A high thermal conductivity Zr3Si2 ceramic, its preparation method and application

Abstract

The application belongs to the technical field of non-oxide-based materials, and discloses a high-thermal-conductivity Zr3Si2 ceramic as well as a preparation method and application thereof. The method comprises the following steps: mixing Zr powder, ZrSi2 powder and a solvent through high-energy ball milling and drying to obtain Zr-ZrSi2 mixed powder; and sintering the Zr-ZrSi2 mixed powder at 1600-1750 DEG C under vacuum, and introducing argon during heat preservation at a pressure of 0.3-0.5 MPa to obtain the high-thermal-conductivity Zr3Si2 ceramic. The application can effectively improve the grain boundary energy through spark plasma sintering, so that the Zr-rich powder fully penetrates into the crystal lattice of ZrSi2, the preparation method of the Zr3Si2 ceramic can be simplified, the production rate of the Zr3Si2 ceramic is improved, and the Zr3Si2 ceramic can be applied in the fields of nuclear energy, automobiles or electronics.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, and more specifically, relates to a high thermal conductivity Zr3Si2 ceramic, its preparation method and application. Technical Background

[0002] Zirconium silicide ceramics, due to their excellent coefficients of thermal expansion, thermal fusion, thermal diffusivity, and thermal conductivity, are currently being studied as neutron reactor materials for next-generation nuclear power plants, gas-cooled rapid reactors (GFRs), universal atomic energy multiplier modules (EM2), and fast modular reactors (FMRs). Their superior thermodynamic properties also suggest broad applications in nuclear energy and new energy vehicles. However, during the sintering process, the liquid Si phase tends to vaporize at high temperatures, leading to a reduction in Si content. Therefore, improving the thermodynamic properties of zirconium silicide ceramics while maintaining the overall proportions is a key research direction.

[0003] Currently, there are two main methods for preparing high-performance zirconium silicide ceramics. The first method involves arc melting and mixing powders, adding acetone, and then ball milling them using zirconium carbide microspheres in a high-energy ball mill, followed by sintering using high-energy ball milling (HP). The problem with this method is that the wear of the zirconium carbide microspheres during ball milling can introduce zirconium carbide impurities into the powder, and the process is cumbersome, making it prone to introducing uncontrollable byproducts in the final product. The second method is similar to the first, but uses SPS sintering in the final step. While this improves density and promotes grain growth, it cannot effectively address the impurities introduced during ball milling and is also prone to oxide formation.

[0004] Current research on zirconium silicide ceramics mainly focuses on synthesizing zirconium silicide ceramics with excellent strength and thermodynamic properties through various methods, or improving their thermodynamic properties by combining them with other alloys. For example, Starosta, W et al. improved the overall thermodynamic properties of zirconium carbide by spraying a zirconium silicide coating onto it, and applied this material to solar heating panels, using zirconium silicide spraying to enhance the overall thermodynamic properties of the material. Minrak Kim et al. used electrophoretic deposition (EPD) and physical vapor deposition (PVD) to modify the structure of the material, forming porous zirconium silicide ceramics. Although this preparation method reduces the strength of the material from a mechanical property perspective, the porous structure helps to improve the thermodynamic properties of the material and gives it better oxidation resistance, thus improving its safety as a cladding material. Je'ro^me Canel et al. improved the purity of zirconium silicide ceramics through in-situ synthesis and obtained relatively excellent thermodynamic properties. Due to the limitations of current processes, there is an urgent need to develop a zirconium silicide ceramic with low cost, simple and efficient preparation process, excellent mechanical properties, and high thermal conductivity. Summary of the Invention

[0005] In order to overcome the shortcomings and disadvantages of the existing technology, the purpose of this invention is to provide a method for preparing Zr3Si2 ceramics with high thermal conductivity, which simplifies its complicated processing steps.

[0006] Another object of the present invention is to provide a Zr3Si2 ceramic with high thermal conductivity prepared by the above method, which has excellent mechanical properties and high thermal conductivity.

[0007] Another object of the present invention is to provide applications of the above-mentioned high thermal conductivity Zr3Si2 ceramic.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for preparing Zr3Si2 ceramic with high thermal conductivity includes the following steps:

[0010] S1. Zr powder, ZrSi2 powder and solvent are mixed by high-energy ball milling and dried to obtain Zr-ZrSi2 mixed powder;

[0011] S2. The Zr-ZrSi2 mixed powder is placed in a spark plasma sintering furnace and heated to 500-650℃ under vacuum, then to 1600-1750℃. Argon gas is introduced during the holding period, with a pressure of 0.3-0.5 MPa. After holding for 10-20 minutes, the temperature is lowered to 1400-1500℃ and held for 10-15 minutes, then lowered to 900-1000℃ and cooled with the furnace to obtain Zr3Si2 ceramic with high thermal conductivity.

