JP2021155305A - Nanocarbon composite infrared ray radiation ceramic - Google Patents

Abstract

To provide a nanocarbon composite infrared ray radiation ceramic having high emissivity of infrared ray over a broad wavelength region, even when fine pores or voids spotted on a surface are filled or covered in order to improve water repellency or surface hardness of a surface of an infrared emitter.SOLUTION: A filling layer and/or a coating layer is formed on the a part or the entirety of a surface so as to cover the pores or voids scattered on the surface of the infrared radiation ceramics in which nanocarbon material is uniformly dispersed in the ceramic. The filling layer and/or the coating layer are mainly made of silicone or fluorine based water repellent resin. The value of the emissivity of infrared rays of 6000 to 400 cm-1 at 25°C measured by the JFCC method is 80% or larger.SELECTED DRAWING: Figure 5

Description

The present invention relates to nanocarbon composite infrared radiating ceramics. In particular, the present invention relates to nanocarbon composite infrared radiation ceramics having a high emissivity of infrared rays over a wide wavenumber range (expressed by the wavenumber which is the reciprocal of the wavelength in the present invention).

Infrared rays are an energy-efficient heating method because they can directly heat an object without heating the air layer in the middle by radiation. Therefore, the heating method using infrared radiation is used in a wide range of applications such as heating and drying. On the other hand, the amount of infrared rays emitted from a substance is unique to the substance and is represented by the emissivity of infrared rays. Moreover, it changes greatly not only by the type of the substance but also by its surface state, surface temperature, and wavelength (wave number).

Further, in recent years, there has been increasing interest in heating, heating, and drying by low-temperature infrared rays. For example, it has come to be used for drying agricultural products such as vegetables, shiitake mushrooms, tea, and rice, and is attracting attention as a drying method that does not impair the flavor of food.

As a material that emits infrared rays, a carbon material is known and has been widely used. However, although carbon materials have excellent infrared emissivity, they are often difficult to use in terms of physical characteristics. Therefore, ceramic materials have come to be widely used as materials having excellent physical characteristics, high emissivity of infrared rays, and excellent energy efficiency. For example, materials such as silica, alumina, and zirconia are often used.

However, in the widely used conventional ceramic materials, there is a region where the emissivity is weak depending on the wavelength (wave number). For example, 5 [mu] m or less in the wavelength region (2000 cm ^-1 The following wavenumbers), the wavelength range of 8 to 12 .mu.m (wavenumber range of 1250～833Cm ^-1), even 19μm or more in a wavelength range (526cm ^-1 or more wavenumbers) In many cases, the emissivity decreases.

On the other hand, the infrared wavelength range (wavenumber range) absorbed by a substance is unique to that substance. For example, in the case of drying crops by infrared irradiation, the absorption wavelength range (wave number range) of infrared rays differs depending on the type of crop to be dried, so there is a problem that the degree of drying differs even if the same infrared radiator is used. there were.
In addition, when drying an object in which a plurality of types of agricultural products are mixed, there is a problem that uniform drying cannot be performed.

Therefore, when used as an infrared radiator for drying, it is necessary to use infrared radiators having different wavelength ranges (wavenumber ranges) properly, or to combine a plurality of types of infrared radiators. In particular, it is particularly important in low-temperature infrared drying with low energy.

Therefore, an infrared radiator having a high emissivity of infrared rays over a wide wavelength range (wavenumber range) is desired. For example, Patent Document 1 below proposes a composite ceramic material for infrared radiation having carbon fine particles surrounding the ceramic particles. The infrared emissivity of this material was measured at 140 ° C, which can be called low-temperature infrared rays, and reported to be good.

However, in Patent Document 1 below, a special manufacturing method is required for the operation of covering the ceramic particles with carbon fine particles. In addition, the emissivity differs depending on the particle size of the carbon fine particles surrounding the ceramic particles, and unless the particle size is reduced, the wavelength range of 5 μm or less (2000 cm- ¹ or less wavenumber range) and the wavelength range of 8 to 10 μm (1250). There is data that the emissivity decreases in the (wavenumber range of ~ 1000 cm ^{-1), and more complicated operations are required.}

On the other hand, the present inventions have previously proposed in Patent Document 2 below a nanocarbon composite ceramic in which nanocarbon is composited with general-purpose ceramic particles conventionally used as an infrared radiator, and a method for producing the same. This nanocarbon composite ceramic can be manufactured by almost the same operation as the conventional manufacturing process, and the infrared emissivity is high and stable over a wide wavelength range (wavenumber range).

Japanese Patent No. 5147101 Japanese Patent Application No. 2019-069803

By the way, the infrared radiator using the nanocarbon composite ceramics according to Patent Document 2 can be used for various purposes, and is particularly effectively used for drying agricultural products such as vegetables, shiitake mushrooms, tea and rice. .. On the other hand, in this nanocarbon composite ceramic, the nanocarbon material is uniformly dispersed in the ceramic, and fine pores or voids are scattered on the surface thereof.

Therefore, when the dried matter of the infrared radiator is an agricultural product or the like, it is often in a wet state. In this case, there may be a problem that the wet agricultural product comes into contact with the surface of the infrared radiator and the infrared radiator gets wet, and water invades the inside from the pores or voids on the surface to deteriorate the infrared radiator. There is sex. In addition, when the crop is tea leaves, it is efficient if it can be dried by using heat conduction by contact with a hot plate in addition to infrared radiation. In this case as well, if the wetting of the surface can be controlled, it can be a more effective drying means.

In addition, when the object to be dried is an agricultural product or the like, these are often in a hard state. In this case, hard crops may come into contact with the surface of the infrared radiator and damage the nanocarbon composite ceramics on the surface of the infrared radiator, which may also cause a problem of deterioration of the infrared radiator.

In order to deal with these problems, it is conceivable to form a packing layer or a coating layer having water repellency or a certain hardness so as to cover the fine pores or voids scattered on the surface of the nanocarbon composite ceramics. .. However, as mentioned above, the amount of infrared radiation emitted by a substance is unique to the substance. When the surface of the nanocarbon composite ceramic is coated with another substance, infrared rays peculiar to the coated substance are emitted, and there is a problem that the radiation performance of the conventional nanocarbon composite ceramic cannot be maintained.

Therefore, in order to deal with the above problems and improve the water repellency and surface hardness of the surface of the infrared radiator, the present invention fills or covers fine pores or voids scattered on the surface. Even in such a case, it is an object of the present invention to provide nanocarbon composite infrared radiation ceramics having a high emissivity of infrared rays over a wide wave number range.

