JP3276940B2 - Carbide-nitride composite fine powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a raw material fine powder for a carbide-nitride composite ceramic material having excellent high thermal conductivity and high electrical insulation as well as high-temperature strength and corrosion resistance, particularly an AlN-SiC composite. The present invention relates to fine body powder and its manufacturing method.

[0002]

2. Description of the Related Art Aluminum nitride (AlN) has excellent corrosion resistance and heat resistance, so it has been put to practical use as a crucible for manufacturing compound semiconductors, and has been applied as an electronic material utilizing high thermal conductivity and high electrical insulation. Has high expectations.

[0003] On the other hand, silicon carbide (SiC) is a man-made mineral that does not naturally occur. Since it was first synthesized about 100 years ago, it has been mainly used as an abrasive until today, and also has high-temperature corrosion resistance, abrasion resistance, and the like. It is used as a material for refractory bricks and high-temperature heating elements that take advantage of properties such as high strength.

AlN-SiC-based composite ceramics are expected to exhibit high thermal conductivity and high electrical insulation as well as corrosion resistance and heat resistance, as in the case of the above-described single component, and furthermore, have a mechanical effect due to the particle dispersion effect. Improvement in mechanical strength and fracture toughness is expected. However, non-oxides such as nitrides and carbides have poor sintering properties. Therefore, in order to produce dense ceramics, the raw material powder for sintering needs to be made finer and ultrafine.

[0005] The methods for producing the ultrafine particles are roughly classified into a method based on breakdown in which natural raw materials are pulverized and classified, and a method based on build-up in which reaction and precipitation are used to grow from the molecular level. Among these methods, it is difficult to efficiently produce fine particles having a particle diameter of 1 μm or less by the breakdown method, and contamination of impurities from the pulverizer material in the pulverization process is inevitable. Since the particle size distribution can be controlled and ultrafine particles having a particle size of 1 μm or less can be easily obtained, it is suitable for a method for producing a fine powder having excellent characteristics.

[0006] In order to produce composite ceramics using the above-mentioned ultrafine particles, it is necessary to compound ultrafine particles. Although the mixing means is simple, it is not suitable for a method of producing an excellent functional material because the ultrafine particles aggregate together and cannot be uniformly dispersed, and contamination from a mixer cannot be avoided. In recent years, a fluidized-bed CVD method has been developed as a technique for obtaining a composite powder. The synthesis of the composite powder in the conventional two-component CVD method is Al
Whereas the atoms bonded to the metal are limited to those of the same type, such as ₂ O ₃ —TiO ₂ or AlN—Si ₃ N ₄ , this fluidized-bed CVD method uses one component powder. increases the degree of freedom in the combination of powder composite does not react is, Al ₂ O ₃ -TiN based or AlN-S
There is an advantage that a quaternary composite powder such as an iC type can be synthesized.

However, in this fluidized bed CVD method,
In order to fluidize the fine particles, an aggregate of about 50 μm must be formed.
It has been found that there is a problem in the uniformity of D and the uniformity of dispersion of the composition.

[0008]

As described above, the fluidized-bed CVD method is an excellent production method for producing a composite powder.
It is necessary to form aggregates of μm, and this fluidized bed CVD
In the method, high thermal conductivity and high strength as high temperature structural materials,
When producing a composite powder having various properties such as high toughness, for example, an AlN-SiC-based composite powder, uniformity of CVD and dispersion uniformity of the composition in the aggregate of ultrafine particles cannot be obtained. There were manufacturing challenges. That is,
It has been desired to develop a means for combining ultrafine particles capable of producing a composite powder having high dispersion uniformity.

Therefore, an object of the present invention is to eliminate the necessity of forming an aggregate of about 50 μm as in the case of the fluidized-bed CVD method while using a primary fine powder having a submicron particle size, thereby suppressing aggregation of the fine powders. SiC-
It is an object of the present invention to provide a method capable of synthesizing a carbide-nitride-based composite fine powder such as AlN, and at least a highly homogeneous composite fine powder suitable as a raw material of a composite ceramic material which can be produced by the synthesis method.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, have been found to make carbide powders such as SiC float and fluidize and to mix AlN to form a composite.
As a result of investigating the effect of synthesis conditions on the composite ratio and the morphology of the synthesized composite powder in the method of synthesizing the composite powder by a floating fluidized-bed CVD method for CVD synthesis of isonitride, the synthesis of nitride fine particles and their fine carbides were investigated. The present inventors have found that complexation by coating a powder can be performed in one step, and have reached the present invention.

