Core-shell structured FeSiBCCr@SiO2 amorphous soft magnetic composites (ASMCs) with tunable insulating layer thicknesses have been designed and fabricated by the powder metallurgy method. The growth ...process of the coatings obtained via the sol-gel method has been systematically studied based on the analysis of the growth mechanism and the insulating layer thicknesses calculated by a modified method. In the powder-coating process using small quantities of tetraethyl orthosilicate (TEOS) (0.025–0.1 mL/g), a relatively uniform insulating layer is formed on the surface of the powders. Increasing the TEOS concentration further (0.25–1 mL/g) greatly enhances the reaction kinetics of the hydrolysis and condensation reactions. Consequently, the SiO2 shells of the amorphous powder rapidly grow in thickness and also generate aggregates. The evolution of the thickness of the coatings under different growth conditions also corresponds to the variation of the magnetic performance of the ASMCs. The ASMCs with an appropriate SiO2 insulating layer exhibit stability at high frequencies and significantly lower the contribution of eddy current to the total loss. Conversely, a thick insulation layer results in a high fraction of the non-magnetic phase and consequently enhances the hysteresis loss. Thus, an enhanced magnetic performance of the FeSiBCCr ASMCs can be achieved by adjusting the TEOS concentration (0.025–0.1 mL/g) or the thickness of the SiO2 insulating layer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Surface coating on metal substrates has remained a difficult challenge for researchers due to the conflicting requirements for different properties. In recent years, due to their mechanical, thermal, ...electrical, and tribological properties in many advanced engineering applications, functionally graded coatings (FGCs) have become fascinating materials for researchers worldwide to obtain coatings with specific requirements. FGCs are a novel type of traditional composites in which phases are not equally distributed to form a smooth gradient structure; thus, gradient coatings have shown a new research path. Therefore, this paper critically reviews the different FGC processing techniques by describing the fundamental problems and potential of these processes based on existing literature. Additionally, this research presents the most important potential applications and future challenges for gradient coatings. Consequently, the results expected from the paper are considered a guideline that enables the interested in this field to make informed decisions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
High cutting temperatures are induced in the dry cutting process of Inconel 718 for its high hardness 439 HBW and low thermal conductivity 13.4 W/(m K). Due to its thermal barrier effect and ...antifriction effect, the TiAlN coatings have been deposited on carbide tools with various coating thicknesses for dry turning Inconel 718. However, the influences of TiAlN coating thickness on cutting temperature of dry turning Inconel 718 were not investigated in details. In this research, PVD TiAlN tools with coating thickness 1 μm and 2 μm were fabricated and characterized. The cutting temperatures and cutting forces of dry turning Inconel 718 were measured within cutting speed ranges 30−120 m/min. Average friction coefficient at coated tool-chip interface was calculated to analyze the coating antifriction effect. Thicker coating induced large temperature increment of 19−30 °C compared with thinner coating within cutting speed ranges of 30−120 m/min in initial tool wear stage. The results showed that PVD TiAlN coated tool with coating thickness 1 μm was more suitable for dry turning Inconel 718 within cutting speed ranges 90−120 m/min by obtaining better coating antifriction effect and lower cutting temperature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, a low carbon material of γ-dicalcium silicate (γ-C2S) was examined, with an emphasis on the properties influenced by its particle packing and water coating thickness (WCT). Differences ...in morphology and reactivity from that of cement particles render γ-C2S particles have different particle packing behavior and water film surrounding each particle. However, limited research has been conducted on it to deepen the understanding of γ-C2S-based materials. To fill this gap, the wet packing density of γ-C2S particles was measured and the WCT was varied at different water to solid ratios. At each WCT, the carbonated γ-C2S samples were characterized by techniques of X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) consistently. Experimental results revealed little early strength gain when the WCT exceeded a certain value. Moreover, a critical carbonation depth was identified. Below the critical depth, the amounts and characteristics of carbonation products dominated, whilst above the critical depth, the strength gain was influenced by CO2 diffusion rate. An optimal WCT exists for achieving the highest strength and CO2 uptake. This work shall advance the development of low carbon γ-C2S-based materials from the perspective of particle packing.
