JP2018100781A - Manufacturing method of heat reservoir and heat reservoir - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a spherical heat reservoir made of ceramic that is suitable for mass-production and can be easily manufactured regardless of its large diameter.SOLUTION: A plastic, cylindrical forming body 10a is formed from a forming raw material that becomes a porous ceramics sintered body by burning, and outer force is operated from a plurality of variable directions, thus plastically deforming and making spherical individual forming bodies. By sintering a spheroidized forming body 10b to form a heat reservoir substrate, a surface is covered with a filling material containing at least one of a glassy filler that becomes glass by heating and a ceramics filler containing oxide ceramics, and a filling material is allowed to penetrate toward the inside, thus forming a three-layer structured heat reservoir comprising a porous layer at the center, a covering layer in which the surface is covered with the filling material, and an inclined layer in which a ratio of non-filled pores continuously decreases toward the covering layer from a porous layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a ceramic heat storage body, and a heat storage body manufactured by the manufacturing method.

  In a heat exchange type device such as a device using a regenerative burner (regenerative burner), spherical alumina (alumina balls) has been frequently used as a ceramic heat storage body filled in the heat exchange section (for example, Patent Document 1). A large number of spherical heat accumulators can be easily filled in the heat exchange section. In particular, the heat exchanging part of a small device is often a size that an operator cannot enter, and it is difficult for the operator to reach from the opening for putting in and out the heat storage body to the back of the heat exchanging part. Many. In such a case, there is a great advantage that it is a spherical shape that automatically rolls and fills the heat exchanging portion when it is thrown in, without requiring the work of arranging and stacking the heat storage elements.

  Spherical ceramic sintered bodies have been formed in a shape close to a sphere by using two hemispherical molds and preforming them by uniaxial pressing, followed by isostatic pressing. Is manufactured by firing and then processed into a spherical shape by polishing. In this manufacturing method, since it is necessary to provide a gap between the two molds during the preforming, band-shaped protrusions inevitably remain in the circumferential direction of the fired body, and this must be removed by polishing. Don't be. Since the ceramic sintered body has a very high hardness, it is difficult to remove the band-like protrusions. In addition, the isotropic pressure molding is performed after the pre-molding because the pressure acting on the molded body becomes non-uniform in the case of the uniaxial pressing when the mold has a shape close to a sphere. In order to perform pressure molding, it is necessary to put the molded body in a flexible bag such as rubber and deaerate, and the work is complicated and inefficient. Therefore, this manufacturing method is not suitable for mass production.

  In addition, as a method for producing a spherical ceramic sintered body, a method of forming a spherical shape by a rolling granulation method and then firing it is also carried out. The rolling granulation method uses a rotating drum type granulator or a rotating dish type granulator, rotates ceramic powder with a binder, collides the powder particles with each other, aggregates them, and grows the particles in a snowball style It is. In some cases, fine particles that become the core of particle growth are added. According to this manufacturing method, it is difficult to obtain a large-diameter sphere, and it is said that it is not practical to manufacture a sphere having a diameter of 10 mm or more.

JP 2003-343829 A

  Therefore, in view of the above circumstances, the present invention is a method of manufacturing a spherical ceramic heat storage body, which is suitable for mass production and is capable of being easily manufactured even with a large diameter. An object of the present invention is to provide a manufacturing method and a heat storage body manufactured by the manufacturing method.

In order to solve the above-described problem, a method for manufacturing a heat storage body according to the present invention (hereinafter sometimes simply referred to as “manufacturing method”)
“A method for producing a spherical ceramic heat storage element,
With a forming raw material that becomes a porous ceramic sintered body by firing, a cylindrical formed body having plasticity is formed,
By applying an external force from a plurality of non-constant directions to the cylindrical molded body, the respective molded bodies are plastically deformed and spheroidized without uniting a plurality of the molded bodies,
After making the spheroidized shaped body into a heat storage body base by firing,
The surface of the heat storage substrate is covered with a filler containing at least one of a glassy filler that becomes glass upon heating and a ceramic filler containing oxide ceramics, and the interior of the heat storage substrate By infiltrating the filler material towards
A porous layer in which pores are not filled with the filling material at the center of the heat storage body substrate, a coating layer in which the filling material covers the surface of the heat storage body substrate, and the coating layer from the porous layer to the coating layer The heat accumulator has an inclined layer in which the proportion of pores not filled with the filler material is continuously reduced toward the "."

