Papers by Author: Jing De Zhang

Abstract: The graphite was used as pore-forming agent to prepare porous NiO-Yttria-stabilized zirconia (YSZ) anode material. The influence of the content of pore-forming agent of the anode material, and the change of the anode material before and after the reduction of NiO were investigated. It was found that the porosity and shrinkage rate of the anode increased with the addition of the pore-forming agent, and the thermal shock resistance also improved. We chose Y(NO₃)₃·6H₂O and ZrOCl₂·8H₂O as raw materials, ethylene glycol monomethyl ether as solvents to make collosol. And electrolyte membrane on the Si piece was prepared by spin-coating. The electrolyte membrane would be thinner if it spined faster and longer. Then we chose the anode material as support to prepare electrolyte membrane. The thickness of the electrolyte membrane increased with the increase of the number of layers. Two layers were the most appropriate.

Abstract: A comparative study has been carried out on the effects of pore-forming agents on the microstructural characteristics and properties including porosity, microstructures, linear sintering shrinkage and mechanical strength of NiO/yttria stabilized zirconia (YSZ). Different pore-forming agents (soluble starch, graphite and activated carbon) were incorporated into NiO/YSZ at various mass mixing ratios (5%, 10% and 15%). The experimental results show that under the condition of same content, sintered samples using activated carbon as pore-forming agent had a higher porosity than that with identical content of the other two kinds of pore-forming agents. Sintered samples with 10.0 wt% activated carbon had a porosity of 35%. Section morphologies show that pores distributed uniformly and connected very well in the anode with activated carbon as pore-forming agent. The mechanical strength of these sintered samples with carbon as pore-forming agent was also higher. With the activated carbon particle size decreasing (from 100 mesh to 320 mesh), the open porosity of porous NiO/YSZ was reduced (from 31.7% to 30.9%). It may be concluded that The activated carbon is the better choice as pore-forming agent for NiO/YSZ anode.

Abstract: Different contents of bismuth oxide doped in 3YSZ material and the mixed powder formed. After press forming,the samples were sintered at 850°C, 900°C, 1000°C and 1100°C respectively. The electrical properties,the thermal shock resistance,the phase components and the microstructure morphology were analyzed to study the solid solution mechanism of Bi₂O₃-Y₂O₃-ZrO₂ three-phase system. It was found that the Bi₂O₃ can effectively reduce sintering temperature as a flux. Sintered at 1000°C, t-ZrO₂ can be induced into m-ZrO₂ by Bi₂O₃ doped. With the increasing of Bi₂O₃ content, system shock resistance decreases. The thermal shock resistance of the 2-3mol% Bi₂O₃-YSZ is the best. In the different content of Bi₂O₃ system, 3mol% doped materials has the highest conductivity.

Abstract: To combine the merits of both metals and ceramics into one material, many researchers have been studying the deposition of alumina coating using plasma spray on metal substrates. However, as the coatings are deposited at a high temperature, residual thermal stresses develop due to the mismatch of thermal expansion coefficients of the coating and substrate and these are responsible for the initiation and expansion of cracks, which induce the possible failure of the entire material. In this paper, the residual thermal-structural analysis of a Fe3Al/Al2O3 gradient coating on carbon steel substrate is performed using finite element modelling to simulate the plasma spray. The residual thermal stress fields are obtained and analyzed on the basis of temperature fields in gradient coatings during fabrication. The distribution of residual thermal stresses including radial, axial and shear stresses shows stress concentration at the interface between the coatings and substrate. The mismatch between steel substrate and composite coating is still the dominant factor for the residual stresses.