JPH03170382A - Production of magnetic porous bonded material of oxide - Google Patents

Abstract

PURPOSE:To obtain a magnetic porous bonded material of oxide having high dimensional accuracy and low dielectric constant without deteriorating magnetic characteristics by approximately simultaneously carrying out orientation, molding under pressure and discharge electrization bonding of flaky magnetic material of oxide having relatively large particle diameter and showing approximately a monodisperse phase while causing electric discharge between powder particles. CONSTITUTION:A flaky magnetic material 14 of oxide having 1-5mm maximum diameter, >=3 maximum diameter/average thickness and showing an approximately monodisperse phase is packed into inner space between a cell 10 comprising carbon, WC, etc., and electrodes 12 composed of carbon, etc., also used as a pressure punch. Then, given pressure is applied to the electrodes 12 by a pressurizing mechanism and the electrodes 12 are connected to an electric source 18 for bonding. The electric source 18 sends an electric current of DC to which AC is superimposed to the electrodes 12 while controlling the electric current by a regulator 20. Therefore, orientation, molding under pressure and discharge electrization bonding of flaky magnetic material are approximately simultaneously carried out while causing electric discharge to the flaky particles 22 by impression of electric voltage. Consequently, a bonded material 24 wherein particles 22 are mutually bonded directly can be inexpensively produced in an extremely short time (about several minutes) in good reproducibility.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses flake-like or filament-like oxide magnetic materials to directly bond particles to each other without using a binder by performing discharge/current bonding. The present invention relates to a method for manufacturing a porous composite body.

[Prior art] No method has yet been developed to reproducibly produce oxide magnetic materials with high dimensional accuracy, in which the crystal grains are continuous and most of the pores are open pores. . As a method for manufacturing an oxide magnetic material with high dimensional accuracy, the only known method is, for example, a method for manufacturing a resin-bonded oxide magnetic material using an injection molding method or the like.

[Problems to be Solved by the Invention] For example, in a core for a deflection yoke of a CRT display, there is a strong demand for higher dimensional accuracy in order to improve image accuracy. This type of core is large and has a morning glory shape, and there is a limit to its dimensional accuracy using the conventional ceramic sintering manufacturing process. Therefore, post-processing such as grinding was required to meet strict dimensional accuracy. A resin-bonded type using an injection molding method or the like improves dimensional accuracy, but the continuity of the bonded body deteriorates, making it impossible to obtain desired good magnetic properties.

On the other hand, for example, in cores for rotary transformers of VTRs, etc., there is a strong demand for lower dielectric constants in order to achieve wider bands as the amount of information increases. In order to achieve a low dielectric constant without impairing magnetic properties, it is most advantageous to produce a porous oxide magnetic material in which the crystal grains of the sintered body are continuous. However, if a resin-bonded structure is used, the magnetic properties deteriorate as described above.

An object of the present invention is to solve the above-mentioned technical problems and provide a method for manufacturing an oxide magnetic porous composite with high dimensional accuracy and a low dielectric constant without deteriorating magnetic properties. .

[A Thousand Steps to Solve the Problem] The present invention, which can achieve the above objects, has a maximum diameter of 1 to 5 m.
m, the ratio of the maximum diameter to the average thickness is 3 or more, and is almost a single phase, or the average length is 1 to 7I, the ratio of the average length to the average diameter is 2 or more, and is almost a single phase. A filament-shaped oxide magnetic material exhibiting a phase is used. Then, these materials are filled into a mold for forming and bonding, and while voltage is applied to cause interparticle discharge, orientation, pressure forming, and discharge/current bonding are performed almost simultaneously to form flake-like or filament-like particles. This is a method for producing a porous composite of oxide magnetic materials to obtain a directly bonded composite.

Here, the term "substantially exhibiting a single phase" refers to a single phase to the extent that no different phase is detected by powder X-ray diffraction.

In order to manufacture such an oxide magnetic material exhibiting a substantially single phase, there are a method using a solid phase reaction (dry method), a method of pulverizing a sintered body, and the like. In the case of the dry method, it is produced through the steps of mixing, calcination, and pulverization of solid powder raw materials. Ferrites other than Mn-Zn-based ferrites basically become a single phase when subjected to a certain temperature (approximately 800°C or higher, depending on the relationship with time).In the case of Mn-Zn-based ferrites, , a method of calcining under reduced pressure or vacuum, a method of forcibly removing oxygen using a reducing agent such as hydrogen or waterweed, a method of calcining the stoichiometric composition in a nitrogen atmosphere, or f?e,04 There is also a method of adding and pulverizing the mixture.

