Oriented silicon steel is vital for power transformer cores, while the high-temperature annealing process limits the industrialization of environmentally friendly coatings on the surface. In this paper, the high-temperature binders Al(H2PO4)3 solution and silica sol were introduced innovatively. They condensed into macromolecular polymer chains, network structures and SiO2 particles at high temperatures, providing high-temperature stability and adhesion. The influence of types of silica sol, additives and functional fillers on the corrosion resistance of the coating was studied. The prepared environmentally friendly inorganic insulating coating for oriented silicon steel has excellent corrosion resistance after curing at 475 °C and annealing at 800 °C, which was matched with the currently rolling process of oriented silicon steel. The salt-spray resistance can last for more than 24 h and up to 72 h.
This research proposes using a hybrid core consisting of foam metal and a ceramic tile to enhance the impact resistance of the sandwich construction. We assess the impact response of such an enhanced sandwich under a low-velocity drop-hammer load. Two thicknesses and three positions of the ceramic tile were considered. The low-velocity impact experiment was performed with a 16 mm hemispherical hammerhead and an impact energy range of 30–70 J. The results indicate that the ceramic tile significantly increases the impact resistance of the sandwich. A sandwich with a ceramic tile in the middle of the aluminum foam core had the highest peak force, perforation resistance, and energy absorption. Moreover, the performance was better for the thicker ceramic tiles, and the different damage patterns of the post-mortem sandwiches were analyzed. The underlying mechanisms of enhanced performance are discussed schematically in detail for the sandwiches. These results indeed showed that this proposed sandwich construction could be considered as a potential candidate in high-performance protective component.
Ultralight sandwich constructions with corrugated channel cores (i.e., periodic fluid-through wavy passages) are envisioned to possess multifunctional attributes: simultaneous load-carrying and heat dissipation via active cooling. Titanium alloy (Ti-6Al-4V) corrugated-channel-cored sandwich panels (3CSPs) with thin face sheets and core webs were fabricated via the technique of selective laser melting (SLM) for enhanced shear resistance relative to other fabrication processes such as vacuum brazing. Four-point bending responses of as-fabricated 3CSP specimens, including bending resistance and initial collapse modes, were experimentally measured. The bending characteristics of the 3CSP structure were further explored using a combined approach of analytical modeling and numerical simulation based on the method of finite elements (FE). Both the analytical and numerical predictions were validated against experimental measurements. Collapse mechanism maps of the 3CSP structure were subsequently constructed using the analytical model, with four collapse modes considered (face-sheet yielding, face-sheet buckling, core yielding, and core buckling), which were used to evaluate how its structural geometry affects its collapse initiation mode.
Abstract Metal-assisted etching of silicon in HF aqueous solution has attracted widespread attention due to its potential applications in electronics, photonics, renewable energy, and biotechnology. In this paper, the basic process and mechanism of metal assisted electrochemical etching of silicon in vapor or liquid atmosphere based on galvanic cells are reviewed. This paper focuses on the use of gas-phase oxidants O 2 and H 2 O 2 instead of liquid phase oxidants Fe(NO 3 ) 3 and H 2 O 2 to catalyze the etching of silicon in the vapor atmosphere of HF aqueous solution. The mechanism of substrate enhanced metal-assisted chemical etching for the preparation of large-area silicon micro nanostructure arrays is summarized, and the impact of substrate type and surface area on reactive etching is discussed.
In conventional sandwich construction, the core component is typically made of Nomex honeycomb and sandwiched between two facesheets, a lower and an upper facesheet. To enhance the load-bearing capacity of this Nomex honeycomb core sandwich (NHCS) construction, we propose a NHCS construction that is continuously encased by a composite fabric facesheet on all four sides. We experimentally and numerically examine the bending response of this encased NHCS construction through a three-point bending test. We consider and discuss the effect of the orientation of the honeycomb core component and the formation of the facesheet separately to reveal the mechanism by which the composite facesheet encasing enhances the construction. Our results demonstrate that composite facesheet encasing significantly improves the bending response of the NHCS construction, with a much greater advantage than the increase in mass compared to conventional sandwich construction. The superiority of the encased composite facesheet is significantly influenced by the orientation of the honeycomb cell and the direction of the fiber ply-stacked laminate facesheet. In addition, we compare the bending response of the encased honeycomb sandwich construction with that of competing sandwiches and show that the proposed sandwich with a continuously encased composite facesheet has a superior lightweight advantage.
Abstract As demand for high-performance electric vehicles, portable electronic equipment, and energy storage devices increases rapidly, the development of lithium-ion batteries with higher specific capacity and rate performance has become more and more urgent. As the main body of lithium storage, negative electrode materials have become the key to improving the performance of lithium batteries. The high specific capacity and low lithium insertion potential of silicon materials make them the best choice to replace traditional graphite negative electrodes. Pure silicon negative electrodes have huge volume expansion effects and SEI membranes (solid electrolyte interface) are easily damaged. Therefore, researchers have improved the performance of negative electrode materials through silicon-carbon composites. This article introduces the current design ideas of ultra-fine silicon structure for lithium batteries and the method of compounding with carbon materials, and reviews the research progress of the performance of silicon-carbon composite negative electrode materials. Ultra-fine silicon materials include disorderly dispersed ultra-fine silicon particles such as porous structures, hollow structures, and core-shell structures; and ordered ultra-fine silicon, such as silicon nanowire arrays, silicon nanotube arrays, and interconnected silicon nano-films. The article analyzes and compares the composite method of ultrafine silicon and carbon materials with different structural designs, and the effect of composite negative electrode materials on the specific capacity and cycle performance of the battery. Finally, the research direction of silicon-carbon composite negative electrode materials is prospected.
Abstract Silicon nanostructures are attracting growing attention due to their properties and promising application prospects in solar energy conversion and storage devices, thermoelectric devices, lithium-ion batteries, and biosensing technologies. The large-scale and low-cost preparation of silicon nanostructures is critical for silicon-based advanced functional devices commercialization. In this paper, the feasibility and mechanism of silicon nanostructure fabricated by non-metallic carbon catalytic etching, as well as the currently existing problems and future development trend are reviewed.
Due to its high practicability, metal assisted chemical etching (MACE) has become a popular silicon micro-nano structure preparation method. This paper explores the metal nanoparticle film dissolution and re-deposition evolution behavior in oxidizing HF solution during the MACE process. The results show Ag nanoparticles experience both oxidation dissolve and reduction deposit during MACE in HF–H2O2–H2O and HF–Fe(NO3)3–H2O corrosion solution. The Au nanoparticle can remain stable in the HF–Fe(NO3)3–H2O solution, providing a strategy to keep the patterns' high etching accuracy of the silicon micro-nano structure. This work illuminates the reaction principle and provides a new insight to improving the etching accuracy, stability, and speed of the MACE technology.
Coal tar pitch is the residual black substance after the distillation of tar, which has low value; It mainly contains anthracene, phenanthrene, pyrene and other components that are difficult to volatilize. It has stable performance and rich carbon content. The proportion of carbon is more than 90% in coal tar pitch. It is theoretically feasible to use the coal tar pitch as carbon source to prepare graphene. At the same time, the preparation of expensive graphene from low-cost coal tar pitch has great advantages in economic benefits.
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