Method of preparing polymer composite using unidirectionally solidified giant magnetostrictive material

Abstract

Disclosed is a preparation method of a polymer composite using a giant magnetostrictive material, which is advantageous in that electric resistivity and magnetostrictive strain are increased while the unidirectionally solidified texture in the material is maintained as it is. The method consists of removing the rare earth or the eutectic phase from a unidirectionally solidifed rare earth giant magnetostrictive material; and infiltrating a polymer resin to the rare earth or cutectic phase-removed void, followed by curing the infiltrated resin. Thereby, there can be provided the polymer composite, which is advantageous in that eddy current loss is decreased due to increased electric resistivity, and magnetostrictive strain is improved as well as fracture resistance is higher due to the soft and tough properties of polymer.

Description

TECHNICAL FIELD [0001] The present invention pertains, in general, to methods of preparing a polymer composite using a giant magnetostrictive material, and more particularly, to a polymer composite having various improved properties, characterized in that the advantageous structure of the giant magnetostrictive material produced by unidirectional solidification can be maintained as it is by removing the rare earth phase or the eutectic phase from the magnetostrictive material and replacing the phase-removed void with a polymer resin. PRIOR ART [0002] In general, the term magnetostriction means that a material has various lengths in response to change of a magnetic field and, as its reverse reaction, a magnetization state of the material is altered in response to external mechanical strain. Compared to PZT piezoceramic materials and nickel based magnetostrictive materials conventionally used as transducers or actuator devices, rare earth (hereinafter, abbreviated to “RE”)-transition ...

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Benefits of technology

[0016] Therefore, it is an object of the present invention to alleviate the problems in the prior art and to provide a method of preparing an aligned polymer composite, exhibiting excellent properties in high frequency ranges due to increased electric resistance and having high fracture resistance due to improved toughness of the material as well as improved magnetic properties, while a unidirectionally aligned texture of a unidirectionally solidified magnetostrictive material is maintained as it is.

Problems solved by technology

However, this alloy suffers from the disadvantages of short span life and difficult processing, due to high brittleness of a Laves phase (REFe2 phase, in which RE means a complete solid solution of Tb and Dy).

The major disadvantage of the unidirectionally solidified RE-transition metal magnetostrictive material is its low electric resistance, attributable to the metal.

Thus, since heat generation and energy loss are large due to eddy currents upon use of such a material in the ranges of high frequencies, the use of the above material is limited in the application fields requiring high frequency ranges.

But such layering process is difficult and expensive to perform because the RE-transition metal magnetostrictive material is hard and very fragile.

However, since small grains having magnetostrictive property are dispersed in a non-magnetic polymer matrix, the above composite is disadvantageous in light of inferior crystal orientation and low magnetization strength and thus much lower magnetostrictive strain, compared to the unidirectionally solidified material.

At present, the polymer composite is considerably lower in magnetostrictive strain than the unidirectionally solidified bodies, since the grains of the magnetostrictive material are very small and have poor crystal orientation.

However, such annealing process may cause the following problems, in which the RE phase or eutectic phase is melted at a temperature higher than the eutectic temperature and flows out of the material.

In the RE phase-removed structure, the magnetic properties are improved but toughness of the material become much worse because the RE phase-removed portion forms a void, and the material is easily fractured.

However, the former case is disadvantageous because of a smaller heat treatment effect, and the latter case suffers from the drawback of low toughness.

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