Effect Of Mn⁴⁺ Addition On Structure And Properties Of Corundum-Mullite Ceramics

Combining with the experimental research on ceramic proppant at home and abroad,it is found that manganese ore powder can reduce sintering temperature and promote sintering,but manganese ore powder contains not only manganese ions with different valences,but also many impurity elements,of which Mn⁴⁺is the most abundant.In order to determine the mechanism of Mn⁴⁺in sintering process and guide the production of ceramic proppant according to the experimental results,this paper studied.The main contents of this paper are as follows:Firstly,using high purity alumina and silica as main raw materials and manganese dioxide as additive,the effects of Mn⁴⁺addition on the structure and properties of pure corundum and corundum-mullite composite ceramics were studied.The research is mainly focused on five aspects:phase composition,microstructure,bulk density,apparent porosity and flexural strength.The results show that the proper addition of manganese dioxide can promote the grain growth of corundum phase and improve its mechanical properties for corundum samples.The optimum addition of manganese dioxide is 6wt%,the apparent porosity was48%,the bulk density was 2.05 g/cm³,and the flexural strength was 16.44 MPa.For corundum-mullite samples,when the manganese dioxide content reaches6wt%,mullite phase begins to form,and the addition of manganese dioxide can promote the formation of mullite phase.With the formation of mullite phase,the flexural strength of materials has been greatly improved.When the additive amount of manganese dioxide is 10wt%,the maximum flexural strength of materials is 70.91 MPa.Secondly,using high purity alumina and silica as main raw materials,calcium carbonate and magnesium carbonate as additives,the effects of calcium carbonate and magnesium carbonate on the structure and properties of corundum and corundum-mullite composite ceramics were studied.The results show that alumina reacts with calcium carbonate and magnesium carbonate to form Ca Al₁₂O₁₉ during sintering.With the increase of additive amount,Ca Al₁₂O₁₉increases and corundum phase decreases,resulting in the decrease of density and mechanical properties of corundum samples,and the maximum flexural strength can only reach 8.75 MPa.For corundum-mullite samples,the addition of calcium carbonate and magnesium carbonate can promote the formation of mullite,but with the increase of the amount of calcium carbonate and magnesium carbonate,glass phase is formed during sintering process,which inhibits the formation of mullite phase.Glass phase fills the grain gap and makes the material dense.Thirdly,using high purity alumina and silica as main raw materials,manganese dioxide as main additive,calcium carbonate and magnesium carbonate as auxiliary additives,the effects of Mn⁴⁺addition amount on the structure and properties of corundum-mullite composite ceramics with the presence of glass phase were studied.Through the study of the structure and properties of the samples,it is found that when the sintering temperature is1350℃,with the increase of manganese dioxide content,the performance of the samples is improved most obviously.When the additive amount of manganese dioxide is 10wt%,the maximum flexural strength is 73.14 MPa.The formation and development of mullite phase are inhibited by the formation of glass phase,but glass phase can fill the pores between grains,make the bonding between grains occur,increase the density of materials,and enhance the mechanical properties.