JP5166223B2 - Method for joining members to be joined of silicon nitride ceramics - Google Patents

Description

  The present invention relates to a method for bonding ceramic materials containing silicon nitride.

  Silicon nitride ceramic materials are already widely used in various industrial fields because they are superior in heat resistance, corrosion resistance, wear resistance and the like as compared with metals.

  Generally, silicon nitride ceramic products are roughly classified into two types.

  The first method is a method using silicon nitride powder as a raw material. In this method, a molded body is first manufactured from silicon nitride powder or a mixture obtained by adding a sintering aid thereto. Further, various solvents, binders and / or dispersants may be added depending on the molding method. As a method for producing the molded body, a die pressing method, a cold isostatic pressing method, an extrusion method, an injection molding method, a slip casting method, and the like are used. For example, the cold isostatic pressing method is also called a CIP method, and is a method of obtaining a molded body by placing a rubber mold filled with raw material powder in a pressure vessel and applying hydrostatic pressure. In the slip casting method, a slurry containing raw material powder is poured into a gypsum mold and moisture is sucked, so that the slurry is solidified and a molded body can be obtained. Next, a silicon nitride ceramic product is obtained by sintering the formed body formed by any method. Generally, the sintering temperature is in the range of about 1600 ° C to 2000 ° C.

  The second method uses silicon powder as a raw material. Also in this method, a molded body is produced by the same method as described above. However, in this method, a process of converting silicon powder into silicon nitride, so-called “reactive sintering process”, is required. Usually, the reaction sintering process is performed by heating the compact containing silicon powder to any temperature in the range of about 1100 ° C. to 1450 ° C. in a nitrogen atmosphere. Furthermore, if necessary, a post-sintering process is performed in the range of about 1600 ° C. to 2000 ° C. after the reaction sintering process in order to improve the strength of the sintered body.

  The excellent characteristics of the silicon nitride ceramic as described above are serious problems in terms of productivity, particularly in terms of workability. In particular, silicon nitride ceramic products have a problem that it is difficult to make them complex and / or large.

  Therefore, it has been studied to realize a complicated shape and / or an increase in size of a product by joining two or more silicon nitride ceramic members through a joining material.

  For example, Patent Document 1 discloses a material system different from silicon nitride, but in a system such as alumina and aluminum nitride, ceramic parts calcined in advance at a temperature equal to or lower than a sintering temperature and other calcined ceramic parts. Between the ceramic powders, which are sintered at the same sintering temperature as these parts, have the same shrinkage, and have a thermal expansion coefficient substantially equal to those of these ceramic parts. A method is described in which two ceramic parts are sintered together in a pressed state, thereby joining the ceramic parts together.

In addition, the ceramic sintered body is heated and bonded between two ceramic sintered bodies to be bonded members, and then the metal is oxidized, carbonized, and nitrided, thereby producing ceramics. A method for joining sintered bodies has been proposed (Patent Document 2).
Japanese Patent Laid-Open No. 11-43379 JP-A-6-115009

  However, since the method described in Patent Document 1 is not a method assuming a silicon nitride ceramic product manufactured by reactive sintering, the second method, that is, silicon powder is used as a starting raw material. It cannot be applied to a method of manufacturing a silicon nitride ceramic product. Also, with this method, it is necessary to press-contact two ceramic parts at the time of joining. When trying to apply such a method to the manufacture of a large product, a large press-contacting device (press machine, etc.) There is a problem that it becomes necessary.

  On the other hand, in the method described in Patent Document 2 described above, for example, when a plate-like material is assumed as the form of the metal interposed between the bonded ceramic members, the plate-like material is reacted at a high temperature, There is a problem that it is extremely difficult to obtain a bonded portion having properties equivalent to those of the ceramic member to be bonded, such as material composition, denseness (density), porosity, and mechanical properties. In this case, finally, a joined body having different characteristics between the member to be joined and the joining material is obtained. Therefore, in such a method, there is an increased risk of defects occurring in the bonded interface between the member to be bonded and the bonding material in the bonded body after manufacture. Further, when such a non-uniformity in characteristics exists in the joined body, there is a problem that strength is locally reduced and cracking or damage is likely to occur at that location.

  Therefore, there is a demand for a method of joining silicon nitride ceramic members that can be easily applied to large-sized products, is less prone to defects at the joints, and can provide a generally uniform joined body.

  The present invention has been made under such a background, and the present invention can be applied to a product having a large shape and / or a complicated shape. It is an object of the present invention to provide a method for joining silicon nitride ceramic members capable of obtaining a substantially homogeneous joined body.

In the present invention, a method of joining members to be joined of silicon nitride ceramics,
(A) preparing a first raw material mainly composed of silicon particles;
(B) forming a molded body from the first raw material;
(C) A step of holding the molded body at a temperature in the range of 1100 ° C. to 1450 ° C. in a nitrogen atmosphere and subjecting silicon particles in the molded body to a reactive sintering treatment, whereby silicon nitride A step of obtaining a porous bonded member made of a ceramic based material
(D) A step of preparing a second raw material containing silicon particles, which is included in the second raw material when the particle size distributions of the silicon particles contained in the first raw material and the second raw material are compared. At least one parameter value among the maximum particle size, the mode particle size, and the ratio of the particles having the mode particle size is ± 20% of the same parameter value of the silicon particles contained in the first raw material. Steps within the range of
(E) preparing a slurry from the second raw material;
(F) Injecting the slurry into the gap between the members to be joined, where the joining material is formed later, causing the joined member to absorb moisture in the slurry, solidifying the slurry, and forming a joining material Obtaining an assembly by:
(G) holding the assembly at a temperature in the range of 1100 ° C. to 1450 ° C. in a nitrogen atmosphere and subjecting the silicon particles in the bonding material to reactive sintering;
Have
The steps (a) to (c) are performed before or after the steps (d) to (e), or the steps (a) to (c) are the steps (d) to (e). A method implemented in parallel is provided.

