RU2315382C1 - Method for producing polymeric magnetic compositions on nanometric ferrite particles for pieces of radio equipment - Google Patents

Abstract

FIELD: electrical engineering; high-frequency radio equipment incorporated in motor vehicle electrical equipment.

SUBSTANCE: proposed method includes production of polymeric composition that has thermoplastic polymeric matrix with nanometric ferrite particles introduced therein by way of high-speed thermal decomposition; in the process of decomposing metal-containing compounds in polymer melt the latter is subjected in addition to short-pulse electrical discharge at high voltage of 15-20 kV for 1-10 μs, pulse number being 80 to 100.

EFFECT: stabilized particle-size composition and uniform distribution of ferrites in matrix.

3 cl, 1 dwg, 1 tbl, 4 ex

Description

The invention relates to a technology for producing magnetic polymer composite materials that are widely used as magnetic components in radio engineering products and electrical systems of vehicles, various kinds of transformers, resonant structures, antennas, etc.

A technical solution is known (LI Rybkin. High-frequency ferromagnets. M., 1960, 528 p.), In which alloys of alsifer, permalloy and carbonyl iron were used as magnetic ferromagnetic powders, and the binder consisted of becquilite, polystyrene, and liquid glass, glass enamels.

Magnet plastics were obtained by mechanical mixing of magnetic powders and polymer binders in certain weight proportions with thorough mixing and subsequent mechanical pressing.

This method was later improved by additional sintering of powders and plasticizers at high temperatures (US Patent No. 5772820).

The disadvantages of the proposed methods is the difficulty both in obtaining and in regulating the particle size distribution of low-dispersed (less than 1 μm) magnetic powders, which, ultimately, fundamentally affects the quality of work of radio devices in the high-frequency radio range.

The use of various physical methods for producing films by vapor deposition (US Pat. No. 6,030,454), upon evaporation of ferrite targets by laser (US Pat. No. 5,320,881) or in vacuum (US Pat. No. 5,460,704) is difficult, as expensive equipment is required, and The resulting magnetic systems have low adhesion stability and are limited when they are implemented on large surfaces.

The closest is the invention (RF Patent No. 2239250, IPC ⁷ H 01 F 10/00), in which magnetic compositions were obtained from magnetically ordered single-domain particles ranging in size from 1 to 30 nm with a concentration of up to 50 wt.% Organometallic compounds of the form

R _x M ₁ M ₂ X _m ,

(where R _x is the organic radical, M ₁ is the transition metals Fe, Co, Ni, Mn, Cr, Cu; M ₂ is the rare-earth metals of the lanthanum subgroup, their oxides, or combinations of these metals or oxides, carbon, nitrogen, silicon, germanium, boron and copper; X _m is the volatile radical, their solutions or combinations), by the method of high-speed thermal decomposition of carbonyls, acetates, metal formates with their uniform distribution in the melt of the polymer matrix from softening upon heating and hardening upon cooling of polyethylene, polyethylene glycol, polystyrene, polik Rbonate, polyamide, nylon, nitrile, sulfochlorinated polyethylene.

According to the method proposed above, an initial mixture containing up to 45 wt.% Metal in mineral oil was added dropwise through a metering device to a reactor filled with an inert gas (argon) and a polymer binder melt. The reaction mixture at a temperature of 250-350 ° C (± 5 ° C) was intensively mixed for 60 minutes As a result of thermal exposure, the organometallic compounds R _x M ₁ M ₂ X _m decomposed into metals with the release of gaseous products of CO, CO ₂ , hydrogen and water.

The disadvantage of the invention is the following.

Nanoscale particles of ferromagnetic metals obtained from organometallic compounds R _x M ₁ M ₂ X _m have high surface energy by the method of high-speed thermal decomposition. Therefore, in the synthesis process, they spontaneously agglomerate (stick together). As a result of the technological process, up to 50% adhered metal particles with a size of 10-15 microns are formed in the polymer binder, which makes the process uncontrollable and fundamentally reduces the magnetic characteristics of the magnetic polymer composition as a whole.

