CN115108828A - Rare earth hafnate ceramic material and preparation method and application thereof - Google Patents

Rare earth hafnate ceramic material and preparation method and application thereof Download PDF

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CN115108828A
CN115108828A CN202110285518.4A CN202110285518A CN115108828A CN 115108828 A CN115108828 A CN 115108828A CN 202110285518 A CN202110285518 A CN 202110285518A CN 115108828 A CN115108828 A CN 115108828A
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rare earth
ceramic material
hafnium
hafnate
ceramic
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CN115108828B (en
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范武刚
张兆泉
陈向阳
卢俊强
康龙武
梁锁贤
李聪
朱丽兵
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Shanghai Institute of Ceramics of CAS
Shanghai Nuclear Engineering Research and Design Institute Co Ltd
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Shanghai Institute of Ceramics of CAS
Shanghai Nuclear Engineering Research and Design Institute Co Ltd
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Abstract

The invention relates to a rare earth hafnate ceramic material and a preparation method and application thereof, wherein the rare earth hafnate ceramic material has a chemical composition of ((Tb) hafnate x Dy 1‑x ) 2 O 3 ) y ‑(HfO 2 ) 1‑y Wherein x is more than or equal to 0.2 and less than or equal to 0.6, and y is more than or equal to 0.4 and less than or equal to 0.6; preferably, the relative compactness of the rare earth hafnate ceramic material is 90-100%.

Description

Rare earth hafnate ceramic material and preparation method and application thereof
Technical Field
The invention relates to a rare earth hafnate ceramic material, a preparation method thereof and application thereof in manufacturing a nuclear reactor control rod and a neutron shielding material, belonging to the field of materials.
Background
As a control rod material of a nuclear reactor, the material needs to have a high thermal neutron absorption cross section, radiation resistance, long service life and good mechanical properties. The neutron absorbing material of the control rod of the pressurized water reactor commonly used at present comprises boron carbide (B) 4 C) Hafnium (Hf), silver-indium-cadmium (Ag-In-Cd) alloy, and dysprosium titanate (Dy) 2 O 3 -TiO 2 ) And the like. The boron carbide material has low cost, easy acquisition and excellent neutron absorption capacity 10 Large neutron absorption cross section of B isotope. But it has the disadvantages that 10 B undergoes alpha decay to lithium after neutron absorption 7 Li) and helium gas ( 4 He), and the radiation swelling caused by the release of large amounts of helium bubbles may cause breakage of the material and the metal can. The neutron absorption cross section of various isotopes of the metal hafnium is high, the physical and chemical stability is high, cladding is not needed, and gamma rays with long half-life period are not generated, so that the hafnium has long service life as a control rod absorber material. Its disadvantages are complex purification and processing process, and large load of driving structure (density 13.31 g/cm) 3 ). The Ag-In-Cd alloy has a good absorption effect on neutrons In a wide energy range, but the Ag-In-Cd has a limited absorption value, has a melting point of only about 800 ℃, is difficult to meet accident fault tolerance requirements, and has insufficient safety margin for a high-power pressurized water reactor. Dy (Dy) 2 TiO 5 The titanate-based ceramic materials have good neutron irradiation resistance and water corrosion resistance, but have the problem of insufficient absorption value.
The neutron absorption material of the control rod of the high-power commercial pressurized water reactor not only needs to meet the requirements of high material absorption value and long service life, but also needs to have good radiation resistance and accident fault tolerance. Considering neutron absorption value, melting point, structural stability, irradiation resistance and the like, hafnate formed by rare earth and hafnium has better performance and application prospect.
At present, the combination of a plurality of elements with large thermal neutron absorption cross section and slow absorption value attenuation is selected as an important direction for the design of control rod materials.
Disclosure of Invention
To this end, the inventors considered terbium element (Tb) based on the material phase diagram and the source of the raw material 3+/4+ ) The valence change and crystal structure relationship of (a) to (b) provide a practical form of the rare earth hafnate ceramic material. The conditions for realizing fluorite-structured rare earth hafnate ceramic phase and high-density structure are preferably selected, so that the conditions can meet various requirements of the nuclear reactor control rod, and the preparation process with simple process and low cost is also provided.
