JPS5940786B2 - Manufacturing method for ceramic sintered bodies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a sintered body of heat-resistant ceramics.

More specifically, the present invention involves mixing polyzirconocarbosilane as an additive with known heat-resistant ceramics, molding the mixture, and simultaneously or after the molding, inert gas, reducing gas, hydrocarbon, etc. The present invention relates to a method for producing a heat-resistant ceramic sintered body, which comprises heating and sintering in an atmosphere containing at least one gas selected from among gases.

Conventionally, sintered bodies that have been used in many ways as ceramics with excellent heat resistance include, for example, A1203tB.
Oxides such as 4Al203tB402, 5i02, si
Carbide such as c+'ric, wc1134c, S i3
N4. Nitride such as BN, AlN, T i B2,
Borides such as Z r B2 and even Mo S 12
Silicides such as j ws 12 j Cr S t2 and composite compounds thereof are known.

These ceramic sintered bodies have been manufactured by molding the respective powders and heating and sintering them at extremely high temperatures.

Recently, there has been active research into producing high-density sintered bodies with few pores using relatively low pressure and sintering temperatures.

In other words, by using the above-mentioned appropriate additives, the self-sintering properties of ceramics can be improved, and at the same time, the abnormal growth of grains in the sintered body can be suppressed to prevent pores from remaining between the grains. This is because grain boundaries can be filled with a high density by the agent, and a high-density sintered body can be economically advantageously obtained.

Conventionally used additives include, for example, Al2O
3 contains MgO or NiO, and ZrO2 contains CaO or TiO.
2, Al2O3 or ¥203 for Si3N4, SiC
B, Si or C for TiC, Ni or WC for TiC, ZrB
No. 21 uses ZrO2 and CrB2 as additives, and many of them are oxide-based additives, but there are also other additives that are added as single metal elements, and for example, other carbides. , Other borides are often added to boride.

These additives are selected because they create a reciprocity window between the base ceramic and the additive to assist in the sintering of ceramics with poor self-sintering properties, or because the additive becomes plastic at high temperatures. This is because sintering progresses more easily because it becomes a liquid phase or becomes a liquid phase.

However, the conventional additives mentioned above have the following drawbacks.

In a high-density sintered body that utilizes a solid phase reaction between additives and a ceramic matrix, a second reaction occurs between the additive and the ceramic matrix. A third phase appears and exists mainly at grain boundaries, and at high temperatures plastic deformation tends to occur from these grain boundary constituents, making it difficult to form sintered bodies that aim for high-temperature strength. .

For example, when MgO is added to S A3 N4, a glassy phase called S + M g Oa is formed as a second phase, and high density is achieved by filling the grain boundaries. The mechanical strength of the body has a disadvantage that it rapidly decreases from around 1000° C. due to the softening of the glassy phase.

Furthermore, even in high-density sintered bodies that utilize plasticization or liquid phase of additives, they have the same drawback that the strength decreases significantly due to plastic deformation and liquid flow at grain boundaries at high temperatures. There is.

On the other hand, as additives that do not cause the above-mentioned reduction in high-temperature strength, it is promising to use additives that exclude oxides that tend to become glassy or simple metals that tend to turn into a liquid phase. Since boride-based materials generally have poor self-sintering properties, sufficient densification cannot be expected even if they are used as additives.

The present invention has properties that do not cause plastic deformation at high temperatures, densely fill grain boundaries during the sintering process, improve the sinterability of the base ceramic, and suppress coarse grain growth of the ceramic. By using new additives, despite having a lower density than conventional ceramic sintered bodies, it has the same or higher mechanical strength at room temperature and high temperature and (excellent heat resistance) than conventional ceramic sintered bodies. An object of the present invention is to provide a method for producing a sintered ceramic body.

Next, polyzirconocarbosilane, which is an additive used in the present invention, and its manufacturing method will be explained.

