A lanthanum-lead intermetallic compound LaPb3 sphere and its preparation method

Abstract

The invention discloses a ball material of a lanthanum-lead intermetallic compound LaPb3 and a preparation method thereof. The invention belongs to the technical field of new materials, and specifically relates to the technical field of nuclear fusion neutron multiplier materials. The invention comprises the following steps: placing LaPb3 raw material, grinding balls, and liquid additives in a ball mill protected by inert gas in proportion; subjecting the ball mill to 360-degree all-round ball milling; screening the material after ball milling, and obtaining the ball material after drying. The preparation method realizes the preparation of lanthanum-lead intermetallic compound LaPb3 ball material at room temperature by regulating the agglomeration and forming of raw materials through wet ball milling, and can meet the appearance and size requirements of neutron multiplier materials. The invention solves the problem of balling of lead-lanthanum intermetallic compounds, avoids the problems of material decomposition and volatilization and burning loss of lead and lanthanum elements caused by high-temperature ball making, and the method is simple, easy to operate, and low in cost, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of new material technology, specifically to the field of nuclear fusion neutron multiplier material technology, and in particular to a lanthanum-lead intermetallic compound LaPb 3 Ball material and preparation method thereof. Background Art

[0002] Within the framework of the development of breeder blankets for future fusion demonstration reactors (DEMO), neutron multipliers are needed to ensure tritium self-sustaining reactors. So far, the pebble bed concept consisting of alternating layers of beryllium and lithium ceramic spheres is considered for the helium-cooled pebble bed tritium breeder modules of the first experimental nuclear fusion reactor ITER as well as for the next DEMO. However, due to the limited natural reserves of beryllium, its cost is quite high and it is highly toxic. In order to reduce costs, researchers are investigating alternative neutron multiplier solutions based on lead. One of the most promising lead-based solid compounds for breeder blankets is LaPb 3 Since the melting point is above 1100 degrees Celsius, it can be used in solid form. The tritium breeding performance of the breeder blanket using this neutron multiplier is comparable to that of the breeder blanket filled with pure liquid lead.

[0003] In the DEMO design, solid neutron multiplier materials and lithium ceramic materials will be presented in the form of a ball bed, with a ball size of about 1 mm. The current priority is to prepare spherical neutron multiplier blocks. However, there is little research on the development of mass production methods for neutron multiplier balls, and there is no research on LaPb 3 At present, metal-based materials are mainly regulated by plasma synchronization or hot extrusion methods to control specific shapes. In the field of nuclear fusion material science, metal beryllium-based neutron multiplier ball materials are mainly prepared by plasma rotating electrode process. This method requires plasma local heating of the metal beryllium target material, and then it is thrown out and cooled into balls after reaching the melting point and liquefying. However, this method is not suitable for lanthanum-lead intermetallic compounds, LaPb 3 The formation energy of lanthanum-lead intermetallic compounds is low, and heat treatment at too high a temperature may lead to decomposition. In addition, lead and lanthanum are volatile, and serious metal raw material burning will occur during the preparation process of the plasma rotating electrode method. 3 It will react with water and decompose, so it cannot be processed by conventional solution methods.

[0004] In summary, lanthanum-lead intermetallic compound LaPb 3 The material properties make it impossible to prepare spherical bulk materials by conventional methods, which seriously limits the preparation of LaPb 3 Application research in the field of nuclear fusion. Therefore, it is necessary to develop a ball material preparation process that is both economical and large-scale production to address the high-temperature decomposition and volatilization problems of lead-lanthanum intermetallic compounds. Summary of the invention

[0005] The present invention aims to provide a lanthanum-lead intermetallic compound LaPb 3 Ball material and preparation process thereof, the present invention controls the LaPb in the wet ball milling process by designing low-cost liquid additives 3 The viscous agglomeration behavior between the powders was used to control the shape of the agglomerates by ball milling at room temperature to obtain LaPb 3 Ball material, after annealing and drying, spherical LaPb 3 The sample provides an economically feasible large-scale industrial production solution for the research and development of lead-based neutron multipliers. Specifically, the present invention adopts the following technical solutions:

[0006] On the one hand, the present invention provides a lanthanum-lead intermetallic compound LaPb 3 The ball material preparation method comprises the following steps:

[0007] (1) LaPb 3 The raw materials, grinding balls and liquid additives are placed in a ball mill protected by inert gas according to the proportion;

[0008] (2) performing 360-degree all-round ball milling on the ball mill in step (1);

[0009] (3) Screening and cleaning the material after ball milling in step (2), and drying it to obtain ball material.