In one aspect, the present invention provides a rare earth hafnate ceramic material having a chemical composition ((Tb) or Tb) x Dy 1-x ) 2 O 3 ) y -(HfO 2 ) 1-y Wherein x is more than or equal to 0.2 and less than or equal to 0.6, and y is more than or equal to 0.4 and less than or equal to 0.6.
In the invention, Tb, Dy and Hf which are naturally abundant in the rare earth hafnate ceramic material are used as neutron absorbers, and the proportion between Tb and Dy and the proportion between rare earth and Hf can be adjusted according to the design requirement of neutron absorption value. The material has high neutron absorption value, better accident fault tolerance performance and excellent mechanical property, and is an ideal nuclear reactor control rod absorber material.
Preferably, x is more than or equal to 0.5 and less than or equal to 0.6, and y is more than or equal to 0.4 and less than or equal to 0.6. Within the range, the rare earth hafnate ceramic material has excellent mechanical properties.
Preferably, the relative compactness of the rare earth hafnate ceramic material is 90-100%, and preferably 92-99.5%.
Preferably, the rare earth hafnate ceramic material also contains at least one of Al, Mg, Si and Ca which are introduced as sintering aids, and the mass percentage of each element is less than or equal to 5 percent, preferably less than or equal to 2 percent
In another aspect, the present invention further provides a method for preparing the rare earth hafnate ceramic material, including:
(1) weighing rare earth raw materials and hafnium raw materials according to a stoichiometric ratio to serve as raw material powder, and mixing to obtain mixed powder;
(2) and pressing and molding the obtained mixed powder, and sintering at 1500-1750 ℃ for 2-12 hours to obtain the rare earth hafnate ceramic material.
Preferably, the rare earth raw material is at least one selected from oxides, metals, hydroxides, carbonates, sulfates, chlorides and nitrates of the Re element, wherein the Re element is Tb and Dy; the hafnium raw material is at least one selected from the group consisting of hafnium metal, hafnium oxide, hafnium hydroxide, hafnium carbonate, hafnium chloride, hafnium sulfate and hafnium nitrate.
Preferably, a sintering aid is further added to the mixed powder, the sintering aid is a compound containing at least one of Mg, Si, Ca and Al, and the mass of Mg, Si, Ca and Al in the sintering aid is not more than 5wt%, preferably not more than 2%, of the total mass of the raw material powder. In the present invention, it is preferable that a liquid phase is formed during sintering by introducing a sintering aid (Si, Mg, Al, Ca, etc.) having a lower melting point, thereby accelerating the diffusion process and lowering the densification barrier. Moreover, the sintering aid adopted by the invention is specially considered, the neutron absorption cross sections of Si, Mg, Al and Ca elements are small, and a certain concentration is allowed to exist in the nuclear field. However, the added amount can not obviously influence the neutron absorption value and the characteristics of the rare earth hafnate ceramic, and can not obviously influence the performances of the material, such as compression resistance, water corrosion resistance, nuclear waste radioactivity and the like.
Further, it is preferable that the sintering aid is at least one selected from the group consisting of silica, tetraethoxysilane, silicic acid, magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium oxide, calcium carbonate, calcium hydroxide, aluminum oxide, aluminum hydroxide and aluminum carbonate.
Preferably, the mixing mode is ball milling mixing; the rotation speed of ball milling mixing is 80-300 r/min, the time is 0.5-12 hours, and the ball milling medium is water or/and an organic solvent; preferably, at least one of a binder and a defoaming agent is also added during the ball-milling mixing process; more preferably, the binder is at least one selected from polyvinyl alcohol, polyvinyl butyral, cellulose, terpineol and polyethylene glycol, and the addition amount is 0.5-5 wt% of the total mass of the mixed powder, and the defoaming agent is at least one selected from glycerol, simethicone, dodecanediol and heptanediol, and the addition amount is 0.2-0.8 wt% of the total mass of the mixed powder.
