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Preparation and characterization of bi-phasic magnetic nanoparticles
Alemayehu, Adam ; Tyrpekl, Václav (advisor) ; Brázda, Petr (referee)
Title: Preparation and characterization of bi-phasic magnetic nanoparticles Author: Bc. Adam Alemayehu Department: Department of Innorganic Chemistry Supervisors: doc. RNDr. Daniel Nižňanský, Ph.D. RNDr. Václav Tyrpekl, Ph.D. Consultant: M.Sc. Dominika Zákutná Abstract The work is focusing on the magnetic properties of ferrimagnetic spinel ferrites before and after the introduction of a shell on a core particle with different magnetic properties. The core nanoparticles were prepared by hydrothermal decomposition of oleate precursors. The introduction of shell was carried out by hydrothermal treatment of the already prepared core particles. The phase composition, spinel structure and the sizes of the prepared samples were investigated by powder X-ray diffraction and by transmission electron microscopy. Formation of the shell on top of the core particle was determined indirectly, using Mössbauer spectroscopy at room temperature. The interparticle interactions and the particle shape was studied by small angle X-ray scattering. The magnetic properties of the prepared samples were measured on a SQUID magnetometer. Key words: magnetic nanoparticles, core, shell, spinel structure, powder X-ray diffraction, Mössbauer spectroscopy, magnetic measurements, TEM
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Preparation of Fe2O3/SiO2 Nanocomposites from Molecular Precursor by Sol Gel Method and Doping of Iron(III) by Trivalent Metal Cations
Brázda, Petr ; Nižňanský, Daniel (advisor) ; Matějec, Vlastimil (referee) ; Grenéche, Jean-Marc (referee)
Přírodovědecká fakulta Univerzity Karlovy v Praze katedra anorganické chemie a Univerzita Štrasburk Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague and Université de Strasbourg Příprava nanokompozitů Fezos/Sioz z moleku!árního prekurzoru metodou so! gel a dopování Že|ezitých kationtů jinými trojmocnými kationty Preparation of Fezos/Sioz Nanocomposites from Molecutar Precursor by sol Gel Method and Doping of lron(lll) by Trivalent Metal Cations Souhrn disertačnípráce Summary of Thesis Petr Brázda Šrotitete(Supervisors): RNDr. Danie| NiŽňanský, PhD' Dr. Jean-Luc Rehspringer Praha 2009 Y Abstract Iron (III) oxide fonns two well-known polymorphs - the maghemite (y-Fe2O3), which is in fact a metastable phase, and is transformed into the hematite (cr-Fe2O3) at higher temperatures. At certain conditions, elusive e-Fe2O3 can be obtained as an intermediate between these two phases. e-Fe2O3 crystallizes in orlhorhombic space group Pna\ with lattice constants a: 509.5, b = 87g.9 and c:943.7 pm and is isomophous with r-A12O3, e-Ga2O3, AIFeO: and GaFeO3. Oxygen atoms form close pseudohexagonal packing with layers ABAC. kon cations occupy four different sites, three of them are octahedrally and one is tetrahedrally coordinated. There is eight formula units in unit cell. Structure of...
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