JPH0355402B2 - - Google Patents

Description

[Detailed description of the invention]

Technical field of the invention The present invention relates to silicon aluminum oxynitride (Si-Al-O-N compound) and rare earth oxide.
Silicon aluminum oxynitride (RO _x/2・Si−
The present invention relates to a method for producing powder of Al-O-N compound). Technical Background of the Invention A sintered body or powder thereof, which is known as a so-called SiAlON-based compound and is made of silicon aluminum oxynitride, which is a type of non-oxide material, and a rare earth oxide therein, has a heat-resistant property. , ceramics with excellent electrical insulation and corrosion resistance are attracting attention. This silicon aluminum oxynitride and rare earth oxide/silicon aluminum oxynitride are
Their chemical compositions are Si ₆ −zAlzN ₈ −zO ₂ (z is a number from 0 to 4, but does not include 0), RO _x/2・Si ₆ −
zAlzN ₈ -zO ₂ is represented by (z is a number from 0 to 4, but does not include 0, R is a rare earth element, and x is the valence of R). SiAlON-based compounds generally use silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), aluminum oxide (Al ₂ O ₃ ), or silicon dioxide (SiO ₂ ) as starting materials, and convert these materials into desired SiAlON-based compounds. The mixture is blended according to the chemical composition of the compound, and the resulting mixture is produced, for example, by firing at a temperature range of 1500° C. or higher in an atmosphere containing nitrogen gas as a main component. When producing a RO _x/2 ·SiAlON-based compound, a desired amount of RO _x/2 is further added to the above-mentioned formulation. Another method has been attempted in which a mixture of SiO ₂ , metallic aluminum (Al) and metallic silicon (Si) is used as a starting material, and after first reducing SiO ₂ with Al, the resulting Si is nitrided. There is. Problems with the background technology Among the above manufacturing methods, the former method requires
Since the solid-phase reaction in the above-mentioned high-temperature range is applied, the reaction process requires a large amount of thermal energy and requires complicated and expensive production equipment or processes. On the other hand, the latter method has the disadvantage that it is not only not advisable from a thermal energy point of view, but also requires a high degree of skill to control the reaction process and is poor in mass productivity. Purpose of the Invention The present invention starts calcination at a temperature much lower than the calcination temperature conventionally applied, and then proceeds with the calcination reaction using the reaction heat to produce SiAlON-based compounds and RO _x/2・SiAlON-based compounds. The object of the present invention is to provide a manufacturing method that can produce a compound and is therefore excellent in terms of thermal energy. Summary of the Invention The present invention was accomplished by focusing on the fact that the nitriding reaction of aluminum is an exothermic reaction as shown by the following formula. 2Al＋N ₂ →2AlN−152.8Kcal In other words, Al powder is heated to 650 Kcal in N ₂ atmosphere.
When heated to a temperature above ℃, the reaction shown above occurs to produce AlN, and at the same time the reaction system generates heat and rises in temperature. The method of the present invention reduces the amount of heat generated in this reaction system.
It is used as part of the amount of heat required to generate SiAlON-based compounds. The method of the present invention includes Si ₆ −zAlzN ₈ −zO ₂ (z is 0 to 4
(excluding 0), SiAl ₄ N ₄ O ₂ ,
When synthesizing silicon aluminum oxynitride powder having a chemical composition represented by SiAl ₅ N ₅ O ₂ , SiAl ₆ N ₆ O ₂ or SiAl ₆ N ₃ O ₂ , in accordance with the chemical composition, (1) aluminum (2) At least one of aluminum oxide and aluminum nitride; and (3) A predetermined amount of each powder of at least one of silicon dioxide and silicon nitride is blended, provided that the amount of aluminum is 2 to 37% of the mixed powder. 650% by weight, and the resulting mixed powder was heated in an atmosphere containing nitrogen gas as the main component.
Start firing in the temperature range of ~900°C; and the following formula: RO _x/2・Si ₆ −zAlzN _8-z O _z , RO _x/2・
SiAl ₄ N ₄ O ₂ , RO _x/2・SiAl ₅ N ₅ O ₂ , RO _x/2・
SiAl ₆ N ₆ O ₂ or RO _x/2・SiAl ₆ N ₃ O ₂ (where z is 0
~4 numbers, but not including 0, R is Y, Ce, La,
Represents at least one rare earth element selected from the group of Sc. x represents the valence of R. ) When synthesizing a rare earth oxide/silicon aluminum oxynitride having the chemical composition shown in (1) aluminum; (2) at least one of aluminum oxide and aluminum nitride; (3) ) at least one of silicon dioxide and silicon nitride; and (4) a predetermined amount of each rare earth oxide powder, provided that the amount of aluminum is 2 to 37% by weight of the mixed powder, and the obtained mixed powder 650 in an atmosphere containing nitrogen gas as the main component.
