JPS62223068A - Ceramic formed body and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a ceramic molded body and its! Concerning how to send money.

Conventional technology Reinforced silicon is processed into molded bodies by various methods, and the molded bodies have different properties depending on which method is applied. Heat-pressed or isostatically pressed silicon nitride contains compression aids, which are
In other words, temperatures above 1000°C result in premature strength loss because the glass-containing grain interfaces soften, resulting in grain slippage and possible grain boundary corrosion. It is from. Of course, the strength of silicon nitride is extremely high at low and medium temperatures. Sintered silicon nitride has a similar composition to hot-pressed silicon nitride, but partially contains higher amounts of sintering aids. In this case too, the strength is good at medium and low temperatures, but
At high temperatures, the strength of thermally or isostatically pressed silicon nitride also decreases significantly.

Traditional silicon nitride has a low elevation strength due to its characteristic porosity, but it retains this low strength even at extremely high 6°1. This is because the silicon nitride is virtually free of softening impurities. The tensile strength is not sufficiently high in silicon nitride of the type (5 MPa, rarely reaching values greater than 7'ii-, but the good mechanical properties of the fibers are During the sintering or hot-pressing process, the usually microcrystalline fibers deteriorate significantly due to grain growth, reaction with the ceramic matrix, or abrasiveness.Therefore, conventionally manufactured nine-piece silicon nitride fiber bars are The material had very low strength.It is also known to strengthen ceramic materials by introducing them onto monocrystalline fibers.However, until now it has not been possible to incorporate the properties of these fibers, called whiskers, into ceramic materials. I was only able to move it enough.

Whiskers have extremely advantageous properties. This is up to 23% for silicon nitride and silicon carbide whiskers.
It has an extremely high mechanical strength of GPa.

Whiskers also have a high modulus of elasticity and a mostly theoretical density. The whisker's properties allow it to be moved through a hot press or hot isostatic press relatively without damage.

Problems to be Solved by the Invention The object of the invention was to provide a complete process by which ceramic molded bodies having outstanding properties with respect to strength and tensile strength can be produced and which can be carried out easily.

Means for Solving the Problems The problem was solved by converting the silicon V) bed to SiC and/or 814
Mixing with whiskers consisting of N, forming this N compound,
This formed body is overlaid with one or more layers of a mixture of silicon and silica and optionally a sintering aid, followed by a layer of a mixture of silicon and/or silicon nitride and a silicon dioxide-containing material. coated, then nitrided and heated to the outermost vitrified layer, followed by subsequent post-compression at elevated temperatures and isostatic pressure: solved by a method for producing ceramic compacts characterized by: be done.

The ceramic molded body produced according to the present invention has high toughness over the entire usable degree range. The strength of the molded body is greater than that of conventional stress-stimulated silicon. The molded article produced according to the present invention also has excellent creep resistance that has not been previously available. The manufacturing method according to the invention can be implemented simply. It is also advantageous that final processing can be carried out in the raw state.

In order to produce ceramic compacts according to the invention, silicon powder is mixed with whiskers. The heating of the silicon powder and the whiskers is preferably carried out in the range of the P/M mixture.

Therefore, in the formed body, whiskers made of silicon nitride or silicon carbide are included, and the amount of whiskers made of silicon powder is preferably 5 to 50% by volume, more preferably 10 to 50% by volume.
It is 60%.

The whisker is 0.05 to 10 μm, particularly preferably 1 to 5 μm.
It has a diameter of μm.

As the silicon powder, preferably a powder having a particle size that allows reaction sintering is used. More preferably about 1 to 30
Powders with an average particle size of μm are also used. This particle size is obtained, for example, if the silicon powder is prevented from cohesive wear. For example, silicon powder is ground for 2 hours in a grinding mill with n-hexane as the grinding liquid and Y-TZP- or hard metal spherules as the grinding body. Next, add this silicon powder to 1
Mix with whiskers, for example by rolling with a silastic ball in n-hexane. Preferably, the whiskers are dispersed using ultrasound.

