JPH01197375A - Porous body and production of porous body - Google Patents

Abstract

PURPOSE:To obtain a porous body which is integrated with acicular bodies which are not changed in the initial state of the acicular bodies and a frame body and has a large specific surface area by calcining raw material particles of Si, etc., deposited on the surface of the frame body forming a porous supporting frame under prescribed conditions. CONSTITUTION:The heat resistant frame material 2 which forms the porous supporting frame having plural holes 2c is prepd. The raw material particles consisting of Si or a mixture composed of Si and Al are deposited on the surface of the frame material 2. The porous supporting frame after the deposition of said particles is calcined under the conditions of 1200-1370 deg.C and Si1 hour in the atmosphere of a reducing gas contg. gaseous N2 or gaseous H2 contg. steam. The porous body having the porous supporting frame which forms the many holes 2c and the aciular bodies 3 which grow thickly over the entire inside circumference of the holes 2C and cover the entire aperture of the holes 2C is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Further details [Industrial Application Field] The present invention relates to a porous body having a large specific surface area and a method for producing a porous body.

[Prior art] Porous materials have a large specific surface area and are often used as catalyst carriers that disperse and support organic catalyst components such as enzymes or microorganisms and inorganic catalyst components, and as heat dissipators with high heat dissipation efficiency from the surface. Members and the like are common examples of such porous bodies. In particular, honeycomb materials are popular as catalyst carriers for removing harmful substances from automobile exhaust gas.

However, in recent years, there has been a demand for further improvements in performance, such as improvements in the ability to disperse and support catalyst components. Therefore, instead of porous materials such as honeycomb materials, short taM (hereinafter referred to as
The following porous fiber bodies using fibers (simply referred to as fibers) have been developed.

The fiber porous body includes a casing or frame of a predetermined shape,
It is made of fibers, blankets made from fibers, nonwoven fabrics, etc., and is constructed by laminating or inserting fibers or blankets into a housing, or by sandwiching or pasting them to a frame. A porous fiber body having such a structure is also used as a dust removal material. In particular, a ceramic fiber porous body using ceramic fibers or ceramic whiskers as the above-mentioned fibers is a useful and high value-added porous body that takes advantage of the heat resistance and chemical resistance specific to ceramics.

[Problems to be Solved by the Invention] Although the porous fiber bodies including the ceramic fiber porous body described above are porous bodies with extremely large specific surface areas, the following problems remain.

The fiber layers laminated inside the casing, the fiber blanket sandwiched between the frames, and the like, which form the external shape of the porous fiber body, are composed of a large number of fibers entangled with each other. Therefore, a porous body made of fibers mainly consists of fibers that are directly fixed to a casing etc. and fibers that are held by mutual entanglement.
It maintains a predetermined shape. Therefore, when external forces such as vibration, the weight of the fiber, and the pressure of the blown gas are applied,
The entanglement between the fibers becomes unraveled, making it impossible to maintain the initial state of the fibers, such as the laminated thickness of the fibers, over a long period of time, resulting in a decrease in the original properties of the porous fiber material, such as the efficiency of dispersing and supporting catalyst components, which is undesirable. .

Furthermore, porous fiber bodies have a wide variety of uses and locations, and in order to obtain uniform properties, such as dust removal ability, it is necessary to make uniform the amount and thickness of the fibers laminated inside the housing. Or the amount of fiber depending on the application,
Work is required to adjust the thickness, etc. These operations are not only complicated, but in some cases, for example, it is difficult to uniformly stack fibers inside a complexly curved housing.

The present invention has been made to solve the above problems, and the first object is to integrate each of the fibers, that is, short fiber-like needle-like bodies with a frame, etc., so that the initial state of the needle-like bodies can be changed. The purpose of the present invention is to provide a porous body that does not cause any damage. The second purpose is to create a porous body in which each of the needle-shaped bodies and the frame are integrated, and the initial state of the needle-shaped bodies does not change, without being affected by the shape of the porous body. An object of the present invention is to provide a method for producing a porous corpus luteum that can be easily produced.

