Responsive Smart Windows from Nanoparticle–Polymer Composites

Windows play significant roles in commercial and residential buildings and automobiles, which direct and control light illumination, thermal insulation, natural ventilation, and aesthetics. Various approaches are attempted to make windows “smart” by tailoring their transparency and thermal insulation in response to environmental changes. Hence, there has been much effort to develop smart windows that can dynamically modulate the transmission and reflectance of the visible light and solar radiance into buildings according to weather conditions or personal preferences. Development of smart window materials is also beneficial to applications including wearable sensors, energy harvesting and storage, and medical devices. By carefully matching the refractive indices of nanoparticle (NPs) and polymer matrix, surface chemistry, and their mechanical properties, particle‐embedded polymer composites can exhibit synergistic effects with improved chemical and mechanical stability, enhanced dispersion of NPs, and optimized and stimuli‐responsive optical properties. Here, an overview of recent progresses in the development of smart windows based on electro‐, thermo‐, and mechanoactuations is provided. Additional functionalities, e.g., flexibility, stretchability, and mechanical/chemical stability, can also be achieved by careful choices of NPs and polymers.     

High‐Tensile Strength,Composite Bijels through Microfluidic Twisting

Rope making is a millennia old technique to collectively assemble numerous weak filaments into flexible and high tensile strength bundles. However, delicate soft matter fibers lack the robustness to be twisted into bundles by means of mechanical rope making tools. Here, weak microfibers with tensile strengths of a few kilopascals are combined into ropes via microfluidic twisting. This is demonstrated for recently introduced fibers made of bicontinuous interfacially jammed emulsion gels (bijels). Bijels show promising applications in use as membranes, microreactors, energy and healthcare materials, but their low tensile strength make reinforcement strategies imperative. Hydrodynamic twisting allows to produce continuous bijel fiber bundles of controllable architecture. Modelling the fluid flow field reveals the bundle geometry dependence on a subtle force balance composed of rotational and translational shear stresses. Moreover, combining multiple bijel fibers of different compositions enables the introduction of polymeric support fibers to raise the tensile strength to tens of megapascals, while simultaneously preserving the liquid like properties of the bijel fibers for transport applications. Hydrodynamic twisting shows potentials to enable the combination of a wide range of materials resulting in composites with features greater than the sum of their parts.     

A Generalized System for Photo-Responsive Membrane Rupture in Polymersomes

Polymersomes are vesicles whose membranes are comprised of self-assembled block co-polymers. We recently showed that co-encapsulating conjugated multi-porphyrin dyes in a polymersome membrane with ferritin protein in the aqueous lumen confers photo-lability to the polymersome. In the present study, we illustrate that the photo-lability can be extended to vesicles containing dextran, an inert and inexpensive polysaccharide, as the luminal solute. Here we explore how structural features of the polymersome/porphyrin/dextran composite affect its photo-response. Increasing dextran molecular weight, decreasing block copolymer molecular weight, and altering fluorophore-membrane interactions results in increasing the photo-responsiveness of the polymersomes. Amphiphilic interactions of the luminal encapsulant with the membrane coupled with localized heat production in the hydrophobic bilayer likely cause differential thermal expansion in the membrane and the subsequent membrane rupture. This study suggests a general approach to impart photo-responsiveness to any biomimetic vesicle system without chemical modification, as well as a simple, bio-inert method for constructing photo-sensitive carriers for controlled release of encapsulants.     

扫描隧道显微镜钨针尖的制备与表征

采用直流电化学刻蚀方法制备扫描隧道显微镜钨针尖,研究了电化学刻蚀过程中NaOH溶液浓度、钨丝浸入长度和刻蚀电压对针尖形貌的影响。通过扫描电子显微镜(SEM)测量针尖曲率半径和针尖纵横比值,以表征针尖的尺寸和形状;通过能谱仪(EDS)分析针尖表面成分,以表征表面清洁度;通过场发射显微镜(FEM)得到Fowler-Nordheim (F-N)曲线来检测针尖发射性能。实验结果表明,当溶液浓度为2 mol/L、钨丝浸入长度为4 mm、刻蚀电压为3 V时,可以得到曲率半径约为100 nm、纵横比值为13的针尖,且表面无钨的氧化层。FEM结果显示当对针尖施加500 V的负偏压时,针尖可以稳定发射50 nA量级的电流,且针尖性能具有良好的一致性。     

基于NIOS Ⅱ的光纤以太网CCD相机系统设计

光纤以太网络相机是目前最具前景的相机应用模式之一.设计了基于NIOS Ⅱ的光纤以太网相机系统,利用FPGA的N1OS Ⅱ内核对网卡芯片W315OA进行配置及驱动,实现图像采集模块与计算机通过TCP/IP协议实现网络传输数据.该相机系统能在1S之内完成一幅2MByte图像数据的网络传输,在速度上能满足系统的技术要求.文章介绍了系统的实现方案.

