添加MgB_2对镁碳耐火材料抗氧化性能的影响

Effect of Adding MgB_2 on the Oxidation Resistance of MgO-C Refractories

以MgB2作为抗氧化剂应用于镁碳耐火材料,分别在埋碳和空气气氛下煅烧,利用热重分析(TG-DSC)研究了MgB2在空气气氛下的反应行为,用X射线衍射分析(XRD)研究了埋碳条件各温度下的物相组成,用扫描电子显微镜(SEM)结合能谱分析仪(EDX)观察了试样的显微组织结构,并与Al、Si、B4C、Al+B4C、Al+MgB2对比评价了MgB2的抗氧化性能。结果表明:MgB2在温度高于1000℃与CO反应,生成MgO、B2O3和C,MgO与B2O3进一步反应生成Mg3B2O6;当温度高于1340℃,Mg3B2O6熔化成为液相,填充在MgO骨料与基质周围,使得镁碳耐火材料结构致密,对抗氧化起到重要作用;B2O3(l)蒸发与MgO反应生成Mg3B2O6在镁碳耐火材料表面形成致密层;MgB2抗氧化效果次于B4C,优于Al粉,Si粉,镁碳耐火材料中MgB2的合理添加量约为3%;实验中还发现添加Al+10%MgB2的镁碳耐火材料取得了较好的抗氧化效果。

MgB2 was used as an antioxidant in MgO-C refractories. The samples were heated in the air or under the condition of reduction atmosphere . The reaction behavior of MgB2 in the air was investigated by thermogravimetric analysis（TG-DSC）. The phase constituent at different temperature under the condition of reduction atmosphere was studied by X-ray diffraction （XRD）. The microstructure of the samples was observed using a scanning electron miscroscope（SEM） with energy dispersive X-ray spectroscopy （EDX）. The oxidation resistance of MgB2 was evaluated in contrast with Al, Si, B4C, Al ＋ B4C and Al ＋ MgB2. The result shows that MgB2 was found to react with CO gas, to form MgO,B2O3 ,and C ,when the sample was heated above 1000℃. Then B2O3 reacts with MgO and results in ng3B2O6. When the temperature is above 1340℃ , Mg3B2O6 melts and fills in the gap between MgO aggregates and matrix, which makes the MgO-C refractories more denser and plays an important role in suppression of carbon oxidation; Meanwhile, B2O3 （1） evaporates and reacts with MgO to form the dense layer of Mg3B206 on the surface of MgO-C refractories. The oxidation resistance of MgB2 is better than Al, Si, worse than B4C, and the approrite additive amount of MgB2 is about 3%. It is obtained that the addition of Al ＋ 10% MgB2 has got a good oxidation resistance.