JPS58185484A - Manufacture of ceramic matter and product - 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 The present invention relates to a method of forming ceramic materials and articles, and to ceramic materials and articles formed by the method. This invention relates to materials broadly referred to as substituted silicon nitrides that have special properties, high strength and hardness, and are useful for making tool tips, gas turbine components and seals by sintering operations.

A typical example of substituted silicon nitride is silicon nitride (811□
It has a β-phase lattice structure of N16), which is expanded by replacing some of the silicon atoms with aluminum atoms and replacing some of the nitrogen atoms with oxygen atoms. However, it can be seen that the β-phase silicon nitride lattice may have substituent elements other than aluminum and oxygen at its atomic positions while maintaining valence balance.

Another example of substituted silicon nitride has an alpha-phase silicon nitride lattice,
This is developed by replacing some of the silicon atoms with aluminum atoms and introducing modifying cations such as yttrium, calcium and lithium in the interstitials 11 to achieve valence balance. This valence balance is usually achieved through the use of oxides of these modifying cations, with the result that oxygen will eventually be introduced at some of the nitrogen positions in the lattice. should be interpreted in this way.

S, Hampshire; H-K, Park;
D. P. Thompson and H. Jack
Author: rX'-8ialon GeramicsJ
(Nature.

vol 274 @ No, 5674 + 880~88
24-G, 8B31, 1978), the radiograph in Figure 5 shows that α' reacts with An,03 to give β', and this is illustrated by the formula: alpM 1 y z=2.84 However, as pointed out in the previous British patent M1578434, the strength of β'-sialon begins to decrease when the binary value becomes larger than the order of 1.5, and the above-mentioned Nature
As shown in the magazine article, α′-sialon has a high Z value with a second phase containing ythtrium! - When converted to sialon, such products do not function well as engineering ceramics.

The powder contains a high proportion of α-phase substituted silicon nitride, less than 10% by weight of alumina (33% by weight in Nature) and/or at least one silicon nitride (as defined below). ), a β'-phase substituted silicon nitride having a binary value of 1.5 or less is produced with a controlled amount of other crystalline phases and a controlled amount of a glass phase, and The strength of the product is acceptable for engineering ceramics, and the product can withstand high temperatures (approximately 1200C).
The present inventor found that the properties are well maintained at .

The inventors have also found that increasing the alumina content below 10% by weight in the starting mixture leads to a reduction in β-substituted silicon nitride phases with a binary value of less than 1.5, with a controlled amount of glass. The α-substituted silicon nitride phase in the sintered product gradually increases, which results in not only good strength at room and high temperatures, but also hardness, which is higher than that of the product without α-phase substituted silicon nitride with the same minimum glass content. I found that it can be improved. However, when the alumina content is progressively reduced, the β-phase substituted silicon nitride has a very low binary value (<0.7
5) It has been found that it becomes increasingly difficult to form products with If the addition of alumina to a powder containing a high proportion of α-phase substituted silicon nitride is supplemented or partially or completely replaced by the addition of silicon nitride, the binary value of β-phase substituted silicon nitride is 0.75. It has been found that it can be lowered to less than Therefore, by adding silicon nitride or alumina in an amount not exceeding 10% by weight (or by adding both silicon nitride and alumina, the amount of alumina is determined by adding powder containing a high proportion of α-phase substituted silicon nitride). Ceramic products consisting of binary β-phase substituted silicon nitride up to 5.1.5 can be made with controlled amounts of other crystalline and glassy phases (not exceeding 00% by weight). It will be appreciated that the crystalline phase may include alpha phase substituted silicon nitride. Although silicon nitride and/or alumina are mentioned above as additives to α-phase substituted silicon nitride, other additives that provide the necessary elements, such as silicon, nitrogen, aluminum, and oxygen, such as silicon oxynitride and/or silicon, can also be used. The so-called polytype, which is silicon aluminum oxynitride having a crystal lattice structure of aluminum nitride, in which valence balance is maintained by partially replacing aluminum atoms and oxygen atoms partially replacing nitrogen atoms, is a suitable addition. It can be a thing. In this specification, the term silicon nitride should be understood in this way.

A first object of the invention is a method for making high-density ceramic products, with the formula % (%) (where X is not greater than 2 and M is a modifying cation such as yttrium, calcium, lithium, magnesium, cerium ) of mixing a ceramic powder containing a high proportion of α-phase substituted silicon nitride with at least one silicon nitride and/or alumina, provided that the alumina exceeds 10% by weight of the mixture. Must not be;
and this mixture is sintered at a temperature of 1700 to 1900 C in a non-oxidizing atmosphere to obtain (1) formula 8% (where 2 is greater than zero and not greater than 1.5).

