CN117326869A - Low-value loss control rod ceramic material and preparation method and application thereof - Google Patents
Low-value loss control rod ceramic material and preparation method and application thereof Download PDFInfo
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- 229910010293 ceramic material Inorganic materials 0.000 title claims abstract description 29
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 239000000919 ceramic Substances 0.000 claims abstract description 50
- 238000000034 method Methods 0.000 claims abstract description 38
- 239000000463 material Substances 0.000 claims abstract description 32
- 238000005245 sintering Methods 0.000 claims abstract description 17
- 230000008569 process Effects 0.000 claims abstract description 14
- 239000000843 powder Substances 0.000 claims description 23
- 238000000498 ball milling Methods 0.000 claims description 13
- ULZGEWUJZZYASQ-UHFFFAOYSA-N europium(3+) gadolinium(3+) oxygen(2-) Chemical compound [Eu+3].[O-2].[Gd+3].[O-2].[O-2] ULZGEWUJZZYASQ-UHFFFAOYSA-N 0.000 claims description 11
- 239000002243 precursor Substances 0.000 claims description 10
- 230000009257 reactivity Effects 0.000 claims description 10
- OERNJTNJEZOPIA-UHFFFAOYSA-N zirconium nitrate Chemical compound [Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O OERNJTNJEZOPIA-UHFFFAOYSA-N 0.000 claims description 10
- 235000015895 biscuits Nutrition 0.000 claims description 9
- 238000007873 sieving Methods 0.000 claims description 8
- 239000011812 mixed powder Substances 0.000 claims description 7
- 238000000227 grinding Methods 0.000 claims description 6
- GAGGCOKRLXYWIV-UHFFFAOYSA-N europium(3+);trinitrate Chemical compound [Eu+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O GAGGCOKRLXYWIV-UHFFFAOYSA-N 0.000 claims description 5
- MWFSXYMZCVAQCC-UHFFFAOYSA-N gadolinium(iii) nitrate Chemical compound [Gd+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O MWFSXYMZCVAQCC-UHFFFAOYSA-N 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 5
- 238000003825 pressing Methods 0.000 claims description 5
- 239000011358 absorbing material Substances 0.000 claims description 4
- 238000007670 refining Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 238000001354 calcination Methods 0.000 claims description 3
- 238000009694 cold isostatic pressing Methods 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 238000000465 moulding Methods 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 238000000748 compression moulding Methods 0.000 claims description 2
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- 238000006243 chemical reaction Methods 0.000 abstract description 6
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- 238000005979 thermal decomposition reaction Methods 0.000 abstract description 2
- 239000012071 phase Substances 0.000 description 30
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- 230000007797 corrosion Effects 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 229910052693 Europium Inorganic materials 0.000 description 6
- 238000001069 Raman spectroscopy Methods 0.000 description 6
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 description 6
- 229910001940 europium oxide Inorganic materials 0.000 description 6
- AEBZCFFCDTZXHP-UHFFFAOYSA-N europium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Eu+3].[Eu+3] AEBZCFFCDTZXHP-UHFFFAOYSA-N 0.000 description 6
- 238000005259 measurement Methods 0.000 description 6
- 229910052761 rare earth metal Inorganic materials 0.000 description 6
- 238000001237 Raman spectrum Methods 0.000 description 5
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 5
- 230000008859 change Effects 0.000 description 5
- 238000000975 co-precipitation Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 229910000925 Cd alloy Inorganic materials 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 239000010436 fluorite Substances 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 150000002910 rare earth metals Chemical class 0.000 description 3
- 238000010532 solid phase synthesis reaction Methods 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 229910052688 Gadolinium Inorganic materials 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- BCEYEWXLSNZEFA-UHFFFAOYSA-N [Ag].[Cd].[In] Chemical group [Ag].[Cd].[In] BCEYEWXLSNZEFA-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 238000005253 cladding Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 229910002108 dysprosium titanate Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000004992 fission Effects 0.000 description 2
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 description 2
