晶硅太阳能电池背面银浆所用片状银粉的研究

为了确保晶硅太阳能电池在拥有较高光电转换效率的同时降低投入成本,本文研究了45wt;的低固相含量状态下不同粒径及振实密度的片状银粉对背面银浆性能的影响.将球形银粉经过不同时间的球磨得到不同粒径的片状银粉.用这四种银粉制成背面银浆并经过印刷烧结形成背电极,研究了粒径、振实密度对背电极烧结膜形态及电性能的影响.结果证明平均粒径为2.5 μm的片状银粉具有最高的振实密度,由其制备背电极的烧结膜最为致密,焊接强度达到8.5 N,硅太阳能电池的光电转换效率达到18.09;,可以满足目前背面银浆的商业使用需要.     

多元素协同掺杂对氢氧化镍正极高温性能的影响

选取Co、Zn、Ca、Mg、Cu和Mn元素与Ni元素以一定化学计量比共沉积,并对其进行修饰或掺杂,制备出新型氢氧化镍正极材料.采用恒电流充放电技术测试其在不同温度不同倍率下的充放电性能,并测试了样品的粒径和振实密度.研究结果表明:粒径尺寸分布适中,振实密度较高;通过多元素协同掺杂,可显著提高析氧电位,抑制析氧副反应的发生.多元素之间的协同掺杂是改善氢氧化镍正极材料高温大电流充放电性能的有效途径.     

电气石表面TiO2微孔空心球簇的制备及光催化活性研究

用溶胶-凝胶技术在紫铜表面制备含电气石矿物粉末的TiO2复合薄膜,研究薄膜的制备方法、显微结构及其光催化活性.用SEM技术研究电气石-TiO2复合薄膜的微观结构和电气石表面TiO2的显微结构,测量了TiO2空心球直径、TiO2空心球簇大小,同时用电子探针对电气石-TiO2复合薄膜中的TiO2空心球簇表面及球簇周围TiO2膜进行了成分分析;并用电气石/TiO2复合薄膜光催化降解甲基橙水溶液,研究电气石对TiO2薄膜光催化活性的影响.结果发现,紫铜表面上电气石微粒均匀分布在TiO2薄膜中,且在电气石微粒表面可形成TiO2微孔空心球和微孔空心半球构成的微孔空心球簇,空心球和空心半球的平均粒径为2μm;经紫外线照射180min后,与不含电气石的TiO2薄膜相比,含电气石0.5;的TiO2复合薄膜对甲基橙的光催化降解率可提高31.9;,电气石可以明显提高TiO2薄膜的光催化活性.     

莫来石空心球的制备与表征

以工业氢氧化铝为铝源,粉煤灰漂珠为模板,五氧化二钒和氟化铝为添加剂,采用固相反应原位制备了莫来石空心球.粉煤灰漂珠与工业氢氧化铝按质量比为45∶55配料,外加4wt;V2O5与3wt; AlF3,5wt; PVA溶液,通过粘附法,在900℃至1200℃下恒温2h随炉冷却.采用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)对莫来石空心球进行了表征.结果表明:在1000℃至1200℃下制备的空心球主晶相为莫来石相,空心球球壳是由细长针状的莫来石组合而成,其长度约为8μm,长径比平均为25∶1,球壳内部莫来石未发育完全,而是形成了比较致密的内部结构体.     

Cu掺杂ZnO铁磁性的研究

采用基于密度泛函理论(DFT)和局域密度近似(LDA)的第一性原理分析了Cu掺杂ZnO的磁性质.计算了6个不同几何结构的铁磁(FM)和反铁磁(AFM)耦合自由能,结果表明FM耦合更稳定.FM性质主要来源于Cu 3d与O2p原子之间的杂化.O空位和N杂质对Cu掺杂ZnO铁磁性的研究表明,O空位和N杂质不利于稳定其铁磁性质.通过研究Cu3d能级之间的耦合,阐述了Cu掺杂ZnO铁磁性产生的原因.另外,也分析了晶格轴应变和剪切应变对Cu掺杂ZnOFM耦合影响.     

Ce∶KNSBN晶体两波耦合动态过程研究

本文在非同时读出条件下,采用实时数据采集系统,实验研究了e偏振光写入Ce∶KNSBN晶体两波耦合动态过程,发现不同的写入光强比和写入总光强对晶体中两波耦合过程产生明显的影响;当He-Ne 632.8nm激光通过Ce∶KNSBN晶体时,光扇效应存在明显的写入光强阈值特性,其阈值约为20mW/cm2.依据实验结果对考虑光扇影响的耦合波方程进行了修正,其数值计算与实验结果基本符合.     

