KR100623183B1 - Joining method of ceramic substrates using transient nano-particle layer - Google Patents

Abstract

TECHNICAL FIELD This invention relates to the joining method of a ceramic base material. More specifically, It is related with the method of joining a ceramic base material using a ceramic material as a joining material. The present invention provides a method of joining two ceramic substrates, the method comprising: providing a nanoparticle layer comprising a compound constituting the ceramic substrate on at least one of the bonding surfaces of the two ceramic substrates; And aligning the two ceramic substrates with respect to a bonding surface, and bonding the two ceramic substrates by pressurizing and heating the two ceramic substrates. According to the present invention, a ceramic sintered body and a single crystal bonded body having excellent bonding properties throughout the bonding interface, having a bonding strength equivalent to that of a monolithic substance, and having no deterioration of chemical stability and light transmittance at the interface can be produced. .

Bonding, Ceramics Substrate, Nanoparticle Layer, Abnormal Grain Growth

Description

Joining method of ceramic substrate using abnormal grain growth technique {JOINING METHOD OF CERAMIC SUBSTRATES USING TRANSIENT NANO-PARTICLE LAYER}

1 is a procedure showing the bonding step of the ceramic substrate according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating one embodiment of providing a nanoparticle layer of FIG. 1.

3 is a diagram illustrating a process in which a nanoparticle layer disappears due to abnormal grain growth of a substrate.

4 is a view schematically showing a heating press device used in the embodiment of the present invention.

FIG. 5A is a scanning electron microscope of a nanoparticle layer formed on the surface of an alumina single crystal substrate according to an embodiment of the present invention, and FIG. 5B is a scanning image of a cut surface of a bonded body prepared by subjecting the single crystal substrate of FIG. Electron micrograph.

FIG. 6A is a scanning electron microscope of a nanoparticle layer formed on the surface of an AlN sintered body substrate according to an embodiment of the present invention, and FIG. 6B is a cross-sectional view of the bonded body prepared after pressure-heating the single crystal substrate of FIG. 6A. Scanning electron micrograph.

7A is a scanning electron microscope photographing a nanoparticle layer formed on the surface of a Si ₃ N ₄ sintered body substrate according to an embodiment of the present invention, and FIG. 7B is a cross-sectional view of the bonded body formed by subjecting the single crystal substrate of FIG. It is a scanning electron microscope photograph taken.

8 is a scanning electron micrograph of the cut surface of the SiC sintered body manufactured according to an embodiment of the present invention.

TECHNICAL FIELD This invention relates to the joining method of a ceramic base material. More specifically, It is related with the method of joining a ceramic base material using a ceramic material as a joining material.

In general, joining processes are used to easily make products of larger and more complex shapes using two or more objects. Ceramics are of great industrial importance because of their high hardness, high temperature strength, chemical stability and heat resistance. However, compared to metals that can be easily joined by welding or rivets, ceramics cannot be welded and difficult to machine due to high hardness, making it difficult to manufacture ceramics of complex shape.

Conventional bonding between ceramics is a method using the thermal expansion coefficient difference between the ceramics disclosed in Japanese Patent Application Laid-Open No. 2004-149401, a method using a synthetic resin adhesive disclosed in Japanese Patent Application Laid-Open No. 2002-368151, and Japanese Patent Publication No. 1995-069750 A brazing method using a metal layer, a method using a glass flux disclosed in Japanese Patent Laid-Open No. 1997-338295, a method using a ceramic cement disclosed in Japanese Patent Laid-Open No. 1994-256067, and the like.

Among the above methods, the method using the coefficient of thermal expansion difference between ceramics has a problem that the bonding strength of the bonded body is limited by the low strength of the ceramics, and it is difficult to apply to complex shapes, and the bonding method using an adhesive or glassy flux or cement has a bonding interface. The low strength and thermal stability, low chemical stability exhibits a problem that the physical properties of the conjugate is significantly reduced compared to the single body. In addition, the bonding method using brazing is also limited to the melting point of the metal used in the bonding, so that it cannot be used at high temperatures and satisfactory bonding strength cannot be obtained, and the chemical resistance is degraded by the brazing layer. there was.

