Papers by Author: Wen Chen

Abstract: The hybrid guest-host nanocomposite films based on poly (ethylene oxide) (PEO) and molybdenum doped vanadium pentoxide (V_0.975Mo_0.025)₂O₅nH₂O were prepared by sol-gel and hydrothermal reaction via a two-part process. The electrical properties along and across V-O layers have been evaluated. The results indicate that the proper amount of PEO can increase the electrical conductivity of the films. The electrochromism of the films were investigated by cyclic voltammetry, the ex-situ transmission spectra and photographs. The films display a reversible multichromism (orangegreenbluebrown) upon Li⁺ ion insertion/extraction.

Abstract: Aluminophosphate molecular sieves (AlPO₄-5s) with fibrous morphology were readily prepared via hydrothermal method at 180 °C with the initial molar ratio of Al(OiPr)₃: H₃PO₄: TrPA: HF: H₂O as 1: 0.83: 1: 0.8: 70. The morphology and structure of the prepared AlPO₄-5s were characterized by XRD, SEM, TEM and nitrogen sorption measurement. The morphology development and structure evolution mechanism were proposed.

Abstract: Ordered high surface area microporous carbon molecular sieves containing well-dispersed platinum nanoparticles have been prepared by chemical vapor deposition method. Acetonitrile was employed as carbon and nitrogen precursors to yield N-doped carbon molecular sieves. N-doped carbons have an average nitrogen content of ~ 4.1 wt%. Electrochemical tests showed that the rectangular-shaped CVs of N-doped carbons could be well retained over a wide range of scan rates (5~100 mV/s), and the CV curves presented a steep current change at the switching potentials. N-doped carbons exhibited excellent performance as an electrochemical supercapacitor with a calculated specific capacitance of 168 F/g. Meanwhile, it was noticed that a reasonable Pt loading would help to improve the capacitance. It was proposed that the polarizability or surface state modification by nitrogen doping and regular interconnected porous structure might contribute to the improvement of N-doped carbons’ electrochemical properties.

Abstract: A piezoelectric generator based on the piezoelectric stacked elements is applied to realize electro- mechanical energy conversion in this paper. The piezoelectric stacked generator is constructed. The relational expression about output electrical characteristic parameters, the constructional dimension parameters of piezoelectric stack elements and external driving forces is discussed here. Theoretical predictions confirmed by experimental results show that the piezoelectric generator produces electrical power with higher efficiency, and energy harvesting circuit can harvest energy from the piezoelectric generator effectively.

Abstract: Nanoflakes β-Ni(OH)₂ microspheres were successfully synthesized by a facile hydrothermal. The microstructures and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical properties studies were carried out using cyclic voltammetry (CV), galvanostaitc charge/discharge and electrochemical impedance spectroscopy methods, respectively. The results exhibited that the β-Ni(OH)₂ single electrode had high specific capacitance in KOH electrolyte. A maximum specific capacitance of 1929 F/g could be achieved in 6 M aqueous KOH with 0 to 0.4 V potential at a charge-discharge current density of 6 mA/cm². Therefore, the obtained nanoflakes β-Ni(OH)₂ microspheres can be a potential application electrode material for supercapacitors.

Abstract: Low-temperature sintered Ca[(Li_1/3Nb_2/3)_0.8Ti_0.2]O_3-δ (CLNT) microwave dielectric ceramics with V₂O₅ and ZnO additives were prepared by the conventional solid state reaction method. The sintering behavior and microwave dielectric properties of CLNT ceramics were investigated. The main diffraction peaks of all the specimens sintered at the temperature under 1150^◦C split due to the coexistence of the non-stoichiometric phase and stoichiometric phase, which all possess CaTiO3-type perovskite structures. ZnO and V₂O₅ combined additives lowered the sintering temperature of CLNT ceramics from 1150^◦C to 1090^◦C. and the Qf values were improved from 18,210 GHz to 20,740 GHz. The CLNT ceramics with 4 wt% ZnO addition sintered at 1090^◦C showed good microwave dielectric properties with ε_r ~39.7, Qf ~20,740 GHz, τf ~8.6 ppm/^◦C. The relationship between dielectric properties and the sintering behavior was also discussed.

Abstract: Nanostructured α-Ni(OH)₂/ mesoporous carbon composites were synthesized by a facile solvothermal method using sodium dodecyle sulfate as a soft template and urea as a hydrolysis-controlling agent. The obtained products were characterized by X-ray diffraction(XRD), and scanning electron microscopy(SEM). Electrochemical properties studies were carried out using cyclic voltammetry(CV) and galvanostaitc charge/discharge method. The results exhibited that the α-Ni(OH)₂/ mesoporous carbon composites single electrode had high specific capacitance in KOH electrolyte. The maximum specific capacitance of the α-Ni(OH)₂/ mesoporous carbon composites single electrode was up to 2191 F/g in 6 M KOH solution at a charge-discharge current density of 4 mA/cm², when the mass percent of mesoporous carbon was 5%. It is suggested its potential application in the electrode material for supercapacitors.

Abstract: Ni(OH)₂/multiwalled carbon nanotubes (Ni(OH)₂/MWNTs) nanocomposites were synthesized by hydrothermal method. The microstructures of such nanocomposites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Electrochemical properties studies were carried out using cyclic voltammetry (CV), galvanostaitc charge/discharge and electrochemical impedance spectroscopy method. The presence of MWNTs network in the Ni(OH)₂ significantly improved the electrical conductivity of the host Ni(OH)₂ by the fromation of conducting network of MWNT and the active sites for the redox rection of the metal hydroxide. The specific capacitance of the new composites was significantly improved (MWNTs of 20 wt.%, 2144 F/g) compared to Ni(OH)₂ (MWNTs of 0 wt.%, 1772 F/g) in 6 M KOH solution at a charge-discharge current density of 4 mA/cm². Therefore, the Ni(OH)₂/MWNTs nanocomposites can be a potential application electrode material for electrochemical capacitors.

Abstract: Mesoporous carbon with MoO3 loading (MoO3/CMK-3) was obtained via ultrasonic assembly with CMK-3 as the host material and MoO3 as the guest material which was yield from MoO3ּpH2O2ּqH2O sol precursor. The microstructures of such MoO3/CMK-3 composites were characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption, X-ray photoelectron spectra (XPS), Fourier-transform infrared (FTIR) and transmission electron microscopy (TEM). The results show that the method of ultrasonic assembly was efficient to highly disperse MoO3 nanoparticales into the channels of mesoporous carbon.

Abstract: In this work, 1-3 composites, which required for different devices applications, with the (PZT)-based (PZT-5, PMnS-PZN-PZT and PSN-PZN-PZT) piezoelectric fibers produced via a VPP method have been investigated. The relationship between the dielectric and piezoelectric properties of the 1-3 composites and different ceramic fibers with various aspect radios has been compared. We conclude that the properties of the 1-3 composites are well followed with the properties of the piezoelectric fibers, so the performance of the 1-3 composites can be improved for various devices by tuning the fiber properties.