•The packing density of γ-dicalcium silicate particles was measured by wet method.•The water coating thickness and water film thickness of the mixtures were measured.•Advanced microstructural and chemical characterization techniques were employed.•A critical carbonation depth was identified to distinguish the drivers of strength gain.•An optimal water coating thickness exists for the highest strength and CO2 uptake.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Emittance of absorber coatings dictates radiative heat loss from solar thermal receivers.•A measurement method for high-temperature thermal emittance was developed.•Pyromark 2500 ...emittance had a strong thickness and temperature dependence.•Thicker coatings have an emittance with weaker temperature dependence.•Inner coating and substrate material impact effective emittance of samples.
The emittance of solar absorber coatings is a crucial parameter that determines the radiative heat loss from concentrating solar thermal (CST) receivers. However, measuring emittance of CST coatings at typical operating temperatures (up to 800℃) is technically challenging. Currently there is no available data on the effect of coating thickness and degradation on emittance at these temperatures. We develop a method for measuring emittance at high temperatures. We compare emittance measured at ambient temperature and temperatures up to 800℃ for Pyromark 2500 with coating thickness (from 10 µm to 80 µm). We found that the emittance of Pyromark increases with coating thickness, particularly for wavelengths below 8 µm. In thin coatings, this trend is attributed to the contribution of materials within coating (oxide layers or the substrate) to the total emissive power received by the detector. The total emittance of Pyromark increases monotonically with temperature, with a steeper increase for temperatures below 400℃ and for thinner coatings. This study reveals the significance of measuring emittance at temperatures representative of the operating temperatures of receivers rather than at room temperature. The difference in the estimated emission loss for emittance measurements at room temperature and 800℃ can be as large as 10%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Brittle coatings are often used to protect underlying ductile substrates from damage. Recent experimental observations show that the fracture of a brittle coating can cause the micro-cracking of the ...ductile metal substrates, threatening the safety and reliability of engineering structures. The cracking mode of the substrates is unclear and the corresponding mechanism remains poorly understood. In the present work, by performing room-temperature uniaxial tension experiments with a 10−4 s−1 straining rate, we have observed cleavage cracking in ductile-metal substrates (pure iron, AISI 1020 steel and brass) coated with WC-10%Co-4%Cr. Theoretical analysis reveals that the cleavage cracking is the result of brittle coating and its fracture, which synergically inhibit the local plastic deformation of the underlying substrate via two mechanisms. One is to restrain the dislocation nucleation and mobility near the interface of the substrate. The other is to bring a local high strain rate loading to the substrate, due to fast crack propagation in the brittle coating. The coupling of two effects leads to the nucleation of cleavage crack in the normally ductile substrates and causes significant loss in their ductility. This detrimental effect will be much more pronounced with the increase in the coating thickness. The findings shed new light on the failure mechanisms of brittle coating-metal substrate and provide guidelines in the material design of such systems.
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The effects of multiple factors on the coating process in a top-spray fluidized bed coater were systematically investigated. The intra-particle coating variability could be assessed by the SEM ...measurement. Fluidizing gas temperature (0.5–0.9, normalized by the boiling point of water), injection velocity (0.115–0.397 m/s) and concentration (2.1–5.2 wt%) of the coating liquids, atomizing pressure (1.0–3.0 bar) and nozzle height (378 and 470 mm) were found to impact particle agglomeration, coating efficiency and thickness dramatically. Their impact trends and mechanisms were analyzed in detail. The effect of the particle size (0.22–1.26 mm) on particle agglomeration behavior was highlighted. Critical injection velocities and the corresponding agglomeration ratios were experimentally determined. Finally, it was established that there were no universal optimum conditions for the spray coating process, and they can be experimentally determined according to the attributes of interest.
