JP6179288B2 - Method for producing silicon nitride powder - Google Patents

Description

  The present invention is a method for producing silicon nitride powder by firing amorphous Si-N (-H) compound powder using a rotary kiln furnace suitable for mass production, regardless of the inner diameter of the core tube of the rotary kiln furnace. The present invention relates to a method for producing silicon nitride powder, which can always produce silicon nitride powder having excellent sintering characteristics.

  A silicon nitride sintered body obtained by molding and heat-sintering silicon nitride powder is excellent in mechanical strength, corrosion resistance, thermal shock resistance, thermal conductivity, electrical insulation, etc. It is used as a wear-resistant member such as a bearing, a high-temperature structural member such as an automobile engine part, and a circuit board. A silicon nitride sintered body is usually produced by mixing a sintering aid with silicon nitride powder, forming a molded body by press molding, injection molding, extrusion molding, or the like, and sintering the molded body.

  In order to produce a silicon nitride sintered body with good mechanical properties, a silicon nitride powder with good sintering properties, that is, a silicon nitride powder consisting of granular crystals with high crystallinity and high α fraction is required. It is said. As a method for producing such a high-quality silicon nitride powder, a method of firing an amorphous Si—N (—H) compound in a nitrogen-containing inert gas atmosphere or a nitrogen-containing reducing gas atmosphere is already known. It has been.

As a method for producing a high-quality silicon nitride powder as described above, Patent Document 1 discloses an amorphous silicon nitride powder and / or a nitrogen-containing silane compound (the amorphous Si—N (—H) of the present invention described later). The same compound as the system compound powder, hereinafter referred to as amorphous Si—N (—H) system compound powder) is compression molded to have a bulk density of 0.3 to 0.8 g / cm ³ , a short axis Disclosure of a granular material having a diameter of 1 mm or more and a major axis diameter of 20 mm or less and firing the granular material at a temperature increase rate of 1200 ° C. to 1400 ° C. over 10 ° C./min. Has been. However, as can be seen from the examples of Patent Document 1, this production method has a firing time of 6.5 to 8.3 hours until heating at room temperature and holding at the maximum firing temperature is completed. In terms of production speed and power requirements, it is difficult to say that this is a low-cost and highly productive manufacturing method.

On the other hand, as a production method capable of producing a large amount of high-quality silicon nitride powder as described above, Patent Document 2 discloses that an amorphous Si—N (—H) -based compound powder is compression-molded to obtain a bulk density of 0.1. ^{3 to} 0.8 g / cm ³ , a short-axis diameter of 1 mm or more and a long-axis diameter of 20 mm or less, and the granular material is 1400 to 1700 ° C. using a continuous firing furnace, specifically a rotary kiln furnace. A method for producing silicon nitride powder that is fired at a temperature of 5 ° C is disclosed. The publication describes that silicon nitride powder can be produced in a large amount in a short time by using a continuous firing furnace such as a rotary kiln furnace.

JP-A-4-209706 Japanese Patent Laid-Open No. 5-148032

  Although the manufacturing method using a rotary kiln furnace as disclosed in Patent Document 2 is a method suitable for mass production of silicon nitride powder, in order to actually increase the production amount of silicon nitride powder, the core tube of the rotary kiln furnace is used. Increasing the feed amount of the raw material to the core tube by increasing the inner diameter of the core tube has caused a problem that, depending on the inner diameter of the core tube, a silicon nitride powder having a high crystallinity and a high α fraction cannot be obtained. That is, until now, even if the inner diameter of the core tube of the rotary kiln furnace is increased to increase the production amount, a technical index that can always produce silicon nitride powder having a high crystallinity and an α fraction has not been obtained. The silicon nitride powder having a high degree of crystallinity or α fraction is useful as a raw material for a silicon nitride sintered body, as will be described below.

  When a silicon nitride powder having a high degree of crystallinity, that is, a silicon nitride powder having a low content of amorphous silicon nitride is sintered, the sintering rate becomes uniform during sintering. Therefore, a sintered body obtained by sintering silicon nitride powder having a high degree of crystallinity has few residual pores inside and a large aspect ratio (major axis diameter / minor axis diameter ratio) of the particles. High mechanical strength at high temperatures.

  Sintering silicon nitride powder with high α fraction, that is, silicon nitride powder with low β fraction, promotes the growth of columnar crystals that accompany the transition from α phase to β phase of silicon nitride during sintering. . Therefore, the obtained silicon nitride sintered body has a high fracture toughness because the ratio of columnar crystals having a large aspect ratio is high.

As mentioned above, although the manufacturing method of the silicon nitride powder which bakes amorphous Si-N (-H) type compound powder in a rotary kiln furnace is a manufacturing method suitable for mass production, in order to expand a production amount Increasing the inner diameter of the core tube of a rotary kiln furnace makes it difficult to stably obtain a silicon nitride powder having a high crystallinity and a high α fraction, which is necessary for obtaining a silicon nitride sintered body having good mechanical properties. Had problems. An object of the present invention, the amorphous Si-N (-H) compounds Oite method of manufacturing a silicon nitride powder by sintering the powder, crystallinity and α fraction high silicon nitride using a rotary kiln furnace It is to provide a method for producing silicon nitride powder, which can always produce powder.

The inventors of the present invention used an externally heated rotary kiln furnace having a cylindrical furnace core tube having an inner diameter of 16 to 30 cm to convert amorphous Si—N (—H) -based compound powder into a nitrogen-containing inert gas atmosphere or As a result of extensive research on the method of producing silicon nitride powder by firing in a nitrogen-containing reducing gas atmosphere, it is managed to maintain the maximum thickness of the powder layer at the core tube outlet of the rotary kiln furnace within a specific range. As an index, regardless of the inner diameter of the core tube, a silicon nitride powder having a high crystallinity and an α fraction, specifically, a crystallinity of 98% or more and an α fraction of 85% or more is always produced. The present invention has been completed by finding out what can be done.