1. Means for Solving the Problems The means used in the present invention to achieve the above object are as follows: A porous support frame in which a plurality of holes are formed by a frame material, and substantially the entire inner periphery of each hole. The gist of the porous body is a porous body characterized by comprising needle-shaped bodies that grow densely over the surface and cover all the openings of the pores.

Furthermore, the procedure used in the present invention for producing such a porous body to achieve the above object includes adding silicon or silicon and aluminum to the surface of a heat-resistant frame material forming a porous support frame having a plurality of holes. After applying raw material particles consisting of a mixture of the following, each hole support frame is baked in a gas atmosphere of a reducing gas containing nitrogen gas or hydrogen gas containing water vapor at a temperature of 1200°C to 1370°C for at least 1 hour. The gist is a method for producing a porous corpus luteum.

[Function] The porous support frame of the porous body according to the present invention has a predetermined shape of the porous body, for example, a sheet-like, cylindrical, etc. external shape, and a plurality of pores covered by needle-like bodies described below. do. The acicular bodies that grow densely over almost the entire inner peripheral surface of the pores are integrated with the frame material forming the pores, cover all the openings of the pores, and increase the specific surface area of each pore cylinder. That is, the needle-like body is a porous body with pores independent of the pore cylinder. In this way, the porous support body and the needle-shaped body provided with a plurality of holes constitute a porous body having a predetermined shape, which is a collection of porous bodies of the pore tubes.

Note that there is no restriction on how the needle-shaped bodies are densely grown, as long as they cover all the openings of the pores. For example, whether the needles grow densely in one direction or in different directions,
It is sufficient that the entire opening of the pore is covered by the needle-shaped body.

Moreover, according to the above-described method for manufacturing a porous body of the present invention,
First, raw material particles made of silicon or a mixture of silicon and aluminum are deposited on the surface of a heat-resistant porous support frame by an appropriately selected deposition method. The raw material particles become the raw material for whiskers generated in the next step of firing.

There are various methods for the above-mentioned deposition. For example, there are methods such as adding raw material particle powder to an organic solvent such as tertiary butyl alcohol or ketone to form a slurry, applying this slurry, spraying, electrostatic coating, or immersing it in this slurry. Alternatively, the raw material particles can be deposited by a thin film manufacturing method such as vapor deposition or sputtering. In addition, in methods such as coating and dipping, it is desirable to use air drying in combination to evaporate the organic solvent and prevent the raw material particles from separating from the surface of the frame material. In order to improve wettability, other metals or the like may be attached to the surface of the frame material in advance. Among these deposition methods, methods such as coating and dipping are easy methods for deposition. The above-mentioned mixture of silicon and aluminum may be either a physical mixture obtained by stirring and mixing powder particles of each of the two substances using a rotary mixer or the like, or a chemical mixture in which the two substances are combined.

Next, the porous support frame after application is fired in a gas atmosphere of reducing gas containing nitrogen gas or hydrogen gas containing water vapor at a temperature of 1200'C to 1370°C for at least 1 hour. Whiskers, which are reaction products of the material of the raw material particles and nitrogen or oxygen in the gas atmosphere, are grown on the surface, and these whiskers cover all the openings of the pores of the porous support frame.

As long as the firing temperature and firing time are within the above ranges, whiskers can be suitably grown and all the openings of the pores can be covered with whiskers. However, if the temperature is lower than 1200°C or the firing time is less than 1 hour, whisker growth will be insufficient, so the porosity of the whisker itself (hereinafter simply referred to as (referred to as porosity) decreases. The entire opening of the pore is therefore not covered by whiskers. Further, at a temperature exceeding 1370° C., since the temperature is close to the melting point of the raw material particles, the growth of whiskers becomes insufficient and the porosity decreases.

