JP2011236070A - Filter for warming fluid and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter for warming a fluid, which can stably raise the temperature of the fluid within a short time, and a method for manufacturing the same.SOLUTION: The filter for warming a fluid comprises silicon and silicon carbide and is heated by microwave upon use.

Description

  The present invention relates to a fluid temperature raising filter and a method for producing the same. More specifically, the present invention relates to a fluid temperature increasing filter that can raise the temperature of a fluid stably and in a short time, and a method for manufacturing the same.

  Conventionally, silicon carbide sintered bodies have been used as various materials for high temperatures because they have excellent heat resistance, thermal conductivity, electrical conductivity, and chemical stability. In particular, porous silicon carbide sintered bodies in which the structure of the silicon carbide sintered body is porous are used in the fields of catalyst carriers, high-temperature gas purification filters, molten metal filtration filters, breathable heat insulating materials, and the like.

  For example, Patent Document 1 discloses a method for manufacturing a ceramic porous body in which a silicon carbide powder slurry is impregnated into a sponge, sintered, and then melt impregnated with silicon.

  Non-Patent Document 1 discloses that an iron oxide composite powder that absorbs microwaves and generates heat is attached to urethane foam, and then fired to produce a ceramic foam. The heat generation characteristics when microwaves of 80, 200 and 600 W are irradiated inside, and the heat removal effect when carbon black is deposited on the ceramic foam and then irradiated with microwaves are shown.

JP 2000-109376 (April 18, 2000)

Hiroaki Katsaki, “Development of hazardous substance removal system by electrochemical process”, Saga Ceramic Technology Center, 2005 Business Report 2005

  However, in the method for producing a ceramic porous body disclosed in Patent Document 1, since silicon carbide is basically sintered using a silicon carbide slurry, the ceramic porous body obtained by the production method is If the bulk density is less than 0.3, the strength is insufficient, and the preferred bulk density is 0.45 to 0.6. Therefore, the ceramic porous body obtained by the method for producing a ceramic porous body disclosed in Patent Document 1 has a low bulk density and a thin and uniform skeleton structure, and the strength is insufficient. When there is no problem in strength, the bulk density becomes high, the skeleton portion is thick, and there are many collapsed pore portions. Therefore, when heated by microwaves, the temperature does not rise stably throughout.

  Moreover, in the fluid temperature rising filter shown in Non-Patent Document 1, the temperature rises by 200 ° C. in 100 seconds, and the temperature rising rate is slow.

  An object of the present invention is to provide a fluid temperature increasing filter capable of stably increasing the temperature of a fluid in a short time and a method for manufacturing the same. In the fluid temperature raising filter of the present invention, the temperature rises by about 200 ° C. in 10 seconds.

  In view of the above problems, the present inventor has intensively studied the reason why the ceramic porous body disclosed in Patent Document 1 cannot be used for raising the temperature of the fluid from an original viewpoint.

  A sponge-like three-dimensional structure is most suitable as a heater structure for raising the temperature of the entire fluid. As a silicon carbide porous body having a sponge-like three-dimensional structure, there is a ceramic porous body disclosed in Patent Document 1. The ceramic porous body is obtained by attaching a silicon carbide powder slurry to a polyurethane sponge and sintering the silicon carbide powder. In order to increase the sintering strength, the amount of silicon carbide powder adhering to the sponge surface is required to some extent. Therefore, the adhering slurry cannot be sufficiently squeezed, the skeleton is thick, and the porosity is as low as 85%. There are many cells that collapse. Further, when the cell is crushed, the heat capacity of the portion becomes large, the temperature rise becomes uneven, the microwave cannot enter the inside, and the pressure loss becomes large.

  In addition, the ceramic porous body disclosed in Patent Document 1 often has silicon carbide aggregated, and when silicon carbide is aggregated (not a uniform thin skeleton), heating by microwaves (hereinafter referred to as the “porous ceramic body”) , Also referred to as microwave heating), heat generation is low.

  Note that the corrugated board structure has only a microwave effect on the surface and has a planar structure, so that the electrical resistance is low and the amount of heat generated is small. On the other hand, in the case of a sponge-like porous body, since the skeleton is thin and uniform, the electric resistance is also uniform, and microwaves can enter inside (heating is performed not only on the surface of the porous body but also inside). Moreover, in the resistance heating element having the sponge structure, it is necessary to fix the electrode part. However, since the stress is easily applied to the low-strength porous heating element part, it is difficult to fix the electrode part.