That is, the present invention uses an externally heated rotary kiln furnace provided with a cylindrical furnace core tube having an inner diameter of 16 to 30 cm that is inclined with respect to the horizontal direction, and has an amorphous surface area of 400 to 1200 m ² / g. Si-N (-H) based compound powder is introduced into the core tube from the inlet of the core tube, and flows in layers in the core tube, under a nitrogen-containing inert gas atmosphere or a nitrogen-containing reducing gas atmosphere, A method for producing silicon nitride powder that is fired at a maximum temperature of 1400 to 1700 ° C. and is taken out from the outlet of the core tube, wherein the maximum thickness of the powder layer of silicon nitride powder at the outlet of the core tube is maintained in the range of 1 to 8 cm. The present invention relates to a method for producing silicon nitride powder, characterized in that silicon nitride powder is produced using the management index as a management index.

  The present invention also relates to a method for producing silicon nitride powder, wherein the maximum temperature is 1450 to 1550 ° C.

According to the present invention, since a silicon nitride powder having a high crystallinity and a high α fraction can be produced, it becomes possible to produce a large amount of silicon nitride powder having excellent sintering characteristics at low cost. . Moreover, even if the production amount is adjusted depending on the equipment scale of the rotary kiln used, it is possible to always provide a silicon nitride powder having excellent sintering characteristics by producing the silicon nitride powder using the management index of the present invention. It becomes possible.

It is a schematic diagram of the powder layer of the silicon nitride powder in the core tube exit of the rotary kiln furnace of this invention. It is a schematic diagram of the cross section of the powder layer of the amorphous Si-N (-H) type compound powder at the time of crystallization when the maximum thickness of the powder layer of the silicon nitride powder at the furnace tube outlet is larger than 8 cm. It is a schematic diagram which shows the state which attached the gauge for measuring the maximum thickness of the powder layer of the silicon nitride powder in a furnace core tube exit to the outer side of the observation window installed in the furnace core tube exit of a rotary kiln furnace.

  Below, the manufacturing method of the silicon nitride powder in connection with this invention is demonstrated in detail.

In the present invention, the amorphous Si—N (—H) -based compound powder is fired in a nitrogen-containing inert gas atmosphere or a nitrogen-containing reducing gas atmosphere to produce silicon nitride powder. The amorphous Si—N (—H) compound used in the present invention is Si obtained by thermally decomposing part or all of a nitrogen-containing silane compound such as silicon diimide, silicon tetraamide, silicon chlorimide, It is an amorphous compound containing each element of N and H, or an amorphous silicon nitride containing Si and N, and is represented by the following composition formula (1).
Si ₆ N _2x (NH) _12-3x (1)
(However, x = 0.5 to 4 in the formula, and is not specified in the composition formula, but includes a compound containing halogen as an impurity)

Note that in the present invention, the amorphous Si—N (—H) -based compound is obtained from Si ₆ N ₁ (NH) _10.5 represented by x = 0.5 in the composition formula (1). All the series of compounds up to amorphous Si ₃ N ₄ represented by ₄ are included, and Si ₆ N ₆ (NH) ₃ represented by x = 3 is called silicon nitrogen imide. .

As the nitrogen-containing silane compound according to the present invention, silicon diimide, silicon tetraamide, silicon chlorimide and the like are used. These compounds are represented by the following composition formula (2). In the present invention, for convenience, a nitrogen-containing silane compound represented by y = 8 to 12 in the following composition formula (2) is represented as silicon diimide.
Si ₆ (NH) _y (NH ₂ ) _24-2y (2)
(However, in the formula, y = 0 to 12 and is not specified in the composition formula, but includes a compound containing halogen as an impurity)

  The amorphous Si—N (—H) -based compound powder according to the present invention is obtained by reacting ammonia in a gas phase with a known method, for example, silicon halide such as silicon tetrachloride, silicon tetrabromide, silicon tetraiodide and the like. Or a method of reacting the liquid silicon halide with liquid ammonia.

  In addition, as the amorphous Si—N (—H) -based compound powder according to the present invention, a known method, for example, a method in which the nitrogen-containing silane compound is thermally decomposed at a temperature of 1200 ° C. or lower in a nitrogen or ammonia gas atmosphere. Those produced by a method of reacting ammonia with silicon halide such as silicon tetrachloride, silicon tetrabromide, silicon tetraiodide and the like are used.

In the present invention, an amorphous Si—N (—H) compound powder having a specific surface area of 400 to 1200 m ² / g is used as a raw material of the silicon nitride powder. If the specific surface area of the amorphous Si—N (—H) compound powder is smaller than 400 m ² / g, rapid crystallization occurs in the temperature range of 1000 to 1400 ° C. during firing, and the resulting silicon nitride powder Then, acicular particles and aggregated particles are formed. Even if a sintered body is produced with such a powder, a homogeneous structure is not formed, and the strength of the obtained sintered body is reduced. On the other hand, when the specific surface area is larger than 1200 m ² / g, the α fraction of the obtained silicon nitride powder becomes small, so that the sinterability deteriorates and the strength of the sintered body becomes small.

  The specific surface area of the amorphous Si—N (—H) -based compound powder can be adjusted by the specific surface area of the nitrogen-containing silane compound as a raw material and the maximum temperature when the nitrogen-containing silane compound is thermally decomposed. The specific surface area of the amorphous Si—N (—H) compound powder can be increased as the specific surface area of the nitrogen-containing silane compound is increased and the maximum temperature during the thermal decomposition is decreased. When the nitrogen-containing silane compound is silicon diimide, the specific surface area of the nitrogen-containing silane compound is, for example, a known method shown in Patent Document 2, that is, silicon halide and liquid when reacting silicon halide with liquid ammonia. It can be adjusted by a method of changing the ratio with ammonia (silicon halide / liquid ammonia (volume ratio)). The specific surface area of the nitrogen-containing silane compound can be increased by increasing the silicon halide / liquid ammonia.

  In the present invention, when the amorphous Si—N (—H) compound powder is fired in a nitrogen-containing inert gas atmosphere or a nitrogen-containing reducing gas atmosphere, the cylindrical powder is inclined with respect to the horizontal direction. Using an externally heated rotary kiln furnace for firing an object to be heated put in the furnace core tube by heating from outside while rotating the core tube around the axis, The Si—N (—H) -based compound powder is fired at a temperature of 1400 to 1700 ° C. When the firing temperature is lower than 1400 ° C., crystallization is not sufficient, and a large amount of amorphous silicon nitride powder is contained in the silicon nitride powder, which is not preferable. On the other hand, when the firing temperature is higher than 1700 ° C., not only coarse crystals grow, but also decomposition of the produced silicon nitride powder starts, which is not preferable.

