JP6695712B2 - Fiber reinforced porous body - Google Patents

Description

  The present invention relates to a fiber-reinforced porous body obtained by reinforcing a porous substrate with a fibrous substance.

  BACKGROUND ART Ceramics porous bodies are excellent in functions such as heat resistance, chemical resistance, and sound absorbing properties, and are used in various applications such as fire resistant members, heat insulating materials, catalyst supporting members, and sound absorbing members. Further, when it has a continuous vent hole, it allows a fluid to pass therethrough, so that it can also be used as a filter member for gas or liquid.

  However, when the porosity of the porous body is high, there is a problem that the mechanical strength is low. Therefore, conventionally, a fiber-reinforced porous body in which the porous body is reinforced with a fibrous substance is known (Patent Documents 1 and 2). ). For example, Patent Document 1 describes a method of forming silicon nitride whiskers in the pores of porous silicon by disposing silicon as a reaction aid around porous silicon and heating in a nitrogen gas atmosphere. ing. Further, Patent Document 2 describes a method of filling alumina-silica fibers or whiskers in the voids of a skeleton structure formed of silicon nitride or alumina-silica and sintering the same.

JP, 2008-50218, A JP-A-60-46979

  However, in the above-mentioned conventional technique, since the porous substrate is reinforced by filling the pores with whiskers or fibers, there is a problem that it is not suitable for applications utilizing the function of the continuous ventilation hole. Further, when the whiskers and the fibers are thin, there is a problem that a sufficient reinforcing effect cannot be obtained.

  The present invention has been made to solve the above problems, and can be implemented as the following modes.

(1) According to one aspect of the present invention, there is provided a fiber-reinforced porous body having an oxide porous base material having a large number of communicating pores and a fibrous substance that reinforces the porous base material. It In this fiber-reinforced porous body, the porosity of the fiber-reinforced porous body is 32% or more and 96% or less, and the fibrous substance is layered on the wall surface of the pores without filling the pores of the porous substrate. The fiber-reinforced layer is formed as a closely adhered fiber-reinforced layer, and the fiber-reinforced layer includes a bonding phase for bonding the fibrous substance to the wall surface of the pores, and the bonding phase is Si, P, B, Li, Na, K. , Mg, Ca, Ba, Sr, Zn, Al, Ni, Co, and at least two elements are included .
Since this fiber-reinforced porous body has a porosity of 36% or more and 96% or less, a relatively high mechanical strength can be secured. In addition, since the fibrous substance is formed as a fiber-reinforced layer deposited on the wall surface of the pores in layers, the mechanical strength of the porous body can be increased without filling the pores of the porous substrate. Moreover, since the fibrous substance can be firmly adhered to the wall surface of the pores of the porous substrate by the bonding phase, the mechanical strength can be increased.

(2) According to another aspect of the present invention, there is provided a fiber-reinforced porous body having an oxide porous base material having a large number of communicating pores and a fibrous substance that reinforces the porous base material. To be done. In this fiber-reinforced porous body, the porosity of the fiber-reinforced porous body is 32% or more and 96% or less, and the fibrous substance is layered on the wall surface of the pores without filling the pores of the porous substrate. It is formed as a closely adhered fiber reinforced layer, the content of the fibrous substance in the surface layer portion existing on the surface of the fiber reinforced porous body, in the main body portion of the fiber reinforced porous body existing below the surface layer portion. It is characterized in that the content is higher than the content of the fibrous substance.
Since this fiber-reinforced porous body has a porosity of 36% or more and 96% or less, a relatively high mechanical strength can be secured. In addition, since the fibrous substance is formed as a fiber-reinforced layer deposited on the wall surface of the pores in layers, the mechanical strength of the porous body can be increased without filling the pores of the porous substrate. In addition, mechanical strength such as impact resistance can be increased by increasing the content of the fibrous substance in the surface layer portion of the fiber-reinforced porous body as compared with the main body portion. Further, even if a part of the main body portion is damaged, it is possible to maintain the shape of the entire fiber-reinforced porous body.

(3) In the fiber-reinforced porous body, the fibrous substance may have an average fiber diameter of 2 μm or more and 30 μm or less and an average fiber length of 450 μm.
According to this structure, since the porous base material is reinforced by the short fibers having an average fiber diameter of 2 μm or more and 30 μm or less and an average fiber length of 450 μm, it is easy to form the fiber-reinforced layer on the wall surface of the pores without filling the pores. Can be formed.