[0010] As one of the preferred embodiments of the present invention, in step (1), the grinding balls are one or both of zirconium balls and alumina balls, with a diameter of less than 3 mm. The impact force generated during the ball milling process is too large, which is not conducive to the agglomeration of the sample. The total volume of the grinding balls occupies 1 / 3 to 2 / 3 of the space of the ball mill, preferably 1 / 2. Ensure that the grinding balls can roll normally without generating excessive impact force to hinder the agglomeration of the sample.

[0011] As one of the preferred embodiments of the present invention, in step (1), LaPb 3The raw material is a powder with a particle size of less than 1mm. The small size of the raw material powder is conducive to uniform dispersion and agglomeration of the additive. The relative movement between the grinding balls during the ball milling process can roll the agglomerates into balls. If the powder size is too large, the additives with lower viscosity used in the scheme cannot agglomerate. Moreover, if the raw material size is too large, the probability of collision with the grinding balls increases, and the effect of ball milling is dominant. During the treatment process, it will preferentially collide and crush into small-sized powders. The mass of the raw material is not more than 1 / 10 of the mass of the grinding balls, preferably 1 / 20~1 / 10, and more preferably 1 / 15~1 / 10. If the mass of the raw material is too large, the viscosity of the precursor formed with the additive is low and cannot form agglomerations. Moreover, the excessive mass of the raw material increases the probability of collision and crushing of the raw material by the grinding balls, which is not conducive to the agglomeration of the raw material into balls. Therefore, the mass of the raw material (relative to the mass of the grinding balls) is selected to be lower than the conventional ball milling process.

[0012] Wherein, the LaPb 3 The raw materials can be prepared by literature methods or by making them yourself. The homemade methods can be as follows:

[0013] (1) Lead and lanthanum are mixed as raw materials in a molar ratio of 3:1.1, and the materials are mixed by ball milling at a speed of 150-160 revolutions per minute in a high-purity nitrogen environment for more than 12 hours to ensure uniform mixing; the mixed raw materials are then placed in a glass tube for sealing at a vacuum degree of 5 Pa, and the volume of the raw materials accounts for 1 / 10 of the volume of the vacuum sealing tube; the encapsulated raw materials are then sintered in a muffle furnace, and the temperature is raised from room temperature to a sintering temperature zone at a heating rate of 10°C per minute, the sintering temperature is maintained in the range of 600°C for 15 hours, and then reduced to room temperature at a rate of 10°C per minute, and the obtained material is then manually ground to obtain LaPb with a particle size of less than 1 mm. 3 Raw powder.

[0014] As one of the preferred embodiments of the present invention, in the step (1), a liquid additive is added to the ball mill, which can be selected from one or more of anhydrous ethanol, acetone, and isopropanol; the total mass of the additive to the mass of the raw material is 1-2:1, and this ratio needs to be strictly limited. If the additive content is too low relative to the raw material mass, the raw material will be close to dry powder after mixing and cannot agglomerate; if the additive content is too high, the fluidity of the raw material will be increased and it will be impossible to agglomerate and shape.

[0015] As one of the preferred embodiments of the present invention, in step (1), the inert gas filled in the ball mill is one or more of high-purity nitrogen, argon, and helium to prevent the water and oxygen environment from causing LaPb 3 break down.

[0016] As one of the preferred embodiments of the present invention, in step (2), the ball mill adopts a 360-degree omnidirectional planetary ball mill, that is, rotation plus revolution, the rotation speed is 100 to 200 revolutions per minute, and the revolution speed is 5 to 10 revolutions per minute. The rotation parameter involved in the present invention is a 360-degree omnidirectional planetary ball mill, which is used for spherical shaping of agglomerates. In the conventional 180-degree ball milling process, the agglomerates will settle to the bottom of the ball mill and cannot be shaped into a spherical shape. The rotation parameter involved is a low speed (closer to the minimum speed required by the motor of the planetary ball mill equipment). Too high a speed will accelerate the collision between the grinding balls to enhance the crushing effect, and it will not be possible to agglomerate and shape.

