Abstract
The purpose of this work is to fabricate self-assembled microstructures by the sol–gel method and study the morphological, structural and compositional dependence of ε-Fe2O3 nanoparticles embedded in silica when glycerol (GLY) and cetyl-trimethylammonium bromide (CTAB) are added as steric agents simultaneously. The combined action of a polyalcohol and a surfactant significantly modifies the morphology of the sample giving rise to a different microstructure in each of the studied cases (1, 3 and 7 days of magnetic stirring time). This is due to the fact that the addition of these two compounds leads to a considerable increase in gelation time as GLY can interact with the alkoxide group on the surface of the iron oxide precursor micelle and/or be incorporated into the hydrophilic chains of CTAB. This last effect causes the iron oxide precursor micelles to be interconnected forming aggregates whose size and structure depend on the magnetic stirring time of the sol–gel synthetic route. In this paper, crystalline structure, composition, purity and morphology of the sol–gel coatings densified at 960 °C are examined. Emphasis is placed on the nominal percentage of the different iron oxides found in the samples and on the morphological and structural differences. This work implies the possibility of patterning ε-Fe2O3 nanoparticles in coatings and controlling their purity by an easy one-pot sol–gel method.
Highlights
Epsilon iron oxide is a collinear ferrimagnetic material with a Curie transition at around 500 K and a coercive eld of 2 T at room temperature.[1,2,3,4] it is considered an attractive magnetically hard material which could be used as a composite to produce a new family of oxide-based permanent magnets
For the fabrication of this iron oxide phase several methods have been developed to synthesize this material with a high crystallinity: e.g. pulsed laser deposition (PLD),[9,13,14] chemical vapour deposition (CVD)[15] or sol–gel synthesis.[16,17,18,19,20,21,22,23,24,25,26,27]
This study shows the importance of controlling the agitation time during the synthesis of 3-Fe2O3 nanoparticles produced by sol–gel method
Summary
Epsilon iron oxide is a collinear ferrimagnetic material with a Curie transition at around 500 K and a coercive eld of 2 T at room temperature.[1,2,3,4] it is considered an attractive magnetically hard material which could be used as a composite to produce a new family of oxide-based permanent magnets. Several studies have demonstrated the modulation of the resonance frequency depending on different elements substituted in the crystalline structure of the 3-Fe2O3 phase.[5,6,7,8] Specially in thin lm form, this. For the fabrication of this iron oxide phase several methods have been developed to synthesize this material with a high crystallinity: e.g. pulsed laser deposition (PLD),[9,13,14] chemical vapour deposition (CVD)[15] or sol–gel synthesis.[16,17,18,19,20,21,22,23,24,25,26,27] Of these techniques, the sol–gel method is the most widely used to synthesize it. The oxide is difficult to obtain, and complications arise when it is microstructured to enhance and/ or tune some of the above mentioned properties
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