(4) In the fiber-reinforced porous body, the content of the fibrous substance in the surface layer portion existing on the surface of the fiber-reinforced porous body is the main body portion of the fiber-reinforced porous body existing below the surface layer portion. It may be higher than the content of the fibrous substance.
According to this configuration, the content of the fibrous substance in the surface layer portion of the fiber-reinforced porous body is made larger than that in the main body portion, whereby mechanical strength such as impact resistance can be enhanced. Further, even if a part of the main body portion is damaged, it is possible to maintain the shape of the entire fiber-reinforced porous body.

  The present invention can be realized in various modes. For example, it can be realized in the form of a device such as a sound absorbing material or a filter using a fiber reinforced porous body, and a method for producing them.

Explanatory drawing which shows the fiber-reinforced porous body as 1st Embodiment of this invention. Explanatory drawing which shows the fiber reinforced porous body as 2nd Embodiment of this invention. The flowchart which shows the manufacturing method of a fiber reinforced porous body. The figure which shows the experimental result regarding the strength of a fiber reinforced porous body.

  FIG. 1 (A) is a schematic plan view of a fiber-reinforced porous body as a first embodiment of the present invention, and FIG. 1 (B) is a BB sectional view thereof. The fiber-reinforced porous body 100 has a porous substrate 110 having a large number of communicating pores 114. In FIG. 1, for convenience of illustration, the state in which the pores 114 communicate with each other is not drawn, but in reality, a large number of pores 114 communicate with each other so that fluid (gas or liquid) can pass in any direction. Has been formed. Further, in FIG. 1, individual members are drawn in a size different from the actual size, and the size of the pores 114 is drawn in a greatly exaggerated manner. In the present specification, the portion of the porous base material 110 other than the pores 114 is also referred to as “a porous body skeleton”.

  FIG. 1C is an enlarged schematic view of a part of the cross section of the porous substrate 110. The fiber reinforced layer 120 that reinforces the porous substrate 110 is layered and adheres to the wall surface of the pores 114 of the porous substrate 110 (that is, the skeleton surface of the porous body). The fiber reinforced layer 120 is a layer containing a large number of fibrous substances 122. The fibrous substance 122 is bonded to the wall surface of the pores 114 by a bonding phase 124 such as a glass phase. In this case, the fiber-reinforced layer 120 is a layer in which the fibrous substance 122 and the bonding phase 124 are mixed. Alternatively, the fibrous substance 122 may be adhered to the wall surface of the pores 114 by firing without using the bonding phase 124. When the fibrous substance 122 and the porous base material 110 are made of different materials when they are adhered to each other by firing, the firing forms a reaction phase between them at the interface between the fiber reinforced layer 120 and the porous base material 110. It On the other hand, when the fibrous material 122 and the porous base material 110 are made of the same material, the fiber reinforced layer 120 and the porous base material 110 are sintered and bonded to each other by firing.

  The pores 114 are preferably not filled with the fibrous substance 122 that constitutes the fiber-reinforced layer 120. As used herein, the phrase "fibrous material 122 fills pores 114" means that fibrous material 122 is disposed across the center of pores 114. On the other hand, the phrase “the fibrous substance 122 does not fill the pores 114” means that the fibrous substance 122 is arranged in layers on the wall surface of the pores 114 without traversing the center of the pores 114. In the present embodiment, since the fibrous substance 122 does not fill the pores 114, there is an advantage that it is possible to suppress impairing the functions of the pores 114 (filter function and muffling function).

As the material of the porous substrate 110, for example, various oxides such as alumina (Al ₂ O ₃ ), silica (SiO ₂ ), cordierite, mullite, or a mixture thereof can be used. is there. A method of forming a large number of communicating pores 114 in these materials will be described later.

  The porosity of the fiber-reinforced porous body 100 is preferably 32% or more and 96% or less. By adopting this porosity range, a relatively high mechanical strength can be secured without impairing the function of the communicating pores 114. The porosity of the porous base material 110 not including the fiber-reinforced layer 120 is larger than that of the fiber-reinforced porous body 100, and the difference is preferably 1% or more and 3% or less.

As the fibrous substance 122, for example, ceramic fiber, glass fiber, rock wool, or the like can be used, and it is preferable to use oxide fiber. As the ceramic fibers, alumina fibers containing alumina (Al ₂ O ₃ ) as a main component, silica fibers containing silica (SiO ₂ ) as a main component, titania fibers containing titania (TiO ₂ ) as a main component, and zirconia (ZrO ₂ ). ₂ ) zirconia fiber as main component, alumina / silica fiber as main component of alumina and silica, alumina / zirconia fiber as main component of alumina and zirconia, alumina / glass fiber as main component of alumina and glass, etc. It is available.

