Preparation and characterization of TiO2 bulk porous nanosolids

A novel TiO₂ bulk porous nanosolid (also called a “TiO₂ nanosponge”) was prepared by a solvothermal hot-press (SHP) technique, using TiO₂ nanoparticles (average particle size of 15 nm) and various solvents as the starting materials. The pore diameters of the nanosolids were rather uniform, and the maximum value of pore volume and specific surface area were 0.249 cm³/g and 59.455 m²/g, respectively. The pore volume and diameter of TiO₂ bulk porous nanosolid could be controlled by changing either the type or the amount of the solvent used in the experiment. No residual solvents could be detected by FTIR analysis, which means that the solvents had entirely escaped from the samples during the process of preparing TiO₂ bulk porous nanosolids.     

溶剂热法制备不同微米结构的氧化亚铜

以乙酸铜为原料,采用溶剂热法合成了球形直径约为2~3μm和八面体粒径大小约为4μm的氧化亚铜颗粒。通过选用不同的还原剂如三乙醇胺和乙二醇,系统研究了不同反应体系中如反应温度、溶剂、原料配比和添加表面活性剂十六烷基三甲基溴化铵(CTAB)对微米结构氧化亚铜晶型与形貌的影响,选出制备氧化亚铜八面体和球形的最佳条件,并初步探讨了氧化亚铜微米颗粒的生长机理。     

纳/微蒲公英状氧化锌材料的制备

采用溶剂热法,以Zn粉为锌源,通过柯肯特尔效应制备出由单晶ZnO纳米棒组成的三维蒲公英状的氧化锌纳米结构.通过XRD、SEM、RDS、SEAD、TEM和HRTEM等方法对样品的组成,结构和形貌进行了研究.该方法可作为一种新的大规模制备纳/微ZnO纳米材料而被广泛应用.     

纳米氧化锌的溶剂热法合成及其光学性能

以醋酸锌为原料,以乙二胺一水为混合溶剂,利用溶剂热法低温快速制备出分散均匀的氧化锌(ZnO)纳米粒子.探讨了溶剂热条件如温度和时间对于ZnO纳米晶的形成及其形貌和光学性能的影响.X-射线粉末衍射和能量散射x-射线能谱分析表明,产物是纯的六方纤锌矿结构的ZnO.透射电镜形貌观察显示,产物为均匀纳米粒子,直径为20～30 nm.所合成粉体紫外可见光谱表明,其紫外吸收大约为2.98eV,计算其直接带隙宽度为3.10eV.光致发光光谱显示ZnO纳米粒子具有良好的结晶性和光学性质.     

PEG辅助的溶胶凝胶法制备多孔ZnO薄膜

以醋酸锌为前驱体,乙醇为溶剂,二乙醇胺为络合剂,通过聚乙二醇(PEG)辅助的溶胶--凝胶法在玻璃基片上制备了ZnO多孔薄膜.利用IR、TG-DTA、XRD及SEM等测试方法对薄膜的结构和特性进行了分析.探讨了样品在溶胶-凝胶及煅烧过程中的物理化学变化.研究了前驱体浓度、PEG2000加入量对薄膜结构和性能的影响.结果表明,当Zn2 的浓度为0.6mol/L的溶胶在70℃水浴时,加入PEG2000后,有利于ZnO多孔结构的形成,而且孔尺寸及密度也随PEG加入量的增大而增大.     

Investigation of ZnO nanorods synthesized by a solvothermal method, using Al-doped ZnO seed films

ZnO nanorods were successfully grown on common glass substrates using a simple solvothermal method via the precursors of zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O) and Hexamethylenetetramine (C₆H₁₂N₄) with equal molar concentration at 0.01 mol/l, 0.025 mol/l, 0.05 mol/l, and 0.075 mol/l. The ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning electron microscopy, UV-Vis absorption spectrophotometer and photoluminescence (PL) spectrometer. XRD results indicated that all the ZnO nanorods were preferentially grown along [0 0 0 1] direction (c-axis). With an increase of Zn(CH₃COO)₂·2H₂O and C₆H₁₂N₄ concentration, the diffraction intensity of ZnO nanorod along c-axis also increased. Scanning electron microscopy images showed that the well-faceted hexagonal ZnO nanorods were grown vertically from the common glass substrates. In addition, with the increase of Zn(CH₃COO)₂·2H₂O and C₆H₁₂N₄ concentration, the exciton band of ZnO nanorods determined by UV-Vis absorption spectra gradually became narrow and the intensity of exciton band also remarkably augmented. Photoluminescence spectra showed that with the increase of Zn(CH₃COO)₂·2H₂O and C₆H₁₂N₄ concentration, the position of emission peak of ZnO nanorod blue-shifts towards shorter wavelength in UV region and the luminescence intensity remarkably enhances in visible emission range (470-630 nm).     

