四脚状氧化锌晶须的研究现状及展望

四脚状氧化锌晶须(T-ZnOw)是目前发现的具有独特空间三维结构的晶须,并且其针部具有单晶性,由于其独特的晶体结构使得它在耐磨、减震、吸波等各个方面有着广阔的应用前景.阐述了T-ZnOw的晶体结构,介绍了氧化锌晶须的气-固(VS)和气液-固(VLS)生长机理,总结了其主要制备方法,如预处理氧化法、蒸气氧化法、平衡气量法、真空制备法和电化学沉积法等,并介绍了它的性能及其在增强复合材料、抗静电、抗菌和吸波方面的应用,总结展望了今后的研究方向.     

四脚状氧化锌晶须的微波电磁性能

以锌粉为原料,采用碳还原剂控制法制备了四脚状氧化锌晶须。用光学显微镜、扫描电子显微镜及X射线衍射分析方法对产物进行了表征。实验结果表明,该晶须为纯氧化锌,属于六方晶系纤锌矿结构;整个氧化锌晶须基本为四脚状晶须结构。通过热力学分析及试验表明,在1220~1350 K的温度时,可以得到完整的四脚状氧化锌晶体。用波导法对所得晶须进行了磁导率和介电常数的测量。微波电磁性能试验表明,四脚状氧化锌晶须是一种介电损耗材料,具有一定的微波吸收性能。     

膨润土催化制备四脚状氧化锌晶须的研究

采用膨润土作为催化剂,通过高温气相氧化法制备了四脚状氧化锌(T-ZnO)晶须,并研究了实验条件对产物的影响.结果表明:实验温度、催化剂含量和空气流量对T-ZnO晶须的尺寸、规整性、产率等有显著的影响,实验温度为920～980 ℃,膨润土含量为33%左右以及适当的空气流量条件下,可以得到尺寸均一、结构规整、四脚状含量和晶须产率都较高的T-ZnO晶须.     

平衡气量法制备四针状氧化锌晶须生长动力学研究

以金属锌为主要原料,用平衡气量控制法制备了具有四针状结构的氧化锌晶须,并对晶须生长过程进行了研究,发现通过控制反应原料锌的氧化速度可以分别控制晶须核心体部分和针状体部分的生长速度.提出了将锌的氧化反应、晶核形成过程、晶体生长过程等复杂反应简化为简单一级反应加以控制,通过控制反应区氧气量来控制整个反应速度和晶须结构,测定出四针状氧化锌晶须核心体生成和针状体生长两个阶段的速度常数分别为0.30 min-1和1.08 min-1,计算出ZnO晶须核心部分和针状体部分的重量比约为1:20.     

氧化锌晶须在纯化学发泡制备硅橡胶泡沫中的应用研究

采用氧化锌晶须增强改善硅橡胶,运用纯化学发泡技术制备硅橡胶泡沫材料.研究了氧化锌晶须对硅橡胶混炼胶塑性值、硅橡胶泡沫泡孔结构及分布和泡沫压缩应力松弛性能的影响.结果表明:氧化锌晶须用量对硅橡胶混炼胶塑性值影响不大,氧化锌晶须可以改善泡沫泡孔结构和分布,明显降低了硅橡胶泡沫材料的压缩应力松弛性能.     

T-ZnO_w制备过程中工艺参数的影响

采用常压下直接热蒸发锌粉的方法制备了四针状氧化锌晶须(T-ZnOw)。研究了升温速率及保温温度对晶须产量、结构及形态的影响。利用SEM及XRD对产物进行了表征。实验结果表明前期升温速率为3℃/min时,所制备T-ZnOw形貌最为规整,且产率高达95%。随着前期升温速率的提高,产物是不均匀的四针状氧化锌晶须,晶须尺寸增加。随着保温温度的增加,晶须细化,但晶须结构的完整性及产量都有所下降。     

纳米T-ZnOW的制备及其生长机理研究

以锌粒为原料，分子筛为催化剂，利用真空控氧高温气相氧化法，制备了纳米四针状氧化锌晶须（T—ZnOw）。利用XRD和SEM、TEM对产物进行物相分析和形貌观察。结果表明：产物为纯六方晶系纤锌矿结构氧化锌；体系压力和反应温度是影响晶须形貌的两个重要因素。当温度恒定为1038℃，而压力低于11083Pa时，均可获得根部直径为20—80nm、针长500nm-2μm、形貌规整的纳米T—ZnOw。TEM研究表明，纳米T—ZnOw的针部为单晶，而核心为多重孪晶结构，其生长遵循气固生长机理。     

氧化锌晶须(ZnOW)水泥基复合材料微波吸收特性研究

研究了氧化锌晶须(ZnOw)水泥基复合材料的材料制备,测试了试件在微波3mm,8mm,3cm等波段的微波吸收特性.研究结果表明,氧化锌晶须(ZnOw)能够有效调整水泥基复合材料的介电常数,改变反射及透射特性,但本身对微波的吸收并不明显,甚至还降低了常规混凝土的透射衰减性能.该结论对澄清氧化锌晶须(ZnOw)的微波吸收应用前景猜测有实际意义.     

