JP2977408B2 - Method for producing α'-sialon sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an α'-sialon ceramic sintered body having excellent strength, corrosion resistance and wear resistance.

[0002]

2. Description of the Related Art As a method for producing an α'-sialon ceramics sintered body, generally, Si ₃ N ₄ —Al ₂ O ₃ —A
1N-based mixed powder and M metal (M is Li, Mg, Ca, M
After molding the oxides of n, Y and lanthanide metals), 170
Sintering is performed at a temperature of 0 ° C. or higher.

However, this method requires a high temperature or time to form a solid solution of Al, O, or M metal in Si ₃ N ₄ because of powder mixing on the order of microns, so that sialon particles are coarse. However, if the powder is insufficiently mixed, a non-target sialon phase appears or a large amount of a glass phase remains.

Further, silicon oxide or a silicon compound which forms silicon oxide by heating, aluminum oxide or an aluminum compound which forms aluminum oxide by heating, carbon and M metal oxide or M metal oxide by heating Japanese Patent Application Laid-Open No. 62-167209 discloses a method for producing an α-sialonic powder produced by heating a composition mixture composed of an M compound in a nitrogen stream.

However, in this method for producing powder, it is necessary to mix carbon by a mechanical method, and since it is a method of mixing fine powder, α is considered from the embodiment.
-Sialon single phase powder is not easily obtained.

On the other hand, as a method for obtaining high quality ceramics, a synthesis method by hydrolysis of a metal alkoxide has been studied.

[0007] The so-called sol-gel method using a metal alkoxide is a fine powder which can be obtained at a high purity and can be produced at a low temperature, as compared with a general method of mixing and calcining powders. Since it has many advantages such as easy production of a body, it is expected to be applied to the development of high-performance ceramics.

[0008]

In the present invention, the disadvantages of the above-mentioned conventional methods are the low purity, coarseness of the sialon particles due to heterogeneous mixing, and the phases other than α'-sialon (including the glass phase) after firing. To solve the drawbacks such as the appearance of carbon dioxide and the difficulty of uniformly adding carbon in the reductive nitridation reaction, and to carefully consider the raw materials and hydrolysis conditions, etc., for a gel that is more uniform than the powder obtained by precipitation by alkoxide hydrolysis. And a method for obtaining an α′-sialon sintered body.

[0009]

The general formula M _x (Si, A
l) ₁₂ (O, N) ₁₆ (M is Li, Mg, Ca, Mn, Y
And one or more selected from lanthanide metals,
0 <method of manufacturing a α'- sialon represented by x ≦ 2), were allowed to mixed combined and reacting the aluminum alkoxide and an alkanolamine compound 0 <molar ratio of hydroxyl group / aluminum alkoxide <3 in an alkanolamine, Mix a silane coupling agent, and further add Li,
One or more alkoxides selected from the group consisting of Mg, Ca, Mn, Y and lanthanide metals are added to obtain a homogeneous solution, which is added to the aluminum alkoxide in an amount of 0.5%.
The obtained sol is hydrolyzed by using ２０20 mole times of water and an acidic catalyst, gelled by aging, and then calcined at a temperature higher than 1300 ° C. in a nitrogen atmosphere to obtain α. A method for producing an α'-sialon sintered body characterized by normal pressure or pressure sintering at a temperature of 1500 ° C. or more after producing '-sialon powder, and a general formula M _x (S
i, Al) ₁₂ (O, N) ₁₆ (M is Li, Mg, Ca, M
In the method for producing α′-sialon represented by one or more kinds selected from n, Y and lanthanide metals, 0 <x ≦ 2), the aluminum alkoxide and the alkanolamine compound are converted to 0 <hydroxyl group in alkanolamine /
Aluminum alkoxide <3 molar ratio in the presence of an alcohol in the presence of an alcohol, followed by mixing and reaction, then adding a silane coupling agent, adding magnesium or / and calcium metal, and refluxing while heating to form a homogeneous solution. ,
Water which is 0.5 to 20 mole times the aluminum alkoxide is hydrolyzed using an acidic catalyst, and the obtained sol is gelled by aging. After drying, the temperature is higher than 1300 ° C. in a nitrogen atmosphere. After calcining at a temperature to produce an α′-sialon powder, a method for producing an α′-sialon sintered body characterized by being sintered at a temperature of 1500 ° C. or more under normal pressure or pressure is found. completed.

Hereinafter, the present invention will be described in detail.

