JP6927915B2 - Insulation member for ceramic composites and carbon fiber manufacturing equipment - Google Patents

Description

The present disclosure relates to ceramic composites and heat insulating members for carbon fiber manufacturing equipment.

Conventionally, in a high-frequency dielectric heating device or a microwave heating device, a heat insulating sleeve is arranged on the outer peripheral side or the inner peripheral side of the heating tube so as not to let heat escape. These heating devices have a structure in which a heating source such as a high-frequency oscillator or a microwave oscillator is installed outside the heating tube to supply heat to the heating tube.

As such a heat insulating sleeve, in Patent Document 1, long fibers containing 99.0% by mass or more of alumina as a main component are woven into a string having an air core portion, and the purity is contained in the air core portion of the string. A heat insulating sleeve is proposed in which short fibers containing 94.0% by mass or more of alumina as a main component ^{are filled so as to have a density of 0.20 to 0.30 g / cm 3} and formed into a sleeve shape by this string. ing.

Since the heat insulating sleeve made of alumina fiber described in Patent Document 1 has low heat resistance and durability, a mixture of alumina, silica, magnesia and the like is exemplified in Patent Document 2 as an alternative material. The material of the heat insulating sleeve described in Patent Document 2 has a high function of transmitting microwaves (hereinafter, the function of transmitting microwaves is referred to as microwave transparency).

However, lengthening of the heat insulating sleeve is required, and the heat insulating sleeve obtained by sequentially molding and firing the powder of such a mixture tends to cause a large warp after firing, and when such a warp occurs, Residual stress accumulates partially. Therefore, in order to obtain a long heat insulating sleeve, as shown in Patent Document 3, two porous ceramic tubes are arranged in contact with each other, and a reinforcing ring made of the same ceramic is attached to the outer peripheral portion thereof. , Aron Ceramic (registered trademark) is filled in between, and then fired. According to this method, the residual stress can be reduced as compared with the long heat insulating sleeve which is integrally formed and the residual stress is partially accumulated.

Japanese Unexamined Patent Publication No. 5-141873 International Publication No. 2015/152019 Japanese Unexamined Patent Publication No. 7-8731

As described in Patent Document 3, when the main component of the porous ceramic tube and the reinforcing ring is aluminum oxide, there is a problem that the heat insulating performance is lowered due to the heat conduction property of aluminum oxide. Further, there is a problem that the mechanical strength required for the reinforcing ring is insufficient.

The present disclosure provides a ceramic composite and a heat insulating member for a carbon fiber manufacturing apparatus, which is long but has excellent heat insulating performance and mechanical strength.

The ceramic composite of the present disclosure is made of aluminum oxide ceramics, and is an annular body made of a tubular body having air permeability between the outer peripheral surface and the inner peripheral surface and a zirconium oxide ceramic having higher strength than the tubular body. And at least. There are a plurality of the tubular bodies, and the end faces of the adjacent tubular bodies are located so as to face each other. Further, the annular body is located in contact with any of the adjacent tubular bodies at a joint portion including a portion where the end faces face each other.

The heat insulating member for a carbon fiber manufacturing apparatus of the present disclosure includes the above-mentioned ceramic composite.

The ceramic composite and the heat insulating member for a carbon fiber manufacturing apparatus of the present disclosure are excellent in heat insulating performance and mechanical strength.

An example of the ceramic composite of the present disclosure is shown, (a) is a perspective view, and (b) is a vertical sectional view. (A) is a perspective view and (b) is a vertical sectional view showing another example of the ceramic composite of the present disclosure. (A) is a perspective view and (b) is a vertical sectional view showing another example of the ceramic composite of the present disclosure.

Hereinafter, the ceramic composite of the present disclosure will be described in detail with reference to the drawings. 1 to 3 are perspective views and vertical sectional views showing a plurality of examples of the ceramic composites of the present disclosure. The vertical cross-sectional view can be rephrased as a cross section along the axial direction of the tubular body or a cross section along the penetrating direction of the tubular body.

