Research On In-situ Mullite Whisker Reinforced Sanitary Ceramic Body

In this paper,based on the formula of traditional sanitary ceramic body,high-silicon raw materials such as β-quartz and Ganzhou sand,and high-aluminum raw materials such as andalusite and bauxite were introduced,and high-strength sanitary ceramics body were prepared by using talc and calcite as fluxes.The effects of formula composition,particle size and firing system on the properties of sanitary ceramics were systematically studied by means of XRD,DTA-TG,XRD,FE-SEM,SEM-EDS and TEM.The effects of the morphology and distribution of in-situ mullite whiskers on the flexural strength of sanitary ceramics were preliminarily explored.The samples with flexural strength up to132.1 MPa were successfully prepared,which laid a foundation for the application of thin sanitary ceramics.Firstly,the effects of the type and amount of high silicon raw materials on the phase composition,microstructure and properties of sanitary ceramics were studied.The research results show that the introduction of β-quartz has the greatest increase in the flexural strength of the sample.When the amount of β-quartz is 10.0 wt.%,sintered at1200 ℃,and kept for 2 h,the flexural strength of the sample increases from 58.5 MPa to75.6 MPa,from the XRD pattern and FE-SEM photos,it can be seen that the intensity of the mullite diffraction peak of the best sample increases,and the number of mullite whiskers generated in-situ increases,so the flexural strength of the sanitary ceramic body is effectively improved.In order to further improve the flexural strength of the sanitary ceramic body,on the basis of the high silicon formula,spodumene was used as a flux,and the effects of the type and dosage of high alumina raw materials on the phase composition,microstructure and properties of the sanitary ceramic body were studied.The research results show that when the amount of andalusite is 18 wt.%,sintered at 1200 ℃ and kept for 2 h,the flexural strength of the prepared sample is as high as 111.3 MPa.The content of mullite crystals was increased from 10% to 11.7%,the distribution of mullite whiskers was more uniform,and the aspect ratio was higher,so the flexural strength of the sample was greatly improved.Due to the high price of spodumene and the limited output,other fluxes were used to replace spodumene.The research results show that when the amount of talc is 2 wt.%,sintered at 1200 ℃ and kept for 2 h,the flexural strength of the prepared sample is as high as 119.3 MPa,which is higher than that of the optimal sample added with spodumene（111.3 MPa）.It can be seen from the SEM-EDS and FE-SEM photos that the mullite whiskers in the sample are fully developed and evenly distributed in the green body,and some whiskers are interwoven into a network,which effectively improves the sample’s Flexural strength.Finally,on the basis of the optimal formula,the influence of process factors such as particle size,sintering temperature and holding time on the phase composition,microstructure and properties of sanitary ceramics was studied.The research results show that the flexural strength of the samples increased from 119.3 MPa to 132.1 MPa when the ball milling time was 3 h（D50=6.19 μm,D90=33.1 μm）,and the samples were fired at 1210 ℃ for 2 h.From the XRD pattern,SEM-EDS and FE-SEM photos,it can be seen that the content of mullite crystal phase of the best sample is increased to 13.2%,the whiskers are more fully developed,distributed more uniformly,and interwoven more closely,so the flexural strength of the best sample is greatly increased.It can be seen from the TEM photos that the mullite whiskers in the sample are of single crystal structure,with relatively complete development and preferential growth along the [001]direction.