DE2736882A1 - Spherical ferrite powder prodn. - by spraying an alcohol suspension of ferrite powder into a hot atmosphere - Google Patents

Abstract

Finely divided ferrite-forming powder (mixt.) is suspended in alcohol and sprayed in a hot atmosp. at 700-1500 degrees C. This is followed by granulation, ferrite forming and sintering. At the bottom centre of a vertical cylinder provided with refractory lining is a slurry spraying nozzle and on top of this container is an exhaust outlet. From this hot air inlet, along the inner peripheral wall of the container, is set up a hot air guide. Through this guide, while making circular motion, a slurry is continuously sprayed from the nozzle toward the axial direction of hot air rising in the container.

Description

Method and device for the production of

Ferrite powder with spherical grain Description The invention relates relates to a method and an apparatus for producing a ferrite powder with spherical grain. In particular, the invention relates to a method and to a device for the continuous, instantaneous formation of a Ferrite powder with spherical grain.

Heretofore, a ferrite powder such as e.g.

a ferrite powder used as a carrier in a dry process copier serves has been manufactured by a process that has a number of separate steps such as a step of granulating and drying the raw material, which is generally used carried out in a spray dryer, and a separate step for sintering of the dried product, which is generally in a muffle furnace, is carried out in a rotary kiln or similar furnace.

The prior art method of the above However, the type described has a number of disadvantages. B. in general ve or three separate process steps needed. Also, you have to when the sintering is carried out in a muffle furnace, with a dwell time of at least 2h and sometimes even count from 10 o'clock. Alternatively, if the sintering is carried out in a rotary kiln cause problems such as the clinker sticking to the inner surface of the Oven or the agglomeration of the grains is often a concern. This is how the manufacturing process is homogeneous spherical grain ferrite powders suffer from a number of difficulties been accompanied.

, The invention is therefore a new method and a Apparatus for the production of a ferrite powder with spherical grain, whereby the immediate production of the aforementioned ferrite powder directly from Ferrite-forming raw materials and / or from raw materials that are formed by ferrite have, is guaranteed.

According to the invention it has surprisingly been found that all of the reaction steps required for the production of ferrite, such as granulation, the Perform ferrite formation from ferrite-forming raw materials and sintering immediately and spherical grain ferrite powder can be easily obtained by making a suspension of various raw materials that have formed ferrite or the ferrite form, produces in alcohol and the suspension is sprayed into a high temperature zone. In this way, the process according to the invention consists of the following reaction steps: (1) the step of dispersing the finely powdered ferrite-forming raw material in alcohol, (2) the process step of spraying the resulting suspension into a Hot air zone with a temperature in Range from 7000C to 15000C and (3) the step of placing the sprayed raw materials in the hot air zone are kept to the granulation, ferrite formation and sintering of the materials to be performed while in the high temperature zone.

The expression used in the description * ferrite-forming (s), finely powdered (s) Raw MaterialSienl "includes a large number of different materials. The inventors have followed many leads and thereby confirmed that almost all mixtures, which can form a compound with the general formula MO Fe 2 O 3, where M is a is divalent metal in practicing the invention Procedure can be used. Representative examples of such materials can be classified in the manner described below.

a) Oxide or carbonate type materials: combinations of (1) Fe2O3 and one, two or more types of these materials, including Mn-, Ni-, Zn-, Co, Mg, Cu, Li and similar oxides or carbonates and combinations of (1) Fe 2 O 3 and (2) one or two or more materials such as Ba, Sr and the like Oxides or carbonates.

b) Ferrite powder of the simple or complex spinel or hexagonal Type produced by reactions in the solid phase from the materials given in (a) at a temperature in the range of 8000C to 1500OC.

c) Fine-grained materials, alone or in a mixture, of ferrites of the simple spinel type with an average grain size of 5 nm to 10 nm, which are obtained by the neutralization method "according to the following equation: wherein M represents Mn, Ni, Zn, Co, Mg and like metals and R represents Na, K, NH4 and like alkali ions.

(d) Grained ferrites of the simple or complex spinel type with an average grain size of 0.1 μm to 1 μm, which were produced by the "oxidation method" according to the following equation: where M represents Mn, Co, Mg, Zn and like metals and R represents Na, K, NH4 and like alkali metal ions.

(e) hydroxide or carbonate, or a mixture of both, acting as Raw material for hexagonal ferrite can be used and the ntch of the "Mitschlagungsmethodew" produced were tun22 except for Fe one or two or more ions selected Ba, Sr2 and like ions.

