Zhaoxian Xiong

Highly oriented BaTiO3 film self-assembled using an interfacial strategy and its application as a flexible piezoelectric generator for wind energy harvesting

A high output flexible piezoelectric generator based on a highly oriented BaTiO3 film self-assembled using an interfacial strategy is reported. We have successfully controlled the morphology and orientation of BaTiO3 particles and obtained a BaTiO3 film using a facile interfacial self-assembled method. The BaTiO3 film is transferred onto an ITO coated PET substrate and packaged with PDMS (polydimethylsiloxane) to form a flexible piezoelectric energy harvesting device. The interfacial assembling strategy can effectively increase the volume fraction of active piezoelectric materials in composite films. The BaTiO3 film-based piezoelectric generator was demonstrated to harvest wind energy by employing a windmill and the output power was large enough to light a LCD.

Hydrothermal synthesis and photoluminescent properties of Li2Sr0.996SiO4:Pr3+0.004 phosphors for white-LED lightings

Abstract Red phosphors, Li 2 Sr 0.996 SiO 4 : Pr 3+ 0.004 , with different hydrothermal conditions were prepared via hydrothermal synthesis and then heat-treatment. The chemical structures of the phosphors were identified with X-ray diffraction (XRD). Surface morphological features were observed by scanning electron microscopic (SEM) investigation. Spectra of excitation and emission for the phosphors were also obtained by a spectrophotometer. Results showed that the optimum conditions were as follows: pH value of solution was 1−2, reaction temperature was at 180 °C for 24 h. The as-prepared phosphors exhibited two excitation dominant peaks at 451 and 486 nm, attributed to transitions of 3 H 4 → 3 P 2 and 3 H 4 → 3 P 0 of Pr 3+ , respectively. A narrow emission peak at 610 nm corresponded to the energy level transition of 3 P 0 → 3 H 6 of Pr 3+ under excitation of light at 451 nm, which indicated promising candidate red phosphors for blue LED chips.

Preparation and characterization of lead zirconate titanate ceramic fibers with alkoxide-based sol-gel route

Lead zirconate titanate (PZT) fibers with diameters from 10?m to 40?m were prepared via a sol-gel route. Several kinds of chemicals were used, including lead acetate trihydrate, zirconium n-butoxide and titanium n-butoxide, in addition to butanol as a solvent. As a water source for hydrolysis reaction, Pb(CH3COO)2?3H2O was directly used without further adding of water or catalyst conventionally. Acetylacetonate and acetate were added as stabilization agents to obtain stable sols for fiber drawing. The gel-to-ceramic conversion was characterized with thermal analysis, infrared spectroscopy and X-ray diffraction. A pure perovskite phase was obtained after heat treatment at 650?C for 1h. By using scanning electron microscope (SEM), it was observed that a lower rate of heat treatment resulted in a denser microstructure of the fibers. The relative permittivity and the P-E hysteresis loop of the crystalline PZT fibers were also measured and discussed in the paper.

Piezoelectric PZT fiber composite as a low frequency vibration sensor

The recently developed macro fiber composites (MFCs) with in-plane aligned PZT fibers embedded in polymeric thick films combine the excellent piezoelectric property of PZT fibers and the flexibility of polymer, which are suitable for many smart materials and intelligent structure applications. In this paper, we present both theoretical and experimental studies of a low frequency vibration sensor using the PZT fiber composite in a simple cantilever structure. Global parameters of the PZT fiber composite were substituted into the lumped and distributed parameter models for cantilevered piezoelectric unimorph vibration sensors to predict the voltage output sensitivity and frequency response. Experimental studies were carried out and the predicted performance of the low frequency vibration sensor agrees well with the experimental results. With excellent flexibility, tailorable elastic, dielectric and piezoelectric properties, and large time constant, the PZT fiber composite works well as vibration sensor that has very low resonant frequency.

Preparation and Mechanical Energy Harvesting of BaTi0.9Zr0.1O3 Ceramic Nanofibers

Piezoelectric barium zirconate-titanate ceramic nanofibers were prepared by combination of Sol-Gel processing and electrospinning technique. The average diameter of barium zirconate-titanate ceramic nanofibers is nearly 200 nm. The x-ray diffraction pattern of the fibers showed that their crystalline structures displayed tetragonal perovskite structures. Interdigitated electrodes were sprayed on an epoxy resin substrate. BaTi0.9Zr0.1O3 nanofibers were then aligned on the interdigitated electrodes and covered with the solution of epoxy resin, so as to obtain Piezoelectric Fiber/polymer Composites. The periodic output voltages with maximum value of 0.26V were obtained under harmonic excitation, by using a finger to apply a dynamic load on the top of the composites.