The objective of the proposed method for producing magnetic polymer compositions is to ensure the stability of the particle size distribution of nanosized ferrite particles during high-speed thermal decomposition of organometallic compounds and their introduction into the polymer matrix.

The technical result is to reduce the concentration and time dispersion of nanoscale ferromagnetic metal particles and their agglomerates due to the fact that during the entire cycle of obtaining a magnetic polymer composition, the reaction mixture is additionally subjected to a high-voltage short-pulse electric discharge.

The problem is solved in that in the method for producing magnetic polymer compositions on nanosized ferrite particles for radio engineering products, including high-speed thermal decomposition of metal-containing compounds in the polymer melt, according to the solution during the decomposition, the melt is exposed to a 15-20 kV high-voltage short-pulse electric discharge, the number of pulses 80-100.

The invention is illustrated in the drawing, which shows the installation diagram for implementing the method, where:

1 - reactor with heater, 2 - stirrer, 3 - stirrer electric motor, 4 - thermocouple adjustment, 5 - thermocouple, 6 - gas inlet pipe (argon), 7 - gas outlet pipe (argon), 8 - container with a solution of a metal-containing compound, 9 - a dispenser of a metal-containing compound, 10 - electrodes of a high-voltage pulse installation.

The method is based on the preparation of a polymer composition consisting of a thermoplastic polymer matrix into which nanosized 1-30 nm ferrite metal particles are introduced by high-speed thermal decomposition with a concentration of up to 50 wt.%.

The method is as follows. Mineral oil and polymer are placed in a metal reactor with heating system 1. As the polymer, materials softening upon heating and hardening upon cooling are selected, such as polyethylene, polycarbonate, polyethylene glycol, polystyrene, polyamide, nylon, nitrile, sulfonated polyethylene, etc.

The mixture of oil and polymer while heating the reactor 1 is brought to a melt. Next, the reactor 1 is filled with an inert gas, for example argon, through an inlet pipe 6, the excess of which leaves through the tube 7. Using an electric motor 3, a stirrer 2 is turned on and a solution of the compounds is introduced dropwise through a container 8 and a dispenser 9 into the reactor 1, containing metal, such as carbonyls, acetates, metal formates, organometallic compounds of the form R _x M ₁ M ₂ X _m , where R _x is an organic radical, M ₁ is transition metals Fe, Co, Ni, Mn, Cr, Cu; M ₂ is a rare earth metal; X _m is a volatile radical, or combinations thereof.

The synthesis temperature through the controller 4 and thermocouples 5 is maintained at a level of 250-350 ± 5 ° C.

The resulting mixture is continued to be heated at the same temperature for another 60 minutes after adding the entire calculated amount of metal-containing material with continuous stirring by the stirrer 2. During the synthesis, a high-voltage pulse discharge (electro-hydraulic shock) with a voltage of 15-20 kV, pulse duration 1- 10 ms, the number of pulses 80-100.

The mixture is then cooled to room temperature, poured from reactor 1, filtered and dried in air.

It has been experimentally proved that such an effect on the resulting heterogeneous melt under the above conditions leads to the fact that each solid ferrite particle is enveloped by a system of gas bubbles that keep it afloat for a long time, preventing it from agglomerating with others. This helps to improve the wettability at the interface between the surface of the "solid particle - liquid", which provides a stronger adhesion of gas bubbles on the surface of solid particles, and, as a result, agitation and flotation. All this stabilizes and preserves the particle size distribution of particles for a long time (more than 24 hours).

The following examples illustrate but do not limit the essence of the invention.