The ceramic composite body 10 of the present disclosure is made of aluminum oxide ceramics, and is made of a tubular body 1 having air permeability between an outer peripheral surface and an inner peripheral surface, and a zirconium oxide ceramic having higher strength than the tubular body 1. It includes at least an annular body 2. In each figure, an example in which three of the tubular bodies 1 are connected is shown, and in the following description of the joint portion, the tubular body 1 located at the uppermost portion is located at the first tubular body 1a and the middle portion. The tubular body 1 will be described as a second tubular body 1b.

The tubular body 1 shown in FIGS. 1 and 2 is a porous body and has air permeability from the inner peripheral surface to the outer peripheral surface or from the outer peripheral surface to the inner peripheral surface. The tubular body 1 is a plurality of tubular bodies 1, and the adjacent tubular bodies 1, for example, the first end surface 1aa of the first tubular body 1a and the second end surface 1bb of the second tubular body 1b are located so as to face each other. ..

The annular body 2 is located in contact with both the adjacent first tubular body 1 and the second tubular body 1b at the joint portion including the portion where the first end surface 1aa and the second end surface 1bb face each other. That is, the ceramic bonded body 10 of the present disclosure is formed by bonding the first tubular body 1a and the second tubular body 1b by the annular body 2.

As an example of contacting both the first tubular body 1a and the second tubular body 1b adjacent to each other at the joint portion, FIGS. 1 and 3 show an example of contacting on the inner peripheral side, and FIG. Shows an example of contact on the outer peripheral side. Further, the annular body 2 shows an example in which the annular body 2 is fitted to the stepped portion formed in the first tubular body 1a and the second tubular body 1b.

As described above, since the annular body 2 has a smaller thermal conductivity value than aluminum oxide, which is the main component of the tubular body 1, and has higher mechanical strength than the tubular body 1, it is bonded by the annular body 2. The ceramic composite 10 is excellent in heat insulating performance and mechanical strength. Therefore, such a ceramic binder 10 is arranged on the outer peripheral side or the inner peripheral side of the heating tube (not shown), and heat is supplied to the heating tube by a high-frequency dielectric heating device or a microwave heating device (neither is shown). In that case, the release of heat can be suppressed. Further, even if the tubular body 1 expands and contracts due to repeated heating and cooling, it can be used for a long period of time because it is bonded by the annular body 2.

Here, the porous aluminum oxide ceramics are specifically aluminum oxide ceramics having a pore ratio of more than 10% by volume, and the aluminum oxide ceramics are among 100% by mass of all the components constituting the ceramics. It means that the content of aluminum oxide obtained by converting Al into Al ₂ O _{3 is 80% by mass or more.} Further, the zirconium oxide ceramic having a strength higher than that of the tubular body 1 is, for example, a zirconium oxide ceramic having a pore ratio of 10% by volume or less, and the zirconium oxide ceramic is a total component 100 constituting the ceramic. It means that the content of zirconium oxide in which Zr is _{converted to ZrO 2} is 80% by mass or more in mass%.

Here, the porosity of each ceramic may be obtained by the Archimedes method. Further, the components constituting the ceramics can be identified from the measurement results by an X-ray diffractometer using CuKα rays, and the content of each component can be determined by, for example, an ICP (Inductively Coupled Plasma) emission spectroscopic analyzer or a fluorescent X-ray. It can be obtained by an analyzer.

The tubular body 1 may have a porosity of 25% by volume or more and 35% by volume or less. When the porosity is in this range, for example, it has high microwave transparency while having the mechanical strength required for a heat insulating sleeve.

Further, in the ceramic composite body 10 of the present disclosure, as shown in FIG. 3, the tubular body 1 is a dense ceramic (dense body) having a plurality of branch holes 4 and having a porosity of 10% by volume or less. You may. In such a case, the branch holes 4 may be arranged so that the central angle is 30 ° or more and 45 ° or less, for example, at predetermined intervals along the axial direction and along the circumferential direction of the tubular body 1. good.

