JPH06287068A - Production of alpha'-sialon sintered compact - Google Patents

Abstract

PURPOSE:To improve the strength, corrosion and abrasion resistance by hydrolyzing a specific solution, gelatinizing the resultant sol, drying the prepared gel and sintering the dried gel. CONSTITUTION:(a) An aluminum alkoxide is mixed and made to react with (b) an alkanolamine at molar ratios of 0<hydroxyl groups in the component (b)/the component (a)<3 to provide a reactional product. A silane coupling agent is then added to the resultant reactional product to afford a solution. One or more alkoxides selected from Li, Mg, etc., are subsequntly added to the prepared solution and water in a molar amount of 0.5-20 times based on the component (a) and an acidic catalyst are then added to the resultant solution. A sol obtained by hydrolyzing the obtained solution is further aged to afford a gel, which is then dried and subsequently calcined at >=1300 deg.C in an atmosphere of N2 to provide (c) alpha'-sialon powder expressed by the formula [M is one or more selected from Li, Mg, Ca, Mn, Y and La metals; 0<=(x)<=2]. The component (c) is then sintered under ordinary pressure or a higher pressure to produce the objective alpha'-sialon sintered compact.

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 ceramics sintered body excellent in 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 is used.
1N mixed powder and M metal (M is Li, Mg, Ca, M
After molding oxides of n, Y and lanthanide metal), 170
Sintering is performed at a temperature of 0 ° C. or higher.

However, this method requires a high temperature or a long time to form a solid solution of Al and O or M metal in Si ₃ N ₄ because it is a powder mixture of micron order, so that the sialon particles are coarse. However, if insufficient mixing of the powders occurs, other sialon phases that are not intended will appear, and a large amount of glass phase will remain.

Further, silicon oxide or a silicon compound which produces silicon oxide by heating, aluminum oxide or an aluminum compound which produces aluminum oxide by heating, carbon and M metal oxides or M metal oxides upon heating. Japanese Unexamined Patent Publication No. 62-167209 discloses a method for producing an α-sialonaceous powder, which is produced by heating a composition mixture containing an M compound in a nitrogen stream.

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

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

The so-called sol-gel method using a metal alkoxide is a fine powder capable of low-temperature production process, which has a high purity as compared with the generally used method of mixing powders and calcining. Since it has many advantages such as easy manufacturing of the body, it is expected to be applied to the development of highly functional ceramics.

[0008]

In the present invention, the disadvantages of the above-mentioned conventional method are low purity, coarsening of sialon particles by non-uniform mixing, phases other than α'-sialon after firing (including glass phase). To eliminate the drawbacks such as the appearance of alkoxide and the difficulty of uniformly adding carbon in the reduction nitriding reaction, and to carefully consider the raw material and the hydrolysis conditions, etc. for a more uniform gel than the powder obtained by the precipitation method by the hydrolysis of alkoxide. The present invention is intended to provide a method for producing an α′-sialon sintered body by the method described above.

[0009]

[Means for Solving the Problems] 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,
In the method for producing α′-sialon represented by 0 <x ≦ 2), the aluminum alkoxide and the alkanolamine compound are mixed in the presence of alcohol in a molar ratio of 0 <hydroxyl group / aluminum alkoxide <3 in alkanolamine,
After mixing and reacting, a silane coupling agent is mixed, and one or more alkoxides selected from Li, Mg, Ca, Mn, Y and lanthanide metals are added to form a uniform solution. Is hydrolyzed with 0.5 to 20 moles of aluminum alkoxide and an acidic catalyst, and the resulting sol is aged to gel, and after drying, it is dried at 1300 ° C. in a nitrogen atmosphere. A method for producing an α'-sialon sintered body and a general formula, characterized by calcination at a higher temperature to produce α'-sialon powder, and then sintering at atmospheric pressure or pressure at a temperature of 1500 ° C or higher. M _x (Si, Al) ₁₂ (O, N) ₁₆ (M is L
α ′ represented by 0 <x ≦ 2), one or more selected from i, Mg, Ca, Mn, Y and lanthanide metals
-In the method for producing sialon, an aluminum alkoxide and an alkanolamine compound are mixed and reacted in a molar ratio of 0 <hydroxyl group / aluminum alkoxide <3 in alkanolamine in the presence of alcohol, and then a silane coupling agent is mixed, Obtained by adding magnesium or / and calcium metal and refluxing with heating to make a homogeneous solution, which is hydrolyzed with 0.5 to 20 mol times water and an acidic catalyst with respect to the aluminum alkoxide. The sol was gelled by aging, dried and then calcined at a temperature higher than 1300 ° C in a nitrogen atmosphere to produce α'-sialon powder, and then 1500 ° C.
The present invention has been completed by finding out a method for producing an α'-sialon sintered body characterized by performing normal pressure or pressure sintering at the above temperature.

