High-thermal-conductivity Zr3Si2 ceramic as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of non-oxide-based materials, and discloses 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 a high-energy ball mill, and drying to obtain Zr-ZrSi2 mixed powder; the Zr-ZrSi2 mixed powder is sintered in a vacuum state at the temperature of 1600-1750 DEG C, argon is introduced during heat preservation, the pressure is 0.3-0.5 MPa, and the high-thermal-conductivity Zr3Si2 ceramic is prepared. According to the method, the grain boundary energy can be effectively improved through spark plasma sintering, so that the Zr-rich powder is fully permeated into crystal lattices of ZrSi2, the preparation method of the Zr3Si2 ceramic can be simplified, the production rate of the Zr3Si2 ceramic can be improved, and the Zr3Si2 ceramic can be applied to the fields of nuclear energy, automobiles, electronics and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic materials, and more specifically, relates to a high thermal conductivity Zr3Si2 ceramic and a preparation method and application thereof. Technical Background

[0002] Zirconium silicide ceramic materials have excellent thermal expansion coefficient, thermal melting coefficient, thermal diffusion coefficient, thermal conductivity, and are currently used as neutron reaction materials for the next generation of nuclear power plants, gas-cooled rapid cooling devices (GFR), general atomic energy multiplier modules (EM2) and fast modular reactors (FMR) material research. Due to the excellent thermodynamic properties of this material, it can be widely used in the fields of nuclear energy and new energy vehicles in the future. However, during the sintering process of this type of ceramic, the liquid phase of Si is easily gasified at high temperatures, which easily leads to a reduction in Si content. Therefore, while ensuring the overall ratio, improving the thermodynamic properties of zirconium silicide ceramics is one of the main research directions.

[0003] There are currently two main methods for preparing high-performance zirconium silicide ceramics. One is to use arc melting to mix the powder, add acetone, put it in a high-energy ball mill, use zirconium carbide balls for ball milling, and finally use HP to sinter and form. The problem with this method is that the wear of the zirconium carbide balls during the ball milling process will cause zirconium carbide impurities to appear inside the powder, and the process is cumbersome, which makes it easy for some uncontrollable products to appear in the final product. The second method is the same as the previous method, but SPS sintering is used in the last step, but the result is to improve its density and promote grain growth. The impurities introduced during the ball milling process cannot be well resolved, and oxides are also easily generated.

[0004] At present, the main research on zirconium silicide ceramics is to synthesize zirconium silicide ceramics with excellent strength and thermodynamic properties through various methods, or to improve its thermodynamic properties by combining with other alloys. For example, Starosta, W et al. sprayed a zirconium silicide coating on zirconium carbide to improve its overall thermodynamic properties, and applied the material to solar heating panels, and sprayed zirconium silicide to improve the overall thermodynamic properties of the material. Minrak Kim et al. used electrophoretic deposition (EPD) and physical vapor deposition (PVD) to change the structure of the material and formed a porous structure of zirconium silicide ceramics. Although this preparation method reduces the strength of the material from the perspective of mechanical properties, this porous structure helps to improve the thermodynamic properties of the material and enable it to have better antioxidant properties to improve its safety as a cladding material. Je'ro^me Canel et al. improved the purity of zirconium silicide ceramics through an in-situ synthesis method and obtained relatively excellent thermodynamic properties. Due to the limitations of the current process. Therefore, it is urgent to develop a zirconium silicide ceramic with low cost, simple preparation process and high efficiency, excellent mechanical properties and high thermal conductivity. Summary of the invention

[0005] In order to solve the above-mentioned deficiencies and shortcomings of the prior art, the object of the present invention is to provide a method for preparing high thermal conductive Zr3Si2 ceramics, which simplifies the complicated processing steps.

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

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

[0008] The purpose of the present invention is achieved through the following technical solutions:

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

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

[0011] S2. Place the Zr-ZrSi2 mixed powder into a spark plasma sintering furnace, heat it to 500-650°C under vacuum, and then heat it to 1600-1750°C. During the insulation, argon gas is introduced. The pressure of the argon gas is 0.3-0.5MPa. After insulation for 10-20 minutes, the temperature is lowered to 1400-1500°C and maintained for 10-15 minutes. The temperature is then lowered to 900-1000°C and cooled with the furnace to obtain high thermal conductivity Zr3Si2 ceramics.

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

[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 rate of heating to 500-650°C is 100-150°C / min, and the rate of heating to 1600-1750°C is 110-120°C / min; the rate of cooling to 1400-1500°C is 20-50°C / min, and the rate of cooling to 900-1000°C is 100-110°C / min.

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

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

[0018] The high thermal conductivity Zr3Si2 ceramic is used in the fields of nuclear energy, automobiles or electronics.

[0019] The present invention is based on the orthorhombic lattice structure (space group cmcm) of traditional zirconium silicide ceramics (ZrSi2) showing excellent performance at room temperature. However, under high temperature environment, the lattice structure of ZrSi2 will undergo changes, forming silicon atom vacancies, and silicon atoms tend to migrate from the inside 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, supplementing the silicon content therein, so that traditional ZrSi2 ceramics can be converted into Zr3Si2 ceramics.

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

[0021] 1. The present invention adopts a simpler method, abandons the traditional method, and realizes the preparation of high-purity (more than 96%) Zr3Si2 ceramics in a safer and more reliable manner.

