JPH03261662A - Ceramic composition and production of ceramic member using same composition - Google Patents

Abstract

PURPOSE:To obtain the subject ceramic composition capable of providing a ceramics having low dimensional shrinkage by blending metal Si powder or mixture powder composed of ceramic powder and the said Si powder with a specified amount of an organic binder, a deflocculant and water. CONSTITUTION:A metal Si powder or a mixture powder composed of a ceramic powder (e.g. Si3N4 powder) and the same powder is blended with 6-25wt.% organic binder (e.g. thermoplastic acrylic resin), a deflocculant and water to produce a ceramic composition. The resultant ceramic composition (3S) is poured into a cylindrical unit 2 made of a high-density sintered ceramics placed on a mold 1 of a porous material followed by water-absorption solidification. The water-absorption solidified composition (3F) is then heated for evaporation and removal of the organic binder and subsequently sintered in an atmosphere of nitrogen to produce its sintered material united into one body with the cylindrical unit 2. A ceramic member suitable for a piston, etc., of an adiabatic engine can be obtained thereby.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ceramic composition containing ceramic particles, metal particles, a binder, etc., and a method for manufacturing a ceramic member using the composition.

[Conventional technology]

A conventional method for molding silicon nitride ceramics using slurry casting is disclosed in Japanese Patent Application Laid-Open No. 64-5977. This molding method involves adding 0.1 to 0.7% by weight of ammonium salt of polyacrylic acid as a deflocculant to the slurry powder of silicon nitride ceramic 7x, and adding an acrylic emulsion as a binder to the slurry powder. It is added to the liquid and molded by casting.

In addition, as a manufacturing method for Serakkusu products, JP-A-59-1
There is one disclosed in Japanese Patent No. 74571. The method for manufacturing ceramic products involves molding, degreasing, and sintering a mixture of ceramic manufacturing raw materials and an organic binder, and using thermosetting resin as an essential component of the organic binder. A mixture of an organic binder containing the thermosetting resin and the raw material for producing ceramics is heated to a temperature above the softening point of the mixture to impart fluidity, and a desired shape is formed at a temperature below the softening point of the mixture. It was shaped, then degreased and sintered.

[Problem to be solved by the invention]

However, in the molding method disclosed in the above-mentioned Japanese Patent Application Laid-open No. 64-5.977, an acrylic emulsion or the like is added to a silicon nitride slurry, and even if the amount of the acrylic emulsion is In comparison, the viscosity of the slurry does not change significantly and its shape retention is improved, but the dimensional change is minimized throughout the process from the state where the slurry is cast to water absorption and firing (roller-free). This effect cannot be exhibited from the viewpoint of shapeability). However, in the cough-bottom method, since the amount of binder is small and the slurry contains 1-2% silicon nitride when water is absorbed, dimensional shrinkage of 15-20% occurs during firing.

Furthermore, the manufacturing method for ceramic products disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 59-174571 suppresses the occurrence of defects by performing a prescribed process using a thermosetting organic binder containing an acrylic resin. be. Therefore, when the thermosetting organic binder is heated above its softening point in the manufacturing process of ceramic products, it has no or a small expansion coefficient.

The purpose of this invention is to solve the above problems,
A large amount of acrylic binder was added to a powder made of metal Si powder, and a large amount of acrylic binder was added to the bottom shape. After casting, water absorption, drying, and binder removal were performed, followed by reaction firing in nitrogen gas. By adding a large amount of it, dimensional shrinkage during water absorption and drying can be suppressed to an extremely small level, and during firing, the reaction between the 51 particles and nitrogen gas causes silicon nitride S.
It is an object of the present invention to provide a method for producing ceramics in which i3N4 is produced, which is not accompanied by dimensional changes, and therefore can produce ceramics with extremely small dimensional shrinkage throughout the entire process.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention provides metal S1 powder or a mixed powder obtained by adding ceramic powder to the metal S1 powder,
6 to 25% by weight of the total weight of i powder or the above mixed powder
The present invention relates to a ceramic U precept characterized by containing an organic binder, a deflocculant, and water in an amount range of .

