Zirconium boride powder and a method for preparing the same

Abstract

The application provides a zirconium boride powder and a preparation method thereof, and relates to the technical field of zirconium boride powder material preparation. The method comprises the following steps: mixing a boron-containing compound, a zirconium-containing compound without chlorine, an alpha hydroxyl carboxylic acid compound, an o-diol compound and a solvent, and then performing a gelation reaction to obtain a wet gel; drying and calcining the wet gel to obtain the zirconium boride powder; and no nitrogen-containing pH regulator is added in the gelation reaction. In the application, the alpha hydroxyl carboxylic acid compound and the o-diol compound containing only C, H and O elements are used to complex zirconium atoms and boron atoms respectively, and no nitrogen-containing pH regulator is added in the gelation reaction, so that the nitrogen element is fundamentally avoided from entering the precursor network, the prepared zirconium boride powder has low nitrogen content and high purity, and is suitable for fields such as aerospace, semiconductors and nuclear industry.

Description

Technical Field

[0001] This invention relates to the field of zirconium boride powder material preparation technology, and in particular to a zirconium boride powder and its preparation method. Background Technology

[0002] Zirconium boride (ZrB2) is an ultra-high temperature ceramic (UHTC) material, possessing the dual properties of both ceramics and metals. It exhibits a high melting point (approximately 3245℃), high thermal conductivity, low coefficient of thermal expansion, excellent corrosion resistance, and good neutron trapping ability. It is widely used in aerospace (e.g., thermal protection structures, rocket nozzles), semiconductors (e.g., evaporation boats, sputtering targets, electrodes), and the nuclear industry (e.g., neutron absorbers, control rods). These applications are extremely sensitive to material purity: even trace amounts of impurities such as nitrogen, halogens, and alkali metals can degrade the material's high-temperature oxidation resistance, mechanical consistency, and semiconductor / nuclear-grade purity requirements during subsequent sintering and service. Therefore, preparing low-impurity, high-purity zirconium boride powder is a crucial prerequisite for the large-scale application of this material.

[0003] Currently, the main methods for preparing zirconium boride powder include direct synthesis, sol-gel method, carbothermal reduction method, chemical vapor deposition method, high-energy ball milling method, and self-propagating high-temperature synthesis method. Their process characteristics and limitations are as follows: (1) The direct synthesis method uses boron powder and zirconium powder as raw materials to directly synthesize zirconium boride under high temperature and inert atmosphere. The process is simple, but the raw materials are expensive and the energy consumption is high. (2) The sol-gel method uses zirconium salt and boron source as raw materials to make a solution, and forms a gel by adding complexing agent and adjusting pH. After dehydration, zirconium boride is obtained by high-temperature calcination. The process is simple and the components are mixed evenly, so it is considered the preferred route for preparing high-purity ultrafine powders. However, conventional processes often use nitrogen-containing compounds such as ammonia to adjust pH to promote sol-gel transformation, resulting in high nitrogen impurity content in the product. (3) The carbothermic reduction method uses zirconium oxide, boron source and carbon as raw materials and reacts in a high temperature inert atmosphere. This method is prone to excess carbon residue, large product particle size and high energy consumption. (4) Chemical vapor deposition uses zirconium halides and boron hydrides as gaseous precursors to deposit zirconium boride on the surface of a high-temperature substrate, which can produce high-purity products, but the process is complex, the equipment is expensive, and the precursors are highly toxic. (5) High-energy ball milling uses mechanical force to react boron powder and zirconium powder to generate zirconium boride. It does not require high temperature and has low energy consumption, but it is easy to introduce metal impurities during the ball milling process. (6) The self-propagating high-temperature synthesis method has a fast reaction rate and low energy consumption, but the reaction process is not easy to control, the reaction is uneven, and there are many impurities.

[0004] Among the methods described above, the sol-gel method has the greatest potential for preparing high-purity ultrafine zirconium boride powder due to its mild process and uniform composition. However, this route has long been limited by its dependence on nitrogen-containing pH adjusters (such as ammonia) during the gelation process. Nitrogenous substances enter the precursor network during complexation / gelation and ultimately remain in the calcined product as nitrogen impurities, making it difficult to meet the requirements of aerospace, semiconductor, and nuclear industries for low-nitrogen, high-purity powders. Carbothermic reduction, ball milling, and self-propagating methods, on the other hand, face other purity bottlenecks such as residual carbon, metallic impurities, and uneven reaction. In summary, existing technologies struggle to maintain the advantages of mild process, uniform composition, and simple process while preventing the introduction of nitrogen impurities at the source.