- 238000007373 indentation Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- ZIKATJAYWZUJPY-UHFFFAOYSA-N thulium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[Tm+3].[Tm+3] ZIKATJAYWZUJPY-UHFFFAOYSA-N 0.000 description 2
- 238000007088 Archimedes method Methods 0.000 description 1
- 229910000712 Boron steel Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910002538 Eu(NO3)3·6H2O Inorganic materials 0.000 description 1
- 229910002617 Gd(NO3)3·6H2O Inorganic materials 0.000 description 1
- 238000007545 Vickers hardness test Methods 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
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- 230000015572 biosynthetic process Effects 0.000 description 1
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 description 1
- 239000012700 ceramic precursor Substances 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
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- 229910021641 deionized water Inorganic materials 0.000 description 1
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- 239000010432 diamond Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 229910003440 dysprosium oxide Inorganic materials 0.000 description 1
- NLQFUUYNQFMIJW-UHFFFAOYSA-N dysprosium(iii) oxide Chemical compound O=[Dy]O[Dy]=O NLQFUUYNQFMIJW-UHFFFAOYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 229910001938 gadolinium oxide Inorganic materials 0.000 description 1
- 229940075613 gadolinium oxide Drugs 0.000 description 1
- CMIHHWBVHJVIGI-UHFFFAOYSA-N gadolinium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[Gd+3].[Gd+3] CMIHHWBVHJVIGI-UHFFFAOYSA-N 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000002065 inelastic X-ray scattering Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
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- 229910052759 nickel Inorganic materials 0.000 description 1
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- -1 rare earth compound Chemical class 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/50—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on rare-earth compounds
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- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
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- C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3231—Refractory metal oxides, their mixed metal oxides, or oxide-forming salts thereof
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Abstract
The invention provides a low-value loss control rod ceramic material, and a preparation method and application thereof. The method provided by the invention adopts a high-temperature sintering method under a vacuum condition, and synthesizes a series of xEu through direct thermal decomposition reaction 2 O 3 ‑(1‑x)Gd 2 Zr 2 O 7 (x= 0.6,0.7,0.8,0.85) two-phase ceramic. xEu is in the temperature range of 25-350 DEG C 2 O 3 ‑(1‑x)Gd 2 Zr 2 O 7 The hardness of the ceramic is stable in temperature dependence. Thermal expansion coefficient and Thermal Expansion Coefficient (TEC) indicate xEu 2 O 3 ‑(1‑x)Gd 2 Zr 2 O 7 The ceramic has excellent high temperature phase stability. xEu 2 O 3 ‑(1‑x)Gd 2 Zr 2 O 7 As a control rod material with lower theoretical reaction value loss, the ceramics can further reduce xEu 2 O 3 ‑(1‑x)Gd 2 Zr 2 O 7 The thermal expansion rate of the ceramic is improved, and the heat conductivity coefficient of the ceramic is improved. The preparation method has the advantages of simple process, good controllability, no sintering aid, relatively simple sintering condition, easy operation, mass production and the like.
Description
Technical Field
The invention belongs to the technical field of preparation of ceramic materials, and particularly relates to a ceramic material capable of being used as a neutron absorption rod, in particular to a low-value loss control rod ceramic material, and a preparation method and application thereof.
Background
Energy is the basic power for the development and progress of social production and life, nuclear energy is an ideal renewable energy source, and the safe operation of the nuclear energy is important. Safe, reliable, economical operation of a water cooled nuclear power reactor is largely dependent on the reliable operation of the control assemblies that regulate and shut down the reactor. Control rods are an important component of maintaining the ideal state of fission reactions inside a nuclear reactor, which constitute real-time control of the fission process. The control rods are lifted and lowered in the reactor core to realize the starting, power adjustment, shutdown and safe control under accident conditions of the nuclear reactor, so that the safety and the controllability of the nuclear reactor are ensured.
