally, under conditions of near-constant water temperature and kinematic viscosity within the Anio Novus aqueduct channel, the travertine crystal growth ripple wavelengths increased with decreasing flow velocity, indicating that systematic changes took place in flow rate during travertine deposition. This study establishes that travertine crystal growth ripples such as those preserved in the Anio Novus provide a sensitive record of past hydraulic conditions, which can be similarly reconstructed from travertine deposited in other ancient water conveyance and storage systems around the world.

Estimation method for layered ground thermal conductivity using genetic algorithm based on a 2-D heat transfer model

Estimation of ground thermal conductivity plays an important role in design of borehole heat exchanger (BHE) for ground source heat pump (GSHP) systems, and the ground is usually heterogeneous with layered thermal properties. Therefore, this study presented a novel estimation method for layered ground thermal conductivity by using distributed thermal response test (DTRT) and genetic algorithm. Firstly, a comprehensive new 2-D heat transfer model for coaxial BHE was built to simulate borehole fluid temperature profiles, it revealed that the distribution of ground thermal conductivity showed a significant influence on outlet temperature and temperature profiles. Then, based on the built model, the vertical distribution of ground thermal conductivity was estimated through DTRT data by using the genetic algorithm. It was found that the DTRT data at 2 h was effective to estimate the layered ground thermal conductivity by using the new 2-D heat transfer model. Furthermore, the estimated distribution of ground thermal conductivity was almost independent of numbers or thickness of sub-layer, and the largest difference in distributions of ground thermal conductivity among different layer thickness was less than 0.3 W/(m·K). Also, the estimation convergence showed independence with layer thickness, converged results could be obtained after 10 iterations for different layer conditions.

Solid-state reaction in Ni/Si multilayered films, characterized by magneto-optical and optical spectroscopies

Abstract Solid-state reactions, induced by ion-beam mixing (IBM) and thermal annealing, in Ni/Si multilayered films (MLF) with an overall stoichiometry of Ni2Si, NiSi and NiSi2, and with a constant Ni sublayer thickness (nominally, 3.0 nm), were studied by optical and magneto-optical spectroscopies as well as X-ray diffraction (XRD). The layer mixing was performed with Ar+ ions of an energy of 80 keV and a dose of 1.5 × 1016 Ar+/cm2. It was shown that the IBM leads to structural changes in the Ni/Si MLF, which cannot be easily detected by XRD but are recognized by optical tools. An annealing at 1073 K of the Ni/Si MLF with an overall stoichiometry of NiSi and NiSi2 induces formation of predominantly the η-NiSi and the NiSi2 phases, respectively. IBM of all the investigated Ni/Si MLF leads to the formation of regions with a short-range order of the crystalline NiSi silicide, and of Ni2Si (and/or Ni3Si) additionally for the Ni/Si MLF with an overall stoichiometry of Ni2Si.

The onset of penetrative convection in a three-layered porous–air–porous system with internal heat source

The study is devoted to a linear stability problem for a system of two horizontal porous sublayers separated by an air interlayer under the influence of the gravity field. The porous sublayers are capable of generating heat with a constant volumetric strength of heat source proportional to the solid volume fraction. Equal temperatures are maintained at the external boundaries of the three-layered system. The onset value for internal convection is numerically determined in the limiting case of a thin air sublayer. The critical wave number is also found, upon reaching which the equilibrium stability is lost in the system, and convective patterns begin to arise. The influence on the convective stability of the ratio of the permeabilities of the layers, the relative thickness of the lower porous sublayer, and the parameter of the air interlayer is analyzed. This parameter is the ratio of the air sublayer thickness raised to the third power to the Darcy number. New results are obtained that take into account the localization of the convective flow. It is shown that the permeability ratio can both destabilize and stabilize the motionless state. An increase in the interlayer parameter unambiguously reduces the convection onset value. A map for the local and large-scale convective regimes has been constructed in the coordinates of permeability ratio versus the air interlayer parameter. A demarcation line of the transition from one regime to another on the map corresponds to the parameters at which the critical internal Rayleigh–Darcy numbers for the two minima of the bimodal neutral curve have equal values. One of the minima belongs to the region of small wave numbers (a long-wave minimum) and defines the onset value for large-scale convection, and the other one is in the region of large wave numbers (a short-wave minimum) and indicates the onset value for local convection. It is shown that with an increase in the air interlayer parameter, the ratio of permeability required for a transition from large-scale to local convective regimes decreases.

