KR0139326B1 - Method of manufacturing composite material for ferrite - Google Patents

Abstract

The present invention is iron oxide. The present invention relates to a method for producing a ferrite composite oxide using the heat of oxidation of iron powder in an oxidizing atmosphere by adding iron powder to zinc oxide and nickel compound. According to the present invention, the iron powder content is 8 of the total mixed powder. -27 weight%. Its size is 100 µm or less, and the oxygen partial pressure in an oxidizing atmosphere is not more than 0.4 atm, so that there is no unreacted oxide and no molten portion is generated.

Description

Manufacturing method of composite oxide for ferrite raw material

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ferrite composite oxide. The present invention relates to an improvement of a method for producing a ferrite composite oxide using heat of oxidation of iron powder in an oxidative atmosphere by adding iron powder to iron oxide, zinc oxide and nickel compound.

In general, the industrial method for producing ferrite is a metal oxide, such as iron oxide, zinc oxide, nickel oxide, mechanically mixed in a predetermined molar fraction, calcined (calcination), and then pulverized to prepare a powder of the raw material and then to form the raw powder The method of sintering at high temperature has been used.

However, this method has the following problems. That is, the calcination step is performed at a relatively high temperature and a long time, therefore, the incorporation of impurities and quality of microstructure in the production process affects the properties of the product such as nonuniformity, and also the productivity such as prolongation of production time and excessive energy required. There is a problem in this respect. In addition, due to the rapid development of the electronics industry, electronic devices are increasing in frequency, and development of high quality ferrite cores is required. In order to satisfy these demands, the spray roasting method has been developed as a new composite powder production method in Japan as an advanced ferrite production method compared with the prior art (Japanese Patent Publication No. 47-11550). Merzhanov et al., Russia, proposed the possibility of producing ferrite composite oxides by chain high temperature synthesis (PCT / SU / 00009). The ferrite structure is generated and the sintering process can be omitted and the ferrite core can be manufactured directly, thereby simplifying the process and reducing the cost. However, when the spray roasting method is used, the apparatus for producing the complex oxide is expensive, and it is less mass-produced than the conventional method, and is applied to only some expensive products. On the other hand, the chain high temperature synthesis method is a very economical method because the device for producing a complex oxide is simple in its configuration, does not require heat supply from the outside and does not consume power.

The chain high temperature synthesis method is a method that can economically produce intermetallic compounds and metal carbides, nitrides, oxides, and the like without using energy by using the heat generated when metals and metals or gases react with each other. In Russia, the chain high temperature synthesis method is used for intermetallic compounds such as MoSi ₂ , NiTi, NiAl, metal carbides such as Tic, SiC, NbC, TaC, or nitrides such as Si ₃ N ₄ A1N and oxides such as LiNb0 ₃ and ferrite. Economical manufacturing possibilities are presented. Among these, in ferrite, iron powder is reacted with coral in an oxidizing atmosphere to cause Fe. Mn. Mg. Ni. Cu. Zn. Various ferrites containing metal oxides, such as Li, have been attempted, suggesting that ferrite composite oxides can be prepared by a chain high temperature synthesis method. However, ferrite, unlike other materials, is a functional material that utilizes the magnetic properties of the material. Therefore, even when the ferrite powder is prepared by using a chain high temperature synthesis method, the ferrite powder has desired magnetic properties unless the reaction conditions are properly controlled in the powder manufacturing step. Since the ferrite core cannot be manufactured, it is not practical.

In general, the characteristics required for the ferrite composite oxide before sintering should have a fine particle size of less than 1㎛ the powder particles and uniform particle size distribution. In addition, it is necessary to have a uniform composition in the microstructure, low incorporation of impurities in the grinding process, and low manufacturing cost.

