Preparation method of prismatic titanium diboride powder

Abstract

The invention 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 titanium source preparation, boron source preparation, material mixing, cold isostatic pressing and carbon thermal reduction reaction. The step of preparing the titanium source comprises the following steps: heating TiO2 powder body liquid, raising the temperature to 52-55 DEG C, adding a tetrabutyl titanate solution, uniformly stirring, adding an ammonia water solution to adjust the pH value to 7.0, and carrying out heat preservation stirring for 2.7-3.2 hours to obtain the titanium source; the step of preparing the boron source comprises the following steps: adding B4C powder into absolute ethyl alcohol, carrying out ultrasonic dispersion, then adding a mixed solution, controlling the adding rate of the mixed solution to be 0.8-1.2 g / min, heating to 34-37 DEG C, and carrying out heat preservation and stirring for 3.8-4.2 hours to obtain the boron source; the titanium diboride powder obtained through the method is in a prism shape and is uniform in particle, high in density and purity and poor in high-temperature oxidation resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium diboride powder, and particularly relates to a method for preparing prismatic titanium diboride powder. Background Art

[0002] Titanium diboride is a high-performance ceramic material with a melting point of over 3000°C, a Vickers hardness of ≥34GPa, and excellent electrical and thermal conductivity. Titanium diboride plays a key role in many fields due to its outstanding performance. In the field of metal / ceramic composites, titanium diboride can be used 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 for cathode coatings in aluminum electrolytic cells and has good resistance to molten salt corrosion. In the field of ultra-high temperature components, it can be used as a thermal protection material for spacecraft.

[0003] In practical applications, the morphology of powders has a significant impact on the performance of composite materials. Traditional spherical or irregular titanium diboride powders are prone to accumulation in composite materials, resulting in weak interfacial bonding and anisotropic performance, thus affecting the overall performance of the composite materials.

[0004] Prismatic titanium diboride, due to its regular crystal plane orientation, can significantly improve the fracture toughness and load transfer efficiency of the composite material, ultimately improving the stability of the composite material; Therefore, the preparation of prismatic titanium diboride powder has important research significance and application value.

[0005] The existing large-scale preparation processes of titanium diboride mainly include direct chemical reaction method, sol-gel method and carbothermal reduction method; The direct chemical reaction method involves 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, and a dominant lamellae morphology. Although the sol-gel method can control nano-scale powders, the process is complex, the boron source utilization rate is as low as 85%, and hard agglomerates appear after calcination. Conventional carbothermal reduction mainly uses TiO2, B2O3, and C, but gaseous B2O3 escapes in the reaction zone, resulting in a loss of control of the stoichiometric ratio. TiO2 or Ti3B4 impurity phases often remain in the product, and the impurity content is relatively high.

[0006] It is particularly noteworthy that the existing technology has weak control over crystal morphology. Prismatic growth relies on the control of gas-solid reaction interface energy, but the uneven density of traditional powder compacts (<55% theoretical density) hinders the mass transfer process, resulting in a narrow reaction temperature window (±20°C), making it difficult to achieve stable control of the axial preferential growth of crystals. Summary of the Invention

[0007] In order to solve the technical problems existing in the prior art, the present 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 the impurity content.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for preparing prismatic titanium diboride powder includes the steps of preparing a titanium source, preparing a boron source, mixing, cold isostatic pressing, and carbothermal reduction. The specific operations are as follows: 1. Preparation of Titanium Source The TiO2 powder is placed in anhydrous ethanol and stirred to obtain a TiO2 powder liquid; tetrabutyl titanate is added to the anhydrous ethanol and stirred to obtain a tetrabutyl titanate solution; the TiO2 powder liquid is heated to 52-55°C, and then the tetrabutyl titanate solution is added and stirred to obtain a titanium source; an ammonia solution is added to adjust the pH value to 7.0, and the mixture is stirred at this temperature for 2.7-3.2 hours. After the stirring is completed, the mixture is centrifuged and dried to obtain a titanium source; The TiO2 powder has a D50 of 1-5 μm; In the TiO2 powder liquid, the mass ratio of TiO2 powder to anhydrous ethanol is 8-12:90-110; In the tetrabutyl titanate solution, the mass ratio of tetrabutyl titanate to anhydrous ethanol is 1.8-2.3:18-25; The mass ratio of the TiO2 powder liquid and tetrabutyl titanate solution is 98-122:20-27; The mass concentration of the ammonia solution is 18-22%.

