JP2002128563A - Ceramic member for thermal treatment which has good thermal shock resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous ceramic member for thermal treatment which has good thermal shock resistance. SOLUTION: This is a ceramic member for thermal treatment consisting of an alumina sintered material composed of Al2O3 of 95 wt.% or more and MgO of 0.3 wt.% or less. The alumina sintered material is characterized by (a) its pores being practically closed, (b) its average closed pore size of 2-50 μm, (c) its average crystal size of 5-50 μm, (d) its average closed pore size/ average crystal size of 0.1-6 and (e) its relative density of 70-95%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ceramic heat treatment member which is a sintered body selected from the group consisting of alumina, magnesia and spinel having excellent thermal shock resistance. Note that the heat treatment member according to the present invention includes electronic component materials such as piezoelectrics and dielectrics, lithium ion 2
Container for heat treatment of secondary battery positive electrode material, phosphor material and ceramic material, crucible for growing single crystal, crucible for melting metal,
Core tubes for various electric furnaces, support tubes, radiant tubes, gas injection tubes, gas sampling tubes, thermocouples for temperature measurement, protective tubes for various devices, support jigs, and the like.

[0002]

2. Description of the Related Art Alumina, magnesia, and spinel sintered bodies have excellent corrosion resistance and heat resistance, are inexpensive and easy to handle compared to other ceramics, and have been used since ancient times for high temperature members and heat treatment containers. It is used in a wide range of fields, such as, setters, furnace tubes, and protective tubes for temperature measurement.

In recent heat treatments of electronic materials and phosphor materials, such as cathode materials for lithium secondary batteries, in order to minimize evaporation components and to reduce fluctuations in composition,
In addition, rapid heating and cooling treatments are performed to increase production efficiency. Although the heat treatment member made of a dense sintered body is excellent in corrosion resistance, it has a risk of cracking due to thermal shock when the temperature is rapidly increased or decreased. On the other hand, a porous heat treatment member has a higher thermal shock resistance than a dense member but lacks airtightness, and the components in the heat treatment member may be mixed as impurities into the heat-treated material or may be mixed. The composition of the heat-treated material changes due to reaction with the heat-treated material, and the components evaporating from the heat-treated material are adsorbed or reacted with the heat-treating member by the heat treatment, resulting in a decrease in corrosion resistance and a decrease in mechanical properties. The problem has arisen.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic heat treatment member having excellent thermal shock resistance.

[0005]

SUMMARY OF THE INVENTION The present invention has been intensively studied in view of the above situation, and as a result, alumina, magnesia and spinel sintered bodies have a specific relative density and a roundness. Excellent thermal shock by controlling the closed pore size and crystal grain size, controlling the ratio of the closed pore size and crystal grain size, and controlling the relative density of the sintered body. A heat treatment member made of an alumina, magnesia and spinel sintered body having resistance has been found. In the present invention, the thermal shock resistance means not only resistance to cracking and cracking due to rapid heating and rapid cooling, but also durability due to repeated heating and cooling.

A first aspect of the present invention is that the Al ₂ O ₃ content is 95%.
(A) the pores are substantially sealed, and (b) the average airtightness of the sintered body. Hole diameter 2-5
0 μm, (c) the average crystal grain size of the sintered body is 5 to 50 μm,
(D) The average closed pore diameter / average crystal grain diameter of the sintered body is 0.1
And (e) a ceramic heat treatment member comprising an alumina sintered body, wherein the relative density of the sintered body is 70 to 95%.

[0007] In the present invention, the formation of the closed pores is carried out by using organic spherical particles such as acrylic resin spherical particles and polysaccharide spherical particles as pore forming agents so that the pulverized / dispersed slurry has a predetermined relative density and a predetermined pore diameter. It is necessary to use such organic and rounded particles. When this pore-forming agent is added to the ceramic powder, mixed and molded, and then fired, the organic pore-forming agent is burned off, leaving closed pores as traces. The shape becomes a shape based on the shape of the forming agent, and the pores are rounded and sealed as shown in FIGS. 1 (A) and 1 (B) as defined in (a) of the claim (1). The pores are substantially independent. When the pore shape is not rounded, stress is easily applied to the pores when a stress is applied to the sintered body, which is not preferable because the strength is reduced and further the thermal shock resistance is reduced. The term “closed pores” as used in the present invention refers to internal pores that are not communicated to the outside, and the relative density is (bulk density of sintered body /
It represents the value calculated by (theoretical density) × 100 (%).

