JPS63129067A - Ceramic material 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 the Invention This invention relates to improved ceramic materials, and more particularly to improved engineering ceramic materials and methods of making the same.

Engineering ceramics are silicon, aluminum,
Materials such as oxides, nitrides and carbides of metals such as boron and zirconium.

These materials are characterized by high strength and hardness, which properties can theoretically be maintained at extremely high temperatures (>7000° C.). Two types of ceramic materials of this type are considered to be the most promising: the sialon family + and the zirconia family.

Sialon ceramics are silicon and aluminum.

Those whose basic elements are oxygen and nitrogen, hence the acronym (
acronym). Particularly useful commercially available sialons have a 71-si,N4 crystal structure;
It is β'-sialon in which some of its silicon atoms are replaced by aluminum atoms and some of its nitrogen atoms are replaced by oxygen atoms to balance the valence. These ciarons are usually S+5N4. At2
03, AtN is mixed with a metal oxide (Y2O3 is often used) and the resulting powder is compressed into the desired shape (
Then, heat the obtained material to 1710℃.
by firing to a temperature of up to 2.3 hours.

The action of this metal oxide is to react with the alumina and silica layers (which are always present on the surface of each silicon nitride particle) to form a liquid phase, which dissolves the reactants. It also acts to precipitate the product. When this liquid phase (still containing dissolved nitrides) is cooled, glass forms between the μ'-sialon grains. For example, nftβ'-sialon densified with Y2O3 is approximately /j volume 1% (DY -Si -At-0-N
glass and approximately rs capacity of β'-sialon.

At temperatures above roo℃, this glass begins to soften,
Strength decreases. The glass/sialon can be crystallized by heat treatment at temperatures up to 1300'C. In the case of β'-sialon and glass, the glass crystallizes to give Y5At50,2 (termed itrogarnet or YAG) and a small amount of additional β'-sialon. In the case of glass/0'-sialon,
This crystallization results in the formation of Y2Si207 (yttrium disilicate) and a small amount of additional O'-sialon. This crystallization process destroys the room temperature strength of the material, but this reduced strength is retained up to higher temperatures. The reason why the strength decreases with crystallization is not completely clear, but it is probably because the crystalline YAG is replaced by the crystalline YAG and occupies a smaller volume than the original glass, i.e. due to crystallization. The waxy grain boundary phase is a necessary evil in these materials, thought to be due to the fact that smaller cracks (fluxes) remain, which are the residues of such densification processes (
Remnant).

Another useful ceramic system is tetragonal zirconia Zr
It is based on 02. Tetragonal zirconia is typically dispersed in a matrix of mullite, alumina or cubic zirconia.

Tetragonal zirconia is toughened by a method known as transfer toughening. Essentially, the composite is fired at high temperatures (at least 1100° C.) to densify the ceramic material and the zirconia exists in its high temperature tetragonal form. Upon cooling, tetragonal zirconia attempts (but fails) to transform into its low-temperature monocrystalline form. That is,
The matrix of zirconia is constrained to a tetragonal form which is metastable at 1r:U temperature. This transition is 3 ~! of the volume of each zirconia crystal! Accompanied by an increase in capacity of about 1. This has the effect of imparting compressive stress throughout the matrix, similar to that of unstressed concrete. Any cracks that form in such ceramics tend to trigger a tetragonal to monoclinic transition, which creates compressive stresses that tend to close the cracks. . This method becomes more efficient if the matrix is highly rigid. This is because a highly rigid matrix can better constrain the metastable tetragonal tz structure at room temperature. This method becomes less effective at high temperatures;
Above this, toughening will not be achieved at all. This is because at high temperatures, tetragonal zirconia is not metastable but stable.

Siaron toughened with zirconia is not only rigid (hard and strong, but also very strong), and is initially extremely strong, so it is desirable to toughen Siaron with zirconia. However, at the same time, zirconia chemically reacts with β'-sialon to partially form zirconium oxynitride (zircon).
It has already been recognized by those skilled in the art that the reduction to oxynitri-des) is also possible.

The present inventors have now surprisingly discovered the fact that 0'-sialon does not react with zirconia and instead forms a stable complex with zirconia.

The present invention has been achieved based on this knowledge.

Accordingly, the present invention provides a ceramic material containing a composite of zirconia and O'-sialon or silicon oxynitride.

The ceramic material of the present invention has s based on the total volume of the composition.
-, yz capacity - may be contained.

