TiO2/MXene纳米复合材料的可控制备及在光催化和电化学中的应用研究进展

TiO2纳米材料因其存在高的光生电子-空穴对复合速率、电子迁移率低、导电性差以及可逆容量低等问题,使其在光催化和电化学等领域的应用受到限制.MXene(Mn+1 Xn Tx)作为一种新型的二维过渡金属碳化物、氮化物或碳氮化物,具有独特的二维层状结构、良好的金属导电性和较高的载流子迁移率等特性,将其引入TiO2纳米材料中构建TiO2/MXene纳米复合材料,利用两者的协同作用可进一步提高光电性能.本文从TiO2纳米材料的角度出发,系统综述了零维、一维和二维TiO2与MXene纳米复合材料的可控制备、结构性能及在光催化和电化学领域应用的最新研究进展,并着重介绍了纳米复合材料的构筑机理及MXene对提高TiO2的光催化和电化学性能的增强机制等,分析了目前TiO2/MXene复合材料的制备及其在光催化和电化学领域应用中存在的不足.此外,从优化制备工艺、提升性能和探索相应的性能增强机制等方面对未来TiO2/MXene复合材料的研究方向进行了展望.     

改性碳纳米材料在低温燃料电池中的应用

碳纳米材料(如炭黑、介孔碳、碳纳米管、石墨烯、碳纳米纤维、碳纳米角等)因其优异的电学性能和结构特性(良好的导电性能和超大的比表面积),被研究者广泛用作低温燃料电池贵金属催化剂的载体。然而,作为催化剂载体的这类碳纳米材料通常都存在电化学腐蚀的问题,碳载体的腐蚀通常会导致贵金属纳米催化剂的聚集,这将使催化剂的性能降低。为了改善碳载体的抗腐蚀性能,提高金属纳米粒子的活性和稳定性,许多研究工作致力于制备特殊结构的碳纳米材料,或对碳纳米材料进行表面修饰、掺杂等。与此同时,为了取代价格昂贵的贵金属催化剂,非贵金属催化剂的研究也成为一大热点,掺杂碳纳米材料就是研究热点之一。对近几年来围绕碳纳米材料制备、改性,以及这些改性碳纳米材料作为金属纳米粒子载体等的研究工作做了较为详细的综述,同时介绍了掺杂碳纳米材料作为氧还原催化剂的研究进展。     

三种碳纳米材料改性PTFE复合材料摩擦磨损特性

对3种碳纳米材料(碳纳米管、纳米石墨及碳黑)/PTFE(聚四氟乙烯)复合材料进行了摩擦磨损性能研究,对磨损表面进行了分析。结果表明:3种碳纳米材料均可改善PTFE复合材料耐磨性,以纳米碳黑改善效果较好,其最佳添加含量为7%。纳米石墨可减小PTFE复合材料摩擦系数,碳纳米管和纳米碳黑会增大PTFE复合材料摩擦系数,且含量越高,复合材料摩擦系数增幅越大。无定形纳米碳黑对PTFE耐磨性的改善效果较好,其表面为轻微粘着磨损;结晶型纳米石墨和碳纳米管与PTFE相容性差,其表面为严重粘着磨损。     

