Preparation method of approximately spherical superfine high-abundance boron carbide powder

Abstract

The preparation method comprises the following steps: S1, high-abundance boric acid, an organic carbon source and polytetrafluoroethylene are uniformly mixed according to a certain ratio, and the ratio of the high-abundance boric acid to the organic carbon source to the polytetrafluoroethylene is (5-8): 1: (0.05-0.2); s2, the raw materials in the S1 are subjected to a carbon thermal reduction reaction in a vacuum sintering furnace at the high temperature, and the high-abundance boron carbide powder is prepared. According to the technical scheme, the near-spherical superfine high-abundance boron carbide powder can be prepared, the raw material utilization rate is high, and the near-spherical superfine high-abundance boron carbide powder can be directly used as a superfine powder raw material for a subsequent sintering process.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a method for preparing near-spherical ultrafine high-abundance boron carbide powder. Background Technology

[0002] Most existing methods for preparing boron carbide powder employ carbothermal reduction and Azison smelting. The Azison smelting method is crude, with only 50% utilization of high-abundance boric acid, making it difficult to control powder uniformity and resulting in numerous impurities. Traditional carbothermal reduction produces coarse-grained powder requiring secondary refining, which easily introduces impurities, reducing boron carbide powder abundance. Furthermore, the lengthy secondary refining process increases the cost of high-abundance boron carbide.

[0003] This invention solves the problems of difficulty in controlling powder uniformity, low raw material utilization, and poor sphericity in existing boron carbide powder preparation methods. Summary of the Invention

[0004] The present invention discloses a method for preparing near-spherical ultrafine high-abundance boron carbide powder, which uses high-abundance boric acid and organic carbon source as raw materials, and polytetrafluoroethylene as template, and prepares near-spherical ultrafine high-abundance boron carbide powder by carbothermal reduction method.

[0005] The specific technical solution of this invention is as follows: S1: Mix high-abundance boric acid, organic carbon source and polytetrafluoroethylene in a certain proportion, wherein the mass ratio of high-abundance boric acid, organic carbon source and polytetrafluoroethylene is (5-8):1:(0.05-0.2).

[0006] S2: High-abundance boron carbide powder is prepared by carbothermic reduction reaction of the raw material in S1 at high temperature in a vacuum sintering furnace.

[0007] In S1, high abundance boric acid 10 B abundance ≥ 97%, purity ≥ 99.5%, particle size D 90 ≤25µm, moisture ≤0.5%; In S1, the organic carbon source includes one or more of glucose, starch, cellulose, and carbon nanotubes; In S1, polytetrafluoroethylene (PTFE) emulsion is mixed with an organic carbon source and PTFE and then fed into a high-pressure homogenizer for pre-emulsification. The pre-emulsification conditions are 50 MPa pressure, 0.2 mm cavity gap, and 25°C for continuous processing for 5 min. Then, high-pressure homogenization is performed under the following conditions: 100 MPa pressure, 0.1 mm cavity gap, and 25°C for continuous processing for 25-30 min. This step further breaks down all components in the emulsion through nanoscale shearing, which can effectively reduce the particle size of the final boron carbide powder. In step S2, the pre-emulsified emulsion is immediately fed into a two-fluid nozzle for spray quenching. The atomization is carried out under a 0.3 mm aperture and a nitrogen pressure of 0.6 MPa. The inlet temperature is 200°C, the outlet temperature is 90°C, and the instantaneous quenching time is ≤1 ms. This step uses PTFE emulsion and undergoes spray quenching treatment, which helps to induce the formation of near-spherical boron carbide. In step S2, after spray quenching, the vacuum sintering furnace is started to raise the temperature. In the first stage, the temperature is raised to 1000℃ and held for 0.5h, with a heating rate of 8-10℃ / min. In the second stage, the temperature is gradually raised to the highest temperature and held, with a heating rate of 5-8℃ / min. In S2, the highest temperature is 1700-1950℃, and the holding time after reaching the highest temperature is 0.5-2h.

[0008] If the heating rate is too fast in the first stage, the boron carbide powder will be coarse; if the holding time is too short, the final sphericity of the powder will be poor. If the temperature is too low or the heat preservation time is too short in the second stage, the sphericity will decrease.

[0009] Boron carbide obtained according to the above preparation method 10 B abundance ≥ 97%, purity ≥ 99.99%, D 50 The thickness is 1-1.5 μm, and the sphericity is ≥0.90. Attached Figure Description

[0010] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0011] Figure 1 The XRD test results are for the high-abundance boron carbide powder prepared in Example 3; Figure 2 The image shows the microstructure of the high-abundance boron carbide powder prepared in Example 3. Beneficial effects

[0012] 1. The technical solution of the present invention can prepare near-spherical ultrafine high-abundance boron carbide powder with high raw material utilization rate, and can be directly used as ultrafine powder raw material for subsequent sintering process.

