以铁铝尖晶石和镁砂为原料,采用烧结法制备了氧化镁铁铝尖晶石耐火材料.检测了各烧后试样的体积密度、显气孔率和常温耐压强度,利用应力应变法检测了烧后试样的弹性模量,利用X射线衍射(XRD)检测了烧后试样的物相组成,采用扫描电子显微镜(SEM)观察和分析了烧后试样的显微结构.研究结果表明: 1600 ℃时各试样体积密度最大,显气孔率最小,试样达到了烧结;镁砖中加入铁铝尖晶石会引起材料常温强度降低,铁铝尖晶石加入量在3%～4%为宜;铁铝尖晶石以颗粒形式加入的试样的弹性模量比以细粉形式加入的试样要大,所以铁铝尖晶石以颗粒形式加入的试样的抗热震性相对较好;热力学计算表明:当加热温度高于182 ℃时, MgO与FeAl_2O_4开始反应生成MgAl_2O_4;从显微结构照片也可以看出, MgO与FeAl_2O_4中的FeO发生互扩散,FeO扩散进镁砂颗粒中,MgO扩散进铁铝尖晶石内部,与Al_2O_3反应生成MgAl_2O_4,在镁砂颗粒周围形成MgAl_2O_4环,并伴有微裂纹产生.
The magnesia-hercynite refractories were prepared with magnesia and hercynite by sintering process. The bulk density, apparent porosity and cold crushing strength were measured. The elastic modulus of samples was measured by the method of stress and strain. The phase constituents of specimens was analyzed by X-ray diffraction (XRD), and the microstructure was observed with scanning electron microscopy (SEM).The experimental results show that the appropriate sintering temperature for samples is 1600 ℃ with the highest bulk density and the lowest apparent porosity . The cold crushing strength of samples decreases with the adding of the content of hercynite. The optimum content of hercynite is 3%-4%. The specimens with addition of hercynite particles have higher elastic modulus, so the specimens with addition of hercynite particles have better thermal shock resistance than the specimens with hercynite powder. Thermodynamic calculation show that: the magnesia reacts with hercynite resulting in magnesia-alumina spinel at temperature higher than 182 ℃. The microstructure photos also show that iron protoxide in hercynite can diffuse into magnesia particle and reacts with magnesium oxide, and forms magnesia-alumina spinel ring around magnesia when magnesia-hercynite refractories are sintered at high temperature. The reaction leads to produce microcrack between hercynite and magnesia particle.
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