JP2008162866A - Composite ceramic material for infrared emission, method for producing the same, member for cookware and rice cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite ceramic material for infrared emission having an excellent far-infrared absorptivity, and to provide a method for producing a composite ceramic material for infrared emission. <P>SOLUTION: The method for producing a composite ceramic material for infrared emission comprises: a stage where a carbon feeding material and a boride are allowed to exist in a nonoxidizing atmosphere, and ceramic particles are treated at 1,000 to 1,200°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a composite ceramic material for infrared radiation that can be used for cooking utensils, bedding and electrical appliances intended for far-infrared radiation, a method for producing the same, a member for cooking utensils using the composite ceramic material for infrared radiation, and It relates to rice cookers.

  Unless the temperature is as low as absolute zero (−273 ° C.), all materials emit electromagnetic waves such as far infrared rays, and the higher the temperature, the greater the amount of radiation (energy). Even at the same temperature, the amount of radiation varies depending on the type of material and its surface condition. Among these, ceramics are known to emit a lot of far infrared rays. Although metals emit a large amount of radiation, they are used as a reflector on the back of the heater because they reflect in reverse.

  Many substances except plastics around us (plastic paint, fiber, wood, rubber, food, etc.) absorb a lot of electromagnetic waves in the wavelength range of 2.5μm to 30μm (mainly far infrared region). Infrared rays are 0.78 μm to 3 μm).

Ceramics mainly absorb infrared rays in this wavelength region when heated. As for gas, air (N ₂ and O ₂ ) does not absorb far infrared rays so much, but carbon dioxide (CO ₂ ), water, and water vapor (H ₂ O) absorb far infrared rays.

  The energy of far infrared rays is almost absorbed from the skin surface of the human body to a depth of about 200 μm, and is converted into heat. The absorbed heat is efficiently transmitted to the inside (core) of the body by blood and the body warms up. Near infrared light penetrates from the skin surface to a depth of several millimeters. A method for authenticating an individual by using the near-infrared feature and examining the vein pattern inside the finger or palm with the near-infrared ray has been developed.

  Infrared emissivity can be cited as an index representing the degree of infrared radiation. Infrared emissivity is the amount of energy of infrared rays of a certain wavelength radiated from the surface of a substance at a certain temperature, and the amount of energy emitted from a black body (a virtual object that absorbs 100% of the energy given by radiation) at the same temperature. The ratio.

  The infrared emissivity is specific to a substance, and its size changes depending on the surface state and wavelength as well as the kind of the substance. Ceramics (for example, metal oxides) generally have high emissivity at wavelengths in the far-infrared region (approximately 70% to 90%), and can effectively radiate and transfer the applied energy, so they are widely used as far-infrared radiation materials. Has been.

  Conventionally, it has been a well-known fact that the far-infrared taste-enhancing effect on the food to be cooked, such as the surface of a gas stove or the inner surface of a cooking pan, so that a substance that emits far-infrared rays is given to the cooking utensil. However, it is often done in recent years. A carbon material is known as a material that emits infrared rays, and is applied to an inner pot of a rice cooker (Patent Document 1). In patent document 1, the invention which performed the fluororesin coat | court processing which contains the microparticles | fine-particles which radiate | emit the infrared rays of charcoal or bamboo charcoal on the inner pot inner surface of a rice cooker is proposed.

  However, although carbon materials are excellent in infrared radiation ability, physical properties may not be sufficient, so various composite materials have been proposed for the purpose of improving physical properties and the like.

  As the fine particles that emit infrared rays, various types of far-infrared ceramics are used, and most of them have a single composition (silica, alumina, zirconia, etc.).

  For example, Patent Document 2 proposes an invention in which a material having a far-infrared effect is applied to an inner layer on the surface of a cooking utensil or the like, and a coating containing a fluororesin is applied to an outer layer.

  As a conventional technique for producing such a composite ceramic material, a method of combining carbon with ceramic particles is disclosed (Patent Document 3).

The method of Patent Document 3 is a method of attaching spherical carbon fine particles to the surface of a ceramic powder.
JP 2000-287846 A JP 2003-276129 A JP-A-7-257920

  However, the method described in Patent Document 3 requires firing at a high temperature of 2000 ° C. or higher for production of the material, and high cost is required for production. Further, since the method described in Patent Document 3 does not aim at a material suitable for infrared radiation, sufficient infrared radiation has not been realized.

  This invention is made | formed in view of the said subject, and it aims at providing the composite ceramic material for infrared rays radiation excellent in the far-infrared absorptivity, and its manufacturing method.

