JPH07108766B2 - Method for producing complex oxide powder - Google Patents

Description

The present invention relates to a method for producing a composite oxide powder. The present invention relates to mullite powder (3Al ₂ O ₃ · 2SiO ₂ ), spinel powder (M
gO.Al ₂ O ₃ ) and cordierite powder can be used for the production method.

Mullite _{(3Al 2 O 3 · 2SiO 2} ) showed a uniform thermal expansion, greater resistance to spalling resistance and deformation under load, change with temperature in the mechanical properties is small, also
At 1600 ℃, it has almost the same strength as alumina. In addition, mullite is impermeable and can hold a vacuum up to 1400 ° C, and has the characteristic that it is highly resistant to corrosion by iron oxide, slag, and glass. So, for example, mullite is
Used for grinding mills, linings, grinding balls, combustion boats, combustion tubes, etc. At present, these properties are expected to be promising as other structural ceramics.

[Prior Art] In the production of complex oxides, for example, mullite, which is rarely produced in nature, conventionally, single oxides of alumina (Al ₂ O ₃ ) and silica (SiO ₂ ) were mixed. It was performed by sequentially performing the process of, the process of calcining the mixed product at 1200 to 1300 ° C., the process of crushing the calcined product with a ball mill or the like.

However, the above-mentioned manufacturing method has a problem that a solid-phase reaction is difficult to occur and a homogeneous mullite is hard to be obtained. 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 manner has a glass matrix,
Above 00 ° C, there is a sharp drop in temperature due to softening. At present, the synthesis is attempted by metal alkoxide spray decomposition called Numelite, but all of them are expensive and not suitable for practical use.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and an object thereof is to use a metal powder containing at least one of aluminum and silicon as a raw material, which is inexpensive, homogeneous and of high purity. Another object of the present invention is to provide a method for producing a composite oxide powder having a uniform particle size.

[Means for Solving Problems] In the method for producing a composite oxide powder according to the present invention, a metal powder containing at least one of aluminum and silicon to be a composite oxide and at least oxygen are supplied into a container.
And a second step of igniting a flame in a container to form a flame, and using the flame as a reaction flame generated by the reaction of metal powder and oxygen, and combusting the metal powder to synthesize a composite oxide powder. The third step of collecting the synthesized composite oxide powder from the container together with the combustion exhaust gas is sequentially performed.

In the first step, metal powder containing at least one of aluminum and silicon forming the composite oxide and at least oxygen are supplied into the container. When forming the mullite powder, aluminum powder and silicon powder as metal powders prepared in the mullite composition are supplied into the container. Further, when forming the spinel powder, magnesium powder and aluminum powder as powders having a spinel composition are supplied into the container. Further, when forming cordierite powder, aluminum powder, magnesium powder as a metal powder blended in the cordierite composition,
Supply silicon powder into the container.

In the first step, the above-mentioned aluminum powder and silicon powder may be mixed in advance to form a mixed powder, and the mixed powder may be supplied into the container together with the carrier gas. In some cases, aluminum powder, silicon powder, etc. may be separately supplied into the container together with the carrier gas.

Considering the combustibility in the second step, the inside of the container used in the first step needs to be an oxidizing atmosphere. As the carrier gas, it is generally preferable to use an inert gas such as argon gas or an oxidizing gas such as oxygen gas, but oxygen gas is preferable in view of the combustibility in the second step.
The container preferably has an ignition source. The ignition source can be one that produces a spark. The container is preferably lined with a heat insulating material such as alumina brick. In the first step, the amount of metal powder supplied into the container is preferably about 1 to 3 kg per hour, and in this case, the internal volume of the container is preferably about 50 to 100.

In the second step, the powder is ignited in the container to form a flame, and the metal powder is burned to synthesize a composite oxide powder containing at least one of an aluminum oxide and a silicon oxide. In the second step, a high temperature flame is formed because it is usually performed at a high temperature of about 400 to 1000 ° C. In this case, a flame can be formed with propane gas and oxygen gas. By carrying out such a second step, the metals constituting the metal powder are rapidly burned and mixed in an oxidizing atmosphere, so that a homogeneous composite oxide powder is obtained.

