Preparation method of samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite connection

Abstract

The invention discloses a preparation method of a samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite connection, and belongs to the technical field of adhesive material preparation. The invention aims to solve the problem that the bonding strength of a traditional aluminum phosphate adhesive and mullite ceramic is insufficient. The preparation method mainly comprises the following steps: mixing boron carbide and silicon powder to prepare an inorganic filler; samarium oxide, aluminum hydroxide and dilute phosphoric acid are used as raw materials, a samarium-aluminum-phosphorus macromolecular phosphate gum base solution is synthesized through a hydrothermal reaction, and the performance is optimized by accurately regulating and controlling the element proportion of samarium, aluminum and phosphorus; and finally, fully mixing the gum base solution with the inorganic filler to obtain the high-temperature adhesive. The key improvement of the invention lies in that through samarium oxide modification, a stable and compact complex phase structure composed of samarium phosphate (SmPO4) and aluminum phosphate is generated in a system, and the structure enhances the matrix strength. After heat treatment at the temperature of 1300 DEG C, the bonding strength to mullite ceramics is not lower than 20 MPa, and excellent high-temperature resistance and bonding performance are shown.

Description

Technical Field

[0001] This invention belongs to the field of adhesive material preparation technology, specifically relating to a method for preparing a samarium oxide-modified aluminum phosphate-based high-temperature adhesive for mullite bonding. Background Technology

[0002] Mullite ceramics, with their excellent thermal insulation performance, low high-temperature creep rate, and good thermal shock resistance, have become indispensable thermal protection materials in extreme high-temperature environments in aerospace, metallurgy, and energy fields. In the actual assembly and application of mullite ceramic components, reliable connection is a key technical challenge that ensures the overall performance of the components and enables their engineering applications, and this challenge urgently needs to be overcome.

[0003] Currently, the mainstream adhesives used for joining ceramic components mainly include phosphate-based adhesives and polycarbosilazane alkyl adhesives. Among them, phosphate-based adhesives are widely used in the field of ceramic bonding due to the easy availability of raw materials and the relatively simple preparation process. For example, phosphate-based adhesives are prepared by using phosphoric acid, alumina, zinc oxide, magnesium oxide, and silicon oxide as raw materials through a specific preparation process. When this adhesive is applied to alumina ceramic bonding, test results show that its shear strength can reach over 3 MPa, which can meet the basic connection requirements of alumina ceramic components.

[0004] However, existing phosphate-based adhesive formulations are mostly designed for common ceramics such as alumina, without being specifically optimized for the characteristics of mullite ceramics. If these phosphate-based adhesives are directly applied to the bonding of mullite ceramics, their shear strength will decrease significantly, typically falling below 1 MPa, far from meeting the reliability requirements of mullite ceramic components under extreme high-temperature environments. The core reason for this problem lies in the unique chemical composition (Al₂O₃·2SiO₂) and crystal structure of mullite ceramics, making its reactivity with phosphate-based adhesives far less compatible than that with alumina ceramics. Under these circumstances, phosphate-based adhesives struggle to form a dense and stable bonding interface on the surface of mullite ceramics, thus significantly weakening the shear load-bearing capacity of the bonded joint. This deficiency directly limits the practical application of phosphate-based adhesives in the bonding of mullite ceramic components. Therefore, developing a mullite-specific adhesive designed based on the characteristics of mullite ceramics and possessing high shear strength is of significant technological breakthrough and practical application value.

[0005] Existing research findings provide key references for solving the aforementioned technical challenges: introducing samarium oxide into phosphate systems can improve the interfacial bonding performance between the system and mullite ceramics through multiple mechanisms. For example, Chinese patent CN202311824071.0 (Patent title: A method for preparing dense mullite from rare earth modified coal gangue) demonstrates in related research on mullite material preparation that samarium oxide, as a core component of rare earth composites, can regulate the interfacial reaction kinetics, making the diffusion rate of aluminum and silicon ions more compatible with the crystal structure of mullite, ultimately achieving a significant increase in the density of mullite materials and reducing the porosity to below 0.96%. The aforementioned mechanism of samarium oxide regulating interfacial effects can be further applied to adhesive systems, providing key technical support for solving the technical challenge of weak interfacial bonding between phosphate-based adhesives and mullite ceramics. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a samarium oxide-modified aluminum phosphate-based high-temperature adhesive for mullite bonding. This method, by introducing samarium oxide and optimizing the preparation process, aims to obtain an adhesive product with high bonding strength at high temperatures.

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

[0008] (1) Mix silicon powder and boron carbide in a certain mass ratio, put them into a ball mill jar, and use a ball mill to mill them at a certain speed for a certain time to obtain a composite inorganic filler suitable for high temperature adhesives. Take it out for use.

