JPH04503591A - A method for creating very high quality magnetic materials - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] very high quality magnetic materials How to create Background of the invention The invention relates to a method for making magnetic materials of very high quality, and more particularly to Qualitatively, solid-state magnets obtained from liquid-phase solidification or solid-state diffusion near their melting temperature. Regarding sexual materials.

The production of very high quality magnetic materials encounters problems that impair the quality of the material after solidification, Among the problems, mention must be made of the influence of walls and convection phenomena in the liquid phase.

These problems are related to the coexistence of compositional, temperature or density gradients on the one hand, and to gravitational fields on the other hand. It is something that exists. Sedimentation and stratification phenomena also occur in suspensions of solids, or in immiscible Occurs in liquids containing suspensions of liquid, with the heaviest suspension moving downwards. these Various effects include lack of homogeneity in composition and defects in the magnetic material after solidification. Cause.

In order to overcome these various problems, it is important to introduce zero gravity or microgravity conditions. It is proposed that the material be produced in a satellite or in free fall in order to It has been.

However, this represents a powerful but expensive measure.

The purpose of this invention is to partially or completely resemble the situation encountered in microgravity. The present invention provides a method for producing magnetic materials while ensuring the same situation in a simple manner. Is Rukoto.

To achieve this objective, this invention has a magnetic force factor χ which includes the following steps. provides a method for preparing a sample of a magnetic compound, the steps of which include a. ) with a magnetic induction gradient dB/dz, where B, dB/dz is at the selected reference axis. The magnetic force (χ, B, dB /dz)/μ0 provides a perpendicular magnetic induction B such that it is higher than the weight, and To, b) heating at a temperature close to the melting temperature.

According to a feature of the invention, after step (b) the magnetic induction B and the magnetic induction gradient are There follows a step consisting in cooling the sample in the presence of the distribution dB/dz.

According to a first embodiment of the invention, the sample is heated to a melting temperature during step (b). heated at a higher temperature.

According to a second embodiment of the invention, the sample is heated to a melting temperature during step (b). It is heated at a lower temperature and adapted to increase the internal diffusion of atoms.

Brief description of the drawing The foregoing and other objects, features and advantages of this invention will be apparent from the preferred embodiments illustrated in the accompanying drawings. Of the figures, FIG. , a perspective view of an assembly illustrating a first implementation according to the invention; Figure 2 shows the strength of the magnetic induction generated by the coil along the axis and this magnetic induction Let the induced accumulation due to the slope of and further, FIG. 3 is a cross-sectional view of another assembly illustrating a second implementation according to the invention. Ru.

Detailed description of the invention FIG. 1 shows an assembly illustrating a first embodiment of the method according to the invention. Ace The assembly includes a coil l. The Cartesian coordinate system (x, y, z) is The origin is at the center of the equally spaced coils. The coil is aligned with the two reference axes. is placed so that its corresponding axis is oriented along the gravitational field, and this orientation is referred to below as It's called "Naono".

A cylindrical crucible 2 is introduced into which the magnetic material in solid or small powder form is introduced. However, in coil l, the crucible axis coincides with the coil axis, and the bottom 4 of the crucible is at position z= It is positioned above 0. The material is initially placed at the bottom of the crucible at Z=2. high placed in the Crucible 2 is vertically displaceable and made of non-magnetic material . A furnace (not shown) is provided within the coil and surrounds the crucible.

First, the current is applied to the coil in order to generate positive magnetic induction in the selected reference frame. is allowed to flow. The induced strength B on the Z axis is a function of the height Z in Figure 2. is shown.

The induction is maximum for z==0 and decreases progressively with increasing absolute value of 2.

Therefore, for Z values different from zero along the coil axis, the magnetic induction B However, on the other hand, there is a magnetic induction gradient dB/dz. Outside the axis, the magnetic induction gradient dB/d Magnetic induction B1 vertical gradient dB/dz and horizontal component of x and dB/dy are weight be done.

If a magnetic material has a positive magnetic coefficient χ, as is the case for paramagnetic compounds, , magnetic materials have a force (x, B (Z,), dB (Z,)/dz )/uO (μ0 = 4π, 10-' in international units -1, U).

The curves representing B, dB/dz as a function of the position Z on the coil axis are also shown in Figure 2. expressed. Induction is always positive.

For Z values smaller than zero, the induction increases as 2 approaches zero; The induced slope is positive. Therefore, B, dB/dz and such magnetic force (χ, B, dB/d2)/μ0 is positive because the magnetic force factor is positive. They are induction songs Position 2 = 2, which corresponds to the maximum slope area of the line. , the maximum value is reached. Positive 2 For values, the induction is positive and its strength decreases as Z increases.

The slope is negative. B, dB/dz and the magnetic force (χ.

B, dB/dz)/μ0 is negative. They are the region of highest negative slope on the induction curve A second maximum value is reached for position 2 corresponding to .