In the third step, the synthesized composite oxide powder is collected together with the combustion exhaust gas. In this case, generally, it can be performed by connecting the 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. Here, the collection drum type fine powder collection device is a device mainly composed of a housing having a drum storage chamber and a collection drum rotatably arranged in the drum storage chamber of the housing and having a cooling unit. In the collection drum type fine powder collection device, the combustion exhaust gas containing the powder of the complex oxide is introduced into the drum housing chamber of the housing, and the powder of the complex oxide is collected by the collection drum at about 100 to 150 ° C. Adhere to the surface,
Then, the composite oxide powder is separated from the collecting surface of the collecting drum by a scraper or the like. Since the temperature of the combustion exhaust gas generated in the second step is generally about 1000 ° C or higher, if it is carried out while cooling the collecting drum to about 100 to 150 ° C, the temperature of the collecting drum will be reduced by thermophoresis. It is possible to efficiently collect fine powdery complex oxides such as mullite on the collecting surface.

Here, the thermophoresis phenomenon is due to the effect of heat moving from the high temperature side to the low temperature side when a hot air flow of about 800 to 1000 ° C containing powder of complex oxide such as mullite flows between the high temperature side and the low temperature side. ,
This is a phenomenon in which fine powder migrates to the low temperature side and adheres to the low temperature side.

[Effect of the Invention] According to the method for producing a composite oxide powder according to the present invention, a metal powder containing at least one of aluminum and silicon is used as a raw material powder, and since these have a high enthalpy of reaction formation, flame To a reaction flame having a higher temperature and a larger flame than a normal combustion flame, and therefore, as shown in the test results of the mullite powder described later, it is homogeneous and of high purity, and the particle size is almost the same. A uniform composite oxide powder (containing at least one of an aluminum oxide and a silicon oxide) can be manufactured at low cost.

[Example] An example in which the manufacturing method according to the present invention is applied to a method for manufacturing mullite will be described.

(First step) First, the valve 40 is opened to supply air from the pipe 4 at a rate of 8 m ³ N per hour, and the valve 60 is opened to pass propane gas through the pipe 6 at 1.8 m ³ per hour. Supply at a rate of N, open valves 50 and 70, and pass pipe 5 and pipe 7 to supply oxygen gas at an amount of 13 m ³ per hour.
It is jetted at a speed of N, and the combustor 8 and container 10 are
Preheated to about 00 ℃. After that, the air sent from the pipe 4 was changed to oxygen gas.

On the other hand, the aluminum powder and silicon powder as the metal powder obtained by compounding the composition of mullite _{(3Al 2 O 3 · 2SiO 2} ) V
A mixed powder 2 was obtained by mixing in a mold mixer for about 1 hour.

The aluminum powder used had a purity of 99.9%, and the silicon powder used had a purity of 98%. The particle size of the aluminum powder was about 20 to 30μ, and the particle size of the silicon powder was about 70 to 90μ.

Approximately 2 kg of mixed powder 2 formed as described above in hopper 1.
Inserted. Then, the valve 40 is opened, and oxygen gas (pressure of ² kg / cm ² ) as a carrier gas is introduced into the pipe 4 at a rate of 8 m ³ N per hour, whereby the mixed powder 2 from the hopper 1 to the combustor 8 is introduced. Introduced in.

In the first step, the mixed powder 2 was supplied to the combustor 8 at a rate of 3 kg per hour.

Here, oxygen gas (pressure of 5000 mmAg) is introduced into the combustor 8 at a rate of about 3 m ³ N per hour through the pipe 5 with the valve 50 opened, and the pipe 6 with the valve 60 opened.
Propane gas (pressure: 5000 mmAg) is introduced into the combustor 8 at a rate of 1.8 m ³ N per hour.

(Second Step) The mixed powder 2, oxygen gas, and propane gas introduced into the combustor 8 as described above are mixed and swirled by the swirler 9 to form an air flow in a dust state, and the container 10 is swirled while swirling.
Will be introduced in.

Further, in order to improve the combustibility of propane gas, oxygen gas is passed through the pipe 7 at a rate of about 10 m ³ N per hour to the combustor 8
Sent in.

As a result, the propane gas and oxygen gas introduced into the container 10 are ignited and continuously burned (at 2000 ° C. or higher) to form a flame having high brightness.

