KR20130132983A - Alumina conjugate and bonding method for alumina sintered bodies - Google Patents

Abstract

The alumina sintered bodies are the alumina conjugates joined through the joint part. The joint is made of alumina having a thickness of 30 μm or more, coarse independent pores having a hole diameter in the thickness direction of the joint of 40 to 100% of the thickness of the joint, and a hole diameter of 5 μm or less. It is formed of an alumina conjugate formed of a microcrystalline region including fine pores and a dense sintered region having a relative density of 98% or more.

Description

Bonding method of alumina conjugate and alumina sintered body {Alumina conjugate and bonding method for alumina sintered bodies}

The present invention relates to an alumina conjugate bonded to alumina sintered bodies and a method for joining an alumina sintered body, and more particularly, to an alumina conjugate capable of satisfying the requirements of high purity and high strength, which can be applied to a large member up to several m in length. It relates to a joining method of an alumina sintered body for producing the same alumina bonded body.

In recent years, in order to improve the quality and productivity in various manufacturing fields, the engineering ceramic member used for a production use is required to enlarge and high purity. In particular, in the production of a large member of several meters, it is difficult to cope with conventional integrated ceramic molding and firing techniques. Therefore, the development of the technique which manufactures and combines several small ceramics sintered bodies (block), joins by locally heating only the part which joins them, and produces the desired member is needed. Moreover, in the semiconductor manufacturing apparatus, chemical plant, etc. which require heat resistance and corrosion resistance, incorporation of the impurity element into a product is restrict | limited severely, The thing of high purity is calculated | required for the member used. In particular, in the large-scale ceramic pipe (tubular member) used as a structural member of the rotary kiln used for manufacture of the positive electrode material for lithium ion secondary batteries, it has high purity, high temperature strength, and has a diameter up to 30. There is a need for large products that are about 5 inches in length and up to 5 meters in length.

Although the bonding method of a common ceramic sintered compact includes the oxide solder method, the high melting-point metal method, etc., these joining methods are unpreferable in the above uses, since mixing of impurity elements and deterioration of high temperature strength arise. In addition, as in the solid state pressure bonding method, it is difficult in the production of a large member to load a high pressure material to be joined during heating, and it cannot meet the demand for production of such a large member.

On the other hand, as a bonding method in which ceramic sintered bodies are bonded under no pressure, and the obtained bonded body can maintain high purity, the technique of bonding, firing, and bonding by using a slurry in which ceramic particles having the same composition as the ceramic sintered body is dispersed in pure water. This is known (refer patent document 1).

However, in the joining method described in the patent document 1, in addition to the problem that the joining strength is less than 100 MPa and the joining strength is not sufficient, the joining layer has a problem that it cannot be applied to joining large members because the joining layer is very thin at 0.5 탆. There was. This is because the surface to be joined of the ceramic sintered body (block) used for joining for the production of a large member is, for example, a tubular sintered body having a diameter of several centimeters or more, so that the flatness of the cross section is 1 μm or less. This is generally difficult, and it is because it is not practical to use a large production cost to complete the surface to be joined at a flatness of up to about 0.1 μm, which is considered necessary for the bonding method described in Patent Document 1. As described above, it is not preferable to finish the cross section of the large ceramic sintered body by grinding with high precision. Therefore, a joining method that can tolerate even unevenness of the surface to be joined is required even if several tens of micrometers are required.

As another joining method, in joining a beta alumina tube and a ceramic tube, an alumina slurry is applied to the surface to be joined as an insert material at a thickness of about 0.2 mm, the both tubes are abutted and dried, and then a joining material is obtained by microwave heating. The technique is known (refer patent document 2).

