A method of obtaining a magnetic powder material based on carbonyl iron

 

The invention relates to powder metallurgy, namely, to obtain magnetic powder materials intended for the manufacture of composite radar absorbing materials and coatings in the range of microwave frequencies. In the proposed method, including the grinding of carbonyl iron powder in a protective environment in high-energy grinding unit and post-processing, according to the invention, the grinding is carried out at specific kinetic energy impact of grinding media on the material being processed from 65 j/kg up to 600 j/kg to obtain a scaly shape of the powder particles with a specific surface area of not less than 1.4 m2/g and the value of the tangent of the microwave magnetic loss is not less than 1.0, when the production of these composites containing milled powder carbonyl iron. The method provides an improvement of microwave magnetic losses and efficiency of radar absorbing materials based on it. 8 C.p. f-crystals, 1 Il.

The invention relates to powder metallurgy, in particular to obtain magnetic powder materials intended for the manufacture of composite radar absorbing materials and coatings in the range of ultra-high frequencies (who by electronic means to enhance noise immunity and solve electronic compatibility, and for shielding equipment anechoic chambers for biological protection from the influence of powerful radiation, to reduce the radar signature of various objects, also in electronics and automation.

In these areas of technology as the magnetic powder material is usually used industrial brand carbonyl iron R-10, R-20, R-100, which are highly dispersed powders consisting of spherical particles with a particle size of from 2.0 to 10 μm and their agglomerates with an iron content of up to 97 wt.% (EN 2107705 C1, 27.03.1998).

The use of industrial grades of carbonyl iron particles having a spherical form, allows to derive the composites with the tangent of the microwave magnetic loss at frequencies of 6 GHz and above not more than 0.6 (the concentration of powder in the composite - 40 vol.%).

Increase the specified composite is not achieved when using as filler carbonyl iron powder obtained by the process of restoring the original carbonyl iron powder in a hydrogen environment at a temperature of 450-500With that allows you to get more pure iron with the contents of the main phase to 99 wt.%. Processing is for no change to their spherical shape and also does not lead to a substantial increase of microwave magnetic losses composites filled with these powders (Properties carbonyl ferroprobe. Overview, Y., Kiryanov, etc., M., 1974, pages 26-29).

It is known the use of high-mills type attritors for processing mixtures of powders of copper, Nickel, chromium, thorium, etc. and also for obtaining composite materials systems metal-ceramics (EN 2021382 Cl, from l5.10.1994). When this happens, the process of mechanical alloying with the formation of alloys and various composites of the original powders.

In known technology for the processing of powder materials is carried out by a dry process at high shaft speeds from 300 to 1500 rpm, at which accelerate the grinding bodies, and their collisions cause an increase of stress in the processed powders, the deformation of the particles and the motion of dislocations, which leads to a change in crystal structure and mechanochemical reactions. This process allows for mechanical alloying of powder materials, but the problem of increasing of microwave magnetic loss if this does not solve.

The closest solution is the method of obtaining a magnetic powder material based on carbonyl iron, is described in patent publication US 2002/0134282 A1). A known method of mechanical obline leads to higher static magnetic permeability of the powder material, that is, solves a similar problem, and that the proposed invention.

But if this is not achieved the required level of magnetic properties of composites to obtain radar absorbing materials with high microwave magnetic losses.

The main aim of this known method of processing carbonyl iron is the improvement of the characteristics of carbonyl iron as a pigment (luster, hiding power, and so on), and does not increase the magnetic losses based composites in the field of microwave, which is an important parameter when creating an effective stealth microwave materials. In addition, this method requires pre-annealing of the powder carbonyl iron in the environment of hydrogen to reduce the hardness of the material.

The invention is aimed at improving the magnetic properties of carbonyl iron powders, in particular to increase the microwave magnetic loss commercial powders of carbonyl iron by the method of complex machining.

The present invention is to obtain a magnetic powder material based on carbonyl iron, which has a higher tangent microwave magnetic loss (microwave magnetic loss) by mechanical processing in vysokoenergichnym the basis of stealth and other magnetic materials.

The technical result of the invention is the increase of microwave magnetic losses that characterize the obtained magnetic powder material based on carbonyl iron, and improving the efficiency of radar absorbing materials made with its use, which will reduce the thickness and weight of the coatings.

This technical result is achieved by means of mechanical processing of powders, in which the original carbonyl iron powder in certain modes sequentially exposed to the first high-energy grinding in a protective, such as liquid, medium (organic solvent type ethyl alcohol, isopropyl alcohol, white spirit, etc). Then, if necessary, additionally to stabilize the properties of the thus obtained powders of carbonyl iron can be dry grinding, for example, in a ball mill.

