Growth Of Layer Research Articles

Skeletochronology of amphibians and reptiles: fundamentals of methodology, variety of problems and prospects

Skeletochronology, a method for determining individual age in poikilothermic animals with annual cyclic growth, has become widespread due to its reliability, the ability to determine the age of living animals, and the ability to retrospectively estimate body size from the size of annual growth marks. The purpose of the review is to give an idea of the practical features of the use of skeletochronology and of the various applied and general theoretical problems that arise on the basis of the age data obtained. The formation of recording structures (growth layers and lines of arrested growth) in long bones, other recording structures, the main problems solved based on the results of applying the method, the main advantages and limitations of the technique are considered.

High temperature fencing for continuous steelmaking unit

A new method of iron recovery and continuous steel production with in-line vacuuming is described. Constructive solutions for refractory fencing are proposed, as well as the evaluation and selection of materials for the multilayer lining of the proposed installation. Technical solutions have been selected to extend the service life of high-temperature fencing using water-cooled panels that ensure the formation of a garnish. Numerical modeling of the process of the growth of the garnish layer is carried out.

Simulations on perturbation growth and mixing of a shocked light fluid layer with two different interfaces

The Richtmyer–Meshkov instability of a light fluid layer with two different interface modes is studied numerically. By fixing the wavelength of the second interface (I2) while varying that of the first interface (I1), we examine distinct cases with identical wavelengths at both interfaces, as well as smaller or larger wavelengths at I1, to explore the effects of initial layer configurations on instability development. The larger wavelength interface significantly transmits modes to the smaller wavelength interface, whereas mode transmission in the reverse direction is limited. This results in two primary consequences: (i) the smaller wavelength interface and the overall mixing layer evolve periodically with the larger wavelength; (ii) compared to the identical wavelength case, the linear amplitude growth duration of I2 is slightly extended for the smaller I1 wavelength case, but significantly prolonged for the larger I1 wavelength case. The linear amplitude growth rate of I2 for all cases can be predicted by the model of Jacobs et al. [J. Fluid Mech., vol. 195, 23–42 (1995)]. For cases with identical wavelengths and larger I1 wavelengths, the collisions of finger structures at both interfaces occur earlier, suppressing the growth of mixing width at early times while enhancing the mixed mass. In the later stages, the overall mixing efficiency in these cases significantly declines, despite continuous increases in both mixing width and mixed mass. This decline is attributed to severe deformation of the mixing layer due to interactions between finger structures, confining intense mixing to localized regions.

Identifying the Mechanism of Interaction Between Soil Moisture State and Summertime MCS Initiations in Weakly Forced Synoptic Environments Using Convective-Permitting Simulations.

This work aims to identify a mechanism of interaction between soil moisture (SM) state and the incidence of weakly forced synoptic scale MCS events during boreal summer by performing a sensitivity study using the Weather Research and Forecasting (WRF) model over the US Great Plains. A uniformly dry SM patch at a 5°×5° scale is centered at the point of a documented MCS initiation to observe spatiotemporal changes of the simulated MCS events, totaling 97 cases between 2004 and 2017. A storm-centered composite analysis of SM at the location of simulated MCS events depicted SM heterogeneity [O(100) km] structured as significantly drier soils to the southwest (SW) transitioning to wetter soils northeast (NE) of the mean simulated initiation. Further analyses showed that this SM configuration influenced near-surface fluxes, which created a gradient of 2m-temperature and 2m-humidity, also aligned SW-to-NE, which affected the growth of the planetary boundary layer to trigger MCS initiations earlier in time (∼1-2hr on average) compared to Control simulations. The implementation of the dry SM perturbation introduced drier-to-wetter SM gradients along the edges of the perturbed area, and MCS initiations were subsequently preferred on the drier side of those transition zones, with the most common orientation of simulated MCS events embedded within southwesterly flow. These results emphasize the importance of the low-level wind field alignment to organized SM gradients, which suggests that SM heterogeneity can drive MCS initiation related to near-surface atmospheric variable fluctuations as the main mechanism of interaction in weakly forced synoptic environments.

