锗钨酸盐的电化学性能及GeW11Co/P-oPD/GC电极对过氧化氢的电催化还原

研究了杂多酸-钴取代三聚Keggin结构锗钨酸盐（[Co（H2O）3（α-GeW11CoO38）3]10-）的电化学性能.实验表明,在玻碳（GC）电极上,锗钨酸盐循环伏安曲线呈现2对可逆的氧化还原峰,峰电位差分别为31 mV和35 mV,各对应于2电子4质子和2电子3质子电极反应,其过程受表面吸附控制.经过电聚合将Ge...     

Investigations on mesa width design for 4H–SiC trench super junction Schottky diodes

Mesa width(WM) is a key design parameter for SiC super junction(SJ) Schottky diodes(SBD) fabricated by the trench-etching-and-sidewall-implant method. This paper carries out a comprehensive investigation on how the mesa width design determines the device electrical performances and how it affects the degree of performance degradation induced by process variations. It is found that structures designed with narrower mesa widths can tolerant substantially larger charge imbalance for a given BV target, but have poor specific on-resistances. On the contrary, structures with wider mesa widths have superior on-state performances but their breakdown voltages are more sensitive to p-type doping variation. Medium WMstructures(～ 2 μm) exhibit stronger robustness against the process variation resulting from SiC deep trench etching.Devices with 2-μm mesa width were fabricated and electrically characterized. The fabricated SiC SJ SBDs have achieved a breakdown voltage of 1350 V with a specific on-resistance as low as 0.98 m?·cm~2. The estimated specific drift onresistance by subtracting substrate resistance is well below the theoretical one-dimensional unipolar limit of SiC material.The robustness of the voltage blocking capability against trench dimension variations has also been experimentally verified for the proposed SiC SJ SBD devices.     

低温热压缩机系统的数值模拟与实验研究

本文对低温热压缩机系统进行了数值模拟和实验研究,首先对低温热压缩机的运行参数进行了研究,结果表明提高运行频率、增大平均力、降低预冷温度均可增大系统的压比,但同时也会消耗更多的预冷量。之后对热压缩机所需的预冷量和各项热损失进行了分析,结果表明排出器运动产生的损失所占比例最大,是进一步优化的重点。最终本文所研究的低温热压缩机系统,在2 Hz运行频率下、平均压力1 MPa时,所需要的冷量约为54 W@77K,系统可产生1.95的压比。基于此热压缩机系统,进一步驱动单级多路旁通脉冲管制冷机,可成功获取3.8 K的最低温度。     

低温VM制冷机实验研究进展

VM制冷机是一种结构紧凑的热驱动斯特林型制冷机,主要靠工作热源间的温差在系统内产生制冷所需压力波动。通过对系统内部往复运动的排出器设置合适的相位角,VM制冷机可以实现从高温热源和低温热源吸热,向中间热源放热。此外,VM制冷机还具有磨损和振动小、寿命长等优点。到目前为止,气耦合脉冲管型的两级VM制冷机已经能够获得2.49K的无负荷温度,在4.2K可提供36m W制冷量。在总结单级和多级低温VM制冷机的实验进展的基础之上,进一步探讨了低温VM制冷机的应用领域,为低温VM制冷机的发展及实际应用提供了参考。     

g-C3N4/Fe3O4/BiOI磁性材料的制备及其可见光助芬顿催化性能

采用共沉淀-回流法制成g-C₃N₄/Fe₃O₄/BiOI磁性复合材料作为异相光助芬顿(Fenton)催化剂。运用扫描电镜(SEM)、透射电镜(TEM)、X-射线衍射(XRD)、振动样品磁强计(VSM)和N₂吸附-脱附等手段分别对催化剂的形貌、结构、组成、磁性和比表面积等进行了表征，并以罗丹明B(RhB)为模型污染物考察了材料的可见光催化性能。实验结果表明，当BiOI的负载质量为50%时，在可见光照射下，复合材料具有最好的光催化性能，180 min内对RhB的降解效率可达到99.20%。较高的光催化性能归因于所制备材料对RhB较强的吸附、强烈的可见光响应以及异质结构促进了光生载流子的分离。进一步在光催化体系中加入适量的H₂O₂后，可极大提高三元复合材料可见光助Fenton降解RhB的效率，30 min内即可达到98.44%,这得益于体系中发生Fenton反应产生较多具有强氧化性的羟基自由基，同时光生电子可加速Fe³⁺