RU2410200C1 - Method of producing ferrite articles - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: formed billets are placed in resistance furnace, heated to sintering temperature and sintered. After sintering, said billets are removed from the furnace and cooled down to 780-800°C. After reaching said temperature, billets are subjected to electron beam penetration radiation at 780-800°C for 50-60 minutes, along with ultrasound effects at 0.15 to 5 MHz. Now, the billets are cooled to room temperature.

EFFECT: higher dielectric coefficient and reduced loss tangent of ferrite.

1 dwg, 1 tbl

Description

The invention relates to the field of powder metallurgy and can be used in the electronic and radio industries in the production of ferrite materials and products.

The closest adopted for the prototype is a method of manufacturing ferrite products (RF Patent No. 2287403, IPC 7 H01F 1/10, 1/34, publ. November 20, 2006, bull. No. 32).

The method is based on molding preforms of ferrite powder, subsequent heating of preforms by pulsed irradiation with a penetrating electron beam to a sintering temperature, exposure at a given temperature under irradiation, cooling under irradiation to a temperature of 780-800 ° C, exposure at a given temperature under irradiation for 50-60 minutes with simultaneous exposure to the workpiece by ultrasound with a frequency of 0.15 to 5 MHz and subsequent cooling to room temperature under irradiation.

The disadvantage of this method is the low dielectric characteristics of sintered ferrites.

The objective of the invention is to improve the dielectric characteristics of ferrites, in particular the dielectric constant and the dielectric loss tangent.

The solution to this problem is proposed to be carried out by a method of manufacturing ferrite products, which, as in the prototype, preforms are formed from ferrite powder, the preforms are irradiated with a penetrating electron beam at an irradiation temperature of 780-800 ° C for 50-60 minutes with simultaneous exposure to the workpiece by ultrasound with a frequency of 0.15 to 5 MHz, cool the workpiece to room temperature.

In contrast to the prototype in the proposed method, after molding, the preforms are sintered in a resistance furnace, then they are cooled to a temperature of 780-800 ° C, at which the preforms are irradiated with a penetrating electron beam and exposed to ultrasound, after which the preforms are naturally cooled to room temperature.

During sintering of ferrite products, their dielectric characteristics are formed, such as dielectric constant and dielectric loss tangent. In the production of ferrite products in the microwave range, these dielectric characteristics of the products are important, since they determine the amount of electrical loss in the material of the products when operating in the microwave range. In general, the dielectric characteristics of ferrite products are determined by their oxygen stoichiometry. The higher the stoichiometry, the higher the dielectric constant and the higher the quality of the sintered products. The direction of the redox processes in ferrite depends on temperature. Under atmospheric conditions, at a temperature equal to the sintering temperature, the recovery process prevails, i.e. oxygen leaves the ferrite billet (oxygen stoichiometry decreases), and during cooling of ferrite products the reverse process is observed - oxidative. During cooling, the ferrite is saturated with oxygen and, as a consequence, an increase in oxygen stoichiometry. The most intense absorption of oxygen from the surrounding atmosphere is observed in the temperature range of 780-800 ° C.

In the prototype method, at a sintering temperature, radiation exposure by a penetrating electron beam enhances the recovery process, thereby reducing even more stoichiometry of the workpiece in oxygen compared to thermal sintering at the same temperature. Due to the high efficiency of the recovery process during irradiation with a penetrating electron beam, the degree of decrease in stoichiometry is high. This leads to a decrease in the efficiency of exposure to a penetrating electron beam and ultrasound at a workpiece temperature of 780-800 ° C, aimed at increasing the oxygen stoichiometry of the sintered workpiece. As a result, in the prototype method, the highest possible values of the dielectric characteristics of sintered ferrites are not achieved.

This disadvantage is eliminated by introducing a sintering operation in a resistance furnace. In this case, before starting the billet exposure under irradiation with a penetrating pulsed beam at a temperature of 780-800 ° C, they have a greater oxygen stoichiometry, which contributes to obtaining the highest dielectric characteristics of the finished products.

In this case, cooling after exposure to irradiation with a penetrating pulsed beam at a temperature of 780-800 ° C is sufficient to naturally occur in air, since with decreasing temperature the diffusion processes in the material of the workpieces sharply slow down, which makes the use of a penetrating electron beam at this stage ineffective.

The drawing shows a schematic illustration of a plant for sintering ferrites.

Table 1 presents the results of measurements of the dielectric and electromagnetic characteristics of samples prepared by the proposed method and the prototype method,

where ε is the dielectric constant

tgσ is the dielectric loss tangent,

B _m is the saturation induction,

B _r - residual induction,

H _c - coercive force.

The method was carried out using an installation for sintering ferrites, a schematic representation of which is shown in the drawing.

The installation contains an electron accelerator 1 (UE), a resistance furnace 2 (PS), a device for moving samples 3 (UPR), a support for samples 4, an ultrasonic generator 5 (UG), a waveguide link 6.

Under the outlet (not indicated) of the electron accelerator 1 (UE) there is a stand for samples 4, which, using the sample transfer device 3 (UPR) located outside the electron beam region, can move workpieces located on its surface or into the volume of resistance furnace 2 (PS) ) located also outside the region of incidence of the electron beam, or in the plane of incidence of the electron beam. When the blanks are located in the plane of incidence of the electron beam, the support for samples 4 is lowered by means of a device for moving samples 3 (UPR) to the end of the waveguide link 6 connected by the opposite end to an ultrasonic generator 5 (UG) located outside the region of incidence of the electron beam.