Further, in the tubular body 1, the average pore diameter of the portion corresponding to the connecting portion may be smaller than the average pore diameter of the central portion of the length in the communication direction. Here, the portion corresponding to the joint portion refers to a radial portion of the step portion including the first end surface 1aa in the first tubular body 1a in FIGS. 1 to 3. Further, the central portion of the length in the communication direction refers to an intermediate portion of 40% to 60% of the length corresponding to the vertical direction shown in (b) of each figure. When satisfying such a configuration, the ceramic binder 10 is further excellent in mechanical strength because the portion to be the joint portion has high mechanical strength. Further, the risk of damage to the tubular body 1 when the annular body 2 is fitted is reduced.

The difference in average pore diameter between the portion corresponding to the connecting portion of the tubular body 1 and the central portion of the length in the communication direction may be, for example, 2 μm or more. Then, when the tubular body 1 is a porous ceramic as shown in FIGS. 1 and 2, the average pore diameter may be obtained by using a mercury press-fitting method. When the tubular body 1 is a dense ceramic as shown in FIG. 3, the average pore diameter is a polishing machine made of tin using diamond abrasive grains having an average particle size of 1 μm or more and 5 μm or less. After polishing, the polished surface may be analyzed and obtained with an image analysis device (Win ROOF manufactured by Mitani Shoji Co., Ltd.).

Further, in the aluminum oxide ceramics, in the grain boundary phase between the aluminum oxide crystals, the portion adjacent to the aluminum oxide crystal is the first region, and the portion farther from the aluminum oxide crystal is the second region. When defined as a region, the first region may have a lower Na content than the second region. When Na is contained, the dielectric loss increases, but when it is abundant in the second region and small in the first region, the dielectric loss is suppressed to a low level and the amount of heat in the through hole 3 can be maintained. Therefore, the object to be processed can be heated efficiently. The first region in the grain boundary phase is the range from the surface of the aluminum oxide crystal to 5 nm, and the portion exceeding 5 nm is the second region.

The Na content in the first region and the second region can be confirmed by the following method. First, a part of aluminum oxide ceramics is etched using a processing device such as an ion thinning device to obtain a measurement surface. Next, using a transmission electron microscope (JEM-2010F manufactured by TEM JEOL), the grain boundary phase is observed at a magnification of 10,000 to 100,000 times in a specific field of view of the measurement surface with an acceleration voltage of 200 kV. In addition, in order to confirm the Na content depending on the position, the triple point is observed.

Then, at the triple point, the portion corresponding to the first region and the portion corresponding to the second region are measured by energy dispersive X-ray analysis (EDS), and the Na content is confirmed to confirm the content of the grain boundary phase. The Na content at the position can be confirmed.

_{Further, when the content of Na converted to Na 2} O in the grain boundary phase is A, and the total content of components other than Al and Na converted to oxides is B, the ratio A / B is It may be 0.11 or less. When the ratio A / B is in the above range, the dielectric loss can be further suppressed.

Here, the ratio A / B can be obtained as follows. First, a measurement surface obtained by etching a part of aluminum oxide ceramics using a processing device such as an ion thinning device is subjected to TEM, and a specific field of view of the measurement surface is magnified 10,000 to 100,000 times under the condition of an acceleration voltage of 200 kV. After observing, EDS measurement of the grain boundary phase was performed, the content of each obtained component was determined, converted into an oxide, the content of Na converted into Na ₂ O was defined as A, and the other components were oxidized. The ratio A / B may be calculated by assuming that the total content converted into the product is B. In one grain boundary phase, EDS measurements were performed at two linearly located first regions and one second region, the ratio A / B was calculated using the average value, and the decimal point was calculated. Round to the third place.

When Al is not contained in the grain boundary phase, a part of the aluminum oxide ceramics is crushed, the obtained powder is dissolved in a solution such as hydrochloric acid, and then an ICP emission spectrophotometer is used. The content of Na and other components other than Na may be measured, and the ratio (A / B) may be calculated using the values converted into oxides.

