EDTA辅助水热法制备不同形貌的氟化镁钠

以氟化钠、六水合氯化镁为主要原料, EDTA (乙二胺四乙酸二钠盐)为辅助剂, 通过水热法制备出不同形貌的氟化镁钠。考察了溶液pH、反应温度、时间和络合剂对产物形貌和物相的影响, 并对其形成机理进行了探讨。采用扫描电镜(SEM)、X射线衍射(XRD)和傅里叶变换红外光谱(FT-IR)等手段对产物形貌和物相进行了表征。结果表明: 在该反应体系中, EDTA既作为原料提供钠离子, 又作为络合剂与镁离子形成络合物; 反应温度、pH和络合剂对产物的形貌和物相有较大影响; 所得产物结晶度高, 有表面光滑的微米立方体晶体和纳米粒子聚集的微米空心球颗粒, 粒径均在1~3 μm之间。     

Hydrothermal synthesis of hexagonal ZnO clusters

Hydrothermal process was applied to synthesize zinc oxide nanocrystals. X-ray powder diffraction and scanning electron microscopy were used to analyze the crystal structure and surface morphology. XRD pattern analysis showed that the ZnO clusters are single hexagonal phase of wurtzite structure (space group P63 mc) with no impurity of Zn and Zn(OH)₂. Also, SEM images revealed that the size of a single ZnO crystal is between 200-500 nm in diameter and 2-5 μm in length. The influence of potassium iodide (KI) as a surfactant on the crystallinity of ZnO has been investigated.     

Hydrothermal treatment of ZnO nanostructures

Hydrothermal treatment of ZnO nanostructures involves low temperatures (150-200 °C) and elevated water vapor pressure for the purpose of the improvement in the material properties. Under such moderate conditions, no significant changes in the morphology would be expected. Nevertheless, such treatment results in a significant change of nanostructured morphologies of ZnO. The observed changes are dependent on the starting material properties and the substrate used for the growth. In the case of Si substrate, hydrothermal treatment results in significant Si contamination of the samples. In terms of the optical properties, improvements are observed only in some cases, while samples with excellent starting optical properties are degraded by the treatment. Mechanisms responsible for the observed changes are discussed.     

MnO2的生长机理及其对罗丹明B的快速降解

采用水热法以高锰酸钾和四水合氯化锰为原料,在180℃下制备了α-MnO₂、β-MnO₂及γ-MnO₂;观察分析了不同晶型MnO₂的物相、形貌及微观结构,探究了水热时间对MnO₂晶型的影响及MnO₂的生长机理;研究了α-MnO₂+γ-MnO₂对罗丹明B(RhB)的降解性能。结果表明:在180℃水热条件下,最先产生α-MnO₂并伴有少量γ-MnO₂,适当延长水热反应的时间,MnO₂发生晶型转变,逐渐由α-MnO₂和γ-MnO₂向柱状β-MnO₂转变。此外,研究发现α-MnO₂+γ-MnO₂对RhB具有高效快速的催化降解能力,当RhB溶液为60 mL时,10 min后MnO₂对RhB的降解率可高达93%;当增加RhB溶液到100 mL时,30 min后降解率可达93%,可见,MnO₂在催化降解有机染料方面具有极好的应用前景。     

Hydrothermal synthesis of HgTe rod-shaped nanocrystals

HgTe nanorods composed of crystalline particles with the diameter of 100-300 nm and length of up to 2-3 μm have been prepared by a hydrothermal method, and characterized by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX). It was found that ammonia played a key role in the formation of HgTe nanorods.     

水热法制备过程中TiO2纳米纤维成形机理研究

采用水热法制备出φ20～30nm, 长度达微米级的TiO2纳米纤维, 以XRD、TEM、IR等手段对不同工艺条件下获得的产物晶型结构、微观形貌以及化学组成进行了表征, 对TiO₂纳米纤维成形机理进行探讨, 并就洗涤过程中pH值对纤维结构的影响进行分析. 结果表明, TiO₂纳米纤维的形成机理可能是锐钛矿型TiO₂纳米颗粒在强碱作用下生成K₂Ti₆O₁₃颗粒, 小颗粒沿一定晶轴生长, 遵循溶解-生长机理, 逐渐长成纳米纤维. 清洗溶液的pH值对产物的成分和结构有较大影响, 通过控制清洗溶液的pH值和热处理温度, 可以获得组成分别为K₂Ti₆O₁₃、H₂Ti₃O₇和TiO₂的纳米纤维. 在pH=7、80℃烘干条件下得到的主要是H₂Ti₃O₇纳米纤维, 400℃煅烧后转变为TiO₂纳米纤维.     