Flake materials with a maximum diameter of 1 mm or more can be made by directly shaping them by extrusion, injection molding, sheet shaping, etc., or by crushing thin plates made by these methods. can.

The filamentary material can be manufactured by extrusion molding or the like. In that case, the minimum length is limited to a few tenths of a millimeter. The material can also be obtained by crushing a long and narrow sintered body.

Discharge/current-carrying bonding uses an apparatus with the structure shown in Figure 1. Molds for sintering are made of carbon, tungsten carbide,
It is a combination of a cell 10 made of silicon carbide, metal, etc., and an electrode 12 made of carbon, etc., which also serves as a pressure punch, and its internal space is filled with a flake-shaped or filament-shaped oxide magnetic material 14 serving as a sample. A desired pressure force can be applied to the electrode 12 by a pressure mechanism 16, and the electrode 12 is connected to a bonding power source 18. Junction power supply 1
Reference numeral 8 is a device capable of supplying a current in which alternating current is superimposed on direct current, and these are controlled by a control device 20. In addition, although not shown, the cell 10 is provided with an orientation mechanism, and is configured to be able to monitor the temperature inside the cell 10 as well as the amount of deformation under pressure. As the orientation method, vibration molding method, magnetic field molding method, etc. can be adopted.

The oxide magnetic material used in the present invention has a maximum diameter of 1 to 5 mm in the case of flake-like particles, and an average length of 1 to 7 I in the case of filament-shaped particles. The optimum range of the particle size to be used varies depending on the shape and properties of the particles, the dimensions of the combined body, the required properties, etc. The reason why the particle size is specified as above is that if the diameter and length are too small, such as less than 1 mm, sintering will proceed and it will be difficult to obtain open pores. Further, in the case of a filament, if the size exceeds 7 mm, it may not be possible to properly fill the mold unless the product is extremely large.

The present invention is suitable for producing Mn-Zn ferrite, NiZn ferrite, MgZn ferrite, and the like.

In the present invention, "porous" refers to a material having a porosity of approximately 10% or more. The oxide magnetic porous composite obtained by the present invention may be used as it is, or may be impregnated with a resin to improve strength.

[Function] The present invention produces an oxide magnetic material with high dimensional accuracy that is porous (porosity is about 10% or more), has continuous crystal grains, and most of the pores are open pores. A conjugate of can be obtained.

Particles are oriented and filled in the mold by vibration molding or magnetic field shaping. When a high voltage is applied to the flake-like or filament-like oxide magnetic material filled in the mold, the powder causes dielectric breakdown and discharges. This discharge energy activates the particle surface, removes dirt, etc., and cleans it. When pressurizing force is applied in such a state, the grains come into contact with each other, and electricity is generated directly in the grain network centered around the contact area, generating Joule heat. At the same time, discharge energy due to plasma impact pressure is added, and if the cell is electrically conductive, indirect current heating is also added. The particles are heated under pressure and bonded at the interface of the particles. This bonding takes place in a short period of time, on the order of minutes.

In this way, as shown enlarged in FIG. 2, the structured crystal grains 22 are oriented and continuous in a state close to surface contact (in the case of flake-like particles) or line contact (in the case of filament-like particles), Furthermore, a combined body 24 in which most of the pores are open pores can be obtained. Therefore, unlike the joining of granular materials (in that case, it is close to a point contact), the magnetic properties are improved because it is a surface or line contact.

[Example 1] Fe203 is 46 mol%, MgO is 30 mol%, M
Highly purified raw materials were weighed in a blending ratio of 3 mol % nO, 1 mol % CuO, and 20 mol % ZnO, and oxide magnetic particles were produced by a general dry method. The specific steps are as follows.

After mixing with a vibrating mill, add water using a mixer and cook for 7~
It was granulated to about 8 mmφ. It was calcined in air at 850° C. for 2 hours using a rotary kiln, and coarsely ground using an atomizer. Water was added to the coarsely ground product, which was then finely ground using an attritor and dried. A binder and a solvent were added and kneaded, and flake-like particles were produced by shaping and crushing a thin plate with a roller, and filament-like particles were produced by extrusion. These particles were sintered at 1100° C. for 2 hours in the air to provide experimental samples.

The granular particles shown as a comparative example are sintered bodies of pre-shaped products obtained by liquid granulation and granulation.

These oxide magnetic materials had a single phase in terms of X-ray diffraction. This oxide magnetic material was subjected to a shape bonding process using an apparatus having the structure shown in FIG. The experimental results are shown in Table 1.

1st table Common processing conditions are as follows.

