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The Synthesis, Characterization, and Properties of Iron Oxides and Iron Oxide Hydroxides Nanomaterials

Author: OuPing
Tutor: HanGaoRong；XuGang
School: Zhejiang University
Course: Materials Science
Keywords: alpha - Fe2O3 Fe34 alpha - FeOOH Hydrothermal Solvothermal Nanostructure Small size effect
CLC: TB383.1
Type: Master's thesis
Year: 2007
Downloads: 523
Quote: 2
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Abstract


Iron oxide (Fe x O y ) and hydroxides (FeOOH), including alpha-Fe 2 the O 3 < / sub>, the Fe 3 O 4 and alpha-FeOOH belong oxide magnetic material. With the reduction in the size and morphology of the nano-structure due to the small size effect, surface effect, quantum size effect and macroscopic quantum tunneling effect, leading to a variety of electromagnetic properties or physical characteristics change, resulting in pigments, catalysts, magnetic The recording medium, magnetic coatings, gas sensors, as well as gas desulfurization in the process of environmental protection, waste treatment and other industrial applications exhibit more excellent performance than the block material. In addition, the Fe x O y , FeOOH nano-structure in other cutting-edge fields such as clinical diagnosis, pharmaceutical transmission, magnetic fluid application prospects have also been people's attention. Therefore, different morphology and size of the the Fe x the O y , the FeOOH nanostructures synthesis, characterization and properties of great significance. In this thesis, hydrothermal / solvothermal method to synthesize iron oxide (Fe x O y ) and hydroxides (FeOOH) nanomaterials. Fe (NO 3 ) 3 · 9H 2 O, and KOH (mineralizing agent) the reactants, solvents, surface modifier, The reaction temperature mineralization concentration, reaction time and other factors departure Preparation of Fe x O y , FeOOH nanostructure formation and characteristics of regularity and mechanism of action. The main contents and results of the thesis is as follows: 1. Fe (NO 3 ) 3 · 9H 2 O and KOH ethanol as solvent, polyvinyl alcohol (PVA) as the reactants stabilizers, solvothermal method with a diameter of 20 to 100 nm of α-Fe 2 O 3 nanoparticles, more uniform particle size distribution, dispersion, and crystalline better. The studies show that the appropriate amount of polymer modification can improve the uniformity of dispersion and size of the nanocrystals, freedom PVA structure strongly polar hydroxyl group may be formed between the metal ion chelate key, tightly clad around the metal ion, is formed a PVA chain limits the limited structure of the shape, so that the size of the synthesized nanoparticles is limited and difficult to form aggregates having a good stabilizing effect. 2. Solvothermal method using Fe (NO 3 ) 3 · 9H 2 O and KOH the reactants, ethylene glycol as the solvent, 220 ° C under reaction for 24 hours to synthesize a large number of uniform size Fe 3 O 4 nanoparticles with a diameter of about 16nm, preferably crystallization. The influence of temperature and mineralization concentration on the morphology of the product. The results show that the regulation of temperature and mineralizer concentration can be obtained particle size controllable, uniform cubic phase Fe 3 O 4 nanoparticles. Using this method prepared Fe 3 O 4 nano-particles, the method is simple, large output, and the preparation of the crystal has the small size effect. 3. Fe (NO 3 ) 3 · 9H 2 O and KOH reaction materials, ethylene glycol as the solvent, the introduction of appropriate amount of PEG as a surface modification agent, solvothermal nanomaterials, found that the morphology of the product a certain amount is about 5 nm in diameter, about 30 ~ 50nm Fe 3 O 4 nano needle. The amount of PEG added form Fe 3 O 4 nano needle, and to explore the mechanism of PEG to promote the growth of nano-needle. 4. Hydrothermal method, Fe (NO 3 ) 3 · 9H 2 O and KOH reaction mass to react for 6 hours at 100 ℃, Synthesis of a mass having a large aspect ratio of alpha-FeOOH nanowire diameter 80nm, a length of 1.5 ~ 2μm, the single nanowire good crystallinity and quadrature phase goethite structure of alpha-FeOOH, and along the nanowire goethite structure of alpha-FeOOH [001]-axis oriented growth. Studied reaction temperature mineralizing agent concentration and reaction time on the morphology. The results showed that: when the temperature falls below a certain value (40 ° C), whether it is in conditions of low concentration of mineralizing agent or under conditions of high concentration of mineralizing agent are not alpha-FeOOH, the product was amorphous phase; at 100 ° C when, as the mineralizing agent concentration increases, more and is not conducive to the synthesis of alpha-FeOOH nano-wire; alpha-FeOOH at high temperature (200 ° C), is generated in a very short period of time, and with rapid phase transition with the extension of time for the alpha-Fe 2 O 3 . 5. In this paper the synthesis of alpha-FeOOH nanowires as raw material, heat treatment is carried out at different temperatures, and incubated for 0.5 hours. The results showed that: different temperatures during the heat treatment in the alpha-FeOOH to render the same phase change pathway, i.e. dehydrated to form alpha-Fe 2 O of , phase transition temperature 240 to 295.1 ° C and the temperature after heat treatment of alpha-Fe 2 O 3 to keep the original alpha-FeOOH nanowire shape, line holes on the surface. The catalytic properties of ammonium perchlorate (AP) experimental results show that: the AP obtained by heat treatment at different temperatures α-Fe 2 O 3 nanowires pyrolysis temperature significantly decline, in which the heat treatment temperature of 350 ° C, the product of the AP high temperature decomposition temperature drop to 71.4 ° C.

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