A reducing gas containing nitrogen gas, for example, ammonia decomposition gas, supplies nitrogen, and in this gas atmosphere, when the raw material particles are silicon particles, silicon nitride (Si3Na) whiskers are grown, and the raw material particles form the mixture. In the case of particles, silicon nitride whiskers, aluminum nitride (AQN>
Grow whiskers. Hydrogen gas containing water vapor supplies oxygen, and in this gas atmosphere, when the raw material particles are silicon particles, silica (SiOz) whiskers are grown,
When the raw material particles are particles of the mixture, silica whiskers and mullite (AQsSi2013) whiskers are grown. Note that the above mixture in a hydrogen gas atmosphere contains silicon: 23 to 30% by weight and aluminum 70 to 77% by weight.
A mixture of these is preferable because it allows selective growth of extremely heat-resistant mullite whiskers.

The degree to which all the openings of the pores are covered by the whiskers described above is determined by the opening area of the pores, the opening volume, and the firing conditions of temperature and time.

[Example] Next, an example using the present invention will be described using the drawings.

First, in order to obtain 1 q of whisker raw materials, 500 ml of silicon powder is required.
g in 500 ml of tertiary butyl alcohol, and put this solution into a polyethylene crushing container with an internal volume of 1.51 mm along with alumina coccules with a purity of 99.9% and a particle size of 10 mm.
The container is rotated at 34 rpm for 24 hours to finely pulverize the silicon particles.

In this way, the slurry (
(hereinafter referred to as silicon slurry) is generated.

Example 1 FIG. 1 is an explanatory diagram for explaining the manufacturing process of the cylindrical porous body 1 shown in FIG.
FIG. 2 is a perspective view of a cylindrical frame 2 for manufacturing. The cylindrical frame 2 has a cylindrical basket shape with an outer diameter of 100 mm and a depth of 100 mm, and is composed of a cylindrical member 2a and a bottom plate 2b, each made of 200 mesh nichrome wire mesh. A cylindrical porous body 1 is obtained from this cylindrical frame body 2 in the following manner.

First, this cylindrical frame 2 is immersed in the silicon slurry, and silicon fine particles are coated on the entire surface of the cylindrical frame 2 via tertiary butyl alcohol. In this embodiment, the cylindrical frame 2 after immersion is air-dried to evaporate the tertiary butyl alcohol to prevent fine silicon particles from coming from the surface of the cylindrical frame 2.

Next, the coated cylindrical frame 2 is fired at 1280"CX for 1 hour in an ammonia decomposition gas atmosphere to grow silicon nitride whiskers, which are reaction products of nitrogen and silicon, from the surface of the cylindrical frame 2. In this way, a cylindrical porous body 1 in which the cylindrical frame 2 and the silicon nitride whiskers are integrated is obtained.

FIG. 1(B) is a perspective view and a partially enlarged view of the cylindrical porous body 1 manufactured by the above manufacturing method, and FIG.
C) is a sectional view taken along the line II of the enlarged view in FIG. 1(B). This cylindrical porous body 1 has silicon nitride whiskers 3 uniformly and densely grown directly on the surface of a cylindrical frame 2 in each pore tube, as shown in the enlarged view. Therefore, even if external forces such as vibrations are applied, the uniform dense state of silicon nitride whiskers 3 is maintained. This silicon nitride whisker 3 covers all the openings of the 8 holes 2C of the cylindrical frame 2 as shown in FIG. 1(C), and
The specific surface area of the cylindrical porous body 1 is increased for each hole 2C.

The entire opening of the eight holes 2C of the cylindrical porous body 1 of this embodiment is covered by a large number of silicon nitride whiskers 3 integrated with the cylindrical frame 2. Therefore, the cylindrical porous body 1 having a plurality of pores 2C is a porous body having an extremely large specific surface area. Furthermore, by utilizing the heat resistance of the nichrome wire mesh and silicon nitride whiskers, it is a porous material that can be used as a catalyst carrier, dust removal material, etc. even at high temperatures. Note that this cylindrical porous body 1
has a dust removal ability that removes particles with a particle size of about 5 to 7 μm and a porosity of 81%.

Further, according to the manufacturing method of this embodiment, the frame body is the cylindrical frame body 2.
Even if the wire rod is made of a wire rod and has a complicated shape, the acicular silicon nitride whiskers 3 can be easily and uniformly densely grown on the surface of the wire rod. Therefore, in the manufacturing method of this embodiment, each silicon nitride whisker and the frame are integrated, and it is possible to easily manufacture the wire mesh-like cylindrical porous body 1 having the above-mentioned properties such as dust removal ability. This is the manufacturing method.