In order to solve this problem, Japanese Laid-Open Patent Publication No. 2000-026172 has proposed a method of simultaneously firing a ceramic molded body and US Pat. No. 4,440,22, a method of obtaining a joint by diffusion of ceramics by heat-treating the ceramic sintered body at high temperature and high pressure. However, the method of co-firing the molded body is not only easy to handle due to the low strength of the molded body, but also difficult to control the degree of shrinkage during firing. There is a difficult problem. In addition, the ceramic bonding method by diffusion requires high temperature close to the sintering temperature of ceramics and high pressure of 200 atm or higher for good bonding due to the low diffusion rate of ceramics. Strength reduction was inevitable. In addition, in the case of single crystals, due to the difficulty of plastic deformation due to the diffusion method, even when the high temperature close to the melting point and the high pressure of 400 atm or more are combined, the bonding interface is not uniform and only a part of the bonding is bonded. There was a weak issue.

Therefore, there is an urgent need for a new ceramic bonding method for maintaining high strength and chemical resistance, which are advantages of ceramics, and at the same time obtaining high bonding strength.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of joining a ceramic base material, in which the interface characteristics of the joined body are significantly improved as compared with the prior art.

In order to achieve the above technical problem, the present invention provides a method for joining two ceramic substrates, the nanoparticle layer comprising a compound constituting the ceramic substrate as a component on at least one of the bonding surfaces of the two ceramic substrates. A step of aligning the two ceramic substrates with respect to the bonding surface of the two ceramic substrates, and the two ceramic substrates by pressurizing heating the ceramic substrates comprising the step of bonding the two ceramic substrates.

In order to achieve the above technical problem, the present invention provides a method for joining two ceramic substrates of metal oxides, the method comprising: providing a metal oxide nanoparticle layer on at least one of the bonding surfaces of the two ceramic substrates. And aligning the two ceramic substrates with respect to the bonding surface of the ceramic substrate, and bonding the two ceramic substrates by pressurizing and heating the two ceramic substrates.

In addition, the present invention can be applied to the case where the ceramic substrate is a metal carbide, wherein the nanoparticle layer is composed of a metal carbide. In addition, when the ceramic substrate is a metal nitride, the nanoparticle layer is composed of a metal nitride.

In the present invention, the average particle diameter of the nanoparticle layer is preferably 100 nm or less, and the thickness is preferably 10 nm to 5 μm. In addition, the nanoparticle layer may be provided by sputtering.

In the present invention, the pressure of the bonding step is 2 to 200 atm, the temperature of the bonding step is preferably about 1000 ~ 1900 ℃.

According to an embodiment of the present invention, the two ceramic substrates are preferably made of the same material, and in this case, the nanoparticle layer is preferably made of the same material as the ceramic substrate. In contrast, the nanoparticle layer is different from the ceramic substrate. It should be a ceramic material that can be dissolved in the ceramic substrate. The ceramic material which can be used here is not necessarily a complete solid solution, and is applicable to a partial solid solution having a solid solubility of 1 at% or more in the ceramic substrate at the junction temperature. This is because the thickness of the nanoparticle layer is very thin, so that even when a small amount of solid solution to the ceramic substrate is displayed, the nanoparticle layer is easily absorbed and disappears from the ceramic substrate.

In addition, when the nano-particle layer is a ceramic material which can be solid-dissolved simultaneously in the two ceramic substrates, the method of the present invention may be applied even when the two ceramic substrates are different materials.

In order to achieve the above technical problem, the present invention provides a method for joining two ceramic substrates made of metal oxides, the metal comprising a metal element constituting the metal oxide on at least one of the bonding surfaces of the two ceramic substrates. Forming a thin film layer, forming a nanoparticle layer including a metal oxide by heat-treating the ceramic substrate on which the metal thin film layer is formed at a first temperature in an oxidizing atmosphere, aligning a bonding surface of the two ceramic substrates, and the two ceramics And bonding the two ceramic substrates by pressing the substrate at an oxidizing atmosphere and at a second temperature higher than the first temperature.

The method of the present invention is also applicable to the case where the ceramic substrate is metal carbide or metal nitride. At this time, the nano-particle layer forming step is performed in a carbonized atmosphere or a nitride atmosphere, respectively.

In the present invention, the alignment step may be performed before the nanoparticle layer forming step.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Definitions of terms used in the specification of the present invention are as follows.

First, 'ceramic' refers to a solid material manufactured using an inorganic nonmetallic material as a main component, and refers to a state in which constituent materials are chemically and firmly bound beyond the aggregated state. Even if the material is an inorganic non-metallic material, it is excluded from the ceramics of the present invention, which is merely molded by pressurization, whereas there is no sintered body or grain boundary composed of a plurality of particles, and the particles are bonded by a grain boundary. It includes single crystals with a single crystal structure. 'Ceramic substrate' refers to any type of ceramic material to be joined.

