Tantalum hafnium ceramic nanopowder containing whiskers and preparation method thereof

Abstract

The present invention belongs to the technical field of ultra-high temperature ceramics, and specifically relates to a tantalum hafnium ceramic nanopowder containing whiskers and a preparation method thereof. The present invention utilizes HfCl4 and TaCl5 as Hf sources and Ta sources, and an organic carbon source, to prepare a precursor containing Hf, Ta, and C through a sol-gel method, which can achieve atomic-scale mixing between the raw materials, facilitating subsequent reactions. The precursor is then subjected to a carbon thermal reduction reaction to obtain a tantalum hafnium ceramic nanopowder (Ta4HfC5) containing whiskers. The preparation process is simple and the whiskers have a special structure. The preparation method provided by the present invention has the advantages of easy availability of raw materials, a simple method, easy operation, and mild reaction conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-high temperature ceramics, and in particular relates to a tantalum-hafnium ceramic nanopowder containing whiskers and a preparation method thereof. Background Art

[0002] The material with the highest known melting point is tantalum-hafnium alloy (Ta4HfC5), which has a melting point of 4215°C and can be used in hypersonic aircraft. It has very good mechanical properties and oxidation resistance and is a very promising ultra-high temperature ceramic material.

[0003] The prior art "Synthesis and ceramisation of organometallic precursors for Ta4HfC5 and TaHfC2 ultra-fine powders through a facile one-pot reaction" (Cheng, Jun, et al. Journal of Alloys and Compounds. 898 (2022): 162989) reports the synthesis of Ta4HfC5 by the sol-gel method, but it involves the synthesis of organometallic precursors, has a high impurity content, a complex mechanism, is difficult to obtain raw materials, and has a complicated preparation process. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a tantalum-hafnium ceramic nanopowder containing whiskers and a preparation method thereof. The preparation method provided by the present invention has a simple process and readily available raw materials, and the prepared tantalum-hafnium ceramic nanopowder contains a whisker structure.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing tantalum-hafnium ceramic nanopowder containing whiskers, comprising the following steps:

[0007] Hafnium chloride, tantalum chloride, an organic carbon source, a surfactant, an alcohol aqueous solution and an alkali are mixed to undergo a gel reaction, and the obtained sol is dried and then calcined to obtain a precursor;

[0008] The precursor is subjected to a carbothermal reduction reaction under a protective gas to obtain tantalum-hafnium ceramic nanopowder containing whiskers.

[0009] Preferably, the organic carbon source comprises sucrose.

[0010] Preferably, the surfactant comprises polyethylene glycol.

[0011] Preferably, the base is aqueous ammonia.

[0012] Preferably, the burning temperature is 300-400° C., and the holding time is 0.5-2 h.

[0013] Preferably, the temperature of the carbothermal reduction reaction is 1500-1600° C., and the holding time is 1.5-2.5 hours.

[0014] Preferably, the protective gas is argon.

[0015] Preferably, before the carbothermal reduction reaction, the method further comprises: crushing the precursor.

[0016] The present invention also provides a tantalum-hafnium ceramic nanopowder containing whiskers prepared by the preparation method described in the above technical solution, comprising Ta4HfC5 nanopowder and Ta4HfC5 whiskers; the diameter of the Ta4HfC5 nanopowder is 50-200nm, the diameter of the Ta4HfC5 whiskers is 250nm-1μm; the length of the whiskers is 10-50μm.

[0017] Preferably, the mass percentage of Ta4HfC5 whiskers in the whisker-containing tantalum-hafnium ceramic nanopowder is 30-60%.

[0018] The present invention provides a method for preparing tantalum and hafnium ceramic nanopowder containing whiskers, comprising the following steps: mixing hafnium chloride, tantalum chloride, an organic carbon source, a surfactant, an alcohol aqueous solution and an alkali to carry out a gel reaction, drying the obtained sol and then calcining it to obtain a precursor; and subjecting the precursor to a carbothermal reduction reaction under a protective gas to obtain the tantalum and hafnium ceramic nanopowder containing whiskers.