Next, an example of using the above-mentioned cylindrical porous body 1 as a dust removal material will be explained. FIG. 2 schematically shows the usage state in which the cylindrical porous body 1 is installed in the exhaust pipe of a diesel engine. The cylindrical porous body 1 is attached to the inside of the large-diameter exhaust pipe 4b via the mounting bracket 5 with the bottom plate 2b side protruding.

Exhaust gas flows from the small diameter exhaust pipe 4a to the large diameter exhaust pipe 4b through the holes 2 in the peripheral wall and bottom plate of the cylindrical porous body 1, as shown by the arrow in the figure.
It flows out through C. The cylindrical porous body 1 has a particle size of 5 to 7μ.
It has a dust removal ability that removes 8 m of particles, so the exhaust gas
Unburned carbon particles in the exhaust gas can be attached to the surface of the silicon nitride whiskers 3 and removed when the exhaust gas passes through the holes.

In this embodiment, the cylindrical frame 2 is made of a nichrome wire mesh, so current is passed through the cylindrical frame 2 to generate heat in the silicon nitride whiskers 3 integrated with the cylindrical frame 2. Unburnt carbon particles attached to the whiskers 3 can be burned and decomposed.

That is, the cylindrical porous body 1 is a porous body that can be used at high temperatures, utilizes electrical heat generation, and can be used as a dust removal material with high reuse efficiency.

Table 1 shows the porosity of the cylindrical porous body obtained in experiments under firing conditions of firing temperature and firing time different from those of this example.

Table 1 As is clear from the table, the porosity of experiments B, C, and D was low, and the entire opening of the flower was not covered with whiskers.

Example 2 FIG. 3 is an explanatory diagram for explaining the manufacturing process of the alumina porous body 11 described later, and FIG. 3 (A> is an alumina honeycomb material ( 12 (hereinafter referred to as alumina material). The alumina material 12 is a honeycomb material with a wall thickness Q of 2 mm and a pitch of 1 mm, and has a disc shape with an outer diameter of 100 mm and a thickness of 5 mm. From this alumina material 12, the following Then, an alumina porous body 11 is obtained.

First, this alumina material 12 is immersed in the silicon slurry, and silicon fine particles are coated on the entire inner peripheral wall surface of the famous flower 12a of the alumina material 12 via tertiary butyl alcohol. In this embodiment, the immersed alumina material 12 is air-dried to evaporate the tertiary butyl alcohol to prevent silicon fine particles from leaving the surface of the alumina material 12.

Next, the alumina material 12 after deposition is fired at 1330'CX for 1 hour in a hydrogen gas atmosphere containing water vapor with a dew point of 10°C.
Silica whiskers, which are a reaction product of oxygen and silicon, are grown from the inner peripheral wall surface of the flower 12a of the alumina material 12. In this way, an alumina porous body 11 in which the alumina material 12 and silica whiskers are integrated is obtained.

FIG. 3(B) is a perspective view and a partially enlarged view of the top surface of the alumina porous body 11 manufactured by the above manufacturing method. As shown in the enlarged view, this alumina porous body 11 has silica whiskers 13 uniformly and densely grown in each pore directly on the inner peripheral wall surface of the flower 12a of the alumina material 12. Therefore, even if an external force such as vibration is applied, the silica whiskers 13 can maintain a uniform dense state. And this silica whisker 1
3 covers all the openings of the famous flower 12a of the alumina material 12, and the specific surface area of the alumina porous body 11 is
It is increasing every time.

The fine flower 12a of the alumina porous body 11 of this embodiment is covered with a large number of silica whiskers 13 integrated with the alumina material 12 over its entire opening in the thickness direction. Therefore, the alumina porous body 11 having a plurality of pores 12a is a lightweight porous body having an extremely large specific surface area. Note that this alumina porous body 11 has a dust removal ability for removing fine particles having a particle size of about 2 to 5 μm and a porosity of 74%. Therefore, the alumina porous body 11 is a porous body that can be used as a high-performance dust removal material installed at the air cooling ventilation opening of electronic equipment used in a clean room, and promotes weight reduction of electronic equipment.

