添加La2O3对菱镁矿制备烧结镁砂性能的影响

Effect of La2O3 addition on properties of sintered magnesia prepared from magnesite

以低品位菱镁矿为原料,向其添加0~3%(w)的La2O3,于1 600℃下保温3 h煅烧,测定了烧后试样的体积密度、显气孔率、常温抗折强度等,并分析了烧后试样的物相组成和显微结构。结果表明:在菱镁矿中添加La2O3,生成的硅酸钙镧矿物相呈树枝状交错分布在MgO晶界处,枝晶增韧,增大了抗折强度。加入2%(w)La2O3时试样的力学性能最佳,烧结试样的抗折强度达到103.1 MPa。La2O3可以促进方镁石晶粒的生长,当La2O3加入量超过2%(w)时,方镁石晶粒尺寸的增长有减缓的趋势,这可能是由于大量的第二相存在于晶界处,抑制了方镁石晶粒的生长,从而抵消了部分La2O3对晶粒生长的促进作用。

The specimens were prepared using low grade magnesite as the raw material,added with 0-3 mass%La 2O 3,calcined at 1600℃for 3 h.The bulk density,the apparent porosity and the cold modulus of rupture of the specimens were measured.The composition and microstructure of the calcined specimens were analyzed.The results show that adding La 2O 3 into magnesite can form lanthanum calcium silicate,which is dendritic and interlaces at MgO grain boundaries,and the dendrite toughens the specimen and increases the modulus of rupture.When 2 mass%La 2O 3 is added,the mechanical properties of the specimen are the best,and the modulus of rupture of the specimen reaches 103.1 MPa.La 2O 3 can promote the growth of periclase grains.When the La 2O 3 addition exceeds 2 mass%,the growth of periclase grains slows down,which may be due to the large number of second phases presenting at grain boundaries,inhibiting the growth of periclase grains,thus partly offsetting,the promotion of grain growth by La 2O 3.