Abstract：

Optical fiber Ethernet camera is one of the most promising application modes of cameras.With the chip W3150A,which is configured and driven by NIOSⅡ core of FPGA,the data transfer between the image acquisition module and a computer is realized through TCP/IP.2 Mbyte image data can be transferred within Is,which meets the technical requirement.The scheme based on NIOS Ⅱ is presented.     

DF100A型发射机宽频带放大器工作原理及故障分析

主要针对DF100A型发射机200 W宽频带放大器的工作原理,故障现象分析和处理方法。对于宽频带放大器的未来发展方向提供一种新的思路,从根本上解决宽频带放大器的故障率较高的问题。     

Cu/Al复合材料的制备及其对RDX热分解性能的影响

为了改善铝粉的表面氧化,提高其对含能材料热分解的催化作用,以电爆炸铝粉和二水合氯化铜(CuCl_2·2H_2O)为原料,利用置换反应法,实现了纳米铜粒子在铝粉表面的快速沉积,制备了包覆均匀的Cu/Al复合材料。利用扫描电镜(SEM)、透射电镜(TEM)、X?射线粉末衍射(XRD)、电子能谱(EDS)等对其结构和形貌进行了表征。在不同的升温速率下测试了Cu/Al复合材料与黑索今(RDX)(质量比1∶5)混合物的DSC曲线。计算了该混合物热分解反应的动力学参数。结果表明,电爆炸铝粉表面的氧化层通过氟化铵的刻蚀作用被剥离,复合材料含有单质铝和单质铜晶相,无氧化铜及氧化铝晶相,纳米级铜颗粒均匀包覆在铝粉表面,复合材料粒径为200～500 nm。加入Cu/Al复合材料后,RDX的初始分解温度和分解峰温分别降低8.51℃和26.43℃,分解热提高296 J·g~(-1),热分解活化能降低19.19 kJ·mol~(-1),表明Cu/Al复合材料可促进RDX的热分解行为。     

Electromagnetic shielding of nylon-66 composites applied to laser modules

Electromagnetic shielding of nylon-66 composites applied to laser modules was studied experimentally and theoretically. The effects of conductive carbon fiber length and weight percentage upon the shielding effectiveness (SE) of nylon composites were investigated. The SE of long carbon fiber filled nylon-66 composites was found to be higher than short carbon fiber composites under the same weight percentage of carbon fibers. In addition, higher electromagnetic shielding was obtained for the composite with higher carbon fibers contents at the same length. The SE of conductive carbon fiber filled nylon-66 composites was measured to be 42 dB at a low frequency of 30 MHz and 50 dB at a high frequency of 1 GHz. The SE predicted by theoretical models and measured by experiments were in good agreement for filled nylon-66 composites with different length fiber.     

Lead-free solder reinforced with multiwalled carbon nanotubes

In this study, varying weight percentages of multiwalled carbon nanotubes were successfully incorporated into 95.8Sn-3.5Ag-0.7Cu solder to synthesize novel lead-free composite solders. The composite solders were synthesized using a powder metallurgy route consisting of blending, compaction, sintering, and extrusion. The extruded materials were then characterized for their physical, thermal, and mechanical properties. With the addition of increasing weight percentage of carbon nanotubes, the composite solders experienced a corresponding decrease in density values and an improvement in wetting properties. The melting temperatures of the composite solders were found to be unchanged with additions of carbon nanotubes. However, improvements in the mechanical properties, in terms of microhardness and tensile properties, were observed with increasing weight percentages of carbon nanotubes.     

Stable,Superhydrophobic, and Conductive Polyaniline/Polystyrene Films for Corrosive Environments

A polyaniline/polystyrene composite film with a lotus‐leaf‐like structure is prepared via a simple electrospinning method. The film shows stable superhydrophobicity and conductivity, even in many corrosive solutions, such as acidic or basic solutions over a wide pH range, and also in oxidizing solutions. The special surface composition and morphology are the two important aspects that induce such unusual properties. The polystyrene content can strongly influence the morphology of the composite films, which thus display different superhydrophobicities and conductivities.