JP2001130968A - Ceramic slurry, method for producing the same, and ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a ceramic slurry by which a homogeneous slurry capable of providing a homogeneous high-density ceramic is readily produced at a short time, and further to provide the ceramic slurry obtained by the method, and the homogeneous high-density ceramic. SOLUTION: This method for producing the ceramic slurry is characterized by a step for mixing a ceramic powder with a dispersion medium while radiating ultrasonic wave. The ceramic slurry obtained thereby and the ceramic are also provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a ceramic slurry, a method for producing the same, and a ceramic.

[0002]

2. Description of the Related Art Conventionally, ceramics have been expected as structural members for semiconductor manufacturing equipment parts, electronic information equipment parts, vacuum equipment, and the like. Is researched every day.

[0003] Above all, reduction and simplification of the manufacturing time are major issues, and improvement in cost is desired. In particular, in the case of ceramics produced by dispersing ceramic powder through a slurry process (for example, a slurry for casting molding, a slurry for preparing granules by press molding, etc.), its slurry properties are important. To improve the production time has an effect on shortening, simplification, and cost of manufacturing.

[0004] Usually, a ceramic slurry is prepared by mixing a mixture of a ceramic powder, a dispersion medium, and, if necessary, a deflocculant and a binder. The mixing includes a mixing method of stirring with a stirring blade, a ball mill method of adding a ball together with the compound and homogenizing, and the ball mill method is generally used. However, in each case, it takes a long time, usually 16 to 24 hours, to homogenize the composition. In particular, in the ball milling method, it is necessary to separate the composition from the balls. Was causing an increase in the number.

[0005] Further, since the ceramic slurry also greatly affects the physical properties (density and the like) of the obtained ceramic, it is necessary to produce a uniform ceramic slurry even if the time or the number of steps is increased.

[0006]

That is, an object of the present invention is to produce a ceramic slurry capable of easily and in a short time producing a uniform ceramic slurry capable of obtaining a homogeneous and high-density ceramic. The present invention provides a method, a uniform ceramic slurry obtained thereby, and a homogeneous and dense ceramic.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a compound containing a silicon carbide powder and a dispersion medium is irradiated with ultrasonic waves so that the compound can be easily, quickly and uniformly mixed. It has been found that a ceramic slurry having a high density can be produced, and that a uniform and high-density ceramic can be produced by using the ceramic slurry. That is, the present invention

<1> A method for producing a ceramic slurry, comprising a step of irradiating an ultrasonic wave to mix a ceramic powder and a dispersion medium.

<2> The ultrasonic wave is transmitted at a frequency of 20 kHz to 20 kHz.
The method for producing a ceramic slurry according to <1>, wherein the irradiation is performed at MHz.

<3> The method for producing a ceramic slurry according to <1> or <2>, wherein the ultrasonic wave is irradiated for 2 to 10 minutes.

<4> The method for producing a ceramic slurry according to any one of <1> to <3>, wherein the ceramic powder is a silicon carbide powder.

<5> A ceramic slurry obtained by the method for producing a ceramic slurry according to any one of <1> to <4>.

<6> A ceramic obtained by using the ceramic slurry described in <5>.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION [Method for Producing Ceramic Slurry] The method for producing a ceramic slurry of the present invention has a step of mixing a ceramic powder and a dispersion medium by irradiating ultrasonic waves. By irradiating the ultrasonic waves in this manner, a uniform ceramic slurry can be easily and quickly manufactured.

In the method for producing a ceramic slurry of the present invention, the mixing of the ceramic powder and the dispersion medium may be performed only by ultrasonic irradiation, or may be performed by separate mixing such as ultrasonic irradiation and stirring by a stirring blade. The method may be used in combination. In any case, a uniform ceramic slurry can be produced easily and in a short time.

In the method for producing a ceramic slurry according to the present invention, the time for irradiating the ultrasonic wave is preferably 2 to 10 minutes, more preferably 3 to 5 minutes. If the frequency is less than 2 minutes, sufficient dispersion may not be obtained, and the aggregation of the ceramic powder may not be deflocculated. On the other hand, if the frequency exceeds 10 minutes, reagglomeration or the like occurs, and the dispersibility of the slurry becomes poor. May decrease.