Electron Accelerator 1 (UE) is an ILU-6 pulsed electron accelerator, which makes it possible to obtain, under atmospheric conditions, a pulsed electron beam with an energy of up to 2.4 eV with a beam current of up to 800 A, a pulse duration of up to 600 μs and a pulse repetition rate of (2-50) Hz . The resistance furnace 2 (PS) is an industrial resistance furnace of the SNOL type with a maximum heating temperature of 1600 ° C. As the ultrasonic generator 5 (UG), the PMS1-1 magnetostrictive transducer was used. As the waveguide link 6, a metal plate made of 40X steel was used. The sample transfer device 3 (UPR) is a movement mechanism provided with an external control panel (not shown).

The proposed method was carried out as follows.

They took a ferrite powder composition, wt.%:

LiCO ₃ - 10.71,

TiO ₂ - 13,

MnCO ₃ - 2,

ZnO - 3.8,

Bi ₂ O ₃ - 0.22,

the rest is Fe ₂ O ₃ .

A 10% aqueous solution of polyvinyl alcohol was added to the powder in an amount of 12% by weight of the powder, and it was first wiped through a 0.9 sieve and then through a 0.45 sieve.

The obtained powder was placed in the mold and the PGR-10 press formed the blanks in the form of tablets with a thickness of 3 mm and a diameter of 16 mm. The density of the workpieces is 3.0 G * cm ^-3 .

The pressed billet was placed on a sample stand 4 and placed using a sample transfer device 3 (UPR) into the volume of a resistance furnace 2 (PS), preheated to a temperature of 1010 ° C, equal to the sintering temperature of the billets, and kept at this temperature for 60 minutes. Then, using the device for moving samples 3 (UPR), the support for samples 4 together with the workpiece was moved to the plane of incidence of the electron accelerator 1 (UE) beam at a distance of 30 cm from the outlet device (not indicated). During the natural cooling of the billet, its temperature was controlled by a Pt-PtRh thermocouple and a PP-63 potentiometer. When the workpiece temperature reached 800 ° С, the electron accelerator 1 (RE) was turned on. At the same time, the ultrasonic generator 5 (UG) was turned on and the work on the workpiece through the waveguide link 6 was started with ultrasonic radiation of 5 MHz frequency.

The accelerator parameters were set as follows: the electron energy in the beam was 2.4 meV, the beam current per pulse (300-800) A, the duration of one irradiation pulse was 600 μs, and the pulse repetition rate was (2-50) Hz. Irradiation was carried out in air at normal atmospheric pressure. The temperature of the workpiece was controlled by a Pt-PtRh thermocouple and a PP-63 potentiometer.

By selecting the repetition rate of the electron pulses, the workpiece temperature was kept at 800 ° C and, fixing this frequency, the workpiece was kept at a given temperature for 60 minutes.

After the exposure time under irradiation and exposure to ultrasound, the sample stand 4 together with the workpiece using the device for moving samples 3 (UPR) was moved away from the plane of incidence of the electron beam and naturally cooled under atmospheric conditions.

The indicated sequence of actions for heating, holding in a heated state, cooling and holding at a given temperature under irradiation by a penetrating electron beam was repeated for the irradiation temperature of 790 and 780 ° C. After that, all these actions were repeated for irradiation temperatures of 800, 790, 780 ° C for other workpieces according to the prototype method.

For blanks manufactured by the proposed method and the prototype method, dielectric and electromagnetic characteristics were measured. The measurement results are listed in table 1.

The dielectric constant was measured using the RVD-T2 setup. The installation is designed to measure the complex permittivity of solid dielectric materials in the microwave range (1-5) GHz. The dielectric permittivity ε and the dielectric loss tangent tgσ were measured.

The electromagnetic characteristics of the workpieces were measured using an F 5063 ferrometer. The frequency of the magnetizing field is 50 Hz, the field magnitude is 5 E. The magnetizing and measuring windings are 40 turns each. The following characteristics were measured: B _m — saturation induction, B _r — residual induction, N _s — coercive force.

The results of the averaged measurements of the dielectric and electromagnetic characteristics of the samples prepared by the proposed method and prototype method, are listed in the corresponding columns of table 1. Averaging was carried out by measurements on 10 samples made by the proposed method and prototype method, respectively.

From a comparison of the results shown in table 1, it is seen that the dielectric characteristics of ferrite products made by the proposed method are 10-15% higher than the corresponding characteristics of products made by the prototype method. Those. the proposed method will improve the dielectric characteristics of sintered ferrites.

Table 1 Preparation method Irradiation temperature, ° С Dielectric characteristics Electromagnetic characteristics ε tgσ B _m , G B _r H _c Prototype method 800 22.3 7.5 * 10 ^-4 1721 1608 1.30 790 22.1 7.7 * 10 ^-4 1725 1610 1.29 780 22.0 7.9 * 10 ^-4 1724 1609 1.28 The proposed method 800 24.7 4.5 * 10 ^-4 1724 1615 1.31 790 24.5 4.3 * 10 ^-4 1723 1616 1.32 780 24.3 5.5 * 10 ^-4 1720 1617 1.31

Claims (1)

A method of manufacturing ferrite products, including the molding of preforms from ferrite powder, irradiating the preforms with a penetrating electron beam at an irradiation temperature of 780-800 ° C for 50-60 minutes while simultaneously treating the preforms with ultrasound at a frequency of 0.15 to 5 MHz, cooling the preforms to room temperature, characterized in that after molding the sintering of the preforms is carried out in a resistance furnace, then they are cooled to a temperature of 780-800 ° C, at which the preforms are irradiated with a penetrating electron beam and exposed terazvukom, after which the workpiece is cooled to room temperature in a natural way.

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