燃烧法合成花状、四针状氧化锌及其气敏性能研究

研究了以锌粉为原料,活性炭为催化剂,高温气相氧化反应制备花状、四针状和无定形氧化锌的合成条件及形貌.X射线衍射结果表明该晶体属六方晶系纤锌矿结构.扫描电镜研究结果表明活性炭催化剂用量、反应温度对产物氧化锌晶须的形态影响很大,对所有样品的气敏元件在浓度范围为5×10(-6)～2×10(-4)的甲醇、乙醇、丙酮和正丙醇气体...     

四针状氧化锌晶须的最新研究进展

四针状氧化锌晶须是近年来发展起来的一种新型多功能材料,因具有独特的性能而在多领域得到广泛应用。本文综述了氧化锌晶须的结构、基本性能、制备方法及在增强材料、抗静电、抗菌和光催化等方面的应用。指出了存在问题,对今后的发展方向进行了展望。     

空气中热氧化电沉积Zn纳米晶制备一维ZnO纳米针及其生长机制与场发射效应的研究

在金属基板表面电沉积一层金属Zn纳米晶，将该纳米晶置于高温炉中，通过热氧化法成功制备了一维ZnO纳米针。研究了不同的热氧化温度因素对一维ZnO纳米针的制备及其形貌的影响。在本方法中，一维ZnO纳米针材料对应于初始电沉积层的Zn纳米晶颗粒，这与其他方法中ZnO的生长机制不同，可以认为本方法的ZnO的生长遵从自催化扩散机制。同时，研究了一维ZnO纳米针薄膜的场发射效应。     

Preparation of nanosized Pt-Au alloy catalyst and its activity in methanol oxidation

The alloy catalyst has been widely used because it will be able to improve the activity and selectivity of the single metal catalyst in a given chemical reaction. In this study, the preparation and characteristics of nanosized Pt and Au particles on alumina and their catalytic activity were described. Nanosized Pt-Au catalysts were prepared by impregnation (IMP) method and deposition (DP) method using alumina or ZnO/Al2O3 as support. The size of Pt and Au particles were observed by transmission electron microscopy (TEM), energy dispersive spectroscope (EDS), and X-ray diffraction (XRD). Catalytic activity for oxidation of methanol was measured using a flow reactor. It could be seen that the Pt particle size and dispersion in the alloy catalysts was rarely influenced by preparation methods and Au particles coated by deposition method were well dispersed. TEM images showed that Au particles were well dispersed in the Pt/Au/ZnO/Al2O3 catalyst of which Au particles was supported by deposition method. The catalytic activity for methanol are given in the order of Pt-Au[IMP]/ZnO/Al2O3 > Pt[IMP]/Au[DP]/ZnO/Al2O3 > Au[DP]/Pt[IMP]/ZnO/Al2O3 > Pt-Au[DP]/ZnO/Al2O3. Therefore, Au particle size was doing not play an important role in increasing the oxidation activity, but the Au particles may promote the methanol oxidation.     

Microstructure and optical properties of Ag-doped ZnO nanostructures prepared by a wet oxidation doping process

Silver-doped zinc oxide (Ag:ZnO) nanostructures were prepared by a facile and efficient wet oxidation method. This method included two steps: metallic Zn thin films mixed with Ag atoms were prepared by magnetron sputtering as the precursors, and then the precursors were oxidized in an O(2) atmosphere with water vapour present to form Ag:ZnO nanostructures. By controlling the oxidation conditions, pure ZnO and Ag:ZnO nanobelts/nanowires with a thickness of ～ 20 nm and length of up to several tens of microns were synthesized. Scanning electron microscopy, transmission electron microscopy, cathodoluminescence and low temperature photoluminescence (PL) measurements were adopted to characterize the microstructure and optical properties of the prepared samples. The results indicated that Ag doping during magnetron sputtering was a feasible method to tune the optical properties of ZnO nanostructures. For the Ag:ZnO nanostructures, the intensity of ultraviolet emission was increased up to three times compared with the pure ones. The detailed PL intensity variation with the increasing temperature is also discussed based on the ionization energy of acceptor in ZnO induced by Ag dopants.     

High-yield chemical synthesis of hexagonal ZnO nanoparticles and nanorods with excellent optical properties

Large yield and low temperature growth of nanostructures are key requirements for fulfilling the demand of large scale applications of nanomaterials. Here, we report a highly efficient chemical method to synthesize high quality hexagonal ZnO nanoparticle and nanorods utilizing the low temperature oxidation of metallic zinc powder in the presence of an appropriate catalyst. This one-step method has advantages such as low temperature (90 degrees C) and atmospheric pressure synthesis and a high yield (> 90%). Microstructure and optical properties of the as-synthesized ZnO nanoparticles are found to be identical or better than those of the commercial ZnO nanopower (Sigma-Aldrich). In particular, in comparison to the commercial nanopowder the as-grown ZnO nanorods and nanoparticles exhibit stronger UV absorption at 376 nm and intense UV photoluminescence emission at -382 nm, with negligible defect emission band. This method is suitable for large-scale production of nanosized ZnO and could be extended for the synthesis of other metal oxides.     