In solving the above problems, as a result of diligent research, the present inventors have controlled the type of substance to be filled or coated on the surface of the infrared radiator, the surface area to be filled or coated, the thickness to be coated on the surface, and the like. , The present invention has been completed by finding that the above object can be achieved.

That is, according to the description of claim 1, the nanocarbon composite infrared radiating ceramics according to the present invention are described.
A packing layer and / or a coating layer is formed on a part or the whole of the surface so as to cover the pores or voids scattered on the surface of the infrared radiation ceramic in which the nanocarbon material is uniformly dispersed in the ceramic.
It is characterized in that the value of the infrared emissivity in the wave number range of 6000 to 400 cm ^{-1 at 25 ° C. measured by the JFCC method is 80% or more.}

Further, the nanocarbon composite infrared radiating ceramic according to the present invention is the nanocarbon composite infrared radiating ceramic according to claim 1, according to claim 2.
The value of the infrared emissivity in the wave number range of 6000 to 1250 cm- ^{1 at 25 ° C. measured by the JFCC method is 90% or more.}

Further, the nanocarbon composite infrared radiating ceramic according to the present invention is the nanocarbon composite infrared radiating ceramic according to claim 1 or 2, according to the description of claim 3.
A three-dimensional lattice is formed by a plurality of scanning points in the horizontal direction (X-axis-Y-axis direction) and the depth direction (Z-axis direction) parallel to the surface of the infrared radiation ceramics by laser Raman spectroscopy.
The first mapping operation using the peak area indicating the presence of the material forming the packed bed and / or the coating layer from the Raman spectrum obtained at each scanning point and the second using the peak area indicating the presence of the carbon material. Perform mapping operations and
The scanning point at which the presence of the material forming the packed layer and / or the coating layer can be confirmed in the depth direction (Z-axis direction) from the surface of the three-dimensional lattice in the first mapping operation is defined as the surface scanning point. The horizontal (X-axis-Y-axis) lattice plane where the surface scanning points are gathered is defined as the outermost surface of the infrared radiation ceramics.
The scanning point at which the presence of the carbon material can be confirmed in the depth direction (Z-axis direction) from the surface of the three-dimensional lattice in the second mapping operation is set as an effective scanning point, and the effective scanning point is the horizontal direction (X). A lattice plane existing in 80% or more in the axis-Y-axis direction) is defined as an effective surface of the infrared radiation ceramics.
The distance from the outermost surface to the effective surface is 100 μm or less.

Further, the nanocarbon composite infrared radiating ceramic according to the present invention is the nanocarbon composite infrared radiating ceramic according to claim 3, according to claim 4.
The distance from the outermost surface to the effective surface is 10 μm or less.

Further, the nanocarbon composite infrared radiating ceramic according to the present invention is the nanocarbon composite infrared radiating ceramic according to any one of claims 1 to 4, according to the description of claim 5.
The packing layer and / or coating layer is mainly made of a silicone-based or fluorine-based water-repellent resin.
It is characterized in that the value of the contact angle measured by the wettability test method (droplet method) of the substrate glass surface of JIS R3257 is 80 ° or more.

Further, the nanocarbon composite infrared radiating ceramic according to the present invention is the nanocarbon composite infrared radiating ceramic according to any one of claims 1 to 5, according to the sixth aspect of the invention.
It is characterized in that the value of the hardness of the surface including the coating layer and the packing layer measured by the mechanical properties (scratch hardness; pencil method) of the coating film of JIS K5600-5-4 is 2H or more.

Further, the nanocarbon composite infrared radiating ceramic according to the present invention is the nanocarbon composite infrared radiating ceramic according to any one of claims 1 to 6, according to the description of claim 7.
The nanocarbon material is characterized by being carbon nanotubes, carbon nanofibers, graphene, or a compound thereof.

Further, the nanocarbon composite infrared radiating ceramic according to the present invention is the nanocarbon composite infrared radiating ceramic according to claim 7, according to claim 8.
It is characterized by containing cellulose nanofibers in addition to the nanocarbon material.

Further, the nanocarbon composite infrared radiating ceramic according to the present invention is the nanocarbon composite infrared radiating ceramic according to any one of claims 1 to 8, according to the description of claim 9.
The ceramic particles are characterized by containing 90% by weight or more of alumina, silica, zirconia, cordierite, or a mixture thereof.

According to the above configuration, in the nanocarbon composite infrared radiating ceramics according to the present invention, most of the nanocarbon materials are uniformly dispersed in the ceramics without forming aggregates. Fine pores or voids are scattered on the surface of the nanocarbon composite infrared radiating ceramics, and a filling layer and a filling layer and the entire surface of the nanocarbon composite infrared radiating ceramics are covered so as to cover the pores or voids. / Or a coating layer is formed. Further, the value of the infrared emissivity in the wave number range of 6000 to 400 cm ^{-1 at 25 ° C. measured by the JFCC method is 80% or more.}

As described above, despite the fact that the packing layer and / or the coating layer is formed on the surface of the nanocarbon composite infrared radiation ceramics, the nanocarbon composite infrared radiation ceramics having a high emissivity of infrared rays over a wide wave number range are provided. can do.

Further, according to the above configuration, the nanocarbon composite infrared radiating ceramics according to the present invention have an infrared emissivity value of 90% or more ^{in the wave number range of 6000 to 1250 cm -1 at 25 ° C. measured by the JFCC method.} preferable. As a result, the above-mentioned action and effect can be more effectively exerted.

Further, according to the above configuration, the nanocarbon composite infrared radiation ceramics according to the present invention are subjected to the laser Raman spectroscopy in the horizontal direction (X-axis-Y-axis direction) and the depth direction parallel to the vicinity of the surface of the infrared radiation ceramics. A three-dimensional lattice is formed by a plurality of scanning points in the (Z-axis direction). Next, the first mapping operation using the peak area indicating the presence of the material forming the packed bed and / or the coating layer from the Raman spectrum obtained at each scanning point and the peak area indicating the presence of the carbon material were used. Perform the second mapping operation.

Next, in the first mapping operation, the scanning point at which the presence of the material forming the packing layer and / or the coating layer can be confirmed from the surface of the three-dimensional lattice in the depth direction (Z-axis direction) is defined as the surface scanning point. The horizontal (X-axis-Y-axis) lattice plane where the surface scanning points are gathered is defined as the outermost surface of the infrared radiation ceramics. Further, in the second mapping operation, the scanning point at which the presence of the carbon material can be confirmed in the depth direction (Z-axis direction) from the surface of the three-dimensional lattice is set as the effective scanning point, and the effective scanning point is the horizontal direction (X-axis direction). A lattice plane existing at 80% or more in the −Y axis direction) is defined as an effective surface of infrared radiation ceramics. The distance from the outermost surface to the effective surface is preferably 100 μm or less. As a result, the above-mentioned action and effect can be exerted more concretely.