However, the bonding method described in the said patent document 2 is a special method by which the application is limited to the beta alumina which a microwave absorption is large. It is alpha alumina generally used as structural ceramics, and since the absorption of the microwave is very small, heating by microwave is generally difficult. If heating by microwave is desired, it is necessary to add an impurity which absorbs microwaves well, but in that case, the alumina joining member becomes not high purity. In addition, since the thermocouple cannot be used for heating by microwaves, temperature measurement is difficult, and since the temperature of the to-be-joined material cannot be controlled accurately, there is a fear of damage of the to-be-joined material due to unexpected heat generation and heating with reproducibility. I have a problem that I can't. Moreover, the said patent document 2 does not have description of joining strength, and considering the said problem, it is a question whether joining strength could be obtained stably, Even if a joining body could be obtained, the strength is probably 10 MPa or less, It is easily assumed that this was a large imbalance of the measurements.

In addition, in the joining method described in Patent Document 2, it is recorded that the ceramic sintered body is rotated at 10 revolutions per minute in the microwave sintering apparatus while the pressed material is placed on the joined material for uniform heating. It is technically difficult to rotate under the same conditions in the device. From these problems, this method is not practical as a joining method of a large alumina sintered compact which requires high purity.

As described above, since there is no high strength joining method for the dense alumina sintered compact which can maintain high purity at present, as a large ceramic pipe for rotary kiln, a pipe made of porous ceramics integrally calcined with a large molded article or a dense The products of large pipes, which are mechanically connected by placing them in a frame having a special structure and applying compressive stress from both ends, are only sold. However, in the former case, since the porosity is high at a maximum of about 25% and the bending strength is only about 8 MPa at the maximum, there is a problem in that it cannot endure high stress. In the latter case, there is a problem in that there is a step in the joint or the apparatus becomes complicated and large in size.

JP 2010-18448 A JPH8-59358 A

This invention is made | formed in order to solve the said technical subject, The objective is to have a high joint strength and the outstanding corrosion resistance, and to be comprised so that a junction part may not contain an impurity, and the to-be-joined surface of a to-be-joined material It has a high tolerance to the flatness of and consists of alumina conjugates which can be applied to large-scale members very suitably and these alumina conjugates, and the structural members of rotary kilns used for the production of positive electrode materials for lithium ion secondary batteries. It is providing the joining method of the alumina sintered compact which can produce the tubular member and these alumina joined bodies which are used suitably as a heat processing under low load.

In order to achieve the said objective, the joining method of the following alumina joined body, a pipe member, and an alumina sintered compact is provided by this invention.

[1] An alumina bonded body in which alumina sintered bodies are joined through a joint, wherein the joint is made of alumina having a thickness of 30 µm or more, and the pore diameter in the thickness direction of the joint is 40 to 100% of the thickness of the joint. An alumina conjugate formed by coarse independent pores having a length, a microcrystalline region including fine pores having a pore diameter of 5 μm or less, and a dense sintered region having a relative density of 98% or more.

[2] Flexural strength in the atmosphere at 1200 ° C. measured at a room temperature of 200 MPa or more based on JIS R1601, using a test piece cut from the alumina bonded body to include the junction, and measured according to JIS R1601. The alumina conjugate as described in said 1 whose value is 100 Mpa or more.

[3] A pipe member comprising the alumina bonded body according to [1] or [2], wherein the dense alumina sintered bodies having a relative density of 95% or more have a joined structure in which the joined structure is joined through the joined portion.

[4] The tube member according to [3], which is used as a structural member of a rotary kiln used for producing a positive electrode material for a lithium ion secondary battery.

[5] In the joining method of the alumina sintered body in which the alumina sintered bodies are joined, an alumina slurry in which pure water to which a dispersant is added is used as a dispersion medium and in which only alumina particles having a purity of 99.8% or more is added as a solid content is prepared. After applying the slurry to the to-be-joined surface of the alumina sintered body, it is made to dry by adjusting the junction to be bonded to each other and the thickness of the junction portion made of the alumina slurry interposed between the to-be-joined surface to be 30 μm or more. And alumina for sintering the joint by heat-treating the temporary bonded body in an air at a temperature of 1300 ° C. or more and 1700 ° C. or less with a load applied such that the surface pressure of the surface to be bonded is 0.015 MPa or more, and joining the alumina sintered bodies. Joining method of sintered body.

