JPH0532341B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing dense and homogeneous ceramics. More specifically, raw material powder is wet-dispersed into primary particles (in this specification, "dispersed into primary particles" means breaking up particle aggregates and dispersing them in a processing liquid). The same applies hereafter) and
Separating the dispersion treatment liquid and the dispersion treatment powder, adjusting the amount of organic binder in the treatment powder to 40 to 10000 p.pm, and molding the separation treatment powder at a press molding pressure of 4000 kg/cm ² or more, The object of the present invention is to provide a method for producing a dense and homogeneous ceramic sintered body by normal pressure firing. (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 dispersion-treated 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 an organic binder to make a granule of a size of about 30 to 100 μm, and make 4000 kg of the granulated powder / ^cm2
A ceramic sintered body is manufactured by molding at the following molding pressure and firing the molded product under normal pressure, or a ceramic sintered body is manufactured by pressure firing using hot isostatic pressure sintering (HIP), hot press, etc. are doing. (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 larger amount of organic binder than necessary, if 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 a granular powder, the cohesive force may decrease or the size of the granules may become uneven, or the cohesive force 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 present inventors have developed a method of granulating powder by simply mixing and dispersing raw material powder and an organic binder and spray-drying it as in the past, or by spray-drying a dispersed powder that does not contain an organic binder. As a result of intensive research in an attempt to solve the above problems by improving the manufacturing process of ceramic sintered bodies, we have developed a method to wet-disperse raw material powder with an organic binder and disperse it into 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 ² or more, and the molded body is baked under normal pressure to prevent warpage and distortion. This research was completed by discovering that it was possible to produce a ceramic sintered body that was not previously available, and that the inside of the sintered body was denser and more homogeneous than ever before. (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 an organic binder, wet-dispersing it into primary particles, and performing the dispersion treatment. Separating the liquid and the dispersion-treated powder, adjusting the amount of organic binder in the treated powder to 40 to 10,000 p.pm, molding the dispersion-treated powder at a press molding pressure of 4,000 kg/cm ² or more, and firing under normal pressure. It is characterized by: The raw material powder used in the present invention includes aluminum oxide (Al ₂ O ₃ ), boron carbide (B ₄ C), boron nitrogen (BN), titanium carbide (TiN), silicon carbide (SiC),
Examples include zirconium oxide (ZrO ₂ ), 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 dispersing machine used when dispersing raw material powder in a wet manner include a planetary ball mill, a rotary ball mill, a vibrating ball mill, and the like, but a planetary ball mill is preferable because of its high efficiency. In addition, organic binders added to wet dispersion treatment include methylcellulose (MC), ethylcellulose (EC), carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC),
Polyvinyl alcohol (PVA), polyvinyl methyl ether (PVM), vinyl methyl ether-maleic anhydride copolymer, polyvinyl pyrrolidone (PVP), polyvinyl oxazolidone, polyvinyl sulfonic acid, polyethylene oxide (PEO), polyethylene imine (PEI), polyacrylic acid type, polyacrylamide type, gelatin,
Examples include casein, gum arabic, and starch, and one or more of these may be used, with PVA and MC being preferred. Furthermore, when foam is generated during wet dispersion treatment, a polyalkylene derivative, a nonionic surfactant, etc. are added as an antifoaming agent. Typical wet dispersion treatment liquids include water-soluble solvents such as water and/or alcohol, or water-insoluble solvents such as carbon tetrachloride, aromatic hydrocarbons such as benzene, toluene, and xylene, and aliphatic hydrocarbons such as hexane. One or more of these may be used. After wet dispersion treatment, the dispersion treatment liquid and the dispersion treatment powder can be separated by the usual method using paper or cloth, but if the powder has good dispersibility, ultraviolet filtration or It is preferable to use a pressurized filter, a centrifugal filter, or the like. In other words, the dispersion-treated powder obtained by separating the dispersion-treated liquid and the dispersion-treated powder has the minimum necessary amount of organic binder adsorbed on the surface of each primary particle to make the powder uniform during press molding. , and is an essential condition for achieving an amount that allows complete degreasing 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. The 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. Furthermore, if it exceeds 70% by weight, the viscosity of the dispersion increases during dispersion treatment, making it impossible to uniformly disperse fibers. Furthermore, the amount of organic binder added during dispersion treatment is based on 100 parts by weight of raw material powder.