In addition, in the specification of the present invention, 'metal oxide' means Al ₂ O ₃ , ZrO _2, TiO ₂ , MgO, BeO, CaO, ZnO, BaTiO ₃ , SnO _2, ITO (Sn doped In ₂ O ₃ ), Nonmetallic compounds prepared by reacting periodic metallic elements with oxygen such as PZT (Pb (Zr, Ti) O ₃ ), PMN-PT (Pb (Mg _1/3 , Nb _2/3 ) O ₃ -PbTiO ₃ ) The term 'metal nitride' refers to a nonmetallic compound produced by the reaction of a periodic metallic element with nitrogen such as AlN, Si ₃ N ₄ , TiN, GaN, ZrN, etc., and 'metal carbide' means SiC, TiC. It refers to a nonmetallic compound produced by the reaction of a metallic element on the periodic table with carbon such as VC, TaC, WC, (W, Ti) C, and the like. In addition, in the detailed description of the present invention, metal oxides, metal nitrides, and metal carbides exclude components other than metals, oxygen, nitrogen, and carbon, such as hydrogen (H), chlorine (Cl), and sulfur (S), in their composition formulas. And the compounds produced by the reaction of two or more elements of carbon, nitrogen, and oxygen with a metal, such as Ti (C, N), Si (O, N), and Ti (C, O). Therefore, nitride used in the specification of the present invention is used in the sense including a complex compound such as Ti (C, N), AlON.

Referring to FIG. 1, first, a ceramic nanoparticle layer is provided on a bonding surface of two ceramic substrates to be bonded (S110). In the present invention, the ceramic substrate is preferably composed mainly of metal oxides, metal nitrides or metal carbides. Of course, the technical idea of the present invention can be applied to the case where other nonmetallic compounds such as fluoride and chloride such as MgF ₂ form the main component of the substrate.

A single compound may be used as the compound that forms the main component of the ceramic substrate, but an oxide / carbide complex compound such as Al ₂ O ₃ -TiC may be used. In addition, it is preferable that the two ceramic substrates to be bonded in the present invention are the same compound. However, when the thermal expansion coefficients are similar to each other and easily form a solid solution, it is also possible to use a ceramic substrate mainly composed of different kinds of compounds.

The ceramic nanoparticle layer may be provided on both bonding surfaces of the two ceramic substrates, or may be provided only on one bonding surface of the two ceramic substrates.

In the present invention, the nanoparticle layer is preferably made of the same composition as the ceramics or single crystal substrate, or at least includes at least one component. This ensures that the nanoparticle layer is extinguished by grain growth of the ceramic substrate in the subsequent pressure heat treatment step.

When the components of the nanoparticle layer are different from the ceramic substrate, only grain growth occurs in the nanoparticle layer, which causes a problem that the bonding layer remains on the bonding surface of the ceramic substrate. Therefore, even if the nanoparticle layer does not contain the same compound as the ceramic substrate, the composition may be used as the nanoparticle layer when the composition includes a component that can be easily dissolved in the ceramic substrate. For example, since the MgO compound is easily dissolved in alumina to form a solid solution and does not precipitate as a secondary phase, the alumina substrate may be bonded by forming a nanoparticle layer with the MgO compound.

In addition, in the present invention, when the compound constituting the ceramic substrate is a composite compound, the nanoparticle layer may include a part of components of the composite compound. For example, when the ceramic substrate is an alumina-zirconia composite, alumina or zirconia may be used as the nanoparticle layer. This is because the grain growth of the ceramic substrate is also possible through the alumina or zirconia monolith.

In addition, in the case where the constituents of ceramics, such as BaTiO ₃ , contain two or more metal elements, good bonding is achieved even when the particle layer is formed of BaO or TiO ₂ alone, which means that BaTiO ₃ has some non-chemical stoichiometry. stoiciometry), because excess BaO or TiO ₂ may exist in solid solution inside the lattice. At this time, however, BaO or TiO ₂ should not be used in an excessive amount so as to precipitate as a secondary phase.

In the present invention, the thickness of the nanoparticle layer is preferably 10nm-5㎛. When the thickness of the nanoparticle layer is 10 nm or less, a portion in which the nanoparticle layer does not come into contact with the ceramic substrate may occur due to the surface roughness of the ceramic substrate bonding surface, thereby resulting in poor bonding such as pores. When the nanoparticle layer is thicker than 5 μm, the nanoparticle layer may remain on the bonding surface after bonding, thereby degrading the properties of the bonded body such as bonding strength and high temperature properties.

