JPH0361610B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing manganese (Mn) ferrite, and particularly to a method for obtaining fine powder thereof. The conventional method for producing ferrite has been to mix a divalent metal oxide and a trivalent iron oxide in powder form and heat the mixture to, for example, 1300°C to 1500°C to cause a reaction. However, in this method, ferrite is obtained by reacting a mixture of solid particles, so the composition is essentially non-uniform, and the high temperature reaction results in large ferrite particles and a wide particle size distribution. For high performance,
It has not been possible to manufacture a material with high dimensional accuracy that allows for highly reliable microfabrication. In addition, according to the conventional method, when the raw material oxides are mixed and reacted at high temperature, the ferrite layer is only formed by reaction and diffusion between the surfaces where the particles are in contact with each other, and the deep part of the particles is Therefore, in order to obtain highly uniform ferrite, the heating reaction and crushing operations must be repeated. Therefore, it takes a long time to manufacture, requires a large-scale crushing device, and requires a large furnace to maintain high temperatures. Furthermore, since the process of pulverization and heating is repeated, contamination with foreign substances is unavoidable, making it difficult to obtain highly pure products. In view of these drawbacks, the present invention provides a method for producing high-purity Mn ferrite using molecular-sized fine particles, which can be produced by a low-temperature reaction in a liquid phase, and does not require large-scale reaction equipment. It was made for the purpose of providing. The method for producing Mn ferrite of the present invention involves preparing a composite alkoxide (alcohol compound) of at least one of iron (Fe) and a metal at least partially consisting of Mn with an alkali metal, and combining the other (Fe) with an alkali metal. Alternatively, by heating a compound of the aforementioned metal in a solvent to perform a substitution reaction, a composite alkoxide of Fe and the aforementioned metal is produced, and by hydrolyzing the composite alkoxide, a hydroxide of Fe and the aforementioned metal is produced. This is a method for obtaining Mn ferrite by preparing a solid solution of and oxidizing the solid solution in an oxygen atmosphere at 40°C to 80°C for 5 hours or more. In the present invention, when each alkoxide of Fe and Mn is produced, or when each alkoxide of Fe, Mn, and Zn is produced, these are produced simultaneously or separately. Fe and Mn compounds used as starting materials in the present invention include halides such as chlorides. Furthermore, methanol, ethanol (Et), butanol, and the like are used as alcohols for forming alkoxides. Also, as alkali metals, sodium (Na), lithium,
Potassium is used. The present invention will be explained below using experimental examples. first,
Prepare iron chloride (FeCl ₂ ) and manganese chloride (MnCl ₂ ), which have been heated at 200°C for 3 hours to remove attached water, and mix them with 0.04 mol of FeCl ₂ so that Fe:Mn=2:1. 0.02 mol _MnCl2 and ethanol (Et)
The solution was dissolved in 100 ml and refluxed at approximately 70°C for 1 hour while passing N ₂ gas (a process in which solvent vapor generated by heating is cooled and liquefied and returned to the solution), and Fe(OEt) ₂ and Mn(OEt) ₂ was produced. FeCl ₂ +2EtOH→Fe(OEt) ₂ +2HCl …(1) MnCl ₂ +2EtOH→Mn(OEt) ₂ +2HCl …(2) Next, 0.02 mol of Na was added to this solution, and the mixture was heated in a N ₂ gas atmosphere for about 1 hour. The mixture was refluxed at 70°C to carry out the following substitution reaction. NaOH + 2Mn (OEt) ₂ +EtOH →NaMn ₂ (OEt) ₅ +H ₂ O …(3) NaMn ₂ (OEt) ₅ +4Fe (OEt) ₂ →2MnFe ₂ (OEt) ₆ +NaOEt …(4) Next, a sufficient amount of hot water was added and refluxed at about 70° C. for 1 hour under a N ₂ gas atmosphere to carry out hydrolysis, and the product was filtered. This hydrolysis product is
It is a solid solution of Fe(OH) ₂ and Mn(OH) ₂ . Air was flowed through the suspension of the hydrolyzed product obtained by the above operation at a flow rate of 2/min, and oxidation was carried out in the air while varying the temperature and time. This product was centrifuged and then vacuum dried. The table below shows the results of X-ray diffraction when the temperature and time of oxidation of the product in air were varied.