  In the present invention, the cylindrical molded body having plasticity is spheroidized by applying an external force from a plurality of non-constant directions to cause plastic deformation. Therefore, the spheronization process is simple and suitable for mass production. In addition, when it is desired to increase the diameter of the spherical heat storage body, it is only necessary to increase the diameter and height of the cylindrical molded body, so that even a large diameter can be easily manufactured and the size can be adjusted. Is easy.

  Furthermore, if the heat storage substrate is dense, cracks and cracks are likely to occur due to thermal expansion and contraction associated with heat storage and heat dissipation during use. On the other hand, in this configuration, since the ceramic sintered body constituting the heat storage base is made porous, thermal expansion and thermal contraction are absorbed by the pores, and it is possible to suppress the occurrence of cracks and cracks accompanying heat storage and heat dissipation. it can.

  On the other hand, since the heat storage substrate is porous, the mechanical strength may be reduced as compared with a dense case. In particular, in the present invention, since it is assumed that the heat storage body is filled in the arrangement space by charging, it is a problem that the mechanical strength is low. In addition, when the mechanical strength is low, even if thermal expansion and thermal contraction are absorbed by the pores, thermal shock resistance may be reduced by causing cracks and cracks even with slight thermal expansion and thermal contraction. Therefore, in this configuration, the pores are left in the central portion of the heat storage body base, the pores are partially filled with the filling material on the outer side, and the surface of the heat storage body base is covered with the filling material. Accordingly, the filling material partially filling the pores and the filling material covering the surface of the heat storage body base while exhibiting the action of absorbing the thermal expansion and contraction in the pores remaining in the central portion Thus, the mechanical strength of the heat storage body is increased. Thereby, even if it puts in an installation space, it is hard to produce a crack and a crack, and the thermal storage body excellent in thermal shock resistance can be manufactured.

  In addition, the layer between the porous layer in which the pores are not filled with the filling material and the coating layer coated with the filling material is a pore that is not filled with the filling material from the porous layer toward the coating layer. It is a graded layer in which the ratio of is decreasing continuously. Therefore, since the magnitude of the action of absorbing thermal expansion and contraction in the pores changes gradually without abruptly changing in the depth direction of the heat storage body, cracks and cracks due to thermal expansion and contraction are not caused. More effectively suppressed.

  Moreover, the coating layer which is the outermost layer in the heat storage body is a layer of a filler material containing at least one of a glassy filler that becomes glass by heating and a ceramic filler containing oxide ceramics. Therefore, even when the ceramic constituting the heat storage body is made of non-oxide ceramic, contact with oxygen is blocked by the coating layer during use in a high-temperature oxidizing atmosphere, and the progress of oxidation can be suppressed. . Thereby, a heat storage body base | substrate can be comprised with the non-oxide ceramics which are high in covalent bond, are hard compared with oxide ceramics, and are excellent in thermal characteristics.

  In addition, when a filling material contains the vitreous filler used as glass by heating, glass softens by the heating at the time of use of a thermal storage body. Therefore, even if a crack occurs during use, the softened glass is plastically deformed to fill it, so that the crack is prevented from extending and breaking.

Next, the heat storage body according to the present invention is:
"A heat storage body substrate made of a porous ceramic sintered body and having a two-dimensional circularity of 0.86 to 0.90 when viewed from at least three different directions,
A filling material containing at least one of glass and oxide ceramics comprises a coating layer covering the surface of the heat storage substrate; and
The heat storage body substrate has a porous layer whose pores are not filled with the filler material in the center, and pores not filled with the filler material from the porous layer toward the coating layer. It has a graded layer with a continuously decreasing proportion ".

  This is because heat treatment is performed after all the steps in the above manufacturing method, and when the filling material contains a vitreous filler, it is vitrified by heating, and when the filling material contains a ceramic filler, the oxide ceramics is heated. It is the structure of the heat storage body manufactured through the process of baking or hardening. The spheroidizing means in the above manufacturing method is to plastically deform a cylindrical molded body having plasticity by an external force in a non-constant direction. The degree of being able to approach the true sphere in the processing time was “the circularity of the two-dimensional shape when viewed from at least three different directions is 0.86 to 0.90, respectively”. Even if an attempt is made to lengthen the spheroidizing treatment time in order to make it closer to a true sphere, the plasticity of the molded body decreases with the passage of time.

