Preparation method of neodymium oxide modified aluminum phosphate-based high-temperature adhesive for aluminum nitride connection

Abstract

The invention belongs to the technical field of preparation of high-temperature-resistant adhesives, and discloses a preparation method of a neodymium oxide modified aluminum phosphate-based high-temperature adhesive for aluminum nitride connection. Aiming at the problems of insufficient high temperature resistance, low bonding strength, high brittleness, poor thermal shock resistance and water resistance and the like of a pure aluminum phosphate adhesive, the comprehensive performance of the adhesive is improved through neodymium oxide doping modification and process optimization. The preparation method comprises the following steps: reacting neodymium oxide with dilute phosphoric acid to prepare adhesive cement, and adding silicon and boron carbide for modification to prepare the adhesive. The adhesive does not need high-temperature sintering, is primarily cured at normal temperature for 24 hours, can be used after being dried at 150 DEG C, and is suitable for industrial mass production. After high-temperature treatment at the temperature of 1300 DEG C, the bonding strength is not lower than 35 MPa and is far better than that of a pure aluminum phosphate adhesive; stable ceramic phase structures such as aluminum phosphate and neodymium phosphate are formed at high temperature, the interface compatibility is excellent, the thermal stability is outstanding, the problem of high-temperature bonding of aluminum nitride ceramic can be effectively solved, and the aluminum nitride ceramic can be widely applied to the fields of high-temperature structure connection such as aerospace and steel manufacturing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-temperature resistant adhesive preparation, and particularly relates to a preparation method of a neodymium oxide modified aluminum phosphate-based high-temperature adhesive for aluminum nitride connection. BACKGROUND

[0002] In the field of material science, material connection technology is crucial when designing composite materials for extreme environments. In particular, for aluminum nitride ceramics, due to their excellent heat resistance and mechanical properties, they become the preferred material for high-temperature applications. Aluminum nitride ceramics are known for their high melting point (about 2200℃) and excellent wear resistance, making them perform well in high-temperature environments. The application of these ceramics in furnace linings, crucibles, and high-temperature reactors demonstrates their reliability under extreme conditions.

[0003] In order to further improve the performance of these ceramics, material connection technology is used to combine aluminum nitride with other materials to form composite materials with enhanced performance. In recent years, the application range of organic adhesives has become wider and wider, and the bonding technology has also become more and more perfect, gradually becoming an indispensable technology in current industrial production, especially in high-tech application fields. Some traditional connection methods have their inherent defects, but the bonding technology can overcome them and gradually become a new technology with strong practicality. Especially in the field of aerospace, it has a great effect on reducing mass and saving cost. In recent decades, people have increasingly high requirements for materials and are committed to researching materials that are resistant to high temperatures, lightweight, pollution-free, and meet special purposes.

[0004] However, there are still some problems in using high-temperature resistant adhesives to bond aluminum nitride, such as insufficient high-temperature resistance, pure aluminum phosphate adhesive is prone to crystal phase transition above 800℃, resulting in a sharp drop in bonding strength, usually less than 2.0MPa; the adhesive is brittle, the crosslinking density is low after curing, it is easy to crack at high temperature, the thermal shock resistance is poor, the strength loss after cold and hot cycle is more than 40%, the water resistance is poor, the aluminum phosphate is easy to absorb water and deliquesce, and the bonding interface fails after long-term contact with water vapor.

[0005] The above problems show that the technical challenges faced by high-temperature resistant adhesives in bonding aluminum nitride need to be solved through material modification, development of new adhesives, and progress in application technology. Through investigation, it is found that rare earth elements can refine the grain size of aluminum phosphate-based adhesives, significantly improve the high-temperature resistance and thermal stability, and enhance the bonding strength. The addition of rare earth elements can regulate the performance of aluminum phosphate-based high-temperature resistant adhesives. By studying the doping rules of neodymium oxide, the thermal performance of aluminum phosphate-based high-temperature resistant adhesives can be precisely controlled, effectively solving the problem of insufficient bonding performance, and further expanding the application of aluminum phosphate-based high-temperature resistant adhesives in high-temperature structural connection scenarios in the fields of aerospace, steel manufacturing, etc. SUMMARY

[0006] To address the aforementioned problems, the present invention aims to provide a method for preparing a neodymium oxide-modified aluminum phosphate-based high-temperature resistant adhesive. This method, by introducing neodymium oxide and optimizing the preparation process, aims to obtain an adhesive product exhibiting high bonding strength, excellent interfacial bonding performance, and good thermal stability at high temperatures.

