阅读说明：本技术 陶瓷成形体的脱脂方法和陶瓷烧成体的制造方法 (Method for degreasing ceramic molded body and method for producing ceramic fired body ) 是由 小野木哲也 于 2019-02-20 设计创作，主要内容包括：包含陶瓷粉末和有机粘合剂的陶瓷成形体包含可氧化的陶瓷粉末作为陶瓷粉末,或者,包含可氧化的金属或金属化合物,或者,与包含可氧化的金属或金属化合物的固体相接。将该陶瓷成形体在氢气氛中以超过25℃/h的升降温速度升温和/或降温至在1100℃以上且1400℃以下的范围内设定的最高温度,然后在该最高温度进行脱脂。(The ceramic shaped body comprising a ceramic powder and an organic binder comprises an oxidizable ceramic powder as the ceramic powder, or comprises an oxidizable metal or metal compound, or is connected to a solid comprising an oxidizable metal or metal compound. The ceramic compact is heated and/or cooled to a maximum temperature set in a range of 1100 ℃ to 1400 ℃ in a hydrogen atmosphere at a temperature increase/decrease rate exceeding 25 ℃/h, and then degreased at the maximum temperature.)

1. A method for degreasing a ceramic molded body, characterized by degreasing a ceramic molded body comprising a ceramic powder and an organic binder,

the ceramic shaped body comprises an oxidizable ceramic powder as the ceramic powder, or comprises an oxidizable metal or metal compound, or is connected to a solid body comprising an oxidizable metal or metal compound,

the ceramic compact is heated to a maximum temperature set within the range of 1100 ℃ to 1400 ℃ at a temperature rise rate of more than 25 ℃/h in an atmosphere of a simple hydrogen gas or an atmosphere of a mixed gas of an inert gas and hydrogen gas having a hydrogen gas concentration of 20 vol% or more, is degreased at the maximum temperature, and is then cooled at a temperature decrease rate of more than 25 ℃/h.

2. A method for degreasing a ceramic molded body, characterized by degreasing a ceramic molded body comprising a ceramic powder and an organic binder,

the ceramic shaped body comprises an oxidizable ceramic powder as the ceramic powder, or comprises an oxidizable metal or metal compound, or is connected to a solid body comprising an oxidizable metal or metal compound,

the ceramic compact is heated at a heating rate of more than 25 ℃/h to an intermediate temperature set in a range of 600 ℃ to 1100 ℃ in an atmosphere of a simple hydrogen gas or an atmosphere of a mixed gas of an inert gas and hydrogen gas having a hydrogen gas concentration of 20 vol% or more, is then held at the intermediate temperature for a predetermined time, is subsequently heated at a heating rate of more than 25 ℃/h to a maximum temperature set in a range of 1100 ℃ to 1400 ℃ so as to exceed the intermediate temperature, is degreased at the maximum temperature, and is then cooled at a cooling rate of more than 25 ℃/h.

3. The method of degreasing a ceramic molded body according to claim 1 or 2,

the oxidizable ceramic powder is aluminum nitride, silicon nitride or silicon carbide.

4. The method for degreasing a ceramic molded body according to any one of claims 1 to 3,

the oxidizable metal is Ni, W or Mo, and the oxidizable metal compound is WC or MoC.

5. The method for degreasing a ceramic molded body according to any one of claims 1 to 4,

the temperature increase/decrease speed is 50 ℃/h or more and 500 ℃/h or less.

6. The method for degreasing a ceramic molded body according to any one of claims 1 to 5,

the ceramic compact has a porosity of 20 vol% or more and 70 vol% or less.

7. A method for producing a ceramic fired body, comprising:

a degreasing step of degreasing a ceramic molded body containing a ceramic powder and an organic binder; and

a firing step of firing the degreased ceramic molded body,

the degreasing method of the ceramic molded body according to any one of claims 1 to 6 is used in the degreasing step.

