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| Author(s): |
Fabiana Rodrigues Arantes
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física (IF/SBI) |
| Defense date: | 2010-05-20 |
| Examining board members: |
Daniel Reinaldo Cornejo;
Antonio Martins Figueiredo Neto;
Kleber Roberto Pirota
|
| Advisor: | Daniel Reinaldo Cornejo |
| Abstract | |
In this work we studied the magnetic behavior of potassium laurate lyotropic liquid crystals doped with magnetite nanoparticles. Zero-field cooling (ZFC) and field-cooling (FC) measurements with 50 Oe applied field showed a blocking behavior of magnetic nanoparticles at room temperature due to the micelle presence, while presenting superparamagnetic behavior when dispersed in water. Monte Carlo simulations suggest that this increase in the nanoparticles\' blocking temperature when immersed in lyotropic liquid crystals can be acquired taking into account an exchange-like strong interaction between the nanoparticles\' superficial magnetic moments and an extra layer playing the role of the micelles. ZFC-FC and magnetic susceptibility measures allowed us to find the transition temperatures between the isotropic micellar and the discotic nematic phases. The magnetization curve in the discotic phase resembles the behavior of the order parameter in that phase. We obtained nickel nanowires by AC electrodeposition in anodic porous alumina to dope lyotropic liquid crystals in the isotropic phase. The ZFC-FC measurements in those systems were more intricate given the weak magnetization of the samples and low solubility of the nanowires in the liquid crystal. We refined the technique for dissolution and doping of the crystals, but more studies are needed in order to improve the samples\' stability. (AU) | |
| FAPESP's process: | 07/06388-0 - Study on the magnetic behavior of magnetite nanoparticles and nickel nanowires diluted in nematic fluids. |
| Grantee: | Fabiana Rodrigues Arantes |
| Support Opportunities: | Scholarships in Brazil - Master |