That is, the present inventors, as shown in the schematic diagram of FIG. 1, have a reactor 1 composed of a vertical tubular body, a floating portion 2 provided at the bottom of the reactor, and a connection to an upper portion of the reactor. Collecting section comprising a connecting pipe 4, a collector 5, and a filter 6, and an electric furnace 3 provided around the reactor 1.
The method of synthesizing the composite powder by the floating type fluidized bed CVD method was studied using the composite fine powder synthesizing apparatus of the embodiment composed of the above, and the SiC powder introduced into the floating part 2 was mixed with the diluted N source gas. While the inside of the reactor 1 was levitated and transported, AlCl was heated by a mantle heater or the like provided outside the reactor.
₃ is heated and sublimated, and introduced into the reaction section at the center of the reactor 1, that is, a high-temperature reaction zone, together with the inert N-based carrier gas to synthesize AlN and simultaneously coat the individual SiC particles with the surface. And heating the synthetic composite powder collected from the collecting section to produce NH ₄ C, a by-product.
to obtain highly homogeneous AlN-SiC
We succeeded in synthesizing the fine particles of the composite.

Further, the research results are further developed,
The above synthetic composite method uses Si ₃ N ₄ , Ti instead of AlN.
Vapor phase synthesis of other nitrides such as N, ZrN and HfN;
On the other hand, instead of SiC, other carbide fine powders such as TiC, ZrC and HfC are floated and fluidized to form the AlN-Si.
The present invention was confirmed to be effective for the purpose of synthesizing and compounding a nitride-carbide-based composite fine powder equivalent to the C-based composite fine powder, and completed the present invention. That is, the present invention provides a method for producing a composite fine powder as described below, and a carbide-nitride-based composite fine powder obtained by the method.

In the present invention, a carbide fine powder having a submicron particle size and a carrier gas containing an N source gas are simultaneously and continuously introduced into the bottom of a vertical tubular reactor, and the carbide fine powder is added to the carrier. The gas is floated and transported to an upper high-temperature reaction zone in the tubular reactor and a metal source gas is simultaneously supplied, and is generated by a gas phase reaction between the N source gas and the metal source gas in the high-temperature reaction zone. A composite fine powder obtained by coating the particle surface of the carbide fine powder with a nitride and then collecting the collected fine particles in a collection unit, wherein the carbide fine powder is SiC, Ti
A metal selected from the group consisting of C, ZrC and HfC, wherein the metal source gas is different from an element constituting the carbide fine powder selected from the group consisting of Al, Si, Ti, Zr and Hf sources. An element reaction gas, wherein the nitride is any of AlN, Si ₃ N ₄ , TiN, ZrN and HfN, and the composite fine powder is
The average particle size is 3 to 10 μm, and the content ratio of the nitride is 5
An object of the present invention is to provide a carbide-nitride composite fine powder, which is a highly homogeneous mixture comprising fine particles of 0 mol% or more.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The composite fine powder synthesized according to the method of the present invention is a composite fine powder obtained by surface-coating individual carbide fine powder particles having a submicron particle size with a nitride. Since the whole fine powder is a highly homogeneous mixture of carbide and nitride, this fine powder is used as a raw material to provide a composite material with extremely favorable characteristics in which carbide and nitride compensate each other for defects. can do. Nitride is contained in the form of individual carbide fine powder as core particles and is uniformly deposited and coated in the form of particles or films on the surface, but the deposition thickness of this nitride can be arbitrarily large. It is possible. That is, the content ratio of the nitride in the entire composite fine powder is not low as in the case of, for example, an organic substance having a film formed on the particle surface by surface treatment of the powder, and is set to a large value on the order of the mixture. By changing the reaction conditions at the time of synthesis and synthesis, for example, the content of nitride can be reduced to 1
Can be any value in the range of ~ 99 mol%,
If necessary, the content ratio may be outside the above range. A highly uniform carbide-nitride composite fine powder having such a submicron-size carbide as a core particle and having a mixing ratio on the order of a mixture has not existed conventionally, and the powder itself has been used. It is a new product developed according to the present invention. One particularly preferred example of such a composite fine powder is the AlN—SiC composite fine powder described in the Examples. This fine powder has excellent high thermal conductivity, high strength, corrosion resistance and heat resistance of AlN and SiC, and also has good sinterability. Become.