  Here, in the method, the first raw material and / or the second raw material may further contain an additive substance.

  The additive substances are Mg (magnesium), Al (aluminum), Y (yttrium), Sc (scandium), La (lanthanum), Ce (cerium), Zr (zirconium), Yb (ytterbium), Hf (hafnium). ), Ti (titanium), Lu (ruthenium), and a metal selected from the group consisting of two or more of these, or an oxide of the metal, or a nitride of the metal.

In the method, the first raw material and / or the second raw material may further include TiN (titanium nitride), SiC (silicon carbide), BN (boron nitride), C (carbon), ZrO ₂ (zirconia). ) May be included.

  The first raw material and the second raw material may have substantially the same composition.

In the method, after the step (g),
(H) having a step of post-sintering the obtained joined body,
The temperature of the post-sintering process is higher than the temperature of the reactive sintering process in the step (c) and the step (g), and / or the post-sintering process includes the step (c) and the step ( The reaction may be performed in a nitrogen atmosphere at a pressure equal to or higher than the pressure of the nitrogen atmosphere in the reactive sintering process in g).

  In this case, the post-sintering treatment may be performed in a temperature range of 1600 ° C. to 2000 ° C. in a nitrogen atmosphere of 1 to 9.5 atm.

  In the method, the slurry prepared in step (e) may contain water and a dispersant and / or a binder.

  In the present invention, a silicon nitride-based ceramic member that can be applied to a product having a large shape and / or a complicated shape, can significantly reduce defects in the joint portion, and can obtain a relatively homogeneous joined body. A joining method is provided.

  Hereinafter, the present invention will be described in more detail.

  The present invention uses a “similar” raw material for a member to be bonded and a bonding material in a method for bonding bonded members of silicon nitride ceramics to each other. One characteristic is that a homogeneous bonded body is obtained as a result of performing a “similar” reaction sintering process on the bonding material (precisely, the bonding material slurry is solidified). Is.

More specifically, the method of the present invention comprises:
(A) preparing a first raw material mainly composed of silicon particles;
(B) forming a molded body from the first raw material;
(C) A step of holding the molded body at a temperature in the range of 1100 ° C. to 1450 ° C. in a nitrogen atmosphere and subjecting silicon particles in the molded body to a reactive sintering treatment, whereby silicon nitride A step of obtaining a porous bonded member made of a ceramic based material,
(D) preparing a second raw material containing silicon particles having a particle size distribution “similar” to that of the silicon particles contained in the first raw material;
(E) preparing a slurry from the second raw material;
(F) Injecting the slurry into the gap between the members to be joined, where the joining material is formed later, causing the joined member to absorb moisture in the slurry, solidifying the slurry, and forming a joining material Obtaining an assembly by:
(G) holding the assembly at a temperature in the range of 1100 ° C. to 1450 ° C. in a nitrogen atmosphere and subjecting the silicon particles in the bonding material to reactive sintering;
Have

  Note that the expression “silicon nitride ceramics” is used because the method of the present invention can be widely applied not only to pure silicon nitride ceramic products but also to ceramic products mainly composed of silicon nitride. . That is, in the present application, “silicon nitride ceramic” means a generic name of ceramics mainly composed of silicon nitride.

  In the present application, the “reactive sintering process” means a process of obtaining a silicon nitride ceramic sintered body by nitriding silicon particles to produce silicon nitride and simultaneously sintering the produced silicon nitride. means.

  Due to the characteristic configuration as described above, the method of the present invention provides the following effects.

  (I) The bonding material and the member to be bonded are converted from the “similar” raw material to the silicon nitride ceramics through the “similar” reactive sintering process.

  Therefore, in the finally obtained joining material and to-be-joined member, characteristics of both, for example, composition, physical properties (density, porosity, thermal expansion coefficient, etc.), mechanical properties (strength, etc.), and / or chemical properties ( Chemical resistance, wettability, etc.) can be brought close enough. For this reason, the joined body obtained by the present invention is more homogeneous than the joined body obtained by the conventional joining method.

  Here, the present invention is characterized in that the same raw material as the first raw material for the member to be joined is used as the second raw material for the bonding material. Silicon particles similar to the silicon particles contained in one raw material are included. For example, in the step (d), the particle size of the silicon particles contained in the second raw material is made substantially equal to the particle size of the silicon particles contained in the first raw material. In general, when the particle diameters of silicon particles are substantially equal, a substantially equivalent silicon nitride ceramic sintered body can be obtained by performing substantially the same reaction sintering treatment. Therefore, in this case, the state of the bonding material obtained through the subsequent reaction sintering process can be brought close to the state of the member to be bonded.

