JP2003012382A - Method of manufacturing porous compact and porous compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous compact of high productivity, needless of long time heat treatment, and having uniform density in thickness direction. SOLUTION: This porous compact is characterized in that the porous compact is a sintered compact containing Mg, Al, and Si, the crystal phase of which has diffraction peaks 1, 2, at 2θ is 24.6-24.8 deg. and 24.7-24.9 deg., the coefficient of thermal expansion at 0-25 deg.C is 0-3×10<-6> / deg.C, the specific gravity is <=2.0, and the porocity is 25-80 vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous body which can be widely used in various industrial fields such as a machine tool, a precision machine, an evaluation device, and a semiconductor manufacturing device, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Metals have been frequently used for members used for mechanical structural parts and the like. However, in recent years, since properties such as lightweight, high rigidity, high hardness, and low thermal expansion of ceramics are superior to metals, oxides such as Al ₂ O ₃ , S
The use of ceramics such as carbides such as iC and nitrides such as Si ₃ N ₄ is increasing.

[0003] In particular, in various industrial fields, the weight reduction of structural members is a modern trend. For example, in a moving structure such as a stage device, the lighter the lighter, the faster the movement can be made. The load can be reduced, and the lighter the weight, the lower the inertia force and the higher the controllability. Therefore, weight reduction of the members is strongly required.

[0004] Even ceramics such as silicon nitride and silicon carbide alumina, which are generally lighter than metals and have higher rigidity, have a specific gravity of 3 or more, and it is difficult to further reduce the weight.

[0005] In order to solve such a problem of weight reduction, pores are contained therein to reduce the weight. For example, after a ceramic powder is preliminarily mixed with a particulate or bead-shaped organic material and molded, or after a ceramic powder slurry is carried on an organic material on a sponge, the organic material is simultaneously fired by firing. Japanese Patent Application Laid-Open No. 6-247778 describes that lightweight ceramics are produced by burning and burning to form pores.

Further, a foaming agent is added to a ceramic powder slurry, foamed, cast, dried, degreased, and fired to produce a lightweight ceramic having a porous sintered body and a dense surface layer. JP-A 5-310
No. 482.

[0007]

However, the method for manufacturing lightweight ceramics described in Japanese Patent Application Laid-Open No. Hei 6-247778 uses a sponge or a foaming agent, and removes a large amount of organic substances mixed in ceramic powder by burning. Therefore, there is a problem that a long heat treatment is required.

In the method for producing lightweight ceramics described in Japanese Patent Application Laid-Open No. Hei 5-310482, the pores are inclined and oriented, because the slurry is cast using a foaming agent.
There is a problem that unevenness in density occurs in the thickness direction. Also, there is a problem in productivity such as difficulty in controlling bubbles in the slurry even in the internal porous body, leading to an increase in cost.

Therefore, a light-weight, low-thermal-expansion porous body and a porous body having a uniform density can be provided by a highly productive production method which does not require a long-term heat treatment without using any special organic substance. The purpose is to:

[0010]

Means for Solving the Problems The porous body of the present invention can be easily formed into a homogeneous, lightweight, low-thermal-expansion porous body by using a raw material containing nitride and controlling the firing temperature to cause self-foaming. Based on the finding that it can be obtained.

That is, the method for producing a porous body according to the present invention comprises the steps of: providing a cordierite powder, at least one nitride powder of a group consisting of Mg, Al and Si and a non-nitride element of the group of elements; A powder comprising at least one of oxides, hydroxides, and carbonates, and a molded body in which Mg, Al, and Si have a substantially cordierite composition in terms of oxides are prepared.
It is characterized by firing at 50 ° C. to 1500 ° C., and does not require a large amount of organic matter degreasing step, and can form a good foamed structure with high productivity. Further, since self-foaming is used, it is not particularly necessary to control bubbles in the slurry even in the internal porous body, so that the porous body can be obtained at low cost.

In particular, it is preferable to perform firing in a substantially non-oxidizing atmosphere. Thereby, rapid decomposition of the nitride in the raw material powder can be suppressed, and the formed amorphous phase contains nitrogen, and the rigidity can be increased.

Further, X, which contains Mg, Al and Si elements,
By line diffraction, 2θ was 24.6 to 24.8 °, 24.7.
It contains a crystal phase having two main diffraction peaks at 〜24.9 ° and a coefficient of thermal expansion at 0 ° C. to 25 ° C. of 0 to 3 × 10 ⁻⁶ /.
C., specific gravity of 2.0 or less, and porosity of 25 to 80% by volume. This makes it possible to realize a porous body in which pores are uniformly distributed and density unevenness is small.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for producing a porous body according to the present invention will be described.