The bale moldings of silicon powder and whiskers can be processed by any surface forming method. For example, it can be formed into a desired shape by full injection molding, constant pressure constant press, etc. Optionally, shaping can also be followed by further cutting methods, such as turning, drilling or milling. After this final 2JD process, the main molded body is covered. This is because if a high AT is applied to a ceramic molded body containing whiskers in an oxidizing atmosphere, the whiskers may break.

The formed green body with included whiskers is coated with one or more layers, especially 1 to 3 layers, of a mixture of silicon and silicon nitride, optionally containing sintering aids. Preferably, a mixture of silicon and silicon nitride is prepared in the form of a slip.

The resulting form is then completely immersed in this slip.

If several layers are applied, the mixtures of the individual layers preferably have different compositions, with varying proportions between silica and silicon nitride. Furthermore, it is particularly preferred that the amount of silicon nitride in the layer increases from the inside to the outside, whereas the amount of silicon in the layer decreases in the melt from the inside to the outside.

In a highly preferred embodiment, the green body is first dipped several times into a slip consisting of 70 parts of silicon and 30 parts of silicon nitride. This formed body is then mixed with 50 parts of silicon and 50 parts of silicon nitride.
and then into a slip consisting of 60 parts silicon and 70 parts silicon nitride.

In another preferred embodiment, the green body is immersed in a mixture consisting of silicon and silicon nitride and additionally containing whiskers. The amount of whiskers in the mixture is preferably between 5 and 50%, particularly preferably between 10 and 30%.

Next, the silicon and/or outermost mt consists of silicon nitride and silicon dioxide gold-containing materials and optionally sintering aids.
- Apply and then dry the formed form thus produced.

For such an outermost layer, preferably silicon dioxide 5
~100% by volume, 0 to 95% by volume of silicon nitride and optionally a mixture of forsterite, forsterite, mullite and/or fushinite.

A particularly preferred mixture for the final layer is silicon dioxide 6
0-50 parts, silicon nitride 60-50 parts and silicon 10-5
The entire suspension consisting of 0 parts is used. This layer is also not disadvantageous during the nitriding process, since the temperature is too low for the layer to sinter. High nitrogen permeability can be obtained depending on the amount of silicon nitride.

* f'Jsann1 dried molded body, 1200~14
Nitriding at a temperature in the range of 00°C. The nitriding process can be easily performed. This is because the capacitance change between the silicon raw product and the fully silicon nitride body is minimal, so that the compressive blocking stress is virtually negligible. Since the whiskers are incorporated into the reaction-dependent silicon nitride substrate in a thermally expanded state, the desired original stress is generated at low levels.

Now, after this reaction sintering is completed, the molded body is made of glass t-f.
Vacuum heating is performed once more until the outermost layer with f1 becomes tightly packed. In this case, the temperature is approximately 1500-1700°C.

Then, by supplying nitrogen at high pressure at an even higher temperature,
The collection form is post-compacted. For this, 10-200
A pressure of MPa'tAii is used. In this case, the temperature is preferably 1600-1900°C, especially 1700-1800°C.

Using the method according to the invention, at a temperature of 1300 °C
A ceramic molded body having a strength of over 50 MPat is obtained. The tensile strength values are even in the range above Q Mpai. The molded body produced in this manner has high strength and high toughness. Moreover, the molded body is oxidation resistant and can be easily manufactured into a VC. The layers adhere very well through interlocking with the core, which is attributable to the configuration of the layers and the core.

The method according to the invention can be carried out capacitively. The manufacturing process is simpler than known manufacturing methods such as OVD or PVD processing.

Another object of the invention is a ceramic molded body consisting of a reaction-dependent silicon nitride core in which whiskers of silicon carbide and/or silicon nitride are incorporated. The core is made of silicon nitride and reaction-dependent silicon nitride, optionally of sintered assisted capped silicon and/or of silicon nitride and silicon dioxide containing materials.

The layer applied on the hanging part particularly preferably has 5 to 5 whiskers.
Total content is 0% by volume.

The ceramic molded body according to the invention has high strength and toughness,
It also has extremely good tensile strength. The molded bodies are distinguished by a very high density compared to other molded bodies in the public domain.

In a variant of the process according to the invention, a mixture is prepared from silicon powder and whiskers consisting of silicon carbide and/or silicon nitride. Next, the mixture is molded in a conventional manner and then nitrided.