Further, according to the above configuration, the distance from the outermost surface to the effective surface is preferably 10 μm or less. As a result, the above-mentioned action and effect can be more effectively exerted.

Further, according to the above configuration, the packing layer and / or the coating layer may be mainly composed of a silicone-based or fluorine-based water-repellent resin. At this time, on the surface of the nanocarbon composite infrared radiation ceramics, the value of the contact angle measured by the wettability test method (droplet method) of the substrate glass surface of JIS R3257 is preferably 80 ° or more. As a result, the water-repellent performance of the surface of the infrared radiator is improved, and even when the object to be dried of the infrared radiator is wet, water penetrates into the inside through the pores or voids on the surface to emit infrared radiation. There is no problem of deterioration of the body.

Further, according to the above configuration, the value of the hardness of the surface including the coating layer and the packing layer measured by the mechanical properties (scratch hardness; pencil method) of the coating film of JIS K5600-5-4 is 2H or more. preferable. As a result, even if the object to be dried of the infrared radiator is in a hard state, the object to be dried comes into contact with the surface of the infrared radiator and the nanocarbon composite ceramics on the surface of the infrared radiator are damaged, resulting in the infrared radiator. There is no problem of deterioration.

Further, according to the above configuration, the nanocarbon composite infrared radiation ceramics according to the present invention may be carbon nanotubes, carbon nanofibers, graphene, or a compound thereof as the nanocarbon material. As a result, the above-mentioned action and effect can be exerted more concretely.

Further, according to the above configuration, the nanocarbon composite infrared radiation ceramics according to the present invention may contain cellulose nanofibers in addition to the nanocarbon material. As a result, the above-mentioned action and effect can be exerted more concretely.

Further, according to the above configuration, the nanocarbon composite infrared radiating ceramics according to the present invention may contain, as ceramic particles, alumina, silica, zirconia, cordierite, or a compound thereof in an amount of 90% by weight or more. .. As a result, the above-mentioned action and effect can be exerted more concretely.

As described above, according to each of the above configurations, in order to improve the water repellency and surface hardness of the surface of the infrared radiator, the fine pores or voids scattered on the surface are filled or covered. However, it is possible to provide nanocarbon composite infrared radiation ceramics having a high emissivity of infrared rays over a wide wave number range.

It is an electron micrograph of the surface of an infrared radiation ceramic intermediate which is not filled or coated with resin. It is an image figure which shows the state of the pore part or the void part appearing in the infrared radiation ceramic intermediate. 6 is an electron micrograph showing a state in which the surface of an infrared radiation ceramic intermediate is filled or coated with a silicone resin or the like. It is an image figure which shows the state which the pore part or the void part which appears in the infrared radiation ceramics intermediate is filled or coated with silicone resin and the like. It is an infrared spectrum at 25 degreeC of the nanocarbon composite infrared radiation ceramics of an Example. An example of silicone mapping and carbon mapping when the nanocarbon composite infrared radiating ceramics of the example is measured by laser Raman spectroscopy is shown.

In the nanocarbon composite infrared radiating ceramics according to the present invention, the radiating surface is covered with infrared radiating ceramics in which the nanocarbon material is uniformly dispersed in the ceramics, and the pores or voids scattered on the surface are covered. A packing layer and a coating layer are formed on the surface. Therefore, the infrared radiation ceramic itself in which the nanocarbon material is dispersed may constitute both the substrate and the radiation surface. Further, the surface of the substrate containing no nanocarbon material may be coated with infrared radiation ceramics in which the nanocarbon material is dispersed. In this case, the substrate containing no nanocarbon material may be an ordinary ceramic substrate, or may be used as a hot plate such as a metal plate.

Hereinafter, the nanocarbon composite infrared radiating ceramics according to the present invention will be described with reference to embodiments. Here, an example will be described in which the surface of a ceramic substrate containing no nanocarbon material is coated with infrared radiation ceramics in which the nanocarbon material is dispersed. The present invention is not limited to the following embodiments.

In this embodiment, first, a ceramic substrate produced by firing and solidifying is produced. Nanocarbon is not compounded on this ceramic substrate. Next, a nanocarbon mixed ceramic slurry is prepared, and this is applied and solidified on a ceramic substrate to prepare an infrared radiation ceramic intermediate. Further, the surface of the infrared radiating ceramic intermediate is filled and coated with a resin to produce the nanocarbon composite infrared radiating ceramic according to the present embodiment. Hereinafter, the description will be given based on the manufacturing method.

(1) Fabrication of Ceramic Substrate Here, a ceramics substrate that is not composited with nanocarbon, which is a substrate for nanocarbon composite infrared radiation ceramics, is manufactured.

<Step of adjusting ceramic slurry for substrate>
In this step, a ceramic slurry composed of ceramic particles is prepared. The ceramic particles used for the ceramic substrate are not particularly limited. For example, alumina, mullite, zirconia, silicon carbide, silicon nitride, aluminum nitride and the like may be used, or a combination thereof may be used.

In the present invention, it is preferable to use ceramic particles conventionally used for infrared radiators. For example, alumina _{(Al 2 O} 3), silica _(SiO 2), zirconia _(ZrO 2), cordierite _{(2MgO · 2Al 2 O 3 ·} 5SiO 2), or can use these formulations. Further, in the present invention, it is not necessary to contain a large amount of additives such as other metal oxides as in the conventional infrared radiator, in addition to alumina, silica, zirconia, cordierite, or a combination thereof. ..

The method for adjusting the ceramic slurry in this step is not particularly limited, and can be performed by an apparatus and method generally used for adjusting the ceramic slurry. For example, a ball mill such as a nylon pot mill may be used to disperse the ceramic particles in water with a dispersant.

In this step, an alkali hydration reaction or a so-called ceramic adhesive can be used. The alkali hydration reaction solidifies even at a low temperature, but solidification of the ceramic adhesive requires heat curing at about 100 ° C. to 200 ° C. In the case of a ceramic adhesive, for example, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), and calcium oxide (CaO) are blended in a predetermined amount, and a ball mill such as a nylon pot mill is used. , The ceramic particles may be dispersed in water by a dispersant.

<Process of adjusting molding material>
In this step, the molding material is prepared from the ceramic slurry prepared in the previous step. First, a molding material is prepared by mixing an auxiliary component called a binder for adjusting the water content and viscosity of the ceramic slurry to facilitate molding. As the binder component, an organic polymer or the like that disappears by firing in a subsequent process is used. For example, a wax emulsion, a water-soluble acrylic resin, a water-soluble polyether resin, and the like.