Study of atomic diffusion behavior in diffusion welding of NiTi alloy - based on molecular dynamics

NiTi alloy with nearly equiatomic ratios of Ni and Ti, has a unique shape memory effect and biocompatibility. Atomic diffusion is a determinant factor for the diffusion welding of NiTi alloys joining. In general, the atomic diffusion may be mediated by the temperature, time and pressure and so on. Despite the importance of technology, Ni and Ti atoms’ diffusion mechanism, however, still remains un-elucidated. Few works have investigated the movement rules of atoms from the atomic scale. Molecular dynamics simulations of diffusion welding were performed for 200-800ps to investigate the diffusion process of the NiTi alloy composite plate at temperatures of 1000, 1100, 1200, and 1300K. The results show that the holding temperature had the greatest effect on diffusion, with pressure having the least effect. The diffusion coefficients of NiTi, Ni, and Ti were calculated at temperatures of 1000, 1100, 1200, and 1300K, respectively. The diffusion degree of Ni atoms was higher than that of Ti atoms. The diffusion coefficients of Ni and Ti atoms satisfied the Arrhenius equation, and the diffusion activation energy of Ni atoms was lower than that of Ti atoms. Furthermore, this study demonstrates at the atomic scale that the growth of the diffusion layer at high temperatures follows the parabolic growth kinetics law.

Unveiling Trigonal Anti-Prismatic Structure and Stacking Sequences in InTe.

Polymorphic phases of 2D van der Waals layered materials attract significant research interest due to their diverse properties. There is a growing need to synthesize novel polymorphs and explore their atomic-level structures. In this study, molecular beam epitaxy (MBE) is used to grow indium telluride, a III-VI metal chalcogenide with promising applications, on graphene substrates. Atomic resolution scanning transmission electron microscopy reveals that the grown layers exhibit both the well-known trigonal prismatic structure and a less common trigonal anti-prismatic structure, leading to novel stacking sequences. The stability of this unconventional structure is further analyzed using density functional theory calculations, and its potential topological properties are investigated. These findings indicate that III-VI metal chalcogenides are capable of forming polymorphs with diverse symmetries and topological phases beyond their conventional structures. Furthermore, MBE proves to be a viable method for synthesizing such polymorph.

Facile growth of a heteroepitaxial layer on perovskite oxide surfaces for active and durable fuel cell cathodes

Polycrystalline perovskite oxide particles are promising candidates for cathode materials in solid oxide fuel cells. However, their limited activity and stability pose significant challenges for practical applications. In this study, we demonstrate a novel approach to achieve both high activity and durability in a PrBaCo2O5+δ catalyst through a simple epitaxial layer growth strategy. We found that an amorphous precursor of the highly durable catalyst SmBa0.5Ca0.5CoCuO5+δ can spontaneously adhere to the surface of PrBaCo2O5+δ particles. Upon heat treatment, it grows along the perovskite lattice, forming a heteroepitaxial layer with just a few atomic layers thickness. This heterostructure enhances the operational stability of PrBaCo2O5+δ transforming a 78% decrease over 100 h into a 7% increase. After 100 h, the power output density of the cell with the modified sample is more than 500% higher than that of unmodified PrBaCo2O5+δ. This work presents a new strategy for fabricating heteroepitaxial layers on polycrystalline ceramic catalysts and introduces a pioneering approach for developing high-performance oxygen reduction catalysts and related materials.

Effects of High-Temperature Treatments in Inert Atmosphere on 4H-SiC Substrates and Epitaxial Layers

Silicon carbide is a wide-bandgap semiconductor useful in a new class of power devices in the emerging area of high-temperature and high-voltage electronics. The diffusion of SiC devices is strictly related to the growth of high-quality substrates and epitaxial layers involving high-temperature treatment processing. In this work, we studied the thermal stability of substrates of 4H-SiC in an inert atmosphere in the range 1600–2000 °C. Micro-Raman spectroscopy characterization revealed that the thermal treatments induced inhomogeneity in the wafer surface related to a graphitization process starting from 1650 °C. It was also found that the graphitization influences the epitaxial layer successively grown on the wafer substrate, and in particular, by time-resolved photoluminescence spectroscopy it was found that graphitization-induced defectiveness is responsible for the reduction of the carrier recombination lifetime.