Capillary rise properties of porous mullite ceramics prepared by an extrusion method with various diameters of fiber pore formers

Porous mullite ceramics with unidirectionally oriented pores were prepared by an extrusion method using rayon fibers as the pore formers. Rayon fibers of 8.1, 9.6, 16.8, and 37.6 μm in diameter were used as the pore formers and were kneaded with alumina powder, kaolin clay, China earthen clay, and water to form pastes. These pastes were extruded into cylindrical tubes, dried, and fired at 1500 °C for 4 h. The apparent porosities ranged from 45.7 to 48.2 %. The pore size distributions showed a sharp peak at 9.4, 10.0, 15.6, and 30 μm with increasing fiber diameters. The height of the capillary rise was 1780, 1670, 1320, and 950 mm with increasing fiber diameter. The maximum capillary rise is much higher than previously reported. The contact angle and effective pore radius that determine the capillary rise ability were calculated by fitting the capillary rise curves using the Fries and Dreyer’s equation.     

乙二醇溶剂热法制备纳米TiO2

用乙二醇溶剂热法制备了锐钛矿相纳米TiO2,用X射线粉末衍射(XRO)、红外光谱仪(FTIR)、热重分析(TG-DTA)和透射电子显微镜(TEM)对制备的样品进行了表征,研究了乙二醇浓度、含水量、反应温度和反应时间对纳米TiO2晶型和晶粒尺寸的影响.结果表明:所得的纳米TiO2粒径分布窄,单分散性好.随着溶剂热反应温度的升高,纳米TiO2的晶粒尺寸逐渐变大,但随着溶剂热反应时间的延长,纳米TiO2的晶粒尺寸却几乎不变.     

水热法制备不同形貌的氧化锌纳米结构

采用水热法,用甲酰胺水溶液和锌片建立反应体系,在不同种晶层上制备出不同形貌的ZnO纳米结构,所用基底有Si片、镀有ZnO薄膜的Si片、镀有ITO薄膜的Si片、涂有ZnO粉末的Si片等,研究了不同的种晶层对ZnO纳米结构的形貌的影响。在不同温度下,分别在镀有ZnO薄膜和ITO薄膜的医用载玻片衬底上生长ZnO纳米结构,研究了温度在水热法中的作用及种晶层对纳米杆长度的影响。实验中用扫描电子显微镜（SEM）和X射线衍射仪（XRD）对纳米聚集体进行了表征。SEM表征结果表明不同种晶层上获得的ZnO纳米结构形貌差异很大;反应时间、甲酰胺水溶液浓度以及反应温度对ZnO纳米阵列形貌都有着一定的影响;在ZnO薄膜上生长的纳米杆较在ITO薄膜上生长的纳米杆长。SEM图像同时表明氧化锌纳米杆随着温度的增大,纳米杆的长度和杆径增大。X射线衍射峰在34.6℃有很强的（002）纤锌矿衍射峰,该峰表明衬底上有高度c轴取向的大面积纳米杆阵列和较好的结晶质量。     

制备多孔壳聚糖膜的新方法:选择性酶解原位成孔

利用溶菌酶对中等脱乙酰度壳聚糖的选择性降解,将其与高脱乙酰度壳聚糖以不同比例混合浇铸成膜.考察了降解过程中材料的失重和溶液还原糖含量的变化,用傅立叶红外光谱分析了混合膜的成分改变和降解过程中膜的变化,并用扫描电镜观察了混合膜降解后的形态变化.结果表明,壳聚糖混合膜中的中等脱乙酰度壳聚糖被溶菌酶选择性的降解,而且当混合膜中该组分含量为0.5时,降解后膜表面及内部均产生了互相贯穿的纳米尺寸的孔,剩余的高脱乙酰度成分表现为纳米尺寸的纤维.该方法通过壳聚糖的选择性酶解原位成孔,为制备纳米结构的多孔壳聚糖膜提供了一个新颖的途径.     

Preparation of porous boehmite nanosolid and its composite fluorescent materials by a novel hydrothermal hot-press method

Boehmite (AlO(OH)) porous nanosolid has been successfully prepared by a novel hydrothermal hot-press (HHP) method, using Al₂O₃ nanoparticles as the starting material. Furthermore, a new organic fluorescent material (E,E)-4-{2-[P′-(N,N-di-n-butylamino)stilben-p-yl]vinyl}pyridine (DBASVP) was assembled into the pores of the boehmite porous nanosolid, thus a DBASVP/boehmite porous nanocomposite was obtained. Because of the interaction between DBASVP molecules and the surface of boehmite porous nanosolid, a red-shift of the fluorescent peak was observed in boehmite/DBASVP composite by comparing with that of DBASVP.     

Preparation of indium-tin oxide (ITO) aciculae by a novel concentration-precipitation and post-calcination method

Indium-tin oxide (ITO) aciculae were prepared by adding tin into indium hydroxide aciculae, which were synthesized by a concentration-precipitation method, and subsequent calcining. X-ray powder diffraction (XRD) indicated that indium hydroxide aciculae were partially crystallized and ITO aciculae were a well-crystallized solid solution, and both of them had a cubic structure. Using scanning electron microscope (SEM), it was found that the cross-sectional diameters of most of ITO aciculae were in the range of 2 to 9 μm, and the aspect ratios of about 95% of aciculae were more than 6. Energy dispersion spectrometer (EDS) and phenylfluorone spectrophotometry analysis were used to measure Sn content of ITO aciculae, and it was revealed that the Sn content of the surface layer was higher than that of the bulk. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) showed that the intensive dehydration of In(OH)₃ took place in the temperature rage of 260–280 °C and the formation of ITO solid solution started at temperature higher than 280 °C. According to the results of XRD, TGA–DTA and N content analysis, indium-containing nitrates or nitrites maybe existed in indium hydroxide aciculae. The specific resistance of the pellet formed by pressing ITO aciculae at a pressure of 10 MPa was measured by a four-probe method at room temperature, and it was as low as 1.2×10⁻² Ω cm.     

