JPS5948800B2 - Method for producing magnetic refrigeration working materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing magnetic refrigeration working materials, and in particular,
The present invention relates to a manufacturing method that enables removal of a Kaloe strain layer on the surface through a simple process.

[Background technology of the invention and its problems]

Conventionally, magnetic refrigerators that utilize the magnetocaloric effect of magnetic materials are known.

This magnetic refrigerator has a higher refrigerating capacity per unit volume than a gas refrigerator, and as a result has the advantage that the refrigerator can be made smaller. By the way, in the case of a magnetic refrigerator, there is a heat exhaustion process in which the heat generated in the magnetic material is released to the outside through adiabatic magnetization, and an endothermic process in which the cooled magnetic material is removed from the cold object by adiabatic demagnetization. It is necessary to perform the two heat exchange processes alternately.

Therefore, refrigeration efficiency depends on the time required for heat exchange between heat absorption and exhaust heat. For this reason, the magnetic material, ie, the magnetic refrigeration material, is desired to have not only a large magnetic moment but also a high thermal conductivity within the operating temperature range of the refrigerator. Generally, magnetic refrigeration materials are manufactured by cutting and shaping a magnetic single crystal block, but the thermal conductivity of these materials usually increases as the temperature decreases, reaching 10 to 40. It reaches the maximum and shows a tendency to decrease as the temperature further decreases.

Then, the thermal conductivity on the lower temperature side than the above peak value is
It varies depending on the surface condition of the work material, and if processing strain remains on the surface, the thermal conductivity decreases. Therefore, when processing a magnetically frozen workpiece in a desired shape from a magnetic single crystal block, it is possible to easily remove processing distortion on the surface, producing a high-quality workpiece with good thermal conductivity. The reality is that there is a strong desire for a manufacturing method that can do this. [Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to easily remove processing distortion on the surface without complicating the manufacturing process, and to An object of the present invention is to provide a method for producing a magnetic refrigeration material that exhibits excellent heat conduction properties in an extremely low temperature region.

[Summary of the invention]

In the present invention, when a magnetic refrigeration material having a desired shape is obtained by processing a magnetic single crystal block, in the final step, a process-strained layer on the surface of the material is removed by etching. It is characterized by

〔Effect of the invention〕

By employing the above manufacturing method, the strained layer existing on the surface of the magnetic refrigeration workpiece can be easily and reliably removed.

Therefore, a magnetic refrigeration material with good thermal conductivity can be produced at extremely low temperatures without complicating the production process. [Embodiments of the Invention] Examples of the present invention will be described below.

First, a single crystal block of gadolinium gallium garnet (GGG) was prepared as a magnetic single crystal block.

Next, two rectangular parallelepiped blocks were cut out from the single crystal block, and the surfaces of these two rectangular parallelepiped blocks were finished by wrapping. Subsequently, the surface of one of the blocks was brought into contact with phosphoric acid at 160 DEG C. to remove the surface layer to a thickness of 50 to 60 .mu.m, and this was designated as sample A. The other block, which was only subjected to a wrapping finish, was designated as reference sample B. The thermal conductivities of Sample A and Reference Sample B at extremely low temperatures were measured, and the results shown in the figure were obtained.

As can be seen from the figure, it was confirmed that sample A, whose surface layer was removed by etching, had a significantly improved thermal conductivity compared to reference sample B in the temperature range of 20K or less. This is the result of the etching process eliminating the strained layer on the surface and improving the surface condition. Therefore, as in the present invention, by etching the surface of the magnetic refrigeration material in the final step, it is possible to produce a magnetic refrigeration material with excellent thermal properties. Note that the present invention is not limited to the above embodiments.

That is, in addition to GGG, Dy, AIl5O,2, Gd
By etching the surface of magnetic single crystal blocks such as 3Al, Ol2, GdPO4, Dy2Ti2O, etc. with hot phosphoric acid in the final step, we have achieved excellent thermal conductivity at extremely low temperatures. Magnetic refrigeration working materials can be produced.

[Brief explanation of the drawing]

The figure compares the thermal conductivity properties of a magnetic refrigeration material (sample A) produced by the production method according to the present invention with those of a magnetic refrigeration material (reference sample B) obtained by another production method. FIG.

Claims (1)

[Claims] 1. In obtaining a magnetic refrigeration material in a desired shape from a magnetic single crystal block by processing, the process-strained layer on the surface of the material is removed by etching in the final step. A method for producing a magnetic refrigeration working material.