Next, a mixed slurry containing a binder is prepared by adjusting the water content and viscosity. If necessary, it is put into a rotary disc type spray dryer or the like for granulation. However, the method for adjusting the molding material such as granulation is not limited to this. When a rotary disc type spray dryer is used, the disc rotation speed, inlet temperature, outlet temperature, and the like may be appropriately selected.

When the alkali solidification reaction or heat curing is used, the molding material is used in the form of a slurry (thickened slurry) in this step, so that there is no need for granulation. When the alkali solidification reaction is carried out, a predetermined amount of an alkaline aqueous solution or the like is mixed with the mixed slurry in this step to prepare a molding material (slurry).

Here, examples of the alkaline aqueous solution include aqueous solutions such as lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, sodium aluminate, and potassium aluminate. The amount (concentration) of the alkaline aqueous solution to be mixed is an amount obtained by eluting silica (SiO ₂ ), alumina (Al ₂ O ₃ ), a calcium compound, etc. contained in the mixed slurry into the alkaline aqueous solution to cause a curing reaction. Make an appropriate selection.

<Process of preparing the preformed body>
In this step, the molding material prepared in the previous step is stored in a predetermined container to prepare a preformed body. Specifically, the molding material adjusted by granulation or the like is molded into a preformed body by a dry mold press or the like. The molding apparatus and molding method of the molding material are not particularly limited, and a molding machine for ceramics may be used.

When the molding material is in the form of a slurry, a dry mold press device or the like is not used, but a container having a predetermined shape such as a silicone mold is used. The shape and size of the container used at this time may be appropriately selected according to the purpose of use.

<solidification process of preformed body>
In this step, the solidification of the preformed body prepared in the previous step is completed. In this embodiment, solidification is performed by firing. Since the preformed body according to the present embodiment does not contain a nanocarbon material, it may be fired in the air, and if necessary, it may be fired in a nitrogen atmosphere or an argon atmosphere. Conditions such as the firing temperature and the temperature rise time are not particularly limited, but for example, the temperature is raised at a temperature of about 100 ° C. to 250 ° C./h, and the temperature is raised at a temperature of about 1000 ° C. to 1400 ° C. for 0.5 hours or more. It may be baked for about 2 hours. In this way, a ceramic substrate in which nanocarbon is not composited is produced.

When solidification is carried out by an alkali solidification reaction in this step, the curing reaction is carried out until the reaction between the ceramic material and the alkaline aqueous solution is completed. Further, when this step is solidification by a curing reaction, it may be carried out in any temperature range from room temperature to high temperature. For example, it can be carried out under normal pressure at a temperature of room temperature to 130 ° C. On the other hand, in the case of ceramic adhesives and the like, solidification is performed by heat curing. The heat solidification may be carried out, for example, by heating at a temperature of about 100 ° C. to 200 ° C. for about 1 hour to 2 hours.

(2) Preparation of Infrared Radiating Ceramic Intermediate Here, an infrared radiating ceramic intermediate is prepared by preparing a nanocarbon mixed ceramic slurry and applying and solidifying it on a ceramic substrate.

<Step of adjusting ceramic slurry for intermediate>
In this step, a ceramic slurry composed of ceramic particles is prepared in the same manner as in the above-mentioned step of adjusting the ceramic slurry for a substrate. Further, in the adjustment of the ceramic slurry, the same operation as the above-mentioned step of adjusting the ceramic slurry for a substrate may be performed. In this step as well, an alkali hydration reaction or a so-called ceramic adhesive can be used in the same manner as in the step of preparing the ceramic slurry for a substrate.

<Step of adjusting nanocarbon-aqueous dispersion liquid>
In this step, the nanocarbon-aqueous dispersion liquid to be mixed with the ceramic slurry for intermediates prepared in the previous step is prepared. The nanocarbon material used in the present invention is a nano-sized or micro-sized microcarbon-based substance. If you try to increase the emissivity of infrared rays using carbon black (CB) or carbon fiber (CF), which are ordinary carbon materials, it is necessary to add about 15% by weight to the ceramic radiator, which is excellent in physical properties. It is not possible to form a ceramic radiator.

In the present invention, a wide wavenumber range is obtained by adding a small amount of nanocarbon material to the ceramic particles and by uniformly dispersing most of the small amount of nanocarbon material in the ceramics without forming aggregates. The emissivity of infrared rays can be increased. Here, most of the nanocarbon materials are not particularly limited in numerical values. However, preferably, 50% or more of the nanocarbon material, more preferably 80% or more of the nanocarbon material is uniformly dispersed without forming aggregates.

The nanocarbon material used in the present embodiment refers to, for example, carbon nanotube (CNT), carbon nanofiber, graphene (GP), or a combination thereof. The carbon nanotube may be a multi-wall carbon nanotube (MWCNT) or a single-wall carbon nanotube (SWCNT). Further, the size (diameter, length, etc.) of each nanocarbon material is within a generally defined range and is not particularly limited. For example, it is said that the diameter of CNT is 0.4 to 100 nm (single layer to multilayer), the thickness of GP is 2 to 10 nm, the area size is 5 to 30 μm, and the diameter of CNF is 4 to 100 nm.

The method for preparing the nanocarbon-aqueous dispersion liquid in this step is not particularly limited, but it is preferable that the nanocarbon material is in a monodispersed state in water. For example, as a method for dispersing nanocarbons, a single-composition micelle or a mixed micelle aqueous solution made of a hydrophilic and hydrophobic surfactant (see, for example, Japanese Patent Application Laid-Open No. 2007-039623) is prepared, and carbon is prepared therein. Examples thereof include a method of adding nanotubes and performing a dispersion treatment. Further, a dispersion method using an orifice (see Japanese Patent Application Laid-Open No. 2015-013772) has also been proposed.

In the present embodiment, first, a wet treatment was performed using a ball mill or the like to give the hydrophobic nanocarbons a water affinity. Next, a surfactant or the like was added to the nanocarbon wet-treated using a bead mill or the like to carry out a dispersion treatment. The ratio of the nanocarbon material in the nanocarbon-aqueous dispersion is the operability when mixed with the ceramic slurry in the subsequent step and the ratio of the nanocarbon material to the surface of the finally produced nanocarbon composite infrared radiation ceramics. Adjust in consideration of.

Further, in this step, since firing is not performed, other organic substances can be mixed with the nanocarbon-aqueous dispersion liquid. In the present embodiment, cellulose nanofibers are used for the purpose of improving the dispersion state of the nanocarbon material in the nanocarbon-aqueous dispersion liquid and making the dispersion of the nanocarbon material in the ceramics uniform in the nanocarbon composite infrared radiation ceramics. (CNF) is preferably blended. Here, the cellulose nanofiber refers to a fiber substance having a diameter of several nm to 100 nm and a length of 100 times or more the diameter, which is mainly composed of cellulose derived from the cell wall of a plant.

