JPS61286260A - Manufacture of 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 relates to a method for producing dense and homogeneous ceramics.More specifically, the present invention relates to a method for producing dense and homogeneous ceramics. -Dispersing into large particles means breaking up particle aggregates and dispersing them in the processing liquid.The same applies hereinafter].

Separating the dispersion treatment liquid and the dispersion treatment powder, molding the limited treatment powder at a press molding pressure of 4000 kg/cm2 or more, and firing under normal pressure to produce a dense and homogeneous ceramic sintered body. The purpose is to provide law.

(Prior art) The manufacturing method for ceramic sintered bodies usually involves mixing and dispersing raw material powder with an organic binder and spray-drying the dispersed product in order to improve powder fluidity during molding. Granulate to a size of about 30 to 100 μm, or spray dry a dispersed powder that does not contain a binder to a size of about 3 μm.
A granular powder with a size of 0 to 100 μm is prepared, the granulated or granulated powder is molded at a molding pressure of 4000 kg/cm2 or less, and the molded product is fired at normal pressure to prepare a ceramic sintered body, or Ceramic sintered bodies are manufactured by pressure firing using hot isostatic pressure sintering (HIP), hot press, etc.

(Problems to be Solved by the Invention) In the case of a granulated powder obtained by mixing and dispersing raw material powder and an organic binder and spray drying the dispersion, there is a residue on the surface of the granule or as a binder for the powder. Because there is a large amount of organic binder in the required mass-market products, when such granulated powder is molded and fired, when the organic binder is degreased, it causes pores inside the ceramic sintered body, resulting in a dense and homogeneous product. A sintered body cannot be obtained. In addition, when a dispersed powder that does not contain an organic binder is spray-dried to form granules, the cohesive force may decrease, the size of the granules may become uneven, or the cohesive forces between particles may differ. During molding, it does not fit well and a homogeneous molded product cannot be obtained.

Sintering such a non-uniform molded body causes warping and distortion, and furthermore, the inside of the sintered body is dense and not homogeneous. Furthermore, even if a molded body is pressure-fired using granulated powder or granular powder, a dense and homogeneous sintered body cannot be obtained due to the same problem as described above. Further, the pressure firing apparatus has many other drawbacks, such as being large-scale and very expensive.

Therefore, the inventors of the present invention have decided to either simply mix and disperse the raw material powder with a machine binder and spray dry it to granulate it, as in the past, or spray dry a dispersed powder that does not contain an organic binder to granulate it. As a result of intensive research in an attempt to solve the above problems by improving the manufacturing process of ceramic sintered bodies, instead of treating the raw material powder with an organic binder, we wet-dispersed the raw material powder with an organic binder to form primary particles. The dispersion liquid and the dispersion-treated powder are separated, the separated dispersion-treated powder is molded at a press molding pressure of 4000 kg/cm or more, and the molded body is fired at normal pressure to prevent warpage. We discovered that it is possible to produce a ceramic sintered body without distortion, and that the interior of the sintered body is denser and more homogeneous than ever before.
This led to the completion of this research.

(Means for Solving the Problems) That is, the method for producing ceramics according to the present invention involves mixing a raw material powder into a dispersion treatment liquid containing a mechanical binder, wet-dispersing it into primary particles, and dispersing the dispersion. The treatment liquid and the dispersion-treated powder were separated, and the dispersion-treated powder was heated at 4000 kg/cm.
It is characterized by being molded at two or more press molding pressures and then fired under normal pressure.

The raw material powder used in the present invention is aluminum oxide (A
I 2033, boron carbide (BO), boron nitride (B
NI, titanium carbide (TiNl, silicon carbide (Sin),
Examples include zirconium oxide (ZrO2) or zirconium oxide partially stabilized with oxides such as yttrium, calcium, hafnium, magnesium, and aluminum. Zirconium oxide partially stabilized with oxides of yttrium, calcium, hafnium, and aluminum is preferred.