) with a β-phase substituted silicon nitride and a small amount of another phase containing a modifying cationic element as described above, or (2) a β-phase substituted silicon nitride as described above, in a controlled amount (e.g. 0. 05% by weight to 90% weight
i:t> formula % formula %) α-phase substituted silicon nitride according to K and a small amount (for example, 0.05 weight % to 20
% by weight) of another phase.

The required sintering time depends on the sintering temperature and is at least 10 minutes for a sintering temperature of 1900C, with longer times required at lower temperatures in the aforementioned range.

Due to the excellent properties of substituted silicon nitride, both the final and intermediate products are extremely difficult to process;
Much research has been devoted to developing methods for producing the final product that minimize processing of materials.

In an effort to devise economical manufacturing routes, much research has been devoted to ways to simplify the operation and signing of meters, such as avoiding the use of high pressures, reducing time, temperature, and also avoiding other costly steps. It's here.

In order to make the above-mentioned high-density ceramic product (2), it is preferred that the amount of kl 293 in the mixture to be sintered is not more than 7.5% by weight.

In making substituted silicon nitride products, we make intermediate materials,
It is advantageous to comminute into a powder and then react this intermediate material powder with other powdered components to obtain the final product.

Such a method is described in British Patent A1573199, in which a mixture of aluminum, silicon and alumina is heated under a nitriding atmosphere and subjected to a controlled heating schedule to substantially suppress exotherm. This is followed by crushing and grinding this material and keeping it! ! It is sintered in the environment to create an intermediate product. This is a ceramic material containing 5 silicon aluminum oxynitride according to a different chemical formula than the desired chemical formula of the final product.

This material is polytypic. Following sintering, the intermediate ceramic material is crushed and ground into a powder. This powder is mixed with silicon nitride powder containing silicon as an impurity and a temporary binder. - or several glass-forming oxides such as oxides of magnesium, manganese, iron, boron, lithium, yttrium and other rare earth oxides may be added to the mixture. This mixture is cold pressed to form a preform, which is then spray coated with a wire retention mixture consisting of boron nitride and silicon in ketone as a carrier liquid. This preform is then open sintered by heating at a temperature of 1200 to 2000C. Make the final ceramic products. It has a crystal structure based on β-silicon nitride, but with increased unit cell size, and has the general formula % (where 2 is greater than zero and not greater than 5).
at least 90% by weight of a single-phase silicon aluminum oxynitride according to the invention. This type of method has numerous advantages. First, it is possible to avoid using aluminum nitride as the base material. Aluminum nitride is highly hygroscopic and therefore difficult to store and handle, and requires application under anhydrous conditions. Second, an open sintering method is used to create the final shape of the ceramic product.

However, this method requires the use of costly show crushers during the production of the intermediate ceramic material and on the intermediate material before it is used to produce the final product.

Conventional milling with d-phase substituted silicon nitride is intended to produce dense and hard products, and the powder obtained by comminution of such products is used according to the first subject of the present invention. Although it is possible to use it as one of the starting materials in a process, it is unattractive to do so as a manufacturing process. It is possible to make prior art α-phase substituted silicon nitrides and avoid all steps in the process that aid in densification, and such an approach facilitates comminution and is the first subject of the present invention. Although it allows the method to be carried out more easily, it still requires a costly comminution stage such as a show crusher.

It must also be noted that the comminution process, apart from increasing manufacturing costs, introduces impurities into the reactants, which adversely affects the reproducibility of the final product.

A second object of the present invention is to provide a method for producing the above-mentioned ceramic powder containing a high proportion of α-phase silicon nitride, which does not require a costly crushing step such as a show crusher. It is.

A second object of the invention is a method for producing ceramic materials, in which powder mixtures of silicon, aluminum, alumina and oxides or nitrides of modifying cationic elements (for example yttrium, calcium, lithium, magnesium, cerium) are used. Performing a first stage nitriding by heating the first stage nitriding mixture to a temperature below the melting point of aluminum in a nitriding atmosphere until the first stage nitriding is substantially complete; maintaining the first stage nitriding mixture in a nitriding atmosphere; the second stage of nitriding is carried out at a temperature below the melting point of silicon until the second stage of nitriding is substantially complete, thereby producing a brittle material; comminution of the material; and subsequent sintering of the comminuted friable material at a temperature between 1500C and 1900C while maintaining a non-oxidizing atmosphere to obtain the formula % (where I is from 2). A brittle ceramic material containing more than 50% by weight of α-phase substituted silicon nitride according to the formula 8 (where M is a cationic element for modification) or the above-mentioned α-phase substituted silicon nitride and formula 8% (where M is a cationic element for modification). 2 is greater than zero and not greater than 1.5) 50% by weight of the mixture with β-phase substituted silicon nitride according to K
A method for producing a ceramic material consisting of steps to obtain a more easily friable ceramic.