That is, the above-mentioned polyzirconocarbosilane mainly has a main chain skeleton represented by the general formula (wherein R represents a hydrogen atom, a lower alkyl group, or a phenyl group) and has a number average molecular weight of 200 to 200.
10,000 polycarbosilane and an organic zirconium compound represented by the general formula Z r A derived polyzirconocarbosilane having a number average molecular weight of 700 to 100,000, wherein at least a portion of the silicon atoms of the polyzirconocarbosilane are bonded to zirconium atoms via oxygen atoms, and Total number of +5i-CH2+ structural units in polyzyl core carbosilane +
The ratio of the total number of structural units of Zr-0+ is 2 = 1 to 200
: A polymer within the range of 1.

Further, such polymers include monofunctional polymers, difunctional polymers, trifunctional polymers, and tetrafunctional polymers as illustrated below.

(However, R and The ratio of the total number of units to the total number of structural units of the organic zirconium compound (Zr-0+) is 2
:1 to 200:1, and on the contrary, obtained by heating reaction in an inert atmosphere.

The polyzirconocarbosilane used as an additive in the present invention can be obtained as a viscous liquid or powder.

Even if it is obtained as a powder, it can be easily made into a viscous liquid by heating or melting, so unlike conventional powder additives, it can be uniformly distributed throughout the base ceramic granules. Can be distributed.

Further, this polyzirconocarbosilane is fired at a heating temperature of 800 to 2300°C in a vacuum, in an atmosphere of one or more selected from inert gas, reducing gas, and hydrogen carbonate gas. As a result, highly active 5iyZ
r, CyO and volatile substances are produced, and when these come into contact with the ceramic base, the sinterability of the ceramic can be improved.

Furthermore, the highly active (1) S ] t Zr 7
C, generated from S t C> Z r C.

Solid solution of SiC and ZrC and ZrC1-)((0<x
< 1) s High melting point substances such as 13N4 (slightly produced when heating in N2) and C, and various high melting point substances produced by reaction with the ceramic base, exist mainly in the grain boundaries and form a part of the ceramic grains. The high melting point substance that suppresses abnormal grain growth and fills the grain boundaries has extremely high mechanical strength at high temperatures, so it has excellent advantages such as not causing a decrease in the strength of the entire sintered body at high temperatures. can get.

As mentioned above, polyzirconocarbosilane used as an additive is thermally decomposed by heating, organic substances containing some carbon, hydrogen, oxygen, silicon, and zirconium are volatilized as volatile components, and the remaining carbon, Oxygen, silicon, and zirconium react with the base ceramic to form a compound that fills the gaps between the ceramic powder particles.

The reaction begins at about 500°C and is completed at about 1500°C.

During this time, the ceramic particles are also self-sintered, and during this sintering, the additives not only act as a binder but also act as a sintering aid and grain growth inhibitor.

Since the various compounds formed at the ceramic grain boundaries during the heating process are composed of extremely small particles, usually 100A or less, the sintered body has excellent thermal shock resistance.

Moreover, these compounds are mainly SiC. ZrC, SiC and Z
Solid solution of rC and ZrC1-X (0<x<1)
S iaN+ (slightly produced when heated in N2)C
etc., it has excellent high-temperature mechanical strength, oxidation resistance, corrosion resistance, and thermal shock resistance, and has chemically stable properties, so the entire sintered body also has these excellent properties. reflected.

In the present invention, the additives are usually added and mixed in a range of 0.05 to 20% by weight to the ceramic powder.

The amount of this addition varies depending on the pressure sintering method as described below, but if the addition amount is 0.05 weight or less, it will be difficult to obtain a high-strength sintered body, and if it is added 20 weight or more, the sintered body will Since some swelling occurs and the strength deteriorates, it is usually advantageous for the amount added to be within the range of 0.05 to 20% by weight.

Further, in the present invention, known heat-resistant ceramics are used as ceramics, for example, All 20s t B e
O.