[0012] Preferably, the purity of the Zr powder in step S1 is above 99%, and the particle size is 0.5 to 1 μm; the purity of the ZrSi2 powder is above 99.9%, and the particle size is 0.5 to 1 μm; the mass ratio of the Zr powder to the ZrSi2 powder is (15 to 21):(78 to 84).

[0013] Preferably, the solvent in step S1 is acetone, ethanol, or xylene.

[0014] Preferably, the drying temperature in step S1 is not higher than 60°C.

[0015] Preferably, in step S2, the heating rate to 500-650°C is 100-150°C / min, the heating rate to 1600-1750°C is 110-120°C / min, the cooling rate to 1400-1500°C is 20-50°C / min, and the cooling rate to 900-1000°C is 100-110°C / min.

[0016] A Zr3Si2 ceramic with high thermal conductivity is prepared by the method described above.

[0017] Preferably, the Zr3Si2 ceramic has a relative density of 96% or higher and a fracture toughness of 1.9–3 MPa / m. 1 / 2 The coefficient of thermal expansion is 9.11 × 10⁻⁶. -6 ~7.11×10 -6 k -1 Its thermal conductivity is 20.5–28.5 W / mk.

[0018] Applications of the aforementioned high thermal conductivity Zr3Si2 ceramic in the fields of nuclear energy, automobiles, or electronics.

[0019] This invention leverages the superior performance of the orthorhombic lattice structure (space group cmcm) of traditional zirconium silicide ceramics (ZrSi2) at room temperature. However, at high temperatures, the lattice structure of ZrSi2 undergoes changes, creating silicon atom vacancies. Silicon atoms tend to migrate from the interior of the lattice to the surface, thereby enhancing the oxidation resistance of ZrSi2 at high temperatures. By adding Zr powder to ZrSi2, Zr atoms can penetrate into the lattice of ZrSi2 ceramics under high-temperature conditions, replenishing the silicon content and transforming traditional ZrSi2 ceramics into Zr3Si2 ceramics.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. This invention employs a simpler method, abandoning traditional methods, and achieves a safer and more reliable preparation of high-purity (above 96%) Zr3Si2 ceramics.

[0022] 2. Compared with traditional preparation methods, the raw materials used in this invention are more readily available. Compared with the traditional sintering method of zirconium powder plus silicon powder, this method is simpler and safer.

[0023] 3. The sintering process of the present invention using the spark plasma sintering method is shorter. The traditional sintering method first uses electric arc melting, then crushing, and finally hot isostatic pressing sintering. This method takes longer and is more dangerous. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0025] Example 1

[0026] 1. Zr powder (purity 99%, particle size 0.5-1μm) and ZrSi2 powder (purity above 99%, particle size 0.5-1μm) in a mass ratio of 15.3:94.7 are mixed with acetone by high-energy ball milling and then dried in rotary evaporation to obtain Zr-ZrSi2 mixed powder.

[0027] 2. The Zr-ZrSi2 mixed powder was placed in a spark plasma sintering furnace and heated to 650°C at 150°C / min under vacuum, and then heated to 1750°C at 110°C / min. Argon gas was introduced during the holding period, and the pressure of argon gas was 0.5MPa. After holding for 20 min, the temperature was lowered to 1500°C at 20°C / min and held for 10 min. Then, the temperature was lowered to 900°C at 100°C / min and cooled with the furnace before being removed to obtain Zr3Si2 ceramic.

[0028] The Zr3Si2 ceramic in this embodiment has a relative density of 96% and a fracture toughness of 1.9 MPa / m. 1 / 2 The average coefficient of thermal expansion is 8.11 × 10⁻⁶. -6 k -1 The thermal conductivity is 22.5 W / mK. This Zr3Si2 ceramic exhibits excellent mechanical properties (flexural strength and fracture toughness), high hardness, and high thermal conductivity.

[0029] Example 2

[0030] The difference from Example 1 is that in step 1, the mass ratio of Zr powder (purity above 99%, particle size 0.5-1μm) and ZrSi2 powder (purity above 99.99%, particle size 0.5-1μm) is 18:82. After grinding, mixing and drying, Zr-ZrSi2 mixed powder is obtained.

[0031] The Zr3Si2 ceramic prepared in this embodiment has a relative density of 97.6% and a fracture toughness of 2.2 MPa / m. 1 / 2 The average coefficient of thermal expansion is 7.91 × 10⁻⁶. -6 k -1 Its thermal conductivity is 22.9 W / mk.

[0032] Example 3

[0033] The difference from Example 1 is that in step 1, the mass ratio of Zr powder (purity above 99%, particle size 0.5-1μm) and ZrSi2 powder (purity above 99.99%, particle size 0.5-1μm) is 19:81. After grinding, mixing and drying, Zr-ZrSi2 mixed powder is obtained.

