气-固反应法合成准一维纳米结构材料的研究

综述了利用气-固反应法合成准一维纳米结构材料的研究进展,简要介绍了气-固反应法与气相法的不同点,重点讨论了用气-固反应法直接热氧化或硫化铜、铁、锌等金属以合成准一维纳米结构氧化物、硫化物的过程以及气-固反应法的生长机理,并介绍了准一维纳米结构材料的潜在应用.     

气-固反应法制备纳米结构及其生长机制

利用滚压振动磨在干法室温条件下,将金属锌制备成为尺度大约在3～5nm的锌量子点,并将纳米锌量子点加热到250℃并与水蒸气进行反应,得到纳米氧化锌与纳米锌的混合物。分别利用能量发射谱仪(EDS)、X射线多晶体衍射仪(XRD)、透射电镜(TEM)测试样品的化学成分和表面形貌。结果表明:锌粉加热到250℃与水蒸气反应得到的产物具有良好的分散性,其特征是棒状和片状结构共存,纳米棒有明显的沿着[0,1,-1,1]晶向的生长趋势。一维ZnO纳米棒材料对应于初始锌纳米晶颗粒,与其他方法中ZnO的生长机制不同,可以认为本文中的ZnO的生长遵从顶端生长机制。     

结构可控的纳米多孔气凝胶材料

综述了气凝胶材料的发展及潜在的应用前景。     

气-液反应法合成包覆型纳米铁粒子

采用气-液反应法合成了纳米级铁粒子,利用TEM、XRD、VSM等仪器对合成产物的晶态、物相、形貌、粒度和磁性进行了表征。结果表明,合成的产物为纳米级α-Fe,且粒子被均匀地包覆了表面活性剂,抗氧化性能明显提高。粒子的平均粒径为17.2nm,饱和磁化强度为113.57A·m2/kg,磁性能相对稳定。     

微波固相法合成纳米氧化镁

以乙酸镁和草酸为原料,用微波固相法制备了立方晶系结构的纳米氧化镁.TGA对前驱体的热分析表明微波处理能降低分解温度.采用XRD、TEM和IR对不同制备条件下MgO的晶型、晶粒尺寸、以及表观形貌等进行了表征,结果表明:焙烧温度、时间、微波加热时间对粒径影响较大;在600℃下焙烧3h制备的MgO平均晶粒尺寸为14.33nm.     

纳米氧化锌材料的制备方法及结构表征

文章介绍了纳米ZnO材料的常用制备方法,如应用较多的气-固-液法、气相法、水热法和有着较好应用前景的电化学法,以及各类纳米ZnO材料的结构表征,并展望了纳米ZnO材料的发展前景。     

室温固相合成纳米ZnS及其气敏性能研究

以无机盐ZnSO₄·7H₂O和Na₂S·9H₂O为原料,用室温固相化学反应合成了ZnS;用XRD、TEM对产物的组成、大小、形貌进行了表征;用TG-DTA确定了ZnS的稳定温区.结果表明,产物为纳米颗粒,平均粒径为15nm左右,且610℃以下能在空气中稳定存在.另外还采用静态配气法测定了材料的气敏性能,发现ZnS对H₂S有很高的灵敏度,且抗干扰能力强,有很好的应用前景.     

溶胶-凝胶法纳米α-Fe2O3材料的合成、结构及气敏性能

在硝酸铁乙二醇甲醚溶液中,用溶胶-凝胶法制备了氧化铁纳米晶,通过加入高效缩合催化剂钛酸丁酯不但极大加速了凝胶化过程而且均匀的将钛掺入氧化铁晶格,形成钛酸铁.结合TEM,XRD和TG-DTA分析手段对产物粉体的粒度、晶相和热稳定性进行表征并测试了其气敏性能.结果表明单独钛掺杂即可显著提高元件对被测气体的灵敏度,若再掺入少量锑,就能进一步增加灵敏度.对掺杂后材料的气敏机理做了探讨并测试了其响应-恢复时间,证明该材料具有迅速的响应-恢复性能,因而具有良好的应用前景.     

高分子基固-固相变材料的研究进展

简要介绍了近年来兴起的高分子固-固相变材料的研究进展,从机理、应用、优缺点等各方面对各类材料进行了阐述比较,并通过分析得到目前研究的高分子固-固相变材料主要为物理共混类与化学接枝共聚类,着重讲解了各类材料的制备过程与性能表征,并展望了今后高分子固-固相变材料的发展前景.     

气-液-固法在半导体纳米线生长中的应用

气-液-固法(VLS)是目前生长各种准一维纳米结构的主要工艺技术.本文首先介绍了VLS的生长原理,然后以生长机制为主线,着重评论了近3-5年内它在ZnO、GaN、Si以及SiC等纳米线及其阵列合成中应用的某些新进展.最后提出了改进VLS方法的几项措施,并展望了它的今后发展趋势.     

热剂反应自蔓延高温合成材料研究进展

热剂反应是自蔓延高温合成反应的一个分支,它采用成本低廉的天然氧化物作原料,比元素直接合成材料具有更显著的经济效益.通过对工业和实验中最具代表性的两种热剂反应--铝热剂与镁热剂反应研究及应用的介绍,阐述了热剂反应的发展状况,并指出了热剂反应研究的不足和有待进一步研究的若干问题.     