[0009] (2) Dilute concentrated phosphoric acid to a certain concentration, transfer it to a water bath heating pot equipped with a cooling reflux device, heat it to a certain temperature, and under mechanical stirring at a certain speed, rapidly add samarium oxide and aluminum hydroxide to the above dilute phosphoric acid solution according to a certain molar ratio of samarium, aluminum and phosphorus.

[0010] (3) Then continue to heat up and maintain the water bath system at a certain temperature. First stir at high speed for a certain time, then switch to low speed and stir for a certain time to obtain the paste.

[0011] (4) Add the composite inorganic filler obtained in step (1) to the mortar prepared in step (3) according to a certain solid-liquid mass ratio, and stir at a certain speed for a certain period of time with alternating fast and slow speeds to obtain the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding.

[0012] Preferably, in step (1), the mass ratio of silicon powder to boron carbide is 5.2-8.5:1.5-4.8, the ball mill speed is 200-400 r / min, and the ball milling time is 5-9 h.

[0013] Preferably, in step (1), the elemental silicon powder is a nano-scale regulating component with a particle size of 0.5-1 μm and a purity of not less than 99%; boron carbide is a non-standard mineral raw material with a particle size of 8-10 μm and a purity of not less than 99%.

[0014] Preferably, in step (2), the concentration of concentrated phosphoric acid is 85 wt.%, the concentration after dilution is 60-65 wt.%, the temperature after heating is 70-80℃, the rotation speed is 400-700 r / min, and the molar ratio of samarium, aluminum and phosphorus is 0.05-0.35:0.55-0.95:0.7-1.5.

[0015] Preferably, in step (3), the water bath temperature after the heating is continued is maintained at 80-85℃, the high speed is 700-900r / min, and the corresponding stirring time is 1-3h; the low speed is 300-500r / min, and the corresponding stirring time is 6-10h.

[0016] Preferably, the solid-liquid mass ratio in step (4) is 1:3-7.

[0017] Preferably, in step (4), the stirring is performed at a certain speed with alternating fast and slow speeds for a certain period of time, specifically: first stirring at a speed of 600-800 r / min for 2-3 hours, then stirring at a speed of 500-600 r / min for 2-4 hours, and finally stirring at a speed of 450-500 r / min for 3-6 hours.

[0018] Preferably, the stirring processes involved in steps (2), (3), and (4) must be completed while the cooling reflux device is in operation.

[0019] Compared with the prior art, the preparation method of the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding provided by the present invention has the following advantages:

[0020] 1. Excellent bonding strength: After being treated at 1300℃, the adhesive of the present invention has a bonding strength of not less than 25MPa to mullite ceramics, which is much higher than that of unmodified aluminum phosphate adhesive (<1MPa).

[0021] 2. Stable multiphase ceramic structure: At high temperature, the adhesive is transformed into a stable and dense multiphase ceramic structure composed of interwoven aluminum phosphate (AlPO4) and samarium phosphate (SmPO4), which has both high strength and good toughness.

[0022] 3. Controllable process and easy to implement: The preparation process parameters of this invention are clear, the operating conditions are mild (water bath heating), no special equipment is required, and it is easy to achieve large-scale production. Attached Figure Description

[0023] Figure 1 This is a shear strength diagram of mullite ceramic bonding parts bonded with samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding prepared in Example 1, after being treated at different temperatures and tested at room temperature.

[0024] Figure 2 The XRD pattern of the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding prepared in Example 1 after treatment at 1300℃ is shown.

[0025] Figure 3 This is a SEM image of the bonding surface of the mullite ceramic bonded with the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding prepared in Example 1 after treatment at 1300℃. Detailed Implementation

[0026] 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.

[0027] This invention provides a technical solution: a method for preparing a samarium oxide-modified aluminum phosphate-based high-temperature adhesive for mullite bonding, specifically including the following steps:

[0028] Example 1:

[0029] (1) Mix silicon powder and boron carbide at a mass ratio of 7.7:2.3, put them into a ball mill jar, and ball mill them at 300 r / min for 7 h to obtain a composite inorganic filler suitable for high temperature adhesives. Take it out for later use.

[0030] (2) Dilute the concentrated phosphoric acid with a mass fraction of 85 wt.% to 62 wt.%, transfer it to a water bath heating pot equipped with a cooling reflux device, heat it to 75°C, and then, under mechanical stirring at 500 r / min, quickly add samarium oxide and aluminum hydroxide to the dilute phosphoric acid solution according to the molar ratio of samarium, aluminum and phosphorus of 0.25:0.75:0.81.

[0031] (3) Then continue to heat up and maintain the water bath system at 83°C. Stir at 800 r / min for 2 hours, then switch to 400 r / min for 7 hours to obtain the paste.