[0013] 2. Through the directional induction effect of polytetrafluoroethylene and spray quenching treatment, boron carbide grains can form near-spherical powder during the nucleation and growth process. Through pre-emulsification and high-pressure homogenization steps, the uniformity of the powder can be effectively controlled, and the particle size can reach the nanoscale, without the need for secondary refinement treatment.

[0014] 3. By gradually raising the temperature to the maximum level through a two-stage heating mode and controlling the heating rate and holding time, the high abundance of boron carbide powder can be guaranteed, meeting the requirements for nuclear power neutron absorption and shielding applications. Detailed Implementation

[0015] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0016] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0017] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Before description, it should be understood that the terminology used in the specification and appended claims should not be construed as limited to its general and dictionary meaning, but rather should be interpreted based on the principle of allowing the inventors to appropriately define the terminology for the best interpretation, and based on its meaning and concept corresponding to the technical level of the invention. Therefore, the description herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention; thus, it should be understood that other equivalent implementations and modifications can be made without departing from the spirit and scope of the invention.

[0018] In this document, the terms “comprising,” “including,” “having,” “containing,” or any similar terms are open-ended transitional phrases intended to encompass non-exclusive inclusions. For example, a composition or article containing a plural element is not limited to the elements listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated otherwise, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously encompassing closed or semi-closed transitional phrases such as “composed of” and “substantially composed of.”

[0019] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0020] If a quantity or other numerical value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are separately disclosed. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0021] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover a range from 39.50 to 40.49.

[0022] In addition, unless otherwise stated, the following reagents and solvents were purchased from: High-abundance boric acid: Shandong Chengwu Yixin Environmental Protection Technology Co., Ltd. PTFE emulsion: Aladdin High-pressure homogenizer: SCIENTZ-150 experimental high-pressure homogenizer from Ningbo Xinzhi Biotechnology Co., Ltd. Example 1

[0023] S1: Mix high-abundance boric acid, organic carbon source and polytetrafluoroethylene in a certain proportion, wherein the ratio of high-abundance boric acid, organic carbon source and polytetrafluoroethylene is 6:1:0.1.

[0024] S2: High-abundance boron carbide powder is prepared by carbothermic reduction reaction of the raw material in S1 at high temperature in a vacuum sintering furnace.

[0025] In S1, high abundance boric acid 10 B abundance ≥ 97%, purity ≥ 99.5%, particle size D 90 ≤25µm, moisture ≤0.5%; In S1, the organic carbon source is cellulose; In S1, polytetrafluoroethylene (PTFE) emulsion is mixed with an organic carbon source and PTFE and then fed into a high-pressure homogenizer for pre-emulsification. The pre-emulsification conditions are 50 MPa pressure, 0.2 mm cavity gap, and 25°C for continuous processing for 5 min. Then, high-pressure homogenization is performed under the following conditions: 100 MPa pressure, 0.1 mm cavity gap, and 25°C for continuous processing for 30 min. In step S2, the pre-emulsified emulsion is immediately fed into a two-fluid nozzle for spray quenching. The atomization is carried out under a 0.3 mm aperture and a nitrogen pressure of 0.6 MPa. The inlet temperature is 200°C, the outlet temperature is 90°C, and the instantaneous quenching time is ≤1 ms. In step S2, after spray quenching, the vacuum sintering furnace is started to raise the temperature. In the first stage, the temperature is raised to 1000℃ and held for 0.5h at a rate of 9℃ / min. In the second stage, the temperature is gradually raised to the highest temperature and held at a rate of 7℃ / min. In S2, the highest temperature is 1850℃, and the holding time after reaching the highest temperature is 1 hour; Boron carbide obtained according to the above preparation method 10 B abundance ≥ 97%, purity ≥ 99.9%, D 50 The particle size is 1.3 μm, the sphericity is ≥0.90, and the raw material utilization rate is 69%. Example 2

[0026] S1: Mix high-abundance boric acid, organic carbon source and polytetrafluoroethylene in a certain proportion, wherein the ratio of high-abundance boric acid, organic carbon source and polytetrafluoroethylene is 5:1:0.05.

[0027] S2: High-abundance boron carbide powder is prepared by carbothermic reduction reaction of the raw material in S1 at high temperature in a vacuum sintering furnace.