  In the present application, the particle size distribution of silicon particles is a value measured by a laser diffraction / scattering method (microtrack method). Further, “the particle size distribution of silicon particles is substantially (substantially equal)” means that particles having a maximum particle diameter, a mode particle diameter, and a mode particle diameter in the particle size distributions of two types of silicon particles to be compared. The case where at least one of the ratios is within a range of ± 20% shall be said. For example, when the mode particle size of silicon particles contained in the first raw material is 10 μm and the mode particle size of silicon particles contained in the second material is in the range of 8 μm to 12 μm, the particle size distribution of both silicon particles is , Almost (substantially) equal.

  In the step (g), since the silicon particles in the bonding material formed by solidifying the slurry are subjected to a reactive sintering process, the assembly is subjected to 1100 ° C. to 1100 ° C. in a nitrogen atmosphere as in the step (c). It is held at any temperature in the range of 1450 ° C. Generally, when a reactive sintering process is performed at a temperature in the range of 1100 ° C. to 1450 ° C. in a nitrogen atmosphere using a raw material containing similar silicon particles, the silicon nitride system in a substantially equivalent state A ceramic sintered body is obtained. Therefore, the state of the joining material obtained by step (g) can be brought close to the state of the member to be joined.

  For example, the slurry for the bonding material may be prepared using substantially the same raw material as the raw material for the member to be bonded. Moreover, the slurry for joining materials may be subjected to reaction sintering treatment using, for example, substantially the same reaction sintering treatment conditions as the members to be joined.

  (Ii) In the present invention, a slurry having high fluidity is used as a form for introducing the bonding material. In this case, when the slurry is injected into the gap between the members to be joined in step (f), the liquid component such as water contained in the slurry passes through the pores of the porous member to be joined from the gap portion. And easily discharged to the outside. In addition, unlike the paste, the slurry has high fluidity, so that the silicon particles contained in the slurry move so as to fill the minute space portion in the gap as the liquid such as water flows. By this step, the gap portion is filled with silicon particles uniformly and with a high packing density. Therefore, finally, a joined body with few defects can be obtained inside the joining material and at the interface between the joining material and the non-joining material.

  (Iii) In the above-described step (g), during the reactive sintering process, the silicon particles contained in the bonding material slurry change from both the liquid phase and the gas phase to silicon nitride. That is, during the reactive sintering process, some of the silicon particles become molten or semi-molten due to reaction with an oxide layer (glass) on the silicon surface or a sintering aid, and this liquid phase is nitrogen in the atmosphere. Reacts with it to form silicon nitride. Further, another part of the silicon particles is vaporized by heat and reacts with nitrogen in the atmosphere in a gas phase state. In the latter case, the obtained silicon nitride is generated in a whisker shape so as to fill a portion that is not filled with a liquid phase and a solid phase, that is, a space portion, among the bonded portions. Therefore, when silicon particles in the joint portion are converted into silicon nitride ceramics through reaction sintering, the gap in the joint portion is filled, and after the treatment, the inside of the joint material and the interface between the joint material and the non-joint material are filled. In addition, a bonding material with few defects can be obtained.

  (Iv) In the method of the present invention, the silicon particles can be easily filled in the gap portion by injecting the slurry into the joining portion (gap portion) between the members to be joined. The joining process does not include a step of pressing the members to be joined together. Therefore, a special pressure welding apparatus is not required and can be easily applied to joining large products. Similarly, it can be easily applied to complex shaped products.

  (V) In the method of the present invention, it is not necessary to perform a specific surface finish in advance on the joint surface of the member to be joined. This is because the fluidity of the slurry is high, so that even if there are some irregularities on the joint surface of the members to be joined, the silicon particles can be uniformly filled into the joint surface. (It is necessary to keep in mind that in a conventional method for joining ceramic members, it is necessary to perform a specific finish on the surface in advance, such as smoothing the joining surface.) The bonded objects can be bonded by a very simple processing process, and the processing cost is suppressed.

  As described above, in the method according to the present invention, a joined body having a small difference in characteristics between the joining material and the member to be joined and having few defects in the joined portion can be obtained relatively easily.

  Hereinafter, the present invention will be described more specifically with reference to the drawings.

  FIG. 1 shows an example of a schematic flow diagram for carrying out the method of the present invention.

  As shown in FIG. 1, the method according to the present invention includes a step of preparing a first raw material for a member to be joined (S110), and a step of obtaining a molded body of the member to be joined using the first raw material ( S120), a step of reaction-sintering the obtained molded body to obtain a bonded member (S130), a step of preparing a second raw material for a bonding material (S140), and the second raw material A step of preparing a slurry for bonding material (S150), a step of forming the bonding material by injecting and solidifying the slurry into the bonding portion of the member to be bonded (S160), and the bonding A step of obtaining a joined body in which the materials are subjected to reaction sintering, whereby the members to be joined are joined via the joining material (S170), and a step of post-sintering the obtained joined body (S180); Have

  Note that steps S140 to S150 may be performed at any stage before and after steps S110 to S130, or may be performed in parallel with steps S110 to S130. Further, the step of post-sintering the last joined body (S180) may be omitted.

  Hereinafter, each step will be specifically described.

(Step S110)
In this step, a first raw material is prepared in order to manufacture a silicon nitride ceramic member to be bonded. The first raw material contains silicon powder as a main component.