The control rod is mainly prepared from neutron absorbing materials, and the components of the control rod comprise a black rod component and an ash rod component. The main absorber material of the black rod control component is silver-indium-cadmium alloy, so that rapid reactivity change can be compensated, and axial power distribution can be controlled; the gray rod control assembly can provide reactive compensation for load following control, minimizing the need for varying the concentration of soluble boron. During reactor operation, the control rods are constantly exposed to neutron irradiation from within and above the active region of the core. On one hand, the effective absorption components in the control rod are continuously reduced, and after a certain service time is reached, the neutron absorption capacity of the control rod is reduced, and the reactivity value is reduced; on the other hand, the irradiation resistance of the control rod absorber and the cladding material is gradually deteriorated, and phenomena such as irradiation swelling, cladding deformation cracking and the like can occur. Considering the harsh environment of a nuclear reactor, the control rod material needs to meet the requirements of low reactive value loss, and also needs to have the characteristics of high melting point, good high-temperature phase stability, high heat conductivity, good mechanical property, excellent irradiation resistance, excellent corrosion resistance and the like.
The control rod materials currently in use mainly comprise boron carbide (B 4 C) Or boron steel, low-melting point composite silver-indium-cadmium alloy (Ag-In-Cd) and high-radiation-resistant rare earth compound dysprosium titanate (Dy) 2 TiO 5 )。B 4 C due to its 10 B has a large neutron absorption cross section and is widely used in the nuclear industry as a control rod element and shielding material. However, these materials appear to be composed of 10 B (n, α) reactions and helium bubble formation, the absorber material is subject to extensive radiation damage by the gaseous products of the nuclear reaction, leading to strong expansion of the material and failure of the outer envelope.
The absorption cross sections of 6 isotopes of Hf element are relatively high, and the service life is long. In addition, hf also has excellent corrosion resistance, good workability and thermal stability, and is a relatively ideal control rod material. However, the plasticity of the Hf material is reduced after neutron irradiation, so that the impact load resistance of the Hf material is reduced, brittle fracture of the material can be possibly caused, and the reactivity value is not ideal.
Ag-In-Cd alloy rods are currently the most widely used commercial control rod absorber materials, with similar initial reactivity values and consumption rates as Hf rods. However, ag-In-Cd alloys have poor mechanical properties, can lead to rapid deformation during operation, and their nuclear reactivity drops to about 80% of the initial value after five years of operation, with excessive loss of reactive value.
Dy 2 TiO 5 Dy having a fluorite phase structure but a fluorite phase structure 2 TiO 5 The pellets risk phase changes during reactor operation, which can affect the irradiation swelling properties of the absorber material, affecting the integrity of the absorber pellets within the reactor. In addition, dy 2 TiO 5 The neutron absorption capacity of (2) decreases rapidly with increasing service time, and is not suitable for long-term operation of the coreIn the reactor.
Therefore, in order to ensure the reliability and safety of the cluster control assembly, there is an urgent need to find a novel control rod material with extremely low reactivity loss, outstanding irradiation resistance and long service life.
In recent years, due to the large neutron absorption cross section, some rare earth elements and oxide materials thereof have been widely studied, such as europium oxide (Eu) 2 O 3 ) Gadolinium oxide (Gd) 2 O 3 ) Dysprosium oxide (Dy) 2 O 3 ) And thulium oxide (Tm) 2 O 3 ). Therefore, the substitution of boron materials with rare earth-based materials that absorb thermal neutrons by the (n, γ) reaction has been a focus of attention.
Europium element has relatively high neutron capture section and has chain type absorption behavior, namely 151 Eu absorbs a neutron 152 Eu， 152 Eu absorbs a neutron again to form 153 Eu， 153 Eu absorbs a neutron again to form 154 Eu, and so on. Therefore, the europium-based material can maintain good neutron absorption performance in long-term nuclear reactor operation, and can be used as an absorbent to maintain longer service life. However, eu has the following drawbacks as a neutron absorbing material: its thermal conductivity is low, and its decay chain has high radioactivity, high loss of reactive value and poor corrosion resistance. Therefore, it is of great importance to develop a control rod material with stable thermal performance, low loss of reactive value and good corrosion resistance.
