JPH04357169A - Silicon nitride sintered product and its production - Google Patents

Abstract

PURPOSE:The invention relates to a silicon nitride sintered product having an intergranular glass phase having a high solid phase temperature and to a method for producing the sintered product. CONSTITUTION:A method for producing a silicon nitride sintered product in which spaces between silicon nitride granules are filled with an intergranular glass phase containing Al-Er-Si or Al-Yb-Si bonds, characterized by compounding silicon nitride powder, aluminum oxide powder, and erbium oxide or ytterbium oxide powder so that the amount of the oxide powder is 2-20wt.%, homogeneously mixing the compounded product together with a dispersing agent in an organic solvent, drying the mixture, molding the dried mixture, defatting the demolded product and subsequently sintering the defatted molded product at 1600-1950 deg.C in an inert gas atmosphere.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon nitride sintered body used for heat-resistant high-temperature members, wear-resistant parts, etc., and a method for manufacturing the same.

0002

[Prior Art] Silicon nitride sintered bodies are expected to be used as high-temperature structural materials and wear-resistant materials that require heat resistance, but since they are difficult to sinter, they are used as sintering aids such as Al2 O3 and Y.
A method of adding 2 O3, MgO, etc. and firing was adopted. The sintered body created by this method is Al2 O3 -Y2 O
3 -The solidus temperature of the grain boundary glass phase (temperature at which a liquid phase begins to appear upon heating) of the -MgO-SiO2 system, etc. is approximately 130
Since the temperature is as low as 0°C, there are problems in that the strength is low in the high temperature range of around 1300°C and the oxidation resistance at high temperatures is insufficient.

0003

[Problems to be Solved by the Invention] In order to solve this problem in view of the above-mentioned state of the art, the present invention provides a silicon nitride sintered body having a grain boundary glass phase with a high solidus temperature and a method for manufacturing the same. That is.

0004

[Means for Solving the Problems] The present invention provides (1) gaps between silicon nitride particles are filled with a grain boundary glass phase containing Al-Er-Si or a grain boundary glass phase containing Al-Yb-Si. A silicon nitride sintered body characterized by:

(2) Silicon nitride powder, aluminum oxide powder, erbium oxide or ytterbium oxide powder were adjusted so that the oxide powder was 2 to 20% by weight, and uniformly mixed with a dispersant in an organic solvent. A method for producing a silicon nitride sintered body, which comprises drying, molding, degreasing, and heating and sintering in an inert atmosphere at 1,600 to 1,950°C. It is.

That is, the present invention uses silicon nitride (Si3N
4) Add 2 to 20% by weight of powder, a total of two types of oxide powder, aluminum oxide (Al2O3) powder and erbinium oxide (Er2O3) powder or ytterbium oxide (Yb2O3) powder, and add this to ethanol, toluene, etc. After adding a dispersant such as polyvinyl alcohol or polyethylene amine in an organic solvent and mixing uniformly,
After drying and shaping, it is degreased and then fired at a temperature of 1,600 to 1,950°C under a pressurized atmosphere of an inert gas such as nitrogen. High Al-Er-Si or Al-Yb-S
A silicon nitride sintered body filled with a grain boundary glass phase containing i is obtained.

[0007] In the present invention, a molded body of raw material powder such as Si3N4 is degreased by heating to 300 to 700°C in vacuum, and then heated to 1600 to 19°C in a pressurized atmosphere of nitrogen gas.
A preferred embodiment is a method of firing at a temperature of 50°C.

Furthermore, in the above explanation, Al2 O3 and E
Although only the combinations of r2 O3 , Al2 O3 and Yb2 O3 have been explained, the combination of Al2 O3 and Er2
O3 and Yb2 O3 may be combined. In this case as well, the amount of oxide powder added is 2 to 2 to
Needless to say, the content is 20% by weight.

