ε-Fe2O3/SiO2 Nanoparticles ESR in-situ Study. Spatial Stabilization and the Size Effect
Доклады на конференциях
uring the last decades systems based on ε-Fe2O3 nanoparticles attract particular and growing attention. The ε-Fe2O3 phase, is the intermediate between α- and γ-Fe2O3. ε-Fe2O3 phase, which displays high (up to 20 kOe) coercivity at room temperature, two magnetic transitions in low and high temperature region, and is stable only in the form of nanoparticles, thanks to its low surface energy .
The majority of works on the ε-Fe2O3 phase is dedicated to the investigation of the magnetic properties of this phase and the search for the routes to synthesize ε-Fe2O3 in the form of stable and bulk particles (up to 200 nm). Most researches try to study magnetic properties of the ε-Fe2O3 without taking into account size effects. However in some cases, such as catalysis, studying a few nanometers sized particles can be crucial. In the Boreskov Institute of Catalysis ε-Fe2O3/SiO2 nanoparticle system was created for the first time that has no other detectable iron-oxide polymorphs with narrow size distribution of e-Fe2O3 supported nanoparticles .
ESR method in situ in comparison with HR TEM, XRD, Mossbauer spectroscopy, and magnetization measurements data were applied to investigate the initial stages of the ε-Fe2O3/SiO2 nanoparticles formation [3,4]. It was shown that the stabilization of the nanoparticles precursor on the silica support is the key factor to obtain the system clear from admixture of other iron oxide polymorphs.
Support by Russian Science Foundation (Grant No. 17-12-01111).
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