[0019] The present invention utilizes HfCl4 and TaCl5 as Hf and Ta sources, and an organic carbon source, to prepare a precursor containing Hf, Ta, and C through a sol-gel method. This allows the raw materials to achieve atomic-scale mixing, which is beneficial for subsequent reactions. The precursor is then subjected to a carbothermal reduction reaction to obtain a tantalum-hafnium ceramic nanopowder (Ta4HfC5) containing whiskers. The preparation process is simple and the whiskers contain a special structure. The presence of the whiskers can enhance the fracture toughness of the ceramic as a structural ceramic. The preparation method provided by the present invention uses an inorganic precursor and has the advantages of readily available raw materials, a simple mechanism, a simple and easy-to-operate method, and mild reaction conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the XRD pattern of the whisker-containing tantalum and hafnium ceramic nanopowder prepared in Example 1 of the present invention;

[0021] Figure 2 This is an SEM image of the whisker-containing tantalum and hafnium ceramic nanopowder prepared in Example 1 of the present invention;

[0022] Figure 3This is an SEM image of the whisker-containing tantalum and hafnium ceramic nanopowder prepared in Example 2 of the present invention;

[0023] Figure 4 This is an SEM image of the whisker-containing tantalum and hafnium ceramic nanopowder prepared in Example 3 of the present invention;

[0024] Figure 5 This is a HRTEM image of the whisker-containing tantalum and hafnium ceramic nanopowder prepared in Example 1 of the present invention;

[0025] Figure 6 This is an EDS image of the whisker-containing tantalum and hafnium ceramic nanopowder prepared in Example 1 of the present invention;

[0026] Figure 7 This is a SEM image of the tantalum hafnium carbide (Ta4HfC5) powder synthesized in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing tantalum-hafnium ceramic nanopowder containing whiskers, comprising the following steps:

[0028] Hafnium chloride, tantalum chloride, an organic carbon source, a surfactant, an alcohol aqueous solution and an alkali are mixed to undergo a gel reaction, and the obtained sol is dried and then calcined to obtain a precursor;

[0029] The precursor is subjected to a carbothermal reduction reaction under a protective gas to obtain tantalum-hafnium ceramic nanopowder containing whiskers.

[0030] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used, and commercially available products known to those skilled in the art can be used.

[0031] The invention mixes hafnium chloride, tantalum chloride, an organic carbon source, a surfactant, an alcohol aqueous solution and an alkali to carry out a gel reaction to obtain a sol.

[0032] In the present invention, the alcohol-water solution preferably includes ethanol and water; the volume ratio of the ethanol and water is preferably 5:1; the organic carbon source preferably includes sucrose; the surfactant preferably includes polyethylene glycol; the base is preferably ammonia water; the mass concentration of the ammonia water is preferably 20-30%, more preferably 25%.

[0033] In the present invention, the mass ratio of hafnium chloride to tantalum chloride is preferably (0.2-0.5): (0.894-2.235), more preferably (0.2-0.4): (0.894-1.788); the mass ratio of hafnium chloride to organic carbon source is preferably (0.2-0.5): (3.2-8), more preferably (0.2-0.4): (3.2-6.4); the mass ratio of hafnium chloride to surfactant ...). ):(0.1~0.3146), more preferably (0.2~0.4):(0.1~0.2); the ratio of the mass of the hafnium chloride to the volume of the alcohol aqueous solution is preferably (0.2~0.5) g:(20~50) mL, more preferably (0.2~0.4) g:(20~40) mL; the mass ratio of the hafnium chloride and the alkali is preferably (0.2~0.5):(27~70), more preferably (0.2~0.4):(27~56).

[0034] In the present invention, hafnium chloride, tantalum chloride, an organic carbon source, a surfactant, an alcohol aqueous solution and an alkali are mixed to carry out a gel reaction, preferably: hafnium chloride and tantalum chloride are dissolved in an alcohol aqueous solution, a surfactant is added, an alkali is added under stirring to start oil bath heating, and an organic carbon source is added to carry out a gel reaction to obtain a sol.

[0035] In the present invention, the stirring rate is preferably 100-150 rpm, more preferably 120-150 rpm; the stirring is preferably magnetic stirring; the temperature of the oil bath heating is preferably 70-80°C, more preferably 80°C; the time of the gel reaction is preferably 30-60 min, more preferably 30 min.

[0036] In the present invention, HfCl4 and TaCl5 undergo hydrolysis and condensation chemical reactions to form a stable transparent sol system in the solution. After aging, the sol particles slowly polymerize to form a gel with a three-dimensional network structure. The gel network is filled with a solvent that has lost its fluidity to form a gel.

[0037] After the gel reaction is completed, the product obtained by the gel reaction is preferably aged; the aging time is preferably 12 to 36 hours, more preferably 16 to 24 hours. The present invention obtains a precipitate with complete crystal shape, large particles and purity through aging.

[0038] After obtaining the sol, the present invention dries the sol to obtain a xerosol.

[0039] In the present invention, the drying temperature is preferably 60-80°C, more preferably 70-80°C; the drying holding time is preferably 24-48h, more preferably 36h; the drying is preferably oven drying; the drying equipment is preferably an oven.

