A method of manufacturing a high-density ferrite products


C04B35/30 - with zinc oxide

 

(57) Abstract:

Usage: the invention relates to the field of powder metallurgy, in particular, to methods for producing ferrite products used as cores for the memory of the computer cores of magnetic heads, current collectors and other parts of microwave equipment. Object of the present invention to provide a method of manufacturing a high-density ferrite products. The inventive when implementing the proposed method is achieved by the following technical result: increased density of products, reduced shrinkage. This technical result is achieved in the method of manufacturing a high-density ferrite products Nickel-zinc system, comprising mixing a source of oxides, briquetting, sintering material, grinding, mixing the resulting material, the introduction of a plasticizer, pressing and sintering, and extrusion is used ferrite powder composed of particles, the ratio of which corresponds to the possibility of their hexagonal or cubic close-packing. table 1.

The invention relates to the field of powder metallurgy, in particular, to methods izgotovleniyu and other parts of microwave equipment.

Known methods of increasing the density of the sintered ferrite products: introduction to press the powder of surface-active substances [1] conducting sintering in a cyclically varying redox environments at low temperatures [2] introduction to the binder of ammonium thiocyanate [3] holding isostatic pressing of powders in elastic shells [4] the rolling powder sheet and sintering in the holder under pressure [5]

In addition, known methods for producing ceramic powders having a specific particle size [6-9]

However, all the above methods of obtaining sintered products not regulated by the size ratio of the particles of the mixture subjected to pressing. As a result, between particles voids, which, even after pressing though reduced in size, but remain relatively large in volume, and the average density of the sintered material is not high enough. The presence of voids between the particles of the sintered mixture also leads to the increase in the duration of sintering and, therefore, grain growth, which affects the mechanical and electromagnetic parameters of space allcauses in mixing the source of oxides, briquetting, calcining the material, grinding, mixing the resulting material, the introduction of a plasticizer, pressing and sintering [10]

The disadvantage of this method is the lack of accounting for differences in the size of the particles constituting the mixture, which affects the parameters of the obtained material.

Object of the present invention to provide a method of manufacturing a high-density ferrite products.

In the implementation of the proposed method is achieved by the following technical result: increased density of products, reduced shrinkage.

The technical result is achieved in the method of manufacturing a high-density ferrite products Nickel-zinc system, comprising mixing a source of oxides, briquetting, sintering material, grinding, mixing the resulting material, the introduction of a plasticizer, pressing and sintering, and for pressing use ferrite powder composed of particles, the ratio of which corresponds to the possibility of their hexagonal or cubic close-packing; namely, 91,39 wt. particle radius (R) is not more than 0.25 mm, 6,53 wt. particle radius 0,415 R and 2,08 wt. particle radius 0,225 R.

In dense packs (face-centered cubic or hexagonal) for balls of the same diameter are void of two varieties of tetrahedral and octahedral. In any three-dimensional close-packing number of tetrapolar twice the number of balls, the number of octopuses equal to the number of balls.

In the void, you can place particles (balls) smaller, contiguous with the main spheres of radius R. the Radius of such a ball for tetrahedral voids (rtequal 0,225 R, and octahedral (rabout) 0,415 R. Filling of all Tetra - and octopuses in dense packings leads to an increase of the coefficient of compactness 7% Coefficient of compactness It is used to quantify the density of packing:

< / BR>
Naturally, the particles press powder or chaotic distribution, even under pressure will not fit perfectly in accordance with the geometry of the dense packing. However, as a result forming (pressing) powders of large voids (larger than the part of the one a large number of other particles, i.e. are formed parts with the structure of dense packing. Of course, voids remain, but their sizes are much smaller compared to the dimensions of the main particles, the number and size of voids close to the parameters of the dense packing. When filling these voids particles of the appropriate size factor compactness molded press-powders will increase. When sintering in this case, the shrinkage of the material will decrease, which will provide a higher density of sintered products.

In the present method are requested to specify the particle size of the ferrite powder for moulding articles: "n" particles of radius R should be "n" particles of radius rabout0,415 R and 2n particles of radius rt0,225 R which ideally should match the set of particles for the implementation of the dense packing filled with Tetra - and actually.

Since the mass of the particles is proportional to their volume, and the volume of the particles of the balls is determined by the formula:

VR= 4/3R3< / BR>
where VRthe volume of a ball of radius R, we obtain the following relation for the mass-selected particles:

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Relations (1) and (2) means that for every 100 g of particles of radius R should be taken pri that a given particle size distribution of the powder will have a more dense packing of the particles, than in the case when all particles have the same size.

