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Preparation and Characterization of Iron (III) Oxide Nanocomposites Substituted with Scandium
Kaščáková, Dorota ; Nižňanský, Daniel (advisor) ; Tyrpekl, Václav (referee)
In this work a preparation and characterization of nanoparticles of iron(III) oxide substituted with scandium in SiO2 matrix is described. The nanoparticles were prepared by the sol-gel method yielding mostly β-Fe2O3 substituted with various amount of scandium(III) ions. Mossbauer spectroscopy was carried out to determine purity of the samples and the content of other iron oxides phases. System was characterized by magnetic measurements. Powder X - ray diffraction was used to verify the composition and to determine the lattice parameter and particle size. β-Fe2O3 is formed at the temperatures of 1000 and 1100 ◦ C at composition Fe2−xScxO3 for x ≥ 0.2 and at temperature 1100 ◦ C for x = 0.1. Lattice parameter is linearly dependent on the scandium content and depends also on the annealing temperature. At temperatures higher than 1250 ◦ C, β-Fe2O3 is transformed into hematite. Key words: iron(III) oxide, scandium, sol-gel, Mossbauer spectroscopy, X-ray diffraction, magnetic measurements 1
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Relaxivity of magnetic nanoparticles
Kubíčková, Lenka ; Kohout, Jaroslav (advisor) ; Lančok, Adriana (referee)
Magnetic nanoparticles have found broad applications in medicine, in particular as contrast agents for T1- and T2-weighted magnetic resonance imaging (MRI). The ability of a contrast agent to influence the proton relaxation rate in a tissue is described by its relaxivity. In the submitted bachelor thesis we characterise physical properties of samples of ε-Fe2O3 nanoparticles coated with amorphous silica (SiO2), particularly with the aim to determine the dependences of their relaxivities on the magnetic field, temperature and thickness of silica coating. The distribution of the particle sizes was derived from the TEM pictures giving the median ~ 20 nm and the thickness of the silica coating ~4; 8; 13; 19 nm. The lattice parameters and presence of ˂ 2% admixtures of α phase were ascertained by XRD analysis; hyperfine parameters obtained by Mössbauer spectroscopy indicate no change of magnetic properties of the particles by silica coating. The relative amount of ε-Fe2O3 and SiO2 in the samples was specified from the magnetic measurements. Aqueous suspensions of different concentrations of coated nanoparticles were prepared, and their relaxivities r1, r2 were measured in different magnetic fields. Temperature dependence of relaxivities of a chosen sample was obtained in fields 0.47 T and 11.75 T....
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Crystal chemistry of pyralspite garnets
Soumar, Jan ; Skála, Roman (advisor) ; Ulrych, Jaromír (referee)
Bohemian garnets have been known as a jewellery stone for many centuries. There is still a lot of interest in them, however, the reserves in traditional locations are getting smaller. That is why search for alternative source of similar garnets in gem quality started. Shavaryn Tsaram deposit in Mongolia is considered as one of the potential sources. Pyrope samples from eight Bohemian localities of two areas (České středohoří [The Central Bohemian Uplands] and Podkrkonoší [The Giant Mountains]) and from Shavaryn Tsaram deposit in Mongolia were analysed using electron microprobe, LA-ICP-MS, ICP-OES, Mössbauer spectroscopy and x-ray powder diffraction. The data were compared with the conclusion that the Mongolian garnets from Shavaryn Tsaram deposit are so different from the Bohemian ones that it will not be possible to use them as a gem material of similar qualities. Bohemian garnet can be characterised as a red garnet with refraction index 1.747 (+/- 0.001) with dominant pyrope component of the average composition Py78Alm17Gr5 and Cr2O3 content above 1 wt.%. The data were also evaluated from two classification schemes point of view. The schemes by Schulze (2003) and Grütter (2004) are used in determining source materials and in diamond prospection. According to them source rocks of Bohemian garnets...
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Study of hyperfine interactions in nanoparticles present in biological systems
Kubániová, Denisa ; Kohout, Jaroslav (advisor) ; Závěta, Karel (referee)
In the submitted bachelor thesis we studied iron oxides by zero-field and in-field Mössbauer spectroscopy at room and liquid helium temperature. The relative composition in synthe- tically prepared nanoparticles of ferric oxide in SiO2 matrix is investigated in dependence on ferric oxide concentration and heating temperature and further the phase composi- tion and structure of biological nanoparticles produced by Geoalkalibacter ferrihydriticus bacteries in dependence on concentration of quinone in the cultivating solution. By data analysis the chemical and phase composition of the samples and hyperfine parametres of 57 Fe cations in nonequivalent crystallographic positions are determined. 1
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Příprava Fe-Ti kompozitů mletím v kulovém mlýnku
Roupcová, Pavla ; Schneeweiss, Oldřich
The materials were prepared by mechanical alloying in the ball mill. The first type of sample consists of pure commercial precursors (TiH2 and ferrihydride). The slightly changes of phase composition of the powder were under the detection limit of X-ray powder diffraction. The MS determined the changes from the first step of milling. The second type of sample was prepared from turnings. The reduction of the splinters volume and the mechanical alloying was running simultaneously. The huge crystalline size differences decreased the credibility of computation of phase composition by XRD. MS was able determined phase composition more exactly and in additional to differentiate crystalline and amorphous FeTi phase.
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Changes of Phase Composition of NaAlH4 Based Complex Hydrides
Roupcová, Pavla ; Schneeweiss, Oldřich
The Mössbauer study is target to valence of Fe-doped phase and its changes during preparation by mixing with NaAlH4 and charging and discharging cycles. The 2 mol % FeCl2·4H2O powder was contained in the asmixing material. The dry milled sample did not transformed during the milling in the protective atmosphere. The significant change was approved in the firstly hydrogenation step only. The analysis shows FeClO which released the most significant component in the dehydrogenation and hydrogenation steps. The amount of FeClO was decreased with the all following step of hydrogenation and dehydrogenation. The fine paramagnetic particles of iron oxides were detected and their amount increased influenced of gas impurities. The longer period of heat treatment shows the agglomeration of iron oxides and their magnetic effect.
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Vlastnosti nanokrysltalického Zr-Fe-H
Roupcová, Pavla ; Schneeweiss, Oldřich
In this paper, we describe some results obtained by synthesis of Fe-Zr alloys and the study of the phase transformations in these materials induced by hydrogen. Mossbauer spectroscopy was used as the most sensitive method for determination of Fe-Zr based phases in a nanocrystalline form.
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