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Catalyzed Synthesis of α-Fe2O3 Nanoparticles in the Microreactor

Author: HanLiHong
Tutor: WeiYu
School: Hebei Normal
Course: Physical and chemical
Keywords: Micro-reactor Pseudoternary phase diagram Catalytic phase transformation α-Fe2O3 Nanoparticles
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 93
Quote: 1
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Abstract


The nano α-Fe the 2 O 3 in the field of catalysis, corrosion, pigments and magnetic recording materials have a wide range of applications. Many optical, electrical, magnetic, and other properties of the nanomaterials is only the size of the material is more uniform when the macro performance, so the preparation of uniform size monodisperse materials become a hot spot of research in materials science. The laboratory based on many years engaged in the study of the iron oxide, a synthetic nano α-Fe 2 O 3 particles, a new method - liquid catalytic phase transformation method. Although this method is very difficult to control nano-α-Fe responsive, process equipment is simple, low cost, but in the aqueous phase 2 O 3 nucleation and the growth process and lead to a wide particle size distribution, and difficult to get to the small size of the nano-α-Fe 2 the O 3 particles. On the basis of the preliminary studies, the catalyst Fe (Ⅱ) ions added to the microemulsion droplets in the microemulsion system, the catalytic phase transformation mechanism is applied to the micro-reactor under boiling reflux conditions direct synthesis of nano-α-Fe 2 O 3 . In this way, eliminating the need for high-temperature calcination step must be used by the microemulsion method to prepare nano oxides, overcome by the liquid method nano-α-Fe 2 O 3 when the particle size is uneven, the poor reproducibility shortcomings, while also retaining the advantages of these two methods, process equipment, uniform particle size, the particle size is controlled. The main contents of this thesis is as follows: (1) This article is drawn CTAB / n-butanol / octane / water (or FeCl the 2 -FeCl 3 mixed solution or NaOH the solution) microemulsion system pseudoternary phase diagram, and the effects of pH, solution concentration, n Fe (II) / n of Fe (III) values ??stable microemulsion The area of ??impact. The results showed that: in the range of pH 7 ~ 13, the microemulsion system showing a better pH stability; gradually decreases with increasing electrolyte concentration, the stable region of the microemulsion; n Fe (II) / n Fe (Ⅲ) smaller value of the stable region of the microemulsion. (2) study the influencing factors in the micro-reactor, trace Fe (Ⅱ) ions on Ferrihydrite catalytic transformation. The results show that: the preparation of microemulsions mixed method to the Fe (II) ions, can ensure that the Fe (II) ions directly into each microreactor;, Fe (II) ions in the range of pH5 ~ 9 Ferrihydrite phase transformation also has a significant role in promoting, phase inversion and accelerate the speed with n Fe (Ⅱ) / n Fe (Ⅲ) value increased the but n Fe ( II) / n of Fe (III) ≥ 0.12, the product impurity phase α-FeOOH generation. High Fe (Ⅲ) ion concentration, is conducive to the phase transformation rate increases;, is conducive to the formation of α-Fe 2 O 3 of high heating rates. (3) found in the micro-reactor by Ferrihydrite to the α-Fe 2 O 3 transformed optimal conditions: pH = 7, the NaOH solution micro emulsion slowly added FeCl 2 -FeCl 3 mixed solution (C of Fe (III) = 0.3mol / L, n of Fe (II speed heated to boiling) / n Fe (Ⅲ) = 0.08) microemulsion prepared precursor Ferrihydrite, 7.2 ℃ · min -1 , the 4.5h available pure phase of α-Fe 2 O 3 . (4) microreactor trace Fe (Ⅱ) ion presence Ferrihydrite catalytic phase transformation for α-Fe 2 O 3 reaction factors on nano-α-Fe 2 the O 3 size and morphology of; controllable product particle size can be achieved by controlling the reaction conditions. The results show that: ω (ω = nH 2 O / nCTAB) value increases and the initial FeCl 3 concentrations are conducive to the formation of large-size nano-α-Fe 2 O 3 ; mC 4 H 9 the OH / mCTAB value increases and the precursor formation temperature increases, nano α -Fe 2 O 3 particle size are reduced gradually increasing; With mC 8 H 18 / mCTAB value decreases, the nano-α-Fe 2 O 3 particle size decreases gradually; pH ??value of nano-α-Fe 2 O 3 particle size of the impact is not obvious.

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