ZnO/BaTiO3纳米复合材料的制备及其发光性质

采用溶胶-凝胶技术制备了ZnO/BaTiO₃纳米复合材料,用X射线衍射仪(XRD)、透射电子显微镜(TEM)测定了不同温度处理后样品的组成、结构、形貌和尺寸.对复合材料室温下的光致发光谱分析发现,复合材料的发光强度比纯的纳米ZnO发光显著增强;纳米ZnO中氧空位引起的510nm发光带的峰位随着热处理温度的不同而分别出现蓝移和红移现象.其中蓝移主要是量子尺寸效应引起的,而红移则可能与致密化的BaTiO₃所提供的高介电场有关.     

热氧化法制备纳米ZnO薄膜及其发光特性的研究

用热氧化ZnS薄膜方法制备纳米ZnO薄膜．并用X射线衍射谱．光致发光谱表征和研究纳米ZnO薄膜结构特征及热氧化温度对薄膜质量的影响。X射线衍射结果表明纳米ZnO薄膜具有六角纤锌矿结构．且随热氧化温度升高．薄膜晶粒尺寸逐渐增大。光致发光谱是由紫外激子发光和与氧空位有关的深能级缺陷发光组成的．且随热氧化温度升高，激子发光峰发生红移．激子发光和深能级缺陷发光强度之比逐渐增大．在热氧化温度为800℃时，其比值为10。     

纳米ZnO/低密度聚乙烯复合材料的介电特性

为探讨纳米ZnO/低密度聚乙烯（LDPE）复合材料的介电特性,首先,采用硅烷偶联剂和钛酸酯偶联剂对纳米ZnO进行改性,并利用两步法制备了不同纳米ZnO质量分数、不同纳米ZnO粒径、不同纳米ZnO表面修饰方式和不同冷却方式的纳米ZnO/LDPE复合材料;然后,通过FTIR、SEM、DSC和热激电流（TSC）测试了纳米ZnO在基体中的分散情况、复合材料的等温结晶过程参数变化及陷阱密度;最后,在不同实验温度下分别进行了交流击穿、绝缘电导率、介电常数和空间电荷实验。结果表明:纳米ZnO的加入使纳米ZnO/LDPE复合材料内部陷阱深度和密度均有所增加;当纳米ZnO的粒径为40 nm且质量分数为3%时,复合材料的结晶速度最快,纳米ZnO在基体中的分散性较好,击穿场强达到最高值133.3 kV/mm,电导率及介电常数也相对较低,加压时复合材料内部空间电荷少,短路时释放电荷速度快,介电性能较好;由于纳米粒子增加了材料内部的热传导速率,降低了复合材料随着温度升高而降解的速度,因而相对于纯LDPE,随着实验温度的提高,纳米ZnO/LDPE复合材料的击穿场强下降幅度及电导率上升幅度均较小。      

纳米碳管/氧化锌异质结构的合成及发光性质

以纳米碳管（CNTs）为基体、铜为催化剂,采用催化碳热还原方法直接合成出具有异质结构的纳米碳管/氧化锌（CNT/ZnO）复合材料。利用扫描电镜、透射电镜及X射线衍射等手段研究了异质结构CNT/ZnO复合材料的形态和结构。发现氧化锌纳米线在纳米碳管表面的生长过程遵循催化剂诱导的汽-液-固（VLS）机制;氧化锌纳米线与铜催化剂和纳米碳管之间分别存在明显的界面,并且氧化锌纳米线与纳米碳管均保持了规整的晶体结构。同时也发现在大直径纳米碳管上易于形成高密的氧化锌纳米线;随沉积温度的升高ZnO的形态由线到棒最后形成颗粒。异质结构CNT/ZnO复合材料的诱导发光性能不同于氧化锌纳米线和纳米碳管,在蓝光区域的发光强度远大于紫外发光强度。     

钛酸钡/环氧树脂复合材料的制备及其介电性能的研究

钛酸钡/环氧树脂(BaTiO3/EPR)复合材料是最有潜力用于嵌入式电容器的储能介质材料.以不同粒径BaTiO3(BT)与环氧树脂(EPR)复合制备了BaTiO3/EPR复合材料,主要研究了粒径和温度对其介电性能的影响.研究发现复合材料的介电常数和介电损耗均随着温度的升高而升高,这是由环氧树脂基体的膨胀以及BaTiO3的相转变共同引起的.0.1μm的BaTiO3(BT-01)和环氧树脂基体的界面结合力好,组成的复合材料比0.7μm的BaTiO3(BT-07)组成的复合材料介电性能的温度稳定性较好.     

