Wide-band underwater acoustic absorption based on locally resonant unit and interpenetrating network structure

The interpenetrating network structure provides an interesting avenue to novel materials. Locally resonant phononic crystal (LRPC) exhibits excellent sound attenuation performance based on the periodical arrangement of sound wave scatters. Combining the LRPC concept and interpenetrating network glassy structure, this paper has developed a new material which can achieve a wide band underwater strong acoustic absorption. Underwater absorption coefficients of different samples were measured by the pulse tube. Measurement results show that the new material possesses excellent underwater acoustic effects in a wide frequency range.Moreover, in order to investigate impacts of locally resonant units,some defects are introduced into the sample. The experimental result and the theoretical calculation both show that locally resonant units being connected to a network structure play an important role in achieving a wide band strong acoustic absorption.     

Large-scale SiO2 photonic crystal for high efficiency GaN LEDs by nanospherical-lens lithography

Wafer-scale SiO2 photonic crystal （PhC） patterns （SiO2 air-hole PhC, SiO2-pillar PhC） on indium tin oxide （ITO） layer of GaN-based light-emitting diode （LED） are fabricated via novel nanospherical-lens lithography. Nanoscale polystyrene spheres are self-assembled into a hexagonal closed-packed monolayer array acting as convex lens for expo- sure using conventional lithography instrument. The light output power is enhanced by as great as 40.5% and 61% over those of as-grown LEDs, for SiO2-hole PhC and SiO2-pillar PhC LEDs, respectively. No degradation to LED electrical properties is found due to the fact that SiO2 PhC structures are fabricated on ITO current spreading electrode. For SiO2- pillar PhC LEDs, which have the largest light output power in all LEDs, no dry etching, which would introduce etching damage, was involved. Our method is demonstrated to be a simple, low cost, and high-yield technique for fabricating the PhC LEDs. Furthermore, the finite difference time domain simulation is also performed to further reveal the emission characteristics of LEDs with PhC structures.     

An in-situ Observation on Initial Aggregation Process of Colloidal Particles near Three-Phase Contact Line of Air, Water and Vertical Substrate

The self-assembling process near the three-phase contact line of air, water and vertical substrate is widely used to produce various kinds of nanostructured materials and devices. We perform an in-situ observation on the selfassembling process in the vicinity of the three phase contact line. Three kinds of aggregations, i.e. particle-particle aggregation, particle-chain aggregation and chain-chain aggregation, in the initial stage of vertical deposition process are revealed by our experiments. It is found that the particle particle aggregation and the particle-chain aggregation can be qualitatively explained by the theory of the capillary immersion force and mirror image force, while the chain-chain aggregation leaves an opening question for the further studies. The present study may provide more deep insight into the self-assembling process of colloidal particles.     

TiO2薄膜的制备方法及其对染料敏化太阳电池性能的影响

采用溶胶 凝胶、浆体涂敷、磁控溅射等方法制备了二氧化钛单层以及多层膜.通过透射电镜、扫描电镜以及X射线衍射实验分析了不同薄膜的结构.通过比较不同薄膜制作的染料敏化太阳电池性能探讨了薄膜结构的影响.实验所获得的电池开路电压可达708mV,短路电流可达13.26mA(电池面积为1.8cm²).     

苯乙烯/丙烯酸正丁酯/丙烯酸共聚微球的制备及其性能表征

通过乳液聚合法和无皂乳液聚合法制备了苯乙烯/丙烯酸正丁酯/丙烯酸共聚微球.讨论了乳化剂用量、引发剂用量、功能单体、软硬单体用量比等对微球粒径和形态的影响.利用扫描电子显微镜(SEM)、傅立叶变换红外光谱仪(FTIR)对微球的粒径、形貌和表面基团进行分析.红外光谱表明,实验室所制备的苯乙烯/丙烯酸正丁酯/丙烯酸共聚微球表面存在丰富的羧基.利用竖片生长法得到自组装的多层胶体微球薄膜.通过对薄膜的反射光谱测量,发现随着湿度的增加,峰位会产生3nm左右的红移.     

Role of Convection Flow on the Pattern Formation in the Drying Process of Colloidal Suspension

We study the macroscopic drying patterns of aqueous suspensions of colloidal silica spheres. It was found that convection strength can influence pattern formation. Uniformed films are obtained at weaker convection strength. In addition, we make clear that it is not reasonable to discuss individually the effect of temperature and humidity on the colloid self-assembly. The physical mechanism is that these factors have relationship with the evaporation rate, which can affect the convection strength.     

水热法制备ZnO二维周期有序孔结构薄膜

在由溶胶-凝胶法制备的纳米ZnO薄膜衬底上,以Zn(NO3)2.6H2O和六亚甲基四胺(HMT)等摩尔浓度配制成前驱体溶液,在单层聚苯乙烯(PS)微球模板辅助下,采用水热法制备了具有规则多孔结构的ZnO薄膜。探讨了PS微球作为模板对ZnO纳米棒生长的限制作用以及柠檬酸钠在水热制备方法中对晶体生长的影响。利用扫描电子显微镜(SEM)和X射线衍射(XRD)表征了水热反应后所得二维有序ZnO膜表面形貌和取向性,测量了ZnO薄膜的光致发光(PL)光谱并研究其相应机理。