Study On Synthesis Of Magnesium-iron-aluminum Composite Spinel Material By Sintering Method

At present,refractories for the burning zone of cement rotary kiln firing are made of mainly magnesium-iron-aluminum spinel brick.In the productive process of magnesium-iron-aluminum spinel bricks,the sources of iron are mainly hercynite.However,there is no pure hercynite in the nature.The iron oxide and alumina are used as raw materials synthesizing hercynite by fusing and sintering.No direct synthesis of magnesium-iron-aluminum composite spinel used ferric hydroxide as the source of iron has been reported.In this paper,the sources of magnesia were from fused magnesia,high-purity magnesia,light burned magnesia,fused magnesia aluminum spinel,ferric hydroxide and iron oxide were used as the sources of iron and the source of alumina was from activated alumina,buried graphite and added graphite were burned respectively to study the influence of buried graphite,added graphite,different sources of magnesium and different sources of iron on the synthesis of magnesium-iron-aluminum composite spinel raw materials and magnesium-iron-aluminum composite spinel brick was prepared from synthetic magnesium-iron-aluminum composite spinel.Ferric hydroxide used in this paper was factory waste,so it was more practical significance.The phase composition of the sample was characterized by X-ray diffractometer.The microstructures of the samples was analyzed by scanning electron microscopy.The mechanism of the formation of magnesium-iron-aluminum composite spinel is described by thermodynamics.The results show that the buried graphite samples that used fused magnesium,activated alumina and iron oxide as raw materials,magnesium oxide and alumina were respectively subjected to carbothermal reduction with graphite,generating magnesium vapor and aluminum vapor,the sample structure loose,not dense;the proportion of the magnesium-iron-aluminum composite spinel in the sample sintered with graphite was higher than that of the sample buried in the graphite,and the reduction atmosphere was determined to be made by adding graphite;Fused magnesia and iron oxide respectively as the source of magnesium and iron,there were more intragranular pores in the sample,the structure loose;the source of iron was from Ferric hydroxide,the size of the grain in the sample was different,there was a big difference in grain size,intergranular pores;The source of magnesium was from high-purity magnesia,the source of iron was from iron oxide,there were more pores in the sample and the structure was not dense;The grains in the samples with ferric hydroxide as the source of iron developed more mature grains with more complete grain boundaries than the grains with ferric oxide as the source of iron;Thethe source of magnesium was from light burned magnesium,the grains in the samples with ferric hydroxide as the source of iron were more mature than the specimens with ferric oxide as the source of iron,adding 20% light burned magnesium sample grain boundaries more complete,lattice defect at least,this method was the best synthesis of magnesium-iron-aluminum composite spinel program;magnesium-iron-aluminum composite spinel pre-synthesized with high purity magnesia as raw material,The room temperature compressive strength and bulk density of the synthesized magnesium-iron-aluminum composite spinel brick were larger than that of the magnesium-iron-aluminum composite spinel brick synthesized from fused fused aluminum spinel and high-purity magnesia,corrosion resistance was also superior to the magnesium-iron-aluminum composite spinel brick that used fused hercynite and high purity magnesia as raw materials.