The first raw material may further contain an additive substance. For example, the first raw material may include a sintering aid of about 0.1 wt% to 10 wt% with respect to the weight of the entire first raw material. Usually, metals, oxides or nitrides are used as sintering aids. Examples of metal sintering aids are Mg (magnesium), Al (aluminum), Y (yttrium), Sc (scandium), La (lanthanum), Ce (cerium), Zr (zirconium), Yb (ytterbium), Hf (Hafnium), Ti (titanium), Lu (ruthenium), and combinations of two or more thereof. Examples of oxide and nitride sintering aids include the aforementioned metal oxides and nitrides. Sintering aid, for _example, is _{Y 2 O 3 -Al 2 O 3} , Y 2 O 3 -Al 2 O 3 -MgO, ZrO 2 -Al 2 O 3, ZrO 2 -Al 2 O 3 -MgO , etc. .

The first raw material may further contain TiN (titanium nitride), SiC (silicon carbide), BN (boron nitride), C (carbon), ZrO ₂ (zirconia), and the like as still another additive substance. By adding these additive substances, various properties can be imparted to the finally obtained silicon nitride ceramic member to be joined. For example, the conductivity of the member to be joined can be improved by adding TiN to the first raw material. Further, by adding SiC (silicon carbide) to the first raw material, the oxidation resistance, strength, and toughness of the bonded members can be improved. Further, by adding BN (boron nitride) to the first raw material, it is possible to improve the thermal shock resistance of the bonded member or to prevent the molten metal from adhering. Furthermore, by adding C (carbon) to the first raw material, it is possible to improve the wear resistance and conductivity of the bonded members. Further, by adding ZrO 2 _(zirconia) to the first material, it is possible to improve the toughness of the bonded members. Two or more kinds of these additive substances may be added. The addition amount of these additive substances is about 5 wt% to 30 wt% with respect to the weight of the entire first raw material.

  It will be apparent to those skilled in the art that the substances described here are merely examples, and various other substances may be added to the first raw material.

  By sufficiently mixing these components, the first raw material can be obtained. In mixing (stirring), an appropriate liquid such as alcohol or water may be added. In that case, after mixing (stirring), the mixed powder is obtained by removing the liquid component by an appropriate drying means (using a dryer, spray drying, etc.). In addition, various powder treatments may be performed according to the molding method in the next step (S120).

(Step S120)
Next, a molded body for a member to be joined is formed using the first raw material obtained in step S110. This molding method is not particularly limited, and any molding method may be adopted. For example, the molding method may be a die pressing method, a cold isostatic pressing method (CIP method), an extrusion method, an injection molding method, a slip casting method, or the like.

(Step S130)
Next, a reaction sintering process (hereinafter referred to as “first reaction sintering process”) is performed using the molded body. The conditions for the first reactive sintering treatment are not particularly limited, and any conditions may be adopted as long as the silicon contained in the molded body is changed to silicon nitride. In general, by maintaining the molded body in a temperature range of 1100 ° C. to 1450 ° C. in a nitrogen atmosphere of 1 atm, reactive sintering occurs, and silicon particles change to silicon nitride.

  In the present invention, silicon nitride ceramics subjected to reactive sintering is used as a member to be joined. This is because, in a molded body that has not been subjected to reactive sintering, bonding between silicon particles is weak, and in subsequent step S160, when the slurry is injected into the gap between the members to be bonded, the members to be bonded become wet and expand. This is because there is a risk that the member to be joined is cracked due to collapse or shrinkage during drying. In contrast, when silicon nitride-based ceramics that have been subjected to reactive sintering are used as bonded members, the silicon nitride particles are firmly bonded to each other, so that the bonded members are affected by wetting and drying. There is no.

  By this treatment, a porous bonded member made of silicon nitride ceramic is obtained.

(Step S140)
In this step, a second raw material to be a bonding material later is prepared. Here, the same raw material as the first raw material is used as the second raw material. That is, the second raw material contains silicon powder “similar” to the first raw material described above as a main component. For example, the silicon particles contained in the second raw material have a particle size substantially equal to the particle size of the silicon particles contained in the first raw material. In addition, the second raw material may further contain the additive material as described above. In particular, the same material as the first material may be used as the second material.

  Due to such features, the silicon nitride ceramic bonding material obtained through the following steps can exhibit the same characteristics as the bonded member.

(Step S150)
Next, a slurry for a bonding material is prepared using the second raw material. The method for preparing the slurry is not particularly limited. The slurry is prepared, for example, by adding water to the above-mentioned second raw material, further adding a dispersant and / or a binder, and sufficiently stirring the mixed solution. As the dispersing agent, for example, ammonium polyacrylate, ammonium polycarboxylate or the like is used. Moreover, as a binder, polyvinyl alcohol, polyvinyl acetal, an acrylic emulsion etc. are used, for example. The added amount of each of the dispersant and the binder is, for example, about 0.2 wt% to 3 wt% with respect to the second raw material.

  The resulting slurry has a viscosity of 500 cps or less, for example, in the range of 50 cps to 300 cps. Therefore, this slurry has a relatively high fluidity, unlike a so-called “paste”.

(Step S160)
Next, it is assembled through a gap so that at least two members to be joined produced in step S130 have a predetermined shape, and the slurry prepared in step S150 is injected into this gap portion.