First, the raw materials used in the present invention will be described. Al (OR) as aluminum alkoxide
₃ (R: alkyl group)
R represents a methyl group, an ethyl group, an n-propyl group, is
o-propyl group, n-butyl group, sec-butyl group, t
Examples thereof include an tert-butyl group.

In consideration of the uniformity of the reaction and the operability, it is desirable to use aluminum alkoxide which is liquid at ordinary temperature. However, alkoxide which is solid at ordinary temperature should be dissolved in an organic solvent in which the alkoxide is soluble. Can be.

[0013] In terms of operability and cost, aluminum s
ec-butoxide is most preferred.

Alkanolamine is used as a stabilizer for aluminum alkoxide.

[0015] The stabilizer is a compound which can be substituted for an alkyl group of aluminum alkoxide or added to an aluminum atom to slow the hydrolysis rate of alkoxide.

Nitrogen is introduced into the gel and an alkanolamine must be used to facilitate reductive nitridation during firing.

Specifically, there are monoethanolamine, diethanolamine, triethanolamine and the like, which are not particularly specified.

The silane coupling agent generally means Si
(OR ′) _n X _4-n (n = 1, 2, 3), where X is an alkyl group, amino group, vinyl group, epoxy group, etc., and OR ′ is hydrolyzable Methoxy group, ethoxy group and the like.

Specifically, methyltrimethoxysilane,
Methyltriethoxysilane, vinylmethoxysilane, γ
-Anilinopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, dimethyldiethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, trimethylmethoxysilane and the like.

In the present invention, a group containing carbon is required in the portion of X which does not contribute to the hydrolysis of the silane coupling agent.

That is, the part X is left in the gel after hydrolysis, aging, and drying, so that carbon is uniformly mixed, so that reduction nitridation at the time of firing proceeds.

From the viewpoint of introducing nitrogen into the gel, a silane coupling agent further containing an amino group at the portion X is most preferred.

One or more alkoxides selected from the group consisting of Li, Mg, Ca, Mn, Y and lanthanide metals are preferably alkoxides which are liquid at room temperature in consideration of the uniformity and operability of the reaction. Even alkoxides that are solid at room temperature can be used by dissolving them in an organic solvent in which the alkoxide is soluble.

Since Mg and Ca metals are often oxidized on the surface, they are used after washing with an acid or alcohol.

Next, the manufacturing method of the present invention will be described.

First, an aluminum alkoxide is reacted with an alkanolamine. The reaction can be carried out by mixing both at room temperature or under heating. However, mixing in a solution state is desirable from the viewpoint of the uniformity of the reaction. As described above, the organic solvent used here is aluminum alkoxide. Specifically, alcohols represented by methanol, ethanol, n-propanol, iso-propanol, n-butanol, etc., aromatic compounds represented by toluene, benzene, xylene, etc., tetrahydrofuran, dimethyl Formamide and the like can be used. Of these, alcohol is preferred
No.

This reaction involves a hydrogen atom of a hydroxyl group in the alkanolamine and an aluminum alkoxide.

The number of moles of alkanolamine hydroxyl groups is 1 mole for monoalkanolamine, 2 moles for dialkanolamine, and 3 moles for trialkanolamine.

The amount of alkanolamine used is three times the number of moles of hydroxyl groups in the alkanolamine with respect to the number of moles of aluminum alkoxide so that the subsequent hydrolysis reaction proceeds and a uniform transparent gel is produced. Must be less.

If the ratio is three times or more, the aluminum alkoxide becomes completely stable, the hydrolysis reaction does not proceed, and the gel does not form.

If the aluminum alkoxide is not stabilized by this operation, a non-uniform hydrolysis occurs due to a difference in the hydrolysis rate between the aluminum alkoxide and the silane coupling agent in the subsequent hydrolysis step, and Al—
Atomic level bonds of O—Si are not formed, and a uniform gel is not obtained.

Next, the silane coupling agent is mixed with the solution in which the aluminum alkoxide has been stabilized with an alkanolamine at room temperature or under heating. This produces a transparent homogeneous solution.

Thereafter, one or two or more alkoxides selected from Li, Mg, Ca, Mn, Y and lanthanide metals are added to form a uniform solution.

When Mg or Ca is used as the M metal,
Mg, C washed after adding silane coupling agent
It was added a, occurring when a metal subjected to reflux at a temperature of about 60 ° C. to 80 ° C. was reacted alkanolamine and aluminum alkoxide alcohol, or during the reaction
If alcohol is used as a solvent, it is reacted with the used alcohol to form a homogeneous solution.