<Step of adjusting mixed slurry>
In this step, the ceramic slurry for intermediates prepared in the previous step and the nanocarbon-aqueous dispersion liquid are mixed to prepare a mixed slurry. First, the ceramic slurry is put into a stirring container and stirred. Next, the nanocarbon-aqueous dispersion is added with stirring. Further, stirring is continued for a predetermined time to prepare the mixed slurry. The stirring device and the stirring torque and stirring time may be appropriately selected depending on the viscosity of the ceramic slurry for the intermediate, the mixing amount of the nanocarbon-aqueous dispersion liquid, and the like.

In this step, it is necessary to consider the ratio of the ceramic particles to the nanocarbon material on the surface of the finally produced nanocarbon composite infrared radiation ceramics. In the present embodiment, the amount of the nanocarbon material added to the ceramic particles is preferably in the range of 0.5% by weight to 5.0% by weight. When the amount of the nanocarbon material added is less than 0.5% by weight, the emissivity of infrared rays cannot be increased over a wide wavenumber range. On the other hand, when the amount of the nanocarbon material added is more than 5.0% by weight, the nanocarbon material in the ceramics agglomerates and cannot be uniformly dispersed. Therefore, it is not possible to manufacture nanocarbon composite infrared radiation ceramics having excellent surface physical characteristics.

<Process of coating and solidifying on ceramic substrate>
In this step, first, the mixed slurry prepared in the previous step is applied to the surface of the ceramic substrate already prepared. The coating method is not particularly limited, but the surface of the ceramic substrate may be coated with a coater, a roller, a squeegee, a brush, or the like. Alternatively, the ceramic substrate may be immersed in a bath of the mixed slurry to dip the entire surface. By adjusting the viscosity of the mixed slurry and the number of times of coating, the thickness of the mixed slurry layer coated on the surface of the ceramic substrate can be adjusted.

Next, the ceramic substrate coated with the mixed slurry is dried if necessary, and then heated to complete the solidification of the mixed slurry to prepare an infrared radiation layer. The conditions for heat solidification are not particularly limited, and for example, heating may be performed at a temperature of about 150 ° C. to 200 ° C. for about 1 hour to 2 hours. In this way, an infrared radiating ceramic intermediate is produced.

Fine pores or voids are scattered on the surface of the infrared radiation layer of the infrared radiation ceramic intermediate produced as described above. Such pores or voids do not exist only on the surface of the infrared radiating ceramic intermediate, but may extend to the inside of the infrared radiating layer. FIG. 1 is an electron micrograph of the surface of an infrared radiating ceramic intermediate. Further, FIG. 2 is an image diagram showing pores or voids appearing in the infrared radiating ceramic intermediate. In FIG. 2, (A) shows the state of the surface, (B) shows the state of the cross section, and the portion drawn in black is the pore portion or the void portion appearing on the surface or the cross section. As can be seen from FIGS. 1 and 2, many fine pores or voids are scattered on the surface and cross section of the infrared radiating ceramic intermediate. In this embodiment, a part or all of these pores or voids are filled or covered from the surface side.

As shown in FIG. 2, the presence of pores or voids on the surface of the infrared radiation layer may make the strength of that portion more brittle than the other portions, resulting in deterioration of the infrared radiation layer. Further, as shown in FIG. 3, when the pore portion or the void portion reaches the inside of the infrared radiation layer, water may invade from the portion and the infrared radiation layer may be deteriorated. The present invention is intended to eliminate these drawbacks, and further provides a drying means having high drying efficiency in which heat conduction by contact with a hot plate is used in addition to infrared radiation.

(3) Fabrication of Nanocarbon Composite Infrared Radiation Ceramics Here, the surface (infrared radiation layer) of the infrared radiation ceramics intermediate is filled and coated with resin to improve the water repellency and surface hardness if necessary. Then, the nanocarbon composite infrared radiating ceramics according to the present embodiment are produced.

<Step of forming a packing layer or a coating layer on the surface of the infrared radiation layer>
In this step, resin is filled and coated so as to cover the pores or voids scattered on the surface of the infrared radiation layer. By this coating, a filling layer or a coating layer is formed on a part or the whole of the surface of the infrared radiation layer.

In the present invention, the material for forming the packing layer or the coating layer is not particularly limited, but it is preferable to use a material having an affinity for ceramic particles or a nanocarbon material. For example, a silicone resin or a fluororesin (including polytetrafluoroethylene) can be used. Further, a silane coupling agent, a silica sol and the like can also be used.

In this embodiment, a water-repellent silicone resin was used. As the silicone resin, a reactive silicone resin, a non-reactive silicone resin, or the like can be used. Further, when water repellency is particularly required, it is preferable to use a silicone resin having a dimethyl silicone-based main chain. In this embodiment, a reactive silicone resin having a dimethyl silicone as a main chain and a silanol group as a functional group was used. These resins form a water-repellent and hard film having a three-dimensional network structure by a dehydration condensation reaction of silanol groups.

The method of applying the resin to the infrared radiation layer is not particularly limited, but the resin liquid may be coated with a coater, a roller, a squeegee, a brush, or the like. Alternatively, the infrared radiation layer may be immersed in a bath of the resin liquid to dip the entire surface. By adjusting the viscosity of the resin liquid and the number of times of application, the thickness of the packing layer and the coating layer formed on the surface of the infrared radiation layer can be adjusted. In this way, the nanocarbon composite infrared radiating ceramics in which the filling layer and the coating layer are formed on the surface of the infrared radiating layer are completed.

The silicone resin film may mainly form a packed layer so as to cover only the pores or voids scattered on the surface of the infrared radiation layer. Further, the coating layer may be formed so as to cover the entire surface of the infrared radiation layer including the pores or voids.

FIG. 3 is an electron micrograph showing a state in which the surface of the infrared radiation ceramic intermediate is filled or coated with a silicone resin or the like. Comparing FIG. 3 with FIG. 1 described above, it can be seen that the silicone resin is filled and the surface is coated. Further, FIG. 4 is an image diagram showing a state in which the pores or voids appearing in the cross section of the infrared radiating ceramic intermediate are filled or coated with a silicone resin or the like. In FIG. 4, the portion drawn in black is the pore portion or the gap portion appearing in the cross section, and the portion drawn in gray is the covering portion extending over the filling portion.