  As described above, in this step, the liquid component contained in the slurry is easily discharged to the outside from the gap portion via the fine pores contained in the porous member to be joined. In addition, due to the high fluidity of the slurry, the silicon particles contained in the slurry move so as to densely fill the space with the flow of the liquid component. Therefore, by this step, the silicon particles can be uniformly and highly packed in the gap portion.

  Here, because of the characteristics of such a slurry, it is not necessary to perform a special surface finish on the bonding surface of each member to be bonded before performing this step. Due to the fluidity of the slurry, even if there are some irregularities on the joint surface, when the liquid component flows out, the silicon particles move to fill the irregularities on the joint surface, resulting in uniform silicon particles. It is because it is arranged.

  In the present invention, since the gap portion is filled with the slurry component by injecting slurry, the width of the gap portion is not particularly limited, and can be easily applied to the gap portion of any size. There is a feature.

(Step S170)
After step S160, the obtained assembly may be optionally dried. The drying process may be performed, for example, by holding the assembly in a room temperature atmospheric environment. By the drying treatment, moisture that has flowed out toward the member to be joined can be removed from the gap portion into which the slurry has been injected.

  Next, the entire assembly is heated under a nitrogen atmosphere (reaction sintering treatment of the bonding material). Thereby, the silicon particles in the bonding material formed in the gap portion are reactively sintered, and the bonding material is changed to silicon nitride ceramics.

  The reactive sintering process in this step (hereinafter referred to as “second reactive sintering process”) is performed under the same conditions as the first reactive sintering process. For example, the second reaction sintering process is performed by, for example, maintaining the entire assembly at a temperature in the range of 1100 ° C. to 1450 ° C., for example, in a nitrogen atmosphere of 1 atm. In particular, the temperature during the second reaction sintering process is preferably within a range of ± 50 ° C. with respect to the temperature during the first reaction sintering process. In this case, a very similar sintered state can be obtained between the member to be joined and the joining material.

  Here, as described above, since the silicon particles are filled in the gap portion with a uniform and high filling density, a uniform bonding material is formed by this treatment. Further, an interface in which defects and cracks are significantly suppressed occurs between the member to be joined and the joining material.

  The bonding material is formed using the same raw material as the member to be bonded, through the reaction sintering process conditions similar to the reaction sintering process conditions performed on the member to be bonded. Therefore, a silicon nitride ceramic bonding material having characteristics equivalent to those of the members to be bonded is formed in the gap portion.

  Therefore, in the joined body obtained through this step, the difference in characteristics between the member to be joined and the joining material is significantly suppressed, and a joined body that is homogeneous throughout is obtained.

(Step S180)
Although the silicon nitride ceramic joined body having the features of the present invention can be obtained by the above-described steps, if necessary, a post-sintering process is further performed using the joined body obtained in step S170. . By this treatment, a more uniform and highly sintered silicon nitride ceramic joined body can be obtained. The post-sintering treatment is performed, for example, by maintaining the joined body at a temperature of 1600 ° C. to 2000 ° C. under an atmospheric pressure or a pressurized nitrogen atmosphere. The nitrogen pressure is, for example, in the range of 1 atmosphere to 9.5 atmospheres. The processing time is, for example, about 1 hour to 10 hours.

  Of course, in this post-processing step, the entire bonded body is processed under the same conditions. Therefore, even after this processing, there is little difference in characteristics between the member to be bonded and the bonding material, that is, overall. The homogeneous state is maintained as it is.

  Next, the effects of the present invention will be described in more detail with reference to examples.

Example 1
First, silicon powder (purity 98%) having a particle size of # 600 or less (average particle size 22 μm) and a sintering aid are sufficiently mixed by a ball mill as a raw material for a member to be joined and dried to obtain a mixed powder. It was. As the sintering aid, zirconia (ZrO ₂ ) particles (average particle size 2 μm) and spinel (MgAl ₂ O ₄ ) particles (average particle size 4 μm) were used. Each particle was mixed so that the composition after sintering was Si ₃ N ₄ -5 wt% ZrO ₂ -5 wt% MgAl ₂ O ₄ .

  Next, using this mixed powder, molding was performed by the CIP method described above to obtain two molded bodies. The treatment pressure (hydrostatic pressure) was 100 MPa. Both of the molded bodies thus obtained had a plate shape with dimensions of about 60 mm in length, 40 mm in width, and 6 mm in thickness.

  Furthermore, these compacts were subjected to a reactive sintering treatment to obtain a silicon nitride ceramic porous plate-like member to be joined. The reactive sintering treatment was carried out by heating the molded body from room temperature to 1450 ° C. over 30 hours in a nitrogen atmosphere of 1 atm and then holding at this temperature for 2 hours.

  Next, a slurry for a bonding material was prepared by adding 0.7 wt% dispersant, 1 wt% binder, and 35 wt% water to the above-mentioned mixed powder weight and sufficiently stirring. As the dispersant, ammonium polyacrylate was used. Moreover, polyvinyl alcohol was used for the binder. The viscosity of the slurry was 110 cps and the solid content concentration was 55%.

  Next, the above-mentioned two plate-like members to be joined were joined by the following method using the aforementioned slurry for joining material.