In the method for producing a ceramic slurry according to the present invention, the frequency of the ultrasonic waves to be irradiated is 20 kHz to 20 kHz.
It is preferably 20 MHz, more preferably 30 MHz.
kHz to 30 MHz. This frequency is 20kHz
If it is less than 20 MHz, a force for breaking the aggregation of the ceramic powder may not be obtained. On the other hand, if it exceeds 20 MHz, the attenuation may increase and an effective force for dispersing may not be obtained.

In the method for producing a ceramic slurry according to the present invention, the intensity (output) of the radiated ultrasonic wave is 10 to 10.
500W is preferred, more preferably 100-400W
It is. If the intensity (output) is less than 10 W, sufficient dispersibility may not be obtained, while if it exceeds 500 W, re-aggregation may be caused.

In the method for producing a ceramic slurry according to the present invention, as the ultrasonic generator for generating the ultrasonic waves to be irradiated, any apparatus capable of generating ultrasonic waves satisfying the above-mentioned conditions such as frequency and intensity may be used. There is no particular limitation.

In the method for producing a ceramic slurry according to the present invention, the mixing device is not particularly limited as long as it has an ultrasonic generator for generating ultrasonic waves to be irradiated. May be used, or a conventionally known stirring device using a stirring blade may be provided with an ultrasonic generator.

The method for producing a ceramic slurry of the present invention can be adapted to the production of any kind of ceramic slurry, for example, the production of silicon carbide powder, the production of silicon nitride, the production of aluminum nitride, the production of oxides (for example, (Alumina, zirconia, etc.). Further, conventionally known materials such as a ceramic powder, a dispersion medium, and an additive to be used can be used.

When the method for producing a ceramic slurry of the present invention is adapted to the production of a silicon carbide slurry, at least a silicon carbide powder and a dispersion medium are used as the ceramic powder. As the medium, those shown below are preferable. Further, conventionally known additives such as a sintering aid and a deflocculant may be used in combination.

(Silicon Carbide Powder) Examples of the silicon carbide powder include α-type, β-type, amorphous, and mixtures thereof. Of these, β-type silicon carbide powder is particularly preferable. The proportion of β-type silicon carbide in the entire silicon carbide component is preferably 70% or more, more preferably 80% or more, and may be 100% β-type silicon carbide.

The amount of the β-type silicon carbide powder in the silicon carbide powder is preferably 60% by weight or more.
It is more preferably at least 65% by weight. If the amount is less than 60% by weight, the content of β-type silicon carbide in the silicon carbide component of the obtained silicon carbide sintered body may be outside the above numerical range. The grade of the β-type silicon carbide powder is not particularly limited. Therefore, a commercially available β-type silicon carbide powder can be suitably used.

The average particle size of the silicon carbide powder is as follows:
From the viewpoint of obtaining a high-density silicon carbide sintered body, the particle size is preferably small, and specifically, 0.01 to 10 μm.
m is preferable, and 0.05 to 1 μm is more preferable. If the average particle size is less than 0.01 μm, it is difficult to handle at the time of processing such as weighing and mixing, and if it exceeds 10 μm, the specific surface area (adjacent silicon carbide powder etc. come into contact with each other) Area), it may be difficult to obtain a high-density silicon carbide sintered body.

The particle size distribution of the silicon carbide powder is as follows:
Although not particularly limited, during the production of the silicon carbide sintered body, from the viewpoint of improving the packing density of the raw material powder (such as silicon carbide powder), and from the viewpoint of improving the reactivity of silicon carbide, The distribution preferably has two or more maximum values.

The silicon carbide powder has an average particle size of 0.05 to 1 μm, a specific surface area of 5 m ² / g or more,
Those having a free carbon content of 1% or less and an oxygen content of 1% or less are particularly preferred.

-Method for Producing Silicon Carbide Powder-The above silicon carbide powder is a step of firing a mixture of a silicon compound and an organic compound which generates carbon by heating (hereinafter referred to as a silicon carbide powder production step). Is preferably obtained by

--Silicon Compound (Silicon Source)-The silicon compound is not particularly limited as long as it is a compound that generates silicon by heating, and any liquid or solid silicon compound may be used. From the viewpoints of high purity, uniform dispersion, and at least one, it is necessary that at least one type is a liquid silicon compound.

Preferred examples of the liquid silicon compound include alkyl silicate, (mono-, di-, tri-, and tetra-) alkoxysilanes and polymers of tetraalkoxysilanes.

