RU1841349C - Method for producing ferrite materials - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: invention relates to the field of radio engineering, in particular, the technology of manufacturing radio-absorbing materials based on ferrites and ferritodielectrics.

The claimed method for obtaining ferrite materials includes the preparation of the charge, its firing, grinding, preparation of press powder, pressing and sintering of products. After grinding the burnt charge, 5-50% of the resulting powder is subjected to additional firing at a temperature 50-150°C above the sintering temperature. The preparation of the press powder is carried out by introducing an additional burnt powder with a particle size of 15-40 microns into the powder obtained after grinding.

EFFECT: technical result is an increase in the magnetic properties of ferrite material.

1 cl, 2 dwg

Description

The present invention relates to the field of radio engineering, in particular to the technology of manufacturing radio-absorbing materials based on ferrites and ferritodielectrics. The proposed solution can be used to control the electromagnetic parameters of ferrites with a rectangular hysteresis loop, with a high initial magnetic permeability (μ _n ) and ferrites used in microwave devices, since the characteristics of the microstructure largely determine the level of electromagnetic parameters of these types of ferrites _; including changing the coercive force, reducing magnetic and electrical losses, increasing the activity of ferrite elements.

Known ways to influence the microstructure by introducing various kinds of additives (see ed. mon. USSR No. 1841347, MKI H01F 1/10, and ed. mon. USSR No. 1841348, MKI H01F 1/12).

In the first, by adding copper oxide, some operational parameters of the radio-absorbing ferrite material were improved (reflection coefficient decreased, the operating range expanded, mechanical strength increased), but at the same time, the addition of copper oxide led to a decrease in the Curie temperature of the material, as well as to an increase in the temperature coefficient of the initial magnetic permeability - T _to μ _n , which accordingly worsened the temperature stability of the operational parameters of the ferrite.

In ed. certificate No. 1841348 in the composition based on Nickel-manganese-magnesium ferrite was added indium to reduce the coercive force - N _with .

However, along with the positive effect of reducing the value of H _with the introduction of the addition of indium led to a decrease in the squareness coefficient, the squareness of the hysteresis loop, and also to an increase in the temperature coefficient of the initial magnetic permeability - T _to μ _n .

In addition, with the help of the mentioned methods of influencing the microstructure, it is not possible to accurately control the size and grain composition of the microstructure of the finished ferrite products.

The closest to the proposed method is the method of regulating the microstructure, described in the book of Rabkin L.I. and others. "Ferrites", ed. "Energy", Leningrad, 1968, in which to improve the electromagnetic parameters of ferrites, a change in the temperature regimes of sintering and the introduction of various kinds of additives were used.

The known method includes the following technological operations: preparation of a mixture of powdered oxides; mixing and grinding of raw materials, drying of the mixture, briquetting of the mixture, pre-burning of briquettes, grinding of burnt briquettes, preparation of press powder, pressing of products, drying and sintering of products.

The disadvantage of this method is the limited ability to control the microstructure due to the fact that the temperature range of sintering is limited, on the one hand, the possibility of thermal decomposition of ferrite, and on the other hand, it has a significant effect on the density of the sintered material and its mechanical strength.

Thus, the purpose of the present invention is to expand the possibility of regulating the structure-sensitive parameters of ferrites by controlling their microstructure, i.e. production of ferrites with a given grain size with their high uniformity in size.

This goal is achieved by the fact that from 5 to 50 wt. 5÷10 times larger than the particle size of the main fraction of the ferrite powder - the product of the first firing. In order to avoid secondary recrystallization, the introduced particles are fired at a temperature of 50÷100°C higher than the firing temperature of finished product compacts.

In this case, to limit the growth of particles of the main fraction of the ferrite powder, finely dispersed up to 1 micron refractory oxides are introduced into the press powder, for example, aluminum oxide in an amount of 1-3 wt.%.