[6] The method for joining the alumina sintered body according to [5], wherein the content of the alumina particles in the alumina slurry is more than 65% by mass and less than 77.5% by mass.

Since the alumina bonded body of the present invention can form a joined portion by sintering in the air without heating by microwaves, as in the joining method of the alumina sintered compact of the present invention described below, the joined portion contains impurities which absorb microwaves well. There is no need to add, and not only the alumina sintered body which is a to-be-joined material, but also the junction part which joins these can be comprised only according to the high purity alumina. Therefore, the alumina conjugate of the present invention exhibits no corrosion resistance or deterioration in strength due to impurities remaining in the joint, exhibits high bonding strength and excellent corrosion resistance, and is free from contamination by impurities. For this reason, the alumina conjugate of the present invention can be widely applied to various large-scale structural members, and is particularly suitable for production applications such as semiconductor manufacturing apparatuses and chemical plant members, which are required to be composed of high-purity materials without the possibility of mixing of impurity elements. It can be used suitably as a large member used. Moreover, since the alumina joined body of this invention is 30 micrometers or more in thickness, even if the flatness of the to-be-joined material end surface (surface to be joined) is several micrometers, it can absorb the unevenness | corrugation, and by this, The demand for finishing can be reduced. That is, since high precision processing with respect to a large to-be-joined material becomes unnecessary, even a large joined body can be manufactured at low cost. In addition, as the above-described joining portion having a margin in thickness absorbs the unevenness of the joining surface, joining is possible on the front surface to be joined, and high joining strength is exerted. In addition, as described above, since the joining portion can be formed only according to high-purity alumina, and it can be made free of impurities such as glass, it is possible to maintain high bonding strength even in a high temperature environment of 1200 ° C., and to be used for applications requiring heat resistance. It also becomes possible.

The tubular member of this invention applies the alumina joined body of this invention to the tubular member which is one of the typical uses. Since this tube member exhibits the effect of the alumina bonded body of this invention as mentioned above, the rotary structure used for manufacture of the large structural member especially required for high purity and high strength, for example, the positive electrode material for lithium ion secondary batteries. It can be used suitably as a structural member of a kiln.

According to the joining method of the alumina sintered compact of this invention, the alumina joined body of this invention which has the outstanding effect as mentioned above can be manufactured. Moreover, since the alumina sintered compact of the present invention can be joined by heat-treating the alumina sintered compact, which is a material to be joined, at low cost in the air, even when producing a large joined body, a large hot press furnace It is possible to join by a normal air atmosphere furnace without using such.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows schematic structure of an example of the alumina conjugate of this invention, and the provisional conjugate which is its precursor.
2 is a SEM photograph of a cross section of a junction of an alumina conjugate of the present invention.
3 is an optical photomicrograph of the junction of the alumina conjugate of Comparative Example 2. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, although this invention is demonstrated based on specific embodiment, this invention is not limited to this and is interpreted, Various changes and correction are based on the knowledge of a person skilled in the art, unless it deviates from the range of this invention. We can add improvement.

In the alumina bonded body of the present invention, the alumina sintered bodies are joined through a joined part, and the joined part is made of alumina having a thickness of 30 µm or more, and the pore diameter in the thickness direction of the joined part is 40 to 100% of the thickness of the joined part. Its main feature is that it is formed of coarse independent pores having a length, fine grain regions including fine pores having a pore diameter of 5 µm or less, and dense sintered regions having a relative density of 98% or more.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows schematic structure of an example of the ceramic joined body of this invention, and the provisional bonded body which is its precursor.

The ceramic joined body of the present invention having the above characteristics can be produced according to the joining method of the alumina sintered body of the present invention.

In the joining method of the alumina sintered compact of this invention, first, pure water to which the trace amount of dispersing agent is added is used as a dispersion medium, and only the alumina particle of 99.8% or more of purity as solid content is added to this dispersion medium, and it mixes and stirs and prepares an alumina slurry. . When a sintering aid or the like is added as a solid content, impurities remain in the joining portion, which leads to deterioration of corrosion resistance, deterioration of high temperature strength, contamination by impurity elements, and the like, which is not preferable. As a dispersing agent, polyammonium salt etc. can be used, for example. In addition, when no dispersant is added to pure water, it is difficult to add more alumina particles at a high concentration in a fluid state, and it is difficult to obtain a joint with high bonding strength.