The relative proportion of α-phase substituted silicon nitride to β-phase substituted silicon nitride depends on the temperature of the sintering step, ranging from 1500C to 19
The higher the temperature in the 00C range, the greater the proportion of alpha phase material will be for a given treatment time.

The powder mixture used in the method described above may contain silicon nitride and/or aluminum nitride.

Preferably, the brittle ceramic material comprising a mixture of alpha and beta phases of substituted silicon nitride has more than 50% by weight alpha
This is preferably done by carrying out the final sintering step at a temperature between about 1700tll' and 1900C.

The proportions of the components of the powder mixture used will, of course, depend on the type of friable ceramic product required. Most preferably, the proportions of the components of the powder mixture are selected such that the resulting friable ceramic material consists essentially entirely of alpha phase material or substantially entirely a mixture of alpha and beta phase material. Ru.

When calcium is used as the modifying element, the alpha phase ceramic material may have the formula % formula % or the formula Ca08S192Aj2 gol 2N148.

When the modifying cationic element is lithium, the alpha-phase ceramic material typically has the formula %. When the modifying cationic element is yttrium, the alpha-phase ceramic material typically has the formula 92”28011N14e.

That is, the proportions of the components are preferably substantially balanced according to a suitable formula.

The friable ceramic material formed by the method according to the second subject of the invention is a dense ceramic product consisting essentially of the aforementioned β-phase material and a small proportion of other phases comprising the aforementioned modifying cationic elements; or a dense mass consisting essentially of the aforementioned β-phase material, a controlled amount (e.g. 0.05% to 90% by weight) of the alpha-phase material, and a small proportion of other phases containing the aforementioned modifying cationic elements. Suitable as an intermediate for the formation of ceramic products.

A third object of the invention is therefore a method for making a ceramic article, in which the brittle ceramic material in powder form produced by the method according to the second object of the invention contains at least one silicon nitride and/or mixing with alumina,
However, the alumina should not exceed 10% by weight of the mixture;
The mixture was heated in a non-oxidizing atmosphere for 1700 t:' to 190 t.
Sintering at a temperature of 01:' (1) General formula % formula % (where 2 is greater than zero and greater than 1,5...).

) with a β-phase substituted silicon nitride and small amounts of other phases containing the aforementioned modifying cationic element M; or (2) a β-phase substituted silicon nitride as described above, a controlled amount of ( For example, α-phase substituted silicon nitride according to the above formula (% formula %) of o, osmi-% to 90 wt qb) and a small amount containing the above-mentioned modifying cationic element M (for example, 0.05 wt qb to 20 wt qb)
% by weight) of other phases.

The required sintering time depends on the sintering time and is at least 10 minutes at 1900C, with longer times required if lower temperatures within the ranges mentioned above are employed.

Conveniently, the ceramic powder is 5-96.5% by weight of the mixture containing the ceramic powder.

Conveniently, the ceramic powder is present in an amount of less than 30% by weight of the mixture comprising the ceramic powder and contains yttrium oxide, calcium oxide, lithium oxide, cerium oxide, rare earth oxides and oxides of lanthanide series elements, At least one glass-forming metal oxide selected from magnesium oxide, manganese oxide and iron oxide is included in the mixture containing the ceramic powder described above.

Most conveniently, the at least one glass-forming metal oxide as described above is part of the mixture comprising the ceramic powder as described above.
Contained in an amount less than 0% by weight.

Preferably, silicon nitride is present in an amount up to 75% by weight of the mixture comprising the ceramic powder described above, more preferably from 5 to 7%.
Represents an amount of 5% by weight.

Conveniently, the product after cooling is reheated, preferably at a temperature not exceeding 1400C, in order to devitrify the glass phase. ' In Example 1 according to the first object of the present invention, silicon nitride powder (containing about 90% α phase) having an average particle size of 2 microns and containing 5% by weight of silicon as an impurity (
Aluminum nitride powder (5tark: Yttrium oxide (Rare E) with a particle size of approximately 1 micron and
7.
The mixture comprising 7 parts by weight was ball milled for 24 hours using alumina balls. This resulted in an increase in alumina of 2% by weight in addition to the alumina contained in the aluminum nitride powder. The mixed powder was then placed in the furnace in loose form and the temperature of the furnace was slowly increased to 1820 tl:' in the presence of a nitriding atmosphere and held for 5 hours.

The cooled product contains a high proportion (98%) and a small proportion (2%) of α-phase substituted silicon nitride in which yttrium is the modifying cation.
estimated to be on the order of . ) Formula 8 Formula % (2 is a value on the order of 0.3).

