JP2024023759A - Al4SiC4 composition or Al4SiC4 powder - Google Patents

Abstract

The present invention provides an Al4SiC4 composition or Al4SiC4 powder that is substantially free of Al4C3 and sulfur. [Solution] The integrated intensity of the diffraction peak of Al4C3 near 2θ=55.1° measured by powder X-ray diffraction IAl4C3 (cps・deg) and the integrated intensity of the diffraction peak of Al4SiC4 near 2θ=56.0° IAl4SiC4 (cps・deg) ratio IAl4C3/IAl4SiC4 is 0.1% or less, sulfur content is 150 mass ppm or less, and Al4SiC4 at around 2θ=31.7° measured by powder X-ray diffraction. The Al4SiC4 composition or Al4SiC4 powder has a crystallite size of 1000 to 1500 Å calculated from the diffraction peak. [Selection diagram] Figure 2

Description

_The present invention relates to _Al4SiC4 compositions or _{Al4SiC4 powders} .

Al ₄ SiC ₄ is a carbide made of aluminum and silicon, and has recently attracted attention as a new functional additive for carbon-containing refractories. One of the effects of adding Al ₄ SiC ₄ is densification of the refractory structure. It is estimated that the densification of the refractory structure occurs when Al ₄ SiC ₄ present in the refractory structure reacts with CO gas in the atmosphere. That is, as shown in equation (1), gas containing Al is generated from Al ₄ SiC ₄ at high temperatures, diffuses into the voids in the refractory structure, reacts with CO gas, and condenses again as Al ₂ O ₃ . It is estimated that this is caused by filling the voids.

Al ₄ SiC ₄ +6CO→2Al ₂ O ₃ +SiC+9C (1)

As a method for producing Al ₄ SiC ₄ , Non-Patent Document 1 describes mixing starting materials of an aluminum source, a silicon source, and a carbon source, and sintering the mixed raw materials in an inert gas atmosphere to synthesize Al ₄ SiC ₄ . A method is disclosed.

It is estimated that the synthesis of Al ₄ SiC ₄ is performed in the following two steps. That is, as the temperature rises due to heating, Al ₄ C ₃ and SiC are first generated as shown in equations (2) and (3), and then at 1300°C or higher, Al ₄ C ₃ and SiC are formed as shown in equation (4). reacts to produce Al ₄ SiC ₄ .

4Al+3C→Al ₄ C ₃ (2)
Si+C→SiC (3)
_Al4C3 + _SiC → _Al4SiC4 ( ₄ )

Journal of the Ceramic Society of Japan 115 [11] 761-766(2007)

However, in the conventional Al ₄ SiC ₄ manufacturing method, the obtained Al ₄ SiC ₄ powder contains Al ₄ C ₃ as an impurity, which is a by-product during Al ₄ SiC ₄ synthesis. Al ₄ C ₃ is easily hydrated, and when Al ₄ SiC ₄ powder containing Al ₄ C ₃ is added to a refractory, the Al ₄ C ₃ hydrates and expands in volume, impairing the shape stability of the refractory. .

Furthermore, in the conventional Al ₄ SiC ₄ manufacturing method, the obtained Al ₄ SiC ₄ powder contains sulfur derived from the carbon source of the starting material. When Al ₄ SiC ₄ powder containing sulfur is added to a refractory, the refractory expands in volume and loses shape stability. The reason for this is that a trace amount of sulfur present in the starting carbon source reacts with Al during the synthesis process of Al ₄ SiC ₄ to produce Al ₂ S ₃ and the like. _{Al2S3 etc.} are easily hydrated, and when _Al4SiC4 powder containing _{Al2S3 etc.} is added to a refractory, the refractory expands _in volume and loses its shape stability.

The present invention has been made in view of the above problems, and aims to provide an Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder that is substantially free of Al ₄ C ₃ and sulfur. Take it as a challenge.

In order to solve the above-mentioned problems, one embodiment _{of the present invention provides an integrated intensity of the diffraction peak of Al4C3 near 2θ=55.1° measured by powder X-ray diffraction IAl4C3 ( cps}・deg) and 2θ = Integrated intensity of the diffraction peak of Al ₄ SiC ₄ around 56.0° I Ratio to _Al4SiC4 (cps・deg) I _Al4C3 /I _Al4SiC4 is 0.1% or less and the sulfur content is 150 mass ppm or less An Al ₄ SiC ₄ composition or Al ₄ SiC ₄ which has a crystallite size of 1000 to 1500 Å calculated from the diffraction peak of Al ₄ SiC ₄ at around 2θ=31.7° measured by powder X-ray diffraction. It is a powder.