[0005] Therefore, there is an urgent need for a method that can retain the advantages of the sol-gel process in terms of its simplicity, while fundamentally avoiding the introduction of nitrogen-containing impurities, thereby obtaining low-nitrogen, high-purity zirconium boride powder. Summary of the Invention

[0006] To address the above problems, this invention provides a zirconium boride powder and its preparation method.

[0007] One objective of this invention is to provide a method for preparing zirconium boride powder, comprising: S1. Dissolve the chlorine-free zirconium-containing compound and the boron-containing compound in solvents according to the specified ratio to prepare zirconium-containing solution and boron-containing solution respectively; S2. Add the boron-containing solution dropwise to the zirconium-containing solution, add an α-hydroxycarboxylic acid compound and stir to mix, then add a vicinal diol compound and stir to mix, to obtain a mixed solution; S3. The mixed solution is kept at 60~80℃ for 6~8h to carry out a gelation reaction to obtain a wet gel; S4. Dry the wet gel in a vacuum environment at 100~120℃ for 8~12h to obtain the precursor powder; S5. The precursor powder is calcined in an inert gas environment at 1500~1600℃ to obtain zirconium boride powder; No nitrogen-containing pH adjuster is added during the gelation reaction; The molar ratio of zirconium in the α-hydroxycarboxylic acid compound to that in the chlorine-free zirconium-containing compound is (1~3):1; The molar ratio of boron in the vicinal diol compound to that in the boron-containing compound is 1:1.

[0008] Preferably, the boron-containing compound includes at least one of boron oxide, metaboric acid, or boric acid; And / or, The chlorine-free zirconium-containing compound includes at least one of zirconium nitrate, zirconium n-propoxide, or zirconium acetate; And / or, The α-hydroxycarboxylic acid compounds include citric acid or tartaric acid; And / or, The vicinal diols include at least one of glucose, sucrose, ethylene glycol, glycerol, mannitol, or sorbitol.

[0009] Preferably, the molar ratio of boron in the boron-containing compound to zirconium in the chlorine-free zirconium-containing compound is (2.2~2.5):1; And / or, The inert gas is high-purity argon, and the argon flow rate is 80~120mL / min; And / or, After the precursor powder is calcined, it is also kept warm for 2-4 hours.

[0010] Preferably, the solvent includes at least one of deionized water, ethanol, or isopropanol; And / or, The heating rate during calcination of the precursor powder is 8~12℃ / min.

[0011] The second objective of this invention is to provide a zirconium boride powder prepared by the method described above.

[0012] The third objective of this invention is to provide an application of the zirconium boride powder described above in the preparation of semiconductor devices, nuclear industry components, or high-temperature structural components for aerospace.

[0013] The beneficial effects of this invention are: This invention employs a chlorine-free zirconium-containing compound combined with a dual complexing agent of α-hydroxycarboxylic acid and vicinal diol. The α-hydroxycarboxylic acid chelates and complexes zirconium atoms through a six-membered ring, while the vicinal diol complexes and complexes boron atoms through a boron-alcohol complex. Furthermore, no nitrogen-containing pH adjuster is added during the gelation reaction, thus preventing chlorine and nitrogen impurities from entering the precursor network at the source. Simultaneously, by first adding a boron-containing solution dropwise into a zirconium-containing solution, followed by the sequential addition of the two complexing agents, and by designing a ratio of α-hydroxycarboxylic acid / Zr = (1~3):1 and vicinal diol / B = 1:1, atomic-level uniform dispersion of the boron-containing and zirconium-containing components is achieved. This ensures the integrity and uniformity of the gel network structure, enabling the production of low-nitrogen, low-chlorine, high-purity, and uniformly composed zirconium boride powder.

[0014] The sol-gel method used in this invention has a gelation temperature of 60~80℃ and a drying temperature of 100~120℃. The process conditions are mild, the steps are clear, and the repeatability is strong. The raw material system contains only five elements: C, H, O, Zr, and B, and does not introduce foreign impurities such as nitrogen, halogens, or alkali metals. It is suitable for industrial-scale preparation of low-nitrogen, high-purity zirconium boride powder. Attached Figure Description

[0015] Figure 1 The image shows the XRD phase analysis of the zirconium boride powder prepared in Example 1. Figure 2 The image shows the XRD phase analysis of the zirconium boride powder prepared in Comparative Example 1. Detailed Implementation

[0016] The present application will now be described in further detail with reference to embodiments. In the following description, certain specific details are included to provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments can be implemented without employing one or more of these specific details, but using other methods, components, materials, etc. Unless otherwise required by the present invention, the terms "comprising" and "including" should be interpreted in an open-ended, inclusive sense, meaning "including but not limited to". Throughout this specification, "an embodiment," "an embodiment," "a preferred embodiment," or "some embodiments" means that at least one embodiment includes a specific reference element, structure, or feature related to that embodiment. Therefore, the phrases "in an embodiment," "in an embodiment," "in a preferred embodiment," or "in some embodiments" appearing in different places throughout the specification do not necessarily all refer to the same embodiment. Furthermore, specific elements, structures, or features may be combined in one or more embodiments in any suitable manner.