Preferably, the compression molding mode is dry compression molding or/and cold isostatic pressing; the pressure of the dry pressing molding is 10-80 MPa, and the pressure of the cold isostatic pressing molding is 150-300 MPa.
Preferably, the sintering atmosphere is a vacuum atmosphere, a reducing atmosphere or an inert atmosphere; the inert atmosphere is preferably an argon atmosphere, and the reducing atmosphere is argon-hydrogen mixed gas.
In another aspect, the invention also provides an application of the rare earth hafnate ceramic material in preparation of neutron absorption materials and reactor control rods. In the invention, the obtained rare earth hafnate ceramic material has compact particle or crystal arrangement, can improve the linear density and space utilization rate of a neutron absorber as a neutron absorbing material, has the advantages of excellent mechanical property, high melting point, high chemical stability and the like, can be used under extreme environmental conditions, and becomes the most main form of the neutron absorbing material of the control rod.
Has the advantages that:
(1) the invention is designed, prepared and applied to the field of nuclear reactor control rods according to the neutron absorption nuclear characteristics of rare earth Tb, Dy and Hf;
(2) the invention provides a rare earth hafnate ceramic neutron absorption material which has a fluorite crystal phase structure, and the absorption value and nuclear characteristics meet the control rod requirements of high power or long service life;
(3) the neutron absorption material provided by the invention has high density and good mechanical property, does not generate gas compared with boron carbide, has better water corrosion resistance, and has lower packaging requirement and more convenience when the control rod is prepared;
(4) the preparation method provided by the invention has the advantages of abundant raw material sources and simple and convenient process flow, and can ensure large-scale production and application of the material.
Drawings
FIG. 1 is ((Tb) prepared in example 1) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 A photograph of the ceramic neutron absorbing material;
FIG. 2 is ((Tb) prepared in example 1) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 The microstructure of the ceramic;
FIG. 3 is ((Tb) prepared in example 2) 0.2 ,Dy 0.8 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 An XRD spectrum of the ceramic neutron absorbing material;
FIG. 4 is ((Tb) prepared in example 4) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 A photograph of a sample of ceramic neutron absorbing material;
FIG. 5 is ((Tb) prepared in example 4) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 A photograph of a sample of ceramic neutron absorbing material;
FIG. 6 is ((Tb) prepared in example 5) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 The micro-morphology of the ceramic material;
FIG. 7 is a schematic diagram of a method of using a rare earth hafnate ceramic cylinder as a control rod neutron absorber;
FIG. 8 is ((Tb) prepared in example 1) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 The control rod absorption value of the ceramic.
Detailed Description
The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.
In the present disclosure, the composition of the rare earth hafnate ceramic material (or rare earth hafnate ceramic neutron absorbing material) includes ((Tb) x ,Dy 1-x ) 2 O 3 ) y -(HfO 2 ) 1-y Wherein x is more than or equal to 0.2 and less than or equal to 0.6, and y is more than or equal to 0.4 and less than or equal to 0.6. The rare earth hafnate ceramic material is a dense sintered body having a relative density of 92% or more, preferably 95% or more. In an alternative embodiment, the rare earth hafnate ceramic material may have a compressive strength of 280 to 520 MPa.
In the invention, rare earth Tb, Dy and Hf is used as a neutron absorber, so that the attenuation trend of neutron absorption value can be inhibited. The material has high density and high neutron absorption value as ceramic. For example, a control rod assembly consisting of an Ag-In-Cd metallic neutron absorber with the composition of Ag-80, In-15, Cd-5 wt.% has an absorption value about 20% lower than the rare earth hafnate ceramic neutron absorber material of the present invention. Moreover, the melting point of Ag-In-Cd is only about 800 ℃, and the risk of fusion and failure under accident conditions exists.
In an alternative embodiment, 0.5 ≦ x ≦ 0.6 and 0.4 ≦ y ≦ 0.6, more preferably, x ≦ 0.5 and y ≦ 0.5. Within this range, the mechanical properties of the rare earth hafnate ceramic material are excellent.
