Dielectric Behavior of Nano-PbTiO3/PVDF Nanocomposites In-situ Synthesized by the Sol-gel Method

PbTiO3 / PVDF nanocomposites were prepared via in-situ growth of nanosized PbTiO3 particles in PVDF matrix by sol-gel method. Nanosized PbTiO3 grown in the composites film was characterized by X-ray diffractometry （XRD） and transmission electron mieroscopy, and the dielectric properties of the composite films prepared were measured. The distribution of PbTiO3 nanoparticles in-situ grown in the PVDF matrix was examined using a scanning electron microscope. The relative dielectric eonstant increases with increasing the weight fracture of PbTiO3 in-situ grown. In particular, the dielectric loss monotonically decreases with the increase of PbTiO3 content at 1 MHz.     

Dielectric Behavior of BaTiO_3/ PVDF Nanocomposites In-situ Synthesized by the Sol-Gel Method

1　IntroductionFerroelectricceramic polymercompositesconsistingofferroelectricceramicpowderembeddedinapolymermatrixhaveattractedmuchattentionsincetheycombinetheexcellentferroelectricpropertiesoftheceramicsandtheflexiblemechanicalpropertiesofthepolymer[1] …     

The Dielectric Properties and Preparation Method of BaTiO3/PVDF 0-3 Composites

A series of 0-3 composties of the polyvinylidene fluoride (PVDF) and BaTiO3 was prepared,BaTiO3 was modified with titanate coupling agent .The dielectric properties and the interfacial interaction of composites by different preparation methods were examined and compared,The result shows that the relaive dielectric constant ε of the composite prepared in solution has a maximum value at about 70% weight fraction of BaTiO3 and the dielectric loss tanδ increases rapidly when the fraction exceeds 70%, For the composite preared in melt, the relative dielectric constant ε almost raches a maximum value at about 60% weght fraction of BaTiO3 and the dielectric loss is comparatively lower,The deielectric proerties of composites ore improved by using a coupling aent.     

BaTiO3薄膜的Sol-Gel制备工艺及性能

利用溶胶－凝胶法（Sol-Gel)在Pt/Ti/SiO2/Si(100)衬底上制备了BaTiO3薄膜，研究了不同退火条件下BaTiO3薄膜的晶相结构及表面形貌，测试了BaTiO3薄膜的电学性能。发现经900℃、120min退火处理的BaTiO3薄膜的介电－温度（εr-T)关系具有明显的弥散相变特性。     

Preparation of Al2O3-SiO2-TiO2-ZrO2 Composite Ceramic Membranes by Sol-Gel Method

Al2O3-SiO2- TiO2-ZrO2 supported membranes were prepared by Sol-Gel method. These composite ceramic membranes are level, even and no macro crack. There exist several crystalline phases such as Al2O3, TiO2 ( anatase ), Al2 SiO5 , and ZrO2 in these membranes. Changing the molar ratio of Al:Si: Ti : Zr ,the kinds and content of crystal phases of composite membranes could be different, which may lend to a variety of microstructure of membranes. The surface nanoscale topography and microstructure of membranes were investigated by XRD, SEM, AFM, EPMA. The effects of additives and heat treatments on the surface nanoscale topography and microstracture of composite ceramic membranes were also analyzed.     

Bactericidal and Photocatalytie Activity of Fe^3＋-TiO2 Thin Films Prepared by the Sol-gel Method

Pure TiO2 thin films and iron doped TiO2 thin films on glass substrate were prepared by sol-gel method, and characterized by X-ray diffractometer （XRD）, thermo-gravimetric analysis （TG-DSC）, high resolution transmission electron microscope （HRTEM）, scanning electron microscope （SEM） and UV-Vis spectroscopy, respectively. The experimental results show that the pure TiO2 thin films and iron doped TiO2 thin films can destroy most of the escherichia coli and bacillus subtillis under the irradiation of 365 nm UV-light. However, the iron doped TiO2 thin film is a better photocatalyst than pure TiO2 thin film. The ultrastructural studies provide direct evidences for understanding the bactericidal mechanism of the TiO2 photocatalyst.     

Effect of Annealing on Ferroelectric Properties of Bi3.25La0.75Ti3O12 Thin Films Prepared by the Sol-gel Method

Bi_3.25La_0.75Ti₃O₁₂(BLT) thin films were prepared on Pt/Ti/SiO₂/Si substrate by the sol-gel method. The effect of annealing on their structures and ferroelectric properties was investigated. The XRD patterns indicate that the BLT films annealed at different temperatures are randomly orientated and the single perovskite phase is obtained at 550°C. The remnant polarization increases and the coercive field decreases with the annealing temperature increasing. The leakage current density of the BLT films annealed at 700°C is about 5.8×10⁻⁸ Al cm² at the electric field of 250 kV/cm. Funded by the National Natural Science Foundation of China (No. 90407023)     

Structure and electrochemical properties of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>−<Emphasis Type="Italic">x</Emphasis>F<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

LiMn₂O₄−_xF_x prepared by the sol-gel method has a perfect crystal formation. The crystal particle size of the material was medium and distributed uniformly. The substitution of F for O increased the specific capacity of the material at the cost of the cycleability. The explanation of this results is that the F decreases the valence of Mn, that is, more Mn³⁺ and less Mn⁴⁺ exist in the material. The increase of Mn³⁺ will improve the initial specific capacity and Mn³⁺ is the original reason for Jahn-Teller effect that caused the poor cycleability of the cathode material by the micro-distortion of the crystal structure. In addition, the expanded measurement of the crystal lattice is also the reason for the poor cycleability. Therefore, the results of F-substitution and cation-substitution are opposite. If the two methods are combined, they can compensate the inability each other and the satisfactory results may be obtained. XIA Jun-lei: Born in 1977 Funded by the National Natural Science Foundation of China (No. 59972026)     