[0017] According to a first aspect of the present invention, a method for preparing zirconium boride powder is provided, comprising the following steps: S1. Dissolve the chlorine-free zirconium-containing compound and the boron-containing compound in solvents according to the specified ratio to prepare zirconium-containing solution and boron-containing solution respectively; S2. Add the boron-containing solution dropwise to the zirconium-containing solution, add an α-hydroxycarboxylic acid compound and stir to mix, then add a vicinal diol compound and stir to mix, to obtain a mixed solution; S3. The mixed solution is kept at 60~80℃ for 6~8h to carry out a gelation reaction to obtain a wet gel; S4. Dry the wet gel in a vacuum environment at 100~120℃ for 8~12h to obtain the precursor powder; S5. The precursor powder is calcined in an inert gas environment at 1500~1600℃ to obtain zirconium boride powder; No nitrogen-containing pH adjuster is added during the gelation reaction; The molar ratio of zirconium in the α-hydroxycarboxylic acid compound to that in the chlorine-free zirconium-containing compound is (1~3):1; The molar ratio of boron in the vicinal diol compound to that in the boron-containing compound is 1:1.

[0018] In this invention, the use of a chlorine-free zirconium source can prevent chlorine impurities from entering the precursor at the source. Residual chlorine impurities will deteriorate the oxidation resistance, mechanical properties and sintering activity of zirconium boride powder at high temperatures, making it difficult to meet the stringent requirements of aerospace, semiconductor and nuclear industries for high-purity powders. In addition, no nitrogen-containing or alkali metal heteroatoms are introduced into the zirconium-containing compound. The entire precursor system consists of only five elements: C, H, O, Zr and B, ensuring the purity of the product from the source.

[0019] The α-hydroxyl group of α-hydroxycarboxylic acid compounds reacts with zirconium ions (ZrO2). 2+ The α-hydroxycarboxylic acid compounds and vicinal diols coordinate to form stable six-membered cyclic chelates, locking zirconium atoms in a soluble complex state and effectively inhibiting the hydrolysis and polymerization precipitation of zirconium ions in the aqueous phase. The ortho-hydroxyl groups of the vicinal diols form boron-alcohol cyclic complexes with boron atoms, achieving complexation stability of boron atoms. Since both α-hydroxycarboxylic acid compounds and vicinal diols are composed only of carbon, hydrogen, and oxygen, the entire precursor system contains only C, H, O, Zr, and B elements, without introducing foreign impurities such as nitrogen, halogens, and alkali metals, ensuring the purity of the product from the source. At the same time, the two complexing agents complex different metal centers respectively, avoiding the problem of competitive coordination between the two metal centers for the same complexing agent in a single complexing agent system, and achieving uniform mixing and dispersion of boron-containing and zirconium-containing components at the molecular level.

[0020] This invention employs a step-by-step feeding process: first, a boron-containing solution is added dropwise to a zirconium-containing solution, followed by the sequential addition of α-hydroxycarboxylic acid compounds and vicinal diol compounds. This approach fully leverages the specialization effect of the dual complexing agents. The boron-containing solution is first added dropwise to the zirconium-containing solution to premix the boric acid and zirconium salt at the molecular scale, ensuring that the two metal centers are evenly distributed in the solution. Then, an α-hydroxycarboxylic acid compound is added and stirred to preferentially and specifically complex zirconium ions to form a six-membered ring chelate, avoiding competitive complexation with boron atoms. Finally, a vicinal diol compound is added and stirred to completely complex and stabilize the boron atoms.

[0021] This phased feeding sequence ensures the uniformity and integrity of the gel network structure, avoiding local oversaturation, component segregation, and phase separation caused by one-time mixing, thus obtaining a zirconium boride precursor powder with uniform composition. If the feeding sequence is reversed or both complexing agents are added simultaneously, zirconium / boron complexation competition and gel network inhomogeneity problems are likely to occur, affecting the purity and compositional uniformity of the final powder.

