分别以轻烧菱镁矿粉和分析纯MgO粉为镁源,以工业α-Al2O3粉为铝源,按n(MgO)∶n(Al2O3)=1∶1的比例配料,经球磨混合、机压成型后,分别在1 550、1 600和1 650℃保温3h合成了两种不同镁源的镁铝尖晶石试样,对比检测了两种试样的致密度、强度、物相组成和显微结构的差异.结果表明:1)利用两种不同镁源合成试样的致密度和强度均随合成温度的升高而增大,在合成温度相同时,以轻烧菱镁矿为镁源的试样的致密度和强度较高.2)以轻烧菱镁矿为镁源、1 650℃合成的试样的主晶相为尖晶石,还有少量CA2和CaSiO3,其尖晶石晶体发育较好,八面体形态可辨；以分析纯MgO为镁源、1 650℃合成的试样中只有单相镁铝尖晶石,但尖晶石晶体发育较差,只有少数形成较完整的八面体形态.3)轻烧菱镁矿中SiO2、CaO杂质的存在有利于试样中形成CaO-Al2O3-MgO-SiO2系低熔点相,促进镁铝尖晶石晶体的发育及试样的烧结.%Two magnesium aluminate spinel specimens were prepared using light-burnt magnesite powder and analytically pure MgO powder as magnesia sources,respectively,industrial α-AI203 powder as alumina source,batching with n(MgO): n(AI2O3) =1:1,ball milling,shaping,then firing at 1 550 ℃,1 600 ℃ and 1 650 ℃ for 3 h,respectively. The densities,strengths,phase compositions and microstructures of the two specimens were compared. The results show that: (l)the densities and strengths of the two specimens increase with synthesis temperature rising;at the same synthesis temperature,the specimen using light-burned magnesite ass magnesia source has higher density and strength;(2) for the specimens synthesized at 1 650 ℃:using light-burnt magnesite as magnesia source,the phases are mainly spinel with a little CA2 and CaSiO3,and the spinel crystals grow well with octahedron morphology;using analytically pure MgO as magnesia source,the main phase is single-phase magnesium aluminate,only a few crystals form completely octahedron morphology; (3)the SiO2 and CaO in light-burnt magnesite are in favor of the formation of the low melting point phase of CaO-AI2O3-MgO-SiO2 system promoting the magnesium aluminate spinel crystals growth and specimen sintering.
展开▼