Technical Field

The present invention relates to a method for degreasing a ceramic compact and a method for producing a ceramic fired body.

Background

As a method for degreasing a ceramic compact, a method is known in which a ceramic compact having a predetermined shape obtained by molding a slurry containing a ceramic powder, an organic binder, and a dispersion medium is subjected to a heat treatment to thereby degrease the ceramic compact. For example, patent document 1 describes that the time required for completion of degreasing can be sufficiently shortened by heat-treating a ceramic molded body in superheated steam containing oxygen at a predetermined oxygen partial pressure. However, in this degreasing method, when an oxidizable substance (for example, aluminum nitride, Ni, or the like) is contained in the ceramic molded body, the oxidizable substance may be oxidized by superheated steam, and the target physical properties may not be obtained.

On the other hand, patent document 2 discloses a method of degreasing a laminate in which a ceramic molded body and an internal electrode are laminated, the ceramic molded body containing a ceramic raw material and an organic binder, the internal electrode containing Ni as a main component, by raising the temperature to a temperature of from room temperature to 1300 ℃. In this method, since degreasing is performed in a nitrogen atmosphere, oxidation of the laminate can be prevented.

Disclosure of Invention

(problems to be solved by the invention)

However, in patent document 2, in order to suppress the occurrence of cracks in the degreased laminate, the temperature rise rate of 20 to 400 ℃ is set to 25 ℃/h or less. Therefore, there is a problem that degreasing requires a long time.

The present invention has been made to solve the above problems, and a main object of the present invention is to reliably degrease a ceramic formed body in a short time while preventing cracks in the ceramic formed body, and to prevent the ceramic formed body and/or a solid body in contact with the ceramic formed body from being oxidized in a degreasing treatment.

(means for solving the problems)

The degreasing method of the ceramic formed body of the invention is a degreasing method of a ceramic formed body for degreasing a ceramic formed body containing ceramic powder and an organic binder, wherein,

the ceramic compact contains an oxidizable ceramic powder as the ceramic powder, or contains an oxidizable metal or metal compound, or is in contact with a solid containing an oxidizable metal or metal compound,

the ceramic compact is heated to a maximum temperature set in a range of 1100 ℃ to 1400 ℃ at a temperature rise rate of more than 25 ℃/h in an atmosphere of a simple hydrogen gas or an atmosphere of a mixed gas of an inert gas and hydrogen gas having a hydrogen gas concentration of 20 vol% or more, then degreased at the maximum temperature, and thereafter cooled at a temperature drop rate of more than 25 ℃/h.

Another degreasing method for a ceramic molded body according to the present invention is a degreasing method for a ceramic molded body in which a ceramic molded body containing a ceramic powder and an organic binder is degreased,

the ceramic compact contains an oxidizable ceramic powder as the ceramic powder, or contains an oxidizable metal or metal compound, or is in contact with a solid containing an oxidizable metal or metal compound,

in a hydrogen gas atmosphere or in a mixed gas atmosphere of an inert gas and hydrogen gas having a hydrogen gas concentration of 20 vol% or more, the ceramic compact is heated at a temperature rise rate of more than 25 ℃/h to an intermediate temperature set in a range of 600 ℃ to 1100 ℃ inclusive, is held at the intermediate temperature for a predetermined time, is heated at a temperature rise rate of more than 25 ℃/h to a maximum temperature set in a range of 1100 ℃ to 1400 ℃ inclusive so as to exceed the intermediate temperature, is degreased at the maximum temperature, and is then cooled at a temperature fall rate of more than 25 ℃/h.

The method for producing a ceramic fired body of the present invention comprises:

a degreasing step of degreasing a ceramic molded body containing a ceramic powder and an organic binder; and

a firing step of firing the degreased ceramic molded body,

the degreasing method of the ceramic molded body is adopted in the degreasing step.