The preparation method of the rare earth hafnate ceramic neutron absorbing material is simple in process, and the prepared rare earth hafnate ceramic neutron absorbing material has a fluorite structure and does not release gas, so that the irradiation swelling of a control rod can be reduced. Meanwhile, the transmutation product of the boron carbide has a small neutron absorption cross section, so that the absorption value is reduced rapidly, and the boron carbide can be used as a burnable poison. In contrast, the transmutation products of Tb, Dy and Hf in the rare earth hafnate still have higher neutron absorption value, so the service life is longer, and the rare earth hafnate is favorable for being used as a neutron absorption material of a large pressurized water reactor control rod with a long refueling period.
In one embodiment of the present invention, a hafnium raw material (containing a hafnium compound) and a rare earth raw material (rare earth compound) are selected as raw material powders, and the raw material powders are mixed, press-molded, and sintered at a high temperature to obtain a rare earth hafnate ceramic neutron absorber. The following is an exemplary description of the preparation method of the rare earth hafnate ceramic neutron absorbing material provided by the present invention.
According to the stoichiometric ratio (Tb) x ,Dy 1-x ) 2 O 3 ) y -(HfO 2 ) 1-y Weighing rare earth raw materials and hafnium raw materials, and mixing to obtain mixed powder. The raw material powder is preferably refined by mixing through a ball milling process. In the ball milling process, a certain amount of liquid (water and organic solvent) is added as a ball milling medium, and auxiliary agents such as a binder, a defoaming agent and the like are added to refine and uniformly mix the particles of the raw material powder, and then the mixture is dried to obtain mixed powder. Wherein, the ball milling and thinning are carried out for 0.5 to 12 hours under the condition that the rotating speed is 80 to 300 r/min. After the autumn is finished, the mixture can be dried in an oven or a rotary evaporator at the temperature of 50-150 ℃ for 0.5-10 h. As an example, at least one solvent of ethanol, water and glycol is added as a liquid phase during ball milling, and the mixed powder is obtained after ball milling and drying at 50-100 ℃.
In an alternative embodiment, the hafnium-containing compound may be selected from at least one of hafnium oxide, hafnium hydroxide, hafnium carbonate, and the like. The rare earth element-containing compound may be at least one selected from rare earth oxides, hydroxides, nitrates, and the like.
In an alternative embodiment, a sintering aid is also added to the mixed powder. The sintering aid can be at least one of Al, Mg, Si and Ca elements. The mass fraction of the element introduced as sintering aid is not more than 5%, preferably not more than 2%, at which range the sintered density can be increased and the densification temperature can be lowered. In a preferred technical scheme, in order to promote sintering, the raw material further comprises a sintering aid, and the sintering aid can be a compound containing aluminum, magnesium and silicon, such as silicon dioxide, tetraethoxysilane, silicic acid, magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium oxide, calcium carbonate, calcium hydroxide, aluminum oxide, aluminum hydroxide and aluminum carbonate.
In alternative embodiments, the binder may be selected from polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, cellulose, terpineol, and the like. The preferred mass percentage of the binder is 0.5 to 5 percent.
And (3) putting the mixed powder into a die, and pressing and forming to prepare a biscuit. Wherein, the compression molding mode can be dry compression molding or/and cold isostatic pressing treatment. The pressure of the dry pressing can be 10-50 MPa. The pressure of the cold isostatic pressing can be 150-250 MPa.
And sintering the biscuit at high temperature to obtain the rare earth hafnate ceramic neutron absorbing material (in the form of a sintered block). Wherein, the sintering can be carried out for 2-12 hours at 1500-1750 ℃. The sintering atmosphere may be vacuum, argon gas or argon-hydrogen mixed gas or a mixture of two or more of the above, and the preferred atmosphere is vacuum or argon-hydrogen mixed gas.
The sintered cake may be prepared into various desired shapes and specifications such as cylinders, rods and cubes by post-processing such as cutting, grinding and the like.
The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.
