Peng Dingkun

Sol-gel synthesis of yttria stabilized zirconia membranes through controlled hydrolysis of zirconium alkoxide

Abstract Yttria stabilized zirconia (YSZ) polymeric sols were synthesized by controlled hydrolysis and condensation of zirconium tetra- n -propoxide. Yttrium nitrate was added before hydrolysis as the source of yttria. Acetylacetone was used as chelating ligand to modify the reaction rate of zirconium alkoxide. The dependence of YSZ sol formation as well as gelation time was investigated experimentally on the contents of acetylacetone, n -propanol (solvent) and water for hydrolysis. With a stable sol, YSZ membranes were prepared on porous α-alumina supports by a dip-coating process. The membranes were characterized by scanning electron microscopy and gas permeability testing. Unsupported YSZ membranes were also prepared with the same sol, and were investigated with isothermal nitrogen adsorption/desorption porosimetry and X-ray diffraction. The results show that YSZ membranes with nanosize pores were successfully prepared by the sol–gel technique with the polymeric sols.

Boehmite sol properties and preparation of two-layer alumina membrane by a sol-gel process

A two layer ultrafiltration alumina membrane was prepared by a sol-gel process using boehmite sol as precursor. The sol was prepared by hydrolysation of aluminium tri-sec-butoxide. Sol properties, such as viscosity as a function of concentration and acidity, were investigated by using capillary viscometry, transmission electron microscopy and laser scattering photometry etc. The viscosity increased with an increase in concentration and a decrease in pH, while the particle shape and size of the sol were mainly determined by pH. The membrane prepared by a dipping procedure was characterized by both scanning electron microscopy and transmission electron microscopy. The results showed that the membrane thickness and surface morphology were affected by the dipping time, the viscosity and the temperature.

Preparation of asymmetric Ni/ceramic composite membrane by electroless plating

Abstract Although a lot of work has been done on electroless nickel coating, work on preparing asymmetric nickel membranes on porous ceramic supports is rarely reported. In this work, microfiltration nickel membranes are prepared on porous alumina supports with electroless plating. A new approach technique, sol–gel process is used to activate the alumina supports. The coated membranes were investigated by means of scanning electron microscopy and gas permeation test. Membrane thickness and amount of nickel increase with plating time. Membrane pore size decreases greatly as electroless coating is processed for 15 min. After 15-min coating the pore size decreases slightly. For a 90-min electroless plated membrane, the thickness reaches 4.5 μm and the mean pore radius is 0.13 μm with a narrow distribution.

New solid state fuel cells - green power source for 21st century

The exhaustion of the major fossil energy sources on earth in near future and the serious environmental pollution from the fuel combustion processes in the presently applied technologies are the most important problems of modern society. The sustainable development of mankind requests strongly to develop “green” power devices characterized by high fuel energy conversion efficiency, less pollution to the environment and convenience to use.Fuel cells have been commonly accepted to be a kind of clean, safe and convenient power source with high energy efficiency and are on the verge of revolutionizing the electric power industry by offering better ways to produce electricity and to deliver it to the consumers.Among all the advanced fuel cells being developed, which one might be the better choice for ideal green power generators in the 21st century? The answer is solid state fuel cells, particularly the solid oxide fuel cells(SOFCs) but not in the present stage of development. The new generation of SOFCs will certainly be based on all the results and experiences achieved so far in the fuel cell field and a lot of R & D work has to be performed furthermore.This paper attempts to present the current status of the R & D work on fuel cells, especially SOFCs, new concepts and trends, problems and possible measures which may initiate further discussion.The present article includes the following sub-topics:The best electric power plants for the 21st CenturyR & D on SOFCs: current status, problems and new trendsIntermediate temperature SOFCs - what do we need to do?Fabrication techniques - soft chemistry routesWhat to do for coming up with “green” power plants?

Superconducting properties in Bi2−x−yPbxSbySr2Ca2Co3Oz (x=0, 0.1, 0.3, 0.5; y=0, 0.1)

Abstract The temperature of zero resistance of the previously reported 120K superconductor in the BiSbSrCaCuO system was 75 K. We added Pb to the BiSbSrCaCuO system, so that the temperature of zero resistance was raised to 108 K.

Preparation and characterization of SrFeCo0.5O3.25+δ by gelcasting

Abstract SrFeCo 0.5 O 3.25+δ powders have been successfully synthesized from SrCO 3 , 2CoCO 3 ·3Co(OH) 2 ·xH 2 O and Fe 2 O 3 based on using the principle of gelcasting. Thermal decomposition of the gelcasting powder was analyzed by differential thermal analysis and thermogravimetry. The crystal structure of the sintered body was investigated by X-ray diffraction. It was found that SrFeCo 0.5 O 3.25+δ samples formed by sintering the gelcasting powder over 1000°C consist mainly of the perovskite phase SrFe 1-x Co x O 3-δ . Electrical conductivity was measured by a DC four-probe technique and oxygen permeation flux was measured by applying oxygen partial pressure difference to a 1.4 mm thick pellet. Both the electrical conductivity and oxygen permeation flux of the gelcasting samples were much higher than that of samples prepared by a traditional solid state reaction method. Though further work should be performed on the higher transfer velocity of electron and oxygen ion, experimental data shows that the gelcasting process is a promising technique for the preparation of mixed conducting SrFeCo 0.5 O 3.25+δ .

Status and future prospects of intermediate, high temperature proton conductor fuel cell

The paper describes the features of fuel cells using proton conductors as electrolyte. Comments on the properties of some intermediate and high temperature proton conductors and their applications for fuel cells are given. Finally, further research areas including the search for new proton conductors and new electrode materials compatible to the electrolytes as well as the development of preparation techniques are proposed.

Soft chemical route and new solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are a promising technology for electric power generation in the 21st century. Recently, research are focusing on reduced temperature SOFCs. The fabrication of thin film electrolytes and electrode membranes for reduced temperatures by a soft chemical route is discussed.

Growth of Diamond Films by Microwave Plasma Chemical Vapor Deposition

Diamond thin films were produced by microwave plasma chemical vapor deposition. The deposit is identified by x-ray diffraction, Raman spectroscopy and Scanning electron microscopy. During the course of diamond growth, the characteristics of the plasma have been measured by means of the Langmuir double probe and emission spectrometer.

The structure phase transition of the quenched YBa2Cu3O7−y with tetragonal phase

The single (123) phase of Y-Ba-Cu oxides with T-phase structure was prepared using the air-quenching technique. From the measurements of electrical resistance, thermal expansion coefficience, specific heat, ac susceptibility and XRD, it is the first time to find the existance of a structure phase transition. It is suggested to be a structure phase transition from Y-phase to O-phase. The explanation for low Tc in this system is also proposed in this paper.