A method for connecting a ceramic shell and a metal core

Abstract

This invention provides a method for connecting a ceramic shell and a metal core, belonging to the field of material preparation technology. In this invention, the ceramic shell and the metal core are formed in one step by powder metallurgy, and then sintered in an inert atmosphere to obtain the finished product. The metal core is prepared by metal and additives with a negative coefficient of thermal expansion. The method for connecting the ceramic shell and the metal core has the advantages of simple process, easy operation and control, and low cost. Furthermore, the method can effectively improve the connection strength between the ceramic shell and the metal core, thereby improving production efficiency and practical application effect.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation technology, specifically relating to a method for connecting a ceramic shell and a metal core. Background Technology

[0002] Structural ceramics possess excellent properties such as high temperature resistance, high strength, high hardness, wear resistance, oxidation resistance, and corrosion resistance, making them widely used in aerospace, power electronics, energy, and transportation fields. However, the inherent brittleness of ceramics results in poor processing performance, making it difficult to manufacture large-sized and complex-shaped components, which limits the application and development of ceramic materials. Metallic materials possess excellent room-temperature strength, ductility, electrical conductivity, and thermal conductivity, forming a clear complementary relationship with ceramic materials in terms of performance. Combining these two materials allows for the full utilization of their respective superior properties, enabling the manufacture of complex components that meet specific requirements. This not only reduces costs but also has significant implications for the application and development of both ceramics and metallic materials. Due to the differences in physical and chemical properties between ceramics and metals, the connection between them has become a hot research topic for scholars both domestically and internationally.

[0003] Currently, the main methods for joining ceramics and metals include mechanical joining, adhesive joining, brazing, solid-phase diffusion joining, instantaneous liquid-phase joining, fusion welding, self-propagating high-temperature synthesis joining, friction welding, microwave joining, and ultrasonic joining. Although there are many methods for joining ceramics and metals, many of them are difficult to put into practical use due to their inherent limitations. Furthermore, the above methods for joining ceramics and metals have the following problems: (1) the bond types of ceramics and metals are different, making it difficult to achieve a good metallurgical connection; (2) the thermal expansion coefficients of ceramics and metals differ greatly, and the joint is prone to generating large residual stress, resulting in low joint strength; (3) the surface wettability of ceramics is poor, making it difficult to determine the joining process. Therefore, it is necessary to provide a joining method that can improve the joining strength of metals and ceramics. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for connecting a ceramic shell and a metal core. In this invention, the ceramic shell and metal core are formed in one step using powder metallurgy, and then sintered in an inert atmosphere to obtain the finished product. The metal core is prepared from metal and additives with a negative coefficient of thermal expansion. This method for connecting the ceramic shell and metal core has the advantages of simple process, easy operation and control, and low cost. Furthermore, the method can effectively improve the connection strength between the ceramic shell and the metal core, thereby improving both production efficiency and practical application effectiveness.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] A method for connecting a ceramic shell and a metal core, the method comprising the following steps:

[0007] A mixture of ceramic phase powder and binder is placed on the outer layer, and a mixture of metal powder and additive powder with a negative coefficient of thermal expansion is placed on the inner layer. The mixture is then formed by dry pressing or isostatic pressing.

[0008] The molded product is then sintered at high temperature in an inert atmosphere to obtain a composite material with a ceramic shell and a metal core.

[0009] Preferably, the ceramic phase powder includes one or more of the oxide powders of Ni, Co, Fe, Al, and Cu; and / or the oxide of M, wherein M is a composite of one or more of Ni, Co, Fe, Al, and Cu.

[0010] Preferably, the adhesive comprises polyvinyl alcohol.

[0011] Preferably, the amount of the binder is 0.5-2% of the mass ratio of the ceramic phase.

[0012] Preferably, the metal powder comprises one or a combination of Fe, Mn, Ni, Al, Cu, and Cr.

[0013] Preferably, the additive powder with a negative coefficient of thermal expansion includes one or a combination of ZrW2O8, LiZr2(PO4)3, KAlSi2O6, and KZr2(PO4)3.

[0014] Preferably, the amount of additive powder with a negative coefficient of thermal expansion is determined according to the coefficient of thermal expansion of the ceramic shell, so that the coefficients of thermal expansion of the metal core and the ceramic shell are matched, thereby reducing stress by making the coefficients of thermal expansion of the metal core and the ceramic shell as close as possible.

