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

• Published in: Journal of crystal growth Vol. 310; no. 2; pp. 513 - 520
• Main Authors: Krehula, S., Musić, S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.01.2008; Elsevier
• Subjects: A1. Crystal morphology; A2. Hydrothermal crystal growth; B1. Goethite; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from solutions; Materials science; Methods of crystal growth; physics of crystal growth; Physics; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; 81.05.Je; 82.80.Ej; 82.80.Gk; B1. Goethite; A1. Crystal morphology; 81.10.Dn; A2. Hydrothermal crystal growth; Crystal growth; 81.05.Je; 81.10.Dn; 82.80.Ej; 82.80.Gk; Scanning electron microscopy; A1. Crystal morphology; A2. Hydrothermal crystal growth; B1. Goethite; Fourier transform spectroscopy; Thermal ageing; XRD; Hydrothermal growth; Crystallites; Iron hydroxide; Iron compounds; Growth mechanism; Microstructure; Crystal morphology; Goethite
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2007.10.072

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 Fe ( OH ) 4 - 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.