Here, the circularity is a numerical value obtained by dividing (4 × circumference ratio × S) by L ² where the area of the two-dimensional shape is S (m ² ) and the circumference is L (m). Yes, the circularity of a perfect circle is 1.0. The circularity has the advantage that it is not affected by the difference in size (difference in the diameter of the circle), but since it is an evaluation of the shape in two dimensions, the circularity should be calculated in at least three different directions. Thus, the degree of spherical shape which is a three-dimensional shape is evaluated. The “at least three different directions” can be three directions orthogonal to each other.

  The reason why the heat storage body is spherical in the present invention is that it is automatically rolled by dropping and filled in the installation space, and it is not necessary to be as close to the true sphere as the ceramic sphere used for the bearing. Therefore, the circularity in the above range that can be realized by the above manufacturing method is suitable for the purpose.

In addition to the above configuration, the heat storage body according to the present invention includes:
“The thermal storage base has cracks extending radially from the inside toward the surface,
The open end of the crack is covered with the covering layer,
The inside of the crack may be partially filled with the filler material.

  In the manufacturing method described above, external force is applied to the molded body from a plurality of non-constant directions to form a spherical shape, and thus the molded body is cracked with high probability. The cracks are generated so as to extend radially from the inside toward the surface of the heat storage body substrate. Usually, a heat storage body having such a crack is regarded as a defective product as a heat storage body having internal defects. In contrast, in the present invention, cracks are also used as voids that absorb thermal expansion and contraction. In the above manufacturing method, since the filling material is infiltrated toward the inside of the heat storage body substrate, the filling material also infiltrates and partially fills the inside of the crack, and the covering layer is formed with the filling material. At the same time, the open ends of the cracks (openings of cracks on the surface of the heat storage substrate) are also covered with the coating layer. Therefore, while the crack of the unfilled part exhibits the effect of absorbing thermal expansion and contraction, the mechanical strength is reduced due to the presence of the crack and the crack extension is suppressed by the filling material.

  As described above, the effect of the present invention is a method for producing a spherical ceramic heat storage body, which is suitable for mass production and can be easily manufactured even with a large diameter. A method and a heat storage body manufactured by the manufacturing method can be provided.

(A)-(c) It is explanatory drawing of the process of spheroidization in the manufacturing method which is one Embodiment of this invention. (A), (b) It is sectional drawing of the thermal storage body manufactured by the manufacturing method which is one Embodiment of this invention. It is a figure which shows the graph which shows the change of the porosity of a depth direction about sample S5 along with the imaging by the scanning microscope of a cut surface. It is a graph which shows the change of the porosity of a depth direction about sample S6.

  Hereinafter, the manufacturing method of the thermal storage body which is one Embodiment of this invention, and the thermal storage body manufactured by the manufacturing method are demonstrated using FIG. 1 thru | or FIG.

  The manufacturing method of this embodiment is a manufacturing method of a spherical ceramic heat storage body, and includes a forming step, a spheroidizing step, a firing step, a covering / filling step, and a heat treatment step.

  More specifically, in the molding step, a cylindrical molded body having plasticity is molded from a molding raw material that becomes a porous ceramic sintered body by firing.

  As a method of making the ceramic sintered body obtained by firing “porous”, a method of controlling the particle size distribution of ceramic particles in the forming raw material, a component that is burned off by firing is contained in the forming raw material, and the burnt scar is a pore. A method of forming a ceramic raw material with reaction, and a method of making the traces of consumed components into pores, a method of containing a component that generates gas by heating in a molding raw material, and a method of making pores with traces out of gas, Can be illustrated.

  As the “ceramics” of the ceramic sintered body, non-oxide ceramics are desirable, and examples of the non-oxide ceramics include carbide ceramics and nitride ceramics. For example, silicon carbide, aluminum nitride, boron nitride, and magnesium nitride are suitable as heat storage materials because of their high thermal conductivity and good heat exchange efficiency. Silicon carbide, silicon nitride, aluminum nitride, and boron nitride are suitable as heat storage elements that repeatedly store and release heat because of their low thermal expansion coefficient and excellent thermal shock resistance. Since silicon carbide and silicon nitride have high mechanical strength at high temperatures, they are suitable as heat storage materials used at high temperatures. Boron carbide and boron nitride have extremely high hardness, and other non-oxide ceramics are generally higher in hardness than oxide ceramics, so that they are suitable as heat storage materials filled in the installation space by being charged.

