Teaspoon An Nguyen - Academia.edu (original) (raw)
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ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development
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Papers by Teaspoon An Nguyen
We report the physical properties of a-Fe 2 O 3 (hematite), synthesized by dry-heating (350-1,000... more We report the physical properties of a-Fe 2 O 3 (hematite), synthesized by dry-heating (350-1,000°C) of a new, poorly ordered iron oxyhydroxide precursor compound that we name carbonated 2-line ferrihydrite. This precursor was characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, electron microscopy, and thermogravimetric analysis, whereas the a-Fe 2 O 3 was studied with X-ray diffraction, scanning and transmission electron microscopy, and magnetic techniques. a-Fe 2 O 3 synthesized at 350°C consisted of single-nanocrystal particles (length 9 width 20 ± 6 nm (L) 9 15 ± 4 nm (W)), which at room temperature exhibited very narrow hysteresis loops of low coercivities (\300 Oe). However, a-Fe 2 O 3 synthesized at higher temperatures (1,000°C) was composed of larger nanocrystalline particle aggregates (352 ± 109 nm (L) 9 277 ± 103 nm (W)) that also showed wide-open hysteresis loops of high magnetic coercivities (*5 kOe). We suggest that these synthesis-temperature-dependent coercivity values are a consequence of the subparticle structure induced by the different particle and crystallite size growth rates at increasing annealing temperature.
We report the physical properties of a-Fe 2 O 3 (hematite), synthesized by dry-heating (350-1,000... more We report the physical properties of a-Fe 2 O 3 (hematite), synthesized by dry-heating (350-1,000°C) of a new, poorly ordered iron oxyhydroxide precursor compound that we name carbonated 2-line ferrihydrite. This precursor was characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, electron microscopy, and thermogravimetric analysis, whereas the a-Fe 2 O 3 was studied with X-ray diffraction, scanning and transmission electron microscopy, and magnetic techniques. a-Fe 2 O 3 synthesized at 350°C consisted of single-nanocrystal particles (length 9 width 20 ± 6 nm (L) 9 15 ± 4 nm (W)), which at room temperature exhibited very narrow hysteresis loops of low coercivities (\300 Oe). However, a-Fe 2 O 3 synthesized at higher temperatures (1,000°C) was composed of larger nanocrystalline particle aggregates (352 ± 109 nm (L) 9 277 ± 103 nm (W)) that also showed wide-open hysteresis loops of high magnetic coercivities (*5 kOe). We suggest that these synthesis-temperature-dependent coercivity values are a consequence of the subparticle structure induced by the different particle and crystallite size growth rates at increasing annealing temperature.