Zese rdhmatenalpowder which can form ferrite or ferrite formed are then suspended in an alcohol.

A number of different alcohols can be used for this purpose will. For example, technical grade methyl alcohol, which is readily available, is suitable is used in the practical implementation of the method according to the invention. The preferable range of solids content of the pulp will be used in each individual case determined experimentally, depending on the raw materials used, the whatever process conditions used, etc., but will generally be a solid content from 10 weight percent to 70 weight percent applied.

The process steps in which this slurry is in a high temperature zone sprayed and where the sprayed materials are kept in the zone, can be done in a continuous manner if one has an apparatus is used as shown in Figure 1 of the accompanying drawings. To this Way is the production of a ferrite powder with spherical grain and with high, homogeneous quality guaranteed. The above-mentioned process steps are hereinafter with reference to the Drawing shown Device explained in more detail.

Fig. 1 shows a vertical cross section through a preferred one Embodiment of the device according to the invention, which in the practical implementation of the process according to the invention is suitably used.

FIG. 2 shows a horizontal cross section through that shown in FIG Device along plane A-A '.

Fig. 3 shows a longitudinal section through a preferred imple mentation shape of the three spray nozzle that can be used in the method according to the invention.

Fig. 4 shows a scanning type electron photomicrograph according to ferrite powder with spherical grain obtained by the process according to the invention. the Numbers in Fig. 1 have the following meaning: 1: refractory brick, 2: insulating brick, 3: nozzle for spraying the pulp, 4: hot air inlet, 5: exhaust gas outlet, 6: hot air guiding device, 7: Hole for temperature measurement (also used as a viewing hole), 8: Outlet for the Reaction product.

As can be seen from these drawings, there is the inventive Device consisting of a vertical, cylindrical container filled with refractory materials (refractory brick 1 and insulating brick 2) is lined. In the middle of the floor there is a jet nozzle 3 through which the pulp is sprayed, in the lower part There is a hot air inlet 4 on the wall and one on the top of the container Outlet opening 5.

The hot air guide device 6 has the shape of a spiral, the starting at the hot air inlet 4 and up along the inner surface of the wall winds, the high temperature zone is formed in the container by a stream of hot air, along the described hot air guide device on the inner surface the wall rises. At the same time, the pulp of raw materials and alcohol becomes continuous through the nozzle 3 in the same direction as the axis of the ascending the Air flow, namely in the direction of the cylinder axis, is sprayed. In Fig. 1 means 7 a hole for temperature testing (and at the same time a viewing hole), 8 an outlet for the reaction products, 9 an iron jacket, 10 a water-based insulation material and 11 a support strut.

The ratio of the diameter to the height (R / L) of the device is about 1/4.

In the practical implementation of the method according to the invention gets hot air with a temperature of about 1200 ° C coming from a kerosene burner is introduced through the inlet 4 into the device described above. At the same time, the pulp consisting of raw materials suspended in alcohol becomes sprayed upwards through the jet nozzle 3 in the vertical direction. In this way the alcohol burns and one achieves that the process steps of granulation, the formation of ferrite and sintering of the powdery materials take place momentarily. The sintered grains produced in this way fall into the reaction container and are discharged through the product outlet 8.

The product obtained in this way directly represents various Uses available as ferrite powder with spherical grain.

The carried out in this way in the method according to the invention Burning of the alcohol appears to be the momentary granulation, ferrite formation and sintering the raw materials consisting of fine grains on the order of µm to allow and helps to standardize the ferrite quality and grains of spherical Form.

Accordingly, the process is generally carried out in an atmosphere whose residual concentration at ° 2 is in the range from 3% to 5%. Depending on the used However, raw materials can produce better results in some cases, if one compares the procedure in one with the one above described Processes more oxidizing or more reducing atmosphere.

With regard to the temperature of the high-temperature atmosphere, it should be noted that that if one uses the aforementioned types of ferrite-forming raw materials is used, good results are achieved when using temperatures in the range from 7000C to 15000C applies. As the nozzle 3 for spraying the slurry, it is suitable to use nozzles of a simple type constructed as shown in Fig. 3 can be used.

The body of this nozzle is made of a heat-resistant metal, wherein the tip of the nozzle or the part of the nozzle t is the one with the pulpy liquid comes into contact, made of a wear and corrosion resistant material, in consists primarily of ceramic.