For sorting of particles used sieve analysis. We assume that all the sieved particles of ferrite powder are balls of a certain radius. Then, for example, to cite the rate of 02 will be all balls with radius which procialis through the previous sieve number 0224 and, therefore, Assuming that the particle size 0,112 mm > R > 0,100 mm should be placed closest way possible to calculate the values of the radius of Oct - and tetrapolar for this case:

< / BR>
The size calculation octopuses in accordance with (3) shows that such particles will remain on the sieve number 008; for tetrapolar appropriate according to (4) will be the particles on the sieve number 0045. Then the recommended particle size must be in accordance with the relations (1) and (2) the following parameters: 100 g (91,39 wt.) powder, shot with sieve number 02 to take 7,147 g (6,53 wt.) powder sieve number 008 and 2,278 g (2,08 wt.) powder sieve number 0045.

Given the applicant's analysis of the prior art, including searching by the patent and scientific information sources and identify sources that contain information about the analogues declared ISO all the existing elements of the claimed invention, the definition of these unique prototype, as the most similar set of features analogues, has identified a set of essential towards perceived by the applicant to the technical result of the distinctive features in the claimed object set forth in the claims.

Therefore, the claimed invention meets the requirement of "novelty" under the current law. To check the compliance of the claimed invention to the requirement of inventive step, the applicant conducted an additional search of the known solutions in order to identify characteristics that match the distinctive features of the prototype of the characteristics of the claimed invention, the results of which show that the claimed invention is not necessary for the expert in the obvious way from the prior art, because of the level specified by the applicant, not the influence provided the essential features of the claimed invention transformations to achieve a technical result.

Therefore, the claimed invention meets the requirement of "inventive step" by applicable law.

The proposed method for izgotovlyayuschei, g:

NiO 10,003

ZnO 23,163

Fe2O366,834

The oxides are thoroughly mixed in a ball mill with the addition of a 10% solution of polyvinyl alcohol at a rate of 10 ml alcohol per 10 g of dry mix. From the resulting mixture under a pressure of 200 MPa pressed samples of cylindrical shape with a height of 12 mm and a diameter of 35 mm, the Samples are subjected to firing at a temperature of 900oC for 6 hours. After cooling in air samples grind. Then conduct a sieve analysis of the obtained press powder on the sieve issue 02, 008 and 0045 take (wt.):

powder with a sieve issue 02 91,39

powder with a sieve number 008 6,53

powder with a sieve number 0045 2,08

A mixture of the obtained fractions are placed in a vibrating mill for 0.5 h, and then add the plasticizer and pressed samples of cylindrical shape with a height of 12 mm and 35 mm in diameter under a pressure of 200 MPa. The sample is sintered at a temperature of 1200oC for 6 h and cooled in air.

Samples with such specified particle size distribution of press powder to prepare for the Nickel-zinc ferrites 2000 brand LV. For comparison prepared control samples ferrite of the same composition, molded from the powder, shot with only one sieve (number 02 or room 008). Before pressing the ferrite on the TIC of various sizes throughout the volume). The technology of molding and sintering the ferrite powders of particle size distribution are designed equally. Comparison based density, shrinkage test and control samples and their electromagnetic parameters given in the table.

The analysis of comparative data table allows to draw the following conclusions:

application for molding powder consisting of particles, the ratio of which corresponds to the possibility of their hexangle or cubic close-packing, allows to obtain products with high density;

the proposed method allows to reduce the time of sintering products, and thus to reduce the growth of grains. The formation of coarse-grained friable structure is complicated, and this contributes to the formation of high-density material.

Thus, the above data confirm that the implementation of the use of the claimed invention the following cumulative conditions:

means, including a claimed invention in its implementation, is intended for use in industry, namely in the manufacture of high-density ferrite products;

for the claimed invention in the form as it is described in Fig before the priority date tools and techniques;

the tool embodying the claimed invention in its implementation is able to achieve a technical result.

Therefore, the claimed invention meets the requirement of "industrial applicability" under the current law.

A method of manufacturing a high-density ferrite products Nickel-zinc system, comprising mixing a source of oxides, briquetting, sintering material, grinding, mixing the resulting material, the introduction of a plasticizer, pressing and sintering, characterized in that for pressing use ferrite powder composed of particles, the ratio of which corresponds to the possibility of their hexagonal or cubic close-packing, namely: 91,39 wt. particles of radius R is not more than 0.25 mm, 6,53 wt. particle radius 0,415 R and 2,08 wt. particles of radius R. 0,225

 

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