新型工艺制备ZnO薄膜的结构与形貌研究

采用了一种新型工艺制备ZnO薄膜。新工艺采用二步法,首先在N型Si(100)衬底上用离子束沉积溅射一层金属Zn膜,然后通过热氧化金属Zn膜制备ZnO薄膜。通过X射线衍射、原子力显微镜对不同制备工艺下的ZnO薄膜进行结构与形貌的分析比较。研究表明,Zn膜的离子束溅射沉积时间、热氧化时间和辅助枪的离子束对热氧化后的ZnO薄膜再轰击处理对ZnO薄膜的结构与形貌都会产生影响。     

Evaluation of photocatalysis of Au supported ZnO prepared by the spray pyrolysis method

Environmental pollution by organic dyes used in industry is a serious problem in developing countries. Environmentally friendly treatment methods are being studied because conventional methods require chemical or additional decomposition treatment. In particular, oxidation via a photocatalyst is a promising alternative due to its chemical and physical stabilities and low cost. However, electron-hole recombination limits the photocatalytic activity in semiconductor photocatalysts such as ZnO and TiO₂. This study investigates control of electron-hole recombination of the photocatalyst by loading Au on ZnO (Au/ZnO). Using the Ultrasonic Spray Pyrolysis (USP) method, Au/ZnO particle generation is easily achieved under various conditions. XRD analysis confirms the crystal peaks of ZnO and Au. The EDX mapping and STEM images of the particles show that the Au crystals are well dispersed in the inner and outer portions of ZnO. The photocatalytic decomposition rate of organic dye (Rhodamine-B) is faster than that of ZnO in all Au/ZnO particles, and the best photocatalytic activity occurs in particles with 0.1 mass% Au supported on ZnO particles. In addition, optimal photolysis activity occurs in 100 mL of 5 mg/L RhB aqueous solution and 10 mg dose of Au/ZnO particles.     

Controlled growth of vertically aligned ZnO nanowires with different crystal orientation of the ZnO seed layer

A novel synthesis and growth method achieving vertically aligned zinc oxide (ZnO) nanowires on a silicon dioxide (SiO(2)) coated silicon (Si) substrate is demonstrated. The growth direction of the ZnO nanowires is determined by the crystal structure of the ZnO seed layer, which is formed by the oxidation of a DC-sputtered Zn film. The [002] crystal direction of the seed layer is dominant under optimized thickness of the Zn film and thermal treatment. Vertically aligned ZnO nanowires on SiO(2) coated Si substrate are realized from the appropriately thick oxidized Zn seed layer by a vapor-solid growth mechanism by catalyst-free thermal chemical vapor deposition (CVD). These experimental results raise the possibility of using the nanowires as functional blocks for high-density integration systems and/or photonic applications.     

Nanocrystalline ZnO thin film for photocatalytic purification of water

ZnO thin film was prepared via evaporation of Zn metal on a glass sheet following by calcination (oxidation) process. The influences of calcination parameters such as temperature and time on the surface morphology and phase structure of ZnO films were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The analysis of XRD patterns indicated that the growth of ZnO nano-structure was controlled by calcination time and temperature. Optimum ZnO nano-fibers can be formed uniformly after 2 h of oxidation at 550 °C. Nanostructured ZnO catalyst exhibited a significantly greater superiority for the photodegradation of 2,4,6-Trichlorophenol (TCP) as a model pollutant in water over photolysis via irradiation with UV of 254 nm wavelength. The role of ZnO catalyst is discussed and the chemical composition of degradation products and intermediates are identified.     

A simple and cheap way to produce porous ZnO ribbons and their photovoltaic response

A simple and cheap method is proposed to achieve porous ZnO ribbons by oxidation of ZnS ribbons in the air. ZnS has a fully transformation to ZnO at an annealing temperature of 700°C from energy dispersive X-ray spectra and X-ray diffraction patterns. Scanning electron microscopy images indicate that ZnO ribbons keep the original shapes of ZnS, but produce some ordered and uniform pores on their surfaces. The photovoltage spectrum of ZnO/N3 indicates such dye-porous ZnO ribbons may be used in the dye-sensitized solar cells. The porous ZnO ribbons may also find potential applications in catalyst, sensor, and molecular selection. This technique to produce porous ribbons may also be applied to prepare other porous metal oxide ribbons.     

Large-scale fabrication of ZnO nanocrystals by a simple two-step evaporation–oxidation approach

Single crystal structures of ZnO nanocrystals were prepared on quartz and polyimide (PI) film substrates by using a thermal coater to promote thermal evaporation, followed by air circulation at 350 °C for 2 h to effect oxidation. HRTEM and TEM images show the individual ZnO nanocrystals have regular lattice order without stacking faults. After dispersion by an ultrasonic bath, ZnO deposited on PI film substrates can consist of individual and well-distributed nanocrystals with an average crystal size of 20–30 nm. In photoluminescence, the nanocrystalline ZnO exhibits strong UV emission at 395 nm, with no emission in the visible spectrum. The synthetic method described in this paper provides a simple and efficient method to fabricate ZnO nanocrystals on a large scale.