Example 1: ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 Ceramic neutron absorbing material
Terbium oxide, dysprosium oxide and hafnium oxide are used as raw materials according to a molar ratio (Tb) 2 O 3 +Dy 2 O 3 ):HfO 2 0.4:0.6 (y is 0.4) batching with the mol ratio of terbium oxide to dysprosium oxide of 0.6:0.4(x is 0.6). Ethanol is used as a ball milling medium, and zirconia grinding balls are adopted to perform ball milling for 6 hours at the rotating speed of 100 r/min. Polyvinyl butyral (PVB) with the mass ratio of 0.5% of the raw material powder of terbium, dysprosium and hafnium is added into the slurry to serve as a binder, and then drying is carried out at the temperature of 80 ℃. Through 60MPa dry pressing and 200MPa cold isostatic pressingAfter pressing, a biscuit is obtained. And sintering the biscuit for 6 hours at 1600 ℃ under the vacuum atmosphere condition to obtain the compact ceramic neutron absorbing material (figure 1). For the obtained ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 XRD analysis is carried out on the ceramic, and the spectrogram shows that the prepared ceramic is of a fluorite structure. The density of the ceramic was tested by the drainage method using the archimedes principle, with a relative density of 95.3%, and the microstructure showed that densification had been achieved according to the scanning electron micrograph (fig. 2).
Example 2: ((Tb) 0.2 ,Dy 0.8 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 The ceramic neutron absorbing material takes hafnium oxide, terbium oxide and dysprosium oxide as raw materials according to a molar ratio (Tb) 2 O 3 +Dy 2 O 3 ):HfO 2 0.4:0.6 (y is 0.4) the molar ratio of terbium oxide to dysprosium oxide is 0.2:0.8(x is 0.2). Deionized water is used as a ball milling medium, and zirconia grinding balls are adopted for ball milling for 4 hours at the speed of 200 r/min. Polyvinyl alcohol (PVA) with the mass ratio of 1% is added into the slurry as a binder, and then the slurry is dried at 80 ℃. And (3) performing 50MPa pressure forming and 220MPa cold isostatic pressing to obtain a biscuit. Sintering at 1700 ℃ for 3 hours under the vacuum atmosphere condition to obtain the hafnate ceramic. Obtained by draining ((Tb) 0.2 ,Dy 0.8 ) 2 O 3 ) 0.4 -(HfO 2 ) 0.6 Has a relative density of 97.1%, and the main phase structure thereof is analyzed by X-ray diffraction to be a fluorite structure (FIG. 3).
Example 3: ((Tb) 0.4 ,Dy 0.6 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 The neutron absorbing material takes hafnium oxide, terbium oxalate and dysprosium oxalate as raw materials according to a molar ratio (Tb) 2 O 3 +Dy 2 O 3 ):HfO 2 0.6:0.4 (y is 0.6) batching with the mol ratio of terbium oxide to dysprosium oxide of 0.4:0.6(x is 0.4). Ethanol is used as a ball milling medium, and a hafnium oxide grinding ball is used for ball milling for 6 hours at a speed of 120 r/min. PVB with the mass ratio of 0.5 percent is added into the slurry to be used as a binder, and then the slurry is dried at 80 ℃. Through 80MPa pressure forming, 200MPa cooling and the likeAnd (5) performing static pressure to obtain a biscuit. The biscuit is sintered for 5 hours at 1650 ℃ under the argon atmosphere condition to obtain (Tb) 0.4 ,Dy 0.6 ) 0.6 -(HfO 2 ) 0.4 Ceramic, 97.2% relative density. The compressive strength value is 340MPa measured by a universal material testing machine.