In FIG. 4, (A) is a state in which the resin is partially filled inside, (B) is a state in which the resin is completely filled inside, and (C) is a state in which the resin is not filled inside and is one of the surfaces. A state in which the portion is covered, (D) is a state in which the resin is partially filled inside and a part of the surface is covered, and (E) is a state in which the resin is not filled in the inside and the entire surface is covered. F) shows a state in which the resin is filled in the entire interior and the entire surface is covered. As described above, although there are various states of being filled or coated with the resin, the effects of the present embodiment can be exhibited in all of these states.

Also, the amount of infrared radiation emitted by a substance is unique to the substance and depends on the surface material of the substance. Therefore, when the surface of the infrared radiation layer in which the nanocarbon material is uniformly dispersed is coated with a silicone resin, it is considered that the amount of infrared rays emitted unique to the silicone resin is exhibited. Then, the performance of the nanocarbon composite infrared radiation ceramics having high performance infrared radiation performance is deteriorated.

Therefore, the present inventors have completed the present invention by paying attention to the thickness of the packing layer or the coating layer covering the entire surface of the infrared radiation layer. Hereinafter, the relationship between the thickness of the packing layer or the coating layer and the infrared radiation performance will be described. First, a method for measuring the emissivity of infrared rays and a method for measuring the thickness of the resin layer by laser Raman spectroscopy will be described.

<Measurement of infrared emissivity>
In this embodiment, the infrared emissivity was measured by the method of the Japan Fine Ceramics Center (JFCC) (hereinafter referred to as "JFCC method"). This method uses a Fourier transform infrared spectrophotometer (FT-IR), which has less noise and better resolution than the conventional method of taking the emissivity ratio of a blackbody and a sample, and measures at room temperature. Made possible. The sample is irradiated with light in the infrared wavelength range (wavenumber range), and the reflected energy is captured in the integral class. It is based on the theory that absorbed energy and radiant energy are inversely equivalent. The total emissivity at the specified temperature is calculated from the spectrum at room temperature according to JIS R 1693-2. Since the JFCC method is known, the details of the measurement method will be omitted here.

<Measurement method of resin layer thickness by laser Raman spectroscopy>
First, using a laser Raman spectrophotometer (JASCO Corporation, NRS-5100), a plurality of nanocarbon composite infrared radiation ceramics in the horizontal direction (X-axis-Y-axis direction) and the depth direction (Z-axis direction) with respect to the surface vicinity. A three-dimensional lattice is formed by the scanning points of the above, and a Raman spectrum is obtained for these scanning points. Next, for each Raman spectrum obtained, a mapping operation (referred to as "first mapping operation" in the present invention) is performed using the peak height appearing in the vicinity of ^{2912 cm-1 (carbon-hydrogen bond: silicone, etc.).} conduct. Further, a mapping operation (referred to as "second mapping operation" in the present invention) is performed using the peak height appearing in the vicinity of 1581 cm- ^{1 (carbon material).}

The measurement conditions with the Laser Raman spectrophotometer are: excitation wavelength: 532 nm, laser intensity: 5 mW, measurement area: 20 μm x 20 μm (3 locations), objective lens: 100 times, spatial resolution: approximately 2 μm, horizontal direction (X-axis-). The measurement interval in the Y-axis direction was 2 μm (11 points × 11 points), and the measurement interval in the depth direction (Z-axis direction) was 2 μm (0 to 200 μm). In this embodiment, the scanning point ratio was obtained from the mapped data group using image processing software (ImageJ).

Specifically, a plurality of measurement regions (20 μm × 20 μm) of the sample in the horizontal direction (X-axis-Y-axis direction) and the depth direction (Z-axis direction) parallel to the vicinity of the surface, respectively. A three-dimensional lattice is formed by scanning points (points at which Raman spectra are measured). Next, the first mapping operation (silicone mapping) is performed using the peak height indicating the presence of the silicone resin from the Raman spectrum obtained at each scanning point. In addition, a second mapping operation (carbon mapping) is performed using the peak height indicating the presence of carbon from the Raman spectrum obtained at each scanning point.

From these mapping operations, the scanning points (resolution: approximately 2 μm range) in which the presence of the silicone resin can be confirmed in the depth direction (Z-axis direction) from the surface of the three-dimensional lattice are set as the surface scanning points, and these surfaces. The horizontal (X-axis-Y-axis) lattice plane where the scanning points are gathered is specified as the outermost surface of the sample (the plane that is greatly affected by the silicone resin and has a small contribution to infrared radiation). Further, the scanning points (resolution: approximately 2 μm range) in which the presence of carbon can be confirmed in the depth direction (Z-axis direction) from the surface of the three-dimensional lattice are set as effective scanning points, and these effective scanning points are in the horizontal direction. A lattice surface having 80% or more in the (X-axis-Y-axis direction) is specified as an effective surface of the sample (a surface having a small influence of the silicone resin and a large contribution to infrared radiation).

In the present embodiment, the distance from the outermost surface to the effective surface is specified as the thickness of the silicone resin layer. In the present embodiment, it is specified by the average value of the thicknesses of the silicone resin layers in the three measurement regions. In addition, when the thickness of the silicone resin layer (thickness of the filling layer or the coating layer) is 100 μm or less, preferably 10 μm or less, the present inventors do not emit infrared rays peculiar to the silicone resin applied to the surface. , It was confirmed that the high-performance infrared radiation performance of nanocarbon composite infrared radiation ceramics can be maintained.

Nanocarbon composite infrared radiation ceramics were produced by each step based on the above embodiment. In addition, the thickness and infrared radiation performance of the surface coating layer of the produced nanocarbon composite infrared radiation ceramics, and physical properties such as water repellency and surface hardness were measured.

(1) Preparation of Ceramic Substrate In this example, a ceramic substrate was prepared as follows.

<Step of adjusting ceramic slurry for substrate>
First, the cordierite-blended particles were prepared before preparing the ceramic slurry for the substrate. First, cordierite _{(2MgO · 2Al 2 O 3 ·} 5SiO 2) 15 wt%, fused silica 55 wt%, by blending Gairome clay 24 wt% and 6 wt% kaolin was adjusted dry powder. Next, 40% by weight of water was mixed with 2 kg of the dry powder, and pulverization and mixing was performed by wet preparation. Then, it was dehydrated to obtain a raw material cake (water content 19%) and dried at 50 ° C. to obtain cordierite-blended particles.

2 kg of the obtained cordierite-blended particles and 600 g of pure water containing a dispersant were put into a nylon pot mill (ball weight 3.2 kg) having a capacity of 10 L and kneaded for 62 hours to bring the cordierite-blended particles into water. The dispersed ceramic slurry for substrates was prepared.

<Process of adjusting molding material>
Next, the molding material was adjusted by adjusting the water content without adding a binder to the obtained mixed slurry to granulate.