[0009]

[Operation] The operation of the present invention will be explained below. Si3
Al2 O3 and Er2 O as sintering aids in N4
3, or when Al2 O3 and Yb2 O3 are added, Al2 O3 -Er2 O3 -SiO2 or Al2 O3 - is produced by reacting with SiO2, which is an oxide contained as an impurity in the Si3 N4 raw material powder, during the sintering process. The solidus temperature of the grain boundary glass phase of the Yb2 O3 -SiO2 system is about 1450 to 1500°C, which is higher than the glass phase in currently known silicon nitride sintered bodies using Al2 O3 and Y2 O3 as auxiliaries. The solidus temperature also increases by about 100° C. or more, and therefore, the sintered body obtained by the present invention has excellent heat resistance.

[0010] Al2 O3, Er2 O3, Yb2
The total addition of oxides such as O3 should be between 2 and 20% by weight. When the total amount of these oxides added is less than 2% by weight, the sintering reaction does not proceed, and even if 20% by weight or more is added, the effect of promoting the increase in density due to sintering of Si3N4 is saturated. Since the effect does not increase commensurately with the amount added, the amount added of the auxiliary agent should be within the above range.

Polyvinyl alcohol, polyethylene amine, etc. are used as dispersants for raw material powders such as Si3 N4 and Al2 O3, and the amount used is preferably 1 to 10 parts by weight per 100 parts by weight of ceramic raw materials. It is preferable to use 50 to 150 parts by weight of the organic solvent such as ethanol and toluene for dispersing. The reason for using such a mixing ratio of the dispersant and the solvent is that if the amount of the dispersant added is less than 1 part by weight, there will be no dispersion effect for the raw material powder, and if it is more than 10 parts by weight, the viscosity of the solution will become too high and the dispersion will be adversely affected. This is because it may cause problems such as making it difficult to use. In addition, as a method for degreasing the dispersant after molding the obtained raw material powder, it is sufficient to heat it to a temperature of 300 to 700° C. in a vacuum.

Finally, the firing conditions for obtaining a dense silicon nitride sintered body are as follows:
Calcinate at a temperature of 50°C. When the sintering aid of the present invention is added, the temperature at which the grain boundary glass phase becomes a liquid phase is high, so if the sintering temperature is 1600° C. or lower, there is no volumetric shrinkage due to sintering and sintering does not proceed. Furthermore, if the firing temperature is higher than 1950°C, the density will not increase due to decomposition, etc., making it impossible to obtain a high-quality sintered body, and there will be problems such as higher manufacturing costs due to processing at higher temperatures. be.

[0013]

[Example] Hereinafter, an example of the present invention will be given to explain the effects of the present invention. The average particle size of the Si3N4 powder used was 0.
．． 3μm, Al2O3 and Er2 added as auxiliaries
The average particle diameters of O3 and Yb2 O3 are each 0.8
, 1.0, 1.0 μm. Polyethylene amine was used as a dispersant and ethanol was used as a solvent.

[0014] After uniformly mixing the raw materials in ethanol with the blending ratio shown in Table 1, they were dried and pressed to a diameter of 60 mm.
Formed into a disk shape with mmφ and thickness of 5mm, weighing 4000kg/
A molded body was obtained by isostatic pressing at a pressure of cm2. This molded body was heated to 500°C in vacuum, held for 1 hour to degrease it, heated to the temperature shown in Table 2 under nitrogen gas pressure of 10 atm, fired, and then cooled in a furnace and nitrided. A silicon sintered body was obtained. Table 2 shows the relationship between the firing conditions and relative density of the obtained sintered body. As a result, it was found that a dense silicon nitride sintered body could be obtained by the manufacturing method provided by the present invention.

[Table 1]

[Table 2]

[0015]

EFFECTS OF THE INVENTION According to the present invention, a dense silicon nitride sintered body and a method for producing the same are obtained, and the obtained heat-resistant and wear-resistant silicon nitride sintered body has great industrial utility value.

Claims (2)

[Claims] Claim 1: The gap between the silicon nitride particles is Al-Er-S.
1. A silicon nitride sintered body filled with a grain boundary glass phase containing i or a grain boundary glass phase containing Al-Yb-Si. 2. Silicon nitride powder, aluminum oxide powder, erbium oxide or ytterbium oxide powder,
The oxide powder is adjusted to 2 to 20% by weight, mixed uniformly with a dispersant in an organic solvent, dried, molded, degreased, and heated and sintered in an inert atmosphere at 1600 to 1950°C. A method for manufacturing a silicon nitride sintered body, characterized by: