SE203512C1 - - Google Patents

Description

Inventors: A L Stufits and H P J Wijn Priordet requested from June 2, 1956 (Nederldnderna) U.S. Pat. No. 2,353,331 to UM: that the process for producing magnetic cores, which are constructed of flattened metal particles by an insulating material. The particles arc arranged in layers and then sintered to each other, whereby a higher permeability is obtained with the same material that can be obtained without said arrangement of the particles. In order to possibly further improve the mode of action, the particles can mechanically continue to oscillate or be exposed to the action of a magnetic field. The fact that the effect of a magnetic field can thereby contribute to an improvement in efficiency is achieved only by the fact that the particles in question are made platformed.

Furthermore, there is a further edge, by means of which crystal particles of a ferromagnetic oxide can be oriented parallel to each other by means of a magnetic field (Philips' Technische Rundschau, 16, pages 223-224, 1954). In this case, the orientation is largely dependent on the presence of a direction of preference for the magnetization in the crystal particles. If the magnetization is strongly bound to this direction of preference, the material can be used for the production of permanent magnets. The technical effect obtained by the orientation is that due to the use of this improved method permanent magnets with a higher value of (BH), flax arise.

The invention relates to bodies with anisotropic, soft-magnetic properties of ferromagnetic wires, and to a process for their preparation. In view of the isotropic but otherwise similar bodies, the initial permeability / co (see R. Becker and W. Diking, "Ferromagnetism", 1939, p. 7) is increased at room temperature in certain directions. The process according to the invention is used for particles of ferromagnetic compounds with a non-cubic crystal structure, the single crystals of which have a preferential plan for the magnetization. The term "prefenplan" shall be explained in the following.

In the case of ferromagnetic materials with hexagonal crystal, the crystallanisotropy given by the expression Fic = sin1? 9 (1) (see R. Becker and W. Doring, «Ferromagnetismus», 1939, p. 114). If for a crystal K 1 'is positive (so-called "positive" crystalline anisotropy) in this crystal the hexagonal axis is the direction of preference for the magnetization. If, on the other hand, K, 'is negative ("negative" crystallanisotropy), this means that the spontaneous magnetization is directed perpendicular to the hexagonal axis and thus parallel to the base surface of the crystal. Furthermore, it is possible that the magnetic energy of the crystal depends on the direction of the spontaneous magnetization in this base surface. If these energy changes were small with respect to what is expressed in formula (1), the base surface is referred to as the "preference plane" for the magnetization. The direction of the spontaneous magnetization Egger in this case in each crystal in the base surface and in this surface the magnetization is much more easily rotatable than in a direction not in this surface. 22O352 In order to determine whether in a particular case these are crystals with a preference plane of the magnetization, e.g. the following attempt is made: A small amount, e.g. 25 mg of the crystal material to be examined is mixed in the form of a finely ground powder with 'Agra drops of a laminating of an organic binder or adhesive in acetone and the mixture is pasteurized on a glass plate.

The usual particle of the powder should, as far as possible, show only a single crystal orientation. The plate is arranged between the poles of an electromagnet in such a way that the magnetic lines of force go perpendicular to the surface of the plate. By increasing the electric direct current through the electromagnet, the magnetic field strength is increased captivatingly, so that the powder particles, if they have a preference plane for the magnetization, rotate in such a field that this preference plane of the magnetization runs approximately parallel to the direction of the magnetic lines. With sufficient care, agglomeration of the powder particles can be avoided. After alignment of the acetone, the powder particles adhere to the glass surface in a magnetically oriented state. With the help of X-ray examination, cla can be determined, if the intended orientation of the powder particles under the influence of the magnetic field in reality ernis. This can be done, among other things, by means of an X-ray diffractometer (for example by means of an apparatus described in) Philips' Technische Rundschau », 16, p. 228-280, 1954-55). It turns out that the ratio between the intensities of the reflections on the surfaces belonging to a single zone and the intensities of the reflections on the surfaces which do not belong to this zone, in the case of an oriented preparation Or stone On, corresponds to the ratio in the case of a non-oriented preparation.

