Flash Sintering Of Al₂O₃ And ZrO₂ Based Ceramic Materials

Al₂O₃ and ZrO₂ based ceramic materials are very widely used structural ceramic materials.However,its manufacture often requires a high sintering temperature and a sintering time for several hours,which not only consumes a lot of energy,but also harms the environment.Therefore,it is great significance which develop low-temperature rapid sintering materials of Al₂O₃ and ZrO₂ based ceramic.In this paper,a new type of electric field assisted sintering method-flash firing method is used to prepare Al₂O₃ and ZrO₂ based ceramic materials.It achieved densification of Al₂O₃ and ZrO₂ based ceramic materials at low temperature and rapid sintering.At the same time,the prepared ceramic material has good mechanical properties.The specific research content and results are as follows:Theα-Al₂O₃ nano-powder was prepared by polymer network gel method,and the（Co,Mn）（Co,Mn）₂O₄ powder was prepared by solvothermal method.（Co,Mn）（Co,Mn）₂O₄powder andα-Al₂O₃ nano-powder are taken as（Co,Mn）（Co,Mn）₂O₄ powder to account for the wight ratio ofα-Al₂O₃ nano-powder 3 wt%and 6 wt%to mix.Then,the mixed powder was pressed into a green body by dry pressing technology,and then a DC electric field of 400-800V/cm and a current limit of 80-120 m A were applied to the green body.The electric field assisted sintering behavior was studied.The research results show that the ceramic green body flashes under certain electric field and furnace temperature.And the densification is completed in a short time.The flashing furnace temperature occurs will decrease as the electric field strength increases.Under the electric field strength of 400 V/cm,flash sintering did not occur at a high temperature of 1500℃,indicating that there is a lower limit to the electric field intensity of flashing.The grain size decreases with the increase of the electric field strength.The sample density increases with the increase of the limiting current.By increasing the ratio of（Co,Mn）（Co,Mn）₂O₄ powder,the flash temperature of Al₂O₃ ceramics was reduced.The actual temperature of the sample during flash sintering was estimated by the blackbody radiation model,and the actual temperature of the sample was much higher than the furnace temperature.Nevertheless,the sintering time is extremely short,and the Joule heating effect alone cannot completely explain the rapid densification phenomenon.We believe that a high concentration of defects and electrochemical reactions may be produced in the sample during flash sintering,resulting in the densification phenomenon of rapid sintering.The Al₂O₃ platelet powder was prepared by the sol-gel method and the molten salt method,and the 3YSZ nano powder was prepared by the polymer network gel method.The Al₂O₃platelet powder and the 3YSZ nano-powder were mixed,and the 3YSZ/Al₂O₃ platelet composite ceramic green body was obtained by dry pressing technology.Applying a DC electric field of 300～800 V/cm and a limiting current of 80～290 m A to the green body.The flash behavior was studied.The results show that when the furnace temperature and electric field reach a certain threshold,the composite ceramic sample flash sintering occurs.Flash temperature decreases with increasing electric field strength;the power dissipation of the power supply is about 20 m W/mm³ when the sample flashing;the grain size increases with the increase of the limiting current.Compared with the traditional sintering method,the flash sintering technology can complete the sintering densification in a short time.At the same time,the prepared grain size is finer and has good mechanical propertiesBy increasing the proportion of Al₂O₃ platelet,the flash sintering behavior of different ratios 3YSZ/Al₂O₃ platelet composite ceramics was studied.The results of the study show that with the increase of the content of Al₂O₃ platelet,the furnace temperature of the composite ceramics sintering and the sample average grain size increase;the steady-state power dissipation of samples with different compound ratios increases slightly as the compound ratio increases.In addition,we found that when the content of Al₂O₃ platelet is large,uneven sintering occurs in the sample.