Chappuis Thierry, Bobowska Izabela, Hengsberger Stefan, Vanoli Ennio, Dietsch Hervé
Ecole d'Ingénieurs et d'Architectes de Fribourg, Boulevard de Pérolles 80, CP 32 CH-1705 Fribourg, Switzerland.
Chimia (Aarau). 2011;65(12):979-81. doi: 10.2533/chimia.2011.979.
We report on the transformation via hydrogen reduction of spindle-type hematite nanoparticles into hematite/magnetite hybrid iron oxide particles. The transformation process consists of the reduction of nanoparticles powder in an autoclave using hydrogen gas at a fixed pressure of 11 bars. Both temperature and time of reduction are varied between 300 °C to 360 °C and 0 to 45 h. X-Ray powder diffraction data on the obtained powder and corresponding Rietveld refinement allow the amount of reduced hematite to be determined as a function of these two parameters. Kinetics parameters are measured and an estimation of the activation energy is obtained through linearization of the Arrhenius equation. While reduction is dramatically accelerated at higher temperature, the morphology of the nanoparticles only remain qualitatively unchanged at 300 °C as seen from transmission electron microscopy images. The mechanisms underlying morphology changes are still under study and seem to be closely related to reactor pressure.
我们报道了通过氢气还原将纺锤形赤铁矿纳米颗粒转变为赤铁矿/磁铁矿混合铁氧化物颗粒的过程。该转变过程包括在高压釜中使用氢气在11巴的固定压力下还原纳米颗粒粉末。还原的温度和时间在300℃至360℃以及0至45小时之间变化。对所得粉末进行的X射线粉末衍射数据及相应的Rietveld精修可确定还原赤铁矿的量与这两个参数的函数关系。测量动力学参数，并通过对Arrhenius方程进行线性化来获得活化能的估计值。虽然在较高温度下还原显著加速，但从透射电子显微镜图像可以看出，纳米颗粒的形态仅在300℃时定性保持不变。形态变化背后的机制仍在研究中，似乎与反应器压力密切相关。