  First, one end face (region of 60 mm length × 6 mm thickness) of each plate-like member to be joined was polished with # 220 polishing paper in order to roughen the surface. Next, each plate-like member to be bonded is placed on an alumina pedestal having a dimension sufficiently larger than that of the plate-like member to be bonded so that the polished end faces face each other with a gap of about 1.5 mm. Arranged. Next, both ends of the gap portion between the plate-like members to be joined were fastened with a sealing material, and the above-described slurry was poured into this gap portion. The slurry was poured until the gap was completely filled with solids.

  In this state, the obtained assembly was kept at room temperature in the atmosphere to sufficiently dry the moisture contained in the assembly.

  Next, this assembly was installed in the atmosphere furnace together with the pedestal, and the reaction material was subjected to reactive sintering treatment (part where the slurry was solidified). The reaction sintering process was carried out by heating the assembly from room temperature to 1450 ° C. over 30 hours under a nitrogen atmosphere of 1 atm, and holding at this temperature for 2 hours. Thereafter, the assembly was cooled to room temperature (furnace cooling) to obtain a joined body (60 mm long × 81.5 mm wide) in which two members to be joined were joined by a joining material.

  Next, post-sintering was performed using the obtained joined body. The post-sintering treatment was performed by raising the temperature of the joined body from room temperature to 1800 ° C. over 3 hours under a nitrogen atmosphere of 5 atm, and then holding at this temperature for 8 hours.

  Hereinafter, the bonded body of silicon nitride ceramics obtained through such a process is referred to as “bonded body according to Example 1”.

(Comparative Example 1)
As raw materials for the members to be joined, silicon nitride powder (purity 99%) having a particle size of # 320 or less (average particle size 4 μm) and a sintering aid were mixed by a ball mill and dried to obtain a mixed powder. As the sintering aid, zirconia (ZrO ₂ ) particles (average particle size 2 μm) and spinel (MgAl ₂ O ₄ ) particles (average particle size 4 μm) were used. Each particle was mixed so that the composition after sintering was Si ₃ N ₄ -5 wt% ZrO ₂ -5 wt% MgAl ₂ O ₄ .

  Next, using this mixed powder, molding was performed by the CIP method in the same manner as in Example 1 to obtain two silicon nitride-based molded bodies. The treatment pressure (hydrostatic pressure) was 100 MPa. Both of the molded bodies thus obtained had a plate shape with dimensions of about 60 mm in length, 40 mm in width, and 6 mm in thickness.

  Furthermore, these molded bodies were subjected to a sintering process (so-called calcination process) to obtain a porous plate-shaped bonded member. The pre-sintering treatment was performed by raising the temperature of the molded body from room temperature to 1300 ° C. over 2 hours in a nitrogen atmosphere of 1 atm and then holding at this temperature for 2 hours.

  Next, a slurry for a bonding material was prepared by adding 0.8 wt% dispersant, 1 wt% binder, and 35 wt% water to the mixed powder weight described above and stirring sufficiently. As the dispersant, ammonium polyacrylate was used. Moreover, polyvinyl alcohol was used for the binder. The viscosity of the slurry was 130 cps and the solid content concentration was 47%.

  Next, the above-mentioned two plate-like members to be joined were joined by the following method using the aforementioned slurry for joining material.

  First, one end face of each plate-like member (60 mm long × 6 mm thick region) was polished with # 220 polishing paper. Next, each plate-like member to be bonded is placed on an alumina pedestal having a dimension sufficiently larger than that of the plate-like member to be bonded so that the polished end faces face each other with a gap of about 1.5 mm. Arranged. Next, both ends of the gap portion between the plate-like members to be joined were fastened with a sealing material, and the above-described slurry was poured into this gap portion. The slurry was poured until the gap was completely filled with solids.

  In this state, the obtained assembly was kept in the atmosphere at room temperature to sufficiently dry the moisture contained in the assembly.

  Next, this assembly was installed in the atmosphere furnace together with the pedestal, and the bonding material (slurry) was sintered. Sintering was carried out by heating the assembly from room temperature to 1300 ° C. over 3 hours under a nitrogen atmosphere of 1 atm and then holding this temperature for 2 hours. Thereafter, the assembly was cooled to room temperature (furnace cooling) to obtain a joined body (60 mm long × 81.5 mm wide) in which two members to be joined were joined by a joining material.

  Next, post-sintering was performed using the obtained joined body. The post-sintering treatment was performed by raising the temperature of the joined body from room temperature to 1800 ° C. over 3 hours under a nitrogen atmosphere of 5 atm, and then holding at this temperature for 8 hours.

  Hereinafter, the bonded body of silicon nitride ceramics obtained through such a process is referred to as “bonded body according to Comparative Example 1”.

(Comparative Example 2)
First, as in the case of Example 1, as a raw material for the member to be joined, silicon powder (purity 98%) having a particle size of # 600 or less (average particle size 22 μm) and a sintering aid are mixed by a ball mill and dried. A mixed powder was obtained. As the sintering aid, zirconia (ZrO ₂ ) particles (average particle size 2 μm) and spinel (MgAl ₂ O ₄ ) particles (average particle size 4 μm) were used. Each particle was mixed so that the composition after sintering was Si ₃ N ₄ -5 wt% ZrO ₂ -5 wt% MgAl ₂ O ₄ .