[0009] 2. Preparation of Boron Source Add trimethyl borate to anhydrous ethanol, stir evenly, then add tartaric acid, and continue stirring to obtain a mixed solution; add B4C powder to anhydrous ethanol, and ultrasonically disperse for 25-35 minutes at an ultrasonic power of 250-300W and an ultrasonic frequency of 32-38kHz. After the ultrasonication is completed, add the mixed solution at a rate of 0.8-1.2g / min. After the addition is completed, raise the temperature to 34-37°C, keep stirring at this temperature for 3.8-4.2 hours, and centrifuge to obtain a boron source; The B4C powder has a D50 of 3-8 μm; In the mixed solution, the mass ratio of anhydrous ethanol, trimethyl borate, and tartaric acid is 38-42:4.0-4.4:0.7-1.0; The mass ratio of the anhydrous ethanol, B4C powder and mixed liquid is 75-85:8-12:42-48.

[0010] 3. Mixing Mixing titanium source, boron source, graphite powder and polyethylene glycol 2000, stirring evenly to obtain a mixed powder; The mass ratio of the titanium source, the boron source, the graphite powder and the polyethylene glycol 2000 is 76-83:26-28:36-42:0.8-1.3; The graphite powder has a D50 of 10-50 μm.

[0011] 4.Cold isostatic pressing The mixed powder is placed into a mold and maintained at a pressure of 5-70 MPa for 5-10 minutes to obtain a green body.

[0012] 5.Carbothermal reduction reaction The green body is placed in a carbon tube furnace, and in an argon atmosphere, the temperature is raised to 1900-2200° C. at a rate of 5-10° C. / min, kept at this temperature for 2-5 hours, and cooled to room temperature to obtain prismatic titanium diboride powder.

[0013] Compared with the prior art, the present invention has achieved the following beneficial effects: 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 temperatures on the other hand. After cold isostatic pressing, the channel for volatilization of B2O3 vapor in the raw material becomes narrower, and the contact time between the gas-solid reaction phase is prolonged, which promotes the reaction, thereby making the titanium diboride grow more fully along the axial direction, thereby obtaining uniform prismatic titanium diboride particles; During the preparation process, the present invention uses titanium dioxide powder and tetrabutyl titanate as a composite titanium source, and coats the surface of the titanium dioxide powder by hydrolyzing tetrabutyl titanate, thereby improving the reaction activity of the titanium dioxide powder, avoiding local agglomeration, and further forming prismatic titanium diboride with regular properties, 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 the boron carbide, enhancing the reaction activity, ensuring close bonding between particles in subsequent reactions, improving the density of the product, promoting the reaction to proceed in the forward direction, reducing the introduction of impurities, and improving thermal conductivity and high-temperature stability. 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%; 3. The prismatic titanium diboride prepared by the method of the present invention is kept at 1200° C. in an air atmosphere for 24 hours, and the mass change rate is 0.42-0.48%. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a SEM image of the titanium diboride powder prepared in Example 2 at 1000 times magnification; Figure 2 This is a SEM image of the titanium diboride powder prepared in Comparative Example 2.1 at 1000 times magnification; Figure 3 This is a SEM image of the titanium diboride powder prepared in Comparative Example 2.2 at 1000 times magnification. DETAILED DESCRIPTION

[0015] In order to more clearly understand the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described.

[0016] Example 1 1. Preparation of Titanium Source 12 g of TiO2 powder was added to 110 g of anhydrous ethanol and stirred to obtain a TiO2 powder liquid; 2.3 g of tetrabutyl titanate was added to 25 g of anhydrous ethanol and stirred to obtain a tetrabutyl titanate solution; 122 g of the TiO2 powder liquid was heated to 55°C, and then 27 g of the tetrabutyl titanate solution was added and stirred to obtain a titanium source; 22 wt% ammonia solution was added to adjust the pH value to 7.0, and the mixture was stirred at this temperature for 2.7 h. After the stirring was completed, the mixture was centrifuged and dried to obtain a titanium source; The TiO2 powder has a D50 of 5 μm.