Further, according to the manufacturing method of this embodiment, even if the frame is a honeycomb material that is an aggregate of pores, silica whiskers 13 are formed on the entire inner peripheral surface of each pore in the thickness direction of the honeycomb material. can be easily and uniformly grown to cover the entire opening of the pores.

Therefore, the manufacturing method of the present example is a manufacturing method in which each of the silica whiskers and the frame are integrated, and a trowel can be manufactured that easily manufactures the honeycomb-shaped alumina porous body 11 having the characteristics such as the above-mentioned dust removal ability. It's a method.

Table 2 shows the porosity of the alumina porous body obtained in an experiment under firing conditions of firing temperature and firing time different from those of this example.

Table 2 As is clear from the table, the porosity of experiments B and C was low and the entire opening of the name tag was not covered by whiskers.

Example 3 FIG. 4 is an explanatory diagram for explaining the manufacturing process of the cordierite porous body 21, which will be described later, and FIG. There is a perspective view of a honeycomb material (hereinafter referred to as cordierite material) 22. Cordierite material 22 has a wall thickness of 0.2 mm and a pitch of 1 mm.
It is a honeycomb material, and has a disc shape with an outer diameter of B□mm and a thickness of 3mm.

A cordierite porous body 21 is obtained from this cordierite material 22 in the following manner.

First, this cordierite material 22 is immersed in the silicon slurry, and silicon fine particles are coated on the entire inner peripheral wall surface of the name tag 22a of the cordierite material 22 via tertiary butyl alcohol. In this embodiment, the cordierite material 22 after immersion is air-dried to evaporate the tertiary butyl alcohol, thereby preventing the silicon fine particles from detaching from the surface of the cordierite material 22.

Next, the cordierite material 22 after deposition is fired at 1280° C. for 1 hour in an ammonia decomposition gas atmosphere to remove silicon nitride whiskers, which are reaction products of nitrogen and silicon, from the inner periphery of the name tag 22a of the cordierite material 22. Grow from the surface of the wall. In this way, cordierite porous body 21 in which cordierite material 22 and silicon nitride whiskers are integrated is obtained.

FIG. 3(B) is a perspective view of the cordierite porous body 21 and a partially enlarged portion of its upper surface. As shown in the enlarged view, this cordierite porous body 21 is directly coated with silicon nitride whiskers 2 on the inner peripheral wall surface of the name tag 22a of the Nisilite material 22.
3 are uniformly densely grown in each hole cylinder. Therefore, even if external forces such as vibrations are applied, the uniform dense state of silicon nitride whiskers 23 is maintained. The silicon nitride whiskers 23 cover all openings of the name tag 22a of the cordierite material 22, and reduce the specific surface area of the cordierite porous body 21 to each hole 2.
It is increased every 2a.

The name tag 22a of the cordierite porous body 21 of this example is as follows:
The entire opening is covered in the thickness direction by a large number of silicon nitride whiskers 23 integrated with the cordierite material 22. Therefore, the cordierite porous body 21 having a plurality of pores 22a is a porous body having an extremely large specific surface area. Furthermore, by utilizing the heat resistance of cordierite and silicon nitride whiskers, it is a porous material that can be used as a catalyst carrier, dust removal material, etc. even at higher temperatures. Note that this cordierite porous body 21 has a dust removal ability to remove particles having a particle size of about 2 to 3 μm and a porosity of 80%.

