JPS59111967A - Ceramic porous body - 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 ceramic porous body having a three-dimensional network cell structure having internal communication spaces, and particularly to a ceramic porous body having high strength at high temperatures.

Ceramic porous bodies with a three-dimensional network cell structure with internal communication spaces have a wide range of uses, such as molten metal furnace materials, catalyst carriers, teasel filters, and even breathable insulation materials, and are widely used in industrial applications. It is useful. However, when used in these applications, the ceramic porous body is required to have high strength at high temperatures because it is often used in environments with temperatures ranging from several hundred degrees to tens of hundreds of degrees.

When strength at such high temperatures is required, it is preferable to form the ceramic porous body with alumina or cordierite as the main component, but a ceramic porous body with even greater strength at high temperatures is desired.

In view of the above circumstances, the inventors of the present invention have conducted extensive research into porous materials with high strength at high temperatures, and have found that a ceramic porous material having a three-dimensional network cell structure with internal communication spaces has been developed. When needle-like crystals are dispersed in the material, it has excellent high temperature creep resistance and high strength at high temperatures, which makes this porous ceramic material suitable for applications that are exposed to high temperatures, such as breathable insulation materials. It has been found that it can be suitably used for. In particular, it has been found that when mullite obtained from alumina and silica is dispersed in a ceramic porous body mainly composed of alumina or cordierite, it exhibits significantly high strength at high temperatures. This is what we have come to.

The present invention will be explained in more detail below.

The ceramic porous body of the present invention has a three-dimensional network cell structure having an internal communication space, and is made up of needle-shaped crystals dispersed in the ceramic forming the porous body.

In this case, the ceramic forming the porous body is preferably one whose main component is alumina or cordierite, and mullite needle-shaped crystals obtained from alumina and silica are dispersed in this ceramic. It is preferable. More preferably, cordierite with a high alumina content is prepared at a temperature close to the decomposition temperature of the cordierite phase ((1350 to 160
Mullite (approximately 0°C) obtained by heating to
3At2o3.2810□) A needle crystal dispersion is used. Here, when alumina is used as the main component as the ceramic forming the porous body, the alumina content is 50 to 9.
The content is preferably 5% by weight, and when cordierite is the main component, the content is preferably 50 to 95% by weight. Furthermore, the content of the needle-like crystals is 1 to 9.
Preferably it is 5% by weight.

When obtaining the ceramic porous body as described above, it is preferable to use one produced by attaching a ceramic slurry to a flexible polyurethane foam without a cell membrane and removing carbonization from the flexible polyurethane foam by sintering the slurry ( In this way, we decided to form a ceramic porous body from a flexible polyurethane foam without a cell membrane, and a cage-shaped ceramic porous body consisting only of the ridges of a regular dodecahedron was obtained. The exhaust gas passes through with little loss, and since the internal communication space is intricate, for example, when this ceramic porous body is used as a breathable heat insulating material, when the exhaust gas passes through the internal communication space, it is (This ensures reliable contact and efficient heat exchange.) However, when producing a ceramic porous body using such a method, a method is adopted in which the needle-like crystals are dispersed in the ceramic slurry in advance. I can do it. However, this method may increase the viscosity of the ceramic slurry, making it difficult to impregnate and remove excess slurry, resulting in poor impregnation and clogging of the porous body. Therefore, there is a method in which the ceramic slurry that does not contain acicular crystals is impregnated, excess slurry is removed, and dried, and acicular crystals are produced during firing, or the obtained ceramic porous body is used to form acicular crystals. It is preferable to reheat the porous ceramic body to a temperature at which the porous ceramic material is dispersed.

The ceramic porous body of the present invention is suitably used in places where high-temperature gases and liquids are allowed to pass, such as molten mud materials, catalyst carriers, diesel particulate filter 1, and air-permeable heat insulating materials. It is effectively used as a thermal insulation material.

When the ceramic porous body of the present invention is used for the above-mentioned purposes, the bulk specific gravity of the ceramic porous body is 0.2.
5 to 0.6, and the average diameter of the internal communication space is 0.2 to 0.6.
10 in darkness, without clogging in any direction, with a porosity of 75 to 95 cm, and with a pressure loss of 0.1 to 0.1 in water column when air passes through one sub-thickness at a wind speed of 1 meter per second. 40
Preferably, it is between. Especially when used as a breathable heat insulating material, the bulk specific gravity is 0.25 to 0.6, preferably 0.25 to 0.5, and the average diameter is 0.2 to 10.
mm - preferably 0.2 to 5 mm, more preferably 0
．． 3-1.5 mn.

The porosity is 75-95%, the trench density is 80-95%, and the pressure drop of air is 0.1-40III++, preferably 5-3 in water column when passing through a thickness of 1 tyn at a wind speed of 1 m/s.
It is necessary that the temperature is 0, and as a result, a highly effective air-permeable heat insulating material with excellent both air permeability and heat insulation properties can be obtained.

