A method for preparing a prismatic titanium diboride powder

Abstract

The application provides a preparation method of prismatic titanium diboride powder and belongs to the technical field of titanium diboride powder; the preparation method comprises the steps of preparing a titanium source, preparing a boron source, mixing, cold isostatic pressing and carbon thermal reduction reaction; in the step of preparing the titanium source, TiO2 powder liquid is heated, the temperature is raised to 52-55 DEG C, tetrabutyl titanate solution is added, after uniform stirring, ammonia water solution is added to adjust the pH value to 7.0, and the temperature is kept for 2.7-3.2 h to obtain the titanium source; in the step of preparing the boron source, B4C powder is added to anhydrous ethanol, ultrasonic dispersion is carried out, then the mixed solution is added, the addition rate of the mixed solution is controlled to 0.8-1.2 g / min, the temperature is raised to 34-37 DEG C, and the temperature is kept for 3.8-4.2 h to obtain the boron source; the titanium diboride powder obtained by the method has prismatic shape, uniform particles, high density and purity, and poor high-temperature oxidation resistance.

Description

Technical Field

[0001] This invention belongs to the field of titanium diboride powder technology, specifically relating to a method for preparing prismatic titanium diboride powder. Background Technology

[0002] Titanium diboride, as a high-performance ceramic material, has a melting point exceeding 3000℃, a Vickers hardness ≥34Gpa, and excellent electrical and thermal conductivity. Due to its superior performance, titanium diboride plays a crucial role in numerous fields. In the field of metal / ceramic composites, it can serve as a reinforcing phase to improve the strength and wear resistance of aluminum / titanium-based composites. In the field of high-temperature electrodes, it can be used as a cathode coating for aluminum electrolytic cells, exhibiting good resistance to molten salt corrosion. In the field of ultra-high-temperature components, it can serve as a thermal protection material for spacecraft.

[0003] In practical applications, the morphology of powder has a significant impact on the performance of composite materials. Traditional spherical or irregular titanium diboride powders tend to accumulate in composite materials, resulting in weak interfacial bonding and anisotropic properties, which in turn affects the overall performance of the composite materials.

[0004] Prismatic titanium diboride, due to its regular crystal orientation, can significantly improve the fracture toughness and load transfer efficiency of composite materials, ultimately enhancing the stability of the composite materials.

[0005] Therefore, the preparation of prismatic titanium diboride powder has important research significance and application value.

[0006] The existing large-scale preparation processes of titanium diboride mainly include direct chemical reaction method, sol-gel method and carbothermal reduction method;

[0007] The direct chemical reaction method involves the direct reaction of titanium and boron at high temperatures. However, it is prone to abnormal grain growth due to local overheating, resulting in a wide particle size distribution (0.1-50 μm) of the product, with a predominantly lamellar morphology.

[0008] Although the sol-gel method can control nanoscale powders, the process is complex, the utilization rate of boron source is as low as 85%, and problems such as hard agglomeration occur after calcination.

[0009] Conventional carbothermic reduction methods mainly use TiO2, B2O3, and C. However, gaseous B2O3 escapes from the reaction zone, leading to uncontrolled stoichiometry. The product often contains residual TiO2 or Ti3B4 impurities, resulting in a high impurity content.

[0010] It is particularly noteworthy that existing technologies have weak control over crystal morphology. Prismatic growth depends on the control of the gas-solid reaction interface, but the uneven density of traditional powder compacts (<55% of theoretical density) hinders the mass transfer process, resulting in a narrow reaction temperature window (±20℃), making it difficult to achieve stable control of axial preferential growth of crystals. Summary of the Invention

[0011] To address the technical problems existing in the prior art, this invention provides a method for preparing prismatic titanium diboride powder, which avoids the problems of uncontrollable crystal morphology and uneven particle size in TiB2 synthesis, while improving the purity of titanium diboride powder and reducing impurity content.