[0022] The molar ratio of α-hydroxycarboxylic acid compounds to zirconium is (1~3):1, for example, 1:1, 2:1, or 3:1. The lower limit of 1:1 corresponds to the stoichiometric relationship of the chelation of α-hydroxycarboxylic acid with the six-membered ring of zirconium ions. Excess α-hydroxycarboxylic acid compounds are used to further suppress the hydrolysis of zirconium ions, ensuring that zirconium atoms are completely complexed and stable. When this molar ratio is lower than 1:1, the zirconium ions are not completely complexed and are prone to hydrolysis, polymerization, and precipitation, affecting the uniformity of the precursor and the purity of the final powder. When this molar ratio is higher than 3:1, excess α-hydroxycarboxylic acid introduces additional carbon residues or leads to an increase in oxygen content during the calcination stage, which is not conducive to further improving the purity of the product. The molar ratio of vicinal diol compounds to boron is 1:1, corresponding to the stoichiometric relationship of the boron-alcohol ring complexation reaction, ensuring that boron atoms are completely complexed and stable. If this molar ratio deviates from 1:1, the boron atoms are not completely complexed or there are residual vicinal diol compounds, both of which will affect the uniformity of the precursor and the purity of the final powder.

[0023] The gelation reaction temperature is, for example, 60℃, 65℃, 70℃, 75℃, or 80℃. When the reaction temperature is below 60℃, the gelation process is too slow, the complexation reaction kinetics are insufficient, and component segregation is prone to occur. When the reaction temperature is above 80℃, the solvent evaporates too quickly, and the gel network is prone to breakage due to violent shrinkage. The gelation reaction time is, for example, 6h, 7h, or 8h. When the reaction time is less than 6h, the complexation and gelation reactions are incomplete. When the reaction time is more than 8h, energy consumption increases but the technical effect is not further improved. By coordinating the temperature and time within a window of 60~80℃ and 6~8h, it is possible to ensure that the dual complexing agent fully completes the specialized complexation of zirconium / boron atoms and forms a complete and uniform gel network structure.

[0024] Drying the wet gel under vacuum at 100–120°C for 8–12 hours efficiently removes residual solvents without damaging the gel network structure, forming a stable precursor powder. When the drying temperature is below 100°C, the drying efficiency is low and the cycle is prolonged; when the drying temperature is above 120°C, the gel network is prone to breakage due to severe shrinkage, affecting the uniformity of the precursor powder. When the drying time is less than 8 hours, residual solvent removal is insufficient, affecting the reaction uniformity in the subsequent calcination stage; when the drying time is more than 12 hours, energy consumption increases but the technical effect is not significantly improved. The vacuum environment can prevent the precursor from being oxidized and ensure the reducibility of the precursor powder. Calcination of the precursor powder in an inert gas environment at 1500–1600°C allows the carbothermic reduction reaction to proceed fully, with boron atoms reacting with zirconium atoms at high temperature to form zirconium boride (ZrB2). The inert atmosphere prevents the oxidation of the generated ZrB2.

[0025] The calcination temperature is, for example, 1500℃, 1550℃ or 1600℃. When the calcination temperature is below 1500℃, the carbothermic reduction reaction is incomplete and too much oxygen-containing / carbon-containing intermediate phase remains in the product. When the calcination temperature is above 1600℃, the energy consumption increases significantly and the powder is prone to sintering and agglomeration.

[0026] Conventional sol-gel methods rely on nitrogen-containing compounds such as ammonia to adjust the pH and promote the sol-gel transition. During the complexation / gel process, nitrogenous substances enter the precursor network and ultimately remain as nitrogen impurities in the calcined product, failing to meet the requirements of aerospace, semiconductor, and nuclear industries for low-nitrogen, high-purity powders. This invention, through the aforementioned dual-complexer mechanism, stably complexes zirconium-containing and boron-containing compounds at the molecular level, forming a stable gel network without the need for external pH adjusters, thus eliminating the introduction of nitrogen at the source. Even when zirconium nitrate is used as the zirconium source, its nitrate ions escape as nitrogen oxides during calcination, not remaining as nitrogen impurities in the zirconium boride powder, thereby obtaining low-nitrogen, high-purity zirconium boride powder.

[0027] In summary, the synergistic effects of the above-mentioned chlorine-free zirconium source, dual complexing agent division of labor mechanism, multi-stage feeding steps, precise proportioning design, and absence of nitrogen-containing pH adjuster simultaneously optimize five aspects: zirconium source, complexing mechanism, feeding process, proportioning relationship, and pH control. This systematically solves the purity bottlenecks such as high nitrogen impurities and residual chlorine impurities in the existing sol-gel method for producing zirconium boride powder, enabling the production of low-nitrogen, low-chlorine, high-purity, and uniformly composed zirconium boride powder.