Content of the alumina particle in an alumina slurry is more than 65 mass%, and it is preferable to set it as less than 77.5 mass%. When alumina content in an alumina slurry is 65 mass% or less, large cavity may be formed in a junction part by evaporation of water at the time of drying of an alumina slurry, and a strength fall may be caused. On the other hand, when the alumina content in an alumina slurry is 80 mass% or more, an alumina slurry will become inferior to fluidity, and it may not be able to apply | coat a slurry uniformly to the whole to-be-joined surface, and a bonding unevenness may arise. Moreover, although a slurry can be apply | coated uniformly at 77.5 mass%, since the crack 30 may arise between a junction part and a to-be-joined surface, as shown in the optical micrograph of FIG. Not. Although the formation mechanism of this crack 30 is not clear, it can be considered as one factor that a slurry surface dries after application | coating and a film | membrane forms, and this impairs the adhesiveness of a to-be-joined surface and a slurry.

Subsequently, the prepared alumina slurry is applied to both to-be-joined surfaces of the alumina sintered bodies 1a and 1b or the other to-be-joined surface, and the to-be-joined surfaces of the alumina sintered bodies 1a and 1b are faced to each other. 1A of temporary joining bodies are manufactured by drying, adjusting so that the thickness of the junction part (bonding part before sintering) 2 which consists of the said alumina slurry interposed between surfaces may be 30 micrometers or more. If the thickness of this junction is less than 30 µm, there is a concern that the alumina sintered bodies 1a and 1b may not be joined without absorbing the unevenness of the surface to be joined. In addition, although the upper limit of the thickness of a junction part is not specifically limited, When the thickness of a junction part is too thick, in some cases, since the size of the coarse independent pore formed in a junction part may become large too much and join strength may become inadequate, a junction part It is preferable to make the thickness of 100 micrometers or less.

Subsequently, the produced temporary joint 1A is heat-treated in air. By this heat treatment, the junction part 2 of the provisional bonded body 1A is sintered, and the alumina joined body 1B of this invention by which the alumina sintered bodies 1a and 1b were joined by the junction part 3 after sintering is obtained. This heat treatment is performed in a state where a load is applied so that the surface pressure of the surface to be joined is 0.015 MPa or more, preferably 0.015 to 0.030 MPa. When the surface pressure of the to-be-joined surface at the time of heat processing is less than 0.015 Mpa, the crack of several 100 micrometers arises between a junction part and a to-be-joined surface, and joining strength deteriorates. Adjustment of the surface pressure of the to-be-joined surface arrange | positions the temporary bonded body 1A so that an alumina sintered compact 1A and 1B may be an up-down direction like FIG. 1, for example, and it is predetermined | prescribed on the upper part of the temporary bonded body 1A. We can carry out by putting mass push stone. As a press stone, an alumina sintered compact can be used suitably, for example. In addition, when the alumina sintered body 1a causes surface pressure of 0.015 MPa or more to be joined on the basis of its own weight alone, there is no need for an external load such as a push stone. For example, when stacking a rectangular parallelepiped or cylinder of an alumina sintered body having a length of 1 m vertically and joining, the surface pressure of the surface to be bonded generated by the magnetic weight of the alumina sintered body is about 0.04 MPa. A joined body having sufficient strength can be obtained without loading a load from the outside. In addition, heat processing under such a fall can be performed using a normal atmospheric furnace.

This heat processing is performed at the temperature of 1300 degreeC or more and 1700 degrees C or less. If the heat processing temperature is less than 1300 degreeC, sintering of the alumina powder of a junction part does not fully advance and sufficient joint strength cannot be obtained in a junction part. On the other hand, when it exceeds 1700 degreeC, there exists a possibility that the grain growth of a sintered compact may arise and the mechanical property of a base material may deteriorate.

