The Preparation Of Ceramic Nanopowders And The Study Of Electric Field-assisted Sintering

Sintering is a very important process in preparing ceramic materials. However, Densification of ceramic materials generally needs high sintering temperatures and long sintering time, which results in large energy consumption. Meanwhile, long sintering time at high temperature makes abnormal grain growth happen, resulting in non-uniform microstructure, which reduces physical and chemical properties of ceramic materials. Thus, lowering the sintering temperature, shortening the sintering time is significant. In this present work, we prepared ZrO₂, ZrO₂-Al₂O₃ and ITO nanopowders. The effect of preparation condition on the phase transformations, morphology, particle size and agglomeration conditions of nanopowders is studied. The sintering behavior of ZrO₂ and ZrO₂-Al₂O₃ nanopowders under the electric field were also studied. The influence of the electric field strength, current density on the densification process was explored.It was found that the particle size and agglomeration condition of ZrO₂ nanopowders were decreased with A: Zr（A represents acrylamide） molar ratio of increasing using a polyacrylamide gel method. When ZrO₂ nanopowders were sintered under the electric field, it is found that the current density increased rapidly at a certain temperature, and the onset temperature decreased when the electrical field is increased. When the electric field strength was 300 V/cm, ZrO₂ nanopowders were sintered at 800 oC for 1 hour with different current densities. The results showed that the relative density and grain size of sample were increased with the increasing of current density.It was found that the particle size and agglomeration condition of Al₂O₃-ZrO₂ nanopowders were decreased with A: Al-Zr molar ratio of increasing using a polyacrylamide gel method. When the Al₂O₃-ZrO₂ nanopowders with a Al₂O₃/ZrO₂ mole ratio of 2/1 were sintered under the electric field, The current density through the sample inital slowly increases with the temperature rise, but not enough to make the sample sintered compact; As the Al₂O₃/ZrO₂ mole ratio became 1/2, the current density increased rapidly at a certain temperature, and the onset temperature decreased when the electrical field is increased. The Al₂O₃-ZrO₂ nanopowders with a Al₂O₃/ZrO₂ mole ratio of 1/2 were sintered at 965 oC for 1 hour under the electric field of 630 V/cm, at a current density of 15 A/cm2, a relative density of 98.2% can be obtained.ITO nanopowders were successfully prepared using polymer gel method. When the A:In was 60:1, the obtained ITO nanopowders were severely agglomerated, had an irregular morphology, and an average particle size of 52 nm. When the A:In was 120:1, the ITO nanopowders had a narrow particle size distribution, weak agglomeration, and a average particle size of 9 nm.