Flexible and lightweight thermal insulation materials with hierarchical microstructures are ubiquitous in thermal management and protection systems.Ceramic aerogels promise high-temperature thermal insulation but lack...Flexible and lightweight thermal insulation materials with hierarchical microstructures are ubiquitous in thermal management and protection systems.Ceramic aerogels promise high-temperature thermal insulation but lack mechanical robustness,while the fibrous materials with excellent mechanical elasticity display modest thermal insulation.Here we describe flexible hierarchical superhydrophobic ceramic insulation nanocomposites through the densified architectured hierarchical nanostructures,radiative insulation coating,and interfacial cross-linking among composites.The lightweight flexible ceramic nanocomposites exhibit a density of 0.13 g/cm^(3),high-temperature fire resistance with thermal conductivity of 0.024 W/(m·K),and super-hydrophobicity with the water contact angle of 152°.The mechanical robustness and high-temperature thermal insulation of ceramic nanocomposites,together with its soundproof performance,shed light on the low-cost flexible insulation materials manufacturing with scalability for high-temperature thermal insulation applications under high mechanical loading conditions.展开更多
Multiferroic charge-transfer crystals have drawn significant interest due to their simultaneous dipolar and spin ordering. Numerous theoretical and experimental studies have shown that the molecular stacking between d...Multiferroic charge-transfer crystals have drawn significant interest due to their simultaneous dipolar and spin ordering. Numerous theoretical and experimental studies have shown that the molecular stacking between donor and acceptor complexes plays an important role in tuning charge-transfer enabled multifunctionality. Herein, we show that the charge-transfer interactions can be controlled by the segregated stack, consisting of polythiophene donor- and fuUerene acceptor-based all-conjugated block copolymers. Room temperature magnetic field effects, ferroelectricity, and anisotropic magnetism are observed in charge-transfer crystals, which can be further controlled by photoexcitation and charge doping. Furthermore, the charge-transfer segregated stack crystals demonstrate external stimuli controlled polarization and magnetization, which opens up their multifunctional applications for all-organic multiferroics.展开更多
Advanced permanent magnets based on rare-earth-free MnBi intermetallic alloys are considered energy-critical materials due to their applications in high temperature power electronics and green energy-related generator...Advanced permanent magnets based on rare-earth-free MnBi intermetallic alloys are considered energy-critical materials due to their applications in high temperature power electronics and green energy-related generators and motors, owing to their positive temperature coefficient of magnetic anisotropy. However, a direct method to achieve high saturation magnetization, without the significant loss of coercivity, is critical for attaining high performance MnBi magnets. Here, we demonstrate the synthesis and processing of magnetic nanocomposites, consisting of metal-redox MnBi nanoparticles and electro-spun FeCo nanowires. The composition ratio, processing dependent magnetism, and increased coercivity with increasing temperature, were studied in MnBi-FeCo nanocomposites. The magnetic performance of nanocomposites was dictated by interfacial coupling between magnetically hard MnBi and semi-hard FeCo nanowires, as well as the composition ratio and processing conditions. Solution processed MnBi-FeCo nanocomposites allow the potential for the development of high temperature and high performance rare-earth-free permanent magnets.展开更多
Ternary FeCoNi metallic nanostructures have attracted significant attention due to their high saturation magnetization, unique mechanical properties, and large corrosion resistance. In this study, we report a controll...Ternary FeCoNi metallic nanostructures have attracted significant attention due to their high saturation magnetization, unique mechanical properties, and large corrosion resistance. In this study, we report a controlled synthesis of ternary FeCoNi nanocrystals using solution-based epitaxial core-shell nanotechnology. The thickness and stoichiometry of the FeCoNi nanocrystals affect their magnetic characteristics, which can be controlled by a phase transformation-induced tetragonal distortion. Furthermore, surface oxidation of the stoichiometry-controlled FeCoNi nanostructures can drastically enhance their magnetic coercivity (up to 8,881.60e for AuCu-FeCo), and optimize the AuCu-FeCo08Ni0.2 performance corresponding to the saturated magnetization of 134.4 emu-g-1 and coercivity of 4,036.70e, which opens the possibility of developing rare-earth free high energy nanomagnets.展开更多
基金We gratefully acknowledge support from the U.S.Department of Energy(DOE),Office of Energy Efficiency and Renewable Energy(EERE)under the Building Technology Office(BTO)Award(No.DE-EE0008675).