Further, in the aluminum oxide ceramics, _{the content of Al converted to Al 2} O ₃ is 99.4% by mass or more, and _{the content of Na converted to Na 2} O is 30 mass ppm or more and 500 mass ppm or less. The value of the dielectric loss tangent at .5 GHz may be 0.5 times or less the value of the content _{of Na converted to Na 2 O.} When the value of the dielectric loss tangent at Al, Na and 8.5 GHz is in the above range, the dielectric loss can be further suppressed.

Further, the aluminum oxide ceramic contains Mg, and the content of Mg in terms of MgO may be 200 mass ppm or more and 1500 mass ppm or less. Mg acts as a sintering accelerator, but when magnesium aluminate (MgAl ₂ O ₄ ) is produced, the dielectric loss becomes high. Therefore, when Mg is in the above range, there _{is little possibility of forming crystals of magnesium aluminate (MgAl 2} O ₄ ), which tends to increase the dielectric loss, and sintering can be promoted, so that the mechanical strength can be promoted. Can be raised.

Further, the zirconium oxide ceramics may have a monoclinic crystal ratio of zirconium oxide crystals of 10% or more and 40% or less. When the monoclinic crystal ratio is in the above range, the zirconium oxide ceramics are less likely to undergo phase transformation, and the volume change due to this phase transformation is less likely to occur. The bond strength of the tubular body 1b is less likely to decrease.

Here, the monoclinic crystal ratio X may be calculated from the area of each peak intensity I of the zirconium oxide crystal obtained from the measurement result by the X-ray diffractometer using the following formula.
X = (Im (111) + Im (11-1)) / (Im (111) + Im (11-1) + It (111) + Ic (111))
Here, Im (111) is the peak intensity of the monoclinic (111) plane, Im (11-1) is the peak intensity of the monoclinic (11-1) plane, and It (111) is the tetragonal (111) plane. The peak intensity of Ic (111) is the peak intensity of the cubic (111) plane.

As described above, the ceramic composite of the present disclosure is excellent in heat insulating performance and mechanical strength, and therefore may be used as a heat insulating member for a carbon fiber manufacturing apparatus.

The carbon fiber manufacturing apparatus includes, for example, a cylindrical waveguide in which one end is a carbon fiber inlet and the other end is a carbon fiber outlet, and a microwave oscillator in which microwaves are introduced into the waveguide. , A cylindrical body arranged inside the waveguide, and this cylindrical body corresponds to the heat insulating member for the carbon fiber manufacturing apparatus.

Next, an example of the method for producing the ceramic composite of the present disclosure will be described. First, an example of a method for manufacturing a tubular body will be described. Aluminum oxide (Al ₂ O ₃ ) A powder having an average particle size of 0.4 to 0.6 μm and aluminum oxide (Al ₂ O ₃ ) B powder having an average particle size of 1.2 to 1.8 μm are prepared. Further, silicon oxide (SiO ₂ ) powder is prepared as the Si source, and calcium carbonate (CaCO _{3) powder is prepared as the Ca source.} As the silicon oxide powder, a fine powder having an average particle size of 0.5 μm or less is prepared. Further, in order to obtain aluminum oxide ceramics containing Mg, magnesium hydroxide powder is used. In the following description, powders other than aluminum oxide A powder and aluminum oxide B powder are collectively referred to as a first subcomponent powder.

Then, each of the first subcomponent powders is weighed in a predetermined amount. Next, the aluminum oxide A powder and the aluminum oxide B powder are mixed so that the mass ratio is 40:60 to 60:40, and Al is added out of 100% by mass of the components constituting the obtained aluminum oxide ceramics. Weigh the product so that the content converted to Al ₂ O ₃ is 99.4% by mass or more to obtain an aluminum oxide-alumina compound powder. Further, preferably, for the first subcomponent powder, the amount of Na in the aluminum oxide compound powder is first grasped, and the amount of Na in the case of aluminum oxide ceramics is _{converted into Na 2} O, and this converted value and the first Sub-components of the above are weighed so that the ratio of the components (Si, Ca, etc. in this example) constituting the powder to the value converted into oxides is 1.1 or less.