In the present invention, the average closed pore diameter of (b) needs to be 2 to 50 μm, preferably 5 to 30 μm, more preferably 5 to 25 μm or less. When the average closed pore diameter is less than 2 μm, the effect of improving the thermal shock resistance by forming pores is small, and when the average closed pore diameter exceeds 50 μm, the closed pores become continuous or the strength is lowered, which is not preferable. The average closed pore diameter was obtained by polishing the sintered body to a mirror finish, observing it with a scanning electron microscope, measuring the pore diameter of 100 pores, finding the average value: P,

## EQU1 ## The average closed pore diameter is determined as 1.5 × P.

In the present invention, the average crystal grain size of the sintered body (c) needs to be 5 to 50 μm. An average crystal grain size of less than 5 μm is not preferred because not only the durability is lowered but also the corrosion resistance is lowered. On the other hand, 50
If it exceeds μm, the thermal shock resistance is undesirably reduced. Preferably it is 10 to 40 μm. The average crystal grain size is determined by mirror finishing the sintered body, performing thermal etching, observing it with a scanning electron microscope, and averaging 10 points by an intercept method. The calculation formula is

D = 1.5 × L / n [D: average crystal grain size (μm), L: measured length (μm),
n: the number of crystals per length L].

In the present invention, the relative density of (e) is 70
９５95%, more preferably 75%
It needs to be ~ 90%. When the relative density is less than 70%, the amount of pores increases, and the pores are connected to each other to increase the diameter of the closed pores, which is not preferable because the strength and the corrosion resistance are reduced. On the other hand, if the relative density exceeds 95%, the thermal shock resistance decreases, which is not preferable.

In the present invention, when the sintered body is an alumina-based sintered body, the alumina content needs to be 95% by weight or more. If the alumina content is less than 95% by weight, the amount of impurities contained in the alumina-based sintered body increases, the second phase and the glass phase formed by impurities at the crystal grain boundaries increase, and only the corrosion resistance decreases. Rather, the mechanical properties, particularly the strength and toughness at high temperatures, are reduced, and as a result, the thermal shock resistance is reduced, which is not preferable. The alumina content is preferably 97% by weight or more, more preferably 99% by weight or more.

In the case of the alumina sintered body of the present invention, it is necessary that MgO be contained in an amount of 0.3% by weight or less based on the alumina sintered body. This has the effect of improving the sinterability and increasing the uniformity of the crystal grain size. Furthermore, when zirconia or MgO is contained, strength deterioration under a reducing atmosphere can be suppressed. It is more preferably at most 0.25% by weight. If MgO is contained in an amount of 0.3% by weight or more, the second phase is likely to precipitate at the alumina crystal grain boundary, and the thermal shock resistance and the durability are poor.

A second aspect of the present invention is a magnesia-based sintered body having an MgO content of 95% by weight or more, wherein (a) the pores are substantially closed, and (b) the sintered body is Average closed pore diameter 2-50 μm, (c) average crystal grain size 5 of the sintered body
５０50 μm, (d) average closed pore diameter / average crystal grain diameter of sintered body is 0.1-6, (e) relative density of sintered body is 70-95
%, Which relates to a ceramic heat treatment member comprising a magnesia sintered body.

In the present invention, when the sintered body is a magnesia sintered body, the MgO content needs to be 95% by weight or more. When the MgO content is less than 95% by weight, the amount of impurities contained in the magnesia sintered body increases, the second phase and the glass phase formed by impurities at the crystal grain boundaries increase, and only the corrosion resistance decreases. Rather, the mechanical properties, particularly the strength and toughness at high temperatures, are reduced, and as a result, the thermal shock resistance is reduced, which is not preferable. The magnesia content is preferably 97% by weight or more, and more preferably 99% by weight or more.

A third aspect of the present invention is that Al ₂ O ₃ / MgO (weight ratio) is 60/40 to 80/20, and Al ₂ O ₃ and MgO are mixed.
(A) the pores are substantially sealed, (b) the average closed pore diameter of the sintered body is 2 to 50 μm,
(C) the average crystal grain size of the sintered body is 5 to 50 μm, (d) the average closed pore diameter / average crystal grain size of the sintered body is 0.1 to 6,
(E) The present invention relates to a ceramic heat treatment member comprising a spinel sintered body, wherein the relative density of the sintered body is 70 to 95%.

