A preparation method of fine spherical hafnium boride, hafnium boride
Through high-frequency current-induced coupling plasma spheroidization technology, hafnium boronide powder is heated and quenched to cool, which solves the problem of difficulty in forming spherical particles in the prior art, achieves high spherical degree and improved processing performance, and expands the application of hafnium boronide in various fields.
Patent Information
- Application Number
- CN202411889429.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-04-04
AI Technical Summary
The existing synthesis method of hafnium boride is difficult to form spherical particles, which leads to difficulties in the pressing process, affecting its subsequent sintering and forming effect.
The electromagnetic force formed by high-frequency current induction coupling acts on the gas medium, ionizes the gas in a plasma state, and adjusts the plasma parameters, heats, quenches, and cures the raw material of hafnium boronide powder to obtain fine spherical hafnium boronide powder. Specific operations include controlling the gas input flow, loading voltage and current in the plasma reactor, injecting hafnium boride powder into the high-temperature zone using carousel gas, and heating to more than 50% of the weight of the particles and forming hafnium boride powder particles with high spherical shape with the aid of surface tension.
The high spherical shape of hafnium boride powder has been achieved, its fluidity, filling and sintering properties have been improved, and its application potential in various fields has been expanded.
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Figure CN119750602A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the technical field of hafnium boride preparation, and more specifically, to a preparation method of fine spherical hafnium boride and hafnium boride powder. Background Art
[0002] Hafnium boride (HfB2) is a compound with excellent properties. Its melting point is as high as 3250℃, and its Vickers hardness is between 2500-3000HV. It has high thermal conductivity and good chemical stability. Its crystal structure is hexagonal, and its graphite-like layered structure makes its performance still stable under extreme conditions.
[0003] In the field of electronic devices, hafnium boride can be used as a heat dissipation material for integrated circuits due to its good electrical and thermal conductivity, which can reduce the operating temperature of the device and improve stability and reliability. It can also be used as an emitter material for field emission displays, with advantages such as high brightness, high resolution and long life. In the field of high-temperature structural materials, its high melting point, high hardness and chemical stability make it possible to use it as a thermal protection coating material for aircraft engines and rocket engines to resist high-temperature oxidation and corrosion. It can also be used as a neutron absorption material for nuclear reactors, with good neutron absorption capacity and thermal stability. In addition, it also has potential application value in the fields of superconducting material doping, catalyst carriers, optical materials and coating materials.
[0004] However, the synthesis of hafnium boride is usually prepared by molten salt electrolysis, using hafnium dioxide, boron carbide, graphite, and amorphous boron as raw materials, and through carbon thermal / borothermal reduction reactions. Although the hafnium boride powder obtained by this method has high purity and good dispersibility, its high purity leads to high surface energy, strong interaction between particles, small particle size and narrow distribution range, making it difficult to form spherical particles during the pressing process, which makes subsequent sintering and molding difficult. Therefore, it is of great significance to study the method of preparing fine spherical hafnium boride powder by radio frequency plasma spheroidization equipment. Summary of the invention
[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing fine spherical hafnium boride and hafnium boride powder, so as to improve the sphericity of the hafnium boride powder, thereby improving its fluidity, filling and sintering properties, etc., and expand its application in various fields.
[0006] To achieve the above objectives, the present disclosure provides the following technical solutions:
[0007] On the one hand, the present application provides a method for preparing fine spherical hafnium boride, the preparation method comprising the following steps:
[0008] The electromagnetic force formed by high-frequency current inductive coupling acts on the gas medium, ionizing the gas into a plasma state;
[0009] Adjust the plasma parameters, heat the hafnium boride powder raw material, rapidly cool it and solidify it, and then separate it to obtain fine spherical hafnium boride powder. The specific operation is as follows:
[0010] Into the plasma reactor, the flow rate of the middle gas input is controlled at 40-50 L / min, the flow rate of the side gas input is 125-145 L / min, the anode voltage of 8.5 kv, the anode current of 7 A, and the grid current of 14 A are loaded on the induction coil, and the igniter discharges at the same time, and the argon gas is ionized to produce an argon plasma torch through the inductive coupling of the high-voltage coil and the corona triggering of the igniter, and the entire plasma reactor is kept in a negative pressure state, and the system negative pressure is 110 mm Hg to 230 mm Hg;
[0011] Irregular hafnium boride powder is injected into the core high temperature zone of an argon plasma torch using a carrier gas. The heating carrier gas input flow rate is 6 L / min, and the hydrogen input flow rate is 8.5-10 L / min. The carrier gas is selected to be a gas that does not chemically react with metal powder in a high temperature environment. The heating time ends as the gas-powder flow "flies away" from the plasma torch, and the duration is 140 milliseconds to 170 milliseconds. The hafnium boride powder absorbs heat in the core high temperature zone, and the particle surface melts. When at least 50% of the particle weight is melted, hafnium boride powder particles with high sphericity are formed with the help of surface tension.
