WEB Flash sintering of 10YSZ nano-particlesFriday (25.09.2020) 09:30 - 09:45 P: Processing and Synthesis 1 Part of:
“Flash Sintering”, as an extremely fast sintering method, has attracted much interest since it was first reported by Cologna et al. in 2010. It has become clear that flash sintering is easy to reproduce and is possible with any ceramic with sufficient electrical conductivity at temperatures below the normal sintering temperature. Nevertheless, YSZ have been studied as model materials and become reference points. It is noted that the nano-particles with the size around 10 nm have hardly been studied, most previous work having concentrated on the commercial YSZ powder with particle size of 50 nm. In the present study, flash sintering of 10YSZ nano-particles was investigated. The densification behavior and the microstructural evolution during flash sintering were compared with the normal sintering and 2step sintering to study the effectiveness of flash sintering for the synthesis of nano-ceramics.
The specimens in this work were made by slip casting. 10YSZ nano-slurry (MEL Chemicals Ltd., Manchester, U.K.) with the mean particle size of about 10 nm was used as starting material for slip-casting. The previous woks were referred for the procedure of slip casting [2-3]. After one week drying, the green bodies were calcined at the temperature of 800 °C for decomposing organic additions. The cross-section of the calcined sample was about 4.1 mm ×1.7 mm. All the specimens had holes separated by 14 mm for the connections to the power supply. Flash sintering was conducted at the isothermal furnace temperature of 900 ◦C. Below 900 ◦C no electric field was applied. Subsequently, the electric field was applied in a stepwise fashion, in steps of 5 – 20 V until the flash event occurred at an applied field of ~135V/cm. The specimen temperature was controlled by changing limiting current from 1.8 to 6.9 A/cm2 in the power supply.
The blackening of the sintered samples propagates from the cathode side. With increasing current density, the area of the blackening extended in a direction to the anode side. Both density and grain size increased with increasing current density. The density of the sample with the current density of 5.0 A/cm2 for 1min reached 95%. Detailed comparisons of densification behavior and microstructural evolution in flash sintering, normal sintering and two step sintering will be discussed in the symposium.