[0028] In a preferred embodiment of the present invention, the inert gas includes high-purity argon, and the argon flow rate is 80~120 mL / min, for example, 80 mL / min, 90 mL / min, 100 mL / min, 110 mL / min or 120 mL / min.

[0029] Typical but not limiting, when zirconium nitrate is selected as the zirconium-containing compound, its nitrate ions decompose into nitrogen oxide gas during the pyrolysis of the precursor and escape, and do not remain in the zirconium boride powder as nitrogen impurities. Therefore, low-nitrogen and high-purity powder can still be obtained by using zirconium nitrate as the zirconium source.

[0030] In a preferred embodiment of the present invention, the boron-containing compound includes at least one of boron oxide, metaboric acid, or boric acid, such as boron oxide, metaboric acid, boric acid, boron oxide and metaboric acid, boron oxide and boric acid, metaboric acid and boric acid, or a combination of boron oxide, metaboric acid, and boric acid; and / or, the chlorine-free zirconium-containing compound includes at least one of zirconium nitrate, zirconium propoxide, or zirconium acetate, such as zirconium nitrate, zirconium propoxide, zirconium acetate, zirconium nitrate and zirconium propoxide, zirconium nitrate and zirconium acetate, zirconium propoxide and zirconium acetate, or a combination of zirconium nitrate, zirconium propoxide, and zirconium acetate.

[0031] Typically, but not limitingly, the zirconium nitrate is zirconium nitrate pentahydrate and does not contain chlorine impurities, making it suitable for high-purity applications.

[0032] In a preferred embodiment of the present invention, the α-hydroxycarboxylic acid compound includes at least one of citric acid or tartaric acid, such as citric acid, tartaric acid, or a combination of citric acid and tartaric acid; and / or, the vicinal diol compound includes at least one of glucose, sucrose, ethylene glycol, glycerol, mannitol, or sorbitol, such as glucose, sucrose, ethylene glycol, glycerol, mannitol, sorbitol, or a combination of any two or three thereof; typically, but not limitingly, mannitol and sorbitol are isomers with similar coordination abilities and can be interchanged in equal amounts.

[0033] In a preferred embodiment of the present invention, the solvent includes at least one of deionized water, ethanol, or isopropanol, such as deionized water, ethanol, isopropanol, or a combination of deionized water and ethanol.

[0034] In a preferred embodiment of the present invention, the molar ratio of boron in the boron-containing compound to zirconium in the chlorine-free zirconium-containing compound is (2.2~2.5):1, for example, 2.2:1, 2.3:1, 2.4:1 or 2.5:1; boron is added in an appropriate excess to compensate for the loss of boron volatilization during high-temperature calcination.

[0035] In a preferred embodiment of the present invention, the vacuum degree of the vacuum environment is -0.08 to -0.10 MPa.

[0036] In a preferred embodiment of the present invention, after the precursor powder is calcined, the process further includes holding the temperature for 2 to 4 hours, for example, 2 hours, 3 hours or 4 hours; typically, but not limitingly, the calcination heating rate is 8 to 12 °C / min, for example, 10 °C / min.

[0037] In a preferred embodiment of the present invention, calcining the precursor powder at 1500-1600°C in an inert gas environment to obtain zirconium boride powder includes: placing the precursor powder in a tube furnace, heating it to 1500-1600°C at 8-120 mL / min under the protection of high-purity argon gas, holding it at that temperature for 2-4 hours, and then cooling it to 20-30°C with the furnace to obtain zirconium boride powder.

[0038] In a preferred embodiment of the present invention, the method for preparing zirconium boride powder specifically includes: S1. Dissolve the chlorine-free zirconium-containing compound and the boron-containing compound in solvents according to the specified ratio to prepare zirconium-containing solution and boron-containing solution respectively; S2. Add the boron-containing solution dropwise to the zirconium-containing solution, add an α-hydroxycarboxylic acid compound and stir to mix, then add a vicinal diol compound and stir to mix, to obtain a mixed solution; S3. The mixed solution is kept at 60~80℃ for 6~8h to carry out a gelation reaction to obtain a wet gel; S4. Dry the wet gel in a vacuum environment at 100~120℃ for 8~12h to obtain the precursor powder; The precursor powder was placed in a tube furnace and heated to 1500-1600℃ at 8-12℃ / min under the protection of high-purity argon at a rate of 80-120 mL / min. The temperature was maintained for 2-4 hours and then cooled to 20-30℃ in the furnace to obtain zirconium boride powder. No nitrogen-containing pH adjuster was added during the gelation reaction.