The ceramic material according to the invention may consist of a dispersion of zirconia in a sialon matrix, such dispersion having an amount of zirconia based on the total volume of the composition.
~30 capacitances, preferably lj - coj capacitances.

The ceramic material of the present invention contains zirconia, yttoria, ceria, lanthanum oxide in the O′-sialon matrix.
It may contain solid solutions with calcium oxide, magnesium oxide or rare earth metal oxides.

The present invention further provides zircon, silicon nitride and optionally alumina or a precursor of alumina, optionally with a reaction sintering aid.
ng aid ) or its precursor/! OO
T:,~/7! There is provided a method for producing a ceramic material as defined above, which comprises reactive sintering at a temperature in the range of rO<0>C.

The main function of the metal oxide sintering aid is to form a solid solution with zirconia. For example, the sintering aid first reacts with the alumina and with the silica surface layer on the silicon nitride to form a transient liquid phase that dissolves the silicon nitride and zircon and removes the zirconia from the solution. and 0'-sialon.

The sintering aid used in the method can be, for example, itria, ceria, lanthanum oxide, calcium oxide, magnesium oxide or rare earth metal oxides or precursors of any of these compounds. For example, the inventors have recognized that the alumina and sintering aid used in the method of the present invention can be provided by the use of spinel.

Preferred spinels for use in the process of the invention are magnesium, calcium or nororium nosbinel, with the use of compounds of 2MgAt204 being particularly preferred.

The spinel is incorporated into the mixture to be sintered in an amount sufficient to provide the desired amount of aluminum in the final O'-sialon matrix. Therefore, it is preferred that Subinel be used in an amount of up to 70% by weight based on the weight of zircon and silicon nitride, preferably in an amount of 6 to 10% by weight.

Other precursors of the various components incorporated into the reaction-sintered mixture according to the method of the invention described above can also be used, thus e.g. from a dispersion of zirconia in an α-sialon matrix. The ceramic material of the present invention can be produced by reactive sintering of a mixture of zircon, silicon nitride, metal silicate and alumina.

The metal silicates can be, for example, calcium, magnesium or barium silicates. It has been found that when metal silicates are heated to sintering temperatures, they react with some zircon and silicon nitride to form a liquid phase, which promotes the reaction and densification through a dissolution-precipitation mechanism. Will.

Oxides which can be used as sintering aids can also be provided with precursor substances, such as carbonates or bicarbonates, which decompose under the sintering conditions into oxides. For example, calcium oxide and magnesium oxide as sintering aids can be provided by calcium carbonate and magnesium carbonate, respectively.

The present inventors further discovered that instead of using zircon (ZrS+04) in the method of the present invention as described above, zirconia l
Friend acknowledged that a mixture of Zr0□) and silica (5iO7) could be used. This modification method is Z in the case of zircon.
While the ratio of r02 to 5iOz is fixed, the ratio of zirconia to silica is 54? : It has the advantage of being able to be changed as required. This is particularly advantageous in certain cases.

Therefore, the present invention further provides that a mixture containing zirconia, silica, silicon nitride and optionally alumina or its precursor is heated at 1 soo C., optionally in the presence of a sintering reaction aid or its precursor. Zirconia and 0'- which are characterized by being reacted and sintered at a temperature of ~/7jO℃
A method of manufacturing a ceramic material comprising a composite of sialon or silicon oxynitride is provided.

The reactive sintering aids or precursors thereof used in the above variant process according to the invention are as described above. Additionally, the alumina and sintering aids used in this method can be provided in compound form, such as through the use of spinels such as those described above.

Example Next, the present invention will be further explained by examples.

Example 1 The following composition was milled in an isopropyl solution for 12 hours using 3fi zirconia mixed media.

The slurry was dried on an IJQ pan and the resulting powder was formed into a billet using an isostatic press (rubber press) at 20,000 psi.

The silicon nitride to zircon to alumina ratio was kept constant while the yttria content was varied from 1 to 20% by weight.