Examples of the dispersion machine used when dispersing the raw material powder in a wet manner include a planetary ball mill, a rotary ball mill, a vibrating ball mill, etc., but a planetary ball mill is preferable because of its high efficiency. The organic binder added to the treatment includes methylcellulose (MO3,
Ethyl cellulose (EC1, carboxymethyl cellulose (CMCI), hydroxyethyl cellulose (HEC)
, polyvinyl alcohol (PVA), polyvinyl methyl ether (PVM), vinyl methyl ether-maleic anhydride copolymer, polyvinyl pyrrolidone (PVPJ,
Examples include polyvinyl oxazolidone, polyvinyl sulfonic acid, polyethylene oxide (PEO), polyethylene imine (PEI), polyacrylic acid type, polyacrylamide type, gelatin, casein, gum arabic, starch, etc., and one or more of these types is used, preferably PVA or MO. Furthermore, when foam is generated during wet dispersion treatment, a polyalkylene conductor, a nonionic surfactant, etc. are added as an antifoaming agent. The wet dispersion treatment liquid includes water and/or a water-soluble solvent such as alcohol, carbon tetrachloride, and benzene.

Water-insoluble solvents such as aromatic hydrocarbons such as toluene and xylene, and aliphatic hydrocarbons such as hexane are typical, and 1M or 2M1 or more of these are used. After the wet dispersion treatment, the dispersion treatment liquid and the dispersion treatment powder can be separated by the usual method using five doors paper or one cloth, but if the dispersibility of the powder is good, there are limitations. It is preferable to use external 5 filtration, pressure filtration, centrifugal S filtration, etc. In other words, the dispersion-treated powder obtained by separating the dispersion-treated liquid and the dispersion-treated powder is uniform during press molding. This is an essential condition for ensuring that the minimum required amount of organic binder is sorbed onto the surface of each primary particle, and that the amount is such that it can be completely degreased during normal pressure firing. In the present invention, in order to wet-disperse the raw material powder, it is possible to apply the powder to an aqueous solution in which an organic binder and an antifoaming agent are dissolved in advance, and/or a solution of a water-soluble solvent, or a solution of a water-insoluble solvent. Raw material powder is added and mixed so that the concentration is 5 to 70% by weight, preferably 10 to 50% by weight. If it is less than 5% by weight, the production efficiency of the dispersed powder is poor. Moreover, if it exceeds 70% by weight, the viscosity of the dispersion increases during dispersion treatment, making it impossible to uniformly disperse it. Further, the amount of the organic binder added during the dispersion treatment is α2 to 8 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the raw material powder. If the amount is less than 0.02 parts by weight, the dispersibility of the dispersion-treated powder is poor and the powder cannot be converted into primary particles. In addition, if it is 8 parts by weight or more, a large amount of organic binder remains in the dispersion-treated powder that is separated into the dispersion-treated liquid and the dispersion-treated powder, and the sintered body formed from this will have pores and become dense. homogeneous ceramics cannot be obtained. In addition, in order to determine the optimum amount of binder in the dispersion-treated powder, the present inventors separated the dispersion-treated liquid and the dispersion-treated powder, and preheated the separated and dispersion-treated powder at 105°C for 8 It was dried for a while and the dispersion treatment liquid was evaporated. The dispersion-treated dry powder was fired at 3 °C, and the amount of organic binder in the dispersion-treated dry powder was determined from the weight change before and after firing.Also, to confirm whether it was an organic binder or not. This was confirmed from the difference spectrum between the dispersion-treated dry powder and the raw material powder using Fourier transform infrared spectroscopy (FT-IR).From these results, the amount of organic binder in the dispersion-treated powder was 40%.
~10000 p, p, m, preferably 100-600
0 p, p, m, quantity. This amount of binder can be obtained by dispersing the powder raw material under the above-mentioned wet dispersion treatment conditions and separating it from the dispersion treatment liquid. The amount of the organic binder is at least the minimum amount for uniformly coating the surface of the primary particles of the raw material powder. Furthermore,
The amount of antifoaming agent during dispersion treatment is preferably the minimum amount that eliminates foam during dispersion treatment, and although the amount is not particularly limited, it is sufficient to add α1% by weight to the dispersion containing the organic binder.

When molding the dispersed powder, a simple and efficient press molding method is preferred. However, a molding pressure of 4000 kg/cm2 or higher is preferable, and if the press molding pressure is 4000 kg/7cm2 or lower, the ceramic sintered body will not become dense and pores will be observed inside the ceramic sintered body.

For firing after press forming, a large-scale HIF device may be used, but ordinary pressure firing g'c' is sufficient. Further, the firing temperature and firing time are not particularly limited, and may be a normal temperature, for example, 1,300 to 2,000°C, and a well-known several hours is sufficient for the firing time.

(Examples) Next, Examples and Comparative Examples will be given to specifically clarify the present invention, but the present invention is not limited thereto. The effectiveness was evaluated using the following test method.