[0039] Example 1 Zirconium nitrate pentahydrate (Zr(NO3)4·5H2O) and boric acid (H3BO3) were weighed to achieve a molar ratio of B to Zr of 2.3:1. Zirconium and boron solutions were prepared by dissolving them separately in deionized water. The boron solution was added dropwise to the zirconium solution, followed by the addition of citric acid (an α-hydroxycarboxylic acid compound with a molar ratio of 2:1 to Zr) and stirring for 30 min. Then, ethylene glycol (a vicinal diol compound with a molar ratio of 1:1 to B) was added and stirred for 60 min to obtain a mixed solution. The mixed solution was subjected to a gelation reaction at 70 °C for 7 h (without adding a nitrogen-containing pH adjuster) to obtain a wet gel. The wet gel was dried in a vacuum environment at 110 °C for 10 h to obtain the precursor powder. The precursor powder was placed in a tube furnace and heated to 1550℃ at a rate of 10℃ / min under the protection of high-purity argon at a rate of 100 mL / min. The temperature was held for 3 hours, and then cooled to 20-30℃ in the furnace to obtain zirconium boride powder. XRD phase analysis was performed on the prepared zirconium boride powder, as shown below. Figure 1 As shown, the diffraction peaks of the sample are located at 2θ = 25.2°, 32.6°, 41.6°, 51.7°, 58.2°, 62.4°, 64.4°, 68.3°, and 74.0°, which are consistent with the ZrB2 standard card (JCPDS No. 34-0423), indicating that the obtained product is a pure phase of ZrB2 and that no other impurity phases are present. The sharp diffraction peaks indicate that the product has good crystallinity.

[0040] Example 2 The difference from Example 1 is that citric acid is replaced with tartaric acid (α-hydroxycarboxylic acid / Zr = 2:1), and ethylene glycol is replaced with glycerol (vicinal diol / B = 1:1), while the B / Zr molar ratio remains 2.3:1. All other conditions are exactly the same as in Example 1.

[0041] Example 3 The difference from Example 1 is that the molar ratio of B to Zr is 2.2:1; and the gelation reaction temperature is 60°C. All other conditions are exactly the same as in Example 1.

[0042] Example 4 The difference from Example 1 is that the molar ratio of B to Zr is 2.5:1; and the gelation reaction temperature is 80°C. All other conditions are exactly the same as in Example 1.

[0043] Example 5 The difference from Example 1 is that the molar ratio of citric acid to Zr is 1:1; and the gelation reaction time is 6 hours. All other conditions are exactly the same as in Example 1.

[0044] Example 6 The difference from Example 1 is that the molar ratio of citric acid to Zr is 3:1; and the gelation reaction time is 8 hours. All other conditions are exactly the same as in Example 1.

[0045] Example 7 The difference from Example 1 is that the calcination temperature is 1500°C and the drying temperature of the wet gel is 100°C. All other conditions are exactly the same as in Example 1.

[0046] Example 8 The difference from Example 1 is that the calcination temperature is 1600°C and the drying temperature of the wet gel is 120°C. All other conditions are exactly the same as in Example 1.

[0047] Example 9 The difference from Example 1 is that zirconium nitrate pentahydrate is replaced with zirconium propoxide (Zr(OC3H7)4), and boric acid is replaced with boron oxide (B2O3). The boron oxide is first dissolved in water at 60-80°C by stirring to form a boric acid solution, and the B / Zr molar ratio is maintained at 2.3:1. All other conditions are exactly the same as in Example 1.

[0048] Example 10 The difference from Example 1 is that zirconium nitrate pentahydrate is replaced with zirconium acetate (Zr(CH3COO)4), boric acid is replaced with metaboric acid (HBO2), and the B / Zr molar ratio is maintained at 2.3:1. All other conditions are exactly the same as in Example 1.

[0049] Example 11 The difference from Example 1 is that ethylene glycol is replaced with mannitol (vicinal diol / B = 1:1). All other conditions are exactly the same as in Example 1.

[0050] Example 12 The difference from Example 1 is that ethylene glycol is replaced with glucose (vicinal glycol / B = 1:1); the calcination holding time is 2 hours (the temperature remains 1550°C). All other conditions are exactly the same as in Example 1.

[0051] Example 13 The difference from Example 1 is that ethylene glycol is replaced with sorbitol (o-diol / B=1:1); the calcination holding time is 4 hours (temperature remains 1550℃). All other conditions are exactly the same as in Example 1.