  Next, using this mixed powder, as in Example 1, molding was performed by the CIP method to obtain two molded bodies. The treatment pressure (hydrostatic pressure) was 100 MPa. Both of the molded bodies thus obtained had a plate shape with dimensions of about 60 mm in length, 40 mm in width, and 6 mm in thickness.

  Further, as in the case of Example 1, these compacts were subjected to a reactive sintering treatment to obtain a porous plate-like member to be joined made of silicon nitride ceramics. The reactive sintering treatment was carried out by heating the molded body from room temperature to 1450 ° C. over 30 hours in a nitrogen atmosphere of 1 atm and then holding at this temperature for 2 hours.

  Next, a paste for a bonding material was prepared by adding 1 wt% binder, 0.5 wt% plasticizer, and 35 wt% water to the mixed powder weight described above and stirring sufficiently. Polyvinyl alcohol was used as the binder. Glycerin was used as the plasticizer. The solid content concentration of the paste was 55% and the viscosity was 940 cps.

  Next, the above-mentioned two plate-like members to be joined were joined by the following method using the above-described paste for joining material.

  First, one end face of each plate-like member (60 mm long × 6 mm thick region) was polished with # 220 polishing paper. Next, each plate-like member to be bonded is placed on an alumina pedestal having a dimension sufficiently larger than that of the plate-like member to be bonded so that the polished end faces face each other with a gap of about 1.5 mm. Arranged. Next, after applying the above-mentioned paste to the gap portion between the plate-like members to be joined, the two plate-like members to be joined were temporarily joined together from both sides, thereby temporarily joining both the plate-like members to be joined. By this operation, the width of the aforementioned gap (paste) was about 70 μm. Next, this assembly was installed in the atmosphere furnace together with the pedestal, and under the same conditions as in Example 1, a reactive sintering process and a post-sintering process of the bonding material (paste) were performed.

  As a result, a joined body (60 mm long × 80 mm wide) in which two members to be joined were joined by the joining material was obtained. Hereinafter, the bonded body of silicon nitride ceramics obtained through such steps is referred to as “bonded body according to Comparative Example 2”.

(Comparative Example 3)
The members to be joined were joined together by the same method as in Comparative Example 2.

  However, in Comparative Example 3, after the reaction sintering process for only the members to be joined, in order to further densify the members to be joined, an additional sintering process was performed for the members to be joined alone. This additional sintering treatment was carried out by heating the member to be joined from room temperature to 1800 ° C. over 3 hours in a nitrogen atmosphere of 5 atm and then holding at this temperature for 8 hours.

  In Comparative Example 3, the width of the gap (paste) was about 30 μm when the two plate-like members were pressed against each other from both sides via the paste.

  Other steps and conditions are the same as in Comparative Example 2.

  Hereinafter, the bonded body of silicon nitride ceramics obtained through such steps is referred to as “bonded body according to Comparative Example 3”.

(Evaluation test for each sample)
An evaluation test was performed using samples obtained by cutting the joined bodies according to Example 1 and Comparative Examples 1 to 3 so that the joining material portion was included in the central portion. As an evaluation test, microscopic observation and strength measurement of the joint portion were performed.

  Microscopic observation was carried out by observing the inside of the bonding material and the interface between the bonding material and the member to be bonded using an optical microscope and SEM (scanning electron microscope). Further, after applying blue ink to the surface of the sample, the penetration state of the blue ink was observed with a stereomicroscope. The strength measurement was performed by a four-point bending test using a test piece cut out in a length of 3 mm, a width of 4 mm, and a length of 40 mm in accordance with a bending strength test method defined in JS-R1601.

  The results of the evaluation test for each sample are summarized in Table 1. In addition, the intensity | strength of each sample was shown by the average value (average intensity | strength) of 10 times of a 4-point bending test.

  In FIG. 2, the SEM photograph of the joining material of the sample of Example 1 is shown. FIG. 3 shows an SEM photograph of the fracture surface of the bonding material after the strength test in the sample of Comparative Example 2. FIG. 4 shows an optical micrograph of the bonding material / bonded member interface in the sample of Comparative Example 3. Further, FIGS. 5 and 6 show examples of states after the blue ink application test in the samples of Example 1 and Comparative Example 1, respectively.

  As a result of microscopic observation, it was found that any sample of Comparative Examples 1 to 3 had defects inside the bonding material. Further, it was confirmed that a defect occurred at the interface between the bonding material and the member to be bonded. For example, it can be seen from FIG. 3 that the sample of Comparative Example 2 contains a large number of defects in the bonding material. Further, as shown in FIG. 4, in the case of the sample of Comparative Example 3, it can be seen that a large number of defects are generated at the positions indicated by arrows on the interface.

  In the blue ink application test, it was confirmed that the blue ink entered the interface between the bonding material and the bonded member in any sample. As an example, FIG. 6 shows the state of the sample of Comparative Example 1 after the blue ink application test.

  Furthermore, as shown in Table 1, in the samples of Comparative Examples 1 to 3, the strength was about 170 to 260 MPa, and it was found that no sufficient strength was obtained. In particular, the strength of the sample of Comparative Example 3 was less than half of the result of Example 1 described later.

  Thus, even if it is the method (comparative example 1) which does not utilize the reactive sintering of a silicon particle, and the method which utilizes reactive sintering, when a paste is used as an introduction form of a joining material (comparative example 2, In 3), it was found that a good bonding state could not be obtained in any case.