As already mentioned, the invention relates to bodies of ferromagnetic materials, the single crystals of which have a non-cubic structure and a preference plane for the magnetization. The particles of a paver of such a ferromagnetic material, which to some extent are freely movable, are oriented in a magnetic field and fixed to a continuous unit. The intended effect appears more clearly the larger the fraction of this powder Or which consists of particles with only a single crystal orientation. Through the described procedure, in comparison with bodies in which no magnetic field was used during the production, the initial permeability will be increased in the direction of the magnetic field, often even to a considerable extent. This magnetic field does not have to be stationary titanium, it can during the described treatment other direction and / or intensity. Preferably, the particles are fixed in that they are preferably compressed in the presence of the magnetic field. Particularly good results are obtained by means of a magnetic field, which can be represented by a vector rotating in a flat surface. In this case, a greater initial permeability is obtained in each direction in this plane.

Fixation of the particles does not necessarily have to be followed by sintering. It has been found that without sintering, an increase in the initial permeability can be achieved.

Example ph (of compounds or mixed crystals of compounds consisting of) materials of which by means of the process according to the invention bodies with high initial permeability and not or only add high loss factor Or among others: a) Materials of the formula: BaM, riFel G MO 27 (in which The Ba ion is completely or partially replaced with Sr ion, the Pb ion and / or tilt at most 40 atom% with Ca ion and in which the Fe "ions can be replaced to a maximum of 1/5 with Al and / or Crions), wherein MII denotes at least one of the ions Lit + Fon 2 or a combination of these ions, in that these materials have a preference plan for the magnetization.These materials have a crystal structure, whose elementary cells in the hexagonal crystal system can be described with a c-axis ph about 32 , 8 A and an a-axis pa ea 5,9 A. b) Materials of the formula: Ba3m, riFe241110 „(whereby Ba can be replaced to a maximum of one third of Sr, maximum to one-fifth of Pb and maximum to one-tenth of Ca), where MI 'denotes at least one of ions rna Fen, LiI FeIII Nil ', Znit, MgII, or a combination of these ions, in which these materials exhibit a preferential plan for the magnetization. These materials have a crystal structure, the elemental cells of the hexagonal crystal system can be described with a c-axis of about 52.3 A. and an a-axis of about 5.9 A. c) Materials of the formula: B aMIIFe, II IO ", Wherein Ba" can be replaced up to a maximum of half with Sr, up to a quarter with Ca or Pb or also a combination of these, wherein Fe "can be replaced up to a tenth with Al and / or Cr and wherein at least one of the ions Mnir , Fen, Con, Ng ', CuII, Aro or a combination of these ions These materials have a rhomboid crystal structure, the elemental cells of the hexagonal crystal system can be described by a c-axis of about 43, A and an a-axis of about 5.0 A. d) Materials of the formula: BaCoaIITiaiv Fe (122a) "019, wherein 1.0 <a <1.6 and wherein the Ba ion can be completely or partially replaced by the Sr ion, the Pb ion and / or up to 40 atomic% of the Ca ion in the material these materials have a preference plan for the magnetization. These materials have a hexagonal crystal structure.

Example I. A mixture of cobalt carbonate, Fell, MnII, Cott, Nih, znn, mg ", Ivintr, Con, Cull, 3 barium carbonate and ferric codd in a ratio of the formula Ba 2 Co 2 Fe 2 O 2 was ground for 15 hours with alcohol in a roller mill, dried then fired for 2 hours in an oxygen stream at 1050 ° C. Then the reaction product was ground again for 15 hours in a roller mill and the powder was heated again for 2 hours in an oxygen stream at 1200 ° C. 130 g of this material was finally ground with alcohol in a The crystals of the powder thus obtained had a structure whose elemental cells in the hexagonal crystal system are described by a c-axis of about 52.3 Å and an a-axis of about 5.9 Å.

A small amount of this powder was mixed with a solution of nitrocellulose in acetone. The suspension thus obtained was spread on slides and one of these slides was arranged between the pole shoes of an electromagnet. The direction of the magnetic field was perpendicular to the plane of the slide. The suspension was allowed to dry, after which an X-ray examination was performed on each one. The intensity of the radiation (coKa) was weaker on examination of the oriented powder than that of the non-oriented powder. It was found that the reflections on the surfaces which had the hexagonal axis as the zone axis compared with the surfaces which did not belong to this zone were stronger with oriented powder than with non-oriented powder. The single crystals of the powder thus had a preference plane for the magnetization perpendicular to the direction of the (hexagonal) crystallographic major axis.