[0028] In S1, high abundance boric acid 10 B abundance ≥ 97%, purity ≥ 99.5%, particle size D 90 ≤25µm, moisture ≤0.5%; In S1, the organic carbon source is carbon nanotubes; In S1, polytetrafluoroethylene (PTFE) emulsion is mixed with an organic carbon source and PTFE and then fed into a high-pressure homogenizer for pre-emulsification. The pre-emulsification conditions are 50 MPa pressure, 0.2 mm cavity gap, and 25°C for continuous processing for 5 min. Then, high-pressure homogenization is performed under the following conditions: 100 MPa pressure, 0.1 mm cavity gap, and 25°C for continuous processing for 25 min. In step S2, the pre-emulsified emulsion is immediately fed into a two-fluid nozzle for spray quenching. The atomization is carried out under a 0.3 mm aperture and a nitrogen pressure of 0.6 MPa. The inlet temperature is 200°C, the outlet temperature is 90°C, and the instantaneous quenching time is ≤1 ms. In step S2, after spray quenching, the vacuum sintering furnace is started to raise the temperature. In the first stage, the temperature is raised to 1000℃ and held for 0.5h at a rate of 8℃ / min. In the second stage, the temperature is gradually raised to the highest temperature and held at a rate of 5℃ / min. In S2, the highest temperature is 1700℃, and the holding time after reaching the highest temperature is 1 hour; Boron carbide obtained according to the above preparation method 10 B abundance ≥ 97%, purity ≥ 99.9%, D 50 The particle size is 1 μm, the sphericity is ≥0.90, and the raw material utilization rate is 71%. Example 3

[0029] S1: Mix high-abundance boric acid, organic carbon source and polytetrafluoroethylene in a certain proportion, wherein the ratio of high-abundance boric acid, organic carbon source and polytetrafluoroethylene is 8:1:0.2.

[0030] S2: High-abundance boron carbide powder is prepared by carbothermic reduction reaction of the raw material in S1 at high temperature in a vacuum sintering furnace.

[0031] In S1, high abundance boric acid 10 B abundance ≥ 97%, purity ≥ 99.5%, particle size D 90 ≤25µm, moisture ≤0.5%; In S1, the organic carbon source is starch; In S1, polytetrafluoroethylene (PTFE) emulsion is mixed with an organic carbon source and PTFE and then fed into a high-pressure homogenizer for pre-emulsification. The pre-emulsification conditions are 50 MPa pressure, 0.2 mm cavity gap, and 25°C for continuous processing for 5 min. Then, high-pressure homogenization is performed under the following conditions: 100 MPa pressure, 0.1 mm cavity gap, and 25°C for continuous processing for 30 min. In step S2, the pre-emulsified emulsion is immediately fed into a two-fluid nozzle for spray quenching. The atomization is carried out under a 0.3 mm aperture and a nitrogen pressure of 0.6 MPa. The inlet temperature is 200°C, the outlet temperature is 90°C, and the instantaneous quenching time is ≤1 ms. In step S2, after spray quenching, the vacuum sintering furnace is started to raise the temperature. In the first stage, the temperature is raised to 1000℃ and held for 0.5h at a rate of 9℃ / min. In the second stage, the temperature is gradually raised to the highest temperature and held at a rate of 8℃ / min. In S2, the highest temperature is 1950℃, and the holding time after reaching the highest temperature is 1 hour; Boron carbide obtained according to the above preparation method 10 B abundance ≥ 97%, purity ≥ 99.99%, D 50 The particle size is 1.5 μm, the sphericity is ≥0.90, and the raw material utilization rate is 75%. Comparative Example 1:

[0032] The steps are the same as in Example 1, but without the pre-emulsification step.

[0033] Boron carbide obtained according to the above preparation method 10 B abundance ≥ 97%, D 50 The particle size was 1.8 μm, and the sphericity was ≥0.5, indicating poor sphericity. Although this did not significantly affect the abundance, it was detected using online ICP-MS. 10 B jump ≥0.2%. Comparative Example 2:

[0034] The steps are the same as in Example 3, except that the second stage in S2 is changed to raise the temperature to the maximum of 1650°C.

[0035] Boron carbide obtained according to the above preparation method 10 B abundance ≥ 97%, D 50 It has a diameter of 1.6 μm and a sphericity ≥ 0.79. Comparative Example 3:

[0036] The steps are the same as in Example 3, except that the heating rate in the first stage is changed to 12°C / min.

[0037] Boron carbide obtained according to the above preparation method 10 B abundance ≥ 96%, D 50It has a diameter of 4.7 μm and a sphericity ≥ 0.88. Comparative Example 4:

[0038] The steps are the same as in Example 3, except that the first stage heat preservation time is changed to 20 minutes.

[0039] Boron carbide obtained according to the above preparation method 10 B abundance ≥ 97%, D 50 It has a diameter of 1.6 μm and a sphericity ≥ 0.78. Comparative Example 5:

[0040] The steps are the same as in Example 3, except that the second stage heat preservation time is changed to 20 minutes.