When grinding in a protective liquid medium particles of carbonyl iron powder become scaly form, thereby increasing the geometric form factor of particles of iron. It reduces the lateral dimension of the particles, which leads to reduction of the effect of skanirovaniya and, as a consequence, welcomesthe (at frequencies above 6 GHz).

The invention consists in that the method for obtaining a magnetic powder material based on carbonyl iron, including the grinding of carbonyl iron powder in a protective environment in high-energy grinding unit and subsequent additional processing. Grinding carbonyl iron is carried out by exposure to high specific kinetic energy of the grinding bodies from 65 j/kg up to 600 j/kg in the treated material to obtain a scaly shape of the powder particles with a specific surface area of not less than 1.4 m2/g and the value of the tangent of the high-frequency magnetic loss of the composites filled with 40% vol. carbonyl iron, not less than 1.0 (at frequencies not lower than 6 GHz).

As high-energy grinding units carbonyl iron powders can be used in different types of attritors, planetary mill, etc.

The best option is to use as high-energy grinding Assembly attritor. When the grinding is carried out at specific kinetic energy impact of grinding media on the material being processed from 65 j/kg up to 600 j/kg

Treatment of carbonyl iron powder may be dry or the wet method in the presence of Amitai protection when grinding use organic liquid and/or inert atmosphere. In particular, as a protective environment may use a liquid containing chlorohydrocarbons, white spirit, ethyl or isopropyl alcohol, etc.

Wet grinding is carried out at a weight of carbonyl iron powder to liquid is from 0.5 to 4, and after grinding conduct further processing of the powder by drying to remove the liquid with subsequent sieving of powder on rotate or produce extra dry grinding of the powder material in a ball mill in the time interval from 1 to 24 hours.

As a protective environment for the grinding may use an inert atmosphere, in particular nitrogen.

To speed up the process of wet grinding of iron powder may be optionally used surfactants, in particular oleic or stearic acid in an amount of from 1 to 7 wt.% in relation to the weight of carbonyl iron powder.

When wet grinding powder carbonyl iron attritor use steel balls with a diameter of 5-15 mm, While the grinding is carried out in a period of 1-15 hours.

The original powder carbonyl iron industrial grades R-10, R-20 and R-F-2 is 70% vol. particle size of from 2.5 to 25 microns.

The drawing shows a distribution curve of the particles infracciones of microanalyzer. Specific surface area of the original powders of carbonyl iron is not more than 1.2 m2/,

After treatment of carbonyl iron powder by wet grinding in attritor distribution curve of the particles of carbonyl iron powder size is shifted towards larger particles (see the drawing, dotted line). In the process of spherical particles of the initial powder deformed, plushevaya, break apart and become scaly form.

To adjust the degree of grinding of the iron particles is possible by changing the process parameters, such as processing time and the specific kinetic energy impact of grinding media per unit mass of the processed powder.

The specific surface of powders of carbonyl iron after wet grinding in a high-energy mill, measured by BET method, is increased to 3-4 m2/g depending on the processing mode.

The method is as follows.

Powder industrial brand carbonyl iron with spherical particles fall asleep in high-energy grinding unit, such as attritor. Thus attritor pre-filled with steel balls and liquid medium grinding in the ratio of 0.5 to 4.0 by weight zagruzhaemoj is in the movement of the grinding body. Depending on the desired values of the specific surface area of the obtained powder vary refining and specific energy impact of grinding media on the material being processed.

After a predetermined time wet grinding powder carbonyl iron unloaded and dried in a drying Cabinet at a temperature of 80To completely remove the liquid. The dried powder is sifted through a sieve or produce grinding in a ball mill dry method for disaggregation formed after drying of the agglomerates of particles of carbonyl iron powder.

The thus obtained powder determine its specific surface area, size distribution and shape of particles. To measure the values of the tangent of the microwave magnetic loss of the resulting powder made reference samples of composites containing 40 vol.% carbonyl iron in the polymer matrix.

Measurement of microwave magnetic loss of control samples of the composites is conducted according to the methods described by D. K. Ghodgaonkar et al., /EEE Trans. Ihstr. Meas., vol.39, No. 2, pp.387-394, 1990/.

The invention is illustrated by the following examples.

Example 1.