The sintered product was a hard sintered cake and it was necessary to use a show crusher to turn it into an intermediate powder that could be subjected to the next process. 90 parts by weight of the intermediate powder crushed in a jaw cracker was then mixed with 10 parts by weight of the silicon nitride used earlier and ball milled again using alumina balls until the alumina increase was 8.45 parts by weight. Ta. The resulting powder was then isotropically pressed at 20,000 psi (140 MN) and sintered in a furnace containing a nitriding atmosphere. The temperature of the furnace was raised to 1750 t:' and heated for 5 hours. Retained.

The crystalline phases detected in the product are β-phase substituted silicon nitride, which accounts for 96% of the total, about 3% of the polytype crystalline phase called 12H, and B-phase (Y2SiA
jO, N). ! The binary value of the mutualistic component is on the order of 1.5, and the fracture nomodulus of the three-point barb is 90.
00 (lpai (62ONM4 )
A method of the first subject of the invention for making products containing silicon oxide has been identified. However, all the following experiments were carried out using an intermediate powder made in accordance with the second object of the invention, ie a friable powder that does not require costly comminution.

In a second experiment, which is a control example for the second object of the present invention, 29.5% of silicon powder (supplied by Kema Nord, Sueten) with a particle size smaller than 20 microns, 29.5% aluminum powder ( Johnso
10.6% by weight of silicon nitride with an average particle size of 2 microns (contains about 90% by weight of alpha phase and 5% by weight of silicon as impurities) Contains: 5i3N4
(K2) supplied by L+ucaa 5yalon Co., Ltd.) 49wt%, alumina powder with an average particle size of 1 micron (The Aluminium of the United States)
Yttrium oxide powder (supplied as ALCIOA XA15 by Rare Earth Produ.
A mixture consisting of 9.5% by weight (supplied by CTS) was homogeneously mixed in a Nautami mixer. The i placement was adjusted so that the atomic ratio of the elements followed the formula %.

Yttrium oxide was present to provide the modifying cation. The mixture was placed in a nitriding furnace and the temperature was increased to 6°C at a rate of about 10-15C per minute under a nitriding atmosphere of nitrogen and hydrogen.
The antithermal reaction started at this temperature, which was increased to 40C, and the mixture was nitrided at 640C for 20 hours. The exothermic reaction was monitored by monitoring the temperature of the mixture and the temperature of the furnace wall.
This was controlled by diluting the nitriding atmosphere with argon when necessary to prevent it from occurring so violently as to exceed the required temperature. That is, it was ensured that the temperature of the mixture did not rise above the melting point of aluminum (approximately 660 U). It was taken to indicate that the first stage of the nitriding process was complete when no exotherm was anymore detected by temperature sensing of the mixture and walls as described above.

The temperature in the furnace was then increased to 1200C while maintaining the same nitriding atmosphere used in the first stage. The mixture was kept at this temperature for 10 hours, then raised to 1250 CK,
The temperature was kept for 5 hours, then raised to 1300C, kept for 5 hours, then raised to 135Or, kept for 5 hours, and finally raised to 1400C and kept at this temperature for 10 hours. The progress of the reaction at this stage was monitored as in the first stage nitridation by monitoring the temperature of the mixture and the furnace wall, and when necessary the temperature was controlled by diluting the atmosphere with argon to prevent it from getting too high. . In this second stage of nitriding, the disappearance of reaction heat was understood to indicate that the nitriding was complete. The resulting material was a friable, nitrided mixture that was easily crushed by simple steel ball milling after cooling. There is no need to use costly comminution means such as jaw crackers at this stage. The powdered material thus obtained was placed in a graphite pot and heated to 1600 tl at a heating rate of 10-15 C per minute in a non-oxidizing atmosphere.
: Heated in a furnace until . In this example, the non-oxidizing atmosphere is 1
Atmospheric nitrogen. This material was kept at this temperature for 5 hours during which time it reacted.

After the reaction, the material was removed from the furnace and allowed to cool to room temperature.

The resulting ceramic material shattered and required only a small amount of force to powder for subsequent use.

However, X-ray spectral analysis of this material revealed that it was 30% by weight of α-phase substituted silicon nitride with the formula % and the formula S'46"1
It was shown to consist of 50% by weight of β-phase substituted silicon nitride of 4N@6ol 4 , further 15% by weight of unreacted α-silicon nitride, and 5% by weight of yttrium oxide. This product does not contain a high proportion of α'-phase substituted silicon nitride and therefore does not fall within the scope of the present invention, and it is considered as a control experiment for the examples below.