The dispersion treatment is carried out in an amount of 0.2 to 8 parts by weight, preferably 0.5 to 5 parts by weight. If the amount is less than 0.2 parts by weight, the dispersibility of the dispersion-treated powder will be poor and the powder will not be able to 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, so that the sintered body formed by molding and firing this binder has pores and is dense. Homogeneous ceramics cannot be obtained. In addition, in order to determine the optimum amount of organic binder in the dispersion-treated powder, the present inventors separated the dispersion-treated liquid and the dispersion-treated powder, and preliminarily heated the separated and dispersion-treated powder at 105°C for 8 hours. It was dried and the dispersion treatment liquid was evaporated. The dispersion-treated dry powder was fired at 800°C, and the amount of organic binder in the dispersion-treated dry powder was determined from the weight change before and after firing. In addition, in order to confirm whether or not it was an organic binder, confirmation was made using a Fourier transform infrared spectrophotometer (FT-IR) based on the difference spectrum between the dispersion-treated dry powder and the raw material powder. From these results, the amount of organic binder in the dispersion-treated powder is 40 to 10,000 p.pm, preferably 100 to 6,000 p.m.
It is the amount of pm. 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. and,
The amount of the organic binder is at least the minimum amount that uniformly coats the surface of the primary particles of the raw material powder. Furthermore, the amount of antifoaming agent during dispersion treatment is
The minimum amount at which bubbles disappear during dispersion treatment is preferable, and although the amount is not particularly limited, it is sufficient to add 0.1% by weight to the dispersion containing the organic binder. When molding the dispersed powder, a simple and efficient press molding method is preferred. However, the molding pressure is preferably 4000 Kg/cm ² or more, and if the press molding pressure is 4000 Kg/cm ² or less, the ceramic sintered body will not be dense and pores will be observed inside the ceramic sintered body. Regarding firing after press forming, extensive
Although a HIP device may be used, ordinary pressure firing is sufficient. Further, the firing temperature and firing time are not particularly limited, but may be a normal temperature, for example, 1300 to 2000°C, and a known firing time of several hours is sufficient. (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. - Density/Homogeneity Test - 1 Observation of the folded surface using a scanning electron microscope The produced ceramic sintered body was held in a vise and cut by hitting it with a hammer, gold was deposited on the folded surface, and the folded surface was observed using a scanning electron microscope. The material was observed and its 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 pores was 0.1 μm or less, it was determined that the ceramic sintered body was dense and homogeneous. 2 Measurement of density of sintered body The dimensions of the ceramic sintered body were measured using a universal projector, and the volume of the sintered body was determined. In addition, 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 30 g of Ittriya (added 3 mol%) partially stabilized zirconia powder was mixed with 70 g of an aqueous solution in which 1.2 g of polyvinyl alcohol was dissolved, and 0.1 ml of an antifoaming agent (polyalkylene derivative) was added to the mixed solution. Dispersion treatment was performed in a ball mill for 2 hours. The dispersion treatment liquid was centrifuged at 10,000 rpm for 30 minutes to obtain a dispersion treatment powder. The obtained dispersed powder was dried at 80° C. for 2 days to obtain 30 g of dispersed powder. Grind dry powder 250
passed through the mesh sieve. The dry powder was filled into a mold, press-molded at a molding pressure of 6000 kg/cm ² , and then baked 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, followed by stirring with a propeller for dispersion.
The dispersion was spray-dried to obtain 30 g of perfectly spherical granulated powder with an average diameter of 70 μm. After filling the granulated powder into a mold and press-molding it at a molding pressure of 3700 kg/cm ² ,
It was baked at 1500°C for 1 hour. After cooling, a ceramic sintered body was obtained. 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 methylcellulose was dissolved.