When the surface pressure and the heat treatment temperature of the surface to be bonded and the heat treatment temperature are set as above, the heat treatment is performed, and the joint portion 2 made of the alumina powder of the temporary bonded body 1A has a volume accompanying the sintering of the alumina powder in a part of the region. Shrinkage occurs and densification proceeds. However, since the alumina sintered bodies 1a and 1b, which are to be joined, do not shrink, densification does not proceed in other regions, leaving a large grain area and leaving many fine pores. In addition, due to the contraction of the densified region as described above, the joining portion is dragged in the horizontal direction in another region, and coarse independent pores are formed in the joining portion. As a result of this heat treatment, the joint part 2 made of the alumina powder of the joined body 1A has coarse independent pores 20c and a hole whose hole diameter in the thickness direction of the joined part is 40 to 100% of the thickness of the joined part. It becomes the junction part 3 formed from the dense sintered area 20b whose relative density is 98% or more in the microcrystal area | region 20a containing the micropore whose diameter is 5 micrometers or less, and this junction part 3 is an alumina sintered compact which is a to-be-joined material. By combining with (1a and 1b), the alumina conjugate 1B of the present invention is obtained.

FIG. 2 is a SEM photograph of a cross section of a junction part of the alumina bonded body of the present invention, and from this photograph, the junction part 3 includes (1) microcrystalline regions 20a and 2 in which micropores having a pore diameter of 5 µm or less are concentrated. ) The dense sintered region 20b having a relative density of 98% or more, and (3) the coarse independent pores whose hole diameter in the thickness direction of the junction 3 is 40 to 100% of the thickness of the junction 3. 20c) can be confirmed. In addition, in the green region 20a and the sintered region 20b, the junction 3 and the upper and lower alumina sintered bodies (bonded materials) are in close contact with each other, and no cracks or the like are observed at the junction interface, and the junction 3 is alumina. It turns out that it is in charge of bonding of a sintered compact.

In addition, since several coarse independent pores 20c exist in the junction part 3, although the part of a to-be-joined surface contains an unbonded area | region which is not joined, these coarse independent pores 20c are not connected but isolate | separated from each other. In this case, the formation of large cracks does not occur, and deterioration of the bonding strength due to the presence of the coarse independent pores 20c is not significant. In the heat treatment, the joining portion is allowed to shrink in the horizontal direction (direction perpendicular to the thickness direction of the joining portion), and it is not necessary to shrink significantly in the vertical direction (thickness direction of the joining portion). ) And the non-grained region 20a also suppress the generation of sharp cracks that cross the inside of the junction 3 in the horizontal direction and do not significantly deteriorate the bond strength.

As a result, the alumina conjugate of this invention expresses high intensity | strength. Specifically, the strength of 200 MPa or more can be expressed as the flexural strength at room temperature measured according to JIS R1601 using a test piece cut from the alumina bonded body of the present invention to include a bonded part. Moreover, the intensity | strength of 100 Mpa or more can be expressed as the bending strength in 1200 degreeC atmosphere measured according to JISR1604.

The tubular member of the present invention is a tubular member made of the alumina joined body of the present invention, and has a joined structure in which dense alumina sintered bodies having a relative density of 95% or more are joined through the joined part. This tubular member applies the alumina joined body of this invention to the tubular member which is one of the typical uses. This tubular member uses a dense material having a relative density of 95% or more as an alumina sintered body to be joined, and exhibits the effect of the alumina bonded body of the present invention as described above, and thus is particularly required to have high purity and high strength. It can use suitably as a structural member of the rotary kiln used for manufacture of a structural member, for example, the positive electrode material for lithium ion secondary batteries.

(Example)

Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to this Example.