It is characterized by starting firing in a temperature range of ~900°C. In the method of the present invention, first, each powder of (1) Al; (2) Al ₂ O ₃ and/or AlN; and (3) SiO ₂ and/or Si ₃ N ₄ has a target SiAlON system. A mixed powder obtained by blending a predetermined amount calculated from the component composition of the compound is used as a starting material. However, the amount of Al is within the range of 2 to 37% by weight of the mixed powder as described below.
Assigned as AlN. When synthesizing RO _x/2 /SiAlON compounds, add RO x/2 or RO _x/2 to each of the above components.
A predetermined amount of a rare earth oxide such as R ₂ O is further blended to constitute the starting material. At this time, Si ₃ N ₄ has a particle size of 2 μm or less, Al ₂ O ₃ has a particle size of 1 μm or less, AlN has a particle size of 2 μm or less, and SiO ₂ has a particle size of 2 μm or less.
1 μm or less, for RO _x/2 or R ₂ O, use a fine powder with a particle size of 5 μm or less, and for Al, use a scale-like powder of 5 μm or less in order to effectively generate heat associated with the nitriding reaction described later. It is preferable. The blending amount of these powders is
It is determined in accordance with the chemical composition of the compound and the RO _x/2 /SiAlON compound. The blending amounts of Al and AlN are set so that the total amount of AlN generated as a result of the nitriding reaction of Al and the amount of AlN mixed from the beginning becomes the value of AlN corresponding to the above chemical composition. . Specifically, Al ranges from 2 to 37% by weight.
If the content of Al is less than 2% by weight, the amount of heat generated as a result of the nitriding reaction is too small to sufficiently supplement the amount of heat required for the synthesis of the SiAlON compound. In addition, if it exceeds 37% by weight, Al and Al
come to exist adjacent to each other, which causes the Al to fuse together (melting point of Al: 660°C) due to the heat generated as a result of the nitriding reaction, resulting in agglomeration without the entire Al becoming AlN. In this sense, it is effective if AlN is mixed in advance because this AlN acts as a kind of Al diluent and eliminates the above-mentioned disadvantages. Generally, it is preferable that the total amount of Al and AlN at the time of blending is less than 50% by weight of the total. The mixed powder of starting materials blended as above preferably has a total weight of 20 g or more,
If this amount is less than 20 g, the amount of heat generated by the nitriding reaction of Al will be small and the reaction of the entire system will not proceed smoothly. Next, this starting material is fired in an atmosphere containing _N2 as a main component. At this stage, the nitriding reaction of Al and the synthesis of the entire SiAlON compound proceed. Firing begins by raising the temperature to a temperature range of 650-900°C. If the firing temperature is less than 600℃, the above
The nitriding reaction of Al does not proceed, and below 650℃,
Due to the calorific value of the nitriding reaction, a sufficient reaction temperature cannot be reached in a short time. Furthermore, if the temperature exceeds 900°C, it will merely supply unnecessary heat and will not provide any thermoeconomic benefits. In this firing step, Al is nitrided to AlN by N ₂ supplied to the surface of Al, and heat is generated at this time. As a result, the reaction system as a whole rises to a higher temperature, exceeding 1500°C, often exceeding 1800°C. Since the heat generated spontaneously from the reaction system is regulated by the surface area of the blended Al powder, in the method of the present invention, it is advantageous to increase the surface area of the Al powder. Therefore, it is preferable to use scaly powder with a particle size of 5 μm or less as the Al powder. Examples of the invention Example 1 490 g of Si ₃ N ₄ with an average particle size of 0.1 μm, an average particle size of 0.3 μm
102 g of Al ₂ O ₃ , 118.4 g of AlN with an average particle size of 1.2 μm,
90 g of SiO ₂ with an average particle size of 0.1 μm and 30 g of flaky Al with a particle size of 2.6 μm were dry mixed in a ball mill. 40g of the obtained mixed powder was placed in a graphite boat with an internal volume of ^80cm3 , and using a horizontal annular electric furnace,
It was fired at 700° C. for 1 hour while flowing N ₂ gas at 300/hr. The temperature of the mixed powder rose to 2100°C, and it was confirmed that the nitriding reaction of Al was progressing rapidly. When the obtained ingot was crushed and its composition analyzed, it was confirmed that it was Si ₄ Al ₂ O ₂ N ₆ . Examples 2 to 7 Mixed powders containing the powders used in Example 1 at the composition ratios (wt%) shown in the table were fired under various firing conditions. The temperature during the synthesis reaction was measured in the same manner as in Example 1. The obtained ingot was crushed and its composition was analyzed. The above results are summarized in the table.