Microhardness of multilayer [(Zn-Ni)base/(Zn-Ni)add]n coatings depending on the nanoscale sublayer thickness

The effect of the thickness of sublayers of multilayer [(Zn-Ni)base/(Zn-Ni)add]n coatings, deposited by two-pulse galvanostatic mode from a polyligand pyrophosphate-citrate electrolyte, on their microhardness has been investigated. It is shown that during the deposition of (Zn-Ni)base sublayers at current density of 40 mA cm−2 and (Zn-Ni)add sublayers at current density of 10 mA cm−2 with a thickness of 11–68 nm, the microhardness of multilayer coatings is higher than the microhardness of single-layer coatings deposited at these current density values, and is in the range of 430–493 HV. The microhardness depends on the ratio of the sublayer thickness and increases at any ratio in the case of a decrease in the thickness of the bilayer.

Evolution of corrosion on microstructure of ceramic coating produced by plasma electrolytic oxidation in molten salt

Low corrosion resistance in an Al alloy is usually overcome with the help of an Al oxide coating. Plasma electrolytic oxidation (PEO) is a highly promising environment-friendly method to achieve a ceramic surface. Traditionally, PEO is carried out in an aqueous electrolyte; however, in this study, PEO was conducted in a molten salt. This approach conserved more energy and led the formation of a pure oxide coating, as confirmed by subsequent phase analysis. The obtained ceramic coating contained two sublayers: a porous outer sublayer and a dense inner sublayer. A study of corrosion evolution was performed on oxide-coated alloys immersed in a NaCl solution for different durations. The corrosion behavior characterized by electrochemical impedance spectroscopy (EIS) was related to the changes in the surface morphology changes examined by electron microscopy. The appearance of pits on the oxide surface was attributed to the adsorption and incorporation theory, previously described for Al alloys. This study revealed that the progress of the corrosion attack by chloride ions affects both sublayers; the thickness of the outer sublayer decreased, and the inner sublayer became more compact, resulting in high resistance properties.

HfO2/SiO2 nanolaminate-based composites prepared by ion beam sputtering for low-loss optics

HfO2 prepared by ion beam sputtering (IBS) is widely used as a high-refractive index material for making low-loss laser films. The challenge of a high-performance HfO2 film is to simultaneously obtain an amorphous morphology with low scattering and a stoichiometric structure with low absorption. Furthermore, nanometer-sized voids are commonly present in IBS films due to excessive oxygen and argon adsorption during deposition, which is the primary barrier to achieve a smooth surface and low optical loss of HfO2. Thin amorphous SiO2 layers were added periodically into HfO2 coatings using the IBS process to synthesize amorphous HfO2 / SiO2 nanolaminate-based composites. The resulting composites exhibited excellent comprehensive performance with a dense amorphous microstructure and a void-free smooth surface. High-temperature annealing was performed to ensure superior stoichiometry and lower absorption. However, the crystalline states and microstructure of some composites evolved during the gradual annealing. We present a detailed study of the crystallization, surface topography, and absorption evolution in HfO2 / SiO2 nanolaminates as a function of HfO2 sublayer thickness and thermal annealing temperature. Moreover, the interplay between crystallization, surface topography, and absorption is elucidated. The HfO2 / SiO2 nanolaminate with 19 thin layers maintained a dense amorphous structure with low absorption after annealing. Finally, a 1064-nm HfO2 / SiO2 nanolaminate-SiO2 high-performance reflector was prepared and achieved lower absorption with a smooth surface after annealing, which demonstrated the great potential of the HfO2 / SiO2 nanolaminates for considerably improving optical loss.

