稳定PbTiO_3陶瓷浆料的制备

以磷酸酯为分散剂,采用胶体电空间稳定机制改善陶瓷粉体水悬浮液的分散性,利用z 电位仪、沉降实验、粘度测定和粒度分析等手段,研究了分散剂的用量和pH值对PbTiO3陶瓷浆料稳定性的影响。并在最佳分散剂用量和pH值条件下,制备出了高固相含量(体积分数为55% )、稳定性和分散性好的PbTiO3陶瓷浆料。     

射频溅射制备钛酸铅薄膜

采用射频磁控溅射方法制备钙钛矿型钛酸铅铁电薄膜。通过各种不同溅射工艺条件研究,在适宜的溅射条件和基片温度下,溅射获得的PbTiO3薄膜表面晶粒大小均匀,膜层致密性好,经XRD分析证实,薄膜为钙钛矿型结构PbTiO3。外加Pt电极对薄膜进行测试表明,溅射得到的PbTiO3薄膜具有较好的电滞回线特性。     

Correlation between the surface morphology and structure and the photoluminescence of amorphous PbTiO3 thin films obtained by the chemical route

A polymeric precursor method was used to synthesis PbTiO₃ amorphous thin film processed at low temperature. The luminescence spectra of PbTiO₃ amorphous thin films at room temperature revealed an intense single‐emission band in the visible region. The visible emission band was found to be dependent on the thermal treatment history. Photoluminescence properties versus different annealing temperatures were investigated. The experimental results (XRD, AFM, PL) indicate that the nature of photoluminescence (PL) must be related to the disordered structure of PbTiO₃ amorphous thin films. Copyright © 2000 John Wiley & Sons, Ltd.     

In Situ Generated Gas Bubble‐Directed Self‐Assembly: Synthesis,and Peculiar Magnetic and Electrochemical Properties of Vertically Aligned Arrays of High‐Density Co3O4 Nanotubes

A novel and versatile gas bubble induced self‐assembly technique is developed for the one‐step fabrication of vertically aligned polycrystalline Co₃O₄ nanotube arrays (NTAs) by the rapid thermal decomposition of Co(NO₃)₂·6H₂O on a flat substrate. In this protocol, the in situ generation and release of gas bubbles, which can be regulated by elaborately adjusting the kinetic factors such as reaction time, decomposition temperature and pressure as well as the content of the chemically adsorbed water, play a vital role in the formation of the Co₃O₄ NTAs. Due to the shape anisotropy, ordered hierarchically porous structure and high surface area, the as‐obtained Co₃O₄ NTAs show unique magnetic properties of a low Néel temperature and a large exchange bias field, as well as an initial discharge capacity up to 1293 mAh·g^?1 at 35 mA·g^?1 and the retention of a charge capacity as high as 895.4 mAh·g^?1 after 10 cycles. This endows them with important potential use in magnetic shielding, magnetic recording media, and lithium ion batteries, etc. Due to the simplicity of the self‐assembly method, this process is applicable to the large‐scale production of the Co₃O₄ NTAs, and may be extended to other materials.     

Origin of a Tetragonal BiFeO3 Phase with a Giant c/a Ratio on SrTiO3 Substrates

A tetragonal BiFeO₃ phase with giant c/a of approximately 1.25 has been of great interest recently as it potentially possesses a giant polarization and much enhanced electromechanical response. This super‐tetragonal phase is known to be a stable phase only under high compressive strains of above approximately 4.5%, according to first principle calculations. However, in previous work, this super‐tetragonal BiFeO₃ phase was obtained in films deposited at high growth rate on SrTiO₃ substrates with compressive strain of only around 1.5%. By detailed structure analysis using high resolution synchrotron X‐ray diffraction, atomic force microscopy, and transmission electron microscopy, the parasitic β‐Bi₂O₃ phase is identified as the origin inducing the formation of super‐tetragonal BiFeO₃ phase on SrTiO₃ substrates. In addition, ab initio calculations also confirm that this super‐tetragonal phase is more stable than monoclinic phase when Bi₂O₃ is present. Using Bi₂O₃ as a buffer layer, an alternative route, not involving strain engineering, is proposed to stabilize this promising super‐tetragonal BiFeO₃ phase at low growth rates.     