[0034] The Zr3Si2 ceramic prepared in this embodiment has a relative density of 97.5% and a fracture toughness of 2.3 MPa / m. 1 / 2 The average coefficient of thermal expansion is 7.41 × 10⁻⁶. -6 k -1 Its thermal conductivity is 24.9 W / mk.

[0035] Example 4

[0036] The difference from Example 1 is that in step 1, the mass ratio of Zr powder (purity above 99%, particle size 0.5-1μm) and ZrSi2 powder (purity above 99.99%, particle size 0.5-1μm) is 20:80. After grinding, mixing and drying, Zr-ZrSi2 mixed powder is obtained.

[0037] The Zr3Si2 ceramic prepared in this embodiment has a relative density of 98% and a fracture toughness of 2.4 MPa / m. 1 / 2 The average coefficient of thermal expansion is 7.31 × 10⁻⁶. -6 k -1 Its thermal conductivity is 25.5 W / mk.

[0038] Example 5

[0039] The difference from Example 1 is that in step 1, the mass ratio of Zr powder (purity above 99%, particle size 0.5-1μm) and ZrSi2 powder (purity above 99.99%, particle size <10nm) is 21:79. After grinding, mixing and drying, Zr-ZrSi2 mixed powder is obtained.

[0040] The Zr3Si2 ceramic prepared in this embodiment has a relative density of 98% and a fracture toughness of 2.8 MPa / m. 1 / 2 The average coefficient of thermal expansion is 7.21 × 10⁻⁶. -6 k -1 Its thermal conductivity is 26.5 W / mk.

[0041] Example 6

[0042] The difference from Example 1 is that in step 1, the mass ratio of Zr powder (purity above 99%, particle size 0.5-1μm) and ZrSi2 powder (purity above 99.99%, particle size <10nm) is 21.1:78.9. After grinding, mixing and drying, Zr-ZrSi2 mixed powder is obtained.

[0043] The Zr3Si2 ceramic prepared in this embodiment has a relative density of 98% and a fracture toughness of 3.0 MPa / m. 1 / 2 The average coefficient of thermal expansion is 7.11 × 10⁻⁶. -6 k -1 Its thermal conductivity is 28.5 W / mk.

[0044] The Zr3Si2 ceramic of the present invention has a relative density of over 96% and a fracture toughness of 1.9–3 MPa. 1 / 2 The average coefficient of thermal expansion is 9.11 × 10⁻⁶. -6 ~7.11×10 -6 k -1 The thermal conductivity ranges from 20.5 to 28.5 W / mK, indicating that this Zr3Si2 ceramic possesses high thermal conductivity, a low coefficient of thermal expansion, and excellent flexural strength. The Zr3Si2 ceramic achieves a thermal conductivity of 10¹⁷ N / cm² both before and after neutron irradiation. 2 With an average linear size change of <0.12%, the material exhibits excellent structural and dimensional stability, demonstrating outstanding resistance to neutron radiation and an extremely low thermal neutron absorption cross section. It shows significant advantages in nuclear fuel cladding materials, possesses extremely high research and application value, and is suitable for the nuclear energy field.

[0045] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high thermal conductivity Zr3Si2 ceramic, characterized in that, Includes the following steps: S1. Zr powder, ZrSi2 powder and solvent are mixed by high-energy ball milling and dried to obtain Zr-ZrSi2 mixed powder; the purity of Zr powder is above 99% and the particle size is 0.5~1μm; the purity of ZrSi2 powder is above 99.9% and the particle size is 0.5~1μm; the mass ratio of Zr powder to ZrSi2 powder is (15~21): (78~84), and the drying temperature is not higher than 60℃; S2. The Zr-ZrSi2 mixed powder is placed in a spark plasma sintering furnace and heated to 500~650℃ under vacuum, then heated to 1600~1750℃. Argon gas is introduced during the holding period, and the pressure of argon gas is 0.3~0.5MPa. After holding for 10~20min, the temperature is lowered to 1400~1500℃ and held for 10~15min. Then, the temperature is lowered to 900~1000℃ and cooled with the furnace to obtain Zr3Si2 ceramic with high thermal conductivity.

2. The method for preparing high thermal conductivity Zr3Si2 ceramic according to claim 1, characterized in that, The solvent mentioned in step S1 is acetone, ethanol, or xylene.

3. The method for preparing high thermal conductivity Zr3Si2 ceramic according to claim 1, characterized in that, In step S2, the heating rate to 500~650℃ is 100~150℃ / min, the heating rate to 1600~1750℃ is 110~120℃ / min; the cooling rate to 1400~1500℃ is 20~50℃ / min, and the cooling rate to 900~1000℃ is 100~110℃ / min.