JPH0723201B2 - Method for producing complex oxide powder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a composite oxide powder, and more specifically, a first oxide powder and a second oxide that form the composite oxide. Burn the mixture with the metal powder in a flame,
The present invention relates to a method for producing a composite oxide powder in which a first oxide is coated with a metal oxide formed from a metal powder that constitutes a second oxide.

[Prior Art] In the production of complex oxides such as mullite, which is rarely produced in nature, it has been conventional to use alumina (Al
₂ O ₃ ), silicon dioxide (SiO ₂ ) single oxides are mixed, the mixture is calcined at 1200 to 1300 ° C, and the calcined mixture is crushed by a ball mill. It carried out by carrying out in order. In addition, synthesis is attempted by spraying decomposition of metal alkoxide called Numelite.

Also, the method using metal alkoxide spray decomposition is expensive and not suitable for practical use.

Further, at present, silicon dioxide (SiO ₂ ) is used as a filler for the resin encapsulant of the IC substrate. Since this silicon dioxide has low thermal conductivity (poor heat dissipation), it has a problem that the degree of integration of the IC substrate cannot be increased so much when it is used as a filler for a resin sealing material. On the other hand, when alumina having a high thermal conductivity is used instead of silicon dioxide, the heat dissipation is improved, but another problem occurs. That alumina order of magnitude more than the usual silicon dioxide many Na ^+, Cl ^-, Ca ⁺⁺
And other ions are included as impurities. Therefore, if alumina is used as the filler for the resin encapsulant, the IC may malfunction due to ion conduction.

[Problems to be Solved by the Invention] However, in the above-mentioned production method, there is a problem that solid-phase reaction is unlikely to occur and uniform mullite is difficult to obtain. In addition, impurities were easily mixed from the crushing device in the crushing process, and there was a limit to the purification of mullite. Moreover, the particle size distribution of the crushed mullite particles varied considerably. Mullite produced in this way has a glass matrix,
Above 0 ° C, there is a sharp drop in temperature due to softening.

The present invention has been made in view of the above situation, and an object thereof is a method for producing a composite oxide that is inexpensive, homogeneous, highly pure, and has a substantially uniform particle size, particularly a composite oxide having a two-layer structure. To provide.

[Means for Solving Problems] The applicant previously proposed in Japanese Patent Application No. Sho 61-22436 a method of synthesizing a metal powder constituting a composite oxide by burning it in a flame. As an improvement method, in Japanese Patent Application No. 62-86463, when burning metal powder in a flame, a cooling gas was ejected to the periphery of the flame to cool the fine oxides produced and prevent the oxides from being granulated. Suggested a way to do. The present invention is this improved method. That is, the above method can only obtain a homogeneous oxide, and cannot coat the surface with another oxide.

A method for producing a composite oxide powder according to the present invention comprises a fine powder of a first oxide forming a composite oxide, and a second oxide forming a composite oxide and different from the first oxide. And a metal powder that forms a second oxide in a flame formed by a combustible gas in the reaction vessel, and the metal powder that constitutes the second oxide is burned and oxidized. Liquefied or vaporized to form a coating layer of the liquefied or vaporized second oxide on the surface of the fine powder of the first oxide.

The composite oxide obtained by the production method of the present invention is a composite oxide having a second layer structure in which a coating layer of a second oxide different from the first oxide is formed on the surface of the first oxide as a nucleus. It is a powder.

In the first step, a mixture of a fine powder of the first oxide forming the composite oxide and a metal powder forming the second oxide is supplied into the reaction vessel together with a carrier gas. The oxides forming the first oxide are alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), magnesia (MgO), titanium oxide (TiO ₂ ).
₂ ) etc. Examples of the metal powder that constitutes the second oxide include aluminum and silicon. This metal powder burns to become an oxide and adheres to the surface of the first oxide to form a coating layer of the second oxide. It is desirable that the oxide and the metal powder have a purity of 90% or more in order to enhance the purity of the product. Further, both of them are preferably fine powders because they react in a combustion flame.

In the first step, the above oxide powder or metal powder may be mixed in advance to form a mixture, and the mixture may be supplied into the container together with a carrier gas. In some cases, the oxide powder and the metal powder may be supplied into the container together with the carrier gas.

Considering the combustibility in the second step, it is necessary to make the inside of the reaction vessel an oxidizing atmosphere. Therefore, air or oxygen gas can be used as the carrier gas. Further, it is preferable to introduce a combustible gas that forms a flame in the reaction vessel. The reaction vessel is preferably lined with a heat insulating material such as alumina brick. The amount of the mixed powder supplied into this reaction container is preferably about 1 to 5 kg per hour, and in this case, the internal volume of the reaction container is preferably about 50 to 100 l. The reaction vessel preferably has an ignition source. The ignition source can be one that produces a spark.

In the second step, a flame is formed by igniting in the reaction vessel,
The metal powder that constitutes the second oxide is burned to form a liquefied / vaporized oxide and adheres to the surface of the fine powder of the first oxide existing in the flame, and then adheres to the surface of the first oxide. A second oxide coating layer is formed.