In the present invention, when the sintered body is a spinel sintered body, the weight ratio of Al ₂ O ₃ / MgO is 60/4.
0-80 / 20, more preferably 65 / 35-75 / 2
5, and the total content of Al ₂ O ₃ and MgO is 95% by weight or more, preferably 97% by weight.
And more preferably 99% by weight or more. Al ₂ O ₃ / MgO weight ratio of 60/40
If it is less than 1, the amount of MgO crystals in the spinel sintered body increases, and the corrosion resistance and mechanical properties, particularly thermal shock resistance and thermal fatigue properties, are unfavorably reduced. Thus, Al ₂ O ₃ / Mg
If the O weight ratio exceeds 80/20, A in the spinel sintered body
The amount of l ₂ O ₃ crystals increases, and the thermal expansion difference between the spinel crystals and the alumina crystals undesirably lowers the thermal shock resistance and the corrosion resistance. Al ₂ O ₃ and Mg
When the total content with O is less than 95% by weight, impurities in the spinel-based sintered body increase, the second phase and the glass phase formed by impurities at the crystal grain boundaries increase, and only the corrosion resistance decreases. In addition, the mechanical properties, especially the high-temperature strength, are not preferred because the thermal shock resistance decreases.

Regardless of whether the sintered body of the present invention is alumina-based, magnesia-based or spinel-based, the sintered body of the present invention contains zirconia in an amount of 5% by weight or less, more preferably 3% by weight or less. preferable. The zirconia crystal grain size is preferably 0.5 μm or less. Zirconia is important not only for improving the strength and toughness of the alumina, magnesia or spinel sintered body, but also for improving the sinterability and forming a microstructure with a small grain size distribution. When the zirconia content exceeds 5% by weight or when the crystal grain size is 0.5 μm
In the case of exceeding, the heating and cooling are repeated, cracks are generated in the sintered body due to the residual expansion due to the difference in thermal expansion between zirconia and alumina, magnesia or spinel, which is not preferable because of poor durability.

In the first to third aspects of the present invention, it is necessary that (d) the average closed pore diameter / average crystal grain diameter of the sintered body is from 0.1 to 6, especially from 0.2 to 5. Preferably, there is. When the average closed pore diameter / average crystal grain size is less than 0.1, the effect on the thermal shock resistance due to the presence of the closed pores is undesirably reduced. On the other hand, if the average closed pore diameter / average crystal grain size exceeds 6, the closed pore size becomes too large compared to the crystal grain size, resulting in a decrease in strength. It is not preferable because the erosion of the components is increased and the corrosion resistance is reduced.

The heat-treating member of the present invention having excellent thermal shock resistance can be produced by various methods, one example of which is shown below.

The raw material powder has a purity of 99% or more (in the case of spinel, the total weight of Al ₂ O ₃ + MgO is 99% or more);
The average particle size is preferably 2 μm or less, more preferably 1.5 μm or less. When the average particle size exceeds 2 μm, many defects are present inside the sintered body, and the mechanical properties such as thermal shock resistance are deteriorated.

The zirconia raw material powder may be a liquid phase
It is preferable to use a powder produced by the method
Product is 5m²/ G or more, more preferably
7m ²/ G or more. Furthermore, zirconia sol and baking
Zirconium compounds (zirconia
Can be used. Zirconia raw material powder
Specific surface area is 5m²/ G or less, zirconia crystal grains
Not only reduces the dispersibility of the
Thermal shock resistance and corrosion resistance due to large luconia crystal particles
It is not preferable because the property is lowered. In addition, zirconia
More preferably, the grit contains 1 to 5 mol%.
No.

The SiO ₂ and TiO contained in the sintered body
₂ , the total content of Fe ₂ O ₃ , CaO, Na ₂ O and K ₂ O is preferably at most 2% by weight, more preferably at most 1% by weight. If the amount of impurities exceeds 2% by weight, a large amount of the second phase and the glass phase are formed at the crystal grain boundaries, and the high-temperature characteristics are deteriorated.