[0040] After obtaining the dry sol, the present invention burns the dry sol to obtain a precursor.

[0041] In the present invention, the calcination temperature is preferably 300-400° C., more preferably 300-350° C., and the holding time is preferably 0.5-2 h, more preferably 1-1.5 h.

[0042] The invention removes the ammonium chloride impurity in the dry sol by burning, oxidizes hafnium chloride and tantalum chloride by burning to generate hafnium oxide and tantalum oxide, and carbonizes the organic carbon source in the dry sol by burning to generate amorphous carbon.

[0043] After obtaining the precursor, the present invention performs a carbothermal reduction reaction on the precursor under a protective gas to obtain a tantalum-hafnium ceramic nanopowder containing whiskers.

[0044] Before the carbothermal reduction reaction, the present invention preferably further comprises: pulverizing the precursor. In the present invention, the pulverization is preferably grinding, more preferably grinding in a mortar; the particle size of the powder obtained by the pulverization is preferably 5 to 20 μm, more preferably 10 to 20 μm.

[0045] In the present invention, the temperature of the carbon thermal reduction reaction is preferably 1500-1600°C, more preferably 1600°C, and the holding time is preferably 1.5-2.5h, more preferably 1.5-2h; the heating rate to the carbon thermal reduction reaction temperature is preferably 5-8°C / min, more preferably 8°C / min; the equipment used for the carbon thermal reduction reaction includes a crucible and a tubular furnace.

[0046] In the present invention, the protective gas is preferably argon; the purity of the argon is preferably 99.9-99.999%, more preferably 99.999%; the flow rate of the protective gas is preferably 80-120 mL / min, more preferably 100 mL / min.

[0047] During the carbothermal reduction reaction, tantalum oxide and hafnium oxide are reduced by carbon to form tantalum carbide and hafnium carbide.

[0048] The present invention also provides a tantalum-hafnium ceramic nanopowder containing whiskers prepared by the preparation method described in the above technical solution, comprising Ta4HfC5 nanopowder and Ta4HfC5 whiskers; the diameter of the Ta4HfC5 nanopowder is 50-200nm, the diameter of the Ta4HfC5 whiskers is 250nm-1μm; the length of the whiskers is 10-50μm.

[0049] In the present invention, the diameter of the Ta4HfC5 nanopowder is preferably 50-100 nm, and the diameter of the Ta4HfC5 whisker is preferably 250-500 nm.

[0050] In the present invention, the mass percentage of Ta in the whisker-containing tantalum and hafnium ceramic nanopowder is preferably 58-65%, more preferably 60-65%, and the mass percentage of Hf is preferably 15-16.06%, more preferably 15.5-16.06%; the mass percentage of Ta4HfC5 whiskers in the whisker-containing tantalum and hafnium ceramic nanopowder is preferably 30-60%, more preferably 40-50%.

[0051] The present invention utilizes HfCl4 and TaCl5 as Hf and Ta sources, and an organic carbon source, to prepare a precursor containing Hf, Ta, and C via a sol-gel method. This allows atomic-scale mixing of the raw materials, facilitating subsequent reactions. The precursor is then subjected to a carbothermal reduction reaction to produce a whisker-containing tantalum-hafnium ceramic nanopowder (Ta4HfC5). The preparation process is simple, and the whisker-containing nanopowder has a unique structure. The preparation method provided by the present invention has the advantages of readily available raw materials, a simple method, ease of operation, and mild reaction conditions.

[0052] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention, but they should not be understood as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] 0.5 g HfCl4 and 2.235 g TaCl5 were dissolved in 40 mL of an alcohol-water solution (ethanol and water in a volume ratio of 5:1), 0.3146 g of polyethylene glycol (PEG) was added, 76 mL of ammonia water (mass concentration of 25%) was added under magnetic stirring at 150 rpm, and the mixture was heated in an oil bath at 70°C. 8 g of sucrose was then added, and the mixture was subjected to a gelation reaction for 30 min. The mixture was aged for 24 h to obtain a sol, which was then dried in an oven at 80°C for 36 h and then calcined in a muffle furnace at 300°C for 1 h to obtain a precursor.

[0055] The obtained precursor was placed in a mortar and ground. After the particle size of the obtained powder was 20 μm, it was placed in a crucible and placed in a tubular furnace. The temperature was raised to 1600°C at a heating rate of 8°C / min and kept warm for 2 hours. The atmosphere was argon (purity of 99.999%) with a flow rate of 100 mL / min. A carbon thermal reduction reaction was carried out to obtain tantalum and hafnium ceramic nanopowder (Ta4HfC5) containing whiskers.

