JP5937506B2 - Ceramic member and heat conduction member - Google Patents

Description

  The present invention relates to a ceramic member and a heat conducting member.

  For example, in the melting of a metal such as aluminum, in order to protect a heater for heating and melting the metal from erosion of the molten metal, a structure used in a state where at least a part is immersed in the molten metal, for example, A ceramic member which is a tubular body sealed at one end is used.

  In firing metal powder, ceramics and the like, a structure used by containing metal powder or ceramics, for example, a ceramic member which is a box-shaped container is used.

  In general, a silicon nitride sintered body having excellent heat resistance is used as the structure. In producing such a silicon nitride sintered body, a sintering aid component is usually added. For example, Patent Document 1 proposes a silicon nitride sintered body to which a metal element oxide is added as a sintering aid component.

Japanese Patent Laid-Open No. 2002-12474

  However, when a silicon nitride sintered body proposed in Patent Document 1 is used to produce a structure in which the inner peripheral surface is in contact with the space, a sintering aid component is formed from the inner peripheral surface in contact with the space by a firing process during manufacturing. Since volatilization occurs, in the region near the inner peripheral surface, thermal conductivity decreases due to the decrease in density due to volatilization of the sintering aid component. Therefore, when a heat source such as a heater is arranged in the space on the inner peripheral surface side of such a structure, there is a problem that the heat of the heat source cannot be efficiently transmitted to the outside. In addition, when metal powder or ceramics is placed in the space on the inner peripheral surface side, when heat is radiated after firing the metal powder or ceramics, the heat of the metal powder or ceramics cannot be efficiently transferred to the outside. there were.

  The present invention has been proposed in order to solve the above-described problems, and an object of the present invention is to provide a ceramic member having high thermal conductivity and a heat conducting member using the same.

  The ceramic member of the present invention is a structure whose inner peripheral surface is in contact with a space, and the structure is made of a silicon nitride sintered body containing magnesium, and the structure is formed from an inner peripheral surface in contact with the space. The first region present in the thickness direction of the structure and a second region other than the first region, and the content of the magnesium present in the first region is the second region The content of magnesium is higher than the content of magnesium.

  The heat conducting member of the present invention is characterized in that a heat source is disposed in the space of the ceramic member.

According to the ceramic member of the present invention, the inner peripheral surface is in contact with the space, the structure is made of a silicon nitride sintered body containing magnesium, and the structure is structured from the inner peripheral surface in contact with the space. The first region present in the thickness direction of the body and the second region other than the first region, the content of magnesium present in the first region is the content of magnesium present in the second region More than quantity. With such a structure, it is considered that magnesium is difficult to be dissolved in silicon nitride crystal particles, so that an increase in the aspect ratio of the silicon nitride crystal particles is suppressed and the silicon nitride crystal particles are easily filled. Due to such a phenomenon, the density of the first region can be increased and the thermal conductivity can be improved.

  Moreover, according to the heat conductive member of this invention, since a heat source is arrange | positioned in the space of the said ceramic member, it can be set as the heat conductive member which improved thermal conductivity.

An example of the ceramic member of this embodiment is shown. (A) is a longitudinal sectional view of the ceramic member, and (b) is an enlarged view of the cross section of the ceramic member taken along line X-X ′ of (a). It is sectional drawing of the ceramic member which shows another example of the ceramic member of this embodiment. It is a longitudinal cross-sectional view which shows an example of the heat conductive member using the ceramic member of this embodiment.

  1A and 1B show an example of a ceramic member according to the present embodiment. FIG. 1A is a longitudinal sectional view of the ceramic member, and FIG. 1B is an enlarged view of a cross section of the ceramic member taken along line XX ′ in FIG. is there.

  The ceramic member 10 of the present embodiment is a structure in which the inner peripheral surface 20 is in contact with the space, and is made of a silicon nitride sintered body containing magnesium. The ceramic member 10 includes a first region 1 existing in the thickness direction from the inner peripheral surface 20 in contact with the space, and a second region 2 other than the first region 1. Here, the first region 1 in the present embodiment is a thickness T from the inner peripheral surface 20 to the outer peripheral surface 21 in the cross section (hereinafter also simply referred to as a cross section) along the line XX ′ in FIG. On the other hand, it refers to a region where the thickness from the inner peripheral surface 20 of the structure is within 50%. In FIG. 1B, a position where the thickness T is 50% is indicated by a broken line 12.

  In the ceramic member 10, the magnesium content present in the first region 1 is greater than the magnesium content present in the second region 2. In the first region 1, magnesium is preferably present as magnesium oxide, but part of it may be present as another compound or simple substance.

  With such a structure, it is considered that magnesium is difficult to be dissolved in silicon nitride crystal particles, so that an increase in the aspect ratio of the silicon nitride crystal particles is suppressed and the silicon nitride crystal particles are easily filled. Due to such a phenomenon, the density of the first region 1 can be increased, and the thermal conductivity can be improved.

