Development of Multifunctional Magnetic Core Nanoparticles
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School of Chemical Technology |
Doctoral thesis (article-based)
| Defence date: 2013-04-26
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Authors
Date
2013
Major/Subject
Mcode
Degree programme
Language
en
Pages
114 + app. 81
Series
Aalto University publication series DOCTORAL DISSERTATIONS, 58/2013
Abstract
Multifunctional magnetic materials have a great importance in various fields of application, e.g., material science, chemistry, physics, environmental chemistry and biomedicine. Although a large number of scientific papers already describe the synthesis of multifunctional materials by various methods and technologies, a simple, fast and economically feasible synthesis procedure to combine all the materials in one system is still of interest. This thesis contributes to the development of multifunctional magnetic-core materials scientifically in three parts. Firstly, the synthesis of magnetic core, i.e., magnetite nanoparticles, was attempted using only ferrous ions (Fe2+) of various concentrations as a magnetite precursor under ambient atmosphere. It was found that the synthesized magnetite was in a non-stoichiometric state, i.e., oxidation occurs. The introduction of Stöber silica (SiO2) layer in the form of a coreshell structure prevented the oxidation of the synthesized particles, as suggested by the low temperature magnetic measurement and Mössbauer study. Secondly, this thesis introduces a simple, room temperature synthesis method for further functionalization of the magnetite-silica coreshell powders with silver (Ag) and silver/silver chloride (Ag/AgCl) nanoparticles. Based on the proposed approaches, the Ag deposition on the silica shells can take place by three possible mechanisms: a) absorption of Ag+ on the silica surface by ionic bonding between the silver ions and hydroxyl groups (OH) of silica followed by the reduction of Ag+ by polyvinylpyrrolidone (PVP), b) hydrogen bonding between the PVP-coated Ag and the SiO2 shells, and c) electrostatic attraction between PVP-coated Ag and SiO2 shells. The silver chloride particles are formed when a certain amount of hydrochloric acid (HCl) is introduced. The particle morphology is controlled by the concentration of HCl. Thirdly, the thesis makes a scientific contribution by introducing novel properties by compacting the magnetite-silica coreshell powders into bulk material by pulsed electric current sintering (PECS). By adjusting the amount of magnetite-core inside the silica structure, it is possible to produce a transparent magnetic compact. In addition, the effects of the sintering atmosphere and temperature on the final properties of the compacts were also studied.Description
Supervising professor
Hannula, Simo-Pekka, Prof., Aalto University, Department of Materials Science and Engineering, FinlandThesis advisor
Hannula, Simo-Pekka, Prof., Aalto University, Department of Materials Science and Engineering, FinlandKeywords
magnetite, silica, silver, silver chloride, pulsed electric current sintering, phase transformation, multifunctional, ferromagnetic
Other note
Parts
- [Publication 1]: Mahmed, N., Heczko, O., S.derberg, O. & Hannula, S-P (2011) Room temperature synthesis of magnetite (Fe3-δO4) nanoparticles by a simple reverse co-precipitation method. IOP Conference Series: Materials Science and Engineering, 18, 032020.
- [Publication 2]: Mahmed, N., Heczko, O., Lancok, A. & Hannula, S-P. The magnetic and oxidation behavior of bare and silica-coated iron oxide nanoparticles synthesized by reverse co-precipitation of ferrous ion (Fe2+) in ambient atmosphere. Submitted to Journal of Magnetism and Magnetic Materials.
- [Publication 3]: Mahmed, N., Jiang, H., Heczko, O., S.derberg, O. & Hannula, S-P (2012) Influence of different synthesis approach on doping behavior of silver nanoparticles onto the iron oxide-silica coreshell surfaces. Journal of Nanoparticle Research, 14, 987.
- [Publication 4]: Mahmed, N., Heczko, O. & Hannula, S-P (2013) Influence of hydrochloric acid concentrations on the formation of AgCl-doped iron oxide-silica coreshell structures. Advances in Science and Technology, 77, 184–189.
- [Publication 5]: Mahmed, N., Heczko, O., Maki, R., S.derberg, O., Haimi, E. & Hannula, SP (2012) Novel iron oxide-silica coreshell powders compacted by using pulsed electric current sintering: Optical and magnetic properties. Journal of the European Ceramic Society, 32, 2981–2988.
- [Publication 6]: Mahmed, N., Friman, M. & Hannula, S-P (2012) Phase transformation of iron oxide-silica coreshell structure during differential scanning calorimetry and pulsed electric current sintering processes: A comparison. Materials Letters, 85, 18–20.
- [Publication 7]: Mahmed, N., Larismaa, J., Heczko, O., Cura, M. E. & Hannula, S-P (2013) Influence of sintering temperature on the properties of pulsed electric current sintered hybrid coreshell powders. Journal of the European Ceramic Society.