[0015] Preferably, the amount of the additive powder with a negative coefficient of thermal expansion is 1-20% of the total mass of the metal core.

[0016] Preferably, the sintering temperature is 1100–1600℃ and the sintering time is 1–6 hours.

[0017] The present invention also provides a composite material for preparing a ceramic shell and a metal core by the above method, wherein the ceramic shell covers the metal core and the ceramic shell and the metal core are metallurgically bonded.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention eliminates residual stress at the metal-ceramic interface by adding an additive with a negative coefficient of thermal expansion to the metal core and adjusting the amount of additive. This allows the coefficient of thermal expansion of the metal core to be matched with the ceramic shell. Furthermore, the metal-ceramic bond between the metal core and the ceramic shell is metallurgically graded, significantly improving the connection strength by an order of magnitude compared to traditional mechanical connections, thus extending product lifespan. It also effectively reduces the contact resistance between the ceramic shell and the metal core, making it widely applicable in electrochemical fields, especially in carbon-free aluminum electrolysis. Attached Figure Description

[0020] Figure 1 The image shows a photograph of the composite material connecting the ceramic shell and the metal core in Example 1, where 1 is the ceramic shell and 2 is the metal core.

[0021] Figure 2 This is a scanning electron microscope (SEM) image of the cross-section of the composite material connecting the ceramic shell and the metal core in Example 1.

[0022] Figure 3 This is a cross-sectional scan of the composite material connecting the ceramic shell and the metal core in Example 2. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0024] Example 1:

[0025] In this embodiment, the composite material connecting the ceramic shell and the metal core is made of Ni. 0.8 Co 0.2 Fe2O4 ceramic powder was used as the raw material for preparing the ceramic shell, and 70% Ni powder, 25% Cu powder and 5% additive ZrW2O8 were selected as the raw materials for preparing the metal core.

[0026] Ni 0.8 Co 0.2 Fe2O4 ceramic powder and polyvinyl alcohol binder are mixed evenly, wherein the amount of polyvinyl alcohol binder is Ni. 0.8 Co 0.2 1.5%wt of Fe2O4 ceramic powder was added to obtain a granulated powder with good flowability, which was designated as the outer shell granulated powder. Then, 70%wt of Ni powder, 25%wt of Cu powder and 5%wt of ZrW2O8 additive were mixed evenly to obtain a granulated powder with good flowability, which was designated as the inner core granulated powder, for later use.

[0027] Two kg of outer shell granulation powder was evenly distributed on the outer layer of a mold, and then 0.6 kg of inner layer granulation powder was distributed on the inner layer of the mold. Cold isostatic pressing was used for molding, and after finishing, the mixture was sintered at 1350℃ for 2 hours in a nitrogen atmosphere to obtain a composite material with a ceramic shell and a metal core. The composite material prepared by this method achieves a metallurgical-grade bond between the ceramic shell and the metal core, with a bonding strength reaching 173 MPa, a significant improvement compared to the 22 MPa of traditional mechanical bonding.

[0028] Figure 1 The image shows a composite material connecting the ceramic shell and the metal core, where 1 is the ceramic shell and 2 is the metal core. As can be seen from the image, the ceramic shell encapsulates the metal core in the composite material. In practical use, the metal core can be machined, as shown in the image, by tapping threads.

[0029] Figure 2 The image shows a cross-sectional scanning electron microscope (SEM) image of the composite material connecting the ceramic shell and the metal core. As can be seen from the image, the ceramic shell and the metal core are perfectly bonded together.

[0030] In this embodiment, a composite material connecting a threaded metal guide rod, a ceramic shell, and a metal core is used as the anode. An electrolysis experiment was conducted at 200A in a KF-NaF-AlF3-Al2O3 electrolyte system, with CR = 1.4 and an anode current density of 1A / cm². 2 The average voltage is 3.89V. The voltage of the electrolytic cell remains stable during long-term operation at 900℃. This is 160mV lower than the average voltage of 4.05V of the traditional mechanically connected anode, indicating that this connection method can ensure good bonding strength and conductivity.

[0031] Example 2:

[0032] Ni 0.9 Cu 0.1 Fe2O4 ceramic powder and polyvinyl alcohol binder are mixed evenly, wherein the amount of polyvinyl alcohol binder is Ni. 0.9 Cu 0.1 0.5%wt of Fe2O4 ceramic powder, 65%wt of Ni powder, 20%wt of Cu powder, 5%wt of Al powder and 10%wt of LiZr2(PO4)3 additive were selected as raw materials for the preparation of the metal core.