Oxides such as MgOt Z r02 t S io2,
SiC.

Carbide such as T i CtWCt B4C, Si3N4
゜Nitrides such as BN and AlN, TiB2. Borides such as ZrB2, and Mo Si2, WS j2,
Examples include silicides such as CrSi2, and composite compounds thereof.

The shape of these heat-resistant ceramics is not particularly limited, but it is usually advantageous to use them by pulverizing them into powder.

Furthermore, in the present invention, the mixture of the polyzirconocarbosilane and the ceramics is sintered in a vacuum, in an atmosphere consisting of at least one selected from inert gas, reducing gas, and hydrocarbon gas. ~23
This is done by heating to 00°C.

Here, the inert gases include nitrogen gas, carbon dioxide gas, argon gas, etc., the reducing gases include hydrogen gas, carbon monoxide gas, etc., and the hydrocarbon gases include methane gas, ethane gas, propane gas, butane gas, etc.

The sintering temperature is preferably 800 to 2300°C, and 80°C to 2300°C.
If it is below 0°C, the mineralization of the mixed polyzirconocarbosilane will not be completed, and if it is above 2300°C, SiC in the mineralized product of the mixed polyzirconocarbosilane will decompose, which is not preferable.

The next sintering method can be roughly divided into a method in which a mixture of ceramic particles and the polyzirconocarbosilane is molded and then heated and sintered, or a hot press method in which molding and sintering of the mixture are performed simultaneously. can be used.

In order to mold the mixture of ceramic powder and additives in the method of separately performing molding and sintering, a mold press method, a rubber press method, an extrusion method, or a sheet method is used.
It is possible to obtain a predetermined shape by applying pressure of 00 to 5000 kg/crA.

Next, the heat-resistant ceramic sintered compact of the present invention can be obtained by sintering the compact.

In addition, when performing sintering using the hot press method, select a mold made of graphite, alumina, boron nitride, etc. that does not react with the respective ceramic base, and
At a pressure of 000 ky/i, a mixture of ceramic powder and additives can be pressed and heated at the same time to form a sintered body.

In a preferred embodiment of the present invention, the mixture of polyzirconocarbosilane and ceramics is heated in a vacuum with at least one gas selected from among an inert gas, a reducing gas, and a hydrocarbon gas before being molded and fired. Preheat at below 800° C. in an atmosphere consisting of seeds.

By carrying out such a treatment, the volumetric shrinkage of the ceramic sintered body is minimized, and a molded body with excellent dimensional accuracy can be obtained.

Furthermore, as another preferred embodiment of the present invention, according to the method of the present invention, a sintered ceramic molded body is impregnated with liquid polyzirconocarbosilane by dipping, spraying, coating, etc. When polyzirconocarbosilane is obtained as a solid, it is made into a liquid by heating or dissolving in a solvent, and then impregnated by the above operation, and if necessary, pressurized to increase the degree of impregnation, and then By performing a series of treatments at least once in a vacuum, in an atmosphere of at least one selected from inert gas, reducing gas, and hydrocarbon gas in a temperature range of 800°C to 2300°C. , a sintered compact with higher density and higher strength can be obtained.

Since the polyzirconocarbosilane to be impregnated as described above needs to be in liquid form, if these compounds can be obtained in liquid form at room temperature or at a relatively low heating temperature, they can be used as is or with the viscosity reduced if necessary. Therefore, a small amount of benzene, toluene, xylene, hexane, ether, tetrahydrofuran, dioxane, chloroform, methylene chloride, petroleum ether, petroleum benzine, ligroin, Freon, DMSO, DMF, and other solvents that can dissolve polyzirconocarbosilane are used to dissolve it. can be put into practical use.

