不同拉伸应变率下金纳米线拉伸力学行为的分子动力学模拟

采用分子动力学方法模拟了不同拉伸应变率下金纳米线的拉伸力学行为。模拟结果表明,相同截面尺寸、拉伸温度、拉伸方向的金纳米线在较高的拉伸应变率下,屈服强度较大,屈服发生的较早;更高应变率下的金纳米线在屈服时对应的应变更大,并且更容易发生二次屈服。金纳米线的弹性模量随着拉伸应变率的增大有所增加,但是幅度不是很明显。     

Modulation of Cathodoluminescence by Surface Plasmons in Silver Nanowires

The waveguide modes in chemically-grown silver nanowires on silicon nitride substrates are observed using spectrally- and spatially-resolved cathodoluminescence (CL) excited by high-energy electrons in a scanning electron microscope. The presence of a long-range, travelling surface plasmon mode modulates the coupling efficiency of the incident electron energy into the nanowires, which is observed as oscillations in the measured CL with the point of excitation by the focused electron beam. The experimental data are modeled using the theory of surface plasmon polariton modes in cylindrical metal waveguides, enabling the complex mode wavenumbers and excitation strength of the long-range surface plasmon mode to be extracted. The experiments yield insight into the energy transfer mechanisms between fast electrons and coherent oscillations in surface charge density in metal nanowires and the relative amplitudes of the radiative processes excited in the wire by the electron.     

ZnO纳米线的气相沉积法自催化生长及发光性能研究

介绍了一种通过气相沉积法自催化生长氧化锌纳米线的方法。氧化锌纳米线的生长方向为〈001〉,其尺寸随反应温度的升高而增大。光致发光分析表明绿光发射强度随氧化锌纳米线尺寸而变化。当氧化锌纳米线直径小至5～10nm时,由于量子效应而表现出非常强的绿光发射。     

ZnO纳米线的制备及其光学性能

采用物理热蒸发ZnS粉的方法,制备出了大规模的线状和棒状ZnO纳米结构.借助扫描电子显微镜、透射电子显微镜、激光拉曼光谱仪以及荧光光谱仪研究了ZnO纳米线的表面形貌、内部结构及其光学性能.结果表明,所得到的ZnO纳米线是六方的单晶结构,而且具有较好的发光性能和良好的结晶性.纳米线长约2～5μm,直径约60nm,其生长机制为气-固(VS)机制.     

定向氧化锌纳米线的制备和生长机理的研究

用化学气相沉积方法(CVD),以纯锌粉为原料,在镀金的硅片上制备出高密度的定向氧化锌(ZnO)纳米线,并用扫描电子显微镜和X射线衍射仪对其形貌、结构及成分进行了表征;对镀金和不镀金的硅片上生长的ZnO纳米结构成分进行比较,证实其生长过程遵循气固生长机理.     

紫光激发提高Ag修饰的ZnO纳米线的气敏特性

为了提高ZnO纳米线的酒敏特性,利用紫光激发经浸渍法获得Ag修饰的ZnO纳米线.利用扫描电子显微镜（SEM）,X射线衍射仪（XRD）对修饰后的ZnO纳米线进行了晶体结构和形貌的表征.结果表明其晶体结构中既有六方纤锌矿结构的ZnO,又有面心立方的Ag.三维网络结构的ZnO纳米线的表面被一层致密的具有高孔隙率的Ag颗粒覆盖,使得ZnO纳米线具有更高的比表面积.纯ZnO纳米线和Ag修饰的ZnO纳米线都用作气敏基料,根据它们在酒精蒸气中紫光照射和无紫光照射条件下电阻的变化来测定它们的气敏特性.结果显示紫光照射下经质量分数为6%AgNO3修饰的ZnO纳米线对酒精蒸气的最大灵敏度由75.8提高到175.77.此过程中光催化氧化-还原反应起到了重要作用.     

ZnO纳米线的制备及场发射特性的研究进展

从ZnO纳米线的生长机制出发,重点讨论了催化剂在制备过程中的作用,比较了采用VLS和VS不同机制生长ZnO纳米线的优缺点,并结合二者特点发现采用金属自催化将是制备高质量ZnO纳米线阵列的一种有效方法.分析了几种有利于提高其场发射性能的后处理方法,经过适当的后处理ZnO纳米线晶体的结构将更加完善,场发射开启场、阈值场将进一步降低,电流密度和场增强因子也将随之大大提高.     