Experimental characterization and similarity scaling of smooth-body flow separation and reattachment on a two-dimensional ramp geometry

The results of an experimental investigation of smooth-body adverse pressure gradient (APG) turbulent boundary layer flow separation and reattachment over a two-dimensional ramp are presented. These results are part of a larger archival smooth-body flow separation data set acquired in partnership with NASA Langley Research Center and archived on the NASA Turbulence Modeling Resource website. The experimental geometry provides initial canonical turbulent boundary layer growth under nominally zero pressure gradient conditions prior to encountering a smooth, two-dimensional, backward facing ramp geometry onto which a streamwise APG that is fully adjustable is imposed. Detailed surface and off-surface flow field measurements are used to fully characterize the smooth-body APG turbulent boundary layer separation and reattachment at multiple spanwise locations over the ramp geometry. Unsteady aspects of the flow separation are characterized. It is shown that the first and second spatial derivatives of the streamwise static surface pressure profile are sufficient to determine key detachment and reattachment locations. The imposed streamwise APG gives rise to inflectional mean velocity profiles and the associated formation of an embedded shear layer, which is shown to play a dominant role in the subsequent flow development. Similarity scaling is developed for both the mean velocity and turbulent stresses that is found to provide self-similar collapse of profiles for different regions of the ramp flow. Despite the highly non-equilibrium flow environment, a new similarity scaling proved capable of providing self-similar turbulent stress profiles over the full streamwise extent of flow separation and downstream reattachment.

The effect of the Zn layer on the microstructural evolution of Al/Cu composite material joints during friction stir spot welding

This study introduced Zn interlayer at the Al/Cu interface to form an Al-Zn-Cu tri-layer composite joint. The growth of the interfacial layer was enhanced by the generation of the liquid phase with increasing rotational speed and heat input during the welding process. Among the phases formed in the Al-Zn-Cu joint, the Cu5Zn8 phase exhibited the highest growth constant, making it the primary phase at the interface. The growth sequence of the Al2Cu phase was found to be between that of the Cu5Zn8 and AlCu phases. As welding progressed, Al2Cu acted as an ‘anchor point’ for the subsequent formation of the AlCu phase and was gradually consumed in the process. No Al4Cu9 phase was observed in the joint.

Effects of the Dynamic Loading Frequency on Performance of the Proton Exchange Membrane Water Electrolysis.

Green hydrogen production via PEM water electrolysis is challenged by fluctuating input power when coupled with renewable energy sources. This study investigates the effects of dynamic loading frequencies on membrane electrode assembly (MEA) performance and durability. We found that higher loading frequencies facilitate the growth of the oxide layer of Ti porous transport layer (Ti-PTL) due to increased duration in the voltage spike region. These thicker and coarser oxide layers directly induce cracks and delamination in the anodic catalyst layers by spontaneously adsorbing an ionomer. These changes negatively impact the interface contact quality and anodic electrochemical active area, ultimately reducing the performance of the MEA, with higher frequencies accelerating this degradation. Additionally, applying a Pt coating to PTL effectively mitigates these adverse effects. This work highlights the importance of dynamic loading studies and reveals that effective management of the Ti-PTL and catalyst/PTL interface is necessary to achieve long-term operational durability of PEM water electrolysis.

Coupling UiO-66 MOF with a Nanotubular Oxide Layer Grown on Ti-W Alloy Accelerates the Degradation of Hormones in Real Water Matrices

Coupling UiO-66 MOF with a Nanotubular Oxide Layer Grown on Ti-W Alloy Accelerates the Degradation of Hormones in Real Water Matrices

Simulation of creep-fatigue crack growth in aluminum alloy layers of hydrogen storage cylinders

ABSTRACT Hydrogen storage cylinders are crucial to hydrogen production and storage systems. During the service of the hydrogen storage cylinders, they undergo frequent hydrogen charging, dwelling, and discharging. The ceep-fatigue problems in the liner of the cylinders typically made of AA6061-T6 should be taken into account. In this paper, the creep-fatigue crack growth experiments on the compact tension specimens of AA6061-T6 are conducted. Based on it, simulations of creep-fatigue crack growth in the liner under six different dwell conditions are performed. Comparative analysis of the stress intensity factor range curves reveals that under the same working conditions, as the dwell time and initial crack depth increase, accelerating the crack growth rate leads to the life decreasing of the liner, thereby hastening the failure of the liner and the overall structure, which should be considered during life assessment.