[0056] Example 2

[0057] 0.2 g HfCl4 and 0.894 g TaCl5 were dissolved in 20 mL of an alcohol-water solution (ethanol and water in a volume ratio of 5:1), 0.1 g of polyethylene glycol (PEG) was added, 30 mL of ammonia water (mass concentration of 25%) was added under magnetic stirring at 120 rpm, and the mixture was heated in an oil bath at 80°C. 3.2 g of sucrose was then added, and the mixture was subjected to a gelation reaction for 30 min. The mixture was aged for 24 h to obtain a sol, which was dried in an oven at 80°C for 36 h and then calcined in a muffle furnace at 300°C for 1 h to obtain a precursor.

[0058] The obtained precursor was placed in a mortar and ground. After the particle size of the obtained powder was 10 μm, it was placed in a crucible and placed in a tubular furnace. The temperature was raised to 1600°C at a heating rate of 8°C / min and kept warm for 2 hours. The atmosphere was argon (purity of 99.999%) with a flow rate of 100 mL / min. A carbon thermal reduction reaction was carried out to obtain tantalum and hafnium ceramic nanopowder (Ta4HfC5) containing whiskers.

[0059] Example 3

[0060] 0.4 g HfCl4 and 1.788 g TaCl5 were dissolved in 40 mL of an alcohol-water solution (ethanol and water in a volume ratio of 5:1), 0.2 g of polyethylene glycol (PEG) was added, 60 mL of ammonia water (mass concentration of 25%) was added under magnetic stirring at 150 rpm, and the mixture was heated in an oil bath at 80°C. 6.4 g of sucrose was then added, and the mixture was subjected to a gelation reaction for 30 min and aged for 24 h to obtain a sol. The obtained sol was dried in an oven at 80°C for 36 h, and then calcined in a muffle furnace at 300°C for 1 h to obtain a precursor;

[0061] The obtained precursor was placed in a mortar and ground. After the particle size of the obtained powder was 20 μm, it was placed in a crucible and placed in a tubular furnace. The temperature was raised to 1600°C at a heating rate of 8°C / min and kept warm for 2 hours. The atmosphere was argon (purity of 99.999%) with a flow rate of 100 mL / min. A carbon thermal reduction reaction was carried out to obtain tantalum and hafnium ceramic nanopowder (Ta4HfC5) containing whiskers.

[0062] Comparative Example 1

[0063] The prior art "Preparation and Characterization of Ultra High-Temperature Ternary Ceramics Ta4HfC5" (Jiang, Jinming, Wang, et al. [2023-10-24]) reports the synthesis of tantalum hafnium carbide (Ta4HfC5) powder from inorganic hybrids by solvent thermal treatment and carbothermal reduction reaction. Tantalum pentachloride, hafnium chloride, and phenolic resin are used as sources of tantalum, hafnium, and carbon, respectively. After heat treatment at 1400-1600°C, the reaction converts it into a single-phase solid solution Ta4HfC5. Its morphology is nanoparticles without a whisker structure, and its structure is as follows: Figure 7 shown.

[0064] Performance Testing

[0065] (1) The tantalum-hafnium ceramic nanopowder containing whiskers prepared in Example 1 was subjected to XRD testing. The results are as follows: Figure 1 shown.

[0066] Depend on Figure 1 It can be seen that compared with the standard Ta4HfC5 PDF card 04-018-7425, the material synthesized by the present invention is cubic phase Ta4HfC5.

[0067] (2) The tantalum hafnium ceramic nanopowder containing whiskers prepared in Example 1 was subjected to electron microscope scanning analysis and testing. The results are as follows: Figure 2 shown.

[0068] Depend on Figure 2 It can be seen that the particle diameter of the whisker-containing tantalum and hafnium ceramic nanopowder prepared by the present invention is 50-100 nm, the whisker diameter is about 250 nm, and the length is 10-50 μm.

[0069] (3) The tantalum hafnium ceramic nanopowder containing whiskers prepared in Example 2 was subjected to electron microscope scanning analysis and testing. The results are as follows: Figure 3 shown.

[0070] Depend on Figure 3 It can be seen that the particle diameter of the whisker-containing tantalum and hafnium ceramic nanopowder prepared by the present invention is 100-200 nm, the whisker diameter is about 500 nm, and the length is 10-50 μm.

[0071] X-ray fluorescence spectroscopy analysis showed that the mass fractions of Ta and Hf in the whisker-containing tantalum and hafnium ceramic nanopowder prepared in Example 2 of the present invention were 58 wt.% and 15 wt.%, respectively, and the composition of Ta, Hf and C elements was close to the stoichiometric 4:1:5, thereby obtaining Ta4HfC5 ultra-high temperature ceramic powder containing whiskers.