  The comparison of the magnesium content in the first region 1 and the second region 2 can be made by measuring the abundance of Mg element by surface analysis using, for example, an electron beam microanalyzer (EPMA). That's fine.

Moreover, although the ceramic member 10 shown in FIG. 1 is a tubular body (bottomed tubular body) sealed at one end, the present invention is not limited to this shape, and has a shape having a space inside. As long as one end is sealed, both ends may be sealed, or both ends may not be sealed. For example, the ceramic member of the present invention may have a cylindrical shape (including an annular shape such as a ring), a casing shape, or a spherical shape.

  In addition, the silicon nitride sintered body in the present embodiment contains 80% by mass or more of silicon nitride as a main crystal phase with respect to the total mass, and more particularly 85% by mass or more has higher thermal conductivity and mechanical strength. This is preferable because it tends to increase. Furthermore, it goes without saying that inevitable impurities are contained in the phase made of silicon nitride. In addition, the component amount of silicon nitride may be measured by fluorescent X-ray analysis or ICP (Inductively Coupled Plasma) emission analysis, and the silicon content of the silicon nitride sintered body is measured. It may be obtained by converting the content of silicon into the content of silicon nitride. Here, although a component containing silicon (excluding silicon nitride) exists in the grain boundary phase, the amount of the component in the entire silicon nitride-based sintered body is very small. Therefore, in calculating the silicon nitride content, silicon nitride All the silicon contained in the sintered material may be regarded as constituting silicon nitride.

  In the ceramic member 10 of the present embodiment, the number of pores per unit area is preferably smaller in the first region 1 than in the second region 2. With such a configuration, the density of the first region 1 can be increased, and the thermal conductivity can be further improved.

The number of pores in the first region 1 and the second region 2 of the ceramic member 10 may be obtained by determining the number per unit area in each cross section. For example, the cross section of the structure is polished, Using an optical microscope, the cross section was photographed with a CCD camera at a magnification of 200 times, and the area of one field of view in the image was 2.25 × 10 using an image analyzer (LUZEX series manufactured by Nireco Corporation).
^-2 mm ² , the number of fields of view is 20, that is, the total measurement area is 4.5 × 10 ⁻¹ mm ² , the number of pores per unit area is counted, and the number of pores in the first region 1 and the second region 2 Should be compared.

  FIG. 2 is a cross-sectional view of a ceramic member showing another example of the ceramic member of the present embodiment.

  The ceramic member 10 ′ contains magnesium and aluminum in a silicon nitride sintered body, and the second region 2 exists in the thickness direction of the structure from the outer peripheral surface 21 of the structure. And the fourth region 4 other than the third region 3, and the aluminum content present in the third region 3 is greater than the aluminum content present in the fourth region 4. Here, the third region 3 is a region in which the thickness from the outer peripheral surface 21 of the structure is within 50% of the thickness T ′ of the second region 2 in the cross section. In FIG. 2, a broken line 13 indicates a position where the thickness from the outer peripheral surface 21 of the structure is 50% with respect to the thickness T ′ of the second region 2.

  With such a configuration, the third region 3 has a higher aluminum content than the fourth region 4, so in the third region 3, aluminum exists as aluminum oxide in the grain boundary phase of silicon nitride. Since the amount of the silicon nitride is large, the silicon nitride crystal particles are strongly bonded to each other. As a result, the mechanical strength of the third region 3 in the silicon nitride sintered body is increased. In other words, the ceramic member 10 'has high mechanical strength in the third region 3 where there is an opportunity to come into contact with another object, and thus is hard to break even when it comes into contact with another object and has high reliability. Further, the mechanical strength in the third region 3 that is the region on the outermost peripheral side of the structure increases, so that the overall mechanical strength of the ceramic member 10 ′ tends to increase. Aluminum is preferably present as aluminum oxide, but a part of it may be present as another compound or as a simple substance.

  In addition, the comparison of the aluminum content in the third region 3 and the fourth region 4 is performed by, for example, using an electron beam microanalyzer (EPMA) to determine the abundance of the Al element in the cross section by surface analysis. What is necessary is just to measure and compare in the area.

  In the ceramic members 10 and 10 ′ of this embodiment, it is preferable that the magnesium content increases from the second region 2 side toward the first region 1 side. With such a configuration, it is possible to suppress a specific decrease in heat conduction from the first region 1 side to the second region 2 side, so the first region 1 side to the second region 2 side. Heat can be transferred efficiently.

  In the ceramic member 10 ′ of this embodiment, the aluminum content is preferably increased from the fourth region 4 side toward the third region 3 side. With such a configuration, the mechanical strength can be increased from the fourth region 4 side toward the third region 3 side. In other words, the strength can be increased toward the outer peripheral side, and the mechanical strength of the entire ceramic member 10 'can be further increased.

