Papers by Author: Han Xing Liu

Abstract: After dissolve PVDF in DMF, porous PVDF beads were prepared by water assistant. The porous beads were better crystallized and possessed greater relative surface than ordinary PVDF. The results suggested that the relative surface of PVDF reach 6.53m2/g while the dripping speed was 0.95ml/min. The material could rise to the modulator to fabricate nanometer fiber polymers.

Abstract: The purpose of this paper is to study the feasibility of nano-material (1~100nm) level powder preparation by wet ball milling. The powder was used to prepare the ceramic and the performance of the ceramic was analyzed. The experimental results show that the average particle size of the powder is close to nano-material level (around 120nm) and the ceramic possess high compactness, high dielectric constant and low dielectric loss.

Abstract: The spinel-type Li₄Ti₅O₁₂ cathode materials were synthesized by a self-combustion method. The effects of synthesis temperature on the structural and electrochemical properties of the Li₄Ti₅O₁₂ were investigated. The prepared samples were characterized by X-ray diffraction (XRD), SEM, TEM and electrochemical analysis. The results revealed that pure phase and well-crystallized Li₄Ti₅O₁₂ with nano-sized could be synthesized at a calcination temperature of 750°C. The sample prepared under the condition had the highest initial discharge capacity of 164 mAh/g and shown good capacity rentention during 50 cycles between 1.0-2.5V at 0.1C.

Abstract: The layered LiNi_1/2Mn_1/2O₂ cathode materials were synthesized by a sol gel method. The effects of calcination temperature and time on the structural and electrochemical properties of the LiNi_1/2Mn_1/2O₂ were investigated. The prepared samples were characterized by X-ray diffraction (XRD) and electrochemical analysis. The results revealed that the layered LiNi_1/2Mn_1/2O₂ material could be optimal synthesized at temperature of 900°C for 10h. The sample prepared under the above conditions has the highest initial discharge capacity of 151 mAh/g and showed no dramatic capacity fading during 20 cycles between 2.5-4.5V at a current rate of 20mA/g.

Abstract: The layered LiNi_0.5Mn_0.5O₂ used as a cathode material for lithium-ion batteries was synthesized from precursor Ni_0.5Mn_0.5CO₃ prepared via a carbonate co-precipitation method. The precursor Ni_0.5Mn_0.5CO₃ was synthesized by the addition of KHCO₃ to an aqueous solution of Ni, Mn sulphates. The powder LiNi_0.5Mn_0.5O₂ was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Spherical LiNi_0.5Mn_0.5O₂ with well development layered structure was obtained by the carbonate co-precipitation method. The LiNi_0.5Mn_0.5O₂ samples adopted the α-NaFeO₂ structure with a space group R-3m. Galvanostatic charge-discharge behavior of the LiNi_0.5Mn_0.5O₂ cathodes delivered a initial charge and discharge capacity of 144.4 mAh/g and 140.2 mAh/g, respectively in the voltage range 2.5-4.5V at a discharge rate of 0.02A/g. The capacity showed no dramatic capacity fading during 50 cycles.

Abstract: An organic–inorganic hybrid perovskite (C₆H₅CH₂NH₃)₂CuCl₄was synthesized successfully by solution method at room temperature and the thin film of (C₆H₅CH₂NH₃)₂CuCl₄ was also prepared by spin-coating on the quartz substrate. The perovskite and the film were characterized with X-ray diffraction (XRD), Scan electronic microscope (SEM), Atomic force microscope (AFM), Fourier transform infrared spectroscopy and Thermo Gravimetric Analyzer. Results show that the obtained perovskite has unique layer structure and good thermal stability with melting point around 243.3°C. And the prepared film appears very smooth, continuous and uniform with a grain size of 0.1μm, highly oriented with the (0 0 l) planes perpendicular to the substrate surface. Its optical photoluminescence spectrum mainly depends on the inorganic part so the bandgap can be tuned by changing the inorganic composition. The carrier mobility is around 0.26cm²V^-1S^-1 , which indicates its potential application in field effect transistor with improved film quality.

Abstract: In this work, we have proposed a simple model to predicte the dielectric constant of CaCu₃Ti₄O₁₂-SrTiO₃ composite ceramics. The model has been established based on the analysis of composition and microstructure. Two different compositions in the composite ceramics correspond to two different grain sizes, large for CaCu₃Ti₄O₁₂, and small for SrTiO₃, which has been identified by the x-ray diffraction, the scanning electron microscope and the energy spectrum analysis. All specimens have been assumed to be the barrier layer dielectrics in the model, according to the complex impedance spectra. The dielectric constant of serial, parallel, and logarithmic mixture models has been discussed. Compared with the experimental results, the model shows the similar variation tendency as SrTiO₃ content increases.

Abstract: A steady layered organic-inorganic perovskite hybrid containing Fe³⁺ was prepared in the air with phenosafranine as organic sheets, the Fe(CN)₆^3- as inorganic sheets. We utilized the Fe(CN)₆^3- as inorganic sheets of perovskite hybrids, which may help to stabilize the unusual metal-deficient layered structures. The results of X-ray diffractometry (XRD) and scanning electron microscopy (SEM) show that the hybrid is typical layered perovskite structure. The hybrid was mixed with paraffin to form a hybrid paste for the hybrid paste electrode. Electrochemical characteristics of carbon paste electrode (CPE) modified by hybrid were investigated with cyclic voltammetry. The modified electrode can accelerate the electron-transfer to improve the electrochemical reaction reversibility and be use for the determination of chemicals. The interactions between sodium nitrite (NaNO₂), sodium bromide (NaBr), hydroxylammonium chloride (NH₂OH·HCl), hydroquinone (C₆H₆O₂) with hybrid were studied. The modified electrode exhibits good electrochemical activity. The hybrid can be used as electrochemical materials.

Abstract: The dielectric properties of Zr substituted CaCu₃Ti₄O₁₂ ceramics have been investigated in detail. Grain size decreases with Zr content increasing. The hetero-electrical microstructures of prepared samples have been confirmed by the impedance spectra. The dielectric loss has been improved by Zr doping because of the enhancement of grain boundary resistivity. A Debye-like boundary relaxation behavior has been observed in the temperature range of 220-600K. As Zr content increases, the relaxation time increases due to the higher grain boundary concentration. This work has provided an additional proof for the origin of giant dielectric response in CaCu₃Ti₄O₁₂ ceramics.

Abstract: Steady organic-inorganic perovskite hybrids with (H22-Ap)3/2Fe(CN)6, (H23-Ap)3/2Fe(CN)6 and (H24-AP)3/2Fe(CN)6 (2-AP = 2-aminopyridine, 3-AP = 3- aminopyridine, 4-AP = 4- aminopyridine) were formed from aqueous solution. Each structure was an unusual layered organic-inorganic structural type. A device was designed to construct electrochemical sensing devices using above organic-inorganic perovskite hybrids. The sequence of redox activity is (H24-Ap)3/2Fe(CN)6 > (H22-Ap)3/2Fe(CN)6 > (H23-AP)3/2Fe(CN)6 and that of electrocatalytical activity is (H22-Ap)3/2Fe(CN)6 > (H23-Ap)3/2Fe(CN)6 > (H24-AP)3/2Fe(CN)6. The variation coefficients (RSD) of successive and interval assays are less than 2.0%. Three electrochemical sensing devices display a remarkable electrochemical sensitivity and stability.