In the present invention, the size of the particles constituting the nanoparticle layer is preferably at most 100nm or less. If the particle size exceeds 100 nm, the plastic deformation is difficult in the subsequent heating and pressing process, so that the gap between the joining sites is not filled, and it remains at the interface, causing deterioration of the bonding properties. This is described in more detail in the bonding mechanism of the present invention. In the present invention, the smaller the size of the particles constituting the nanoparticle layer is preferable and there is no particular limitation.

In the present invention, various conventional methods known as a method of forming a material layer may be used to provide a ceramic nanoparticle layer on a ceramic substrate. For example, various deposition methods, such as chemical vapor deposition and sputtering, can be used. In addition, the nano-particle layer may be prepared by applying a nano-sized fine ceramic powder prepared by the sol-gel method or the like to a ceramic substrate by spraying or the like. Specific techniques for providing a nanoparticle layer by such a method are well known to those skilled in the art to which the present invention pertains and will not be described in detail herein.

In addition, as in some embodiments of the present invention described below, the ceramic nanoparticle layer may be formed by heat treatment. This will be described with reference to FIG. 2.

Referring to FIG. 2, first, a metal thin film layer is formed on a bonding surface of a ceramic substrate (S112). The metal thin film layer may be provided by a method such as physical vapor deposition, and the metal thin film layer may be formed on the bonding surface of either ceramic substrate. The metal thin film layer is preferably a metal element included in the compound composition of the ceramic substrate, and alternatively, the metal thin film layer may be a metal element that can be dissolved in the ceramic substrate. The thickness of the metal thin film layer is appropriately selected such that the thickness of the oxide, nitride or carbide formed by the subsequent heat treatment process is in the above-described thickness range, that is, preferably in the range of 10 nm-5 탆.

Subsequently, the ceramic substrate on which the metal thin film layer is formed is subjected to an atmospheric heat treatment. The heat treatment atmosphere is selected according to the composition of the ceramic substrate (S114). For example, when the ceramic substrate is an oxide, nitride or carbide, respectively, an oxidizing atmosphere, a nitride atmosphere, or a carbonization atmosphere is selected as the heat treatment atmosphere. The oxidizing atmosphere may be performed by leaving the atmosphere or by supplying oxygen gas, and the nitriding atmosphere may be performed by supplying a gas serving as a nitrogen source such as nitrogen or ammonia. The carbonization atmosphere can also be carried out by the supply of a gas that acts as a carbon source, such as methane gas. The metal element constituting the metal thin film layer by the selected atmosphere reacts with the supplied atmospheric gas to form a nanoparticle layer of oxide, nitride or carbide. At this time, the atmospheric heat treatment temperature affects the size of the oxide, nitride or carbide particles formed, it is necessary to pay attention to the temperature selection.

For example, the higher the atmospheric heat treatment temperature, the faster the oxidation, nitriding and carbonization of the metal, while increasing the particle size. When the atmospheric heat treatment temperature is lowered, the opposite phenomenon occurs. Therefore, the atmospheric heat treatment temperature should be appropriately selected in consideration of the size and reaction speed of the particle layer to be formed, the selection of the heat treatment temperature in consideration of such variables can be easily carried out by those of ordinary skill in the art to which this invention belongs. It is about. According to an embodiment of the present invention, the heat treatment temperature is in the range of about 400 to 1400 ° C. depending on the composition of the compound formed by the heat treatment.

Referring back to FIG. 1, the bonding surfaces of the two ceramic substrates on which the nanoparticle layer is formed are aligned (S120). This step is a preliminary step for the subsequent pressing and heating step, in which the joining surfaces are in good contact with each other. In particular, when the two ceramic substrates are single crystals, the orientations of the bonding surfaces of the respective substrates should be aligned to match each other.If the crystal orientation differences of the two substrates are large, the high stress occurs at the interface during the cooling process after heat treatment due to the difference in thermal expansion coefficient. Or the dislocation density increases at the joining interface after joining, thereby deteriorating the physical properties of the joined body. However, it is possible to bond with specific crystallographic orientations in which there is no thermal expansion coefficient difference, such as Σ3, Σ9, twin grain boundaries, or the like.

Subsequently, the two ceramic substrates are pressed and heated to be heat treated (S130). By performing this step, the nanoparticle layer positioned between the two ceramic substrates gradually disappears and the two ceramic substrates are integrally bonded.

Referring to the mechanism of the ceramic substrate is bonded in the step S130 of the present invention as follows.