In the production of ferrite, which is a real soft magnetic material, the properties are greatly changed by the purity and fine structure of the powder. The chain high temperature synthesis method proposed in Russia only suggests that the ferrite phase can be produced, but the iron powder content, particle size, oxygen partial pressure There is a problem such that the unreacted oxide remains or the molten portion is generated because the factors such as these are not considered. Unreacted oxide refers to zinc oxide or nickel or nickel compounds (Zn0 or Ni0, Ni) initially used as raw materials, and when they remain, they form intermediate phases such as ZnFe ₂ O ₄ by phase change during sintering. The volume expands 1.5-2% and 0.3-0.5%, respectively. Therefore, if unreacted oxide remains, compression molding is given to Cyclic Stress due to expansion and contraction during sintering.

As a result, the sintered product finally has a low sinter density, poor accuracy in volume and strength, including defects such as deformation and cracking, and also greatly reduces magnetic properties. On the other hand, the molten part is a phenomenon that occurs when the synthesis reaction temperature is too high in the chain high temperature synthesis method, in which the spinel phase produced by the reaction is melted by high temperature to form a solid solid. Therefore, in order to obtain a desired particle size, a long time grinding process is required, which causes impurities to be mixed due to abrasion of the grinding medium during grinding, and the particle size distribution after grinding is widened, thereby deteriorating the sintering characteristics. Second, unlike the composite oxide powder produced by the reaction, the molten part has a cast structure formed by melting and solidification, so that the sintering pattern is locally changed, which affects the magnetic properties of local grain overgrowth. Occurs.

As described above, in order to manufacture high quality ferrite, the control of microstructure is absolute. Therefore, the presence of unreacted oxide or molten portion in the ferrite composite oxide adversely affects the sintering characteristics of the powder, resulting in excessive growth, cracking and deformation of partial grains. To deteriorate the magnetic properties of the sintered product. Accordingly, an object of the present invention is to propose a method for producing a ferrite composite oxide in which unreacted oxides or molten portions do not occur in the production of ferrite composite oxides using a chain high temperature synthesis method.

An object of the present invention can be realized by controlling the content and size of the iron powder, and the oxygen partial pressure, which is a manufacturing variable.

In the ferrite composite manufacturing process, iron powder, zinc oxide, and nickel compound having an appropriate composition ratio are added to a content of 8 to 27% by weight so as to have a uniform mixing state as a raw material powder. When the mixed powder is dried in a constant temperature bath, filled into a reaction vessel and ignited using a heating element in an oxygen atmosphere of 0.4 to 2.0 atm, the chain synthesis reaction is increased by the heat of oxidation reaction of iron powder, thereby producing a ferrite composite powder.

The reason for limiting the content and size of iron powder and the size of oxygen partial pressure in the production method is as follows.

(1) Iron powder content

The reason for adding the iron powder is to prepare a spinel-like composite oxide using heat of oxidation of iron powder. However, when the content of the iron powder is not appropriate, problems such as melting parts or unreacted oxides remain. When iron powder in excess of 27% by weight is added, excess heat of reaction is generated to melt the resulting spinel phase. This molten portion remains coarse particles that are difficult to grind, requiring a long grind time, thereby increasing the incorporation of impurities by the grind medium during grinding. In addition, the longer the pulverization time has a wider particle size distribution, which lowers the characteristics of the ferrite core formed by partly accelerating grain growth in the sintering process. In addition, mixing of impurities also causes deterioration of characteristics.

On the other hand, when only 7% by weight or less of iron is added, the heat of oxidation is small, leaving unreacted oxide. Such unreacted oxides are subjected to cyclic stress due to expansion and contraction during sintering, resulting in the sintered product finally having low sinter density and inaccurate volume and strength including defects such as deformation and cracking. Magnetic properties are also greatly reduced.

(2) iron powder size

In the method for producing a ferrite composite powder by the chain high temperature synthesis method, the aspect of the reaction also varies depending on the particle size of the iron powder. The smaller the particles of the iron powder added to the reaction, the more unreacted oxides remain. On the other hand, the larger the size of the particles, the larger the amount of iron powder is required so that the unreacted oxides do not remain. Therefore, the conditions under which the unreacted oxide remains depends on the size of the iron powder. When the size of the iron powder is 8 μm or less, the unreacted oxide remains from when the iron powder is 7 wt% or less, and the size of the iron powder increases as the size of the iron powder increases. The content of iron powder in which the reaction oxide begins to remain increases. On the other hand, the condition in which the molten portion starts to occur is more affected by the iron powder content than by the size of the iron powder.