Europium-containing ceramic absorber materials have been studied for their superior corrosion resistance compared to metallic materials. The preparation method of the ceramic material mainly adopts a solid phase method and a coprecipitation method, however, the solid phase method needs to add long-time ball milling in the process of mixing raw materials, new impurities can be introduced by mutual collision between the grinding balls and a ball milling tank, even evaporation loss of reactants can be caused, and the morphology structure and the uniformity of the product are influenced, so that the ceramic performance is influenced. The coprecipitation method is easy to form more hard agglomerates, so that the prepared precursor has higher hardness, and the subsequent grinding and sieving are very difficult; in addition, the experimental process of the coprecipitation method is complicated, the pH value of the precipitant is difficult to regulate and control, and the produced target powder is less, so that the coprecipitation method is not suitable for large-scale preparation.
Therefore, how to prepare a europium-based ceramic material based on europium element, so that the europium-based ceramic material has the advantages of low value loss, good stability, simple preparation process, good photon absorption performance, long service life and good corrosion resistance, and the control rod material becomes a technical problem to be solved.
Disclosure of Invention
The invention aims to solve the technical problems, and provides a low-value loss control rod ceramic material, and a preparation method and application thereof. The technical aim of the invention is to provide a mixed rare earth two-phase control rod ceramic material based on rare earth elements and a preparation method thereof, so that the control rod ceramic material can be better used for long-term nuclear reactor reaction.
The invention firstly provides a preparation method of a low-reactivity value loss control rod ceramic material, which comprises the following steps:
(1) Mixing zirconium nitrate, gadolinium nitrate and europium nitrate according to stoichiometric ratio, adding water and stirring uniformly to form a clear solution; heating at 700 ℃ for 4 hours to obtain fluffy white powder, calcining the white powder at 1000 ℃ for 4 hours to obtain mixed powder, and refining the mixed powder to obtain precursor powder;
(2) Adding the precursor powder obtained in the step (1) into a grinding tool, and performing compression molding to prepare a compact blank;
(3) And (3) placing the compact biscuit prepared in the step (2) in a vacuum environment, sintering at 1820 ℃ for 8 hours to obtain the complex phase ceramic, and processing and polishing to obtain the europium oxide-gadolinium zirconate complex phase control rod ceramic material.
The preparation method provided by the invention adopts a high-temperature sintering method to directly carry out thermal decomposition reaction under vacuum condition, so as to successfully prepare a series of xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 (x= 0.6,0.7,0.8,0.85) complex phase ceramic material. X-ray diffraction and Raman spectrum analysis show that the ceramic material prepared by the method is prepared from monoclinic Eu 2 O 3 Phase sumFluorite Gd 2 Zr 2 O 7 Phase composition. The hardness of the ceramic does not change significantly in the test temperature range of 25-350 ℃. Coefficient of thermal expansion (7.3-10X 10) - 6 K -1 ) Is lower than Dy 2 TiO 5 (9.3-10.4×10 -6 K -1 ) The thermal expansion rate changes linearly with the temperature rise, indicating xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The ceramic has good high-temperature phase stability. The heat conductivity coefficient is 0.96 W.m within the temperature range of 25-800 DEG C -1 ·K -1 ～2.02W·m -1 ·K -1 Dy at a temperature higher than 220-650 DEG C 2 TiO 5 (0.27～0.55W·m -1 ·K -1 ) Has excellent heat conducting performance.
The europium oxide-gadolinium zirconate composite ceramic material prepared by a direct decomposition method dry-pressing molding process is cylindrical, the processed sample is 8.5mm in diameter and 15mm in height, the preparation of high-density composite ceramic is realized by using a vacuum sintering technology, and the vacuum sintering technology can enable the sample to discharge internal pores in the process of heating at a high temperature in vacuum to form a compact structure, so that higher density is achieved, and the application condition of the sample as a control rod material is further met. In addition, the preparation method has the advantages of simple process, good controllability, no sintering aid, relatively simple sintering condition, easy operation, mass production and the like.
Through thermal diffusion coefficient, heat conductivity coefficient, thermal expansion coefficient and Vickers hardness detection, the ceramic material synthesized by the invention has good phase stability and hardness stability at high temperature, and the thermal expansion coefficient and the heat conductivity coefficient meet the application requirements of the reactor. Therefore, xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The ceramic has good neutron absorption capacity and extremely low loss of reactivity value, and has great practical application potential in the field of reactor control rods.
