Spherical tungsten-lanthanum composite powder and preparation method thereof

Abstract

The present invention discloses a spherical tungsten-lanthanum composite powder and a preparation method thereof, the method comprising: (1) mixing metatungstate, lanthanum salt and water to obtain a feed liquid; (2) spraying and granulating the feed liquid to obtain a precursor powder; (3) firstly keeping the precursor powder warm in an inert atmosphere, and then heating and reducing it in a hydrogen atmosphere to obtain a lanthanum-containing tungsten powder; (4) spheroidizing the lanthanum-containing tungsten powder to obtain a tungsten-lanthanum composite powder. The spherical tungsten-lanthanum composite powder prepared by the method has the characteristics of high sphericity, good fluidity, uniform lanthanum distribution, etc., and the method has a short process and is easy to implement.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation, and in particular relates to a spherical tungsten-lanthanum composite powder and a preparation method thereof. Background Art

[0002] Nuclear energy has attracted wide attention as a high-energy-density, clean, and long-term energy source, and its application prospects are very broad. However, while nuclear energy creates value for mankind, it also produces nuclear radiation, which can cause serious damage to human health and seriously pollute the ecological environment. In order to avoid nuclear radiation damage, nuclear shielding materials are needed for radiation protection. Among the various radiation rays, neutrons and gamma rays in particular have high energy and strong penetrating power, and the damage they cause is more serious, so nuclear shielding materials are needed to focus on radiation protection.

[0003] As a high atomic number and high density metal element, tungsten has a good shielding effect on gamma rays. In addition, tungsten has high hardness and is a potential choice as a structural material. The rare earth element lanthanum has the characteristics of high neutron absorption cross section and wide absorption energy range. Therefore, the composite material with tungsten as the matrix element and lanthanum as the doping element will be a new type of composite shielding material.

[0004] Therefore, the preparation of tungsten-lanthanum composite materials with excellent performance has become an urgent problem to be solved. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide a spherical tungsten-lanthanum composite powder and a preparation method thereof, wherein the spherical tungsten-lanthanum composite powder prepared by the method has the characteristics of high sphericity, good fluidity and uniform lanthanum distribution, and the method has a short process and is easy to implement.

[0006] In one aspect of the present invention, the present invention provides a method for preparing spherical tungsten-lanthanum composite powder. According to an embodiment of the present invention, the method comprises:

[0007] (1) mixing metatungstate, lanthanum salt and water to obtain a feed solution;

[0008] (2) spraying and granulating the liquid material to obtain a precursor powder;

[0009] (3) keeping the precursor powder warm in an inert atmosphere and then reducing it by heating in a hydrogen atmosphere to obtain lanthanum-containing tungsten powder;

[0010] (4) Spheroidizing the lanthanum-containing tungsten powder to obtain a tungsten-lanthanum composite powder.

[0011] According to the method for preparing spherical tungsten-lanthanum composite powder according to the embodiment of the present invention, metatungstate and lanthanum salt are mixed with water, and metatungstate and lanthanum salt are uniformly mixed to form a liquid. Then the liquid is sprayed and granulated to obtain a lanthanum-doped precursor powder. Then the precursor powder is first kept warm in an inert atmosphere. During this process, the metatungstate in the precursor powder will lose ammonia and water to generate WO3, and the lanthanum salt will decompose to generate La2O3. Then the temperature is increased and reduced in a hydrogen atmosphere. WO3 will react with hydrogen to generate single substance W to obtain lanthanum-containing tungsten powder. Finally, the lanthanum-containing tungsten powder is spheroidized to obtain a spherical tungsten-lanthanum composite powder with high sphericity, good fluidity and uniform lanthanum distribution. At the same time, the method has a short process and is easy to implement.

[0012] In addition, the method for preparing spherical tungsten-lanthanum composite powder according to the above embodiment of the present invention may also have the following additional technical features:

[0013] In some embodiments of the present invention, in step (1), the lanthanum salt and the metatungstate are mixed in a ratio of the mass of La to the total mass of La and W of (0.2-0.8):100.

