Scale Layer Research Articles

Исследование жаростойкости металла покрытия, полученного наплавкой порошковой проволокой 10Г7М3С2АФТЮ

The processes in petrochemical industries often take place at high temperatures, which determines the use of materials with high heat resistance for parts and components of technological equipment in this industry. When exposed to high temperatures, scale is formed on the metal surface, which leads to deterioration of its mechanical and operational properties. Therefore, the problem of improving the performance of parts operating under the conditions when they do not only wear out but also have to endure high temperatures is of great practical importance. Heat resistance of 10G7M3S2AFTYu-coated steel was studied under the temperature of 900°С. It was established that the main increase in the mass of scale for this steel occurred in the first hours, and later this dependence was almost straight-line. The average weight gain of the metal scale of such a coating at 900°С was 0.0035 kg/(m2·h). The presence of selective intercrystalline high-temperature interaction was determined, the products of which were carbides, oxides and nitrides of active alloying elements along with simple iron and manganese oxides. It was shown that the basis of the surface layer of the 10G7M3S2AFTYu metal scale was formed from compounds Fe2O3, Fe3O4, VO, MoO2 that have average protective properties, as well as Fe1,26Mn0,74O3, Мn2О3, SiC, VNi0,81, AlC3N3 that have relatively high protective properties. It was concluded that flux-cored wire 10G7M3S2AFTYU could be used for surfacing parts and units of heat transfer systems.

Thermodynamic Prediction and Experimental Verification of Multiphase Composition of Scale Formed on Reheated Alloy Steels

The structure, phase, and composition of scale formed on a continuously cast steel slab during reheating depend on intrinsic factors (steel chemistry, microstructure, and as-cast surface condition) and extrinsic parameters (temperature, time, composition, and velocity of combustion gas atmosphere). The scale that forms on a slab normally has several layers with differing compositions and phases and knowledge of this scale structure is important in subsequent descaling and hot rolling processing steps. Formation of multiphase scale structures on steel during high temperature oxidation in reheat furnace proceeds according to a local thermodynamic equilibrium, while thickness of layers depends on kinetic conditions (mostly by diffusion). In this study, the local thermodynamic equilibrium conditions through the scale layer were simulated using different oxygen/steel ratios, which mimicked the conditions for scale formation at the external, internal, and sublayer oxide region at metal/scale boundary. Experiments were performed in a simulated combustion atmosphere using typical industrial reheat time/temperature conditions. The phases that developed in layered scale structure were documented using SEM/EDX and Raman spectroscopy. The predicted scale compositions and phases were in good agreement with the experimental results for studies with Mn and Si-alloyed carbon steel, Cr-alloyed ferritic, and Cr, Ni-alloyed austenitic steels.

Adsorption of Se on Cu(1 0 0) and formation of two-dimensional copper selenide layer

In order to understand the adsorption process of selenium (Se) and Se-based molecules on noble metal surfaces, we report here on the properties of a thin film of Se on Cu(1 0 0) substrate. The deposition was carried out by incubating of a clean Cu(1 0 0) surface into Na 2 Se solution under controlled conditions. The film properties were analysed as a function of the annealing temperature of the sample, using Low Energy Electron Diffraction (LEED) and photoemission techniques. A progressive structural transition from disordered thick layer to a two-dimensional Copper Selenide CuSe thin layer is obtained upon the thermal treatment. Our study proves that a large scale, well-ordered, and highly-stabilized metal chalcogenide layer can be produced for promising use in potential applications.

Moth wings are acoustic metamaterials

Metamaterials assemble multiple subwavelength elements to create structures with extraordinary physical properties (1-4). Optical metamaterials are rare in nature and no natural acoustic metamaterials are known. Here, we reveal that the intricate scale layer on moth wings forms a metamaterial ultrasound absorber (peak absorption = 72% of sound intensity at 78 kHz) that is 111 times thinner than the longest absorbed wavelength. Individual scales act as resonant (5) unit cells that are linked via a shared wing membrane to form this metamaterial, and collectively they generate hard-to-attain broadband deep-subwavelength absorption. Their collective absorption exceeds the sum of their individual contributions. This sound absorber provides moth wings with acoustic camouflage (6) against echolocating bats. It combines broadband absorption of all frequencies used by bats with light and ultrathin structures that meet aerodynamic constraints on wing weight and thickness. The morphological implementation seen in this evolved acoustic metamaterial reveals enticing ways to design high-performance noise mitigation devices.