Experiment (2) above was repeated for several samples (Examples 3-6), except that in the last sintering step:
The temperature of each sample was set successively higher and kept at the specified temperature for 5 hours as in Example 2. The results of these experiments are shown in Table 1.

From Examples 2 to 5 of Table 1, it can be seen that the ratio of α-phase material to β-phase material in the ceramic material made can be controlled by the temperature of the last sintering step, and at a constant sintering time. It can be seen that the higher the temperature, the more α-phase material is present. Under the conditions described above, ie, under 1 atmosphere of nitrogen in the experiment described above, the maximum temperature at which the maximum amount of α-phase substituted silicon nitride was formed was of the order of 18201:'. And α
The minimum temperature at which a high proportion of phase-substituted silicon nitride is present, ie greater than 50%, was determined to be on the order of 1650U.

A further series of experiments were carried out using the pre-sintered samples according to Example 2 to study the effect of time on temperature and of temperatures higher than the maximum temperature used in the experiments in Table 1. The results are shown in Table 2.

Consideration-1 From the table above, for example from Examples 11.8 and 6, it can be seen that the α/β phase ratio increases as the time at a given temperature increases. However, from Examples 8 and 9, it can be seen that when the temperature is increased to 1870C for 2 hours under the condition of 1 atm nitrogen, the α/β phase ratio starts to decrease slightly, whereas from Example 10 at 1900t:
It can be seen that after 2 hours, dissociation has occurred and other phases begin to appear in the friable product. Therefore, in conclusion, α
Phase-rich products can be made at temperatures on the order of up to 1900C, and temperatures on the order of 1820T:' allow precise control of the product with reasonable sintering times (on the order of 5 hours). It seems so. It is also understood that the absolute value of such temperature will also be influenced by other conditions within the furnace, e.g. pressure, and some preliminary steps should be taken to quantify the conditions of the manufacturing equipment to be used. It may be useful to perform an experiment.

In the example above, the starting materials are silicon, aluminum,
Although silicon nitride, alumina, and yttrium oxide have been used, useful brittle ceramic materials may be used with nitride of yttrium and/or with other modifying cations such as oxides and/or nitrides of calcium, lithium, magnesium, or cerium. It will be understood that it can be obtained using objects. Furthermore, it will be appreciated that the use of silicon nitride as one of the starting materials is not essential. However, since the nitriding operation is antithermal, it is advantageous to include silicon nitride. This is because this not only helps to control the exothermic reaction, but also allows high nitriding temperatures to be used without thermal runaway, thus allowing an overall highly efficient nitriding step. It is from. For the same reason, aluminum nitride can be included as one of the starting materials in addition to or instead of aluminum. However, as the amount of silicon nitride and/or aluminum nitride is progressively increased while decreasing silicon and/or aluminum, respectively, the effectiveness of the present invention decreases. Preferably, therefore, silicon nitride and/or aluminum nitride may be included in an amount such that the weight ratio of silicon nitride to silicon or the weight ratio of aluminum nitride to aluminum is not greater than 3:1.

In a series of examples according to the first and third objects of the invention, having 72% by weight α' phase and 28% by weight β' phase (β phase substituted silicon nitride), made according to Example 4,
A friable intermediate powder sample with a high proportion of α-phase substituted silicon nitride was ground using a spherical mill containing various Al2O, poles (i.e. 1/4", 1/2#, 3//). , 3.47wt% Al2 over 24 hours
O, increased or milled for 24 hours in a cylindrical mill to give a weight of 5.41 Al2O.

gave an increase. Another 800 g sample was run in a cylindrical mill using 1/4" diameter balls for 6.5 hours each for 24 hours.
Grinded to give 88 wt% A4203 gain and 9.19 wt% AI, O, gain in 48 hours.

All treatments were performed using isopropyl alcohol (i-p-a).
was used as a carrier liquid. Each slurry was heated in an air furnace for 12 hours.
Dry in the oror, sieve the powder, then 20,000 pst (
It was pressed isotropically at 140 MN-2) to form a billet for sintering in a nitrogen atmosphere. Table 3 shows the processing conditions.
The products obtained and their properties are shown.

It can be seen from Examples 12-15 that useful engineering ceramics with good density, strength and hardness properties were made. Estimated to be more than 7.5% by weight A/, O
, the α' phase is not detected, but the predominant phase under this condition is the β' phase of the order of 855% by weight. If the alumina content is less than about 7.5% by weight,
The amount of α′ phase gradually increases. In the examples herein, if the intermediate phase contains on the order of 288% by weight of β' phase, making a high-quality final product containing less than this amount of β' phase without adding aluminum nitride to the mixture I can't.