Example 4: ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 The ceramic neutron absorbing material takes hafnium oxide, terbium oxalate and dysprosium hydroxide as raw materials according to a molar ratio (Tb) 2 O 3 +Dy 2 O 3 ):HfO 2 0.6:0.4 (y is 0.6), and the molar ratio of terbium oxide to dysprosium hydroxide is 0.6:0.4(x is 0.6). The ethylene glycol is used as a ball milling medium, and zirconia grinding balls are adopted for ball milling for 12 hours at the speed of 150 r/min. PVB with the mass fraction of 0.5 percent is added into the slurry to be used as a binder, and then the slurry is dried at 80 ℃. And (3) performing 50MPa pressure forming and 180MPa cold isostatic pressing to obtain a biscuit. The biscuit was sintered at 1620 ℃ for 8 hours under an argon-hydrogen mixed atmosphere to obtain a rare earth dense ceramic (fig. 4) having a relative density of 94.6%, and the XRD result showed that the sintered ceramic had a fluorite phase structure with high crystallinity (fig. 5).
Example 5: ((Tb) 0.6 ,Dy 0.4 ) 2 O 3 ) 0.6 -(HfO 2 ) 0.4 The ceramic neutron absorbing material takes hafnium hydroxide, terbium oxide and dysprosium oxide as raw materials according to a molar ratio (Tb) 2 O 3 +Dy 2 O 3 ):HfO 2 0.6:0.4 (y is 0.6), the molar ratio of terbium oxide to dysprosium oxide is 0.4:0.6(x is 0.6), and tetraethoxysilane (calculated by Si element, which is 0.2 percent of the mass fraction of the raw material powder) is added as a sintering aid. Deionized water is used as a ball milling medium, and zirconia grinding balls are adopted to perform ball milling for 6 hours at 120 r/min. PVA with the mass ratio of 2 percent is added into the slurry to be used as a binder, and then the slurry is dried at 80 ℃. And (3) performing 80MPa pressure forming and 250MPa cold isostatic pressing to obtain a biscuit. The biscuit was sintered at 1650 ℃ for 8 hours under argon atmosphere to obtain a ceramic block with a relative density of 97.6%, and the scanning electron micrograph shows that only a small amount of closed pores (FIG. 6) exist and are ceramicAnd (4) microstructure. The material is used as neutron absorption material value and B in control rod 4 C decreased more slowly than with the change in burnup, and therefore the absorption value was more stable as a control rod material for long-term use (fig. 7).
Example 6:
the rare earth hafnate ceramic material of example 6 was prepared according to example 3, except that: x is 0.2 and y is 0.6.
Example 7:
the rare earth hafnate ceramic material of this example 7 was prepared by reference to example 3, except that: x is 0.3 and y is 0.4.
Example 8:
the rare earth hafnate ceramic material of this example 8 was prepared by reference to example 3, except that: x is 0.5 and y is 0.6.
Example 9:
the rare earth hafnate ceramic material of example 9 is prepared by reference to example 3, except that: x is 0.5 and y is 0.5.
Example 10:
the rare earth hafnate ceramic material of this example 10 was prepared by reference to example 3, except that: the sintering aid added is magnesium carbonate, and the content of Mg element is 0.2 percent of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression resistance properties is shown in table 1.
Example 11:
the rare earth hafnate ceramic material of this example 11 was prepared by reference to example 3, except that: the sintering aid is added to be alumina, and the content of Al element is 0.2 percent of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression resistance properties is shown in table 1.
Example 12:
the rare earth hafnate ceramic material of this example 11 was prepared by reference to example 3, except that: the sintering aid is added to be calcium oxide, and the content of Ca element is 0.2 percent of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression resistance properties is shown in table 1.
Example 13:
the rare earth hafnate ceramic material of this example 13 was prepared by reference to example 3, except that: the sintering aid is tetraethoxysilane, and the content of Si element is 0.2 percent of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression resistance properties is shown in table 1.
Example 14:
the rare earth hafnate ceramic material of this example 14 was prepared according to example 3, except that: the sintering aid is tetraethoxysilane, and the content of Si element is 1 percent of the total mass of the raw material powder. The effect of the sintering aid on the compaction and compression resistance properties is shown in table 1.
Example 15:
the rare earth hafnate ceramic material of this example 15 is prepared by reference to example 3, except that: the sintering aid is tetraethoxysilane, and the content of Si element is 2 percent of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression resistance properties is shown in table 1.
