Xiang Yun Deng

Ferroelectric and Piezoelectric Properties of (1-x)BaTi0.8Zr0.2O3-xBa0.7Ca0.3TiO3 Ceramics Prepared by Sol-Gel Technique

The(1-x)BaTi0.8Zr0.2O3-xBa0.7Ca0.3TiO3 ceramics have been prepared by sol-gel technique, where x is from 0.2 to 0.6. It reveals that the dense ceramics can be obtained when the sintered temperature is above 1250°C. It is lower than that of solid state reaction ceramics. In particular, when x=0.3, at which is near the MPB composition, the ferroelectric and piezoelectric properties are more excellent than the others. The maximum dielectric constant is above 9000, which can be observed in the butterfly shape curves of dielectric constant as a function of electric field. The maximum piezoelectric coefficient d33 can reach 400 pm/V, and it is obtained from the piezoelectric response loops.

Fabrication of Mullite Fiber Reinforced SiC Porous Ceramic

Ceramic fibers and whiskers have been used for modification of toughness because they increase fracture energy due to their high elastic modulus strength. The mechanism of this increase is well known to be pull-out, crack deflection and a bridging mechanism. This study focused on the increase in toughness, strength and thermal shock resistance when using mullite fibers in a gas filter for high temperatures. The green body uses the average 230μm particle diameter of SiC powders, which used as a skeletal material , the length to diameter ratio greater than 10 of the mullite fibers and the mixture of kaolin, feldspar and silica, which was used as a binder. The pore former be made up of graphite and active carbon. The molding pressure is 3MPa, and sintering temperature is 1300°C. The mullite fiber reinforced SiC porous ceramic has low filter pressure drop, 30.36% porosity and 35.66MPa flexural strength, which is higher than the SiC porous ceramic whitout mullite fibers. And the flexural strength degradation was only 5.4% after thermal shock tests.

Enchancement of Mechanical Properties in BaTiO3 Ferroelectric Thin Films

Surface structure and mechanical properties of BaTiO3 thin films prepared by sol-gel process were investigated by XP-2 profiler and nano-indention. The results indicated that the thickness of thin films got thicker with sintering temperature and the thickness-increasing rate differ from different solvent. The hardness and elastic modulus were enhanced due to the presence of residual stress which was compression and probably induced by fabrication method. The maximum hardness is 9.98GPa when the Young’s modulus is 127.41GPa with ethanol as solvent sintered at 1000oC.

The Influence of Sintering Temperature on Properties of Silicon Carbide Porous Ceramic Filter Membrane

The average particle size of SiC used as raw materials is 60 μm, the filter membrane in a mass ratio of each component are: SiC : binder: sodium carboxymethyl cellulose (CMC): deionized water =9:1:1:20. Method of producing membrane by means of spin coating, the sintering temperature was set in different ranges. The Archimedes drainage method was used to measure its porosity, and the filter pressure of membrane was charactered by the filter pressure testing system, SEM was performed to characterize its surface morphology and microstructure. The results show that: when the temperature rises from 1225 °C to 1325 °C, the filter pressure of SiC porous ceramic filter membrane decrease firstly and then increase; the atlas trend of the porosity is roughly opposite with the filter pressure, the maximum of the porosity value is about 42% when the temperature reaches 1300°C, at this temperature, the filter pressure reaches a minimum value and the surface of the filtration membrane is the most flat. When the temperature reaches 1350 °C, the surface of the film started showing a plaque.

Preparation and Properties of Silicon Carbide Porous Ceramic Filter Membrane

Spin coating method was adopted for preparation of two types of SiC filter membrane with different particles size. Sintering temperature was set at 1300°C. SEM was performed in order to characterize its micro-structure. For measuring the porosity of the membrane, we used Archimedes drainage method. The filter pressure testing system was used to character the membrane filter pressure drop. The experiment results indicated that, when the filter membrane was composed of average diameters 45μm and 23μm SiC particles, with their thickness reached about 300μm and 150μm respectively and the amount of ceramic binder was 10%, the porosity of the membrane achieved 43%, the surface of filtration membrane structure was uniform, and its filter pressure was smaller. On the premise of satisfying specific filtering accuracy and efficiency, larger size of silicon carbide particle could offer better performance of the membrane.