Experimental investigation and modeling of thermal oxidation deposition of RP-3 jet fuel under high Reynolds number

The modeling and numerical prediction of thermal oxidation deposition process under high heat flux and high Reynolds number are challenging. In this paper, experimental investigations on RP-3 jet fuel were carried out under wide range of wall heat flux (0.095–3.6 MW/m2), residence time (1.95–0.06 s), and inlet Reynolds number (522–5220). As turbulence intensified, the enhanced convective mass transfer transferred more precursors into the laminar sublayer to promote the formation of deposits, while the decreased residence time, the decreased laminar sublayer thickness, and the increased wall shear force inhibited the deposition process. These factors together led to the variation that the average deposition rate per unit fuel first decreased, then increased and decreased again in the later stage. Since current numerical methods ignored the effect of turbulence diffusion on mass transfer and the kinetic parameters of global reactions depicted the formation of SMORS and insoluble precursors were based on experimental data under low Reynolds number, it could not precisely simulate the promotion of insoluble precursors formation by enhanced convective mass transfer. Based on the experimental data, two functions were proposed to modify the convective mass transfer process of original numerical method. The error between the experimental data and the original simulated results could reach more than 500%, while the error decreased to less than 15% with the application of modified functions.

Automated Analysis of Choroidal Sublayer Morphologic Features in Myopic Children Using EDI-OCT by Deep Learning.

PurposeThe purpose of this study was to analyze the choroidal sublayer morphologic features in emmetropic and myopic children using an automatic segmentation model, and to explore the relationship between choroidal sublayers and spherical equivalent refraction (SER).MethodsWe collected data on 92 healthy children (92 eyes) from the Ophthalmology Department of Peking University First Hospital. The data were allocated to three groups: emmetropia (+0.50 diopters [D] to −0.50 D), low myopia (−0.75 D to −3.00 D), and moderate myopia (−3.25 D to −5.75 D). We performed standardized optical coherence tomography (OCT) and developed a new segmentation technique to measure choroidal thickness (CT), large-vessel choroidal layer (LVCL), medium-vessel choroidal layer (MVCL), and small-vessel choroidal layer thickness (SVCL), and evaluated the choroidal vascular system (choroidal vascular volume [VV], choroidal vascular index [CVI], and choroidal vascular density [CVD]).ResultsAll choroidal sublayers (LVCL, MVCL, and SVCL) were significantly thinner in myopic than in emmetropic eyes (P < 0.05), the thinnest choroidal region being the nasal outer subfield (P < 0.05). In all choroidal regions of SVCL, a positive correlation was found between SER and thickness ratio (P < 0.001). In most subfields of MVCL, a similar correlation was found (P < 0.050), the exceptions being the two nasal subfields (0.050 < P < 0.300). In contrast, the thickness ratio of LVCL decreased in all subfields (P < 0.050). VV correlated with SER negatively in LVCL in all subfields (all P < 0.001) and most subfields in MVCL except for two temporal subfields (0.050 < P < 0.200). However, no significant correlations were found between CVI and SER in LVCL (P > 0.050) and MVCL (with the exception being the temporal inner subfield, P = 0.011).ConclusionsThickness of choroidal sublayers was reduced with higher myopic SER, whereas changes in thickness ratio varied between sublayers. No significant correlations between CVI and SER suggested that both choroidal stromal and vascular volume decreases proportionately.Translational RelevanceAutomatic segmentation model will be helpful for future clinical trials to quantify choroidal sublayer morphologic features in myopia.

Evolution of structure, residual stress, thermal stability and wear resistance of nanocrystalline multilayered Al0.7Cr0.3N-Al0.67Ti0.33N coatings

The fundamental understanding of the relation between the architecture and the development of structure and residual stress in multilayer coatings is a challenging task. In this work, cross-sectional X-ray nanodiffraction with a spatial resolution of 50 nm, performed at the cross-section of a Al 0.7 Cr 0.3 N/Al 0.67 Ti 0.33 N multilayer coating was used to investigate its depth gradients of the phase composition and residual stress. It could be demonstrated that the cubic structure can be stabilized in a substrate bias range between −100 and −200 V developing stress values above −5 GPa. Below −100 V and above −200 V a dual phase microstructure developed with reduced stress values compared to the pure cubic regime. Based on the results of the cross-sectional X-ray nanodiffraction investigation, five multilayer architectures, differing in the sublayer thickness, interface design and microstructure were developed to test the wear resistance by ball-on-disc experiments at temperatures up to 700 °C. It could be demonstrated that a sublayer thickness between 70 and 100 nm has been proven to be an ideal thickness for such an Al 0.7 Cr 0.3 N/Al 0.67 Ti 0.33 N multilayer to decrease the wear rate by a factor of 10 at 600 °C compared to their monolithic counterparts. • Cross-sectional X-ray nanodiffraction with a spatial resolution of 50 nm • Investigation of depth gradients of the microstructure and residual stress • Demonstration of various approaches to (de)stabilize the metastable cubic phase • Increase in wear resistance due to bi-layer and substrate bias voltage variations