In Fig. 1, the intensity I of the reflections has been indicated in an arbitrary unit as a function of the deflection angle of the non-oriented powder free, varying also the surface index (hkl) are indicated. Fig. 2 refers to the odentered powder.

From this powder various bodies were produced. la) A part of the powder was pressed without the use of a magnetic field into a ring. This ring is fired for 2 hours in an oxygen stream at 1300 ° C. Ph the ring thus obtained was measured at room temperature and Yid a frequency ph 2 kHz an initial permeability pc ay 10.4. lb) A part of the powder was pressed into a cube in a magnetic field with a field strength of about 3000 orsted, which can be represented by a vector rotating in the plane perpendicular to the direction of pressing, which has a speed of about 1 vary per second. In view of the other device, in this example and in the following examples, a rotating magnetic field was used, the plane in which the magnetic field rotates perpendicular to the pressure direction of the cube. The body is then burned for 2 hours at 1300 ° C in an oxygen stream. From the thus obtained sintering product a ring is excised, the axis of which ran parallel to the pressure direction of the body. At this ring, at room frequency at a frequency of 2 kHz, an initial permeability p., Of 29.7 was measured. In a similar way, another cube was constructed only with the difference that no magnetic field with constant intensity was used, but a rotating field which periodically after a rotation angle of 90 ° showed a maximum value of about 2000 orsted and which oscillated between this maximum yard and zero. In the sintered product thus obtained, a ring is cut, the axis of which runs parallel to the pressure direction of the body. On this ring, at room temperature at a frequency of 2 kHz, an initial permeability yo of 21.9 was measured.

A portion of the powder was pressed without any breathing ay magnetic field into a cake. After 2 hours of sintering at 1290 ° C in an oxygen stream, the initial ball permeability of the PC was measured at room temperature on a stick cut out of the sintered cake. The or correction for aymagnetization erhallna vardet ph po was about 15.

Some of the powder was pressed into a cube in a magnetic field with a field strength of about 3000 orsted, which Iran is represented by a vector perpendicular to the direction of the press at a speed of a vary per second rotating vector. The cube was sintered clarph for 2 hours in an oxygen stream yid 1290 ° C. A stay was cut from the sintered cube, the axis of which ran perpendicular to the pressure direction of the cube. At room temperature, the ph derma stay was ballistically measured the initial permeability yo, which after correction for the demagnetization amounted to about 30.

Some of the powder was pressed into a cake under the influence of a magnetic field with a field strength of about 5000 orsted, which during the pressing was continuously directed in the pressing direction. The cake was then sintered for 2 hours in an oxygen stream at 1290 ° C. A stay was cut from the sintered cake whose axis was parallel to the press direction of the cake. At room temperature, the initial permeability yo was measured ballistically on the rod, which after correction for demagnetization amounted to about 24.

A portion of the powder was pressed without the use of a magnetic Mt into a ring. On the ring thus obtained, an initial permeability pc of 2.5 was measured at room temperature and at a frequency of 260 MHz. At this high frequency, the electromagnetic losses were expressed in a loss factor tg6 = - (see J. Smit and HP / le J. Wijn, Advances in Electronics, VI, 1954, p. 69, formula no. 27) less than 0 , 05.

A part of the powder was pressed into a ring under the influence of a magnetic field with a fact strength of about 3000 arsted, which path is represented by a vector rotating in the plane perpendicular to the axis of the ring at a speed of about 1 vary per second. On this ring, at room temperature and at a frequency of 260 MHz, an initial permeability of 2.8 was measured, while the loss factor tgo was less than 0.05. Example II. A mixture of zinc oxide, barium carbonate and ferric oxide in an inboard ratio of the formula BaZnFe6011 was ground for 15 hours with alcohol in a roller mill. After drying, the mixture is fired for 2 hours at 1100 ° C in an oxygen stream. The reaction product was triturated after cooling in an impact mortar, after which the smallest particles were exposed and ground for 32 hours with alcohol in a mill.

