JP2023054859A - Al4SiC4 POWDER AND MANUFACTURING METHOD THEREOF - Google Patents

Abstract

To provide Al4SiC4 powder substantially free of Al4C3.SOLUTION: Al4SiC4 powder is provided in which the ratio IAl4C3/IAl4SiC4 of the peak integrated intensity IAl4C3(cps/deg), which originates from Al4C3 around 2θ=55.1°, to the peak integrated intensity IAl4SiC4(cps/deg), which originates from Al4SiC4 around 2θ=56.0°, is 0.1% or less, and the color space (L*,a*,b*) is within the range of any of (22 to 29, 11 to 14, 12 to 20), (16 to 26, 12 to 13, 20 to 23), (0 to 5, 0 to 2, -4 to 0), and (2 to 15,0 to 2, -4 to 0).SELECTED DRAWING: None

Description

The present invention relates to Al ₄ SiC ₄ powder and its production method.

Aluminum silicon carbide (Al ₄ SiC ₄ ) is a carbide composed of aluminum and silicon. In recent years, Al ₄ SiC ₄ powder has attracted attention as a new functional additive for carbon-containing refractories. As an effect of adding Al ₄ SiC ₄ powder, densification of the structure of the refractory is mentioned. It is presumed 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 formula (1), a gas containing Al is generated from Al ₄ SiC ₄ at a high temperature, diffuses into the voids in the refractory structure, reacts with CO gas, and regenerates Al ₂ O ₃ and carbon. It is presumed that it is brought about by condensing as
_Al4SiC4 + _6CO → _2Al2O3 +SiC+9C ₍ 1)

As a method for synthesizing Al ₄ SiC ₄ powder, Non-Patent Document 1 discloses that raw materials including aluminum powder, silicon powder, and carbon powder are blended in a theoretical molar composition ratio of Al:Si:C=4:1:4, A method of mixing raw materials and heating the mixed raw materials under an inert gas atmosphere to synthesize Al ₄ SiC ₄ powder is disclosed. Synthesis of Al ₄ SiC ₄ is presumed to be 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 in formulas (2) and (3), and then, at 1300 ° C. or higher, Al ₄ C ₃ and SiC are generated as in formula (4). reacts to form 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 103 [1] 20-24 (1995)

However, in the conventional method for synthesizing Al ₄ SiC ₄ powder, if the blending ratio of the raw materials is inappropriate or the heating temperature is insufficient, the equation (4) does not proceed, so unreacted Al ₄ C ₃ may be generated. Al ₄ C ₃ is very easy to hydrate, and when Al ₄ SiC ₄ powder containing Al ₄ C ₃ is added to the refractory, the Al ₄ C ₃ hydrates and expands in volume, and the shape stability of the refractory increases. may be damaged. Therefore, it is necessary to synthesize the Al ₄ SiC ₄ powder so as not to generate Al ₄ C ₃ . Al ₄ C ₃ is a Class 3 hazardous material defined by the Fire Defense Law, and is designated as a spontaneous combustible substance and a water-reactive substance. Al ₄ SiC ₄ powder in which Al ₄ C ₃ remains as an unreacted product requires careful storage and handling.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an Al ₄ SiC ₄ powder substantially free of Al ₄ C ₃ and a method for producing the same.

In order to solve the above problems, one embodiment of the present invention provides a peak integrated intensity I _Al4C3 (cps/deg) due to Al ₄ C ₃ near 2θ=55.1° measured by powder X-ray diffraction and 2θ A ratio I _Al4C3 /I _Al4SiC4 to a peak integrated intensity I _Al4SiC4 (cps/deg) due to Al ₄ SiC ₄ near =56.0° is 0.1% or less, and the color space (L*, a*, b*) is (22-29, 11-14, 12-20), (16-26, 12-13, 20-23), (0-5, 0-2, -4-0), (2- 15, 0 to 2, -4 to _{0 )} .

Another aspect of the present invention is a method for producing Al ₄ SiC ₄ powder, which comprises heating Al ₄ SiC ₄ powder containing Al ₄ C ₃ at 400° C. to 1000° C. in an air atmosphere.

