Flexible Piezoelectric ZnO–Paper Nanocomposite Strain Sensor

The fabrication of a mechanically flexible, piezoelectric nanocomposite material for strain sensing applications is reported. Nanocomposite material consisting of zinc oxide (ZnO) nanostructures embedded in a stable matrix of paper (cellulose fibers) is prepared by a solvothermal method. The applicability of this material as a strain sensor is demonstrated by studying its real‐time current response under both static and dynamic mechanical loading. The material presented highlights a novel approach to introduce flexibility into strain sensors by embedding crystalline piezoelectric material in a flexible cellulose‐based secondary matrix.     

Carbon nanomaterials for advanced energy conversion and storage

It is estimated that the world will need to double its energy supply by 2050. Nanotechnology has opened up new frontiers in materials science and engineering to meet this challenge by creating new materials, particularly carbon nanomaterials, for efficient energy conversion and storage. Comparing to conventional energy materials, carbon nanomaterials possess unique size-/surface-dependent (e.g., morphological, electrical, optical, and mechanical) properties useful for enhancing the energy-conversion and storage performances. During the past 25 years or so, therefore, considerable efforts have been made to utilize the unique properties of carbon nanomaterials, including fullerenes, carbon nanotubes, and graphene, as energy materials, and tremendous progress has been achieved in developing high-performance energy conversion (e.g., solar cells and fuel cells) and storage (e.g., supercapacitors and batteries) devices. This article reviews progress in the research and development of carbon nanomaterials during the past twenty years or so for advanced energy conversion and storage, along with some discussions on challenges and perspectives in this exciting field.     

聚丙烯酰胺/氧化石墨纳米复合材料的研究

氧化石墨具有良好的层状结构,其层间具有丰富的官能团,能与有机聚合物形成插层纳米复合材料进而改善材料的性能．采用层离吸收-原位聚合法制备了聚丙烯酰胺／氧化石墨纳米复合材料,并采用XRD、HREM及DSC等对其结构和性能进行了表征。结果表明,聚丙烯酰胺与氧化石墨两者之间存在着较强的相互作用,材料的玻璃化转变温度得到提高,层离吸收-原位聚合法是获得聚丙烯酰胺／氧化石墨层纳米复合材料的有效途径,聚丙烯酰胺在氧化石墨中存在着多种排列方式,不同层间距(1．6nm和2．8nm)的聚丙烯酰胺／氧化石墨纳米复合结构同时存在。     

炭材料在能量储存与转化中的应用

通过评述炭材料在能量储存和转化领域的研究和发展现状,如:炭材料是燃料电池重要的催化剂载体、双极板和气体扩散层材料,也是太阳能电池构建碳-硅PN结、全碳PN结以及透明导电膜的核心材料,锂离子电池和超级电容器的关键电极材料.另外,炭材料在气体存储、蓄能蓄热、核能、风能等领域也具有重要的应用.认为:炭材料形态结构多样性及其所具有的诸多优异物理和化学特性,是其在能量储存和转化领域中广泛应用的根本.提出:炭材料必须向纳米化、有序化、复合化方向发展,实现功能炭材料的可控制备、纳米结构调控、复合材料的优化设计与制备对能量转化和存储器件升级,炭材料必将获得更加广阔的发展和应用空间.     

Flexible Nanodielectric Materials with High Permittivity for Power Energy Storage

Study of flexible nanodielectric materials (FNDMs) with high permittivity is one of the most active academic research areas in advanced functional materials. FNDMs with excellent dielectric properties are demonstrated to show great promise as energy‐storage dielectric layers in high‐performance capacitors. These materials, in common, consist of nanoscale particles dispersed into a flexible polymer matrix so that both the physical/chemical characteristics of the nanoparticles and the interaction between the nanoparticles and the polymers have crucial effects on the microstructures and final properties. This review first outlines the crucial issues in the nanodielectric field and then focuses on recent remarkable research developments in the fabrication of FNDMs with special constitutents, molecular structures, and microstructures. Possible reasons for several persistent issues are analyzed and the general strategies to realize FNDMs with excellent integral properties are summarized. The review further highlights some exciting examples of these FNDMs for power‐energy‐storage applications.     

穿孔式双浮体装置水动力及波能转换特性研究

为进一步解决波能转换装置向深水环境推进过程中存在能量转换效率问题,在现有双浮体点吸式波能装置基础上考虑穿孔阻尼板,提出新的穿孔双浮体带支撑立柱的结构形式.基于线性微幅波假设,通过特征函数展开和边界匹配的势流半解析方法,并结合多自由度振动理论,探索穿孔阻尼板对获能系统水动力、运动响应及俘获宽度比的影响.计算结果表明,阻尼...     

Sol-gel cobalt oxide-silica nanocomposite thin films for gas sensing applications

Various metal oxide-silica nanocomposite films have been recently proposed as gas-sensitive materials. This paper presents results on cobalt oxide-SiO₂ mesoporous nanocomposite thin films templated by a cationic surfactant. The films were deposited on glass substrate by dip-coating process, using [Co(CH₃COO)₂]·4H₂O and tetraethoxysilane (TEOS) as starting materials. The effect of withdrawal speed, number of layers and thermal treatment on the crystalline structure, morphology, Co-doping states, optical, electrical and gas sensing properties of the thin films has been investigated using X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, optical transmittance and room temperature photoreduction-oxidation data.     