[0012] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0013] A method for preparing prismatic titanium diboride powder includes the steps of preparing a titanium source, preparing a boron source, mixing materials, cold isostatic pressing, and carbothermic reduction reaction. The specific operations are as follows:

[0014] 1. Preparation of titanium source

[0015] TiO2 powder was added to anhydrous ethanol and stirred until homogeneous to obtain a TiO2 powder liquid; tetrabutyl titanate was added to anhydrous ethanol and stirred until homogeneous to obtain a tetrabutyl titanate solution; the TiO2 powder liquid was heated to 52-55℃, and then the tetrabutyl titanate solution was added and stirred until homogeneous. Ammonia solution was added to adjust the pH to 7.0, and the mixture was kept at this temperature and stirred for 2.7-3.2 hours. After stirring, the mixture was centrifuged and dried to obtain the titanium source.

[0016] The TiO2 powder has a D50 of 1-5 μm.

[0017] In the TiO2 powder liquid, the mass ratio of TiO2 powder to anhydrous ethanol is 8-12:90-110;

[0018] In the tetrabutyl titanate solution, the mass ratio of tetrabutyl titanate to anhydrous ethanol is 1.8-2.3:18-25;

[0019] The mass ratio of the TiO2 powder liquid to the tetrabutyl titanate solution is 98-122:20-27.

[0020] The mass concentration of the ammonia solution is 18-22%.

[0021] 2. Preparation of boron source

[0022] Trimethyl borate was added to anhydrous ethanol and stirred until homogeneous. Tartaric acid was then added and stirred until homogeneous again to obtain a mixture. B4C powder was added to anhydrous ethanol and ultrasonically dispersed for 25-35 min at a power of 250-300 W and a frequency of 32-38 kHz. After ultrasonication, the mixture was added at a rate of 0.8-1.2 g / min. After addition, the temperature was raised to 34-37℃ and stirred for 3.8-4.2 h. The mixture was then centrifuged and dried to obtain the boron source.

[0023] The B4C powder has a D50 of 3-8 μm.

[0024] In the mixture, the mass ratio of anhydrous ethanol, trimethyl borate, and tartaric acid is 38-42:4.0-4.4:0.7-1.0;

[0025] The mass ratio of anhydrous ethanol, B4C powder, and the mixture is 75-85:8-12:42-48.

[0026] 3. Mixing

[0027] Titanium source, boron source, graphite powder and polyethylene glycol 2000 are mixed and stirred evenly to obtain a mixed powder.

[0028] The mass ratio of the titanium source, boron source, graphite powder, and polyethylene glycol 2000 is 76-83:26-28:36-42:0.8-1.3.

[0029] The graphite powder has a D50 of 10-50 μm.

[0030] 4. Cold isostatic pressing

[0031] The mixed powder is loaded into a mold and held under pressure of 5-70 MPa for 5-10 minutes to obtain a green blank.

[0032] 5. Carbothermic reduction reaction

[0033] The blank is placed in a carbon tube furnace and heated to 1900-2200℃ at a rate of 5-10℃ / min under an argon atmosphere. It is held at this temperature for 2-5 hours and then cooled to room temperature to obtain prismatic titanium diboride powder.

[0034] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0035] 1. The present invention adopts a cold isostatic pressing process, which can improve the density of the powder on the one hand, and suppress the volatilization of gases such as B2O3 at high temperature on the other hand. After cold isostatic pressing, the channel for B2O3 vapor volatilization in the raw material becomes narrower, the contact time between the gas-solid reaction phases is prolonged, and the reaction is promoted, thereby making the titanium diboride grow more fully along the axial direction, thus obtaining prismatic titanium diboride with uniform particles.