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•Evaluating the coating thickness by theoretical calculation and SEM measurement.•Establishing SEM measurement to assess the intra-particle coating variability.•Investigating the effects of multiple factors on the coating process.•Determining critical spray rates and agglomeration ratios for six particle sizes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To investigate the effects of coating properties on the antiviral ability of architectural coatings, calcite and diatomite were selected as fillers. Three types of architectural coatings with ...different pore structure characteristics and surface properties were prepared with a 502 styrene-acrylic emulsion and vinyl acetate-ethylene (VAE) emulsion. The surface pore structure, pore distribution and surface charge of the architectural coatings were analyzed by field-emission–scanning electron microscopy (FE-SEM), mercury porosimetry and zeta potential analysis, respectively. The porosity of the diatomite coatings was approximately 2.5 times that of the calcite coating. The two diatomite coatings with different emulsions had similar pore structures and broad pore size distributions. The zeta potentials of the 502 and VAE diatomite coatings were −66.46 mV and −13.08 mV, respectively. Measurements of the antiviral activity toward viruses (bacteriophage φA039 and bacteriophage MS2) of the architectural coatings revealed that the diatomite coating had stronger antiviral activity than calcite coating, and the antiviral activity of diatomite coating was linearly related to its thickness. The diatomite coating can make the virus lose its infectivity through adsorption, and finally make the virus inactivity naturally in the pores. The antiviral performance of the diatomite coating was improved by increasing the size of virus, enhancing the hydrophilicity of the coating, and decreasing the electrostatic repulsion between the virus and the coating. The results showed that porous coatings with broad-spectrum antiviral activity could be prepared according to the characteristics of both viruses and coatings.
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•The architectural diatomite coating has antiviral activity.•The properties of virus and coating affect antiviral activity.•Providing the theoretical basis for the design of antiviral architectural coating.•Reducing the risk of virus transmission by passive adsorption.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Owing to the advantages of non-line-of-sight deposition，the aluminide coating preparation technology is widely used on key hot-end components of gas turbines， and can prepare oxidation-resistant and ...corrosion-resistant aluminide coatings on the outer surface and inner cavity surface of the components.The microstructure of the coating is the key factor affecting its service performance，but how to adjust the microstructure of the aluminide coating to obtain a coating with ideal performance is a difficult problem in current research.Aiming at this problem， the effect of temperature， a key preparation parameter， on the microstructure of aluminide coatings was studied in this work.Firstly， aluminide coatings at different deposition temperatures were prepared on the surface of Mar-M247 nickel-based superalloy by chemical vapor deposition(CVD).Then， the microstructure， phase composition and distribution of alloying elements in the aluminide coating were analyzed by scanning electron microscope (SEM)， X-ray diffracto
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•Silane was chemically bonded onto Ni-rich NCM with self-limited thickness.•The silane coatings enhanced cycle performance of the CAMs.•The CAMs show improved environmental moisture ...repellency.
Intimate conformal coating with well-controlled thickness and rational-designed composition could work as an artificial cathode electrolyte interphase (CEI) to greatly enhance the cycle stability, moisture tolerance and even kinetics performance of Ni-rich layered oxides (NROs). While complicated treatment is usually required in coating thickness control. Inspired by the amphipathicity and monolayer self-assembling properties of silane coupling agent, herein two kinds of silanes with short hydrophobic functional group, allyltrimethoxysilane (ALTS) and propyltrimethoxysilane (PRTS), are adopted in NRO modification. We find that the silanes could form a conformal coating with self-limited thickness controlled by its reaction with the inevitable –OH or lithium residues on NRO surface. The optimal material, CGAP, not only shows enhanced cycle stability and rate performance, but also impressive moisture tolerance. It retains 93.9% of its capacity in 200 cycles at 25°C, and a high reversible capacity of 192.8 mAh g−1 even after 7 days of exposure in the environment with 60% humidity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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