Morphological effect on electrochemical performance of nanostructural CrN

Size and morphology are critical factors in determining the electrochemical performance of the supercapacitor materials, due to the manifestation of the nanosize effect. Herein, different nanostructures of the CrN material are prepared by the combination of a thermal-nitridation process and a template technique. High-temperature nitridation could not only transform the hexagonal Cr₂O₃ into cubic CrN, but also keep the template morphology barely unchanged. The obtained CrN nanostructures, including (i) hierarchical microspheres assembled by nanoparticles, (ii) microlayers, and (iii) nanoparticles, are studied for the electrochemical supercapacitor. The CrN microspheres show the best specific capacitance (213.2 F/g), cyclic stability (capacitance retention rate of 96% after 5000 cycles in 1-mol/L KOH solution), high energy density (28.9 Wh/kg), and power density (443.4 W/kg), comparing with the other two nanostructures. Based on the impedance spectroscopy and nitrogen adsorption analysis, it is revealed that the enhancement arised mainly from a high-conductance and specific surface area of CrN microspheres. This work presents a general strategy of fabricating controllable CrN nanostructures to achieve the enhanced supercapacitor performance.     

Manipulating metal-insulator transitions of VO2 films via embedding Ag nanonet arrays

Manipulating metal-insulator transitions in strongly correlated materials is of great importance in condensed matter physics, with implications for both fundamental science and technology. Vanadium dioxide (VO₂), as an ideal model system, is metallic at high temperatures and shown a typical metal-insulator structural phase transition at 341 K from rutile structure to monoclinic structure. This behavior has been absorbed tons of attention for years. However, how to control this phase transition is still challenging and little studied. Here we demonstrated that to control the Ag nanonet arrays (NAs) in monoclinic VO₂(M) could be effective to adjust this metal-insulator transition. With the increase of Ag NAs volume fraction by reducing the template spheres size, the transition temperature (T_c) decreased from 68° to 51°. The mechanism of T_c decrease was revealed as:the carrier density increases through the increase of Ag NAs volume fraction, and more free electrons injected into the VO₂ films induced greater absorption energy at the internal nanometal-semiconductor junction. These results supply a new strategy to control the metal-insulator transitions in VO₂, which must be instructive for the other strongly correlated materials and important for applications.     

微秒脉冲电场下Pb_(0.99)(Zr_(0.95)Ti_(0.05))_(0.98)Nb_(0.02)O_3陶瓷击穿过程电阻变化规律

陶瓷作为应用非常广泛的一种材料,其电击穿问题一直是研究的重点和热点.由于击穿过程涉及热、光、电多场耦合效应,目前还没有一个普适的模型能够解释陶瓷击穿问题.针对此问题进行分析,实验中采用脉冲高压发生装置击穿陶瓷,通过对陶瓷击穿过程中等效电阻的研究,揭示了PZT95/5陶瓷样品体击穿和沿面闪络形成过程的异同.结果显示,在两种击穿模式下,陶瓷样品内部均会在40 ns左右形成导电通道,陶瓷等效电阻急剧下降至10~5?量级;然后体击穿与沿面闪络的导电通道以不同的速率继续扩展;电阻减小速率与导电通道上载流子的浓度有关,二者的等效电阻以不同速率减小,直至导电通道达到稳定.     

OBE理念下高职物理课程教学改革与实践——以驻马店幼儿师范高等专科学校为例

以驻马店幼专五年制学前教育专业物理课程改革为例,基于OBE理念,在调研的基础上重新制定专业针对性强的课程大纲,依托C30教育云平台、智慧教室开展混合式教学,采取“线上学习”+“线下研讨”+“技能展示”+“课程思政”+“创新拓展”的形式反向设计课程,并构建多元化的考核评价体系.这种基于OBE理念,针对高职物理课程的线上线下混合式教学改革实践,可以为高职物理课程改革提供新的思路.     

垫层对破片冲击起爆带壳炸药影响的数值模拟

将战斗部简化为带钢壳和垫层的炸药组件,用3种不同厚度的材料作垫层,利用非线性有限元软件AUTODYN对高速破片侵彻、引爆带壳炸药的作用过程进行了数值模拟,得到了高速破片冲击起爆带壳带垫层炸药的波后压力剖面。对不同厚度多种材料作为垫层时带壳炸药的冲击到爆轰距离进行了对比分析,结果表明,通过控制垫层的材料和厚度,可以对破片冲击起爆带壳炸药进行有效抑制。研究结果对战斗部破片起爆的防护设计具有指导意义。     

FeNiMo/SiO2复合粉芯的制备与软磁性能调控

目前金属软磁粉芯材料在高频电感等电子元件的应用前景广阔,然而其主要的构成元素属于过渡金属,表面易形成致密的氧化层,影响其软磁性能的调控.为了解决这些问题,本文引入H₂/Ar混合气体高温预处理工艺对FeNiMo原粉进行还原,证实了还原性气氛高温处理可以有效地去除材料表面的金属氧化物,增加金属单质的含量,进而显著提升FeNiMo原粉的有效磁导率.对预处理后的FeNiMo粉末进行SiO₂绝缘包覆,所获得的FeNiMo/SiO₂软磁复合材料表面包覆均匀;与未处理FeNiMo原粉包覆SiO₂所形成的软磁复合粉芯相比, H₂/Ar混合气体高温预处理后的FeNiMo/SiO₂具有更高的有效磁导率、更低的损耗.与同类其他软磁复合粉芯相比,通过H₂/Ar混合气体高温预处理工艺和绝缘包覆工艺的协同效应,所制备的FeNiMo/SiO₂复合粉芯具有优异的软磁性能.因此经过还原性气氛高温预处理工艺后的绝缘包覆可以更大程度地提升软磁粉芯复合...     

一种重构强反射光纤布拉格光栅的新方法

阐述了光纤布拉格光栅的重构理论及被广泛采用的剥层算法,指出了剥层算法在重构强反射光栅时的弊端,提出了一种剥层算法和遗传算法相结合的方法来重构强反射光栅。此方法先由剥层算法得到光栅耦合系数的初始值,再依据重新采样后的初始值创建初始种群,通过遗传算法实现对剥层算法所得结果的后半部分进行优化。数值模拟表明此方法有效地改善了剥层算法的结果,具有较快的收敛速度和很好的精度,能适用于大多数强反射光栅的重构。     

论证式教学在高中物理概念课中的应用策略

构建论证式教学模式及流程,着力搭建联系物理概念课教学与培养学生科学论证能力之间的“桥梁”,文章从营造论证氛围、显化论证语言、丰富论证资料、提升论证能力4个维度阐述在物理概念课上进行论证式教学的策略.