Example 15:
the rare earth hafnate ceramic material of this example 16 was prepared by reference to example 3, except that: the sintering aid is tetraethoxysilane, and the content of Si element is 3 percent of the total mass of the raw material powder. The effect of the sintering aid on the densification and compression resistance properties is shown in table 1.
Comparative example 1
The process for the preparation of rare earth hafnate ceramic material of this comparative example 1 is referred to example 1 with the difference that: x is 0.8 and y is 0.2. As can be seen from fig. 8, the initial neutron absorption value of the material of comparative example 1 is less than that of example 1.
Table 1 shows the composition and performance parameters of the rare earth hafnate ceramic material prepared according to the present invention:
x y sintering aid Sintering of Relative density/%) Compressive strength/MPa
Example 1 0.6 0.4 - 1600℃/6h 95.3％ 360
Example 2 0.2 0.4 - 1700℃/3h 97.1％ 320
Example 3 0.4 0.6 - 1650℃/5h 97.2％ 340
Example 4 0.6 0.6 - 1620℃/8h 94.6％ 436
Example 5 0.6 0.6 Si element/0.2% 1650℃/6h 97.6％ 485
Example 6 0.2 0.6 - 1650℃/5h 97.4％ 521
Example 7 0.3 0.4 - 1650℃/5h 97.1％ 513
Example 8 0.5 0.6 - 1650℃/5h 96.9％ 417
Example 9 0.5 0.5 - 1650℃/5h 97.7％ 390
Example 10 0.6 0.4 Mg element/0.2% 1650℃/5h 98.2％ 442
Example 11 0.6 0.4 Al element/0.2% 1650℃/5h 97.8％ 395
Example 12 0.6 0.4 Ca element/0.2% 1650℃/5h 98.5％ 432
Example 13 0.6 0.4 Si element/0.2% 1650℃/5h 98.2％ 459
Example 14 0.6 0.4 Si element/1% 1650℃/5h 99.4％ 396
Example 15 0.6 0.4 Si element/2% 1650℃/5h 99.2％ 472
Example 16 0.6 0.4 Si element/5% 1650℃/5h 97.6％ 408
Comparative example 1 0.8 0.2 - 1600℃/6h 95.5％ 372
Example 16
The embodiment discloses a neutron absorber material which can be used for a control rod, the neutron absorber material can be processed into a cylinder according to the length and the diameter required by the design of a reactor core, and the neutron absorber material is fixed in a metal cladding by adopting multi-section splicing to form the control rod. FIG. 8 is a schematic diagram of an application of a control rod, which comprises a rare earth hafnate ceramic absorber 1, a cladding 2, a spring 3, a top plug 4 and a bottom end plug 5, wherein the absorber 1 is processed by using the neutron absorbing material prepared by the method described in examples 1-16.
The absorber of the control rod disclosed by the embodiment of the disclosure has excellent radiation swelling resistance and radiation creep resistance. Compared with boron carbide, the absorption value is higher, no gas is released, the packaging is convenient, and the service life is longer; compared with silver, indium and cadmium, the alloy has higher melting point and better accident fault tolerance.

Claims (10)

1. A rare earth hafnate ceramic material, wherein the rare earth hafnate ceramic material has a chemical composition of ((Tb) hafnate ceramic material x Dy 1-x ) 2 O 3 ) y -(HfO 2 ) 1-y Wherein x is more than or equal to 0.2 and less than or equal to 0.6, and y is more than or equal to 0.4 and less than or equal to 0.6; preferably, the relative compactness of the rare earth hafnate ceramic material is 90-100%.
2. The rare earth hafnate ceramic material of claim 1, wherein 0.5 ≦ x ≦ 0.6, 0.4 ≦ y ≦ 0.6.
3. The rare earth hafnate ceramic material of claim 1 or claim 2, further comprising at least one of Al, Mg, Si, Ca introduced as a sintering aid, in a total content by mass of 5% or less, preferably 2% or less.
