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Superior thermal stability of polymer capped Fe 3 O 4 magnetic nanoclusters
Author(s) -
Sathya Ayyappan,
Ravindran Thoguluva R.,
Philip John
Publication year - 2018
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15197
Subject(s) - nanoclusters , materials science , superparamagnetism , maghemite , thermal stability , annealing (glass) , thermal decomposition , magnetite , chemical engineering , nanoparticle , magnetization , inert gas , analytical chemistry (journal) , nanotechnology , chemistry , composite material , metallurgy , organic chemistry , magnetic field , physics , quantum mechanics , engineering
In general, the technologically important ferrites nanoparticles, magnetite and maghemite, are converted from cubic to the more stable rhombohedral structure above 500°C‐700°C under air/vacuum/inert atmosphere. Here, we report, the superior thermal stability of polymer capped Fe 3 O 4 ( PCIO ) nanocluster (synthesized using microwave‐assisted polyol approach) up to 1000°C under vacuum and inert atmosphere. Raman spectra of post annealed PCIO nanoclusters show the Fe 3 O 4 phase with carbon signature due to the decomposition of polymer matrix. The carbon layer seems to act as a thermal shield and increases the activation energy thereby preventing the intrusion of heat, oxygen, volatiles mass into the magnetic core. The presence of carbon layer was further confirmed from the high‐resolution transmission electron microscopic image. After thermal annealing at 1000°C, PCIO nanoclusters showed superparamagnetic behavior with a saturation magnetization of 89 emu/g, close to the bulk saturation magnetization of Fe 3 O 4 phase. In contrast, the uncoated Fe 3 O 4 ( UCIO ) nanoclusters decompose at 700°C into α‐Fe 2 O 3 and FeO phases under similar annealing conditions. Our findings open up new possibilities of stabilizing nanomaterials for high‐temperature applications.