According to one aspect of the present invention, an Al ₄ SiC ₄ powder that is substantially free of Al ₄ C ₃ can be provided. The Al ₄ SiC ₄ powder of the present invention _has its color space (L*, a*, _b *) _{within the} above range. can be clearly distinguished from the color space (L*, a*, b*) of

According to another aspect of the present invention, the Al ₄ SiC ₄ powder containing Al ₄ C ₃ is heated at 400° C. to 1000° C. in an air atmosphere, so that the Al ₄ C ₃ can be decomposed and eliminated. On the other hand, the composition of Al ₄ SiC ₄ can be left substantially unchanged. Therefore, Al ₄ SiC ₄ powder substantially free of Al ₄ C ₃ can be produced from Al ₄ SiC ₄ powder containing Al ₄ C ₃ .

FIG. 4 shows the mineral composition of Al ₄ SiC ₄ powder before heating; Fig. 2 shows the mineral composition of Al ₄ SiC ₄ powder after heating; It is a graph which shows the relationship between heating temperature, ratio _IAl4C3 / _IAl4SiC4 and ratio _IAl2O3 / _IAl4SiC4 .

EMBODIMENT OF THE INVENTION Hereafter, based on an accompanying drawing, embodiment of _{the Al4SiC4} powder of this invention and its manufacturing method is described in detail. However, the Al ₄ SiC ₄ powders and methods of making same of the present invention may be embodied in various forms and are not limited to the embodiments set forth herein. The present embodiments are provided with the intention of allowing those skilled in the art to fully understand the invention through a thorough disclosure of the specification.
( _{Al4SiC4 powder} )

The Al ₄ SiC ₄ powder of this embodiment does not substantially contain Al ₄ C ₃ . This point is due to the peak integrated intensity I _Al4C3 (cps/deg) due to Al ₄ C ₃ near 2θ = 55.1° and Al ₄ SiC ₄ near 2θ = 56.0° measured by powder X-ray diffraction. is specified by calculating the ratio I _Al4C3 /I _Al4SiC4 to the integrated peak intensity I _Al4SiC4 (cps/deg) caused by . The ratio _IAl4C3 / _IAl4SiC4 is 0.1% or less, preferably 0.05% or less, more preferably 0.01%, and more preferably Al ₄ C near 2θ=55.1°. ₃ is not observed.

When Al ₄ SiC ₄ powder containing Al ₄ C ₃ is added to the refractory, the Al ₄ C ₃ hydrates and expands in volume, impairing the shape stability of the refractory. Therefore, in the present embodiment, the ratio I _Al4C3 /I _Al4SiC4 is set to 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 grain. By calculating the ratio of the integrated intensity, it becomes possible to quantitatively evaluate the existence probability of a certain crystal grain. Here, the proportion of Al ₄ C ₃ in the Al ₄ SiC ₄ powder can be analyzed quantitatively.

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. Diffraction measured in a graph with the horizontal axis as the X-ray incident angle 2θ (°) and the vertical axis as diffraction intensity (cps) Intensities were plotted. For the calculation of the integrated intensity (cps·deg), Rigaku's "Unified powder X-ray analysis software PDXL" ver.2.7.3.0 was used.

In addition, the Al ₄ SiC ₄ powder of the present embodiment has a color space (L*, a*, b*) of (22 to 29, 11 to 14, 12 to 20), (16 to 26, 12 to 13, 20 ~23), (0 to 5, 0 to 2, -4 to 0), (2 to 15, 0 to 2, -4 to 0). The reason why the color space is within the above range will be described later in [Example]. The Al ₄ SiC ₄ powder of the present embodiment _{has the color space (L*, a*, b*) of the Al 4 SiC 4 powder} (L*, a*, b*) can be clearly distinguished.

A color space (L*, a*, b*) is a kind of color system used to represent the color of an object, and was standardized in 1976 by the International Commission on Illumination (CIE). It is also standardized in Japan as JIS Z 8781-4:2013.

For the measurement of the color space (L*, a*, b*), the Al ₄ SiC ₄ powder was ground into a 10 cc container, and the surface was leveled to prepare a sample. Then, the color space (L*, a*, b*) at an arbitrary point on the sampled powder surface was measured. If the color space (L*, a*, b*) at any point is within the above range, it is within the scope of the present invention. The measurement method complied with JIS Z 8722:2009. Under the D65 light source, the color space (L*, a*, b*) was measured at a viewing angle of 10° using a color difference meter (color analyzer, TC-8600A, manufactured by Tokyo Denshoku Co., Ltd.).