Further, the molar ratios of zirconium nitrate, gadolinium nitrate and europium nitrate used in step (1) are 0.102-0.385:0.102-0.385:1 (the following four molar ratios of 0.385:0.385:1,0.248:0.248:1,0.145:0.145:1,0.102:0.102:1 are studied in the examples of the present invention).
Further, in the step (1), the fluffy white powder is ground, sieved and then calcined.
Further, the sieving is a 200 mesh sieving.
Further, the refining in the step (1) comprises ball milling, drying, grinding and sieving the mixed powder to prepare refined precursor powder.
Further, the ball milling process comprises the following steps: ball-to-material ratio of ball milling is controlled to be 27:1, and rotational speed of ball milling is 200r/min.
Further, the press forming process in the step (2) is as follows: the pressure was maintained for 2 minutes at a pressure of 2MPa and then for 15 minutes at a pressure of 250 MPa.
Further, the press forming adopts pre-pressing and cold isostatic pressing.
It is a further object of the present invention to provide a low reactive value loss control rod ceramic material prepared by the method as described in any of the preceding claims.
It is a further object of the present invention to provide the use of a low reactive value loss control rod ceramic material as described above, including use in neutron absorbing materials.
The beneficial effects of the invention are as follows:
(1) The invention provides a two-phase xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 (x= 0.6,0.7,0.8,0.85) ceramic materials with good neutron absorption capacity and extremely low loss of reactivity values have great practical application potential in the field of reactor control rods.
(2) The invention provides the preparation of xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Compared with the solid phase method and the coprecipitation method, the method for preparing the (x= 0.6,0.7,0.8,0.85) ceramic material has the advantages of simple process, good controllability, no sintering aid, relatively simple sintering condition, easy operation, mass production and the like.
(3) Compared with other rare earth-based materials existing at present, the biphase composite ceramic material provided by the invention has better neutron absorption capacity and heat conduction performance, and has good corrosion resistance.
Drawings
FIG. 1 is xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 (x is 0.6,0.7,0.8 and 0.85, respectively) phase characterization of the ceramic; (a) x-ray diffraction; (b) raman mode; (c) a raman pattern having vibrational peaks.
FIG. 2 shows the europium oxide-gadolinium zirconate powder and xEu prepared by the method described in this example 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The XRD pattern of the ceramic is compared with a PDF card, and the obtained target phase is the complex combination of europium oxide and gadolinium zirconate.
FIG. 3 is xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 SEM images of ceramic fracture; (a) x=0.6; (b) x=0.7; (c) x=0.8; (d) x=0.85; (e) xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 (x=0.8) typical microstructure of ceramics.
FIG. 4 is xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Ceramic sample physical diagram.
Fig. 5 is: (a) xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Hardness and young's modulus of ceramics (x=0.6, 0.7,0.8, and 0.85); (b) xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The hardness of the ceramics (x=0.6, 0.7,0.8 and 0.85) varies with temperature.
FIG. 6 is xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Thermal conductance and thermal expansion coefficient curves for ceramics below 800 ℃.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be specifically described with reference to the following examples, which are provided for explaining and illustrating the present invention only and are not intended to limit the present invention. Some non-essential modifications and adaptations of the invention according to the foregoing summary will still fall within the scope of the invention.
Example 1
The powder raw materials involved in this example were as follows:
Eu(NO 3 ) 3 ·6H 2 o (purity 99.99%, china Qixin chemical);
Gd(NO 3 ) 3 ·6H 2 o (purity 99.99%, china Qixin chemical);
Zr(NO 3 ) 4 ·5H 2 o (purity 99.99%, qixin chemical industry, china).
