IRON(III) OXIDES FORMED DURING THERMAL CONVERSION OF RHOMBOHEDRAL IRON(III) SULFATE
IRON(III) OXIDES FORMED DURING THERMAL CONVERSION OF RHOMBOHEDRAL IRON(III) SULFATE
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菱形硫酸铁 (III) 热转化过程中形成的氧化铁 (III)
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
P. Bezdička
中科院分区：
文献类型：
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作者：
R. Zbořil;M. Mashlan;L. Machala;P. Bezdička
菱面体硫酸铁（III）在空气中的热分解机制主要取决于SO 3的扩散条件（温度、粉末层厚度、粒度）。在600 °C下使用57 Fe穆斯堡尔谱和XRD研究了粒度对反应机理的影响。结果表明，固相转化产物为刚玉型α-Fe 2 O3、方铁锰矿型β-Fe 2 O3和斜方晶系e-Fe 2 O3。各个多晶型物的相对含量（x-Fe_2 O_3/xFe_2O_3）的时间依赖性是用于监测反应过程中它们的形成和热转化的机制的合适手段。从相应的光谱区域获得的定量穆斯堡尔谱数据表明，不同的转换发生在硫酸盐颗粒的表面层和本体。从硫酸盐颗粒的表面层松散SO 3后形成的β-Fe 2 O3颗粒在600 °C下相对稳定，如由非常缓慢的结构变化到赤铁矿所证明的。复杂的e-Fe_2 O_3结构的形成可能与SO_3从硫酸盐颗粒中缓慢扩散有关。与β-Fe_2O_3相比，e-Fe_2 O_3的热稳定性较低，因此其向赤铁矿的等化学转化更快。
The mechanism of thermal decomposition of rhombohedral iron(III) sulfate in air depends significantly on the conditions for diffusion of SO3 (temperature, thickness of the powdered layer, particle size). The influence of particle size on the reaction mechanism was studied at 600 °C using 57Fe Mossbauer spectroscopy and XRD. Corundum-type α-Fe2O3, bixbyite-type β-Fe2O3, and orthorhombic e-Fe2O3 were identified as solid conversion products. Time dependence of the relative contents of individual polymorphs (x-Fe2O3/ΣFe2O3) is a suitable means for monitoring the mechanism of their formation and thermal transformation during the reaction process. The quantitative Mossbauer data obtained from the corresponding spectral areas demonstrate that different transformations occur in the surface layer and in the bulk of sulfate particles. Particles of β-Fe2O3 formed after loosening of SO3 from the surface layer of sulfate particles are relatively stable at 600 °C as documented by the very slow structural change to hematite. The formation of complicated e-Fe2O3 structure is probably related with the slow diffusion of SO3 from the bulk of sulfate particles. The isochemical transformation of e-Fe2O3 to hematite occurs more quickly due to its lower thermal stability in comparison with β-Fe2O3.