JP7816158B2 - SiSiC member, heating tool, and method for manufacturing SiSiC member - Google Patents

Description

The present invention relates to a SiSiC component, a heating tool, and a method for manufacturing a SiSiC component.

Conventionally, SiSiC components, which are composite materials containing silicon carbide (SiC) and silicon (Si), have been known (Patent Document 1).

International Publication No. 2019/194137

SiSiC members are expected to be used in a variety of applications due to their excellent properties such as thermal conductivity, and the development of new SiSiC members is also desired.
For example, even if you try to drill a long hole with an inner diameter of 2 mm or less and a length of 100 mm or more in a SiSiC member using a drill, the SiSiC member is so hard that the drill bends and you cannot achieve this.Even when using a laser, it is not possible to reach a depth of 100 mm while maintaining an inner diameter of 2 mm or less.

The present invention was made in consideration of the above points and aims to provide a novel SiSiC component that has never been seen before.

After extensive research, the inventors discovered that the above objective can be achieved by adopting the following configuration, and thus completed the present invention.

That is, the present invention provides the following [1] to [12].
[1] A SiSiC member having at least one elongated hole formed therein, the elongated hole having a diameter a of 2.0 mm or less and a length b of 100 mm or more, and having a tubular region A that is a region on the periphery of the elongated hole, the tubular region A containing at least one kind selected from the group consisting of simple C, SiC, and SiSiC.
[2] The SiSiC member according to [1] above, having a thermal conductivity i of 170 W/(m·K) or more.
[3] The SiSiC member according to [1] or [2] above, wherein the tubular region A is divided into a plurality of regions.
[4] The SiSiC member according to [3] above, wherein the dividing interval f of the divided tubular region A is 0.15 mm or less.
[5] The SiSiC member according to any one of [1] to [4] above, wherein the amount of Si ejected from the elongated hole g is less than 1 mm.
[6] A SiSiC member according to any one of [1] to [5] above, wherein the ratio g/d of the amount of Si ejected in the elongated hole g to the thickness d of the tubular region A is 3/4 or less.
[7] The SiSiC member according to any one of [1] to [6] above, wherein the ratio e/d of the positional deviation e of the tubular region A to the thickness d of the tubular region A is less than 1/3.
[8] The SiSiC member according to any one of [1] to [7] above, wherein the axial misalignment amount c of the elongated hole is less than 0.3 mm.
[9] The SiSiC member according to any one of [1] to [8] above, wherein the impurity amount k is 100 mass ppm or less.
[10] A SiSiC member according to any one of [1] to [9] above, having a thickness of 2.0 to 15.0 mm, at least one surface, and an area of the surface of 100 cm ² or more.
[11] A heating device comprising the SiSiC member according to any one of [1] to [10] above, wherein a rod-shaped member is inserted into the elongated hole.
[12] A method for producing a SiSiC member according to any one of [1] to [10] above, comprising the steps of: preparing a SiC molded body having a groove; arranging a pipe in the groove; subsequently, placing a filler containing SiC; and impregnating the SiC molded body with the filler in the groove with heated and melted elemental Si.

The present invention makes it possible to provide novel SiSiC components that have never been available before.

FIG. 1 is a perspective view showing a SiSiC member. FIG. 2 is a schematic cross-sectional view showing the tubular region A. FIG. 3 is a schematic cross-sectional view showing the tubular region A in the longitudinal direction. FIG. 4 is a schematic cross-sectional view showing the tubular region A divided into a plurality of regions. FIG. 5 is a cross-sectional view showing a SiC compact. FIG. 6 is a cross-sectional view showing a state in which a pipe is placed in a groove of a SiC compact. FIG. 7 is a cross-sectional view showing a state in which the grooves of the SiC compact are filled with a filler material. FIG. 8 is a schematic cross-sectional view showing a state in which Si spouts are present in a long hole. FIG. 9 is a cross-sectional view showing a SiSiC member having a bonding surface. FIG. 10 is a schematic cross-sectional view for explaining the region C.

FIG. 1 is a perspective view showing a SiSiC member 1.
The SiSiC member 1 is a composite material containing silicon (Si) and silicon carbide (SiC), and has, for example, a low coefficient of thermal expansion and excellent heat resistance, wear resistance, thermal conductivity, strength, and the like.
Inside the SiSiC member 1, a slot 2 is provided that is long in one direction.

Although only one slot 2 is shown in Figure 1, the SiSiC member 1 may have multiple slots 2. When multiple slots 2 are present, the slots 2 may be parallel to each other or may intersect with each other, and this is set appropriately depending on the application of the SiSiC member 1. The slot 2 may be bent.
There is no particular upper limit to the number of long holes 2, but from the viewpoint of increasing the thermal conductivity of the SiSiC member 1 and improving heating efficiency, for example, the proportion of the cross-sectional area of the portion corresponding to the long holes 2 (long hole portion) to the entire cross-sectional area of the SiSiC member 1 is preferably 20% or less, more preferably 13% or less, even more preferably 8% or less, particularly preferably 4% or less, more particularly preferably 1% or less, and most preferably 0.5% or less.
The elongated hole 2 may have one end sealed, or may penetrate from one end to the other end of the SiSiC member 1. The elongated hole 2 is appropriately set depending on the application of the SiSiC member 1.

The shape and dimensions of the SiSiC member 1 are appropriately set depending on the application of the SiSiC member 1. The SiSiC member 1 shown in Fig. 1 has a rectangular parallelepiped shape, but may have another shape such as a disk shape.
The SiSiC member 1 preferably has at least one surface (for example, the top surface of the SiSiC member 1 shown in FIG. 1 ). From the viewpoint of practical convenience, the area of this surface is, for example, 100 cm ² or more, preferably 300 cm ² or more, more preferably 500 cm ² or more, even more preferably 700 cm ² or more, and particularly preferably 800 cm ² or more.
On the other hand, the upper limit of the area is not particularly limited, but from the viewpoint of cost-effectiveness, it is, for example, 10,000 ^cm2 or less, preferably 5,000 ^cm2 or less, more preferably 2,000 ^cm2 or less, even more preferably 1,500 ^cm2 or less, and particularly preferably 1,000 ^cm2 or less.