If a product containing 28% less β' phase by weight is required in the final product, the intermediate phase must have an appropriate amount of β' phase or an appropriate amount of aluminum nitride must be added.

The alumina content is less than 100% by weight, and 7
．． More than K on the order of 5% by weight, 0.7
It can be ensured that a product is obtained which is rich in β' phase with a binary value of 5 < z < 1.5 and has a controlled amount of other crystalline phases.

In Example 16 according to the second and third objects of the present invention, in order to expand the range of products obtained, it is possible to control the binary value of the β' phase to a lower value than that obtained by increasing the alumina in % alone. In order to do this, silicon nitride powder was used in addition to alumina powder.

75'i parts of the intermediate powder according to Example 5 were added to Ke
Silicon nitride powder 25 supplied by nnametal
parts by weight and ball milled in isopropyl alcohol using alumina balls for 72 hours. At this point the starting mixture was found to have an alumina gain of 8.89 parts by weight. The fine powder thus produced was then dried and isostatically pressed as in Examples 12-15, under nitrogen atmosphere at 16000 for 2 hours followed by 17501:l'
It was sintered for 5 hours.

The obtained product contains β' phase material as the main constituent, and 3
Contains with 12H on the order of % by weight, 3.231ce
Density of −', fracture modulus of three-point crushing in chamber −89,8
00 psi (620 MN m-2), exhibiting a Rockwell A hardness of 92. The binary value of the β' phase material was found to be 0.8.

Additionally, samples were made using St, N4, and Al2O3 as in Example 13, and using the brittle intermediate of Example 5. The treatments and products are shown in Table 4.

Examples 16-19 consistently make it possible to make products with a high proportion of β' phase while allowing the binary value to be lowered to less than that obtained with alumina alone.

It will be noticed that in Example 19 Y2O3 was added to the starting materials. This is because the amount of intermediate phase is small <(2
8.6 parts by weight), therefore yttrium from the α' phase is insufficient in glass formation to aid in densification. Therefore, Y2O3 was added to compensate for this deficiency.

However, it is understood that other glass-forming metal oxides or nitrides may also be added, such as oxides or nitrides of magnesium, manganese, iron, lithium, calcium, cerium and the lanthanide series 9 and other rare earth elements. Good morning.

These additives can be in the form of compounds which can be transformed into the required state, but preference is given to using oxides of metals which form cations of the α' phase.

According to a comparison of Examples 18 and 19, a binary increase in the final β' phase can be achieved by increasing the amount of alumina and intermediate phases and decreasing the amount of silicon nitride. Examples 18 and 1
9, the total amount of yttrium is substantially the same. K, Examples 16 and 17 to create the α' phase in the final product, the alumina content was adjusted to 6.13 and 8.1%, respectively.
Reduce to t% and repeat. The resulting product contains an α' phase, using the starting material of Example 16, but with a lower Aj of 20. Example 1
Using the starting material No. 7, but with a low Al2O3 content, it was found to contain 5% by weight of α' phase. Example 1
6 (i.e., using a high proportion of intermediate powder and high α' phase content) was repeated with the amount of alumina reduced to 2% by weight. The product obtained contained 800% by weight α' phase.

In Example 20 of the present invention, a friable ceramic material made according to Example 5 (92.6% α' phase, 7.
95 parts by weight of 4% β' phase) were mixed with 5 parts by weight of silicon nitride from Example 1 and the mixture was ground to fine particles in a colloid 9 mill. It will be appreciated that in colloid milling, no enrichment from the grinding media occurs as occurs in alumina ball milling. Pour the powder into a 2 inch (
51 to 1) diameter graphite die (this is richly coated with nitride) and 4600 p.
1750t for 1 hour under pressure of si (31,7MPa)
：', mainly (90%) α′ phase substituted silicon nitride and 8%
A dense product was formed consisting of a β' phase (binary value = 0.2), 2% glass containing yttrium and traces of free silicon. Although high density was achieved in this example by heat pressing, it is possible to achieve the same density without using pressure by ensuring that some alumina is included in the mixture, for example by alumina ball milling. can.

However, such incorporation of alumina reduces the weight proportion of alpha-phase substituted silicon nitride of the general formula % in the final product.

Although examples are shown using yttrium as the cation-modifying element, the methods and products of the invention are equally accomplished using other cation-modifying elements such as calcium, lithium, magnesium, and cerium.

In the embodiments described above, alumina and/or silicon nitride
It will be understood that silicon, nitrogen, aluminum and oxygen can be introduced by using other compounds in place of or in conjunction with the compounds mentioned above. For example, silicon oxynitride or the polytype mentioned at the beginning could be used.