BaTiO3基Au纳米颗粒复合薄膜的制备及其光学性质研究

采用溶胶-凝胶（sol-gel）方法，成功的将高体积面分比的Au纳米颗粒复合到BaTiO3的非晶薄膜中，并对其光学性质进行了研究。用XRD、TEM、椭偏仪、吸收光谱、光克尔效应OKE（Optical Kerr Effcet）方法对薄膜进行了表征和测试。从吸收光谱观察到表面等离子体共振SPR（Surface Plasma Resonance)峰随热处理温度升高而红移的现象。光学非线性测试表明薄膜具有高的三阶非线性极化率Χ^(3)和超快的响应时间。     

高性能BaTiO_3/PVDF介电复合材料及其薄膜电容器应用

选用柔性高分子材料聚偏氟乙烯（PVDF）作为基体,纳米钛酸钡陶瓷（BaTiO3）作为填充相,采用简单的溶液共混以及流延工艺制备BaTiO3/PVDF薄膜。通过SEM观察了复合材料体系的微观结构,研究了BaTiO3/PVDF介电复合材料的介电性能。把所制备的BaTiO3/PVDF复合材料薄膜（70mm×30mm×25μm...     

激光辐照对CdSe/PMMA纳米复合材料光致发光的影响

本文用共混法制备CdSe/PMMA纳米复合材料,用荧光光谱(PL)研究了该复合材料的发光性质.通过延长激光照射时间并进行原位PL跟踪测试,我们发现了该复合材料中有机物基体发光不断减弱而CdSe纳米粒子发光不断增强且稍许红移的现象.我们对于这一现象的起因做出了初步的解释.     

BaTiO3纳米晶机械力化学合成

在氮气保护下，采用高能球磨BaO，锐钛矿型TiO2混合粉体，机械力化学法成功地合成了BaTiO3纳米晶，并讨论了反应机制。发现在一定操作参数条件下，粉磨初期为无定形形成期（15h以前），混合物颗粒粒度减小，晶格畸变，转变为无定形；粉磨中期为固相反应期（15－30h），BaO与TiO2在机械力的作用下产生固相反应生成BaTiO3，同时BaTiO3晶粒长大；粉磨后期又转入动态平衡期（30h以后），固相反应基本结束，已生成的BaTiO3的晶粒生长与粉磨引起的晶粒减小处于动态平衡；XRD，SEM，TEM研究表明：合成BaTiO3纳米晶体的晶粒尺寸为10－30nm。     

尺寸分布和界面混合对InAs/GaAs量子点光学性质的影响

研究了自组织生长模式(S-K modes)下量子点尺寸的不均匀分布对量子点发光性质的影响,对其光致发光峰进行了拟合计算.研究发现,量子点尺寸的不均匀分布导致了量子点发光峰的展宽以及发光峰位的红移.另一方面,后处理工艺中的退火及质子注入引起的界面混合导致了量子点PL谱发光峰的蓝移及半高宽的减小.     

退火CdS/SiO2介孔组装体系光吸收的行为

用溶胶-凝胶法获得多孔SiO2载体，浸泡合成法得到不同复合量的CdS/SiO2块材料介孔组装体系。研究了复合量、气氛条件及退火温度对其光吸收特征的影响，发现吸收边随复合量增加往长波方向移动；在氮气和空气中退火时，随退火温度升高前者表现为红移而后者表现为蓝移，这归属于量子尺寸效应。     

退火CdS/SiO2介孔组装体系光吸收的行为

用溶胶-凝胶法获得多孔SiO₂载体,浸泡合成法得到不同复合量的CdS/SiO₂块材介孔组装体系.研究了复合量、气氛条件及退火温度对其光吸收特性的影响,发现吸收边随复合量增加往长波方向移动;在氮气和空气中退火时,随退火温度升高前者表现为红移而后者表现为蓝移,这归属于量子尺寸效应.     