First, cordierite powder adjusted to a particle size of 1 to 6 μm is prepared. The amount of cordierite to be added is preferably 80% by weight or less, particularly preferably 70% by weight or less, and more preferably 60% by weight or less, in order to contain the following nitrides for stable and sufficient foaming.

Further, at least one kind of nitride powder of Mg, Al and Si element groups of 2 μm or less and oxides, hydroxides, AlON,
It is important to prepare a powder consisting of at least one of the carbonates. By adding the nitride, it is possible to foam at a relatively low temperature and to distribute the bubbles uniformly.

For example, if Mg, Al and Si are compounds other than cordierite and contain nitrides,
It can be used in a combination of gO powder, Al ₂ O ₃ powder and Si ₃ N ₄ powder. Other nitrides include MgN, A
1N and SiAlON, MgOH as a hydroxide, and MgCO ₃ as a carbonate.

Among the raw materials used for producing the porous body, raw materials excluding cordierite powder, ie, Mg, Al and Si
It is important that Mg, Al and Si have a substantially cordierite composition in terms of oxide in the powder containing. For example, Mg
The ratio of O: Al ₂ O ₃ : SiO ₂ is 1-3: 1-3: 4-6
Is preferable in that good foaming is obtained.

Next, the above powders are mixed. For the mixing, a known mixing and pulverizing method such as a ball mill, a mixer, and a bead mill can be used. The obtained mixed powder is formed into a desired shape. As a molding method, a known molding method such as die pressing, casting, CIP or the like can be used.

It is important that the obtained molded body is fired at 1350 to 1500 ° C. If it is lower than 1350 ° C., the self-foaming is insufficient, and if it exceeds 1500 ° C., it completely melts. Since the size of the voids at the time of foaming becomes uniform and sufficient pores are generated, especially at 1360 to 1450 ° C,
Further, the temperature is preferably 1370 to 1420 ° C.

The firing is preferably performed in a non-oxidizing atmosphere such as an inert atmosphere or a reducing atmosphere in order to form a good foamed structure. In particular, firing in an inert gas such as nitrogen, hydrogen, an ammonia decomposition gas, or Ar, or a mixed gas thereof is preferable. Among them, nitrogen and a mixed gas of nitrogen and hydrogen are preferable in terms of improving characteristics, safety and reducing costs. When a mixed gas of nitrogen and hydrogen is used, the amount of hydrogen gas is preferably 5 to 20% for safety.

When firing is performed in an atmosphere containing oxygen,
According to X-ray diffraction, neither diffraction peak 1 at 2θ of 24.6 to 24.8 ° nor diffraction peak 2 at 24.7 to 24.9 ° was observed, and there was a tendency to form cordierite. In addition,
Even in an atmosphere containing oxygen, the molded body may be simulated to be a reducing atmosphere by firing by burying the molded body in carbon powder or the like and converting the oxygen around the molded body into carbon oxide. .

Further, by firing in a non-oxidizing atmosphere such as an inert atmosphere or a reducing atmosphere, rapid decomposition of nitrides is suppressed, and the formed amorphous phase contains nitrogen and has high rigidity. There is also an effect that a porous body can be obtained.

According to the above-mentioned manufacturing method, it is possible to manufacture a porous body having a uniform density, a simple control of bubbles, and a high productivity.

The porous body of the present invention can be produced by the above method, and has a small atomic weight as a constituent element.
It is important that Mg, Al, and Si elements that can obtain low-density ceramics are mainly contained, and that these exist as a crystalline phase in the sintered body. This crystalline phase is C
According to X-ray diffraction using a u-tube, 2θ was 24.6 to 2
The diffraction peak 1 is located at 4.8 ° from 24.7 to 4.9 °.
The diffraction peak 2 can be observed at the position.

Although these crystal phases are unknown crystal phases that have not been reported on the JCPDS card, the formation of these crystals makes it possible to obtain a porous ceramic having good foaming properties. If this crystal phase does not substantially exist, cordierite is the main component, and there is a problem that sintering is not performed in the shape of a molded body, and foaming does not occur or foaming is insufficient.

FIGS. 1 to 3 show examples of the above two diffraction peaks. FIG. 1 shows that the diffraction peak 1 and the diffraction peak 2 are main, that is, the maximum peak intensity. FIG. 2 shows a case where the intensity of the diffraction peak 1 and the intensity of the diffraction peak 2 are moderate, and the other maximum peak is observed. The maximum peak in FIG. 2 was cordierite. FIG. 3 shows the case where the intensity of the diffraction peak 1 and the diffraction peak 2 is small, but the self-foaming was sufficient.