The present invention will be described in detail below.

First, the raw materials used in the present invention will be described. As the aluminum alkoxide, Al (OR)
₃ (R: alkyl group),
R is methyl group, ethyl group, n-propyl group, is
o-propyl group, n-butyl group, sec-butyl group, t
An ert-butyl group and the like are exemplified.

Considering the uniformity of the reaction and the operability, it is desirable to use an aluminum alkoxide that is liquid at room temperature, but even an alkoxide that is solid at room temperature should be used by dissolving it in an organic solvent in which the alkoxide is soluble. You can

From the viewpoint of operability and price, aluminum s
Most preferred is ec-butoxide.

Alkanolamines are used as stabilizers for aluminum alkoxides.

The stabilizer is a compound capable of substituting the alkyl group portion of aluminum alkoxide or adding to the aluminum atom to delay the hydrolysis rate of alkoxide.

Nitrogen is introduced into the gel and alkanolamines must be used to facilitate the reductive nitriding during firing.

Specific examples thereof include monoethanolamine, diethanolamine, triethanolamine and the like, which are not particularly specified.

The silane coupling agent is generally Si.
(OR ′) _n X _4-n (n = 1, 2, 3), X is an alkyl group, an amino group, a vinyl group, an epoxy group or the like, and OR ′ is hydrolyzable. A compound which is a methoxy group, an ethoxy group or the like, which is another group.

Specifically, methyltrimethoxysilane,
Methyltriethoxysilane, vinylmethoxysilane, γ
Examples thereof include anilinopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, dimethyldiethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane and trimethylmethoxysilane.

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

That is, the X portion remains in the gel after hydrolysis, aging and drying, whereby carbon is uniformly mixed, and reduction nitriding during firing proceeds.

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

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

Since the surfaces of Mg and Ca metals are often oxidized, they are used after washing with acid or alcohol.

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

First, an aluminum alkoxide is reacted with an alkanolamine. It is possible to react by mixing both at room temperature or under heating, but it is preferable to mix them in a solution state from the viewpoint of the uniformity of the reaction. As described above, the organic solvent used here is an 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 or the like can be used.

The hydrogen atom of the hydroxyl group in the alkanolamine and the aluminum alkoxide participate in this reaction.

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

The amount of alkanolamine used is 3 times the number of moles of the hydroxyl groups in the alkanolamine relative to the number of moles of the aluminum alkoxide so that the subsequent hydrolysis reaction proceeds and a uniform transparent gel is produced. We have to do less.

When the amount is 3 times or more, the aluminum alkoxide becomes completely stable, the hydrolysis reaction does not proceed, and a gel is not obtained.

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

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

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

When Mg or Ca is used as the M metal,
Mg, C washed after adding the silane coupling agent
a is added and refluxed at a temperature of about 60 ° C. to 80 ° C. to react the metal with the alcohol used when the alkanolamine and the aluminum alkoxide are reacted to form a uniform solution.

The amount of alcohol at that time is Mg, Ca
Although it depends on the amount of the metal, the amount by which the sufficient reaction proceeds is preferably about 4 to 10 mol times the aluminum alkoxide.

Then, the transparent homogeneous solution is hydrolyzed. Examples of the method include adding a mixture of water and an organic solvent that dissolves water, such as ethanol, or adding water by dropping it directly into a homogeneous solution, and the method is not particularly limited.