[0012] Furthermore, the carrying gas is a mixed gas of argon and hydrogen.
[0013] Furthermore, the middle gas input flow rate is 40 L / min, the side gas input flow rate is 125 L / min, the hydrogen input flow rate is 8.5 L / min, and the heating time is 140 milliseconds.
[0014] Furthermore, the middle gas input flow rate is 50 L / min, the side gas input flow rate is 145 L / min, the hydrogen input flow rate is 10 L / min, and the heating time is 170 milliseconds.
[0015] Furthermore, the system negative pressure is 110 mm Hg.
[0016] Furthermore, the system negative pressure is 230 mm Hg.
[0017] Furthermore, the injected hafnium boride powder is rapidly heated and melted under the action of four heat transfer mechanisms: radiation, convection, conduction and chemistry. When at least 50% of the total weight of the injected hafnium boride powder is melted, the molten particles form highly spherical droplets under the action of surface tension, and are rapidly cooled under an extremely high temperature gradient and enter a heat exchange chamber for rapid solidification, thereby forming spherical particles.
[0018] Furthermore, the preparation method also includes: after the spheroidization is completed, the gas is extracted, processed and discharged, and the spheroidized powder enters a collection tank for automatic metering and collection.
[0019] Furthermore, the hafnium boride powder raw material is a hafnium boride powder with high purity and narrow particle size distribution prepared by molten salt electrolysis.
[0020] Another aspect of the present application provides a hafnium boride powder obtained by any of the above-mentioned preparation methods; the spheroidization rate of the hafnium boride powder is ≥80%.
[0021] In summary, the present disclosure has the following beneficial effects:
[0022] 1) Maintaining material properties: Hafnium boride has a high melting point (about 3250-3380°C) and chemical stability, which helps maintain particle integrity and performance during the spheroidization process. Its good electrical and thermal conductivity may be further optimized after spheroidization, making spherical hafnium boride particles potentially applicable in electronics, thermal management and other fields. 2) Improving processing performance: The spheroidized hafnium boride powder significantly improves fluidity and filling properties, and the contact area and friction between spherical particles are reduced, which is conducive to powder flow and filling, and is crucial to improving the uniformity and efficiency of the material processing process. 3) Optimizing sintering performance: Hafnium boride is difficult to sinter and densify due to its high melting point and strong covalent bond characteristics. Spheroidization can improve its sintering performance to a certain extent. Although it usually needs to be combined with other sintering processes and additives, it provides the possibility of improving the sintering effect. 4) Realizing customized production: The spheroidization process of hafnium boride can be customized according to customer needs, including the adjustment of parameters such as particle size, purity, and shape, which can meet the diverse needs of different application fields.
[0023] Compared with the traditional mechanical spheroidization method, the present invention avoids the introduction of impurities and the damage to material properties, and can achieve higher sphericity and uniformity. Compared with complex and expensive methods such as chemical vapor deposition, the process of the present invention is relatively simple, the equipment cost is low, and it is more conducive to large-scale production, providing a feasible solution for the industrial application of hafnium boride spheroidization. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 The figure is a schematic diagram of the process of preparing fine spherical hafnium boride according to an embodiment of the present disclosure. DETAILED DESCRIPTION
[0025] The present disclosure is further described in detail below in conjunction with the accompanying drawings.
[0026] This specific embodiment is merely an explanation of the present disclosure and is not a limitation of the present disclosure. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.