  Regarding the dimensions of the fibrous substance 122, it is preferable to use short fibers having an average fiber diameter of 2 μm or more and 30 μm or less and an average fiber length of 450 μm or less. By reinforcing the porous base material 110 with such short fibers, the fiber-reinforced layer 120 can be easily adhered to the wall surface of the pores 114 without filling the pores 114. If the average fiber diameter is less than 2 μm, the fibers may be too thin to obtain a sufficient reinforcing effect. Further, when the average fiber diameter is more than 30 μm, the adhesion state of the fibrous substance 122 tends to be deteriorated, so that a sufficient reinforcing effect may not be obtained. Further, if the average fiber length exceeds 450 μm, the fibers may be entangled with each other and a sufficient reinforcing effect may not be obtained. On the other hand, even if the fiber length is excessively short, a sufficient reinforcing effect may not be obtained, so the average fiber length is more preferably 80 μm or more.

  When the fiber-reinforced layer 120 includes the bonding phase 124, the materials of the bonding phase 124 include Si, P, B, Li, Na, K, Mg, Ca, Ba, Sr, Zn, Al, Ni, and Co. It is possible to use a material containing an oxide of at least two of the elements. A typical material of the bonding phase 124 (oxide phase) is glass. A typical example of glass that can be used is silicate glass such as borosilicate glass. In the present specification, the term “glass” is used in a broad sense including a crystallized glass part of which is crystallized. If the fibrous substance 122 is brought into close contact with the wall surface of the pores 114 by using the bonding phase 124 as described above, the adhesion of the fibrous substance 122 is improved and the amount of fibers can be easily increased. The reinforcing effect of the layer 120 can be further improved.

  In the fiber-reinforced porous body 100 of the first embodiment described above, the porosity is 32% or more and 96% or less, and the fibrous substance 122 is formed as the fiber-reinforced layer 120 adhered to the wall surface of the pores 114 in a layered manner. Therefore, the mechanical strength of the porous body can be increased without impairing the function of the communicating pores 114.

  The fiber-reinforced porous body 100 is, for example, a sound absorbing material for a duct through which a high-temperature / high-pressure gas flows, a sound absorbing material for a muffler of exhaust gas of an internal combustion engine, a catalyst filter material for exhaust gas treatment, a filter material for water treatment. It can be used as a member such as.

  FIG. 2 is an explanatory diagram showing a fiber-reinforced porous body 100a as a second embodiment of the present invention. The difference from the first embodiment is that, as shown in FIG. 2 (B), the fiber-reinforced porous body 100a includes a surface layer portion 101 rich in the fibrous substance 122 and a body portion 102 existing below the surface layer portion 101. Other points are the same as those of the fiber-reinforced porous body 100 of the first embodiment.

  FIG. 2C is a partially enlarged schematic view of the main body portion 102 of the fiber reinforced porous body 100a, and FIG. 2D is a partially enlarged schematic view of the surface layer portion 101 of the fiber reinforced porous body 100a. is there. The main body portion 102 has the same configuration as that of FIG. 1C of the first embodiment. The surface layer portion 101 has a larger thickness of the fiber reinforced layer 120 than the body portion 102. In other words, the surface layer portion 101 has a higher content of the fibrous substance 122 per unit weight than the body portion 102. However, even in the surface layer portion 101, the state in which the pores 114 communicate with each other is maintained. By adopting such a configuration, mechanical strength such as impact resistance of the fiber-reinforced porous body 100a can be further enhanced without impairing the function of the communicating pores 114. Further, even if a part of the main body portion 102 is damaged, it is possible to maintain the overall shape of the fiber-reinforced porous body 100a. The thickness of the surface layer portion 101 is preferably in the range of, for example, 0.3 mm or more and 1 mm or less.

  FIG. 3 is a flowchart showing an example of a method for manufacturing a fiber-reinforced porous body. In step T110, the slurry (ceramics slurry) that is the raw material of the porous substrate 110 is adjusted.

  In step T120, an unfired molded body of porous substrate 110 is produced using the slurry prepared in step T110. As the molding method, for example, the following method can be adopted.

<Molding method 1>
First, a polyurethane foam having a large number of pores communicating with each other is prepared, and the polyurethane foam is impregnated with the slurry prepared in step T110. Next, the excess slurry is removed, and the polyurethane foam impregnated with the slurry is dried. As a result, a molded body is obtained in which porous polyurethane foam is impregnated with the unfired ceramics member.

<Molding method 2>
First, the slurry prepared in step T110 is put into a container having a substantially same size as the outer shape of the porous substrate 110. Next, a large number of granular pore-forming materials (resin balls, carbon, etc.) that disappear by firing are charged and the slurry is dried. As a result, a molded body of a ceramic unfired member containing a large number of granular pore-forming materials is obtained.