不同形貌Bi2WO6的可控合成及光催化机理研究

采用水热、溶剂热的合成方法制备了Bi2WO6纳米材料,利用X射线衍射(XRD)、拉曼光谱、扫描电子显微镜(SEM)和紫外–可见漫反射光谱(UV-Vis DRS)研究了水热、表面活性剂、溶剂热制备方法及制备条件对Bi2WO6材料的形貌、结晶性、粒径等性质及Bi2WO6可见光催化性能的影响.结果表明:与水热法合成的圆片型和花瓣状Bi2WO6相比,醇热法合成的空心球形貌的Bi2WO6具有最高的光催化效果.随着焙烧温度升高,空心球逐渐塌陷,样品的光催化活性也大幅度下降.捕获剂活性实验表明,空心球Bi2WO6在光催化降解罗丹明B反应中的主要活性物种为空穴(h+)和超氧自由基(·O2-).     

阳离子聚合物聚乙烯亚胺诱导的碳酸钙仿生矿化研究

以富含胺基的阳离子聚合物聚乙烯亚胺(PEI)为碳酸钙生长的矿化调节剂,采用气体扩散的方法,研究了不同PEI浓度以及不同矿化时间对碳酸钙形貌和晶型的影响.分别采用扫描电子显微镜(SEM)、X射线粉末衍射(XRD)、傅里叶红外光谱(FT-IR)等实验手段对所得的样品进行了表征.结果表明,在较低的聚乙烯亚胺浓度下获得空心球状的球霰石和方解石,在较高浓度下,为方解石的聚集体,并随着矿化时间的延长,方解石的形貌趋于规则.     

中科院上硅所所在空心球结构纳米材料制备方法研究中取得进展

目前,纳米材料的结构控制和性能研究已成为全球纳米技术的研究热点。发展具有结构可控和优异性能的纳米功能材料成为材料科学领域的首要任务之一。空心球纳米材料是一大类重要的纳米结构材料,其制备技术已日趋成熟并逐步实用化,在药物释放、气敏等领域具有很多重要的应用。然而,常规制备空心球纳米材料的技术,如模板法和Oswald熟化生长等需要相对复杂的操作工艺,通用性不好,有一定的局限性。     

微乳液法制备不同形貌低维硒化锌纳米晶

利用微乳液法,实现了多晶硒化锌纳米空心球、单晶硒化锌纳米棒以及ZnSe量子点的低温合成.通过调整Triton X-100/环己烷/水体系中表面活性剂Triton X-100的浓度分别制备出直径在120 nm左右,壁厚在6nm左右的ZnSe多晶纳米空心球体、长度达1μm的单晶纳米棒和直径位于4～6nm的ZnSe量子点.紫外可见吸收光谱显示不同形貌ZnSe纳米结构的吸收特征具有较大的差别.     

Space-resolved dynamics of a tracer in a disordered solid

The dynamics of a tracer particle in a glassy matrix of obstacles displays slow complex transport as the free volume approaches a critical value and the void space falls apart. We investigate the emerging subdiffusive motion of the test particle by extensive molecular dynamics simulations and characterize the spatio-temporal transport in terms of two-time correlation functions, including the time-dependent diffusion coefficient, the frequency-dependent conductivity, as well as the wavenumber-dependent intermediate scattering function. We rationalize our findings within the framework of critical phenomena and compare our data to a dynamic scaling theory.     

Tuning of a Dye Laser By a Liquid Crystal†

We describe how a cholesteric liquid crystal device can be used in a laser cavity to induce tuning of the laser line. Tuning of the order of 10Å is obtained by applying low voltages to the liquid crystals film. The problems, the advantages and the feasibility of the method is discussed, reporting several experimental data.     

Mechanical properties of a TAS fiber: a preliminary study

The mechanical properties, including elastic moduli, hardness, fracture toughness and tensile strength of a glass fiber in the Te-As-Se system (TAS) were studied. The values for the hardness (1.4 GPa) and the fracture toughness (0.18 MPa √m) show that this glass is both soft and brittle in comparison to glasses from other systems. However, indentation measurements should be interpreted with caution due to an indentation creep phenomenon and to a delayed fracture process. In addition, the effect of treatments in air (relative humidity about 60%) at different temperatures below T_g were investigated. The main result of this study is that the studied TAS glass is sensitive to the presence of humidity, and aging treatments have a pronounced detrimental effect on the strength of the uncoated fibers.     

