JPS59169963A - High strength ceramic foam and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-strength ceramic foam suitable for use in catalyst carriers for automobile exhaust gas treatment, diesel particulate (dust) trapping materials, etc., and a method for producing the same.

Cordierite ceramic foam has been receiving a lot of attention in recent years as being ideal as a carrier for collecting diesel particulate matter. It has been proposed to use additives to densify the porous parts of cordierite and improve its mechanical strength. .

The present invention eliminates the problems of the prior art and provides a high-strength ceramic 7 ohm with improved mechanical strength without impairing the excellent thermal shock resistance of the cordierite ceramic foam, and a method for manufacturing the same. The purpose is to provide. Thus, the high-strength ceramic foam of the present invention is characterized by being composed of cordierite and β-subodumene. In addition, the method for producing a high-strength ceramic foam of the present invention (c) includes adding lithium oxide (L) to a ceramic foam made of cordierite and mullite.
i2O) and silicon dioxide (S 102 ), and is fired at a temperature of 1000° C. to 1200° C. to produce β-sposimene.

A 7-ohm ceramic made of cordierite and mullite used in the production of the high-strength ceramic foam made of cordierite and β-spodumene of the present invention is obtained by a conventional method. In other words, the composition range in which cordierite and mullite can be produced is silica 4
The weight ratio is 5 to 55, the alumina is 30 to 45, and the magnetic mass is 11 to 16. Examples of compositions in which mullite can be clearly identified by X-ray diffraction within this composition range include 52 weight parts of silica, 37 weight parts of alumina, and 11 weight parts of magnefluoride. A mixture of talc, kaolin, and aluminum hydroxide, water, an organic binder, and a surfactant are mixed and stirred to form a slurry.

The process of immersing, for example, an organic porous body in this slurry and drying is repeated, and a predetermined amount of the slurry is adhered to the organic porous body to obtain a core 1 as shown in the figure.

Next, side 2 of this core 1 that is not involved in ventilation
A slurry is also applied to the core 1, and the slurry is applied in a spray form to the end face 3 of the core 1 which is involved in ventilation. When the slurry is attached to the organic porous body in this way and then fired, the organic porous body disappears and a 7-ohm ceramic made of cordierite and mullite is formed.
can get.

The above firing is usually performed at a temperature of 1350°C to 1410°C,
Do this for 3 to 7 hours. The organic binder used for thickening the above-mentioned slurry includes, for example, polyvinyl alcohol. It is also used to produce ceramic foam consisting of cordierite and mullite.
An example of the five-hole structure is urethane foam.

Lithium oxide (L12
0) and silicon dioxide (S IO2), and then calcined at a temperature of 1000"C to 1200°C to produce β-sponoyumene. A strong ceramic foam can be obtained.

The reason why the above firing temperature was limited to 1000°C to 1200°C is that below 1000°C, β-sposomene does not form, whereas when it exceeds 1200°C, β-sposomene melts, resulting in high frequency ceramic foam formation. This is because it cannot be obtained.

The high-strength ceramic foam of the present invention has high mechanical strength because the porous portion of cordierite is densified with β-spodumene. Furthermore, both cordierite and β-sponomene are base materials with low thermal expansion properties, and in particular, the coefficient of thermal expansion of β-sponomene is smaller than that of cordierite, so it has the advantageous properties of conventional cordierite ceramic foam. High strength can be achieved without reducing thermal shock resistance. That is,
Because the ceramic foam of this invention has high strength, the temperature difference at which cracks occur due to thermal shock is the same as that of cordierite ceramic foam, but since the growth of the crack is suppressed, the temperature difference at the time of cracking leading to fracture is reduced. will improve.

Further, according to the method of the present invention, ceramic or kutuom made of cordierite and mullite is impregnated with a water bath solution containing L120 and 5IO2, and fired.
Since sponomene is generated, it is possible to uniformly generate β-sponomene even in the porous portion inside the cordierite, and as described above, it is possible to obtain a mechanically strong ceramic foam made into a carpet. can. Furthermore, according to the method of the present invention, L1
Since the aqueous solution containing L120 and S r O2 is impregnated and fired, the formation of β-sposomene through the reaction of L120 and SiO2 with mullite becomes uniform, and an excellent high-strength ceramic foam can be obtained.

Further, in the method of the present invention, the amount of β-spodumene in the ceramic can be adjusted as appropriate by adjusting the amount of mullite and the amount of L i 20 and S r 02 to be impregnated.

Furthermore, in the method of this invention, L120 and S
The molar ratio with r 02 is not particularly limited.

Examples of the present invention will be described below.

Example Raw material mixture 10 consisting of talc, kaolin and aluminum hydroxide blended to have a composition of 52 parts by weight of silica, 37 parts by weight of alumina and 11 parts by weight of Magnefoot.
0 parts by weight, 70 parts by weight of water, 1.5 mt parts of polyvinyl alcohol as an organic binder, and 1 part by weight of a surfactant were mixed and stirred to form a slurry.

The process of immersing the urethane foam in this slurry and drying it was repeated to adhere a predetermined amount of the slurry to the urethane foam to obtain the core 1 shown in the figure.

Next, a slurry was applied to the side surface 2 of the core 1 that does not participate in ventilation, and the slurry was sprayed and adhered to the end surface 3 of the core 1 that is involved in ventilation.