<Process of preparing the preformed body>
Next, the molding material was put into a pressure molding machine equipped with a plaster mold, and a preformed body was prepared under a pressure of 1 kg / cm3.

<solidification process of preformed body>
Next, solidification of the preformed body was completed by firing solidification. As for the firing conditions, the temperature was raised to 1050 ° C. in the atmosphere for 6 hours, and the firing was performed at a temperature of 1050 ° C. for 0.5 hours. In this way, a ceramic substrate composed of only cordierite-blended particles was produced.

(2) Preparation of Infrared Radiating Ceramic Intermediate In this embodiment, the infrared radiating ceramic intermediate is manufactured by heat curing without firing. Specifically, a so-called ceramic adhesive (BX-83, manufactured by Asahi Chemical Co., Ltd.) was used as the ceramic particles. Further, as a nanocarbon material, in addition to multiwall carbon nanotubes (MWCNT) and graphene (GP), a nanocarbon-aqueous dispersion liquid (hereinafter referred to as “GTF dispersion liquid”) in which cellulose nanofibers (CNF) are uniformly dispersed is used. used. Hereinafter, the ceramic particles are represented by "ceramic adhesive", and the nanocarbon material is represented by "GTF". In this example, an infrared radiation ceramic intermediate was prepared in which the amount of GTF added to the ceramic adhesive was 1% by weight.

<Step of adjusting ceramic slurry for intermediate>
The ceramic adhesive used in this example had a solid content ratio of 80% by weight _{of silica (SiO 2} ), 11% by weight of _{alumina (Al 2} O _{3 ), 4.8% by weight of zirconia (ZrO 2} ), and calcium oxide (CaO). ) 4.2% by weight was used. A ceramic slurry composed of 17% by weight of water was prepared with respect to 83% by weight of these solids.

<Step of adjusting nanocarbon-aqueous dispersion liquid>
In this example, a predetermined amount of GTF (MWCNT 1.5% by weight, GP 0.5% by weight, CNF 0.12% by weight) is added to a wetting liquid containing a predetermined amount of deionized water and DMSO (Dimethyl Sulfoxide). The mixture was added and wetted for a predetermined time using a ball mill (filled with 50% of zirconia beads having a diameter of 20 mm). Next, the wet-treated GTF slurry was taken out, a predetermined amount of surfactant or the like was added thereto, and a bead mill (filled with 70% of zirconia beads having a diameter of 0.3 mm) was used to adjust the particle size distribution to D90 <50 nm. The dispersion treatment was carried out until it became complete, and a nanocarbon-aqueous dispersion liquid having a predetermined concentration was prepared.

Here, the concentration of the GTF dispersion liquid was adjusted in consideration of 1% by weight of the amount of GTF added to the ceramic adhesive (solid content). The materials used were CNT (MWCNT: manufactured by Nanocil, NC7000, diameter 9.5 nm, length 1.5 μm), GP (manufactured by Ito Graphite Industry Co., Ltd., expanded graphite dispersed and used, thickness 2 to 2). It was 5 nm, GP 3 to 8 sheets, and used in a size of 1 to 5 μm in width) and CNF (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Leocrysta, diameter 3 nm, length 5 μm or more).

<Step of adjusting mixed slurry>
The ceramic slurry prepared in each of the above steps and the nanocarbon-aqueous dispersion liquid were mixed to prepare a mixed slurry. In this example, since the viscosity of the ceramic adhesive is so high that a stirrer cannot be used, the mixed slurry was prepared using a mortar.

<Process of coating and solidifying on ceramic substrate>
Here, the mixed slurry prepared in the previous step was applied by brush coating to the surface of the ceramic substrate prepared in the above step. Next, after the ceramic substrate coated with the mixed slurry was dried, it was heated at a temperature of 200 ° C. for 1 hour to complete the solidification of the mixed slurry. In this example, a plurality of infrared radiating ceramic intermediates were prepared in order to change the coating amount of the silicone resin performed in the next step.

(3) Fabrication of Nanocarbon Composite Infrared Radiating Ceramics In this example, a plurality of infrared radiating ceramic intermediates prepared in the above step are filled and coated with a silicone resin to provide water repellency and surface surface. A series of nanocarbon composite infrared radiation ceramics with improved hardness are produced.

<Step of forming a packing layer or a coating layer on the surface of the infrared radiation layer>
Specifically, using a dehydration condensation type reactive silicone resin (KR-242A, manufactured by Shin-Etsu Chemical Co., Ltd.), the surface of the infrared radiation layer is brushed once, twice, and three times. Six samples having different coating amounts were prepared by changing the number of coatings up to 5, 5, and 10 coatings. Each sample after coating was heated at a temperature of 160 ° C. for 1 hour to complete the dehydration condensation reaction of the silicone resin. In this example, a total of 7 samples were prepared, 6 samples in which the amount of the silicone resin applied was changed and 1 sample in which the silicone resin was not applied.

(4) Confirmation of performance Next, the infrared emissivity of the seven samples prepared in the above step was measured by the JFCC method. The measurement of emissivity, wavenumber range 6000～400Cm ^-1 from the spectrum of the room (wavelength region 1.67～25Myuemu), and, wavenumber range 6000～1250Cm ^-1 of infrared (wavelength region 1.67～8Myuemu) The emissivity was measured. Table 1 shows the measured infrared emissivity (25 ° C.) values. FIG. 5 is an infrared spectrum of a part of the nanocarbon composite infrared radiating ceramics of this example (samples coated 5 times, 8 times, and 10 times) and the used silicone resin at 25 ° C. In addition, FIG. 5 also shows the infrared spectrum of a commercially available ceramic heater (existing product) for comparison. In FIG. 5, the horizontal axis is the wave number (wave number range 6000 to 400 cm ^-1 ), and the vertical axis is the infrared emissivity (%).

In the infrared spectrum of FIG. 5, the wave numbers measured for each of the samples coated 5 times (reference numeral 1), 8 times (reference numeral 2), and 10 times (reference numeral 3) despite the large amount of silicone resin applied. infrared emissivity of 80% or more in a range 6000~400cm ^-1, there almost 90% or more in the wavenumber range 6000~1250cm ^-1, shows a high degree of infrared radiation force. On the other hand, the infrared emissivity (reference numeral 4) of a commercially available ceramic heater (existing product) greatly decreases in ^{the wave number range of 6000 to 2000 cm -1.} Further, the infrared emissivity (reference numeral 5) of the silicone resin used for filling and coating in this embodiment shows a high emissivity at a specific wave number, but is significantly reduced in the ^{wave number range of 6000 to 4000 cm -1.} do. As described above, it can be seen that each of the samples coated 5 times, 8 times and 10 times is not affected by the silicone resin even though the surface is filled or coated with the silicon resin.