[0017] 2. Preparation of Boron Source To 42 g of anhydrous ethanol, 4.4 g of trimethyl borate was added, and after stirring, 1.0 g of tartaric acid was added, and stirring was continued to obtain a mixed solution; 12 g of B4C powder was added to 85 g of anhydrous ethanol, and ultrasonic dispersion was performed for 35 min at an ultrasonic power of 250 W and an ultrasonic frequency of 38 kHz. After the ultrasonic dispersion was completed, 48 g of the mixed solution was added at a rate of 1.2 g / min. After the addition was completed, the temperature was raised to 37°C, the mixture was stirred at this temperature for 3.8 h, and the boron source was obtained by centrifugal drying; The B4C powder has a D50 of 8 μm.

[0018] 3. Mixing Mixing titanium source, boron source, graphite powder and polyethylene glycol 2000, stirring evenly to obtain a mixed powder; The mass ratio of the titanium source, boron source, graphite powder and polyethylene glycol 2000 is 83:28:42:1.3; The graphite powder has a D50 of 50 μm.

[0019] 4.Cold isostatic pressing The mixed powder was placed into a mold and maintained at a pressure of 70 MPa for 5 minutes to obtain a green body.

[0020] 5.Carbothermal reduction reaction The blank was placed in a carbon tube furnace, heated to 2200° C. at a rate of 10° C. / min in an argon atmosphere, kept at this temperature for 2 hours, and cooled to room temperature to obtain prismatic titanium diboride powder.

[0021] The titanium diboride powder prepared by the method of Example 1 is prismatic, has a purity of 99.31%, a density of 98.7%, and a mass change rate of 0.44% after being kept at 1200° C. in an air atmosphere for 24 hours.

[0022] Example 2 1. Preparation of Titanium Source 10 g of TiO2 powder was added to 100 g of anhydrous ethanol and stirred to obtain a TiO2 powder liquid; 2 g of tetrabutyl titanate was added to 20 g of anhydrous ethanol and stirred to obtain a tetrabutyl titanate solution; 110 g of the TiO2 powder liquid was heated to 54°C, and then 22 g of the tetrabutyl titanate solution was added and stirred to obtain a titanium source; 20 wt% ammonia solution was added to adjust the pH value to 7.0, and the mixture was stirred for 3.0 h. After the stirring was completed, the mixture was centrifuged and dried to obtain a titanium source; The TiO2 powder has a D50 of 3 μm.

[0023] 2. Preparation of Boron Source To 40 g of anhydrous ethanol, 4.2 g of trimethyl borate was added, and after stirring, 0.8 g of tartaric acid was added, and stirring was continued to obtain a mixed solution; 10 g of B4C powder was added to 80 g of anhydrous ethanol, and ultrasonic dispersion was performed for 30 min at an ultrasonic power of 270 W and an ultrasonic frequency of 35 kHz. After the ultrasonic dispersion was completed, 45 g of the mixed solution was added at a rate of 1.0 g / min. After the addition was completed, the temperature was raised to 36°C, the mixture was stirred at this temperature for 4.0 h, and the boron source was obtained by centrifugal drying; The B4C powder has a D50 of 5 μm.

[0024] 3. Mixing Mixing titanium source, boron source, graphite powder and polyethylene glycol 2000, stirring evenly to obtain a mixed powder; The mass ratio of the titanium source, boron source, graphite powder and polyethylene glycol 2000 is 80:27.5:40:1.0; The graphite powder has a D50 of 30 μm.

[0025] 4.Cold isostatic pressing The mixed powder was placed into a mold and maintained at a pressure of 30 MPa for 8 minutes to obtain a green body.

[0026] 5.Carbothermal reduction reaction The green body was placed in a carbon tube furnace, heated to 2000° C. at a rate of 7° C. / min in an argon atmosphere, kept at this temperature for 3 hours, and cooled to room temperature to obtain prismatic titanium diboride powder.