Ag掺杂对ZnO纳米线气敏性能的影响

以采用物理热蒸发法制备的纯ZnO纳米线和Ag掺杂ZnO纳米线为气敏基料，制备成旁热式气敏元件，用静态配气法对浓度均为100ppm的无水乙醇蒸汽、氨气、甲烷及一氧化碳四种气体进行气敏性能测试，结果表明，Ag掺杂后，ZnO纳米线对四种气体灵敏度的最高值分别提高了230％，92％，158％，49％，缩短了响应时间和恢复时间。     

Effects of Surface Orientation and Temperature on Tensile Deformation of Gold Nanowires

Molecular Dynamics (MD) simulations have been performed using the EAM potential to investigate the deformation behaviors and mechanical properties of <100>/{100} gold nanowires with square cross-section at a certain strain rate under different temperatures ranging from 10 K to 700 K. It is found that <100>/{100} gold nanowires at high temperatures tend to form the extended stable nanobridges-Helical Multi-shell Structure (HMS), which is similar to the deformation behavior of <110> gold nanowires at room temperature reported in the previous experimental observations and simulations. The effect of temperature on the mechanical properties and deformation behaviors of gold nanowires was analyzed. The results showed that the yield stress and modulus of the nanowires with rectangular cross-section decrease with increasing temperature at certain strain rate. In addition, we investigated <100>/{110} and <110> gold nanowires under the same conditions, and found that the surface orientation plays a significant role in the formation and stability of gold nanobridges. Based on these investigations, we discussed the combined effects of surface orientation and temperature on the mechanical properties and structural behaviors. Moreover, the length of HMS and toughness of nanowires with different orientations was analyzed as a function of temperature.     

Sn掺杂ZnO半导体纳米线的制备、表征及光学性能

采用化学气相沉积法获得了Sn掺杂含量约为2.4%(原子分数)的Sn掺杂ZnO半导体纳米线。X射线衍射结果表明,Sn的掺杂并没有改变ZnO的纤锌矿结构。掺杂纳米线的室温光致发光光谱在409.2nm和498.0nm处出现了蓝绿光发光峰。探讨了其发光机制,认为前者可能来源于从导带到Zn空位形成的浅受主能级的跃迁以及从氧空位形成的浅施主能级到价带的跃迁;而后者来源于从氧空位形成的浅施主能级到锌空位浅受主能级的跃迁。     

Full Field Tensile Strain Shearography of Welded Specimens

Digital shearography is a coherent optical method used in conjunction with digital image processing. It allows the shearogram, which depicts directly displacement derivatives, in real time to be observed and to be evaluated numerically. Strains are functions of the displacement derivatives. Thus, the shearogram contains the strain information, but usually it includes both the in‐plane strain, e.g. ?u/?x, and the out‐of‐plane component, e.g. ?w/?x. In order to get the pure in‐plane strain as well as the pure out‐of‐plane component, two linearly independent directions of illumination (usually the same but mutual and sequential illuminations) are introduced in the measuring device. The shearograms for each illuminating direction are evaluated by applying the phase shifting technique. The result by subtracting the phase maps of the two shearograms yields a new fringe pattern depicting the pure in‐plane strain component and the result by adding the phase maps corresponds to the pure out‐of‐plane component. The theory and an application to non‐destructive tensile testing are demonstrated in this paper. Its applications for determining the strain distribution of the homogeneous and inhomogeneous material and an error analysis are presented.     

电子束辐照对氧化锌纳米线Ⅰ-Ⅴ特性的影响

在扫描电镜中,采用纳米微操纵仪构成一个2探针电流-电压(I-V)测试装置.测试了单根ZnO纳米线接触钨电极构成的金属-半导体-金属(M-S-M)结的I-V特征曲线.ZnO纳米线的I-V曲线呈现出较弱的肖特基特性.研究了电子束辐照对ZnO纳米线的I-V曲线的影响.30 keV电子束辐照使ZnO纳米线的总电阻减小.计算得到ZnO纳米线的电导率σ=0.24 S/cm,载流子浓度n=1.64×1016 cm-3.为了对比,还测试了单根碳纤维接触钨电极的I-V特征曲线.在30 keV电子束辐照下,碳纤维的总电阻保持不变,电导率σ＝22 S/cm.