АКТУАЛЬНОСТЬ МОДЕЛЕЙ ЗАГРЯЗНЕНИЯ ДЛЯ ДИАГНОСТИКИ СОСТОЯНИЯ ПЛАСТИНЧАТЫХ ТЕПЛООБМЕННИКОВ

The article analyzes various theoretical approaches to describing the processes of formation of scale layers on the working surfaces of heat exchangers. The main tasks include analyzing existing models of contamination of heat exchange channels, determining the main mechanism of salt deposition on the heating surface of plate heat exchangers of heat supply systems, determining the main factors that determine the intensity of salt deposition on the working plate in accordance with the dynamics of heat and hydraulic processes in heat exchange channels formed by corrugated plates, as well as forming trends for further research. The article presents the main results of research devoted to the study of contamination processes on heating surfaces. Inaccuracies in the proposed approaches to describing the nature of the formation of salt deposition layers are identified. By generalizing existing approaches to the mathematical description of pollution processes, the main assumptions are revealed when describing the processes of salt deposition on working plates. A hypothesis is proposed about the influence of the location of channels relative to the inlet pipe on the uniformity of the flow distribution between parallel channels in the device. There is a fairly large gap between the existing computational methods for modeling pollution processes and the actual distribution of scale layers during the operation of heat exchange equipment of heat supply systems

Immunohistochemical detection of sulfhydryl oxidase in chick skin appendages and feathers suggests that the enzyme contributes to maturation of the corneous material

Maturation of the corneous material of feathers, scutate scales, claws and beak is a special case of hard cornification since it mainly derives from the accumulation of small feather corneous beta proteins (FCBPs) of 9–12 kDa with a central beta-pleated sheet region, formerly indicated as feather beta keratins. FCBPs contain a relatively high amount of cysteines that likely form numerous –S-S- in the corneous material of these skin appendages. The present immunocytochemical study shows that sulfhydryl oxidase and FCBPs are associated in the differentiating keratinocytes and corneous layers of the epidermis, scales, claws, beak and barb-barbule cells during chick development. The enzyme appears localized in pre-corneous and corneous layers and in differentiating barb-barbule cells where it likely determines formation of -S-S- bonds. This maturation transformation completed in corneous layers of scales, beak, claws and feathers determines increase of hardness and mechanical resistance that, in feathers, is needed for protection and sustaining flight. The process of cornification in chick skin appendages and feathers is discussed in relation to the general process of formation of hard corneous material in vertebrate skin appendages. This occurs by the association of intermediate filament proteins (IFKs, formerly indicates as alpha-keratins) and keratin-associated proteins (KAPs) or CBPs.

The effect of systematic variation of Ni:Co ratio on the oxidation behaviour of γ-γ′ Ni-Co-Al-Ti-Cr alloys

The effect of Co:Ni ratio on the oxidation performance of γ-γ′ alloys based on the (Ni,Co)75Al5Ti5Cr15 system (at.%) was investigated. Seven model superalloys of Co concentration 0, 9, 19, 28, 38, 47 and 56 at.% underwent isothermal oxidation in air at 800 °C using both box-furnace exposure (1000 h) and thermogravimetric analysis (100 h). Following 1000 h oxidation at 800 °C, alloys containing 28, 38 and 47 at.% Co exhibited a flatter, more compact external scale and Cr2O3 layer as well as reduced oxygen ingress compared with alloys of lower Co content. The alloy containing 47 at.% Co exhibited two distinct morphologies.