  Here, magnesium or aluminum is applied from the second region 2 side to the first region 1 side or from the fourth region 4 side to the third region 3 side in the cross section of the ceramic member 10, 10 ′. For example, as shown below, the concentration distribution of the element content in the cross-section of the ceramic members 10 and 10 ′ may be confirmed as follows.

  First, in the cross section of the structure, at least five locations in each region from the second region 2 side to the first region 1 side or from the fourth region 4 side to the third region 3 side. select. Then, the contents of magnesium or aluminum at those selected locations are measured by surface analysis using an electron beam microanalyzer (EPMA). Then, it can be considered that the distribution of the measured values indicates the concentration distribution of the measured element in the cross section of the structure. When the concentration distribution is viewed, does the concentration of the measurement element tend to increase from the second region 2 side toward the first region 1 side or from the fourth region 4 side toward the third region 3 side? May be determined by approximating the measured value by the least square method.

  Note that the concentration distribution of the contents of magnesium and aluminum may be confirmed by line analysis instead of surface analysis in the cross section of the hollow ceramic member 10, 10 ′ using, for example, an electron beam microanalyzer (EPMA). It doesn't matter.

Further, in the ceramic members 10 and 10 ′ of the present embodiment, it is preferable that the grain boundary phase of silicon nitride contains at least one of FeSi ₂ , WSi ₂ , CrSi ₂ , NiSi ₂ and MoSi ₂ .

  Since silicide is thermodynamically stable, if the above-described silicide is contained in the grain boundary phase, the grain boundary phase is unlikely to undergo phase transformation even when mechanical stress or thermal stress is applied. Therefore, the thermal shock resistance at high temperatures of the ceramic members 10 and 10 'can be improved.

The grain boundary phase preferably contains FeSi ₂ and WSi ₂ among the above-described silicides. The reason for this is that the crystal structures of FeSi ₂ and WSi ₂ are particularly approximate. When these silicides are adjacent to each other, the mechanical strength is stabilized even when the use environment temperature of the ceramic members 10 and 10 ′ is high. This is because the thermal shock resistance at high temperatures can be further improved.

The mechanical properties of the ceramic members 10, 10 ′ of this embodiment are as follows: the four-point bending strength is 650 MPa or more, the dynamic elastic modulus is 300 GPa or more, the Vickers hardness (Hv) is 13 GPa or more, and the fracture toughness ( K _1C ) is preferably 5 MPam ^1/2 or more. Because these mechanical properties are in the above range, when the ceramic member 10 or 10 'is used as a heat conducting member, it is possible to improve the creep resistance and durability against heat cycle, so it has high reliability. Can be used for a long time.

In addition, when the ceramic members 10 and 10 ′ of the present embodiment are porous bodies, the mechanical properties are such that the four-point bending strength at room temperature is 35 MPa or more, and the four-point bending strength at 800 ° C. is 25 MPa or more. The dynamic elastic modulus is 35 GPa or more, and the Vickers hardness (Hv) is 13 G.
It is preferable that it is Pa or more and the fracture toughness (K _1C ) is 5 MPam ^1/2 or more.

Here, regarding the four-point bending strength, JIS R 1601-2008 (ISO 17565: 2003 (
MOD)). However, when the thickness T of the ceramic members 10 and 10 ′ is thin and the thickness of the cut specimen cannot be 3 mm, the thickness T is evaluated as it is as the thickness T of the specimen, and the result is the above It is preferable to satisfy the numerical value.

  Further, the dynamic elastic modulus of the ceramic member 10, 10 'may be measured in accordance with the ultrasonic pulse method defined in JIS R 1602-1995. However, when the thickness T is thin and the thickness of the test piece cut out from the ceramic members 10 and 10 ′ cannot be 10 mm, the cantilever resonance method is used for evaluation, and the result is the above numerical value. It is preferable to satisfy.

Vickers hardness (Hv) and fracture toughness (K _1C ) are in accordance with the indenter press-in method (IF method) defined in JIS R 1610-2003 (ISO 14705: 2000 (MOD)) and JIS R 1607-1995, respectively. To measure. In the case where the ceramic members 10 and 10 ′ are porous bodies, the nanoindentation method may be used for the Vickers hardness (Hv). Further, the thickness T of the ceramic members 10 and 10 ′ is thin, and the thickness of the test piece cut out from the ceramic members 10 and 10 ′ is defined by the indenter press-in method (IF method) of JIS R 1610-2003 and JIS R 1607-1995, respectively. When the thickness of 0.5 mm and 3 mm cannot be reduced, it is preferable that the thickness T is evaluated as it is as the thickness of the test piece and the result satisfies the above numerical value. However, when the thickness T is so thin that the above-mentioned numerical value cannot be satisfied by evaluation with a test piece having the thickness T as it is, for example, when the thickness T is 0.2 mm or more and less than 0.5 mm, the test force applied to the ceramic members 10 and 10 ′ and Vickers hardness (Hv) and fracture toughness (K _1C ) may be measured by setting the indentation load to 0.245 N for both the test force and the time for holding the indentation load for 15 seconds.