  In order to obtain a “plastic” shaped body, the forming material can be a material obtained by adding a liquid component such as a binder, a surfactant, water or an organic solvent to ceramic particles and mixing them.

  Examples of the molding method of “columnar molded body” include extrusion molding, cast molding, and wet pressure molding. However, since extrusion molding can continuously mold a molded body having the same shape, Efficiency is desirable. In addition, as shown in the left figure of Fig.1 (a), if the height of the column-shaped molded object 10a is made the same with the outer diameter R of a cylinder, spheroidization in a later process will become easier.

  In the spheroidizing step, external forces are applied to the cylindrical molded body from a plurality of directions that are not constant, so that the molded body is plastically deformed to be spheroidized. As a method of applying an external force to the molded body from a plurality of non-constant directions, as schematically shown in the upper diagram of the center in FIG. 1A, molding is performed between two flat plates 91 arranged vertically. The body 10a is interposed, and at least one of the flat plates 91 is moved so as to draw a circle or a spiral in the surface direction, the distance between the two flat plates 91 is reduced, and the molded body 10a is moved and pressed. Thus, a method of changing the cylindrical shaped body 10a into a spherical shaped body 10b can be exemplified. Alternatively, as schematically shown in the middle diagram in the center of FIG. 1A, the molded body 10a is vibrated on a flat plate 92 on which the wall body 93 rises from the periphery, and the molded body 10a is moved to the wall body 93 or As shown schematically in the lower figure of the center in FIG. 1A, the molded body 10a is vibrated in a container 95 surrounded by a wall, The method of making the molded object 10a collide with a wall body and making it the spherical molded object 10b can be illustrated.

  Unlike the rolling granulation method, ceramic particles (powder) are not supplied to the formed body in the course of the spheroidizing step, and a plurality of formed bodies are not combined. In the spheroidizing step of the present embodiment, each molded body is plastically deformed to be spheroidized, and one spheroidized molded body is formed from one cylindrical molded body.

  In the firing step, the spheroidized compact is fired to sinter the ceramic particles to obtain a heat storage substrate made of a porous ceramic sintered body. When firing non-oxide ceramics, the firing atmosphere is a non-oxidizing atmosphere. The non-oxidizing atmosphere can be an inert gas atmosphere such as argon or helium, a nitrogen gas atmosphere, a mixed gas atmosphere thereof, or a vacuum atmosphere. Further, when the ceramic is a nitride, the nitrogen in the firing atmosphere can be at least part of the nitrogen constituting the sintered body.

  In the coating / filling step, the surface of the heat storage body substrate is covered with the filling material, and the filling material is infiltrated toward the inside of the heat storage body substrate. This step can be a step of applying the filling material to the heat storage substrate or a step of spraying. In this case, by adjusting the viscosity and wettability of the filling material, not only can the surface of the heat storage body substrate be coated with the filling material, but also the filling material can be infiltrated into the inside of the heat storage body substrate, and the penetration depth thereof. Can be adjusted. Further, the covering / filling step can be a step of degassing the open pores of the heat storage body base and impregnating the filling material. Accordingly, the filling material can be more smoothly infiltrated into the heat storage body base, and the impregnation depth can be adjusted by the degree of deaeration, the viscosity of the impregnation liquid, the pressurization of the impregnation liquid, and the like.

  As a filler, it contains both a filler containing a glassy filler that becomes glass upon heating, a filler containing a ceramic filler containing an oxide ceramic, both a glassy filler and a ceramic filler. Filling materials can be used.

  “Glass” produced by heating the vitreous filler can be silicate glass, borosilicate glass, borate glass, or phosphate glass. The glassy filler contains an alkali metal component / alkaline earth metal component such as sodium, potassium, calcium, etc., thereby adjusting the viscosity of the glass when heated in the heat treatment step, The ease of entering the pores can be adjusted. By containing aluminum oxide or aluminum hydroxide in the glassy filler, the strength of the formed glass can be adjusted. Furthermore, the vitreous filler may contain silicon carbide powder. Silicon carbide contained in the filling material is easily oxidized to silicon dioxide upon heating, and silicon dioxide just formed is highly reactive and easily vitrified.