Nanofiltration scaling influenced by coexisting pollutants considering the interaction between ferric coagulant and natural organic macromolecules

The aim of present study was to evaluate the effects of the interaction between ferric coagulant and natural organic macromolecules (NOMs) on gypsum scaling during nanofiltration. Both crystallization process and membrane flux behavior were taken into consideration. Although bulk crystallization could be enhanced by ferric coagulant and humic acid (HA), it was hindered by the mixture of these coexisting pollutants due to their interaction in aqueous solution. According to the variation in zeta potential and the prediction with the NICA-Donnan model, Fe3+ could compete with Ca2+ for binding to HA, while the interaction between coagulant and HA reduced the concentration of active ingredients in the coagulant which could enhance scaling development. FTIR-ATR spectra showed that ferric coagulant and NOMs could promote the attachment of each other on membranes. Unlike bulk crystallization, surface crystallization could be enhanced by the combination of HA and ferric coagulant on nanofiltration membranes. Therefore, both ferric coagulant and HA could increase scaling layer resistance, and there were synergistic effects on aggravating the flux decline between them. Moreover, the effects of salt saturation and system pressure on coagulant-influenced gypsum scaling in nanofiltration were also investigated. Modified Hermia’s models were applied to theoretically verify the membrane fouling mechanisms. In addition, ferric coagulant was found to decrease the retention efficiency of ions and atrazine by nanofiltration membranes by weakening the steric hindrance.

Fouling formation and under deposit corrosion of boiler firetubes

The most severe problem in firetube boilers is fouling formation and under deposit corrosion (UDC) on the tube surfaces, leading to water or steam leakage into the fire–side and emergency shutdowns. In this work, fouling propensity and UDC mechanism on the outer surfaces of firetubes of seawater boilers are investigated. The novelties of this work are characterization of a composite fouling layer, including corrosion scales and inorganic deposits, and assessment of pH–phosphate convergence to control the fouling and UDC phenomena on the outer surfaces of firetubes of such boilers. For this aim, two industrial 3–pass seawater steam–boilers in the pressure range of 200 psi were monitored over a period of six years. After periodical shutdowns, the chemical composition of deposits on the outer surfaces of firetubes was inspected by XRF and XRD patterns. During the working period of steam–boilers, pH, phosphate concentration and dissolved oxygen level of boiler water were determined. The results revealed that the outer layer of corrosion scales has been formed mainly from carbonates and hematite minerals, while γ-FeOOH was the main component of the inner layer. Moreover, using phosphate congruent control (PCC) diagrams the risk of fouling formation and UDC propagation is decreased and the predictive maintenance of such boiler systems will be improved.

Internal Oxidation Behavior of Fe-33Ni-19Cr Alloy

Fe-33Ni-19Cr alloy is the Ni-based alloy used at high temperature condition due to its excellent ability to form protective oxide layer at high temperature. Fe-33Ni-19Cr alloy was undergo a series of solution treatment process to vary the grain size of the alloy. The Fe-33Ni-19Cr alloy was solution-treated at 3 different temperature, namely 1000°C, 1100°C and 1200°C, for 3 hours soaking time, followed by water quench. The solution-treated alloys were then experienced an isothermal oxidation test at 900°C for 500 hours in laboratory air. The oxidized Fe-33Ni-19Cr alloy were characterized in terms of phase analysis and cross-sectional analysis using XRD and SEM-EDX to investigated the effect of different grain size alloy to the oxidation behavior. The solution treatment process was produced varies grain size of Fe-33Ni-19Cr alloy. The solution-treated Fe-33Ni-19Cr alloy at 1000°C exhibited the fine grain size, while solution-treated Fe-33Ni-19Cr alloy at 1200°C produced a coarse grain size. The oxidized Fe-33Ni-19Cr alloy recorded a formation of several oxide phases consists of Cr-rich oxide, Fe-rich oxide, Ti-rich oxide and spinel oxides structure. The cross-sectional analysis displays a several layer of oxide scales formed on the alloy surface with evidence of internal oxide penetration through the grain boundary area.