・Joining time...1 minute ・Maximum pressurizing force...500 kg/cm2 ・Pressing speed...250 kg/cm2 ・minutes ・Heating up time...2 minutes ・Atmosphere... Air/Cell material...Carbon As seen from Table 1, the porosity of the bonded body is quite high, yet the magnetic permeability is high. Furthermore, the bonding time is only a few minutes, which is extremely efficient. As is clear from comparison with the case of the granular material in the comparative example, it can be seen that when flake-like or filament-like particles are used, the magnetic permeability increases several times, and in particular, in the case of flake-like particles, it becomes even higher. This is because the particles come into contact with each other on their surfaces, improving the continuity of the magnetic material.

The processing temperature was measured by forming a through hole in the cell from the side and inserting a thermocouple in contact with the sample. The combined body has a diameter of 20 mmφ and a height of 10 mm. The upper and lower surfaces 3
Surface grinding for each IIITR and ultrasonic machining to reduce outer diameter to 8
IIIIIIlφ, punched into a toroidal shape with an inner diameter of 6lφ,
A sample whose surface had been processed to remove strain with phosphoric acid or hydrochloric acid was used as a sample for magnetic measurement.

[Example 2] Mn-Zn ferrite material was used as a processing material. The power of the group is Fe. O,l is 52 mol%, MnO is 26 mol%
, ZnO is 22 mol%. The method for producing filamentous particles is basically the same as in Example 1 above. Discharge/current bonding was performed using materials with different average particle sizes. The measured results are shown in Table 2.

11 Table 2 The processing conditions were the same as in Example 1, except that the processing atmosphere was nitrogen gas. In this case as well, as can be seen from Table 2, the porosity of the bonded body is quite high, yet the magnetic permeability is sufficiently high.

[Example 3] A Ni-Zn ferrite material burnt out in the atmosphere was used as a treatment material. The power of the group is 49.5 for Fe2r3.
NiO is 17.7 mol% and ZnO is 32.8 mol%. The method for producing the granules is basically the same as in Example 1 above. Discharge and current-carrying bonding was performed using materials with different particle shapes. The measured results are shown in Table 3.

12 No. 3 table Note that the processing conditions are the same as in Example 1 above.

In this case as well, as can be seen from Table 3, the porosity of the bonded body is quite high, yet the magnetic permeability is sufficiently high.

[Effects of the Invention] As described above, the present invention is capable of orienting a flake-like or filament-like oxide magnetic material that is relatively large in size and exhibits an almost single phase using a magnetic field or vibration while causing an electric discharge between the particles. Because this method performs pressurization and discharge/current bonding almost simultaneously, it is possible to form an oxide magnetic porous composite in which particles are directly bonded to each other in an extremely short time (about a few minutes) without using a binder. Can be manufactured at low cost with good reproducibility. The composite obtained by the present invention has high magnetic properties because the crystal grains are continuous in planes or lines.

In the bonded body obtained in this way, netshape or near netshape is used to form and join at the same time.
) can be easily obtained. Therefore, post-processing is not required at all, or even if necessary, the amount of processing is reduced, so that processing costs can be reduced. This is particularly effective in technical fields that require high dimensional accuracy, such as cores for deflection yokes in CRT displays.

Furthermore, since most of the pores in the composite obtained by the present invention are open pores, it is possible to simultaneously achieve a low dielectric constant and a relatively high magnetic permeability. Further, it is also possible to impregnate the material with a resin afterwards to improve its strength. Therefore, it is particularly effective in cores for rotary transformers, etc., where a low dielectric constant is strongly desired.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a compact bonding device used in the present invention, and FIG. 2 is an enlarged explanatory diagram of a porous bonded body obtained by the present invention. DESCRIPTION OF SYMBOLS 10... Cell, l2... Electrode, 14... Oxide magnetic material, l6... Pressure mechanism, 18... Power source for bonding, 2
0...Control device, 22...Construction crystal particle, 24...
- Combined body.

Claims (2)

[Claims] 1. A flaky oxide magnetic material with a maximum diameter of 1 to 5 mm, a ratio of maximum diameter to average thickness of 3 or more, and a nearly single phase is filled into a mold for forming and joining, and the particles are separated by applying a voltage. A method for producing an oxide magnetic porous composite body, which comprises performing orientation, pressure molding, and discharge/current bonding almost simultaneously while generating electric discharge to obtain a composite body in which flake-like particles are directly bonded to each other. 2. A filament-shaped oxide magnetic material with an average length of 1 to 7 mm, a ratio of average length to average diameter of 2 or more, and a nearly single phase is filled into a mold for forming and joining, and voltage is applied to separate the particles. Orientation, pressure forming, and discharge while causing electrical discharge.
1. A method for producing an oxide magnetic porous composite body, which comprises performing electrical bonding almost simultaneously to obtain a composite body in which filamentary particles are directly bonded to each other.