Then, 1 to 1.5 parts by mass of PVA (polyvinyl alcohol) with respect to a total of 100 parts by mass of the aluminum oxide compound powder, the first subcomponent powder, the aluminum oxide compound powder and the first subcomponent powder. A binder such as, 100 parts by mass of a solvent, and 0.1 to 0.5 parts by mass of a dispersant are placed in a stirrer and mixed and stirred to obtain a slurry.

Then, after the slurry is spray-granulated to obtain granules, it is molded using a hydrostatic pressure pressurizing device or a uniaxial pressurizing device, and if necessary, cutting is performed to obtain a tubular ceramic molded body. obtain. Alternatively, a molded product is obtained by an extrusion molding method. For example, in the case of obtaining a dense ceramic having a branch hole, a pilot hole of the branch hole may be formed by cutting from the outer peripheral surface to the inner peripheral surface of the molded body.

In the aluminum oxide ceramics which are tubular bodies, in order to make the average pore diameter of the portion corresponding to the joint portion smaller than the average pore diameter of the central portion of the length in the communication direction, uniaxial addition is performed. It may be molded using a pressure device.

Then, by holding the tubular ceramic molded body at a firing temperature of 1200 ° C. or higher and 1500 ° C. or lower for 1 hour or more and 3 hours or less, a tubular sintered body made of porous ceramics can be obtained. By setting the firing temperature to 1400 ° C. or higher and 1700 ° C. or lower and holding the calcined product for 1 hour or more and 3 hours or less, a tubular sintered body made of dense ceramics can be obtained.

When the porosity of the aluminum oxide ceramics is 25% by volume or more and 35% by volume or less, it may be maintained at 1300 ° C. or more and 1500 ° C. or less for 1 hour or more and 3 hours or less.

Then, among the end portions of the tubular sintered body, the stepped portion with which the annular body abuts may be formed by grinding.

The reason why the dielectric loss tangent can be lowered by the above-mentioned method is not clear, but by using a fine silicon oxide powder of 0.5 μm or less, Na, which is an unavoidable impurity contained in the aluminum oxide compound powder, is used. The oxide of Na is captured by silicon oxide, and the oxide of Na is covered together with the oxide of the component constituting the first subcomponent powder, so that the oxide of Na is present inside the grain boundary phase. It is thought that this is because it can be done.

Next, an example of a method for producing an annular body will be described. First, a barrel mill, a rotary mill, a vibration mill, and a bead mill are used to prepare a zirconium oxide powder as a main component, a magnesium oxide powder as a stabilizer, a dispersant for dispersing the zirconium oxide powder if necessary, and a binder such as polyvinyl alcohol. , Sand mill, agitator mill, etc. for 40 to 50 hours wet mixing to obtain a slurry.

Here, the average particle size (D ₅₀ ) of the zirconium oxide powder is 0.1 μm or more and 2.2 μm or less, and the content of the magnesium oxide powder in a total of 100% by mass of the powder is 2.0% by mass or more 4 It shall be 0.0% by mass or less.

Next, an organic binder such as paraffin wax, PVA (polyvinyl alcohol) and PEG (polyethylene glycol) is weighed in a predetermined amount and added to the slurry. Further, a thickening stabilizer, a dispersant, a pH adjuster, an antifoaming agent and the like may be added.

Then, the slurry is spray-dried to obtain granules. Next, the granules are filled in a molding die, the molding pressure is set to, for example, 80 MPa or more and 200 MPa or less, and an annular molded body is obtained using a uniaxial pressurizing device. Then, the annular body can be obtained by holding the firing temperature at 1400 ° C. or higher and 1700 ° C. or lower, preferably 1600 ° C. or higher and 1700 ° C. or lower, for 1 hour or longer and 3 hours or lower.

