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141.
ZnO naorods on ZnO-coated seed substrates were fabricated by solution chemical method from Zn(NO3)2/NaOH under assisted electrical field. The working mechanism of electrical field was analyzed and the factors affecting the rod growth such as potential, precursor concentration and growth temperature were elucidated. The structural and optical properties are characterized by SEM, TEM, XRD, HRTEM and UV-vis. The results indicated that the nanorods have wurtzite structure without electrical field and are primarily of zincite structure under electrical field; when the electrical field is 1.1-1.3 V, not only the elevation of ion diffusion and adsorption lower the crystallite/solution interfacial energy and then the crystal nucleation barrier by increasing charge intensity, but also the production of H+ through oxidation of OH− increases properly the degree of solution supersaturation near the substrate, and thus lowers the activation energy. Both the two processes do favor to rod growth. With increasing precursor concentration in this system, the average diameter and length of ZnO nanorods increase, leading to decreasing of optical transmittance. The maximum rod growth rate at given concentration of Zn2+ occurs at a specific temperature. 相似文献
142.
143.
掺Eu3+硅基材料的发光性质 总被引:9,自引:5,他引:4
通过溶胶-凝胶技术制备了掺Eu^3 的硅基材料并测试了其三维荧光光谱、激光谱和发射光谱,结果显示,最佳激发波波长为350nm,最强荧光波长为620nm;在350nm光激发下的发射光谱显示Eu^3 的特征发射光谱,产生4条谱带,分别是577nm(^5D0-^7F0),588nm(^5D0-^7F1),596nm(^5D0-^7F1)和610nm(^5D0-^7F2)。 相似文献
144.
Z.X. Cheng S.J. ZhangF. Song H.C. GuoJ.R. Han H.C. Chen 《Journal of Physics and Chemistry of Solids》2002,63(11):2011-2017
Erbium and ytterbium codoped double tungstates NaY(WO4)2 crystals were prepared by using Czochralski (CZ) pulling method. The absorption spectra in the region 290-2000 nm have been recorded at room temperature. The Judd-Ofelt theory was applied to the measured values of absorption line strengths to evaluate the spontaneous emission probabilities and stimulated emission cross sections of Er3+ ions in NaY(WO4)2 crystals. Intensive green and red lights were measured when the sample were pumped by a 974 nm laser diode (LD), especially, the intensities of green upconversion luminescence are very strong. The mechanism of energy transfer from Yb3+ to Er3+ ions was analyzed. Energy transfer and nonradiative relaxation played an important role in the upconversion process. Photoexcited luminescence experiments are also fulfilled to help analyzing the transit processes of the energy levels. 相似文献
145.
荧光光纤光栅传感特性的实验研究 总被引:2,自引:2,他引:0
在载氢掺铒光纤上写入Bragg光纤光栅,得到新型光子学器件-荧光光纤光栅.分别对其Bragg波长(λB)及荧光寿命(τ)的温度(T)及应变(ε)响应特性进行了实验研究,并且给出了λB和τ分别关于(T,ε)的拟合方程.实验结果表明:荧光光纤光栅的λB对T和ε的响应具备一般Bragg光纤光栅的优良特性,测得温度灵敏度为11.1pm /℃,应变灵敏度为1.19pm/με;而且τ对T和ε的响应也具有良好的线性关系,温度灵敏度为0.59 μs/℃,应变灵敏度为6.16 ns/με.实验结论为解决温度应力交叉敏感、实现温度应力的同时监测提供一条新颖的途径. 相似文献
146.
A new microtensile tester for the study of MEMS materials with the aid of atomic force microscopy 总被引:4,自引:0,他引:4
An apparatus has been designed and implemented to measure the elastic tensile properties (Young's modulus and tensile strength)
of surface micromachined polysilicon specimens. The tensile specimens are “dog-bone” shaped ending in a large “paddle” for
convenient electrostatic or, in the improved apparatus, ultraviolet (UV) light curable adhesive gripping deposited with electrostatically
controlled manipulation. The typical test section of the specimens is 400 μm long with 2 μm×50 μm cross section. The new device
supports a nanomechanics method developed in our laboratory to acquire surface topologies of deforming specimens by means
of Atomic Force Microscopy (AFM) to determine (fields of) strains via Digital Image Correlation (DIC). With this tool, high
strength or non-linearly behaving materials can be tested under different environmental conditions by measuring the strains
directly on the surface of the film with nanometer resolution. 相似文献
147.
The objective of this paper is to investigate the role of the set of irrational numbers as the codomain of order-preserving
functions defined on topological totally preordered sets. We will show that although the set of irrational numbers does not
satisfy the Debreu property it is still nonetheless true that any lower (respectively, upper) semicontinuous total preorder
representable by a real-valued strictly isotone function (semicontinuous or not) also admits a representation by means of
a lower (respectively, upper) semicontinuous strictly isotone function that takes values in the set of irrational numbers.
These results are obtained by means of a direct construction. Moreover, they can be related to Cantor’s characterization of the real line to obtain much more general results on the semicontinuous
Debreu properties of a wide family of subsets of the real line.
相似文献
148.
基于超分子结构共掺杂纳米复合薄膜的制备与荧光特性 总被引:5,自引:0,他引:5
为改善功能分了的特性,提出一种基于金属纳米粒子-偶氮染料复合物共掺杂超分子结构功能材料的设计新方法.并依照此方法制备出复合材料,观测了其显微结构,测量了其紫外-可见光吸收,研究了该超分子结构复合体系的荧光特性.实验发现,由于金属银纳米粒子的掺杂,使得超分子结构复合体系中功能分子甲基橙在溶液态体系的荧光强度增强近5倍,而在两种不同结构(共混结构和包覆结构)的薄膜态超分子结构体系中,其荧光强度分别被猝灭15%和20%.研究结果表明,复合膜中采用超分子结构完全能够改善功能分子的特性. 相似文献
149.
C. Devaux J.P. Chapel E. Beyou Ph. Chaumont 《The European physical journal. E, Soft matter》2002,7(4):345-352
Thin layers of polystyrene were grown from surface-grafted nitroxide initiators via controlled “living” free radical polymerization.
The “reactive” Langmuir-Blodgett deposition method allowed an effective control of the initiator layer density leading to
PS brushes with different and high grafting density and stretching. The influence of the grafting density on the layer structure
was studied. Comparison with theoretical predictions for monodispersed brushes in bad solvent was discussed. The thickness
was found to vary linearly with molecular weight and the density dependence was shown using wetting measurements. Special
features of controlled radical nitroxide polymerization from a surface were discussed. A direct comparison of the molecular
weight and polydispersity between surface and bulk polymers was made by de-grafting the brushes into a toluene/HF solution.
Finally, some evidence of a “surface Fischer” effect was shown from re-initiated layers.
Received 20 December 2001 相似文献
150.
Eu3+掺杂硼酸盐玻璃的光谱性质研究 总被引:1,自引:0,他引:1
测试了不同浓度掺杂下Eu^3+离子在硼酸盐玻璃的吸收光谱、激发光谱与发射光谱,根据荧光光谱计算了各样品的强度参数力2与/24,分析了Eu^3+离子掺杂浓度对其发光强度的影响.研究结果表明:在Eu^3+离子高掺杂浓度时,会发生浓度猝灭效应,但由于Eu^3+激活离子之间能量传递几率很小,使得Eu^3+离子猝灭浓度较高。 相似文献