[0041] Boron carbide obtained according to the above preparation method 10 B abundance ≥ 97%, D 50 It has a diameter of 1.5 μm and a sphericity ≥ 0.77.

[0042] The phase composition, microstructure, and particle size of the powder were tested to verify the technical effect of the present invention.

[0043] The testing method is as follows: The phase composition of the powder was tested using a Smart Lab X-ray diffractometer from Rigaku Corporation of Japan, with a testing range of 10-90°. The microstructure of the powder was tested using a JSM7610F thermal field emission scanning electron microscope from NEC Corporation of Japan. The particle size of the powder was tested using a Masterizer-2000 laser particle size analyzer from Malvern Corporation of the United Kingdom.

[0044] Particle size test results show that the powder D prepared in this invention 50 It is 1-1.5μm.

[0045] like Figure 1 As shown, Figure 1 The XRD test results of the powder in Example 3 show that the diffraction peaks in the XRD pattern are sharp, indicating that the powder of the present invention has high crystallinity and high purity; the carbon peak intensity in the XRD pattern is low and there are no other impurity peaks, indicating that the carbothermic reduction reaction of the present invention is complete and the carbon content is low.

[0046] like Figure 2 As shown, Figure 2 The powder microstructure of Example 3 shows that the powder particles are nearly spherical, uniformly distributed, and without any non-spherical structures, indicating that the powder grows uniformly.

[0047] The method for determining the raw material utilization rate is as follows: The raw material utilization rate in this invention refers to the utilization rate of high-abundance boric acid. The raw material utilization rate is: (mass of boron in product B4C / total mass of boron in boron-containing raw materials) × 100%.

[0048] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing near-spherical ultrafine high-abundance boron carbide powder, characterized in that, Includes the following steps: S1: Mix high-abundance boric acid, organic carbon source and polytetrafluoroethylene in a certain proportion, wherein the mass ratio of high-abundance boric acid, organic carbon source and polytetrafluoroethylene is (5-8):1:(0.05-0.2). S2: High-abundance boron carbide powder is prepared by carbothermic reduction reaction of the raw material in S1 at high temperature in a vacuum sintering furnace.

2. The method for preparing near-spherical ultrafine high-abundance boron carbide powder according to claim 1, characterized in that, In S1, high abundance boric acid 10 B abundance ≥ 97%, purity ≥ 99.5%, particle size D 90 ≤25µm, moisture ≤0.5%.

3. The method for preparing near-spherical ultrafine high-abundance boron carbide powder according to claim 1, characterized in that, In S1, the organic carbon source includes one or more of glucose, starch, cellulose, and carbon nanotubes.

4. The method for preparing near-spherical ultrafine high-abundance boron carbide powder according to claim 1, characterized in that, In S1, polytetrafluoroethylene (PTFE) emulsion is mixed with organic carbon source and PTFE and then sent to a high-pressure homogenizer for pre-emulsification. The pre-emulsification conditions are 50 MPa pressure, 0.2 mm cavity gap and 25°C for continuous treatment for 5 min. Then, high-pressure homogenization is performed under the following conditions: 100 MPa pressure, 0.1 mm cavity gap and 25°C for continuous treatment for 25-30 min.

5. The method for preparing near-spherical ultrafine high-abundance boron carbide powder according to claim 1, characterized in that, In step S2, the pre-emulsified emulsion is immediately fed into a two-fluid nozzle for spray quenching. The atomization is carried out under a 0.3 mm aperture and a nitrogen pressure of 0.6 MPa. The inlet temperature is 200°C, the outlet temperature is 90°C, and the instantaneous quenching time is ≤1 ms.

6. The method for preparing near-spherical ultrafine high-abundance boron carbide powder according to claim 1, characterized in that, In step S2, after spray quenching, the vacuum sintering furnace is started to raise the temperature. In the first stage, the temperature is raised to 1000℃ and held for 0.5h, with a heating rate of 8-10℃ / min. In the second stage, the temperature is gradually raised to the highest temperature and held, with a heating rate of 5-8℃ / min.

7. The method for preparing near-spherical ultrafine high-abundance boron carbide powder according to claim 1, characterized in that, In S2, the highest temperature is 1700-1950℃, and the holding time after reaching the highest temperature is 0.5-2h.

8. Boron carbide obtained by the method for preparing near-spherical ultrafine high-abundance boron carbide powder according to any one of claims 1-7, 10 B abundance ≥ 97%, purity ≥ 99.99%, D 50 The thickness is 1-1.5 μm, and the sphericity is ≥0.90.

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