  Examples of oxide ceramics contained in the ceramic filler include mullite, alumina, silica, zirconia, and magnesia. Oxide ceramics can be in the form of powder, sol, or gel, and an additive such as a binder or a liquid such as water or an organic solvent can be added to the oxide ceramic to form a ceramic filler.

  By passing through the coating / filling process, there is a porous layer that is not filled with pores in the center of the heat storage body substrate, and there is a coating layer of a filling material (before heat treatment) on the surface of the heat storage body substrate. It will be in the state which has the inclination layer in which the ratio of the pore which is not filled with the filling material (before heat processing) toward the coating layer is reducing continuously.

  In the heat treatment step, when the filling material contains a vitreous filler, the glass component is melted by heating and then cooled to be vitrified and fixed to the heat storage substrate. Further, the glass component melted by heating further enters the pores inside the heat storage substrate. When the filler material contains only the ceramic filler, the heat treatment temperature may be a temperature at which the oxide ceramic is sintered, or a temperature at which the oxide ceramic is not sintered but the filler material is cured.

  Through the above steps, as schematically shown in FIG. 2 (a), a spherical heat storage body substrate 20 made of a porous ceramic sintered body and a filling material containing at least one of glass and oxide ceramics (after heat treatment) ) Includes a coating layer 30 covering the surface of the heat storage body base 20, and the heat storage body base 20 has a porous layer 21 whose pores are not filled with a filling material in the center. In addition, the heat storage body 1 having the inclined layer 22 in which the proportion of pores not filled with the filling material from the porous layer 21 toward the coating layer 30 continuously decreases is manufactured. The degree of the spherical shape of the heat storage body base 20 in the heat storage body 1 is that the circularity of the two-dimensional shape when viewed from at least three different directions is 0.86 to 0.90, respectively, as will be described later. is there.

  Here, when a cylindrical molded body is molded by extrusion molding, as shown in FIG. 1 (b), a crack 15 extending in the extrusion direction through the approximate center of the molded body 10a may be formed. This is because in extrusion molding, the die from which the kneaded product of the molding raw material is extruded has a tapered portion, so that a compression force acts on the outer peripheral edge near the die in the extruded molded body, and the pressure is high. On the other hand, the central portion is at a low pressure and the consolidation is likely to be insufficient. Normally, such a crack 15 is undesirable as an internal defect, and molding is performed by searching for a condition in which the crack 15 does not occur, or a molded body in which the crack 15 is generated is excluded as a defective product. Then, such a crack 15 is also a void that absorbs thermal expansion and contraction of the heat storage body.

  Further, when a cylindrical shaped body is plastically deformed by applying external forces from a plurality of directions that are not constant, as shown in FIG. 1 (c), from the inside toward the surface. The radially extending cracks 16 occur with a high probability. Such a crack 16 is also usually undesirable as an internal defect, but in the present embodiment, such a crack 16 is also a void that absorbs thermal expansion and contraction of the heat storage body. In addition, in FIG.1 (c), when the spherical molded object 10b has both the crack 15 extended in the single direction which generate | occur | produced at the time of extrusion molding, and the substantially radial crack 16 which generate | occur | produced at the spheronization process. Is illustrated.

  Since the filling material enters the cracks 15 and 16 in the covering and filling process, the inside of the cracks 15 and 16 is partially filled with the filling material, and the open ends of the cracks 15 and 16 are covered with the covering layer. Covered with. Accordingly, through the heat treatment step, as schematically shown in FIG. 2B, the heat storage body base 20 has a spherical shape and has a crack 15 (a crack generated at the time of extrusion molding) extending only in a single direction. ) And cracks 16 (cracks generated in the spheroidization process) extending radially from the inside toward the surface, and the open ends of the cracks 15 and 16 are covered with the coating layer 30. In addition, the heat storage body 1 having a configuration in which the insides of the cracks 15 and 16 are partially filled with the filling material is manufactured. By having such a configuration, while exhibiting the action of absorbing thermal expansion and contraction in the cracks 15 and 16 of the unfilled portions, the mechanical strength is reduced and the cracks are extended due to the presence of the cracks 15 and 16. It can be suppressed by the filling material.