First, the nanoparticle layer located between the ceramic substrates generates plastic deformation due to the pressure applied at a high temperature. Such hot plastic deformation of ceramics is called super plasticity and has been widely known since published in Advanced Ceramics Materials 1, 259, (1986) by F. Wakai. As in the present invention, nano-sized particles have a very high superplasticity, so they are easily deformed even by low pressure, filling the pores existing between the conjugates and forming a dense contact surface. Therefore, the pressure required at this time is very low compared to the pressure used in the conventional ceramic bonding method by diffusion.

Next, the nanoparticle layer disappears due to abnormal grain growth of the particles constituting the ceramic substrate during the high temperature heat treatment, so that the structure of the interface layer cannot be distinguished from the microstructure of the ceramic substrate.

3 is a diagram illustrating a process in which the nanoparticle layer disappears due to abnormal grain growth of the single crystal substrate when the ceramic substrate is a single crystal. As shown in (a) of FIG. 3, the nanoparticle layer 110 positioned at the interface between the ceramic substrates 100 under the heat and pressurized state has a very small particle size compared to the particles constituting the substrate 100. It is absorbed into the substrate and disappears according to the difference in the radius of curvature. Accordingly, the interfaces 112 and 114 of the substrate and the nanoparticle layer gradually move to the center of the nanoparticle layer 110, and ultimately, the two interfaces 112 and 114 meet and the nanoparticle layer 110 disappears. At this time, when the crystal orientations of the single crystals, which are the bonding substrates, coincide, the difference in the crystallographic orientations between the two interfaces 112 and 144 disappears, and as a result, the bonding substrate is one single crystal as shown in FIG. It becomes like 120. As such, the phenomenon in which coarse particles remain due to the grain growth of coarse particles that are much larger than the average particle diameter is called abnormal grain growth, and is particularly referred to as introduction to ceramics such as WD Kingery. , John Wiley & Sons, Inc., New York, pp 461 (1960)). At this time, the reduction of interfacial energy between particles acts as a driving force for abnormal grain growth. Since the nanoparticle layer of the present invention is composed of fine particles and has a very large grain boundary energy, it is absorbed by coarse grains on the ceramic sintered substrate or grain growth of a single crystal substrate. This reduces the grain boundary energy.

In the present invention, the particle size of the nanoparticle layer greatly affects the bonding properties. First, as the particle size of the nanoparticle layer increases, the grain boundary energy decreases, thereby reducing the driving force of abnormal grain growth. Therefore, the particle layer remains at the bonding interface even after the bonding.

In addition, as the particle size of the nanoparticle layer increases, the size of pores present in the nanoparticle layer also increases. If the pore size is small, the mobility of the pores is fast enough, so the interface and the pores are not separated at the time of abnormal grain growth, so the pores are quickly removed by the grain boundary diffusion. The pores and grain boundaries are easily separated and captured inside the ceramic matrix particles. In this way, the trapping pores must be removed through the intra-diffusion process, and the trapping pores remain because the intra-diffusion rate is very slow. Such residual pores cause a great decrease in the strength and light transmittance of the interface.

Therefore, as described above, in order for the particle layer to completely disappear at the bonding interface in the present invention, the nanoparticle layer preferably has an average particle size of 100 nm or less.

Referring back to Figure 1, in the present invention, the pressure applied in the pressing and heating step (S130) is preferably 2 to 200 atm. If the pressure is less than 2 atm, the contact between the joining does not occur sufficiently, the rearrangement of the nanoparticles due to the pressure is difficult to cause pores in the bonding interface, if the pressure is more than 200 atm, the deformation of the conjugate is severed by creep there is a problem.

In the present invention, the heat treatment temperature during the pressure heat treatment is preferably 1000 degrees or more, and preferably 100 degrees or more below the sintering temperature of the ceramic sintered body or lower than the single crystal melting point. When the heat treatment temperature is 1000 degrees or less, since the diffusion speed of the particles is very slow, the nanoparticle layer is hard to disappear due to grain growth, which causes a problem of remaining. In addition, when the heat treatment temperature is close to the sintering temperature of the sintered body, excessive grain growth occurs in the ceramic substrate itself due to the heat treatment, so that the strength of the ceramic substrate itself decreases, or the deformation of the bonded body becomes severe due to creep. There is a problem in that defect density such as dislocations and vacancy increases in the single crystal.

In the present invention, the gas atmosphere during the pressurized heat treatment is preferably an oxygen atmosphere when the ceramic substrate is an oxide, a nitrogen atmosphere when the nitride is nitride, and a hydrocarbon gas atmosphere such as methane for the carbide. If the gas atmosphere is not properly controlled during heat treatment, there is a problem in that the decomposition ceramic material is decomposed on the surface of the ceramic substrate or an oxide film is formed on the surface of the substrate.