In carrying out the method of the present invention, for example, A
AlN ₃ sources (purity: 98.0 ° C.) and NH ₃ (purity: 99.9 ° C.)
%), And N ₂ gas (purity 9%) was used as the AlCl ₃ carrier gas and the NH ₃ diluent gas.
9.999%) was used. On the other hand, a commercially available β-type SiC fine powder having a purity of 90% or more and an average particle diameter of 0.15 μm was used as the raw material. One example of an apparatus used in the method of the present invention has a structure as shown in FIG.
At the lower part of the reactor, a floating part 2 is provided. The central part of the reactor 1 can be controlled in temperature by an electric furnace 3 for heating, and the upper part of the reactor comprises a connecting pipe 4, a collector 5 and a filter 6. What is necessary is just a mechanism which has a collection part.

In the operation of synthesizing the composite fine powder, first, SiC fine powder is sequentially supplied from the hopper 7 to the floating part 2, and then, for example, NH 1 which is a first reaction gas as an N source is supplied to the floating part 2. _{While a} mixed gas of N ₂ + NH ₃ composed of N ₃ and N ₂ as an inert carrier gas is introduced as a gas for floating the SiC powder, the gas is jetted from the nozzle 8 to float and transport the SiC fine powder in the reactor while Al is transported. AlCl ₃ as a source is heated to 150 to 200 ° C. by a mantle heater to be sublimated to form a second reaction gas.
_{The three} gases are mixed with N ₂ gas as an inert carrier gas, and introduced into the highest temperature region in the center of the reactor, which is a reaction zone, through the introduction pipe 9.

The synthesis temperature in the highest temperature range is 900 to 1,100 ° C. in the case of AlN synthesis, the synthesis time is about 60 min, and the SiC containing the first reaction gas (NH 3) is used.
The flow rate of the powder levitation mixed gas (NH ₃ + N ₂ ) is 900 to 2,
500 cm ³ / min, and the concentration of NH _{3 in} this mixed gas is 40 v
ol%, and the synthesis conditions in which the flow rate of the AlCl ₃ carrier gas (N ₂ ) in the second mixed gas was 100 cm ³ / min was confirmed to be a preferable example.

Observation of the morphology with a scanning electron microscope (SEM) and the like revealed that a mechanically mixed powder prepared for comparison was a mixture of aggregates rich in either Si or Al. On the other hand, the composite fine powder obtained by the method of the present invention is a mixture of aggregates obtained by coating SiC with AlN particles or an AlN film, and thus the composite fine powder has higher dispersion uniformity. In addition, the composite fine powder can be used for forming aggregates of 1 μm or less into AlN and Si.
Since the presence of both C was confirmed, it was found that the AlN particles adhered to and covered even the fine SiC aggregates.

That is, according to the production method of the present invention, it was found that a fine carbide-nitride composite fine powder having an average particle diameter of 3 to 10 μm was obtained using carbide having a submicron particle size. It was also found that this composite fine powder was extremely excellent in dispersion uniformity, and that each individual fine particle maintained uniform vapor deposition. That is, the composite fine powder as a whole has extremely high homogeneity and is an excellent raw material for a dense composite ceramic material.
Hereinafter, the present invention will be further described with reference to examples.

[0020]

EXAMPLES Example 1 As shown in FIG.
Through an electric furnace 3 with a mullite tube with an inner diameter of 42 mm and a length of 800 mm.
Using the composite fine powder synthesizer installed vertically
SiC fine powder (Mitsui Toatsu, purity 99% or more, average grain size)
0.15μm, β-type) from the hopper 7 to the floating part 2
And the N 2 containing the first reaction gas
_Two -NH _Three The mixed gas is 1,20
0cm^Three/ min and float SiC powder for a certain time (20 min)
I let it. On the other hand, AlCl_Three Is provided outside the introduction pipe 9
Heated to 150-200 ° C with a heated mantle heater (not shown).
Sublimation by heating, this AlCl_Three Gas to the second reaction gas
As inert N_Two 200cm with carrier gas^Three/ min
In the reactor at a flow rate, through an inlet pipe 9 provided above the floating part
It was introduced into the reaction zone, the highest temperature zone in the core. This place
In this case, a mullite tube is used as the inlet tube 9 and its outlet is
Place the molybdenum alloy support above so that it is in the center.
Attached slightly below the mouth.

The composite temperature of the composite of AlN and SiC in the highest temperature range was 1,100 ° C., and the composite time was controlled to be about 60 min. The particles were deposited on the portions indicated by A to G in 1, and these deposited powders were separately collected in an Ar atmosphere. Next, the collected synthetic composite powder is
By heating at 500 ° C for 3 hours in an air stream, NH ₄ which is a by-product
The Cl was removed to obtain an AlN-SiC-based composite fine powder.