  The heat conducting member of the present embodiment is composed of the ceramic members 10 and 10 'described above, and it is preferable to use a heat source disposed in the space.

  As described above, the heat conducting member of the present embodiment is made of the ceramic member 10 or 10 'having improved heat conductivity, so that loss of heat supplied by the heat source is suppressed and heat is efficiently transmitted to the outside. Can do. An example of such a heat conducting member is a heater tube. Moreover, the heat conductive member without a heat source in space may be sufficient, and as such a heat conductive member, a burner tube, a radiant tube, etc. are mentioned. Further, the ceramic member can be used for a thermocouple protection tube, a ladle, a stalk, a degassing rotor, a fishing gear guide member, a seal ring, a firing container, a spherical or roller-shaped rolling element, and the like.

  FIG. 3 is a longitudinal sectional view showing an example of a heat conducting member using the ceramic member of the present embodiment.

  A heat conducting member 30 shown in FIG. 3 is used for melting a metal such as aluminum, and supplies power to the heater 5, the ceramic member 10 or 10 ′ for enclosing and protecting the heater 5, and the heater 5. And a power source 6 for performing the operation.

The heat conducting member 30 is arranged so that at least a part of the ceramic member 10 is immersed in a molten metal (not shown), and electric power is supplied from the power source 6 to heat the heater 5. The heat generated from the heater 5 can be efficiently transferred to the molten metal through the ceramic member 10. In addition, it cannot be overemphasized that a heat conductive member can also be used for heating uses other than molten metal.

  Next, a method for manufacturing the ceramic members 10 and 10 'according to the present embodiment will be described.

First, metal silicon powder and silicon nitride powder having a β conversion ratio of 20% or less are prepared, and the mass ratio of (metal silicon powder) / (silicon nitride powder) is 1 or more and 10 or less. To obtain a first mixed powder. Here, depending on the particle size of the metal silicon powder, there is a risk of insufficient nitriding and insufficient sintering. Therefore, the metal silicon powder is cumulative when the total volume of the particle size distribution curve is 100%. The particle size (D ₉₀ ) with a volume of 90% is 10 μm or less,
Those having a size of 6 μm or less are preferably used.

Further, as a sintering aid, a metal compound powder and a magnesium aluminate powder are mixed to form a second mixed powder. The metal compound is made of at least one of aluminum oxide, silicon oxide, zirconium oxide and calcium carbonate. The content of the second mixed powder is preferably 10% by mass or more and 23% by mass or less when the total of the first mixed powder and the second mixed powder is 100% by mass. As another sintering aid, a mixture of rare earth element oxide powder and magnesium compound powder may be used as the second mixed powder. The magnesium compound is composed of at least one of magnesium hydroxide, magnesium oxide and magnesium carbonate. When a mixed powder of rare earth element oxide powder and magnesium compound powder is used as the second mixed powder, when the total of the first mixed powder and the second mixed powder is 100% by mass, The rare earth element oxide powder may be 10 mass% to 14 mass%, and the magnesium compound powder may be 2 mass% to 4 mass%.

Also, at least one powder of iron oxide, tungsten oxide, chromium oxide, nickel oxide and molybdenum oxide is added in an amount of 0.02 parts by mass or more and 4 parts by mass with respect to 100 parts by mass in total of the first mixed powder and the second mixed powder. A part or less may be added. Iron oxide, tungsten oxide, chromium oxide,
Nickel oxide and molybdenum oxide react with silicon during firing to release oxygen and produce a silicide with a high melting point in the grain boundary phase. By containing silicide in the grain boundary phase, The mechanical properties and thermal shock resistance at high temperatures can be improved.

  Next, the first mixed powder and the second mixed powder weighed in a predetermined amount together with a solvent are mixed and pulverized in a wet manner by a conventional method such as a barrel mill, a rotary mill, a vibration mill, a bead mill, etc. to obtain a slurry. As the pulverizing media used in this pulverization, a silicon nitride sintered body, a zirconia sintered body, an alumina sintered body, or the like can be used, but the influence of impurities when mixed is reduced. It is preferable to use a pulverizing medium made of a silicon nitride sintered body having the same material composition or approximate composition as the silicon nitride sintered body to be produced.

Note that this wet pulverization is preferably performed until the particle size (D ₉₀ ) is 3 μm or less in order to improve the sinterability. In order to obtain the particle size distribution to be obtained, the set values such as the outer diameter, amount, or grinding time of the grinding media may be appropriately adjusted.