From the standpoint of cost-effectiveness and preventing cracking due to physical impact, the thickness of the SiSiC member 1 is, for example, 2.0 to 15.0 mm, preferably 3.0 to 13.0 mm, more preferably 4.0 to 12.0 mm, even more preferably 5.0 to 10.0 mm, particularly preferably 6.0 to 9.0 mm, and most preferably 7.0 to 8.0 mm.

As shown in FIG. 1, the SiSiC member 1 has a tubular region A, which is a region on the outer periphery of the slot 2, and an extra-tubular region B, which is a region outside the tubular region A.
The tubular region A preferably contains at least one material selected from the group consisting of elemental C, SiC, and SiSiC. SiSiC is a composite material of SiC and elemental Si.

More preferably, the tubular region A contains elemental C or SiC.
In this case, it is more preferable that the content of elemental C or SiC (unit: volume %) in the tubular region A is greater than the content of elemental C or SiC (unit: volume %) in the extra-tubular region B. When manufacturing the SiSiC member 1 having the tubular region A and the extra-tubular region B, if the tubular region A is formed using a pipe (carbon pipe or SiC pipe) as described below, it is preferable that the tubular region A and the extra-tubular region B satisfy these requirements.

<Diameter of long hole a>
FIG. 2 is a schematic cross-sectional view showing the tubular region A.
From the viewpoint of increasing the thermal conductivity of the SiSiC member 1, the diameter a of the long hole 2 is 2.0 mm or less, preferably 1.8 mm or less, more preferably 1.5 mm or less, even more preferably 1.2 mm or less, even more preferably 0.8 mm or less, particularly preferably 0.7 mm or less, and most preferably 0.4 mm or less.
On the other hand, if the diameter a of the slot 2 is too small, the slot 2 is likely to be clogged even when only a small amount of Si ejection occurs, as described below. From the viewpoint of suppressing such clogging, the diameter a of the slot 2 is preferably 0.1 mm or more, more preferably 0.2 mm or more, and even more preferably 0.3 mm or more.

<Thickness d of tubular region A>
Please continue to refer to FIG.
If the thickness d of the tubular region A is too thin, cracks may occur, causing problems. From the viewpoint of suppressing such cracks, the thickness d is preferably 0.05 mm or more, more preferably 0.07 mm or more, even more preferably 0.10 mm or more, particularly preferably 0.12 mm or more, and most preferably 0.15 mm or more.
On the other hand, although there is no particular upper limit, from the viewpoint of providing flexibility to the pipe during production and making it easy to handle, the thickness d is, for example, 2.0 mm or less, preferably 1.5 mm or less, more preferably 1.0 mm or less, even more preferably 0.8 mm or less, even more preferably 0.6 mm or less, particularly preferably 0.4 mm or less, and most preferably 0.25 mm or less.

<Length of slot b>
FIG. 3 is a schematic cross-sectional view showing the tubular region A in the longitudinal direction.
From the viewpoint of practical convenience, the length b of the long hole 2 is 100 mm or more, preferably 125 mm or more, more preferably 150 mm or more, even more preferably 180 mm or more, even more preferably 210 mm or more, particularly preferably 240 mm or more, more particularly preferably 270 mm or more, and most preferably 290 mm or more.
On the other hand, from the viewpoint of cost-effectiveness, the length b is, for example, 800 mm or less, preferably 600 mm or less, more preferably 400 mm or less, even more preferably 350 mm or less, and particularly preferably 300 mm or less.

The diameter a of the long hole 2, the length b of the long hole 2, and the thickness d of the tubular region A correspond to the inner diameter, length, and thickness of the pipe (carbon pipe or SiC pipe) described below, respectively.

As described below, when the tubular region A is divided (see Figure 4), the diameter a of the elongated hole 2, the length b of the elongated hole 2, and the thickness d of the tubular region A shall be the values that would be obtained if the tubular region A were not divided.

<Axis misalignment amount c>
Please continue to refer to FIG.
The length b of the slot 2 is the distance from the center line _L1 of the slot 2.
For example, in the process of manufacturing a SiSiC member, the center line of the slot 2 may become a warped center line _L2 instead of the original center line _L1 . This is called axial misalignment.
On the warped center line _L2 , the position farthest from the original center line _L1 is defined as P. The shortest distance from position P to the center line _L1 is defined as the amount of axial deviation c.
The smaller the value of the axial misalignment c, the better. Specifically, the axial misalignment c is preferably 0.5 mm or less, more preferably less than 0.4 mm, even more preferably less than 0.3 mm, even more preferably less than 0.2 mm, particularly preferably 0.1 mm or less, and most preferably 0.05 mm or less.

<Number of divisions h>
FIG. 4 is a schematic cross-sectional view showing the tubular region A divided into a plurality of regions.
The tubular region A may be divided into a plurality of regions as shown in FIG. 4 when viewed in cross section from a direction in which the ring shape can be seen.
The number of divisions of the tubular region A (hereinafter also referred to as "number of divisions h") is 2 in Fig. 4, but may be 3 or more. There is no particular upper limit, and for example, the number of divisions h is 8 or less, and preferably 6 or less.
In FIG. 4, the tubular region A is divided equally, but it does not have to be equally divided.

