Solvent-free synthesis of hierarchical Tb^(3+)-doped Yttrium benzene-1,3,5-tricarboxylate metal organic framework nanosheets for fast and highly sensitive fluorescence detection of Fe3+and Cr2O72−ions

Controllable synthesis of luminescent metal-organic frameworks (MOFs) having the merits of ease preparation, outstanding sensitivity and stability is of great significance for exploring their efficient sensing applications. Herein, we report a hierarchical terbium-doped yttrium-benzene-1,3,5-tricarboxylate MOF nanosheet via solvent-free synthetic strategy with a topological structure of MIL-78. The fluorescence property of the hierarchical Tb^(3+)-doped Y-based MOF nanosheets can be tuned by adjusting the molar ratio of Tb^(3+) to Y^(3+) ions, and the Tb_(0.5)Y_(0.5)-MOF nanosheet-like morphology with the optimum characteristic Tb^(3+) ion green emission exhibited great potential acting as fluorescence probe for highly sensitive Fe^(3+) and Cr_(2)O_(7)^(2−) detection. The Tb^(3+)-doped Y-MOF nanosheets show a fast response time of less than 1 s for Fe^(3+) ions. They also have low detection limits of 0.40 and 0.26 µM toward Fe^(3+) and Cr_(2)O_(7)^(2−) ions, respectively, as well as excellent stability. This work paves the way to explore intriguing hierarchical MOF-based luminescent materials for efficient fluorescence sensing applications.

磁屏蔽对电磁出钢系统中感应加热电源功率损耗的影响

为降低钢包结构对电磁出钢系统中电源功率损耗的影响,提出了在线圈下侧与四周布置磁屏蔽材料的方法。采用数值模拟的方法分析了磁屏蔽对感应线圈周围磁感应强度和线圈最佳加热位置的影响,并通过实验进行了验证。确定了适用于电磁出钢技术的最佳的磁屏蔽尺寸和结构。结果表明,采用磁屏蔽的方法能够有效降低线圈的功率损耗,并提高线圈的最佳加热区域。当使用Cu作为磁屏蔽材料时,其最佳尺寸为高度200 mm、长度和宽度290 mm及厚度1 mm,并且网状结构在不影响水口座砖寿命的同时能够达到与传统结构基本相同的磁屏蔽效果。此时线圈的最佳加热位置会上移20.2 mm,这有利于电磁出钢系统中感应线圈的安装及其使用寿命的提高。