Sputtered quaternary alloy coating of Fe4CoNiCu for solid oxide fuel cell steel interconnects application

A quaternary Fe4CoNiCu alloy coating is applied on SUS 430 steel substrate for solid oxide fuel cell (SOFC) interconnects application via magnetron sputtering technology. The oxidation behavior of the coated steels is investigated in air at 800 °C. During initial oxidation, Fe and Co in the alloy coating is oxidized preferentially, forming Fe-rich oxide. Ni is oxidized to NiO by inward diffusion of oxygen. Slight Cu diffuses to or near the surface of the oxide scale to form CuO. Some Cu reacts with Fe3O4 to form CuFeO2 inside the oxide scale. The alloy coating is thermally converted into a quaternary spinel coating of (Fe,Co,Ni,Cu)3O4 with a small quantity of CuO existing on the surface and a protective Cr2O3 layer is formed at the steel/coating interface. The (Fe,Co,Ni,Cu)3O4 spinel layer effectively inhibits the growth of Cr2O3 layer and the outward diffusion of Cr. The scale ASR is 13.08 mΩ cm2 at 800 °C after 1680 h oxidation.

Research on the microstructure and mechanism of high content Sn modified A356 alloy

The effect of Sn alloying on the casting structure of A356 aluminium alloy, especially on the morphology of eutectic silicon, is investigated in detail. With the increase of Sn content, the eutectic silicon gradually changed from sheet to fine coral, and the α-Al dendrites are significantly refined. Within the modified eutectic silicon, there are high density crossed stacking faults located in the <111>Si direction. The analysis reveals that these stacking faults are caused by the segregation of Al-Mg-Sn atomic clusters on the {111}Si growth plane, which hinders the stacking of Si atoms on the growth step and induces lateral growth of eutectic silicon. Mg2Sn phase formed by Sn and Mg enrichment will preferentially nucleate and grow in the {111}Si growth layer, which will also hinder the macroscopic growth of eutectic silicon. In this paper, the phenomenon of stacking faults induced by Al-Mg-Sn atomic clusters leading to the eutectic modification is proposed and investigated for the first time.

Data-driven AI for the automated classification of the isothermal heat-treated thermal barrier coatings using pulsed infrared thermography

Abstract Development of reliable age prediction models are crucial in monitoring the formation of oxide layer and degradation of TBC at regular intervals. This study proposes an automated classification of isothermal heat-treated TBC samples using temperature data, which helps in predicting the TBC life and monitoring the TBC degradation. TBC-coated samples are isothermal heat-treated at 1000 °C, and the initial growth of thermally grown oxide is monitored using a non-destructive thermal imaging technique. The proposed study integrates data-driven AI (DAI) models and feature extraction techniques to interpret complex thermal patterns measured from the TBC coating surface. The performance of the proposed classification framework is tested using deep learning and classical machine learning models with different types and window sizes of input data. Input data used for validation are raw experiment data, logarithmic of experiment data, polynomial fit data, and thermal signal reconstruction fit coefficients. The maximum classification performance is obtained with gated recurrent unit with accuracy and F1-score of 89.2% and 89.0%, respectively with raw temperature data as input of window 300. The study demonstrates that the proposed DAI approach effectively predicts the age of thermal barrier coatings under isothermal heat-treatment conditions by correlating the thermal response with coating degradation.

