Study on Two-Step Sintering of α-Al2O3
Date Issued
2005
Date
2005
Author(s)
Chieh, Lin Chung
DOI
en-US
Abstract
Abstract
In this research, sintering behavior of two α-Al2O3 powders with average particle size 0.1μm (Slurry B) and 0.2 μm (Slurry A) were investigated. Several heating
processes were tried. One followed a two-step sintering method given by Chen and Wang [1], The effects of temperature, holding time, initial grain size and porosity
were controlled. Various thermal treatments were also done comparing to the conventional (one-step) process. Secondly, TMA was used to analyze the sintering behaviors of the α-Al2O3 at various heating rates, from 2 to 90 oC/min. Finally, an infra-red fast sintering furnace was designed and used to study the heating effect on the fine α- Al2O3.
A high density (>99% T.D.) and small average grain size (0.86 μm) were achieved by the two-step sintering of Al2O3 and better than the results by the
conventional sintering (1500 oC for 1 h). The other case, sintered Al2O3 – B samples, in a smaller grain size (0.57μm) and a good density (>98% T.D.) were achieved by
heating to 1450 oC, then holding at 1350 oC for 20 h. Lower first-step temperature and second-step temperature than the temperatures of sample – A were noted.
Different sintering rates indeed influence the sintered densities, e.g. the results of Al2O3 – B, but no influence on the average grain size. The results showed, while the sintering rate increased from 2 oC /min to 90 oC /min, the sintered density decreased from full density to 97%TD if heating to 1500oC then holding for 1 h. For both cases,
the initial sintering temperature increased with the heating rate, due to the limitation of heat transfer in Al2O3 samples. Maximum shrinkage rate and the corresponding
temperature increased with the heating rate, too. The sintering mechanism of rapid-heating rate has been determined by Young and Cutler [36]. The mechanism of
initial sintering belongs to a lattice diffusion, and the activation energy is 688 kJ/mole, which is interpreted as a volume diffusion of Al3+ ions in polycrystalline matrix.
Subjects
兩階段燒結
加熱速度
粒徑
燒結機制
燒結密度
紅外線快速加熱
two-step sintering
heating rate
grain size
sintering mecha-nism
sintered density
Infra-red fast sintering
Type
thesis