From the viewpoints of uniform reactivity, shortening of manufacturing process time, and operability, hydrolysis by addition of a mixture of water and an organic solvent capable of dissolving water is most preferable.

The number of moles of water added during the hydrolysis must be 0.5 times or more and 20 times or less that of 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.

When it is more than 20 times, phenomena such as non-uniform hydrolysis and white precipitation occur, and a transparent gel is not obtained after aging.

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

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

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

Acid catalysts 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 does not leave a residue after firing.

The amount of addition is preferably about 0.01 times the number of moles of aluminum alkoxide.

A homogeneous solution, which has undergone a hydrolysis step, is generally called a fluid sol.

By aging this, A having no fluidity was obtained.
A gel having l-O-Si atomic level bonds is used.

The aging is preferably carried out by keeping the sol at room temperature or under heating so that it does not come into contact with moisture in the air, and leaving it to stand.

This causes the sol to become a non-flowing, unitary or transparent bulk gel within hours to days.

In this case, the gel, called syneresis, is in a state of floating in the organic solvent. When this state is reached, it is judged that ripening has ended.

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

The freezing temperature of water is required to be 0 ° C. or higher, and the organic solvent and alcohol produced from alkoxide by hydrolysis are dried in a temperature range where they do not boil. 60
C is the most desirable temperature.

Due to the drying, the gel remains transparent for about 1 cm.
It breaks into small pieces. The criteria for judging the end of drying is not particularly defined, but the place where the smell of alcohol or organic solvent disappears for about one day to one week is judged to be the end of drying.

A small gel after drying was placed in a nitrogen atmosphere for 130 minutes.
Calcination is performed at a temperature of 0 ° C or higher. The flow rate of nitrogen in the furnace is not particularly specified depending on the size of the furnace and the like, but it must be sufficient to cause the nitriding reaction.

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

When firing 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 produced later, the sinterability deteriorates. The most preferable firing temperature is around 1500 ° C.

The holding time at the temperature is not particularly specified, but if the holding is performed for 12 hours or more, grain growth occurs. Therefore, it is desirable to hold for 2 to 5 hours, which is sufficient for nitriding to proceed. .

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

This powder is molded and sintered. Molding is a general method conventionally used, that is, mold molding, C
IP molding, cast molding, injection molding, etc. 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, and therefore a higher temperature is required.

If the temperature is 1700 ° C. or higher, β '
-Temperatures below it are preferred for the appearance of the sialon phase. It can be fired at normal pressure or under pressure. The pressure sintering is preferably gas pressure sintering, hot press sintering, HIP sintering or the like.

[0062]

According to the present invention, a highly pure α'-sialon sintered body having a fine grain size and a small glass phase can be produced.

Since the method of the present invention uses the sol-gel method, that is, it uses a high-purity alkoxide and a coupling agent as raw materials, the final α'-sialon has a high purity and contains Si, Al and carbon. In order to use a gel that is homogeneously mixed at the atomic or molecular level, it is necessary to prepare α'-sialon having less glass phase than the method obtained by not using an ordinary mixed powder of Si ₃ N ₄ —Al ₂ O ₃ —AlN system. You can

In the process of appearance of this α'-sialon phase, carbon-containing groups that do not contribute to the hydrolysis of the silane coupling agent, that is, alkyl groups, amino groups, vinyl groups, epoxy groups, etc., are present in the gel. It is considered that the reduction nitriding reaction occurs due to the remaining and temperature rise, and nitrogen is introduced to form the α'-sialon phase.

Therefore, unlike the conventional method of reducing and nitriding, 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 is used.
Unlike the method in which the e type sol) is uniformly dispersed, an α'-sialon single-phase ceramic can be easily manufactured because an ester gel such as Al-O-Si is used.

[0067]

Embodiments will be described in detail below with reference to embodiments.

[0068]

Example 1 To 0.2 mol of aluminum sec-butoxide, 0.4 mol of butanol, which had been sufficiently dewatered, and 0.067 mol of triethanolamine were added, and the reaction was carried out 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 was sufficiently removed, was added dropwise to the above homogeneous solution for hydrolysis. The above operation was performed while avoiding contact with water in the air.