When zirconia is added to alumina, magnesia, or spinel, the zirconia is blended with each raw material powder so that the zirconia content is a predetermined amount, and water or an organic solvent is used as a solvent, and a pot mill or an aluminum solvent is used. It is pulverized, dispersed and mixed by a pulverizer such as a trission mill.

The average particle size of the powder obtained as described above needs to be 1.5 μm or less, more preferably 1.0 μm or less. If the particle size is outside these ranges, the formability is reduced, and not only the obtained sintered body has many defects but also the sintered body having the microstructure of the present invention cannot be obtained, This is not preferred because not only the properties are reduced, but also other mechanical properties and corrosion resistance are reduced.

When MgO is added to alumina, it may be added in the form of a magnesia compound such as hydroxide or carbonate at the time of pulverization, dispersion, and mixing, or powder previously added to alumina raw material powder may be used. good.

When a molding method such as press molding or rubber press molding is employed, if necessary, a known molding aid (eg, wax emulsion, PVA, acrylic resin, etc.) is added to the pulverized / dispersed slurry and sprayed. It is dried by a known method such as a drier to produce a molding powder, and molded using this. When the casting method is adopted, a known binder (for example, wax emulsion, acrylic resin, etc.) is added to the pulverized / dispersed slurry as necessary, and the slurry is cast and filled using a plaster type or a resin type. It is formed by casting and pressure casting. Furthermore, when the extrusion molding method is adopted, the slurry that has been pulverized and dispersed is dried, sized, and water and a binder (eg, methyl cellulose or the like) are mixed using a mixer to prepare a kneaded material, and the extrusion molding is performed. I do. The molded body obtained as described above was
00 to 1800 ° C, more preferably 1600 to 1750
A sintered body is obtained by firing at ℃.

[0027]

The present invention will be described below with reference to examples.
The present invention is not limited thereby.

Examples 1-22 and Comparative Examples 1-22 Alumina having a purity of 99.5% and an average particle diameter of 2 μm,
When zirconia was added to magnesia or spinel powder, a predetermined amount of zirconia powder was blended and ground, dispersed, and mixed in a pot mill using water or ethanol as a solvent to prepare a slurry. In addition, when adding magnesia to alumina, a predetermined amount of magnesium carbonate is blended,
It carried out similarly to the case where zirconia powder was added. As the pore-forming agent, spherical particles of acrylic resin or spherical particles of polysaccharide were added and mixed so as to have predetermined porosity and pore diameter.

The zirconia powder is prepared by adding Y ₂ O ₃ to 0-5.
A powder containing 0.1 mol% and having a specific surface area of 15 m ² / g was used. The resulting slurry is cast using a gypsum mold and fired at 1450-1800 ° C.
A square heat treatment container having a square shape of mm and a height of 50 mm was prepared. Table 1 shows the characteristics of the sintered body of the obtained heat treatment container.
It is shown in FIG. To check the thermal shock resistance of the obtained heat treatment container, 500 g of 40-mesh fused alumina powder was put into the obtained heat treatment container, and the lid was put into an electric furnace kept at a predetermined temperature. After heating for 30 minutes, the product was immediately taken out of the furnace, rapidly cooled at room temperature, and the thermal shock resistance was evaluated based on the presence or absence of cracks. In addition, in the case of alumina, evaluation was made on the presence or absence of cracks due to repetition at 600 ° C under the same conditions as described above, and in the case of magnesia and spinel at 500 ° C.

