Preparation method of strontium hexaboride nano powder

Abstract

The invention belongs to the technical field of preparation of alkaline earth metal hexaboride powder, and provides a preparation method of strontium hexaboride nanopowder, which comprises the following steps: drying SrCl2. 6H2O powder to obtain SrCl2 powder; the preparation method comprises the following steps: grinding and mixing SrCl2 powder and NaBH4 powder to obtain mixed powder a; the mixed powder a and LiCl-KCl eutectic salt are mixed, and mixed powder b is obtained; performing high-temperature reaction on the mixed powder b to obtain mixed powder c; and dissolving the mixed powder c in water, and sequentially filtering, drying, pickling and washing to obtain the strontium hexaboride nano powder. The average particle size of the prepared nano powder is 30-80 nm, and the nano powder has good cubic morphology, has the characteristics of high surface activity, large specific area and the like, and has wide application prospects as multifunctional ceramic powder. Meanwhile, the preparation cost can be effectively reduced, and a new thought for preparing the SrB6 powder is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of alkaline earth metal hexaboride powder, and in particular to a method for preparing strontium hexaboride nanopowder. Background Art

[0002] Divalent alkaline earth hexaboride MB6 (M = Ca, Ba, Sr) is A cubic structure of CsCl-type symmetry space group, with metal atoms at the (0, 0, 0) positions and octahedral boron atoms at the (0.5, 0.5, x) positions. As an internal parameter, x determines the ratio between the inter-octahedral distance and the intra-octahedral BB distance. Due to the strong covalent bonding of the BB atoms in this structure, it exhibits excellent properties such as a high melting point, high chemical stability, and high hardness, as well as other novel properties such as a low work function and low thermal expansion coefficient. Due to these outstanding advantages, alkaline earth hexaborides have the potential to be used as electron sources and thermoelectric materials.

[0003] As a boride with unique properties, SrB6 has potential applications in a variety of fields, garnering considerable research attention. For example, in the energy sector, it could be used in radioisotope energy sources; in optics, SrB6 nanoparticles dispersed in transparent acrylic sheets can be used to block infrared wavelengths while allowing visible light to pass through; and in materials science, it can be used to prepare Al-SrB6 composites. Current research on SrB6 powder focuses on exploring optimal preparation methods to obtain high-purity, fine, and uniformly sized powders to meet the demands of preparing high-performance crystalline materials. Furthermore, research also focuses on optimizing the performance of SrB6 powders in various application areas and exploring their mechanisms. Currently, the main methods for preparing SrB6 powder include pure element chemical synthesis and carbothermal reduction. Pure element chemical synthesis uses Sr and B elemental powders as raw materials through a high-temperature chemical reaction. However, this method suffers from high reaction temperatures, typically above 1800°C, and the high cost of the elemental powders. Furthermore, the oxygen concentration must be kept extremely low during the reaction to prevent the reactants from being easily oxidized. The carbothermal reduction method uses SrCO₃, B₄C, and activated carbon powder as raw materials to produce SrB₆ powder through a solid-phase synthesis reaction. For example, a literature study synthesized SrB₆ powder using SrCO₃, B₄C, and activated carbon powder at 1400°C for 2.5 hours. However, the resulting powder had a coarse particle size of approximately 50 μm.

[0004] In summary, a preparation method with low synthesis temperature, small particle size and high-quality single-phase SrB6 powder is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing strontium hexaboride nanopowder, so as to achieve high-quality production of the powder and obtain strontium hexaboride nanopowder with high purity, fine and uniform particle size.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing strontium hexaboride nanopowder, comprising the following steps:

[0008] (1) drying SrCl2·6H2O powder to obtain SrCl2 powder;

[0009] (2) Grinding and mixing SrCl2 powder and NaBH4 powder to obtain mixed powder a;

[0010] (3) Mixing powder a and LiCl-KCl eutectic salt in a powder mixer to obtain mixed powder b;

[0011] (4) subjecting the mixed powder b to a high-temperature reaction to obtain mixed powder c;

[0012] (5) After dissolving the mixed powder c in water, the mixed powder c is filtered, dried, acid-washed, and washed with water in sequence to obtain the strontium hexaboride nanopowder.

[0013] Preferably, the drying temperature in step (1) is 200-300° C., and the drying time is 2-6 hours.