  The amorphous Si—N (—H) -based compound powder is preferably formed into a granular material and charged into the furnace core tube, and the granular material particularly preferably has a diameter of 1 mm or more and 20 mm or less. When the amorphous Si—N (—H) compound powder is formed into granules, the fluidity of the amorphous Si—N (—H) compound powder in the core tube is improved, and the amorphous Si—N This is because the heat dissipation of the crystallization heat generated with the crystallization of the (—H) -based compound powder is improved, so that the uniformity of the quality of the obtained silicon nitride powder is improved. When the diameter of the granule is 1 mm or more and 20 mm or less, the fluidity of the amorphous Si—N (—H) compound powder is particularly improved, and the uniformity of the quality of the resulting silicon nitride powder is particularly improved.

  The rotary kiln furnace used in the present invention includes a cylindrical core tube inclined with respect to the horizontal direction, and the core tube is heated from outside while rotating the core tube around the axis, thereby In an externally heated rotary kiln furnace in which a raw material supplied from the inlet of the core tube installed at one end of the core tube is fired and the fired product is taken out from the outlet of the core tube installed at one end of the core tube. is there. Generally, in a rotary kiln furnace, when raw material powder is supplied from an inlet provided on the high side of a cylindrical core tube inclined with respect to the horizontal direction, the supplied raw material powder is in the cross-sectional direction of the core tube. Swirls by rotating the core tube and sliding the powder layer in the maximum tilt direction. In the axial direction, the powder moves to the outlet direction provided on the lower side of the core tube and is discharged by the inclination of the core tube. In the present invention, the amorphous Si—N (—H) compound powder is supplied from the inlet of the core tube into the core tube of the rotary kiln furnace of the present invention, baked and crystallized in the core tube, and silicon nitride from the outlet of the core tube. Remove the powder. In the present invention, the amorphous Si—N (—H) compound powder until it is supplied into the core tube of the rotary kiln furnace may be referred to as a raw material powder. Further, the powder that flows in the furnace core tube during firing may be referred to as a powder to be fired. Examples of the powder to be fired include amorphous Si—N (—H) compound powder and silicon nitride powder.

  The maximum temperature inside the furnace core tube in firing in the rotary kiln, that is, the firing temperature is in the range of 1400 to 1700 ° C, preferably in the range of 1450 to 1550 ° C. When the firing temperature is lower than 1400 ° C., the silicon nitride powder is not sufficiently crystallized, and a large amount of amorphous silicon nitride is contained in the silicon nitride powder, so that a silicon nitride powder having a high crystallinity cannot be obtained. On the other hand, when the firing temperature is higher than 1700 ° C., a coarse crystal grows or a part or all of the silicon nitride powder is decomposed, and a silicon nitride powder with good sinterability cannot be obtained.

  In the present invention, when an amorphous Si—N (—H) compound powder is fired in a nitrogen-containing inert gas atmosphere or a nitrogen-containing reducing gas atmosphere using a rotary kiln furnace, silicon nitride at the furnace tube outlet is baked. The management index is to maintain the maximum thickness of the powder layer of the powder in the range of 1 to 8 cm.

  Regardless of the inner diameter of the core tube of the rotary kiln, when the maximum thickness of the silicon nitride powder layer at the core tube outlet is less than 1 cm, the β fraction of the resulting silicon nitride powder increases and the α fraction decreases. To do. By making the maximum temperature during firing lower than 1400 ° C., a decrease in the α fraction can be suppressed, but in that case, as described above, a silicon nitride powder having a high crystallinity cannot be obtained.

  On the other hand, regardless of the inner diameter of the core tube of the rotary kiln furnace, when the maximum thickness of the silicon nitride powder layer at the outlet of the core tube exceeds 8 cm, the crystallinity of the obtained silicon nitride powder becomes low. When the maximum temperature during firing is higher than 1700 ° C., the degree of crystallinity can be increased. However, when the maximum temperature during firing is higher than 1700 ° C., as described above, coarse crystals grow, or part of silicon nitride powder or Since everything decomposes, a silicon nitride powder with good sinterability cannot be obtained.

  The maximum thickness of the silicon nitride powder layer at the core tube outlet according to the present invention is the maximum value of the distance from the bottom to the surface of the silicon nitride powder layer immediately before the silicon nitride powder is taken out from the core tube outlet. Yes, the thickness of the powder layer of the silicon nitride powder immediately before the collapse of the surface shape of the powder layer accompanying the discharge of the silicon nitride powder from the furnace core tube outlet occurs. The maximum thickness of the powder layer of silicon nitride powder at the core tube outlet according to the present invention can be calculated as follows.

  FIG. 1 is a schematic diagram of a cross section in a core tube of a rotary kiln furnace showing a state in which silicon nitride powder flows in a layered state immediately before the surface shape of the powder layer collapses due to discharge from the core tube outlet. The maximum thickness of the silicon nitride powder layer flowing in the core tube, that is, the maximum distance from the bottom to the surface of the silicon nitride powder layer, is perpendicular to the surface of the silicon nitride powder layer. This is the distance from the inner wall of the core tube to the surface of the powder layer of silicon nitride powder on the center line of the cross section in the tube (A in FIG. 1).

  In the present invention, the powder layer of silicon nitride powder at a position immediately before the collapse of the surface shape of the powder layer accompanying discharge from the core tube outlet can be observed from a direction perpendicular to the thickness direction of the powder layer. In addition, a viewing window is provided on the outlet side of the core tube. And the powder layer of the powder layer of the silicon nitride powder at the position immediately before the collapse of the surface shape of the powder layer is on the center line (A in FIG. 1) of the cross section in the reactor core tube perpendicular to the surface of the powder layer The distance from the surface of the tube to the inner wall of the core tube that is not the bottom of the powder layer (the length of B in FIG. 1) is measured with a gauge attached to the outside of the viewing window, or an image taken from the viewing window Measure by analysis. The distance obtained by subtracting the measured “length of B in FIG. 1” from the inner diameter of the core tube is the maximum distance from the bottom to the surface of the powder layer of the silicon nitride powder, and the powder layer of the silicon nitride powder of the present invention Is the maximum thickness.