[0014] In some embodiments of the present invention, in step (1), the concentration of the feed solution is 190-240 g / L.

[0015] In some embodiments of the present invention, in step (2), the inlet air temperature of the spray granulation is 210-260° C., the outlet air temperature is 110-150° C., and the feed rate is 0.5-0.9 L / h.

[0016] In some embodiments of the present invention, in step (3), the precursor powder is first sintered at 520-580°C for 0.5-2.5 h in an argon atmosphere, and then heated to 650-850°C for a second sintering in a hydrogen atmosphere for 1.0-2.5 h.

[0017] In some embodiments of the present invention, in step (3), the flow rate of the argon gas is 200 to 350 L / h, and the flow rate of the hydrogen gas is 200 to 400 L / h.

[0018] In some embodiments of the present invention, in step (4), the lanthanum-containing tungsten powder is spheroidized using a plasma spheroidization device, the carrier gas flow rate of the spheroidization is 5 to 13 L / min, and the plasma gas flow rate is 3 to 7 L / min.

[0019] In some embodiments of the present invention, in step (4), the rotation speed of the spheroidization is 0.4-5 r / min, and the current is 90-120 A.

[0020] In the second aspect of the present invention, the present invention provides a spherical tungsten-lanthanum composite powder. According to an embodiment of the present invention, the spherical tungsten-lanthanum composite powder is prepared by the above method. Therefore, the spherical tungsten-lanthanum composite powder has the characteristics of high sphericity, good fluidity and uniform lanthanum distribution.

[0021] In addition, the spherical tungsten-lanthanum composite powder according to the above embodiment of the present invention may also have the following additional technical features:

[0022] In some embodiments of the present invention, the fluidity of the spherical tungsten-lanthanum composite powder is not less than 6.0s / 50g, and the bulk density is not less than 9.8g / cm 3 , the sphericity rate is not less than 85%.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0025] Figure 1 It is a schematic flow chart of a method for preparing spherical tungsten-lanthanum composite powder according to an embodiment of the present invention;

[0026] Figure 2 This is a process flow chart of a method for preparing spherical tungsten-lanthanum composite powder according to an embodiment of the present invention;

[0027] Figure 3 : is the SEM picture of the spherical tungsten-lanthanum composite powder obtained in Example 1. DETAILED DESCRIPTION

[0028] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0029] In one aspect of the present invention, a method for preparing spherical tungsten-lanthanum composite powder is provided. Figure 1 and Figure 2 , the method comprising:

[0030] S100: Mix metatungstate, lanthanum salt and water

[0031] In this step, refer to Figure 2, by uniformly mixing metatungstate, lanthanum salt and water, a feed liquid can be obtained. The concentration of the feed liquid is 190-240 g / L. The inventors found that if the concentration of the feed liquid is too high, the precursor powder particles sprayed out later will be too coarse, which is not conducive to subsequent reduction. If the concentration of the feed liquid is too low, the subsequent spraying efficiency will be low and the cost will be increased.

[0032] Further, the lanthanum salt and the metatungstate are mixed according to the ratio of the mass of La to the total mass of La and W (0.2-0.8):100. The inventors found that if the mass of La is too high, it will affect the performance of W, and if the mass of La is too low, it will affect the nuclear shielding performance of La. It should be noted that the specific types of metatungstate and lanthanum salt are not particularly limited, and those skilled in the art can select them as needed. For example, the metatungstate can be ammonium metatungstate, and the lanthanum salt can be lanthanum nitrate.

[0033] S200: Spraying liquid into granules

[0034] In this step, the feed liquid is sprayed and granulated to obtain the precursor powder. Specifically, the feed liquid is sprayed and granulated using a spray drying tower, the inlet air temperature of the spray granulation is 210-260°C, the outlet air temperature is 110-150°C, and the feed rate is 0.5-0.9L / h.