In this ceramic composition, the ceramic powder contains at least one of Si, N, aluminum titanate, mullite, zirconia, and potassium titanate.

In this ceramic composition, the organic binder is a thermoplastic acrylic resin.

Alternatively, the present invention provides a porous ceramic composition containing an organic binder, a deflocculant, and water in an amount ranging from 6 to 25% by weight based on the total weight of a metal Si powder or a mixed powder obtained by adding a ceramic powder to the metal Si powder. A process of injecting into a cylinder of a dense ceramic sintered body on a material mold to absorb water and solidify it, a process of heating the water-absorbed and solidified composition to volatilize and remove the organic binder, and a process of removing the volatilized composition with nitrogen. The present invention relates to a method for producing a ceramic member, which comprises a step of producing a sintered body integrally structured with an inscribed cylinder by firing in a gas atmosphere.

[Effect]

The ceramic composition according to the present invention and the method for manufacturing a ceramic member using the Mi-like substance are constructed as described above, and operate as follows.

In this Ceramic &ll Kaimono, the amount of organic binder added was within the range of 6 to 25% by weight of the total weight of the organic binder and metal Si powder or mixed powder, so the shrinkage rate during molding in the cast molding method was For example, it can be suppressed to 1/10 or less of the conventional value, and during firing, silicon nitride Si3N4 is generated by the reaction between Si particles and nitrogen gas, and the silicon nitride Si
There is no dimensional change in 3N-, and therefore a ceramic member with extremely small dimensional shrinkage throughout the entire process can be obtained.

In addition, since the organic binder in this ceramic composition is a thermoplastic acrylic resin, the organic binder has a large expansion coefficient when heated above its softening point, and this property can be used to create ceramic members with extremely small dimensional shrinkage. Obtainable.

Alternatively, the method for manufacturing a ceramic member according to the present invention includes:
The above ceramic & Il parabolite is injected into a cylindrical body of a dense ceramic sintered body on a mold made of porous material and solidified by water absorption, and the water-absorbed and solidified composition is heated to remove the organic binder by volatilization, and then volatilization is removed. The ceramic composition was fired in a nitrogen gas atmosphere to produce a sintered body integral with the cylindrical body. After casting the ceramic composition, water absorption, drying, and binder removal were performed, and then the ceramic composition was fired in a nitrogen gas atmosphere. Reactive firing is carried out, and by adding a large amount of heat-softening organic binder, dimensional shrinkage during water absorption and drying is suppressed to an extremely small level, and during firing, silicon nitride (5i)Nn is produced by the reaction of Si particles and nitrogen gas. . Therefore, it is possible to manufacture a ceramic member with extremely small dimensional shrinkage throughout the entire process.

〔Example〕

Examples of the ceramic U paraboloid and the method for manufacturing ceramics according to the present invention will be described in detail below.

The ceramic & Il$ product according to the present invention is free from metal Si powder or a mixed powder of metal Si powder and ceramic powder, a deflocculant, water and an organic binder, and the amount of the organic binder added is adjusted to the amount of the organic binder. and 6 to 25% by weight of the total weight of the metal Si powder or the mixed powder. The ceramic powder contains at least one of S I 3N m, aluminum titanate, mullite, zirconia, and potassium titanate.
It contains more than one species. In particular, thermoplastic acrylic resin is used as the organic binder contained in this ceramic composition, which can suppress dimensional shrinkage during the manufacturing process of the ceramic member.