At this time, the amount of alcohol is Mg, Ca
Although depending on the amount of the metal, the amount at which a sufficient reaction proceeds is preferably about 4 to 10 times the mole of the aluminum alkoxide.

Thereafter, the transparent homogeneous solution is hydrolyzed. Examples of the method include, but are not particularly limited to, addition of a mixture of water and an organic solvent dissolving water such as ethanol, or addition of water by directly dropping it into a homogeneous solution.

Hydrolysis by addition of a mixture of an organic solvent capable of dissolving water and water is most preferred from the viewpoints of uniform reactivity, reduction of the production process time and operability.

The number of moles of water to be added during the hydrolysis must be 0.5 times or more and 20 times or less with respect to the aluminum alkoxide.

When the amount is less than 0.5 times, the hydrolysis reaction does not sufficiently occur and the gel does not become transparent after aging.

If it is more than 20 times, phenomena such as uneven hydrolysis and white precipitation occur, and the gel does not become transparent after aging.

That is, the fact that the gel does not become a transparent gel after aging means that it is a non-uniform gel, and does not finally become a preferable α'-sialon phase single phase after firing.

An acidic catalyst is added during the hydrolysis step. Thereby, the bonding of Al—O—Si at the atomic level due to the reaction between the hydroxyl group and the alkoxyl group during the aging is promoted, and a uniform transparent gel can be produced.

That is, when the acidic catalyst is not used, the reaction between the hydroxyl group and the alkoxyl group is not promoted, and aluminum hydroxide or silicon hydroxide is formed, and the gel becomes white and A
Atomic level bonding of l-O-Si does not occur.

Examples of the acidic catalyst include hydrochloric acid, nitric acid, hydrofluoric acid,
Sulfuric acid, acetic acid and the like can be mentioned, and hydrochloric acid and nitric acid are preferable in view of safety and the like, which do not leave residue after firing.

The addition amount is desirably about 0.01 times in mole number with respect to the aluminum alkoxide.

Through the hydrolysis step, the homogeneous solution becomes what is generally called a fluid sol.

By aging this, A
A gel having l-O-Si atomic level bonds.

The aging is preferably performed by leaving the sol tightly closed at room temperature or under heating so that the sol does not come into contact with moisture in the air.

The sol then becomes an unflowable, ie, transparent, bulk gel in a matter of hours to days.

In this case, the gel is suspended in an organic solvent, which is called syneresis. When this state is reached, it is determined that the ripening is completed.

Thereafter, the gel having the Al—O—Si bond is released from the sealed state and dried at 0 ° C. or higher for several days.

The temperature at which water freezes at 0 ° C. or higher is required, and drying is performed in a temperature range in which an organic solvent or alcohol generated from alkoxide or the like by hydrolysis does not boil. 60
C is the most desirable temperature.

By drying, the gel remains transparent about 1 cm.
Break into small pieces. Although the criterion for determining the end of the drying is not particularly defined, the end of the drying is determined when the smell of the alcohol or the organic solvent has disappeared for about one day to one week.

The dried small gel was placed in a nitrogen atmosphere at 130
Calcinate at a temperature of 0 ° C or higher. The flow rate of the nitrogen flowing into the furnace is not particularly limited by the size of the furnace or the like, but it must be sufficient to cause a nitriding reaction.

If the calcination temperature is lower than 1300 ° C., a phase such as mullite or X-sialon is formed,
α'-sialon phase does not become single phase.

When baked at a temperature higher than 1700 ° C., grain growth occurs, resulting in coarse grains or decomposition to β ′
-When a sialon phase appears and a sintered body is to be prepared later, the sinterability deteriorates. The most preferable firing temperature is a temperature around 1500 ° C.

The holding time at this temperature is not particularly limited, but if holding for 12 hours or more causes grain growth, it is preferable to hold for 2 to 5 hours, which is sufficient for nitriding to proceed. .

The α'-sialon produced by this method is in a powder form, but may be pulverized by a ball mill or the like in order to further improve sinterability.

This powder is molded and sintered. Molding is performed by a general method conventionally used, that is, mold molding, C
IP molding, casting molding, injection molding and the like are used.

The sintering atmosphere is preferably an argon or nitrogen atmosphere. If the sintering temperature is lower than 1500 ° C., the density after sintering is insufficient, so a higher temperature is required.

When the temperature is 1700 ° C. or more, β ′
-Temperatures below that are preferred for the appearance of the sialon phase. It can be fired at normal pressure or under pressure. Pressure sintering is preferably gas pressure sintering, hot press sintering, HIP sintering, or the like.