  As a result of intensive studies in view of the above, the present inventor has made it possible to maintain a state in which silicon carbide is dispersed in silicon by allowing silicon to exist together with silicon carbide, and to provide a porous material with low bulk density and strength. A porous body having a uniform skeleton, and when a filter in which silicon carbide is present together with silicon is heated by microwaves, the temperature is stable over the entire filter. The inventors have found that the temperature rises and that the heated filter stably maintains its high temperature state, and have completed the present invention.

  That is, in order to solve the above problems, the fluid temperature rising filter of the present invention has a thin skeleton and a uniform cell diameter, contains silicon and silicon carbide, and is heated by microwaves and used. It is characterized by.

  According to the above configuration, since both silicon and silicon carbide are contained, it is possible to maintain a state in which silicon carbide is dispersed in silicon. Thereby, silicon carbide can exist throughout the filter.

  As a result, the temperature of the fluid temperature rising filter of the present invention is stably increased by the microwave heating, and the heated filter stably maintains the high temperature state. Therefore, the fluid temperature raising filter of the present invention can raise the temperature of the fluid stably and in a short time, and therefore can be used for raising the temperature of the fluid.

  Furthermore, since the silicon carbide self-heats by microwave heating, the fluid temperature rising filter of the present invention can raise the temperature of the fluid in a short time.

Moreover, filters for fluid heating of the present invention has a bulk density of higher than 0.05 g / cm ^3, preferably in the range of less than 0.3 g / cm ^3.

  As a result, the fluid temperature raising filter of the present invention is lightweight and can reduce pressure loss.

  In the fluid temperature rising filter of the present invention, the silicon carbide content relative to the whole is preferably in the range of 20 wt% or more and 90 wt% or less. In addition, the one where content of the said silicon carbide is large is preferable. Further, the smaller the skeleton thickness is, the more uniformly it is heated.

  Thus, in the fluid temperature rising filter of the present invention, the silicon carbide absorbs microwaves by microwave heating. As a result, the temperature of the fluid temperature rising filter of the present invention rises more stably over the entire filter by microwave heating, and maintains the high temperature state more stably.

  In the fluid temperature increasing filter of the present invention, the silicon content relative to the whole is preferably in the range of 10 wt% to 80 wt%.

  Thereby, the filter for raising the temperature of the fluid according to the present invention can easily maintain a state in which silicon carbide is dispersed in silicon. In addition, since the skeleton is thin, microwaves easily enter the inside, and the temperature is raised by resistance heating, so that heat is easily generated. As a result, the temperature of the fluid temperature rising filter of the present invention rises more stably over the entire filter by microwave heating, and maintains the high temperature state more stably.

  In order to avoid arc discharge, the fluid temperature rising filter of the present invention is preferably coated with a material having high electrical resistance such as oxide so as to increase electrical resistance. If the silicon layer is oxidized, it is covered with a silicon oxide layer. However, when an oxide other than silicon oxide is covered, the silicon layer may be oxidized to improve wettability. preferable.

  In the fluid temperature rising filter of the present invention, when metallic silicon is present on the surface of the filter, arc discharge may occur. Thus, arc discharge can be prevented by oxidizing the surface of the filter. This oxidation treatment can be easily formed by firing in air at a temperature of about 300 ° C. or higher. Moreover, since the surface becomes hydrophilic by this oxidation treatment, the corrosion resistance and oxidation resistance can be improved by further coating with alumina, titanium oxide or the like.

  Further, the fluid temperature rising filter of the present invention is a silicon carbide based porous structure having a sponge-like three-dimensional skeleton made of ceramics containing silicon carbide and continuous pores formed between the three-dimensional skeleton. And a metal silicon layer formed on the surface of the three-dimensional skeleton containing the silicon, and a silicon oxide layer formed by oxidizing at least a part of the metal silicon layer.

  Further, in the method for producing a fluid temperature rising filter of the present invention, it is preferable to further mix silicon carbide powder with a slurry containing a resin serving as a carbon source and silicon powder.

  Conventionally, a filter containing silicon carbide has been manufactured by immersing a polyurethane sponge in a slurry of silicon carbide powder, attaching an excess slurry to the surface of the polyurethane sponge, and sintering the powder. In order for the strength of the sintered body to be sufficiently high, an excess slurry is required. For this reason, the polyurethane skeleton becomes thick and many crushed cells exist. In this case, since the skeleton structure is not uniform, when microwave heating is performed, the temperature rise is not uniform, and the microwave cannot penetrate into the inside.