According to the X-ray diffraction, 2θ is 20 to
Third diffraction peak broad at 40 ° (Diffraction peak 3)
Is observed. This diffraction peak 3 also contributes to foaming. Although difficult to recognize in FIGS. 1 to 3, the diffraction peak 3 can be observed by measuring the main peak off the vertical axis so as to observe the minute peak.

If a diffraction peak is observed at the above angle,
Since the foaming property is sufficiently ensured, another diffraction peak may be present. Such diffraction peaks include cordierite (Mg ₂ Al ₄ Si ₅ O ₁₈ ), sapphirine ((Mg ₄ Al ₄ ) (Al ₄ Si ₅ ) O ₂₀ , (Al ₅ Mg ₄ )
Compound phases such as (Al ₄ Si ₂ ) O ₂₀ ) and Al ₂ Re ₄ O ₉ (where Re represents a rare earth) and additive phases such as unreacted silicon nitride, aluminum nitride, and alumina can be exemplified.

In order to promote sinterability, alkaline earth metal compounds (CaO, CaCO ₃ ), rare earth metal compounds (Yb ₂ O ₃ , Y ₂ O ₃ , Er ₂ O ₃ , Sm ₂ O _3, etc.) May be added in the range of 0.1 to 10% by weight. Among these, the rare earth oxides Yb ₂ O ₃ , Y ₂ O ₃ and Sm ₂ O ₃ are preferable in terms of water resistance and chemical stability. If the rare earth is added, the composition becomes dense, and if the rare earth does not exist, it does not sinter, and as a result, a foam cannot be obtained.

The thermal expansion coefficient at 0 ° C. to 25 ° C. is 0 to 3
× 10 ^{- 6} / a is important that ° C., especially 0 to 2 ×
10 ^-6 / ° C., and more preferably 0~1 × 10 ^-6 / ℃. When the coefficient of thermal expansion is reduced in this way, deformation of equipment and machinery used near normal temperature can be suppressed to a small extent, so that accurate parts can be manufactured and precise measurement can be performed. If it exceeds 3 × 10 ⁻⁶ / ° C., the deformation of the member due to changes in the environment will increase.

Further, it is important that the specific gravity is 2.0 or less, so that a moving structure such as a stage device can be made lighter, can be moved faster, and a load on a driving source can be reduced. It is possible to reduce the inertia force and obtain a structure with high controllability. In terms of weight reduction,
In particular, it is preferably 1.8 or less, more preferably 1.5 or less, and more preferably 1 or less.

When the porosity is 25 to 80% by volume, sufficient weight reduction can be achieved.

When the specific gravity exceeds 2.0 or when the porosity is 2
When the volume is less than 5% by volume, the weight is not sufficiently reduced, and particularly when there is a driving unit such as a stage, a problem occurs that a large load is applied to the driving motor. Further, when the porosity exceeds 80% by volume, it is easily broken even by a slight impact.

The porous body having such a structure has features of light weight and low thermal expansion, and can be used for machine tools, precision machines,
It can be suitably used for lightweight ceramic members in various industrial fields such as evaluation devices and semiconductor manufacturing devices.

[0036]

EXAMPLE 2 μm cordierite powder having a purity of 99.8% after synthesis, Mg (OH) ₂ powder _, MgCO ₃ powder, MgO powder, Al ₂ O ₃ powder, AlN powder having an average particle diameter of 2 μm or less.
Powder, SiO ₂ powder, SiC powder, Si ₃ N ₄ powder, Yb ₂ O ₃ powder having an average particle size of 2 μm or less as a sintering aid, Y
₂ O ₃ powder and Sm ₂ O ₃ powder were adjusted to the ratio shown in Table 1,
The mixture was mixed for 24 hours in a mill containing IPA as a solvent and wear-resistant alumina balls as a mixed medium. The average particle size of the obtained mixed powder was 2 μm. Thereafter, paraffin wax was added to obtain a granulated powder, which was molded at 98 MPa.

The obtained compact was heat-treated in a nitrogen stream at 250 ° C. for 2 hours, and then placed on a Mo metal plate and calcined under normal pressure under the conditions shown in Table 1.

Sample No. 25 is H ₂ and CH ₃ S
Silicon carbide was produced by thermal CVD at 1400 ° C. using iCl ₃ .