Effect of Sintering Temperature on Structure and Electric Properties of (Ba0.96Ca0.04)(Zr0.05Ti0.95)O3 Ceramics

Barium calcium titanate (Ba0.96Ca0.04)(Zr0.05Ti0.95)O3 ferroelectric ceramics were prepared by sol–gel technique. The ceramics were sintering at 1290°C-1370°C. X-ray diffraction was employed to investigate the microstructure, and the surface topography was investigated by SEM graphs. The dielectric constant vs temperature was measured by Temperature dielectric spectrometer, and TF Analyzer 2000 measured the ferroelectric properties. It can be found that all the ceramics show pure perovskite structure suggesting that solid solution were formed. SEM showed that the samples uniform in grain size at 1330 °C. Our study revealed that when the sintering temperature is 1330 °C the maximum dielectric constant was 29,600, the maximum piezoelectric coefficient d33 could reach 399pm/V and the remanent polarization (Pr) was 8.3 μc/cm2, respectively.

Preparation SiC Ceramic Composite Filtration Membrane Materials by Dry Pressing and Synchronous Sintering Method

Silicon carbide ceramic composite filter membrane materials were prepared by dry pressure molding and synchronous sintering process at sintering temperature of 1300oC for 3h. and research the influence of on the molding pressure structure of SiC filtration membrane,effect of particle size on porosity, average pore size and filter pressure drop of filtration membrane, SEM was performed to examine the morphology, The porosity ,average pore size and filter pressure drop of filtration membrane were tested by Archimedes method ,bubble point method and filter pressure drop instrument. It is demonstrated that while the molding pressure (F) varied from 1MPa to 10MPa, the filter membrane material achieved preferable morphology and best performance when F equals to 5MPa. Under this modeling pressure, while silicon carbide particle size increased from 1 to 23μm, the pore ratio decreased from 48.0% to 36.2% and the average pore size increased from 0.35μm to 9.4μm, while the air gas velocity changed from 0 to 0.112m/s, the filter pressure drop increased, when the velocity is stable, the filter pressure drop reduced as the silicon carbide particle size.

Effect of External Fields on the Switching Current in (Ba0.97Ca0.03) (Zr0.18Ti0.82) O3 Ceramics

Lead-free (Ba0.97Ca0.03) (Zr0.18Ti0.82) O3 (BCZT) ceramic is prepared by sol-gel technique. The sample shows a pure perovskite structure through the XRD pattern. Well-developed grain morphology and a dense microstructure are acquired at an optimistic sintering temperature (~1330°C). The BCZT ceramic shows a surprisingly high piezoelectric coefficient of d33=675 pm/V. The switching current curves are acquired in the different external fields by TF-2000 Ferroelectric Analyzer. It is found that with increasing the temperature, there is a decrease in the coercive field (Ec), and with increasing the electric field, there is an increase in the switching current obviously. Sintering temperature has an effect on switching current. The effect of temperature and electrical field on switching current is analyzed from viewpoint of the energy.

The Hydrothermal Synthesis of BaTiO3 Nanotubes Arrays with Good Electrical Property

Barium titanate nanotubes arrays were synthetized by in-suit hydrothermal method using TiO2 nanotubes as both template and reactant in titanium substrate. Highly ordered nanotubes arrays and the spacing between nanotubes are apparent. XRD indicates that the samples have excellent crystallization and perovskite structure. Typical ferroelectric hysteresis loop of as-formed barium titanate nanotubes arrays with remanent polarization and coercive field are 6.72 and 48.7kV/cm.

Ferroelectric and Dielectric Properties of La2O3-Doped BaTiO3 Ceramics

The different concentration La2O3-doped BaTiO3 ceramics were prepared by sol-gel method. The ferroelectric and dielectric properties of the ceramics are characterized by TF analyzer 2000. With the increased amount of La2O3-doped, the dielectric constant increase gradually, when the sintering temperature is 1250 °C, the dielectric constant has reached 4648 for La2O3 with 0.4％-doped. With the temperature increased the dielectric constant of La-BaTiO3 increase gradually, when the sintering temperature is 1290 °C, the dielectric constant has reached 7066 for La2O3 with 0.4％-doped.