In the degreasing method for a ceramic molded body according to the present invention, the ceramic molded body is treated in an atmosphere containing a suitable amount of hydrogen gas, and therefore, the ceramic molded body and/or a solid in contact with the ceramic molded body can be prevented from being oxidized in the degreasing treatment. Further, since hydrogen gas has good thermal conductivity and high diffusibility, temperature variation is less likely to occur in the ceramic molded body at the time of temperature rise or temperature fall. Therefore, even if the temperature increase/decrease speed is set to a speed exceeding 25 ℃/h and the degreasing is performed in a short time, cracks are less likely to occur in the ceramic molded body. Further, since the degreasing is performed at the highest temperature set in the range of 1100 ℃ to 1400 ℃, the ceramic compact can be reliably degreased. It is considered that carbon generated from the organic binder is generated by, for example, C +2H₂→CH₄Is removed from the ceramic shaped body. As described above, according to the degreasing method of the present invention, it is possible to reliably degrease the ceramic formed body in a short time while preventing cracks in the ceramic formed body, and to prevent the ceramic formed body and/or a solid body in contact with the ceramic formed body from being oxidized in the degreasing treatment.

When the ceramic compact is thick, the ceramic compact is preferably heated at a heating rate exceeding 25 ℃/h to an intermediate temperature set in a range of 600 ℃ to 1100 ℃ before being degreased at a maximum temperature set in a range of 1100 ℃ to 1400 ℃ and then held at the intermediate temperature for a predetermined time. In this way, the degreasing can be performed more reliably and the time from the start of temperature increase to the end of temperature decrease can be shortened, as compared with the case where the degreasing is not maintained at the intermediate temperature for a predetermined time.

Drawings

Fig. 1 is an explanatory diagram illustrating an example of a mode in which a solid 12 is embedded in a molded body 14.

Fig. 2 is an explanatory diagram illustrating an example of a mode in which the solid 12 is embedded in the molded body 14.

Fig. 3 is an explanatory diagram showing an example of a manner in which the solid 12 is laminated on the molded body 14.

FIG. 4 is an explanatory view showing steps of production of a ceramic compact and heat treatment.

Detailed Description

The following describes an embodiment of the method for degreasing a ceramic molded body according to the present invention. The method of degreasing the ceramic compact of the present invention is not limited to the following embodiments, and various methods can be implemented as long as they fall within the technical scope of the present invention.

The method of degreasing the ceramic compact according to the present embodiment is a method of degreasing a ceramic compact including ceramic powder and an organic binder. The ceramic shaped body comprises an oxidizable ceramic powder as the ceramic powder, or alternatively comprises an oxidizable metal or metal compound, or is connected to a solid body comprising an oxidizable metal or metal compound. In the degreasing method of the present embodiment, the ceramic compact is heated at a temperature increase rate of more than 25 ℃/h to a maximum temperature set in a range of 1100 ℃ to 1400 ℃ in a hydrogen atmosphere, and then degreased at the maximum temperature, and thereafter, the temperature is reduced at a temperature decrease rate of more than 25 ℃/h. Alternatively, the ceramic compact is heated at a temperature increase rate of more than 25 ℃/h in a hydrogen atmosphere to an intermediate temperature set in a range of 600 ℃ to 1100 ℃ inclusive, then held at the intermediate temperature for a predetermined time, subsequently heated at a temperature increase rate of more than 25 ℃/h to a maximum temperature set in a range of 1100 ℃ to 1400 ℃ inclusive so as to exceed the intermediate temperature, then degreased at the maximum temperature, and thereafter cooled at a temperature decrease rate of more than 25 ℃/h.