In Example 21 of the present invention, an intermediate powder according to Example 7 (containing 877 parts by weight α' phase and 133 parts by weight β' phase) was used.

) with 76 parts by weight of silicon nitride, 7 parts by weight of the substance 21R1 of GB 41573199 and 5 parts by weight of Y2O3 (added due to the small amount of intermediates as described in Example 19). Mix and ball mill the whole using alumina media to give a weight gain of 2.91 parts.

Sintering at 1750R for 5 hours followed by annealing at 1400C for 5 hours to 99,700 psi (69
0MNm), 52,200 psi (3
A product with a modulus of 60 MNFIL-2) and a Rockwell A hardness of 92 was obtained. This is a high proportion of β′
This confirms an α' phase with a weight ratio of about 5%. The binary value of β phase is 1.
It was 2. Control of Z Ii& can be increased by decreasing the silicon nitride and increasing the amount of polytype and/or alumina by that amount, or vice versa for decreasing the binary. Also, if it is desired to increase the α' phase content in the final product, this can be done by increasing the amount of intermediate while decreasing the amount of silicon nitride, and by decreasing the alumina content; or by increasing the amount of Y2O3 added. This is achieved by increasing the intermediate content while decreasing the When reducing the α' phase of the final product, it is desirable not to reduce the amount of intermediates below 5% of the starting mixture and to keep the weight proportion of the intergranular glass layer within acceptable limits.

Examples 12 to 21 contain a high proportion of α-phase substituted silicon nitride in the starting mixture, made by the second method of the invention (i.e., a method that does not require an expensive comminution process and provides a more friable powder). Although a powder was used containing powders, the powders can be made in other ways, such as the method described in Example 1, and can also be good products obtained according to the first subject of the invention. However, it is clearly preferred to use powders made according to the second subject of the invention.

Examples include controlled β-phase substituted silicon nitride, and good products with or without alpha-phase substituted silicon nitride are
Although scales made from powders containing α-phase substituted silicon nitride with or without β-phase substituted silicon nitride are illustrated,
It is preferred to use starting powders that are high in α-phase substituted silicon nitride (>90%) as this enhances the thermodynamic behavior of the reactants. A high proportion of α-phase intermediates is preferred. Another reason is that it is the absence of α-phase intermediates).
It is possible to have a wider range of control over the composition of the resulting product compared to products obtained by the route using IJ type intermediates.

Procedural Amendment (Rabbe) June 6, 1981 Patent Application No. 29599' 2. Name of the invention: Ceramic proboscis hook and Ceramic Ivy, f, J (7) L
Complaint Law 3 Relationship with the person making the amendment Case Patent applicant name Lucas Industries Buffrick
Limiad Kanzeni - May 11, 1982 (
Date of dispatch: 5JJ51, 1937) 6 Number of inventions increased by amendment: 0 7, Subject of amendment: 1. ,...91e
1 (no history in the content) 8 Contents of the amendment 3'1K (no')

Claims (1)