  Next, the reason why a silicon nitride powder having a high crystallinity and a high α fraction is always obtained by maintaining the maximum thickness of the powder layer of the silicon nitride powder at the core tube outlet within a specific range as a management index. Is considered.

  It is the crystallization behavior of the amorphous Si—N (—H) compound powder that affects the crystallinity and α fraction of the silicon nitride powder according to the present invention. On the other hand, the silicon nitride powder at the core tube outlet is a powder that has been crystallized, and is a silicon nitride powder taken out from the core tube outlet, that is, a silicon nitride powder obtained by the present invention. Therefore, maintaining the maximum thickness of the powder layer of silicon nitride powder at the core tube outlet within a specific range can affect the crystallinity and α fraction of the silicon nitride powder, which can affect the amorphous Si—N (—H ) Does not directly affect the crystallization behavior of the system compound powder.

  However, for the following reasons, maintaining the maximum thickness of the silicon nitride powder layer at the core tube outlet in a specific range affects the crystallinity and α fraction of the silicon nitride powder. This is considered to indirectly affect the crystallization behavior of the —N (—H) compound powder.

  The density of the raw material amorphous Si—N (—H) compound powder is almost constant, and the density of the obtained silicon nitride powder is also almost constant if the powder has a specific high crystallinity and α fraction. is there. Further, the ratio of the mass of the amorphous Si—N (—H) -based compound powder put into a predetermined furnace core tube and the mass of the obtained silicon nitride powder is also the amorphous Si—N (—H) -based compound. Since the mass reduction rate accompanying the decomposition during crystallization of is almost constant, it is almost constant. Therefore, the ratio between the maximum thickness of the silicon nitride powder layer at the furnace tube outlet and the maximum thickness of the amorphous Si-N (-H) -based compound powder during crystallization is always a substantially constant value. Become. That is, if the maximum thickness of the powder layer of silicon nitride powder at the core tube outlet is maintained within a specific range, the maximum thickness of the powder layer of amorphous Si—N (—H) compound powder during crystallization is reduced. It can be maintained within a specific range. Therefore, maintaining the maximum thickness of the silicon nitride powder layer at the core tube outlet in a specific range indirectly affects the crystallization behavior of the amorphous Si—N (—H) compound powder. it is conceivable that. Since the maximum thickness of the powder layer of the amorphous Si—N (—H) compound powder at the time of crystallization is difficult to measure because the position is far from both the inlet and the outlet of the core tube, the present invention In this method of manufacturing silicon nitride powder, instead of this, the maximum thickness of the powder layer of silicon nitride powder at the outlet of the core tube, which is easy to measure, is used as a management index.

  Next, when the maximum thickness of the powder layer of amorphous Si—N (—H) -based compound powder during crystallization is 1 to 8 cm when the maximum thickness of the powder layer of silicon nitride powder at the core tube outlet is 1 to 8 cm When a silicon nitride powder is produced by firing amorphous Si—N (—H) compound powder while maintaining a specific range corresponding to the above, a silicon kiln powder having a high crystallinity and α fraction is converted into a rotary kiln furnace. The reason why the core tube can be manufactured regardless of the inner diameter of the core tube will be discussed.

  When the maximum thickness of the powder layer of silicon nitride powder at the furnace tube outlet is less than 1 cm, that is, when the maximum thickness of the powder layer of amorphous Si—N (—H) compound powder during crystallization is small It is considered that the α fraction of the obtained silicon nitride powder is lowered by the following mechanism.

  A slip occurs between the powder layer of the amorphous Si-N (-H) compound powder and the inner wall of the core tube, and the amorphous Si-N (-H) compound powder stops swirling, The fluidity becomes worse. If the amorphous Si—N (—H) compound powder is fired in a state of poor fluidity, the heat of crystallization is hardly removed from the powder layer, and the amorphous Si—N (—H) The temperature of the powder layer of the compound powder rises rapidly, and at least a part of the powder layer of the amorphous Si—N (—H) -based compound powder exceeds 1700 ° C. When the temperature of the powder layer of the amorphous Si—N (—H) compound powder exceeds 1700 ° C. even locally or in a short time, β-type crystal, which is a high-temperature crystal of silicon nitride, is precipitated and obtained. The α fraction of the silicon nitride powder is lowered.

  The above is the case where the maximum thickness of the silicon nitride powder layer at the outlet of the core tube is less than 1 cm, that is, the maximum thickness of the amorphous Si—N (—H) compound powder layer during crystallization is small. In this case, it is considered that the α fraction of the obtained silicon nitride powder is lowered.

  On the other hand, when the maximum thickness of the powder layer of silicon nitride powder at the core tube outlet is larger than 8 cm, that is, when the maximum thickness of the powder layer of amorphous Si—N (—H) compound powder during crystallization is large It is considered that the crystallinity of the obtained silicon nitride powder is lowered by the following mechanism.

  The form of heat transfer to the powder to be fired in the externally heated rotary kiln furnace includes conduction heat transfer from the inner wall of the furnace core tube in contact with the powder, radiation heat transfer from the opposite wall surface, and convection heat transfer from the pyrolysis gas. There is. The total of these is the total heat transfer, but the heat transfer from the outer periphery of the powder layer other than the convective heat transfer from the pyrolysis gas. Even if most of the heat transfer to the powder to be fired is from the outer periphery of the powder layer, in the externally heated rotary kiln furnace, the powder to be fired is swirled by the rotation of the furnace core tube. Can be heated uniformly.

