High toughness zrn ceramic and preparation method and application thereof

Abstract

The application belongs to the technical field of ceramics, and discloses a high-toughness ZrN ceramic and a preparation method and application thereof. The method is as follows: ZrN powder is oxidized at 250-400 DEG C in air to form a thin ZrO2 layer on the surface of the ZrN; nano-Al2O3 powder is calcined at 1100-1300 DEG C to obtain dendritic Al2O3 powder; the oxidized ZrN powder and the dendritic Al2O3 powder are mechanically mixed to obtain a mixed powder; the mixed powder is pre-pressed into a shape, heated to 1600-1800 DEG C under an atmosphere or vacuum, and sintered by hot-pressing or spark plasma sintering under a pressure of 20-60 MPa to obtain the ZrN ceramic. The ZrN ceramic has a density of more than 97%, a toughness of 7-9.3 MPa*m 1 / 2 , and a thermal conductivity of 8.6-11 W·(m ‑1 ·K ‑1 ), and can be applied in the field of nuclear energy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-oxide ceramics, and more particularly relates to a high-toughness ZrN ceramic and a preparation method and application thereof. BACKGROUND

[0002] Nitride ceramics are a mixture of ionic, covalent and metallic bonds. This combination gives the material unusual advantages, such as high hardness and very high melting temperature, as well as good thermal and electrical conductivity. Due to these properties, zirconium nitride is increasingly attracting attention, and can replace some metals for use in cutting tools, advanced nuclear power plants, and as ultra-high temperature ceramics in extreme environments, due to its higher hardness, thermal conductivity and high-temperature stability. However, the toughness of zirconium nitride ceramic is low, and it is difficult to achieve sintering densification, and the preparation temperature is high, which limits its application. Therefore, it is urgent to develop a preparation method to improve the toughness of zirconium nitride ceramic, and to prepare dense zirconium nitride ceramic at a lower temperature. SUMMARY

[0003] In order to solve the above-mentioned problems and shortcomings of the prior art, the purpose of the present application is to provide a preparation method of high-toughness ZrN ceramic, which can prepare dense ZrN ceramic at a lower temperature, and improve the toughness of ZrN ceramic.

[0004] Another purpose of the present application is to provide high-toughness ZrN ceramic prepared by the above-mentioned method.

[0005] Still another purpose of the present application is to provide the application of the above-mentioned high-toughness ZrN ceramic.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A preparation method of high-toughness ZrN ceramic, comprising the following specific steps:

[0008] S1. ZrN powder is oxidized in air at 250-400 DEG C to form a thin ZrO2 layer on the surface of ZrN, and nano-Al2O3 powder is calcined at 1100-1300 DEG C to obtain dendritic Al2O3 powder;

[0009] S2. The oxidized ZrN powder and the dendritic Al2O3 powder are mechanically mixed to obtain a mixed powder;

[0010] S3. The mixed powder is pre-pressed into a shape, heated to 1600-1800 DEG C under a protective atmosphere or vacuum, and pressed at 20-60 MPa to prepare high-toughness ZrN ceramic by hot-pressing sintering or spark plasma sintering.

[0011] Preferably, the particle size of the ZrN powder in step S1 is 0.4-30 microns, the purity of the ZrN powder is above 97%, the particle size of the nano-Al2O3 powder is 10-400 nm, and the purity of the nano-Al2O3 powder is above 96%.

[0012] Preferably, the oxidation time in step S1 is 0.5-2 hours, and the calcination time is 2-6 hours.

[0013] Preferably, the mass percentage of the ZrN powder and the dendritic Al2O3 powder after oxidation in step S2 is (75-95)wt%:(5-25)wt%.

[0014] Preferably, the mechanical mixing time in step S2 is 10-26 hours, and the rotating speed is 200-300 r / min.

[0015] Preferably, the protective atmosphere in step S3 is argon, and the vacuum degree of the vacuum is 10 -4 -10 Pa.

[0016] Preferably, the heating rate of the hot-press sintering in step S3 is 5-15 ℃ / min, and the heating rate of the spark plasma sintering is 50-150 ℃ / min, and the sintering time is 10-240 min.

[0017] A high-toughness ZrN ceramic prepared by the method.

[0018] Preferably, the density of the high-toughness ZrN ceramic is above 97%, the fracture toughness of the ZrN ceramic is 7-9.3 MPa·m 1 / 2 , and the thermal conductivity is 8.6-11 W·(m -1 ·K -1 ).

[0019] Application of the high-toughness ZrN ceramic in the field of nuclear energy.