[0035] S300: The precursor powder is first kept warm in an inert atmosphere, and then heated up and reduced in a hydrogen atmosphere

[0036] In this step, the precursor powder is first kept warm in an inert atmosphere. During this process, the metatungstate in the precursor powder will lose ammonia and water to generate WO3, and the lanthanum salt will decompose to generate La2O3. Then, the temperature is increased in a hydrogen atmosphere for reduction, and WO3 will react with hydrogen to generate single substance W to obtain lanthanum-containing tungsten powder. Specifically, in an argon atmosphere, the precursor powder is first sintered at 520-580°C for 0.5-2.5 hours, and then heated to 650-850°C for a second sintering in a hydrogen atmosphere for 1.0-2.5 hours. The inventors found that if the temperature of the first sintering is too high, it is easy to make the WO3 particles grow. If the temperature of the first sintering is too low, it is easy to make the metatungstate dehydrate and deammoniate incomplete, affecting the subsequent reduction of WO3; if the temperature of the second sintering is too high, it is easy to make the W powder particles grow. If the temperature of the second sintering is too low, it will lead to incomplete reduction of WO3 and easy to leave intermediate products such as WO2.

[0037] Furthermore, the flow rate of argon gas is 200 to 350 L / h, and the flow rate of hydrogen gas is 200 to 400 L / h.

[0038] S400: Spheroidizing lanthanum-containing tungsten powder

[0039] In this step, the lanthanum-containing tungsten powder is spheroidized to obtain a tungsten-lanthanum composite powder. Specifically, the lanthanum-containing tungsten powder is spheroidized using a plasma spheroidizing device. The spheroidizing carrier gas flow rate is 5 to 13 L / min, the plasma gas flow rate is 3 to 7 L / min, the spheroidizing speed is 0.4 to 5 r / min, and the current is 90 to 120 A.

[0040] In the second aspect of the present invention, the present invention proposes a spherical tungsten-lanthanum composite powder. According to an embodiment of the present invention, the tungsten-lanthanum composite powder is prepared by the above method. As a result, the spherical tungsten-lanthanum composite powder has the characteristics of high sphericity, good fluidity and uniform lanthanum distribution. Furthermore, the fluidity of the obtained spherical tungsten-lanthanum composite powder is not less than 6.0s / 50g, and the bulk density is not less than 9.8g / cm 3 , the sphericity rate is not less than 85%.

[0041] It should be noted that the characteristics and advantages described above for the method for preparing spherical tungsten-lanthanum composite powder are also applicable to the spherical tungsten-lanthanum composite powder, and will not be repeated here.

[0042] The present invention has at least one of the following advantages:

[0043] (1) Using front-end liquid phase doping can achieve uniform mixing of doping elements at the molecular level;

[0044] (2) The precursor powder is directly calcined and reduced in a hydrogen atmosphere, so that the toxic nitrogen oxide gas generated by the calcination of the lanthanum salt can be discharged in time, ensuring the safety of operators and the ecological environment. In addition, the "one-step calcination and reduction" can avoid the precursor powder being placed in a high-temperature system multiple times, thereby effectively reducing the breakage of the hollow sphere particles formed by spray granulation, ensuring the fluidity of the precursor powder, and facilitating the smooth feeding during plasma spheroidization;

[0045] (3) By adjusting the parameters of plasma spheroidization, the prepared spherical tungsten-lanthanum composite powder can have the characteristics of high sphericity, good fluidity and uniform lanthanum distribution.