[0062]

According to the present invention, a high-purity α'-sialon sintered body having a small particle size and a small glass phase can be produced.

In the method of the present invention, since the sol-gel method is used, that is, since a high-purity alkoxide and a coupling agent are used as raw materials, the final α'-sialon has a high purity, and contains Si, Al and carbon. In order to use a gel uniformly mixed at the atomic or molecular level, α'-sialon with a smaller glass phase than the method obtained without a normal Si ₃ N ₄ —Al ₂ O ₃ —AlN mixed powder Can be.

The process in which the α′-sialon phase appears is that a group containing carbon that does not contribute to the hydrolysis of the silane coupling agent, ie, an alkyl group, an amino group, a vinyl group, an epoxy group, etc., is contained in the gel. It is considered that the residual nitridation reaction occurs by raising the temperature and nitrogen is introduced to form an α′-sialon phase.

For this reason, unlike the conventional reductive nitridation method, there is a feature that it is not necessary to add carbon.

Also, a very fine powdery sol such as colloidal silica or colloidal alumina may be used.
e type sol) is uniformly dispersed, and since an ester gel such as Al-O-Si is used, an α'-sialon single-phase ceramic can be easily produced.

[0067]

The present invention will be described in detail below with reference to embodiments.

[0068]

Example 1 To 0.2 mol of aluminum sec-butoxide was added 0.4 mol of butanol from which water had been sufficiently removed, and 0.067 mol of triethanolamine was added, and the mixture was reacted at room temperature with stirring.

Thereafter, 2 mol of γ- (2-aminoethyl) aminopropyltrimethoxysilane was added, and 0.1 mol of yttrium n-butoxide (xylene solution) was further added to obtain a uniform solution.

A mixed solution of 0.4 mol of butanol, 1 mol of water, and 0.002 mol of hydrochloric acid (as HCl), from which water had been sufficiently removed, was added dropwise to the homogeneous solution to carry out hydrolysis. The above operation was performed without touching the moisture in the air.

The sol obtained by the hydrolysis was transferred to a polypropylene container, and aged at 60 ° C. for 2 days while keeping the airtight. This resulted in a colorless and transparent gel.

The container was opened and dried at 60 ° C. for 3 days. A small piece of gel of about 1 cm was obtained.

When the gel was examined using a Fourier transform infrared spectrophotometer, an absorption peak due to a Si—O—Al bond was observed.

The gel was placed in an alumina boat and calcined at 1500 ° C. for 3 hours in a nitrogen stream.

When the produced phase of the produced powder was examined by X-ray diffraction (CuKα ray) and observed with a scanning electron microscope, it was confirmed that the powder consisted of an α′-sialon single phase and 0.3 μm.

After the powder was lightly pulverized in a mortar, it was molded in a mold at a molding pressure of 1 ton, and then subjected to CIP molding at 10 tons to produce a compact. Sintering was performed in nitrogen at normal pressure and 1600 ° C. for 8 hours.

The resulting phase of the sintered body was analyzed by X-ray diffraction (C
Inspection by uKα ray) revealed that the phase was α'-sialon phase single phase.

[0078]

Example 2 1 mol of butanol from which water was sufficiently removed was added to 0.2 mol of aluminum sec-butoxide, 0.1 mol of monoethanolamine was added, and the mixture was reacted at room temperature with stirring.

Thereafter, 4 mol of methyltrimethoxysilane was added, and then 0.2 mol of magnesium metal washed with acid and alcohol was added, and the mixture was refluxed at 80 ° C. for about 24 hours to obtain a homogeneous solution.

A mixed solution of 0.4 mol of butanol, 1 mol of water, and 0.002 mol of hydrochloric acid (as HCl), from which water had been sufficiently removed, was added dropwise to the homogeneous solution to carry out hydrolysis. The above operation was performed without touching the moisture in the air.

The sol obtained by the hydrolysis was transferred to a polypropylene container and aged at 60 ° C. for 2 days while keeping the airtight. This resulted in a colorless and transparent gel.

The container was opened and dried at 60 ° C. for one week. A small piece of gel of about 1 cm was obtained. The gel was placed in an alumina boat and calcined at 1400 ° C. for 5 hours in a nitrogen stream.

The produced powder was pulverized with a ball mill for 24 hours in order to further improve the sinterability. The powder was sintered at 1600 ° C. in nitrogen in a hot press.

The resulting phase of the sintered body was analyzed by X-ray diffraction (C
Inspection by uKα ray) revealed that the phase was α'-sialon phase single phase.