利用等离子体技术制备和改性碳基纳米材料的研究进展

碳纳米材料如碳纳米管、石墨烯等具有超高的电导率、良好的力学强度及大的比表面积,近年来对它们的研究重点由碳纳米材料自身的性能逐渐扩展到碳纳米材料衍生物及碳基纳米复合材料的构建、性质及应用。碳基纳米材料的传统合成方法主要是化学法和电化学法,但步骤较繁琐、容易引入杂质元素等缺点制约了这些传统方法的进一步发展。作为一种制备与处理纳米材料的全新方法,等离子体技术得到了越来越广泛的关注。利用等离子体技术合成与改性碳基纳米材料的研究方向主要有:(1)通过改进等离子体源,提高其稳定性及工作效率,使其更适合制备和处理碳基纳米材料;(2)通过与不同的异质纳米材料复合,改善碳基纳米材料的物理化学性能;(3)拓展碳基纳米材料在环境保护和其他领域的应用。研究发现,相比于传统合成方法,等离子体技术具有较少引入杂质、产物催化活性较高、反应时间较短等特点。特别是低功率低气压条件下的电感耦合等离子体源,其对碳纳米材料的损伤较小,通过改变等离子体气氛,可以有效地还原或氧化碳纳米材料,这不仅去除了碳纳米材料表面的有害基团,还在其表面引入有益的化学基团,极大地提高材料的水溶性和吸附性能。直流等离子体源在大气压条件下可以稳定放电,通过改变功率和气体流速等参数可以有效控制碳纳米材料的生长方向,得到具有特殊性质的碳纳米柱或石墨烯墙。电子回旋共振等离子源有较好的稳定性,处理时几乎不会引入杂质元素,可以用于制备高精度的电子元器件。采用这些改进后的等离子体源可以将金属或有机物大分子基团负载于碳纳米材料表面,得到的衍生物能够更好地吸附环境污染物。通过等离子体技术能够将高导电率的铂粒子与碳纳米材料复合,并提高铂粒子在碳纳米材料表面的分散,这可以赋予铂粒子抗一氧化碳中毒的特性,可用作高性能燃料电池催化剂。此外,经等离子体改性的碳基纳米材料用于污染物传感器时具有较高的灵敏度和力学强度。本文主要介绍了近些年等离子体技术在碳纳米材料、碳纳米材料衍生物及碳基纳米复合材料的合成与改性方面的研究进展,归纳了经等离子体技术合成或改性的碳基纳米材料在环境保护、燃料电池催化剂、传感器等方面的应用尝试。     

改性碳纳米材料在低温燃料电池中的应用

碳纳米材料(如炭黑、介孔碳、碳纳米管、石墨烯、碳纳米纤维、碳纳米角等)因其优异的电学性能和结构特性(良好的导电性能和超大的比表面积),被研究者广泛用作低温燃料电池贵金属催化剂的载体.然而,作为催化剂载体的这类碳纳米材料通常都存在电化学腐蚀的问题,碳载体的腐蚀通常会导致贵金属纳米催化剂的聚集,这将使催化剂的性能降低.为了改善碳载体的抗腐蚀性能,提高金属纳米粒子的活性和稳定性,许多研究工作致力于制备特殊结构的碳纳米材料,或对碳纳米材料进行表面修饰、掺杂等.与此同时,为了取代价格昂贵的贵金属催化剂,非贵金属催化剂的研究也成为一大热点,掺杂碳纳米材料就是研究热点之一.对近几年来围绕碳纳米材料制备、改性,以及这些改性碳纳米材料作为金属纳米粒子载体等的研究工作做了较为详细的综述,同时介绍了掺杂碳纳米材料作为氧还原催化剂的研究进展.     

聚四氟乙烯纳米复合材料摩擦学性能研究进展

本文综述了聚四氟乙烯(PTFE)纳米复合材料在摩擦学领域的研究进展,指出纳米Al2O3最能显著增强PTFE耐磨损性能。纳米粒子增强PTFE耐磨损性能的机理还在探索中,但可能与裂纹捕获、填料富集、转移膜形成、磨屑尺寸减小、填料/基底界面作用、摩擦化学反应等因素有关。纳米材料易团聚及无机-有机物相容性差仍是PTFE纳米复合材料发展过程中亟待解决的问题。     

CMC/金属(金属氧化物)复合纳米材料的研究进展

高分子纳米复合材料表现出优异的光、电、热以及力学性质从而引起广泛地关注,而羧甲基纤维素(CMC)是天然生物可降解的线性高分子多糖,是用于制备CMC/金属(金属氧化物)复合纳米材料的绿色反应介质,从而成为复合纳米材料研究的热点。文中综述了CMC/金属(金属氧化物)的制备条件、反应机理、纳米粒子的结晶结构及其特殊的性质。在此基础上,指出了CMC/金属(金属氧化物)复合纳米材料所存在的问题并对其发展趋势进行了展望。     