Composition A Zircon j 6.0 y Silicon nitride j i'j f Alumina Hiroshi, 72゛Itria o,ry Composition B Zircon! ! ,Ko? Silicon nitride 3g, 3? Hiroshi Alumina, 62 Itztoria /,! f (weight 1% based on ZrO□) Composition C Zircon j j, Co2 Silicon nitride j fOy Alumina Hiroshi, 62 Ittria 2. -1 (6 weight it% based on ZrO2) Composition D Zircon Yohiro, +r? Silicon nitride J 7,7 g Alumina Hiroshi, 62 Ittria 3.0f (Ite f weight II 1% based on Zr02) Composition E Zircon J Hiroshi, Hiroshi silicon nitride 37. Hiro? Alumina Hiroshi, jt Ittria 3.7F (10 weight tqb based on ZrO2) Composition F Zircon! Co, j f Silicon nitride j A, / f Alumina Hiroshi, Part 2 Ittoria 7. Of < λ0il-1196 based on ZrO2K) each of the above compositions was
The mixture was baked at /700°C for j hours in a t furnace.

From the X-ray diffraction pattern of the fired and ground ceramics, it was found that in the case of no addition of indium, the zirconia was in the monoclinic form containing a trace amount of nitrogen-stabilized cubic zirconia. The content of tetragonal zirconia increases with the ytria content, reaching more than j% in the case of composition E. The X-ray diffraction pattern for Composition E is shown in FIG. This °
The X-ray diffraction pattern of f17'tH was obtained by irradiating steel with α-X rays.
It is something.

The porosity and density are shown in FIG. If the amount of IJA added is small, an insufficient temporary liquid phase is formed to provide complete densification. When the addition amount of yttrium is moderate, the ceramic is partially densified. When the addition amount of IJ is large, the ceramic is densified by more than 25%. In this case, most of the zirconia is stabilized as tetragonal zirconia.

Examples - Zircon (jj, 4'f>, silicon nitride (J ir, i
r) and magnesium spinel, MgAt204
, 16.44? ) and 20,
Formed into a billet using an isostatic press at 000 psi. Then, these billets were made into 7100
Next, bake for 3 hours at a temperature of ℃. The thermally calcined product is zirconia dispersed in an O'-sialon matrix. An electron micrograph of this product is shown at a magnification of so
o.

It showed a glass grain boundary phase at 100% magnification.

Example 3 Zirconia (J 6.j f ), silica (/ 7j
f).

Silicon nitride (37, reference), alumina (Hiroshi, JF) and itria (7,7f > f) are thoroughly mixed together and 2
It was formed into a billet using an isostatic press at 0.000 ps+. Next, this billet f1750℃3
Baked for an hour. The product Fio' thus obtained is zirconia dispersed in a sialon matrix, with a density FiJ, j t f7<-.

Examples Zircon (4LD, Of), Silica (2,0f),
Silicon nitride (Hiro6.Of), alumina (!, jf)
and Ittria (2,2f) are thoroughly mixed and 2
Formed into a billet using isostatic press at 0,000 pSi. Next, this billet)? /3 at 700℃
Baked for an hour. The product is sufficiently dense, lj volume ik
It has a composition of zirconia of 1 and O'-sialon of tj capacity.

Example! Zirconia (76,7f), silica (17,rit)
l silicon nitride C ≠ 1 Jt) and ittria (J, 7 y
) were thoroughly mixed together and heated to 20,000 psi.
It is then formed into a billet using an isostatic press.

This billet was then calcined at 7700° C. for 5 hours, and the product was zirconia dispersed in silicon oxynitride matrix, with a density of ij J, J 6 f/d.
(Met.

Example 6 Zirconia (37, rit), silica (/1.j f
+.

Silicon nitride (3R, Rit) and alumina (Hiroshi, 72) were thoroughly mixed and formed into a solid shape using an isostatic press at 20,000 psi. Next, this billet was fired at 47,700℃ for 5 hours. The product is 3. Hiro 7
It has a density of t/dl.

FIG. 3 is an X-ray diffraction pattern of a composition obtained using steel f and a ray irradiation. This X-ray diffraction diagram shows that everything is composed of monoclinic zirconia, except for a very small peak 'frJO° corresponding to a trace amount of zirconium oxynitride. (Zr02 stabilized f' in Ittria
(Tetragonal Zr02) also exhibits a tlHc peak similar to that of a friend, so yttria is excluded from this composition. ) Figure 3 is an electron micrograph of this composition at a magnification of $1,000. The white phase is zirconia and the black phase is LfiO'-sialon. The original label shown on this photo represents 70 μm (micrometer).

Zircon (26,7f l, silicon nitride (6/, J f
) and aluminum nitride (/2.Of) are thoroughly mixed and formed into a billet by isostatic pressing at λ0,000 p5i. This billet was then fired at -f/700°C for a long time. This product t'
i/' - zirconia dispersed in sialon;
3. It has a density of ≠6f/-. Although this composition was very well densified without the addition of itria, the resulting product contained a large amount of zirconium oxynitride. This can be clearly seen from FIG. 5, which is an X-ray diffraction pattern of the composition obtained by irradiating copper with α-rays. The peak at J 00 is due to zirconium oxynitride.