The raw material slurry is fed to the nozzle under pressure by means of a plunger pump or supplied from the pressure tank at a pressure, e.g. in the range of 2 kg / cm2 up to 50 kg / cm2.

A grain size of the preferred ferrite with spherical grain can be through the appropriate selection of various factors, including the outside diameter, the Pressure applied to the slurry, the solids concentration of the slurry and similar factors can be controlled. The following examples serve to provide more detailed information Explanation of the invention.

Example 1 Finely powdered oxides of Ni, Zn and Fe with an average Grain sizes of 1.0 µm or less were weighed out to be a mixture with 15 percent by weight NiO, 35 percent by weight ZnO and 50 percent by weight Fe 2 O 3 received.

The mixture was dissolved in technical grade methyl alcohol to form a Slurry suspended with a solids content of 45%.

The resulting slurry was blown using a pressure of 2 kg / cm 2 a jet nozzle and was fed from the nozzle into the reaction container with the sprayed structure shown in Fig. 1 of the accompanying drawings, the interior of the container by the combustion gases of a petroleum burner, which by means of the Hot gas inlet were supplied at a temperature in the range from 12000C to 1250 ° C was held. A series of reactions were obtained immediately such as granulation, ferrite formation and sintering the powdered product. How by means of As confirmed by X-ray diffraction analysis, this powder had the structure of a ferrite of the Ni-Zn type. The powder had a saturation magnetization (ds) of 50 emu / g and a density (d) of 5.0 g / cm3. The grains were spherical in shape. 90% of the grains had a grain size in the range from 30 μm to 200 μm. An electron photomicrograph of the scanning type of product grains is shown in FIG.

Example 2 Finely powdered carbonates and oxides of Cu, Zn and Fe with an average grain diameter of 1.0 µm or less as raw materials were weighed to form a preparation with the following composition: 25 percent by weight CuO, 25 percent by weight ZnO and 50 percent by weight Fe203.

This preparation was suspended in technical methyl alcohol, a slurry having a solids content of 40% was obtained. The procedure complied that described in Example 1, except that the above-described slurry as the raw material was used for spraying. The powdery product obtained in this way was Cu-Zn ferrite with the saturation magnetization (6s) 38 emu / g and the density 4.9 g / cm³. The grains were spherical in shape. 90% of the grains were sized from 30 pm to 200 grain.

Example 3 Finely powdered oxides and carbonates of Mg, Zn and Fe with an average grain size of 1.0 µm or less were formed a preparation weighed which had the following composition: 25 percent by weight MgO, 25 percent by weight ZnO and 50 percent by weight Fe 2 O 3. This preparation was made suspended in technical grade methyl alcohol to form a slurry with a solids content of 50%. This slurry was sprayed into the reaction vessel as a raw material, otherwise the procedure of Example 1 was repeated.

Mg-Zn ferrite with saturation magnetization (s5)) 40 was obtained emu / g and the density (d) 4.7 g / cm3. Grains between 50 cun and 250 in size Fm accounted for 80% of the total.

Example 4 Carbonates and oxides of Ba and Fe with an average Grain sizes of 1.0 pin or less were weighed out to make the preparation for BaOX5w5Fe203 and then to form a 508 solids slurry suspended in technical grade methyl alcohol. This pulp was made using a A pressure of 2.5 kg / cm2 is conveyed to the reaction vessel and sprayed there, as in Fig. 1 of the accompanying drawings, wherein it is at a temperature in the range was held from 12000C to 13000C. That in this way in the device after Termination of granulation, ferrite formation and sintering produced barium ferrite powder with spherical grain, the saturation magnetization (68) was 58 emu / g. This too Powder contained grains of distinctly spherical shape, as in those described above Examples were obtained and had a density (d) of 4.9 g / cm3.

90% of the grains were between 30 and 200 pin in size.

Example 5 The same process steps as described in Example 4 were repeated except that SrO instead of BaO was used. The spherical grain strontium ferrite thus prepared had a Saturation magnetization of 53 emu / g and a density (d) of 4.7 g / cm3. 90% the grains were between 30 μm and 200 μm in size.

Example 6 NiFe2O4 and ZnFe204, both according to the "Neutrallsatlonsverfahren1 were dried at low temperatures. Then these connections became as raw materials in powder form to form a preparation the same Composition like that described in Example 1, weighed out. This preparation was treated under the same conditions as described in Example 1, wherein a nickel-zinc ferrite was obtained. This product was a spherical powder Grain with saturation magnetization (& s) 55 emu / g 3 5 and density (d) 4.9 g / cm. 90% of the grains were 50 µm to 200 µm in size.