Furthermore, the method for manufacturing a ceramic member using the ceramic composition according to the present invention includes a method for producing a ceramic member using a metal Si powder or a metal Si powder.
A mixed powder in which ceramic powder is added to powder, a deflocculant, water and an organic binder, and the amount of the organic binder added is 6 to 25% by weight of the total weight of the organic binder and the metal Si powder or the mixed powder. A step of manufacturing a ceramic composition within the range, a step of injecting the ceramic composition into a cylinder made of a dense ceramic sintered body placed in a porous mold and solidifying it by water absorption to form a molded body. a step of heating the molded body to volatilize and remove an organic binder contained in the molded body; and a step of firing the molded body in a nitrogen gas atmosphere to produce a sintered body having an integral structure with the cylindrical body. It is something to be warned against.

When manufacturing ceramic parts using this ceramic paraboloid, shrinkage during water absorption or drying during casting is caused by particles moving toward the center as the water content in the slurry decreases. It is thought that it does. The thermoplastic acrylic resin binder as an organic binder, ie, the acrylic binder, exists in the slurry as colloidal particles, but even when the water content decreases, these binder particles intervene between the ceramic particles and suppress particle movement. do. The degree of suppression of particle movement depends on the amount of the acrylic binder added, and the larger the amount added, the more the movement of the ceramic particles is suppressed, and therefore the amount of shrinkage of the molded body during water absorption and solidification of the slurry of the ceramic composition becomes smaller. Further, in this invention, after the slurry absorbs water and solidifies, 5
The acrylic binder is evaporated and removed by heating to about 00°C. During this process, the molded body expands slightly. This expansion action can cancel the shrinkage that occurred during the water absorption and solidification of the slurry.Next, the molded body from which the acrylic binder has been volatilized and removed is fired. In this case, when the molded body from which the organic binder has been volatilized is fired, the firing progresses due to the reaction between Si and the atmospheric gas, that is, nitrogen gas N2, and silicon nitride Si3N4 is produced. In this reaction sintering, the phenomenon of dimensional shrinkage does not occur. Therefore, for example, when a molded body formed inside a cylinder made of silicon nitride S r z N 4 is fired to produce a sintered body having an integral structure with the cylinder, the gap between the cylinder and the sintered body is There are no gaps etc.

Next, a specific example of a method for manufacturing a ceramic member using a ceramic composition according to the present invention will be described with reference to FIGS. 1, 2, and 3.

First, in order to produce a ceramic composition, powders of silicon Si, silicon nitride 5isN4, aldinium titanate, and mullite were mixed in a weight ratio of silicon Si; 50, silicon nitride 5isN4.
A mixed powder was prepared by mixing N4; 20, aluminum titanate; 15, and mullite; 15. To this mixed powder, an acrylic binder consisting of distilled water of the same weight as the mixed powder, 1% by weight of a deflocculant, and a predetermined amount of thermoplastic acrylic resin was added, and after being heated in a ball mill for 10 hours, defoaming was performed. After processing, slurry 33 was obtained. Here, several types of Ceramic & Illuminant Slurry 3S were prepared in which the amount of distilled water, powder composition ratio, and overall weight were kept constant, and only the amount of acrylic binder added was changed.

Next, as shown in FIG. 1, cylindrical bodies 2 made of silicon nitride 5rsNa and having annular grooves 5 formed on their inner circumferential surfaces are placed on the plaster mold l for each type of slurry 3S. Regarding this cylinder 2,
For example, outer diameter: φ80, wall thickness: 311, height: 4 (
An annular groove 5 with a depth of 1.5 mm and a width of 10 grooves was formed at a position between 1+ m and 6 from the bottom.Next, as shown in FIG. 35 were respectively poured into the plaster, and the water contained in the slurry 3S was absorbed into the plaster. If left in this state for about 20 hours at room temperature, the slurry 33 will solidify, but as shown in FIG. It was observed with a microscope and the radial shrinkage rate of the powder-filled part at this point was measured based on the inner diameter of the cylinder. These results are shown in FIG. 4 by the symbols.