According to the present invention, it is possible to provide an Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder that is substantially free of Al ₄ C ₃ and sulfur. Since it does not substantially contain Al ₄ C ₃ and sulfur, even if the Al ₄ SiC ₄ powder of the present invention is added to a refractory, the volume of the refractory will expand and its shape stability will be affected. You can prevent damage.

Large crystallite size indicates growing crystal morphology. Al ₄ SiC ₄ particles having such a crystallite size have enhanced hydration resistance. Therefore, the functionality in the refractory structure is less likely to deteriorate.

FIG. 1 is a diagram illustrating the pre-heating treatment of the carbon source according to the present embodiment (FIG. 1(a) shows the state where the carbon source is placed in the inner container, and FIG. 1(b) shows the state where the inner container is embedded in the coke granules. ). 2 is a chart obtained by X-ray diffraction analysis of the Al ₄ SiC ₄ powder produced in Example 1. FIG. 3 is an enlarged view of the chart of FIG. 2 at 50° to 60° on the horizontal axis. FIG. 3 is an enlarged view of the chart of FIG. 2 at 20° to 30° on the horizontal axis.

DESCRIPTION OF EMBODIMENTS Hereinafter, an Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder according to an embodiment of the present invention and a method for producing the same will be described in detail based on the accompanying drawings. However, the present invention can be embodied in various forms and is not limited to the embodiments described herein. Rather, these embodiments are provided with the intention that this disclosure will be thorough and thorough, and will fully enable those skilled in the art to understand the invention.
( _Al4SiC4 composition _{or Al4SiC4 powder} )

First, the Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder will be explained. The Al ₄ SiC ₄ composition is obtained by firing a mixture containing an aluminum source, a silicon source, and a carbon source. Al ₄ SiC ₄ powder is obtained by grinding an Al ₄ SiC ₄ composition.

The Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder of this embodiment does not substantially contain Al ₄ C ₃ . Specifically, the integrated intensity of the diffraction peak _{of Al4C3} around 2θ=55.1° measured by powder X-ray diffraction _IAl4C3 (cps・deg) and the _Al4SiC around 2θ=56.0° Integrated intensity of the diffraction peak of ₄ I _Al4SiC4 (cps deg) Ratio I _Al4C3 /I _Al4SiC4 is 0.1% or less, preferably 0.05% or less, more preferably 2θ = 55.1° The diffraction peak of Al ₄ C ₃ in the vicinity is not observed.

When Al ₄ SiC ₄ powder containing Al ₄ C ₃ is added to a refractory, the Al ₄ C ₃ hydrates and expands in volume, impairing the shape stability of the refractory. Therefore, in this embodiment, I _Al4C3 /I _Al4SiC4 measured by powder X-ray diffraction is 0.1% or less.

Among the information obtained from powder X-ray diffraction, the area occupied by the waveform of the diffraction peak is the integrated intensity. The integrated intensity is the product of the diffraction angle of the sample in the powder and the geometric existence probability (peak height) of a certain crystal grain. By calculating the ratio of integrated intensities, it becomes possible to quantitatively evaluate the existence probability of a certain crystal grain. Here, the ratio of graphite remaining in the Al ₄ SiC ₄ powder can be quantitatively analyzed, and the ratio of Al ₄ C ₃ remaining in the Al ₄ SiC ₄ powder can be quantitatively analyzed.

Powder X-ray diffraction was performed under the following conditions.

The above powder X-ray diffraction using CuKα rays was performed using RINT2000 manufactured by Rigaku Co., Ltd., and the diffraction measurements were made in a graph where the horizontal axis is the X-ray incident angle 2θ (°) and the vertical axis is the diffraction intensity (cps). The intensity was plotted. To calculate the integrated intensity (cps/deg), "Integrated powder X-ray analysis software PDXL" ver. 2.7.3.0 manufactured by Rigaku Co., Ltd. was used.

The Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder of this embodiment does not substantially contain sulfur. Specifically, the sulfur content (sulfur in simple sulfur and sulfur compounds such as Al ₂ S ₃ ) is 150 mass ppm or less, preferably 130 mass ppm or less, and more preferably 100 mass ppm or less.

When Al ₄ SiC ₄ powder containing sulfur is added to a refractory, the refractory expands in volume and loses shape stability. The reason for this is that sulfur present in a trace amount in the starting carbon source reacts with Al during the synthesis process of Al ₄ SiC ₄ to produce Al ₂ S ₃ . _{Al2S3 is} easily hydrated, and when _Al4SiC4 powder containing _Al2S3 is added to a refractory, _the volume of _the refractory expands, impairing its shape stability. Therefore, in this embodiment, the sulfur content contained in the Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder is 150 mass ppm or less.

The sulfur content was measured using a combustion-infrared absorption method, specifically, using a material carbon/sulfur analyzer (manufactured by Horiba, Ltd., EMIA-810). When the sample is burned at high temperature in an oxygen stream, the sulfur contained in the sample is gasified and extracted as sulfur dioxide. The extracted sulfur dioxide was measured with an infrared detector, and the measured value of sulfur dioxide was converted to the sulfur content in the sample. This method for quantifying sulfur content is standardized in JIS R 2016-2:2009.

It is desirable that the Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder of this embodiment does not substantially contain graphite. Specifically, the integrated intensity I _G (cps・deg) of the diffraction peak of graphite near 2θ = 26.5° measured by powder X-ray diffraction and the diffraction of Al ₄ SiC ₄ near 2θ = 56.0°. Peak integrated intensity I _Al4SiC4 (cps・deg) ratio I _G /I _Al4SiC4 is 0.01% or less, preferably 0.005% or less, more preferably graphite around 2θ=26.5° No diffraction peak is observed.

Graphite is derived from the starting carbon source. Graphite has oxidation resistance up to around 1000°C. When Al ₄ SiC ₄ powder containing graphite is added to a refractory, the reactivity of Al ₄ SiC ₄ decreases. Densification of the refractory structure occurs when Al ₄ SiC ₄ reacts with oxidizing gas (CO gas), so when graphite coexists with Al ₄ SiC ₄ , the effect of adding Al ₄ SiC ₄ is inhibited. Therefore, in this embodiment, I _G /I _Al4SiC4 measured by powder X-ray diffraction is 0.01% or less.

The Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder of this embodiment preferably has a large crystallite size. Specifically, the crystallite size calculated from the diffraction peak of Al ₄ SiC ₄ near 2θ = 31.7° measured by powder X-ray diffraction is 1000 to 1500 Å, more preferably 1100 to 1500 Å, and Preferably it is 1100 to 1450 Å.

Large crystallite size indicates growing crystal morphology. Al ₄ SiC ₄ particles having such a crystallite size have enhanced hydration resistance. Therefore, the functionality in the refractory structure is less likely to deteriorate. If the crystallite size is too large, functionality (reactivity with CO gas) decreases, so 1000 to 1500 Å is optimal.

The crystallite size of Al ₄ SiC ₄ is calculated by measuring the half width of the diffraction peak around 2θ=31.74° in powder X-ray diffraction using CuKα rays and using Scherrer's formula. Specifically, "Integrated Powder X-ray Analysis Software PDXL" ver. 2.7.3.0 manufactured by Rigaku Co., Ltd. was used to calculate the crystallite size.

The particle size of the Al ₄ SiC ₄ powder of this embodiment is not particularly limited, but in the volume-based particle size distribution, the difference between the cumulative 90% particle size and the cumulative 10% particle size is divided by the cumulative 50% particle size (D ₉₀ - D ₁₀ )/D ₅₀ : The particle size distribution span value is preferably 1.7 to 2.5.

The reason why the particle size distribution span value is set to 1.7 to 2.5 is from the viewpoint of defining the range (width) of the particle size distribution. If it is less than 1.7, there is a problem that the range of particle size distribution is narrow and agglomeration of particles tends to occur, whereas if it is 1.7 or more, aggregation can be suppressed and the performance as an additive can be improved. . Moreover, when it exceeds 2.5, there is a problem that the ratio of coarse particles to fine particles increases, which affects the performance as an additive. The optimum particle size distribution span value is between 1.7 and 2.5, preferably between 1.8 and 2.4.