1) Density and homogeneity test - 1] Observation of folded surfaces using a scanning electron microscope The produced ceramic sintered body was held in a vise and cut by hitting with a hammer, gold was deposited on the folded surface, and folded using a scanning electron microscope. The surface was observed, and the density and homogeneity were determined visually based on the presence and size of pores. That is, if there were no pores or the size of the pores was 01 μm or less, it was determined that the ceramic sintered body was dense and homogeneous.

2) Density measurement of the sintered body Measure the dimensions of the ceramic sintered body using a universal projector.
The volume of the sintered body was determined. Further, the weight of the sintered body was measured, and the density was determined from the volume and weight, and it was determined that the higher the density, the denser it was.

Example 1 Water solution 270 in which 1.2g of polyvinyl alcohol was dissolved
30 g of partially stabilized zirconia powder based on Ittriya (3 mol % added) was mixed with the mixture, and 0.1 ml of an antifoaming agent (polyalkylene derivative) was added to the mixture, followed by dispersion treatment in a planetary ball mill for 2 hours.

The dispersion treatment liquid was centrifuged at 1000 Or, p, m, r for 3030 minutes to obtain a dispersion treatment powder.

The obtained dispersed powder was dried at 808C for 2 days to obtain 30 g of dispersed powder. The dry powder was ground and passed through a 250 mesh sieve. The dry powder was filled into a mold and heated to 60
After press molding at a molding pressure of 00 kg/cm2,
It was fired at 1500'C for 1 hour.

After cooling, a ceramic sintered body was obtained.

Comparative Example 1 A dispersion treatment was carried out under the same conditions as in Example 1, and 900 ml of purified water was added to the dispersion treatment liquid and the mixture was stirred with a propeller for dispersion. The dispersion was spray-dried to obtain 30 g of true spherical A-grain powder with an average diameter of 70 μm. The granulated powder was filled into a mold and heated to 3700 m
After press molding at a molding pressure of kg/cm2, 1500
It was baked at ℃ for 1 hour.

After cooling, a ceramic sintered body was obtained.

Actual Example 2 10 g of Ittriya (3 mol% addition) partially stabilized zirconia powder was mixed with 90 g of a 10% aqueous methanol solution in which 0.5 g of methyl cellulose was dissolved, and 1 ml of antifoaming agent (polyalkylene derivative) α was added to the mixture. was added and subjected to dispersion treatment for 2 hours in a planetary ball mill. 1,500 ml of the dispersion treatment liquid
Centrifugation was performed for 30 minutes at Or, p, m to obtain a dispersed powder. The obtained dispersed powder was dried at 80° C. for 2 days to obtain 10 g of dispersed powder. Grind the dry powder to 250
passed through the mesh sieve. The dry powder was filled into a mold, press-molded at a molding pressure of 4000 kg/cm 2 , and then baked at 1500°C for 1 hour. After cooling, a ceramic sintered body was obtained.

Comparative Example 2 Dispersion treatment was carried out under the same conditions as Example 2, and 10% of the dispersion treatment liquid was
% methanol aqueous solution was added and dispersed by stirring with a propeller. The dispersion was spray dried to give an average of 50
10 g of a true spherical granulated powder of μm was obtained. The granulated powder was filled into a mold, press-molded at a molding pressure of 3700 kg/cm2, and then fired at 1500°C for 1 hour. After cooling, a ceramic sintered body was obtained.

Next, we will discuss the results of denseness and homogeneity tests of the manufactured ceramic sintered bodies.

1) Observation of the folded surface using a scanning electron microscope The folded surface of the ceramic sintered body produced in Example 1 was observed using a scanning electron microscope and is attached to Figure 1. The state of the folded surface of the ceramic sintered body manufactured in Comparative Example 1 is attached to FIG.

The state of the folded surface of the ceramic sintered body manufactured in Example 2 is attached to FIG. Furthermore, the state of the folded surface of the ceramic sintered body manufactured in Comparative Example 2 is attached in FIG. All the attached photos were observed at 10,000x magnification.

As can be seen from the state of these folded surfaces, the ceramic sintered body manufactured in Example 1 (Figure 1) and the ceramic sintered body manufactured in Example 2 (Figure 3) are different from the ceramic sintered body manufactured in Comparative Example 1. Compared to the sintered body (Figure 2) and the ceramic sintered body manufactured in Comparative Example 2 (Figure 4), it can be seen that the pores are smaller than 0.1 μm and are extremely dense and homogeneous.Comparative Example 1 and Comparison The ceramic sintered body produced in Example 2 had very large pores, indicating that it was not dense and had poor homogeneity.