[0007] To achieve the above objectives, the present invention provides a method for preparing a neodymium oxide modified aluminum phosphate-based high-temperature resistant adhesive, comprising the following steps performed in sequence:

[0008] (1) Mix silicon powder and boron carbide at a mass ratio of 6-8.5:2.4-4, place them in a ball mill jar, and ball mill them at 200-500 r / min for 8-12 hours. After taking them out, you will get inorganic filler for high-temperature adhesives.

[0009] (2) Dilute 85wt.% concentrated phosphoric acid to 60-65wt.% and place the diluted phosphoric acid in a water bath equipped with a cooling reflux device and heat it to 75-85℃. Under high-speed mechanical stirring at 450-650r / min, add neodymium oxide and aluminum hydroxide to the above-mentioned dilute phosphoric acid, wherein the molar ratio of neodymium, aluminum and phosphorus is 0.03-0.3:0.6-0.9:0.8-1.2. Then maintain the water bath heating temperature at 75-85℃, stir at 700-800r / min for 1-3h, and then stir at 300-500r / min for 7-9h. All stirring in each stage of this step is carried out under the cooling reflux device.

[0010] (3) Reduce the temperature of the water bath heating pot in step (2) to 50-60℃. After it stabilizes in this range, add the inorganic filler from step (1) to the adhesive from step (2) at a solid-liquid mass ratio of 1:3-8. Then stir at a speed of 400-800 r / min with alternating fast and slow speeds for 8-12 hours to obtain the neodymium oxide modified aluminum phosphate-based high-temperature resistant adhesive.

[0011] Preferably, in step (1), the silicon powder is a nanoscale modifier with a particle size of 0.5-1 μm and a purity higher than 99%; and the boron carbide is a non-standard mineral with a particle size of 8-10 μm and a purity higher than 99%.

[0012] Preferably, in step (2), the concentrated phosphoric acid is analytical grade with a purity higher than 98%; the aluminum hydroxide is sieved through a 1500-mesh sieve with a purity higher than 95%; and the neodymium oxide is sieved through a 1500-mesh sieve with a purity higher than 99%.

[0013] Preferably, in step (3), the mixing process of alternating fast and slow speeds in the speed range of 400-800 r / min is as follows: first, mixing for 3-4 hours in the speed range of 700-800 r / min, then mixing for 2-4 hours in the speed range of 500-600 r / min, and finally mixing for 2-4 hours in the speed range of 400-500 r / min.

[0014] Compared with existing technologies, the preparation method of neodymium oxide modified aluminum phosphate-based high-temperature adhesive provided by the present invention has the following beneficial effects:

[0015] 1. Significantly improved mechanical properties after high-temperature treatment: After high-temperature treatment at 1300℃, the bonding strength is not less than 35MPa, which is significantly improved compared to 2MPa when pure aluminum phosphate is added.

[0016] 2. Formation of a stable ceramic phase structure: After calcination at 1300℃, the main components of the adhesive are transformed into various ceramic phase substances such as aluminum phosphate and neodymium phosphate. These ceramic phase substances, due to their high-temperature resistance and excellent mechanical properties, exhibit characteristics highly conducive to forming stable adhesive joints under high-temperature environments.

[0017] 3. Simple process: No high-temperature sintering is required. It can be initially cured at room temperature (24h) and can be used after drying at 150℃. It is suitable for industrial mass production. Attached Figure Description

[0018] Figure 1 These are the shear strength curves of aluminum nitride ceramic adhesives bonded with neodymium oxide modified aluminum phosphate-based high-temperature adhesives prepared in Example 1, tested at room temperature after treatment at different temperatures.

[0019] Figure 2 The XRD pattern of the neodymium oxide modified aluminum phosphate-based high-temperature adhesive prepared in Example 1 after treatment at 1300℃ is shown.