In addition, an organic binder such as paraffin wax, PVA (polyvinyl alcohol), and PEG (polyethylene glycol) is added in an amount of 1 to 10 parts by mass with respect to a total of 100 parts by mass of the first mixed powder and the second mixed powder. As a result, the formability can be improved by mixing with the slurry. Further, a dispersant may be added to enhance the dispersibility.

  Further, when the silicon nitride sintered body of the present embodiment is a porous body, a pore forming agent made of resin beads may be mixed into the slurry.

For example, in order to obtain a porous body having a porosity of 20% by volume or more and 60% by volume or less, the amount of the pore forming agent added is 100% by mass of the total of the mixed powder and the above powder as a sintering aid. 2 mass% 6
What is necessary is just mass%.

As the pore forming agent, for example, suspension-polymerized non-crosslinkable resin beads comprising at least one of silicone beads, polystyrene, and polyacryl-styrene are preferably used. Since these resin beads have a low compressive strength of 1.2 MPa or less, they can be easily plastically deformed in the pressurizing direction in the molding process, and the occurrence of microcracks that tend to occur with elastic recovery can be suppressed. .

Next, the pulverized slurry is passed through a sieve until the particle size (D ₉₀ ) is 3 μm or less, and then granulated granules are obtained using a spray dryer.

Next, the obtained granules are formed into a bottomed cylindrical body by press molding, CIP molding (Cold Isostatic Pressing), or the like. If the molding pressure is in the range of 50 to 120 MPa, it is preferable from the viewpoint of improving the density of the molded body and the collapsibility of the granules.

  Moreover, you may use shaping | molding methods, such as casting molding, injection molding, and tape shaping | molding. In addition, after forming a molded body by molding by each molding method, the molded body may be cut, laminated, or bonded to form a bottomed cylindrical body.

Next, the molded body obtained in a silicon armor made of silicon carbide or a carbon whose surface is covered with silicon nitride crystal particles is placed and degreased in a nitrogen atmosphere or in a vacuum. The degreasing temperature varies depending on the kind of the added organic binder, but is preferably 900 ° C. or less. In particular, it is preferably 450 ° C. or higher and 800 ° C. or lower. The removal of lipid components such as organic binder from the molded body is called degreasing, and the degreased body is called degreased body.

  Next, a degreased body is placed in the nitriding furnace, and nitriding is performed at a temperature higher than the temperature when degreasing in a nitrogen atmosphere.

  As the nitriding step, nitriding at a high temperature (second nitriding step) may be performed after nitriding at a low temperature (first nitriding step).

First, as the first nitriding step, the pressure of nitrogen is set to 10 to 200 kPa, and held at a temperature of 1000 to 1200 ° C. for 15 to 25 hours, so that 10 to 70 mass% of metallic silicon (Si) in the degreased body is obtained. Nitrid. Next, as the second nitriding step, the remaining portion of the metal silicon (Si) in the degreased body is nitrided by holding at a temperature between the temperature of the first nitriding step and 1400 ° C. for 5 to 15 hours. Get.

And after arrange | positioning the nitride in the shell which consists of a silicon carbide sintered body installed in the baking furnace, volatilization of the oxide containing magnesium is suppressed on the inner peripheral surface side of the nitride. Further, for example, a gas supply pipe is arranged on the inner peripheral surface side of the nitride, and while continuing to raise the temperature while supplying nitrogen, the temperature is set to 1760 ° C. or higher and 1860 ° C. or lower and held for 8 to 12 hours. The ceramic member 10 of this embodiment can be obtained by lowering the temperature at a rate of 120 ° C./hour or more and less than 200 ° C./hour.

  Here, the relative density of the silicon carbide based sintered body is preferably 95% or more. When the relative density is within this range, it is difficult for heat to escape, so that firing can be performed efficiently.

Here, in order to obtain a ceramic member 10 having a smaller number of pores per unit area in the first region 1 than in the second region 2 in the cross section, the inner peripheral surface side of the nitride is more than the outer peripheral surface side. The silicon (Si) and silicon dioxide (SiO ₂ ) powders are mixed at a molar ratio of Si: SiO ₂ = 0.6 to 1.4: 1 and arranged on the inner peripheral surface side of the nitride so that the heat capacity increases. A cylindrical porous firing container is filled, or a slurry is prepared by mixing powder and water mixed in the molar ratio, and this slurry is applied to the inner peripheral surface of the nitride and dried. That's fine. In addition, when the above powders are mixed and filled into a cylindrical porous firing container disposed on the inner peripheral surface side of the nitride, the firing container may be removed after firing the nitride. .