The europium oxide-gadolinium zirconate complex phase ceramic is prepared by dry pressing molding and vacuum sintering by using a direct decomposition method, and comprises the following steps of:
(1) Preparation of precursor powder: weighing zirconium nitrate, gadolinium nitrate and europium nitrate according to the chemical mass ratio of 60%, 70%, 80% and 85% of europium oxide in the product (the molar ratio is 0.385:0.385:1,0.248:0.248:1,0.145:0.145:1 and 0.102:0.102:1 respectively), adding a proper amount of deionized water, and uniformly stirring the mixed salt solution by using a magnetic stirrer; transferring the uniformly stirred mixed solution into a pit furnace, heating for 4 hours at 700 ℃ to obtain fluffy powder, sieving the fluffy powder (200 meshes), placing the sieved powder into a muffle furnace, calcining for 4 hours at 1000 ℃ to obtain europium oxide-gadolinium zirconate complex phase precursor mixed powder, heating to 3 ℃/min, cooling to room temperature at 4 ℃/min, ball milling the obtained powder (ball milling in ethanol for 20 hours at the speed of 200r/min to obtain uniformly mixed slurry, ball milling ball-to-ball ratio of 27:1), drying and sieving to obtain uniform and well sintered europium oxide-gadolinium zirconate complex phase ceramic precursor powder.
(2) And (3) forming: the europium oxide-gadolinium zirconate complex phase ceramic biscuit is obtained by combining a dry pressing method with a cold isostatic pressing process, and the specific process is as follows: and (3) adding the precursor powder obtained in the step (1) into a customized metal mold, placing the mold into a dry press, maintaining the pressure at 2MPa for 2 minutes, taking out the biscuit, vacuumizing and sealing the biscuit, placing the biscuit into a cold isostatic press, and maintaining the biscuit at 250MPa for 15 minutes to obtain a relatively compact biscuit.
(3) Sintering: placing the prepared europium oxide-gadolinium zirconate compact biscuit in a vacuum degree of 10 -4 Sintering for 8 hours at 1820 ℃ under the vacuum environment of Pa to obtain the ceramic sample.
(4) And (3) processing: the sintered ceramic was processed into a columnar body having a diameter of 8.5mm and a height of 15 mm.
The ceramic materials prepared by different europium oxide ratios are recorded as follows: xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 (x= 0.6,0.7,0.8,0.85), wherein the values of x represent europium oxide ratios of 60%, 70%, 80% and 85%, respectively.
Test example 1
The control rod ceramic prepared in example 1 was characterized as follows:
cu K alpha filtered with nickel by X-ray diffraction (XRD, X-2700, denshone, china) 1 Radiation ofThe diffraction pattern was recorded in the range of 2 theta (10 deg. -70 deg.), with a resolution of 0.05 deg./step. Raman spectra were collected at 532nm and structure and phonon energy were measured (HR 800; horiba JobinYvon, france).
The morphology and elemental distribution of the ceramic was observed using scanning electron microscopy (SEM, JSM-IT500HR, japan) and a spectrometer (EDS, aztec Energy X-Max 20, oxford, UK).
Vickers hardness (H) V ) Measured using the vickers indentation method (Buehler, omnimet MHT, lake blue, USA) under a load of up to 2N. Prior to measurement, the sample surface was carefully polished with diamond abrasive. The vickers hardness was calculated according to formula (1):
in the formula (1), F is indentation load, and d is indentation diagonal length; each sample was measured 5 times to reduce experimental uncertainty and then the average was calculated.
Variable temperature hardness using equipment custom made by Tianjin medium ring electric furnace Co., ltdAnd (5) measuring. xEu was measured using an ultrasonic pulser/receiver apparatus (TECLAB, UMS-100, chelles, france) 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Longitudinal (V) of ceramic L ) And a transverse direction (V) T ) Sound velocity.
By V L And V T The following different parameters were calculated:
Young’s modulus:
Bulk modulus:
Shear modulus:
Poisson’s ratio:
Average acoustic velocity:
the TEC of the sintered ceramic was measured using a thermal analyzer (DIL 402Expedis Supreme,NETZSCH, germany). The measurements were performed in flowing argon, all samples were processed into cylinders of approximately 5mm diameter prior to measurement to accommodate the measurement vessel. Under the protection of argon with the temperature rising rate of 5K/min, TEC is obtained within the range of 298-1273K. The thermal diffusivity (α) of the sample was measured using a laser thermal conductivity meter (LFA 457, NETZSCH, germany) and graphite was coated on the front and rear surfaces of the sample. These coatings minimize thermal radiative heat transfer and ensure complete absorption and maximum emissivity during testing. The sample was processed into a sheet of 12.5 mm diameter to accommodate the measurement vessel. The thermal diffusivity was measured at 25, 200, 350, 600, and 800 c under argon and at least three independent measurements were made. The thermal conductivity is calculated from the thermal diffusivity, specific heat and bulk density: wherein the bulk density ρ is measured by an archimedes method, cp is the specific heat, calculated using the Neiman-Colophony rule.