[0020] Figure 3 This is a SEM image of the bonding surface of an aluminum nitride ceramic bonded with neodymium oxide modified aluminum phosphate-based high-temperature adhesive prepared in Example 1 after treatment at 1300℃. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a method for preparing a neodymium oxide-modified aluminum phosphate-based high-temperature adhesive for aluminum nitride bonding. Specific embodiments are as follows:

[0023] Example 1:

[0024] (1) Take silicon powder and boron carbide, mix them evenly in a mass ratio of 7:3 and put them into a ball mill jar; use a ball mill to ball mill them at a speed of 335r / min for 9 hours and then take them out. The resulting material is the modified filler for high-temperature adhesives.

[0025] (2) Dilute 85 wt.% concentrated phosphoric acid to 63 wt.%, pour it into a water bath equipped with a reflux reflux device, and heat it to 80°C. Under high-speed mechanical stirring at 550 r / min, rapidly add neodymium oxide and aluminum hydroxide to the dilute phosphoric acid solution at a molar ratio of neodymium, aluminum, and phosphorus of 0.2:0.7:0.9. Then, maintain the water bath heating temperature at 82°C, stir at 750 r / min for 2 hours, and then stir at 400 r / min for 8 hours.

[0026] (3) Reduce the set temperature of the water bath heating pot in step (2) to 55°C. After the temperature stabilizes in this range, add the mixed modified filler obtained in step (1) to the light purple mortar obtained in step (2) at a solid-liquid mass ratio of 1:4.5. Stir at 750 r / min for 3.5 h, 550 r / min for 3 h, and 450 r / min for 3 h in sequence to obtain neodymium oxide modified aluminum phosphate-based high temperature adhesive.

[0027] Example 2:

[0028] (1) Take silicon powder and boron carbide, mix them in a mass ratio of 6:2.4 and place them in a ball mill jar; ball mill them at a speed of 200 r / min for 8 hours, and the material obtained is the modified filler for high-temperature adhesives.

[0029] (2) Dilute 85 wt.% concentrated phosphoric acid to 60 wt.%, place it in a water bath equipped with a cooling reflux device, and heat it to 75°C. Under high-speed mechanical stirring at 450 r / min, rapidly add neodymium oxide and aluminum hydroxide to the dilute phosphoric acid solution at a molar ratio of neodymium, aluminum, and phosphorus of 0.03:0.6:0.8. Then, maintain the water bath heating temperature at 75°C, stir at 700 r / min for 1 h, and then stir at 300 r / min for 7 h.

[0030] (3) Adjust the set temperature of the water bath heating pot in step (2) to 50°C. After the temperature reaches this range, add the mixed modified filler obtained in step (1) into the light purple slurry obtained in step (2) at a solid-liquid mass ratio of 1:3. Stir at 700 r / min for 3 h, 500 r / min for 2 h, and 400 r / min for 2 h in sequence to obtain neodymium oxide modified aluminum phosphate-based high temperature adhesive.

[0031] Example 3:

[0032] (1) Take silicon powder and boron carbide, mix them in a mass ratio of 8.5:4 and put them into a ball mill jar; use a ball mill to ball mill at a speed of 500 r / min for 12 hours, and the material obtained after taking it out is the modified filler for high temperature adhesive.

[0033] (2) Dilute 85 wt.% concentrated phosphoric acid to 65 wt.%, pour it into a water bath equipped with a reflux reflux device, and heat it to 85°C. Under high-speed mechanical stirring at 650 r / min, rapidly add neodymium oxide and aluminum hydroxide to the dilute phosphoric acid solution at a molar ratio of neodymium, aluminum, and phosphorus of 0.3:0.9:1.2. Then, maintain the water bath heating temperature at 85°C, stir at 800 r / min for 3 hours, and then stir at 500 r / min for 9 hours.

[0034] (3) Reduce the set temperature of the water bath heating pot in step (2) to 60°C. After the temperature stabilizes, add the mixed modified filler obtained in step (1) to the light purple slurry obtained in step (2) at a solid-liquid mass ratio of 1:8. Stir at 800 r / min for 4 hours, 600 r / min for 4 hours, and 500 r / min for 4 hours in sequence to obtain neodymium oxide modified aluminum phosphate-based high-temperature adhesive.