The surface layer of the obtained sample was polished, the dimensions were measured using calipers and a micrometer, and the weight was measured to calculate the specific gravity. The porosity was determined by a mercury intrusion method. The obtained porous body was crushed in a mortar and subjected to X-ray diffraction at 2θ from 20 ° to 80 ° using a Cu tube, a tube voltage of 50 kV, a tube current of 200 mA, and a step width of 0.02. °, counting time 0.5s
ec. The coefficient of thermal expansion is TAS-20 manufactured by Rigaku Corporation.
The elongation of the sample at 0 to 100 ° C. was measured by the TMA method using a zero measuring device, and the coefficient of thermal expansion at 0 to 25 ° C. was calculated.
The results are shown in Tables 1 and 2.

[0040]

[Table 1]

[0041]

[Table 2]

Sample No. of the present invention 1-4, 7-13, 1
5, 16, 18 to 24 have diffraction peaks 1 and 2 at 24.6 to 24.8 ° and 24.7 to 24.9 °, and diffraction peak 3 is broadly observed at 20 to 40 °. The specific gravity was 1.95 or less, the porosity was 25 to 71% by volume, and the coefficient of thermal expansion was 0.51 to 2.46 × 10 ⁻⁶ / ° C. In each of the above samples, the pore distribution was uniform and the specific gravity did not substantially vary.

On the other hand, Sample No. out of the scope of the present invention using only cordierite as a raw material was used. In No. 5, a peak of only cordierite was observed in the X-ray diffraction, and 24.6 to 24.
No diffraction peaks were observed at 8 ° and 24.7 to 24.9 °.

Further, Sample No. which does not contain nitrides and is out of the scope of the present invention. In No. 6, a peak of cordierite alone was observed in X-ray diffraction, and no diffraction peak was observed at 24.6 to 24.8 ° and 24.7 to 24.9 °.

Further, Sample No. having a firing temperature as low as 1335 ° C., which is out of the range of the present invention. 14 had a low porosity of 17% by volume and a high specific gravity of 2.13.

Further, Sample No. having a firing temperature as low as 1550 ° C., which is out of the range of the present invention. In No. 17, the sample was melted.

In addition, Sample No. out of the range of the present invention consisting of silicon carbide was used. ^{Sample No.} 25 had a large coefficient of thermal expansion of 3.5 × 10 ⁻⁶ / ° C.

[0048]

According to the present invention, in addition to the cordierite powder, at least one of the group consisting of Mg, Al and Si is used.
By sintering at 1350 to 1500 ° C. using a raw material containing a kind of nitride powder and a powder of at least one of oxides, hydroxides and carbonates of elements other than nitride, A light-weight, low-thermal-expansion porous body is obtained.

The porous body of the present invention has a coefficient of thermal expansion at 0 to 25 ° C. of 0 to 3 × 10 ⁻⁶ / ° C., a specific gravity of 2.0 or less, and a porosity of 25 to 80% by volume. In addition, it has a feature of low thermal expansion, and can be suitably used for lightweight ceramic members in various industrial fields such as machine tools, precision machines, evaluation devices, and semiconductor manufacturing devices.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction spectrum of a porous body of the present invention.

FIG. 2 is another X-ray diffraction spectrum of the porous body of the present invention.

FIG. 3 is another X-ray diffraction spectrum of the porous body of the present invention.

[Explanation of symbols]

1, 11, 21 ... diffraction peak 1 2, 12, 22 ... diffraction peak 2 14, 24 ... diffraction peaks of other crystals

Continuation of front page    F-term (reference) 4G001 BA01 BA03 BA06 BA08 BA09                       BA22 BA32 BA36 BA42 BB01                       BB22 BB32 BB36 BB42 BD05                       BD11 BD38 BE01 BE31                 4G019 GA02 GA04                 4G030 AA07 AA36 AA37 AA51 AA52                       CA01 CA09 GA24 GA27

Claims (3)

[Claims] 1. A cordierite powder comprising Mg, Al and S
i. a powder comprising at least one nitride powder of the element group and at least one of oxides, hydroxides, and carbonates of other elements that are not nitrides in the group of elements;
A method for producing a porous body, characterized by firing a molded body in which Al and Si have a substantially cordierite composition in oxide conversion at 1350 ° C to 1500 ° C. 2. The method for producing a porous body according to claim 1, wherein the firing is performed in a substantially non-oxidizing atmosphere. 3. It contains Mg, Al and Si, and has 2θ of 24.6 to 24.8 ° and 24.7 to 2 by X-ray diffraction.
It consists of a sintered body containing a crystal phase having two main diffraction peaks at 4.9 °, and has a thermal expansion coefficient of 0 to 3 at 0 to 25 ° C.
× 10 ^-6 / ° C, specific gravity of 2.0 or less, porosity of 25 to 80
A porous body characterized by volume%.