非酶纳米电化学传感器用于有机磷农药残留物 检测综述

近年来,非酶纳米电化学传感器检测有机磷农药的研究受到广泛关注。非酶纳米电化学传感器具有检测成本低、操作方便、灵敏度高、响应快速等优点。碳纳米材料、纳米金属颗粒、纳米金属氧化物和纳米导电聚合物及其复合材料的出现,大大提高了有机磷农药电化学传感器的性能。随着纳米技术的出现,在合成纳米材料用于分析物特异性检测方面取得了进展,这些材料可用于构建高特异性、强选择性和经济有效的电化学传感器,以取代其他分析技术。鉴于各类纳米材料新结构的重要性,对非酶纳米电化学传感器领域的最新研究进展进行综述,并重点介绍纳米复合材料在有机磷农药检测中的应用。     

高性能MXenes纳米复合材料研究进展

二维过渡金属碳/氮化物(MXenes)以其优异的力学和电学性能,在多个领域展示出巨大的应用前景。近年来,高性能MXenes纳米复合材料(包括一维纤维、二维薄膜和三维块体)的研究取得了显著进展,但其力学性能仍远低于MXenes纳米材料的本征力学性能,这主要归因于MXenes纳米复合材料中存在的孔隙缺陷、MXenes纳米片取向度低以及界面相互作用弱等关键科学问题。针对上述问题,本文首先讨论了MXenes纳米材料的本征力学性能,总结讨论了不同类型高性能MXenes纳米复合材料的发展历程,并介绍了高性能MXenes纳米复合材料的最新研究进展,包括如何消除孔隙缺陷、提高MXenes纳米片的取向度以及增强界面相互作用。同时,介绍了高性能MXenes纳米复合材料在电热、热伪装、电磁屏蔽、传感以及储能等领域的应用。最后,梳理了高性能MXenes纳米复合材料存在的挑战,并展望了未来的发展方向。     

聚合物热电复合材料的研究进展

本文综述了碳纳米材料/聚合物、半导体合金/聚合物、金属纳米粒子/聚合物以及聚合物/聚合物等热电复合材料的研究进展。简要分析了热电复合材料的性能提升机理及现有材料尚存在的问题,并指出了聚合物热电复合材料今后的发展方向。     

Composite electromagnetic interference shielding materials for aerospace applications

Electromagnetic interference (EMI) occurs when electronic devices are subject to electromagnetic radiation from unwanted sources at the same frequency ranges that these devices operate. Metals typically serve as excellent EMI shielding agents, but their heavy weight, high cost and susceptibility to forms of environmental degradation make them an undesired choice for many current electronic devices. Conversely fibre reinforced polymeric (FRP) composite materials are normally light weight, and can be cheaper to produce, but typically lack the inherent EMI shielding capabilities that may be required. This research work addresses the viability FRP composite materials for use as EMI shielding structures, specifically for aerospace applications. It was found that carbon fibre could suffice this purpose, but likely required filler materials to enhance electrical conductivity and shielding effectiveness (SE).     

碳纤维增强水泥基复合材料屏蔽性能的研究

现代电子技术的迅速发展不可避免地带来了电磁辐射所造成的环境污染.选择合适的屏蔽材料,利用其反射、吸收、多层反射等功能是消除电磁污染的有效手段.碳纤维除具有高弹性、高模量、低密度、耐腐蚀等优良性能被当作许多复合材料的增强体外,还具有良好的导电性,将其加入到水泥基体中制成碳纤维增强水泥基复合材料(CFRC),不仅使水泥自身力学性能得到改善,而且可作为防止电磁辐射或核辐射的优良屏蔽体.     