Example 1

Iron pentacarbonyl Fe (CO) _{5 is} dissolved in mineral oil with a concentration of 45 wt.%, Placed in a container 8 (see drawing) and, through dispenser 9, is poured dropwise into reactor 1, in which polyethylene is pre-melted, and through tubes 7 and 8 Argon inert gas is passed. The synthesis is carried out with vigorous stirring of the reaction mixture in the reactor 1 with a stirrer 2 equipped with an electric motor 3. The process temperature is 320 ° C for 60 minutes The temperature is maintained with an accuracy of ± 5 ° C due to the temperature controller 4 thermocouple 5. Synthesis proceeds by reaction

Fe (CO) ₅ = Fe ↓ + 5CO ↑.

During the synthesis, a voltage of 15-20 kV, a pulse duration of 3 ms, and a pulse number of 80-100 are applied to the electrodes 10.

Example 2

To prove the effectiveness of the effect of electro-hydraulic effect on the kinetics of heterogeneous melt sedimentation, 50 ml of a 20% mixture of metal nanosized particles of iron or nickel in mineral oil immediately after synthesis was placed in a measuring cylinder with a diameter of 2 cm and a capacity of 100 ml. With sedimentation, the concentration of nanosized magnetic particles increases in time closer to the bottom of the cylinder.

As a result, it is concluded that during the synthesis of nanoparticles of ferrite powders according to the method described in the known invention (RF Patent No. 2239250, MPI 7 H 01 F 10/00), coarsening of nanosized particles was observed after 2-3 hours).

The electro-hydraulic effect on heterogeneous melts, as described in example 1, slows down the sedimentation process to five days, which makes the system more stable in time and thereby more technologically advanced.

These data are confirmed by optical methods: monitoring the process of sedimentation in the catheter lens; as well as independent physical research methods such as small-angle X-ray scattering, transmission electron and Mössbauer spectroscopy.

Studies have shown the presence in the heterogeneous melt and in the polymer matrix of up to 80% of metal particles 1-30 nm in size, which begin to slowly agglomerate after about two days and almost end after 10 days.

Example 3

The samples obtained in accordance with example 1 had a high specific saturation magnetization in excess of 40 G · cm ³ / g

Example 4

The table shows the various modes of electro-hydraulic action in the synthesis of nanoscale ferromagnetic particles of metal-containing compounds in polymer matrices. The pulse duration is 1-10 ms.

TABLE № / № п / п Electrode voltage, kV Number of pulses Note one 8-10 80-100 A large concentration and time dispersion of nanoscale ferromagnetic metal particles and their agglomerates is observed. 2 8-10 120-140 A large concentration and time dispersion of nanoscale ferromagnetic metal particles and their agglomerates is observed. 3 12-14 80-100 The concentration and time dispersion of nanoscale ferromagnetic metal particles and their agglomerates is observed. four 22-25 80-100 The decomposition of mineral oil and a polymer binder is observed. 5 22-25 50-60 The decomposition of mineral oil and a polymer binder is observed. 6 15-20 80-100 The concentration and time dispersion of nanoscale ferromagnetic metal particles and their agglomerates is minimal. Particle agglomeration begins in two days.

Claims (3)

1. A method of producing magnetic polymer compositions on nanosized ferrite particles for electronic products, comprising high-speed thermal decomposition of metal-containing compounds in a polymer melt, characterized in that during the decomposition, the melt is additionally exposed to a 15-20 kV high-voltage short-pulse electric discharge with a duration of 1-10-10 ms, with the number of pulses 80-100. 2. The method according to claim 1, characterized in that the polymer is selected as polyethylene, or polycarbonate, or polyethylene glycol, or polystyrene, or polyamide, or nylon, or nitrile, or sulfonated polyethylene. 3. The method according to claim 1, characterized in that carbonyls, or acetates, or metal formates, organometallic compounds of the form R _x M ₁ M ₂ X _m , where R _x is an organic radical, M ₁ are transition metals, are selected as metal-containing compounds Fe, Co, Ni, Mn, Cr, Cu; M ₂ is a rare earth metal; X _m is a volatile radical.