The second step can be performed while maintaining combustion conditions (a temperature lower than the melting point of the oxide used) in which the fine powder of the first oxide does not melt in the flame. When the fine powder of the first oxide exists as fine powder, liquefied or vaporized metal oxide adheres and grows with the fine powder as a nucleus to form a coating layer. In order to form a coating layer, this oxide needs to have a particle size of several + μm or less, and if the particle size is larger than this, it becomes difficult to form a uniform coating layer. Further, since the second step is usually performed at a high temperature of about 800 to 1600 ° C., a high temperature flame is formed. In this case, a flame can be formed with propane gas and oxygen gas. Usually, the melting point of the metal powder is lower than the melting point of the metal oxide. Therefore, the metal powder is easily oxidized and liquefied or vaporized by appropriately selecting combustion conditions in a flame having a temperature lower than the melting point of the first oxide. . A coating layer can be formed on the surface of the first oxide powder by the liquefied or vaporized oxide.
That is, the temperature of the flame can be adjusted by adjusting the supply temperatures of the mixed powder and the combustible gas, whereby a coated composite oxide is obtained. Particularly in the case of an oxide having a high melting point, the oxide serves as a nucleus to easily form a coating layer to form a composite oxide. The synthesized composite oxide powder is collected together with the combustion exhaust gas. In this case, generally, the reaction can be performed by connecting the reaction container and the dust collector and driving the dust collector. As the dust collector, an electric dust collector, a bag filter, a collection drum type fine powder collection device, or the like can be used.

[Effect of the Invention] The present invention supplies the first oxide and the second oxide to the reaction vessel together with the metal powder constituting the second oxide and the carrier gas in the first step, and in the second step, the surface of the first oxide is supplied. It is a method for producing a composite oxide in which a liquefied or vaporized substance of an oxide synthesized by combustion of a second metal powder is adhered to form a coating layer.

According to this method, it is possible to easily produce a composite oxide having a shape covered with another type of oxide. This composite oxide is a useful material because it has the special features of each oxide. For example, a composite oxide formed by ZrO ₂ and aluminum powder is promising as a highly tough material. Also Ti
A composite oxide of O ₂ and aluminum powder is used as a low expansion material. As described above, this manufacturing method can easily and inexpensively manufacture a highly pure composite oxide having a substantially uniform particle size.

[Examples] Hereinafter, the present invention will be described with reference to Examples.

FIG. 1 shows a manufacturing apparatus according to the manufacturing method of the present invention. This manufacturing apparatus includes a reaction container 15, a raw material supply unit 10, and a product separation unit 20.

The reaction vessel 15 has an inner wall surrounded by heat-resistant bricks 5, a discharge port 11a communicating with the discharge passage 11 on the side wall, and the raw material supply unit 1 on the top wall.
And a burner 8 connected to 0. Raw material supply unit 10
Is provided with a hopper 1 for storing the raw material powder 2, a pipe 3 serving as a passage for a carrier gas 12 for carrying the raw material powder 2, and a pipe 4 for introducing a combustible gas 13. The product separation unit 20 is provided with a discharge passage 11, and a powder dust collector 6 and a blower 7 that discharges exhaust gas along the discharge passage 11.

Using the reactor configured as described above, the following reactions were performed to synthesize a composite oxide.

First, a carrier gas (oxygen) 12 is introduced into the reaction container 15 through the pipe 3, and a combustible gas (propane gas) 13 is introduced into the reaction container 15 through the pipe 14 and ignited by the burner 8 to form a flame 9. The reaction container 14 was dried sufficiently.

The carrier gas was supplied into the reaction vessel 15 at a flow rate of 8 m ³ / hour and the combustible gas at a flow rate of 0.4 m ³ / hour. Then raw material powder 2
A mixture of aluminum oxide powder having a particle size of 10 to 20 μm and a purity of 99.8% and metallic silicon powder having a particle size of 40 μm and a purity of 99.8% (mixing ratio 2: 1) was burned from the hopper 1 by the carrier gas 13 at a rate of 2 kg / hr. It was supplied into the reaction vessel 15 through 8 and burned in the flame 9.

This flame 9 has a temperature below the melting point at which metal powder is burned but oxide alumina is not liquefied. Then, the blower 7 was operated to discharge the combustion exhaust gas through the discharge passage and the dust collector to the outside of the system to collect and separate the product by the dust collector.

In the obtained composite oxide, the surface of aluminum oxide was covered with silicon dioxide. For this coating structure, X-
Confirmed by line diffraction. This product has high thermal conductivity and low ionic conductivity, which are advantages of both aluminum oxide and silicon dioxide, and was useful as a filler for resin encapsulants of IC substrates.

Zirconium oxide (Zr
It was possible to synthesize a composite oxide coated with aluminum oxide using aluminum as the metal powder using O ₂ ) or titanium dioxide (TiO ₂ ). This composite oxide can be used as a ceramic raw material having excellent sinterability.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a manufacturing apparatus used in this embodiment. 1 ... Hopper, 2 ... Mixed powder 3, 4 ... Pipe, 6 ... Dust collector 8 ... Burner, 9 ... Flame 10 ... Raw material supply section, 15 ... Reaction vessel 20 ... Product separation Department

Claims (2)

[Claims] 1. A carrier comprising a fine powder of a first oxide forming a composite oxide and a metal powder forming a composite oxide and forming a second oxide different from the first oxide. A first step of supplying the gas together with a gas into a reaction vessel; and in a flame formed by a combustible gas in the reaction vessel, the metal powder forming the second oxide is burned to be oxidized and liquefied or vaporized, On the surface of the first oxide powder,
And a second step of forming a coating layer of the liquefied or vaporized second oxide. 2. The method for producing a composite oxide powder according to claim 1, wherein the second step is performed under a combustion condition in which the differential powder of the first oxide does not melt.