  Still, when the maximum thickness of the powder layer of silicon nitride powder at the core tube outlet is larger than 8 cm, that is, when the maximum thickness of the powder layer of amorphous Si-N (-H) compound powder during crystallization is large In this case, a part having a poor flowability is generated because a part of the powder is not given a spiraling force. FIG. 2 shows a schematic diagram of a cross section of the powder layer of amorphous Si—N (—H) compound powder during crystallization when the maximum thickness of the powder layer of silicon nitride powder is larger than 8 cm. The powder to be fired is given a force that swirls in the direction opposite to the direction of rotation of the core tube, but when the maximum thickness of the powder layer is large, as shown in FIG. A portion with poor fluidity is generated as an elliptical region. Then, the amorphous Si—N (—H) -based compound powder having a poor fluidity in the powder layer reaches the core tube outlet in a state where it is not heated as much as the powder having a good fluidity. Then, since the obtained silicon nitride powder includes silicon nitride powder that has not been sufficiently heated for crystallization, the crystallinity of the obtained silicon nitride powder is lowered.

  The above is the case where the maximum thickness of the silicon nitride powder layer at the core tube outlet is larger than 8 cm, that is, the maximum thickness of the amorphous Si—N (—H) -based compound powder during crystallization is large. In this case, it is considered that the crystallinity of the obtained silicon nitride powder is lowered.

  If silicon nitride powder is produced with the management index of maintaining the maximum thickness of the powder layer of silicon nitride powder at the furnace tube outlet in the range of 1 to 8 cm, amorphous Si-N (-H) during crystallization A spiral motion is given to the center of the powder layer of the amorphous Si-N (-H) compound powder during crystallization so that no slip occurs between the powder layer of the compound compound powder and the inner wall of the core tube. Therefore, it is considered that a silicon nitride powder having a high crystallinity and an α fraction can be produced regardless of the inner diameter of the core tube of the rotary kiln furnace.

  In the present invention, the maximum thickness of the powder layer of the silicon nitride powder at the outlet of the core tube is the supply speed of the amorphous Si—N (—H) -based compound powder into the core tube, the inclination angle of the core tube, and the core tube It can be controlled by the rotation speed of. When the supply rate of the amorphous Si—N (—H) compound powder into the core tube is increased, the maximum thickness of the powder layer of the silicon nitride powder increases, and the amorphous Si—N (—H) compound powder is increased. When the feed rate is reduced, the maximum thickness of the silicon nitride powder layer is reduced. Increasing the tilt angle of the core tube decreases the maximum thickness of the silicon nitride powder layer, and decreasing the tilt angle of the core tube increases the maximum thickness of the silicon nitride powder layer. Further, when the rotational speed of the core tube is increased, the maximum thickness of the powder layer of silicon nitride powder is decreased, and when the rotational speed of the core tube is decreased, the maximum thickness of the powder layer of silicon nitride powder is increased.

  Moreover, in this invention, it is preferable that the residence time in the heating zone in a furnace core tube of an amorphous Si-N (-H) type compound powder shall be 5 minutes or more. Here, the heating zone is a temperature zone in which the temperature in the core tube of the rotary kiln furnace is 1400 ° C. or more and the maximum temperature or less. This is because if the residence time is less than 5 minutes, the crystallinity of the resulting silicon nitride powder may be lowered. On the other hand, even if the residence time is increased, the quality of the obtained silicon nitride powder does not deteriorate, but the amount of electric power required per unit mass of the obtained silicon nitride powder increases, and the production cost is relatively large. Therefore, the residence time in the heating zone in the furnace core tube is preferably 20 minutes or less.

  The residence time of the amorphous Si—N (—H) -based compound powder in the heating zone in the core tube can be controlled by the inclination angle of the core tube and the rotational speed of the core tube. Increasing the inclination angle of the core tube shortens the residence time. Further, when the rotational speed of the core tube is increased, the residence time is shortened.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples.

(Composition analysis method of amorphous Si-N (-H) compound)
The silicon (Si) content ratio of the amorphous Si-N (-H) compound powder conforms to "7 Quantitative determination method of total silicon" in "JIS R1603 Chemical analysis method of fine silicon nitride powder for fine ceramics". Measured by ICP emission analysis. The nitrogen (N) content ratio of the amorphous Si—N (—H) compound powder was measured by a steam distillation separation neutralization titration method based on “8 Quantitative determination method of total nitrogen” of “JIS R1603”. In addition, the oxygen (O) content ratio of the amorphous Si—N (—H) compound powder is measured by an inert gas melting-carbon dioxide infrared absorption method according to “10 Oxygen determination method” of “JIS R1603”. did. However, in order to suppress oxidation of the amorphous Si—N (—H) compound powder, in the case of measurement of the silicon content ratio and in the case of measurement of the elementary content ratio, until immediately before the sample pretreatment for measurement. The atmosphere at the time of sample storage was a nitrogen atmosphere, and in the case of measuring the oxygen content ratio, the atmosphere at the time of sample storage and measurement immediately before the measurement was a nitrogen atmosphere. The proportion of hydrogen (H) contained in the amorphous Si—N (—H) compound powder is higher than the total amount of the amorphous Si—N (—H) compound powder in terms of silicon (Si), nitrogen (N) and oxygen. (O) Calculated as the remainder excluding the total content. This is because the amorphous Si—N (—H) compound powder according to the present invention is composed of only silicon (Si), nitrogen (N), hydrogen (H) and oxygen (O) except for a small amount of impurities. . From the above, the ratio of Si, N, and H was determined, and the composition formula of the amorphous Si—N (—H) compound powder was determined.

(Measurement method of oxygen (O) content ratio of silicon nitride powder)
The oxygen (O) content ratio of the silicon nitride powder is determined by the inert gas melting-carbon dioxide infrared absorption method according to “10 Quantitative determination method of oxygen” in “JIS R1603 Chemical analysis method of fine silicon nitride powder for ceramics”. It was measured. However, when measuring the oxygen (O) content ratio of the amorphous Si—N (—H) compound powder, in order to suppress oxidation of the amorphous Si—N (—H) compound, immediately before the measurement The atmosphere at the time of sample storage and measurement was a nitrogen atmosphere.

(Measurement method of specific surface area of amorphous Si—N (—H) compound powder and silicon nitride powder)
The specific surface areas of the amorphous Si—N (—H) compound powder and the silicon nitride powder were measured by the BET one-point method (Shimadzu Corporation, Flowsorb 2300) by nitrogen gas adsorption.