  According to the above manufacturing method, the ceramic constituting the heat storage body base is silicon carbide, silicon nitride, or aluminum nitride, the diameter of the heat storage body base after the firing process is about 20 mm, and the appearance before the coating / filling process after the firing process Samples S1 to S9 having different porosities were produced. Samples S1 and S2 were not subjected to the coating / filling step. Samples S3 to S8 are coated with a filler containing a vitreous filler that becomes silicate glass upon heating, and sample S9 is coated with a filler containing a ceramic filler that is mullite. -The filling process was performed. The type of additive added to the filling material, the viscosity, the length of processing time, and the like were adjusted, and the penetration depth of the filling material into the heat storage substrate was adjusted.

  For each sample, the apparent porosity, the circularity, the thickness of the coating layer, and the thickness of the inclined layer were measured by the following methods, and an oxidation resistance evaluation test and a thermal shock resistance evaluation test were performed. Each measurement and evaluation test was performed using a plurality of test pieces for one sample.

<Apparent porosity>
The heat storage body substrate after the firing step and before the coating / filling step was cut into a predetermined size and measured by the Archimedes method.

<Circularity>
The heat storage body substrate after the firing process and before the coating / filling process was photographed from three directions orthogonal to each other. In imaging, the sample and the background were identified by binarization, the area S and the peripheral length L of the two-dimensional shape of the sample were obtained by image processing, and the circularity was calculated.

<Thickness of coating layer, thickness of inclined layer>
The sample after the heat treatment step was cut at a surface passing through the center, embedded in resin, and the cut surface was polished. The cut surface after polishing was photographed with a scanning electron microscope. The imaging was image processed, and unfilled pores and pores and matrix portions filled with filler material were identified by binarization. In imaging, a rectangular region including the covering layer to the porous layer is set so that the direction of the pair of sides coincides with the depth direction of the sample, and the region is divided by a predetermined length (100 μm) in the depth direction. The ratio of the area of pores (unfilled pores) in each area was calculated as the porosity (%). A graph plotting the porosity with respect to the depth from the surface of the sample was prepared. As an example, the graph of the sample S5 is shown in FIG. 3 together with the image of the scanning electron microscope, and the graph of the sample S6 is shown in FIG. In the measurement of the thickness of the coating layer and the thickness of the inclined layer, a region free of cracks was used in imaging.

  In any sample, the porosity close to zero increased discontinuously in the vicinity of the surface, and the discontinuously changing depth was defined as the boundary between the coating layer and the gradient layer. As the depth increased from the boundary, the porosity became almost constant after continuously increasing. Therefore, the outermost depth in the range where the porosity was constant was defined as the boundary between the inclined layer and the porous layer. .

<Oxidation resistance>
The sample was heated in an air atmosphere at a temperature of 1300 ° C. for 36 hours, and the mass before and after that was measured. Since both carbides and nitrides increase in mass due to oxidation, the mass increase rate per unit time is calculated, and the case where the mass increase rate per hour is 0.01% or less is evaluated as being excellent in oxidation resistance. Expressed as “◯”, and when exceeding 0.01%, it was evaluated as having no oxidation resistance and expressed as “x”. The mass increase rate is calculated as follows.
Mass increase rate (%) = (mass after heating−mass before heating) × 100 / mass before heating

<Heat shock resistance>
The sample was heated at a temperature of 1000 ° C. for 30 minutes, placed in water, rapidly cooled and held for 5 minutes, and then held in air at room temperature for 15 minutes, and this cycle was repeated. The case where the failure does not occur even after repeating 5 cycles is evaluated as “◯”, indicating that it is excellent in thermal shock resistance, and if it is destroyed before reaching 5 cycles, it is evaluated as “having no thermal shock resistance”. " Although it did not break even after repeating 5 cycles, the case where peeling of the coating layer occurred was represented by “Δ”.

  As a result of the above measurement, the circularity in three different directions was in the range of 0.86 to 0.90 for any sample. In all samples, the thickness of the coating layer was about 200 μm. Table 1 shows the apparent porosity, the thickness of the inclined layer, the evaluation of oxidation resistance, and the evaluation of thermal shock resistance, which are other measurement results, together with the types of ceramics and fillers for each sample.