[Claims] 1.Formula %Formula %) (wherein, X is not greater than 2, and M is a modifying cation/
It is. ) mixing a ceramic powder containing a high proportion of α-phase substituted silicon nitride according to K with at least one nitride of silicon and/or alumina, provided that the alumina does not exceed 10% by weight of the mixture; and this mixture is sintered in a non-oxidizing atmosphere at a temperature of 1700t:' to 1900C to obtain (1) the general formula %, where 2 is greater than zero (and not greater than 1.5). ), and a small amount of another phase containing the above-mentioned modifying cation M; or (2) the above-mentioned β-phase substituted silicon nitride,
The production of a dense ceramic article consisting essentially of a controlled amount of α-phase substituted silicon nitride according to the formula %) and a small amount of another phase containing the above-mentioned modifying cation M Law. 2. A powder mixture of silicon, aluminum, alumina, and an oxide or nitride of a modifying cation is heated in a nitriding atmosphere at a temperature below the melting point of aluminum until this first stage of nitridation is substantially complete. Performing the first stage nitriding by: heating the first stage nitrided mixture at a temperature below the melting point of silicon while maintaining a nitriding atmosphere;
A second stage of nitriding is carried out by heating until this second stage of nitriding is substantially completed, thereby producing a brittle material; and the brittle material thus obtained is comminuted; , the finely divided brittle material is sintered at a temperature between 1650C and 1900T:'' while maintaining a non-oxidizing atmosphere, with the formula %, where I is not greater than 2 and M is the modifying cation. ) A brittle ceramic material containing more than 50% by weight of K-sub5α-phase substituted silicon nitride, or the above-mentioned α-phase substituted silicon nitride with the formula 8% (where 2 is greater than zero and 1.5 (not greater than 50% by weight) of a mixture of β-phase substituted silicon nitrides according to K
To obtain a friable ceramic material containing more: Mixing the ceramic powder formed from the above-mentioned friable ceramic material with silicon nitride and/or alumina, provided that the alumina should not be more than 10% by weight of the mixture: and this mixture at 1700 to 190 (1”
Sinter for at least 10 minutes at 1900C in a non-oxidizing atmosphere at a temperature of (1), where 2 is greater than zero and not greater than 1.5. (2) a β-phase substituted silicon nitride as described above, or (2) a β-phase substituted silicon nitride as described above;
Ceramics comprising the steps of making a dense ceramic article consisting essentially of a controlled amount of α-phase substituted silicon nitride according to the above formula 8) and a small amount of another phase containing the above-mentioned modifying cation M. How the product is manufactured. 3. The method according to claim 1 or 2, wherein the modifying cation is yttrium, calcium, lithium, magnesium, or cerium. 4. The method according to claim 1 or 2, wherein the high-density ceramic product (2) contains 0.05 to 90% by weight of α-phase substituted silicon nitride according to the formula 8. 5. Ceramic (,1) or ceramic (2) is 0.0
4. A method according to claim 1 or claim 2, comprising from 5 to 20% by weight of another phase. 6. The alumina content of the mixture containing ceramic powder is 7.
5% by weight or less Claim 1]lJ or 2nd claim
The method described in section. 7. A method according to claim 1 or 2, wherein the ceramic powder is 5 to 96.5% by weight of the mixture containing the ceramic powder. 8. Ceramic powder is present in an amount of less than 30% by weight of the mixture containing the ceramic powder, and yttrium oxide, calcium oxide, lithium oxide, cerium oxide, rare earth element oxide is present in the mixture containing the ceramic powder. and oxides of lanthanide elements, magnesium oxide,
3. The method of claim 1 or 2, wherein at least one glass-forming metal oxide selected from manganese oxide and iron oxide is included. 9. The method of claim 8, wherein the at least one glass-forming metal oxide is present in an amount less than 10% by weight of the mixture containing the ceramic powder. 10. A method according to any one of claims 1 to 9, wherein silicon nitride is present in an amount up to 75% by weight of the mixture comprising the ceramic powder. 11. 5 of the mixture containing silicon nitride and ceramic powder
11. The method of claim 10, wherein the amount is present in an amount of -75% by weight. 12. The method according to any one of claims 1 to 11, wherein the product is reheated after cooling to devitrify the glass phase. 13. The method according to claim 12, wherein the reheating temperature is higher than 1400C. 14. Heating a powder mixture of silicon, aluminum, alumina, and an oxide or nitride of a modifying cation under nitrogen at a temperature below the melting point of aluminum until this first stage of nitridation is substantially complete. The first stage nitriding is carried out by heating the first stage nitrided mixture at a temperature below the melting point of silicon while maintaining a nitriding atmosphere until this second stage nitriding is substantially complete. This is the second step of making a friable material: Next, the material is made into a finely friable material (165
Sintering while maintaining a non-acidic atmosphere at a temperature between 0 C and 1900 t:' according to the formula % (where E is not greater than 2 and M+ is the converting cation). A friable ceramic material containing up to 50% by weight of α-phase substituted silicon nitride, or the above-mentioned α-phase substituted silicon nitride and formula 3% (where 2 is greater than zero (and not greater than 1.5). 15. A process for producing a ceramic material comprising the steps of: obtaining a brittle ceramic material containing up to 50 wt. 14. The method of claim 14, wherein sintering is carried out at a temperature of about 1820 G, and the alpha-phase substituted silicon nitride accounts for more than 90]1 t% of the friable product. 17. The method of claim 14, wherein the sintering is carried out at a temperature of about 1820C for about 5 hours, and the alpha phase substituted silicon nitride accounts for more than 95JI of the brittle product. The method of claim 15 or 16. 18. The modifying cation is calcium and the elements in the powder mixture are substantially balanced according to the formula %.
The method according to any one of Items 4 to 17. 19. Claim 1, wherein the modifying cation is calcium and the elements in the powder mixture are substantially balanced according to the formula %.
The method according to any one of Items 4 to 17. 20. Claim 1, wherein the cationic element for modification is lithium, and the elements in the powder mixture are substantially balanced according to the formula %.
The method according to any one of Items 4 to 17. 21. Claim 1, wherein the cationic element for modification is yttrium, and the elements in the powder mixture are substantially balanced according to the formula %.
The method according to any one of Items 4 to 17. 22. Claim 1, wherein the cationic element for modification is yttrium, and the elements in the powder mixture are substantially balanced according to the formula %.
The method according to any one of Items 4 to 17.