2), Density measurement of sintered body Table 1 shows the density measurement results of the ceramic sintered bodies.

Table 1 Density of Ceramic Sintered Body As can be seen from the density measurement results in Table 1, the density of the ceramic sintered body produced in Example 3 and Example 2 was 5.95 or higher, which is 99% of the theoretical density. It can be seen that it is very precise. In comparison, the density of the ceramic sintered bodies manufactured in Comparative Example 1 and Comparative Example 2 was approximately 5.4, which was 90% of the theoretical density, indicating that it was not dense.

Example 3 Aqueous solution in which 0.25 g of polyvinyl alcohol was dissolved 50
50 g of partially stabilized zirconia powder based on Ittriya (3 mol % added) was mixed with g, and 1 ml of an antifoaming agent (polyalkylene derivative) was added to the mixture, and the mixture was subjected to a dispersion treatment for 2 hours in a planetary ball mill. The treatment liquid was heated to 1000 Or, p
, m, for 30 minutes to obtain a dispersed powder. The obtained dispersion-treated powder was dried at 50° C. for 3 days to obtain 50 g of dispersion-treated powder. The dry powder was ground and passed through a 100 mesh sieve. The dry powder was filled into a mold and heated to 5000
After press molding at a molding pressure of kg/cm2, 15
It was baked at 00°C for 1 hour. After cooling, a ceramic sintered body was obtained. This sintered body was also subjected to folded surface observation using a scanning electron microscope (not shown) and was found to be a dense and homogeneous ceramic sintered body.

(Effects of the Invention) According to the manufacturing method of the present invention, a dense and homogeneous ceramic sintered body can be easily obtained.

Since the dense and homogeneous ceramic sintered body produced by the present invention has high strength and toughness, II.
! It is ideal for manufacturing magnetic materials, hard materials, strength materials, optical materials, biochemical materials, and high-precision processing materials.

[Brief explanation of drawings]

FIG. 1 is a scanning electron micrograph of the folded surface of the ceramic sintered body produced in Example 1. FIG. 2 is a scanning electron micrograph of a folded surface of the ceramic sintered body produced in Comparative Example 1. FIG. 3 is a scanning electron micrograph of the folded surface of the ceramic sintered body produced in Example 2. FIG. 4 is a scanning electron micrograph of the folded surface of the ceramic sintered body produced in Comparative Example 2.

Claims (1)

[Scope of Claims] 1. Mix the raw material powder in a dispersion treatment liquid containing an organic binder, wet-disperse it into primary particles, separate the dispersion treatment liquid and the dispersion treatment powder, and prepare the dispersion treatment powder. 4000kg body
A method for producing ceramics, characterized by forming at a press forming pressure of /cm^2 or more and firing under normal pressure. 2. The raw material powder is made of aluminum oxide, boron carbide, boron nitride, titanium carbide, titanium nitride, silicon carbide, zirconium oxide, or zirconium oxide partially stabilized with oxides such as yttrium, calcium, hafnium, magnesium, aluminum, etc. The method for producing ceramics according to claim 1, wherein the selected powder is one. 3. The organic binder is methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyvinyl methyl ether, vinyl methyl ether-maleic anhydride copolymer, polyvinyl pyrrolidone, polyvinyl oxazolidone, polyvinyl sulfonic acid, polyethylene oxide, polyethylene imine, polyacrylic. acidic compounds,
Polyacrylamide compounds, gelatin, casein,
The method for producing ceramics according to claim 1, wherein the ceramic is one or a mixture of two or more selected from gum arabic and starch. 4. Claim 1, wherein the dispersion treatment liquid is a mixture of one or more of water and/or water-soluble solvents such as alcohol, and water-insoluble solvents such as carbon tetrachloride and aromatic hydrocarbons.
Method for manufacturing ceramics described in Section 1. 5. The raw material powder concentration in the dispersion treatment liquid is 5 to 70% by weight.
A method for producing ceramics according to claim 1. 6. The amount of organic binder added to the raw material powder in the dispersion treatment liquid is 0.2 to 8 parts by weight per 100 parts by weight of the raw material powder.
The method for producing ceramics according to claim 1, wherein the range is in parts by weight. 7. The method for producing ceramics according to claim 1, wherein the wet dispersion of the raw material powder is performed using a planetary ball mill, a rotary ball mill, or a vibrating ball mill.