The Al ₄ SiC ₄ powder of this embodiment is preferably substantially free of Al ₂ O ₃ . This point is due to the peak integrated intensity I _Al2O3 (cps/deg) due to Al ₂ O ₃ near 2θ = 35.1° and Al ₄ SiC ₄ near 2θ = 31.7° measured by powder X-ray diffraction. is specified by calculating the ratio I _Al2O3 /I _Al4SiC4 to the integrated peak intensity I _Al4SiC4 (cps/deg) caused by . The ratio I _Al2O3 /I _Al4SiC4 is 0.1% or less, preferably 0.05% or less, and more preferably no diffraction peak due to Al ₂ O ₃ near 35.1° is observed. .

When Al ₄ SiC ₄ powder containing Al ₂ O ₃ is added to a refractory, there is a problem that the fine particles of Al ₂ O ₃ affect the morphology of the refractory such as the molded bulk specific gravity and porosity. Therefore, in the present embodiment, it is desirable to set the ratio I _Al2O3 /I _Al4SiC4 to 0.1% or less.

Furthermore, it is desirable that the Al ₄ SiC ₄ powders of the present embodiments have large crystallite sizes. The crystallite size is 1000-1500 Å, more preferably 1100-1500 Å, and even more preferably 1100-1450 Å. A large crystallite size indicates a growing crystal morphology. Al ₄ SiC ₄ particles with large crystallite size have enhanced hydration resistance. Therefore, it becomes difficult to reduce the functionality in the refractory structure. On the other hand, if the crystallite size is too large, the functionality (reactivity with CO gas) decreases, so 1000 to 1500 Å is optimal.

The crystallite size is specified by measuring the half width of the diffraction peak of the (101) plane near 2θ=31.74° in powder X-ray diffraction and calculating using Scherrer's formula. For the calculation of the crystallite size, "integrated powder X-ray analysis software PDXL" ver.2.7.3.0 manufactured by Rigaku Co., Ltd. was used.
(Method for synthesizing Al ₄ SiC ₄ powder)

An example of a method for synthesizing Al ₄ SiC ₄ powder will be described.

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. It is desirable to use metal Al powder from the aspect of purity and production efficiency.

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

As a carbon source, flake graphite, artificial graphite, carbon black, or the like is used.

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

Next, the starting materials are mixed using a mixer such as a dry Henschel mixer or a dry ball mill. The mixing time is not particularly limited, but mixing for 5 minutes or more is desirable in order to sufficiently mix the raw materials.

Next, the obtained mixed raw material is loaded into a crucible, the crucible is placed in a furnace such as a tubular furnace or a resistance heating furnace, and the mixed raw material is heated in an argon gas stream at, for example, 1650° C. to 1900° C. for 1 to 10 hours. Al ₄ SiC ₄ powder is thereby synthesized. 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 in formulas (2) and (3), and then, at 1300 ° C. or higher, Al ₄ C ₃ and SiC are generated as in formula (4). reacts to form Al ₄ SiC ₄ . If the temperature is lower than 1650°C, Al ₄ C ₃ tends to remain after the reaction, and if the temperature is 1650° C. or higher, the rate of formation of Al ₄ SiC ₄ remarkably increases.
4Al+3C→Al ₄ C ₃ (2)
Si+C→SiC (3)
_{Al4C3 +} SiC→ _Al4SiC4 ( ₄ )

After synthesis, the crucible is removed from the furnace. Then, the Al ₄ SiC ₄ powder synthesized from the crucible is taken out, and the taken-out Al ₄ SiC ₄ powder is pulverized by a pulverizer such as a roll crusher or a ball mill.
(Method for producing Al ₄ SiC ₄ powder of the present embodiment)

A method for producing the Al ₄ SiC ₄ powder of this embodiment will be described.