The ceramic compact may be dried after forming a slurry containing a ceramic powder, an organic binder and a dispersion medium into a predetermined shape, or may be formed into a predetermined shape after dry-mixing a raw material powder containing a ceramic powder and a solid organic binder. The porosity of the ceramic compact is not particularly limited, but is preferably 20 vol% or more and 70 vol% or less. When the porosity is within this range, hydrogen gas easily passes through the inside of the ceramic formed body, and therefore degreasing of the ceramic formed body is completed in a shorter time. If the porosity is less than 20 vol%, hydrogen gas is less likely to pass through the inside of the ceramic compact, and therefore, it takes some time to degrease the ceramic compact, or the ceramic compact may be damaged due to an increase in internal pressure caused by decomposition gas. If the porosity exceeds 70 vol%, the strength of the ceramic molded body may be reduced, and handling may be difficult. In the case of a ceramic molded body obtained by molding the slurry, voids (open pores) are generated in the ceramic molded body by drying, and the porosity is a value calculated based on the voids. The thickness of the ceramic compact is not particularly limited, and when a method of holding at an intermediate temperature is selected as the degreasing method of the ceramic compact, the thickness of the ceramic compact is preferably 3mm or more and 30mm or less, and more preferably 15mm or more and less than 30 mm. When the ceramic compact is thin, the degreasing is sufficiently performed even without holding at an intermediate temperature. Therefore, when a method in which the ceramic compact is not held at the intermediate temperature is selected as the degreasing method for the ceramic compact, the thickness of the ceramic compact is preferably 3mm or more and less than 15 mm.

The ceramic powder may be an oxide-based ceramic powder or a non-oxide-based ceramic powder. Examples of the powder include powders of aluminum oxide, yttrium oxide, aluminum nitride, silicon carbide, samarium oxide, magnesium fluoride, ytterbium oxide, and the like. These powders may be used alone in 1 kind, or in combination of 2 or more kinds. The oxidizable ceramic powder is a ceramic powder that can be oxidized, and examples thereof include aluminum nitride, silicon nitride, and silicon carbide.

Examples of the organic binder include polyurethane resins, vinyl butyral resins, vinyl alcohol resins, vinyl acetal resins, vinyl formal resins, polyimide resins, phenol resins, melamine resins, epoxy resins, coumarone-indene resins, acrylic resins, aromatic vinyl resins, maleic acid resins, celluloses and cellulose derivatives, gelatins and gelatin derivatives, waxes, starches, and the like. The amount of the organic binder used is not particularly limited, and is, for example, 1 part by mass or more and 30 parts by mass or less, preferably 3 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the ceramic powder.

As the organic binder, a gelling agent may be used. As the gelling agent, for example, isocyanates, polyols, and a catalyst may be contained. Among them, the isocyanate is not particularly limited as long as it has an isocyanate group as a functional group, and examples thereof include Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and modified products thereof. The molecule may contain a reactive functional group other than the isocyanate group, and may contain a large amount of reactive functional groups like polyisocyanate. The polyol is not particularly limited as long as it has 2 or more hydroxyl groups capable of reacting with an isocyanate group, and examples thereof include Ethylene Glycol (EG), polyethylene glycol (PEG), Propylene Glycol (PG), polypropylene glycol (PPG), polytetramethylene glycol (PTMG), polyhexamethylene glycol (PHMG), polyvinyl alcohol (PVA), and the like. The catalyst is not particularly limited as long as it promotes the urethane reaction between the isocyanate and the polyol, and examples thereof include triethylenediamine, hexamethylenediamine, and 6-dimethylamino-1-hexanol. When a substance containing an isocyanate, a polyol and a catalyst is used as a gelling agent, a polyurethane resin is produced by a gelling reaction. The polyurethane resin functions as an organic binder.

Examples of the dispersion medium include water, alcohols, ketones, esters, ethers, aromatic hydrocarbons, and polybasic acids. Examples of the alcohols include isopropanol, 1-butanol, ethanol, 2-ethylhexanol, terpineol, ethylene glycol, glycerol, and the like. Examples of the ketone include acetone and methyl ethyl ketone. Examples of the esters include butyl acetate, dimethyl glutarate, and glyceryl triacetate. Examples of the ethers include ethylene glycol monoethyl ether, diethylene glycol butyl ether, and diethylene glycol butyl ether acetate. Examples of the aromatic hydrocarbons include toluene, xylene, solvent naphtha, and the like. Examples of the polybasic acids include glutaric acid and the like. When a gelling agent is used as the organic binder, a mixture of a polybasic acid ester (e.g., dimethyl glutarate) and an aliphatic polybasic acid ester (e.g., triacetin) is preferably used as the dispersion medium.