[0017] As one of the preferred embodiments of the present invention, in step (2), the single continuous ball milling time is no more than 30 minutes, preferably 10 to 30 minutes, the room temperature cooling is no less than 10 minutes, preferably 10 to 30 minutes, and the cumulative ball milling time is no less than 10 hours, preferably 10 to 20 hours. During the ball milling process, the grinding balls generate heat due to collision. Long-term continuous ball milling will cause the overall problem of the ball mill to be higher than the room temperature, affecting the agglomeration process.

[0018] As one of the preferred embodiments of the present invention, in step (3), the cleaning agent used for cleaning is one or more of anhydrous ethanol, acetone, and isopropanol. It is used to wash away the powder attached to the periphery of the ball material, and the LaPb obtained by ball milling 3 The sphere is relatively dense and can maintain its shape during the cleaning process. Use a low-cost, volatile solvent that must not contain water.

[0019] As one of the preferred embodiments of the present invention, in step (3), the drying temperature ranges from 80-150°C, preferably from 100-120°C.

[0020] As is known, wet ball milling is a process for grinding materials (usually in a liquid medium) to obtain a finer particle size. The present invention uses a wet ball milling process to control the agglomeration effect of the raw materials under the action of additives to achieve LaPb 3 Agglomeration and shaping of raw materials, and preparation of lanthanum-lead intermetallic compound LaPb with spherical appearance 3 The ball material sample can meet the appearance size requirements of the neutron multiplier material. The present invention adopts a specific ball milling process to grind LaPb with a particle size of less than 1 mm. 3 The raw material powder was made into LaPb with a ball size greater than 1 mm. 3 The ball material solves the problem of forming lead-lanthanum intermetallic compounds into balls, avoids the problems of material decomposition and lead-lanthanum volatilization burning loss caused by high-temperature ball making, and the method is simple and easy to operate with low cost, and can realize the production of lanthanum-lead intermetallic compounds LaPb at a low economic cost. 3 Large-scale batch production of ball materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a photo of the ball mill before the experiment in Example 1;

[0022] Figure 2 The lanthanum-lead intermetallic compound LaPb obtained in Example 1 3 Photos of the ball's appearance;

[0023] Figure 3 The lanthanum-lead intermetallic compound LaPb obtained in Example 1 3 SEM micrograph of the ball material;

[0024] Figure 4 This is a photo of the ball mill before the experiment of Comparative Example 1;

[0025] Figure 5 The lanthanum-lead intermetallic compound LaPb obtained in Comparative Example 1 3 Photos of the sample’s appearance and morphology;

[0026] Figure 6 The lanthanum-lead intermetallic compound LaPb obtained in Comparative Example 2 3 Photos of the sample’s appearance and morphology;

[0027] Figure 7 The lanthanum-lead intermetallic compound LaPb obtained in Comparative Example 3 3 Photo of the sample's appearance. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with specific implementation examples so that those skilled in the art can better understand the present invention. However, the protection scope of the present invention is not limited to the following embodiments, and the scope of rights of the present invention shall be subject to the scope of the claims.

[0029] Example 1

[0030] A lanthanum-lead intermetallic compound LaPb 3 The preparation method of the ball material is as follows:

[0031] (1) Zirconium beads with a diameter of 1 mm and LaPb particles with a particle size of less than 1 mm 3 The raw material powder and anhydrous ethanol were added into a ball mill in a nitrogen atmosphere, and zirconium beads and LaPb 3 The mass ratio of raw materials to anhydrous ethanol is 10:1:1. Figure 1 shown.

[0032] (2) The ball mill was subjected to 360-degree all-round ball milling at a rotation speed of 300 revolutions per minute and a revolution speed of 5 revolutions per minute. The mill was stopped for cooling for 30 minutes after every 30 minutes of operation, with a total operating time of 10 hours.

[0033] (3) The ball-milled material was sieved, washed with anhydrous ethanol, and dried at 100°C for 20 minutes.

[0034] After the above steps, LaPb with spherical appearance can be prepared. 3 Samples, appearance and morphology Figure 2 shown.

[0035] The sample was analyzed by electron microscopy, and its SEM image is as follows Figure 3 shown.