[0035] In the neodymium oxide-modified aluminum phosphate-based high-temperature adhesive prepared in this invention, the core main binder phase originates from the synergistic reaction of dilute phosphoric acid, aluminum hydroxide, and neodymium oxide, ultimately forming a macromolecular phosphate emulsion with excellent dispersibility, laying the foundation for the adhesive's basic bonding ability to aluminum nitride ceramics. In this invention, the precise doping of neodymium oxide can regulate the particle size distribution and colloidal stability of the macromolecular phosphate emulsion, avoiding localized performance inhomogeneity caused by emulsion agglomeration, ensuring uniform wettability of the aluminum nitride ceramic surface during adhesive bonding, improving adhesion to the ceramic surface, and reducing interfacial bonding defects. Simultaneously, the neodymium element in the neodymium oxide can act as a crystal phase regulator, guiding the directional growth of aluminum phosphate crystals under high-temperature conditions, inhibiting the formation of disordered impurity phases, and forming a compatible bond with the crystal structure of aluminum nitride ceramics, providing a stable crystal phase framework for subsequent three-dimensional structure construction. As the temperature rises, the macromolecular phosphate gradually decomposes, generating aluminum phosphate, which has high-temperature bonding activity, and neodymium phosphate in the form of needles and rods. The two intertwine to form a dense three-dimensional composite structure, which not only significantly improves the interfacial bonding force between the adhesive and aluminum nitride ceramics, but also endows it with structural stability to meet the application requirements of aluminum nitride ceramics under high-temperature conditions.

[0036] To verify the bonding effect of the neodymium oxide-modified aluminum phosphate-based high-temperature adhesive provided in the above embodiments, the inventors conducted the following verification experiment on the neodymium oxide-modified aluminum phosphate-based high-temperature adhesive prepared in the embodiments. The experimental steps are as follows:

[0037] (1) Lay multiple aluminum nitride ceramic substrates (40×10×5mm) that have been polished, cleaned and dried flat on a smooth and flawless glass plate with the bonding surface facing up.

[0038] (2) The high-temperature adhesive obtained in the three examples was applied to the bonding surface of the aluminum nitride ceramic substrate using a scraper. The bonding area was controlled to be 10×10mm. Then, the thickness of the high-temperature adhesive on each bonding surface was controlled to be 150μm using a coater.

[0039] (3) Press the bonding surfaces of the two substrates together by hand, and after 10 seconds, place them at room temperature to cure. At the same time, to ensure the stability of the curing process, apply pressure to the center of the bonding surface with a heavy object.

[0040] (4) The cured adhesive parts are placed in a muffle furnace for calcination at temperatures of 500℃, 700℃, 900℃, 1100℃, 1300℃ and 1500℃, respectively, for 2 hours at each temperature.

[0041] (5) Room Temperature Shear Test: The approximate shear strength of the bonded parts of different embodiments after treatment at different temperatures was tested using a CSS-44001 universal testing machine to evaluate the bonding performance of the high-temperature adhesive. The shear strength curves of the aluminum nitride ceramic bonded parts bonded with the neodymium oxide modified aluminum phosphate-based high-temperature adhesive after different temperature treatments at room temperature are shown below.Figure 1 As shown.

[0042] Depend on Figure 1 This graph illustrates the relationship between the adhesive's shear strength and processing temperature. Overall, the shear strength increases significantly with increasing temperature. At lower temperatures (500℃ and 700℃), the shear strength is relatively low, approximately 8.35 MPa and 10.76 MPa, respectively. After reaching 900℃, the strength increases dramatically, remaining around 35.67-38.77 MPa between 900-1300℃. At 1500℃, the shear strength surges to approximately 55.61 MPa, a significant increase. This bonding strength is far greater than that of the unmodified aluminum phosphate adhesive. This indicates that the adhesive exhibits excellent bonding performance at high temperatures (especially ultra-high temperatures).

[0043] (6) High-Temperature Adhesive Composition Analysis: The high-temperature adhesive prepared in the example was ground into powder after being treated at 1300℃, and then its composition was analyzed using a D / Max2500v / PCXRD analyzer. Its XRD pattern is shown below. Figure 2 As shown.