  In the method for producing a fluid temperature rising filter according to the present invention, the silicon carbide powder is mixed with the slurry containing the resin serving as the carbon source and the silicon powder, or further, the silicon carbide content is increased. be able to. The silicon powder is preferably a fine powder having an average particle size of 30 μm or less. Those having a large particle size are preferably used after being pulverized by a ball mill or the like. A slurry obtained by further mixing silicon carbide powder with a slurry containing resin and silicon powder can also be used. The silicon carbide powder has an average particle size of 10 μm or less, preferably 5 μm or less. Moreover, it is preferable that the weight of the silicon carbide powder is within a range of 3 times the weight of the silicon powder. If the weight of the silicon carbide powder exceeds 3 times the weight of the silicon powder, mixing may be insufficient.

  Further, after impregnation with the slurry, the cell can be tightly squeezed so as not to be crushed by the slurry. After carbonization, it becomes a porous carbonaceous structure having the same skeleton structure as the polyurethane skeleton. Then, carbon from the resin and silicon powder react and sinter into porous silicon carbide. If the pores in this skeleton are further melt impregnated with silicon and reacted with excess carbon, it becomes dense silicon carbide, and the excess silicon fills the pores in the skeleton and densifies the skeleton part. A skeleton having the same thickness as the sponge, but a dense and high-strength porous body can be obtained. On the other hand, in the conventional sintering method, since the silicon carbide powder is sintered, the strength is drastically reduced if the silicon carbide adhesion amount is small.

  As a result, it is possible to manufacture a filter whose temperature rises due to microwave heating by the method for manufacturing a filter for heating fluid according to the present invention.

  In the method for producing a fluid temperature rising filter of the present invention, it is preferable that the slurry further contains alcohol or the like as a solvent. Water or alcohol may be used as long as the solvent dissolves the resin. As the resin that is a carbon source, a resin that dissolves in a solvent to form a solution can be used, and examples thereof include phenol resins, furan resins, and organometallic polymers such as polycarbosilane. One kind selected from these may be used, or a plurality of kinds may be mixed and used. Further, carbon powder, graphite powder, carbon black or the like may be added as an additive.

  Thereby, the method for producing the fluid temperature rising filter of the present invention is added to the silicon carbide produced by the reaction between the carbon atom obtained by carbonizing the phenol resin in the slurry and silicon, or further added to the slurry. Since the silicon carbide powder can be contained, it is possible to produce a filter whose temperature is further increased by microwave heating.

In addition, the method for producing a fluid temperature rising filter of the present invention includes impregnating the above-mentioned slurry into a sponge made of polyurethane, polyethylene or rubber, and squeezing and drying the slurry liquid to such an extent that the continuous pores are not blocked. An impregnation step for forming a sponge-like porous body, a carbonization step for carbonizing the sponge-like porous body to form a carbonized porous body, and the silicon powder for the carbonized porous body. It comprises a firing step in which carbon is reacted and sintered, followed by a melt impregnation step in which silicon for melt impregnation is further melt impregnated. The obtained silicon / silicon carbide porous body is oxidized at 300 ° C. or higher in the air to form a silicon oxide (SiO ₂ ) layer on the surface, thereby preventing arc discharge.

  Thereby, since the manufacturing method of the fluid temperature rising filter of the present invention includes the impregnation step, silicon and silicon carbide can be contained even inside the sponge. Moreover, since the slurry liquid is squeezed to such an extent that the slurry liquid does not block the continuous pores, the cell is hardly crushed by excess slurry. As a result, the method for producing a fluid temperature rising filter of the present invention becomes a porous material having a uniform thin skeleton, and it is possible to produce a filter whose temperature is further increased by microwave heating.

  Further, in the method for producing a fluid temperature rising filter of the present invention, at least a part of the metal silicon layer formed on the surface of the three-dimensional skeleton in the melt impregnation step is oxidized, and the silicon oxide layer is formed on the three-dimensional skeleton. It is preferable to further include an oxidation step for forming.

  As described above, the fluid temperature rising filter of the present invention contains silicon and silicon carbide, and is used by being heated by microwaves. In addition, it is preferable that the filter for temperature rising of this invention is preventing the discharge by oxidizing the surface.

  Therefore, the fluid temperature increasing filter of the present invention has an effect that the temperature of the fluid can be stably increased in a short time.

It is a figure which shows the external appearance of the filter for fluid temperature rising containing the silicon | silicone and silicon carbide in one Example of this invention. It is a graph which shows the temperature fall process after the microwave irradiation in one Example (heating for 10 second with a 13 mesh filter) of this invention. It is a graph which shows the temperature-fall process after microwave irradiation in one Example (10-second heating with an 8 mesh filter) of this invention. It is a graph which shows the temperature fall process after the microwave irradiation in one Example (heating for 5 seconds with an 8 mesh filter) of this invention.