In the method for synthesizing the Al ₄ SiC ₄ powder, if the theoretical molar composition ratio of the starting materials is inappropriate or the heating temperature is insufficient, Al ₄ C ₃ may be produced as an unreacted product. Al ₄ C ₃ is very easy to hydrate, and when Al ₄ SiC ₄ powder containing Al ₄ C ₃ is added to the refractory, the Al ₄ C ₃ hydrates and expands in volume, and the shape stability of the refractory increases. may be damaged. Therefore, the method for producing Al ₄ SiC ₄ powder of the present embodiment changes Al ₄ SiC ₄ powder containing Al ₄ C ₃ to Al ₄ SiC ₄ powder substantially free of Al ₄ C ₃ .

In the method for producing the Al ₄ SiC ₄ powder of this embodiment, first, the Al ₄ SiC ₄ powder containing Al ₄ C ₃ is heated at 400° C. to 1000° C. in an air atmosphere. Specifically, Al ₄ SiC ₄ powder containing Al ₄ C ₃ is filled in a crucible, the crucible is placed in a furnace such as a tubular furnace or a resistance heating furnace, and heated in the atmosphere (RH (humidity) 20 to 90%). Heat to 400°C to 1000°C. After reaching 400° C. to 1000° C., the temperature is maintained for, for example, 1 to 10 hours, and then the temperature is lowered. After reaching 400° C. to 1000° C., the temperature may be lowered without maintaining the temperature. The rate of temperature rise and temperature drop is, for example, 5° C. to 15° C./min.

By heating in the atmosphere, Al ₄ C ₃ reacts with water vapor in the air as shown in formula (5) or with oxygen in the air as shown in formula (6). Therefore, Al ₄ C ₃ decomposes and disappears. On the other hand, the composition of Al ₄ SiC ₄ does not substantially change. Therefore, an Al ₄ SiC ₄ powder substantially free of Al ₄ C ₃ can be produced.
_Al4C3 + _12H2O →4Al(OH) _{3 + 3CH4} (5)
_Al4C3 + _6O2- > _{2Al2O3 + 3CO2 (} 6)

Here, Al ₂ O ₃ in formula (6) is amorphous Al ₂ O ₃ . Al(OH) ₃ in formula (5) also changes to amorphous Al ₂ O ₃ . Therefore, analysis of the mineral composition of the Al ₄ SiC ₄ powder by X-ray powder diffraction does not identify Al ₂ O ₃ . Amorphous Al ₂ O ₃ does not change to crystalline when heated again from 400° C. to 1000° C. after the above heating, and remains amorphous, so no problem occurs.

The optimum range of heating temperature is 400°C to 1000°C. If the heating temperature is less than 400° C., Al ₄ C ₃ cannot be sufficiently decomposed, whereas if the heating temperature is 400° C. or higher, Al ₄ C ₃ can be completely eliminated. When the heating temperature exceeds 1000° C., amorphous Al ₂ O ₃ changes to crystalline Al ₂ O ₃ , so Al ₂ O ₃ affects the mineral composition of the Al ₄ SiC ₄ powder.

After the Al ₄ SiC ₄ powder containing Al ₄ C ₃ is heated as described above, the crucible is removed from the furnace and the Al ₄ SiC ₄ powder substantially free of Al ₄ C ₃ is removed from the crucible.

In the method for producing the Al ₄ SiC ₄ powder of the present embodiment, it is desirable to adjust the particle size of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ to 500 μm or less, preferably 250 μm or less, more preferably 150 μm or less before heating. . Particle size adjustment is performed by pulverizing Al ₄ SiC ₄ powder containing Al ₄ C ₃ with a pulverizer such as a roll crusher or ball mill, and 500 μm or less by dry sieving based on the sieving test method defined in JIS Z 8815: 1994. make adjustments to This is because if the particle size of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ is larger than 500 μm, uneven heating occurs and the Al ₄ C ₃ cannot be completely eliminated. In addition, when the particle size of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ is 500 μm or less, it is not necessary to adjust the particle size.

In the method for producing the Al ₄ SiC ₄ powder of this embodiment, it is desirable to use powder X-ray diffraction to analyze the mineral composition of the Al ₄ SiC ₄ powder before and after heating. Specifically, it is desirable to measure the Al ₄ C ₃ content of the Al ₄ SiC ₄ powder before and after heating. By measuring the Al ₄ C ₃ content before heating, it is possible to know whether or not heating is necessary. Moreover, by measuring the Al ₄ C ₃ content after heating, it is possible to know whether or not Al ₄ C ₃ has disappeared. The Al ₄ C ₃ content is measured using the ratio I _{Al 4 C3} /I _{Al 4 SiC 4} described above. The Al ₄ C ₃ content before heating is greater than 0.1% (for example, 4%), and the Al ₄ C ₃ content after heating is 0.1% or less.