<Positional deviation amount e and division interval f>
As shown in FIG. 4, dividing the tubular region A may cause misalignment between the divided regions (hereinafter also referred to as "positional misalignment") or gaps between the divided regions.
From the viewpoint of manufacturing the elongated hole 2 with a diameter as designed and from the viewpoint of reducing the value of the Si ejection amount g described later, the positional deviation e is preferably 0.30 mm or less, more preferably 0.20 mm or less, even more preferably 0.15 mm or less, even more preferably 0.10 mm or less, particularly preferably 0.05 mm or less, and most preferably 0.02 mm or less. The lower limit of the positional deviation e is preferably 0 mm.
For the same reasons, the ratio (e/d) of the positional deviation e of the tubular region A to the thickness d of the tubular region A is preferably 2/3 (0.666...) or less, more preferably less than 1/3 (0.333...), even more preferably less than 1/4 (0.25), even more preferably less than 1/10 (0.1), particularly preferably less than 1/20 (0.05), more particularly preferably less than 1/30 (0.033...), and most preferably less than 1/50 (0.02).
As shown in FIG. 4, the positional deviation amount e is the distance between the ends (ends on the same side) of the divided areas.

When carbon (C) reacts with silicon (Si) to form silicon carbide (SiC), the volume expands as shown in the following formula.
C (52.1 cm ³ ) + Si (96.8 cm ³ ) → SiC (100.0 cm ³ )
Therefore, when a carbon-containing material is used for the tubular region A, when the introduced Si reacts with the carbon to generate SiC, volume expansion occurs, and a dense layer is formed in the gap between the pipes. This makes it difficult for the introduced Si to pass between the pipes. This suppresses the blowout of Si described below, making it easier to insert a thermocouple or the like into the long hole.
In order to make it difficult for Si to pass through by forming a dense layer between the pipes, it is preferable that the dividing interval f of the divided tubular region A is small.
If SiC, a material that does not contain carbon, is used for the tubular region A, such a dense layer will not be formed. However, the narrower the dividing spacing f between the divided tubular regions A, the more difficult it is for Si to pass through, and the smaller the amount of Si ejection g described below will be.
From the viewpoint of reducing the value of the Si ejection amount g described below, the division interval f of the divided tubular region A is preferably 0.15 mm or less, more preferably 0.14 mm or less, even more preferably 0.10 mm or less, even more preferably 0.07 mm or less, particularly preferably 0.05 mm or less, more particularly preferably 0.03 mm or less, and most preferably 0.02 mm or less.
On the other hand, there is no particular lower limit, and the division interval f is, for example, 0.000 mm or more, preferably 0.005 mm or more, and more preferably 0.010 mm or more.
As shown in FIG. 4, the division interval f is the distance between adjacent end faces (cut surfaces) of the divided regions.

<Thermal conductivity i>
From the viewpoint of improving heating efficiency, the thermal conductivity i of the SiSiC member is preferably 170 W/(m·K) or more, more preferably 180 W/(m·K) or more, even more preferably 190 W/(m·K) or more, even more preferably 200 W/(m·K) or more, particularly preferably 210 W/(m·K) or more, more particularly preferably 220 W/(m·K) or more, and most preferably 230 W/(m·K) or more.
The thermal conductivity i is measured at room temperature (23°C) by the laser flash method using an LFA457 MicroFlash (manufactured by NETZSCH). More specifically, the thermal conductivity of a 25.4 mm diameter area including the tubular region A of the SiSiC member at its center is defined as the thermal conductivity i (thermal conductivity i1). The measurement thickness is 6 mm.

Thermal conductivity i can also be determined using the improved unsteady planar measurement method (ASTM D7984) with a thermal conductivity measuring device TCi (manufactured by C-Thermtechnologies). More specifically, the thermal conductivity of a 17.8 mm diameter area that includes the tubular region A of the SiSiC component at its center is taken as thermal conductivity i (i2). The measurement thickness is the same as that of the SiSiC component. However, to eliminate the influence of air gaps, mirror-finished SiSiC components are stacked to a total thickness of 15 mm or more. In this case, measurement accuracy can be achieved with approximately ±5%.

Let the thermal conductivity of only the outer region B be thermal conductivity j.

<Impurity amount k>
The impurity amount k of the SiSiC member is preferably 100 mass ppm or less, more preferably 80 mass ppm or less, even more preferably 60 mass ppm or less, particularly preferably 40 mass ppm or less, and most preferably 20 mass ppm or less.
The impurity is, for example, at least one element selected from the group consisting of Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Sb, Sn, Sr, Ti, V, Zn, and Zr. The impurity amount k is the total amount of these elements.
As will be described later, when a bonding surface is provided on a SiSiC member having a slot (see FIG. 9), if an adhesive containing impurities such as Cu is used on this bonding surface, the value of the impurity amount k is likely to be large.
On the other hand, by fabricating a SiSiC member without providing such a bonding surface, the value of the impurity amount k can be reduced.
The amount of impurities k is determined using an ICP (inductively coupled plasma) optical emission spectrometer (SPS5520, manufactured by Hitachi High-Tech Science Corporation).

Most of the impurities are attached to voids formed inside the SiC crystal.
Therefore, SiC particles (e.g., α-SiC particles) used as a raw material are crushed to a predetermined particle size before use, so that impurities such as Fe present in voids formed inside the SiC crystals are exposed to the particle surface and can be removed by washing.
For example, α-SiC particles synthesized by the Acheson method are crushed and classified to have a maximum particle size of 44 μm or less and an average particle size in the range of 2 to 25 μm, and then washed with a mixed acid of hydrofluoric acid and nitric acid and pure water, thereby reducing the impurity Fe present in the α-SiC particles to 5 ppm by mass or less.
The average particle size means the particle size at 50% of the cumulative value in the particle size distribution (cumulative mass distribution) determined by a laser diffraction/scattering method (the same applies hereinafter).

<Manufacturing method>
A method for manufacturing a SiSiC member will be described with reference to FIGS.

<<Preparation of SiC Molded Body>>
FIG. 5 is a cross-sectional view showing the SiC compact 3.
First, a SiC molded body 3 is formed. The SiC molded body 3 is a molded body containing SiC particles (not shown) and has a U-shaped groove 4. The shape of the groove 4 is not particularly limited as long as it is a shape into which a pipe 5 (see FIGS. 6 and 7 ), which will be described later, can be fitted.