Facile synthesis and novel microwave electromagnetic properties of flower-like Ni structures by a solvothermal method

Flower-like Ni structures composed of leaf-like flakes were synthesized through a facile solvothermal approach independent of surfactants or magnetic force. The evolution of the morphology was closely related to the variation of NaOH and volume ratios of ethylene glycol to water. The microwave absorbing properties of the flower-like Ni wax-composite were evaluated based on the complex permittivity (ε_r = ε′ ? jε″) and permeability (µ_r = µ′ ? jµ″). The Ni wax-composite exhibited excellent microwave absorption performances with a minimum reflection loss of ?46.1 dB at 13.3 GHz, corresponding to a matching thickness of 2.0 mm. In particular, the absorption bandwidth of RL below ?10 dB was 3.6 GHz (11.7–15.3 GHz). The attenuation of microwave could be attributed to the dielectric loss and unique flower-like structure.     

Synthesis of sealed sponge ZnO nanospheres through a novel NH(3)-evaporation method

Sealed sponge ZnO nanospheres are prepared through a novel NH(3)-evaporation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and N(2) physisorption analysis show that the samples obtained are ZnO nanospheres with hexagonal wurtzite structure. The particle size is in the range 80-130?nm and the pores inside are estimated to be in the range 2-35?nm. During the preparation process, the carboxyls derived from the polyacrylamide hydrolyzation tend to attach to the particle surface and bring about the interaction between particles by hydrogen bonding. Results show that the polyacrylamide and alcohol are crucial to the formation of the sealed sponge ZnO, by forming a diffusion layer around the particle. The formation mechanism is considered to be controlled by the diffusion of Zn(2+) through the diffusion layer, and the mass transmission between the initial particles.     

Growth of ZnO nanocrystals by a solvothermal technique and their photoluminescence properties

ZnO nanocrystals with various morphologies such as nanorod arrays, flower like assemblies, spherical particles, hexagonal cones, and self assembled microstructures were prepared by a solvothermal approach. It was observed that morphology of the ZnO nanostructures were very much solvent dependent in solvothermal approach. Water, ethylenediamine, and ethylene glycol-water mixture favors the formation of nanorods. Flower like assemblies of ZnO were produced in benzene. Spherical as well as cone like nanoparticles and their assemblies were produced in ethylene glycol. The ZnO nanostructures were characterized by X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence studies.     

Preparation of nano-sized flower-like ZnO bunches by a direct precipitation method

In this work, nano-sized ZnO particles were prepared by a direct precipitation method with Zn(NO₃)₂·6H₂O and NH₃·H₂O as raw materials, and the impact of the synthesis process was studied. The optimal thermal calcined temperature of precursor precipitates of ZnO was obtained from the differential thermal analysis (DTA) and the thermal gravimetric analysis (TGA) curves. The purity, microstructure, morphology of the calcined ZnO powders were studied by X-ray diffraction (XRD), energy dispersive X-ray spectrum (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized ZnO powders had a wurtzite structure with high purity. The final products were of flower-like shape and the nanorods which consisted of the flower-like ZnO bunches were 20–100 nm in diameter and 0.5–1 μm in length. The effect of process conditions on the morphology of ZnO was discussed.     

Preparation of barium titanate nanocube particles by solvothermal method and their characterization

Barium titanate (BaTiO₃) nanocube particles below 20 nm were prepared by solvothermal method. A selection of organic solvent and inorganic materials of Ba and Ti sources was most important for the preparation of nanocubes. A nucleation and particle growth of BaTiO₃ nanoparticles led to a formation of the BaTiO₃ nanocubes with a size of 10–15 nm at temperatures above 200 °C.     

Investigation of defects in N-doped ZnO powders prepared by a facile solvothermal method and their UV photocatalytic properties

A facile synthetic procedure for N-doped ZnO powders was proposed. In this work, N-doped ZnO crystals were synthesized in diethylene glycol (DEG) with ammonia solution via solvothermal process. Incorporated N concentration increases with the amount of ammonia solution. In order to confirm the defects of as-gained ZnO powders, the samples were characterized by XRD, PL, and EPR. In our results, the N-related defects were considered to be (N)_O centers as acceptors, other than (N₂)_O. And, the donors defects were confirmed to H_i. UV photocatalytic activity of the N-doped ZnO crystals was assessed from the photodegradation kinetics of methyl orange (MO). The result shows that the UV photocatalytic activity of N-doped ZnO decreases with the incorporated N concentration. This was caused by abundant acceptors hindered the photoinduced holes generating.