Nc-ZnO可见光谱响应特性研究

利用分光光度法测定了纳米晶氧化锌对可见光的响应光谱和利用率,并利用量子理论对所得的数据进行分析讨论,结果显示,量子尺寸效应将会导致吸收光谱的蓝移和红移,在光谱波长320nm-1020nm范围内具有60%-100%的光催化效率。     

Effects of symmetrical and asymmetrical bumps on plasmonic behavior in a metallic grating

The influence was investigated of symmetrical and asymmetrical bumps on plasmonic behavior in a metallic grating. Compared with the resonant peaks of a smooth-slit grating, the peaks of odd (even) modes exhibit a blue-shift (red-shift) and the transmission properties are tunable by the size of bumps when the bumps are laid symmetrically. However, the peaks of all modes only exhibit a red-shift when the grating is engraved with a bump and a cut in the same slit (namely bend slit), and the bend slit can achieve the properties of a straight slit. Additionally, it is found that the dips in transmission spectrum can be adjusted by altering the size of the bumps if the bumps are set asymmetrically. Fabry–Pérot-like resonance, field interference and phase resonance mechanisms have been suggested for the physical origins of these observations.     

Transparent Ni-doped ZnO-Al2O3-SiO2 system glass-ceramics with broadband infrared luminescence

We report transparent Ni²⁺-doped ZnO-Al₂O₃-SiO₂ system glass-ceramics with broadband infrared luminescence. After heat-treatment, ZnAl₂O₄ crystallite was precipitated in the glasses, and its average size increased with increasing heat-treatment temperature. No infrared emission was detected in the as-prepared glass samples, while broadband infrared luminescence centered at 1310 nm with full width at half maximum (FWHM) of about 300 nm was observed from the glass-ceramics. The peak position of the infrared luminescence showed a blue-shift with increasing heat-treatment temperature, but a red-shift with an increase in NiO concentration. The mechanisms of the observed phenomena were discussed. These glass-ceramics are promising as materials for super broadband optical amplifier and tunable laser.     

Annealing effects on the cathodoluminescence properties of individual ZnO nanowire

Annealing effects on cathodoluminescence of single zinc oxide nanowire are investigated. It is found that ultraviolet emission is gradually decreased and further disappears with temperatures in all the atmospheres. Deep-level emission is blue-shift with temperature in both argon and vacuum, compared with fresh nanowire. Oxygen vacancies are the main defects for the blue-shift in the oxygen-deficient condition such as argon and vacuum. However, deep-level emission is red-shift in oxygen atmosphere with temperature. It is thought that complex defects zinc vacancies and oxygen interstitials should be responsible for the interesting red-shift of deep-level emission.     

A Raman study of CdSe and ZnSe nanostructures

Raman studies have been carried out on CdSe nanotubes and ZnSe nanorods produced by surfactant-assisted synthesis. The Raman spectrum of CdSe nanotubes shows modes at 207.5 and 198 cm-1; the former arises from the longitudinal optic phonon mode red-shifted with respect to the bulk mode because of phonon confinement, and the latter is the l = 1 surface phonon. Analysis based on the phonon confinement model demonstrates that the size of the nanoparticle responsible for the red-shift is about 4 nm, close to the estimate from the blue-shift of the photoluminescence. The Raman spectrum of ZnSe nanorods shows modes at 257 and 213 cm-1, assigned to longitudinal and transverse optic phonons, blue-shifted with respect to the bulk ZnSe modes because of compressive strain. The mode at 237 cm-1 is the surface phonon.     

Sn催化的Ga掺杂ZnO纳米线的制备及其光致发光性能研究

采用化学气相沉积的方法,以Sn粉为催化剂制备出大长径比的Ga掺杂ZnO纳米线。采用扫描电子显微镜观察制备的产物,发现样品为直径约25～90nm的纳米线。通过比较不同Ga掺杂含量样品的室温光致发光谱,发现一定掺杂含量的Ga可以提高ZnO纳米线的紫外发光强度,同时,Ga的掺杂也会引起ZnO紫外发光峰的蓝移。随着Ga含量的增加,蓝移程度越来越小,甚至发生红移。Sn的引入只对Ga掺杂ZnO纳米线的蓝绿光有贡献。     

Spectral shift of an electromagnetic Gaussian Schell-model beam propagating through tissue

Based on the unified theory of coherence and polarization for stochastic electromagnetic beams, spectral changes of an electromagnetic Gaussian Schell-model (EGSM) beam propagating through tissue are investigated in detail. Numerical results show that the spectral shift of an electromagnetic GSM beam is closely determined by the parameters of the tissue (e.g. the fractal dimension of tissue and the ensemble-averaged variance of the refractive index fluctuations). The spectral shift changes from blue-shift to red-shift with the increase of the transverse coordinate.