醋酸酯淀粉/聚乙烯醇共混膜形态结构与性能

以溶液共混法制备了醋酸酯淀粉(SA)/聚乙烯醇(PVA)共混膜,通过扫描电镜(SEM)观测其表面形貌、X射线衍射仪(XRD)表征其结构、Zwick强力仪测试其力学性能.结果表明,醋酸酯化变性及SA与PVA之间的共混比对共混膜的形态结构及力学性能均有影响.随着淀粉醋酸酯化变性程度的增大,共混膜的断裂伸长率增大;当变性取代度达到0.035之后,断裂强度明显增大.增加SA的质量分数,共混膜的断裂伸长率减小,断裂强度先降低后增大;当共混比为50∶50时,断裂强度最小.     

〈111〉晶向冲击加载下单晶铜中纳米孔洞增长的早期动力学行为

利用分子动力学方法模拟计算了单晶铜中纳米孔洞在沿〈111〉晶向冲击加载下增长的早期过程.测量发现不同加载强度下等效孔洞半径随时间近似成线性变化.观测到单孔洞增长的两种位错生长机理：加载强度较低时，只在沿着冲击加载方向的孔洞顶点附近区域有位错的成核和运动；而随着加载强度超过一定阈值，在沿冲击加载和其垂直方向的孔洞顶点区域都观察到位错的成核和运动.在前一种机理作用下，孔洞只沿加载方向增长；在后一种机理作用下，孔洞同时沿加载和垂直于加载方向增长.分析孔洞表面原子的位移历史，发现沿加载及与其垂直方向的孔洞顶点沿径向的速度基本恒定，由此提出了一个孔洞生长模型，可以解释孔洞增长的线性生长规律. 关键词： 纳米孔洞 分子动力学 冲击加载 位错     

Photocatalysts of Cr Doped TiO2 Film Prepared by Micro Arc Oxidation

通过微弧氧化法在Na3PO4+K2Cr2O7电解液中制备了系列铬掺杂二氧化钛薄膜. X射线和扫描电镜显示薄膜的主要晶相为锐钛矿型二氧化钛,且表面为多孔结构. 在可见光照射下,薄膜对降解亚甲基蓝和分解水有着较好的光催化性能,这主要是由铬的掺杂引起的.由于铬的掺杂,一方面在二氧化钛中形成了Cr3+/Cr4+离子对,另一方面在带隙中形成了氧的空位能级. 前者降低了电子-空穴的复合几率,而后者在二氧化钛的禁带中形成了新的能级. 新能级的形成使得由二氧化钛价带跃迁至氧空位能级所需的光子能量减少. 另外探讨了微弧氧化形成掺杂二氧化钛薄膜的机制.     

The degradation mechanism of an AlGaN/GaN high electron mobility transistor under step-stress

Step-stress experiments are performed in this paper to investigate the degradation mechanism of an AlGaN/GaN high electron mobility transistor(HEMT).It is found that the stress current shows a recoverable decrease during each voltage step and there is a critical voltage beyond which the stress current starts to increase sharply in our experiments.We postulate that defects may be randomly induced within the AlGaN barrier by the high electric field during each voltage step.But once the critical voltage is reached,the trap concentration will increase sharply due to the inverse piezoelectric effect.A leakage path may be introduced by excessive defect,and this may result in the permanent degradation of the AlGaN/GaN HEMT.     

Effect of Mg-Preflow for p-AlGaN Electron Blocking Layer on the Electroluminescence of Green LEDs with V-Shaped Pits

In GaN-based green light-emitting diodes(LEDs) with and without Mg-preflow before the growth of p-Al GaN electron blocking layer(EBL) are investigated experimentally.A higher Mg doping concentration is achieved in the EBL after Mg-preflow treatment,effectively alleviating the commonly observed efficiency collapse and electrons overflowing at cryogenic temperatures.However,unexpected decline in quantum efficiency is observed after Mg-preflow treatment at room temperature.Our conclusions are drawn such that the efficiency decline is probably the result of different emission positions.Higher Mg doping concentration in the EBL after Mg-preflow treatment will make it easier for a hole to be injected into multiple quantum wells with emission closer to pGaN side through the(8-plane rather than the V-shape pits,which is not favorable to luminous efficiency due to the preferred occurrence of accumulated strain relaxation and structural defects in upper QWs closer to p-GaN.Within this framework,apparently disparate experimental observations regarding electroluminescence properties,in this work,are well reconciled.     

Efficient and stable wireless power transfer based on the non-Hermitian physics

As one of the most attractive non-radiative power transfer mechanisms without cables,efficient magnetic resonance wireless power transfer(WPT)in the near field has been extensively developed in recent years,and promoted a variety of practical applications,such as mobile phones,medical implant devices and electric vehicles.However,the physical mechanism behind some key limitations of the resonance WPT,such as frequency splitting and size-dependent efficiency,is not very clear under the widely used circuit model.Here,we review the recently developed efficient and stable resonance WPT based on non-Hermitian physics,which starts from a completely different avenue(utilizing loss and gain)to introduce novel functionalities to the resonance WPT.From the perspective of non-Hermitian photonics,the coherent and incoherent effects compete and coexist in the WPT system,and the weak stable of energy transfer mainly comes from the broken phase associated with the phase transition of parity-time symmetry.Based on this basic physical framework,some optimization schemes are proposed,including using nonlinear effect,using bound states in the continuum,or resorting to the system with high-order parity-time symmetry.Moreover,the combination of non-Hermitian physics and topological photonics in multi-coil system also provides a versatile platform for long-range robust WPT with topological protection.Therefore,the non-Hermitian physics can not only exactly predict the main results of current WPT systems,but also provide new ways to solve the difficulties of previous designs.     

2MeV有箔注入器的束流调试

为２０ＭｅＶ ＬＩＡ建造的２ＭｅＶ注入器的束流技术指标经过一年多实验调试已达到能量２ＭｅＶ、束流３ｋＡ、亮度大于或等于１０＾８Ａ／（ｍ．ｒａｄ）＾２。建立了二维数字模型，对注入器的电子发射和束流传输过程进行了模拟，用模拟结果指导实验调试，并同实验结果进行对照，重点分析了有箔情况下自有的聚焦作用。     

水相中磷钼酸催化三组分合成烯丙基胺

以磷钼酸作为催化剂，芳香醛、胺和三丁基烯丙基锡三组分在水作为溶剂，室温下高产率的得到相应的烯丙基胺。