In yet another embodiment of the method of the invention, in the step of making the first blend of the invention, the ceramic to be mixed with the polyzirconocarbosilane is powdered and the polyzirconocarbosilane is mixed in a vacuum. By using ceramic powder obtained by pulverizing after firing in an atmosphere consisting of at least one selected from inert gas, reducing gas, and hydrocarbon gas, high-density and high-strength ceramics can be produced. A sintered shaped body can be obtained.

The ceramic powder in this case is mainly SiC.

ZrC, solid solution of SiC and ZrC, and Z r C1
−X (o<x<1), and (7) in addition to C2
A small amount of S la N4 (produced when heating in N2) is included.

In addition to applications utilizing heat resistance, the ceramic molded body obtained by the present invention can be used for applications such as B4 C, TiB2 tZ, etc.
r In the case of a B2 molded body, it can be used as a neutron absorbing material.

In addition, (1) Building materials - panels, domes, trailer houses, walls, ceiling materials, floor materials, cooling towers, septic tanks, sewage tanks, water supply tanks, hot water supply piping, drainage pipes, heat pipes for heat conversion, etc. 2) Equipment materials for aircraft and space development - fuselages, wings, helicopter drive shafts, jet engine compressors, rotors, stators, blades, compressor casings, housings, nose cones, rocket nozzles, brake materials, tire cords, etc. (3) ) Marine materials - boats, yachts, fishing boats, work boats, etc. (4) Road transport equipment materials - vehicle front head, side panels, water tanks, toilet units, seats, car bodies, containers,
Road equipment, guardrails, pallets, tanks for tank lorries, bicycles, motorcycles, etc. (5) Corrosion-resistant equipment materials - tanks, tower ducts, staffs, pipes, etc. (6) Electrical materials - surface heating elements, pariscours, igniters , thermocouples, etc. (7) Sports equipment - boats, bows, skis, snowmobiles, water skis, gliders, tennis rackets,
Golf shafts, helmets, bats, racing jackets, etc. (8) Mechanical elements - gaskets, packings, gears, brake materials, wear materials, abrasive materials, etc. (9) Medical equipment materials - prosthetic legs, prosthetic limbs, etc. (10) Audio equipment Materials - Can be used for cantilevers, tone arms, speaker cones, voice coils, etc.

The present invention will be explained below with reference to Examples.

Reference Example 1 2.51 g of anhydrous xylene and 400 g of sodium were placed in a 51-sized three-lough flask, heated to the boiling point of xylene under a nitrogen gas stream, and dimethyldichlorosilane 11 was added dropwise over 1 hour.

After the dropwise addition was completed, the mixture was heated under reflux for 10 hours to form a precipitate.

This precipitate was filtered and washed first with methanol and then with water to obtain 420 g of white powder polydimethylsilane.

On the other hand, 759 g of diphenyldichlorosilane and 12 g of boric acid
4 g in n-butyl ether under nitrogen gas atmosphere, 10
The resulting white resinous material was heated at a temperature of 0 to 120°C and further heated in vacuum at 400°C for 1 hour to obtain 530 g of polyborodiphenylsiloxane.

Next, 8.2'# of the above polyborodiphenylsiloxane was added and mixed to 250 g of the above polydimethylsilane, and the mixture was heated to 350°C under a nitrogen stream in a 21 quartz tube equipped with a reflux tube.
Polycarbosilane, which is one of the starting materials of the present invention, was obtained by heating to 6 hours and polymerizing for 6 hours.

After cooling at room temperature, xylene was added and taken out as a solution. The xylene was evaporated and concentrated under a nitrogen stream at 320°C for 1 hour to obtain 140 g of solid. The number-average molecular weight of this polymer was determined by vapor pressure osmometry (VPO). It was 995 when measured by method).

Reference Example 2 100g of tetramethylsilane was weighed out and heated at 770°C under a nitrogen atmosphere for 2 hours using a recyclable flow system.
The reaction was carried out for 4 hours to obtain polycarbosilane, which is one of the starting materials of the present invention.