  One embodiment of the present invention will be described in detail below, but the scope of the present invention is not limited to these explanations, and modifications other than the following exemplifications are made as appropriate without departing from the spirit of the present invention. Can be implemented. Specifically, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

<Fluid temperature rising filter of the present invention (structure)>
The fluid temperature rising (porous) filter of the present invention contains silicon and silicon carbide. The fluid temperature increasing filter of the present invention is used after being heated by microwaves. Moreover, filters for fluid heating of the present invention has a bulk density of higher than 0.05 g / cm ^3, preferably in the range of less than 0.3 g / cm ^3. In the fluid temperature rising filter of the present invention, the silicon carbide content relative to the whole is preferably in the range of 20 wt% or more and 90 wt% or less. In the fluid temperature increasing filter of the present invention, the silicon content relative to the whole is preferably in the range of 10 wt% to 80 wt%.

<Fluid used in the present invention>
In the fluid temperature rising filter (structure) of the present invention, as the fluid (substance passed through the filter), soot generated during idling of gas, particularly diesel exhaust gas, VOC (Volatile Organic Compounds), Examples include liquids.

<Silicon carbide used in the present invention>
The fluid temperature rising filter of the present invention contains silicon carbide (SiC). The content of the silicon carbide with respect to the entire filter is preferably in the range of 20% by weight to 90% by weight.

  The silicon carbide used in the present invention is preferably a powder having a particle size of 10 μm or less, preferably 5 μm or less. In addition, what has a large particle diameter should just pulverize and pulverize with a ball mill etc.

  Here, the silicon carbide powder is a mixture with at least one substance selected from the group consisting of magnesium, aluminum, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, niobium, molybdenum and tungsten. It can also be used.

  Silicon carbide has advantages such as being lightweight, having heat resistance, and being excellent in wear resistance and corrosion resistance.

<Silicon used in the present invention>
The fluid temperature rising filter of the present invention contains silicon (Si). The content of the silicon with respect to the entire filter is preferably in the range of 10% by weight to 80% by weight, and more preferably in the range of 30% by weight to 60% by weight.

Note that it is difficult to produce a lightweight sponge-like porous body having a bulk density of about 0.1 g / cm ³ with silicon carbide alone, and such an ultralight porous body contains free silicon.

  The slurry silicon used in the present invention is preferably a powder having a particle size of 10 μm or less. In addition, what has a large particle diameter should just pulverize and pulverize with a ball mill etc.

  Here, the silicon powder is used as a mixture with at least one substance selected from the group consisting of magnesium, aluminum, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, niobium, molybdenum and tungsten. You can also.

<Weight ratio (weight ratio) of silicon carbide to silicon in the slurry used in the present invention>
The mixing ratio of the resin and the silicon powder in the slurry is preferably in the range of Si / C = 0.05 to 5.00 in terms of atomic ratio. If this atomic ratio is less than 0.05, the amount of porous silicon carbide produced by reaction sintering is reduced, which is not practical as a heating element. On the other hand, when the atomic ratio exceeds 5.00, the amount of silicon powder in the slurry increases, and precipitation tends to occur.

  The weight ratio (weight ratio) of silicon carbide to silicon used in the present invention is preferably in the range of 0.1 or more and 3 or less, and more preferably in the range of 0.5 or more and 2 or less. . If the weight of the silicon carbide powder exceeds 3 times the weight of the silicon powder, mixing may be insufficient.

<Microwave heating in the present invention>
The microwave heating in the present invention means that heat is generated from the inside of the material to be heated by the interaction between the microwave and the material to be heated. The heat is generated because charged particles, electric dipoles, and the like in the heated material rotate or vibrate due to the influence of an oscillating electromagnetic field caused by microwaves.

  A substance having electrical conductivity such as silicon carbide is heated by induction by absorption of microwaves by a resistance component. However, a material having high electrical conductivity such as a metal shorts the electric field near the surface, and thus discharge occurs near the surface. On the other hand, the insulator is dielectrically heated by dielectric loss.

  Note that the thinner the skeleton of the object to be heated, the easier it is for microwaves to enter, so it is considered that the object to be heated can be heated.

  If silicon carbide is contained, microwave heating is possible. In the case of silicon carbide, the temperature rises by induction heating (Joule heating). On the other hand, in the case of water, the temperature rises due to dielectric heating. Furthermore, the uniform and thin silicon carbide skeleton is suitable for uniform heating.