[0032] (4) The composite inorganic filler obtained in step (1) is incorporated into the white mortar obtained in step (3) at a solid-liquid mass ratio of 1:6. The mixture is stirred at 700 r / min for 2.5 h, then at 550 r / min for 3 h, and finally at 480 r / min for 5 h, thereby preparing a samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding.

[0033] Example 2:

[0034] (1) Mix silicon powder and boron carbide at a mass ratio of 5.2:4.8, put them into a ball mill jar, and ball mill them at 200 r / min for 5 h to obtain a composite inorganic filler suitable for high temperature adhesives. Take it out for later use.

[0035] (2) Dilute the concentrated phosphoric acid with a mass fraction of 85 wt.% to 60 wt.%, transfer it to a water bath heating pot equipped with a cooling reflux device, heat it to 70°C, and then, under mechanical stirring at 400 r / min, quickly add samarium oxide and aluminum hydroxide to the dilute phosphoric acid solution according to the molar ratio of samarium, aluminum and phosphorus of 0.05:0.95:1.5.

[0036] (3) Then continue to heat up, keep the water bath system at 80°C, stir at 700 r / min for 1 hour, then switch to 300 r / min for 10 hours to obtain the paste;

[0037] (4) The composite inorganic filler obtained in step (1) is incorporated into the white mortar obtained in step (3) at a solid-liquid mass ratio of 1:3. The mixture is stirred at 600 r / min for 2 h, then at 500 r / min for 2 h, and finally at 450 r / min for 3 h, thereby preparing a samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding.

[0038] Example 3:

[0039] (1) Mix silicon powder and boron carbide at a mass ratio of 8.5:1.5, put them into a ball mill jar, and ball mill them at 400 r / min for 9 hours to obtain a composite inorganic filler suitable for high-temperature adhesives. Take it out for later use.

[0040] (2) Dilute the concentrated phosphoric acid with a mass fraction of 85 wt.% to 65 wt.%, transfer it to a water bath heating pot equipped with a cooling reflux device, heat it to 80°C, and then, under mechanical stirring at 700 r / min, quickly add samarium oxide and aluminum hydroxide to the dilute phosphoric acid solution according to the molar ratio of samarium, aluminum and phosphorus of 0.35:0.55:0.7.

[0041] (3) Then continue to heat up, maintain the water bath system at 85°C, stir at 900 r / min for 3 hours, then switch to 500 r / min for 6 hours to obtain the paste;

[0042] (4) The composite inorganic filler obtained in step (1) is incorporated into the white mortar obtained in step (3) at a solid-liquid mass ratio of 1:7. The mixture is stirred at 800 r / min for 3 h, then at 600 r / min for 4 h, and finally at 500 r / min for 6 h, thereby preparing a samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding.

[0043] In the samarium oxide-modified aluminum phosphate-based high-temperature adhesive for mullite bonding prepared using the method of this invention, the main binder phase is a macromolecular phosphate emulsion prepared by reacting dilute phosphoric acid with aluminum hydroxide and samarium oxide. Silica powder can improve the viscosity of the adhesive, thus regulating viscosity, and can also be oxidized at high temperatures to generate silica, thereby improving the density of the adhesive matrix structure. In this invention, boron carbide can be oxidized at high temperatures for volume compensation. At high temperatures, the macromolecular phosphate decomposes to generate aluminum phosphate with high-temperature bonding properties and needle-like samarium phosphate. The two are interspersed to form a high-strength composite structure. This structure directly solves the problem of significantly reduced shear load-bearing capacity of ordinary phosphate-based adhesives, ensuring the reliability of mullite ceramic bonding.

[0044] To verify the effectiveness of the high-temperature adhesive provided in the above embodiments, the inventors conducted the following verification experiment on the high-temperature adhesive prepared in Example 1. The experimental steps are as follows:

[0045] (1) Lay multiple mullite 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.

[0046] (2) The high-temperature adhesive obtained in Example 1 was applied to the bonding surface of the mullite ceramic substrate using a scraper. The bonding area was controlled to be 15×10mm. Then, the thickness of the high-temperature adhesive on each bonding surface was controlled to be 200μm using a coater.

[0047] (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.

[0048] (4) The cured adhesive parts are placed in a muffle furnace for calcination at temperatures of 700℃, 900℃, 1100℃ and 1300℃, respectively, for 2 hours at each temperature.

[0049] (5) Room temperature shear test: The approximate shear strength of the bonded parts of Example 1 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 room temperature bond strength of the high-temperature adhesive after treatment at different temperatures is as follows: Figure 1 As shown.

