磁致旋光效应的发现

介绍了莫里奇尼和赫谢耳探索磁和光相互作用方面的工作,回顾了法拉第发现磁致旋光效应的历程;分析了法拉第捕捉科学前沿与哲学思考相结合的研究特点,以及法拉第在研究工作中的顽强毅力与创新精神.     

纳米银负载三聚氰胺泡沫基相变复合材料的一步法制备及结构与性能

以轻质柔性的三聚氰胺泡沫(MF)作为基体,将其置于由乙二醇(EG)、硝酸银(AgNO₃)、聚乙烯吡咯烷酮(PVP)和氯化铜(Cu Cl₂)组成的反应溶液中,利用高温环境中发生的氧化还原反应在泡沫骨架上生成纳米银(Ag),随后通过真空浸渍法在泡沫基体中封装月桂酸(LA)制备相变复合材料.采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、差示扫描量热仪(DSC)和红外热成像仪等对制得的相变复合材料的形貌、结构和热性能进行研究.结果表明,当Ag NO₃浓度为4 mg/m L时,纳米Ag均匀致密地沉积在MF骨架表面,且同时存在Ag纳米粒子(Ag NPs)和Ag纳米线(Ag NWs)两种形态.相变复合材料的相变焓高达144.0 J/g,相变焓效率超过了80%,呈现出优异的温度调节和储热能力.本文提供了一种制备综合性能优异的相变复合材料的新策略,有利于拓宽相变复合材料的应用领域.     

Forward-wave enhanced radiation in the terahertz electron cyclotron maser

Based on the principle of electron cyclotron maser (ECM), gyrotrons are among the most promising devices to generate powerful coherent terahertz (THz) radiation and play a vital role in numerous advanced THz applications. Unfortunately, THz ECM systems using a conventional high-Q cavity were theoretically and experimentally demonstrated to suffer from strong ohmic losses, and, accordingly, the wave output efficiency was significantly reduced. A scheme to alleviate such a challenging problem is systematically investigated in this paper. The traveling-wave operation concept is employed in a 1-THz third harmonic gyrotron oscillator, which strengthens electron-wave interaction efficiency and reduces the ohmic dissipation, simultaneously. A lossy belt is added in the interaction circuit to stably constitute the traveling-wave interaction, and a down-tapered magnetic field is employed to further amplify the forward-wave (FW) component. The results demonstrate that the proportion of ohmic losses is nearly halved, and output efficiency is nearly doubled, which is promising for further advancement of high-power continuous-wave operation of the ECM-based devices.