碳纳米管/寡聚胸腺嘧啶复合体系与汞离子作用的光谱研究

利用寡聚胸腺嘧啶核苷酸(PolyT)与碳纳米管(CNTs)之间的自发非共价修饰作用形成稳定的CNTs/PolyT纳米复合体系,采用共振光散射(RLS)和紫外-可见吸收光谱考察了该复合体系与汞离子的相互作用.实验结果表明,水相中单链PolyT能与CNTs形成稳定而均匀的分散体系,而单链Po1yT极易捕获汞离子生成特异性的...     

纳米金属Tm的电子浓度研究

电子浓度是与金属的宏观特性相关的重要参数.反射光谱和霍尔效应分别是得出电子浓度和载流子浓度的基本实验.两个纳米稀土金属铥Tm样品(样品1,平均粒径100nm,样品2,平均粒径10nm)的红外---紫外反射光谱实验表明,金属铥Tm表面的反射光学性质具有金属的特征,6s能带具有与碱金属相近的电子浓度n_p,数值分别为2.434×10²⁸/m³和1.701×10²⁸/m³.而样品的霍尔效应实验测得金属Tm的载流子是电子-空穴型的,载流子浓度n_H仅分别为8.032×10²⁴/m³和7.679×10²⁴/m³,仅仅是费米面附近的电子-空穴状态.另外,铥Tm的电导率比半导体的大3个量级.晶粒纳米化使电子浓度n_p减小,电导率σ减小,载流子浓度减小,而霍尔系数R_H增大.     

增强UV－B辐射对植物光能传递过程的影响

为探讨增强的紫外线-B (280~315 nm)辐射对光合作用原初光能传递的光物理过程的影响,对菠菜类囊体膜及光系统II的吸收光谱、稳态荧光发射谱进行了分析.结果显示在实验条件下（温室,紫外线-B施加于植物成熟期,紫外线-B剂量1.152 kJ·m－2·d－1）,增强紫外线-B辐射并没有抑制原初光能传递过程,植物通过一系列调节机制（增强吸收短波光色素的吸收强度,调节两个光系统间能量分配,变化光合系统中色素蛋白构象、位置）保证了原初光能传递的光物理过程,将能量传递到反应中心用于光合作用.     

离心式喷嘴内气液两相流动的数值模拟

求解三维不可压NS方程,并应用VOF方法捕获气液分界面,计算不同压降下离心式喷嘴内的气液两相流动状况,研究了不同压降对喷嘴内流动的影响。计算很好地模拟了喷嘴内的气液两相流动,并得到了出口液膜速度、喷雾锥角以及液膜厚度等参数,数值计算所得结果同试验符合得较好,好于经验公式的结果。     

Effects of dipolar interactions on magnetic properties of Co nanowire arrays

Magnetic properties and magnetization processes of Co nanowire arrays with various packing densities are investigated by means of object-oriented micromagnetic framework(OOMMF) software package with finite difference micromagnetic simulations. The packing density of nanowires is changed with the diameter, number of nanowires and center-to-center spacing between the wires. The magnetization reversal mechanism and squareness of the hysteresis loops of the nanowire arrays are very sensitive to the packing density of nanowires. Clear steps and plateaux on the demagnetization are visible,which turns out that dipolar interactions among the wires have a significant influence on switching field.     

Micromagnetism simulation on effects of soft phase size on Nd_2Fe_(14)B/α-Fe nanocomposite magnet with soft phase imbedded in hard phase

In this study, micromagnetism simulation by using finite difference method is carried out on the Nd_2Fe_(14)B/α-Fe nanocomposite magnet with soft phase imbedded in hard phase. The effects of soft magnetic phase size(S) on the magnetic properties and magnetic reversal modes are systematically analyzed. As S increases from 1 nm to 48 nm,the remanence(J_r) increases, while the coercivity(H_(ci)) decreases, leading to the result that the magnetic energy product [(BH)_(max)] first increases slowly, and then decreases rapidly, peaking at S = 24 nm with the(BH)_(max) of 72.9 MGOe(1 MGOe = 7.95775 kJ·m~(-3)). Besides, with the increase of S, the coercivity mechanism of the nanocomposite magnet changes from nucleation to pinning. Furthermore, by observing the magnetic moment evolution in demagnetization process, the magnetic reversal of the soft phase in the nanocomposite magnet can be divided into three modes with the increase of S: coherent rotation(S 3 nm), quasi-coherent rotation(3 nm ≤S 36 nm), and the vortex-like rotation(S 36 nm).     

铌、钛取代对高镓低硼烧结Nd-Fe-B磁体磁性能、微结构和力学性能的影响

高Ga低B烧结钕铁硼磁体可以在具有较高矫顽力的基础上减少重稀土的使用,因此具有重要的研究价值。本文制备了含0.2%（质量分数）Nb的高性能48H高Ga低B烧结钕铁硼磁体,与0.2%Ti掺杂磁体进行了系统的对比,分析了Nb与Ti元素掺杂对高Ga低B磁体的磁性能、微观结构、元素分布以及耐磨性能的影响与差异。与Ti取代磁体相比,Nb取代磁体的晶界相更连续、更厚同时磁隔绝效果更好,因此具有更高的矫顽力。此外Nb更容易富集在三角晶界处,抗断裂性相对较差,更容易磨损,因此具有更好的加工性能。这为优化高Ga低B磁体的显微结构制备高性能的烧结磁体提供了有意义的指导。