In the present invention, since the temperature and pressure at the time of joining are very low compared with the conventional diffusion bonding method, there is almost no change in physical properties or shape of the ceramic substrate. Only the nanoparticle thin film layer causes deformation due to superplasticity, but its thickness is very thin, such as 5 μm or less, so that the numerical deformation in the bonded body is negligibly small. In addition, since the heat treatment is performed at a temperature lower than the sintering temperature, the ceramic substrate particles hardly cause grain growth, and only nanoparticles having a very high grain boundary energy disappear due to abnormal grain growth to the ceramic substrate or single crystal.

Hereinafter, the present invention will be described in detail by explaining preferred embodiments of the present invention. However, embodiments of the invention may be modified in many different forms and should not be construed as limited to the embodiments set forth below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

4 is a view schematically showing a heating press device used in the embodiment of the present invention. As shown, the ceramic sintered body or single crystal substrate 100 having the nanoparticle layer 110 formed on one or both bonding surfaces is aligned with each other by the pressing device 130 provided in the chamber 180 of the device. The heating element 140 for heating the substrate is provided around the substrate 100. In addition, the apparatus includes a gas inlet 150 for introducing a suitable atmosphere gas and a gas outlet 160 for discharging the introduced atmospheric gas according to the constituents of the ceramic substrate. In addition, the chamber 180 of the device is provided with a pressure gauge 170 for measuring the pressure applied to the junction and a thermometer 190 such as a thermocouple for temperature measurement.

As the heating element 140, a carbon material is generally used, but when it is necessary to maintain a high oxygen partial pressure as the gas atmosphere, it is preferable to use SiC or MoSi ₂ that is strong in the oxidation atmosphere.

Experimental Example

An Al thin film was deposited at room temperature to a thickness of 50 nm by thermal evaporation, respectively, on the bonding surface ((0001) surface) of two Al ₂ O ₃ single crystal substrates of 20 mm × 20 mm × 5 mm. Subsequently, each substrate on which the Al thin film was formed was heat-treated at 500 ° C. for 1 hour in air to form a metal oxide nanoparticle layer on the surface of the substrate. 5A shows the surface of the substrate after heat treatment with a scanning electron microscope. It can be seen that a nanoparticle layer having an average particle diameter of about 30 nm was formed by the heat treatment. XRD analysis confirmed that the nanoparticle layer was γ-alumina.

After aligning the crystal directions of the Al ₂ O ₃ single crystal substrate coated with the nanoparticle layer was subjected to pressure heat treatment in a pressure heating apparatus. At this time, the pressure of the pressurization apparatus was about 10 atmospheres, the temperature increase rate was 10 degrees / min, the heat processing temperature was 1700 degreeC, and the heat processing time was 1 hour. Argon gas having a purity of 99.5% was used as the heat treatment atmosphere gas. Since the argon gas contains 0.1% or more of oxygen as an impurity, the argon gas may provide an oxidation atmosphere that does not cause decomposition of the Al ₂ O ₃ single crystal.

5B is a scanning electron micrograph of the cross section of the Al ₂ O ₃ single crystal assembly after the pressure heat treatment.

On the high magnification (× 330) electron microscope, it can be seen that the bonding was performed to such an extent that the interface (arrow) between the two ceramic substrates (A, B) was not distinguished. In addition, when observed visually, the conjugate was found to have a light transmittance similar to that of a single crystal.

Table 8 shows the results of measuring four points of bending strength after preparing eight specimens for measuring the bending strength from the Al ₂ O ₃ single crystal assembly prepared according to the present invention around the bonding interface. Table 1 lists the four-point bending strength measurement results for the Al ₂ O ₃ single crystal for comparison with the present invention. It can be seen from Table 1 that the conjugate produced by the present invention exhibits the same bond strength as that of the monolith. In addition, it was confirmed that the breakage of the conjugate did not originate at the bonding interface in all eight specimens tested.

Al ₂ O ₃ single crystal monolith Al ₂ O ₃ single crystal conjugate σ ₁ (MPa) 267 269 σ ₂ 272 271 σ ₃ 287 277 σ ₄ 295 285 σ ₅ 307 294 σ ₆ 311 310 σ ₇ 341 329 σ ₈ 350 347 Average 304 ± 30 298 ± 29

Comparative Experiment

The bonded body was manufactured under the same conditions as in the first experimental example except that the nanoparticle layer was not formed on the bonded surface of the ceramic substrate. Thus prepared conjugate exhibited a weak bond strength that can be easily separated by a slight impact.