[0046] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0047] Example 1

[0048] (1) ammonium metatungstate and lanthanum nitrate hexahydrate were mixed in a ratio of the mass of La to the total mass of La and W of 0.4:100, and then dissolved in water to prepare a clarified liquid with a concentration of 210 g / L;

[0049] (2) spray granulation of the clarified liquid obtained in step 1 by using a spray drying tower to obtain a precursor powder, wherein the inlet air temperature of the spray drying tower is 220° C., the outlet air temperature is 110° C., and the feed rate is 0.7 L / h;

[0050] (3) placing the precursor powder obtained in step 2 in a tube furnace, first sintering at 530° C. for 1.0 h in an argon atmosphere, with an argon flow rate of 250 L / h, and then heating to 700° C. for 1.5 h in a hydrogen atmosphere for a second sintering, with a hydrogen flow rate of 250 L / h, to obtain lanthanum-containing tungsten powder;

[0051] (4) The lanthanum-containing tungsten powder obtained in step 3 is spheroidized by a plasma spheroidization device. The carrier gas flow rate of the spheroidization is 8 L / min, the plasma gas flow rate is 5 L / min, the feed speed is 1.0 r / min, and the current is 105 A. The fluidity is 5.0 s / 50 g and the bulk density is 11.5 g / cm 3 , pure phase spherical tungsten-lanthanum composite powder with a sphericity of 92%.

[0052] The obtained spherical tungsten-lanthanum composite powder was tested by electron microscopy. The obtained SEM image is shown in Figure 3 .pass Figure 3 It can be seen that the obtained spherical tungsten-lanthanum composite powder has a high sphericity and good fluidity.

[0053] Example 2

[0054] (1) ammonium metatungstate and lanthanum nitrate hexahydrate were mixed in a ratio of the mass of La to the total mass of La and W of 0.2:100, and then dissolved in water to prepare a clarified liquid with a concentration of 190 g / L;

[0055] (2) spray granulation of the clarified liquid obtained in step 1 by using a spray drying tower to obtain a precursor powder, wherein the inlet air temperature of the spray drying tower is 210° C., the outlet air temperature is 100° C., and the feed rate is 0.5 L / h;

[0056] (3) placing the precursor powder obtained in step 2 in a tube furnace, first sintering at 510° C. for 0.5 h in an argon atmosphere, with an argon flow rate of 200 L / h, and then heating to 650° C. for 1.2 h in a hydrogen atmosphere for a second sintering, with a hydrogen flow rate of 200 L / h, to obtain lanthanum-containing tungsten powder;

[0057] (4) The lanthanum-containing tungsten powder obtained in step 3 was spheroidized using a plasma spheroidization device. The carrier gas flow rate of the spheroidization was 5 L / min, the plasma gas flow rate was 3 L / min, the feed speed was 0.5 r / min, and the current was 95 A. The fluidity was 5.3 s / 50 g and the bulk density was 10.8 g / cm 3, pure phase spherical tungsten-lanthanum composite powder with a sphericity of 87%.

[0058] The obtained spherical tungsten-lanthanum composite powder was subjected to electron microscopy testing. From the SEM image, it can be seen that the obtained spherical tungsten-lanthanum composite powder has a high sphericity and good fluidity.

[0059] Example 3

[0060] (1) ammonium metatungstate and lanthanum nitrate hexahydrate were mixed in a ratio of the mass of La to the total mass of La and W of 0.6:100, and then dissolved in water to prepare a clarified liquid with a concentration of 230 g / L;

[0061] (2) spray granulation of the clarified liquid obtained in step 1 by using a spray drying tower to obtain a precursor powder, wherein the inlet air temperature of the spray drying tower is 250° C., the outlet air temperature is 120° C., and the feed rate is 0.8 L / h;

[0062] (3) placing the precursor powder obtained in step 2 in a tube furnace, first sintering at 560° C. for 1.5 h in an argon atmosphere, with an argon flow rate of 300 L / h, and then heating to 720° C. for 2.0 h in a hydrogen atmosphere for a second sintering, with a hydrogen flow rate of 300 L / h, to obtain lanthanum-containing tungsten powder;

[0063] (4) The lanthanum-containing tungsten powder obtained in step 3 is spheroidized by a plasma spheroidization device. The carrier gas flow rate of the spheroidization is 11 L / min, the plasma gas flow rate is 6 L / min, the feed speed is 2 r / min, and the current is 115 A. The fluidity is 5.6 s / 50 g and the bulk density is 10.3 g / cm 3 , pure phase spherical tungsten-lanthanum composite powder with a sphericity of 85%.