[0033] Two kilograms of outer shell granulation powder were evenly distributed on the outer layer of a mold, and then 0.55 kilograms of inner layer granulation powder were distributed on the inner layer of the mold. The mixture was then cold isostatically pressed and, after finishing, sintered at 1200°C for 6 hours in a nitrogen atmosphere to obtain a composite material with a ceramic shell and a metal core. The composite material prepared by this method achieves a metallurgical-grade bond between the ceramic shell and the metal core, with a bonding strength reaching 196 MPa, a significant improvement compared to the 18 MPa of traditional mechanical bonding.

[0034] Figure 3 The image shows a cross-sectional scanning electron microscope (SEM) image of the composite material connecting the ceramic shell and the metal core. As can be seen from the image, the ceramic shell and the metal core are perfectly bonded together.

[0035] In this embodiment, the composite material connecting the metal guide rod and the ceramic shell and metal core is welded together. An electrolysis experiment was conducted in a KF-NaF-AlF3-Al2O3 electrolyte system at 200A, with CR = 1.5 and an anolyte current density of 1A / cm³. 2 The average voltage is 3.93V. The voltage of the electrolytic cell remains stable during long-term operation at 830℃. This is 180mV lower than the average voltage of 4.11V of the traditional mechanically connected anode, which indicates that this connection method can ensure good bonding strength and conductivity.

[0036] Example 3:

[0037] In this embodiment, the composite material connecting the ceramic shell and the metal core uses NiAl2O4 ceramic powder with 2%wt polyvinyl alcohol binder as the raw material for preparing the ceramic shell, and 65%wt Fe powder, 13%wt Ni powder, 3%wt Mn powder, 1%wt Cr powder, 2%wt KAlSi2O6 and 16%wt KZr2(PO4)3 additives as the raw material for preparing the metal core.

[0038] 1.8 kg of shell granulation powder was evenly distributed on the outer layer of the mold, and 0.51 kg of inner layer granulation powder was distributed on the inner layer of the mold. The mixture was then cold isostatically pressed and, after finishing, sintered at 1580°C for 4 hours in a nitrogen atmosphere to obtain a composite material with a ceramic shell and a metal core.

[0039] The composite material prepared by this method achieves a metallurgical-grade bond between the ceramic shell and the metal core, with a bonding strength of up to 218 MPa, which is a significant improvement over the 23 MPa of traditional mechanical connections.

[0040] In this embodiment, the composite material connecting the metal guide rod and the ceramic shell and metal core is welded together. An electrolysis experiment was conducted at 200A in the KF-NaF-AlF3-Al2O3 electrolyte system, with CR = 1.4 and an anolyte current density of 1A / cm³.2 The average voltage is 3.97V. The voltage of the electrolytic cell remains stable during long-term operation at 860℃. Compared with the average voltage of 4.2V of the traditional mechanically connected anode, it is reduced by 230mV, indicating that this connection method can ensure good bonding strength and conductivity.

[0041] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for connecting a ceramic shell and a metal core, characterized in that, include: A mixed powder consisting of ceramic phase powder and binder is placed on the outer layer, and a mixed powder consisting of metal powder and additive powder with a negative coefficient of thermal expansion is placed on the inner layer. The mixture is then formed by dry pressing or isostatic pressing. The molded product is then sintered at high temperature in an inert atmosphere to obtain a composite material with a ceramic shell and a metal core. The ceramic phase powder is Ni. 0.8 Co 0.2 Fe2, Ni 0.9 Cu 0.1 Fe2 or NiAl2O4; The adhesive is polyvinyl alcohol; The amount of the binder is 0.5-2% of the ceramic phase mass ratio; The metal powder is one or a combination of Fe, Mn, Ni, Al, Cu, and Cr; The additive powder with a negative coefficient of thermal expansion is one or a combination of ZrW2O8, LiZr2(PO4)3, KAlSi2O6, and KZr2(PO4)3. The amount of additive powder with a negative coefficient of thermal expansion is determined according to the coefficient of thermal expansion of the ceramic shell, so that the coefficients of thermal expansion of the metal core and the ceramic shell are matched. The sintering temperature is 1100~1600℃, and the sintering time is 1~6 hours.

2. The composite material with a ceramic shell and a metal core connected by the method of claim 1, characterized in that, In the composite material, a ceramic shell covers a metal core, and the ceramic shell and the metal core are metallurgically bonded.

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