Further, according to the manufacturing method of this example, even if the frame is a honeycomb material that is an aggregate of pores, silicon nitride whiskers are formed on the entire inner peripheral surface of each pore in the thickness direction of the honeycomb material. 23 can be easily and uniformly densely grown to cover the entire opening of the pore. Therefore, in the manufacturing method of this embodiment, each of the silicon nitride whiskers and the frame are integrated, and the honeycomb-shaped cordierite porous body 21 having the above-mentioned properties such as the dust removal ability can be easily produced by I! This is a manufacturing method that allows for

Next, an example of use of the above cordierite porous body 21 will be explained. FIG. 5 schematically shows the usage state in which the cordierite porous body 21 is installed on the upper part of the combustion tube of a stove. ing. When the fuel is combusted in the wick 32 inside the combustion tube 31, the heated air passes through each hole 22a8 of the cordierite porous body 21 as shown. Since the cordierite porous body 21 has the above-mentioned dust removal ability, soot in the air passing through the pores 22a is attached to the surface of the silicon nitride whiskers 23 and removed. In addition, since the cordierite porous body 21 is heated by combustion in the fire wick 32, it burns and decomposes the soot adhering to the silicon nitride whiskers 23, and emits far infrared rays from the surface of the silicon nitride whiskers 23. The heat dissipation effect of 30 can also be improved.

Table 3 shows the porosity of cordierite porous bodies obtained in experiments under firing conditions of firing temperature and firing time different from those of this example.

Table 3 As is clear from the table, the porosity of Experiment C was low and all the openings of the pores were not covered by whiskers.

The porous body according to the present invention is not limited to the above embodiments, and can be implemented without departing from the scope of the invention. For example, if mullite whiskers are grown from a mixture of silicon and aluminum as in the above embodiment, a porous body with higher heat resistance can be obtained. Table 4 shows the experimental results regarding porous bodies densely populated with mullite whiskers obtained by firing in a hydrogen gas atmosphere containing water vapor at various dew points.

Note that the honeycomb material is the same as in Example 3.

Table 4 As is clear from the table, the porosity of Experiments E and F was low and the entire openings of the pores were not covered by whiskers.

Further, the porous body of the present invention can be used not only as a dust removal material but also as a catalyst carrier with high dispersion and support efficiency of catalyst components, a heat insulating material, and the like.

1. As described above in detail including the examples, the porous body according to the present invention has needle-shaped bodies densely growing from almost the entire inner peripheral surface of the pores, and the needle-shaped bodies cover all the openings of the pores. It is a porous material that not only has a large specific surface area because it is covered, but also integrates each needle-like body with the frame, etc., and does not change the initial state of the needle-like body. Therefore, the porous body according to the present invention is a porous body that can be used for desired purposes over a long period of time.

Further, according to the method for producing a porous corpus luteum according to the present invention, needle-shaped bodies are densely grown on almost the entire inner peripheral surface of the pores, regardless of the shape of the porous body, and the needle-shaped bodies cover all the openings of the pores. Can be easily covered. Therefore, the method for producing a porous body of the present invention is a porous corpus luteum in which each needle-like body and frame are integrated, and it is possible to easily produce a porous body with no change in the initial state of the needle-like body. This is the manufacturing method.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining a porous body and its manufacturing method according to the first embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining the usage state of the porous body, and FIG. The figure is the second
FIG. 4 is an explanatory diagram for explaining a porous body and its manufacturing method as a third embodiment, and FIG. It is an explanatory view for explaining the use state of the porous body of the 3rd example. 1... Cylindrical porous body 2... Cylindrical frame made of nichrome wire mesh 2C... Hole 3... Silicon nitride whisker 1
1... Alumina porous body 12... Alumina honeycomb material (alumina material) 12a... Hole 13...
Silica whisker 21... Cordierite porous body 2
2... Cordierite honeycomb material (cordierite material) 22a... Hole 23... Silicon nitride whisker Agent Patent attorney Tsutomu Sadatsu (and 2 others) (B) (C) Fr Fig. 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A porous support frame in which a plurality of holes are formed by a frame material, and a needle-shaped body that grows densely over almost the entire inner peripheral surface of each of the holes and covers the entire opening of each of the holes. A porous body characterized by comprising: 2. Apply raw material particles made of silicon or a mixture of silicon and aluminum to the surface of a heat-resistant frame material forming a porous support frame with a plurality of pores, and then heat the porous support frame with nitrogen after deposition. 1. A method for producing a porous body, which comprises firing at a temperature of 1200° C. to 1370° C. for at least 1 hour in a gas atmosphere of a reducing gas containing a gas or a hydrogen gas containing water vapor.