The range of the measured particle size distribution (D ₀ to D ₁₀₀ ) is 7 to 350 μm. Based on this, D ₉₀ −D ₁₀ (width of particle size distribution) of the molecule can be defined. The denominator D ₅₀ is in the range 7-350 μm, preferably 30-120 μm.

The volume-based cumulative 10% particle diameter, cumulative 50% particle diameter, and cumulative 90% particle diameter are measured by a laser diffraction scattering method. The method for measuring particle size distribution using laser diffraction scattering is standardized in JIS R 1629:1997. Specifically, the measurement was performed using a laser diffraction scattering particle size distribution analyzer MT3000II manufactured by Nikkiso Co., Ltd. Distilled water was used as the solvent, and the particle size was measured after dispersing the powder using ultrasonic waves using a sample circulator that comes standard with the device.
(Method _for producing _Al4SiC4 composition or _{Al4SiC4 powder} )

Next, a method for producing the Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder will be explained.

An aluminum source, a silicon source, and a carbon source are used as starting materials.

Metal Al, aluminum oxide, aluminum hydroxide, or the like can be used as the aluminum source. In terms of purity and production efficiency, it is desirable to use metallic Al powder.

Metallic Si, silicon dioxide, or the like can be used as the silicon source. From the viewpoint of purity and production efficiency, it is desirable to use metallic Si powder. Note that Al--Si alloy powder can also be used as the aluminum source and silicon source.

At least a portion of the carbon source is a heat-treated carbon source that has been previously heat-treated in coke granules. Carbon black is used as the heat-treated carbon source.

Preheating treatment in coke granules will be explained. As shown in FIG. 1(a), carbon black 1 is placed in an inner container 2 such as a crucible, covered with a lid 2a, and as shown in FIG. 1(b), the inner container 2 is placed in an outer container 3 such as a crucible. , embedded in coke particles 4 such as coke breeze. After that, if the outer container 3 is placed in a heating furnace and heated in an argon gas atmosphere, heat treatment in the coke granules 4 becomes possible.

Carbon black is an artificial carbon with high industrial value, and is a material that will have a stable supply in the future. Some types of carbon black originally have a relatively low sulfur content. By preheating such carbon black, the sulfur content can be further reduced. The reason for this is that free sulfur present in carbon black is oxidized at high temperatures by oxygen contained in carboxyl groups and hydroxyl groups, which are surface functional groups of carbon black particles, and is removed by gasification. . On the other hand, sulfur present in the molecules constituting carbon black is difficult to gasify and difficult to remove even by the above-mentioned method, so it tends to remain.

In addition to carbon black, graphites such as scaly graphite and artificial graphite can also be used as the heat-treated carbon source. However, naturally produced graphite is unevenly distributed as a resource, and artificial graphite has a limited range of industrial uses and is not very versatile as a raw material. When graphite is used as a carbon source, a diffraction peak of graphite is observed in powder X-ray diffraction. By using pre-heat-treated carbon black as a carbon source, the diffraction peak of graphite can be reduced. Specifically, the integrated intensity of the diffraction peak of graphite measured by powder X-ray diffraction I _G and Al ₄ SiC ₄ The ratio of the integrated intensity of the diffraction peak I to _Al4SiC4 I _G /I _Al4SiC4 can be reduced to 0.01% or less.

The carbon source preferably contains 80 mass% to 100 mass% of the above-mentioned carbon black that has been preheated as a main material. By using carbon black as the main material of the carbon source, the diffraction peak of graphite can be effectively reduced.

The carbon source desirably contains 20 mass% or less of an auxiliary material consisting of at least one of coke (preferably petroleum coke), expanded graphite, or activated carbon. Petroleum-based coke and activated carbon are carbon particles with porous surfaces. Expanded graphite is graphite with expanded interlayers. Since petroleum coke, expanded graphite, and activated carbon all have porous surfaces, they can promote the synthesis reaction of Al ₄ SiC ₄ and make it difficult for Al ₄ C ₃ to remain. If there is no residual Al ₄ C ₃ , the synthesis yield of Al ₄ SiC ₄ will improve. Note that petroleum coke, expanded graphite, and activated carbon have higher sulfur content than carbon black, so these are blended so that the sulfur content after synthesis does not exceed 150 mass ppm. It is also possible to pre-heat-treat petroleum coke, expanded graphite, and activated carbon, but even if these are pre-heat-treated, the sulfur content cannot be reduced as much as carbon black.

