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Microstructural characterization of nanostructured Al2O3-ZrO2 eutectic layer by laser rapid solidification method
摘要： In the present work, nanostructured surface layers of Al2O3-ZrO2 eutectic with a thickness of approximate 1000 μm and free of cracks and pores were produced on the surface of conventionally-sintered Al2O3-ZrO2 ceramic via the laser irradiation rapid solidification process. The molten pool geometry and microstructure were characterized by scanning electron microscopy and Raman spectroscopy. The geometrical evolution of molten pool in response to laser power and laser scanning velocity was established, where the top view of molten pool exhibits a circular shape at low velocities and gradually evolves into an oval-shaped surface at high velocities. Singular Al2O3-ZrO2 eutectic colonies with a size of 100-200 μm, which is formed around a spontaneously nucleated dendritic ZrO2 core, are found on the surface of laser-remelted layer. The eutectic colony has an interphase spacing of 190-280 nm. The variation of eutectic spacing with growth rate is essentially linear on the logarithmic scale as λ=KV-0.4 by binary regression analysis. Predicted by the Jackson-Hunt theory on eutectic solidification (JH theory), the eutectic spacing is consistent with the inverse-square-root dependence on growth rate with a proportionality constant of 3.32. The eutectic colonies consist of α-Al2O3, t-ZrO2 and m-ZrO2 phases, where α-Al2O3 and t-ZrO2 are the dominant phases and the m-ZrO2 phase increases with the decrease of laser scanning velocity.
关键词： Al2O3-ZrO2,Nanoeutectic layer,Laser remelting,Surface nanostructuring
更新于2025-11-28 14:24:20
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[IEEE 2019 IEEE 28th International Symposium on Industrial Electronics (ISIE) - Vancouver, BC, Canada (2019.6.12-2019.6.14)] 2019 IEEE 28th International Symposium on Industrial Electronics (ISIE) - Digital Holography for Industrial Applications
摘要： Metal–insulator–metal (MIM) capacitors with full atomic-layer-deposition Al2O3/ZrO2/SiO2/ZrO2/Al2O3 stacks were explored for the first time. As the incorporated SiO2 film thickness increased from 0 to 3 nm, the quadratic and linear voltage coefficients of capacitance (α and β) of the MIM capacitors reduced significantly from positive values to negative ones. For the stack with 3-nm SiO2 film, a capacitance density of 7.40 fF/μm2, α of ?121 ppm/V2, and β of ?116 ppm/V were achieved, together with very low leakage current densities of 3.08 × 10?8 A/cm2 at 5 V at room temperature (RT) and 5.89 × 10?8 A/cm2 at 3.3 V at 125 °C, high breakdown field of 6.05 MV/cm, and high operating voltage of 6.3 V for a 10-year lifetime at RT. Thus, this type of stacks is a very promising candidate for next generation radio frequency and analog/mixed-signal integrated circuits.
关键词： metal-insulator-metal,Al2O3/ZrO2/SiO2/ZrO2/Al2O3,Atomic-layer-deposition,voltage coefficients of capacitance
更新于2025-09-19 17:13:59
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Analysis of Melt-Pool Behaviors during Selective Laser Melting of AISI 304 Stainless-Steel Composites
摘要： The melt-pool behaviors during selective laser melting (SLM) of Al2O3-reinforced and a eutectic mixture of Al2O3-ZrO2-reinforced AISI 304 stainless-steel composites were numerically analyzed and experimentally validated. The thermal analysis results show that the geometry of the melt pool is significantly dependent on reinforcing particles, owing to the variations in the melting point and the thermal conductivity of the powder mixture. With the use of a eutectic mixture of Al2O3-ZrO2 instead of an Al2O3 reinforcing particle, the maximum temperature of the melt pool was increased. Meanwhile, a negligible corresponding relationship was observed between the cooling rate of both reinforcements. Therefore, it was identified that the liquid lifetime of the melt pool has the effect on the melting behavior, rather than the cooling rate, and the liquid lifetime increases with the eutectic ratio of Al2O3-ZrO2 reinforcement. The temperature gradient at the top surface reduces with the use of an Al2O3-ZrO2 reinforcement particle due to the wider melt pool. Inversely, the temperature gradient in the thickness direction increases with the use of an Al2O3-ZrO2 reinforcement particle. The results of melt-pool behaviors will provide a deep understanding of the effect of reinforcing particles on the dimensional accuracies and properties of fabricated AISI 304 stainless-steel composites.
关键词： FEM,Al2O3,Al2O3-ZrO2,304,composite,SLM,additive manufacturing,selective laser melting,stainless
更新于2025-09-16 10:30:52
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Improving Performance and Stability of Planar Perovskite Solar Cells through Grain Boundary Passivation with Block Copolymers
摘要： Al2O3–ZrO2 ceramic coatings were fabricated on titanium alloy substrate by ultrasonic assisted laser cladding. The effects of ultrasonic on the microstructure and mechanical properties of the coatings are investigated through experiments. A novel laser cladding method by ultrasonic assisted is used in this paper. In this method, ultrasonic waves are directly applied on the micro-zone of molten pool. Experimental results indicated that the grain size and mechanical properties of the coatings are improved with the ultrasonic assisted. The amount of coatings cracks are decreased due to the application of ultrasonic vibration in the laser cladding.
关键词： Al2O3–ZrO2 ceramics,ultrasonic,laser cladding,mechanical properties
更新于2025-09-11 14:15:04