  The microwave heating in the present invention is performed by irradiating the microwave absorbing material with microwaves. When the microwave absorbing material is irradiated with microwaves, the microwave absorbing material is heated by self-heating (self-heating).

  The microwave heating in the present invention is not particularly limited as long as it is a method of heating using microwaves, and examples thereof include heating in a (household) microwave oven. In the case of microwave heating in a home microwave oven, the microwave irradiation in the microwave oven is non-uniform, so the temperature rise effect will vary slightly depending on the location and placement in the home microwave oven. However, rapid heating at 100 ° C. is possible, for example, by irradiating a 500 W microwave for 10 seconds.

  When microwave heating is performed on the filter containing silicon and silicon carbide of the present invention, the temperature of the filter itself increases (self-heats). Specific examples of self-heating in the filter will be described later.

<Microwave Absorbing Substance in the Present Invention>
Silicon carbide is used as the microwave absorbing material in the present invention.

<Filter after microwave heating>
In the filter after microwave heating, if metallic silicon is present on the surface, there is a risk of arc discharge if it is left as it is. Therefore, by oxidizing the surface, it is possible to reduce electrical conductivity and prevent arc discharge.

  Examples of the method for oxidizing the surface include a method of heating in an electric furnace at a temperature in the range of 300 ° C. to 1200 ° C. in air. The holding time may be short (or none). The heating temperature is optimally in the range of 600 ° C. or higher and 800 ° C. or lower.

Here, the method for oxidizing the surface suppresses arc discharge by heat-oxidizing the surface to form a thin silica (silicon dioxide / SiO ₂ ) layer of several tens of μm on the surface. .

<Antioxidant in the present invention>
As described above, in the filter after microwave heating, the surface of the filter may be oxidized in order to prevent arc discharge.

  Therefore, in order to suppress arc discharge, the surface of the filter of the present invention is preferably coated (coated) with an oxidizing agent such as alumina, silica, mullite, titanium oxide, silicon carbide, or silicon nitride. Further, the coating agent may be various catalysts or microwave absorbing materials such as iron oxide.

  The method of coating the oxidation-resistant agent is not particularly limited, and examples thereof include a method of coating various sols such as alumina sol and solutions of organosilicon compounds such as polycarbosilane. Examples of the method for coating the solution include dip coating, chemical vapor deposition (CVD), and sputtering.

  In the case of containing silicon and silicon carbide, arc discharge is generated because silicon has high conductivity. (Silicon carbide is a semiconductor and has electrical conductivity but is not considered to cause arc discharge. On the other hand, silicon is considered to cause arc discharge because of its low resistance.) To suppress this, surface resistance Need to be a little higher. (There is no need to increase the resistance of the surface until it becomes an insulator.) To that end, the surface may be oxidized to a silica layer.

<Method for Producing Fluid Temperature Raising Filter of the Present Invention>
In the method for producing a fluid temperature rising filter of the present invention, it is preferable to mix silicon carbide powder into a slurry containing silicon powder. In the method for producing a fluid temperature raising filter of the present invention, it is preferable that the slurry further contains a resin and a solvent.

  As the resin that is a carbon source, a resin that dissolves in a solvent to form a solution can be used, and examples thereof include phenol resins, furan resins, and organometallic polymers such as polycarbosilane. One kind selected from these may be used, or a plurality of kinds may be mixed and used. Carbon powder, graphite powder, carbon black, etc. may be added as additives, and silicon nitride, zirconia, zircon, alumina, silica, mullite, molybdenum disilicide, boron carbide, aggregates and antioxidants may be added. Boron powder and the like can also be added.

  The silicon powder is preferably a fine powder having an average particle size of 30 μm or less. Those having a large particle size are preferably used after being pulverized by a ball mill or the like. The silicon powder may be a pure silicon powder, or a silicon alloy powder containing a metal such as Mg, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, W, Alternatively, a mixed powder of pure silicon powder and these metal powders can be used.

  The mixing ratio of carbon and silicon powder obtained by carbonizing the resin in the slurry is preferably in the range of Si / C = 0.05 to 5.00 in terms of atomic ratio. If this atomic ratio is less than 0.05, the amount of porous silicon carbide produced by reactive sintering is reduced, and no silicon melt impregnation occurs. On the other hand, when the atomic ratio exceeds 5.00, the amount of silicon powder in the slurry increases, and precipitation tends to occur.

