Thesis Type: Doctorate
Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Arts and Sciences, Department of Chemistry, Turkey
Approval Date: 2010
Student: ÖZGE ACARBAŞ BALTACI
Supervisor: MÜRVET VOLKANAbstract:
The aim of this study is to produce maghemite nanoparticles by using different production methods. To achieve this purpose Sol-Gel Processing and Microwave Synthesis methods were employed. Suitable characterization techniques like XRD, TEM, BET, and VSM were performed to control the properties of the synthesized particles whether they are suitable for certain applications. In the sol-gel part of the study two different routes were employed to obtain maghemite nanoparticles. In the first route TEOS (tetraethoxysilane) was used as the precursor. Approximate particle sizes of these samples lie between 12.0-23.4 nm. From the magnetization measurements saturation magnetization (Ms) values are obtained between 4-12 emu/g. In the second route of the sol-gel method ethylene glycol and diethylene glycol were used as starting materials. Ms value was found as 28 emu/g for the ethylene glycol sample as the highest magnetization value due to having the highest amount of maghemite phase. The superparamagnetic behavior observed in these samples was tried to explain by curve fitting. Langevin and tangent hyperbolic functions were used to fit the magnetization curves. From the XRD study particle sizes of these samples lie in the 4.0-48.5 nm range and these results are consistent with the size distributions obtained from the TEM study. In the last part of the study microwave method was used to produce maghemite nanoparticles. Most of the samples contain maghemite and hematite phases together and particle sizes were between 3-30 nm. Ms values of these microwave samples were lower than that of the sol-gel samples with a value about 3.0 emu/g. Keywords: Maghemite, nanoparticle, superparamagnetism, sol-gel, microwave.