Zirconia 2! el1. This composition is stabilized by nitrogen.

[Brief explanation of the drawing]

Figure 1 shows the X@ diffraction diagram of the sintered and crushed ceramic material of composition E in Example 2, and Figure 2 shows the relationship between the amount of IJA added and the porosity and density of the resulting ceramic material. The graph shown in Figure 3 is an XIM diffraction diagram of the ceramic material obtained in Example 6, Figure ψ is an electron micrograph of this material,
No.! The cause is the X-ray diffraction pattern of the ceramic material according to the prior art obtained in Comparative Example 7. /Ng! . Ittria content (Gravity % based on Zr02 content n) i21
Surface cleaning C: (no change in content) Fig. 4 Procedural procedure rn official book (method) 1, Indication of Ii 1985 Special J Application No. 130031, Title of invention Ceramic materials and their manufacturing method 3, Ministry to make amendments F1 Which relationship Patent applicant's office Location: E.C.2.Buy, London, United Kingdom. 7.A.D., 14 Gresham Street Name
Kutukuson Group LLC 6, Brief description of drawings in the specification subject to amendment and Drawing 7, Contents of amendment (1) Specification, page 20, lines 8 to 9, 1, Figure 4 is・
. . . Photographic diagram," is replaced by "Figure 4 is the same (100 magnification of the structure of the ceramic material obtained in Example 6).
"Electron micrograph at 0x magnification." (2) Correct Figure 4 as shown in the attached sheet. In addition, the l11iff stating the applicant's representative name and the inside certifying the substitute pH right are dated July 22, 1986.
Attached to the procedural amendment (method) submitted on the date (!J L'U
I have already received the information.

Claims (14)

[Claims] 1. A ceramic material comprising a composite of zirconia and O'-sialon or silicon oxynitride. 2. Ceramic material according to claim 1, containing from 5 to 95% by volume of zirconia, based on the total volume of the composition. 3. A ceramic material according to claim 1 or 2, comprising a dispersion of zirconia in an α-sialon matrix. 4. Ceramic material according to claim 3, containing from 5 to 30% by volume of zirconia, based on the total volume of the composition, preferably from 15 to 25% by volume. 5. Ceramic according to any one of claims 1 to 4, wherein the composite contains therein a solid solution of zirconia and yttria, ceria, lanthanum oxide, calcium oxide, magnesium oxide or rare earth metal oxide. material. 6. reacting zircon, silicon nitride and optionally alumina or its precursor at a temperature of 1500°C to 1750°C in the presence or absence of a sintering reaction aid or its precursor;
A method for producing a ceramic material comprising a composite of zirconia and O'-sialon or silicon oxynitride, characterized in that it is sintered. 7. A mixture containing zirconia, silica, silicon nitride and optionally alumina or its precursor is heated at 1500°C in the presence or absence of a sintering reaction aid or its precursor.
A method for producing a ceramic material comprising a composite of zirconia and O'-sialon or silicon oxynitride, characterized in that it is reacted and sintered at a temperature of ~1750C. 8. 8. The manufacturing method according to claim 6 or 7, wherein the sintering aid is yttria, ceria, lanthanum oxide, calcium oxide, magnesium oxide, or a rare earth metal oxide. 9. 2. A method as claimed in claim 1, wherein the alumina and sintering aid used in the reaction are provided by the use of a compound such as spinel. 10. 10. The manufacturing method according to claim 9, wherein the spinel is a magnesium, calcium or barium spinel. 11. 11. The manufacturing method according to any one of claims 6 to 10, wherein the precursor used as a sintering reaction aid is a precursor of calcium oxide, magnesium oxide, or a rare earth metal oxide. 12. 12. Process according to any of claims 9 to 11, characterized in that spinel is included in the mixture to be sintered in an amount of up to 10% by weight, based on the weight of silicon nitride. 13. A method for producing a ceramic material comprising a composite of zirconia and α-sialon or silicon oxynitride, characterized in that a mixture of zircon, silicon nitride, alumina and a metal silicate is reacted and sintered. 14. 14. The method according to claim 13, wherein the metal silicate is a calcium, magnesium or barium silicate.