Comparative Example 1 deviates from the requirements of the present invention in terms of MgO content, Comparative Example 2 deviates from the requirements of the present invention in terms of Al ₂ O ₃ content, and Comparative Example 3 departs from the requirements of the present invention. Comparative Example 4 deviated from the requirements of the present invention in terms of average crystal grain size.
Deviates from the requirements of the present invention in terms of the average closed pore diameter, Comparative Example 5 deviates from the requirements of the present invention in terms of the content of Al ₂ O ₃ and zirconia, and Comparative Example 6 departs from the average. The requirements of the present invention are deviated in terms of crystal grain size, and Comparative Example 7
(Average closed pore diameter) / (Average crystal grain size) deviates from the requirements of the present invention, Comparative Example 8 deviates from the requirements of the present invention in terms of relative density, and Comparative Example 9 shows a relative density. The requirements of the present invention are deviated in terms of density, and Comparative Example 10 is deviated from the requirements of the present invention in terms of continuous pores, and Comparative Example 11
Deviates from the requirements of the present invention in terms of relative density, Comparative Example 12 deviates from the requirements of the present invention in terms of zirconia content, and Comparative Example 13 departs from the average crystal particle diameter and the average airtightness. The requirement of the present invention is deviated in terms of (pore diameter) / (average crystal grain size), Comparative Example 14 is deviated from the requirement of the present invention in terms of relative density, and Comparative Example 15 is deemed in terms of MgO content. Comparative Example 16 deviates from the requirements of the present invention in terms of the average closed pore diameter, and Comparative Example 16 deviates from the requirements of the present invention.
No. 7 does not satisfy the requirements of the present invention in terms of Al ₂ O ₃ / MgO (weight ratio), and Comparative Example 18 has a zirconia content and (average closed pore diameter) / (average crystal grain size). The requirements of the present invention are deviated, Comparative Example 19 deviates from the requirements of the present invention in terms of relative density, and Comparative Example 20 is formed of Al ₂
The requirement of the present invention is deviated in terms of the total amount of O ₃ and MgO, Comparative Example 21 is deviated from the requirement of the present invention in terms of the average crystal grain size, and Comparative Example 22 is devoid of Al ₂ O ₃ / Comparative Example 23 was out of the requirement of the present invention in terms of MgO (weight ratio).
Deviate from the requirements of the present invention in terms of relative density. It is clear that the heat treatment member of the present invention has excellent thermal shock resistance and excellent durability.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

The heat-treating member of the present invention is excellent in thermal shock resistance and corrosion resistance, and thus heat-treats electronic component materials such as piezoelectrics and dielectrics, lithium ion secondary battery positive electrode materials, phosphor materials and ceramic materials. Containers, crucibles for growing single crystals, crucibles for melting metals, furnace tubes for various electric furnaces, support tubes, radiant tubes, gas injection tubes, gas sampling tubes, thermocouples for temperature measurement, protective tubes for various devices, and support It is useful for jig materials.

[Brief description of the drawings]

FIG. 1 (A) is a microstructure photograph of one sample of the ceramic heat treatment member of the present invention, and FIG. 1 (B) is a diagram showing the pore distribution state of one sample of the ceramic heat treatment member of the present invention. Show.

Continued on the front page (72) Inventor Toshio Kawanami 3-2-2, Enri-Onocho, Sakai-shi, Osaka F-term in Nikkato Co., Ltd. 4G030 AA07 AA12 AA17 AA37 BA01 BA09 BA10 BA21 BA23 BA28

Claims (4)

[Claims] An Al ₂ O ₃ content of 95% by weight or more,
An alumina-based sintered body having a MgO content of 0.3% by weight or less, wherein (a) its pores are substantially closed; (b) the average closed pore diameter of the sintered body is 2 to 50 μm;
(C) the average crystal grain size of the sintered body is 5 to 50 μm, (d) the average closed pore diameter / average crystal grain size of the sintered body is 0.1 to 6,
(E) A ceramic heat treatment member comprising an alumina-based sintered body, wherein the relative density of the sintered body is 70 to 95%. 2. A magnesia-based sintered body having an MgO content of 95% by weight or more, wherein (a) its pores are substantially closed, and (b) an average closed pore diameter of the sintered body. ~ 5
0 μm, (c) the average crystal grain size of the sintered body is 5 to 50 μm,
(D) The average closed pore diameter / average crystal grain diameter of the sintered body is 0.1
(E) A ceramic heat treatment member comprising a magnesia sintered body, wherein the relative density of the sintered body is 70 to 95%. 3. An Al ₂ O ₃ / MgO (weight ratio) of 60 /
40 to 80/20, a spinel sintered body having a total content of Al ₂ O ₃ and MgO of 95% by weight or more,
(A) the pores are substantially sealed; (b)
Average sintered pore diameter of the sintered body is 2 to 50 μm, (c) average crystal grain size of the sintered body is 5 to 50 μm, (d) average closed pore diameter / average crystal grain size of the sintered body is 0.1 to 6, (E) A ceramic heat treatment member comprising a spinel sintered body, wherein the relative density of the sintered body is 70 to 95%. 4. The ceramic heat treatment member according to claim 1, wherein zirconia is contained in an amount of 5% by weight or less.