The above aluminum source, silicon source, and carbon source are weighed in amounts such that the molar ratio of aluminum, silicon, and carbon contained in each source is 4:1:4.

Next, the aluminum source, silicon source, and carbon source are mixed using a mixer such as a dry Henschel mixer. Although the mixing time is not particularly limited, it is desirable to mix for 5 minutes or more in order to mix the raw materials sufficiently.

Next, the mixed raw materials are loaded into a crucible, and the crucible is placed in a batch furnace such as a resistance heating furnace or a tube furnace, or a continuous furnace such as a tunnel furnace, and the mixed raw materials are inert at a temperature of 1650 to 1900°C for 1 to 10 hours. Firing in a gas atmosphere.

Al ₄ SiC ₄ is synthesized by firing. Synthesis of Al ₄ SiC ₄ is performed in the following two steps. That is, as the temperature rises due to firing, Al ₄ C ₃ and SiC are first generated as shown in equations (2) and (3), and then at 1300°C or higher, Al ₄ C ₃ and SiC are formed as shown in equation (4). reacts to produce Al ₄ SiC ₄ . At temperatures below 1650°C, Al ₄ C ₃ tends to remain after the reaction, and at temperatures above 1650°C, the production of Al ₄ SiC ₄ is significantly promoted. If the firing temperature exceeds 1900°C, a part of Al ₄ SiC ₄ will be thermally decomposed, so it is preferably 1900°C or lower.

4Al+3C→Al ₄ C ₃ (2)
Si+C→SiC (3)
_Al4C3 + _SiC → _Al4SiC4 ( ₄ )

By mixing an aluminum source, a silicon source, and a carbon source at the above molar ratio and firing the mixed raw material at the above temperature for the above period, Al ₄ C ₃ can be reduced. Ratio of the measured integrated intensity of the diffraction _peak of _Al4C3 I _Al4C3 ( _{cps・deg) and the integrated intensity of the diffraction peak of Al4SiC4 I Al4SiC4 ( cps}・deg) _Al4C3 /I _Al4SiC4 is 0.1 % or less.

After the synthesis of Al ₄ SiC ₄ , the crucible is removed from the furnace and the Al ₄ SiC ₄ composition is removed from the crucible. Dry crushing of the Al ₄ SiC ₄ composition with a roll crusher yields Al ₄ SiC ₄ powder.
(Industrial applicability)

The Al ₄ SiC ₄ powder of this embodiment does not contain sulfur-containing compounds such as Al ₄ C ₃ and Al ₂ S ₃ that are digestible with water, and contains graphite that reduces the reactivity of Al ₄ SiC ₄ . do not. The Al ₄ SiC ₄ powder of this embodiment can be used as a functional additive that improves shape stability, strength improvement, and infiltration resistance of carbon-containing refractories. The Al ₄ SiC ₄ powder of this embodiment is not limited to being used as a functional additive for carbon-containing refractories, but can also be used, for example, as an antioxidant.

(Example 1)
Metal Al powder (-75 μm), metal Si powder (-45 μm), and preheated carbon black (60 to 280 nm) were mixed in a theoretical molar ratio of Al:Si:C=4:1:4, and dry Henschel Mixed with a mixer for 10 minutes. The mixed raw materials were loaded into a crucible, heated to 1800°C in an argon gas stream, and kept at 1800°C for 10 hours.

Power to the furnace was removed and the crucible was allowed to cool to ambient temperature. After cooling, the crucible was taken out from the furnace, the Al ₄ SiC ₄ composition was taken out from the crucible, and the Al ₄ SiC ₄ composition was dry-pulverized with a roll crusher.

The physical properties of the obtained Al ₄ SiC ₄ powder were measured by powder X-ray diffraction. The physical properties were measured according to the method described above.

FIG. 2 is a chart obtained by X-ray diffraction analysis of Al ₄ SiC ₄ powder. The horizontal axis is the incident angle 2θ (unit: °), and the vertical axis is the diffraction intensity (unit: cps).

FIG. 3 is an enlarged view of the chart in FIG. 2 at 50° to 60° on the horizontal axis. The diffraction peak of Al ₄ C ₃ near 2θ=55.1° was not observed, and I _Al4C3 /I _Al4SiC4 was 0. FIG. 4 is an enlarged view of the chart in FIG. 2 at 20° to 30° on the horizontal axis. No graphite diffraction peak was observed near 2θ=26.5°, and I _G /I _Al4SiC4 was 0.

