JPH0667792B2 - Method of manufacturing three-dimensional mesh structure made of ceramics - Google Patents

Description

Detailed Description of the Invention A. Object of the Invention (1) Field of Industrial Application The present invention relates to a method for producing a ceramic three-dimensional network structure having innumerable pores.

(2) Conventional technology Conventionally, when manufacturing this kind of structure, an organic foam having a three-dimensional network structure is immersed in a ceramic sludge to adhere the ceramic sludge to the surface of the organic foam and A technique is used in which the pores are filled with a ceramic slurry, the ceramic slurry is dried and solidified, and then the organic foam is burned and the ceramic is sintered.

(3) Problems to be Solved by the Invention However, when the above method is adopted, there are the following problems.

(a) Since the organic foam corresponds to the pores of the structure,
Since the pores are large, it is not possible to obtain the structure in which the fine pores are substantially uniformly distributed over the entire structure.

(b) Sintering of the ceramic is performed after the organic foam is burned and removed, so in order to ensure the dimensional accuracy of the ceramic, it is necessary to start the sintering of the ceramic immediately after the removal of the organic foam. I won't. In order to meet this requirement, a sintering aid that exhibits a sintering promotion function at low temperatures is used,
Since the ceramic is sintered at a low temperature, the strength of the structure is low.

(c) A lot of man-hours are required to manufacture an organic foam having a three-dimensional network structure.

It is an object of the present invention to provide a method for manufacturing the structure that can solve the above problems.

B. Configuration of the Invention (1) Means for Solving the Problems The method for producing a ceramic three-dimensional network structure according to the present invention comprises an Al ₂ O ₃ —Na ₂ O—B ₂ O ₃ —SiO ₂ -based powder or Al. _A step of obtaining a molded body by using a mixed powder in which a pore-forming powder which is made of at least one of ₂ O ₃ -B ₂ O ₃ -SiO ₂ -K ₂ O based powder and which can be eluted by an acid is dispersed in a ceramic powder; A step of subjecting the molded body to a sintering treatment to obtain a sintered body; and a step of subjecting the sintered body to an elution treatment for imparting ultrasonic vibration to an acid to elute the pore-forming powder. Characterize.

(2) Action According to the method, since the specific pore-forming powder dispersed in the sintered body is eluted while applying ultrasonic vibration to the acid, the elution treatment is efficiently performed, and the fine powder is finely divided. It is possible to obtain a three-dimensional network structure in which the pores are distributed almost uniformly over the whole.

Further, since the ceramic powder can be sintered under normal sintering conditions, it is possible to obtain a high-strength sintered body, and thus a three-dimensional network structure. Generally, the ceramic powder contains impurities that contribute to the reduction of the strength of the structure. However, since the impurities are almost completely removed from the sintered body by the elution treatment, the elution treatment is performed by the structure. It is also effective in improving the strength of the body.

(3) Example Ceramic powder constitutes a three-dimensional network structure,
As the seed powder, Si ₃ N ₄ , S having a diameter of 5 μm or less is used.
Single powders such as iC and ZrO ₂ and mixed powders thereof are applicable.

The pore-forming powder that can be eluted by acid is used to positively form fine pores in the sintered body and obtain a three-dimensional network structure having a predetermined porosity from the sintered body. The following are applicable as powders.

That is, Al ₂ O ₃ 20 wt% or less Na ₂ O 8 to 40 wt% B ₂ O _{3 30 to} 65 wt% SiO ₂ 40 wt% or less of each powder is mixed, and the mixed powder is at least one of CaO and MgO. Of Al ₂ O ₃ —Na having a glassy diameter of 1 to 5 μm and obtained through the steps of melting and pulverizing
_{2 O-B 2 O 3 -SiO} 2 based powder, and Al ₂ O ₃ 20 wt% or less B ₂ O ₃ 30 to 65 wt% _SiO 2 40 wt% or less K ₂ O 40% by weight of a mixture of powders At least one of CaO and MgO is added to the mixed powder, and Al ₂ having a diameter of 1 to 5 μm, which is vitreous and is obtained through each step of melting and crushing as described above.
O ₃ is _{-B 2 O 3 -SiO 2 -K 2} O -based powder.

The reason for limiting the blending amount of each powder as described above is that if the blending amount deviates from the above blending amount, crystals precipitate in the pore-forming powder to form a non-uniform structure, and elution with acid becomes impossible.

Furthermore, in order to improve the sinterability of the ceramic powder, a sintering aid powder is used if necessary. As the seed powder, Al ₂ O ₃ , Y ₂ O ₃ having a diameter of 0.1 to 1 μm,
Single powders such as MgO and SiO ₂ and mixed powders thereof are applicable.

The compounding amounts of the ceramic powder, the sintering aid powder and the pore forming powder are: ceramic powder 75 to 97% by weight, sintering aid powder 10% by weight or less and pore forming powder 15% by weight or less.

The reason for limiting the blending amount of the sintering aid powder as described above is
This is because the sinterability of the ceramic powder does not change so much even if it is mixed in an amount exceeding 10% by weight. The amount of the pore-forming powder mixed varies depending on the target porosity of the structure, but if the amount of the pore-forming powder exceeds 15% by weight, the porosity becomes too high and the strength decreases.

When a molded body is obtained by using a mixed powder composed of the ceramic powder, the sintering aid powder and the pore forming powder, various molding methods such as a slip casting method, a pressure molding method and an injection molding method are used. A molding pressure of 25 to 150 MPa is suitable.