  A slurry obtained by further mixing silicon carbide powder with a slurry containing resin and silicon powder can also be used. In this case, the weight of the silicon carbide powder is preferably within a range of 3 times the weight of the silicon powder. If the weight of the silicon carbide powder exceeds 3 times the weight of the silicon powder, mixing may be insufficient.

  The solid content concentration in the slurry is not particularly limited as long as it is a viscosity capable of impregnating the organic porous structure with the slurry. Moreover, the solvent used in the slurry is not particularly limited, but a solvent capable of dissolving the resin is used. In order to impregnate the organic porous structure with the slurry, it may be simply dipped and pulled up, or is preferably impregnated under reduced pressure.

  In the removing step, excess slurry is removed from the organic porous structure to form a skeleton of the organic porous structure and a precursor having the slurry attached to the surface thereof. The reason why the excess slurry is removed from the organic porous structure is to remove the slurry filled in the continuous pores, such as centrifugation, a method of sucking the excess slurry from the organic porous structure, or the organic porous structure. For example, a method of squeezing the mass structure to remove excess slurry can be used. By removing the excess slurry, a precursor is formed in which the slurry adheres to the inside or the surface of the organic porous structure.

  Also, the method for producing a fluid temperature rising filter of the present invention comprises impregnating a sponge made of polyurethane, polyethylene or rubber with a silicon carbide-containing slurry in which the silicon carbide is mixed with the slurry, thereby forming a sponge-like porous body. An impregnation step for forming the carbonized material, carbonizing the sponge-like porous body to form a carbonized porous body, and a firing step for reacting and sintering the silicon to the carbonized porous body, A melt impregnation step of melt-impregnating the silicon for melt impregnation after the silicon is reactively sintered;

  Here, “... after” is not limited to “immediately after ...”, but “after” is included in the present invention if it is “after”. For example, for the operation of “melting and impregnating silicon after reacting and sintering silicon”, “after reacting and sintering silicon, another step is performed, and after the other step, silicon is melted and impregnated”. This operation is also included.

<Slurry containing silicon used in the present invention, silicon carbide-containing slurry>
The slurry containing silicon used in the present invention may contain other substances in addition to silicon. Moreover, the silicon carbide containing slurry used for this invention may contain another substance other than silicon and silicon carbide.

<Solvent used in the present invention>
Although it does not restrict | limit especially as a solvent used for this invention, The thing which can melt | dissolve resin is used, For example, ethyl alcohol, methyl alcohol, etc. are mentioned. Of these, ethyl alcohol is preferred for safety reasons. In addition, you may use denatured alcohol as alcohol.

<Sponge made of polyurethane, polyethylene or rubber>
The sponge made of polyurethane, polyethylene or rubber in the present invention is not particularly limited as long as it has water absorbability mainly composed of polyurethane, polyethylene or rubber. That is, if polyurethane, polyethylene, or rubber is the main component, the present invention includes substances other than polyurethane, polyethylene, and rubber. In the present invention, it is most preferable to use a polyurethane sponge from which the cell membrane has been removed.

<The suitable manufacturing method of the fluid temperature rising filter of this invention>
In the method for producing a fluid temperature rising filter containing silicon and silicon carbide according to the present invention, after the sponge is impregnated with a slurry containing silicon powder or further silicon carbide powder, the slurry filled in the continuous pores is removed. .

  The method for producing a fluid temperature rising filter containing silicon and silicon carbide of the present invention is preferably dried after impregnation with slurry. The drying is preferably performed at 70 to 90 ° C. for about 3 hours.

  In the method for producing a fluid temperature rising filter containing silicon and silicon carbide of the present invention, the sponge is preferably squeezed after impregnating the sponge with a slurry containing silicon powder or further silicon carbide powder. The method for squeezing the sponge is not particularly limited.

  The fluid temperature rising filter containing silicon and silicon carbide of the present invention can be obtained, for example, as follows.

  First, a sponge made of polyurethane, polyethylene or rubber is impregnated with a slurry containing silicon powder or further silicon carbide powder, and then excess slurry is removed and carbonized at 800 ° C. to 1300 ° C. in an inert atmosphere. In order to promote the thermal decomposition of organic matter, carbonization is more preferably performed at 900 ° C to 1300 ° C. The carbonized porous body obtained in this way is obtained as a structure in which the sponge is no longer thermally decomposed, so that a carbon portion obtained by carbonizing a resin and the like and silicon powder or further silicon carbide powder are mixed.