Using a dual-tree complex wavelet transform for denoising an optical coherence tomography angiography blood vessel image

High image quality is of great importance for precise diagnosis and therapeutics of eye disease in clinic. A human retina OCT angiography (OCTA) image can be extracted from multiple OCT B-scans to visualize the distribution of blood vessels. However, OCTA suffer from the degeneration of image quality due to inherent Gaussian noise of the OCT system while the blood vessel’s signal is extracted. The degeneration of the noise in OCTA image will be more conducive to the evaluation of abnormal and normal blood vessels in the human eye. To precisely assist diagnosis and therapeutics in clinic by reducing the Gaussian noise in the OCTA image, an OCTA image denoising method is proposed based on the dual-tree complex wavelet transform and bilateral shrinking Bayes frame. Initially, OCTA images are extracted from the raw data based on the optical microangiography algorithm. Then, the image is decomposed into the wavelet domain using the dual-tree complex wavelet transform. The signal and noise among different wavelet scale layers are separated on the basis of the Bayesian posterior probability. Finally, the inverse wavelet transform is employed to reconstruct the denoised image. Through the noise reduction process of the algorithm, the PSNR and CNR of the OCTA image are increased by 49.15% and 47.91%, respectively. According to the results, the wavelet transform can effectively separate the blood flow signal and noise in processing the OCTA signal, which will provide an effective image processing method for the clinical evaluation requiring high-quality OCTA images.

Atmospheric air oxidation of 9Cr-1Mo steel: Depth profiling of oxide layers using glow discharge optical emission spectrometry

Modified 9Cr-1Mo steel is used as a steam generator tube material of fast breeder reactors. Although air oxidation behavior of modified 9Cr-1Mo steel is qualitatively studied, the exact nature of oxide layers formed across the thickness of the film from nanometer to several microns depth is not studied systematically. In this work, the oxide scales formed on modified 9Cr-1Mo steel on air oxidation at 650 °C up to 200 h duration using Glow Discharge Optical Emission Spectrometer (GDOES) with depth profiling, X-ray Diffraction (XRD), Laser Raman Spectroscopy (LRS) and Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy(SEM-EDS) were investigated. The weight changes increase and did not follow the conventional parabolic kinetics. The top layer of the oxide scales after 25 and 50 h air oxidized samples comprised of MnCr2O4, Cr2O3 and Fe, Cr spinel oxides; however, the oxide scales of 100 and 200 h oxidized samples mainly consist of hematite. GDOES analysis indicated the presence of Fe rich oxides on the top surface of the oxide films in the case of 100 and 200 h oxidized samples. For 25 and 50 h samples, the oxide layer consists of manganese oxides in addition to Cr and Fe spinel oxides. All the samples consist of Fe and Cr spinel oxides at the interface of the oxide and alloy surfaces. SEM analysis indicated the formation and growth of oxides from small crystal and flakey type morphology to fully grown bigger size particles as the oxidation progresses. GDOES technique provided useful insights into the nature of oxide films through the thickness of the film. The intensity depth profiles of the oxide layers obtained by GDOES-DiP (Differential Interferometric Profiling) is complemented by other techniques such as XRD, LRS and SEM-EDS.

A fusion method for infrared and visible images based on iterative guided filtering and two channel adaptive pulse coupled neural network

ABSTRACT In order to make full use of the important features of the source image, an infrared and visible fusion method based on iterative guided filtering and two-channel adaptive pulse coupled neural network is proposed. The input image is decomposed into basic layer, small scale layer and large scale layer by an iterative guide filter. The base layer is fused by combining pixel energy and gradient energy. Then we fuse the large scale layer and small scale layer via two-channel adaptive pulse coupled neural network. The fused image is obtained by the inverse mixing multi-scale decomposition method. Experimental results show that compared with other multi-scale decomposition methods, the proposed method can better separate spatial overlapping features, and preserve more detailed information in fused image, effectively suppress artefacts.