When obtaining a cyclic body made of zirconium oxide ceramics in which the main component is zirconium oxide and the monoclinic crystal ratio of the zirconium oxide crystal is 10 mol% or more and 40 mol% or less, first, the zirconium oxide powder and the magnesium oxide powder are used. The content of the magnesium oxide powder in a total of 100% by mass is set to 3.0% by mass or more and 3.8% by mass or less, and a molded product is obtained by the above-mentioned method. Then, the molded product may be held at a firing temperature of 1600 ° C. or higher and 1700 ° C. or lower for 1 hour or longer and 3 hours or shorter, and then cooled at a temperature lowering rate of 80 ° C. or higher and 150 ° C. or lower per hour.

Then, the ceramic composite of the present disclosure can be obtained by applying an epoxy-based organic adhesive to the joint surface of the annular body and then contacting and curing the stepped portion of the tubular body.

The ceramic composite obtained by the above-mentioned manufacturing method can have high mechanical strength and heat insulating performance while being long. Therefore, such a ceramic composite is arranged on the outer peripheral side or the inner peripheral side of the heating tube (not shown), and heat is supplied to the heating tube by a high-frequency dielectric heating device or a microwave heating device (neither is shown). In some cases, the release of heat can be suppressed.

1: Cylindrical body 1a: 1st tubular body 1aa: 1st end surface 1b: 2nd tubular body 1bb: 2nd end surface 2: Ring body 3: Through hole 4: Branch hole 10: Ceramic bonded body

Claims (10)

A tubular body made of aluminum oxide ceramics and having air permeability between the outer peripheral surface and the inner peripheral surface,
At least an annular body made of zirconium oxide ceramic, which has higher strength than the tubular body, is provided.
There are a plurality of the tubular bodies, and the end faces of the adjacent tubular bodies are located so as to face each other.
The annular body is a ceramic joint body located in contact with any of the adjacent tubular bodies at a joint portion including a portion where the end faces face each other. The ceramic composite according to claim 1, wherein the tubular body is a porous body having a porosity of 25% by volume or more and 35% by volume or less. The ceramic composite according to claim 1 or 2, wherein the annular body is a dense body having a porosity of 10% by volume or less. The ceramic bond according to any one of claims 1 to 3, wherein the tubular body has an average pore diameter of a portion corresponding to the joint portion smaller than the average pore diameter of a central portion of the length in the communication direction. body. In the aluminum oxide ceramics, in the grain boundary phase between aluminum oxide crystals, a portion adjacent to the aluminum oxide crystal is referred to as a first region, and a portion farther from the first region from the aluminum oxide crystal is referred to as a second region. When you do
The ceramic composite according to any one of claims 1 to 4, wherein the first region has a lower Na content than the second region. In the aluminum oxide ceramics, _{when the content of Na converted to Na 2} O in the grain boundary phase is A, and the total content of components other than Al and Na converted to oxide is B. The ceramic composite according to claim 5, wherein the ratio A / B is 0.11 or less. The aluminum oxide ceramics have an Al _{converted to Al 2} O ₃ content of 99.4 mass% or more, and a Na _{converted to Na 2} O content of 30 mass ppm or more and 500 mass ppm or less. The ceramic composite according to any one of claims 1 to 6, wherein the value of the dielectric loss tangent at 5 GHz is _{0.5 times or less the value of the content of Na converted to Na 2 O.} The ceramic composite according to any one of claims 1 to 7, wherein the aluminum oxide ceramic contains Mg, and the content of Mg in terms of MgO is 200 mass ppm or more and 1500 mass ppm or less. The ceramic composite according to any one of claims 1 to 8, wherein the zirconium oxide ceramic has a monoclinic crystal ratio of 10% or more and 40% or less of the zirconium oxide crystal. A heat insulating member for a carbon fiber manufacturing apparatus, comprising the ceramic composite according to any one of claims 1 to 9.

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