Influence of Au Photodeposition and Doping in CdS Nanorods: Optical and Photocatalytic Study

Au-modified CdS nanorods (100–200 nm × 5–10 nm) are synthesized via two different techniques, namely photodeposition and doping. The prepared samples are characterized by x-ray powder diffraction, transmission electron microscopy (TEM), and UV–vis and fluorescence spectroscopy. X-ray diffraction study confirmed the hexagonal phase of bare and Au-CdS samples, whereas, 5 wt% Au³⁺ doping into CdS resulted in a slight distortion in the crystal structure toward higher degree side. TEM images revealed the fine distribution of Au nanodeposits of size in the range of 2.5–4.5 nm on to the CdS surface in the photodeposited sample. The optical spectrum shows a significant red-shift in absorption onset (485 nm → 515 nm) and band-edge emission (505 nm → 512 nm) of CdS nanorods with the replacement of certain Cd²⁺ ions with Au³⁺. The influence of Au photodeposition and doping in CdS nanorods was comparatively tested by photooxidation of RhB (50 ppm) dye aqueous solution under direct sunlight irradiation (35–40 mWcm^?2). Our results point out that 5 wt% Au³⁺ doping into CdS nanorods remarkably improved its activity and stability due to homogeneous dispersion of charge throughout the crystal, quick Fermi level equilibration, and an improvement in ionic bond formation.     

TiO2纳米棒光阳极的制备及性能改进

首先采用水热法制备 TiO2纳米棒光阳极,并引入 Au@SiO2纳米颗粒对其性能进行改善。结果表明,Au@SiO2纳米颗粒的引入虽然增强了光吸收,但同时减少了染料在 TiO2纳米棒上的吸附量,反而导致了电池器件性能的下降。因此,在 TiO2纳米棒/Au@SiO2纳米颗粒结构上进一步生长一层 TiO2钝化层：一方面可增加染料吸附量;另一方面有利于减少电荷复合。基于这种光阳极组装的染料敏化太阳能电池获得了 2.34%的光电转换效率,较单一 TiO2纳米棒光阳极组装的电池效率提高了 60%。     

On the association between poly(vinyl alcohol) and sodium dodecyl sulfate and its effect on liquid–liquid interfacial tension: A mathematical model

Association between poly(vinyl alcohol-co-vinyl acetate) copolymer (PVA) and sodium dodecyl sulfate (SDS) was studied experimentally and theoretically. It was found that, for the ethyl acetate-aqueous phase interface in which PVA was previously adsorbed, the interfacial tension (γ) increases abruptly to a maximum and then exhibits a relatively mild decay with the addition of SDS to the aqueous phase. The theoretical results indicate that vinyl acetate (VAc) segments determine γ. However, for relatively low concentrations of SDS (C_SDS), this latter plays a major role because through its association with the VAc segments it modulates the extent to which PVA is adsorbed at the interface, indirectly determining the value of γ. As C_SDS approaches to the CMC value for SDS, its influence on γ decreases because SDS tends to self-assembly rather than associates with VAc. These model predictions are consistent with experimental findings reported in the literature.     

Strawberry‐like Core–Shell Ag@Polydopamine@BaTiO3 Hybrid Nanoparticles for High‐k Polymer Nanocomposites with High Energy Density and Low Dielectric Loss

Flexible nanocomposites comprising of polymer and high‐dielectric‐constant (high‐k) ceramic nanoparticles are becoming increasingly attractive for dielectric and energy storage applications in modern electronic and electric industry. However, a huge challenge still remains. Namely, the increase of dielectric constant usually at the cost of significant decrease of breakdown strength of the nanocomposites because of the electric field distortion and concentration induced by the high‐k filler. To address this long‐standing problem, by using nano‐Ag decorated core–shell polydopamine (PDA) coated BaTiO₃ (BT) hybrid nanoparticles, a new strategy is developed to prepare high‐k polymer nanocomposites with high breakdown strength. The strawberry‐like BT‐PDA‐Ag based ferroelectric polymer [i.e., poly(vinylideneflyoride‐co‐hexafluroro propylene), P(VDF‐HFP)] nanocomposites exhibit greatly enhanced energy density and significantly suppressed dielectric loss as well as leakage current density in comparison with the nanocomposites with the core–shell structured BT‐PDA. Coulomb‐blockade effect of super‐small nano‐Ag is used to explain the observed performance enhancement of the nanocomposites. The simplicity and scalability of the described approach provide a promising route to polymer nanocomposites for dielectric and energy storage applications.     