Microstructure and Thermal Properties Analysis of （1-x）As2S3-x CdBr2 Glass System

The homogeneous glass sample for the ( 1 - x ) As2S3-xCdBr2, where x=0. 015,0. 035,0.05, was prepared by the conventional melt-quenched method. Amorphoas ( 1 - x ) As2S3-xCdBr2 alloys were determined by X-ray diffraction, thermal compreheasive analysis and Raman scattering. The glass transittion temperature (TR) deereases a bit with the addition of CdBr2 . Based on the experimental data, the microstrtucture is considered to be the discrete molecule species of AsBr3 and Cd - S atomic bonds or clusters are honigeneously dispersed in a disordered polymer network formed by AsS3 pyramids interlinked by sulfur bridges.     

Dispersing and doping of BaTiO<Subscript>3</Subscript> powder by adsorption

Dispersing and doping of BaTiO3 powder by adsorption method were investigated. Ultrafine BaTiO3 powders were dispersed in the aqueous with ammoniumized citrate （NHa-CA） or ammoniumized citric lanthanum chelate （NH4-La-CA） as dispersant by ultrasonic bath. Better dispersion of BaTiO3 slurry was obtained in the aqueous with NH4-La-CA than that of NH4-CA when the mass ratio of citric acid （CA） to BaTiO3 was less than 0,007. The pH value hardly affects the dispersion property of BaTiO3 suspension dispersed by NH4-La-CA. BaTiO3 powder could be well dispersed （median size D50=0.45 μm） and also doped with high uniformity of added components by adsorbing citric acid chelate on surface. Compared with solid mixing, better microstructure and properties of La/Mn codoped ceramics were obtained by adsorption method.     

Preparation of nanocrystalline BaTiO<Subscript>3</Subscript> ceramics

The high-dense nanocrystalline BaTiO₃ (BT) ceramics with grain size smaller than 100 nm have been successfully prepared by the two step sintering and the spark plasma sintering (SPS) process. The successive transitions in nanograin BT ceramics from rhombohedral to orthorhombic, tetragonal and cubic transitions, similar to those in coarse BT ceramics, were revealed by in-situ temperature dependent Raman spectrum. The multiphase coexistence and the diffused phase transition character were demonstrated in the 8 nm nanocrystalline BT ceramics. Supported by the National Basic Research Program of China (“973” Project) (Grant No. 2002CB613301) and the National Natural Science Foundation of China (Grant No. 50872093)     

Preparation and ferroelectric properties of Bi<Subscript>3.4</Subscript>Ce<Subscript>0.6</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> thin films grown by sol-gel method

We have investigated the preparation and properties of Bi_3.4Ce_0.6Ti₃O₁₂ thin films. The Bi_3.4Ce_0.6Ti₃O₁₂ thin films were fabricated on the Pt/Ti/SiO₂/Si substrates using sol-gel method. The structure and morphology of the films were characterized using X-ray diffraction and atomic force microscopy. The thin films showed a perovskite phase and dense microstructure. The dielectric constant and the dissipation factor of the Bi_3.4Ce_0.6Ti₃O₁₂ thin films were about 172 and 0.031 at 1 kHz, respectively. The 2P _r and 2E _c of the Bi_3.4Ce_0.6Ti₃O₁₂ thin films were 67.1 μC/cm² and 299.7 kV/cm, respectively, under an applied field of 600 kV/cm. The Bi_3.4Ce_0.6Ti₃O₁₂ film did not show fatigue up to 4.46×10⁹ switching cycles at a frequency of 1 MHz, and showed good insulating behavior according to the test of leakage current. Supported by the Natural Science Foundation of Hubei Province (Grants No. 2004ABA082)     

Fabrication and magnetic properties of Sm3(Fe,Ti)29Nx/α-Fe dual-phase nanocomposite permanent magnetic material

Sm3(Fe,Ti)29Nx/α-Fe dual-phase nanometer magnetic material was fabricated through rapid solidification, crystallization and nitridation of Sm-Fe (Ti) alloy. The effect of combination of rapid solidification and Ti alloy addition on the phase formation and microstructure of the Sm-Fe alloy is investigated in this paper. The microstructure of amorphous phase and dual-phase nano-grain crystals before and after crystallization annealing were observed using a high-resolution transmission electron microscope (HREM). The dual-phase nano-grains after annealing were compacted together with a clear interface with the direct exchange-coupling mechanism. Different annealing processes were used to examine the melt-spun alloy. Comparison of the images of SEM showed that annealing at 750℃ for 10 min was most suitable to get homogeneous and nano-grains. No obvious kink was detected in the second quadrant of the hysteresis loop like a single hard magnet, and strong exchange coupling was found between hard magnets and soft magnets.     

Preparation of Poly （ethylene oxide） （PEO） Modified Tungsten Oxide Hybrid Films via Sol-Gel Processing

Poly ( ethylene axide ) ( PEO ) modified WO3 thin films were prepared on glass substrates with special temperature. The sol-gel transition proess was #westigated by using DTA - TG , SEM and XRD. The elec-trochemical characteristic of the films was studied by cyclic voltmmetry measurement. The results show that PEO has heavy effects on the crystallization of W03 during structure evolution because of the interaction between PEO and WO3. It increases the crystallization temperature of the gels and thus improves the electrochemical properties and cyclic life of WO3 film as electrochromic materials.