| In this paper,high-purity aluminum oxide powder was used as raw material to prepare ceramic strip samples by dry pressing.Alumina ceramics were prepared by traditional sintering process and two-step sintering process under normal pressure sintering.The sintered ceramic samples were measured by linear shrinkage,volume density,porosity and flexural strength.SEM was used to observe the micromorphology of the cross section and the grain size was determined by line interception method.The influences of heating rate,sintering temperature and holding time on material properties under traditional sintering process were studied.The influences of T1 and T2 and holding time on the flexural strength of alumina ceramics in two-step sintering were studied.The results show that: the slower the heating rate is,the more energy is received in the sintering system,the denser the material is,and the higher the relative volume density is.With the increase of sintering temperature,the relative volume density also increases.The longer the holding time,the higher the relative volume density.Twostep sintering has an obvious effect on improving the flexural strength of alumina ceramics: T1 makes the relative volume density of alumina ceramics exceed 92%,but does not significantly improve the flexural strength of materials.With the increase of T2 temperature,the greater the driving force of grain boundary diffusion occurs in the body of the billet,the longer the insulation time,the higher the densification degree of the material,and the better the flexural performance of the material.In the traditional sintering process,raw material A was prepared at 1600℃,the heating rate was 2℃/min,and the temperature was kept warm for 3h.The maximum flexural strength of alumina ceramics was 463.95 MPa.Two-step sintering was conducted at T1 at 1540℃ and T2 at 1520℃,and the maximum flexural strength obtained after 25 h of thermal insulation was 478.9 MPa.Two-step sintering could improve the flexural strength of materials. |
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