[0027] The present invention discloses a method for preparing fine spherical hafnium boride, comprising the following steps:
[0028] S1, the electromagnetic force formed by high-frequency current inductive coupling acts on the gas medium, ionizing the gas into a plasma state;
[0029] S2, adjusting the plasma parameters, heating the hafnium boride powder raw material, rapidly cooling and solidifying it, and then separating it to obtain fine spherical hafnium boride powder. The specific operation is as follows:
[0030] S21, the input flow rate of the middle gas to the plasma reactor is 40-50L / min, the input flow rate of the side gas is 125-145L / min, the anode voltage loaded on the induction coil is 8.5kv, the anode current is 7A, and the grid current is 14A. At the same time, the igniter discharges, the high-voltage coil is inductively coupled and the igniter corona is triggered, so that the argon gas is ionized to produce an argon plasma torch. At this time, the entire plasma reactor is kept in a negative pressure state, and the system negative pressure is 110mmHg to 230mmHg, which can ensure the stable operation of the plasma torch.
[0031] S22, using a carrier gas to inject irregular hafnium boride powder (raw powder) into the core high temperature zone of an argon plasma torch for heating. The input flow rate of the carrier gas is 6L / min, and the input flow rate of hydrogen is 8.5-10L / min. The carrier gas can be argon, hydrogen, or other gases that do not chemically react with metal powders in a high temperature environment. The heating time ends as the gas-powder flow "flies away" from the plasma torch, and the duration is only 140 milliseconds to 170 milliseconds. The hafnium boride powder is fed into the core high temperature zone of the plasma torch, absorbs a large amount of heat, and the surface of the particles begins to melt. When 50% (at least) of the weight of the particles is melted, due to the effect of surface tension, hafnium boride powder particles with a high degree of sphericity are formed.
[0032] The specific steps are as follows:
[0033] 1. Use a Roots vacuum pump to evacuate the vacuum to less than or equal to 5.0×10-1Pa; use an oil diffusion vacuum pump to evacuate the vacuum to less than or equal to 1.0×10-4Pa; fill the prepared device with argon gas with a purity of more than 99.995%; use a water ring vacuum pump to maintain the vacuum within the range of (1.0×104±200)Pa;
[0034] 2. The input flow rate of the center gas to the plasma reactor is 40-50L / min, the input flow rate of the side gas is 125-145L / min, the anode voltage loaded on the induction coil is 8.5kv, the anode current is 7A, and the grid current is 14A. At the same time, the igniter discharges, the high-voltage coil is inductively coupled, and the igniter corona is triggered to ionize the argon gas to produce an argon plasma torch. At this time, the entire plasma reactor is kept in a negative pressure state. The system negative pressure is 110mmHg to 230mmHg, which can ensure the stable operation of the plasma torch.
[0035] 3. Use a carrier gas to inject irregular hafnium boride powder (raw powder) into the core high temperature zone of an argon plasma torch for heating. The input flow rate of the carrier gas is 6 L / min, and the input flow rate of hydrogen is 8.5 to 10 L / min. The carrier gas can be argon, hydrogen, or other gases that do not react chemically with metal powders in a high temperature environment. The heating time ends as the gas-powder flow "flies away" from the plasma torch, and the duration is only 140 to 170 milliseconds. The hafnium boride powder is fed into the core high temperature zone of the plasma torch, absorbing a large amount of heat, and the particle surface begins to melt. When 50% (at least) of the particle weight is melted, due to the effect of surface tension, hafnium boride powder particles with a high degree of sphericity are formed.
[0036] 4. The heated and melted hafnium boride powder droplets are cooled and solidified to form spherical hafnium boride powder. Under the action of four heat transfer mechanisms, radiation, convection, conduction and chemistry, the particles are rapidly heated and melted. When the particles are melted to at least 50% (by weight), the molten particles form highly spherical droplets under the action of surface tension and are spherical at extremely high temperature gradients (10 -6 K / m) and enter the heat exchange chamber for rapid solidification, thus forming spherical particles. As long as the process parameters are set appropriately, the spheroidization rate can reach 80%.
[0037] 5. Extract the gas and collect the spherical hafnium boride; after the spheroidization process is completed, the gas is extracted, processed and discharged, and the spheroidized powder enters the collection tank for automatic measurement and collection.