Evaluation Feature of Nano Grain Growth of TiO2 Thin Film via Sol-Gel Route

TiO2 films were successfully coated via a spin coating sol–gel route, using tetrabutyl titanate as the main raw reagent. One batch of samples was sintered at different temperatures, ranges from 300 to 800 °C, for 2 h, while other ones were treated at 700 °C for different soaking times (1–600 min). The phase compositions of the films were identified with X-ray diffraction (XRD). The microstructure of the coating were observed by a scanning electron microscope (SEM). Experimental results indicated that well-developed crystallinity and good morphology of TiO2 could be synthesized above 500 °C for 2 h. The crystallinity and morphology of grains in films were affected by the reaction temperature and time. However, image analysis shows that sintering temperature had a great impact on the crystallinity and particles size of the samples above 700 °C. Kinetic exponents of grain growth were also obtained with image processing software.

Dielectric Properties and Microstrip Patch Antenna Performances of 0.95MgTiO3-0.05CaTiO3 Microwave Ceramics

τMicrowave dielectric properties of 0.95MgTiO3-0.05CaTiO3 ceramics and their performances as H-shaped microstrip patch antenna were investigated. Best values of dielectric constant (εr) and quality factor (Q×f) of 19.00 and 66800GHz, respectively, were obtained for the microwave ceramics sintered at 1300°C for 3h. A near-zero temperature coefficient of resonant frequency (τf) of -4.7ppm/°C was obtained for the ceramics with sintering 1280°C for 3h. A new kind of H-shaped microstrip patch antenna with two resonant frequencies was fabricated by using of this kind of ceramics as antenna substrate. The return loss bandwidth of the patch antenna was extended with the increasing of substrate thickness at both resonant frequencies of the antennas, around 1.530GHz and 2.750GHz, respectively.

BaTiO 3 piezoelectric microfiber composites for mechanical energy harvesting

In this paper, green microfibers of barium titanate precursor were prepared by the combination of Sol-Gel processing and Gel-spinning technique. The piezoelectric microfibers of ceramic BaTiO3 were sintered, with diameter of 15μm and length of 20mm, respectively. Interdigitated electrodes were printed on an epoxy resin substrate. BaTiO3 microfibers were then aligned on the interdigitated electrodes and covered with the solution of epoxy resin, so as to obtain Inter-Digitated Electrodes Piezoelectric Fiber/polymer Composites, IDEPFC. The periodic output voltages with maximum value of 0.86V were obtained under harmonic excitation, by using a finger to apply a dynamic load on the top of the IDEPFC.

Al-Pb, Mg-Pb or Mn-Pb binary cations doping in bi-system high Tc superconductor

Abstract The effect of Mg–Pb, Al–Pb and Mn–Pb binary cations doping on the appearance time of high T c 2223 phase in the Bi-system superconductor was investigated. We found that the binary cations dopants, Mg–Pb, Al–Pb or Mn–Pb tend to speed up the formation of high T c phase distinctly and that the Al 3+ Mn 3+(4+) and Mg 2+ cations occupied certain positions in the crystal lattice of the high T c phases. They play an important role in the formation of the high T c phases and have an effect on the structure and the superconductivity of high T c phases.

High Performance of Rutile Titanium Dioxide Whiskers/Epoxy Resin Composites

Rutile TiO2 whisker/epoxy resin composites were prepared by hot-pressing process method. The effects of different content of TiO2 whiskers on the microstructure, microwave dielectric properties and flexural strength for TiO2/epoxy resin composites were investigated. Results show that flexural strength increased firstly, which can reach the maximum value (105.53 Mpa), then decreased with the content of TiO2 whisker (v%) increase. Moreover, the dielectric constant and dielectric loss of the TiO2/epoxy resin composites increase with the increased of TiO2 whisker (v%). When the content of TiO2 whisker is 60 v%, the TiO2 whisker/epoxy resin composites exhibit a higher permittivity (εr = 10.74) and relatively low dielectric loss (tanθ= 0.021).