k＝αρC p (7)
Results example 1
xEu identified by X-ray diffraction and Raman spectroscopy 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The ceramic phase is shown in fig. 1. With Eu 2 O 3 (ICDD Card: no. 00-34-0072) and Gd 2 Zr 2 O 7 (No. 01-80-0471) diffraction peak comparison, the obtained ceramic exhibits monoclinic Eu phase after vacuum sintering at 1820 DEG C 2 O 3 And fluorite phase Gd 2 Zr 2 O 7 Two phases. Furthermore, eu 2 O 3 Does not change xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The crystal structure of the ceramic has no redundant peak in the XRD spectrum, and the position of the diffraction peak is basically unchanged. Along with Eu 2 O 3 The increase in the content, the change in the position of the diffraction peak was not significant, as compared with Eu 3+ Ion at Gd 2 Zr 2 O 7 The solid solution mechanism in the matrix is related.
FIG. 1 (b) shows xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Room temperature raman spectroscopy of ceramics was used to study the phase structure components. As shown in FIG. 1 (b), monoclinic Eu 2 O 3 The raman spectrum of the phase is consistent with literature reports. Factor group analysis shows that monoclinic Eu 2 O 3 The phase had 19 raman activity modes (12A g +7E g ). However, only 9 vibration peaks can be identified by testing, possibly because some peaks are too weak to identify or appear at lower frequencies. For Gd 2 Zr 2 O 7 Factor group analysis predicts 6 raman activity modes for pyrochlore structure (a 1g +E g +4F 2g ) The fluorite structure has only one raman mode (F 2g ) This indicates 403cm -1 The left and right modes are assigned to the fluorite structure Gd 2 Zr 2 O 7 F of (2) 2g Mode, as shown in fig. 1 (c). Along with Eu 2 O 3 Increased content, monoclinic Eu 2 O 3 The characteristic peaks of (2) are progressively sharper in the raman spectrum, which is consistent with XRD results.
Fig. 2 shows XRD patterns of europium oxide-gadolinium zirconate powder and ceramic prepared in the method of example 1, and the obtained target phase is a complex combination of europium oxide and gadolinium zirconate as can be seen from comparison with PDF cards.
FIG. 3 shows vacuum sintering prepared xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Microscopic cross-section of the ceramic. It can be seen that with Eu 2 O 3 Increased content of xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The porosity of the ceramic was reduced and the through-crystal fracture characteristics appeared for all samples. In addition, when x=0.6, the sample exhibits significant voids, which may reduce the hardness, flexural strength, and creep resistance of the ceramic. xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 As shown in fig. 3 (e), SEM of ceramic (x=0.8) can clearly observe two different phases at different grey scales, which is consistent with the results of XRD and Raman spectra.
Furthermore, xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The microstructure of the ceramic corresponds to the information listed in table 1, and the relative density of the samples synthesized according to the present invention ranges from 95% to 97% (except that the relative density of the samples where x=0.6 is 76%). The porosity of the sintered samples in table 1 was varied from Φ=1 to ρ/ρ 0 Relational determination, wherein ρ 0 Is the theoretical density of the ceramic, obtained from JCPDS.
TABLE 1
xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Young's modulus (E/GPa), bulk modulus (B/GPa), shear modulus (G/GPa), poisson's ratio (v), green's Aisen parameter (γ), debye temperature (Θ) D K) and average sound velocity (V A /m·s -1 ) As shown in table 2.