[0014] Preferably, the molar ratio of SrCl2 powder to NaBH4 powder in step (2) is 1:6.

[0015] Preferably, the grinding rate in step (2) is 30 to 80 r / min, and the grinding time is 0.4 to 0.8 h.

[0016] Preferably, in step (3), the mass ratio of the mixed powder a to the LiCl-KCl eutectic salt is 1:8-12;

[0017] The mass ratio of LiCl to KCl in the LiCl-KCl eutectic salt is 40-50:50-60.

[0018] Preferably, the mixing time in step (3) is 20 to 30 hours.

[0019] Preferably, the temperature of the high-temperature reaction in step (4) is 800-1000° C., the heating rate of the high-temperature reaction is 10-20° C. / min, and the time of the high-temperature reaction is 0.2-1 h.

[0020] Preferably, the pickling in step (5) is hydrochloric acid pickling;

[0021] The molar purity of the hydrochloric acid is 35-37%.

[0022] Preferably, the average particle size of the strontium hexaboride nanopowder in step (5) is 30 to 80 nm.

[0023] The present invention has the following beneficial effects:

[0024] The nanopowder prepared by this method has an average particle size between 30 and 80 nm, a well-defined cubic morphology, high surface activity, and a large specific surface area. It has broad application prospects as a multifunctional ceramic powder. Furthermore, the method has a low reaction temperature, effectively reducing preparation costs and providing a new approach to preparing SrB6 powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a physical picture of the strontium hexaboride nanopowder of Example 1;

[0026] Figure 2 is the XRD pattern of the strontium hexaboride nanopowder of Example 1;

[0027] Figure 3 The SEM image and particle size distribution diagram of the strontium hexaboride nanopowder of Example 1;

[0028] Figure 4 This is the EDS energy spectrum and element distribution diagram of the strontium hexaboride nanopowder of Example 1. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing strontium hexaboride nanopowder, comprising the following steps:

[0030] (1) drying SrCl2·6H2O powder to obtain SrCl2 powder;

[0031] (2) Grinding and mixing SrCl2 powder and NaBH4 powder to obtain mixed powder a;

[0032] (3) Mixing powder a and LiCl-KCl eutectic salt in a powder mixer to obtain mixed powder b;

[0033] (4) subjecting the mixed powder b to a high-temperature reaction to obtain mixed powder c;

[0034] (5) After dissolving the mixed powder c in water, the mixed powder c is filtered, dried, acid-washed, and washed with water in sequence to obtain the strontium hexaboride nanopowder.

[0035] In the present invention, the drying temperature in step (1) is preferably 200-300°C, more preferably 210-290°C, and more preferably 220-280°C;

[0036] In the present invention, the drying time is preferably 2 to 6 hours, more preferably 2.5 to 5.5 hours, and even more preferably 3 to 5 hours.

[0037] In the present invention, the equation for the chemical reaction of SrCl2 and NaBH4 in step (2) is SrCl2+6NaBH4→SrB6+2NaCl+4Na+12H2.

[0038] In the present invention, the molar ratio of SrCl2 powder to NaBH4 powder in step (2) is preferably 1:6.

[0039] In the present invention, the grinding rate in step (2) is preferably 30 to 80 r / min, more preferably 40 to 70 r / min, and even more preferably 50 to 60 r / min.

[0040] In the present invention, the grinding time is preferably 0.4 to 0.8 h, more preferably 0.5 to 0.7 h, and even more preferably 0.5 to 0.6 h.

[0041] In the present invention, the mass ratio of the mixed powder a to the LiCl-KCl eutectic salt in step (3) is preferably 1:8-12, more preferably 1:9-11, and even more preferably 1:10.

[0042] In the present invention, the mass ratio of LiCl to KCl in the LiCl-KCl eutectic salt is preferably 40-50:50-60, more preferably 42-48:52-58, and even more preferably 45:55.

[0043] In the present invention, the mixing time in step (3) is preferably 20 to 30 hours, more preferably 22 to 28 hours, and even more preferably 24 to 26 hours.

[0044] In the present invention, the temperature of the high temperature reaction in step (4) is preferably 800-1000°C, more preferably 820-980°C, and even more preferably 850-950°C.