Note that characteristic X-rays generated from a Cu target were used as the X-ray source used in the measurement. Characteristic X-rays include Kα and Kβ, and Kα further includes Kα ₁ and Kα ₂ . The X-ray used for measurement has Kα ₁ . Kβ appears as a satellite to the strongest peak at 31.7°. In this measurement, most of the peaks can be removed by installing a cut filter, but if the strength of the X-ray source and detector sensitivity of this measurement device are high, Kβ derived from X-rays will have a small peak as shown in Figure 2. appears as As shown in FIG. 3, the peak derived from Kα ₂ begins to separate at a height of about 1/2 from the main peak Kα ₁ as the angle increases.

The sulfur content of the obtained Al ₄ SiC ₄ powder was 90 ppm. The crystallite size calculated from the diffraction peak of Al ₄ SiC ₄ near 2θ=31.7° was 1147 Å. In the volume-based particle size distribution, (D ₉₀ −D ₁₀ )/D ₅₀ : particle size distribution span value was 2.1.
(Example 2)

5 mass% of needle coke was added as an auxiliary material of carbon source. That is, the carbon sources were 95 mass% of preheated carbon black and 5 mass% of needle coke. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

The obtained Al ₄ SiC ₄ powder had I _Al4C3 /I _Al4SiC4 of 0, I _G /I _Al4SiC4 of 0, sulfur content of 140 ppm, crystallite size of 1157 Å, and particle size distribution span value of 2.0.
(Example 3)

20 mass% of needle coke was added as an auxiliary carbon source. That is, the carbon sources were 80 mass% of preheated carbon black and 20 mass% of needle coke. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

The obtained Al ₄ SiC ₄ powder had I _Al4C3 /I _Al4SiC4 of 0, I _G /I _Al4SiC4 of 0, sulfur content of 140 ppm, crystallite size of 1118 Å, and particle size distribution span value of 2.0.
(Example 4)

5 mass% of expanded graphite was added as an auxiliary material for the carbon source. That is, the carbon sources were 95 mass% of preheated carbon black and 5 mass% of expanded graphite. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

The obtained Al ₄ SiC ₄ powder had I _Al4C3 /I _Al4SiC4 of 0, I _G /I _Al4SiC4 of 0, sulfur content of 130 ppm, crystallite size of 1220 Å, and particle size distribution span value of 2.2.
(Example 5)

20 mass% of expanded graphite was added as an auxiliary material for the carbon source. That is, the carbon sources were 80 mass% of carbon black and 20 mass% of expanded graphite which had been preheated. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

The obtained Al ₄ SiC ₄ powder had I _Al4C3 /I _Al4SiC4 of 0, I _G /I _Al4SiC4 of 0, sulfur content of 130 ppm, crystallite size of 1244 Å, and particle size distribution span value of 2.4.
(Example 6)

5 mass% of activated carbon was added as an auxiliary material for the carbon source. That is, the carbon sources were 95 mass% of preheated carbon black and 5 mass% of activated carbon. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

The obtained Al ₄ SiC ₄ powder had I _Al4C3 /I _Al4SiC4 of 0, I _G /I _Al4SiC4 of 0, sulfur content of 120 ppm, crystallite size of 1168 Å, and particle size distribution span value of 1.9.
(Example 7)

20 mass% of activated carbon was added as an auxiliary carbon source. That is, the carbon sources were 80 mass% of preheated carbon black and 20 mass% of activated carbon. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

The obtained Al ₄ SiC ₄ powder had I _Al4C3 /I _Al4SiC4 of 0, I _G /I _Al4SiC4 of 0, sulfur content of 140 ppm, crystallite size of 1212 Å, and particle size distribution span value of 1.8.
(Comparative example 1)

The carbon source was 100 mass% needle coke. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

_{The IAl4C3 / IAl4SiC4} of the obtained _Al4SiC4 powder was 0, the _IG / _IAl4SiC4 was 2.89, the sulfur content was 160 ppm, the crystallite size was 1073 Å, and the particle size distribution span value was 2.3. .
(Comparative example 2)

The carbon source was 100 mass% activated carbon. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