In the selected axis system, the weight is negative. Therefore, the magnetic force (χ, B, dB/ dz)/μ0 is the opposite of the weight when the force is positive, that is, for χ values smaller than zero. It is a pair. If this magnetic force has a strength higher than the strength of its weight, the magnetic compound , will be raised until magnetic and gravitational forces are in exact equilibrium. Figures 1 and 2 are The sample is curve B, dB/dz 2=2. The position placed below the maximum value in 2. It shows the case where it is raised from the ground and stopped at the equilibrium position of 2=21.

During the second step, the sample is heated above its melting temperature. Compound Z is a liquid Can be turned into a magnetic compound. Figure 1 shows that the position of the compound according to the direction Z is the transformation into a liquid. This shows the case where there is no actual change. , however, the magnetic coefficient of some materials may decrease substantially as temperature increases. of the sample in the crucible The height then tends to decrease even though B, dB/dz increases. . By adjusting the induction amplitude, the magnetic force corresponds to the maximum value of the force, at position 2 = 21, the material It is also possible to make the ingredients stimulating.

The existence of a magnetic induction gradient along direction 2 implies the existence of an induction gradient along the horizontal direction , because the relation divB=δB/δX+δB/δy+δB/δ2=0 is not followed. This is because it has to be done. Therefore, the equilibrium is stable on the Z axis, but the horizontal attraction A guiding gradient creates a force that tends to cause magnetic material placed outside the Z-axis to deviate outward. to be accomplished.

The ends of crucible 2 keep the material close to the central coil axis. Thicker material on the outside The shape of 3 is caused by the horizontal induced gradient and the resulting force.

In the previous section, paramagnetic compounds with a positive magnetic power factor have been considered. anti When the magnetic material χ is 0, the equilibrium position in the levitation state corresponds to two positive values, and the A planar induced gradient immediately tries to pull back the area of material outside this axis in the direction of the Z-axis. do.

For example, it is made of niobium-titanium (NbTi) and niobium-tin (Nb, Sn). A superconducting coil with multiple filaments has a high magnetic induction of about 12-18 Tesla. used to generate. The inner diameter of the fill is in this particular case for H=127. slightly higher than 0°05m for 1/10m and H=18T (selected Ru. Cumulative B, dB/dz values range from zero for z=0 to about 0.0 for each coil. The coil varies from 500 to 2000 T”/m for a height of 1 m2. , an annular cylinder that brings a hollow cylinder with a diameter equal to 0.1-0.03 m to standard temperature. located within a cryostat (not shown). Such B, d With the B/dz value, the magnetic compound is ``If the weight is 1.U,/kg, it will float easily.These χ values are based on the or liquid magnetic compounds (water, ice, acetone, ethyl alcohol, some tungsten (e.g. protein quality).

Most elements of the periodic table, and especially gold oxides, actinides and transition metals, , at the melting temperature, 2.　I　O-”1.　U.

/k has a higher magnetic susceptibility than g. For example, holmium is found in superconducting materials. Although it is easily contained in gold, it has a melting temperature of 6.2X10-' at a melting temperature of 1°46BiC. 1. It has a magnetic susceptibility of U,/kg.

Moreover, some magnetic materials can be set in a levitating state to achieve high It is not necessary to have magnetic induction. Compounds like iron-carbon alloys Objects tend to levitate under the induction of 2°3 Tesla because the magnetic susceptibility of molten iron is very high. high, or about 3.2X10-71. This is because U,/kg.

Therefore, with the method according to the invention, obtaining the levitation state in a particularly simple way is possible. Preferably, the material is in a floating state while in a solid or solidified state. set up, and it is heated in front of the induction and induction gradient and then cooled. It will be done. Therefore, this method can be made from a very large number of magnetic materials, especially conductive liquids. gives better homogeneity of ingredients and fewer defects.

In the particular case of diamagnetic materials, the material is set in the levitation state while in the solid state, and to liquefy it and then solidify it again to avoid the material coming into contact with the crucible walls. . In fact, the droplets or large drops of liquid obtained after melting are similar to those seen above. Under the influence of forces associated with horizontal field gradients, sea urchins tend to concentrate automatically. deer However, if we start with the material in the liquid state, these forces will overcome the wetting forces. There's enough to do. As an example, we are dealing with a protein solution that is a solidified liquid (ice). , protein crystal growth in a manner similar to that achieved within the space shuttle. It would therefore be possible to achieve this.

On the other hand, in a liquid of fixed magnetic susceptibility containing materials with similar magnetic susceptibilities, of a material set in a suspended state according to the invention in a solid or liquid suspension. Molecules may remain in suspension regardless of size or weight. these situations Does solidification occur without stratification or precipitation, whatever the meltability of the liquid? Maybe. Therefore, compounds containing precipitates homogeneously distributed in the matrix It is possible to obtain.

Another advantage of this invention is that crystal growth or oriented synthesis of materials can be carried out in a suspended state. What is achieved is that if the material is at its melting temperature, i.e. the axis on which it is most likely to be magnetized with respect to its crystal structure, This is possible if magnetic anisotropy is maintained. Therefore, for example, TmBa* Cut 07-Yo type crystals or very homogeneously oriented polycrystalline compounds, Depending on the cooling rate, it would be possible to form.