The SiC compact is also a porous body having many pores, and therefore, as will be described later, the SiC compact is impregnated with molten elemental Si.
The porosity of the SiC molded body is preferably 10 to 60 volume %, more preferably 12 to 50 volume %, even more preferably 14 to 40 volume %, particularly preferably 16 to 30 volume %, and most preferably 18 to 25 volume %. The porosity is determined by Archimedes' method.

The dimensions and shape of the SiC molded body are not particularly limited and are set appropriately depending on the dimensions and shape of the final SiSiC component.

The method for producing the SiC compact is not particularly limited.
For example, a SiC compact can be produced by pouring a mixture of SiC particles and a binder (a SiC compact raw material) into a mold and drying it. The solid content of the SiC compact raw material can be appropriately changed within a range of, for example, 5 to 100 mass %. After drying, the SiC compact can be sintered by heating at a high temperature (e.g., 1500 to 2300°C) in an inert atmosphere.
Examples of such methods include drain casting, isostatic pressing, and extrusion. In any of these methods, a wider particle size distribution of the SiC particles is preferable because it improves formability and increases the density of the resulting SiC molded body. Specific examples include the method described in Japanese Patent Application Laid-Open No. 5-32458.
Examples of binders include organic binders. Suitable organic binders include phenolic resin, polyvinyl acetate emulsion, and acrylic resin emulsion. When phenolic resin is used as the binder, carbon remains in the resulting SiC molded body. This carbon reacts with molten elemental silicon during the Si impregnation process described below to form β-SiC.

After producing a groove-free SiC molded body, grooves may be formed using a known cutting tool such as an NC (Numerical Control) milling machine before heating it. After the grooves are formed, the SiC molded body with grooves may be sintered by heating it.

The method for producing the SiC compact is not limited to the above method.
For example, methods such as extrusion molding, injection molding, and 3D (three-dimensional) printing such as laser irradiation molding and binder jet molding may be used.

The SiC particles used as the raw material for the SiC compact are preferably α-SiC particles.
The average particle size of the α-SiC particles is preferably in the range of 2 to 25 μm, more preferably 3 to 15 μm, for the following reasons.
If the average particle size of the α-SiC particles is too small, the impurity Fe can be reduced to 5 ppm by mass or less by the above-mentioned washing, but the amount of impurities mixed in during the grinding process may increase, and the washing process may be time-consuming. Also, the pore structure of the resulting SiC molded body may become too fine, making the Si impregnation described below difficult.
On the other hand, if the average particle size of α-SiC particles is too large, many particles will not pass through a sieve during classification before use (e.g., classification to reduce the maximum particle size to 44 μm or less), resulting in a lower usable percentage.Furthermore, the smoothness of the SiC molded body will decrease, which may result in insufficient material properties such as bending strength of the resulting SiSiC member.

Pipe placement
Next, as shown in FIG. 6, a pipe 5 is placed in the groove 4 of the SiC compact 3 .
FIG. 6 is a cross-sectional view showing a state in which a pipe 5 is placed in a groove 4 of a SiC molded body 3.
The pipe 5 is a tubular member, such as a carbon pipe containing carbon (C) or a SiC pipe containing silicon carbide (SiC). The pipe 5 becomes the tubular region A in the resulting SiSiC member 1 (see FIG. 1).

Unlike SiC molded bodies, it is preferable that the pipe is not porous (it is dense). This makes it difficult for molten Si to penetrate the pipe, as described below.

When a carbon pipe is used as the pipe, since carbon has low strength, it is preferable to increase the carbon content in the carbon pipe to a certain extent in order to prevent cracks during the production of the SiSiC member.
Specifically, the carbon content in the carbon pipe is preferably 60% by volume or more, more preferably 70% by volume or more, even more preferably 75% by volume or more, particularly preferably 80% by volume or more, and most preferably more than 80% by volume.
Although there is no particular upper limit, for example, a carbon pipe with a carbon content of 100% by volume has low flexibility and tends to have reduced flexibility when placed in a SiC molded body. Furthermore, if the carbon content of the carbon pipe is 95% by volume or less, molten Si penetrates part or all of the carbon pipe and reacts with the carbon pipe to form SiC. This results in the tubular region A becoming a composite containing carbon and SiC. As a result, the difference in expansion coefficient between the tubular region A and the outer region B becomes smaller, making cracks due to thermal stress during manufacturing or use less likely to occur. Therefore, the carbon content of the carbon pipe is preferably 98% by volume or less, more preferably 95% by volume or less, even more preferably 92% by volume or less, and particularly preferably 90% by volume or less.

When a SiC pipe is used for the pipe, the SiC content in the SiC pipe is preferably as follows, from the viewpoint of reducing the difference in expansion coefficient during Si impregnation, which will be described later.
The SiC content in the SiC tube is preferably 40% by volume or more, more preferably 43% by volume or more, even more preferably 47% by volume or more, and particularly preferably 50% by volume or more.
On the other hand, the SiC content in the SiC pipe is preferably 95% by volume or less, more preferably 85% by volume or less, even more preferably 70% by volume or less, and particularly preferably 60% by volume or less.

The pipe is not limited to a straight pipe, but may be bent.
The pipe may be closed at one end.
Alternatively, a pipe with both ends open may be used, with one end sealed, for example, by gluing a scrap piece of the same material as the pipe to one end of the pipe using adhesive.
Examples of the adhesive to be used include adhesives containing resins such as epoxy resin, polycarbosilane, phenolic resin, methyl cellulose, etc. In addition to these resins, the adhesive may also contain particles such as carbon particles, SiC particles, Si particles, etc.
The adhesive may be a filler containing SiC particles, a mixture of Si particles and SiC particles, or the like.
The content of each component in the adhesive is adjusted appropriately depending on the composition of the pipe (for example, a carbon pipe or a SiC pipe).

In addition, carbon pipes made by winding carbon sheets or the like into a pipe shape may be prone to cracking and causing Si ejection, as described below.

If the tubular region A is to be split (see Figure 4), the split pipe (e.g., a pipe cut longitudinally) is placed in the groove.