[0036] In the preparation process, this invention uses titanium dioxide powder and tetrabutyl titanate as a composite titanium source. The surface of the titanium dioxide powder is coated by the hydrolysis of tetrabutyl titanate, which improves the reactivity of the titanium dioxide powder, avoids local agglomeration, and forms regular prismatic titanium diboride, thereby improving the purity of the product. Then, boron carbide and trimethyl borate are used as a composite boron source, and tartaric acid is used as a chelating agent to promote the combination of trimethyl borate and boron carbide, thereby achieving uniform coating on the surface of boron carbide, enhancing reactivity, ensuring tight bonding between particles in subsequent reactions, improving product density, promoting the reaction to proceed in the forward direction, reducing the introduction of impurities, and improving thermal conductivity and high-temperature stability.

[0037] 2. The prismatic titanium diboride prepared by the method of the present invention has a purity of 98.74-99.58% and a density of 98.5-99.0%.

[0038] 3. The prismatic titanium diboride prepared by the method of the present invention, after being kept at 1200°C in air for 24 hours, has a mass change rate of 0.42-0.48%. Attached Figure Description

[0039] Figure 1 The image shows a 1000x SEM image of the titanium diboride powder prepared in Example 2.

[0040] Figure 2 The image shows a 1000x SEM image of the titanium diboride powder prepared in Comparative Example 2.1.

[0041] Figure 3 This is a 1000x SEM image of the titanium diboride powder prepared in Comparative Example 2.2. Detailed Implementation

[0042] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0043] Example 1

[0044] 1. Preparation of titanium source

[0045] 12g of TiO2 powder was added to 110g of anhydrous ethanol and stirred until homogeneous to obtain a TiO2 powder liquid; 2.3g of tetrabutyl titanate was added to 25g of anhydrous ethanol and stirred until homogeneous to obtain a tetrabutyl titanate solution; 122g of TiO2 powder liquid was heated to 55℃, and then 27g of tetrabutyl titanate solution was added and stirred until homogeneous. Then, 22wt% ammonia solution was added to adjust the pH to 7.0, and the mixture was kept at this temperature and stirred for 2.7h. After stirring, the mixture was centrifuged and dried to obtain the titanium source.

[0046] The TiO2 powder has a D50 of 5 μm.

[0047] 2. Preparation of boron source

[0048] Add 4.4g of trimethyl borate to 42g of anhydrous ethanol, stir until homogeneous, then add 1.0g of tartaric acid, and continue stirring until homogeneous to obtain a mixture. Add 12g of B4C powder to 85g of anhydrous ethanol, and ultrasonically disperse for 35min at a power of 250W and a frequency of 38kHz. After ultrasonication, add 48g of the mixture at a rate of 1.2g / min. After addition, raise the temperature to 37℃, keep warm and stir for 3.8h, and then centrifuge and dry to obtain the boron source.

[0049] The B4C powder has a D50 of 8 μm.

[0050] 3. Mixing

[0051] Titanium source, boron source, graphite powder and polyethylene glycol 2000 are mixed and stirred evenly to obtain a mixed powder.

[0052] The mass ratio of the titanium source, boron source, graphite powder, and polyethylene glycol 2000 is 83:28:42:1.3.

[0053] The graphite powder has a D50 of 50 μm.

[0054] 4. Cold isostatic pressing

[0055] The mixed powder is loaded into a mold and held under pressure of 70 MPa for 5 minutes to obtain a green blank.

[0056] 5. Carbothermic reduction reaction

[0057] The blank was placed in a carbon tube furnace and heated to 2200℃ at a rate of 10℃ / min under an argon atmosphere. The temperature was held for 2 hours and then cooled to room temperature to obtain prismatic titanium diboride powder.

[0058] The titanium diboride powder prepared by the method in Example 1 is prismatic, with a purity of 99.31% and a density of 98.7%. After being kept at 1200°C in air for 24 hours, the mass change rate is 0.44%.