To achieve a uniform distribution of the introduced powders over the volume, the mixture is thoroughly mixed in mixers and then the products of the required shape are pressed.

In the proposed method for the manufacture of ferrites in the process of sintering compacts of finished products, recrystallization is practically absent and the microstructure of the ferrite corresponds to the granularity of the press powder.

The percentage of introduced particles in the press powder determines the final grain size in sintered ferrite, and their uniform volume distribution determines the required high uniformity of grain size distribution in sintered ferrite, and their uniform volume distribution determines the required high uniformity of grain size distribution in sintered ferrite. ferrite. The size of the grains formed determines the value of the coercive force - H _c , the initial magnetic permeability - μ _n of the material, and the degree of uniformity of grain size distribution - the values of the squareness coefficient - α, squareness - R _S of the hysteresis loop and the temperature coefficient of the initial magnetic permeability - T _to μ _n .

Thus, it is possible to obtain the required microstructure in ferrite products, corresponding to the optimal performance.

An example of a specific implementation can be an improvement in electromagnetic parameters, for example, a decrease in the level of microwave losses and the magnitude of the control constant fields of ferrite brand 3C415 composition (in wt.%):

iron oxide 68.11 magnesium oxide 15.23 copper oxide 10.72 manganese oxide 3.77 nickel record 2.17

The preliminary firing of the mixture was carried out at a temperature of 900±20°C for 2 hours.

Introduced particles with a size of 25 μm were prepared from a ferrite powder - a product of secondary firing, fired at a temperature of 1250 ± 30°C and introduced into the press powder. At the same time, aluminum oxide was introduced into the press powder in an amount of 1% by weight of the press powder.

To achieve a uniform distribution of the introduced particles by volume, the press powder, which contained large and small particles in the required ratio, was subjected to mixing in a mixer.

The blanks were pressed using a hydraulic press at a pressure of 1.5 t/cm ² . Roasting of workpieces was carried out at a temperature of 1150±30°C for 20 hours.

Some parameters of ferrite 3S415 are given in Table. 1.

Table 1.

Another example of a specific implementation may be the use of the proposed method in order to increase the initial magnetic permeability - μ _n (gf/e) ferrite grade 2000 NM without changing the temperature stability of its performance parameters. The preliminary firing of the mixture was carried out at a temperature of 1000°C for 5 hours.

Introduced particles with a size of 30-35 μm were prepared from ferrite powder - a product of secondary firing, fired at a temperature of 1350 ± 10 ° C and introduced into the press powder. At the same time, aluminum oxide was introduced into the press powder in an amount of 2% by weight of the press powder. The press powder with the introduced particles was mixed in the mixer.

The workpieces were pressed using a hydraulic press at a pressure of 2 t/cm ² , and the workpieces were fired at a temperature of 1300°C±10°C for 8 hours.

Some parameters of ferrite 2000 NM are given in Table. 2.

Table 2.

The use of the proposed method for producing ferrite materials provides the following advantages in comparison with existing methods:

- the possibility of obtaining ferrite materials with a given microstructure, determined by a complex of structure-sensitive properties and a large grain size uniformity without changing the temperature stability of ferrite elements made from these materials;

- reduction of magnetic and dielectric losses - tg δ _m and tg δ _d ;

- increase in α, R _S of materials and decrease in Tk μ _n , i.e. increasing the noise immunity of manufactured elements, which will significantly improve the quality and reliability of devices using ferrite elements.

Claims (1)

A method for producing ferrite materials, including the preparation of a charge, its firing, grinding of the fired charge, the preparation of press powder, pressing and sintering of products, characterized in that, in order to increase the magnetic properties of the ferrite material, after grinding the fired charge, 5-50% of the resulting powder subjected to additional calcination at a temperature of 50-150°C higher than the sintering temperature, and the preparation of press powder is carried out by introducing additionally calcined powder with a particle size of 15-40 μm into the powder obtained after grinding.