[0020] The present application forms a continuous ZrO2 layer on the surface of the ZrN powder by pre-oxidation of the ZrN powder, and forms dendritic Al2O3 powder by calcination of Al2O3. On the one hand, the ZrO2 layer and the dendritic Al2O3 powder can promote the densification of the ZrN ceramic. On the other hand, ZrO2 is easy to undergo phase transition, which can improve the toughness of the ZrN ceramic by phase transition toughening, and the dendritic structure of Al2O3 is easy to deflect, branch and bridge the cracks, increase the surface energy in the expansion process, hinder the crack propagation, and improve the toughness of the ZrN ceramic.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] 1. The present application obtains ZrO2 and dendritic Al2O3 by oxidizing ZrN and high-temperature calcining Al2O3, which together promote the densification of ZrN ceramic, and a dense ZrN ceramic is prepared at a lower temperature (1600-1800℃).

[0023] 2. The ZrO2 and dendritic Al2O3 of the present application can toughen ZrN ceramic through phase transformation, crack deflection, branching and bridging, and the ZrN ceramic has high toughness. DETAILED DESCRIPTION

[0024] The present application will be further described in conjunction with specific examples, but should not be construed as a limitation of the present application. If not specifically indicated, the technical means used in the examples are conventional means known to those skilled in the art. Unless specifically indicated, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field.

[0025] Example 1

[0026] 1. ZrN powder (purity 98%, particle size 10 μm) was oxidized in air at 250℃ for 2h to form a thin ZrO2 layer on the surface of ZrN. Nano-Al2O3 powder (purity 99.9%, particle size 300 nm) was calcined at 1200℃ for 4h to obtain dendritic Al2O3. Oxidized ZrN and calcined dendritic Al2O3 in a mass percentage of 80wt%:20wt% were mixed and planetary ball-milled at a speed of 300r / min for 12h to obtain a mixed powder.

[0027] 2. The mixed powder was pre-pressed and placed in a spark plasma sintering furnace in an argon atmosphere, a pressure of 50MPa was applied, and the temperature was raised to 1650℃ at a rate of 100℃ / min and maintained for 10min, and the cooling rate was consistent with the heating rate, to obtain a ZrN ceramic.

[0028] The density of the ZrN ceramic prepared in this example was 98.4%, the fracture toughness was 8.6MPa·m 1 / 2 , and the thermal conductivity was 9.1W·(m -1 ·K -1 ).

[0029] Example 2

[0030] 1. ZrN powder (purity 98%, particle size 10 μm) was oxidized in air at 300℃ for 2h to form a thin ZrO2 layer on the surface of ZrN. Nano-Al2O3 powder (purity 99.9%, particle size 100 nm) was calcined at 1200℃ for 6h to obtain dendritic Al2O3. Oxidized ZrN and calcined dendritic Al2O3 in a mass percentage of 85wt%:15wt% were mixed and planetary ball-milled at a speed of 300r / min for 12h to obtain a mixed powder.

[0031] 2. The mixed powder was pre-pressed and placed in a spark plasma sintering furnace, argon atmosphere, 40 MPa pressure, heated to 1700℃ at a rate of 50℃ / min, 10 min holding, cooling rate consistent with heating, to obtain ZrN ceramic.

[0032] The ZrN ceramic prepared in this example has a density of 98.1%, a fracture toughness of 8.9 MPa·m 1 / 2 , and a thermal conductivity of 9.4 W·(m -1 ·K -1 ).

[0033] Example 3

[0034] 1. ZrN powder (purity 99%, particle size 5 μm) was oxidized in air at 350℃ for 1 h to form a thin ZrO2 layer on the surface of ZrN. Nano-Al2O3 powder (purity 99.9%, particle size 50 nm) was calcined at 1150℃ for 4 h to obtain dendritic Al2O3. Oxidized ZrN and calcined dendritic Al2O3 in a mass ratio of 90wt%:10wt% were mixed and planetary ball milled for 18 h at a rotation speed of 250 r / min to obtain a mixed powder.

[0035] 2. The mixed powder was pre-pressed and placed in a spark plasma sintering furnace, nitrogen atmosphere, 30 MPa pressure, heated to 1750℃ at a rate of 100℃ / min, 10 min holding, cooling rate consistent with heating, to obtain ZrN ceramic.

[0036] The ZrN ceramic prepared in this example has a density of 99.4%, a fracture toughness of 7.6 MPa·m 1 / 2 , and a thermal conductivity of 10.8 W·(m -1 ·K -1 ).

