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Study of the Preparation and Properties of α-FeOOH Nanoparticles and the Colloids

Author: MiaoHua
Tutor: LiJian
School: Southwestern University
Course: Condensed Matter Physics
Keywords: α-FeOOH γ-Fe2O3 FeCl2/NaOH solution Phase change Magnetic properties Dielectric properties Magneto-optical effect
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 62
Quote: 1
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Abstract


Firstly, α-FeOOH nanoparticles prepared by chemical precipitation, and by chemical induced phase transition, α-FeOOH as a precursor to the system had γ-Fe2O3 nanoparticles. FeCl3 · 6H2O, NaOH and FeCl2 reaction raw materials (both analytical grade), X-ray diffraction (XRD) to determine the sample phase, transmission electron microscopy (TEM) observation sample morphology, vibrating sample magnetometer (VSM ) detecting the magnetization of the sample properties. Synthesis of α-FeOOH colloid and a magneto-optical study. The main contents and results of this study are as follows: FeCl3 · 6H2O and NaOH reaction raw materials, distilled water as the solvent, chemical precipitation method for the synthesis of α-FeOOH nanoparticles, XRD results show better crystalline α-FeOOH nanoparticles, TEM The results show that the product prepared 8.16nm nanoparticles aggregates VSM results show render the paramagnetic. 2 heat treatment. By FeCl2/NaOH mixture of α-FeOOH precursor synthesis of γ-Fe2O3 nanoparticles. Experimental results show that: the α-FeOOH precursor processing, a mixture of FeCl2 (0.22M) and NaOH (0.19M) of the obtained nanoparticles is a single γ-Fe 2 O 3 < / sub> phase, the average particle diameter of 12.74nm, uniform particle size distribution, good dispersibility, good crystallinity; However, when the FeCl2 solution concentration of less than 0.22M, or NaOH concentration of less than 0.19 M of the obtained nano The particles are two-phase coexistence of α-FeOOH and γ-Fe2O3 composite nanoparticles. TEM observation showed that the fine particles of the two-phase coexistence its form is inconsistent, the single gamma-Fe2O3 nanoparticles is polygonal rather than spherical. Magnetization intensity data obtained by the vibrating sample magnetometer (VSM), suggesting that the phase volume ratio of the two-phase particles in the α-FeOOH phase and the gamma-Fe2O3. 3.α-FeOOH nanoparticles using Fe (NO3) 3 solution (boiling before adding the α-FeOOH nanoparticles) treatment, with the the Massart legal system was prepared α-FeOOH colloidal weakly magnetic. By centrifugation to remove aggregates. Due to α-FeOOH nanomaterials have unique properties (block material is an antiferromagnetic material, nanoparticles presented paramagnetic orthorhombic), we studied the incident light is linearly polarized, respectively, and circularly polarized light, α-FeOOH colloidal constituted by a weakly magnetic nano-particles of the α-FeOOH colloidal ferromagnetic CoFe2O4 nanoparticles in a uniform magnetic field (generated by the Helmholtz coils) under the action of the dichroism and the birefringence effect, the experimental results show that a magnetic liquid having more obvious two dichroism and the birefringence effect, through theoretical and experimental results prove that the intrinsic magnetic moment having a weak non-tetragonal nanoparticles hydrocolloid may be equivalent to the magnetic - dielectric ellipsoid system, such ellipsoid hydrocolloid in the zero magnetic field, the dielectric constant was isotropic. However, when the applied magnetic field, the ellipsoid itself relating to rotation of Brown magnetic moment rotation will induced consistent with the dielectric ellipsoid direction, therefore, the dielectric constant of the colloid will becomes anisotropic. Under magnetic field and having a dielectric ellipsoid orientation orderly colloid can be seen as a class of liquid crystal has an optical anisotropy. This article discloses the synthesis pathway of a new oxide nanoparticles chemical induced phase change. For the synthesis of metal oxide nano-particles, this chemical induced phase change may be an effective way. We have also made a circularly polarized light as the measurement of the light source of α-FeOOH colloidal magnetic (lines) to the hue and the birefringence effect of the magnetic method. This method can be developed into a continuous measurement of the scanner will greatly shorten the measuring time. This measurement method is also applicable to other medium having magnetic (line) two pleochroic magnetic birefringence effect. Through this study, late work provides some possible experimental program.

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