[0027] The SEM image of the prismatic titanium diboride powder obtained in Example 2 at 1000 times magnification is shown in the appendix of the specification. Figure 1 ; The titanium diboride powder prepared by the method of Example 2 is prismatic, has a purity of 99.58%, a density of 99.0%, and a mass change rate of 0.42% after being heated at 1200° C. in an air atmosphere for 24 hours.

[0028] Example 3 1. Preparation of Titanium Source 8 g of TiO2 powder was added to 90 g of anhydrous ethanol and stirred to obtain a TiO2 powder liquid; 1.8 g of tetrabutyl titanate was added to 18 g of anhydrous ethanol and stirred to obtain a tetrabutyl titanate solution; 98 g of the TiO2 powder liquid was heated to 52°C, and then 20 g of the tetrabutyl titanate solution was added and stirred to obtain a titanium source; 18 wt% ammonia solution was added to adjust the pH value to 7.0, and the mixture was stirred for 3.2 h. After the stirring was completed, the mixture was centrifuged and dried to obtain a titanium source; The TiO2 powder has a D50 of 1 μm.

[0029] 2. Preparation of Boron Source To 38 g of anhydrous ethanol, add 4.0 g of trimethyl borate, stir evenly, add 0.7 g of tartaric acid, and continue stirring to obtain a mixed solution; to 75 g of anhydrous ethanol, add 8 g of B4C powder, ultrasonically disperse for 25 min, the ultrasonic power is 300 W, and the ultrasonic frequency is 32 kHz. After the ultrasonication is completed, add 42 g of the mixed solution at a rate of 0.8 g / min. After the addition is completed, raise the temperature to 34 ° C, keep stirring for 4.2 h, and centrifuge to obtain a boron source; The B4C powder has a D50 of 3 μm.

[0030] 3. Mixing Mixing titanium source, boron source, graphite powder and polyethylene glycol 2000, stirring evenly to obtain a mixed powder; The mass ratio of the titanium source, boron source, graphite powder and polyethylene glycol 2000 is 76:26:36:0.8; The graphite powder has a D50 of 10 μm.

[0031] 4.Cold isostatic pressing The mixed powder was placed into a mold and maintained at a pressure of 5 MPa for 10 min to obtain a green body.

[0032] 5.Carbothermal reduction reaction The green body was placed in a carbon tube furnace, heated to 1900° C. at a rate of 5° C. / min in an argon atmosphere, kept at this temperature for 5 hours, and cooled to room temperature to obtain prismatic titanium diboride powder.

[0033] The titanium diboride powder prepared by the method of Example 3 is prismatic, has a purity of 98.74%, a density of 98.5%, and a mass change rate of 0.48% after being kept at 1200° C. in an air atmosphere for 24 hours.

[0034] Comparative Example 2.1 1. Mixing Mixing titanium source, boron source, graphite powder and polyethylene glycol 2000, stirring evenly to obtain a mixed powder; The titanium source is TiO2 powder, D50=3μm; The boron source is B4C powder, D50=5μm; The graphite powder, D50=30 μm; The mass ratio of the titanium source, the boron source, the graphite powder and the polyethylene glycol 2000 is 80:27.5:40:1.0.

[0035] 2. Cold isostatic pressing The mixed powder was placed into a mold and maintained at a pressure of 30 MPa for 8 minutes to obtain a green body.

[0036] 3.Carbothermal reduction reaction The green body was placed in a carbon tube furnace, heated to 2000° C. at a rate of 7° C. / min in an argon atmosphere, kept at this temperature for 3 hours, and cooled to room temperature to obtain prismatic titanium diboride powder.

[0037] The SEM image of the prismatic titanium diboride powder obtained in Comparative Example 2.1 at 1000 times magnification is shown in the appendix of the specification. Figure 2 .

[0038] The titanium diboride powder prepared by the method of Comparative Example 2.1 is prismatic, has a purity of 95.43%, a density of 93.1%, and a mass change rate of 1.85% when heated at 1200° C. in an air atmosphere for 24 hours.