(Measurement method of light packing density and angle of repose of amorphous Si-N (-H) compound powder)
The light packing density of the amorphous Si-N (-H) compound powder conformed to "JIS R9301-2-3 Alumina powder-Part 2: Physical property measurement method-3: Light packing heavy density and heavy loading bulk density". Obtained by method. Specifically, the mass of the same powder collected by dropping the amorphous Si—N (—H) compound powder freely into a container with a known capacity that was prevented from standing still was collected, and this mass was determined. Calculated from the value divided by the volume of water. The angle of repose was calculated | required by the method based on "JIS R9301-2-2 alumina powder-2nd part: Physical property measuring method-2: angle of repose". Specifically, an amorphous Si—N (—H) compound powder was spontaneously dropped from a glass funnel, and the angle formed by the powder when deposited on a horizontal surface was measured.

(Measuring method of residence time of powder to be fired in heating zone in furnace tube)
The residence time of the powder to be fired in the heating zone in the furnace tube, that is, the temperature zone of 1400 ° C. or more and the maximum temperature or less of the furnace tube was measured by the following method. As a tracer, 10 φ5 mm silicon nitride balls that can be identified one by one are put into the core tube together with the raw material powder sequentially from the core tube inlet, and after each silicon nitride ball is introduced from the inlet, the core tube outlet The time until it was further discharged was measured, and the average value was taken as the residence time in the core tube. Since the moving speed of the powder to be fired in the furnace core tube in the axial direction is constant, the ratio of the heating zone length in the furnace core tube to the length of the furnace core tube multiplied by the residence time in the core tube is defined as the residence time in the heating zone.

(Method for measuring the maximum thickness of the silicon nitride powder layer at the core tube outlet)
As shown in FIG. 3, the maximum thickness of the silicon nitride powder layer at the core tube outlet is a gauge attached to the outside of the viewing window provided on the core tube outlet side so that the cross section in the core tube can be observed from the vertical direction. Measured by. Subtract the “distance from the powder layer surface to the inner wall of the core tube on the space side (opposite the powder layer)” in the “center line of the core tube cross section perpendicular to the powder layer surface” from the “core tube inner diameter”. Thus, the maximum thickness of the silicon nitride powder layer at the outlet of the core tube was calculated.

(Measurement method of α fraction of silicon nitride powder)
In the X-ray diffraction method, a powder X-ray diffraction pattern of the obtained silicon nitride powder was measured by a regular step scanning method using a copper tube and a graphite monochromator as a target. Step scan was performed in the range of diffraction angle (2θ) of 15-80 ° in steps of 0.02 °, and α fraction of silicon nitride powder was determined by Rietveld analysis.

(Method for measuring crystallinity of silicon nitride powder)
The precisely weighed silicon nitride powder was added to a 0.5N NaOH aqueous solution and heated to 100 ° C. NH ₃ gas generated by the decomposition of silicon nitride was absorbed in a 1% aqueous boric acid solution, and the amount of NH ₃ in the obtained absorbent was titrated with a 0.1N sulfuric acid standard solution. From the amount of NH ₃ in the absorbing solution and the mass of the silicon nitride powder, the mass ratio of decomposed nitrogen to silicon nitride (the mass ratio of nitrogen generated by decomposition of silicon nitride to silicon nitride) was calculated. The crystallinity of the silicon nitride powder was calculated from the mass ratio of decomposed nitrogen to silicon nitride and the theoretical mass ratio of 39.94% of nitrogen contained in silicon nitride to silicon nitride by the following equation (3).
Crystallinity (%) = 100− (mass ratio of decomposed nitrogen to silicon nitride × 100 / 39.94) (3)

Example 1
After replacing air in a vertical pressure resistant reactor having a diameter of 40 cm and a height of 60 cm maintained at 20 ° C. with nitrogen gas, 40 liters of liquid ammonia and 5 liters of toluene were charged in the reactor. In the reaction vessel, while liquid ammonia and toluene were slowly stirred, liquid ammonia was separated into an upper layer and toluene was separated into a lower layer. A solution (reaction solution) consisting of 2 liters of silicon tetrachloride prepared in advance and 6 liters of toluene containing 0.1% by mass of water was supplied through a conduit to the lower layer in the reaction vessel being slowly stirred. At this time, the volume ratio of silicon tetrachloride supplied into the reaction tank and liquid ammonia in the reaction tank is 5/100. Along with the supply of the solution, a white reaction product was deposited in the vicinity of the interface between the upper and lower layers. After completion of the reaction, the reaction product and the residual liquid in the reaction tank are transferred to a filtration tank, the reaction product is separated by filtration, and batch-washed four times with liquid ammonia, and a silicon diimide having a specific surface area of about 1 kg and 1400 m ² / g. Got.

The obtained silicon diimide was filled in a raw material hopper of a rotary kiln furnace having a diameter of 150 mm and a length of 2800 mm (heating length of 1000 mm), and the inside of the rotary kiln furnace was vacuum degassed to 13 Pa or less, and then nitrogen gas containing 2% oxygen was added. The total gas amount was supplied at a flow rate of 250 NL / hour, and heating was started. When the inside of the rotary kiln furnace reached the maximum temperature (1000 ° C.), the raw material supply screw feeder was rotated, and silicon diimide was supplied from the raw material hopper into the furnace at a supply rate of 3 kg / hour. The amorphous Si—N (—H) compound powder according to Example 1 was heated by setting the tilt angle of the kiln to 2 degrees, the rotation speed to 1 rpm, and the holding time at the maximum temperature to 10 minutes to heat the silicon diimide. Obtained. As shown in Table 1, the amorphous Si—N (—H) compound powder according to Example 1 has a specific surface area of 450 m ² / g and an oxygen content ratio of 0.73 mass%. It was a compound powder represented by ₆ N _8.4 H _1.2 , that is, in the Si ₆ N _2x (NH) _12-3x of the composition formula (1), where x in the formula was 3.6.