The carbonyl iron powder grade R-10 with spherical particles fall asleep in the amount of 2 kg attritor, loaded is at the carbonyl iron powder is carried out at specific kinetic energy impact of grinding bodies 80 j/kg for 5 hours in an inert nitrogen gas. Then the mill unload, the iron powder is separated from the environment of grinding and dried at a temperature of 80C. After drying, the powder material is subjected to subsequent processing is sifted through a sieve, they control the specific surface area and particle size of the powder. To determine the magnetic losses made reference samples of composites containing carbonyl iron powder 40% vol.

The specific surface of the powder material is 1.5 m2/,

The tangent of the microwave magnetic loss equal to 1.0 at a frequency of 6 GHz).

Example 2.

2 kg of the original carbonyl iron powder brand R-20 with spherical particles are loaded into attritor. Add 1.3 litres of white spirit, which is 0.5 by weight of the powder. The treatment is carried out at specific kinetic energy impact of grinding media on the powder 340 j/kg over 5 hours. After drying, the powder material is subjected to subsequent processing is sifted through a sieve and they control the specific surface area and particle size of the powder carbonyl iron.

To determine the magnetic losses made reference samples of composites containing carbonyl iron powder 40% vol.

Milled powder has a specific surface area of 3.0 and a frequency of 6 GHz for the control samples of composites containing carbonyl iron powder 40 vol%).

Example 3.

Receiving the powder material produced in attritor in white-spirit, with specific kinetic energy impact of grinding media on the original iron powder 340 j/kg and the weight of carbonyl iron powder to the weight of liquid medium from 0.5 to 2. The time of grinding vary in the interval from 1 to 15 hours. After processing in atricore the carbonyl iron powder is dried to remove the liquid. The dried powder carbonyl iron additionally grind dry method in a ball mill. Refining ask in the range of from 1 to 3 hours.

The resulting powder has a specific surface area of 3 m2/g, the tangent of the microwave magnetic losses of 1.5, i.e., has parameters similar to those of example 2, but has a higher stability of the magnetic properties.

Thus, as shown in the examples, the proposed method allows to obtain a powder of a magnetic material with flaky particle shape on the basis of carbonyl iron powder having a specific surface area of not less than 1.4 m2/g and the value of the tangent of the microwave magnetic loss of the composite filled with 40% vol. not less than 1.0 at a frequency of 6 GHz), which allows to increase the efficiency of microwave magnetic materials, made with his Imperial based on carbonyl iron, including the grinding of carbonyl iron powder in a protective environment in high-energy grinding unit and subsequent processing, wherein the grinding is carried out at specific kinetic energy impact of grinding media on the material being processed from 65 to 600 j/kg to obtain a scaly shape of the powder particles with a specific surface area of not less than 1.4 m2/g and the value of the tangent of the microwave magnetic loss is not less than 1.0, when the production of these composites containing milled powder carbonyl iron.

2. The method according to p. 1, characterized in that the high-energy grinding unit used attritor.

3. The method according to p. 1, characterized in that a protective environment for grinding organic liquid and/or inert atmosphere.

4. The method according to p. 3, characterized in that the protective environment of the use of the liquid containing the chlorohydrocarbons, white spirit, ethyl or isopropyl alcohol, which hold the wet grinding of carbonyl iron powder.

5. The method according to p. 4, characterized in that the grinding is carried out at a weight of carbonyl iron powder to liquid is from 0.5 to 4.

6. The method according to p. 1, wherein after grinding spend povodjat extra dry grinding in a ball mill in the time interval from 1 to 24 hours

7. The method according to p. 3, characterized in that an inert atmosphere using nitrogen.

8. The method according to p. 1, characterized in that during the grinding of advanced use of surface-active substances, in particular, oleic or stearic acid in an amount of from 1 to 7 wt.% in relation to the weight of iron powder, carbonyl iron.

9. The method according to p. 1, characterized in that the grinding is carried out in a period of 1-15 hours

 

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FIELD: metal powders and electrolytic condenser using the same.

SUBSTANCE: claimed method includes grinding of niobium or tantalum boring at elevated temperature in presence of at least one liquid solvent to produce niobium or tantalum powder followed by reducing treatment of powder; further grinding under the same conditions followed by forming of condenser anode from said powders. Claimed niobium powder contains 40-200 ppm of carbon and 5-200 ppm in total of iron, nickel and chromium.

EFFECT: reduced direct current leakage in niobium and tantalum; accelerated production of powder with high surface area and reduced impurities; and production of flaky niobium and tantalum.

29 cl, 4 dwg, 2 tbl, 16 ex

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