As the alkyl silicate, methyl silicate, ethyl silicate, butyl silicate and the like are preferably mentioned, and ethyl silicate is particularly preferable from the viewpoint of handleability and reactivity. Preferred examples of the (mono-, di-, tri-, and tetra-) alkoxysilanes include tetraalkoxysilanes. Specific examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Tetraethoxysilane is particularly preferable in terms of excellent handleability. The tetraalkoxysilane polymer has a degree of polymerization of 2
~ 15 low molecular weight polymer (oligomer) (for example,
Preferable examples include low-molecular-weight polymers (oligomers) such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, and liquid high-polymer silicate polymers.

As the solid silicon compound, silicon oxide and the like are preferably mentioned. Here, the silicon oxide in the present invention means, in addition to SiO, silica sol (colloidal ultrafine silica containing liquid, containing OH group or alkoxyl group inside), silicon dioxide (silica gel, fine silica, quartz powder) Body) and the like.

Among these silicon compounds, a low molecular weight polymer (oligomer) of tetraethoxysilane, and a low molecular weight polymer (oligomer) of tetraethoxysilane and fine powder are preferable because of their excellent homogeneity and handleability. Mixtures with body silica, ethyl silicate, are particularly preferred, and ethyl silicate is most preferred. These silicon compounds may be used alone or may be used alone.
More than one species may be used in combination.

The total content of impurity elements in the silicon compound is preferably 10 ppm or less, and more preferably 5 ppm.
The following is more preferred. When the total content of the impurity elements is out of the above-mentioned numerical range, the purity of the obtained silicon carbide sintered body may be out of the above-mentioned numerical range. However,
The value is not necessarily limited to a value within the above numerical range as long as it is within an allowable range of purification during heating and sintering.

-Organic compound which generates carbon by heating (carbon source)-The organic compound which generates carbon by heating (hereinafter, may be referred to as "organic compound" as appropriate) is not particularly limited. Any of a liquid and a solid organic compound may be used, but from the viewpoint of high purification and uniform dispersion, it is necessary that at least one of the organic compounds is a liquid organic compound.

The organic compound has a high residual carbon ratio,
Organic compounds that polymerize and crosslink by the presence of a catalyst and / or heating are preferred. For example, phenol resins, furan resins, polyimides, polyurethanes, polyvinyl alcohols, and other resin monomers and prepolymers, and liquid organic compounds such as cellulose, sucrose, pitch, and tar are preferably used. Among these, a phenol resin is preferable, and a resol-type phenol resin is particularly preferable. These organic compounds may be used alone or in combination of two or more.

The purity of the organic compound can be appropriately controlled and selected depending on the purpose. In particular, in order to obtain high-purity silicon carbide powder, the total content of impurity elements must be
It is preferably not more than 5 ppm.

In the silicon carbide powder production step, the mixing ratio of the silicon compound to the organic compound (silicon compound / organic compound (hereinafter, appropriately referred to as “C / Si ratio”)) is set at 1000 ° C. Is defined by elemental analysis of a carbide intermediate obtained by carbonization at a C / Si ratio of 3.0 if the free carbon in the produced silicon carbide powder is 0%. However, in practice, the volatilization of the simultaneously generated SiO gas generates free carbon at a low C / Si ratio, so that the amount of free carbon in the generated silicon carbide powder is C / S in advance so that the amount is not appropriate for the production and use of
It is necessary to determine the i ratio. Normally, when firing at 1600 ° C. or more near 1 atm, the C / Si ratio is set to 2.
A value of 0 to 2.5 is preferable because the generation of free carbon can be suppressed. Further, when the C / Si ratio is set to 2.5 or more, the amount of generated free carbon significantly increases. However, since the free carbon has an effect of suppressing grain growth, it is appropriately selected according to the purpose of forming particles. You can also. However, when the atmosphere is fired at a low pressure or a high pressure, the C / Si ratio for obtaining pure silicon carbide varies. In this case, the ratio is not necessarily limited to the range of the C / Si ratio.
In addition, since the action at the time of sintering of free carbon is very weak as compared with the action by carbon derived from the nonmetallic sintering aid coated on the surface of the silicon carbide powder described below, basically, Can be ignored.

In the silicon carbide powder production process, if necessary, a polymerization or crosslinking catalyst is further added and cured to form a mixed solid for the purpose of mixing the silicon compound and the organic compound more uniformly. Can also. Also,
Examples of the curing method include a method of crosslinking by heating and a method of electron beam or radiation.