[0059] Example 2

[0060] 1. Preparation of titanium source

[0061] 10g of TiO2 powder was added to 100g of anhydrous ethanol and stirred until homogeneous to obtain a TiO2 powder liquid; 2g of tetrabutyl titanate was added to 20g of anhydrous ethanol and stirred until homogeneous to obtain a tetrabutyl titanate solution; 110g of TiO2 powder liquid was heated to 54℃, and then 22g of tetrabutyl titanate solution was added and stirred until homogeneous. 20wt% ammonia solution was added to adjust the pH to 7.0, and the mixture was kept at this temperature and stirred for 3.0h. After stirring, the mixture was centrifuged and dried to obtain the titanium source.

[0062] The TiO2 powder has a D50 of 3 μm.

[0063] 2. Preparation of boron source

[0064] Add 4.2g of trimethyl borate to 40g of anhydrous ethanol, stir until homogeneous, then add 0.8g of tartaric acid, and continue stirring until homogeneous to obtain a mixture. Add 10g of B4C powder to 80g of anhydrous ethanol, and ultrasonically disperse for 30min at a power of 270W and a frequency of 35kHz. After ultrasonication, add 45g of the mixture at a rate of 1.0g / min. After addition, raise the temperature to 36℃, keep warm and stir for 4.0h, and then centrifuge and dry to obtain the boron source.

[0065] The B4C powder has a D50 of 5 μm.

[0066] 3. Mixing

[0067] Titanium source, boron source, graphite powder and polyethylene glycol 2000 are mixed and stirred evenly to obtain a mixed powder.

[0068] The mass ratio of the titanium source, boron source, graphite powder, and polyethylene glycol 2000 is 80:27.5:40:1.0.

[0069] The graphite powder has a D50 of 30 μm.

[0070] 4. Cold isostatic pressing

[0071] The mixed powder is loaded into a mold and held under pressure of 30 MPa for 8 minutes to obtain a green blank.

[0072] 5. Carbothermic reduction reaction

[0073] The blank was placed in a carbon tube furnace and heated to 2000℃ at a rate of 7℃ / min under an argon atmosphere. The temperature was held for 3 hours and then cooled to room temperature to obtain prismatic titanium diboride powder.

[0074] The SEM image of the prismatic titanium diboride powder prepared in Example 2 at 1000x magnification is shown in the appendix to the instruction manual. Figure 1 ;

[0075] The titanium diboride powder prepared by the method in Example 2 is prismatic, with a purity of 99.58% and a density of 99.0%. After being kept at 1200°C in air for 24 hours, the mass change rate is 0.42%.

[0076] Example 3

[0077] 1. Preparation of titanium source

[0078] 8g of TiO2 powder was added to 90g of anhydrous ethanol and stirred until homogeneous to obtain a TiO2 powder liquid; 1.8g of tetrabutyl titanate was added to 18g of anhydrous ethanol and stirred until homogeneous to obtain a tetrabutyl titanate solution; 98g of TiO2 powder liquid was heated to 52℃, and then 20g of tetrabutyl titanate solution was added and stirred until homogeneous. Then, 18wt% ammonia solution was added to adjust the pH to 7.0, and the mixture was kept at this temperature and stirred for 3.2h. After stirring, the mixture was centrifuged and dried to obtain the titanium source.

[0079] The TiO2 powder has a D50 of 1 μm.

[0080] 2. Preparation of boron source

[0081] Add 4.0g of trimethyl borate to 38g of anhydrous ethanol, stir until homogeneous, then add 0.7g of tartaric acid, and continue stirring until homogeneous to obtain a mixture. Add 8g of B4C powder to 75g of anhydrous ethanol, and ultrasonically disperse for 25min at a power of 300W and a frequency of 32kHz. After ultrasonication, add 42g of the mixture at a rate of 0.8g / min. After addition, raise the temperature to 34℃, keep warm and stir for 4.2h, and then centrifuge and dry to obtain the boron source.

[0082] The B4C powder has a D50 of 3 μm.

[0083] 3. Mixing

[0084] Titanium source, boron source, graphite powder and polyethylene glycol 2000 are mixed and stirred evenly to obtain a mixed powder.