Anticorrosive,Ultralight, and Flexible Carbon‐Wrapped Metallic Nanowire Hybrid Sponges for Highly Efficient Electromagnetic Interference Shielding

Metal‐based materials with exceptional intrinsic conductivity own excellent electromagnetic interference (EMI) shielding performance. However, high density, corrosion susceptibility, and poor flexibility of the metal severely restrict their further applications in the areas of aircraft/aerospace, portable and wearable smart electronics. Herein, a lightweight, flexible, and anticorrosive silver nanowire wrapped carbon hybrid sponge (Ag@C) is fabricated and employed as ultrahigh efficiency EMI shielding material. The interconnected Ag@C hybrid sponges provide an effective way for electron transport, leading to a remarkable conductivity of 363.1 S m^?1 and superb EMI shielding effectiveness of around 70.1 dB in the frequency range of 8.2–18 GHz, while the density is as low as 0.00382 g cm^?3, which are among the best performances for electrically conductive sponges/aerogels/foams by far. More importantly, the Ag@C sponge surprisingly exhibits super‐hydrophobicity and strong corrosion resistance. In addition, the hybrid sponges possess excellent mechanical resilience even with a large strain (90% reversible compressibility) and an outstanding cycling stability, which is far better than the bare metallic aerogels, such as silver nanowire aerogels and copper nanowire foams. This strategy provides a facile methodology to fabricate lightweight, flexible, and anticorrosive metal‐based sponge for highly efficient EMI shielding applications.     

Novel carbon nanotube-polystyrene foam composites for electromagnetic interference shielding

A novel carbon nanotube-polystyrene foam composite has been fabricated successfully. The electromagnetic interference (EMI) shielding effectiveness measurements indicated that such foam composites can be used as very effective, lightweight shielding materials. The correlation between the shielding effectiveness and electrical conductivity and the EMI shielding mechanism of such foam composites are also discussed.     

Electromagnetic interference shielding of carbon nanotube-fluoropolymer elastomer composites with layered structure

Abstract

This paper presents carbon nanotubes-containing polymer composites with layered gradient structure having electromagnetic interference (EMI) shielding properties. Polymer composite films were obtained on metal surface by aerosol deposition of a dispersion of carbon nanotubes in the solution of a copolymer of vinylidene fluoride with hexafluoropropylene (SCF-26) in acetone. Single-wall TUBALL (OCSiAl) carbon nanotubes were used. Three-layer coatings were formed with a concentration of nanotubes decreasing in each subsequent deposited layer. The reflection coefficient of electromagnetic radiation in the range of 20–35?GHz was measured. Gradient samples had significantly better characteristics compared to samples with uniform concentration of carbon nanotubes: the reflection coefficient reached ?6dB at 35?GHz. The outer layer of gradient structure with 0.1?wt % CNT provides a better matching of the wave resistance with free space and a smooth entrance of an electromagnetic wave into the sample. The subsequent layers with an increasing concentration of single-walled carbon nanotubes (0.3 and 0.5%) absorb electromagnetic radiation. Polymer elastomer composite EMI shielding coatings with concentration gradient can be applied by aerosol deposition to the surfaces of any composition and shape. Our results could serve as a design tool in carbon nanotubes - based EMI shielding flexible polymer coatings.     

孔隙率对三维针刺C/C复合材料电磁屏蔽性能的影响

通过多次重复先驱体浸渍裂解(PIP)工艺过程,改变材料的孔隙率和体密度,制备不同孔隙率的三维针刺碳/碳(C/C)复合材料,并研究了在8.2~12.4GHz频率范围内(X波段)不同孔隙率C/C复合材料的电磁屏蔽效能。结果表明:适当降低孔隙率有利于提高C/C复合材料的总电磁屏蔽效能和电磁吸收屏蔽效能,当开气孔率为33.4%时,C/C复合材料具有最大的电磁屏蔽效能(40dB),且电磁吸收屏蔽效能(30dB)远大于电磁反射屏蔽效能(12dB),是极具潜力的高吸收低反射电磁屏蔽材料。     