[Table] As shown in this table, the temperature of oxidation in air is 40~
When the oxidation time is 1 to 3 hours at 60℃
The diffraction pattern was that of MnFe ₂ O ₄ and (Mn, Fe) OOH. The changes in the lattice constant of MnFe ₂ O ₄ were investigated when the oxidation time was varied at an oxidation temperature of 70 to 80°C. As a result, as shown in FIG. 1, the lattice constant increased as the oxidation time increased, and was almost saturated at an oxidation time of 5 hours or more. However, it did not reach the lattice constant of MnFe ₂ O ₄ of 8.499. This is because in the synthesis of MnFe ₂ O ₄ by oxidation of (Mn ²⁺ Fe ²⁺ )(OH) ₂ ,
Only Fe ²⁺ is selectively oxidized to Fe ³⁺ , and Mn ²⁺ is oxidized to 2
However, in reality,
The oxidation reaction of Mn ²⁺ →Mn ³⁺ also progresses, and some Mn ²⁺ is
This is thought to be because it is oxidized to Mn ³⁺ , some Fe ²⁺ remains as Fe ²⁺ , and (Mn ²⁺ , Fe ²⁺ ) (Fe ³⁺ , Mn ³⁺ ) ₂ O ₄ is synthesized. . From the above results, it is considered that the optimum oxidation conditions for synthesizing MnFe ₂ O ₄ are a temperature of 40 to 80°C (preferably 70 to 80°C) and an oxidation time of 5 hours or more. This obtained _MnFe2O4 was heated at 200℃ and 400℃ in vacuum _.
When calcined at ℃, there was no change in the X-ray diffraction pattern, but the diffraction peak became sharper as the calcining temperature increased. It is generally known that the stability of Mn ferrite strongly depends on the oxygen partial pressure, and the Mn ferrite prepared in this experiment also has a very small amount of water remaining, as shown in Figure 2c. In case N ₂
Even when heat treated in an air stream, precipitation of Fe ₂ O ₃ was observed during calcination at 800°C due to oxygen generated by water decomposition. However, as shown in Figure 2b, the prepared
Mn ferrite is calcined in vacuum at 400℃ for 3 hours,
Thoroughly dried Mn ferrite was heated at 800 °C in a stream of _N2.
No precipitation of Fe ₂ O ₃ was observed in the sample calcined at ℃. In this way, in order to obtain Mn ferrite that is stable at high temperatures, it is necessary to calcinate it in a vacuum at 400℃ for about 3 hours, but if the purpose is not to use it at particularly high temperatures, the high temperature There is no need for calcination, and there are no problems using the Mn ferrite produced according to the present invention. Mn-Zn ferrite was also synthesized using FeCl ₂ , MnCl ₂ , and ZnCl ₂ as starting materials in the same manner as described above under air oxidation conditions at a temperature of 70 to 80° C. for 5 hours. When the lattice constant of the precipitate was determined by varying the amount of Zn, as shown in Figure 3, the result was that the lattice constant changed almost linearly due to solid solution of Zn. From this,
Zn ferrite becomes Mn in all areas without calcination.
It was found that it dissolves in solid solution in ferrite. The slight variation in the lattice constant at this time is thought to be influenced by changes in the valences of Fe and Mn in the prepared Mn ferrite. These prepared Mn ferrites and Mn
−Zn ferrite was determined by electron microscopy.
The primary particle size was on the order of 0.01μ. As a result of measuring the chemical composition of these particles using an energy dispersive X-ray spectrometer, each particle was found to match the batch composition. As described above, the method of the present invention is a method for obtaining Mn ferrite by utilizing an alkali metal substitution reaction, hydrolysis, and oxidation in an oxidizing atmosphere such as air, and it produces ultrafine powder particles with a uniform composition. can be obtained. Therefore, according to the present invention, Mn ferrite with high purity, high performance, and high reliability can be obtained. Furthermore, according to the present invention, since pulverization and high-temperature heating are no longer necessary, these large-scale devices are no longer necessary, and furthermore, there is no need to repeat operations, so that the manufacturing time is shortened. Furthermore, according to the present invention, crystalline Mn ferrite can be obtained without using a firing process, so by combining it with a polymeric material such as magnetic tape, products can be manufactured without using a firing process (furnace). It is also possible to obtain.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between oxidation time and lattice constant in the present invention, Figure 2 is an X-ray diffraction pattern diagram illustrating the dependence of the stability of Mn ferrite on oxygen partial pressure, and Figure 3 is a diagram showing the dependence of Mn ferrite on oxygen partial pressure. FIG. 3 is a relationship diagram between the composition and lattice constant of Mn ferrite.

Claims (1)

[Scope of Claims] 1 A composite alkoxide of at least one of iron and a metal consisting of at least a portion of manganese is prepared with an alkali metal, and the composite alkoxide and the other compound are heated in a solvent to cause a substitution reaction. By doing so, a composite alkoxide of iron and the metal is produced, and by hydrolyzing the composite alkoxide, a solid solution of iron and the hydroxide of the metal is produced, and the solid solution is heated in an oxygen atmosphere at 40°C to 80°C. A method for producing manganese ferrite, which comprises obtaining manganese ferrite by oxidizing it for 5 hours or more. 2. The method for producing manganese ferrite according to claim 1, characterized in that the metal is made of manganese and zinc, and a manganese ferrite containing zinc is obtained.