JPS6236083A - Manufacture of porous ceramics - 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 "Industrial Application Field" The present invention is applicable to filter media, aeration agents, heat insulating materials, membranes, raw carriers, gas separation membranes, etc. This paper relates to a method for manufacturing quality ceramics.

``Prior art'' As a method for manufacturing oxide-based porous ceramics mainly composed of oxides such as alumina, and non-oxidized porous ceramics mainly composed of carbides or nitrides, (1) fly ash, carbon powder, shirasu, etc. in slurry; Mix the blowing agent.

(2) Gas is introduced while stirring the slurry.

(8) Do not completely sinter.

(4) Mixing combustible particles into the raw material.

The following methods are known, but among these, (1) and (2)
There were drawbacks such as the fact that it was easy to leave residue.

"Problems to be Solved by the Invention" The present invention solves the above-mentioned drawbacks of conventional methods and facilitates control of pore diameter and porosity.

``Means for Solving the Problems'' Inorganic powder containing an organic binder is turned into a slurry and frozen, then vacuum freeze-dried and then fired.

``Operation'' After freezing the inorganic powder slurry, vacuum freeze-drying is performed to sublimate the ice between the inorganic powders and form voids, which are obtained by uniformly dispersing the inorganic powder in the slurry. The vacuum freeze-dried product exhibits a uniform porosity depending on the moisture content of the slurry, and the pore diameter can be controlled by the moisture content of the slurry and the freezing rate as well as the porosity.

“Example” (1) Alumina (Reynolds RC-HP-PDM)
.

Water and organic binder PVA were mixed in the proportions shown in Table 1, and each slurry obtained by mixing was 50m+WX22
Pour into a 0mL x 50+mD stainless steel vat to a thickness of 5cm, freeze at -0.5℃ per minute to -20℃, dry in a vacuum freeze dryer (FD-550 manufactured by Tokyo Rika), and heat in an electric furnace. Table 1 also shows the results of measuring various properties of samples obtained by firing at 1650° C. for 4 hours. However, the bending strength was measured by cutting out a piece measuring 8 mm x 4 m x 85 mm.

From the table above, it is clear that increasing the water content of the slurry increases the porosity and pore size.

(2) Alumina 500f of Sample 45 from the previous example.

Table 2 shows the properties of samples fixed on water 5009 and PVA75P, other conditions being the same as in the previous example, and only the freezing rate being changed.

From the above table, it can be seen that when the mixing amount is fixed and the freezing rate is increased, the pore size is made smaller and the bending strength is increased without changing the porosity; It is revealed that the pore size is obtained.

In both of the above examples, alumina was used as the inorganic powder, but mullite may be used depending on the purpose.

Minerals such as cordierite or powders of mineral composition can be selected, and powders of non-oxide ceramics such as not only oxides but also carbides such as silicon carbide or silicon nitride or nitrides can be used.

Additionally, a liquid such as 8th butyl alcohol may also be used in addition to wood removal.

However, the mixing ratio of these inorganic powders and water is determined according to the desired porosity and pore size, as shown in Table 1, but the pore size is too small to sinter the powder after drying. In terms of bonding between powders, the upper limit for moisture content is 0.1 or more, within twice the weight of the powder, and the particle size of the powder is determined by the organic binder described below and if necessary. 10μ is determined within the range that can be turned into slurry in a state containing a deflocculant.
In the following, the bonding strength of the organic binder is adjusted to be 0.1 μm or more, and the bonding strength of the organic binder is adjusted, but in the case of commonly used PVA, it is preferably 8 to 20 μm based on the total amount of powder and water.

"Effects of the Invention" The present invention is characterized in that an organic powder containing an organic binder is turned into a slurry and frozen, then vacuum freeze-dried and then fired. As described above, the porosity and pore size can be controlled by controlling the moisture content of the slurry, and the desired pore size can be obtained by changing the freezing temperature of the slurry, making it possible to mass produce porous porcelain with desired porosity and pore size. It has the great effect of making it easier.

Claims (1)

[Claims] A method for producing porous ceramics, which comprises turning inorganic powder containing an organic binder into a slurry, freezing it, vacuum freeze-drying it, and then firing it.