The product obtained in the above manner was fired at a temperature of 1380"C for 5 hours to obtain a ceramic foam consisting of cordierite and mullite. The shape of this ceramic foam was 93 cm in diameter and 66 cm in height. O The above ceramic foam made of cordierite and mullite was impregnated with an aqueous solution containing L120 and 5I02 at a total molar ratio of 122, and then dried.
Firing at a temperature of 150° C. resulted in three patterns of ceramic forms A, B and C identified by X-ray diffraction according to the degree of impregnation with the aqueous solution described above.

The three samples A, B and C obtained in this way are 3
It has a dimensional network structure. In addition, regarding the products identified by X-ray diffraction for each sample,
Also listed in the table.

Here, the direct thermal shock tail measurement method involves placing the ceramic foam in an electric furnace with a predetermined island degree, treating it for 20 minutes, and then leaving it to cool at room temperature (20 to 30 degrees Celsius) for about 1 hour. ) at 550°C with melt A %L, repeat this operation twice at the valley temperature, and increase the treatment temperature sequentially at 50°C intervals until the hammering sound of the ceramic foam changes from a clear sound to a dull sound. The temperature at which the crack occurs is evaluated as the crack initiation temperature, and the temperature at which a crack occurs on the external surface and as the crack progresses, force is applied in the direction of rupturing the crack is evaluated as the fracture temperature. did.

Comparative Example I A ceramic foam made of cordierite and mullite was prepared in the same manner as in the example except that the ceramic foam made of cordierite and mullite was not impregnated with an aqueous solution containing L i20 and S IO2 at a molar ratio of 1:2. Ceramic form D wo'4 ta.

The results are shown in the table. The table also shows the products identified by X-ray diffraction of the sample.

Comparative Example 2 As an example of #J, almost no mullite is generated and almost 100% cordierite is produced, a composition of 48% silica, 36% alumina, and 16% magnesia is used. A cordierite surface ceramic 7 ohm E was obtained in the same manner as in the example except that a raw material mixture of Merck, kaolin and aluminum hydroxide blended to have this composition was used.

The results are shown in the table. In addition, X for test'4=+E
Products identified by line diffraction are also shown in the table.

Comparative Example 3 After coating the cordierite ceramic foam E obtained in Comparative Example 2 with γ-alumina and drying it,
Calcined at a temperature of 700°C and coated with γ,-alumina)! Ceramic foam F was obtained.

The results are shown in the table. Note that the products identified by X-ray diffraction for Sample F are also shown in the table.

Comparative Example 4 The cordierite ceramic foam E obtained in Comparative Example 2 was impregnated with an aqueous solution containing Li2O and SiO2 at a molar ratio of 1:4, dried, further coated with γ-alumina, and heated at 1150°C. When fired at a temperature of , two patterns of ceramic foams G and H were obtained, which were identified by X-ray diffraction, depending on the degree of impregnation with the aqueous solution.

The results are shown in the table. Note that the products identified by X-ray diffraction for Samples G and H are also shown in the table.

Comparative Example 5 Li20 and S
After being impregnated with a filtrate solution containing iO2 at a molar ratio of 1:4 and then calcined at a temperature of 1,150°C, the filtrate solution, which was identified by X-ray diffraction, differed depending on the degree of impregnation of the water bath solution. Two patterns of ceramic form J and K are Samurai.

The results are shown in the table. Note that the products identified by X-ray diffraction for Samples J and K are also shown in the table.

As is clear from the results in the above table, the ceramic forms A, B, and C of the present invention, which are mainly composed of cordierite and β-spodumene, are superior to the conventional cordierite ceramic form E shown in Comparative Example 2. , equivalent or superior in thermal shock resistance, and superior in isostatic strength.

Ceramic foam Did of Comparative Example 1 consisting of cordierite and mullite which was not impregnated with an aqueous solution containing L l 20 and 5i02k.Since the coefficient of thermal expansion of mullite is larger than that of cordierite, Ceramic 7 of Comparative Example 2 Compared to Ohm E, it was inferior in both isostatic strength and thermal shock resistance.

Furthermore, ceramic form F shown in lump comparative example 3 also has γ-A
Due to the influence of t203, the thermal shock resistance was poor.

Ceramic 7 ohm G shown in Comparative Examples 4 and 5,
For H, J and K, L120.

Ceramic form A of the present invention can generate β-subosomene on the surface of a ceramic 7 ohm using SiO2 and γ-At2o3.

It is difficult to uniformly generate β-sponomene inside as shown in B and C, and unreacted L120/$10
2.3102 (cristobalite) and α-At20
All of them were inferior in thermal shock resistance because they were ceramics of 7 ohm mixed with 5 etc.

[Brief explanation of drawings]

The figure is a schematic diagram for explaining the names of each part of the ceramic foam shown in Examples and Comparative Examples of the present invention. J... Ceramic foam core, 2... 5il 1 piece of ceramic foam core, 3... End face of ceramic 7 ohm core.

Claims (2)

[Claims] (1) A high-strength ceramic foam characterized by consisting of cordierite and β-sponomene. (2) A cordier characterized in that a ceramic foam made of cordierite and mullite is impregnated with an aqueous solution containing lithium oxide and silicon dioxide, and fired at a temperature of 1000°C to 1200°C to produce β-sposiemene. A method for producing a high-strength ceramic 7 ohm consisting of light and β-sposiemen.