[0037] Example 4

[0038] 1. ZrN powder (purity 99%, particle size 1 μm) was oxidized in air at 300℃ for 1 h to form a thin ZrO2 layer on the surface of ZrN. Nano-Al2O3 powder (purity 99.9%, particle size 30 nm) was calcined at 1150℃ for 4 h to obtain dendritic Al2O3. Oxidized ZrN and calcined dendritic Al2O3 in a mass ratio of 85wt%:15wt% were mixed and planetary ball milled for 24 h at a rotation speed of 200 r / min to obtain a mixed powder.

[0039] 2. The mixed powder was pre-pressed and placed in a hot-pressing sintering furnace, vacuum degree 10 -1Pa, 40MPa pressure is applied, the temperature is increased to 1700℃ at a rate of 10℃ / min, the temperature is kept for 120min, and the temperature is decreased at a rate consistent with the temperature increasing, to obtain ZrN ceramic.

[0040] The ZrN ceramic prepared in the example has a density of 99.1%, a fracture toughness of 9MPa·m 1 / 2 , and a thermal conductivity of 9.1W·(m -1 ·K -1 ).

[0041] Example 5

[0042] 1. ZrN powder (purity 99%, particle size 5μm) is oxidized in air at 300℃ for 1h, to form a thin ZrO2 layer on the surface of the ZrN. Nano-Al2O3 powder (purity 99.9%, particle size 20nm) is calcined at 1300℃ for 4h, to obtain dendritic Al2O3. The mixed powder is obtained by mixing 95wt%:5wt% of the oxidized ZrN and the calcined dendritic Al2O3 and planetary ball milling for 24h at a rotation speed of 200r / min.

[0043] 2. The mixed powder is pre-pressed and placed in a hot-pressing sintering furnace, an argon atmosphere is provided, 30MPa pressure is applied, the temperature is increased to 1800℃ at a rate of 10℃ / min, the temperature is kept for 120min, and the temperature is decreased at a rate consistent with the temperature increasing, to obtain ZrN ceramic.

[0044] The ZrN ceramic prepared in the example has a density of 98.7%, a fracture toughness of 7.6MPa·m 1 / 2 , and a thermal conductivity of 11W·(m -1 ·K -1 ).

[0045] The high-toughness ZrN ceramic of the present application has a density of more than 97%, a fracture toughness of 7-9.3MPa·m 1 / 2 , and a thermal conductivity of 8.6-11W·(m -1 ·K -1 ), and can be applied in the field of nuclear energy.

[0046] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods and are included in the protection scope of the present application.

Claims

1. A method for preparing high-toughness ZrN ceramics, characterized in that, The specific steps include the following: S1. ZrN powder is oxidized in air at 250~400 ℃ to form a thin ZrO2 layer on the ZrN surface. Nano-Al2O3 powder is calcined at 1100~1300 ℃ to obtain dendritic Al2O3 powder. The ZrN powder has a particle size of 0.4~30 µm and a purity of ≥97%. The nano-Al2O3 powder has a particle size of 10~400 nm and a purity of ≥96%. S2. The oxidized ZrN powder and dendritic Al2O3 powder are mechanically mixed to obtain a mixed powder; the mass percentage of the oxidized ZrN powder and the dendritic Al2O3 powder is (75~95) wt%: (5~25) wt%. S3. The mixed powder is pre-pressed and then heated to 1600~1800℃ and pressurized to 20~60MPa under a protective atmosphere or vacuum to obtain ZrN ceramics through hot pressing sintering or spark plasma sintering; the density of the ZrN ceramics is above 97%, and the fracture toughness of the ZrN ceramics is 7~9.3 MPa·m. 1 / 2 Thermal conductivity is 8.6~11 W·(m -1 ·K -1 ).

2. The method for preparing high-toughness ZrN ceramics according to claim 1, characterized in that, The oxidation time in step S1 is 0.5 to 2 hours, and the calcination time is 2 to 6 hours.

3. The method for preparing high-toughness ZrN ceramics according to claim 1, characterized in that, The mechanical mixing time in step S2 is 10~26 h, and the mechanical mixing speed is 200~300 r / min.

4. The method for preparing high-toughness ZrN ceramics according to claim 1, characterized in that, The protective atmosphere in step S3 is argon, and the vacuum degree is 10. -4 ~10 Pa.

5. The method for preparing high-toughness ZrN ceramic according to claim 1, characterized in that, The heating rate of hot pressing sintering in step S3 is 5~15 ℃ / min, the heating rate of spark plasma sintering is 50~150 ℃ / min, and the sintering time is 10~240 min.

6. A high-toughness ZrN ceramic, characterized in that, The ZrN ceramic is prepared by the method described in any one of claims 1-5.

7. The application of the high-toughness ZrN ceramic as described in claim 6 in the field of nuclear energy.