[0085] The mass ratio of the titanium source, boron source, graphite powder, and polyethylene glycol 2000 is 76:26:36:0.8.

[0086] The graphite powder has a D50 of 10 μm.

[0087] 4. Cold isostatic pressing

[0088] The mixed powder is loaded into a mold and held under pressure of 5 MPa for 10 minutes to obtain a green blank.

[0089] 5. Carbothermic reduction reaction

[0090] The blank was placed in a carbon tube furnace and heated to 1900℃ at a rate of 5℃ / min under an argon atmosphere. The temperature was held for 5 hours and then cooled to room temperature to obtain prismatic titanium diboride powder.

[0091] The titanium diboride powder prepared by the method in Example 3 is prismatic, with a purity of 98.74% and a density of 98.5%. After being kept at 1200°C in air for 24 hours, the mass change rate is 0.48%.

[0092] Comparative Example 2.1

[0093] 1. Mixing

[0094] Titanium source, boron source, graphite powder and polyethylene glycol 2000 are mixed and stirred evenly to obtain a mixed powder.

[0095] The titanium source is TiO2 powder with D50=3μm;

[0096] The boron source is B4C powder with D50 = 5 μm;

[0097] The graphite powder has a D50 of 30 μm.

[0098] The mass ratio of the titanium source, boron source, graphite powder, and polyethylene glycol 2000 is 80:27.5:40:1.0.

[0099] 2. Cold isostatic pressing

[0100] The mixed powder is loaded into a mold and held under pressure of 30 MPa for 8 minutes to obtain a green blank.

[0101] 3. Carbothermic reduction reaction

[0102] The blank was placed in a carbon tube furnace and heated to 2000℃ at a rate of 7℃ / min under an argon atmosphere. The temperature was held for 3 hours and then cooled to room temperature to obtain prismatic titanium diboride powder.

[0103] The SEM image of the prismatic titanium diboride powder prepared in Comparative Example 2.1 at 1000x magnification is shown in the attached instruction manual. Figure 2 .

[0104] The titanium diboride powder prepared by the method of Comparative Example 2.1 is prismatic, with a purity of 95.43% and a density of 93.1%. After being kept at 1200℃ in air for 24 hours, the mass change rate is 1.85%.

[0105] Comparative Example 2.1 used untreated TiO2 powder and B4C powder as titanium source and boron source, respectively. The interface between the two is highly inert and has strong agglomeration force, making it difficult for the carbothermic reduction reaction to proceed at high temperature, resulting in incomplete reaction and affecting the purity and density of the product, as well as poor stability in high-temperature air environment.

[0106] Comparative Example 2.2

[0107] 1. Mixing

[0108] Titanium source, boron source, graphite powder and polyethylene glycol 2000 are mixed and stirred evenly to obtain a mixed powder.

[0109] The titanium source is TiO2 powder with D50=3μm;

[0110] The boron source is B4C powder with D50 = 5 μm;

[0111] The graphite powder has a D50 of 30 μm.

[0112] The mass ratio of the titanium source, boron source, graphite powder, and polyethylene glycol 2000 is 80:27.5:40:1.0.

[0113] 2. Filling with powder

[0114] The mixed powder is loaded into a mold and then subjected to vibration treatment for 10 minutes, with a vibration frequency of 80 Hz and an amplitude of 1 mm, to obtain the powder to be reacted.

[0115] 3. Carbothermic reduction reaction

[0116] The powder to be reacted was placed in a carbon tube furnace and heated to 2000℃ at a rate of 7℃ / min under an argon atmosphere. The temperature was held for 3 hours and then cooled to room temperature to obtain prismatic titanium diboride powder.

[0117] The SEM image of the prismatic titanium diboride powder prepared in Comparative Example 2.2 at 1000x magnification is shown in the attached instruction manual. Figure 3 .