[0085]

Example 3 To 0.1 mol of aluminum sec-butoxide was added 0.8 mol of butanol from which water had been sufficiently removed, and 0.1 mol of monoethanolamine was added. The mixture was reacted at room temperature with stirring.

Thereafter, 4 mol of methyltrimethoxysilane was added, and then 0.08 mol of calcium metal washed with acid and alcohol was added, and the mixture was refluxed at 80 ° C. for about 24 hours to obtain a homogeneous solution.

A mixed solution of 1 mol of butanol, 1 mol of water, and 0.002 mol of hydrochloric acid (as HCl), from which water had been sufficiently removed, was added dropwise to the homogeneous solution to effect hydrolysis. The above operation was performed without touching the moisture in the air.

The sol obtained by hydrolysis was transferred to a polypropylene container, and aged at 60 ° C. for 2 days while keeping hermetically sealed. This resulted in a colorless and transparent gel.

The container was opened and dried at 60 ° C. for one week. A small piece of gel of about 1 cm was obtained. The gel was placed in an alumina boat and calcined at 1400 ° C. for 5 hours in a nitrogen stream.

The produced powder was pulverized with a ball mill for 24 hours in order to further improve the sinterability. The powder was sintered at 1600 ° C. in nitrogen in a hot press.

The resulting phase of the sintered body was analyzed by X-ray diffraction (C
Inspection by uKα ray) revealed that the phase was α'-sialon phase single phase.

[0092]

Comparative Example 1 A commercially available alumina sol containing 20 wt% in terms of alumina and 100 g of colloidal silica containing 30 wt% in terms of silica were mixed, and 30.5 g of yttrium nitrate (hexahydrate) and 90 g of carbon black were added. Dispersed. Thereafter, the mixture was evaporated to dryness using a rotary evaporator.

The evaporated and dried product was placed in an alumina boat in the same manner as in Example 1, and calcined at 1500 ° C. for 3 hours in a nitrogen stream to obtain a calcined powder.

It contained α'-sialon and β'-sialon, β-silicon nitride, and AlN.

[0095]

According to the present invention, β'-sialon, β
-An α'-sialon single phase sintered body free of other phases such as silicon nitride and AlN is obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-167209 (JP, A) JP-A-60-118615 (JP, A) JP-A-61-186266 (JP, A) JP-A-61-186266 186267 (JP, A) JP-A-61-186268 (JP, A) JP-A-62-70209 (JP, A) JP-A-2-74508 (JP, A) JP-A-60-210574 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 35/58 C01B 21/082

Claims (2)

(57) [Claims] 1. The general formula M _x (Si, Al) ₁₂ (O, N)
₁₆ (M is one or more selected from Li, Mg, Ca, Mn, Y and lanthanide metals, 0 <x ≦ 2), wherein the aluminum alkoxide and the alkanolamine The compounds are mixed and reacted at a molar ratio of 0 <hydroxyl group in alkanolamine / aluminum alkoxide <3, and then mixed with a silane coupling agent. Further, Li, Mg, Ca, M
One or more alkoxides selected from n, Y and lanthanide metals are added to form a homogeneous solution,
Water which is 0.5 to 20 mole times the aluminum alkoxide is hydrolyzed using an acidic catalyst, and the obtained sol is gelled by aging. After drying, the temperature is higher than 1300 ° C. in a nitrogen atmosphere. A method for producing an α'-sialon sintered body, comprising calcining at a temperature to produce an α'-sialon powder, followed by sintering at a temperature of 1500 ° C. or more under normal pressure or pressure. 2. The general formula M _x (Si, Al) ₁₂ (O, N)
₁₆ (M is one or more selected from Li, Mg, Ca, Mn, Y and lanthanide metals, 0 <x ≦ 2), wherein the aluminum alkoxide and the alkanolamine refluxing a compound 0 <a reacted engaged mixing molar ratio of the hydroxyl group / aluminum alkoxide <3 in alkanolamines, mixed silane coupling agent, was added magnesium and / or calcium metal, with heating The homogeneous solution was added to the aluminum alkoxide in an amount of 0.5 to 2
The obtained sol is hydrolyzed by using water which is 0 mole times and an acidic catalyst, and the obtained sol is aged to be gelled. After drying, it is calcined in a nitrogen atmosphere at a temperature higher than 1300 ° C. A method for producing an α'-sialon sintered body, characterized in that after producing non-sialon powder, normal pressure or pressure sintering is performed at a temperature of 1500 ° C. or more.