(清華大學(xué) 核能與新能源技術(shù)研究院， 北京 100084)
摘 要: 采用溶膠-凝膠法制備了具有高熱穩(wěn)定性的γ-Fe2O3-SiO2復(fù)合材料， 并在其表面進(jìn)行SiO2包覆， 獲得了納米尺寸磁核的單分散球形SiO2/(γ-Fe2O3-SiO2)顆粒。 X射線衍射分析、 熱重差熱分析、 掃描電鏡、 透射電鏡以及振動樣品磁強(qiáng)計(jì)等實(shí)驗(yàn)結(jié)果說明： Fe2O3-SiO2復(fù)合物經(jīng)過700 ℃以上溫度煅燒30 min后才出現(xiàn)γ-Fe2O3晶相， 更高溫度或者更長的煅燒時(shí)間將導(dǎo)致γ-Fe2O3向α-Fe2O3的轉(zhuǎn)變； 經(jīng)SiO2包覆后得到的SiO2/(γ-Fe2O3-SiO2)為粒徑均勻的單分散球形顆粒， 顆粒尺寸在150~200 nm左右， 內(nèi)部核心為γ-Fe2O3顆粒， 外層則被嚴(yán)密的SiO2包裹。 通過將純Fe3O4粉外層直接包覆SiO2做對比實(shí)驗(yàn)表明， SiO2/(γ-Fe2O3-SiO2)具有更加優(yōu)異的磁性能， 是一種優(yōu)良的催化劑磁性載體。
關(guān)鍵字: γ-Fe2O3； 磁性催化劑載體； 熱穩(wěn)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