[0036] Comparative Example 1

[0037] Different from Example 1, this case does not use additional liquid additives. The preparation process is as follows:

[0038] (1) Zirconium beads with a diameter of 1 mm and LaPb particles with a particle size of less than 1 mm 3 The powder was added into a ball mill in a nitrogen atmosphere, and the mass ratio of zirconium beads to raw materials was 10:1. Figure 4 shown.

[0039] (2) The ball mill was subjected to 360-degree all-round ball milling at a rotation speed of 300 revolutions per minute and a revolution speed of 5 revolutions per minute. The mill was stopped for cooling for 30 minutes after every 30 minutes of operation, with a total operating time of 10 hours.

[0040] (3) After ball milling and screening, the sample is obtained, and its appearance is as follows Figure 5 shown.

[0041] The obtained LaPb 3 The sample grain size is smaller and more evenly distributed. This preparation method is similar to the results of conventional dry ball milling process because no liquid additives are added.

[0042] Comparative Example 2

[0043] The difference from Example 1 is that the content of anhydrous ethanol in the liquid additive in this case is relatively high. The preparation process is as follows:

[0044] (1) Zirconium beads with a diameter of 1 mm and LaPb particles with a particle size of less than 1 mm 3 The powder and anhydrous ethanol were added into a ball mill in a nitrogen atmosphere, and the mass ratio of zirconium beads to raw materials and anhydrous ethanol was 10:1:5.

[0045] (2) The ball mill was subjected to 360-degree all-round ball milling at a rotation speed of 300 revolutions per minute and a revolution speed of 5 revolutions per minute. The mill was stopped for cooling for 30 minutes after every 30 minutes of operation, with a total operating time of 10 hours.

[0046] (3) After ball milling, the sample is obtained, and its appearance is as follows Figure 6 shown.

[0047] The LaPb obtained by the preparation method 3 The sample has no fixed shape and is evenly dispersed with anhydrous ethanol, which is similar to the result of conventional wet ball milling process.

[0048] Comparative Example 3

[0049] The difference from Example 1 is that the grinding balls in this case are larger in size and the content of anhydrous ethanol additive is higher than that in Example 1. The preparation process is as follows:

[0050] (1) Zirconium beads with a diameter of 5 mm and LaPb particles with a particle size of less than 1 mm 3 The powder and anhydrous ethanol were added into a ball mill in a nitrogen atmosphere, and the mass ratio of zirconium beads to raw materials and anhydrous ethanol was 10:1:3.

[0051] (2) The ball mill was subjected to 360-degree all-round ball milling at a rotation speed of 300 revolutions per minute and a revolution speed of 5 revolutions per minute. The mill was stopped for cooling for 30 minutes after every 30 minutes of operation, with a total operating time of 10 hours.

[0052] (3) After ball milling, the sample is obtained, and its appearance is as follows Figure 7 shown.

[0053] The LaPb obtained by the preparation method 3 The sample is viscous, with obvious agglomeration and unable to form a spherical shape.

[0054] It should be noted that the grinding balls in the present invention are the type of materials used in conventional ball milling processes, and the diameter of less than 3 mm belongs to the fine material ball milling process in the conventional ball milling process, which is usually used to obtain submicron size powders. If the size of the grinding balls is too large, the impact force generated during the ball milling process is too large, which is not conducive to the agglomeration of the sample. In the conventional ball milling process, the grinding balls occupy less than half of the space of the ball milling jar, leaving enough space for the grinding balls to generate sufficient impact force to grind the sample. The total volume of the grinding balls involved in the present invention occupies between 1 / 3 and 2 / 3 of the space of the ball milling jar, preferably 1 / 2. Ensure that the grinding balls can roll normally but will not generate excessive impact force to hinder the agglomeration of the sample. In addition, the ball mill of the present invention adopts a 360-degree omnidirectional planetary ball mill, that is, rotation plus revolution, the rotation speed is 100 to 200 revolutions per minute, and the revolution speed is 5 to 10 revolutions per minute. The rotation parameters involved in the invention are 360-degree omnidirectional planetary ball milling, which is used for spherical shaping of agglomerates. In the conventional 180-degree ball milling process, the agglomerates will be deposited at the bottom of the ball milling jar and spherical shaping cannot be achieved. The rotation parameter involved in the invention is a low speed (closer to the minimum speed required by the motor of the planetary ball mill). Too high a speed will accelerate the collision between the grinding balls and enhance the crushing effect, making it impossible to agglomerate and shape.