As a method for obtaining split pipes, for example, a method (Method 1) can be mentioned in which a cylindrical carbon rod or SiC rod is first cut along the longitudinal direction to split it (e.g., into two pieces), and then the inside of the resulting split pieces is scraped to obtain split pipes.
Furthermore, there is also a method (Method 2) in which a long hole is formed in a carbon rod or SiC rod using a drill or the like of a machining center, and then the rod is divided to obtain divided pipes.
However, compared with Method 1, Method 2 may be more susceptible to the above-mentioned axial misalignment even if the carbon rod or SiC rod used is linear. Therefore, Method 1 is preferable from the viewpoint of reducing the axial misalignment amount c.

The divided pipes are fixed and placed in the grooves so that the displacement amount e and the division interval f (see FIG. 4) are the desired values.
The divided pipe pieces may be glued together with the adhesive described above to fill the gaps.

"filling"
Next, as shown in FIG. 7, the inside of the groove 4 of the SiC compact 3 and above the pipe 5 is filled with a filler 8 containing SiC particles.
FIG. 7 is a cross-sectional view showing a state in which the grooves 4 of the SiC compact 3 are filled with a filler material 8. As shown in FIG.

For example, a mixture of SiC particles and a binder is placed in the grooves, and then the mixture is dried and heated. This fills the grooves with a filler material that has a similar composition to the SiC compact.

When using the binder jet molding method described above, for example, a mixture of SiC particles and a curing agent is placed in the grooves, and then a binder is sprayed onto the mixture from an inkjet nozzle, thereby filling the grooves with a filler material having the same composition as the SiC compact.
If the grooves are deep, the grooves may be filled with filler in stages by repeatedly pouring the mixture and injecting the binder. The grooves may also be filled with filler by manual application.

Unless otherwise specified, the filler will be treated as part of the SiC compact below.

As described above, the SiC compact (including the filler) may be dried and then heated in an inert atmosphere to be sintered. This makes the SiC compact denser than immediately after drying, improving its strength. Furthermore, impurities are volatilized by heating, improving its purity.
The heating temperature is preferably 1500°C or higher. This provides the SiC compact with sufficient strength to withstand handling during the Si impregnation process described below. When a phenolic resin or the like that leaves carbon in the SiC compact is used as a binder (binding agent) for the SiC compact raw material, the heating temperature can be set to about 1000°C.
On the other hand, if the heating temperature is, for example, 2100°C or higher, crystal growth called recrystallization progresses, causing a change in the structure. However, if the heating temperature is too high (for example, above 2300°C), crystal growth becomes significant, and furthermore, weight loss due to volatilization of SiC may result in a decrease in strength and fracture toughness. For this reason, the heating temperature is preferably 2300°C or lower.

<Si impregnation>
Next, the SiC compact is impregnated with silicon (Si), which will hereinafter also be referred to as "Si impregnation."
Specifically, for example, the SiC molded body and the elemental Si are brought into contact with each other and then heated to melt the elemental Si, which then impregnates the porous SiC molded body with the molten elemental Si due to capillary action.
At this time, by melting the elemental Si while it is placed on the upper surface of the SiC molded body, the molten elemental Si can be more easily impregnated into the SiC molded body by utilizing gravity.
The environment in which the elemental silicon is melted is preferably a reduced pressure environment.

The heating temperature should be equal to or higher than the melting point of Si. The melting point of Si varies slightly depending on the measurement method, but is generally 1410 to 1414°C. A heating temperature of 1430 to 1800°C is preferred.

Some of the Si impregnated into the SiC compact also reaches the pipe, but as described above, if the pipe is a dense body, Si is less likely to be introduced into the pipe.
The Si that has been introduced into the SiC compact and has not reacted with carbon (C) or other elements remains as is. Hereinafter, this Si will also be referred to as "free Si." In this way, a SiSiC component, which is a composite material containing SiC and free Si, is obtained.
In the resulting SiSiC component, the region that was the pipe (carbon tube or SiC tube) becomes the tubular region A (see Figure 1), and the other region (SiC compact and filler) becomes the extra-tubular region B (see Figure 1).
When split pipes are used, the spaces between adjacent split pipes become areas C (see FIG. 10).

The amount of Si introduced into the SiC compact is appropriately set depending on the content of elemental Si in the SiSiC member finally obtained.
If the porosity of the SiC compact is low (the number of pores is small), the number of closed pores increases, making it difficult to impregnate the Si. For example, it is preferable to impregnate the SiC compact with 7 mass % or more of Si.
The content of elemental Si in the resulting SiSiC member is preferably 35 mass % or less, and more preferably 25 mass % or less, which allows for desirable physical properties such as high bending strength to be obtained.

The resulting SiSiC member is sintered by the heat applied when melting the Si element.
That is, SiC (including newly generated SiC) bonds with each other and with SiC, resulting in a dense sintered body.
Therefore, the resulting SiSiC member is a composite material containing Si and SiC, and is also a sintered body.

<Amount of silicon ejected (g)>
Here, the suppression of Si spout-out will be described with reference to FIG.
FIG. 8 is a schematic cross-sectional view showing a state in which a Si outflow 9 exists in the slot 2. As shown in FIG.

The density of silicon (Si) is 2.560 g/cm ³ in the liquid state, while it is 2.293 g/cm ³ in the solid state.
That is, when free Si is cooled from a heated molten state back to a solid state, it expands, increasing its volume by 12%.

Therefore, as shown in FIG. 8, when the tubular region A is divided, the free Si expands in volume, passes through the gaps in the tubular region A, and can protrude into the long hole 2 as a spout (Si spout 9).
If a large Si outflow 9 exists in the slot 2 (the value of the Si outflow amount g in FIG. 8 is large), it is difficult (or impossible) to insert a rod-shaped member such as a thermocouple into the slot 2 .

