engleski

Influence of aging in an alkaline medium on the microstructural properties of α -FeOOH

The influence of the aging in a highly alkaline medium at 160 °C on the microstructural properties of α -FeOOH was monitored by XRD, 57Fe Mössbauer and FT-IR spectroscopies and FE-SEM. In the synthesis of acicular and monodisperse α -FeOOH particles, tetramethylammonium hydroxide was used as a precipitating agent. The crystal growth of α -FeOOH by the mechanism of lateral arraying was observed with prolonged aging time. Smaller α -FeOOH particles were dissolving with time, thus providing ions for the additional growth of α -FeOOH particles and improvement of their crystal shape. The XRD analysis confirmed that the growth of α -FeOOH crystallites perpendicularly to the crystallographic c-axis was favoured. The Mössbauer spectrum of α -FeOOH showed a distribution of the hyperfine magnetic field (HMF) which gradually narrowed with a longer aging time. The average value of the HMF distribution was shifted from 35.3 to 37.1 T between 2 and 168 h of aging. Characteristic IR bands of α -FeOOH were sensitive to the microstructural changes of α -FeOOH particles during their aging in the suspension in a highly alkaline medium at 160 °C.

crystal morphology ; hydrothermal crystal growth ; goethite

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