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

[0023] 3. The sintering process time of the spark plasma sintering method adopted in the present invention is shorter. The traditional sintering method adopts the method of arc melting first, crushing and finally hot isostatic pressing sintering. This method has a long application time and is even longer, and has more dangers. DETAILED DESCRIPTION

[0024] The content of the present invention is further described below in conjunction with specific examples, but it should not be construed as limiting the present invention. If not specifically indicated, the technical means used in the examples 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 the art.

[0025] Example 1

[0026] 1. Add acetone to Zr powder (purity of 99%, particle size of 0.5-1 μm) and ZrSi2 powder (purity of more than 99%, particle size of 0.5-1 μm) with a mass ratio of 15.3:94.7, mix them by high-energy ball milling, place them in a rotary evaporator for drying, and obtain Zr-ZrSi2 mixed powder;

[0027] 2. Place the Zr-ZrSi2 mixed powder into a spark plasma sintering furnace, heat it to 650°C at 150°C / min under vacuum, then heat it to 1750°C at 110°C / min, introduce argon during insulation, the pressure of argon during insulation is 0.5MPa, after insulation for 20min, cool it to 1500°C at 20°C / min, keep it for 10min, then cool it to 900°C at 100°C / min, cool it in the furnace and take it out to obtain Zr3Si2 ceramics.

[0028] The relative density of the Zr3Si2 ceramic in this embodiment is 96%, and the fracture toughness is 1.9 MPa m 1 / 2 The average thermal expansion coefficient is 8.11×10 -6 k -1 , thermal conductivity is 22.5W / mk. The Zr3Si2 ceramic has 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 of more than 99%, particle size of 0.5-1 μm) and ZrSi2 powder (purity of more than 99.99%, particle size of 0.5-1 μm) is 18:82, and the Zr-ZrSi2 mixed powder is obtained by grinding, mixing and drying.

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

[0032] Example 3

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

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

[0035] Example 4

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

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

[0038] Example 5

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

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

[0041] Example 6

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

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

[0044] The relative density of the Zr3Si2 ceramic of the present invention is above 96%, and the fracture toughness is 1.9-3MPa m 1 / 2 The average thermal expansion coefficient is 9.11×10 -6 ~7.11×10 -6 k -1 The thermal conductivity is 20.5-28.5 W / mk, indicating that the Zr3Si2 ceramic has high thermal conductivity, low thermal expansion coefficient and excellent bending strength. The Zr3Si2 ceramic reaches 1017n / cm before and after neutron irradiation. 2 The average linear dimensional change is <0.12%. The material's structure and dimensional stability show excellent resistance to neutron radiation and extremely low thermal neutron absorption cross-section. It has significant advantages in nuclear fuel cladding materials and has extremely high research and application value, and is suitable for the nuclear energy field.

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

Claims

1. A method for preparing a high thermal conductivity Zr3Si2 ceramic, characterized in that: The steps include: S1. The Zr powder, ZrSi2 powder and solvent are mixed and dried by high-energy ball milling to obtain a Zr-ZrSi2 mixed powder; S2. Place the Zr-ZrSi2 mixed powder into a spark plasma sintering furnace, heat it to 500-650°C under vacuum, and then heat it to 1600-1750°C. During the insulation, argon gas is introduced. The pressure of the argon gas is 0.3-0.5MPa. After insulation for 10-20 minutes, the temperature is lowered to 1400-1500°C and maintained for 10-15 minutes. The temperature is then lowered to 900-1000°C and cooled with the furnace to obtain high thermal conductivity Zr3Si2 ceramics.

2. The method for preparing the high thermal conductivity Zr3Si2 ceramic according to claim 1, characterized in that: The purity of the Zr powder in step S1 is above 99%, and the particle size is 0.5-1 μm; the purity of the ZrSi2 powder is above 99.9%, and the particle size is 0.5-1 μm; the mass ratio of the Zr powder to the ZrSi2 powder is (15-21):(78-84).

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

4. The method for preparing the high thermal conductivity Zr3Si2 ceramic according to claim 1, characterized in that: The drying temperature in step S1 is not higher than 60°C.

5. The method for preparing the high thermal conductivity Zr3Si2 ceramic according to claim 1, characterized in that: In step S2, the temperature is increased to 500-650°C at a rate of 100-150°C / min, and the temperature is increased to 1600-1750°C at a rate of 110-120°C / min; the temperature is decreased to 1400-1500°C at a rate of 20-50°C / min, and the temperature is decreased to 900-1000°C at a rate of 100-110°C / min.

6. A high thermal conductivity Zr3Si2 ceramic, characterized in that: The Zr3Si2 ceramic is prepared by the method described in any one of claims 1-5.

7. The high thermal conductivity Zr3Si2 ceramic according to claim 6, characterized in that: The relative density of the Zr3Si2 ceramic is above 96%, and the fracture toughness is 1.9-3MPa m 1 / 2 , the thermal expansion coefficient is 9.11×10 -6 ~7.11×10 -6 k -1 , thermal conductivity is 20.5~28.5W / mk.

8. Application of the high thermal conductivity Zr3Si2 ceramics according to claim 6 or 7 in the fields of nuclear energy, automobiles or electronics.