The polymerization or cross-linking catalyst can be appropriately selected according to the kind of the organic compound. For example, when the carbon compound is a phenol resin or a furan resin, toluenesulfonic acid, toluenecarboxylic acid, acetic acid, oxalate, and the like are used. Examples include acids such as acid, hydrochloric acid, sulfuric acid, and maleic acid, and amines such as hexamine.

In the step of producing the silicon carbide powder, the mixing of the silicon compound, the organic compound and, if desired, the polymerization or crosslinking catalyst is performed by a known mixing means, for example, a mixer or a planetary ball mill. Further, the mixing time is preferably 10 to 30 hours, more preferably 16 to 24 hours. As a material for the mixer, the planetary ball mill, and the like, a synthetic resin containing as little metal as possible is preferable from the viewpoint of obtaining high-purity silicon carbide powder.

In the step of producing silicon carbide powder, a mixture of the silicon compound, the organic compound and, if desired, the polymerization or crosslinking catalyst is calcined for the purpose of improving handling properties and removing volatile gases and moisture. If desired, heating and carbonization can be performed beforehand. The heating and carbonizing are performed in a non-oxidizing atmosphere such as nitrogen or argon, for 500 hours.
It is preferably performed at a temperature of from 1000C to 1000C for 30 to 120 minutes.

--Calcination--In the silicon carbide powder production step, the calcination is preferably performed in a non-oxidizing atmosphere, and the calcination can produce a silicon carbide powder.

In the silicon carbide powder production process, the conditions such as the calcination time and the calcination temperature in the calcination cannot be specified unconditionally because they vary depending on the desired particle size of the silicon carbide powder. 1350 in sexual atmosphere
~ 2000 ° C, preferably from 1600 to 1900
More preferably, it is carried out at a temperature of about 0 ° C. Further, in order to further increase the purity of the silicon carbide powder, after the firing,
It is preferable to perform heat treatment at 000 to 2100 ° C. for 5 to 20 minutes.

The silicon carbide powder production process includes a method for producing a raw material powder described in the method for producing a single crystal previously filed by the applicant of the present application as Japanese Patent Application No. 7-241856, that is, high purity Alkoxysilane, one or more silicon compounds selected from tetraalkoxysilane polymer, and a high-purity organic compound that generates carbon by heating,
Heating the mixture obtained by mixing uniformly under a non-oxidizing atmosphere to obtain a silicon carbide powder, and a step of forming the silicon carbide powder at 1700 ° C. to 20 ° C.
At a temperature of 00 ° C., while maintaining the temperature, 2000 ° C.
Performing a heating treatment at a temperature of １2100 ° C. for 5 to 20 minutes at least once to obtain a silicon carbide powder having a content of each impurity element of 0.5 ppm or less. A characteristic method for producing high-purity silicon carbide powder or the like can also be used.

(Dispersion medium) The dispersion medium is not particularly limited as long as it can disperse silicon carbide powder. Examples thereof include water, organic solvents (eg, alcohols (eg, ethanol, methanol, etc.), Examples thereof include aliphatic hydrocarbons (eg, hexane, decane, etc.), aromatic hydrocarbons (eg, toluene, etc.), and the like.

The mixing ratio between the silicon carbide powder and the dispersion medium (silicon carbide powder: dispersion medium) can be appropriately selected depending on the conditions of molding or sintering.

When the method for producing a ceramic slurry of the present invention is adapted to the production of a silicon carbide slurry, the above-mentioned silicon carbide powder, a dispersion medium, and if necessary, a sintering aid, a deflocculant, etc. A uniform silicon carbide slurry can be obtained easily and in a short time by mixing the additive with the ultrasonic irradiation.

When the method for producing a ceramic slurry of the present invention is adapted to the production of a silicon carbide slurry, it is preferable that the method for producing a ceramic slurry be 0.1%.
A silicon carbide slurry having a viscosity of about 0.5 to 5 Pa · s can be obtained easily and in a short time. In addition, a silicon carbide slurry exhibiting about 2 to 7 levels of thixotropic property can be obtained easily and in a short time. In the present invention, the thixotropic property refers to a viscosity at 6 rpm and a viscosity of 30 rpm measured using a B-type viscometer.
The ratio to the viscosity at pm is shown (thixotropic property = 6).
rpm viscosity / 30 rpm viscosity).

[Ceramic Slurry] The ceramic slurry of the present invention is a ceramic slurry obtained by the method for producing a ceramic slurry of the present invention. The ceramic slurry of the present invention is a uniform ceramic slurry because it is obtained by the method for producing a ceramic slurry of the present invention.