After cooling at room temperature, normal hexane was added to take out as a solution, filtered to remove insoluble matter, normal hexane was evaporated, and concentrated under reduced pressure of 5 mmHg at 180°C for 1 hour to obtain a sticky substance of 14.9. I got it.

The number average molecular weight of this polymer was 450 as measured by the VPO method.

Reference Example 3 250g of polydimethylsilane obtained in Reference Example 1 was placed in an autoclave and heated at 470°C in an argon atmosphere.
Polycarbosilane, which is one of the starting materials of the present invention, was obtained by heating and polymerizing for 14 hours under about 100 atmospheres.

After cooling at room temperature, normal hexane was added to take out as a solution, normal hexane was evaporated, and the solid obtained by concentrating at 280 ° C. for 1 hour under reduced pressure of 1 ml Hg was treated with acetone to remove low molecular weight substances. As a result, 60 g of a polymer having a number average molecular weight of 8,750 was obtained.

Example 1 40.09 g of polycarbosilane obtained in Reference Example 1 and 31.5 g of zirconium tetrabutoxide were weighed out, 400 ml of xylene was added to this mixture to form a mixed solution consisting of a homogeneous phase, and the mixture was heated under a nitrogen gas atmosphere. The reflux reaction was carried out at 130° C. with stirring for 1 hour.

After the reflux reaction was completed, the temperature was further raised to 230°C to distill off the xylene solvent, and then polymerization was carried out at 230°C for 1 hour to obtain polyzirconocarbosilane.

The number average molecular weight of this polymer was determined to be 1677 by the vPO method.

This polymer has a weight ratio of 10 and a SiC of 200 mesh or less.
The powder was mixed in 9 portions, dried, then lightly crushed in a mortar and sieved with a 100-mesh sieve.

This mixed powder was pressure-molded at a molding pressure of 1500 kg/cyit to obtain a powder compact of 10 rrtm x 50 mm x 5 mm.

This powder compact was heated and sintered to 1200°C at a heating rate of 200°C/hr in nitrogen gas.

As a result, the bulk density was 2.68.9/ffl, and the bending strength was 1.4
．． 0 kg/mvt (normal temperature), 1 3. 8k
g/v. A SiC sintered body having a temperature of t7t (1200°C) was obtained.

Example 2 40.0 g of polycarbosilane having a number average molecular weight of 2990 obtained by concentrating the polymer obtained in Reference Example 1 at 330° C. for 3 hours under a nitrogen stream and 75.3 g of zirconium tetraisopropoxide were added. The mixture was weighed out, and 500 ml of benzene was added to this mixture to obtain a mixed solution consisting of a homogeneous phase, and a reflux reaction was carried out with stirring at 70° C. for 5 hours under an argon gas atmosphere.

After the reflux reaction was completed, it was further heated and benzene was distilled off, followed by polymerization at 150°C for 2 hours, resulting in a number average molecular weight of 976.
0 polyzirconocarbosilane was obtained.

This polymer 10 weight ratio and 5i3 of less than 200 mesh
N4 powder (90% by weight) was mixed with an appropriate amount of n-hexane, dried, and preheated at 600°C at a heating rate of 100°C/hr in argon and pulverized.

95 parts by weight of this powder and 5 parts by weight of the above-mentioned polyzirconocarbosilane were further mixed together with an appropriate amount of n-hexane, dried, and pulverized.

This mixed powder was pressure-molded at a molding pressure of 2000 kg/i to obtain a powder compact of 10 mm x 50 mm x 5 mm.

This powder compact was heated and sintered to 1400° C. in argon at a heating rate of 100° C./hr.

As a result, the bulk density is 2.75 El /crif, and the bending strength is 12.11y/rra? t (normal temperature), 11.5kg/
A Si3N4 sintered body of 1200° C. was obtained.

