共沉淀法制备纳米镁铬尖晶石粉体

Synthesis of nano-sized chrome-magnesium spinel powders by coprecipitation method

镁铬尖晶石具有较高的熔点而被广泛应用于耐火材料中。而常规镁铬尖晶石粉体因烧结温度较高,铬蒸发而使得耐火材料的致密度难以提高。为改善镁铬耐火材料的烧结性能,进行了纳米镁铬尖晶石粉体的研究:以Cr(NO3)3,Mg(NO3)2,PEG-400和CO(NH2)2为原料,采用共沉淀法获得了铬酸镁纳米粉(nCr2O3∶nMgO=1∶1)的前驱体,经过超临界流体干燥(SCFD)制备出镁铬二元纳米气凝胶,经600℃煅烧后获得了纳米级立方相镁铬尖晶石粉体。经XRD,DSC-TG,BET和透射电镜分析,结果表明:前驱体纳米粉的比表面积为350～780m2/g,平均粒径为1～2nm,煅烧后的纳米粉的比表面积为36～65m2/g,平均粒径为5～10nm。

The chrome-magnesium spinel MgCr_2O_4 is widely used in refractories because of its high-melting point.But the common MgCr_2O_4 is difficult to be sintered to get high density refractories due to the evaporation of Cr at high sintering temperature.In order to improve the sintering performance of the refractories,the nanometer chrome-magnesium spinel powder is studied,in which the Cr(NO_3)_3,Mg(NO_3)_2,PEG(400) and CO(NH_2)_2 are as raw materials,the precursors of nano-size magnesium chromate powder(n_(Cr_2O_3)∶n_(MgO)=1∶1)are obtained by coprecipitation method,then the precursors are dried by supercritical flowing dry(SCFD) to get the aerogels,the nano-size chrome-magnesium spinel powders with cubic crystal phase are obtained after the above aerogels to be calcined at temperature of 600 ℃. Which is examined by XRD、DSC-TG,BET and TEM.The results show that the specific surface area and average size of the precursors are 350~780 m^2/g and 1~2 nm respectively.And 36~65 m^2/g and 5~10 nm respectively after sintered.