[0052] Comparative Example 1 Weigh zirconium nitrate pentahydrate and boric acid to achieve a B:Zr molar ratio of 2.3:1. Dissolve them separately in deionized water to obtain solutions. Add the boron solution dropwise to the zirconium solution, add citric acid (molar ratio to Zr 2:1), and stir for 30 min. Then add ethylene glycol (molar ratio to B 1:1) and stir for 60 min to obtain a mixed solution. Add a 5 mol / L ammonia solution dropwise to the mixed solution to adjust the pH to 8.0, and then carry out a gelation reaction at 70℃ for 7 h to obtain a wet gel. Dry the wet gel in a vacuum environment at 110℃ for 10 h to obtain a precursor powder. Place the precursor powder in a tube furnace, and under the protection of high-purity argon at 100 mL / min, heat to 1550℃ at 10℃ / min, hold for 3 h, and cool with the furnace to 20-30℃ to obtain zirconium boride powder. Perform XRD phase analysis on the prepared zirconium boride powder, as shown in the figure. Figure 2 As shown. The diffraction peaks of the sample are located at 2θ = 25.2°, 32.6°, 41.6°, 51.7°, 58.2°, 62.4°, 64.4°, 68.3°, and 74.0°, consistent with the ZrB2 standard card (JCPDS No. 34-0423), indicating that the obtained product is pure ZrB2 without other impurity phases. The sharp diffraction peaks indicate good crystallinity of the product. However, the XRD diffraction peaks are generally shifted towards lower angles. This is because N atoms replace B atoms in the ZrB2 lattice, N³⁺… - Ionic radius greater than B³ + Lattice substitution induces lattice expansion, increasing the interplanar spacing d. According to Bragg's equation... An increase in interplanar spacing will decrease the diffraction angle, thus shifting the diffraction peaks to lower angles. Therefore, nitrogen impurities are present in the sample of Comparative Example 1.

[0053] Comparative Example 2 Weigh zirconium nitrate pentahydrate and boric acid to achieve a B:Zr molar ratio of 2.3:1. Dissolve each separately in deionized water to obtain solutions. Add the boron solution dropwise to the zirconium solution, then add citric acid (molar ratio to Zr 2:1) and stir for 30 min, without adding any vicinal diols, to obtain a mixed solution. Add a 5 mol / L ammonia solution dropwise to the mixed solution to adjust the pH to 8.0, then carry out a gelation reaction at 70℃ for 7 h to obtain a wet gel. Dry the wet gel in a vacuum environment at 110℃ for 10 h to obtain a precursor powder. Place the precursor powder in a tube furnace, and under the protection of high-purity argon at 100 mL / min, heat to 1550℃ at 10℃ / min, hold for 3 h, and then cool with the furnace to 20-30℃ to obtain zirconium boride powder.

[0054] Comparative Example 3 Weigh zirconium nitrate pentahydrate and boric acid to achieve a B:Zr molar ratio of 2.3:1. Dissolve them separately in deionized water to prepare solutions. Add the boron solution dropwise to the zirconium solution, add EDTA (ethylenediaminetetraacetic acid, a nitrogen-containing complexing agent) (molar ratio to Zr 2:1), and stir for 30 min. Then add ethylene glycol (molar ratio to B 1:1) and stir for 60 min to obtain a mixed solution. Add a 5 mol / L ammonia solution dropwise to the mixed solution to adjust the pH to 8.0, and then carry out a gelation reaction at 70℃ for 7 h to obtain a wet gel. Dry the wet gel in a vacuum environment at 110℃ for 10 h to obtain the precursor powder. Place the precursor powder in a tube furnace, and under the protection of high-purity argon at 100 mL / min, heat to 1550℃ at 10℃ / min, hold for 3 h, and then cool with the furnace to 20-30℃ to obtain zirconium boride powder.

[0055] The obtained zirconium boride powder was subjected to the following performance tests: (1) Nitrogen content determination An inert gas melting-thermal conductivity method was employed. The powder sample was placed in a graphite crucible and heated at high temperature under a helium atmosphere. Nitrogen released from the sample was measured by a thermal conductivity detector. Instrument model: Leco TC600 oxygen and nitrogen analyzer. Detection limit: 0.0001 wt%.

[0056] (2) Oxygen content determination The inert gas melting-infrared absorption method was employed. The sample was heated at high temperature in a graphite crucible; the released oxygen reacted with the graphite to form CO or CO2, which was measured by an infrared detection cell. Instrument model: Leco TC600 oxygen and nitrogen analyzer. Detection limit: 0.0001 wt%.