Experimental Example 2

An Al thin film was deposited at room temperature to a thickness of 1 μm through thermal evaporation on the joint surfaces of two AlN sintered substrates each having a thickness of 20 mm x 20 mm x 1 mm. The metal Al thin film was heat-treated in a high purity nitrogen atmosphere of 99.999% for 1 hour at 1000 degrees. 6A shows the surface of the substrate after heat treatment with a scanning electron microscope. It was found that a nanoparticle layer having an average particle diameter of about 20 nm was formed by the heat treatment, and it was confirmed through the XRD analysis that the surface nanoparticle layer was an AlN compound.

Subsequently, after the alignment of the AlN sintered body substrate on which the nanoparticle layer was formed, pressurization heat treatment was performed using a heat pressurization apparatus as shown in FIG. 4. At this time, a high-purity nitrogen gas of 99.999% was used as the atmosphere gas, and the temperature was raised to a heat treatment temperature of 1650 degrees at a rate of 10 degrees per minute and maintained for 1 hour. During the heat treatment, the pressurization apparatus maintained a constant pressure of 50 atm.

6B is a scanning electron micrograph of the fracture surface of the AlN conjugate produced by the pressure heat treatment.

As can be seen in Figure 6b, no residue was observed at the interface of the junction, it can be seen that the interface has an interlocking structure (interlocking) structure. This interlocking structure shows that grain growth occurred in both ceramic substrates towards the nanoparticle layer. It can also be seen from the fracture surface photograph shown that the AlN conjugate produced by the present invention does not break through the bonding interface.

Experimental Example 3

The Si thin film was deposited at room temperature to a thickness of 1 μm through thermal evaporation on the joint surfaces of two Si ₃ N ₄ sintered substrates having a thickness of 20 mm x 20 mm x 10 mm. Subsequently, the deposited Si thin film was heat-treated in a high purity nitrogen atmosphere of 99.999% for 1 hour at 1100 degrees. 7A shows the surface of the substrate after heat treatment with a scanning electron microscope. From the photographs shown, it can be seen that a nanoparticle layer having an average particle size of about 40 nm was formed on the surface of the substrate. In addition, XRD analysis showed that the deposited Si thin film was converted into Si ₃ N ₄ crystals.

Subsequently, after aligning the Si ₃ N ₄ sintered base material on which the nanoparticle layer was formed, pressure heat treatment was performed using a pressure heating device. As the atmospheric gas, high purity nitrogen gas of 99.999% was used, and the heat treatment condition was 1550 degrees for 1 hour. At this time, the temperature increase rate was 10 degrees per minute and the pressure of the pressurization apparatus was maintained at 30 atmospheres.

7B is a scanning electron micrograph of the cross section of the Si ₃ N ₄ conjugate after the pressurized heat treatment.

Little residue was observed at the bond interface and the bond interface (arrow) showed the same microstructure as the substrate. As a result of the fracture test of the bonded body, it was confirmed that the bonded body did not break through the interface.

Experimental Example 4

The SiC thin films were deposited to a thickness of 0.5 μm through DC magnetron sputtering on the joint surfaces of two SiC sintered bodies substrates of 20 mm × 20 mm × 10 mm, respectively. The deposition conditions were performed under conditions of a DC power 100 W, a distance of 20 mm between the SiC target and the sintered body, a substrate temperature of 400 degrees, an Ar atmosphere, and a pressure of 2 x 10 ^-2 Torr. The thin film was composed of nanoparticles having an average particle diameter of about 40 nm, and confirmed that the phase of the deposited layer was SiC through XRD analysis.

Subsequently, the nanoparticle layer coated SiC sintered substrate was aligned and subjected to pressure heat treatment. 99.99% high-purity methane gas was used as the gas atmosphere, and maintained at 1700 degrees for 1 hour. At this time, the temperature increase rate was 10 degrees per minute and the pressure of the pressurization device was maintained at 60 atm.

8 is a scanning electron micrograph of the cross-section of the SiC assembly thus prepared.

It can be seen that complete bonding occurs at most junctions along the junction interface (arrows), and none of the pores present in the bonding interface is significantly larger than the size of the pores already present in the substrate to act as a breakdown point. . It was confirmed that the break through the interface does not occur in the fracture test for the conjugate.