Sb2S3/TiO2纳米管异质结阵列的制备和光电性能

结合水热法和阳极氧化法合成了Sb2S3/TiO2纳米管异质结阵列,采用场发射扫描电子显微镜、X射线衍射谱表征了异质结阵列的形貌和晶体结构.暗态下的电流-电压曲线表明Sb2S3/TiO2纳米管异质结阵列具有整流效应.相比于纯的TiO2纳米管阵列,Sb2S3/TiO2纳米管异质结阵列的光电性能有了显著地提升:在AM1.5标准光强作用下,光电转换效率从0.07％增长到0.40％,表面光电压响应范围从紫外光区拓宽至可见光区.结合表面光电压谱和相位谱,分析了Sb2S3/TiO2纳米管异质结阵列中光生载流子的分离和传输性能.     

Hierarchical ZnS‐In2S3‐CuS Nanospheres with Nanoporous Structure: Facile Synthesis,Growth Mechanism,and Excellent Photocatalytic Activity

Without using any templates or surfactants, hierarchical ZnS‐In₂S₃‐CuS nanospheres with nanoporous structure are successfully synthesized via a simple and convenient process. The nanospheres are aggregations of densely packed nanoparticles and nanorods. Different to the oriented attachment (OA) mechanism reported in the literature, the formation of these nanorods is believed to follow a lateral OA mechanism (nanoparticles attach along the direction perpendicular to the crystallographic axes with lateral planes as the juncture) based on the experimental data. This process could be a general phenomenon and would provide a new insight into the OA mechanism. A detailed time‐resolved TEM kinetic study of the formation of the complex structure is shown. The dipole mechanism and electric field‐induced growth are found to be responsible for the final architecture. Photocatalytic activities for water splitting are investigated under visible‐light irradiation (λ > 400 nm) and an especially high photocatalytic activity (apparent yield of 22.6% at 420 nm) is achieved by unloaded ZnIn_0.25Cu_0.02S_1.395 prepared at 180 °C for 18 h because of their high crystallinity, large pore volume, and the presence of nanorods with special microstructures.     

Supramolecular Assembly of Perylene Bisimide with β‐Cyclodextrin Grafts as a Solid‐State Fluorescence Sensor for Vapor Detection

A nanoscopic supramolecular aggregate is constructed from perylene bisimide‐bridged bis‐(permethyl‐β‐cyclodextrins) 1 via π–π stacking interactions. Its self‐assembly behavior in organic and aqueous solutions is investigated by UV–Vis, fluorescence, and ¹H NMR spectroscopy. Transmission electron microscopy and scanning electron microscopy images show the 1D nanorod aggregation of 1 , which is birefringent under crossed polarizer conditions and strongly fluorescent as depicted in the fluorescence microscopy image. X‐ray powder diffraction measurements indicate that 1 forms a well‐ordered crystalline arrangement with a π–π stacking distance of 4.02 Å. Furthermore, the solid‐state fluorescence sensing is explored by utilizing the poly(vinylidene fluoride) membrane‐embedded 1 , giving that 1 , as a novel vapor detecting material, can probe several kinds of volatile organic compounds and, especially, exhibits high sensitivity to organic amines.     