On the other hand, if it deviates from the above range, it will not provide a good breathable heat insulating material. That is, if the bulk specific gravity is less than 0.25, the strength as a heat insulating material is insufficient, and if the bulk specific gravity is greater than 0.6, clogging will occur and pressure loss will increase, and if the average diameter is 0. If the diameter is smaller than 2, the strength will decrease, leading to an increase in pressure loss, and if the average diameter is larger than 10, the contact between the insulation material and the exhaust gas will be insufficient, and the insulation material will not have enough contact with the exhaust gas from the front side (heating side) to the back side. Since radiant heat leaks to the exhaust side (exhaust side), it is not a good breathable insulation material. Furthermore,
When the porosity is less than 75 coefficients, the heat conduction within the solid improves and the temperature difference between the front and back surfaces of the insulation material becomes small, leading to the dissipation of radiant heat from the back surface (exhaust side) of the insulation material. When the porosity exceeds 95 inches, the strength decreases, and furthermore,
Those with a pressure loss of more than 40% often cause problems in combustion in heating furnaces, etc., and likewise cannot provide good air permeable heat insulating materials.

In addition, when the ceramic porous body according to the present invention is used as a breathable heat insulating material, a radiation sickness improving agent is dispersed in the ceramic porous body having the above-mentioned structure, or the entire lattice of the ceramic porous body or the lattice on the exhaust gas inflow side is treated with radiation. The radiation performance of the breathable heat insulating material can be further improved by treating the disease with a disease-improving agent. In this case, silicon carbide, silicon nitride, etc. can be used as radiation sickness improvers, but those that show particularly remarkable effects are transition metal oxides such as vanadium, chromium, manganese, iron, cobalt, and nickel. The oxides can be suitably used. In addition, when dispersing these radiation sickness improving agents in a ceramic porous body, by mixing the radiation sickness improving agent into the ceramic slurry to form the ceramic porous body during the production of the ceramic porous body,
The radiation sickness improving agent can be dispersed in the ceramic porous body, and when the radiation sickness improving agent is coated on the lattice of the ceramic porous body, the entire or part of the formed ceramic porous body is soaked in a solvent such as water. By immersing it in a dispersion containing a radiation sickness improver and drying or sintering it,
The radiation sickness improver can be made into a liquid form. The amount of the radiation sickness improving agent used is based on the total weight of the ceramic porous body from 00 to 90,
In particular, it is preferable to set the amount to 1 to 50%, thereby achieving a high radiation effect. 1. In addition to the above transition metal oxides, or in addition to the above transition metal oxides, one or more metal nitrides and metal carbides are dispersed in the lattice of the ceramic porous body or attached to the lattice surface, and wave peaks are formed. This makes it possible to increase the radiant heat of the ceramic porous body and improve the thermal shock resistance and heat resistance, so it is suitable for applications such as breathable heat insulating materials. Nitrides include TiN and ZrN.

Examples of carbide include St, N4, etc., and 'l”ic as a carbide.
, ZrC1HfC, VC, TaC, NbC, WC, B
Examples include IC and SIC. Also metal borides, such as AtB, SIB, TiB2.

ZrB2. HfB + VB2, TaB, WB
etc. can also be dispersed in the grating or attached to the grating surface.

Examples are shown below.

〔Example〕

Ceramic slurry made from ceramic raw materials containing 85% alumina and silica, etc. is attached to flexible polyurethane foam without cell ILU, and after drying, it is heated to a maximum temperature of 1.
By firing at 450° C., a ceramic porous body having a three-dimensional network cell structure having internal communication spaces without clogging in any direction was obtained.

When this ceramic porous body was observed by taking an electron micrograph at a magnification of approximately 1000 times, it was confirmed that needle-like crystals (mullite) were dispersed.

Note that the bulk specific gravity of this ceramic porous body was 0.42.

Next, the above ceramic porous body (length 150wn).

Width: 50 mm, thickness: 20 wn) A was placed on supports S and B as shown in the drawing, heated to 1400°C, and the deflection amount Δd at that time was measured. The result was Omm, indicating high temperature creep resistance. It was found that it was excellent.

[Brief explanation of drawings]

The drawing is an explanatory diagram of a method for measuring the amount of deflection of a porous ceramic body.

Claims (1)

[Claims] 1. A ceramic or porous body having a three-dimensional network cell structure with internal communication spaces, characterized in that needle-like crystals are dispersed in the ceramic forming the porous body. Ceramic porous body. 2. The ceramic or porous body has a bulk specific gravity of 0.25 to 0.6, and the internal communication space is not clogged in any direction.
2. The ceramic porous body according to claim 1, which has an average diameter of 0.2 to 10 mg and is compressed. 3. The ceramic or porous body according to claim 1 or 2, wherein the ceramic or porous body is mainly composed of alumina or cordierite, and the acicular crystals are made of mullite.