[0044] Depend on Figure 2 It is evident that the 1300℃ treatment in the example produced a significant amount of neodymium phosphate (NdPO4), aluminum hydroxide reacted with dilute phosphoric acid to form aluminum phosphate (AlPO4), and a large amount of Al5BO9 was generated in the adhesive. At high temperatures, Si is oxidized to SiO2 by the oxygen-containing groups within the adhesive. SiO2 can react with Al2O3 at high temperatures to form a high-temperature resistant mullite phase. Mullite significantly improves the high-temperature bonding strength, thermal stability, and service reliability of the adhesive, which is key to its excellent performance at high temperatures. The formation of these high-temperature resistant phases is an important reason why this aluminum phosphate-based adhesive possesses excellent high-temperature bonding performance and thermal stability. This demonstrates that rare-earth modified aluminum phosphate-based adhesives can effectively improve their high-temperature bonding strength and service reliability by generating various high-temperature resistant phases.

[0045] (7) Morphology analysis of the bonding surface: The bonded parts treated at 1300℃ were made into SEM test samples. The microstructure of the cross-section of the bonded parts was observed using a Nanosem430 scanning electron microscope, such as... Figure 3 As shown in the figure; the two sides are aluminum nitride ceramic substrates, and the middle is a high-temperature adhesive layer.

[0046] Depend on Figure 3The core advantages of this adhesive are as follows: First, it has excellent interfacial compatibility, forming a clear and firm bonding area with the aluminum nitride matrix, laying the foundation for high bonding strength; second, it has outstanding high-temperature stability, with the aluminum nitride matrix on both sides maintaining a dense structure, and no obvious cracking or peeling defects in the bonding area, reflecting good thermal stability; third, it has strong high-temperature adaptability, with the spherical structure in the bonding area presumably being a stable phase generated by the high-temperature reaction, which can enhance the structural support capacity at high temperatures and help the adhesive to serve stably under high-temperature conditions.

Claims

1. A method for preparing a neodymium oxide-modified aluminum phosphate-based high-temperature adhesive for aluminum nitride bonding, characterized in that, The following steps are performed sequentially: (1) Mix silicon powder and boron carbide at a mass ratio of 6-8.5:2.4-4, place them in a ball mill jar, and ball mill them at a speed of 200-500 r / min for 8-12 hours. After taking them out, you will get inorganic fillers for high-temperature adhesives. (2) Dilute 85wt.% concentrated phosphoric acid to 60-65wt.% and place the diluted phosphoric acid in a water bath equipped with a cooling reflux device and heat it to 75-85℃. Under high-speed mechanical stirring at 450-650r / min, add neodymium oxide and aluminum hydroxide to the above-mentioned dilute phosphoric acid, wherein the molar ratio of neodymium, aluminum and phosphorus is 0.03-0.3:0.6-0.9:0.8-1.

2. Then maintain the water bath heating temperature at 75-85℃, stir at 700-800r / min for 1-3h, and then stir at 300-500r / min for 7-9h. All stirring in each stage of this step is carried out under the cooling reflux device. (3) Reduce the temperature of the water bath heating pot in step (2) to 50-60℃. After it stabilizes in this range, add the inorganic filler from step (1) to the adhesive from step (2) at a solid-liquid mass ratio of 1:3-8. Then stir at a speed of 400-800 r / min with alternating fast and slow speeds for 8-12 hours to obtain the neodymium oxide modified aluminum phosphate-based high-temperature resistant adhesive.

2. The preparation method according to claim 1, characterized in that, The silicon powder mentioned in step (1) is a nanoscale regulator with a particle size of 0.5-1 μm and a purity higher than 99%; the boron carbide is a non-standard mineral with a particle size of 8-10 μm and a purity higher than 99%.

3. The preparation method according to claim 1, characterized in that, The concentrated phosphoric acid mentioned in step (2) is analytical grade with a purity higher than 98%; the aluminum hydroxide is sieved through a 1500-mesh sieve with a purity higher than 95%; and the neodymium oxide is sieved through a 1500-mesh sieve with a purity higher than 99%.

4. The preparation method according to claim 1, characterized in that, The specific process of alternating stirring in step (3) is as follows: first stir at a speed range of 700-800 r / min for 3-4 hours, then stir at a speed range of 500-600 r / min for 2-4 hours, and finally stir at a speed range of 400-500 r / min for 2-4 hours.

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