[0055] It should also be noted that the LaPb3 raw material used in the present invention is a powder with a particle size of less than 1 mm. The raw material powder size is small, which is conducive to uniform dispersion and agglomeration of the additive. The relative movement between the grinding balls during the ball milling process can roll the agglomerates into balls. If the powder size is too large, the additives with lower viscosity used in the scheme cannot agglomerate. Moreover, if the raw material size is too large, the probability of collision with the grinding balls increases, and the effect of ball milling is dominant. During the treatment process, it will preferentially collide and crush into small-sized powders. The raw material mass is not more than 1 / 10 of the grinding ball mass, preferably 1 / 20~1 / 10, more preferably 1 / 15~1 / 10. If the raw material mass is too large, the precursor viscosity formed with the additive is low and cannot form agglomerations. Moreover, the raw material mass is too large to increase the probability of the grinding balls colliding and crushing the raw materials, which is not conducive to the agglomeration of the raw materials into balls. Therefore, the raw material mass (relative to the grinding ball mass) is selected to be lower than the conventional ball milling process.

[0056] Furthermore, the additive in the present invention is one or more of anhydrous ethanol, acetone, and isopropanol, which are high-purity and free of water. 3 It will decompose with water. The total mass of the additives and the mass of the raw materials are in the ratio of 1 to 2:1. This ratio needs to be strictly limited. Relative to the mass of the raw materials, if the additive content is too low, the raw materials will be close to dry powder after mixing and cannot be agglomerated. If the additive content is too high, the fluidity of the raw materials will be increased and they will not be able to agglomerate and shape. In addition, the cleaning agent used for cleaning in the present invention is one or more of anhydrous ethanol, acetone, and isopropanol. It is used to flush away the powder attached to the periphery of the ball material. The LaPb3 sphere obtained by ball milling is relatively dense and can maintain its shape during the cleaning process. A low-cost volatile solvent is selected, and it must not contain water.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a lanthanum-lead intermetallic compound LaPb3 ball material, characterized in that: The following steps are involved: (1) LaPb3 raw material, grinding balls and liquid additives are placed in a ball mill protected by inert gas; the LaPb3 raw material is powder with a particle size of less than 1 mm, and the mass of the LaPb3 raw material is not more than 1 / 10 of the mass of the grinding balls; the grinding balls are one or both of zirconium balls and alumina balls with a diameter of less than 3 mm; the total volume of the grinding balls occupies 1 / 3 to 2 / 3 of the space of the ball mill; the liquid additive is one or more of anhydrous ethanol, acetone and isopropanol, and the mass ratio of the liquid additive to the mass of the LaPb3 raw material is 1 to 2:1; (2) performing 360-degree all-round ball milling on the ball mill in step (1); the ball milling is performed using a 360-degree all-round planetary ball mill, including rotation and revolution, with the rotation speed being 100 to 300 revolutions per minute and the revolution speed being 5 to 10 revolutions per minute; (3) Screening and cleaning the material after ball milling in step (2), and drying to obtain ball material, wherein the size of the ball material is greater than 1 mm.

2. The method for preparing lanthanum-lead intermetallic compound LaPb3 ball material according to claim 1, characterized in that: In step (1), the inert gas is one or more of high-purity nitrogen, argon, and helium.

3. The method for preparing lanthanum-lead intermetallic compound LaPb3 ball material according to claim 1, characterized in that: In step (2), the single continuous ball milling time does not exceed 30 minutes, the room temperature cooling time is not less than 10 minutes, and the cumulative ball milling time is not less than 10 hours.

4. The method for preparing lanthanum-lead intermetallic compound LaPb3 ball material according to claim 1, characterized in that: In step (3), the cleaning agent is one or more of anhydrous ethanol, acetone, and isopropanol.

5. The method for preparing lanthanum-lead intermetallic compound LaPb3 ball material according to claim 1, characterized in that: In step (3), the drying temperature ranges from 80 to 150°C.

6. Lanthanum-lead intermetallic compound LaPb3 ball material obtained by the preparation method according to any one of claims 1 to 5, with a ball size of more than 1 mm.

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