  The obtained Si—N (—H) -based compound powder was filled into a raw material hopper of a rotary kiln furnace having a silicon carbide core tube having an inner diameter of 16 cm and a length of 2 m. The length of the heating element of the core tube was 1 m. After sufficiently replacing the inside of the furnace core tube of the rotary kiln furnace with nitrogen gas, the temperature is raised until the maximum temperature in the furnace core tube reaches the firing temperature shown in Table 1 in a nitrogen gas circulation atmosphere, and the temperature distribution in the furnace core tube is stabilized The raw material supply screw feeder was rotated, and amorphous Si—N (—H) compound powder was supplied from the raw material hopper into the furnace core tube at a supply rate of 1.0 kg / hour. Amorphous Si—N (—H) -based compound was heated and fired at 1500 ° C. by setting the rotational speed of the core tube to 2 rpm and the inclination angle with respect to the horizontal direction of the core tube to 2 ° to produce silicon nitride powder. . The temperature increase rate was adjusted so that the temperature increase rate in the range of 1000 to 1400 ° C. was 40 ° C./min and the temperature distribution of the core tube and the supply rate were adjusted. When the maximum thickness of the powder layer of the silicon nitride powder at the core tube outlet was measured by the method described in the above (Method for measuring the maximum thickness of the powder layer), it was 1.4 cm as shown in Table 1. . Moreover, the physical property of the obtained silicon nitride powder was measured by the above-mentioned method, and the results shown in Table 1 were obtained. The obtained silicon nitride powder of Example 1 was a silicon nitride powder having an α fraction of 90.3% and a crystallinity of 100%, and both an α fraction and a high crystallinity.

(Example 2)
The silicon nitride powder of Example 2 was obtained in the same manner as in Example 1 except that Si—N (—H) -based compound powder was supplied into the furnace core tube of the rotary kiln furnace at a supply rate of 9.4 kg / hour and fired. Manufactured. The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. The maximum thickness of the silicon nitride powder layer at the furnace tube outlet is 6.9 cm, and the obtained silicon nitride powder of Example 1 has an α fraction of 96.5% and a crystallinity of 100%. The silicon nitride powder had a high α fraction and high crystallinity.

(Examples 3 and 4)
In Example 3, the Si—N (—H) compound powder was fired using a rotary kiln furnace having an inner diameter of 24 cm and a length of 2 m, and the Si—N (—H) compound powder was 2 in Example 3. The silicon nitride powders of Examples 3 and 4 were produced in the same manner as in Example 1 except that it was fed into the core tube of the rotary kiln furnace at a feed rate of 18.4 kg / hour in Example 4. . The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the powder layers of the silicon nitride powder at the core tube outlets of Examples 3 and 4 were 1.8 cm and 6.9 cm, respectively. The silicon powder was a silicon nitride powder having a high α fraction and high crystallinity, with α fractions of 92.6% and 96.8%, respectively, and crystallinity of 100%.

(Examples 5 and 6)
In Example 5, the Si—N (—H) compound powder was fired using a rotary kiln furnace having an inner diameter of 30 cm and a length of 2 m. The silicon nitride powders of Examples 5 and 6 were produced in the same manner as in Example 1 except that the powder was fed into the core tube of the rotary kiln furnace at a feed rate of 2 kg / hour and in Example 6 at 39.0 kg / hour. . The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the powder layers of silicon nitride powder at the core tube outlets of Examples 5 and 6 were 1.7 cm and 7.7 cm, respectively, and nitriding of the obtained Examples 5 and 6 was performed. The silicon powder was a silicon nitride powder having a high α fraction and a high degree of crystallinity, with α fractions of 93.4% and 97.0%, and crystallinity of 100%, respectively.

(Example 7)
When silicon diimide is heated using a rotary kiln furnace, the gas to be introduced is nitrogen gas containing 1% oxygen, the maximum temperature is 800 ° C., the specific surface area is 1150 m ² / g, and the oxygen content ratio is 0.45% by mass, represented by the composition formula Si ₆ N _10.9 H _8.7 , that is, in the Si ₆ N _2x (NH) _12-3x of the composition formula (1), x in the formula is 1. 1 amorphous Si—N (—H) compound powder was obtained, and the obtained Si—N (—H) compound powder was fed into the furnace tube of the rotary kiln at a supply rate of 1.2 kg / hour. A silicon nitride powder of Example 7 was produced in the same manner as in Example 1 except that the powder was fired. The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thickness of the silicon nitride powder layer at the core tube outlet is 1.4 cm, and the obtained silicon nitride powder has an α fraction of 88.5% and a crystallinity of 100 %, And a silicon nitride powder having a high α fraction and high crystallinity.

(Example 8)
The silicon nitride powder of Example 8 was produced in the same manner as in Example 7 except that the Si—N (—H) -based compound powder was fed into the furnace core tube of the rotary kiln furnace at a feeding rate of 7.7 kg / hour and fired. Manufactured. The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thickness of the powder layer of the silicon nitride powder at the core tube outlet is 6.7 cm, the α fraction of the obtained silicon nitride powder is 94.5%, and the crystallinity is 100%. The silicon nitride powder had a high α fraction and high crystallinity.

(Examples 9 and 10)
In Example 9, the Si—N (—H) compound powder was baked using a rotary kiln furnace having an inner diameter of 24 cm and a length of 2 m. The silicon nitride powders of Examples 9 and 10 were produced in the same manner as in Example 7 except that the powder was supplied into the furnace core tube of the rotary kiln furnace at a supply rate of 14.7 kg / hour in Example 10 and fired. Manufactured. The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the silicon nitride powder layers at the core tube outlets of Examples 9 and 10 were 1.6 cm and 6.7 cm, respectively. The silicon powder was a silicon nitride powder having an α fraction and a crystallinity of 91.4% and 97.8%, both having a crystallinity of 100% and a high α fraction and a crystallinity.

(Examples 11 and 12)
The Si—N (—H) compound powder was fired using a rotary kiln furnace having an inner diameter of 30 cm and a length of 2 m, and the Si—N (—H) compound powder was changed to 3 in Example 11. The silicon nitride powders of Examples 11 and 12 were produced in the same manner as in Example 7, except that the powder was fed into the core tube of the rotary kiln furnace at a feed rate of 30.2 kg / hour in Example 12. . The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the silicon nitride powder layers at the core tube outlets of Examples 11 and 12 were 1.8 cm and 7.6 cm, respectively. The silicon powder was a silicon nitride powder with high α fraction and high crystallinity, with α fractions of 95.5% and 96.6%, respectively, and crystallinity of 100%.