Next, each of the molded bodies 3F described above is heated to a maximum temperature of 500°C in a debinding furnace with a nitrogen gas atmosphere to volatilize and remove the acrylic binder, and after cooling the debinding furnace, each molded body 3F is heated in the same manner as above. The bottom portion was observed with a stereomicroscope, and the shrinkage rate in the radial direction at each bottom surface of each molded body 3F was measured. These results are shown by the symbol B in FIG. 4. At this point, as can be seen from the graph, the overall shrinkage rate of each molded body 3F after heating is smaller than the shrinkage rate immediately after water absorption and solidification. Therefore, when heating the molded body 3F to remove the binder, the temperature of about 0
．． It is clear that an expansion phenomenon of about 1 to 0.2% occurred.

Furthermore, these molded bodies 3F were heated to 9.9 kgf/cm"
In a nitrogen gas atmosphere, reaction firing is performed by heating up to a maximum temperature of 1400°C, and the internal bottom body 3F in the cylinder 2 is reaction sintered to form a composite sintered body of silicon nitride Si+N and mullite or aluminum titanate. 3 (see FIG. 5), the radial shrinkage rate at each bottom surface of each sintered body 3 was similarly measured, but no dimensional change was observed in the reaction sintering.

The composite member in which the composite sintered body 3 was filled in the cylinder 2 thus obtained was cut in the longitudinal direction, and the state of filling into the annular groove 5 formed in the cylinder 2 was observed. As can be seen from the cough table shown in the table below, when the amount of acrylic binder added is 20.0% by weight or more, the viscosity of the slurry becomes high and the state of filling into the annular 15 becomes unstable. That was enough.

Furthermore, the ceramic member manufactured using the above-mentioned ceramic composition according to this method for manufacturing a ceramic member is extremely preferable for use in, for example, a piston of an adiabatic engine. That is, as shown in FIG. 5, the piston of this adiabatic engine is made of silicon nitride Si3N, and the upper surface of the sintered body 3 integrally constructed with the cylinder 2 is covered with silicon nitride 5i.
Silicon nitride 5isN by chemical vapor deposition (CVD) of sNn
It can be manufactured by forming a thin film 4 of No. 4. In this piston, the part of the sintered body 3 can provide a high degree of thermal insulation, and the thin film 4 of silicon nitride S i 3 N m
The cylindrical body 2 can provide an adiabatic piston with excellent heat resistance and deformation resistance. Moreover, in manufacturing this heat insulating piston, by utilizing the characteristics of reaction sintering and chemical smoke CVD, we can use the sintered body 3 of the heat insulating material and the cylindrical body 2 of silicon nitride Si3N.
This eliminates the need for a ceramic bonding technique for the thin film 4 of silicon nitride 5izN-, and furthermore, the number of parts to be machined on the product is extremely reduced, making it possible to significantly reduce manufacturing costs. In addition, the sintered body 3 has a large number of small pores in a dispersed state, and silicon nitride 5i3 due to reaction sintering.
Since it is a Na member, it is possible to provide a ceramic member with low thermal conductivity due to the phonon scattering effect due to the thermal insulation particle interface misma.

〔Effect of the invention〕

Since the ceramic composition and the method for producing ceramics according to the present invention are constructed as described above, they have the following effects.

That is, this ceramic composition includes a metal S1 powder or a mixed powder obtained by adding a ceramic powder to the metal S1 powder, an organic binder in an amount of 6 to 25% by weight of the total weight of the metal Si powder or the mixed powder, and a solution. Since it contains glue and water, the shrinkage rate during molding in the cast molding method can be suppressed to less than the conventional l/l O, and during firing, silicon nitride 5isN is generated by the reaction between Si particles and nitrogen gas. There is no dimensional change in the silicon nitride Si3Nm, and therefore a ceramic member with extremely small dimensional shrinkage throughout the entire process can be obtained.

In addition, since the organic binder in this ceramic composition is a thermoplastic acrylic resin, the organic binder has a large expansion coefficient when heated above its softening point, and this property can be used to create ceramic members with extremely small dimensional shrinkage. Obtainable.