碟状氧化锌气相生长及机理的研究

采用气相沉积法制备了碟状的氧化锌,并基于自催化的气-液-固机理及气-固机理结合温度及过饱和度等生长因素对碟状氧化锌的生长机理进行了研究,结果表明,较高的生长温度及适中的过饱和度被归结为碟状氧化锌形成的原因。     

A task specific basic ionic liquid for synthesis of flower-like ZnO by hydrothermal method

Flower-like ZnO morphology, with different shapes, have been successfully synthesized via a novel and environment-friendly hydrothermal method using zinc acetate and a task specific dicationic dibasic ionic liquid, [mmpim]₂[OH]₂, which plays an important role in fabrication of ZnO structure. The structure and morphology of the product were characterized by X-ray diffraction and scanning electron microscopy, which show different flower-like morphologies. Photoluminescence spectrum of the product exhibits a strong ultraviolet emission at 391 nm and two weak blue-green emissions at about 450 and 500 nm.     

Luminescent properties of ZnO structures grown with a vapour transport method

ZnO structures were synthesised on the sapphire (112?0) substrate by a vapour transport method in a gas flowing furnace. The influence of the oxygen content in the gas mixture on the morphology and luminescent properties of ZnO structures grown on a strip-like substrate was investigated, with all other growth parameters being kept nominally identical. Integrated electron microscopy and cathodoluminescence analysis shows gradual variations of structural and optical emission properties for ZnO structures grown on the long substrate. Defect-related green luminescence of ZnO is found to be highly dependent on the oxygen vapour in the growth region of the furnace. Our findings demonstrate that the green luminescence is associated with oxygen deficiency in ZnO.     

花状纳米Zno的低温水浴制备及生长机理

以氯化锌和氢氧化钠为反应原料,利用水浴恒温加热,在溶液中直接制备出呈花状形貌的纳米ZnO;采用扫描电镜、X射线衍射、透射电子显微镜等分析方法对所得产物的形貌和结构进行了表征,结果表明,在低温(45℃)时可制备出大量呈花状形貌的纳米ZnO.     

Structures and properties of the Al-doped ZnO thin films prepared by radio frequency magnetron sputtering

Al-doped ZnO thin films were deposited by radio frequency magnetron sputtering using a ZnO target with 2 wt.% Al₂O₃. The structures and properties of the films were characterized by the thin film X-ray diffraction, high resolution transmission electron microscopy, Hall system and ultraviolet/visible/near-infrared spectrophotometer. The Al-doped ZnO film with high crystalline quality and good properties was obtained at the sputtering power of 100 W, working pressure of 0.3 Pa and substrate temperature of 250 °C. The results of further structure analysis show that the interplanar spacings d are enlarged in other directions besides the direction perpendicular to the substrate. Apart from the film stress, the doping concentration and the doping site of Al play an important role in the variation of lattice parameters. When the doping concentration of Al is more than 1.5 wt.%, part of Al atoms are incorporated in the interstitial site, which leads to the increase of lattice parameters. This viewpoint is also proved by the first principle calculations.     

Improved crystallinity of ZnO thin films grown by the ‘Aurora PLD method’

An ‘Aurora PLD method,’ in which a magnetic field is applied to a plasma plume, was employed to grow ZnO films and to study the mechanism of crystal growth. In the Aurora PLD method, the ZnO target displayed a brighter plume in the vicinity of the magnet (near the substrate holder). The photoluminescence (PL) was double that of a conventionally PLD grown film when the Aurora PLD was used. Furthermore, when a method of Aurora PLD with Ar added was used, the PL intensity increased 3-4 times. Hall effect measurement revealed the reduction of the residual electron concentration due to Aurora PLD growth, suggesting the possible improvement of the crystallinity. These advantages of the Aurora PLD method were compared with respect to an elevated growth temperature of approximately 100 °C.     