(Comparative Examples 1 and 2)
Implementation was performed except that Si—N (—H) -based compound powder was supplied into the core tube of the rotary kiln furnace at a supply rate of 0.3 kg / hour in Comparative Example 1 and 12.0 kg / hour in Comparative Example 2. In the same manner as in Example 1, the silicon nitride powders of Comparative Examples 1 and 2 were produced. The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the silicon nitride powder layers at the core tube outlets of Comparative Examples 1 and 2 were 0.6 cm and 8.7 cm, respectively. The silicon powder is a silicon nitride powder having an α fraction of 83.7% and 97.7%, a crystallinity of 100% and 97.6%, respectively, and a low α fraction or crystallinity. It was.

(Comparative Examples 3 and 4)
In the comparative example 3, the Si—N (—H) compound powder was baked using a rotary kiln furnace having an inner diameter of 24 cm and a length of 2 m. The silicon nitride powders of Comparative Examples 3 and 4 were produced in the same manner as in Example 1 except that it was fed into the core tube of the rotary kiln furnace at a feed rate of 24.7 kg / hour in Comparative Example 4. . The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the powder layers of silicon nitride powder at the core tube outlets of Comparative Examples 3 and 4 were 0.7 cm and 8.9 cm, respectively. The silicon powder is a silicon nitride powder having an α fraction of 82.7% and 97.7%, a crystallinity of 100% and 97.3%, respectively, and a low α fraction or crystallinity. It was.

(Comparative Examples 5 and 6)
In the comparative example 5, the Si—N (—H) compound powder was fired using a rotary kiln furnace having an inner diameter of 30 cm and a length of 2 m. .4 kg / hour, Comparative Example 6 produced silicon nitride powders of Comparative Examples 5 and 6 in the same manner as in Example 1 except that they were fed into the core tube of the rotary kiln furnace at a feed rate of 50.3 kg / hour. . The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the silicon nitride powder layers at the core tube outlets of Comparative Examples 5 and 6 were 0.9 cm and 9.4 cm, respectively. The silicon powder is a silicon nitride powder having an α fraction of 80.6% and 98.0%, respectively, and a crystallinity of 100% and 96.4%, respectively. It was.

(Comparative Examples 7 and 8)
Implementation was performed except that Si—N (—H) -based compound powder was supplied into the core tube of the rotary kiln furnace at a supply rate of 0.4 kg / hour in Comparative Example 7 and 10.4 kg / hour in Comparative Example 8. The silicon nitride powders of Comparative Examples 7 and 8 were produced in the same manner as in Example 7. The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the silicon nitride powder layers at the core tube outlets of Comparative Examples 7 and 8 were 0.8 cm and 8.8 cm, respectively. The silicon powder is a silicon nitride powder having an α fraction of 78.7% and 96.6%, a crystallinity of 100% and 97.8%, respectively, and a low α fraction or crystallinity. It was.

(Comparative Examples 9 and 10)
In the comparative example 9, the Si—N (—H) compound powder was baked using a rotary kiln furnace having an inner diameter of 24 cm and a length of 2 m. The silicon nitride powders of Comparative Examples 9 and 10 were produced in the same manner as in Example 7 except that the powder was fed into the core tube of the rotary kiln furnace at a feed rate of 23.6 kg / hour in Comparative Example 10. . The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the silicon nitride powder layers at the core tube outlets of Comparative Examples 9 and 10 were 0.8 cm and 9.7 cm, respectively. The silicon powder is a silicon nitride powder having an α fraction of 80.8% and 97.4%, respectively, and a crystallinity of 100% and 96.4%, respectively. It was.

(Comparative Examples 11 and 12)
In the comparative example 11, the Si—N (—H) compound powder was fired using a rotary kiln furnace having an inner diameter of 30 cm and a length of 2 m. .3 kg / hour, Comparative Example 12 produced silicon nitride powders of Comparative Examples 11 and 12 in the same manner as in Example 7, except that the feed rate was 41.0 kg / hour in the core tube of the rotary kiln furnace. . The maximum thickness of the powder layer of silicon nitride powder at the outlet of the furnace core tube and the physical properties of the obtained silicon nitride powder were measured by the same method as in Example 1, and the results shown in Table 1 were obtained. As shown in Table 1, the maximum thicknesses of the silicon nitride powder layers at the core tube outlets of Comparative Examples 11 and 12 were 0.7 cm and 9.8 cm, respectively. The silicon powder is a silicon nitride powder having a low α fraction and a crystallinity of 79.6% and 97.7%, respectively, and a crystallinity of 100% and 95.8%, respectively. It was.

  The present invention makes it possible to always produce silicon nitride powder having excellent sintering characteristics regardless of the inner diameter of the core tube of the rotary kiln furnace. Therefore, even if the equipment scale of the rotary kiln furnace is increased, the sintering characteristics are improved. It becomes possible to provide excellent silicon nitride powder. In addition, the production amount can be easily adjusted while maintaining the provision of the silicon nitride powder having excellent sintering characteristics.

Claims (2)

Using an externally heated rotary kiln furnace having a cylindrical core tube having an inner diameter of 16 to 30 cm , an amorphous Si—N (—H) compound powder having a specific surface area of 400 to 1200 m ² / g is used as the core. The furnace core tube is fired at a maximum temperature of 1400 to 1700 ° C. in a nitrogen-containing inert gas atmosphere or a nitrogen-containing reducing gas atmosphere while flowing into the tube from the furnace core inlet and flowing in layers in the furnace core tube. A method for producing a silicon nitride powder to be taken out from an outlet, wherein the silicon nitride powder is produced using a management index to maintain the maximum thickness of the powder layer of the silicon nitride powder at the outlet of the core tube in a range of 1 to 8 cm. A method for producing a silicon nitride powder.   The method for producing silicon nitride powder according to claim 1, wherein the maximum temperature is 1450 to 1550 ° C.

Images