【table】

[Table] Comparative Example A mixed powder having the same composition as in Example 1 was prepared except that Al was not mixed and AlN was 164 g, and this was fired under the same firing conditions as in Example 1. During firing, the temperature of the mixed powder did not rise, and the obtained powder was not converted into SiAlON. Effects of the Invention As is clear from the above explanation, in the production of SiAlON-based compounds and RO _x/2・SiAlON-based compounds,
Since the method of the present invention effectively utilizes the amount of heat generated spontaneously in the nitriding reaction of Al, it is not necessary to input a large amount of thermal energy from the outside as in the conventional method, and its industrial value is great.

Claims (1)

[Claims] Primary formula: Si _6-Z Al _Z N _8-Z O _Z (Z is a number from 0 to 4, but does not include 0), SiAl ₄ N ₄ O ₂ , SiAl ₅ N ₅ O ₂ ,
When synthesizing silicon aluminum oxynitride powder with a chemical composition represented by SiAl ₆ N ₆ O ₂ or SiAl ₆ N ₃ O ₂ , corresponding to the chemical composition, (1) aluminum; (2) aluminum oxide and At least one of aluminum nitride; and (3) a predetermined amount of each powder of at least one of silicon dioxide and silicon nitride is blended, provided that the amount of aluminum is 2 to 37% by weight of the mixed powder, and the obtained 1. A method for producing ceramic powder, which comprises starting firing of the mixed powder at a temperature range of 650 to 900° C. in an atmosphere containing nitrogen gas as a main component to synthesize silicon aluminum oxynitride. 2. The method for producing ceramic powder according to claim 1, wherein the aluminum powder is flaky powder. Tertiary formula: RO _x/2・Si _6-Z Al _Z N _8-Z O _Z , RO _x/2・
SiAl ₄ N ₄ O ₂ , RO _x/2・SiAl ₅ N ₅ O ₂ , RO _x/2・
SiAl ₆ N ₆ O ₂ , or RO _x/2・SiAl ₆ N ₃ O ₂ , (where Z
is a number from 0 to 4, excluding 0, and R represents at least one rare earth element selected from the group of yttrium, cerium, lanthanum, and scandium. x
represents the valence of R. ) When synthesizing silicon aluminum oxynitride having the chemical composition shown in (1) aluminum; (2) at least one of aluminum oxide and aluminum nitride; (3) silicon dioxide and A predetermined amount of each powder of at least one of silicon nitride; and (4) rare earth oxide is blended, provided that the amount of aluminum is 2 to 37% by weight of the mixed powder, and the obtained mixed powder is heated with nitrogen gas. 1. A method for producing ceramic powder, which comprises starting firing in an atmosphere containing the main component at a temperature range of 650 to 900°C to synthesize silicon aluminum oxynitride. 4. The method for producing ceramic powder according to claim 3, wherein the aluminum powder is flaky powder.