Carbonized melamine foam has been recognized as a promising material for microwave absorption due to its exceptional thermal stability,lightweight,and remarkable dielectric properties.In this study,we investigated the...Carbonized melamine foam has been recognized as a promising material for microwave absorption due to its exceptional thermal stability,lightweight,and remarkable dielectric properties.In this study,we investigated the impact of nitric acid oxidation on the surface of carbonized melamine foam and its microwave absorption properties.The treated foam exhibits optimal reflection loss of−21.51 dB at 13.20 GHz,with an effective absorption bandwidth of 7.04 GHz.The enhanced absorption properties are primarily attributed to the strengthened dielectric loss,improved impedance matching,and increased polarization losses resulting from the oxidized surfaces.This research demonstrates a promising new approach for research into surface treatments to improve the performances of microwave absorbers.展开更多
液体泄漏破碎行为研究对核反应堆安全分析具有重要意义,泄漏破碎形成的粒径尺寸分布是影响燃烧速率的重要因素。利用计算流体力学程序FLUENT对液体泄漏破碎进行三维模拟计算,与相关实验结果对比表明:液体流动轨迹、液滴索特尔平均直径(s...液体泄漏破碎行为研究对核反应堆安全分析具有重要意义,泄漏破碎形成的粒径尺寸分布是影响燃烧速率的重要因素。利用计算流体力学程序FLUENT对液体泄漏破碎进行三维模拟计算,与相关实验结果对比表明:液体流动轨迹、液滴索特尔平均直径(sauter mean diameter,SMD)与实验吻合较好,验证了流体体积法-离散颗粒法(volume of fluid-discrete particle model,VOF-DPM)模型模拟液体泄漏破碎行为的适用性。在此基础上分析了不同工质及不同流速对液体破碎行为的影响。研究表明,在液体喷射速度和管道破口直径相同的情况下,工质表面张力越大,破碎形成液滴尺寸越小;随着液体喷射流速增大,所得粒径平均直径减小;液体破碎粒径沿径向方向分布较为对称,液滴在喷射中心区域粒径较小轴向方向靠近破口处粒径较大。展开更多
Photocatalytic carbon dioxide reduction reaction(CO_(2)RR)has been considered as one of most effective ways to solve the current energy crisis and environmental problems.However,the practical application of photocatal...Photocatalytic carbon dioxide reduction reaction(CO_(2)RR)has been considered as one of most effective ways to solve the current energy crisis and environmental problems.However,the practical application of photocatalytic CO_(2)RR is largely hindered by lock of efficient catalyst.Here,hierarchical titanium dioxide(TiO_(2))nanostructures with a highly active{001}surface were successfully synthesized by a facile approach from metal Ti powders.The obtained hierarchical TiO_(2)nanostructures were composed of TiO_(2)nanorods,which have a diameter about 5–10 nm and a length of several micrometers.It is found that these nanorods have exposed{001}facets.On the other hand,these hierarchical TiO_(2)nanostructures have a good light-harvesting efficiency with the help of TiO_(2)nanorods component and large specific surface area.Therefore,these hierarchical TiO_(2)nanostructures exhibit a much better activity for photocatalytic CO_(2)reduction than that of commercial TiO_(2)(P25).This high activity can be attributed to the synergistic effects of active surface,efficient charge transfer along nanorods and good light harvesting in the nanorod-hierarchical nanostructures.展开更多
基金Project(2023RC3066)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(2023JJ50079)supported by the Hunan Provincial Natural Science Foundation,China。
文摘Carbonized melamine foam has been recognized as a promising material for microwave absorption due to its exceptional thermal stability,lightweight,and remarkable dielectric properties.In this study,we investigated the impact of nitric acid oxidation on the surface of carbonized melamine foam and its microwave absorption properties.The treated foam exhibits optimal reflection loss of−21.51 dB at 13.20 GHz,with an effective absorption bandwidth of 7.04 GHz.The enhanced absorption properties are primarily attributed to the strengthened dielectric loss,improved impedance matching,and increased polarization losses resulting from the oxidized surfaces.This research demonstrates a promising new approach for research into surface treatments to improve the performances of microwave absorbers.
文摘液体泄漏破碎行为研究对核反应堆安全分析具有重要意义,泄漏破碎形成的粒径尺寸分布是影响燃烧速率的重要因素。利用计算流体力学程序FLUENT对液体泄漏破碎进行三维模拟计算,与相关实验结果对比表明:液体流动轨迹、液滴索特尔平均直径(sauter mean diameter,SMD)与实验吻合较好,验证了流体体积法-离散颗粒法(volume of fluid-discrete particle model,VOF-DPM)模型模拟液体泄漏破碎行为的适用性。在此基础上分析了不同工质及不同流速对液体破碎行为的影响。研究表明,在液体喷射速度和管道破口直径相同的情况下,工质表面张力越大,破碎形成液滴尺寸越小;随着液体喷射流速增大,所得粒径平均直径减小;液体破碎粒径沿径向方向分布较为对称,液滴在喷射中心区域粒径较小轴向方向靠近破口处粒径较大。
基金Project(21872174)supported by the National Natural Science Foundation of ChinaProjects(2017CX003,20180018050001)supported by the Innovation-Driven Plan in Central South University,China+3 种基金Project supported by State Key Laboratory of Powder Metallurgy in Central South University,ChinaProject(JCYJ20180307151313532)supported by Shenzhen Science and Technology Innovation Project,ChinaProject supported by the Thousand Youth Talents Plan of ChinaProject supported by the Hundred Youth Talents Program of Hunan,China
文摘Photocatalytic carbon dioxide reduction reaction(CO_(2)RR)has been considered as one of most effective ways to solve the current energy crisis and environmental problems.However,the practical application of photocatalytic CO_(2)RR is largely hindered by lock of efficient catalyst.Here,hierarchical titanium dioxide(TiO_(2))nanostructures with a highly active{001}surface were successfully synthesized by a facile approach from metal Ti powders.The obtained hierarchical TiO_(2)nanostructures were composed of TiO_(2)nanorods,which have a diameter about 5–10 nm and a length of several micrometers.It is found that these nanorods have exposed{001}facets.On the other hand,these hierarchical TiO_(2)nanostructures have a good light-harvesting efficiency with the help of TiO_(2)nanorods component and large specific surface area.Therefore,these hierarchical TiO_(2)nanostructures exhibit a much better activity for photocatalytic CO_(2)reduction than that of commercial TiO_(2)(P25).This high activity can be attributed to the synergistic effects of active surface,efficient charge transfer along nanorods and good light harvesting in the nanorod-hierarchical nanostructures.