Add antifoaming agent (polyalkylene derivative) 0.1 to the mixed liquid.
ml was added and subjected to dispersion treatment for 2 hours in a planetary ball mill. The dispersion treatment liquid was centrifuged at 15000 rpm for 30 minutes to obtain a dispersion treatment powder. The obtained dispersed powder was dried at 80° C. for 2 days to obtain 10 g of dispersed powder. The dry powder was ground and passed through a 250 mesh sieve. The dry powder is filled into a mold and 4000Kg/cm ²
After press molding at a molding pressure of 1,000 yen, it was fired at 1500°C for 1 hour. After cooling, a ceramic sintered body was obtained. Comparative Example 2 A dispersion treatment was carried out under the same conditions as in Example 2, and 240 ml of a 10% methanol aqueous solution was added to the dispersion treatment liquid, followed by stirring with a propeller for dispersion. The dispersion was spray-dried to obtain 10 g of perfectly spherical granulated powder with an average size of 50 μm. The granulated powder was filled into a mold, press-molded at a molding pressure of 3700 Kg/cm ² , and then fired at 1500° C. for 1 hour.
After cooling, a ceramic sintered body was obtained. Next, we will discuss the results of tests on the density and homogeneity of the manufactured sintered ceramics. 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 in FIG. 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 produced in Example 2 was
Attached to the figure. Furthermore, the state of the folded surface of the ceramic sintered body produced 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. The sintered body (Figure 2) and the ceramic sintered body manufactured in Comparative Example 2 (Figure 4)
Compared to Figure), it can be seen that the pores are smaller than 0.1 μm and are extremely dense and homogeneous. Comparative example 1 and comparative example 2
It can be seen that the ceramic sintered body produced by the method has very large pores, and is not dense and has poor homogeneity. 2. Density measurement of sintered bodies Table 1 shows the density measurement results of ceramic sintered bodies.

[Table] As seen from the density measurement results in Table 1, Example 1
The density of the ceramic sintered body produced in Example 2 was 5.95 or higher, reaching 99% of the theoretical density, indicating that it was extremely dense. In comparison, the density of the ceramic sintered bodies manufactured in Comparative Example 1 and Comparative Example 2 was
It can be seen that the density is about 5.4, which is 90% of the theoretical density, which is not dense. Example 3 50 g of an aqueous solution containing 0.25 g of polyvinyl alcohol dissolved therein was mixed with 50 g of Ittriya (3 mol% addition) partially stabilized zirconia powder, and 0.1 ml of an antifoaming agent (polyalkylene derivative) was added to the mixture. Dispersion treatment was carried out for 2 hours using a planetary ball mill. The dispersion treatment liquid was centrifuged at 10,000 rpm for 30 minutes to obtain a dispersion treatment powder. The obtained dispersed powder was dried at 50° C. for 3 days to obtain 50 g of dispersed powder. The dry powder was ground and passed through a 100 mesh sieve. The dry powder was filled into a mold, press-molded at a molding pressure of 5000 kg/cm ² , and then baked at 1500° 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 as a result, it 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. The dense and homogeneous ceramic sintered body manufactured by the present invention has high strength and toughness, so it can be used for electromagnetic materials, hard materials, strength materials, optical materials, biochemical materials, and high-precision processed materials. Ideal for manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a scanning electron micrograph of a 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. Raw material powder is mixed into a dispersion treatment liquid containing an organic binder, wet-dispersed into primary particles, the dispersion treatment liquid and the dispersed powder are separated, and the organic 1. A method for producing ceramics, which comprises adjusting the amount of binder to 40 to 10,000 p.pm, molding the treated powder at a press molding pressure of 4,000 Kg/cm ² or more, and firing under normal pressure. 2 The raw material powder is selected from aluminum oxide, boron carbide, boron nitrogen, titanium carbide, titanium nitride, silicon carbide, zirconium oxide, or zirconium oxide partially stabilized with an oxide such as yttrium, calcium, hafnium, magnesium, or aluminum. 1. A method for producing ceramics according to claim 1, wherein the ceramic is a powder made of: 3 The organic binder is methylcellulose, ethylcellulose, carboxymethylcellulose,
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 acid 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. The ceramic according to 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. manufacturing method. 5. The method for producing ceramics according to claim 1, wherein the concentration of the raw material powder in the dispersion treatment liquid is 5 to 70% by weight. 6 The amount of organic binder added to the raw material powder in the dispersion treatment liquid is 100 parts by weight of the raw material powder,
Claim 1 in the range of 0.2 to 8 parts by weight
Method for manufacturing ceramics described in Section 1. 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.