  Further, in order to obtain the ceramic member 10 in which the magnesium content increases from the second region 2 side toward the first region 1 side, the pressure of nitrogen is higher on the inner peripheral surface 20 than on the outer side of the nitride. Nitrogen may be supplied to the inner peripheral surface side of the nitride so that the side becomes higher by, for example, 1 atmosphere or more.

  Further, the structure further contains aluminum, and the second region 2 includes a third region 3 existing in the thickness direction of the structure from the outer peripheral surface 21 of the structure, and a third region other than the third region 3. In order to obtain a ceramic member 10 ′ having an aluminum content in the fourth region 4, the aluminum content existing in the third region 3 is greater than the aluminum content present in the fourth region 4, aluminum oxide, oxidation A mixed powder of a metal compound composed of at least one of silicon, zirconium oxide and calcium carbonate and magnesium aluminate is used as a second mixed powder, and a powder composed of at least one of aluminum oxide and aluminum nitride is used as an atmosphere adjusting material. Lay on the bottom plate of the upper so that it does not come into contact with the nitride placed inside the upper or as a slurry mixed with an atmosphere modifier and water, The slurry may be applied in the same manner as the ceramic member 10 except that the nitride is fired after being applied to the side wall of the upper and dried.

  Here, the particle size of the atmosphere adjusting material is F16 to a particle size defined in JIS R 6001-1998 in consideration of easy handling and high reactivity obtained by increasing the specific surface area. A powder that is F220 may be used.

  In order to obtain a ceramic member 10 ′ in which the aluminum content increases from the fourth region 4 side toward the third region 3 side, the particle size of the atmosphere adjusting material may be set to F24 to F220.

  Further, for example, when obtaining the ceramic member 10, 10 ′ having a relative density of 99% by mass or more, a hot isostatic pressing process may be performed, and by performing this process, the ceramic member 10, 10 ′ may be performed. The thermal conductivity of 'can be further increased.

  In addition, the ceramic members 10 and 10 'obtained by the above-described manufacturing method may be subjected to processing such as polishing and blasting as necessary.

  Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

First, a powder of metal silicon average particle diameter (D ₅₀₎ is 3 [mu] m, an average particle diameter (D ₅₀₎ is 1 [mu] m, the silicon nitride of β rate is 10% (i.e., alpha-conversion rate 90%) And mixed so that the mass ratio of (metal silicon powder) / (silicon nitride powder) is 5.4.
Of mixed powder was obtained. Here, the metal silicon powder had a particle size (D ₉₀ ) of 5 μm at which the cumulative volume was 90% when the total cumulative volume of the particle size distribution curve was 100%.

Next, the mixed powder of the powders of the components shown in Table 1 is used as the second mixed powder, put into a barrel mill together with the first mixed powder, water and a grinding medium made of silicon nitride sintered body, and the particle size (D ₉₀ ) was mixed and ground until it became 1 μm or less. Here, the content of each powder of the second mixed powder was weighed so as to be the amount shown in Table 1 with respect to 100% by mass in total of the first mixed powder and the second mixed powder.

Thereafter, 5 parts by mass of polyvinyl alcohol (PVA) was added to and mixed with 100 parts by mass of the total of the first mixed powder and the second mixed powder to obtain a slurry. The slurry was granulated using a spray dryer to obtain granules.

  Next, the obtained granule was CIP-molded, and further subjected to cutting to obtain a molded body to be the ceramic member 10 having an outer diameter and an inner diameter of 180 mm and 157 mm, respectively, and a length of 1205 mm.

Next, the compact was placed in a silicon carbide armor and degreased by holding at 500 ° C. in a nitrogen atmosphere for 5 hours to obtain a degreased body. Next, the degreased body was placed in a nitriding furnace, and nitrided by sequentially holding at 1050 ° C. for 20 hours and at 1250 ° C. for 10 hours in a nitrogen partial pressure of 150 kPa consisting essentially of nitrogen. Then, the nitrogen pressure P _in on the inner peripheral surface side of the nitride and the pressure P _out of the outer nitrogen were raised as values shown in Table 1, and the firing temperature and the holding time were fired at 1800 ° C. and 12 hours, respectively. Thereafter, by cooling at a cooling rate of 190 ° C./hour, the outer diameter and inner diameter are 150 mm and 130 mm, respectively. 1-12 were obtained.

Sample No. 3, 7, and 11, cylinders in which powders of silicon (Si) and silicon dioxide (SiO ₂ ) are mixed at a molar ratio of Si: SiO ₂ = 1: 1 and arranged on the inner peripheral surface side of the nitride. A step of removing the firing container after filling the cylindrical porous firing container and firing the nitride was added.

  The obtained sample No. The content of silicon contained in 1 to 12 was measured by ICP (Inductively Coupled Plasma) emission spectrometry and converted from the silicon content to the silicon nitride content. All samples had a silicon nitride content of 80. It was confirmed that it was at least mass%.