[0045] In the present invention, the heating rate of the high temperature reaction is preferably 10 to 20° C. / min, more preferably 12 to 18° C. / min, and even more preferably 14 to 16° C. / min.

[0046] In the present invention, the high temperature reaction time is preferably 0.2 to 1 h, more preferably 0.3 to 0.8 h, and even more preferably 0.4 to 0.6 h.

[0047] In the present invention, the drying temperature in step (5) is preferably 60-100°C, more preferably 70-90°C, and even more preferably 75-85°C.

[0048] In the present invention, the powder after acid washing in step (5) needs to be filtered and dried again, and then washed with water after drying. This operation is repeated 2 to 3 times to obtain pure SrB6 nanopowder.

[0049] In the present invention, the pickling in step (5) is preferably hydrochloric acid pickling.

[0050] In the present invention, the molar purity of the hydrochloric acid is preferably 35-37%, more preferably 36-37%, and even more preferably 37%.

[0051] In the present invention, the average particle size of the strontium hexaboride nanopowder in step (5) is preferably 30 to 80 nm, more preferably 35 to 70 nm, and even more preferably 40 to 50 nm.

[0052] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] SrCl2·6H2O powder with a purity of 99.5% was placed in a muffle furnace and dried at 240°C for 4 hours. After cooling, it was taken out to obtain SrCl2 powder. SrCl2 powder and NaBH4 powder (purity of 98%) were ground and mixed in a mortar at a molar ratio of 1:6 at a rate of 50 r / min for 0.5 h to obtain mixed powder a. Powder a and LiCl-KCl eutectic salt (mass ratio of LiCl:KCl is 45:55) were placed in a powder mixer and mixed for 24 hours to obtain mixed powder b. The mixed powder b was loaded into a corundum crucible and placed in a vacuum atmosphere furnace for high-temperature reaction at a heating rate of 15°C / min and a temperature of 900°C for 0.5 h to obtain mixed powder c.

[0055] The mixed powder c is cooled to room temperature and dissolved in water, then filtered and the powder is dried at 80°C. Then, hydrochloric acid with a molar purity of 37% is added to the dried powder for pickling. After pickling, the powder is filtered and dried. After drying, the powder is washed with water. This process is repeated 2 to 3 times to obtain pure SrB6 nanopowder.

[0056] Figure 1 This is the physical picture of the SrB6 nanopowder prepared in this example. Figure 1 It can be seen that the powder is brown in color as a whole.

[0057] Figure 2 The XRD pattern of SrB6 nanopowder prepared in this example is as follows: Figure 2 It can be seen that the target peak corresponds to the standard card one by one, and there are no mixed peaks.

[0058] Figure 3 The SEM image and particle size distribution of SrB6 nanopowder prepared in this example are as follows: Figure 3 It can be seen that the average particle size of SrB6 nanopowder is 43.87nm and has a good cubic morphology.

[0059] Figure 4 The EDS spectrum and element distribution diagram of the SrB6 nanopowder prepared in this example are as follows: Figure 4 It can be seen that Sr and B elements are evenly distributed in SrB6 nanopowder.

[0060] Example 2

[0061] SrCl2·6H2O powder with a purity of 99.5% was placed in a muffle furnace and dried at 240°C for 4 hours. After cooling, it was taken out to obtain SrCl2 powder. SrCl2 powder and NaBH4 powder (purity of 98%) were ground and mixed in a mortar at a molar ratio of 1:6 at a rate of 50 r / min for 0.5 h to obtain mixed powder a. Powder a and LiCl-KCl eutectic salt (mass ratio of LiCl:KCl is 45:55) were placed in a powder mixer and mixed for 24 hours to obtain mixed powder b. The mixed powder b was loaded into a corundum crucible and placed in a vacuum atmosphere furnace for high-temperature reaction at a heating rate of 15°C / min and a temperature of 1000°C for 0.5 h to obtain mixed powder c.

[0062] The mixed powder c is cooled to room temperature and dissolved in water, then filtered and the powder is dried at 80°C. Then, hydrochloric acid with a molar purity of 37% is added to the dried powder for pickling. After pickling, the powder is filtered and dried. After drying, the powder is washed with water. This process is repeated 2 to 3 times to obtain pure SrB6 nanopowder.