As a result, aluminum and silicon in the mixed powder 2 are rapidly mixed in an oxidizing atmosphere to form mullite, which is a homogeneous composite oxide, and vapor containing mullite is formed.

Here, the container 10 is lined with a heat insulating material 10a made of an alumina material and having a thickness of about 10 cm. The heat insulating material 10a is lined to keep the combustion flame warm. The internal volume of the container 10 is about 50.

(Third step) Then, the blower 12 is operated to cause the dust collector 11 to
Combustion exhaust gas containing mullite in 10 is sucked through the pipe 11a. As a result, mullite powder is collected in the collection unit of the dust collector 11. The collected mullite was a white powder. The combustion exhaust gas was released to the outside air.

(Test) The mullite powder produced in this example as described above was subjected to measurement of specific surface area, X-ray diffraction, observation with a scanning electron microscope, and chemical analysis.

The specific surface area was measured by the BET specific surface area measuring method.
The BET specific surface area was specifically measured by weighing about 2.5 gr of a mullite sample, drying it in N ₂ at 1200 ° C. for 30 minutes, and then measuring it with the following device. The measuring instrument used was a SURFACE AREA ANALY2ER model 2200-01 manufactured by Shimadzu Corporation. The measurement result of the specific surface area was 8.3 m ² / g. Thus, since the specific surface area is as high as 8.3 m ² / g, it can be said that the mullite powder produced in this example has excellent sinterability.

For X-ray diffraction, tube Cu, voltage 40KV, current value 30mA,
The sensitivity was 800 cps. The result of X-ray diffraction is shown in FIG. Then, the interplanar spacing determined from each peak of the X-ray diffraction pattern of FIG. 2 and its intensity were compared with known standard data.
As a result, other cristobalite and corundum layers could not be detected, so it can be said that mullite with high homogeneity was obtained by the manufacturing method according to this example.

In the scanning electron microscope observation, the mullite manufactured by the manufacturing method according to the present example was ultrasonically cleaned with alcohol or acetone, and then gold-coated, and under the voltage acceleration of 35 KV, it was performed at about 40,000 times. . A photograph taken with a scanning electron microscope is shown in FIG. 3 (× 40,000 times). As shown in FIG. 3, the particle size of the aluminum powder used as the raw material is about 20 to 30 μ, and the particle size of the silicon powder used as the raw material is about 70 to 90 μ, The mullite manufactured by such a manufacturing method was spherical with a maximum particle size of about 0.8 μm, and the particle size was also uniform as shown in FIG. Therefore, the mullite powder produced in this example is
It can be said that the moldability is excellent.

The chemical analysis was performed according to JIS-R-2212 (1985). As a result of chemical analysis, by weight, aluminum was 39.8%, silicon was 13.2%, and oxygen was 47%.

As described above, according to the method for producing mullite according to this example, it is possible to form mullite powder that is a homogeneous, highly pure, and uniform particle size composite oxide powder as described above.

[Brief description of drawings]

FIG. 1 is a longitudinal side view of an apparatus used in one embodiment according to the present invention, FIG. 2 is a graph showing a characteristic curve of X-ray diffraction, and FIG. 3 is an image taken by a scanning electron microscope. It is a photograph figure which shows the particle structure of mullite powder. In the figure, 1 is a hopper, 2 is a mixed powder, 4 is a pipe, 5 is a pipe, 6 is a pipe, 7 is a pipe, 8 is a combustor, 10 is a container, 10a is a heat insulating material, 11 is a dust collector, and 12 is a blower. Shown respectively.

Continuation of the front page (56) Reference JP-A-60-255602 (JP, A) JP-A-63-185803 (JP, A) JP-B-39-10306 (JP, B1)

Claims (2)

[Claims] 1. A first step of supplying a metal powder containing at least one of aluminum and silicon to be a composite oxide and at least oxygen into a container, and igniting in the container to form a flame, and the flame is generated. A second step of forming a reaction flame generated by a reaction between the metal powder and oxygen and combusting the metal powder to synthesize a composite oxide powder, and combining the synthesized composite oxide powder with combustion exhaust gas from the container A method for producing a composite oxide powder, which comprises sequentially performing a third step of collecting. 2. The method for producing a complex oxide powder according to claim 1, wherein the complex oxide is mullite, and the metal powder constituting the complex oxide is aluminum powder and silicon powder.