  In the case of Comparative Example 1, since the reaction process is not included in the manufacturing process, silicon nitride is not formed from the gas phase, and it is difficult to arrange the silicon nitride in a form that fills the space. It is considered that a simple bonding material was not formed.

  Further, in Comparative Examples 2 and 3, it is difficult to densely fill the silicon particles in the gap due to the low fluidity of the paste, and it is considered that a uniform bonding material was not formed. In particular, in the sample of Comparative Example 3, a member having poor fluidity is used as an installation form of the bonding material, and the bonded members are highly sintered. For this reason, the silicon particles contained in the paste cannot be arranged uniformly and with a high packing density in the gap, and as a result, it is considered that the strength of the bonding material is greatly reduced.

  On the other hand, in the sample of Example 1, no defects were recognized inside the bonding material, and almost no defects were present at the interface between the bonding material and the member to be bonded. In FIG. 2, the SEM photograph of the joining material of the sample of Example 1 is shown. From this photograph, it can be seen that almost no defects are observed inside and at the interface of the bonding material. Moreover, it turns out that the joining material is homogenous with the to-be-joined member, and the boundary is unclear.

  Further, as shown in FIG. 5, as a result of the blue ink application test, it was found that in the sample of Example 1, the blue ink hardly penetrated into the bonding material. Further, as shown in Table 1, it was confirmed that the sample of Example 1 had a strength exceeding 400 MPa, and a sufficiently large strength was obtained as compared with other samples.

  INDUSTRIAL APPLICATION This invention can be utilized for the method of joining the to-be-joined members of silicon nitride ceramics via a joining material.

It is the figure which showed an example of the schematic flow for enforcing the method of this invention. 2 is a SEM photograph of a bonding material of a sample of Example 1. 5 is a SEM photograph showing a fracture surface of a bonding material in a sample of Comparative Example 2. 6 is an optical micrograph of a bonding material / bonded member interface in a sample of Comparative Example 3. 2 is a photograph showing a state after a blue ink application test in the sample of Example 1. FIG. 6 is a photograph showing a state after a blue ink application test in the sample of Comparative Example 1.

Claims (9)

A method of joining members to be joined of silicon nitride ceramics,
(A) preparing a first raw material mainly composed of silicon particles;
(B) forming a molded body from the first raw material;
(C) A step of holding the molded body at a temperature in the range of 1100 ° C. to 1450 ° C. in a nitrogen atmosphere and subjecting silicon particles in the molded body to a reactive sintering treatment, whereby silicon nitride A step of obtaining a porous bonded member made of a ceramic based material,
(D) A step of preparing a second raw material containing silicon particles, which is included in the second raw material when the particle size distributions of the silicon particles contained in the first raw material and the second raw material are compared. At least one parameter value among the maximum particle size, the mode particle size, and the ratio of the particles having the mode particle size is ± 20% of the same parameter value of the silicon particles contained in the first raw material. Steps within the range of
(E) preparing a slurry having a viscosity in the range of 50 cps to 300 cps from the second raw material;
(F) Injecting the slurry into the gap between the members to be joined, where the joining material is formed later, causing the joined member to absorb moisture in the slurry, solidifying the slurry, and forming a joining material Obtaining an assembly by:
(G) holding the assembly at a temperature in the range of 1100 ° C. to 1450 ° C. in a nitrogen atmosphere and subjecting the silicon particles in the bonding material to reactive sintering;
Have
The steps (a) to (c) are performed before or after the steps (d) to (e), or the steps (a) to (c) are the steps (d) to (e). A method that is performed in parallel.   The method according to claim 1, wherein the first raw material and / or the second raw material further includes an additive substance.   The additive substances include Mg (magnesium), Al (aluminum), Y (yttrium), Sc (scandium), La (lanthanum), Ce (cerium), Zr (zirconium), Yb (ytterbium), Hf (hafnium), 3. A metal selected from the group consisting of Ti (titanium), Lu (ruthenium), and a combination of two or more thereof, or an oxide of the metal, or a nitride of the metal. The method described in 1. The first raw material and / or the second raw material is further at least one of TiN (titanium nitride), SiC (silicon carbide), BN (boron nitride), C (carbon), and ZrO ₂ (zirconia). 4. A method according to any one of the preceding claims, comprising one material.   The method according to any one of claims 1 to 4, wherein the first raw material and the second raw material have substantially the same composition. After the step (g),
(H) having a step of post-sintering the obtained joined body,
The temperature of the post-sintering process is higher than the temperature of the reactive sintering process in the step (c) and the step (g), and / or the post-sintering process includes the step (c) and the step ( The method according to any one of claims 1 to 5, wherein the method is performed in a nitrogen atmosphere having a pressure equal to or higher than the pressure of the nitrogen atmosphere in the reactive sintering treatment in g).   The method according to claim 6, wherein the post-sintering treatment is performed in a temperature range of 1600 ° C. to 2000 ° C. in a nitrogen atmosphere of 1 to 9.5 atm.   The method according to any one of claims 1 to 7, characterized in that the slurry prepared in step (e) comprises water and a dispersant and / or binder.   The method according to any one of claims 1 to 8, wherein a gap between the members to be joined is 1.5 mm or more.