Then, using an electron beam microanalyzer (EPMA) (JXA-8530F manufactured by JEOL Ltd.), surface analysis is performed in the cross section at the center in the longitudinal direction of each sample, and the first region 1 and the second region are analyzed. It was determined _M 1 -M _{2 (ΔM);} and a content _M 1, _{M 2} and the difference of the respective magnesium in the region 2. Note _that the M 1 -M ₂ (ΔM), was calculated in terms of weight ratio from the measured values of the EPMA.

Here, in the surface analysis, the acceleration voltage and the irradiation current are 15 kV and 2.0 × 10 ⁻⁷ A, respectively, as measurement conditions of the electron beam microanalyzer (EPMA), and the first region 1 and the second region 2 are used. Each measurement range in was an area of 5.04 mm × 5.04 mm.

  Also, using an electron beam microanalyzer (EPMA), line analysis is performed on the cross section to confirm whether there is an increase in the magnesium content from the second region 2 side to the first region 1 side. did.

As for the number of pores per unit area, the cross section was polished, the magnification was 200 times using an optical microscope, the cross section was photographed with a CCD camera, and an image analyzer (LUZEX manufactured by Nireco Corporation) was used. The first area 1 and the second area are examined by measuring one visual field measurement area in the image as 2.25 × 10 ⁻² mm ² and 20 measurement visual fields, that is, measuring total area 4.5 × 10 ⁻¹ mm ² 2, the number of pores P ₁ and P ₂ per unit area was compared.

In addition, a test piece according to JIS R 1611-1997 is cut out from the first region 1 of each sample,
The thermal conductivity was measured.

As a result of comparing the magnesium contents M ₁ and M ₂ in Table 1, the difference ΔM in the magnesium content, the presence or absence of an increase in the magnesium content, the result of comparing the number of pores P ₁ and P ₂ and the thermal conductivity The measured value is shown.

As shown in Table 1, the sample No. 2 in which the components and contents of the second mixed powder are the same. 1 to 4 are compared, sample No. 2-4, the content M ₁ of magnesium present in the first region 1, since greater than the content M ₂ of the magnesium present in the second region 2, the content of M ₁ is higher than the content M ₂ A small sample No. Higher than the thermal conductivity of Sample No. 1; 2 to 4 are sample Nos. 1 indicates that the thermal conductivity is improved.

  Sample No. 3 has a smaller number of pores per unit area in the first region 1 than in the second region 2, so that the sample No. 3 in which the second region 2 and the first region 1 are the same. 2 has a higher thermal conductivity than Sample No. 2. 3 is a sample No. 3. 2, it can be said that the thermal conductivity is improved.

  Sample No. No. 4 is a sample No. 4 in which the magnesium content increases from the second region 2 side toward the first region 1 side, and no increase is observed. It can be said that heat conductivity is higher than 2 and heat can be efficiently transferred from the first region 1 to the second region 2.

Sample No. 2 in which the components and contents of the second mixed powder are the same. Comparing samples 5 to 8, sample no. 6-8, the content M ₁ of magnesium present in the first region 1, since greater than the content M ₂ of the magnesium present in the second region 2, the content of M ₁ is higher than the content M ₂ A small sample No. Higher than the thermal conductivity of Sample No. 5; 6 to 8 are sample Nos. 5 indicates that the thermal conductivity is improved.

  Sample No. 7 shows that the number of pores per unit area is smaller in the first region 1 than in the second region 2, so that the sample No. 2 in which the second region 2 and the first region 1 are the same. The thermal conductivity is higher than that of Sample No. Sample No. 7 6 indicates that the thermal conductivity is improved.

  Sample No. No. 8 is a sample No. in which the magnesium content increases from the second region 2 side toward the first region 1 side, and no increase is observed. It can be said that the heat conductivity is higher than 6, and heat can be efficiently transferred from the first region 1 to the second region 2.

Sample No. 2 in which the components and contents of the second mixed powder are the same. When comparing 9-12, sample no. 10-12, the content M ₁ of magnesium present in the first region 1, since greater than the content M ₂ of the magnesium present in the second region 2, the content of M ₁ is higher than the content M ₂ A small sample No. Higher than the thermal conductivity of Sample No. 9; Samples Nos. 10-12 are Sample Nos. 9, it can be said that the thermal conductivity is improved.

  Sample No. 11 shows that the number of pores per unit area is smaller in the first region 1 than in the second region 2, so that the second region 2 and the first region 1 have the same sample number. The sample has a thermal conductivity higher than that of Sample No. 10. Sample No. 11 From Fig. 10, it can be said that the thermal conductivity is improved.

  Sample No. Sample No. 12 in which the magnesium content increased from the second region 2 side toward the first region 1 side, and no increase was observed. It can be said that the heat conductivity is higher than 10 and heat can be efficiently transferred from the first region 1 to the second region 2.