Also, it is desirable to measure the Al ₂ O ₃ content of the Al ₄ SiC ₄ powder after heating. By measuring the Al ₂ O ₃ content, it can be known whether amorphous Al ₂ O ₃ has changed to crystalline Al ₂ O ₃ . The Al ₂ O ₃ content is measured using the ratio I _{Al 2 O 3} /I _{Al 4 SiC 4} described above. The Al ₂ O ₃ content after heating is 0.1% or less.

In the method for producing the Al ₄ SiC ₄ powder of the present embodiment, it is desirable to calculate the crystallite size of Al ₄ SiC ₄ of the Al ₄ SiC ₄ powder before and after heating using powder X-ray diffraction. Calculation of the crystallite size may be performed as described above. By calculating the crystallite size of Al ₄ SiC ₄ before and after heating, it is possible to know whether the crystal of Al ₄ SiC ₄ is affected by heating.

Metal Al powder (-45 μm), metal Si powder (-45 μm), and graphite (-75 μm) were blended in a theoretical molar ratio of Al:Si:C=4:1:4 and mixed in a ball mill for 5 hours. The mixed raw material was loaded into a carbon crucible and heated at 1700° C. (heating rate 10° C./min) for 5 hours in an argon gas atmosphere to synthesize Al ₄ SiC ₄ powder.

The synthesized Al ₄ SiC ₄ powder was crushed with a roll crusher, and the mineral composition of the crushed Al ₄ SiC ₄ powder was analyzed by powder X-ray diffraction.

FIG. 1 shows the mineral composition of the Al ₄ SiC ₄ powder before heating. Not only the Al ₄ SiC ₄ peak but also the Al ₄ C ₃ peak was confirmed, and the Al ₄ SiC ₄ powder also contained Al ₄ C ₃ and the Al ₄ C ₃ content was 4%. The crystallite size of Al ₄ SiC ₄ was 1143 Å.

Next, the Al ₄ SiC ₄ powder containing Al ₄ C ₃ was heated at 400° C. in an air atmosphere. The temperature increase rate was 10°C/min. After the temperature in the furnace reached 400°C, the temperature was maintained at 400°C for 5 hours, and the temperature was lowered at a rate of 10°C/min.

FIG. 2 shows the mineral composition of the Al ₄ SiC ₄ powder after heating. The Al ₄ C ₃ peak could not be confirmed, and the ratio I _{Al 4 C3} /I _{Al 4 SiC} 4 was zero. The Al ₂ O ₃ peak was also not confirmed, and the ratio I _{Al 2 O 3} /I _{Al 4 SiC 4} was zero. Al ₄ SiC ₄ was single phase. The crystallite size was 1111 Å, and the crystallite size did not substantially change before and after heating. There was also no agglomeration of Al ₄ SiC ₄ powder.

The four-point color space (L*, a*, b*) on the surface of the Al ₄ SiC ₄ powder is (22, 12, 13), (22, 11, 20), (29, 11, 14), ( 24, 14, 12), and the ranges of the minimum and maximum values of L*, a*, b* were within the ranges of (22-29, 11-14, 12-20).

The heating temperature of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ was set at 600°C. Except for this, the same method as in Example 1 was used to obtain an Al ₄ SiC ₄ powder substantially free of Al ₄ C ₃ .

The obtained Al ₄ SiC ₄ powder had a ratio of I _Al4C3 /I _Al4SiC4 of 0, a ratio of I _Al2O3 /I _Al4SiC4 of 0, and a crystallite size of 1122 Å. Al ₄ SiC ₄ was single phase and there was no aggregation of Al ₄ SiC ₄ powder.

The four-point color space (L*, a*, b*) on the surface of the Al ₄ SiC ₄ powder is (26, 13, 23), (20, 12, 20), (16, 13, 20), ( 21, 13, 22), and the ranges of the minimum and maximum values of L*, a*, and b* were within the ranges of (16-26, 12-13, 20-23).