[0064] The obtained spherical tungsten-lanthanum composite powder was subjected to electron microscopy testing. From the SEM image, it can be seen that the obtained spherical tungsten-lanthanum composite powder has a high sphericity and good fluidity.

[0065] Example 4

[0066] (1) ammonium metatungstate and lanthanum nitrate hexahydrate were mixed in a ratio of the mass of La to the total mass of La and W of 0.8:100, and then dissolved in water to prepare a clarified liquid with a concentration of 240 g / L;

[0067] (2) spray granulation of the clarified liquid obtained in step 1 by using a spray drying tower to obtain a precursor powder, wherein the inlet air temperature of the spray drying tower is 260° C., the outlet air temperature is 130° C., and the feed rate is 0.9 L / h;

[0068] (3) placing the precursor powder obtained in step 2 in a tube furnace, first sintering at 570° C. for 2.5 h in an argon atmosphere, with an argon flow rate of 350 L / h, and then heating to 740° C. for 2.5 h in a hydrogen atmosphere, with a hydrogen flow rate of 380 L / h, to obtain lanthanum-containing tungsten powder;

[0069] (4) The lanthanum-containing tungsten powder obtained in step 3 is spheroidized by a plasma spheroidization device. The carrier gas flow rate of the spheroidization is 13 L / min, the plasma gas flow rate is 7 L / min, the feed speed is 3 r / min, and the current is 120 A. The fluidity is 5.8 s / 50 g and the bulk density is 9.9 g / cm 3 , pure phase spherical tungsten-lanthanum composite powder with a sphericity of 81%.

[0070] The obtained spherical tungsten-lanthanum composite powder was subjected to electron microscopy testing. From the SEM image, it can be seen that the obtained spherical tungsten-lanthanum composite powder has a high sphericity and good fluidity.

[0071] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0072] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing spherical tungsten-lanthanum composite powder, characterized in that: include: (1) mixing metatungstate, lanthanum salt and water to obtain a feed solution; (2) spraying and granulating the liquid material to obtain a precursor powder; (3) keeping the precursor powder warm in an inert atmosphere and then reducing it by heating in a hydrogen atmosphere to obtain lanthanum-containing tungsten powder; (4) spheroidizing the lanthanum-containing tungsten powder to obtain a tungsten-lanthanum composite powder; In step (1), the lanthanum salt and the metatungstate are mixed in a ratio of the mass of La to the total mass of La and W of (0.2-0.8):100; In step (1), the concentration of the feed solution is 190-240 g / L; In step (3), the precursor powder is first sintered at 520-580° C. for 0.5-2.5 h in an argon atmosphere, and then heated to 650-850° C. for a second sintering in a hydrogen atmosphere for 1.0-2.5 h.

2. The method according to claim 1, characterized in that In step (2), the inlet air temperature of the spray granulation is 210-260°C, the outlet air temperature is 110-150°C, and the feed rate is 0.5-0.9 L / h.

3. The method according to claim 2, characterized in that In step (3), the flow rate of the argon gas is 200 to 350 L / h, and the flow rate of the hydrogen gas is 200 to 400 L / h.

4. The method according to claim 1, characterized in that In step (4), the lanthanum-containing tungsten powder is spheroidized by a plasma spheroidization device, the carrier gas flow rate of the spheroidization is 5 to 13 L / min, and the plasma gas flow rate is 3 to 7 L / min.

5. The method according to claim 4, characterized in that In step (4), the rotation speed of the spheroidization is 0.4-5 r / min, and the current is 90-120 A.

6. A spherical tungsten-lanthanum composite powder, characterized in that: The spherical tungsten-lanthanum composite powder is prepared by the method described in any one of claims 1-5.

7. The tungsten-lanthanum composite powder according to claim 6, characterized in that: The fluidity of the spherical tungsten-lanthanum composite powder is not less than 6.0s / 50g, and the bulk density is not less than 9.8g / cm 3 , the sphericity rate is not less than 85%.

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