Sample No. 1 prepared in Example 1 was used. 2 and Sample No. 6 is prepared, and the temperature is raised by setting the pressure P _in of nitrogen on the inner peripheral surface side of these nitrides and the pressure P _out of the outside nitrogen to 1.2 atm and 1 atm, and firing temperature and holding time After being fired at 1800 ° C. for 12 hours and cooling at a temperature drop rate of 190 ° C./hour, the sample No. is a ceramic member 10 ′ having an outer diameter and inner diameter of 150 mm and 130 mm, and a length of 1000 mm, respectively. . 13-18 were obtained.

  Sample No. For 14, 15, 17, and 18, the powder of aluminum oxide whose particle size specified in JIS R 6001-1998 shown in Table 2 was laid on the bottom plate of the mortar as an atmosphere adjusting agent and fired. Here, the particle size defined by JIS R 6001-1998 of the aluminum oxide powder is as shown in Table 2.

  The obtained sample No. The silicon content contained in 13 to 18 was measured by ICP (Inductively Coupled Plasma) emission spectrometry, and the silicon content was converted to the silicon nitride content. As a result, each sample had a silicon nitride content of 80. It was confirmed that it was at least mass%.

Then, using an electron beam microanalyzer (EPMA) (JXA-8530F manufactured by JEOL Ltd.), surface analysis was performed on the cross section of each sample as measurement conditions similar to Example 1, and the third region 3 and The aluminum contents A ₃ and A ₄ in the fourth region ₄ were compared.

  In addition, an electron beam microanalyzer (EPMA) is used to perform a line analysis at a cross section at the center in the longitudinal direction of each sample, and the aluminum region from the fourth region 4 side to the third region 3 side is analyzed. The presence or absence of the increase in content was confirmed.

  Moreover, ten test pieces according to JIS R 1601-2008 were cut out from the third region 3 of each sample, and the four-point bending strength at room temperature was measured. However, the thickness of the specimen of each sample cut out was the thickness of the third region 3.

Table 2 shows the results of comparing the aluminum contents A ₃ and A ₄ .

As shown in Table 2, sample No. 2 in which the components and contents of the second mixed powder are the same. When comparing 13 to 15, sample no. 14 and 15, since the aluminum content A ₃ present in the third region 3 is greater than the aluminum content A ₄ present in the fourth region 4, the mechanical strength is increased, and the ceramic member Sample No. 10 ′ It can be seen that 14 and 15 as a whole have increased mechanical strength.

Sample No. No. 15, since the aluminum content increases from the fourth region 4 side to the third region 3 side, it is mechanical from the fourth region 4 side to the third region 3 side. The strength can be increased, the mechanical strength on the outer peripheral side is further increased, and the mechanical strength is higher than that of sample No. 14 in which no increase is confirmed from the fourth region 4 side toward the third region 3 side. You can see that

Sample No. 2 in which the components and contents of the second mixed powder are the same. When comparing 16-18, sample no. 17 and 18, the content A ₃ of aluminum present in the third region 3, since more than the aluminum content A ₄ residing in the fourth region 4, there is an increasing mechanical strength, ceramic member Sample No. 10 ' It can be seen that the mechanical strength of 17 and 18 as a whole is also increased.

Sample No. 18, since the aluminum content increases from the fourth region 4 side to the third region 3 side, it is mechanical from the fourth region 4 side to the third region 3 side. The strength can be increased, the mechanical strength on the outer peripheral side is further increased, and the mechanical strength is higher than that of sample No. 17 in which no increase is confirmed from the fourth region 4 side toward the third region 3 side. You can see that

1: First area
2: Second region 3: Third region 4: Fourth region
10, 10 ': Ceramic material
20: Inner peripheral surface
21: Outer surface
30: Heat conduction member

Claims (6)

  An inner peripheral surface is a structure in contact with the space, and the structure is made of a silicon nitride sintered body containing magnesium, and the structure exists in a thickness direction from the inner peripheral surface in contact with the space. And the second region other than the first region, and the magnesium content present in the first region is greater than the magnesium content present in the second region. A ceramic member characterized by the above.   2. The ceramic member according to claim 1, wherein the number of pores per unit area is smaller in the first region than in the second region.   The structure further contains aluminum, and the second region includes a third region existing in the thickness direction of the structure from the outer peripheral surface of the structure, and a fourth region other than the third region. The content of the aluminum present in the third region is greater than the content of the aluminum present in the fourth region. Ceramic parts.   4. The ceramic member according to claim 1, wherein the magnesium content increases from the second region side toward the first region side. 5.   5. The ceramic member according to claim 3, wherein the aluminum content increases from the fourth region side toward the third region side. 6.   A heat conduction member, wherein a heat source is disposed in the space of the ceramic member according to claim 1.

Images