Solid state formation of calcium ferrites from thermal decomposition of mixtures Ca3(C6H5O7)2•4H2O-Fe2(C2O4)3•6H2O -: The role of mechanical activation on the mechanism of the thermal decomposition and the temperature of the ferrites formation

被引:5
作者
Berbenni, V. [1 ]
Marini, A. [1 ]
Bruni, G. [1 ]
Milanese, C. [1 ]
机构
[1] Univ Pavia, CSGI, Dipartimento Chim Fis, I-27100 Pavia, Italy
关键词
calcium ferrites; CaFe(2)O(4); C(2)Fe(2)O(5); thermogravimetry; thermal decomposition; solid state reaction mechanism;
D O I
10.1016/j.jaap.2008.04.002
中图分类号
O65 [分析化学];
学科分类号
070302 ; 081704 ;
摘要
The present paper reports a novel synthetic procedure of both calcium ferrites (CaFe(2)O(4) and Ca(2)Fe(2)O(5)) starting from mechanically activated mixtures of organic precursors (calcium citrate tetrahydrate and iron(III) oxalate hexahydrate). With the help of TG analysis the different stages of the mass loss process taking place could be individuated and their chemical nature assessed. The DSC signal, recorded on the same sample, revealed that much higher enthalpies are released from the milled mixtures than those expected on the basis of the reactions taking place. From such enthalpic excess the enthalpies of formation of Ca(2)Fe(2)O(5) and CaFe(2)O(4) have been obtained. X-ray powder diffraction (XRPD) indicated that the mechanically activated mixtures yield, after an 18 h-annealing at 800 degrees C (or 750 degrees C, Ca(2)Fe(2)O(5) (or CaFe(2)O(4)). On the contrary, the same compounds could be obtained, when starting from physical mixtures, only by performing thermal treatments (for t > 18 h) at 1180 degrees C (CaFe(2)O(5)) or 1100 degrees C (CaFe(2)O(4)). (C) 2008 Published by Elsevier B.V
引用
收藏
页码:255 / 259
页数:5
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