Synthesis Methods Of Hercynite

With the development of NSP technology, there is a higher demand forcement kiln refractory, the sintering zone has a more strict demand for refractorymaterials due to its severest working condition, especially. Magnesite chromebrick is the traditional refractory material for sintering zone of cement rotarykiln. But Cr3+in the brick will be oxidated to poisonous Cr6+which can pollutethe environment and water source and is harmful to people and animals when itis used. Magnesium hercynite brick has a good coating adherence and highresistance against corrosion and abrasion, therefore it is the substitute ofmagnesite chrome brick and an ideal refractory material for cement rotary kiln.Hercynite is an indispensable and important component for magnesiumhercynite brick, and it needs to be synthesized because of the rarely occurring ofnatural hercynite in the earth. So the synthesis of hercynite is essential for thepreparation of magnesium herynite brick.In this paper hercynite was synthesized by sintering reaction and molten salt methods, using Al2O3/Fe2O3powder and ferric bauxite as raw materials,respectively. Graphite powder is used in sintering reaction, while graphitepowder and glucose are used in molten salt method as reducing agent,respectively. And the phase composition and microstructure of sample werecharactised by X-ray diffraction (XRD), scanning electron microscope (SEM)and metallographic microscope. The influence of the sintering temperature,atmosphere, addition and types of reducing agent on the sintering product wasstudied. And the results are as follows.(1)Hercynite was synthetised by sintering reaction over1450℃in N2atmosphere, using Al2O3/Fe2O3powder as raw materials, graphite powder asreducing agent. And the crystallinity of synthetic hercynite gets better with theincreasing of the sintering temperature.(2)To synthesize hercynite by molten salt method, using Al2O3/Fe2O3powder as raw materials, graphite powder as reducing agent, the optimalcondition is1100℃under air atmosphere; When using glucose as reducingagent, the optimal condition is that the sintering temperature is1000℃, theamount of NaCl is m(raw material):m(NaCl)=1:1and the reducing agent amountis13.5%.(3)By molten salt method, well crystallized hercynite can be synthetised ata temperate condition, and the sintering temperature can be decreased to1000℃.And glucose is better than graphite as reducing agent.(4)Using ferric bauxite as raw material, graphite powder as reducing agent, hercynite can be synthetised by sintering reaction at1550℃in N2atmosphere.