4. A method of preparing a rare earth hafnate ceramic material of any one of claims 1 to 3, comprising:
(1) weighing rare earth raw materials and hafnium raw materials according to a stoichiometric ratio to serve as raw material powder, and mixing to obtain mixed powder;
(2) and pressing and molding the obtained mixed powder, and sintering at 1500-1750 ℃ for 2-12 hours to obtain the rare earth hafnate ceramic material.
5. The production method according to claim 4, wherein the rare earth raw material is at least one selected from an oxide, a metal, a hydroxide, a carbonate, a sulfate, a chloride, and a nitrate of an Re element, wherein the Re element is Tb and Dy; the hafnium raw material is at least one selected from the group consisting of hafnium metal, hafnium oxide, hafnium hydroxide, hafnium carbonate, hafnium chloride, hafnium sulfate and hafnium nitrate.
6. The preparation method according to claim 4 or 5, characterized in that a sintering aid is further added to the mixed powder, wherein the sintering aid is a compound containing at least one of Mg, Si, Al and Ca, and the total mass of the Mg, Si, Al and Ca in the sintering aid is not more than 5wt% of the total mass of the raw material powder; preferably, the sintering aid is selected from at least one of silicon dioxide, tetraethoxysilane, silicic acid, magnesium oxide, magnesium carbonate, magnesium hydroxide, calcium oxide, calcium carbonate, calcium hydroxide, aluminum oxide, aluminum hydroxide and aluminum carbonate.
7. The production method according to any one of claims 4 to 6, wherein the mixing is performed by ball milling; the rotation speed of ball milling mixing is 80-300 r/min, the time is 0.5-12 hours, and the ball milling medium is water or/and an organic solvent; preferably, at least one of a binder and a defoaming agent is also added during the ball milling mixing process; more preferably, the binder is at least one selected from polyvinyl alcohol, polyvinyl butyral, cellulose, terpineol and polyethylene glycol, and the addition amount of the binder is 0.5-5 wt% of the total mass of the mixed powder, and the defoamer is at least one selected from glycerol, dimethyl silicon, dodecanediol and heptanediol, and the addition amount of the defoamer is 0.2-0.8 wt% of the total mass of the mixed powder.
8. The production method according to any one of claims 4 to 7, wherein the press molding is dry press molding or/and cold isostatic press molding; the pressure of the dry pressing molding is 10-80 MPa, and the pressure of the cold isostatic pressing molding is 150-300 MPa.
9. The production method according to any one of claims 4 to 8, characterized in that the atmosphere for sintering is a vacuum atmosphere, a reducing atmosphere, or an inert atmosphere; the inert atmosphere is preferably an argon atmosphere, and the reducing atmosphere is argon-hydrogen mixed gas.
10. Use of a rare earth hafnate ceramic material of any one of claims 1 to 3 in the manufacture of neutron absorbing materials and reactor control rods.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040067837A1 (en) * 2001-01-19 2004-04-08 Sabin Boily Ceramic materials in powder form
CN110818414A (en) * 2019-09-27 2020-02-21 厦门大学 Europium hafnate neutron absorbing material and application thereof
CN111646794A (en) * 2020-05-29 2020-09-11 中国核电工程有限公司 Neutron absorber material, preparation method thereof and control rod
CN111704459A (en) * 2020-05-29 2020-09-25 中国核电工程有限公司 Neutron absorber material, preparation method thereof and control rod
CN111933313A (en) * 2020-07-21 2020-11-13 上海核工程研究设计院有限公司 Long-life neutron absorbing material

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040067837A1 (en) * 2001-01-19 2004-04-08 Sabin Boily Ceramic materials in powder form
CN110818414A (en) * 2019-09-27 2020-02-21 厦门大学 Europium hafnate neutron absorbing material and application thereof
CN111646794A (en) * 2020-05-29 2020-09-11 中国核电工程有限公司 Neutron absorber material, preparation method thereof and control rod
CN111704459A (en) * 2020-05-29 2020-09-25 中国核电工程有限公司 Neutron absorber material, preparation method thereof and control rod
CN111933313A (en) * 2020-07-21 2020-11-13 上海核工程研究设计院有限公司 Long-life neutron absorbing material

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