(3) oxygen partial pressure

In the chain high temperature synthesis reaction, the reaction pattern is different depending on the oxygen partial pressure during the reaction. When the oxygen partial pressure is small, a thick unreacted layer is formed in the lower layer of the mixed powder where the reaction in the reaction part does not proceed as a whole and oxygen is hard to penetrate sufficiently. Lowers. This unreacted layer disappears when it is above 0.4 atm. The change in the reaction pattern according to the oxygen partial pressure is very sensitive when the oxygen partial pressure is low, but when the oxygen partial pressure increases above 2 atm, the oxygen atom is sufficient to sufficiently advance the reaction, and thus the effect of the change in the oxygen partial pressure is hardly shown. However, in order to maintain the pressure in the reaction tank above 2 atm, it is preferable to limit the oxygen partial pressure to 0.5 to 2 atm since the operation is inconvenient and the price of manufacturing equipment is increased because the reactor must be sealed.

Example 1

Fe and Ni: Zn = 67.1: 24.9: 8.1 (weight ratio), 600 g of a mixture of iron powder, iron oxide, zinc oxide and nickel compounds having a size of 8 µm or less was wet mixed in a ball mill for 12 hours at 80 to 100 ° C. It was dried for at least 8 hours in a thermostat.

The mixed powder is filled into a 40mm × 40mm × 10mm container and the atmosphere is maintained at 1 atmosphere of oxygen partial pressure (atm) in a reactor that can control the atmosphere, and then locally oxidized iron powder using an igniter or a heating element. When the reaction occurs, the ferrite complex oxide is spontaneously generated by the heat generated during the oxidation reaction as a whole by the self-heating during the oxidation reaction.

The composition ratio of the mixture was fixed to have a composition of Fe: Ni: Zn = 67.1: 24.9: 8.1 (weight ratio) and the content ratio of iron powder and iron oxide was changed as shown in Table 1 A ferrite composite oxide having a predetermined composition was prepared by a chain high temperature synthesis method. Table 2 shows the results of the powder produced according to the iron powder content.

Example 2

The ferrite composite oxide was synthesized by changing the size of the iron powder under the same conditions as in the experiment of Example 1. The result is as follows.

Example 3

In the method of Example 1, the iron powder was fixed to 8 μm or less, the iron powder was set to 7, 13 and 17 wt%, respectively, and the oxygen partial pressure was changed to prepare a ferrite composite oxide, followed by X-ray rotation analysis. The presence or absence of the unreacted oxide was confirmed, and the results are shown in Table 4.

According to the present invention, by adding iron powder to iron oxide, zinc oxide, and nickel compound, ferrite composite powder without unreacted oxide or molten portion can be produced in a desired composition by using the heat of oxidation of iron powder in an oxidizing atmosphere. As described in the above description and examples, as a result of performing the chain high temperature synthesis reaction by adjusting the iron oxide content, particle size, and oxygen partial pressure, there is no unreacted oxide. Oxides can be prepared.

Claims (5)

A method for producing a ferrite composite oxide by a chain propagation of an oxidation reaction by heat of oxidation of the iron powder by oxidizing a mixed powder of iron powder, iron oxide powder, zinc oxide powder, and nickel compound powder in an oxidizing atmosphere. The content is 8 to 27% by weight of the total mixed powder, the size is 100㎛ or less, the oxidizing atmosphere is characterized in that the oxygen partial pressure exceeds 0.4 atm. The method according to claim 1, wherein the content of the iron powder is 9 to 23% by weight of the total mixed powder, and the size thereof is 8 µm or less. The method according to claim 1, wherein the content of the iron powder is 17 to 23% by weight of the total mixed powder, and the size is 8 to 44 µm. The method according to claim 1, wherein the content of the iron powder is 21 to 27% by weight of the total mixed powder, and the size is 44 to 100 µm. The method according to claim 1,2,3 or 4, wherein the oxygen partial pressure is 0.5 to 2.0 atm.