[0038] Example 1
[0039] 1) Equipment preparation and pretreatment
[0040] Prepare the RF plasma spheroidization equipment. First, use a Roots vacuum pump to evacuate the equipment until the vacuum degree reaches 5.0×10 -1 Pa. Then switch to the oil diffusion vacuum pump to continue evacuating until the vacuum degree is reduced to 1.0×10 -4 Pa. Then, argon gas with a purity of 99.995% was filled into the equipment, and finally the vacuum degree in the equipment was stabilized at 1.0×10 4Pa. Check whether the various parts of the equipment are tightly connected to ensure that there is no gas leakage, etc. Accurately load the anode voltage of 8.5kv, anode current of 7A, and grid current of 14A on the induction coil to prepare for the plasma torch generation operation.
[0041] 2) Generation and optimization of plasma torch
[0042] Start the igniter discharge, and at the same time, the high-voltage coil inductive coupling and the igniter corona trigger, so that the argon gas is ionized to produce an argon plasma torch. Closely observe the shape, color and stability of the plasma torch, and use professional testing equipment to monitor the temperature, density and other parameters of the plasma. By fine-tuning the gas flow and voltage and current parameters, the plasma torch reaches the optimal state. Adjust the middle gas flow to 40L / min, the side gas flow to 125L / min, and the system negative pressure to 110mm Hg to ensure that the plasma torch burns stably and all parameters meet expectations, providing a stable high-temperature environment for the spheroidization of hafnium boride powder.
[0043] 3) Heating and spheroidization of hafnium boride powder
[0044] A specific batch of high-purity, narrow particle size distribution hafnium boride powder is selected, and the carrier gas (argon and hydrogen mixture, hydrogen flow rate is 8.5L / min) is fully mixed with the hafnium boride powder. The powder is evenly injected into the core high-temperature area of the argon plasma torch using the gas carrying effect, and the heating carrier gas flow rate is maintained at 6L / min. The heating condition of the powder in the high-temperature area and the change of the particle state are observed in real time through monitoring equipment such as high-precision temperature sensors and high-speed cameras. The heating time is strictly controlled to 140 milliseconds to ensure that the particles are efficiently spheroidized with the help of surface tension in a suitable melting state.
[0045] 4) Cooling, solidification and collection
[0046] The spheroidized particle droplets are rapidly cooled, quenched and solidified in the heat exchange chamber under the combined action of radiation, convection, conduction and chemical heat transfer mechanisms to form spherical hafnium boride powder. The spherical hafnium boride powder obtained is collected and its key parameters such as spheroidization rate, particle size, particle size distribution, crystal structure, purity, etc. are detected using advanced detection equipment such as scanning electron microscope (SEM), particle size analyzer, and X-ray diffractometer (XRD). In this embodiment, the spheroidization rate reaches 80%, the particle size distribution is within the expected range, the crystal structure is complete, the purity remains basically unchanged compared with the original powder, and the fluidity and filling properties of the spherical particles are significantly improved compared with the original powder. The filling efficiency is increased by 12% in the simulated filling experiment, and the flow rate is increased by 18% in the powder fluidity test, indicating that the spheroidization effect is good and the processing performance is significantly improved.
[0047] Example 2
[0048] 1) Parameter adjustment and equipment inspection
[0049] Adjust the plasma reactor's middle gas input flow rate to 50L / min, the side gas input flow rate to 145L / min, and the system negative pressure to 230mmHg. Check the equipment status again, including the air tightness of each pipeline, the cleanliness of the electrode, and the electrical performance of the equipment, to ensure the normal operation of the equipment and prepare for the spheroidization operation of the hafnium boride powder.
[0050] 2) Powder spheroidization process control
[0051] Another batch of hafnium boride powder was mixed with a carrier gas (argon and hydrogen mixed, hydrogen flow rate of 10L / min), and then injected into the high temperature area of the plasma torch core at a precise flow rate and pressure, and the heating carrier gas flow rate was still 6L / min. The advanced control system strictly controlled the heating time to 170 milliseconds, so that the hafnium boride powder particles fully absorbed heat in the high temperature area, and the particle surface melted to 55% of the weight (real-time monitoring by thermal analysis technology), and formed particles with extremely high sphericity with the help of surface tension.