  Another object of the present invention is to provide a cooking utensil member and a rice cooker to which the composite ceramic material for infrared radiation is applied.

Means and effects for solving the problems

  In order to solve the above-mentioned problems, the present inventors have intensively studied and as a result, have come up with the following invention. That is, the method for producing a composite ceramic material for infrared radiation of the present invention includes a step of treating ceramic particles at 1000 ° C. or more and 1200 ° C. or less in the presence of a carbon supply material and a boride in a non-oxidizing atmosphere. Features.

  Moreover, the composite ceramic material for infrared radiation of the present invention that solves the above-mentioned problems can be produced by the above method.

  That is, this is a method in which the ceramic particles are heat-treated in the presence of the carbon supply material, so that the carbon fine particles generated from the carbon supply material adhere to the surface of the ceramic particles. Here, by performing the heat treatment in the state of coexisting boride, the carbon fine particles can be attached to the surface of the ceramic particles without affecting the property of emitting infrared rays. Here, the said structure is realizable by setting the range of 1000 to 1200 degreeC as temperature conditions to heat. In other words, as in the prior art, when heating at 2000 ° C. or higher, the properties change due to the reaction with the carbon fine particles produced by the boride, or the boride dissolves in the ceramic particles. From this point of view, it becomes difficult to exhibit sufficient performance.

  When carbon is heated at 2000 ° C. or higher, crystallization of carbon fine particles proceeds and spherical fine particles are formed. On the other hand, according to the method of the present invention, amorphous particles, which can be referred to as bulk carbon particles, with a low degree of crystallization of generated carbon are generated.

  Here, the density, particle size, and particle size of carbon vary greatly depending on the raw material and the production method. For example, in addition to the heat treatment conditions, the substance changes into various forms depending on the presence / absence / type of element to be added. As a result, the carbon material has various forms such as a spherical shape, a lump shape, a powder shape, a thin film shape, and a fibrous shape. When the conventional heating at 2000 ° C. or higher is adopted, the particle size of the generated carbon fine particles is large on the order of μm and becomes spherical, so that the infrared absorption rate is low.

  Further, when the coexisting boride is within the temperature range of the method of the present invention, the chemical reaction between the carbon fine particles and the boride does not proceed, and the action of fixing the carbon fine particles to the surface of the ceramic particles can be exhibited.

  From the viewpoint of improving the infrared radiation ability of the manufactured composite ceramic material for infrared radiation, it is desirable that the non-oxidizing atmosphere contains one or more rare gases selected from the group consisting of argon, krypton and xenon.

The composite ceramic material for infrared radiation according to the present invention that solves the above-mentioned problems includes carbon fine particles having an average particle size of 100 nm or more and 300 nm or less,
Ceramic particles having a surface coated with the carbon fine particles and an average particle size larger than the carbon fine particles,
A boride is contained in the vicinity of a portion where the carbon fine particles and the ceramic particles are in contact with each other.

  The composite ceramic material for infrared radiation of the present invention is one of those produced by the above-described method, in which carbon fine particles are fixed (adhered) to the surface of the ceramic particles with a boride.

  The ceramic particles are preferably zirconium carbide, and the boride preferably contains boron and lanthanum. In particular, the carbon fine particles are preferably composed of amorphous carbon.

  Here, the mass ratio between the carbon fine particles and the zirconium carbide particles is preferably 5:95 to 8:92.

  The average particle size of the carbon fine particles is preferably 100 nm or more and 3000 nm or less. The composite ceramic material for infrared radiation of the present invention preferably has an average particle size of 0.5 μm or more and 10 μm or less.

  A member for a cooking utensil according to the present invention that solves the above-mentioned problems includes a base, a ceramic fine powder made of the above-mentioned composite ceramic material for infrared radiation, an inner layer that covers the base, and a fluororesin. And an outer layer to be coated.

  Further, another cooking utensil member of the present invention for solving the above-mentioned problems comprises a base, a ceramic fine powder comprising the composite ceramic material for infrared radiation according to any one of claims 2 to 8, and the ceramic fine powder. And a coating film containing the fluororesin to be dispersed and covering the substrate.

  The ceramic fine powder is preferably 10% by mass to 40% by mass based on the mass of the coating film.

  The cooking utensil member may be applied to the inner pot of a rice cooker.