According to the present invention, it is possible to provide a bonding method having excellent mechanical and optical properties at the bonding interface in the bonding between ceramics and ceramics. In particular, the conjugates produced according to some embodiments of the present invention have uniform bonding properties throughout the bonding interface and have bonding strengths equivalent to that of monoliths.

In addition, according to the present invention, since the bonded body can be manufactured at a relatively low temperature and pressure, the structure and dimensional deformation of the substrate at the time of joining are minimized, so it is suitable for application in actual industrial sites.

According to the present invention, since ceramics, which have been known to be very difficult to bond compared to conventional metals, can be bonded with a strength similar to that of a single body, it is expected that the present invention can greatly contribute to the manufacture of a ceramic product having a complex and large shape.

Claims (22)

delete delete delete delete delete delete delete delete delete delete delete delete delete In the method of joining two ceramic substrates of metal oxide, Forming a metal thin film layer including a metal element constituting the metal oxide on at least one bonding surface of the bonding surfaces of the two ceramic substrates; Forming a ceramic nanoparticle layer including a metal oxide by heat-treating the ceramic substrate on which the metal thin film layer is formed at a first temperature in an oxidizing atmosphere; Aligning the joining surfaces of the two ceramic substrates; And Bonding the two ceramic substrates by pressing the two ceramic substrates at an oxidizing atmosphere and at a second temperature higher than the first temperature. In the method of joining two ceramic substrates of metal nitride, Forming a metal thin film layer including a metal element constituting the metal nitride on at least one bonding surface of the bonding surfaces of the two ceramic substrates; Forming a ceramic nanoparticle layer including metal nitride by heat-treating the ceramic substrate on which the metal thin film layer is formed at a first temperature in a nitriding atmosphere; Aligning the joining surfaces of the two ceramic substrates; And Bonding the two ceramic substrates by pressing the two ceramic substrates at a nitride atmosphere and at a second temperature higher than the first temperature. In the method of joining two ceramic substrates of metal carbide, Forming a metal thin film layer including a metal element constituting the metal carbide on at least one bonding surface of the bonding surfaces of the two ceramic substrates; Forming a ceramic nanoparticle layer including metal carbide by heat-treating the ceramic substrate on which the metal thin film layer is formed at a first temperature in an oxidizing atmosphere; Aligning the joining surfaces of the two ceramic substrates; And Bonding the two ceramic substrates by pressurizing the two ceramic substrates at a carbonization atmosphere and at a second temperature higher than the first temperature. In the method of joining two ceramic substrates of metal oxide, Forming a metal thin film layer including a metal element constituting the metal oxide on at least one bonding surface of the bonding surfaces of the two ceramic substrates; Aligning the joining surfaces of the two ceramic substrates; Heat treating the ceramic substrate on which the metal thin film layer is formed at a first temperature in an oxidizing atmosphere to form a ceramic nanoparticle layer including a metal oxide; And Maintaining the oxidizing atmosphere and heating to a second temperature higher than the first temperature to pressurize the two ceramic substrates. In the method of joining two ceramic substrates of metal nitride, Forming a metal thin film layer including a metal element constituting the metal nitride on at least one bonding surface of the bonding surfaces of the two ceramic substrates; Aligning the joining surfaces of the two ceramic substrates; Heat-treating the ceramic substrate on which the metal thin film layer is formed at a first temperature in a nitriding atmosphere to form a ceramic nanoparticle layer including metal nitride; And Maintaining the nitriding atmosphere and heating the second ceramic substrate to a second temperature higher than the first temperature to press-bond the two ceramic substrates. In the method of joining two ceramic substrates of metal carbide, Forming a metal thin film layer including a metal element constituting the metal carbide on at least one bonding surface of the bonding surfaces of the two ceramic substrates; Aligning the joining surfaces of the two ceramic substrates; Heat treating the ceramic substrate on which the metal thin film layer is formed at a first temperature in a carbonization atmosphere to form a ceramic nanoparticle layer including metal carbide; And Maintaining the carbonization atmosphere and heating to a second temperature higher than the first temperature to press-bond the two ceramic substrates. The method of claim 14, wherein The said 1st temperature is 400-1400 degreeC, and said 2nd temperature is 1000-1900 degreeC, The joining method of the ceramic base material characterized by the above-mentioned. The method of claim 14, wherein Bonding method of the ceramic substrate, characterized in that the average particle diameter of the nanoparticle layer is 10 ~ 100 nm or less. The method of claim 14, wherein The metal thin film layer has a thickness of 10 nm ~ 5 ㎛ ceramic bonding method of the substrate.

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