[0057] (3) Determination of carbon residue High-frequency induction combustion-infrared absorption method was used. The sample was burned in a high-frequency induction furnace under an oxygen flow; carbon was converted to CO2, which was then measured by an infrared detector. Instrument model: Leco CS600 carbon-sulfur analyzer. Detection limit: 0.0001 wt%. Test results are shown in Table 1: Table 1

[0058] The nitrogen content of the embodiments of the present invention is 0.05~0.06 wt%, which is about 87%~90% lower than that of the comparative example with added ammonia. This indicates that by not adding a nitrogen-containing pH adjuster in the gelation reaction, but relying solely on α-hydroxycarboxylic acid compounds and vicinal diol compounds to complex zirconium and boron atoms respectively, nitrogen can be fundamentally prevented from entering the precursor network and remaining in the calcined product, thus obtaining low-nitrogen, high-purity zirconium boride powder. The nitrogen content of Comparative Example 1 is 0.38 wt%, verifying the technical defect of conventional sol-gel method, which relies on ammonia to adjust pH, resulting in high nitrogen impurities. The nitrogen content of Comparative Example 2 is further increased to 0.45 wt%, indicating that ammonia is more likely to remain in the precursor network without vicinal diol compounds to stabilize boron atoms. The nitrogen content of Comparative Example 3 is the highest, and EDTA itself is a nitrogen-containing complexing agent, which further aggravates the nitrogen impurity residue.

[0059] The oxygen content in the examples ranged from 0.68 to 1.18 wt%, and the carbon residue ranged from 0.10 to 0.40 wt%, which were generally at a low level. Oxygen content was negatively correlated with calcination temperature: Example 7 had the highest oxygen content, indicating incomplete carbothermic reduction; Example 8 had the lowest oxygen content. Carbon residue was positively correlated with the α-hydroxycarboxylic acid / Zr molar ratio: Example 6 had a relatively high carbon residue, while Example 5 had the lowest carbon residue but a relatively high oxygen content. This indicates an inverse relationship between carbon residue and oxygen content; carbon is both a residual impurity and a necessary reducing agent for the carbothermic reduction reaction, requiring a reasonable determination of the complexing agent dosage to achieve a balance between the two. Considering all indicators, the optimal solution is Example 1: B / Zr molar ratio 2.3:1, α-hydroxycarboxylic acid / Zr molar ratio 2:1, vicinal diol / B molar ratio 1:1, gelled at 70℃ for 7h, vacuum dried at 110℃ for 10h, and calcined at 1550℃ for 3h. The product has a nitrogen content of 0.05 wt%, an oxygen content of 0.82 wt%, and a carbon residue of 0.18 wt%, with the best overall purity.

[0060] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing zirconium boride powder, characterized in that, Includes the following steps: S1. Dissolve the chlorine-free zirconium-containing compound and the boron-containing compound in solvents according to the specified ratio to prepare zirconium-containing solution and boron-containing solution respectively; S2. Add the boron-containing solution dropwise to the zirconium-containing solution, add an α-hydroxycarboxylic acid compound and stir to mix, then add a vicinal diol compound and stir to mix, to obtain a mixed solution; S3. The mixed solution is kept at 60~80℃ for 6~8h to carry out a gelation reaction to obtain a wet gel; S4. Dry the wet gel in a vacuum environment at 100~120℃ for 8~12h to obtain the precursor powder; S5. The precursor powder is calcined in an inert gas environment at 1500~1600℃ to obtain zirconium boride powder; No nitrogen-containing pH adjuster is added during the gelation reaction; The molar ratio of zirconium in the α-hydroxycarboxylic acid compound to that in the chlorine-free zirconium-containing compound is (1~3):1; The molar ratio of boron in the vicinal diol compound to that in the boron-containing compound is 1:

1.

2. The preparation method according to claim 1, characterized in that, The boron-containing compound includes at least one of boron oxide, metaboric acid, or boric acid. And / or, The chlorine-free zirconium-containing compound includes at least one of zirconium nitrate, zirconium n-propoxide, or zirconium acetate; And / or, The α-hydroxycarboxylic acid compounds include citric acid or tartaric acid; And / or, The vicinal diols include at least one of glucose, sucrose, ethylene glycol, glycerol, mannitol, or sorbitol.

3. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of boron in the boron-containing compound to zirconium in the chlorine-free zirconium-containing compound is (2.2~2.5):1; And / or, The inert gas is high-purity argon, and the argon flow rate is 80~120mL / min; And / or, After the precursor powder is calcined, it is also kept warm for 2-4 hours.

4. The preparation method according to claim 1 or 2, characterized in that, The solvent includes at least one of deionized water, ethanol, or isopropanol; And / or, The heating rate during calcination of the precursor powder is 8~12℃ / min.

5. A zirconium boride powder, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the zirconium boride powder as described in claim 5 in the preparation of semiconductor devices, nuclear industry components or aerospace high-temperature structural components.

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