When a slurry containing a ceramic powder, an organic binder, and a dispersion medium is molded into a predetermined shape to produce a ceramic molded body, a dispersant, a plasticizer, and the like may be separately added to the slurry. The dispersant is not particularly limited as long as it is a dispersant for uniformly dispersing the ceramic powder in the solvent. Examples thereof include anionic, cationic and nonionic surfactants. Specific examples thereof include a polycarboxylic acid copolymer, a polycarboxylate, a sorbitan fatty acid ester, a polyglycerin fatty acid ester, a phosphate ester copolymer, a sulfonate copolymer, and a polyurethane polymer copolymer having a tertiary amine. Examples of the plasticizer include a phthalic acid plasticizer, a glycol plasticizer, and an adipic acid plasticizer. Examples of the method of forming the slurry into a ceramic molded body having a predetermined shape include casting, extrusion, casting, injection molding, uniaxial press molding, and the like. These molding methods are conventionally known.

The oxidizable metal is not particularly limited as long as it is a metal that can be oxidized and does not melt at the highest temperature during degreasing, and examples thereof include Ni, Mo, and W. Examples of the oxidizable metal compound include MoC and WC. The oxidizable metal or metal compound may be dispersed in the ceramic compact, or may be disposed so that a solid of the non-oxidizable metal or metal compound (for example, a plate-like body, a linear body, a block-like body, etc.) is in contact with the compact. Examples of the method of contacting the solid body with the molded body include a method of embedding the solid body 12 in the molded body 14 as shown in fig. 1 and 2 (in fig. 1, the solid body 12 is embedded in a state where one surface thereof is exposed to the outside from the molded body 14, and in fig. 2, the solid body 12 is completely embedded in the molded body 14), and a method of laminating the solid body 12 on the molded body 14 as shown in fig. 3.

In the degreasing method of the ceramic molded body according to the present embodiment, the hydrogen atmosphere is an atmosphere of a single hydrogen gas or an atmosphere of a mixed gas of an inert gas having a hydrogen concentration of 20 vol% or more and a hydrogen gas. Examples of the inert gas include nitrogen and argon, and nitrogen is preferable in view of cost. The hydrogen atmosphere is allowed to contain a trace amount of impurity gas (e.g., oxygen, etc.) inevitably contained. Since the ceramic compact and/or the solid in contact with the ceramic compact are treated in the above-described hydrogen atmosphere, the degreasing treatment is hardly oxidized. Further, since hydrogen gas has good thermal conductivity and high diffusibility, a temperature difference is less likely to occur in the entire ceramic molded body during temperature increase and decrease. Therefore, even if the temperature increase/decrease speed is set to a speed exceeding 25 ℃/h and the degreasing is performed in a short time, the ceramic molded body is less likely to crack. If the hydrogen concentration of the hydrogen atmosphere exceeds 20 vol%, the effect of such hydrogen cannot be exerted. The temperature increase/decrease speed is preferably set to 50 ℃/h or more in view of degreasing in a shorter time. In consideration of the capacity of the furnace, the temperature increase/decrease speed is preferably set to 500 ℃/h or less. That is, the temperature increase/decrease speed is preferably set to 50 ℃/h or more and 500 ℃/h or less. In addition, in view of avoiding the possibility of cracking of the ceramic molded body due to the difference in thermal expansion, it is preferably set to 300 ℃/h or less.