[0118] Comparative Example 2.2 omits the cold isostatic pressing method and uses a direct powder loading method, which cannot obtain prismatic titanium diboride, and the resulting product is spherical.

[0119] Unless otherwise specified, all proportions mentioned in this invention are mass proportions, and all percentages are mass percentages.

[0120] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing prismatic titanium diboride powder, characterized in that, This includes steps such as preparing a titanium source, preparing a boron source, mixing materials, cold isostatic pressing, and carbothermic reduction reaction. The steps for preparing the titanium source are as follows: heating an anhydrous ethanol solution of TiO2 powder to 52-55°C, adding tetrabutyl titanate solution, stirring evenly, adding ammonia solution to adjust the pH value to 7.0, and stirring for 2.7-3.2 hours to obtain the titanium source; The steps for preparing the boron source are as follows: B4C powder is added to anhydrous ethanol and ultrasonically dispersed; then a mixture is added, with the addition rate of the mixture controlled at 0.8-1.2 g / min; the temperature is raised to 34-37℃; and the mixture is kept warm and stirred for 3.8-4.2 h to obtain the boron source. The mixture is prepared by adding trimethyl borate to anhydrous ethanol, stirring until homogeneous, adding tartaric acid, and continuing to stir until homogeneous. The mixing step involves mixing titanium source, boron source, graphite powder and polyethylene glycol 2000, stirring until uniform, to obtain a mixed powder.

2. The method for preparing prismatic titanium diboride powder according to claim 1, characterized in that, In the step of preparing the titanium source, the mass ratio of the anhydrous ethanol solution of TiO2 powder to the tetrabutyl titanate solution is 98-122:20-27. The mass concentration of the ammonia solution is 18-22%.

3. The method for preparing prismatic titanium diboride powder according to claim 1, characterized in that, In the step of preparing the titanium source, the anhydrous ethanol solution of TiO2 powder is prepared by adding TiO2 powder into anhydrous ethanol and stirring evenly. The TiO2 powder has a D50 of 1-5 μm. In the anhydrous ethanol solution of TiO2 powder, the mass ratio of TiO2 powder to anhydrous ethanol is 8-12:90-110.

4. The method for preparing prismatic titanium diboride powder according to claim 1, characterized in that, In the step of preparing the titanium source, the tetrabutyl titanate solution is prepared by adding tetrabutyl titanate to anhydrous ethanol and stirring until homogeneous; The mass ratio of tetrabutyl titanate to anhydrous ethanol is 1.8-2.3:18-25.

5. The method for preparing prismatic titanium diboride powder according to claim 1, characterized in that, In the step of preparing the boron source, the mass ratio of anhydrous ethanol, B4C powder, and the mixed solution is 75-85:8-12:42-48.

6. The method for preparing prismatic titanium diboride powder according to claim 1, characterized in that, In the boron source preparation step, the B4C powder has a D50 of 3-8 μm. The mass ratio of anhydrous ethanol, trimethyl borate, and tartaric acid is 38-42:4.0-4.4:0.7-1.

0.

7. The method for preparing prismatic titanium diboride powder according to claim 1, characterized in that, In the mixing step, the mass ratio of the titanium source, boron source, graphite powder, and polyethylene glycol 2000 is 76-83:26-28:36-42:0.8-1.

3. The graphite powder has a D50 of 10-50 μm.

8. The method for preparing prismatic titanium diboride powder according to claim 1, characterized in that, The cold isostatic pressing step involves loading the mixed powder into a mold and holding it under pressure of 5-70 MPa for 5-10 minutes to obtain a green blank.

9. The method for preparing prismatic titanium diboride powder according to claim 1, characterized in that, The carbothermic reduction reaction step is as follows: the green blank is placed in a carbon tube furnace, heated to 1900-2200℃ at a rate of 5-10℃ / min under an argon atmosphere, held at the temperature for 2-5 hours, and cooled to room temperature to obtain prismatic titanium diboride powder.

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