Physics

Mechanism of phase transformations $\gamma$- and $\delta$-$\mathrm{FeOOH}$ during heat treatment in solutions $\mathrm{MeOH}$ ($\mathrm{Me}$–$\mathrm{Na}$, $\mathrm{K}$): model of crystal-forming complexes

V. Sh. Mirasov^a, R. R. Klescheva^b, V. A. German^b, D. G. Kleschev^a, Yu. I. Ryabkov<sup>c

a</sup> South Ural State University
^b Ltd. "Scientific research institute Pigmentary materials"
^c Institute of Chemistry, Komi Scientific Center of UB RAS

Abstract: Transformations of nanodispersed ferrum (III) oxy hydroxides of $\gamma$- and $\delta$-modifications at heat treatment in the open air (temperature interval $25$–$900^\circ$С) as well as at hydrothermal treatment ($175$–$220^\circ$С) in water and water solutions $\mathrm{MeOH}$ ($\mathrm{Me}$–$\mathrm{Na}$, $\mathrm{K}$) with concentration $1\leqslant \mathrm{C_{MeOH}}\leqslant 5$ mole/dm$^3$ are studied by methods of $\mathrm{X}$-ray phase analysis, raster and transmission electronic microscopy, thermogravimetry, masspectroscopy and $\mathrm{X}$-ray fluorescence analysis. Spheres of phases $\alpha$-$\mathrm{FeOOH}$ and $\alpha$-$\mathrm{Fe_2O_3}$ formation are specified. Possible structure of crystal-forming complexes formed in solutions and reactions running during their fusion in different atomically rough planes $\alpha$-$\mathrm{FeOOH}$ and $\alpha$-$\mathrm{Fe_2O_3}$ is considered. In terms of a model of crystal-forming complexes experimentally stated dependencies crystal habits as well as phase and disperse structure of formed products on parameters of hydrothermal treatment are explained.

Keywords: hydrothermal treatment, ferrum (III) oxy hydroxides, phase transformations, water solution $\mathrm{MeOH}$.

UDC: 538.9+661.872’02+669.017.3

Received: 08.07.2012