Influence of heat treatment on phase transformation of clay–iron oxide composite

Orolínová, Zuzana; Mockovčiaková, Annamária; Zeleňák, Vladimı́r; Myndyk, M.

doi:10.1016/j.jallcom.2011.08.023

Cited by 15 publications

(5 citation statements)

References 41 publications

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“…[49,50] The phase transition from maghemite to hematite is usually observed at temperatures in the range of 300-650°C, depending on duration of heating, size, and crystal face of the particles and the method of sample preparation. [49,51,52] In the present study maghemite was not detected in the samples by Raman spectroscopy or XRD. It might argue for the firing temperature exceeded 650°C.…”

Section: Discussioncontrasting

confidence: 57%

Raman spectroscopy for firing condition characterization: Case study of Karelian medieval pottery

Chazhengina

Summanen

Светов

2019

J Raman Spectroscopy

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Raman spectroscopy together with the scanning electron microscopy and X‐ray diffraction were applied to study the firing parameters (temperature and atmosphere) of medieval pottery from Karelian hill forts in the North‐Western Ladoga region (Russia). Because the evidences of pottery manufacture including firing facilities were not discovered during the excavations of medieval Karelian fortresses, the application of Raman spectroscopy combined with the other techniques appeared to be an effective approach to reconstruct the technology of ceramic production in medieval Karelia. Scanning electron microscopy ‐energy‐dispersive X‐ray spectroscopy and X‐ray diffraction analysis showed that the Karelian pottery refers to noncalcareous and low‐temperature fired ceramics. Using the thermometer based on the thermal evolution of Raman spectral parameters of the charcoal identified in the ceramic paste of some specimens, the firing temperature for those was estimated to be close to 800 °C. These data are in accordance with the more frequent occurrence of anatase rather than rutile in the studied ceramic sherds that also corresponds to low firing temperature. The presence of hematite suggests firing in oxidizing atmosphere, in rare case the detected magnetite indicated the incomplete oxidizing atmosphere. The reconstruction of Karelian pottery firing procedure based on the obtained data supposes that the firing was carried out in bonfires. The present study contributes to the deciphering the firing conditions for noncalcareous and low‐temperature burnt ceramics, for which no significant modifications of starting minerals during heating are usually observed.

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Section: Discussioncontrasting

confidence: 57%

Raman spectroscopy for firing condition characterization: Case study of Karelian medieval pottery

Chazhengina

Summanen

Светов

2019

J Raman Spectroscopy

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“…Figure (A) shows the XRD pattern of the pure GT, GT 4 hydrogel, and their magnetic nanohydrogels. In Figure (A), the magnetic nanohydrogels showed diffraction peaks at 2θ values of 30.00° (220), 35.40° (311), 48.04° (400), 57.25° (511), and 63.52° (440) . The peaks were identified with WinXPow software, and they coincided with the data of cubic magnetic (JCPDS card no.…”

Section: Resultsmentioning

confidence: 70%

5‐Fluorouracil encapsulated magnetic nanohydrogels for drug‐delivery applications

Jayaramudu

Raghavendra

Varaprasad³

et al. 2016

J of Applied Polymer Sci

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For the first time, green-tea (GT)-based magnetic nanohydrogels were developed for drug-delivery purposes. The hydrogel matrices were fabricated via the in situ polymerization of acrylamide with GT molecules. Magnetic nanoparticles were synthesized by the reduction of the 1:2 molar ratio mixture of ferrous sulfate heptahydrate and ferric chloride hexahydrate with an ammonia solution. A chemotherapeutic drug, 5-fluorouracil, was chosen as a model drug, and its releasing profiles in the presence and absence of the external magnetic field were evaluated at a pH of 7.4. We observed that in the presence of the applied magnetic field, these magnetic nanohydrogels released 2.86% more drug than in the absence of a magnetic field. The magnetic nanohydrogels were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometry, and transmission electron microscopy.

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“…In contrast, when γ-Fe 2 O 3 was coated by amorphous SiO 2 suppression of the phase transition required much thicker coatings. [9] Since γ-Fe 2 O 3 that is precipitated on the external surface of the natural layered silicate montmorillonite [17] is only thermally stable up to 530°C, the stabilization by the electrostatic attraction with only one negatively charged surface is insufficient. Apparently, the sandwich-like fixation from two directions is the crucial factor.…”

Section: Phase Transitionmentioning

confidence: 99%

High Temperature Stable Maghemite Nanoparticles Sandwiched between Hectorite Nanosheets

Ament

Wagner

Meij

et al. 2020

Zeitschrift anorg allge chemie

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Maghemite (γ‐Fe2O3) is a metastable iron oxide phase and usually undergoes fast phase transition to hematite at elevated temperatures (>350 °C). Maghemite nanoparticles were synthesized by the polyol method and then intercalated into a highly swollen (>100 nm separation) nematic phase of hectorite. A composite of maghemite nanoparticles sandwiched between nanosheets of synthetic hectorite was obtained. The confinement of the nanoparticles hampered Ostwald ripening up to 700 °C and consequently the phase transition to hematite is suppressed. Only above 700 °C γ‐Fe2O3 nanoparticles started to grow and undergo phase transition to α‐F2O3. The structure and the phase transition of the composite was evaluated using X‐ray diffraction, TEM, SEM, physisorption, TGA/DSC, and Mößbauer spectroscopy.

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Influence of heat treatment on phase transformation of clay–iron oxide composite

Cited by 15 publications

References 41 publications

Raman spectroscopy for firing condition characterization: Case study of Karelian medieval pottery

Raman spectroscopy for firing condition characterization: Case study of Karelian medieval pottery

5‐Fluorouracil encapsulated magnetic nanohydrogels for drug‐delivery applications

High Temperature Stable Maghemite Nanoparticles Sandwiched between Hectorite Nanosheets

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