The sintering conditions of the molded body are 1200 to 1500 ° C.,
It is 0.5 to 24 hours. The compact exhibits a linear shrinkage of 0.2 to 10% by this sintering treatment.

Further, when a three-dimensional network structure is obtained from the sintered body, the sintered body is immersed in an acid solution of HCl, HNO ₃ single acid or a mixed acid thereof at 30 to 60 ° C. for a predetermined time. At that time, while circulating the acid solution, 16 to 2
Ultrasonic vibration of 5 MHz is applied, whereby the acid solution spreads to almost all impurities contained in the pore forming powder and the powder, the ceramic powder and the sintering aid powder, and the pores are formed in a short time. The elution process of powder and impurities can be completed.

[Example I] Al ₂ O ₃ 10.6 wt% Na ₂ O 24.8 wt% B ₂ O ₃ 40.5 wt% SiO ₂ 20.3 wt% MgO 3.8 wt% was used as a pore-forming powder. Using Al ₂ O ₃ -N which is vitreous and has a diameter of 1 to 5 μm
obtaining _{a 2 O-B 2 O 3} -SiO 2 system powder.

Ceramic powder Si ₃ N ₄ 97.5% by weight Sintering aid powder Al ₂ O ₃ 0.1% by weight Pore forming powder 2.4% by weight are mixed to obtain a mixed powder. A pressure molded body is applied to obtain a plate-shaped molded body having a length of 60 mm, a width of 20 mm and a thickness of 5 mm at a molding pressure of 75 MPa.

The molded body is fired at 1500 ° C. for 8 hours to obtain a sintered body.
In this case, the shaped body exhibits a linear shrinkage of about 8%.

The sintered body was immersed in a flow of 4N HNO ₃ heated to 50 ° C., and while maintaining this state for a predetermined time while applying ultrasonic vibration of 20 MHz to the HNO ₃ , the porosity forming powder and The impurities are eluted to obtain a three-dimensional network structure.

The structure has fine pores with a diameter of 0.5 to 3 μm distributed substantially uniformly over the whole, and the porosity is about 13%.
Is. It is also known to have a high transverse rupture strength of 87 to 92 kg f / mm ² .

FIG. 1 shows the relationship between the elution treatment time for the sintered body and the removal rate of the pore-forming powder. Line a corresponds to the case where the nitric acid is passed, and line b corresponds to the case where the nitric acid is passed and ultrasonic vibration is applied.

As is apparent from FIG. 1, 100% removal of the pore-forming powder requires 4 to 5 hours in the case of the line a, but 7 to 8 minutes in the case of the line b. This indicates that the elution treatment is efficiently performed by applying ultrasonic vibration to the acid.

Although it is possible to perform the elution treatment of the pore-forming powder without flowing nitric acid, in that case, a longer elution treatment time is required than in the case of flowing nitric acid. However, the time can be shortened by using ultrasonic vibration together.

FIG. 2 shows the relationship between the elution treatment time and the transverse rupture strength of the three-dimensional network structure when nitric acid was circulated and ultrasonic vibration was applied. From FIG. 2, the variation width of the transverse rupture strength of the above-mentioned structure decreases with the increase of the elution treatment time, and when the elution treatment is carried out for 30 minutes, the transverse rupture strength of 87 to 92 kg f / mm ² can be obtained. it is obvious.

In FIG. 2, in the region where the elution treatment time is 5 minutes or less, the removal of the pore-forming powder is partially performed, so that the variation of the transverse rupture force is large. On the other hand, since the pore-forming powder is completely removed in the region of 10 minutes or more, the variation in transverse rupture force is caused by impurities. However, when the elution treatment time reaches 30 minutes, the impurities are completely removed, so that the variation range of the transverse rupture strength is reduced and the transverse rupture strength is also increased.

C. EFFECTS OF THE INVENTION According to the present invention, the pore-forming powder specified above as dispersed in the sintered body is eluted while applying ultrasonic vibration to the acid, so that the elution treatment is efficiently performed. As a result, it is possible to obtain a three-dimensional network structure in which fine pores are distributed almost uniformly over the whole. The efficiency of this elution treatment contributes to the improvement of the productivity of the three-dimensional network structure.

Further, since the ceramic powder can be sintered under normal sintering conditions, it is possible to obtain a high-strength sintered body, and thus a three-dimensional network structure. In this case, since the elution treatment can remove almost completely the impurities contained in the ceramic powder and contributing to the reduction in the strength of the structure, the elution treatment has the effect of improving the strength of the structure. Have.

Furthermore, a three-dimensional network structure can be obtained through the steps of mixing, molding, sintering, and elution of each powder, and the productivity is better than that in the case of using a conventional organic foam.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the elution processing time and the removal rate of the pore-forming powder, and FIG. 2 is a graph showing the relationship between the elution processing time and the transverse rupture strength of the three-dimensional network structure.

Claims (1)

[Claims] 1. Al ₂ O ₃ —Na ₂ O—B ₂ O ₃ —SiO.
₂ system powder or _{Al 2 O 3 -B 2 O 3} -SiO 2 -K 2
A step of obtaining a molded body by using a mixed powder which is made of at least one of O-based powders and in which a pore-forming powder capable of being eluted by an acid is dispersed in a ceramic powder; And a step of subjecting the sintered body to an elution treatment in which an ultrasonic wave is applied to an acid to elute the pore-forming powder, the method for producing a three-dimensional mesh structure made of ceramics.