  Hereinafter, the composite ceramic material for infrared radiation of the present invention and the manufacturing method thereof will be described in detail based on the embodiments. The composite ceramic material for infrared radiation of the present invention can be used by being contained (kneaded or the like) in a product to be applied or applied to the surface. For example, (1) cooking appliances such as rice cookers, ovens, frying pans, pans, refrigerators, (2) heating appliances (gas / petroleum / electric stoves, panel heaters, electric kotatsu, floor / wall heating, air conditioners, factory / Heating element of gymnasium / indoor pool / golf driving range, sauna, barn heating, etc.) (3) Infrared radiation fibers kneaded into fibers (applied to clothing, carpets, curtains, insoles, etc.) , Bedding (Mudless, bed pad, pillow, etc.), (4) Tile, ceramics, bath pots and other ceramic products, plastic products, (5) Industrial dryers (paints, printed materials, textile dyeing, ceramics) (6) Other industrial use (baking of rice crackers, roasting of coffee beans, heating of glass substrates for liquid crystal displays, etc.) ), (7) Sensors / measurements (infrared sensors, radiation thermometers, thermography, thermometers, security devices, sensor rides, infrared communications, etc.), (8) medical / bio (hyperthermia (cancer thermotherapy), infrared therapy devices, Applications such as laser scalpel and fundus image photography are conceivable. The surface of the composite ceramic material for infrared radiation according to the present embodiment is covered with amorphous carbon fine particles, and it can be expected that a chemical substance is adsorbed on the surface. Therefore, application as a deodorizing material that expects a deodorizing effect is also conceivable.

(Production method of composite ceramic material for infrared radiation)
The manufacturing method of the composite ceramic material for infrared radiation of this embodiment has the process (heat-processing process) of heat-processing ceramic particles.

  The heat treatment step is a step performed by heating the ceramic particles in the presence of the carbon feed material and the boride. This step is performed in a non-oxidizing atmosphere. The non-oxidizing atmosphere is not particularly limited, and examples thereof include a rare gas such as argon, krypton, xenon, and helium, and the presence of a gas capable of realizing a non-oxidizing atmosphere such as nitrogen and hydrogen, or a vacuum state. In particular, it is desirable to be in the presence of an inert gas such as a rare gas. Among the rare gases, the infrared radiation ability of the composite ceramic material for infrared radiation is improved by selecting one or more gas or mixed gas selected from the group consisting of argon, krypton and xenon.

  This process is a process processed in the temperature range of 1000 degreeC or more and 1200 degrees C or less. By making it into this temperature range, the properties of the generated carbon fine particles and boride are excellent. Specifically, the fine carbon particles and borides that are produced are in a form excellent in infrared radiation as described above.

  Although it does not specifically limit as ceramic particle | grains, Metal carbide, a metal oxide, metal nitride, for example, zirconium carbide, tungsten carbide, alumina, silica, and those complex oxides are mentioned. The particle size of the ceramic particles can be appropriately selected depending on the size of the composite ceramic material for infrared radiation of the present embodiment that is finally required. For example, when it is used in other products such as kneaded in the inner pot of a rice cooker or fiber, the size of the product (5 μm or less, 3 μm for applications kneaded in the inner pot or fiber of a rice cooker) The following can be selected appropriately.

  The carbon supply material is not particularly limited as long as it is a material that is carbonized under a heating condition of 1000 ° C. or higher and 1200 ° C. or lower, but it is preferably a gas or liquid. In particular, it is desirable that the material be gasified under the above heating conditions. For example, hydrocarbon gases such as butane, propane, and methane, and alcohols such as methanol and ethanol can be used.

  The carbon fine particles to be produced preferably have a small particle size. For example, the particle size is desirably 300 nm or less, particularly 200 nm or less. Examples of a method for reducing the particle size include a method of increasing the cooling rate from the maximum temperature to around 800 ° C. (50 to 100 ° C./min).

The boride is not particularly limited. For example, a metal boride is mentioned. Metal boride is a chemically stable compound having a high melting point, hardness, thermal conductivity, and electrical conductivity. Among them, rare earth borides represented by LaB ₆ and CeB ₆ have excellent thermal and electrical conductivity. LaB ₆ and CeB ₆ are known to exhibit thermionic emission (emission characteristics), such as semiconductors (EuB ₆ , V ₆ B ₆ ), heat conduction (VB ₆ ), and ferromagnetism (EuB ₆ ). LaB ₆ is a conductive ceramic composite material that is particularly excellent in thermionic emission characteristics. In addition, as borides, rare earth borides (RB ₂ , RB ₄ , RB ₆ , RB ₁₂ (R is a rare earth: Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy Ho, Er, Tm, Yb and Lu): Among them, preferred examples include lanthanum boride, calcium boride, etc.), borax, boride and the like. In the present invention, lanthanum boride is particularly desirable.

(Composite ceramic materials for infrared radiation)
The composite ceramic material for infrared radiation of this embodiment has ceramic particles and carbon fine particles covering the surface of the ceramic particles. There is a boride between the ceramic particles and the carbon fine particles. Here, as the ceramic particles, the carbon fine particles, and the boride, the same ones as those described in the above-described manufacturing method can be adopted, and the description thereof is omitted here.

  The abundance ratio between the ceramic particles and the carbon fine particles has an appropriate value depending on the particle size and specific surface area of the ceramic particles. That is, it is desirable to have the carbon fine particles so that the surface of the ceramic particles can be covered without gaps. Ceramic particles are larger than the particle size of carbon fine particles.

  The amount of boride is not particularly limited, but the preferred amount depends on the specific surface area of the ceramic particles, and is desirably an amount that can sufficiently bond the carbon fine particles to the surface of the ceramic particles.

  Hereinafter, a specific description of a method for producing a far-infrared radiation composite ceramic material of the present invention and a comparison between the composite ceramic material and a general ceramic material will be given.

(Manufacturing)
While supplying butane gas as a carbon feed material, a mixture of zirconium carbide (average particle size: 1 μm: 100 parts by mass) and lanthanum boride (average particle size: 1 μm: 15 parts by mass or less) as ceramic particles (in advance, a power mill ( Was mixed with a thin plate on a ceramic plate and heated.

  The heating conditions were 1000 ° C. or higher and 1200 ° C. or lower. The mixture was heated in a hydrogen gas atmosphere, and after reaching the set temperature, butane gas was supplied and treated for 45 minutes.

  The amount of butane gas supplied was 2% by mass or more (preferably 3% by mass or more and 4% by mass or less) with respect to zirconium carbide. Actually, since the butane gas concentration differs depending on the space of the atmosphere furnace in which these are sintered, the gas corresponding to the replacement of the hydrogen gas staying in the furnace space with the butane gas was continued.

  After the butane gas injection, the atmosphere furnace was quenched. When enough butane gas was sent, the inflow of air into the furnace caused an oxidation (ignition) phenomenon of unburned carbon, so the gas inflow was stopped immediately.

  This is because if the cooling rate in the furnace is slow, the crystallization of carbon proceeds, so that graphite particles called so-called graphite are generated, and the absorption characteristics of far-infrared rays are deteriorated.

  Therefore, the cooling rate until the temperature reaches 400 ° C. or lower, which is a safe temperature at which carbon does not reignite, is set to 50 ° C./min or higher. For this forced cooling method, an air cooling method was adopted. The cooling method may be other than the air cooling method as long as it can be rapidly cooled to a safe temperature.

  As said manufacturing method, the particle diameter of the carbon fine particle to produce | generate was changed by changing conditions. As a condition for reducing the particle size of the carbon fine particles, a cooling rate of 1200 ° C. to 800 ° C. is increased (for example, 50 to 100 ° C./min).

  Infrared emissivity was measured for each manufactured sample 50 × 50 × 1.5 mm. Specifically, the black body and the sample were set to the same temperature (140 ° C.), and each far infrared ray emitted therefrom was measured by FT-IR. (An ideal black body is an ideal radiator that emits 100% of all wavelengths. Since it does not actually exist, the one close to the ideal black body was used.) The amount of far-infrared emitted from the sample with respect to the amount of far-infrared was calculated and used as the far-infrared emissivity. The Far-Infrared Association has established a standard for far-infrared processing that there is a far-infrared emissivity difference of 5% or more in the entire wavelength range and 10% or more in the specific wavelength range compared to the unprocessed product.

  FIG. 1 shows the measurement results of the carbon fine particles having a small particle diameter (Example 1), and FIG. 2 shows the carbon fine particles having a large particle diameter (Example 2). And the SEM photograph of the sample of Example 1 is shown in FIG. It became clear that massive carbon fine particles (the carbon fine particles of Example 1 have a smaller particle size) were attached as compared to the surface of zirconium carbide of Comparative Example 1 described later.

  And as a far-infrared emissivity, the average value of the far-infrared emissivity of wavelength 4.0-14 micrometers was calculated | required about each. Those with a small particle diameter have a far-infrared emissivity of 94.5% and those with a large particle size of 92%. From this, both particle diameters are far-infrared emissivities close to a black body, and it seems that the far-infrared emissivity is higher when the particle diameter is smaller.