文摘Flexible and lightweight thermal insulation materials with hierarchical microstructures are ubiquitous in thermal management and protection systems.Ceramic aerogels promise high-temperature thermal insulation but lack mechanical robustness,while the fibrous materials with excellent mechanical elasticity display modest thermal insulation.Here we describe flexible hierarchical superhydrophobic ceramic insulation nanocomposites through the densified architectured hierarchical nanostructures,radiative insulation coating,and interfacial cross-linking among composites.The lightweight flexible ceramic nanocomposites exhibit a density of 0.13 g/cm^(3),high-temperature fire resistance with thermal conductivity of 0.024 W/(m·K),and super-hydrophobicity with the water contact angle of 152°.The mechanical robustness and high-temperature thermal insulation of ceramic nanocomposites,together with its soundproof performance,shed light on the low-cost flexible insulation materials manufacturing with scalability for high-temperature thermal insulation applications under high mechanical loading conditions.
文摘Multiferroic charge-transfer crystals have drawn significant interest due to their simultaneous dipolar and spin ordering. Numerous theoretical and experimental studies have shown that the molecular stacking between donor and acceptor complexes plays an important role in tuning charge-transfer enabled multifunctionality. Herein, we show that the charge-transfer interactions can be controlled by the segregated stack, consisting of polythiophene donor- and fuUerene acceptor-based all-conjugated block copolymers. Room temperature magnetic field effects, ferroelectricity, and anisotropic magnetism are observed in charge-transfer crystals, which can be further controlled by photoexcitation and charge doping. Furthermore, the charge-transfer segregated stack crystals demonstrate external stimuli controlled polarization and magnetization, which opens up their multifunctional applications for all-organic multiferroics.
基金We thank the financial support from the U.S. National Science Foundation (NSF) under the CAREER Award No: NSF-DMR-1551948. This work is also supported by U.S. Army Communications-Electronic Research, Development and Engineering Center (CERDEC) Command Power and Integration Directorate (CP & ID) via subcontract through General Technical Services under Grant # GTS-S-15-030.
文摘Advanced permanent magnets based on rare-earth-free MnBi intermetallic alloys are considered energy-critical materials due to their applications in high temperature power electronics and green energy-related generators and motors, owing to their positive temperature coefficient of magnetic anisotropy. However, a direct method to achieve high saturation magnetization, without the significant loss of coercivity, is critical for attaining high performance MnBi magnets. Here, we demonstrate the synthesis and processing of magnetic nanocomposites, consisting of metal-redox MnBi nanoparticles and electro-spun FeCo nanowires. The composition ratio, processing dependent magnetism, and increased coercivity with increasing temperature, were studied in MnBi-FeCo nanocomposites. The magnetic performance of nanocomposites was dictated by interfacial coupling between magnetically hard MnBi and semi-hard FeCo nanowires, as well as the composition ratio and processing conditions. Solution processed MnBi-FeCo nanocomposites allow the potential for the development of high temperature and high performance rare-earth-free permanent magnets.
基金S. R. thanks the financial support from the U.S. National Science Foundation (NSF) (No. NSF-DMR-1551948) (magnetically hard nanocrystals) and (No. NSF- CMMI-1553986) (nanomanufacturing).
文摘Ternary FeCoNi metallic nanostructures have attracted significant attention due to their high saturation magnetization, unique mechanical properties, and large corrosion resistance. In this study, we report a controlled synthesis of ternary FeCoNi nanocrystals using solution-based epitaxial core-shell nanotechnology. The thickness and stoichiometry of the FeCoNi nanocrystals affect their magnetic characteristics, which can be controlled by a phase transformation-induced tetragonal distortion. Furthermore, surface oxidation of the stoichiometry-controlled FeCoNi nanostructures can drastically enhance their magnetic coercivity (up to 8,881.60e for AuCu-FeCo), and optimize the AuCu-FeCo08Ni0.2 performance corresponding to the saturated magnetization of 134.4 emu-g-1 and coercivity of 4,036.70e, which opens the possibility of developing rare-earth free high energy nanomagnets.