(Investigation of Alumina Content in Alumina Slurry)

Commercially available alumina sintered bodies having alumina purity of 99.5% or more and relative density of 99.0% or more were processed to 20 mm × 16 mm × 5 mm, and several test pieces ground 20 mm × 16 mm by grinding wheel # 200 Ready. Nakagyo oil and fat manufactured by Nakagyo Oil & Fat Co., Ltd. which has a polyammonium polyacrylate salt as a main component as a dispersing agent was added so that it might become 17: 1 by mass ratio, and it stirred well, and produced the dispersion medium. About this dispersion medium, 65.0 mass%, 69.5 mass%, 74.5 mass%, 77.5 mass%, 80.0 mass of alumina particle whose purity is 99.8% or more and whose average particle diameter is 600 nm as shown in Table 1, respectively. It added and stirred so that it might become%, and obtained the slurry which the alumina particle disperse | distributed and mixed in the dispersion medium. In addition, this slurry was vacuum degassed for about 2 minutes using a vacuum pump, and air bubbles in the slurry were removed. In this manner, five kinds of alumina slurries having different content of alumina particles were prepared.

Subsequently, the said test piece was made into two sets, and after apply | coating the said alumina slurry to the whole surface of the 20 mm x 16 mm surface of a test piece, the 20 mm x 16 mm surface of the other test piece was matched so that it might cross. Here, it adjusted so that the clearance of two test pieces might be set to about 90 micrometers, The alumina slurry was filled previously, and it dried overnight, and obtained the temporary conjugate. In addition, the thing of 80 mass% of alumina content in an alumina slurry was not able to produce a temporary joint because the fluidity | liquidity was not enough and application | coating to the test piece was not enough.

The temporary bonded body was transferred to the atmosphere, and the alumina sintered compact was placed on the upper part of the temporary bonded body so that the surface pressure of the surface to be bonded was 0.03 MPa, and calcined at 1650 ° C. for 2 hours to prepare an alumina bonded body. The rod-shaped test piece of 3 mm x 2 mm x 10 mm was produced from the alumina joined body obtained in this way, and 3-4 plastic flexural strengths were measured by the 3-point plastic test which set the lower span to 8 mm, and an average value is computed. It was. The result was shown in Table 1, and the effect of the alumina content in an alumina slurry was examined based on the said result.

(Review the results)

In Comparative Example 1 in which the alumina content was 65.0 mass% in the alumina slurry, the amount of evaporation of moisture when the alumina slurry was dried was large, large voids were formed in the joint, and the deterioration of the bond strength was evident. On the other hand, in Comparative Example 3 in which the alumina content in the alumina slurry was 80.0% by mass, as described above, the fluidity of the slurry was not sufficient, and the thickness of the joint was not controlled, so that the provisional conjugate could not be produced. On the other hand, in Examples 1 and 2 in which the alumina content in the alumina slurry was 69.5% by mass and 74.5% by mass, respectively, an alumina bonded body having a flexural strength of about 200 MPa could be produced. However, in Comparative Example 2 in which the alumina content in the alumina slurry was 77.5 mass%, the bonded body could be produced by the preparation of the temporary conjugate and the sintering, but as shown in FIG. Flexural strength was only about 120 MPa. From these results, it turns out that the alumina content in an alumina slurry is larger than 65.0 mass%, and it is suitable that it is less than 77.5 mass%.

(Investigation of the Thickness of the Joint)

Alumina conjugates were prepared in the same manner as above except that the alumina content in the alumina slurry was fixed at 74.5% by mass, and the joint portions of the temporary joints were 60 μm, 40 μm, and 36 μm, respectively. The average value was calculated. The result was shown in Table 2 with the result of the said Example 2 (thing of 90 micrometers in thickness of a junction part), and the effect of the thickness of a junction part was examined based on the said result.

(Review the results)

Sufficient flexural strength of 200 MPa or more was obtained also in the alumina bonded body in any one of Examples 2-5 in which the thickness of a junction part is 30-90 micrometers. In addition, when the thickness of the junction part was less than 30 micrometers, it was thought that the unevenness | corrugation of the to-be-joined surface of an alumina sintered compact cannot fully be corresponded, and the thickness of the junction part here was not manufacturing the alumina joined body below 30 micrometers.