  In step T130, the porous substrate 110 is obtained by firing the molded body obtained in step T120. This firing is performed at a temperature (for example, a temperature of 900 ° C. or higher and 1600 ° C. or lower) according to the material of the porous base material 110.

  In step T140, the fibrous substance 122 is brought into close contact with the wall surface of the pores 114 of the porous substrate 110 to form the fiber-reinforced layer 120. As the contacting method, for example, the following method can be adopted.

<Adhesion method 1: When using the bonding phase 124>
First, a slurry of a mixture of the raw material (for example, glass raw material) of the bonding phase 124 and the fibrous substance 122 is prepared. Next, the step of dipping the porous base material 110 in the slurry and then drying it is repeated a plurality of times as necessary to adhere the slurry to the wall surfaces of the pores 114 of the porous base material 110. Then, the porous base material 110 to which the slurry is attached is fired at a firing temperature suitable for the material of the bonding phase 124 (for example, a temperature of 850 ° C. or higher and 1050 ° C. or lower).

<Adhesion method 2: When the bonding phase 124 is not used>
First, a slurry of a mixture of the raw material of the porous base material 110 and the fibrous substance 122 is prepared. Next, the step of dipping the porous base material 110 in the slurry and then drying it is repeated a plurality of times as necessary to adhere the slurry to the wall surfaces of the pores 114 of the porous base material 110. Then, the porous base material 110 to which the slurry is attached is fired at a firing temperature suitable for the material of the porous base material 110 (for example, a temperature of 900 ° C. or higher and 1600 ° C. or lower).

  Through the above steps T110 to T140, the fiber-reinforced porous body 100 (FIG. 1) in which the fiber-reinforced layer 120 is in close contact with the wall surface of the pores 114 of the porous substrate 110 is obtained.

  In the next step T150, a fiber-rich surface layer portion 101 (FIG. 2) is formed on the surface of the fiber-reinforced porous body 100, if necessary. In this step T150, the thickness of the fiber reinforced layer 120 in the surface layer portion 101 is increased by performing the same step as the above-described step T140 on the surface layer portion 101. As a result, as shown in FIG. 2, the fiber-reinforced porous body 100a in which the content of the fibrous substance 122 in the surface layer portion 101 is higher than the content of the fibrous substance 122 in the main body portion 102 is obtained. Note that when the fiber-rich surface layer portion 101 is not provided, the step T150 is unnecessary. When performing the step T150, the firing performed in the step T140 may be omitted, and the firing for adhering the fiber reinforced layer 120 may be performed in the step T150.

  FIG. 4 is a diagram showing experimental results regarding the strength of the fiber-reinforced porous body. Samples S01 to S25 are samples of the example, and samples S31 to S35 with * added to the sample number are samples of the comparative example. The samples S01 to S25 of the example were manufactured according to the procedure of FIG. 3 described above. However, in Samples S01 to S07, the fibrous substance 122 was brought into close contact with the porous substrate 110 by sintering without using the bonding phase 124. On the other hand, in Samples S08 to S25, the fibrous substance 122 was adhered to the porous substrate 110 by using the bonding phase 124. Further, in the samples S19 to S25, the fiber-rich surface layer portion 101 (FIG. 2) was formed.

  Among the samples S31 to S35 of the comparative example, the samples S31 and S32 have the communicating pores 114, and the samples S33 and S34 do not have the communicating pores 114. Samples S31 and S33 were produced according to the procedure of steps T110 to T130 in FIG. 3, but the fiber reinforced layer 120 was not formed. In addition, in the samples S32 and S34, the fiber-reinforced layer 120 was formed by the procedure shown in FIG.

The specifications and characteristics of each sample were measured as follows.
<Measurement of porosity>
The porosity (volume%) was measured by the mercury penetration method.
<Measurement of average fiber diameter>
An SEM photograph of the skeleton surface of each sample was taken, and the average value of the fiber thickness observed in 250 μm × 250 μm × 3 visual fields was taken as the average fiber diameter.
<Measurement of average fiber length>
A part of each sample was cut out, and a cross section of 250 μm × 250 μm × 10 fields of view was observed. The field of view was selected such that the area occupied by the fiber-reinforced layer 120 was 30% or more of the entire field of view. Then, the average value of the lengths of fibers (including those partially cut because of the cross section) observable in the visual field was calculated using image analysis software.
<Identification of elements contained in the bonding phase 124>
A part of each sample was cut out, and the polished one was analyzed by EPMA to identify the contained element of the bonding phase 124.
<Measurement of compressive strength>
The compressive strength was measured according to JIS 1681 (ball indenter indentation test method for fine ceramics porous body). The porosity of some samples is outside the range of the porosity (30% to 60%) of the porous body targeted by JIS 1681, but the test method is the same as JIS 1681.

