Structural changes of maghemite during thermal conversions of iron minerals - AFM and Mössbauer spectroscopy study

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61989592%3A15310%2F01%3A00001392" target="_blank" >RIV/61989592:15310/01:00001392 - isvavai.cz</a>

Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

Structural changes of maghemite during thermal conversions of iron minerals - AFM and Mössbauer spectroscopy study

Popis výsledku v původním jazyce

Ultrafine superparamagnetic particles of maghemite with the size of 4-10 nm were prepared by conversion of almandine garnet at 800 °C in combination with the postprocessing sedimentation separation (sample I). Larger ferrimagnetic crystallites of maghemite (>30 nm) were synthesized by air oxidation of magnetite at 250 °C (sample II). The heating of sample II resulted in the direct formation of hematite while the orthorhombic e-Fe2O3 was observed during the thermal treatment of sample I at 850 °C. The RTMössbauer spectrum of e-Fe2O3 is complex and can be approximated by four sextets corresponding to the non-equivalent Fe3+ positions in the structure. Two of the octahedral sites are characterized by close Hhyp values (~ 46 T), affecting their overlapping. The third octahedral site exhibits a smaller Hhyp (~ 40 T). The unusually low Hhyp value (~ 26 T) corresponds to the tetrahedral position. AFM analysis of the mixture of polymorphs allowed to distinguish the elongated particles of e-Fe

Název v anglickém jazyce

Structural changes of maghemite during thermal conversions of iron minerals - AFM and Mössbauer spectroscopy study

Popis výsledku anglicky

Ultrafine superparamagnetic particles of maghemite with the size of 4-10 nm were prepared by conversion of almandine garnet at 800 °C in combination with the postprocessing sedimentation separation (sample I). Larger ferrimagnetic crystallites of maghemite (>30 nm) were synthesized by air oxidation of magnetite at 250 °C (sample II). The heating of sample II resulted in the direct formation of hematite while the orthorhombic e-Fe2O3 was observed during the thermal treatment of sample I at 850 °C. The RTMössbauer spectrum of e-Fe2O3 is complex and can be approximated by four sextets corresponding to the non-equivalent Fe3+ positions in the structure. Two of the octahedral sites are characterized by close Hhyp values (~ 46 T), affecting their overlapping. The third octahedral site exhibits a smaller Hhyp (~ 40 T). The unusually low Hhyp value (~ 26 T) corresponds to the tetrahedral position. AFM analysis of the mixture of polymorphs allowed to distinguish the elongated particles of e-Fe

Druh

J_x - Nezařazeno - Článek v odborném periodiku (Jimp, Jsc a Jost)

CEP obor

CF - Fyzikální chemie a teoretická chemie

OECD FORD obor

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Projekt

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Návaznosti

Z - Vyzkumny zamer (s odkazem do CEZ)

Rok uplatnění

2001

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Bulletin de liaison de la Sociéte Francaise de Minéralogie et de Cristallographie

ISSN

0999-5870

e-ISSN

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Svazek periodika

13

Číslo periodika v rámci svazku

N

Stát vydavatele periodika

FR - Francouzská republika

Počet stran výsledku

2

Strana od-do

115-116

Kód UT WoS článku

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EID výsledku v databázi Scopus

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