Opinion-unaware blind picture quality measurement using deep encoder–decoder architecture

Recently, deep-learning-based blind picture quality measurement (BPQM) metrics have gained significant attention. However, training a robust deep BPQM metric remains a difficult and challenging task because of the limited number of subject-rated training samples. State-of-the-art full-reference (FR) picture quality measurement (PQM) metrics are in good agreement with human subjective quality scores. Therefore, they can be employed to approximate human subjective quality scores to train BPQM metrics. Inspired by this, we propose a deep encoder–decoder architecture (DEDA) for opinion-unaware (OU) BPQM that does not require human-labeled distorted samples for training. In the training procedure, to avoid overfitting and to ensure the independency of the training and testing samples, we first construct 6,000 distorted pictures and use their objective quality/similarity maps obtained using a high-performance FR-PQM metric for distorted pictures as training labels. Subsequently, an end-to-end map between the distorted pictures and their objective quality/similarity maps (labels) is learned, represented as the DEDA that takes the distorted picture as the input and outputs its predicted quality/similarity map. In the DEDA, the pyramid supervision training strategy is used, which applies supervised learning over three scale layers to efficiently optimize the parameters. In the testing procedure, the quality/similarity maps of the testing samples that can help localize distortions can be predicted with the trained DEDA architecture. The predicted quality/similarity maps are then gradually pooled together to obtain the overall objective quality scores. Comparative experiments on three publicly available standard PQM datasets demonstrate that our proposed DEDA metric is in good agreement with subjective assessment compared to previous state-of-the-art OU-BPQM metrics.

Hierarchical saliency mapping for weakly supervised object localization based on class activation mapping

Weakly supervised object localization is a basic research in the field of computer vision. In this paper, a hierarchical saliency mapping network for object localization is proposed and designed to avoid missing detailed information of potential object. Based on the classical convolution network, we remove the fully connected part and add multiple information extraction branches. The network extracts information from convolution layers of different scales to generate Hierarchical Saliency Map. Hierarchical Saliency Maps that include Hierarchical-Class Activation Map and Hierarchical-Spatial Pyramid Saliency Map fuse deep-level features and low-level features to locate object. The datasets used for testing are Caltech-UCSD Birds 200, Caltech101 and ImageNet. Compared with Class Activation Map and Spatial Pyramid Saliency Map, the localization accuracy has been improved. This method can be used for fine-grained classification, object tracking and other fields.

Study on the structure and optical imaging characteristics of an all-fiber OCT probe

Aiming at small size, compact structure, strong light-collecting ability, and low loss requirements of optical coherence tomography (OCT) probes used for human body detection, we design an all-fiber OCT probe, which is composed of a single-mode fiber and a multimode fiber (MMF) with spherical lens. By measuring the optical performance of these probes, we found that, when the length of the MMF of the composite probe is 372 μm and the diameter of the ball lens is 300 μm, it has the strongest focusing effect and a large reflected light signal receiving angle. Furthermore, the OCT probe studied was applied to a self-made spectral domain OCT system for validation. The results show that our probe can obtain a clear two-dimensional grayscale image of three layers of glass and fish scales, i.e., the probe manufacturing scheme can be used. Furthermore, it meets the needs of miniature OCT probes, which provides more effective options for measuring human blood vessels or other biological tissues.

The effects of membrane surface wettability on pore wetting and scaling reversibility associated with mineral scaling in membrane distillation