  Next, the carbonized porous body is subjected to reaction sintering of carbon and silicon powder at a temperature of 1300 ° C. or higher in a vacuum or an inert gas atmosphere to produce molten silicon and porous silicon carbide having good wettability ( This reaction is accompanied by a volume reduction of about 38%). The silicon carbide and the remaining carbon are further melt impregnated with silicon at 1400 ° C. to 1800 ° C. in a vacuum or an inert gas atmosphere to form the sponge. And a filter containing silicon and silicon carbide having substantially the same shape can be obtained. The melt-impregnating silicon may be in the form of powder, granules, or lumps.

  The said slurry should just set the mixing condition suitably so that the said conditions can be satisfied, and the mixing condition is not specifically limited. In addition, the slurry is preferably set to a concentration suitable for adhering to the sponge, depending on the components used, and the weight ratio between the phenol resin and the solvent (for example, ethanol) is taken as an example. The concentration is preferably adjusted to about 15 to 50% by weight, and more preferably adjusted to about 20 to 40% by weight.

<Method for Increasing Fluid Temperature in the Present Invention>
The method for increasing the temperature of a fluid in the present invention includes a step of heating a structure containing silicon and silicon carbide by microwaves (microwave heating), and a step of passing a fluid through the heated structure. It is a method of inclusion.

  A filter etc. are mentioned as a structure used for this invention. The explanation of silicon, silicon carbide, microwave heating, and fluid is as described above.

  Hereinafter, the fluid temperature increasing filter of the present invention and the manufacturing method thereof will be described in more detail with reference to examples. However, the fluid temperature rising filter of the present invention and the manufacturing method thereof are not limited to the following examples.

[Example 1]
The mixing amount of the phenol resin and the silicon powder (average particle size of about 20 μm) is set at a ratio in which the molar ratio of carbon to silicon by the carbonization of the phenol resin is Si / C = 1, and silicon Add 0.5 times the weight of silicon carbide powder (average particle size of about 3 μm) to the weight of the powder, and dissolve the phenolic resin with ethyl alcohol about 3.3 times the weight of the silicon powder. A slurry was prepared and mixed in a ball mill for 1 day in order to reduce the particle size of the silicon powder.

  Then, this dispersed slurry was impregnated into 8 and 13 mesh (cell number / inch) polyurethane sponge (trade name “Malt filter”, manufactured by Inoac Co., Ltd.), and the excess slurry was squeezed and removed. Dry for a time to obtain a dry sample. Thereafter, the dry sample was carbonized by heating at 1000 ° C. under an argon gas atmosphere.

  Next, an appropriate amount of silicon granules was placed on the surface of the carbonized porous carbonaceous sponge and fired at 1450 ° C. for 1 hour in a vacuum. In this firing, carbon reacted with silicon powder at a temperature below the melting point of silicon (about 1410 ° C.) to form porous silicon carbide and unreacted carbon. Furthermore, at a temperature equal to or higher than the melting point of silicon, the silicon granules melt and react with unreacted carbon to form silicon carbide, and the cross-linked portion of the sponge-like porous body reacted and sintered with excess metal silicon Reinforced to obtain a Si / SiC filter (a filter containing silicon and silicon carbide). The Si / SiC filter shape was about 5.5 cm × 3 cm × 3 cm.

  The microwave heating experiment of the obtained Si / SiC filter was conducted at 200 watts using a household microwave oven. Specifically, an alumina plate was placed on a turntable, a Si / SiC filter was placed thereon, heated for a predetermined time, the door was opened, and the surface was measured by thermography.

  As a result, the 13-mesh Si / SiC filter after 10 seconds was 162 ° C., and the 8-mesh Si / SiC filter after 10 seconds was 104 ° C. The 8 mesh Si / SiC filter after 5 seconds was 51 ° C.

[Example 2]
The same operation as in Example 1 was performed, except that a silicon carbide powder having a weight of 1 times the weight of the silicon powder was added to prepare a dispersion slurry.

  As a result, the 13-mesh Si / SiC filter after 10 seconds was 156 ° C., and the 8-mesh Si / SiC filter after 10 seconds was 98 ° C. Moreover, the 8 mesh Si / SiC filter after 5 seconds was 61 degreeC.

Example 3
The same operation as in Example 1 was performed except that a silicon carbide powder having a weight twice that of the silicon powder was added to prepare a dispersion slurry.

  As a result, the 13-mesh Si / SiC filter after 10 seconds was 138 ° C., and the 8-mesh Si / SiC filter after 10 seconds was 108 ° C. The 8 mesh Si / SiC filter after 5 seconds was 60 ° C.