Example 3 40 g of polycarbosilane obtained in Reference Example 2 and tetrakis acetylacetonatosilconium 14, L9 were weighed out, and 60 ml of ethanol and 3 xylene were added to the mixture.
001711 was added to form a mixed solution consisting of a homogeneous phase, and a reflux reaction was carried out with stirring at 60° C. for 8 hours under a nitrogen gas atmosphere.

After the reflux reaction was completed, the mixture was further heated to distill out ethanol and xylene, and then polymerized at 180° C. for 3 hours to obtain polyzirconocarbosilane having a number average molecular weight of 1,380.

This polymer 7 weight ratio and α-AA of 200 mesh or less
, 20393 weight ratio and mixed with an appropriate amount of benzene,
After drying, it was crushed.

This mixed powder was pressure-molded at a molding pressure of 3000 kg/d to obtain a powder compact of 10 mrn x 50 mm x 5 mm.

This powder compact was heated and sintered in nitrogen at a heating rate of 200°C/hr to 1000°C.

As a result, the bulk density was 3.15 g/cri, and the bending strength was 6.5.
An Al2O3 sintered body of 1y/ma (room temperature) and 6.0ky/mi (900°C) was obtained.

Example 4 40.0 g of polycarbosilane obtained in Reference Example 3 and 2.6 g of zirconium tetraphenoxide were weighed out, 200 ml of xylene was added to this mixture to form a mixed solution consisting of a homogeneous phase, and the mixture was heated under an argon gas atmosphere. The reflux reaction was carried out at 130°C with stirring for 2 hours.

After the reflux reaction was completed, further heating was performed to distill out xylene, and polymerization was carried out at 300°C for 30 minutes until the number average molecular weight was 1.
9300 polyzirconocarbosilane was obtained.

This polymer has a weight ratio of 15 and a SiC of less than 200 mesh.
Mix the powder with an appropriate amount of tetrahydrofuran for 8 minutes.
After drying, heat at a heating rate of 100°C/hr in argon for 60°C.
It was preheated to 0°C and ground.

This powder was set in a carbon die and hot pressed at 1800°C for 0.5 hour under an argon stream.

As a result, the bulk density is 3. 0 5 9 /ail, bending strength 2 6, 0 kg/mi (room temperature), 2 5.5k
A SiC sintered body of y/mi (1400°C) was obtained.

Claims (1)

[Scope of Claims] 1 Mainly a main chain skeleton represented by the general formula (wherein R represents a hydrogen atom, a lower alkyl group, or a phenyl group) and a number average molecular weight of 200 to 200.
10,000 polycarbosilane and an organic zirconium compound represented by the general formula % (where X in the formula represents an alkoxy group, phenoxy group, or acetylacetoxy group having 1 to 20 carbon atoms). A derived polyzirconocarbosilane having a number average molecular weight of 700 to 100,000, wherein at least a portion of the silicon atoms of the polyzirconocarbosilane are bonded to zirconium atoms via oxygen atoms, and The ratio of the total number of +St CH2+ structural units to the total number of +Z r -0-9- structural units in polyzirconocarbosilane is 2 = 1
A polyzirconocarbosilane within the range of 1 to 200:1 is mixed with a ceramic consisting of at least one selected from oxides, carbides, nitrides, borides, and silicides, and the resulting mixture is molding, and at the same time or after the molding, in a vacuum, inert gas, reducing gas,
A method for producing a ceramic sintered body, which comprises heating and sintering within a temperature range of 800 to 2,300°C in an atmosphere containing at least one kind selected from hydrocarbon gases. 2. A mixture of the polyzirconocarbosilane and the ceramics is heated at 800°C or lower in vacuum in an atmosphere containing at least one selected from inert gas, reducing gas, and hydrocarbon gas. After preheating, molding, and at the same time or after the molding, in vacuum, in an atmosphere consisting of at least one selected from inert gas, reducing gas, and hydrocarbon gas,
The method according to claim 1, characterized in that heating and sintering is carried out within a temperature range of 0°C.