Further, for the prepared 7 samples, the distance from the outermost surface to the effective surface (thickness mainly of the silicone resin layer on the effective surface) was measured by the above-mentioned laser Raman spectroscopy. Table 1 shows the values of the distances from the outermost surface to the effective surface with respect to the prepared 7 samples. FIG. 6 shows an example (sample of 8 times of coating) of silicone 3D mapping (A) and carbon 3D mapping (B) when the nanocarbon composite infrared radiation ceramics of this example were measured by laser Raman spectroscopy. ..

In FIG. 6, it can be seen that the silicone layer is applied to the upper part of the carbon layer (B) by about 100 μm. Since the transparent silicone resin can be detected by the laser Raman spectroscopy, the distance from the outermost surface to the effective surface can be measured. However, carbon can be detected only about 10 μm, and cannot be detected when the amount of carbon increases. Therefore, the lower part of the map of FIGS. 6 (A) and 6 (B) cannot be detected.

In addition, for the prepared 7 samples, the physical property values were the value of the contact angle by the wetness test method (still drop method) of the substrate glass surface of JIS R3257 and the mechanical property (scratch) of the coating film of JIS K5600-5-4. The value of the surface hardness was measured by the hardness (pencil method). The measured values are shown in Table 1.

In Table 1, as the number of times the silicone resin is applied increases, the thickness of the packing layer or coating layer on the effective surface (thickness of the silicone resin layer) measured by laser Raman spectroscopy increases. If the thickness of the resin layer is 13μm or less, the infrared emissivity of 80% or more in the wavenumber range 6000～400Cm ^-1, shows a good value of 90% or more in the wavenumber range 6000~1250cm ^-1. On the other hand, when the thickness of the resin layer is 110 [mu] m, although the infrared emissivity in the wave number range 6000～1250Cm ^-1 is maintained at least 90%, the value of the infrared emissivity in the wave number range 6000～400Cm ^-1 is less than 80% And decrease.

From these facts, it is considered that when the thickness of the resin layer is 100 μm or less, the decrease in infrared emissivity due to the silicone resin covering the surface is suppressed to some extent, and a sufficient infrared emissivity can be obtained. Further, when the thickness of the resin layer is 10 μm or less, the decrease in infrared emissivity due to the silicone resin covering the surface is completely suppressed, and a very good infrared emissivity can be obtained.

The wettability (contact angle) of the surface is 90 ° or more in all the samples, indicating sufficient difficulty in wetting (water repellency). On the other hand, in terms of scratch hardness (surface hardness), the sample not coated is softer than 6B, whereas the sample coated once to three times greatly improves to 3H to 6H. However, as the number of coatings increases, the hardness decreases, and although HB is maintained by applying 5 times, it becomes softer than 6B by applying 8 times. It is considered that this is because the thickness of the silicone resin layer on the surface is increased to indicate the hardness of the silicone resin itself. From these facts, it is preferable to adjust the resistance to wetting (water repellency) and the scratch hardness (surface hardness) depending on the application of the nanocarbon composite infrared radiation ceramics.

As described above, according to the above embodiment, in order to improve the water repellency and surface hardness of the surface of the infrared radiator, fine pores or voids scattered on the surface are filled or covered. Even in this case, it is possible to provide nanocarbon composite infrared radiation ceramics having a high emissivity of infrared rays over a wide wave number range.

Claims (9)

A packing layer and / or a coating layer is formed on a part or the whole of the surface so as to cover the pores or voids scattered on the surface of the infrared radiation ceramic in which the nanocarbon material is uniformly dispersed in the ceramic.
Nanocarbon composite infrared radiating ceramics characterized in that the value of the infrared emissivity in the wave number range of 6000 to 400 cm ^{-1 at 25 ° C. measured by the JFCC method is 80% or more.} The nanocarbon composite infrared radiating ceramics according to claim 1, wherein the value of the infrared emissivity in the wave number range 6000 to 1250 cm ^{-1 measured by the JFCC method at 25 ° C. is 90% or more.} A three-dimensional lattice is formed by a plurality of scanning points in the horizontal direction (X-axis-Y-axis direction) and the depth direction (Z-axis direction) parallel to the surface of the infrared radiation ceramics by laser Raman spectroscopy.
The first mapping operation using the peak area indicating the presence of the material forming the packed bed and / or the coating layer from the Raman spectrum obtained at each scanning point and the second using the peak area indicating the presence of the carbon material. Perform mapping operations and
The scanning point at which the presence of the material forming the packed layer and / or the coating layer can be confirmed in the depth direction (Z-axis direction) from the surface of the three-dimensional lattice in the first mapping operation is defined as the surface scanning point. The horizontal (X-axis-Y-axis) lattice plane where the surface scanning points are gathered is defined as the outermost surface of the infrared radiation ceramics.
The scanning point at which the presence of the carbon material can be confirmed in the depth direction (Z-axis direction) from the surface of the three-dimensional lattice in the second mapping operation is set as an effective scanning point, and the effective scanning point is the horizontal direction (X). A lattice plane existing in 80% or more in the axis-Y-axis direction) is defined as an effective surface of the infrared radiation ceramics.
The nanocarbon composite infrared radiating ceramic according to claim 1 or 2, wherein the distance from the outermost surface to the effective surface is 100 μm or less. The nanocarbon composite infrared radiating ceramic according to claim 3, wherein the distance from the outermost surface to the effective surface is 10 μm or less. The packing layer and / or coating layer is mainly made of a silicone-based or fluorine-based water-repellent resin.
The nanocarbon composite according to any one of claims 1 to 4, wherein the value of the contact angle measured by the wettability test method (droplet method) of the substrate glass surface of JIS R3257 is 80 ° or more. Infrared radiation ceramics. Claims 1 to 1, wherein the value of the hardness of the surface including the coating layer and the packing layer measured by the mechanical properties (scratch hardness; pencil method) of the coating film of JIS K5600-5-4 is 2H or more. The nanocarbon composite infrared radiation ceramics according to any one of 5. The nanocarbon composite infrared radiating ceramics according to any one of claims 1 to 6, wherein the nanocarbon material is carbon nanotubes, carbon nanofibers, graphene, or a compound thereof. The nanocarbon composite infrared radiating ceramic according to claim 7, which contains cellulose nanofibers in addition to the nanocarbon material. The nanocarbon according to any one of claims 1 to 8, wherein the ceramic particles contain alumina, silica, zirconia, cordierite, or a compound thereof in an amount of 90% by weight or more. Composite infrared radiation ceramics.

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