From the experiment described in Example I it was found that in the crystals of the compound BaZnFe6III011 the reflections on the surfaces which bathed the hexagonal axis as the zone axis compared with the reflections on the surfaces which did not belong to this zone of the powder whose particles were oriented under the influence of a magnetic field, were stronger in the case of non-oriented powder. The crystals thus had a preference plane for the magnetization perpendicular to the direction of the (hexagonal) crystallographic major axis. Fig. 3 shows the X-ray diagram relating to non-oriented powder, while Fig. 4 shows the diagram for oriented powder.

A portion of the powder was pressed without the use of a magnetic field into a ring. This ring is burned in an oxygen stream, the highest temperature being 1275 ° C which is maintained for about 10 minutes. On the ring thus obtained, an initial permeability 4a of 15.8 was measured at room temperature and at a frequency of 1 MHz.

A part of the powder was pressed into a cake under the influence of a magnetic field with a field strength of about 3000 orsted, which can be represented by a vector which rotates at about 1 vary per second in the plane perpendicular to the pressing direction. The cake was then heated in an oxygen stream, the highest temperature being 1275 ° C and maintained for 10 minutes. A ring was cut out of the said sintering product, the axis of which ran parallel to the pressure direction of the cake. On this ring, at room temperature and at a frequency of 1 MHz, an initial permeability p, of 34.6, was measured.

Example III. The same was true as in Example II, but with the difference that the sintering took place at 1200 ° C and not at 1100 ° C, Landes produced a powder of the compound BaZnFe6III011. This powder was pressed into two rings and fired, the particles having one ring not oriented, but the particles having the other ring oriented by pressing a magnetic field during the pressing process, which can be represented by a rotating vector in a plane perpendicular to the axis of the ring. . On the first ring, at room temperature and at a frequency of 1 MHz, an initial permeability of 15.0 was measured, on the second ring under the same conditions an initial permeability p, of 30.0.

Example IV. In about the same manner as in Examples II and III and only with the difference that the sintering temperature was now 1260 ° C, a powder was prepared by the compound BaZnFe, HIO In the manner indicated in Example II, two rings were produced by pressing and sintering this powder, no magnetic field being used in the pressing of the first ring, while in pressing the second ring the powder particles were subjected to the action of a magnetic field with a field strength of c: a 3000 orsted, which can be represented by a vector, which rotates at a speed of 1 vary per second in the plane perpendicular to the ring axis. On the first ring, at room temperature at a frequency of 1 MHz, an initial permeability du, of 12.3, was measured. The second ring had an initial permeability kto of 21.3 under the same conditions.

Example V. A mixture of barium carbonate, cobalt carbonate, zinc oxide and ferric oxide in an in-house ratio of formula Ba.3CoZnFe2404 / was ground for 16 hours with alcohol in a roller mill, dried in a barrel and fired for 2 hours in an oxygen stream at 1250 ° C. The reaction product was then crushed in an impact mortar into grains with a diameter of at most 0.5 mm. These grains were ground for 8 hours with alcohol in a grinder to powder. The crystals of this powder having a structure whose elemental cells in the hexagonal crystal system can be described with a c-axis of about 52.3 A and an a-axis of about 5.9 A, showed a preference plan for the magnetization which could pavisas with the experiments described above.

A portion of the powder was pressed without the use of a magnetic field into a ring. This ring was sintered for 2 hours in an oxygen stream at 1240 ° C. At the O .

A portion of this powder was pressed into a ring under the action of a magnetic field with a field strength of 3000 orsted, which can be represented by a 1 vary per second rotating vector in a plane perpendicular to the ring axis. The resulting ring was sintered for 2 hours at 1240 ° C in an oxygen stream. At room temperature and a frequency of 155 MHz, the sintered ring had an initial permeability of 42 and a loss factor of 0.12.

Example VI. From a mixture of barium carbonate, cobalt carbonate, zinc oxide and ferric oxide in an inboard ratio according to the formula Ba3CoOan1.2 Fe24041, a mixed crystal material was ground in a manner similar to Example V, which was ground to a powder. The crystals in this powder, which had a structure whose elemental cells in the hexagonal crystal system can be described with a c-axis of about 52.3 A. and an a-axis of about 5.9 A, showed a preference plan for the magnetization which could be demonstrated. by means of the above experiments.