Example 7 According to the "coprecipitation process", an aqueous solution a mixture of hydroxides and carbonates of Ba and Fe, the 12 Fe ions per 1 Ba ion contained, precipitated. The precipitate was thoroughly washed and dried. The fine-grained powder obtained in this way was then dissolved in technical grade methyl alcohol dispersed. The resulting slurry, which had a solids content of 40%, was using a pressure of 3 kg / cm2 in the interior of the one shown in FIG Reaction container conveyed and sprayed there than the internal temperature of the container Had reached 12000C to 12500C.

The powdery product obtained as the turn in the container the reactions such as granulation, ferrite formation and sintering had occurred Barium ferrite with a saturation magnetization (6s) of 49 emu / g and a density (d) of 4.9 g / cm3. 90% of the grains of this barium ferrite had one Size from 50 µm to 200 µm.

As can be seen from the examples described above, you can when using the device according to the invention and according to the invention Process from a number of different ferrite-forming raw materials instantly get a soft and a hard ferrite.

In addition, the resulting ferrite is more homogeneous, extraordinary high quality and consists of grains of pronounced spherical shape.

It was previously of the opinion that the characteristic properties of ferrite material can best be improved by removing the commingled raw materials pressed or compacted prior to sintering. Taking this fact into account the method according to the invention actually has many advantages: the simplification of the process steps, the shortening of the reaction time and, because of the increased number of adjustable operating factors, a finely adjustable one Possibility of influencing the production process.

L e r s e i t e

Claims (12)

Claims 1. A method for producing a ferrite powder with spherical grain, characterized in that one consists of a very fine powder from one, two or more ferrite-forming raw materials, in a combustible, liquid organic matter suspended, which these raw materials do not in considerable Measures dissolve that the resulting suspension in a high temperature atmosphere sprayed at a temperature above the flash point of the organic liquid and that the granulation, ferrite formation and sintering of the raw materials are immediate performs while in the high temperature atmosphere. 2. The method according to claim 1 for producing a ferrite powder with spherical grain, characterized in that one consists of a very fine powder from one, two or more ferrite-forming raw materials, suspended in an alcohol, that the resulting suspension in a high temperature atmosphere with a Temperature in the range from 7000C to 15000C and that the granulation, Ferrite formation and sintering of the raw materials performs immediately while they are themselves are in the high temperature atmosphere. 3. Process according to Claims 1 and 2, characterized in that the combustible, organic liquid is used in the form of an alcohol. 4. The method according to any one of the preceding claims, characterized in that that one uses the combustible, organic liquid in the form of methyl alcohol. 5. The method according to any one of the preceding claims, characterized in, that the combustible, organic liquid in the form of technical methyl alcohol begins. 6. The method according to any one of the preceding claims, characterized in, that the temperature of the high temperature atmosphere is in the range of 7000C to 15000C chooses. 7. The method according to any one of the preceding claims, characterized in, that a suspension with a solids content of 10 percent by weight to 70 Percentage by weight, based on the total weight of the suspension, is used. 8. The method according to any one of the preceding claims, characterized in, that the raw material powder is used in the form of a mixture which is capable of to form a compound with the general formula MO Fe 2 O 3, where M is a divalent Metal is. 9. The method according to any one of the preceding claims, characterized in, that the suspension using 2 pressure of 2 a pressure of 2 kg / cm2 sprayed up to 50 kg / cm2. 10. The method according to any one of the preceding claims, characterized in, that the reaction is carried out in an upward eddy current of hot air. 11. Device for performing the method for Manufacturing of ferrite powder with spherical grain according to one of the preceding claims, characterized by a vertical, cylindrical one lined with a refractory material Container, through a hot air inlet, located in the lower part of the wall of the vertical Container is located through an outlet opening, which is at the top of the vertical The container is located through a hot air duct that runs along the inner surface the wall of the vertical container and, starting at the hot air inlet, spirals upwards and through a spray nozzle located in the center of the Bottom of the vertical container is located and which is such that the suspension in a continuous ray running in the same direction as the axis of the moving upwards in a circle along the guide described above, hot air flow rises upwards, can be supplied to the container. 12. Ferrite powder with spherical grain, characterized in that it was produced in a process according to any one of claims 1 to 10.