orientation of spinel-based thin film layered precursor Preparation and magnetic properties

　　Title: orientation of spinel-based thin film layered precursor Preparation and magnetic properties of
　　Author: Zhang Premier League
　　Degree-granting units: Beijing University of Chemical Technology
　　Keywords: Hydrotalcite;; ferrite;; film;; film-forming mechanism;; orientation;; superparamagnetic;; exchange bias;; superhydrophobic
　　Abstract:
　　Spinel ferrite thin films in high-density storage, the absorption of electromagnetic waves, magnetic resonance imaging and other fields have a wide range of applications. Thin films developed simple methods to control the film material composition, structure and morphology, thus improving the magnetic properties of thin films has become a hot issue of research in this field. This paper around the spinel ferrite thin-film materials to build their magnetic properties to http://www.999magnet.com/ carry out basic research. Research in the field for the current key scientific problems, using the layered precursor technology, the layered double hydroxides composite metal hydroxide (layered double hydroxides, referred to as LDHs, also known as hydrotalcite-like) films as the precursor materials, high temperature Roasting obtained family-oriented spinel ferrite thin-film-based material. LDHs precursor film by the preparation parameters of modulation and control of the roasting process to achieve the relevant composition of ferrite thin films, morphology, orientation controllable preparation. Meanwhile, the characterization of film assembly process of solvent evaporation, the film explores the driving force of LDHs film and assembly mechanism. Finally, the study tested the orientation of spinel ferrite-based magnetic properties of thin films. The study is expected for the spinel ferrite thin films based on structural design, building process control, application performance and other aspects of the experimental depth lay a foundation.
　　The innovation of this paper and the results are as follows:
　　First, high-density magnetic storage for the existence of ferromagnetic nanoparticles "superparamagnetic limit" of the key scientific issues in order to be prepared by evaporation of the solvent (00l) oriented CoFe-LDHs film as the precursor, under the protection of the use of helium The effects of structural topology LDHs prepared baking (111) oriented series CoFe2O4/CoO nanocomposite films. CoFe2O4 and CoO interface between the strong ferromagnetic / antiferromagnetic interaction CoFe2O4 improve the thermal stability of magnetic nanoparticles. With the same particle size compared to the pure phase CoFe2O4, CoFe2O4/CoO nanocomposite film CoFe2O4 particle blocking temperature (TB) increased more than 100 K. Also found that the magnetic anisotropy of Magnetic lifter the film led to a direction parallel to the membrane surface exchange bias field (HE) values ​​greater than perpendicular to the membrane surface under the conditions of the exchange bias field.
　　Then, (00l) oriented NiFe-LDHs film as the precursor, the first effect of the use of structural topology LDHs were prepared by roasting (111) oriented NiFe2O4/NiO nanocomposite films. Then, using nitric acid dissolution method of this compound in the NiO film removal has been porous (111) NiFe2O4 film. The surface roughness by calcination temperature and time to control acid corrosion. After the organic surface treatment, the porous film showed NiFe2O4 good superhydrophobic properties. With its enhanced surface roughness, film and water contact angle larger. Magnetic and surface wettability of controlled regulation allows the porous spinel ferrite films are based in the harsh external environment may obtain applications.
　　In addition, LDHs film based on the importance of controllable preparation, characterized by studying the assembly of solvent evaporation process, the film explores the driving force of LDHs film and assembly mechanism. At different crystallization temperatures were prepared LDHs nanoparticles. TEM, AFM and other characterization results showed that the crystallization temperature LDHs nanoparticles apparent change in morphology from the spherical-hexagonal sheet, the length to thickness ratio (aspect ratio) that LDHs nanoparticles increase the extent of anisotropy . Film experiments show that long-thickness ratio directly affects the size of the final film after solvent evaporation and particle continuity of (00l) crystal plane orientation degree. Large long-thickness ratio is conducive to inter-LDHs nanoparticles surface - surface interaction enhanced. In the study of NiFe-LDHs system, found that long-thickness ratio greater than 3 to complete the LDHs obtained continuous film.
　　Finally, this paper attempts to use a thin film coating technology to prepare LDHs precursor, and then through the roasting process were obtained MgFe2O4/MgO and NiFe2O4/NiO composite film and pure ferrite phase MgFe2O4 film. Research shows that the composite components uniformly distributed in the ferrite film, magnetic adjustable; and pure phase MgFe2O4 film at room temperature, showed a superior "superparamagnetic" performance.
　　Degree Year: 2010