At this time, the values of the division interval f and/or the positional deviation e (see FIG. 4) are reduced, which makes it difficult for Si to pass through the gaps in the tubular region A. For example, even if the volumetrically expanded Si penetrates the gaps in the tubular region A, it may stop midway through the gap or at the exit.
In this way, the Si blowout 9 is suppressed, and it becomes easier to insert a thermocouple or the like into the slot 2.

For the reason that it is easy to insert a thermocouple or the like into the long hole 2, the amount of Si ejection g is preferably less than 1 mm, more preferably less than 0.7 mm, even more preferably less than 0.4 mm, even more preferably less than 0.2 mm, particularly preferably less than 0.1 mm, more particularly preferably less than 0.05 mm, and most preferably less than 0.01 mm.
For the same reason, the ratio (g/d) of the amount of Si ejected g to the thickness d of the tubular region A (see FIG. 2) is preferably 3/4 (0.75) or less, more preferably 2/4 (0.5) or less, even more preferably less than 1/4 (0.25), particularly preferably less than 1/5 (0.2), and most preferably less than 1/10 (0.1).

<Application>
Although there are no particular limitations on the applications of the SiSiC member having the slots, it is suitable as a heating device due to its excellent thermal conductivity, strength, etc. When the SiSiC member is used as a heating device, for example, the SiSiC member itself and/or a heated object placed on the SiSiC member is heated.
A suitable example of such a heating appliance is a top plate provided in a heating cooker such as an induction heating (IH) cooker.
The top plate of the cooking device is a member on which an object to be heated, such as a pot, is placed.
Ceramics and other materials have traditionally been used for top plates. However, the top plate is required to be able to heat and cool quickly and to have high impact resistance. For this reason, SiSiC members are suitable for use as top plates for cooking appliances.
For temperature control, a thermocouple (not shown) is inserted into a long hole in the SiSiC member, which allows the temperature of the SiSiC member and, ultimately, of an object to be heated placed on the SiSiC member to be monitored.

The cooking appliance may be used as part of a system kitchen.
A system kitchen has a work table, a cooking appliance, and other appliances connected by a worktop, which is made of materials such as stainless steel, artificial marble, and ceramics.
The cooking device is used by being incorporated into an opening provided in a worktop, for example, and in this case, the top plate of the cooking device may form part of the worktop of the system kitchen.

Here, we will consider another embodiment of a SiSiC component with a long hole for use in a heating cooker, based on Figure 9.

FIG. 9 is a cross-sectional view showing a SiSiC member 21 having a bonding surface.
First, in the same manner as described with reference to FIG. 5, a SiC molded body 3 having grooves 4 and a SiC molded body 3 without grooves are produced.
9, the SiC molded body 3 without grooves is placed on the SiC molded body 3 with grooves 4. At this time, the interface between the two is bonded using adhesive 22.

Let's consider the case where the SiSiC member 21 shown in Figure 9 is used as the top plate of a cooking appliance. In this case, an object to be heated (not shown) is placed on the top surface of the SiSiC member 21, and heated from the bottom side. However, depending on the adhesive 22 used, heat may be blocked at the joint surface, making it difficult for heat to be transferred to the object to be heated (i.e., poor thermal conductivity).

In contrast, the SiSiC member 1 (see Figure 1) does not have such a bonding surface, making it relatively easy to heat the object to be heated. In other words, it has good thermal conductivity.

The uses of the SiSiC member are not limited to the top plate of the above-mentioned cooking appliance, but also include heater members for electric furnaces used in heating experiments; members for semiconductor device manufacturing equipment; and the like.
Depending on the application of the SiSiC member, the SiSiC member may be used with a rod-shaped member such as an electrode inserted into the long hole.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples described below.
Below, Examples 1 to 5, 7 to 16, 18, and 20 to 81 are working examples, and Examples 6, 17, and 19 are comparative examples.

<Examples 1 to 73>
α-SiC particles with a maximum particle size of 44 μm and an average particle size of 8 μm, which had been separated using a 325 mesh sieve, were mixed with pure water and a water-soluble phenolic resin to obtain a SiC compact raw material. The solid content of the SiC compact raw material is shown in the table below.
This SiC molded body raw material was poured into a plaster mold to form a solid, and then the remaining SiC molded body raw material (sludge) was drained from the mold (sludge casting method), to obtain a rectangular parallelepiped molded body. The thickness of the SiC molded body was adjusted to the thickness shown in Table 1 below after Si impregnation, which will be described later. The length of one side of the SiC molded body other than the thickness was appropriately selected from the range of 100 to 520 mm depending on the length of the pipe to be used, etc.
The area of the top surface of the SiC molded body (in the table below, simply referred to as "area of SiC molded body") is also shown in the table below.

Next, an NC milling machine was used to form a groove in the SiC molded body that would fit the pipe described below.

Next, one pipe was placed in the groove of the SiC compact. The diameter (inner diameter a), length b, and thickness d of the pipe used are shown in the table below.
The pipes used were carbon or SiC pipes that were equally divided (cut along the longitudinal direction) into the number of divisions h shown in the table below. In the "Pipe Material" column in the table below, for example, if a carbon pipe with a carbon content of 81% by volume was used, it would be listed as "C81," and if a SiC pipe with a SiC content of 48% by volume was used, it would be listed as "SiC48."
More specifically, except for Examples 16 to 19, first, a cylindrical carbon rod or SiC rod was cut along the longitudinal direction and divided (for example, into two), and then the inside of the obtained divided pieces was scraped to obtain divided pipes.
In Examples 16 to 19, first, a long hole was formed in a carbon rod using a drill of a machining center, and then the rod was divided to obtain divided pipes.

Next, the SiC compact raw material described above was placed into the grooves after the pipes were placed and allowed to dry at room temperature for 12 hours. This filled the top of the pipes with a filler material having the same composition as the SiC compacts. This work was performed with the divided pipes fixed in place so that the misalignment amount e and division interval f were as shown in the table below.

