JP2013173643A - Method for producing sintered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dense glass sintered body, because pores generated inside the sintered body not only causes strength decline of the sintered body but also causes scattering of light.SOLUTION: This method for producing a sintered body includes a step of forming a compact from glass powder by dry molding, a step of obtaining a precursor by sintering the compact, and a step of obtaining a sintered body by pressurizing and sintering the precursor under a mixed gas atmosphere containing oxygen; wherein the partial pressure of oxygen in the mixed gas is ≥10 vol.%. The relative density of the precursor is 90-96%, and the relative density becomes higher than the precursor by passing through pressurization sintering under the mixed gas atmosphere.

Description

  The present invention relates to a method for producing a sintered body, and more particularly to a method for producing a dense sintered body of glass powder.

  Conventionally, techniques relating to sintered bodies have been studied by various methods, particularly using ceramic powder. For example, Patent Document 1 discloses a sintered body in which glass and ceramic are mixed, Patent Document 2 discloses a silicon nitride-based sintered body in which silicon nitride particles are filled with a crystallized glass phase of oxynitride, and Patent Document 3 Discloses a method for producing a dense sintered body using zinc oxide, and Patent Document 4 discloses a method for producing a sintered body in which the surface of a ceramic powder is subjected to plasma treatment and then molded and sintered. However, in general, the method for obtaining a dense sintered body using ceramic powder is a solid phase reaction, and the sintering time is as long as about 10 to 30 hours. The obtained sintered body had fine pores and bubbles inside.

  Here, in addition to the ceramic sintered body described above, a method for producing a glass sintered body has also been studied, and is particularly used in the semiconductor field.

  As a manufacturing method of the sintered compact using glass powder, after producing a pellet using glass powder and an organic binder, the method of obtaining a sintered compact by sintering above the glass transition point of the glass powder. The mainstream (Patent Document 5). As described above, pellets using a binder are sintered after the binder is completely removed before sintering, and pores are easily generated in the finally obtained sintered body. For example, Patent Document 6 discloses a glass sintered body having a relative density of 95% or more by forming a molded body, drying and removing moisture contained in the molded body, and sintering it at a melting point or lower in a reduced-pressure atmosphere. Obtaining techniques are disclosed.

JP 2011-225446 A JP 05-330919 A JP 2008-195567 A JP 2002-293649 A JP 2010-195655 A JP 2002-362967 A

  One of the properties of glass is that it has high light transmission and is superior in durability to ultraviolet light, chemicals, heat, etc. compared to resins, etc. Development to members is expected.

  However, the presence of pores and bubbles generated in the sintered body described above not only causes a decrease in strength of the sintered body but also causes light scattering, so that the sintered body is incorporated into an optical article. That was still difficult.

  Accordingly, an object of the present invention is to obtain a dense glass sintered body.

  As a result of the present inventors diligently studying the above-mentioned problems, pores and bubbles in the sintered body are removed by sintering the sintered material while pressing it again, and a dense and transparent sintered material is obtained. It became clear that the body could be obtained.

  That is, the present invention includes a step of forming glass powder by dry molding, a step of sintering the molded body to obtain a precursor, and a step of adding the precursor in a mixed gas atmosphere of oxygen gas and inert gas. And a step of obtaining a sintered body by pressure sintering.

  In the mixed gas, the oxygen partial pressure is 10% by volume or more.

  In the step of obtaining the sintered body, pressure sintering is performed at +10 to + 50 ° C. for 1 to 20 hours with respect to the glass transition point of the glass powder.

  The relative density of the precursor is 90 to 96%.

  According to the present invention, a dense glass sintered body can be obtained. Moreover, since the said glass sintered compact is what suppressed scattering of light, it can utilize for an optical article.

  The present invention includes a step of forming glass powder into a molded body by dry molding, a step of sintering the molded body to obtain a precursor, and sintering the precursor by pressure sintering in a mixed gas atmosphere containing oxygen. A method for producing a sintered body.

  In addition, a molded object shall refer to what the said glass powder was shape | molded by pressing with pressure.

  The molded body is formed by a dry molding method in which heating is not performed, and it is particularly preferable to use a uniaxial pressure molding method that is rich in mass productivity.

  When producing a molded body using the uniaxial pressure molding method, the glass powder in the mold is pressed and solidified. The pressure during pressing is preferably 40 MPa or more and 60 MPa or less. If it is out of the above range, the press may be insufficient or the molded body may be cracked.

  The glass powder used for the pressure molding is an oxide glass, and a glass that can be sintered and does not precipitate crystals in each step of the production may be used. Since the temperature during pressure sintering generally rises to at least 400 ° C., for example, glass powder having a glass transition point of 390 ° C. or higher may be used so that sintering and sintering can be performed.

  In the present invention, since the first heating is performed in the step of obtaining the precursor and the second heating is performed in the step of obtaining the sintered body, the crystal precipitation temperature during reheating is +30 to + 100 ° C. of the glass transition point. It is preferable to use the glass powder which is.

  The glass powder preferably has an average particle size of 0.5 to 5.0 μm. A glass powder of 0.5 μm or less is likely to aggregate, which may make it difficult to produce a precursor. On the other hand, the glass powder exceeding 5.0 μm has too large voids in the molded body, so that it may be difficult to eliminate internal pores and bubbles in subsequent sintering. Moreover, it is good also as 1.0-3.0 micrometers more preferably.