  Zirconium carbide (Comparative Example 1), Alumina (Comparative Example 2), Titanium Oxide (Comparative Example 3), Silica (Comparative Example 4) , Silicon carbide (Comparative Example 5), charcoal (Comparative Example 6), diamond (Comparative Example 7), and aluminum (Comparative Example 8) were measured for far-infrared emissivity in a single state. The measurement result charts are shown in FIGS. The average values of the far-infrared emissivities are 88% for zirconium carbide, 86% for alumina, 58% for titanium oxide, 79% for silica, 86% for silicon carbide, 92% for charcoal, and 86% for diamond. Aluminum was 60%. In particular, an SEM photograph of the sample in Comparative Example 1 is shown in FIG.

  As is apparent from this result, it was found that the composite ceramic material for infrared radiation of this example showed high infrared radiation. In particular, the test sample of Example 1 in which the particle size of the carbon microparticles is small has an effect that surpasses that of charcoal.

  And the infrared radiation composite ceramic material of a present Example has not only the radiant heat transfer which is the heat transfer by a far-infrared ray, but also has the heat transfer effect by a conductive heat transfer as a characteristic of a boride. That is, the heating effect by two types of heat transfer effects can be expected.

2 is an IR chart showing infrared emissivity in a composite ceramic material for infrared radiation of Example 1 (one having a small particle size of carbon fine particles). 6 is an IR chart showing the infrared emissivity of the composite ceramic material for infrared radiation of Example 2 (one having a large particle size of carbon fine particles). 2 is an SEM photograph of the composite ceramic material for infrared radiation of Example 1. It is IR chart which shows the infrared emissivity of the comparative example 1 (zirconium carbide). It is IR chart which shows the infrared emissivity of the comparative example 2 (alumina). It is IR chart which shows the infrared emissivity of the comparative example 3 (titanium oxide). It is IR chart which shows the infrared emissivity of the comparative example 4 (silica). It is IR chart which shows the infrared emissivity of the comparative example 5 (silicon carbide). It is IR chart which shows the infrared emissivity of the comparative example 6 (charcoal). It is IR chart which shows the infrared emissivity of the comparative example 7 (diamond). It is IR chart which shows the infrared emissivity of the comparative example 8 (aluminum). 4 is an SEM photograph of a composite ceramic material for infrared radiation of Comparative Example 1.

Claims (13)

  A method for producing a composite ceramic material for infrared radiation, comprising a step of treating ceramic particles at 1000 ° C. or more and 1200 ° C. or less in the presence of a carbon feed material and a boride in a non-oxidizing atmosphere.   The method for producing a composite ceramic material for infrared radiation according to claim 1, wherein the non-oxidizing atmosphere contains one or more rare gases selected from the group consisting of argon, krypton, and xenon.   The composite ceramic material for infrared radiation which has the said ceramic particle and the carbon fine particle which covers the circumference | surroundings of this ceramic particle, and can be manufactured with the manufacturing method of Claim 1 or 2. Carbon fine particles having an average particle diameter of 100 nm or more and 300 nm or less;
Ceramic particles having a surface coated with the carbon fine particles and an average particle size larger than the carbon fine particles,
A composite ceramic material for infrared radiation, comprising a boride in the vicinity of a portion in contact with the carbon fine particles and the ceramic particles. The ceramic particles are zirconium carbide,
The composite ceramic material for infrared radiation according to claim 2, wherein the boride contains boron and lanthanum.   The composite ceramic material for infrared radiation according to any one of claims 3 to 5, wherein the carbon fine particles are composed of amorphous carbon.   The composite ceramic material for infrared radiation according to claim 5 or 6, wherein a mass ratio of the carbon fine particles to the zirconium carbide particles is 5:95 to 8:92.   The composite particle material for infrared radiation according to any one of claims 2 to 7, wherein the carbon fine particles have an average particle size of 100 nm or more and 3000 nm or less.   The composite ceramic material for infrared radiation according to any one of claims 2 to 8, wherein the average particle size is 0.5 µm or more and 10 µm or less. A substrate;
A film comprising a ceramic fine powder comprising the composite ceramic material for infrared radiation according to any one of claims 2 to 9 and comprising an inner layer covering the substrate and an outer layer containing a fluororesin and covering the inner layer When,
A member for cooking utensils characterized by comprising: A substrate;
Ceramic fine powder comprising the composite ceramic material for infrared radiation according to any one of claims 2 to 9,
A coating containing a fluororesin in which the ceramic fine powder is dispersed and covering the substrate;
A member for cooking utensils characterized by comprising:   The said ceramic fine powder is 10 mass%-40 mass% on the basis of the mass of the said film, The member for cooking appliances of Claim 10 or 11.   A rice cooker having an inner pot made of the cooking utensil member according to claim 10.

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