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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2025-07-06 15:44 |
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Conference: Bucharest University Faculty of Physics 2025 Meeting
Section: Solid State Physics and Materials Science
Title:
Morpho-structural modifications using thermal treatments on iron oxide nanoparticles synthesized by laser pyrolysis using formic acid as a sensitizer
Authors:
Anca Criveanu (1), Florian Dumitrache (1), Iulia Lungu (1), Iuliana Morjan (1), Lavinia Gavrila (1), Claudiu Fleaca (1), Ani Niculescu (1), Adrana Balan (2), Vlad Socoliuc (3,4), Bogdan Vasile (5,6)
Affiliation:
1 National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor St., 077125 Magurele, Romania;
2 Research Center 3NanoSAE, The Faculty of Physics, University Bucharest, 077125 Bucharest, Romania;
3 Romanian Academy-Timisoara Branch, Center for Fundamental and Advanced Technical Research, 24 Mihai Viteazu Ave., 300223 Timisoara, Romania
4 Research Center for Complex Fluids Systems Engineering, Politehnica University of Timisoara, 1 M. Viteazu Ave., 300006 Timisoara, Romania
5 Advanced Research Center for Innovative Materials, Products and Processes National University of Science and Technology POLITEHNICA Bucharest, Splaiul Independentei 313, 060042 Bucharest, Romania;
6 Academy of Romanian Scientists, 3 Ilfov, 050044 Bucharest, Romania
E-mail
anca.criveanu@inflpr.ro
florian.dumitrache@inflpr.ro
Keywords:
iron oxide nanoparticles; laser pyrolysis; formic acid; thermal treatments;
Abstract:
The laser pyrolysis technique was used in the synthesis of magnetic iron oxide nanopowders (NPs) in the presence of formic acid vapors as a sensitizer. This technique uses the energy from a continuous-wave CO2 laser operating at a 9.25 μm wavelength, which is transferred to the reactive precursors via a resonant absorption of formic acid molecules. The iron precursor-Fe(CO)5 and the sensitizer (H-COOH) vapors were obtained by bubbling an argon flow, through the liquid reservoirs. The laser irradiation of reactive gas mixture induces a rapid heating and followed by a decomposition of the Fe(CO)5 vapors in the presence of oxygen. The as synthesized samples were thermally treated at different temperatures between 150 – 550 ºC for 2 hours and their morpho-structural properties were investigated. Furthermore, a treatment at 400 ºC in NH3 environment were also performed in order to induce a superficial nitridation of iron oxide NPs. XRD, TGA, XPS, EDX, DLS, TEM and magnetic analyses were performed on both the as synthesized and the treated ones. As a result, it was observed the consolidation of maghemite phase with increasing temperature up to 400 ºC with a minimal increasing of crystalline dimension between (7.4 – 30.35 nm). The treatments at temperature higher than 450 ºC suggest the solid phase transition from γFe2O3 to αFe2O3 crystalline structure followed by a significand increasing in crystalline dimension. Also, the aqueous NPs suspension having 0.5 g/l concentration were performed. It was observed in the DLS analysis that the suspensions show a spectacular high stability in time for those NPs treated at lower temperature. However, the suspensions become unstable when NPs treated at temperatures higher than 250 ºC were used. TGA analysis performed in air shows different steps of mass decreasing associated with water desorption between 90-130 ºC, followed by a sudden decrease in mass between 150-280 ºC probably as a result of the functional groups disappearance for treatments above 250 ºC. The XPS studies made for O 1s and C1s zones indicate the presence of Fe-OH, C=O and C-O bonds and with treatments at higher temperature such bonds attributed to functional bonds suffer a progressive attenuation.
Acknowledgement:
This work was supported by the Romanian Ministry of Research, Innovation and Digitalization under the Romanian National Nucleu Program LAPLAS VII—contract no. 30N/2023
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