In all cases except for Examples 69 and 70, pipes with open ends were used with one end sealed. The sealing was achieved by adhering a scrap piece of the same material as the pipe to the end of the pipe using an adhesive (Adhesive 1 or Adhesive 2 below). The adhesives used are shown in the table below.
In Examples 69 and 70, open-ended pipes were used without sealing the ends, and in these cases, a "-" is entered in the "Adhesive" column in the table below.

Allylhydridopolycarbosilane (SMP-10, manufactured by Starfire) was used as adhesive 1. After Si impregnation, which will be described later, the SiC content in the region corresponding to adhesive 1 was 72% by volume.
An epoxy resin (SMC-7030H, manufactured by Shin-Etsu Chemical Co., Ltd.) mixed with 15% by mass of carbon particles (SGP-25, manufactured by SEC Carbon Co., Ltd.) having an average particle size of 25 μm was used as adhesive 2. After Si impregnation, which will be described later, the SiC content in the region corresponding to adhesive 2 was 31% by volume.

In Examples 28 and 29, the split pipe pieces were glued together using the adhesive used to seal the ends.
When the content of simple carbon or SiC in region C (see FIG. 10) is 20% by volume or more, region C is regarded as being integral with tubular region A, and the division interval f is set to 0 mm.
In Examples 28 and 29, this content was achieved by using the adhesive described above.
In particular, in Example 28, the tubular region A was made of SiSiC with a SiC content of 71% by volume, while the region C was made of SiSiC with a SiC content of 72% by volume, and the SiSiC had almost the same composition and were integrated together.

Next, the SiC molded body, with the grooves after the pipe placement filled with filler, was dried and then heated in an inert atmosphere in an electric furnace at 1800°C for 5 hours. This resulted in a rectangular SiC molded body.

Next, Si impregnation was carried out. More specifically, in a reactor, elemental Si was placed on top of the SiC molded body and heated to 1,450°C in a reduced pressure environment. This caused the elemental Si to melt and be impregnated into the SiC molded body. At this point, all pores in the SiC molded body were filled with high-purity Si, and at least a portion of the carbon present as a component of the pipe and/or adhesive reacted with Si to form silicon carbide. In this way, a SiSiC component was obtained.

A cross section was cut out at an arbitrary location from the obtained SiSiC member, and the amount of silicon ejected (g) was measured from an optical microscope photograph of the cross section. The results are shown in the table below.
At this time, it was confirmed from the optical microscope photograph that the diameter a of the long hole, the length b of the long hole, the thickness d of the tubular region A, the positional deviation e, and the division interval f were maintained.

The thermal conductivity i (i1 and i2) and thermal conductivity j of the obtained SiSiC components were measured using the method described above. The results are shown in the table below.

The impurity content k of the obtained SiSiC components was measured using the method described above. The results are shown in the table below. The impurities included Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Sb, Sn, Sr, Ti, V, Zn, and Zr.

<Summary of evaluation results>
Looking at the above table, for example, in Examples 42 to 49 and 63 where the dividing interval f exceeded 0.15 mm, the Si blowout amount g was 0.2 mm or more.
In contrast, in the examples where the dividing interval f was 0.15 mm or less, the Si ejection amount g was less than 0.2 mm (excluding examples 23, 41, and 61 where the positional deviation amount e was large).

However, there is a concern that increasing the number of pipes may result in a decrease in the thermal conductivity of the resulting SiSiC component. Therefore, the SiSiC components of Examples 74 to 78 were fabricated as follows, and the thermal conductivity K was calculated based on the following formula:

K={[L-(M×N)]/L}×O
In the above formula,
K: Overall thermal conductivity of the SiSiC member; L: Overall cross-sectional area of the SiSiC member; M: Maximum cross-sectional area of the tubular region A; N: Number of long holes; O: Thermal conductivity of the outer tubular region B.

When the solid content concentration of the SiC compact raw material was 76 mass%, the O was 230 W/(m K), when the solid content concentration was 42 mass%, the O was 182 W/(m K), when the solid content concentration was 58 mass%, the O was 202 W/(m K), and when the solid content concentration was 84 mass%, the O was 232 W/(m K).
In all the examples, the adhesion between the tubular region A and the extra-tubular region B was sufficiently good, and the temperature difference ΔT at the boundary surface was considered to be zero.

Example 74
Ten bisected carbon tubes (outer diameter: 1.9 mm, inner diameter: 0.7 mm, thickness: 0.6 mm, length: 330 mm) were arranged at equal intervals on a SiC molded body (350 mm × 350 mm, thickness: 6.5 mm) made from a SiC molded body raw material (solid content: 76 mass %). The other conditions were the same as in Example 1, and a SiSiC member was produced.
In this case, the cross-sectional area of the long hole portion accounted for 5.1% of the cross-sectional area of the entire SiSiC member. The thermal conductivity of the fabricated SiSiC member was calculated based on the above formula and was found to be 218 W/(m·K).

Example 75
Ten bisected carbon tubes (outer diameter: 4.1 mm, inner diameter: 2.0 mm, thickness: 1.0 mm, length: 280 mm) were arranged at equal intervals on a SiC molded body (300 mm × 300 mm, thickness: 6.5 mm) made from a SiC molded body raw material (solid content: 76 mass %). The other conditions were the same as in Example 6, and a SiSiC member was produced.
In this case, the cross-sectional area of the long hole portion accounted for 12.8% of the cross-sectional area of the entire SiSiC member. The thermal conductivity of the fabricated SiSiC member was calculated based on the above formula and was found to be 201 W/(m·K).

Example 76
Ten bisected carbon tubes (outer diameter: 1.9 mm, inner diameter: 0.7 mm, thickness: 0.6 mm, length: 330 mm) were arranged at equal intervals on a SiC molded body (360 mm × 300 mm, thickness: 6.5 mm) prepared using a SiC molded body raw material (solid content: 49 mass%). The other conditions were the same as in Example 71, and a SiSiC member was prepared.
In this case, the cross-sectional area of the long hole portion accounted for 5.8% of the cross-sectional area of the entire SiSiC member. The thermal conductivity of the fabricated SiSiC member was calculated based on the above formula and was found to be 171 W/(m·K).