Preferably, such a molded body is further coated with 0VD- or P.
VD grade @ is applied to protect the opened molded body from deterioration.

The molded body produced in this way has a good mechanical performance.
They are superior in terms of sex.

The invention will now be illustrated by examples.

Example 41 details (~10 Am) 21 volumes 80 copies and 1310
20 parts of whiskers (1-5 μm in diameter) were mixed in a 1-property tool. The dried powder 8 mixture was pressed under an isostatic pressure of 630 MPa to form a cylinder (1 m×[diameter 1−)]. This formed body was then formed from 5i7Q and 430 parts Si3N into a slip prepared in the same layer, with the addition of A, 0.10% by volume and 10% by volume of Y2O3 as sintering aids. 31il! l Soaked. Next, the dipping process was repeated using a slip consisting of 6150 parts and 81□N450 parts. Further 8130 copies and 813
The dipping process was warped using a slip consisting of 70 parts of N. Finally, the molded body was mixed with 240 parts of E110 and E313.
It was immersed in a paste consisting of 440 parts and 8120 parts of N. Except for the most P layer containing 5102, 81C Whis force 5 volume i&% was added to the three layers existing under 1\fI4:. Next, the molded body was heated to an image normal pressure (0, I
MPa) for 5 hours.

After drying, til! ? The 'J composite was nitrided in a sintering apparatus - H1ppθ at the above temperature and then vacuum heated to 1650° C. within 60 minutes until the outermost layer containing glass no longer had open pores.

Subsequently, a pressure of 150 MPa of Nzffi was introduced without significant temperature drop and the temperature was increased to 1850° at. The resulting layers were each 50-100 μm thick.

Claims (1)

[Scope of Claims] 1. Consisting of a core of reaction-dependent silicon nitride within which whiskers made of silicon carbide and/or silicon nitride are included, the concentric portions consisting of reaction-dependent silicon nitride and silicon nitride, and A glass of a mixture comprising one or more layers of a mixture optionally also containing a sintering aid and further comprising reaction-dependent silicon nitride and/or silicon nitride and silicon dioxide and optionally a sintering aid as the outermost layer. A ceramic molded body characterized by having a textured layer. 2. The molded article according to claim 1, wherein the core and optionally the outer layer contain 5 to 50% by volume of whiskers. 3. Mixing silicon powder with whiskers consisting of silicon nitride and/or silicon carbide, shaping this mixture and applying one or more layers of a mixture consisting of silicon and silicon nitride and optionally sintering aids on the resulting shape. followed by a layer of a mixture of silicon and/or silicon nitride and silicon dioxide-containing materials, then nitrided and heated to the vitrification temperature of the outermost layer, followed by thermal isostatic pressure at a further elevated temperature. A method for producing a ceramic molded body, which comprises post-compressing the ceramic molded body. 4. The method according to claim 3, which uses silicon powder which has been prevented from cohesive wear in advance. 5. The method according to claim 3 or 4, wherein the whiskers are dispersed by ultrasonic waves. 6. A method according to claim 3, wherein the mixture is shaped by injection molding or isostatic cold pressing and optionally followed by turning, drilling or milling. 7. Post compression at a pressure of 10~200MPa and a temperature of 160MPa.
7. The process according to claim 3, wherein the process is carried out at a temperature of 0 to 1900<0>C, preferably 1700 to 1800<0>C. 8. The method according to any one of claims 3 to 7, wherein the mixture for coating the formed body comprises: 10-90% by volume of Si_3N_4 and 90-10% by volume of silicon. 9. As the outermost layer, SiO_25-100%, Si_3
9. The method as claimed in claim 3, wherein a mixture of 40 to 95% N and optionally kinezoite, forsterite, mullite and/or fushinite is applied. 10. The method according to claim 1, wherein the formed body is coated in such a way that the individual layers have a thickness of 10 to 200 μm. 11. A method according to claim 3, in which silicon powder is mixed with whiskers of silicon nitride and/or silicon carbide, the mixture is shaped, and the formed body is then nitrided. 12. The method according to claim 11, wherein the nitrided compact is coated with a PVD or CVD coating.