Effect of bias voltage on high-temperature oxidation resistance and electrical properties of Mn–Co coating with metal interconnects for solid oxide fuel cell

Abstract This study investigated the effects of bias voltage on the microstructure, high-temperature oxidation resistance, electrical conductivity, element diffusion, and barrier of chromium poisoning cathode of Mn–Co coating on the surface of SOFCs metal interconnect SUS441 ferritic stainless steel. A series of Mn–Co coatings were prepared by magnetron sputtering technique at different bias voltages (−10, −50, −90 V) and oxidized at high temperatures for 175 h at 850 °C in an air environment. The results showed that the surface of each coating before oxidation exhibited a cauliflower-like morphology, with the crystallinity of the coating increasing with higher bias voltage. After high-temperature oxidation, especially the Mn–Co coatings prepared at −90 V bias, a dense and stable MnCo2O4 spinel structure was formed, which is crucial in inhibiting the growth of the Cr2O3 oxide layer. In addition, the coating also exhibits excellent electrical conductivity (Ea = 0.35 eV), good high-temperature oxidation resistance (1.182 mg cm−2), and a stronger ability to prevent the diffusion of Cr elements.

Growth of Surface Oxide Layers on Dendritic Cu Particles by Wet Treatment and Enhancement of Sinter-Bondability by Using Cu Paste Containing the Particles

Pastes were prepared using dendritic Cu particles as fillers, and a compression die attachment process was implemented to establish a pure Cu joint using low-cost materials and high-speed sinter bonding. We aimed to grow an oxidation layer on the particle surface to improve sinter-bondability. Because the growth of the oxidation layer by general thermal oxidation methods makes it difficult to use as a filler owing to agglomeration between particles, we induced oxidation growth by wet surface treatment. Consequently, when the oxidation layer was appropriately grown by surface treatment using an acetic acid–ethanol solution, we obtained an improved joint strength, approximately 2.8 times higher than the existing excellent result based on a bonding time of 10 s. The joint formed in just 10 s at 300 °C in the air under 10 MPa compression showed a shear strength of 28.4 MPa. When the bonding time was increased to 60 s, the joint exhibited a higher strength (35.1 MPa) and a very dense microstructure without voids. These results were attributed to the acceleration of sintering by the in situ formation of more Cu nanoparticles, which effectively reduced the increased oxide layers in the particles using a reducing solvent.

Reduction of the Threading Dislocation Density in GaSb Layers Grown on Si(001) by Molecular Beam Epitaxy

AbstractThe monolithic integration of III‐V semiconductors on Si emerges as a promising approach for realizing photonic integrated circuits. However, the performance and reliability of epitaxially grown devices on Si are hampered by the threading dislocation density (TDD) generated during the growth. In this study, the efficiency of a structure, combining III‐Sb‐based insertion layers and thermal annealing is evaluated, on the reduction of the emerging TDD in GaSb buffer layers grown on Si(001) substrates by molecular beam epitaxy. the impact of the thickness, composition, and number of the insertion layers is extensively explored. Then a detailed study of the annealing cycles with different conditions is conducted. A record TDD in the low 107 cm−2 for a 2.25 µm GaSb buffer grown on Si(001) is ultimately demonstrated.

Formation of Twin-Free Single Phase β-In2Se3 Layers via Selenium Diffusion into InP(111)B Substrate.

Indium selenide, In2Se3, has recently attracted growing interest due to its remarkable properties, including room temperature ferroelectricity, outstanding photoresponsivity, and exotic in-plane ferroelectricity, which open up new regimes for next generation electronics. In2Se3 also provides the important advantage of tuning the electrical properties of ultrathin layers with an external electrical and magnetic field, making it a potential platform to study novel two-dimensional physics. Yet, In2Se3 has many different polymorphs, and it has been challenging to synthesize a single phase material, especially using scalable growth methods, as needed for technological applications. We recently reported the growth of twin-free ultrathin layers of In2Se3 prepared by a diffusion driven molecular beam epitaxy approach, and twin-free Bi2Se3 layers grown on these unique virtual substrates. In this paper, we use aberration-corrected scanning transmission electron microscopy to characterize the microstructure of these materials. We emphasize features of the In2Se3 layer and In2Se3/InP interface which provide evidence for understanding the growth mechanism that leads to the twin-free and single phase In2Se3. We also show that this In2Se3 layer provides an ideal substrate for growth of twin-free Bi2Se3 with a nearly defect-free interface. This approach for growing high-quality twin-free single phase two-dimensional crystals using InP substrates is likely to be applicable to other technologically important materials.