[0039] Comparative Example 2.1 used untreated TiO2 powder and B4C powder as titanium source and boron source, respectively. The interface between the two was highly inert and had strong agglomeration, making it difficult for the carbon thermal reduction reaction to proceed at high temperature, resulting in incomplete reaction, which in turn affected the purity and density of the product, and had poor stability in a high-temperature air environment.

[0040] Comparative Example 2.2 1. Mixing Mixing titanium source, boron source, graphite powder and polyethylene glycol 2000, stirring evenly to obtain a mixed powder; The titanium source is TiO2 powder, D50=3μm; The boron source is B4C powder, D50=5μm; The graphite powder, D50=30 μm; The mass ratio of the titanium source, the boron source, the graphite powder and the polyethylene glycol 2000 is 80:27.5:40:1.0.

[0041] 2. Filling powder The mixed powder was placed in a mold and then vibrated for 10 min at a frequency of 80 Hz and an amplitude of 1 mm to obtain a powder to be reacted.

[0042] 3.Carbothermal reduction reaction The powder to be reacted was placed in a carbon tube furnace, heated to 2000° C. at a rate of 7° C. / min under an argon atmosphere, kept warm for 3 h, and cooled to room temperature to obtain prismatic titanium diboride powder.

[0043] The SEM image of the prismatic titanium diboride powder obtained in Comparative Example 2.2 at 1000 times magnification is shown in the appendix of the specification. Figure 3 .

[0044] Comparative Example 2.2 omitted the cold isostatic pressing method and adopted a direct powder filling method, which failed to obtain prismatic titanium diboride and the obtained product was spherical.

[0045] Unless otherwise specified, all ratios and percentages described in the present invention are by mass.

[0046] Finally, it should be noted that the above 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 aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing prismatic titanium diboride powder, characterized in that: The method comprises the steps of preparing a titanium source, preparing a boron source, mixing materials, cold isostatic pressing and carbon thermal reduction reaction; The titanium source preparation step comprises heating the TiO2 powder liquid to 52-55° C., adding tetrabutyl titanate solution, stirring evenly, adding ammonia solution to adjust the pH value to 7.0, and maintaining the temperature and stirring for 2.7-3.2 hours to obtain the titanium source; The steps of preparing the boron source are as follows: adding B4C powder to anhydrous ethanol, performing ultrasonic dispersion, then adding the mixed solution, controlling the addition rate of the mixed solution to 0.8-1.2 g / min, heating to 34-37° C., and stirring at this temperature for 3.8-4.2 hours to obtain the boron source.

2. The method for preparing prismatic titanium diboride powder according to claim 1, wherein: In the step of preparing the titanium source, the mass ratio of the TiO2 powder liquid 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, wherein: In the step of preparing the titanium source, the TiO2 powder liquid is prepared by adding TiO2 powder into anhydrous ethanol and stirring evenly; The TiO2 powder has a D50 of 1-5 μm; In the TiO2 powder liquid, 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, wherein: In the step of preparing the titanium source, the tetrabutyl titanate solution is prepared by adding tetrabutyl titanate to anhydrous ethanol and stirring uniformly; 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, wherein: In the step of preparing the boron source, the mass ratio of the 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, wherein: In the step of preparing the boron source, the mixed solution is prepared by adding trimethyl borate to anhydrous ethanol, stirring evenly, adding tartaric acid, and continuing to stir evenly; The B4C powder has a D50 of 3-8 μm; The mass ratio of the 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, wherein: The mixing step comprises mixing a titanium source, a boron source, graphite powder and polyethylene glycol 2000, and stirring them uniformly to obtain a mixed powder; The mass ratio of the titanium source, the boron source, the graphite powder and the 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, wherein: The cold isostatic pressing step comprises: placing the mixed powder into a mold, maintaining the pressure at a pressure of 5-70 MPa for 5-10 minutes, and obtaining a green blank.

9. The method for preparing prismatic titanium diboride powder according to claim 1, wherein: The carbon thermal reduction reaction step is to place the green body into a carbon tube furnace, heat it to 1900-2200° C. at a rate of 5-10° C. / min under an argon atmosphere, keep it warm for 2-5 hours, and cool it to room temperature to obtain prismatic titanium diboride powder.

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