(清华大学 核能与新能源技术研究院， 北京 100084)
摘 要: 采用溶胶-凝胶法制备了具有高热稳定性的γ-Fe2O3-SiO2复合材料， 并在其表面进行SiO2包覆， 获得了纳米尺寸磁核的单分散球形SiO2/(γ-Fe2O3-SiO2)颗粒。 X射线衍射分析、 热重差热分析、 扫描电镜、 透射电镜以及振动样品磁强计等实验结果说明： Fe2O3-SiO2复合物经过700 ℃以上温度煅烧30 min后才出现γ-Fe2O3晶相， 更高温度或者更长的煅烧时间将导致γ-Fe2O3向α-Fe2O3的转变； 经SiO2包覆后得到的SiO2/(γ-Fe2O3-SiO2)为粒径均匀的单分散球形颗粒， 颗粒尺寸在150~200 nm左右， 内部核心为γ-Fe2O3颗粒， 外层则被严密的SiO2包裹。 通过将纯Fe3O4粉外层直接包覆SiO2做对比实验表明， SiO2/(γ-Fe2O3-SiO2)具有更加优异的磁性能， 是一种优良的催化剂磁性载体。
关键字: γ-Fe2O3； 磁性催化剂载体； 热稳定性； 包覆
（ Institute of Nuclear and New Energy Technology,
Tsinghua University, Beijing 100084, China）
Abstract: Fe2O3-SiO2 composite was prepared with sol-gel method. SiO2/(γ-Fe2O3-SiO2) magnetic catalyst carriers were obtained by coating composite with silica. These obtained samples were characterized by XRD, TG-DTA, TEM, SEM and VSM. The effects of processing temperature, time and initial dosage of iron nitrate on the properties of Fe2O3-SiO2 were studied. The results show that, after calcined at 700 ℃ for 30 min, the composite oxide containing γ-Fe2O3 phase is secured. While further increase of the processing temperature (＞800 ℃) or time results in the formation of α-Fe2O3 phase. SEM and TEM analyses show that the SiO2/(γ-Fe2O3-SiO2) sample is of nano-sized, monodisperse spherical particles with size of 150-200 nm, which are well coated by amorphous SiO2 layer. The VSM data exhibit that SiO2/(γ-Fe2O3-SiO2) has much better magnetic properties than SiO2/Fe3O4. Such nano-composites are very promising in application as magnetic catalyst carriers and sorbent carriers.
Key words: γ-Fe2O3; magnetic catalyst carrier; heat-resistance; coating