In the degreasing method for a ceramic molded body according to the present embodiment, the maximum temperature is set in a range of 1100 ℃ to 1400 ℃. In this way, the ceramic molded body is heated at a relatively high temperature, and therefore the ceramic molded body can be reliably degreased. It is considered that carbon generated from the organic binder is generated by, for example, C +2H₂→CH₄Is removed from the ceramic formed body. If the maximum temperature is less than 1100 ℃, it is difficult to sufficiently degrease the ceramic compact, and the amount of carbon remaining in the ceramic compact increases, which is not preferable. If the maximum temperature exceeds 1400 ℃, the ceramic compact may be partially sintered, which is not preferable. Degreasing at the maximum temperature is performed by holding at the maximum temperature for a prescribed time. The time for holding at the highest temperature may be appropriately set by performing preliminary experiments in advance, but is preferably set to be shortThe selection time is set to 1 hour or more. This is because degreasing can be sufficiently performed if the time is 1 hour or more.

Before degreasing the ceramic compact at the maximum temperature set in the range of 1100 to 1400 ℃, the ceramic compact may be heated at a heating rate exceeding 25 ℃/h to an intermediate temperature set in the range of 600 to 1100 ℃ (preferably 700 to 1000 ℃), and then held at the intermediate temperature for a predetermined time. Wherein the maximum temperature is a temperature exceeding the intermediate temperature. This method is effective when the ceramic compact is thick. In the case where the holding at the intermediate temperature is not performed, in order to sufficiently degrease (remove residual carbon) the ceramic compact to the center portion, it is necessary to increase the holding time at the maximum temperature as the thickness of the ceramic compact becomes larger. In contrast, when the holding at the intermediate temperature is performed, sufficient degreasing can be achieved even if the holding time at the maximum temperature is short. The reason for this is not clear, but is presumed as follows. I.e., C +2H₂→CH₄The methanation reaction (2) is carried out in a temperature range of 600 to 1400 ℃ C (particularly 700 to 1400 ℃ C.), but it is presumed that the low temperature range (for example, 600 to 1100 ℃ C., particularly 700 to 1000 ℃ C.) in the temperature range is mainly amorphous carbon derived from the resin skeleton, and the high temperature range (for example, 1000 to 1400 ℃ C., particularly 1100 to 1400 ℃ C.) is mainly carbon (soot) obtained by further thermal decomposition. It is considered that by maintaining the temperature in the low temperature range for a predetermined time period before degreasing at the highest temperature, an amorphous carbon formation reaction occurs in addition to the methanation reaction, and carbon residue removal proceeds at a relatively high rate. In this low temperature range, a small amount of resin remains as soot having low reactivity, and it is considered that further processing in a high temperature range is necessary to methanize the remaining soot. On the other hand, when the treatment is performed in the high temperature range without the holding in the low temperature range, most of the resin becomes soot having low reactivity, and therefore, it is considered that the treatment time for methanation of the soot becomes long particularly in a ceramic molded body having a large thickness.

The intermediate temperature may be set to a range of 600 ℃ to 1100 ℃, and is preferably set to a range of 700 ℃ to 1000 ℃ for sufficient degreasing. The time for holding at the intermediate temperature is preferably set to 1 hour or more. This is because degreasing can be sufficiently performed if the time is 1 hour or more. Further, the time is preferably set to 2 hours or less. This is because, even if the time is kept for more than 2 hours, the degreasing effect is not greatly different, and it is uneconomical.

The degreasing method of the ceramic compact according to the present embodiment can be used when manufacturing a ceramic fired body. That is, the ceramic compact degreased by the above-described method of degreasing a ceramic compact is fired, whereby a ceramic fired body can be obtained. The firing may be performed by a conventionally known method, and may be, for example, atmospheric firing or pressure firing (for example, hot press firing or HIP firing). The firing atmosphere may be an atmospheric atmosphere or a non-oxidizing atmosphere (for example, a nitrogen atmosphere, an argon atmosphere, or the like). The firing temperature and the firing time may be appropriately set according to the ceramic powder used.