Alternatively, the method for manufacturing a ceramic member according to the present invention includes:
A ceramic composition containing an organic binder, a deflocculant, and water in an amount of 6 to 25% by weight based on the total weight of Metal 3i1 powder or a mixed powder obtained by adding ceramic powder to the powder is molded into a porous material. A step of injecting into the cylinder of the above dense ceramic sintered body and solidifying it by water absorption, a step of heating the water-absorbed and solidified & The process consists of firing in a gas atmosphere to produce a sintered body integrally structured with the cylindrical body, so after casting the ceramic composition, water absorption, drying, and binder removal are performed, followed by reaction in nitrogen gas. By adding a large amount of a heat-softening organic binder, dimensional shrinkage during water absorption and drying is suppressed to an extremely small level. During firing, silicon nitride SI:+ is formed by the reaction between Si particles and nitrogen gas.
N- is generated.

Therefore, throughout the entire process, it is possible to manufacture a ceramic member with particularly small dimensional shrinkage, and it is possible to provide a preferable ceramic component that does not have cracks, cracks, etc., or is difficult to generate cracks, cracks, etc. as a product.

In particular, this method of manufacturing a ceramic member is highly preferred for manufacturing a heat insulating piston. In other words, when this ceramic member is made into a heat insulating piston, the sintered body part has a high degree of heat insulating property, and silicon nitride Si3N
It is possible to provide an adiabatic piston with excellent heat resistance and deformation resistance using a ceramic thin film and cylindrical body such as .

Moreover,! In the II manufacturing method, simply by forming a locking part such as an annular groove on the outer ceramic cylinder, it can be bonded extremely well and firmly to the sintered body that serves as the internal heat insulating material. i.e. reactive sintering and chemical i@c
Utilizing the features of vD not only eliminates the need for ceramic bonding technology, but also greatly reduces the number of parts of the product that require jIi machining, significantly reducing manufacturing costs.

In addition, if the cylinder and the sintered body are made of the same type of ceramic material, the two can be firmly joined to -N.In particular, the sintered body itself has many small pores dispersed in it. , and because of the phonon scattering effect due to the mismatch at the interface of the heat insulating particles, it is possible to provide a heat insulating piston with extremely low thermal conductivity.

[Brief explanation of drawings]

Figures 1, 2, and 3 are explanatory diagrams showing each step of the method for manufacturing a ceramic member according to the present invention, and Figure 4 is the shrinkage rate of the ceramic composition with respect to the amount of acrylic binder added. FIG. 5 is a cross-sectional view showing an example of a piston manufactured by the ceramic manufacturing method according to the present invention. l--・-- plaster mold, 2--- monocylindrical body, 3---
Sintered body, 3F---- molded body, 3S-- slurry,
4--yi membrane, 5-- annular groove.

Claims (4)

[Claims] (1) a metal Si powder or a mixed powder obtained by adding a ceramic powder to the powder; an organic binder in an amount range of 6 to 25% by weight of the total weight of the metal Si powder or the mixed powder;
A ceramic composition comprising a deflocculant and water. (2) The ceramic composition according to claim 1, wherein the ceramic powder contains at least one of Si_3N_4, aluminum titanate, mullite, zirconia, and potassium titanate. (3) The ceramic composition according to claim 1, wherein the organic binder is a thermoplastic acrylic resin. (4) A ceramic composition containing an organic binder, a deflocculant, and water in an amount ranging from 6 to 25% by weight based on the total weight of the metal Si powder or a mixed powder obtained by adding ceramic powder to the metal Si powder is made into a porous material. A step of injecting into a cylinder of a dense ceramic sintered body on a mold and solidifying it by water absorption, a step of heating the water-absorbed and solidified composition to volatilize and remove the organic binder, and a step of volatilizing and removing the composition in a nitrogen gas atmosphere. A method for manufacturing a ceramic member, comprising the step of firing the ceramic member to produce a sintered body having an integral structure with the cylindrical body.