Simulation of mass transfer in a kinetic experiment based on migration of flat layers of a solution in a melt in a temperature gradient field

Mass transfer upon migration of flat liquid layers of a solution in a melt under conditions of slow change in the average temperature at a constant rate has been analyzed for the dislocation and nucleation mechanisms of interface processes. It is shown that the experimental data on the dependence of the migration rate of flat layers on their thickness can be adequately described within the theory developed for strictly steady thermal conditions. A technique is proposed for determining the overall limitations on the mass transfer at interfaces and the migration rate in the diffusion mode from the experimental results obtained in a mixed migration mode.

     

Comparative Study of Mixed Monolayers of a Calixarene with a Fatty Acid and a Non-Amphiphilic Nematic Liquid Crystal

Abstract

Many nematic liquid crystals (NLCs) lack a polar headgroup and thus are not able to form stable monolayers at the air/water (a/w) interface. A way to obtain monomolecular films of these compounds is to incorporate them into host monolayers of amphiphilic molecules. We report a comparative investigation of mixed films of Calix[4]resorcinarene O-octacarboxymethylated (CRO) with the non-amphiphilic NLC MBBA and with the amphiphilic stearic acid (SA). The comparative study is useful for a better understanding of the characteristics of the CRO-MBBA mixed films. Surface-pressure and surface-potential measurements on the monolayers at a/w interface, as well as ellipsometric and spectroscopic measurements on transferred Langmuir-Blodgett (LB) films, confirm that MBBA is additively incorporated into CRO films.     

Dopant concentration profile in a Czochralski flow of liquid metal in a vertical or a horizontal magnetic field

Dopant concentration profiles are obtained for a Czochralski flow of liquid metal in a static crucible under either an axisymmetric vertical magnetic field or a horizontal uniform magnetic field. The latter magnetic field inevitably requires fully three-dimensional cylindrical coordinate model equations, which are successfully solved for the representative parameters Gr = 10⁷, Pr = 0.01, Re = 1620 and Ha 1000. Asymmetric concentration profiles are obtained. The average heat flux decreased with the Hartmann number. The circumferential rotational direction was found to be reversed in a lower regime against that of a top rotating crystal rod in a strong lateral magnetic field. In a vertical magnetic field, the concentration profile approached the pure diffusion state.     

Diffraction reflection of a focused X-ray wave by a multilayer crystal

The Bragg diffraction of a narrow X-ray beam in a multilayer crystal is studied in the reflection geometry. It is shown by computer simulation of the experiment that strong integrated kinematic reflection occurs at any boundary of a multilayer crystal at the point of intersection of a narrow beam with the boundary. In contrast to the dynamic diffraction of a plane wave, attenuation of a narrow incident beam due to the reflection is small in comparison with the conventional absorption. As an example of a multilayer crystal, a Fabry-Perot interferometer is considered, which consists of two 70-μm-thick crystal Si layers separated by a 100-μm-thick air layer. The 12 4 0 reflection is studied at a photon energy of 15 keV. Three methods of formation of a narrow beam are considered: wavefront limitation by a slit, focusing with a parabolic lens, and focusing with a zone plate. It is shown that, for a local analysis of the thickness of layers and scattering parameters, the method of parabolic lens focusing has some advantages in comparison with the other methods.     

Ideal gas in a box — a numerical study

A numerical study of the ideal monoatomic gas in a rectangular box is presented. The spatial distribution of temperature, density, pressure and chemical potential is studied in detail with and without the presence of gravitational forces. Some conclusions are drawn regarding the importance of the particle-wall interaction.     

Grazing-incidence dynamic X-ray diffraction from a crystal with a shaped surface

The dynamic grazing-incidence X-ray diffraction from a crystal with a shaped surface in the form of one-dimensional submicron grating has been investigated. The interaction between the specularly reflected and diffracted waves and grating harmonics is taken into account for noncoplanar diffraction under the conditions of total external reflection. It is shown that this approximation exhibits good convergence in the number of harmonics taken into account. The influence of the angular divergence of the incident beam on the rocking-curve shape is shown.