Example 4
The same operation as in Example 1 was performed except that the silicon carbide powder having a weight 0 times the weight of the silicon powder was added (without adding the silicon carbide powder) to prepare a dispersion slurry.

  As a result, the 13-mesh Si / SiC filter after 10 seconds was 140 ° C., and the 8-mesh Si / SiC filter after 10 seconds was 98 ° C. The 8 mesh Si / SiC filter after 5 seconds was 48 ° C.

(Example summary)
The results of Examples 1 to 4 are summarized in Table 1.

  In Examples 1 to 4, by adding silicon carbide powder and preparing a dispersion slurry, when microwave heating is performed, the temperature of the Si / SiC filter can be slightly increased compared to the case of no addition. The result was that it was possible.

  Here, FIG. 1 is a plan view (photograph) showing the result of observation in the Si / SiC filter.

In the Si / SiC filter shown in FIG. 1, the open porosity is about 95% and the bulk density is about 0.1 g / cm ³ . However, the open porosity and the density can be adjusted, and the density can be higher than 0.1 g / cm ³ . Further, in the Si / SiC filter shown in FIG. 1, the BET (Brunauer Emmett Teller) specific surface area is 0.1 m ² / g or less. Further, the Si / SiC filter shown in FIG. 1 has a low pressure loss. Further, the Si / SiC filter shown in FIG. 1 has heat resistance and thermal shock resistance. Furthermore, it can be seen that the Si / SiC filter shown in FIG. 1 has almost the same structure as that of the raw material polyurethane sponge because of its sharp corners.

  Moreover, FIGS. 2-4 is a graph which shows the temperature fall process after the microwave irradiation in Examples 1-4. 2 shows the result of heating with a 13 mesh filter for 10 seconds, FIG. 3 shows the result of heating with an 8 mesh filter for 10 seconds, and FIG. 4 shows the result of heating with an 8 mesh filter for 5 seconds. 2 to 4, (a) shows the result of Example 3, (b) shows the result of Example 2, (c) shows the result of Example 1, and (d) shows the result of Example 4. Results are shown.

In addition, there was a sample that caused arc discharge in part during the experiment in the examples. This arc discharge could be suppressed by oxidizing the sample in air at 800 ° C. to form a thin silica (silicon dioxide, SiO ₂ ) layer of several tens of μm on the surface of the sample. Moreover, the influence on the temperature rising characteristic by this heat oxidation treatment was not seen. Since the surface of the Si / SiC filter is a silica layer after the heat oxidation treatment, it is not conductive.

  The fluid temperature rising filter containing silicon and silicon carbide of the present invention is a gas heating process in a short time, particularly a soot instantaneous heating process that occurs during idling of diesel exhaust gas, etc. by microwave heating. It can be used for oxidative decomposition treatment of VOC (Volatile Organic Compounds).

Claims (5)

Contains silicon and silicon carbide,
A filter for heating a fluid, wherein the filter is used by being heated by a microwave. Bulk density higher than 0.05 g / cm ^3, the filter fluid heating according to claim 1, characterized in that in the range of less than 0.3 g / cm ^3. A silicon carbide-based porous structure having a sponge-like three-dimensional skeleton made of ceramics containing silicon carbide and a continuous pore formed between the three-dimensional skeleton,
A metal silicon layer formed on the surface of the three-dimensional skeleton containing the silicon;
A silicon oxide layer formed by oxidizing at least a part of the metal silicon layer;
The fluid temperature rising filter according to claim 1, wherein the filter is for heating a fluid. It is a method of manufacturing the fluid temperature rising filter according to any one of claims 1 to 3,
Mixing silicon carbide powder with the slurry containing silicon powder, or further,
The slurry further contains a solvent,
Impregnation in which a sponge made of polyurethane, polyethylene or rubber is impregnated with the slurry, and the sponge is squeezed so that the slurry does not block the continuous pores, and then the sponge is dried to form a sponge-like porous body. Process,
Carbonizing the sponge-like porous body to form a carbonized porous body,
A firing step in which silicon and carbon are reacted and sintered to form a reaction sintered body on the carbonized porous body, and a melt impregnation step in which silicon is further melted and impregnated into the reaction sintered body. A method for producing a fluid temperature rising filter, comprising:   The method further comprises an oxidation step of oxidizing at least a part of the metal silicon layer formed on the surface of the three-dimensional skeleton portion in the melt impregnation step to form a silicon oxide layer on the three-dimensional skeleton portion. Item 5. A method for producing a fluid temperature increasing filter according to Item 4.