Recent progress in the modification of carbon materials and their application in composites for electromagnetic interference shielding

With the development in the modern technologies such as telecommunication instruments and scientific electronic devices, large amount of the electromagnetic radiations are produced, which lead to harmful effect on the highly sensitive electronic devices as well as on the health of human beings. To minimize the effect of electromagnetic radiations produced by different technologies, more efficient shielding materials are required which must be cost-effective, lightweight and good corrosion resistive. In this review, we focused on the shielding materials based on composites of carbon nanotubes and graphene. The typical surface modification of carbon nanotubes and graphene to optimize their interactions with polymers matrix has also summarized. It was found that the composites based on these carbon fillers were more efficient for electromagnetic interference shielding due to their unique properties (i.e., superior electrical, mechanical and thermal) together with lightweight, easy processing. Hence, the carbon nanotubes and graphene-based composites are excellent shielding materials against the electromagnetic radiations.     

Elastomer foam nanocomposites for electromagnetic dissipation and shielding applications

A novel elastomer foamed nanocomposite has been developed with high electromagnetic dissipation and shielding properties. This light weight foamed fluorocarbon incorporates multi-walled carbon nanotubes at low loading concentrations to achieve levels of conductivity and energy shielding that surpass the requirements for electromagnetic static discharge (ESD) and electromagnetic interference (EMI) shielding. Foaming the elastomer reduces that weight by 30% with minimal impact on ESD or EMI characteristics. The percolation threshold is at about 2% carbon nanotubes and the saturation conductivity occurs at 8% carbon nanotubes by weight. Combining the good electrical properties with the flexibility and fluid resistance of fluorocarbon yields a very versatile yet light weight material for a variety of ESD and EMI applications.     

Electrical conductivity and shielding effectiveness of poly(trimethylene terephthalate)/multiwalled carbon nanotube composites

Poly(trimethylene terephthalate) (PTT)/multiwalled carbon nanotube (MWCNT) composites have been fabricated to evaluate the potential of PTT composites as electromagnetic interference (EMI) shielding material. The room temperature electrical conductivity, complex permittivity, and shielding effectiveness (SE) of PTT/MWCNT composites were studied in the frequency range of 8.2–12.4 GHz (X-band). The dc conductivity (σ) of composites increased with increasing MWCNT loading and a typical percolation behavior was observed at 0.48 vol% MWCNT loading. The highest EMI SE of PTT/MWCNT composites was ~23 decibel (dB) at 4.76 vol% MWCNT loading which suggest that these composites can be used as light weight EMI shielding materials. The correlation among the SE, complex permittivity, and electrical conductivity was also studied. The EMI shielding mechanism of PTT/MWCNT composites was studied by resolving the total EMI SE into absorption and reflection loss.     

Electromagnetic interference shielding effectiveness of SiCf/SiC composites with PIP–SiC interphase after thermal oxidation in air

SiC_f/SiC composites with PIP–SiC interphase were prepared as electromagnetic interference (EMI) shielding materials by chemical vapor infiltration method. Effects of thermal oxidation on electrical and EMI shielding properties of the composites in X band were investigated. The as-received composites show high electrical conductivity of 0.12 S/cm and SE_T value of 29 dB, which is ascribed to the free carbon in the composites. The electrical conductivities and weight retentions of the composites decrease with oxidation temperatures or time increase. Likewise, the shielding properties deteriorate to some degree but the SE_T value exhibits more than 17 dB after oxidation at 1000 °C for 2 h and 15 dB at 900 °C for 6 h, respectively. The deterioration of electrical and EMI shielding properties during oxidation process is ascribed to the consumption of free carbon. The high SE_A value and low SE_R value imply that absorption is the dominant EMI shielding mechanism. The SiC interphase can protect the fibers and keep EMI shielding properties of the composites at a high level.