Example 77
Ten bisected carbon tubes (outer diameter: 1.9 mm, inner diameter: 0.7 mm, thickness: 0.6 mm, length: 330 mm) were arranged at equal intervals on a SiC molded body (350 mm × 280 mm, thickness: 6.5 mm) prepared using a SiC molded body raw material (solid content: 58 mass %). The other conditions were the same as in Example 72, and a SiSiC member was prepared.
In this case, the cross-sectional area of the long hole portion accounted for 6.4% of the cross-sectional area of the entire SiSiC member. The thermal conductivity of the fabricated SiSiC member was calculated based on the above formula and was found to be 189 W/(m·K).

Example 78
Ten bisected carbon tubes (outer diameter: 3.1 mm, inner diameter: 1.3 mm, thickness: 0.9 mm, length: 330 mm) were arranged at equal intervals on a SiC molded body (350 mm × 280 mm, thickness: 6.5 mm) prepared using a SiC molded body raw material (solid content: 84 mass%). The other conditions were the same as in Example 73, and a SiSiC member was prepared.
In this case, the cross-sectional area of the long hole portion accounted for 10.4% of the cross-sectional area of the entire SiSiC member. The thermal conductivity of the fabricated SiSiC member was calculated based on the above formula and was found to be 208 W/(m·K).

Example 79
A SiSiC member was produced using a SiC molded body (350 mm × 350 mm, thickness: 6.5 mm) prepared using a SiC molded body raw material (solid content: 76 mass%). A carbon tube (outer diameter: 1.9 mm, inner diameter: 0.7 mm, thickness: 0.6 mm, length: 280 mm) divided into two was placed on the molded body. The other conditions were the same as in Example 1.
In this case, the cross-sectional area of the long hole portion accounted for 0.4% of the cross-sectional area of the entire SiSiC member. The thermal conductivity of the fabricated SiSiC member was calculated based on the above formula and was found to be 229 W/(m·K).

Example 80
Five bisected carbon tubes (outer diameter: 1.9 mm, inner diameter: 0.7 mm, thickness: 0.6 mm, length: 280 mm) were placed on a SiC molded body (350 mm × 350 mm, thickness: 6.5 mm) made from a SiC molded body raw material (solid content: 76 mass %). The other conditions were the same as in Example 1, and a SiSiC member was produced.
In this case, the cross-sectional area of the long hole portion accounted for 2.2% of the cross-sectional area of the entire SiSiC member. The thermal conductivity of the fabricated SiSiC member was calculated based on the above formula and was found to be 225 W/(m·K).

Example 81
Fifteen carbon tubes (outer diameter: 4.1 mm, inner diameter: 1.8 mm, thickness: 1.0 mm, length: 280 mm) were arranged at equal intervals on a SiC molded body (300 mm × 300 mm, thickness: 6.5 mm) made from a SiC molded body raw material (solid content: 76 mass %). The other conditions were the same as in Example 6, and a SiSiC member was produced.
In this case, the cross-sectional area of the long hole portion accounted for 19% of the cross-sectional area of the entire SiSiC member. The thermal conductivity of the fabricated SiSiC member was calculated based on the above formula and was found to be 186 W/(m·K).

The above describes a preferred embodiment of the present invention, but the present invention is not limited to the above embodiment, and various design modifications are possible within the scope of the claims. This application is based on Japanese Patent Application No. 2020-171478, filed on October 9, 2020, the contents of which are incorporated herein by reference.

1: SiSiC member 2: Slot 3: SiC compact 4: Groove 5: Pipe 8: Filler 9: Si ejection 21: SiSiC member 22: Adhesive A: Tubular region B: Outer region C: Region a: Diameter of slot b: Length of slot c: Axial deviation d: Thickness of tubular region e: Position deviation f: Dividing interval g: Amount of Si ejection L ₁ , L ₂ : Center line of slot

Claims (12)

A SiSiC member having at least one long hole formed therein , the SiSiC member being obtained by Si-impregnating a SiC molded body having a carbon tube disposed therein,
The elongated hole has a diameter a of 2.0 mm or less and a length b of 100 mm or more,
a tubular region A that is an outer peripheral region of the long hole;
The SiSiC member, wherein the tubular region A contains at least one selected from the group consisting of simple C, SiC, and SiSiC. The SiSiC component according to claim 1, having a thermal conductivity i of 170 W/(m·K) or greater. The SiSiC component according to claim 1 or 2, wherein the tubular region A is divided into multiple regions. The SiSiC component according to claim 3, wherein the division spacing f of the divided tubular region A is 0.15 mm or less. A SiSiC component according to any one of claims 1 to 4, wherein the amount of Si ejected from the elongated hole (g) is less than 1 mm. A SiSiC component according to any one of claims 1 to 5, wherein the ratio g/d of the amount of Si ejected through the elongated hole g to the thickness d of the tubular region A is 3/4 or less. The SiSiC component according to any one of claims 1 to 6, wherein the ratio e/d of the positional deviation e of the tubular region A to the thickness d of the tubular region A is less than 1/3. The SiSiC component according to any one of claims 1 to 7, wherein the axial misalignment amount c of the elongated hole is less than 0.3 mm. A SiSiC component according to any one of claims 1 to 8, wherein the impurity content k is 100 mass ppm or less. The thickness is 2.0 to 15.0 mm,
The SiSiC member according to any one of claims 1 to 9, having at least one surface, the surface having an area of 100 ^cm2 or more. A SiSiC member according to any one of claims 1 to 10 and a rod-shaped member,
The rod-shaped member is inserted into the long hole. A method for manufacturing a SiSiC component according to any one of claims 1 to 10, comprising:
providing a SiC compact having a groove;
A pipe is placed in the groove, and then a filler containing SiC is placed therein;
A method for manufacturing a SiSiC member, comprising impregnating the SiC molded body with the filler material in the grooves with heated and melted elemental Si.