Hierarchical graphene foam-based phase change materials with enhanced thermal conductivity and shape stability for efficient solar-to-thermal energy conversion and storage

Recently,graphene foam (GF) with a three-dimensional (3D) interconnected network produced by template-directed chemical vapor deposition (CVD) has been used to prepare composite phase-change materials (PCMs) with enhanced thermal conductivity.However,the pore size of GF is as large as hundreds of micrometers,resulting in a remarkable thermal resistance for heat transfer from the PCM inside the large pores to the GF strut walls.In this study,a novel 3D hierarchical GF (HGF) is obtained by filling the pores of GF with hollow graphene networks.The HGF is then used to prepare a paraffin wax (PW)-based composite PCM.The thermal conductivity of the PW/HGF composite PCM is 87％ and 744％ higher than that of the PW/GF composite PCM and pure PW,respectively.The PW/HGF composite PCM also exhibits better shape stability than the PW/GF composite PCM,negligible change in the phase-change temperature,a high thermal energy storage density that is 95％ of pure PW,good thermal reliability,and chemical stability with cycling for 100 times.More importantly,PW/HGF composite PCM allows light-driven thermal energy storage with a high light-to-thermal energy conversion and storage efficiency,indicating its great potential for applications in solar-energy utilization and storage.     

Flexible cellulose and ZnO hybrid nanocomposite and its UV sensing characteristics

Abstract

This paper reports the synthesis and UV sensing characteristics of a cellulose and ZnO hybrid nanocomposite (CEZOHN) prepared by exploiting the synergetic effects of ZnO functionality and the renewability of cellulose. Vertically aligned ZnO nanorods were grown well on a flexible cellulose film by direct ZnO seeding and hydrothermal growing processes. The ZnO nanorods have the wurtzite structure and an aspect ratio of 9 ~ 11. Photoresponse of the prepared CEZOHN was evaluated by measuring photocurrent under UV illumination. CEZOHN shows bi-directional, linear and fast photoresponse as a function of UV intensity. Electrode materials, light sources, repeatability, durability and flexibility of the prepared CEZOHN were tested and the photocurrent generation mechanism is discussed. The silver nanowire coating used for electrodes on CEZOHN is compatible with a transparent UV sensor. The prepared CEZOHN is flexible, transparent and biocompatible, and hence can be used for flexible and wearable UV sensors.     

The use of neural networks in understanding and predicting oxidation and corrosion behaviour in advanced energy conversion systems

Abstract

Neural networks can be a useful tool to analyse the oxidation and corrosion behaviour of materials at high temperature. Examples are given of the use of neural network models to analyse datasets of material behaviour after exposure to combustion, gasification and steam atmospheres. The use of networks to identify changes in mechanism, additional significant experimental parameters and the onset of spallation is demonstrated.

The limitations of neural network modelling are briefly discussed. Although they can be trained to fit any existing dataset, care must be taken in using the networks to predict a time sequence of events.     

以R142b为工质的有机朗肯循环低温发电系统研究

研究了以R142b为循环介质、采用螺杆式膨胀机的低温热能有机朗肯循环发电系统.在热源温度低于80℃的条件下,膨胀机最大能量转化效率为6％,系统总效率5.16％.在系统膨胀效率达97％的情况下,传输能耗导致机械效率仅有48％-65％,因此系统总效率较低,但最大(火用)效率为32％.提高蒸发压力、降低冷凝压力是提升能量转化效率的根本途径.实验研究表明,降低膨胀机入口蒸汽干度对膨胀效率略有促进,主要由于少量液体参与膨胀减少了膨胀环节的渗漏,提高了膨胀效率.实验表明该低温热能发电系统可行,但系统效率较低,有待进一步优化提高.     

利用波动法研究曲梁结构中的波形转换和能量传递

基于Flugge理论,建立了薄壁均质常曲率曲梁面内运动的6阶微分控制方程,得到了曲梁的频散特性曲线和6种波的轴向位移和径向位移的比值,推导了位移和内力响应的表达式以及物理域和波数域的变换矩阵。利用波的传递和反射矩阵对曲梁和半无限长直梁耦合时的能量传递系数和反射系数进行了求解分析。对于半无限长直梁中给定的拉伸波或弯曲波入射,得到了和频率,曲率半径和伸展角度相关的各种波传递和反射的能量系数表达式。数值结果表明,纵波和弯曲波在经过曲梁结构之后发生了波形转换,并研究了能量传递和反射系数随频率,伸展角度,曲梁曲率半径和截面尺寸比的变化。结果表明,无限长直梁和曲梁耦合系统中,低频时,经过曲梁反射和传递后的弯曲波和纵波会相互转化;高频时弯曲波和纵波都能够没有散射地通过曲梁而进行传播。为改善高频时曲梁中的能量衰减效果,研究了在曲梁结构中插入单个、多个中间支撑或阻振质量块时的能量传递和反射系数。结果表明,阻振质量块能够很好地阻止高频时曲梁中能量的传递,对于周期分布的多个阻振质量块,能量传递系数随频率的变化存在周期结构的阻带特征。这些研究结果为曲梁结构的设计提供定性的理论基础。     

载银氧化锌复合纳米粒子的制备与表征

采用沉淀法制备了纳米氧化锌,并以它为前驱物,采用高温分解法对纳米氧化锌进行了裁银改性处理,制备了栽银氧化锌复合纳米粒子,考察了载银前后纳米粒子的粒径与结构。研究发现,采用沉淀法制备的纳米氧化锌尺寸较为均匀,粒径约为170nm,分散性也较好;载银后的复合纳米粒子粒径略有增加,这来源于银在纳米氧化锌粒子外的成功包覆。