According to an embodiment of the first application of the method according to the invention, magnetic induction and magnetic induction gradient In addition to temperature gradients that tend to facilitate the movement of molecules, bubbles, or atoms, transfer can lead to phase separation or purification, and if temperature gradients If the direction of growth associated with is compatible with the direction increased by the magnetic field, then It is possible to achieve granularity. So, oriented ceramic, oriented It is possible to obtain oriented polycrystals or bulk crystals.

FIG. 3 is a cross-sectional view of another assembly illustrating a second application of the method according to the invention. be. Coil 11 is placed within gliostat 12. solid made of magnetic material bar 13 is introduced into the coil such that its central axis substantially corresponds to the vertical coil axis. It will be done. The bar is held by retaining means 14 on both sides of the coil, which move the bar up and down. Permits vertical displacement.

For example, heating comprising a second coil 15 placed between the bar and the cryostat The means melt (or A floating) region 16 is formed. Such floating regions purify the material and allow crystal growth. used for For example, regarding coil heating by moving the bar up and down. The associated motion of the bar provides a more homogeneous material over the entire length and the melted area is set to state.

Moreover, in a gravitational field, the weight of a liquid decreases if the size or weight of the liquid portion increases. This will cause the molten region to deform and break, because the surface tension This is because it allows it to withstand only a small height. Therefore, in practice For all materials except Recon, the height of the melting zone is 2-3 cm. Not more than about 1 centimeter relative to the area diameter. When there is no gravity, the melting region The height of can reach the value πd, where d is the diameter of the melting zone. Therefore Therefore, the melting area capacity can be increased very significantly, thereby increasing the processing and Greatly increases crystal growth efficiency.

Moreover, in the method according to the invention, the flotation step and the heating step can be reversed. is possible. Therefore, in the first step, the sample of magnetic compound is heated to convert it into a liquid, and then in a second step, magnetic induction and It is possible to set up a liquid levitation condition by providing a magnetically induced gradient.

According to a variant of the method according to this invention, magnetic induction and magnetic induction gradients are set A sample of a magnetic compound is heated near but below its melting temperature. After improving internal diffusion, it is cooled. Diffusion transport of suspended material allows atoms to be rearranged and distributed more homogeneously. In that case, the sump solid or dilute samples consisting of small or not-so-small powders. It is easy to become lewd.

Various variations and other modifications will occur to those skilled in the art. For example, lower Applying magnetic induction and magnetic induction gradients in liquids at lower gravity conditions It is possible to set magnetic materials in suspension, thus suspending lower weight molecules. It might be enough to make it liquid.

Similarly, fiber-like molecules with shape anisotropy, or magnetic anisotropy, It has already been shown that for molecules placed in a liquid, a magnetic field allows for the orientation of these molecules. It is knowledge.

In accordance with this invention, this orientation is improved by setting the levitation so that the density difference is allows working with liquid/molecular bonds that do not permit suspension states.

international search report international search report FR9000724 S^　41275

Claims (10)

[Claims] 1. A method of preparing a sample of a magnetic compound having a magnetic susceptibility x, the method comprising: a) has a magnetic induction gradient dB/dz; x. B. dB/dZ is the selected reference axis such that the magnetic force (x.B ．． dB/dz)/μ0 is such that the vertical force is higher than the weight of the sample subject to said force. providing a magnetic induction B; and b) heating at a temperature close to the melting temperature. and a method including. 2. The sample is in a solid state, i.e. step (a) is followed by step (b). The method according to claim 1, sometimes set in a suspended state in a magnetic field and a field gradient. Law. 3. After step (b), in the face of the magnetic induction B and the magnetic induction gradient dB/dz 3. The method according to claim 2, followed by a step consisting in cooling the sample. 4. The sample is heated above the melting temperature during step (b). , a method according to claim 3. 5. The sample is heated during step (b) below its melting temperature. 4. The method according to claim 3, wherein the method is adapted to enhance the internal diffusion of atoms. 6. The magnetic induction B and the magnetic induction gradient dB/dz are caused by the coil (1). The sample (3) is contained in a cylindrical pot (2) made of a non-magnetic material. In some cases, this sump is positioned within said coil, and its axis corresponds to the coil axis. , a method according to claim 4. 7. The magnetic induction B and the magnetic induction gradient dB/dz are generated by the coil (11). The sample is supplied by heating a portion of the magnetic bar (13) locally. formed by a molten region (16) obtained by Accordingly, in the coil along the vertical direction to displace the melting area along the magnetic bar. 5. The method according to claim 4, wherein the method moves at 8. The method according to claim 6, wherein the sample is a superconducting material comprising holmium. . 9. The method according to claim 6, wherein the sample is a compound consisting of an iron-carbon alloy. . 10. The sample is subject to magnetic induction and magnetic induction gradients as well as magnetic gradients. , a method according to claim 6 or 7.