表面活性剂模板法制备介孔材料

自从发现M41S系列介孔分子筛以来,人们对介孔材料的研究越来越活跃.在介孔材料的制备方面,用表面活性剂作模板来组装的方法有着重要的地位.对介孔材料的研究工作进行了简要介绍,讨论了介孔材料的形成机理、制备和影响介孔材料结构的因素.     

Tuning Surface Properties of Low Dimensional Materials via Strain Engineering

The promising and versatile applications of low dimensional materials are largely due to their surface properties, which along with their underlying electronic structures have been well studied. However, these materials may not be directly useful for applications requiring properties other than their natal ones. In recent years, strain has been shown to be an additionally useful handle to tune the physical and chemical properties of materials by changing their geometric and electronic structures. The strategies for producing strain are summarized. Then, the electronic structure of quasi‐two dimensional layered non‐metallic materials (e.g., graphene, MX2, BP, Ge nanosheets) under strain are discussed. Later, the strain effects on catalytic properties of metal‐catalyst loaded with strain are focused on. Both experimental and computational perspectives for dealing with strained systems are covered. Finally, an outlook on engineering surface properties utilizing strain is provided.     

TiCl4-O2体系高温反应制备超细TiO2光催化材料的研究

高温管式气溶胶反应器中,利用ＴｉＣｌ_４气相氧化制备超细ＴｉＯ_２光催化材料,研究了停留时间和反应温度对粒子形态的影响．结果表明ＴｉＯ_２粒度随停留时间延长和反应温度升高而增大;金红石相含量随停留时间延长而增加,当反应温度１３００℃时,粒子中金红石含量出现最大值．以偶氮染料活性艳红Ｘ－３Ｂ为模拟废水;考察粒子光催化活性．光催化活性与粒径和晶型等形态指标有关,等效粒径３６．４ｎｍ、金红石含量１８９７％ＴｉＯ_２的活性高于商品Ｐ２５和ＳＨ－１．     

Solid‐State Explosive Reaction for Nanoporous Bulk Thermoelectric Materials

High‐performance thermoelectric materials require ultralow lattice thermal conductivity typically through either shortening the phonon mean free path or reducing the specific heat. Beyond these two approaches, a new unique, simple, yet ultrafast solid‐state explosive reaction is proposed to fabricate nanoporous bulk thermoelectric materials with well‐controlled pore sizes and distributions to suppress thermal conductivity. By investigating a wide variety of functional materials, general criteria for solid‐state explosive reactions are built upon both thermodynamics and kinetics, and then successfully used to tailor material's microstructures and porosity. A drastic decrease in lattice thermal conductivity down below the minimum value of the fully densified materials and enhancement in thermoelectric figure of merit are achieved in porous bulk materials. This work demonstrates that controlling materials' porosity is a very effective strategy and is easy to be combined with other approaches for optimizing thermoelectric performance.     

低维纳米热电材料研究进展

低维纳米热电材料具有优良的热电性能,近年来受到大量研究者的喜爱。本文讨论低维纳米热电材料的机理,综述了零维纳米热电材料、一维纳米热电材料、二维纳米热电材料的最新研究进展,为低维纳米热电材料的进一步深入研究做了初步的总结和预测。     

Synthetic Two‐Dimensional Materials: A New Paradigm of Membranes for Ultimate Separation

Microporous membranes act as selective barriers and play an important role in industrial gas separation and water purification. The permeability of such membranes is inversely proportional to their thickness. Synthetic two‐dimensional materials (2DMs), with a thickness of one to a few atoms or monomer units are ideal candidates for developing separation membranes. Here, groundbreaking advances in the design, synthesis, processing, and application of 2DMs for gas and ion separations, as well as water desalination are presented. This report describes the syntheses, structures, and mechanical properties of 2DMs. The established methods for processing 2DMs into selective permeation membranes are also discussed and the separation mechanism and their performances addressed. Current challenges and emerging research directions, which need to be addressed for developing next‐generation separation membranes, are summarized.     

Two‐Dimensional Materials for Halide Perovskite‐Based Optoelectronic Devices

Halide perovskites have high light absorption coefficients, long charge carrier diffusion lengths, intense photoluminescence, and slow rates of non‐radiative charge recombination. Thus, they are attractive photoactive materials for developing high‐performance optoelectronic devices. These devices are also cheap and easy to be fabricated. To realize the optimal performances of halide perovskite‐based optoelectronic devices (HPODs), perovskite photoactive layers should work effectively with other functional materials such as electrodes, interfacial layers and encapsulating films. Conventional two‐dimensional (2D) materials are promising candidates for this purpose because of their unique structures and/or interesting optoelectronic properties. Here, we comprehensively summarize the recent advancements in the applications of conventional 2D materials for halide perovskite‐based photodetectors, solar cells and light‐emitting diodes. The examples of these 2D materials are graphene and its derivatives, mono‐ and few‐layer transition metal dichalcogenides (TMDs), graphdiyne and metal nanosheets, etc. The research related to 2D nanostructured perovskites and 2D Ruddlesden–Popper perovskites as efficient and stable photoactive layers is also outlined. The syntheses, functions and working mechanisms of relevant 2D materials are introduced, and the challenges to achieving practical applications of HPODs using 2D materials are also discussed.     

纳米导热材料的研究进展

纳米导热材料的发展为日常生活和工业生产的传热节能提供了大的帮助。文章重点介绍了纳米流体、纳米导热聚合物的种类、制备以及在工业领域的应用,详细阐述了国内外的最新研究成果,分析了纳米导热材料的问题,展望了纳米导热材料的未来。