Ni-SiO2纳米复合材料的制备及磁学性质

以正硅酸乙酯和硝酸镍为原料,利用溶胶-凝胶法制备了纳米NiO-SiO2复合体,再通过氢气还原得到Ni-SiO2纳米复合材料。利用X射线衍射(XRD)确定了样品的相组成,利用透射电子显微镜(TEM)观察了样品的微观结构,利用振动样品磁强计测定了样品的磁性能。研究了成分和焙烧温度对纳米复合颗粒微观结构和性能的影响。研究发现,所形成的纳米颗粒是以Ni为核心,外面包裹着非晶态SiO2层的核壳结构。随着硅含量的增加,包裹层变厚,随着焙烧温度升高颗粒直径增大。讨论了制备条件和SiO2含量对材料的微观形貌和磁学性能的影响。     

Polymer-polymer friction: Adhesion dependence

The friction of pure polyethylene and acrylate grafted films or mixtures of polyethylene and a poly (ethylene-butylacrylate-maleic anhydride) terpolymer is examined at low speed for sliding on a poly(methylmethacrylate)(PMMA) or polyvinylchloride (PVC) substrate. In all cases, the friction coefficient μ at equilibrium is proportional to the adhesion energy of the same films as determined by a peel test. This study shows how much for smooth surfaces, interfacial and mechanical properties intervene simultaneously in polymer-polymer friction.     

纳米碳管/环氧树脂纳米复合材料的研究

采用熔融混合法合成了不同纳米碳管含量的纳米碳管/环氧树脂复合材料,测试了弯曲性能、冲击强度,并利用扫描电镜(TEM)对产物进行了表征,同时,针对纳米碳管对环氧树脂电学性能的影响做了初步研究。结果表明,当纳米碳管含量为0.05%时,纳米碳管/环氧树脂复合材料的冲击强度、弯曲强度最高,弯曲强度提高100%,弯曲模量提高41%,冲击强度提高4倍,纳米碳管在环氧树脂基体中呈单根分散,纳米碳管使环氧树脂的体积电阻下降,导电性增加。     

Structure,properties, and applications of polyacrylonitrile/carbon nanotube (CNT) fibers at low CNT loading

Bi-component, polyacrylonitrile (PAN)/carbon nanotube (CNT) fibers were processed, at different core-sheath area ratios, by gel spinning. A percolated CNT network at 10 wt% CNT in the sheath enhanced electrical conductivity as compared to the neat PAN fiber, while PAN polymer in the core contributed to the good mechanical properties. Fibers with relatively thin sheath allowed overall CNT loading as low as 3.7 wt% to be made with good electrical conductivity, and PAN stabilization by Joule heating was demonstrated. Such fibers with combined good mechanical properties and electrical conductivity can also potentially be used for electrical heating of fabrics, for making smart textiles, and for electromagnetic interference shielding.     

电子辐照PVA/CMC共混水凝胶的成胶研究

本试验利用电子辐照PVA/CMC共混水凝胶,通过外观透明度、凝胶分数、溶胀度和红外光谱分析,研究了样品中结构的变化与外观透明度、凝胶分数和溶胀度的关系,以及辐照剂量对样品中结构和性能的影响.结果表明,不同比例的PVA与相同比例的CMC组成的共混水凝胶,经电子辐照后呈现不同的宏观特性.辐照样品萃取后得到的凝胶比萃取前的混合凝胶拥有更强的吸水性,表明辐照PVA/CMC共混凝胶形成了网状结构凝胶.几种竞争反应导致不同辐照剂量下混合凝胶中凝胶含量随PVA含量的变化变得复杂.辐照后样品的红外光谱分析显示,辐照使凝胶中部分仲醇中C上链接的H原子被取代而转变为叔醇,从而产生交联.     

阻燃聚丙烯/蒙脱土纳米复合材料的制备及性能研究

通过熔融挤出法制备出了膨胀阻燃剂/聚丙烯/有机蒙脱土(IFR/PP/OMMT)阻燃纳米复合材料,XRD分析表明,蒙脱土的层间距扩大,复合材料进入其层闻,形成了纳米复合材料;结果表明,当复合材料中IFR含量为25%时,加入4%的OMMT体系的缺口冲击强度为7.8kJ/m2,拉伸强度为25.3MPa,弯曲模量为1520MPa,极限氧指数(LOI)提高到26,而耐热性也得到提高,复合材料的综合性能最好;通过对膨胀炭层的SEM分析表明,OMMT可以使炭层更加紧密,阻燃性能进一步提高.