The application of membrane distillation (MD) to hypersaline wastewater treatment is constrained by mineral scaling. Although tuning membrane surface wettability has been recently used to mitigate membrane scaling in MD, the effectiveness of this strategy for different scaling types has not been well understood. Furthermore, two important factors that determine the performance of MD membrane, namely wetting resistance and scaling reversibility, have been rarely discussed in MD scaling studies. In this work, we investigated the effects of membrane surface wettability on pore wetting and scaling reversibility associated with gypsum and silica scaling in MD. We challenged a hydrophobic membrane, a Janus membrane with a hydrophilic top layer, and a superhydrophobic membrane with gypsum- and silica-containing feed solutions. Compared to the hydrophobic and Janus membranes, the superhydrophobic membrane delayed scaling induction and enhanced scaling reversibility in gypsum scaling tests, in which the total water recoveries achieved by the tested membranes were inversely correlated to membrane surface hydrophilicity. Also, the superhydrophobic membrane uniquely resisted pore wetting induced by gypsum scaling, probably by preventing feedwater intrusion into membrane pores. In contrast, altering membrane surface wettability was ineffective to improve either scaling reversibility or total water recovery under silica scaling, which did not induce pore wetting for all the tested membranes. We attributed the differences in scaling behaviors as well as the varied responses to membrane surface wettability between gypsum and silica scaling to their distinct scaling mechanisms. The oriented and intrusive gypsum crystallization resulted in pore deformation and discrete crystals that could be detached by physical cleaning. In contrast, the slow kinetics and lack of orientation of silica polymerization formed a thin and crosslinked scaling layer, which was not intrusive but firmly attached to the membrane surface. The results of our study provide valuable insights on the interplays among membrane surface wettability, scaling type, and membrane performance in MD desalination, and suggest that the development of scaling mitigation strategies in MD should be tailored to the varied mechanisms of different scaling types.

Quantitative µ-CT Analysis of Scale Topology Formed During Oxidation of High SiMo Cast Iron

High SiMo cast iron components in automotive exhaust systems are exposed to high-temperature oxidation over time. Quantitative analysis of formed oxide scale is therefore important for the assessment of a component durability. The brittle nature of multilayered scale and thermal stress limits capture of a true topology using traditional 2D destructive cut and polish methods. In this study, nondestructive high spatial-resolution 3D µCT analysis was performed on 2.90-mm-diameter oxidized specimens which permitted direct observation with 3.5 µm pixel resolution. The specimens were oxidized in three sequential time steps for a total 100 h at 700 °C and 800 °C in air and combustion gas atmospheres. A MATLAB-coded algorithm was used to quantify the topology, thickness variation in internal and external scale layers, and scale/metal interface unevenness. Scale topology was linked to oxidation temperature and gas atmosphere. A water vapor environment increases scale/metal interface unevenness and scale layer thickness irregularity which were related to an accelerated oxidation rate.

Silica scaling of reverse osmosis membranes preconditioned by natural organic matter

Reverse osmosis (RO) membranes were preconditioned in this study with humic acid, sodium alginate, or bovine serum albumin, and subsequently examined for silica scaling using the water matrix representative of concentrated brackish groundwater. The results suggested that water matrix combined with organic foulants affected silica scaling. High ambient pH favored the moderate silica ionization and thus the silica homogeneous polymerization to potentially form low molecular weight silica oligomers. The resulting scaling layer was dense and highly impermeable. Under the high Ca proportion at a given hardness, membrane scaling was enhanced through the Ca-induced silica scaling and the formation of intermolecular bridges between adjacent silica species. In contrast, high Mg hardness may facilitate the sustainable growth of silica oligomers to form the ringed high molecular weight oligomers by reducing the required energy for chain deformation. The deposition of these oligomers caused a loose scaling layer with reduced hydraulic resistance to water permeation. During the scaling tests under similar water matrix, the membranes slightly fouled by organics suffered severe flux decline due to an available space provided by the pre-existing organic fouling layer for subsequent silica scaling.

Examining the effect of ionic constituents on crystallization fouling on heat transfer surfaces

The effect of the most abundant constituents in potable water on fouling of aluminium surface has been studied systematically in this work. The role of sodium, chloride, magnesium and sulphate ions and total organic carbon (TOC) on the fouling kinetics and morphology was assessed using a once-through open flow cell. The findings showed that the fouling resistance to heat transfer increases with the concentration of chloride and sodium. A complex influence of magnesium was found on the scaling process, varying between inhibition and promotion of scale formation depending on the concentration. At high concentrations of Mg2+, the formed scale layer consists of needle-like aragonite coated by a crust of magnesium deposits. The inhibitory performance of sulphate SO42− was found to be insignificant when compared with Mg2+ under similar conditions. Even though it is undesirable in potable water, inhibition efficiencies of TOC were 31.3% and 47.9% at concentrations of 2 and 4.3 mg/L respectively. The morphology observations illustrated that the presence of TOC produces a rough scale layer.