The viscosity of the ceramic slurry of the present invention is preferably 0.05 to 5 Pa · s, more preferably 1 to 3 Pa · s. This viscosity is 0.05
If it is less than Pa · s, the sedimentation of the ceramic powder may increase, while if it exceeds 5 Pa · s, the flowability may be poor, and casting may not be possible in the casting.

The ceramic slurry of the present invention preferably has a thixotropy of 2 to 7, more preferably 3 to 5. If the thixotropy is less than 2, the flowability is too good and the slurry may leak in the casting, while if it exceeds 7, the flowability is poor and the casting is shrinkage. Nests may appear.

[Ceramic] The ceramic of the present invention is a ceramic obtained by using the ceramic slurry of the present invention. The ceramic of the present invention is a homogeneous and high-density ceramic because the ceramic slurry of the present invention is used.

The ceramics of the present invention can be produced by using the ceramic slurry of the present invention and passing through a conventionally known forming step or sintering step.

[0055]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 High Purity Silicon Carbide Powder (Average Particle Size 0.8 μm: Impurity Content 5 ppm Produced According to the Production Method described in JP-A-9-48605)
The following silicon carbide: containing 1.5% by weight of silica) 88
g and 12 g of a high-purity liquid resol type phenol resin having a water content of 20% (residual carbon ratio after thermal decomposition is 50%) in 85 g of ethanol, and put the mixture in a mixing tank equipped with an ultrasonic generator. 5 minutes ultrasonic (frequency 35 Hz, intensity 3
(00W) and mixed to obtain a uniform silicon carbide slurry.

The viscosity and thixotropic property of the obtained silicon carbide slurry were measured. The measuring method is shown below, and the results are shown in Table 1.

-Viscosity- Using a B-type viscometer, the viscosity was measured with a No. 2 rotor at 6 rpm.

-Thixotropic property- Using a B-type viscometer, measurement was performed at No. 2 rotor and 6 rpm, and further at No. 2 rotor and 30 rpm, and the ratio of the two viscosities (viscosity at 6 rpm / viscosity at 30 rpm) was determined. .

Next, the obtained silicon carbide slurry is
After drying and granulation with a spray dryer, hot press sintering (conditions: sintering temperature 2360 ° C, pressure 500 kg / c)
m ² for 3 hours) to obtain a silicon carbide sintered body.

The density of the obtained silicon carbide sintered body was measured by the Archimedes method. Table 1 shows the results.

(Comparative Example 1) The same formulation as in Example 1 was used.
The mixture was stirred with a ball mill for 18 hours and mixed well to obtain a silicon carbide slurry. The viscosity and thixotropic property were measured in the same manner as in Example 1. Table 1 shows the results.

Next, using the obtained silicon carbide slurry, a silicon carbide sintered body was obtained in the same manner as in Example 1, and the density was measured. Table 1 shows the results.

[0064]

[Table 1]

As shown in Table 1, the silicon carbide slurry obtained according to the present invention can be easily and quickly obtained in a uniform manner exhibiting suitable viscosity and thixotropy. It can be seen that a silicon carbide sintered body can be obtained.

[0066]

As described above, according to the present invention, a method for producing a ceramic slurry capable of producing a uniform ceramic slurry capable of obtaining a homogeneous and high-density ceramic easily and in a short time. The purpose is to provide a uniform ceramic slurry and a homogeneous and dense ceramic.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G001 BA22 BB22 BC01 BC03 BC42 BD11 4G030 AA47 BA18 BA33 GA05 GA14 GA17 GA18 GA29 PA14 4G036 AB21

Claims (6)

[Claims] 1. A method for producing a ceramic slurry, comprising a step of irradiating a ceramic powder and a dispersion medium with ultrasonic waves to mix them. 2. An ultrasonic wave having a frequency of 20 kHz to 20 MH.
The method for producing a ceramic slurry according to claim 1, wherein the irradiation is performed at z. 3. The method for producing a ceramic slurry according to claim 1, wherein ultrasonic waves are irradiated for 2 to 10 minutes. 4. The method for producing a ceramic slurry according to claim 1, wherein the ceramic powder is a silicon carbide powder. 5. A ceramic slurry obtained by the method for producing a ceramic slurry according to claim 1. 6. A ceramic obtained by using the ceramic slurry according to claim 5.