TABLE 2
The results in Table 2 show that, with Eu 2 O 3 The increase in content increases the Young's modulus and the bulk modulus and shear modulus have similar tendencies to change. The debye temperature is related to the bond strength, and the modulus and debye temperature increase with increasing bond strength. The debye temperature increases with increasing average sound velocity, as shown in equation (8):
poisson's ratio (v) is used to distinguish ductile and brittle characteristics of a material, v=0.57 being the dividing line distinguishing ductile and brittle materials. As is clear from Table 2, xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 V value of 0.26 to 0.31, less than 0.57, indicating xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The ceramic belongs to brittle materials and has lower toughness.
FIG. 5 (a) shows the trend of hardness (6.4 to 6.9 GPa) with Young's modulus, and the hardness increases with the increase of modulus. This indicates that Eu is increased 2 O 3 Can enhance xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The bonding strength of the ceramic ultimately results in higher hardness. Because of the high temperature (about 350 ℃) application of control rod materials, it is critical to evaluate their mechanical properties at different temperatures.
Measuring different Eu 2 O 3 xEu concentration 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Hardness of ceramicsTemperature dependence as shown in fig. 5 (b). For the samples with x=0.6 and x=0.7, the curve exhibited two different parts with different vickers hardness dependence, whereas the samples with x=0.8 and x=0.85 had no apparent temperature dependence in the range 25-350 ℃. As shown in FIG. 5 (b), xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Specific temperature threshold T of ceramic (x=0.6, 0.7) f At about 150℃and 200℃respectively. It can be seen that xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 Ceramics (x= 0.8,0.85) have good hardness stability in the test temperature range, providing an important reference for the application of materials under practical working conditions.
FIG. 6 shows europium oxide-gadolinium zirconate complex phase ceramic xEu 2 O 3 -(1-x)Gd 2 Zr 2 O 7 As can be seen from FIG. 6, xEu has a thermal conductivity and thermal expansion coefficient curve at 800 ℃ or lower 2 O 3 -(1-x)Gd 2 Zr 2 O 7 The thermal expansion rate of the ceramic increases linearly with the rise of temperature, which shows that the ceramic has excellent high-temperature phase stability, and the thermal conductivity of the ceramic is obviously higher than that of dysprosium titanate, thus the ceramic is a control rod ceramic material with great potential.
Claims (10)
1. The preparation method of the low-reactivity value loss control rod ceramic material is characterized by comprising the following steps of:
(1) Mixing zirconium nitrate, gadolinium nitrate and europium nitrate according to stoichiometric ratio, adding water and stirring uniformly to form a clear solution; heating at 700 ℃ for 4 hours to obtain fluffy white powder, calcining the white powder at 1000 ℃ for 4 hours to obtain mixed powder, and refining the mixed powder to obtain precursor powder;
(2) Adding the precursor powder obtained in the step (1) into a grinding tool, and performing compression molding to prepare a compact blank;
(3) And (3) placing the compact biscuit prepared in the step (2) in a vacuum environment, sintering at 1820 ℃ for 8 hours to obtain the complex phase ceramic, and processing and polishing to obtain the europium oxide-gadolinium zirconate complex phase control rod ceramic material.
2. The method according to claim 1, wherein the molar ratio of zirconium nitrate, gadolinium nitrate and europium nitrate in step (1) is: 0.102 to 0.385:0.102 to 0.385:1.
3. the method of claim 1, wherein the fluffy white powder is ground, sieved and then calcined in step (1).
4. A method of preparation according to claim 3 wherein the sieving is a 200 mesh sieve.
5. The method of claim 1, wherein the refining in step (1) comprises ball milling, drying, and grinding and sieving the mixed powder to produce a refined precursor powder.
6. The method according to claim 5, wherein the ball milling process comprises: ball-to-material ratio of ball milling is controlled to be 27:1, and rotational speed of ball milling is 200r/min.
7. The method according to claim 1, wherein the press molding process in step (2) is as follows: the pressure was maintained for 2 minutes at a pressure of 2MPa and then for 15 minutes at a pressure of 250 MPa.
8. The method of claim 7, wherein the press forming uses pre-pressing and cold isostatic pressing.
9. A low reactivity value loss control rod ceramic material made by the method of any one of claims 1-8.
10. The use of the low reactivity value loss control rod ceramic material according to claim 9 including use in neutron absorbing materials.
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