[0052] 3) Post-processing and comprehensive testing
[0053] The spheroidized powder is collected after cooling and solidification, and the collected spherical hafnium boride powder is comprehensively tested using a variety of analytical testing methods. In this embodiment, the spheroidization rate reaches 80.5%, the particle size distribution is more uniform, the purity meets the requirements, and the impurity content is further reduced. In the simulated sintering experiment, compared with the unspheroidized hafnium boride powder, the sintering starting temperature is reduced by 5°C, and the density of the sintered body is increased by 8%, indicating that the spheroidization treatment has a significant improvement in the sintering performance. At the same time, the spherical particles have good fluidity and show higher filling efficiency in the simulated filling experiment. Compared with the unspheroidized hafnium boride powder, the processing performance is significantly improved, providing a better material basis for its application in high-temperature structural materials, electronic devices and other fields.
[0054] The above is only a preferred embodiment of the invention and does not limit the invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the invention shall be included in the protection scope of the invention. It is intended to limit the invention in any form. Therefore, any modification or change made to the invention under the same spirit of the invention shall still be included in the scope of the invention.
Claims
1. A method for preparing fine spherical hafnium boride, characterized in that: The preparation method comprises the following steps: The electromagnetic force formed by high-frequency current inductive coupling acts on the gas medium, ionizing the gas into a plasma state; Adjust the plasma parameters, heat the hafnium boride powder raw material, rapidly cool and solidify it, and then separate it to obtain fine spherical hafnium boride powder. The specific operation is as follows: Into the plasma reactor, the flow rate of the middle gas input is controlled at 40-50 L / min, the flow rate of the side gas input is 125-145 L / min, the anode voltage of 8.5 kv, the anode current of 7 A, and the grid current of 14 A are loaded on the induction coil, and the igniter discharges at the same time, and the argon gas is ionized to produce an argon plasma torch through the inductive coupling of the high-voltage coil and the corona triggering of the igniter, and the entire plasma reactor is kept in a negative pressure state, and the system negative pressure is 110 mm Hg to 230 mm Hg; The irregular hafnium boride powder is injected into the core high temperature zone of an argon plasma torch by using a carrier gas. The heating carrier gas input flow rate is 6 L / min, and the hydrogen input flow rate is 8.5-10 L / min. The carrier gas is selected to be a gas that does not chemically react with the metal powder in a high temperature environment. The heating time ends when the gas-powder flow "flies away" from the plasma torch, and the duration is 140 milliseconds to 170 milliseconds. The hafnium boride powder absorbs heat in the core high temperature zone, and the particle surface melts. When at least 50% of the particle weight is melted, the hafnium boride powder particles with high sphericity are formed by surface tension.
2. The method for preparing fine spherical hafnium boride according to claim 1, characterized in that: The carrying gas is a mixed gas of argon and hydrogen.
3. The method for preparing fine spherical hafnium boride according to claim 1, characterized in that: The middle gas input flow rate is 40 L / min, the side gas input flow rate is 125 L / min, the hydrogen input flow rate is 8.5 L / min, and the heating time is 140 milliseconds.
4. The method for preparing fine spherical hafnium boride according to claim 1, characterized in that: The middle gas input flow rate is 50 L / min, the side gas input flow rate is 145 L / min, the hydrogen input flow rate is 10 L / min, and the heating time is 170 milliseconds.
5. The method for preparing fine spherical hafnium boride according to claim 1, characterized in that: The negative pressure of the system is 110 mm Hg.
6. The method for preparing fine spherical hafnium boride according to claim 1, characterized in that: The negative pressure of the system is 230 mm Hg.
7. The method for preparing fine spherical hafnium boride according to claim 1, characterized in that: The injected hafnium boride powder is rapidly heated and melted under the action of four heat transfer mechanisms: radiation, convection, conduction and chemistry. When at least 50% of the total weight of the injected hafnium boride powder is melted, the molten particles form highly spherical droplets under the action of surface tension, and are rapidly cooled under an extremely high temperature gradient and suddenly solidified in a heat exchange chamber, thereby forming spherical particles.
8. The method for preparing fine spherical hafnium boride according to claim 1, characterized in that: Also includes: After spheroidization is completed, the gas is extracted, processed and discharged, and the spheroidized powder enters the collection tank for automatic measurement and collection.
9. The method for preparing fine spherical hafnium boride according to claim 1, characterized in that: The hafnium boride powder raw material is a hafnium boride powder with high purity and narrow particle size distribution prepared by molten salt electrolysis.
10. A hafnium boride powder obtained by the preparation method according to any one of claims 1 to 9; the spheroidization rate of the hafnium boride powder is ≥ 80%.