Synthesis of textured films of hexagonal barium ferrite on Al2O3/Si3N4 amorphous structure

In this work structural studies of BaFe12O19/Al2O3/Si3N4 thin films with different thicknesses of aluminum oxide and silicon nitride are represented. It is shown that barium hexaferrite crystallizes on the amorphous surface of aluminum oxide with spontaneously formed (00l) uniaxial texture. Microstructural differences in BaFe12O19 films were observed with varying of the thickness of amorphous sublayers, which is explained by the effect of mechanical stress.

Normative Data of Axial Length, Retinal Thickness Measurements, Visual Evoked Potentials, and Full-Field Electroretinography in Female, Wild-Type Minipigs.

PurposeThe purpose of this study was to present normative data of optical coherence tomography (OCT), electrophysiological, and ocular biometry parameters and their correlation in minipigs.MethodsEighty-eight eyes of 44 minipigs underwent full-field electroretinogram (ERG) recording and ocular biometry. However, 10 eyes of 6 minipigs were excluded because of poor OCT image quality. The thickness of the retinal sublayers was measured on a vertical line at 5 locations with a 1 mm interval from the disc margin to the dorsal periphery and at 10 locations on the visual streak. Visual evoked potentials (VEPs) were measured in 15 eyes of 8 minipigs.ResultsAll minipigs were female with a mean age and axial length of 13.83 ± 10.56 months and 20.33 ± 0.88 mm, respectively. The implicit time of the a-wave and b-wave in scotopic 3.0 ERGs was longer than that in photopic 3.0 ERG. The implicit time of the n2-wave and p2-wave in VEP was 25.67 ± 7.41 ms and 52.96 ± 10.38 ms, respectively. The total retinal layer (TRL) and nerve fiber layer (NFL) became thinner near the periphery. The inner retinal sublayers near the visual streak were thicker than those at other locations. Central TRL and NFL thickness on visual streak was 223.06 ± 23.19 µm and 74.03 ± 13.93 µm, respectively. The temporal TRL and NFL on the visual streak were thicker than those on the nasal side.ConclusionsThe normative electrophysiological and OCT parameters used in our study can be used as reference data in further pig studies.Translational RelevanceThis study presents normative data of minipigs, which are adequate animal models for preclinical studies.

Roughness-induced critical phenomenon analogy for turbulent friction factor explained by a co-spectral budget model

Drawing on an analogy to critical phenomena, it was shown that the Nikuradse turbulent friction factor (ft) measurements in pipes of radius R and wall roughness r can be collapsed onto a one-dimensional curve expressed as a conveyance law ftRe1/4=go(χ), where Re is the bulk Reynolds number and χ=Re3/4(r/R). The implicit function go(.) was conjectured based on matching two asymptotic limits of ft. However, the connection between go(.) and the phenomenon it proclaims to represent—turbulent eddies—remains lacking. Using models for the wall-normal velocity spectrum and return-to-isotropy for pressure–strain effects to close a co-spectral density budget, a derivation of go(.) is offered. The proposed method explicitly derives the solution for the conveyance law and provides a physical interpretation of χ as a dimensionless length scale reflecting the competition between the viscous sublayer thickness and characteristic height of roughness elements. Applications of the proposed method to other published measurements spanning roughness and Reynolds numbers beyond the original Nikuradse range are further discussed.

Hard and tough CrN coatings strengthened by high-density distorted coherent grain boundaries

Coherent grain boundaries (CGBs) has been revealed to improve the hardness and toughness simultaneously, but the density are not enough to increase their mechanical properties. Herein, hetero-interfaces are formed by introducing ion bombardment during magnetron sputtering to increase the amount of CGBs in the CrN coatings. By optimizing the sub-layer thickness, the quantity and width of CGBs from the (111) to (200) orientations increase significantly and consequently, the hardness and toughness of the CrN coating increase to 33.4 GPa and 14.98 MPa m1/2, respectively. At last, the effect of the different CGBs to the coating strengthen is discussed.