(Investigation of surface pressure of surface to be joined at sintering)

The alumina content in an alumina slurry was fixed at 74.5 mass%, and the temporary joint body which made the thickness of a junction part 90 micrometers was produced. An alumina bonded body was produced in the same manner as above except that the pressurized stone of the alumina sintered body was mounted on the temporary bonded body so that the surface pressures of the surface to be bonded were 0.015 MPa, 0.008 MPa, and 0 MPa (self-weight only). The average value of flexural strength was calculated. The results are all shown in Table 3 together with the results of Example 2 (the surface pressure of the surface to be bonded is 0.03 MPa), and the effect of the surface pressure of the surface to be bonded at the time of sintering was examined based on the results. It was.

(Review the results)

In Example 2 and 6 which made the surface pressure of the to-be-joined surface at the time of sintering 0.015 Mpa or more, sufficient bending strength of 200 Mpa or more was obtained. On the other hand, in Comparative Examples 4 and 5 in which the surface pressure of the surface to be joined at the time of sintering was set to 0.008 MPa or less, the flexural strength did not reach 200 MPa. From this, it is understood that it is necessary to load a surface pressure of 0.015 MPa or more to the surface to be joined at the time of sintering. In addition, since the surface pressure of the to-be-joined surface obtained by magnetic weight is about 0.04 Mpa in the joining of the alumina sintered compact whose height is 1 m or more, in the joining of such a large sintered compact, it has sufficient strength, without loading a load from the outside. It was found that an alumina conjugate can be obtained.

(Joining of Larger Alumina Sintered Body)

Based on the above examination result, the alumina bonded body was produced using the larger alumina sintered compact (block) for a to-be-joined material, and the 4-point baking test in room temperature and 1200 degreeC atmosphere was implemented. Specifically, first, a commercially available alumina sintered body having alumina purity of 99.5% or more and a relative density of 99.0% or more is processed to 40 mm x 13 mm x 20 mm, and the 40 mm x 13 mm surface is processed with a # 200 grinding wheel. Several ground specimens were prepared. To pure water, a cell or D305 (trade name) manufactured by Nakagyo Co., Ltd. whose main component is ammonium polyacrylate salt was added so as to be 17: 1 by mass ratio, and stirred well to prepare a dispersion medium. About this dispersion medium, the purity was 99.8% or more, and the alumina particle of 600 nm in average particle diameter was added and stirred so that content might be 74.5 mass%, and the slurry which the alumina particle disperse | distributed and mixed in the dispersion medium was obtained. The slurry was vacuum degassed for about 2 minutes using a vacuum pump to remove bubbles in the slurry. In this way, an alumina slurry having a content of alumina particles of 74.5% by mass was prepared.

Subsequently, the said test piece was made into two sets, the said alumina slurry was apply | coated to the whole surface of 40 mm x 13 mm surface of one test piece, and the 40 mm x 13 mm surface of the other test piece was matched. Here, it adjusted so that the space | interval of two test pieces might be set to about 90 micrometers, The alumina slurry was previously filled and dried overnight, and the temporary bonded body of 40 mm x 13 mm x 40 mm was obtained.

This temporary bonded body was moved to the atmosphere, the alumina sintered compact was put on the upper part of the temporary bonded body so that the surface pressure of a to-be-joined surface might be 0.03 Mpa, and it baked at 1650 degreeC for 2 hours, and produced the alumina bonded body. The rod-shaped test piece of 3 mm x 4 mm x 40 mm which conformed to JIS R1601 was produced from the alumina joined body obtained in this way, and the 4-point baking test which made a lower span 30 mm and an upper span 10 mm was performed. It was. The number of the rod-shaped test pieces used for the measurement was made into five in the room temperature baking test, and made into four about the high temperature baking test in 1200 degreeC atmosphere, and computed the average value, respectively. Thus, Table 4 shows the calculation results of the four-point bending strength in the room temperature and 1200 ° C atmosphere using standard test pieces of JIS R1601.

