Goran Šmit

57Fe Mössbauer, FT–IR and TEM investigations of Fe-oxide powders obtained from concentrated FeCl3 solutions

Abstract The chemical and microstructural properties of oxide phases precipitated from concentrated FeCl 3 solutions were investigated using 57 Fe Mossbauer spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. The initial pH of the precipitation system (acidic or highly alkaline medium) determined the mechanism of phase transformations. In a highly alkaline medium two competitive mechanisms exist: (a) the nucleation and crystal growth of α-Fe 2 O 3 inside the condensed Fe(OH) 3 gel and (b) the crystallization of α-FeOOH which transforms to α-Fe 2 O 3 by a dissolution/reprecipitation mechanism. In the present work, spectroscopic results indicated that before α-FeOOH was detectable (or formed) at 60°C, superparamagnetic and/or amorphous Fe-oxide particles (probably α-Fe 2 O 3 ) were formed. Once α-FeOOH was formed, its fraction in the precipitate increased rapidly. In an acidic medium (partially neutralized FeCl 3 solution) α-Fe 2 O 3 , was formed from β-FeOOH by a dissolution/reprecipitation mechanism. The complete interpretations of 57 Fe Mossbauer and FT–IR spectra were given. TEM observation showed that the particle size and morphology of the oxide phases were very dependent on the experimental parameters.

Radon in schools and dwellings of Osijek

Indoor radon concentrations were measured in 10 821 pupils primary schools of Osijek by means of the Radhome silicon detector. The values ranged from 15 to 300 Bq/m3 with the arithmetic and geometric means of 93.4 and 70.6 Bq/m3, respectively. Ten years continuous radon measurements performed with the LR-115 nuclear track detector in three houses of different construction and town area gave means of 27, 96 and 23 Bq/m3; the indoor Rn concentration for a heating period was a factor of 1.5 higher than for the warm season. The average effective dose equivalent for the primary school pupils was 2.8 mSv/y (with occupancy factors of 0.6, 0.2 and 0.2 for home, school and outdoors, respectively). For citizens of Osijek it was 1.7 mSv/y.