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Chemical Auxiliary High Energy Ball Milling SmCo_5 nanoparticles, nanosheets and its physical properties

Author: BaiXue
Tutor: DuXiaoBo
School: Jilin University
Course: Condensed Matter Physics
Keywords: SmCo5 nanoparticles Nanosheets Chemical Auxiliary energy ball milling Surfactants Magnetic properties
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 98
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Abstract


In recent years, due to the high-tech fields, such as computer, information storage, biomedical and micro-nano machinery and other areas of potential applications, monodisperse nano-magnetic materials research increasingly attracted people's attention. However, due to the superparamagnetic effect, to the nano-scale, general coercivity permanent magnet materials are significantly decreased, and only such as SmCo5 material with high magnetic anisotropy to maintain a certain coercive force. SmCo5 permanent magnet materials are all materials in magnetic anisotropy constant Ku (2.3 × 108erg/cm3) the highest, so the superparamagnetic limit is also the smallest, reaching 2.2 nm, is the preparation of nanocrystalline permanent magnet materials ideal material. Preparation of nanocrystalline magnetic materials with physical and chemical both methods. Chemical method is a bottom-up approach, the nano material is better morphology, particle size uniformity, size is relatively easy to control, but the preparation is limited kinds of materials, such as rare earth-containing rare earth permanent magnet materials are difficult to prepared by chemical methods. Physical method is a top-down approach, can be prepared almost all of the permanent magnet materials, but poor uniformity of particle size, surface defects seriously. However, the uniformity of particle size by the centrifugal separation can be improved method. In this thesis, surface milling auxiliary agents were prepared monodisperse nano SmCo5 permanent magnet materials, preparation of studies on the particle size, morphology and magnetic properties. Specific work is as follows: 1 surfactants were prepared by high energy ball milling auxiliary SmCo5 nanoparticles. Oleic acid used in the experiment as a surface, a surface agent and SmCo5 material mass ratio of 1:1, n-heptane as the milling media. Ball mill for the U.S. production SPEX8000M type ball mill, ball mill jar and grinding balls made of high carbon steel. Pellet ratio of 15:1, the milling time is 20 hours. Sample solvent added oleic becomes opaque black, indicating that solvents have produced nanoparticles and suspended in the solvent. Transmission electron microscopy revealed particle diameter of 5-10 nm, good dispersion, no agglomeration of particles poor uniformity. Infrared spectra demonstrate nanomaterials coated oleic acid molecules. Not a member of oleic acid sample solvent colorless and transparent, indicating that no nanoparticles produced proved oleic acid in the process of the formation of nanoparticles play a key role. Magnetic measurements show that the magnetic properties is poor, only 20000e coercivity around, possibly due to the severe impact from the surface and the formation of defects. 2 After adding oleic acid and oleic acid samples did not join, have found a mud-like precipitation. Scanning electron microscopy showed that the addition of oleic acid samples, the mud-like sediment is a flaky particles, the thickness of a few hundred nanometers to several tens of microns in diameter. The flaky particles are arranged in the thickness direction of each string of adsorption and end to end to form a closed loop. This arrangement of particles described by way of spontaneous magnetization perpendicular to the sheet surface. Infrared spectra showed that the particles coated with oleic acid molecules. Since the shape of the flake particles with a large anisotropy, if no other anisotropic particles should be in the spontaneous magnetization plane, rather than perpendicular to the sheet surface. It can be concluded that: the flaky particles having a crystallographic texture and magnetic anisotropy, C-axis that is perpendicular to the axis of easy magnetization of the sheet surface, the magnetic anisotropy was stronger than the effect of shape anisotropy, resulting in a spontaneous magnetization direction in the sheet thickness direction. This formation of the crystal texture for the preparation of anisotropic bonded magnet has a great significance. No added oleic acid was not observed in the sample apparent shape anisotropy, particles of irregular shape, and severe agglomeration. 3 of the surface of the other two common agent, oleylamine and PVP effect in this experiment. Oleylamine found similar effects with the oleic acid, and the PVP nanoparticles and the precipitated crystals textured sheet having a large particle formation does not play a role. 4 to form a closed loop of the flake particle in a magnetic field the magnetization was found closed loop is opened and arranged in the direction along the field, and further that the thickness of the sheet is C-axis direction, i.e. the direction of easy magnetization.

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