From this powder, in the same manner as in Example V, two rings and especially one titanium were used using a magnetic field and the other using a magnetic field. At the first ring, at room temperature and at a frequency of 80 MHz, an initial permeability of 24 and a loss factor tg6 of 0.08 were measured, and at a frequency of 155 MHz one at 26 and a tgS of 0.26. On the second ring, the axis of which ran perpendicular to the plane in which the magnetic field rotated, an initial permeability of 57 and a loss factor VS of 0.10, respectively, were measured under the same conditions. one, u „pa 61 and one tgo pa. 0.26.

Example VII. A mixture of cobalt carbonate, barium carbonate and ferric oxide in a ratio according to the formula Ba., CO2Fe240.1 was ground for 18 hours with alcohol in a rolling mill, then dried and fired for 2 hours in an oxygen stream at 1200 ° C. The reaction product was first ground for 18 hours in a rolling mill and then 8 hours in a syang mill with alcohol. The crystals of this powder showed a preferential plan for the magnetization.

A portion of the powder was pressed without the use of a magnetic field into a cake.

A portion of the powder is pressed into a cake under the action of a magnetic field having a field strength of about 2000 orsted, each field being represented by a vector rotating at a speed of 50 varying per second in a plane perpendicular to the direction of pressing.

The cakes were sintered for two hours in an oxygen stream at 1200 ° C. In the thus obtained sintering products, rings were cut out, the axes of which ran parallel to the pressure direction of the cakes. PA these rings were measured at room temperature and Yid a frequency of 3 MHz an initial permeability o of 11.4 resp. 32, 6.

The following table gives an overview of the procedures and results described in Examples I-IV.

Rotating Rotating magnetic field magnetic field with Iron- with variant in-bel intensity intensity Material No magnet-fait Ba3C0 2Fe2 40 gi BaZnFeG0i, BaZnFe6011 BaZnFea0 „Ba, Col, oZni, o Fe241 Fe2400.

Ba3Co2Fe24041.

Statency train / em 'nart magnetic field 4.8 5.0 4.8 4.8 4.7 4.8 Feed Frequency 2 kHz io 10.4 29.7 21.9 15 30 24 Example tgo in 1b 1 c 2a 2b 2c c: a 3 260 MHz 2,0,0I 3a c: a 3 2,8 0,0I 3b 5,0 1 MHz 15,8 5,0 34, 5,1 1 MHz 15,0 5,3 30, 0 1 5.0 5.2 1 MHz 12.3 21.3 IV 4.8 4.7 155 MHz a 17 42 0.11V 0.12 4.8 80 MHz 155 »24 26 0.08 0.21 VI 4.7 80 »155 a 57 61 0, 0.26 4.7 3 MHz 11.4 VII 5.0 32.6

Claims (4)

Patent claim: A polycrystalline anisotropic, ferromagnetic body consisting ay ea of a unit, under the influence of a, possibly changing or rotating magnetically folded sintered, or compressed powder material, characterized in that the single crystals in the material have a preference plan for magnetization. Ferromagnetic body according to claim 1, characterized in that as ferromagnetic materials compounds of the formula BaM, II Feionic, 27 are used (in which the Ba ion can be completely or partially replaced by Sr-ion, Pb-ion and / or up to atom% with Ca ion and in which the Fem ions can be replaced up to a maximum of 1/5 ay Al and / or Cr ions), MIT denoting at least one of the ions Fen, milli, con, Nin, 6 2 of these ions in which these materials exhibit a preference plan for the magnetization. Ferromagnetic body according to claim 1, characterized in that as ferromagnetic materials compounds of the formula Ba am2i Fe24III041 are used (in which Ba up to a maximum of one third can be replaced by Sr and up to a maximum of one fifth with Pb and maximum up to one tenth with Ca), wherein MIT denotes at least one of the ions Fe 2 in which these materials have a preference plane for the magnetization. 3. A ferromagnetic body according to claim 1, characterized in that as ferromagnetic materials compounds of the formula BaMrr peamoli are used, wherein Ba can be replaced up to half with Sr, up to a quarter with Ca or Pb, or also with a combination of the same, wherein Ferri can be replaced to a maximum of one tenth with Al and / or Cr and wherein Mu represents at least one of the ions of Mill, Feu, Corr, Ng ', cup, znii, 1 ■ 411 or a combination of these ions. 4. A ferromagnetic body according to claim 1, characterized in that as ferromagnetic materials compounds of the formula BaCOaimatv Ferii (in 2_014 are used, wherein 1.0