  In the samples S01 to S25 of the examples, the porosity of the fiber-reinforced porous body 100 was 32% (sample S01) at the minimum and 96% at the maximum (sample S07), and the continuous air holes were formed in all of them. Further, for the samples S01 to S25 of the examples, the adhesion test of the fiber reinforced layer 120 was performed. In this adhesion test, after irradiating each sample with ultrasonic waves in water (26 kHz, 1 minute), it was confirmed that the fiber-reinforced layer 120 was firmly supported on the porous base material 110, and the fiber-reinforced layer was reinforced. It was confirmed that the adhesion of the layer 120 was high.

  In the samples S01 to S25 of the examples, the porosity of the fiber-reinforced porous body 100 is in the range of 32% or more and 96% or less, but the compressive strength is 3.0 MPa or more and all have sufficiently high mechanical strength. I was able to confirm that. On the other hand, the sample S31 of the comparative example had a porosity of 64%, but did not have the fiber reinforced layer 120, and therefore had a low compressive strength of 2.7 MPa. Since the compressive strength of the sample S04 of the example having the same porosity (64%) as the sample S31 shows a high value of 4.6 MPa, it can be understood that the fiber reinforced layer 120 has a sufficient reinforcing effect. ..

  In the sample S32 of the comparative example, the porosity was 97%, which was an extremely high value, and the compressive strength was 1.1 MPa, which was a considerably low value. From this, it can be understood that the porosity of the fiber-reinforced porous body 100 is preferably 96% or less.

  Since the samples S33 and S34 of the comparative example do not have continuous vents, the compressive strength showed an extremely high value. However, since it has no continuous ventilation hole, it is not suitable for applications (for example, filters and sound absorbing materials) that utilize the function of the continuous ventilation hole.

  Among the samples S01 to S25 of the examples, the samples S13 to S25 have an average fiber diameter of 2 μm or more and 30 μm or less and an average fiber length of 450 μm or less. These samples S13 to S25 all have a high compressive strength of 5.4 MPa or more, and are preferable in that the mechanical strength is particularly high.

-Modifications The present invention is not limited to the above-described embodiments and embodiments, and can be implemented in various modes without departing from the scope of the invention.

100, 100a ... Fiber reinforced porous body 101 ... Surface layer portion 102 ... Main body portion 110 ... Porous base material 114 ... Porosity 120 ... Fiber reinforced layer 122 ... Fibrous substance 124 ... Bonding phase

Claims (4)

In a fiber-reinforced porous body having an oxide porous substrate having a large number of communicating pores, and a fibrous substance that reinforces the porous substrate,
The porosity of the fiber-reinforced porous body is 32% or more and 96% or less,
The fibrous substance is formed as a fiber-reinforced layer that adheres to the wall surface of the pores in layers without filling the pores of the porous substrate ,
The fiber-reinforced layer includes a bonding phase for bonding the fibrous substance to the wall surface of the pores, and the bonding phase is Si, P, B, Li, Na, K, Mg, Ca, Ba, Sr, Zn, A fiber-reinforced porous body comprising an oxide of at least two elements of Al, Ni and Co. In a fiber-reinforced porous body having an oxide porous substrate having a large number of communicating pores, and a fibrous substance that reinforces the porous substrate,
The porosity of the fiber-reinforced porous body is 32% or more and 96% or less,
The fibrous substance is formed as a fiber-reinforced layer that adheres to the wall surface of the pores in layers without filling the pores of the porous substrate ,
The content of the fibrous substance in the surface layer portion existing on the surface of the fiber-reinforced porous body is higher than the content of the fibrous substance in the main body portion of the fiber-reinforced porous body present under the surface layer portion. A fiber-reinforced porous body characterized by: The fiber-reinforced porous body according to claim 1 ,
The content of the fibrous substance in the surface layer portion existing on the surface of the fiber-reinforced porous body is higher than the content of the fibrous substance in the main body portion of the fiber-reinforced porous body present under the surface layer portion. A fiber-reinforced porous body characterized by: The fiber-reinforced porous body according to any one of claims 1 to 3 ,
A fiber-reinforced porous body, wherein the fibrous substance has an average fiber diameter of 2 μm or more and 30 μm or less and an average fiber length of 450 μm or less.

Images