  The glass powder may be appropriately determined so that the glass transition point is within the above-described range. Moreover, if it is 50 mass% or less other than glass powder, arbitrary 3rd components may be mixed and a molded object may be formed. For example, functional inorganic fillers and phosphors such as YAG can be used.

  The step of obtaining the precursor is to form the precursor by sintering the molded body by heating, and does not particularly require pressurization. The precursor is obtained by fusing glass powders constituting the molded body by heating, but the precursor scatters light because it is fused while containing pores and bubbles. At this time, the relative density of the precursor is preferably 90 to 96%. When the relative density is less than 90%, it becomes difficult to obtain a dense body having a relative density of 99% or more even after the subsequent sintering step. On the other hand, if it exceeds 96%, the heating time may be long and the production cost may increase. The relative density was measured using the Archimedes method.

  The temperature at the time of sintering should just be a grade which does not produce a crystal | crystallization, for example, is good also as -30- + 50 degreeC with respect to the glass transition point of the glass powder which comprises a molded object.

  In the sintering process, it is preferable to raise the temperature stepwise to the above-described sintering temperature because it is possible to suppress the occurrence of temperature unevenness. When the temperature rise temperature is 1 to 20 ° C./min and the temperature rise time is about 10 to 60 minutes, the precursor can be obtained efficiently.

  The sintering time is a holding time of the sintering temperature, and is preferably 1 to 5 hours. If the holding time is less than 1 hour, the sintering is insufficient and the relative density of the precursor is remarkably lowered, which is not suitable. Further, since the relative density of the precursor becomes constant if sintering is performed for a certain period of time, the upper limit is not particularly limited, but may be, for example, 5 hours or less.

  The step of forming the sintered body is to simultaneously heat and pressurize the precursor by hot isostatic pressing (HIP) or the like to sinter the precursor. The precursor is densely sintered using a medium as a medium.

The mixed gas has oxygen gas and inert gas. Oxygen is preferably contained at 10% by volume or more, more preferably 15% by volume or more. In the absence of oxygen, sintering does not proceed and oxygen is preferably less than 100% by volume for safe production. Further, examples of the inert gas include a rare gas and N ₂ , and Ar is particularly preferably used because it is inexpensive and easily available.

  Moreover, it is preferable that the pressure of mixed gas shall be 100 Mpa or more. If it is less than 100 MPa, the densification may not proceed sufficiently. Moreover, it is good to set it as 200 Mpa or less in order to manufacture safely.

  In the present invention, sintering is performed under high pressure conditions using the above mixed gas. The sintering temperature at this time may be a level at which crystals are not generated as in the case of forming the precursor, but in order to sufficiently sinter, +10 to + 50 ° C. with respect to the glass transition point of the used glass powder. Is preferable.

  Examples of the present invention will be described below.

Example 1
1.5 g of glass powder (glass transition point 470 ° C., average particle size 1.0 μm, product name: B20, manufactured by Central Glass Co., Ltd.) is placed in a mold for uniaxial pressure molding and press molded at 50 MPa to form a molded body. Produced. Next, the obtained molded body was sintered in an air heater at 460 ° C. for 30 minutes using a box furnace heated by an electric heater, in air, with a temperature rising temperature of 10 ° C./min and a temperature rising time of 46 minutes. To obtain a precursor. The relative density was measured about the obtained precursor.

  Next, using the above precursor, a sintered body was produced by a hot isostatic pressing method (hereinafter sometimes referred to as HIP). The pressure sintering apparatus used was a doctor HIP manufactured by KOBELCO. The precursor was placed on a platinum dish and placed in the same apparatus, and after filling a mixed gas containing oxygen gas (20% by volume) and Ar gas (80% by volume) to a pressure of 150 MPa, 490 ° C. Was sintered for 12 hours to obtain a glass sintered body. The relative density was measured about the obtained glass sintered compact. Table 1 shows the relative density and the mixed gas atmosphere during pressure sintering.

Comparative Example 1
A glass sintered body was obtained in the same manner as in Example 1 except that pressure sintering was carried out in Ar gas at 490 ° C. for 2 hours to obtain a sintered body.

Comparative Example 2
A glass sintered body was obtained in the same manner as in Example 1 except that the sintering step for obtaining the precursor was not performed.

In Comparative Example 1 in which sintering was performed in a pure Ar atmosphere, coloring was observed on a part of the glass. Further, in Comparative Example 2 in which the pressure sintering was performed without passing through the precursor, the sintering was insufficient, and pores remained inside the obtained sintered body.

  Since the present invention is a transparent glass sintered body, it can be used as a glass product having a high refractive index. In particular, it is useful as an article requiring a small size, such as a lens or filter of an optical article.

Claims (5)

The step of forming glass powder into a molded body by dry molding, the step of sintering the molded body to obtain a precursor, and the pressure sintering of the precursor in a mixed gas atmosphere of oxygen gas and inert gas A method for producing a sintered body comprising a step of obtaining a sintered body. 2. The method for producing a sintered body according to claim 1, wherein the mixed gas has an oxygen partial pressure of 10% by volume or more. The sintering according to claim 1 or 2, wherein in the step of obtaining the sintered body, pressure sintering is performed at +10 to + 50 ° C for 1 to 20 hours with respect to a glass transition point of the glass powder. Bond manufacturing method. The method for producing a sintered body according to any one of claims 1 to 3, wherein a relative density of the precursor is 90 to 96%. A glass sintered body obtained from the method for producing a sintered body according to any one of claims 1 to 4.