FIG. 2 is an X-ray diffraction diagram of these composite powders. FIGS. 2A to 2G respectively show the collection points A to G in FIG.
3 shows a diffraction diagram for the sample of FIG. At the collection point A, only the diffraction line of AlN was detected, and SiC was detected by BF. In B to G, by-product NH ₄ Cl
, But SiC was not detected in G. In this case, no SiC was detected in A and G, but since the color of the synthetic composite powder was grayish white, it is considered that a small amount was contained.

Example 2 In the synthesis apparatus shown in FIG. 1, a floating test of SiC powder was performed using a transparent glass tube instead of the mullite tube as the reactor 1. In this case, unlike Embodiment 1, without supplying AlCl ₃ , N ₂ was used for floating.
The gas was used as a carrier gas to float only SiC, and the flying height of the SiC and the particle size distribution of the SiC before and after the flying were also measured.

First, the SiC fine powder is lifted up from the hopper.
To the levitation gas (N _Two ) On the levitated surface
And float the SiC fine powder for a certain time (20 min) to collect
Collects SiC deposited on the connecting pipe of the part and measures its mass
did. The flow rate of the floating gas is 700-2,000cm^Three/ min range and
The flow rate of SiC was 700 cm^Three/ min value
Standardized.

As a result, it was observed that the SiC fine powder floated while maintaining a laminar flow state. The relationship between the flow rate of the floating gas and the floating amount of the SiC fine powder was as shown in FIG. As can be seen from this figure, the amount of floating SiC powder increases with an increase in the flow rate of the floating gas.
The floating speed of the C fine powder was 1,200 cm ³ / min for the flow rate of the floating gas.
It was found to be 8 mg / min.

Next, when only SiC was floated, the centrifugal sedimentation diameter of the SiC fine powder before and after the floating was measured. The particle size distribution was as shown in FIGS. 4 (a) and 4 (b). In this case, FIG.
It is a particle size distribution of the iC fine powder, and FIG. 12B shows the result when the gas was levitated at a floating gas flow rate of 1,400 cm ³ / min.
The median diameter was calculated to be 0.28 μm and 0.38 μm, respectively. From these facts, the SiC fine powder after floating is 4 ~
It was found to show an aggregation of 15 μm. This indicates that the method of the present invention can fluidize fine particles with less agglomeration than the ordinary fluidized-bed CVD method.

Example 3 Using the synthesis apparatus shown in FIG. 1, a test was conducted on the synthesis conditions and the AlN / SiC composite ratio. First, the AlCl ₃ carrier gas flow rate was 1,400 cm ³ / m
The relationship between the mixed gas flow rate for SiC levitation and AlN mol% was determined under the conditions of in and synthesis temperature: 1,100 ° C. The results are shown in FIG. As shown in this figure, it can be seen that the proportion of AlN decreases when the flow rate of the mixed gas for floating SiC is increased.
It is considered that the floating amount of the iC fine powder was increased.

Next, the flow rate of the mixed gas for floating: 1,200 cm ³ / m
FIG. 6 shows the relationship between the synthesis temperature and AlN mol% under the conditions of in, AlCl ₃ carrier gas flow rate of 200 cm ³ / min. In this case, it can be seen that increasing the synthesis temperature increases the proportion of AlN. This is presumably because the synthesis reaction rate was increased by increasing the synthesis temperature.
Also, judging from the X-ray diffraction diagram, when the synthesis temperature decreases, A
It is thought that the crystallinity of 1N deteriorated.

Next, the AlCl ₃ sublimation rate and the composite ratio (A
1N content ratio), and the results are shown in FIG. The broken line in the figure AlN78 mol% of the composite fine particles (SiC floating gas mixture flow rate: 1,200cm _³ / min, AlCl ³ carrier gas flow: 200 cm ³ / min, synthesis temperature: synthesized at 1,100 ° C., in the drawing ○ (Indicated by an asterisk)), the theoretical value of which is 100%
In this case, all of the floating SiC fine powders are calculated as composites. Incidentally, AlCl ₃ carrier gas flow, as denoted in the FIG., Each △: 100 cm ³
/ min, ○: 200 cm ³ / min and Δ: 400 cm ³ / min. As a result, the composite ratio (AlN content ratio)
There is a tendency to be strongly influenced by the sublimation rate of AlCl ₃ without being affected by the flow rate of the Cl ₃ carrier gas.

Next, the relationship between the AlCl ₃ carrier gas flow rate and the AlN mol% was determined, and the results are shown in FIG. As can be seen from the figure, there is no clear correlation between the AlCl ₃ carrier gas flow rate and the composite ratio (AlN content ratio), and the composite ratio is not affected by the AlCl ₃ carrier gas flow rate or is smaller than other factors. It is expected that the impact will be very small. In addition, as shown in the figure, the supply rate of AlCl ₃ was ◇: 0.08 g / mi, respectively.
n, ● ■: 0.11 g / min, △: 0.14 g / min, ○: 0.17 g / mi
n and □: 0.27 g / min.

From the above results, the supply rate of AlCl ₃ is A
It was speculated that the lCl ₃ sublimation rate was rate-limiting and hardly affected by the AlCl ₃ carrier gas flow rate.

[0032]

As described above, according to the method of the present invention, the average particle diameter of each particle is 3 to 10 μm and the content ratio of the nitride is increased under a predetermined synthesis condition while using a simple means. Can be obtained as 1-99 mol%, which is a highly homogeneous carbide-nitride system that combines high-temperature strength and corrosion resistance with excellent high thermal conductivity and high electrical insulation, which could not be synthesized conventionally. There is an effect that the raw material powder of the composite material can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an outline of a composite fine powder synthesizing apparatus according to an embodiment of the present invention.

FIG. 2 is an X-ray diffraction diagram of a composite fine powder obtained by using the synthesis apparatus of FIG. 1, and FIGS. 2 (A) to 2 (G) show the collection of each of A to G shown in FIG. FIG. 4 is a diffraction diagram of the sample at a point.

FIG. 3 shows a floating gas flow rate and Si when only SiC is floated without supplying AlCl ₃ using the synthesis apparatus of FIG. 1;
It is a graph which shows the relationship with C flying height.

FIG. 4 is a diagram showing the particle size distribution of the tested SiC fine powder when only SiC is floated by the synthesis apparatus of FIG. 1, and FIG. 4 (a) shows the particle size distribution of the raw SiC fine powder; FIG. 2B is a graph showing the particle size distribution of the SiC fine powder after floating.

FIG. 5 shows the flow rate of the mixed gas for SiC levitation and the AlN of the composite fine powder when the composite fine powder is obtained by the synthesizer of FIG.
It is a graph which shows the relationship with a content ratio.

FIG. 6 is a graph showing the relationship between the synthesis temperature and the AlN content ratio of the composite fine powder when the composite fine powder is obtained by the synthesis apparatus of FIG.

7 is a graph showing the relationship between the sublimation rate of AlCl ₃ and the AlN content ratio of the composite fine powder when the composite fine powder is obtained by the synthesis apparatus of FIG. 1.

FIG. 8 shows the flow rate of AlCl ₃ carrier gas and the A of the composite fine powder when the composite fine powder is obtained by the synthesis apparatus of FIG. 1.
It is a graph which shows the relationship with 1N content ratio.

[Explanation of symbols]

 Reference Signs List 1 reactor 2 floating part 3 electric furnace 4 connecting pipe 5 collector 6 filter 7 hopper 8 nozzle 9 introduction pipe A to G

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35 / 56,35 / 58 C04B 35/622-35/628 C01B 21 / 00,31 / 00

Claims (1)

(57) [Claims] 1. A carrier containing a submicron-sized carbide fine powder and an N source gas at the bottom of a vertical tubular reactor.
Introducing a gas at the same time continuously, the upper part of the high temperature reaction of the tubular reactor and the carbide fine powder by the key <br/> Yariyagasu
The metal source gas while flying transport band co-fed, the carbides nitrides produced by <br/> gas phase reaction of the N source gas and the metal source gas in said <br/> high temperature reaction zone Grain of fine powder
A composite fine powder obtained by covering the surface of the particle and collecting the powder at a collecting part , wherein the carbide fine powder is SiC, TiC, ZrC.
And a carbide selected from the group consisting of HfC and
The metal source gas comprises the carbide fine powder selected from the group consisting of Al, Si, Ti, Zr and Hf sources.
An element and a reaction gas of a different element , wherein the nitride is
Any one of AlN, Si ₃ N ₄ , TiN, ZrN and HfN, and the composite fine powder has an average particle diameter of 3 to 10 μm and a nitride content of 50 mol% or less.
A carbide-nitride-based composite fine powder, which is a highly homogeneous mixture comprising the above fine particles.