[0050] Depend on Figure 1 It can be seen that the adhesive prepared in Example 1 can provide a bonding strength of more than 5 MPa for mullite ceramics after calcination at 700-1300℃; the strength is maintained at about 6-10 MPa in the range of 700-1100℃; and the strength increases sharply after treatment at 1300℃ and can be maintained at 20-30 MPa. This bonding strength is much greater than that of the unmodified aluminum phosphate adhesive.

[0051] (6) High-Temperature Adhesive Composition Analysis: The high-temperature adhesive prepared in Example 1 was treated at 1300℃ and then ground into powder. The composition of the high-temperature adhesive was then analyzed using a D / Max2500v / PCXRD analyzer. Their XRD patterns are shown below. Figure 2 As shown.

[0052] Depend on Figure 2 It can be seen that treatment at 1300℃ resulted in the formation of relatively significant aluminum phosphate (AlPO4). From Figure 2 As can be seen, the samarium oxide in Example 1 has completely reacted, and the rare earth oxides have all been converted into samarium phosphate (SmPO4). The Si within the adhesive is oxidized to SiO2 by the oxygen-containing groups within the adhesive at high temperature. Therefore, in summary, the adhesive of Example 1 not only has a shorter curing time but also improves the adhesive strength.

[0053] (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 mullite ceramic substrates, and the middle is a high-temperature adhesive layer.

[0054] Depend on Figure 3 It can be seen that the adhesive layer after treatment at 1300℃ is relatively full, the structure is dense, no large cracks appear, the adhesive and ceramic are well connected, the interface is continuous, and the bonding effect is excellent.

Claims

1. A method for preparing a samarium oxide-modified aluminum phosphate-based high-temperature adhesive for mullite bonding, characterized in that: The preparation method is carried out in the following steps: (1) Mix silicon powder and boron carbide in a certain mass ratio, put them into a ball mill jar, and use a ball mill to mill them at a certain speed for a certain time to obtain a composite inorganic filler suitable for high temperature adhesives. Take it out for use. (2) Dilute concentrated phosphoric acid to a certain concentration, transfer it to a water bath heating pot equipped with a cooling reflux device, heat it to a certain temperature, and under mechanical stirring at a certain speed, rapidly add samarium oxide and aluminum hydroxide to the above dilute phosphoric acid solution according to a certain molar ratio of samarium, aluminum and phosphorus. (3) Then continue to heat up and maintain the water bath system at a certain temperature. First stir at high speed for a certain time, then switch to low speed and stir for a certain time to obtain the paste. (4) Add the composite inorganic filler obtained in step (1) to the mortar prepared in step (3) according to a certain solid-liquid mass ratio, and stir at a certain speed for a certain period of time with alternating fast and slow speeds to obtain the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding.

2. The preparation method of the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding according to claim 1, characterized in that: In step (1), the mass ratio of silicon powder to boron carbide is 5.2-8.5:1.5-4.8, the ball mill speed is 200-400 r / min, and the ball milling time is 5-9 h.

3. The preparation method of the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding according to claim 1, characterized in that: In step (1), the elemental silicon powder is a nano-scale regulating component with a particle size of 0.5-1μm and a purity of not less than 99%; boron carbide is a non-standard mineral raw material with a particle size of 8-10μm and a purity of not less than 99%.

4. The preparation method of the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding according to claim 1, characterized in that: In step (2), the concentration of concentrated phosphoric acid is 85 wt.%, and its concentration after dilution is 60-65 wt.%. The temperature after heating is 70-80℃, the rotation speed is 400-700 r / min, and the molar ratio of samarium, aluminum and phosphorus is 0.05-0.35:0.55-0.95:0.7-1.

5.

5. The preparation method of the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding according to claim 1, characterized in that: In step (3), the water bath temperature after heating is maintained at 80-85℃, the high speed is 700-900r / min, and the corresponding stirring time is 1-3h; the low speed is 300-500r / min, and the corresponding stirring time is 6-10h.

6. The method for preparing the samarium oxide-modified aluminum phosphate-based high-temperature adhesive for mullite bonding according to claim 1, characterized in that: In step (4), the solid-liquid mass ratio is 1:3-7.

7. The preparation method of the samarium oxide modified aluminum phosphate-based high-temperature adhesive for mullite bonding according to claim 1, characterized in that: In step (4), the stirring is carried out at a certain speed with alternating fast and slow speeds for a certain period of time. Specifically, the stirring is carried out at a speed of 600-800 r / min for 2-3 hours, then at a speed of 500-600 r / min for 2-4 hours, and finally at a speed of 450-500 r / min for 3-6 hours.

8. The method for preparing the samarium oxide-modified aluminum phosphate-based high-temperature adhesive for mullite bonding according to claim 1, characterized in that: The stirring processes involved in steps (2), (3), and (4) must all be completed while the cooling reflux device is in operation.

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