As shown in Table 4, the average flexural strength at room temperature of Example 7 produced as described above was the same high value as the average flexural strength of Example 2 shown in Table 1. From this, it turned out that high intensity | strength can be expressed reproducibly even if the test piece size increases. According to the strength theory of ceramics which discussed the relationship between test piece size and strength, it is generally known that strength decreases with increase in test piece size. This is because the test piece with a larger probability of the presence of a large crack defect dealing with strength becomes larger than the small test piece. However, in this embodiment, the coarse defect which can be considered to deal with the strength is considered to exist mainly in the junction, and in Examples 2 and 7, since the thickness of the junction is the same, the volume of the site where the coarse defect is considered to exist is It does not differ greatly, and as a result, it is thought that almost the same high intensity | strength can be obtained regardless of a test piece size.

In Example 7, the average flexural strength in the atmosphere at 1200 ° C. was also 157 MPa, which was a high value. This can be considered to be because the joint is made of pure alumina sintered body and does not contain a substance that degrades high temperature strength such as glass.

(Industrial availability)

As mentioned above, this invention relates to the alumina bonded body and the joining method of an alumina object, According to this invention, the bending strength to the room temperature of the test piece cut | disconnected to include a junction part is 200 Mpa or more, and is 1200 degreeC atmosphere. It is possible to provide a conjugate made of high purity alumina having a bending strength of 100 MPa or more. By using the joining method of the present invention, it is possible to join large alumina sintered bodies without requiring high flatness on the surface to be joined, and since the constituent material of the joining portion is only high-purity alumina, the joined member is a constituent member of various manufacturing apparatuses. When used in the present invention, contamination by impurity elements can be prevented, and deterioration in strength to high temperatures can be prevented. By this feature, this invention is useful as providing the joining method of the high strength and high purity alumina joined body used for the large manufacturing apparatus member which requires corrosion resistance and heat resistance, and the alumina sintered compact for manufacturing it.

1A: Provisional conjugate 1B: Alumina conjugate
1a, 1b: Alumina sintered compact 2: Joining part (before sintering)
3: Joint part (after sintering) 20a: Unsintered area
20b ： sintered area 20c ： coarse independent groundbreaking
30: crack

Claims (6)

In an alumina bonded body in which alumina sintered bodies are joined through a joining portion, the joining portion is made of alumina having a thickness of 30 µm or more, and the coarse diameter in the thickness direction of the joining portion is 40 to 100% of the thickness of the joining portion. (coarse) An alumina conjugate formed by independent pores, microcrystalline regions including fine pores having a pore diameter of 5 µm or less, and dense sintered regions having a relative density of 98% or more. The method according to claim 1,
The flexural strength at room temperature measured in accordance with JIS R1601 was 200 MPa or more using a test piece cut from the alumina bonded body to include the junction, and the flexural strength in the atmosphere at 1200 ° C. measured in accordance with JIS R1604 was 100 MPa. The alumina conjugate which is above. The tubular member made of the alumina bonded body according to claim 1 or 2, wherein the dense alumina sintered bodies having a relative density of 95% or more have a joined structure joined through the joined portion. The method according to claim 3,
The pipe member used as a structural member of the rotary kiln used for manufacture of the positive electrode material for lithium ion secondary batteries. In the joining method of the alumina sintered body which joins alumina sintered compacts, pure water which added the dispersing agent was used as a dispersion medium, the alumina slurry which added only the alumina particle of 99.8% or more of purity as solid content to this dispersion medium was prepared, and this alumina slurry was prepared as said said After coating on the surface to be bonded of the alumina sintered body, the bonded portions made of the alumina slurry interposed between the surfaces to be joined are adjusted to be 30 µm or more to prepare a temporary bonded body. Bonding of the alumina sintered body which sinters the said joined part by heat-processing in air | atmosphere at the temperature of 1300 degreeC or more and 1700 degreeC or less, in the state which put the load so that the surface pressure of the to-be-joined surface may be 0.015 Mpa or more, and joins the said alumina sintered bodies together. Way. The method according to claim 5,
The joining method of the alumina sintered compact whose content of the alumina particle in the said alumina slurry is more than 65 mass%, and is less than 77.5 mass%.

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