The heating temperature of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ was set at 800°C. Except for this, the same method as in Example 1 was used to obtain an Al ₄ SiC ₄ powder substantially free of Al ₄ C ₃ .

The ratio _IAl4C3 / _IAl4SiC4 of the obtained _Al4SiC4 powder was 0, the ratio _IAl2O3 / _IAl4SiC4 was 0, and the crystallite _size was 1122 Å. The Al ₄ SiC ₄ was single phase, and there was no aggregation of the Al ₄ SiC ₄ powder.

The four-point color space (L*, a*, b*) on the surface of the Al ₄ SiC ₄ powder is (5, 2, −4), (0, 0, 0), (1, 1, −2) , (0, 1, -2), and the range of the minimum and maximum values of L*, a*, b*, respectively, was within the range of (0 to 5, 0 to 2, -4 to 0). .

The heating temperature of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ was set at 1000°C. Except for this, the same method as in Example 1 was used to obtain an Al ₄ SiC ₄ powder substantially free of Al ₄ C ₃ .

The obtained Al ₄ SiC ₄ powder had a ratio of I _Al4C3 /I _Al4SiC4 of 0, a ratio of I _Al2O3 /I _Al4SiC4 of 0, and a crystallite size of 1110 Å. The Al ₄ SiC ₄ was single phase, and there was some aggregation of the Al ₄ SiC ₄ powder.

The four-point color space (L*, a*, b*) on the surface of the Al ₄ SiC ₄ powder is (2, 0, −1), (10, 2, −4), (2, 1, −3 ), (15, 0, 0), and the ranges of the minimum and maximum values of L*, a*, and b* were within the range of (2 to 15, 0 to 2, -4 to 0). .
(Comparative example 1)

The heating temperature of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ was set at 200°C. Except for this, the same method as in Example 1 was used to obtain Al ₄ SiC ₄ powder.

The obtained Al ₄ SiC ₄ powder had a ratio I _Al4C3 /I _Al4SiC4 of 0.04 (4%), a ratio I _Al2O3 /I _Al4SiC4 of 0, and a crystallite size of 1129 Å. It was a mineral phase of Al ₄ SiC ₄ and Al ₄ C ₃ and there was no agglomeration of Al ₄ SiC ₄ powder.

The four-point color space (L*, a*, b*) on the surface of the Al ₄ SiC ₄ powder is (18, 16, 19), (16, 12, 15), (11, 14, 15), ( 21, 14, 16), and the ranges of the minimum and maximum values of L*, a*, b* were within the ranges of (11-21, 12-16, 15-19).
(Comparative example 2)

The heating temperature of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ was set at 300° C., and the holding time was set at 20 hours. Except for this, the same method as in Example 1 was used to obtain Al ₄ SiC ₄ powder.

The obtained Al ₄ SiC ₄ powder had a ratio I _Al4C3 /I _Al4SiC4 of 0.03 (3%), a ratio I _Al2O3 /I _Al4SiC4 of 0, and a crystallite size of 1118 Å. It was a mineral phase of Al ₄ SiC ₄ and Al ₄ C ₃ and there was no agglomeration of Al ₄ SiC ₄ powder.

The four-point color space (L*, a*, b*) on the surface of the Al ₄ SiC ₄ powder is (18, 16, 17), (20, 17, 15), (9, 14, 17), ( 14, 14, 17), and the ranges of the minimum and maximum values of L*, a*, and b* were within the ranges of (9-20, 14-17, 15-17).
(Comparative Example 3)

The heating temperature of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ was set at 1100°C. Except for this, the same method as in Example 1 was used to obtain Al ₄ SiC ₄ powder.

The ratio _IAl4C3 / _IAl4SiC4 of the obtained _Al4SiC4 powder was 0, the ratio _IAl2O3 / _IAl4SiC4 was 0.09 (9% ₎ , and the crystallite size was 1120 Å. It was a mineral phase of Al ₄ SiC ₄ and Al ₂ O ₃ and there was agglomeration of Al ₄ SiC ₄ powder.