Nanodiamond‐Palladium Core–Shell Organohybrid Synthesis: A Mild Vapor‐Phase Procedure Enabling Nanolayering Metal onto Functionalized sp3‐Carbon

A novel approach for the bottom‐up construction of hybrid organic–inorganic nanocomposites with an intimate arrangement between sp³‐carbon 3D molecular‐size nanodiamonds (diamondoids) and a coated palladium surface as nanolayer is reported. The construction process is conducted stepwisely from the gas phase, using first controlled vapor‐phase self‐assembly of tailor‐made functionalized diamantane derivatives, followed by low‐temperature (45 °C) chemical vapor deposition of an organometallic complex in a reducing H₂ atmosphere over the self‐assembled diamondoid scaffold. The use of self‐assemblies of primary diamantane phosphine and phosphine oxide, which are produced with high structural uniformity and reproducibility, yields new hybrid diamondoid‐palladium materials incorporating Pd? O? PH? diamantane bonding motifs. Additional investigations provide evidence for a very challenging issue in the intimate construction of sp³‐C/metal scaffolds. Scanning electron microscopy and transmission electron microscopy microscopies combined with X‐ray photoelectron spectroscopy surface analysis and EDX bulk analysis confirm the formation of diamondoid‐palladium organohybrids with unique surface layering. The vapor phase‐controlled mild synthetic process allows excellent control over nanocomposite formation and morphology from molecular‐level modifications. As such, this bottom‐up composite building process bridges scales from the molecular (functionalized diamondoids) over nanoscopic (self‐assemblies) to microscopic regime (hybrids), in the challenging association of transition metals with an electronically saturated sp³‐carbon organic host material.     

Self‐Assembly of π‐Conjugated Amphiphiles: Free Standing,Ordered Sheets with Enhanced Mobility

Oligo(p‐phenylenevinylenes) (OPVs) with amphiphilic character are synthesized and their self‐assembly characteristics studied. Careful studies point at two morphologically different states of assemblies, with one being two dimensional sheets and the other as rolled tubes. This is also the first time that self‐assembled sheets are achieved for OPVs. Morphological and photo‐physical studies reveal a unique aggregate to aggregate transition between rolled tubes and two dimensional sheets, which is outlined as a more thermodynamic aggregate. The thermodynamic aggregate (2D sheet) is better ordered and consists of chromophores that are better excitonically coupled. The mobilities of these aggregates are also studied for a field effect transistor device and as expected sheets supersede rolled tubes by a couple of orders. More interestingly, the mobility values obtained for the well ordered chromophores in sheets is three orders higher than any other self‐assembled OPV previously reported. It is hypothesized that the better π interactions enforced by the amphiphilic design and the resultant supramolecular organization is a prime factor for such a remarkable rise in mobilities.     

Dramatic Activity of C3N4/BiPO4 Photocatalyst with Core/Shell Structure Formed by Self‐Assembly

Core/shell structured C₃N₄/BiPO₄ photocatalyst is fabricated via a facile ultrasonic dispersion method. The thickness of the shell may be controlled by tuning the amount of C₃N₄ in the dispersion, which determines the enhanced level of photocatalytic activity. The optimum photocatalytic activity of C₃N₄/BiPO₄ at a weight ratio of 4% (C₃N₄/BiPO₄) under UV irradiation is almost 4.5 times as high as that of reference P25 (TiO₂) and 2.5 times of BiPO₄. More attractively, the dramatic visible light photocatalytic activity is generated due to the C₃N₄ loaded. The enhancement in performance is demonstrated to be the match of lattice and energy level between the C₃N₄ and BiPO₄. This match facilitates the separation and transfer of photogenerated electron–hole pairs at the heterojunction interfaces and may be important for other core/shell structured materials. In addition, this method is expected to be extended for other C₃N₄ loaded materials.     

LiCaPO4:Eu3+材料制备白光LED及其发光特性

采用高温固相法制备了LiCaPO4:Eu3+红色发光材料,研究了Eu3+掺杂浓度、R+或Cl-等对材料发光性质的影响.结果显示,在399 nm近紫外光激发下,材料呈多峰发射,分别由Eu3+的5DO→7FJ(J=0,1,2,3,4)能级跃迁产生,主峰为612 nm;监测612 nm发射峰,所得激发光谱由O2-→Eu3+电...