Superhydrophobic Behavior and Optical Properties of ZnO Film Fabricated by Hydrothermal Method

ZnO film with claviform structure was synthesized on quartz substrates through a hydrothermal method at 90℃.The microstructure of the film is composed of clusters of submicrometer rods,which therefore endues the film with good superhydrophobicity.Meanwhile,the film with such tanglesome structure also shows highly crystalline quality testified by a strong ultra-violet (UV) emission and very low deep-level emission observed on the photoluminescence (PL) spectrum as well as high transparence of about 89% transmittance in visible light range.     

Effects of pre-annealing conditions on the characteristics of ZnO nanorods and ZnO/p-Si heterojunction diodes grown through hydrothermal method

Pre-annealing of seed layers before the growth of ZnO nanorods (NRs), at various temperatures (non-annealing ~ 800 °C) and in various atmospheres (vacuum, N₂, or O₂), was systematically studied to investigate the effects of pre-annealing on the material properties of ZnO NRs as well as the rectifying behaviour of ZnO NRs/p-Si heterojunction diodes (HJDs). A seed layer was initially prepared on the Si substrate through hydrothermal (HT) method and subsequently pre-annealed; finally, the ZnO NRs were grown through the same HT method. We found that without the annealed seed layer, the ZnO NRs cannot be grown on the Si template and increase in the pre-annealing temperature led to better crystallization and fewer defect-centres in ZnO NRs. However, at a high pre-annealing temperature, the characteristics of ZnO NRs degraded due to the evaporation of oxygen atoms, resulting in more oxygen-vacancy-related defects. The smallest diameter and shortest length of ZnO NRs were observed on the samples pre-annealed at 450 °C. The short length of ZnO NRs implies a slow growth rate, because of which the NRs have sufficient time to align normal to the surface of the substrate. When the seed layer is pre-annealed in an O₂ atmosphere, the oxygen atoms fill the oxygen-vacancy-related defects, which lead to a higher nucleation density and improved characteristics of ZnO NRs. This leads to an extremely high rectification ratio of 1.8 × 10⁵ in ZnO NR/p-Si HJDs. The related mechanisms were explored in this study.     

水热合成锆钛酸铅微晶体的晶粒度分析

采用Ti02，ZrOCl2·8H2O，Pb（NO3）2为原料，KOH为矿化剂，在不同温度、不同KOH浓度、不同反应时间，进行了锆钛酸铅（PZT）微晶体的水热合成实验。结果表明，水热反应温度与KOH浓度大大影响了PZT微晶体的晶粒度和晶体结构，而水热反应时间只影响了PZT微晶体的晶粒度，对晶体结构没有明显影响。在实验条件下水热合成的PZT微晶的晶粒度为10～20nm之间。     

ZnO单晶体的荧光温度特性

通过变温荧光光谱研究了ZnO激子发光的温度依赖特性。在6K的低温下,其光致发光主要来自束缚激子能量位于3.360eV,半宽为3meV的施主束缚激子发光。而随着测量温度的上升,自由激子及其声子辅助跃迁发光逐渐成为ZnO主要发光机制。文中详细讨论了ZnO荧光随温度的演变过程。特别是自由激子的声子伴线与自由激子发光峰之间的能量间距,随温度的上升逐渐偏离了其特征声子模能量,呈现不断缩小趋势。     

热处理对溶胶-凝胶法制备ZnO薄膜性能的影响

以(CH3COO)2Zn·2H2O为前驱物,利用溶胶-凝胶旋转涂膜法以普通玻璃为基底制备ZnO薄膜。分别采用X射线衍射仪、紫外-可见分光光度计和扫描电子显微镜等对ZnO薄膜的物相组分、透射率和表面形貌进行测量与表征。研究了热处理温度对ZnO薄膜的物相结构和光学特性的影响。实验结果表明,ZnO薄膜的物相结构和可见光透射率都与热处理温度有关,随着热处理温度升高,ZnO薄膜的晶粒尺寸增大,晶格常数逐渐减小,薄膜的透射率增大。     

Hydrothermal synthesis of oriented MnS nanorods on anodized aluminum oxide template

High-density aligned MnS nanorods with a narrow length distribution were prepared on an anodized aluminum oxide (AAO) template under a hydrothermal condition. MnS nanomaterials with different shapes were obtained using different precursor concentrations in the reaction solution. The porous surface of the AAO template and the precursor concentrations may play key roles in the initial nucleation stage of growing oriented MnS nanorods.