The four-point color space (L*, a*, b*) on the surface of the Al ₄ SiC ₄ powder is (18, −3, −2), (5, 0, −3), (0, −1, 0), (32, -1, 0), and the range of the minimum and maximum values of L*, a*, b* is within the range of (0 to 32, -3 to 0, -3 to 0) was in
(Comparative Example 4)

The heating temperature of the Al ₄ SiC ₄ powder containing Al ₄ C ₃ was set at 1200°C. Except for this, the same method as in Example 1 was used to obtain Al ₄ SiC ₄ powder.

The ratio _IAl4C3 / _IAl4SiC4 of the obtained _Al4SiC4 powder was 0, the _{ratio IAl2O3} / _IAl4SiC4 was 0.65 (65%), and the crystallite size was 1123 Å. Al ₄ SiC ₄ , Al ₂ O ₃ and Mullite mineral phases, with agglomeration of Al ₄ SiC ₄ powder.

The four-point color space (L*, a*, b*) on the surface of the Al ₄ SiC ₄ powder is (25, −1, −2), (5, 0, −3), (20, 0, − 2), (52, -3, 0), and the ranges of the minimum and maximum values of L*, a*, and b* are within the range of (0 to 52, -3 to 0, -3 to 0) was in

また、図３に加熱温度と比Ｉ_{Ａｌ４Ｃ３}／Ｉ_{Ａｌ４ＳｉＣ４}・比Ｉ_{Ａｌ２Ｏ３}／Ｉ_{Ａｌ４ＳｉＣ４}との関係をグラフ化した。
（比較例５） The above results are summarized in Tables 1 and 2.

In addition, the relationship between the heating temperature and the ratio I _Al4C3 /I _Al4SiC4 and the ratio I _Al2O3 /I _Al4SiC4 is graphed in FIG.
(Comparative Example 5)

Using the same synthesis method as in Example 1, Al ₄ SiC ₄ powder was synthesized so as not to generate Al ₄ C ₃ , and the Al ₄ SiC ₄ powder was pulverized and dry sieved to a particle size (JIS Z 8815: 1994 defined) was adjusted to 45-32 μm.

The four-point color space (L*, a*, b*) on the surface of the obtained Al ₄ SiC ₄ powder is (27, 8, 32), (26, 8, 33), (25, 10, 31 ), (23, 11, 33) and were within the range of (23-27, 8-11, 31-33). This is different from the range of the color space (L*, a*, b*) of this embodiment.

Claims (7)

Peak integrated intensity I _Al4C3 (cps/deg) due to Al ₄ C ₃ near 2θ=55.1° measured by powder X-ray diffraction and a peak due to Al ₄ SiC ₄ near 2θ=56.0° The ratio I _Al4C3 /I _Al4SiC4 to the integrated intensity I _Al4SiC4 (cps/deg) is 0.1% or less,
Color space (L*, a*, b*) is (22-29, 11-14, 12-20), (16-26, 12-13, 20-23), (0-5, 0-2, -4 to 0), (2 to 15 _, 0 to ₂ , -4 to 0). Peak integrated intensity I _Al2O3 (cps/deg) due to Al ₂ O ₃ near 2θ=35.1° measured by powder X-ray diffraction and a peak due to Al ₄ SiC ₄ near 2θ=31.7° The _Al4SiC4 powder according to claim ₁ , wherein the ratio _IAl2O3 / _IAl4SiC4 to the integrated intensity _IAl4SiC4 (cps/deg) is 0.1% or less. The Al ₄ SiC ₄ powder according to claim 1 or 2, characterized in that the crystallite size of the (101) plane near 2θ=31.7° measured by powder X-ray diffraction is 1000 Å to 1500 Å. A method for producing Al ₄ SiC ₄ powder comprising heating Al ₄ SiC ₄ powder containing Al ₄ C ₃ at 400° C. to 1000° C. in an air atmosphere. 5. The method for producing _{Al4SiC4 powder} according to claim 4, wherein the particle size of _{the Al4SiC4} powder containing _Al4C3 is adjusted _to 500 [mu]m or less before heating. The method for producing Al ₄ SiC ₄ powder according to claim 4 or 5, characterized in that the mineral composition of the Al ₄ SiC ₄ powder before and after heating is analyzed using powder X-ray diffraction. Al ₄ SiC ₄ according to any one of claims 4 to 6, wherein the crystallite size of Al ₄ SiC ₄ of the Al ₄ SiC ₄ powder before and after heating is calculated using powder X-ray diffraction. How to make powder.

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