From the above results, the following can be read.
-If the apparent porosity of the heat storage substrate is about 3%, it does not have thermal shock resistance. This is probably because there are few pores that absorb thermal expansion and contraction.
-If the ceramics that make up the heat storage substrate are non-oxides, the oxidation does not progress much even if the heat storage material is used in a high-temperature oxidizing atmosphere if the apparent porosity is about 3%. However, when the apparent porosity reaches 6%, the oxidation resistance decreases. This is probably because the contact area with oxygen increases through the pores.
-Even if it is a heat storage body base | substrate with an apparent porosity of 6% or more, if it has a coating layer with a thickness of at least 200 micrometers on the surface, it has oxidation resistance. This was the same for the sample S3 having a gradient layer thickness of 2 μm and almost no gradient layer.

When the apparent porosity of the heat storage substrate is 6% to 45% and the filling material is glass, the thermal shock resistance is excellent if it has an inclined layer having a thickness of at least 50 μm. This is because the thermal expansion and contraction are absorbed by the pores remaining without being filled with the filling material, and the pores are partially filled with the filling material, and the ratio does not change rapidly. It is considered that the decrease in mechanical strength due to the presence of pores is suppressed by having the inclined layer that continuously changes. When the filling material was mullite, the sample S9 having the inclined layer thickness of 40 μm was excellent in thermal shock resistance.
In Samples S4 to S9 having excellent thermal shock resistance, the thickness of the inclined layer was 40 μm to 5800 μm. When this is converted into a ratio to the radius of the sample (diameter of about 20 mm), it is 0.4% to 58%.

-Regardless of whether the filling material (after heat treatment) is glass or oxide ceramics, the action of becoming a heat storage body having oxidation resistance and thermal shock resistance due to the presence of the coating layer and the gradient layer was the same.

  Although it has been confirmed that a spherical heat storage body having a diameter of 5 mm to 80 mm can be produced without any problems by the above production method, the range of 10 mm or more in diameter is a range in which production is difficult by the conventional rolling granulation method. There is high significance.

  The present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the above-described embodiments, and various improvements can be made without departing from the scope of the present invention as described below. And design changes are possible.

  For example, in the above embodiment, the case where a filler material containing one of a glassy filler and a ceramic filler is used is exemplified, but a filler material containing both a glassy filler and a ceramic filler is used. Can be used. Mixing with the glassy filler increases the adhesion of the oxide ceramics contained in the ceramic filler to the heat storage substrate.

1 heat storage body 10a molded body (cylindrical molded body)
10b Molded body (spheroidized heat storage body)
20 Thermal Storage Base 21 Porous Layer 22 Gradient Layer 30 Covering Layer

Claims (3)

A method of manufacturing a spherical ceramic heat storage body,
With a forming raw material that becomes a porous ceramic sintered body by firing, a cylindrical formed body having plasticity is formed,
By applying an external force from a plurality of non-constant directions to the cylindrical molded body, the respective molded bodies are plastically deformed and spheroidized without uniting a plurality of the molded bodies,
After making the spheroidized shaped body into a heat storage body base by firing,
The surface of the heat storage substrate is covered with a filler containing at least one of a glassy filler that becomes glass upon heating and a ceramic filler containing oxide ceramics, and the interior of the heat storage substrate By infiltrating the filler material towards
A porous layer in which pores are not filled with the filling material at the center of the heat storage body substrate, a coating layer in which the filling material covers the surface of the heat storage body substrate, and the coating layer from the porous layer to the coating layer A method for producing a heat storage body, characterized in that the heat storage body has an inclined layer in which the proportion of pores not filled with the filling material continuously decreases. A heat storage body substrate made of a porous ceramic sintered body and having a two-dimensional circularity of 0.86 to 0.90 when viewed from at least three different directions;
A filling material containing at least one of glass and oxide ceramics comprises a coating layer covering the surface of the heat storage substrate; and
The heat storage body substrate has a porous layer whose pores are not filled with the filler material in the center, and pores not filled with the filler material from the porous layer toward the coating layer. A heat storage body comprising an inclined layer having a continuously decreasing rate. The heat storage body substrate has cracks extending substantially radially from the inside toward the surface,
The open end of the crack is covered with the covering layer,
The inside of the said crack is partially filled with the said filling material, The thermal storage body of Claim 2 characterized by the above-mentioned.