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

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

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

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

When the produced phase of the produced powder was examined by X-ray diffraction (CuKα ray) and the particle size was examined by a scanning electron microscope, it was found to be α′-sialon phase single phase, 0.3 μm.

The powder was lightly crushed in a mortar, molded with a molding pressure of 1 ton, and then CIP molded with 10 tons to produce a molded body. Sintering was performed in nitrogen at atmospheric pressure and 1600 ° C. for 8 hours.

The produced phase of the sintered body was analyzed by X-ray diffraction (C
When examined by uKα ray), it was α′-sialon phase single phase.

[0078]

Example 2 1 mol of butanol, which was sufficiently dewatered, 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.

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

Hydrolysis was carried out by adding dropwise 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 was sufficiently removed, to the homogeneous solution. The above operation was performed while avoiding contact with water in the air.

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

The container was opened and further dried at 60 ° C. for 1 week. The gel became a small piece of about 1 cm. The gel was placed in an alumina boat and calcined by holding it 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 by hot pressing at 1600 ° C. in nitrogen.

The produced phase of the sintered body was analyzed by X-ray diffraction (C
When examined by uKα ray), it was α′-sialon phase single phase.

[0085]

Example 3 0.8 mol of butanol dewatered sufficiently was added to 0.1 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 0.08 mol of calcium metal washed with acid and alcohol was added, and refluxed at 80 ° C. for about 24 hours to obtain a uniform 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 was sufficiently removed, was added dropwise to the above homogeneous solution for hydrolysis. The above operation was performed while avoiding contact with water in the air.

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

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

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

The produced phase of the sintered body was analyzed by X-ray diffraction (C
When examined by uKα ray), it was α′-sialon phase single phase.

[0092]

[Comparative Example 1] 100 g of commercially available alumina sol containing 20 wt% of alumina and 400 g of colloidal silica containing 30 wt% of silica are mixed, 30.5 g of yttrium nitrate (hexahydrate) and 90 g of carbon black are added, and ultrasonic vibration is applied. Dispersed by. Then, it was evaporated to dryness with a rotary evaporator.

The evaporated dry solid was put into an alumina boat in the same manner as in Example 1 and calcined in a nitrogen stream at 1500 ° C. for 3 hours to obtain a calcined powder.

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

[0095]

According to the present invention, β'-sialon, β
-An α'-sialon single-phase sintered body is obtained in which other phases such as silicon nitride and AlN do not exist.

Claims (2)

[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 compound is mixed at a molar ratio of 0 <hydroxyl group in alkanolamine / aluminum alkoxide <3, and reacted, then a silane coupling agent is mixed, and further Li, Mg, Ca, M is added.
One or two or more kinds of alkoxides selected from n, Y and lanthanide metals are added to form a uniform solution,
Hydrolyze with 0.5 to 20 moles of aluminum alkoxide and an acidic catalyst, and age the resulting sol to gel it, and after drying it, the temperature is higher than 1300 ° C in a nitrogen atmosphere. A method for producing an α'-sialon sintered body, which comprises calcination at a temperature to produce an α'-sialon powder, and then sintering at atmospheric pressure or pressure at a temperature of 1500 ° C. or higher. 2. The general formula M_x(Si, Al)₁₂(O , N)
₁₆(M is Li, Mg, Ca, Mn, Y and lanthanide gold
One or more selected from the genus, indicated by 0 <x ≦ 2)
In a method for producing α′-sialon
The umalkoxide and alkanolamine compound are
Hydroxyl groups in lucanolamine / aluminum alkoxy
In a molar ratio of <3, the mixture is allowed to react in the presence of alcohol.
Then mix the silane coupling agent and
Or / and adding calcium metal, while heating
Aluminum alkoxy was prepared by refluxing into a uniform solution.
Use 0.5 to 20 mole times water and acid catalyst
Gelation by hydrolyzing and aging the resulting sol.
And dry it and then it is higher than 1300 ℃ in nitrogen atmosphere
After calcination at a temperature to produce α'-sialon powder, 1
Sintering at a temperature of 500 ° C or higher under normal pressure or pressure
And a method for producing an α'-sialon sintered body.