[0063] After testing, the powder prepared in this embodiment is pure SrB6 phase, and the average particle size of the powder is 52.35 nm.

[0064] Example 3

[0065] SrCl2·6H2O powder with a purity of 99.5% was placed in a muffle furnace and dried at 240°C for 4 hours. After cooling, it was taken out to obtain SrCl2 powder. SrCl2 powder and NaBH4 powder (purity of 98%) were ground and mixed in a mortar at a molar ratio of 1:6 at a rate of 50 r / min for 0.5 hours to obtain mixed powder a. Powder a and LiCl-KCl eutectic salt (mass ratio of LiCl:KCl is 45:55) were placed in a powder mixer and mixed for 24 hours to obtain mixed powder b. The mixed powder b was loaded into a corundum crucible and placed in a vacuum atmosphere furnace for high-temperature reaction at a heating rate of 15°C / min and a temperature of 900°C for 1 hour to obtain mixed powder c.

[0066] The mixed powder c is cooled to room temperature and dissolved in water, then filtered and the powder is dried at 80°C. Then, hydrochloric acid with a molar purity of 37% is added to the dried powder for pickling. After pickling, the powder is filtered and dried. After drying, the powder is washed with water. This process is repeated 2 to 3 times to obtain pure SrB6 nanopowder.

[0067] After testing, the powder prepared in this embodiment is pure SrB6 phase, and the average particle size of the powder is 40.27 nm.

[0068] As can be seen from the above examples, the present invention provides a method for preparing strontium hexaboride nanopowder, comprising the following steps: drying SrCl2·6H2O powder to obtain SrCl2 powder; grinding and mixing the SrCl2 powder and NaBH4 powder to obtain mixed powder a; mixing mixed powder a with LiCl-KCl eutectic salt to obtain mixed powder b; subjecting mixed powder b to a high-temperature reaction to obtain mixed powder c; dissolving mixed powder c in water, followed by filtering, drying, acid washing, and water washing to obtain the strontium hexaboride nanopowder. The nanopowder prepared by the present invention has an average particle size of 30 to 80 nm, a well-defined cubic morphology, high surface activity, and a large specific surface area, and has broad application prospects as a multifunctional ceramic powder. This method also features a low reaction temperature, effectively reducing production costs, providing a new approach to preparing SrB6 powder.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing strontium hexaboride nanopowder, characterized in that: It includes the following steps: (1) drying SrCl2·6H2O powder to obtain SrCl2 powder; (2) Grinding and mixing SrCl2 powder and NaBH4 powder to obtain mixed powder a; (3) Mixing powder a and LiCl-KCl eutectic salt in a powder mixer to obtain mixed powder b; (4) subjecting the mixed powder b to a high-temperature reaction to obtain mixed powder c; (5) After dissolving the mixed powder c in water, the mixed powder c is filtered, dried, acid-washed, and washed with water in sequence to obtain the strontium hexaboride nanopowder.

2. The preparation method according to claim 1, characterized in that The drying temperature in step (1) is 200-300° C., and the drying time is 2-6 hours.

3. The preparation method according to claim 1, characterized in that The molar ratio of SrCl2 powder to NaBH4 powder in step (2) is 1:

6.

4. The preparation method according to claim 1, characterized in that The grinding rate in step (2) is 30-80 r / min, and the grinding time is 0.4-0.8 h.

5. The preparation method according to claim 1, characterized in that In step (3), the mass ratio of the mixed powder a to the LiCl-KCl eutectic salt is 1:8-12; The mass ratio of LiCl to KCl in the LiCl-KCl eutectic salt is 40-50:50-60.

6. The preparation method according to claim 1, characterized in that The mixing time in step (3) is 20 to 30 hours.

7. The preparation method according to claim 1, characterized in that The temperature of the high-temperature reaction in step (4) is 800-1000° C., the heating rate of the high-temperature reaction is 10-20° C. / min, and the time of the high-temperature reaction is 0.2-1 h.

8. The preparation method according to claim 1, characterized in that The pickling in step (5) is hydrochloric acid pickling; The molar purity of the hydrochloric acid is 35-37%.

9. The preparation method according to claim 1, characterized in that The average particle size of the strontium hexaboride nanopowder in step (5) is 30 to 80 nm.

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