The obtained Al ₄ SiC ₄ powder had I _Al4C3 /I _Al4SiC4 of 0, I _G /I _Al4SiC4 of 0, sulfur content of 180 ppm, crystallite size of 1149 Å, and particle size distribution span value of 1.8.
(Comparative example 3)

The carbon sources were 50 mass% of preheated carbon black, 25 mass% of needle coke, and 25 mass% of expanded graphite. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

The obtained Al ₄ SiC ₄ powder had I _Al4C3 /I _Al4SiC4 of 0, I _G /I _Al4SiC4 of 0, sulfur content of 160 ppm, crystallite size of 1176 Å, and particle size distribution span value of 2.4.
(Comparative example 4)

The carbon sources were 50 mass% of preheated carbon black, 25 mass% of needle coke, and 25 mass% of activated carbon. Except for this, Al ₄ SiC ₄ powder was obtained using the same method as in Example 1.

The obtained Al ₄ SiC ₄ powder had I _Al4C3 /I _Al4SiC4 of 0, I _G /I _Al4SiC4 of 0, sulfur content of 180 ppm, crystallite size of 1203 Å, and particle size distribution span value of 1.7.
The above results are summarized in Table 2.

In the Al ₄ SiC ₄ powders obtained in Examples 1 to 7, no Al ₄ C ₃ peak was observed in powder X-ray diffraction (I _Al 4 C 3 /I _{Al 4 SiC 4} was 0), and no graphite diffraction peak was observed. (I _G /I _Al4SiC4 was 0), and the sulfur content was 150 ppm or less. That is, it was an Al ₄ SiC ₄ powder substantially free of Al ₄ C ₃ , graphite, and sulfur.

In Examples 2 to 7, the sulfur content was slightly increased compared to Example 1 because an auxiliary material was added to the carbon source.

In Example 5, the crystallite size is large because crystallites of Al ₄ SiC ₄ from which expanded graphite, which is crystalline carbon, is synthesized were grown.

On the other hand, in the Al ₄ SiC ₄ powder obtained in Comparative Example 1, a graphite diffraction peak was observed in powder X-ray diffraction (I _G /I _Al4SiC4 was 2.89), and the sulfur content was 160 ppm. This is because the sulfur content of needle coke is high, and the sulfur in needle coke partially reacts with the raw material Al, leaving a small amount of needle coke, and a small amount of unreacted needle coke partially graphitizes and remains. It is assumed that there is.

The Al ₄ SiC ₄ powder obtained in Comparative Example 2 had a sulfur content of 180 ppm. This is because the sulfur content derived from activated carbon is high.

The Al ₄ SiC ₄ powder obtained in Comparative Example 3 had a sulfur content of 160 ppm. This is because the amount of secondary carbon source material is large.

The Al ₄ SiC ₄ powder obtained in Comparative Example 4 had a sulfur content of 180 ppm. This is because the amount of secondary carbon source material is large.

Claims (3)

Integrated intensity I of the diffraction peak of _Al4C3 around _2θ =55.1° measured by powder X-ray diffraction _Al4C3 (cps・deg) and the diffraction peak of _Al4SiC4 around _2θ =56.0° The ratio of integrated intensity I _Al4SiC4 (cps deg) I _Al4C3 /I _Al4SiC4 is 0.1% or less, and the sulfur content is 150 mass ppm or less,
An Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder having a crystallite size of 1000 to 1500 Å calculated from the diffraction peak of Al ₄ SiC ₄ near 2θ=31.7° measured by powder X-ray diffraction. Integrated intensity I of the diffraction peak of graphite around 2θ = 26.5° measured by powder X-ray diffraction I _G (cps・deg) and integrated intensity I of the diffraction peak of Al ₄ SiC ₄ around 2θ = 56.0° The Al ₄ SiC ₄ composition or Al ₄ SiC ₄ powder according to claim 1, wherein the ratio I _G /I _Al4SiC4 to _Al4SiC4 (cps·deg) is 0.01% or less. In the volume-based particle size distribution, the difference between the cumulative 90% particle diameter and the cumulative 10% particle diameter divided by the cumulative 50% particle diameter (D ₉₀ - D ₁₀ )/D ₅₀ is 1.7 to 2.5. The Al ₄ SiC ₄ powder according to claim 1 or 2, characterized in that:

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