[0072] (4) The tantalum hafnium ceramic nanopowder containing whiskers prepared in Example 3 was subjected to electron microscope scanning analysis and testing. The results are as follows: Figure 4 shown.

[0073] Depend on Figure 4 It can be seen that the particle diameter of the whisker-containing tantalum and hafnium ceramic nanopowder prepared by the present invention is 100-200 nm, the whisker diameter is about 250 nm-1 μm, and the length is 10-50 μm.

[0074] X-ray fluorescence spectroscopy analysis showed that the mass fractions of Ta and Hf in the whisker-containing tantalum and hafnium ceramic nanopowder prepared in Example 3 of the present invention were 60 wt.% and 15 wt.%, respectively, and the composition of Ta, Hf and C elements was close to the stoichiometric 4:1:5, thereby obtaining Ta4HfC5 ultra-high temperature ceramic powder containing whiskers.

[0075] (5) The whisker-containing tantalum-hafnium ceramic nanopowder prepared in Example 1 was scanned by high-resolution transmission electron microscopy (HRTEM). The results are as follows: Figure 5 shown.

[0076] Depend on Figure 5 It can be seen that the synthesized Ta4HfC5 powder particles reach the nanoscale and are evenly distributed on the whiskers. The diameter of the whiskers is about 250nm, and the particle size of the unagglomerated particles is about 20-50nm.

[0077] (6) The tantalum hafnium ceramic nanopowder containing whiskers prepared in Example 1 was subjected to X-ray energy dispersive spectroscopy (EDS) testing. The results are as follows: Figure 6 As shown, A is the SEM image of the tantalum-hafnium ceramic nanopowder containing whiskers in Example 1, B is the line scan image of the whiskers in A, and C is the EDS energy spectrum data of the line scan in B.

[0078] Depend on Figure 6 It can be seen that the elements contained in the whiskers are Ta, Hf, and C, and the Ta content is the highest, followed by Hf, and the lowest is C, which proves that the whiskers are Ta4HfC5.

[0079] (7) The whisker-containing tantalum-hafnium ceramic nanopowder prepared in Example 1 was subjected to X-ray fluorescence spectroscopy analysis. The results are shown in Table 1.

[0080] Table 1 XRF data of tantalum-hafnium ceramic nanopowder containing whiskers prepared in Example 1

[0081] element Mass ratio (wt.%) characteristic spectrum Characteristic spectrum intensity Background intensity Ta 64.2596 TaLa 31.278 0.365 Hf 16.0644 HkDJ 7.251 0.279 C 14.5139 CKa 0.223 0.022 O 3.6620 OK 0.074 0.004 Ga 0.7964 GaKa 1.408 0.855 Si 0.5796 SiKa 0.226 0.084 Fe 0.1241 FeKa 0.140 0.044

[0082] As shown in Table 1, the mass fractions of Ta and Hf in the whisker-containing tantalum and hafnium ceramic nanopowder prepared in Example 1 are 64 wt.% and 16 wt.%, respectively, and the composition of Ta, Hf and C elements is close to the stoichiometric 4:1:5, thereby obtaining Ta4HfC5 ultra-high temperature ceramic powder containing whiskers.

[0083] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for preparing tantalum and hafnium ceramic nanopowder containing whiskers, comprising the following steps: Hafnium chloride, tantalum chloride, an organic carbon source, a surfactant, an alcohol aqueous solution and an alkali are mixed to undergo a gel reaction, dried, and then calcined to obtain a precursor; The organic carbon source includes sucrose; The surfactant includes polyethylene glycol; The mass ratio of hafnium chloride to tantalum chloride is (0.2-0.5):(0.894-2.235); The mass ratio of hafnium chloride to the organic carbon source is (0.2-0.5):(3.2-8); The mass ratio of hafnium chloride to surfactant is (0.2-0.5):(0.1-0.3146); Carbothermal reduction of the precursor under a protective gas to obtain whisker-containing tantalum-hafnium ceramic nanopowder; The temperature of the carbon thermal reduction reaction is 1500-1600° C., and the holding time is 1.5-2.5 hours.

2. The preparation method according to claim 1, characterized in that The base is aqueous ammonia.

3. The preparation method according to claim 1, characterized in that The burning temperature is 300-400° C., and the heat preservation time is 0.5-2 hours.

4. The preparation method according to claim 1, characterized in that The protective gas is argon.

5. The preparation method according to claim 1, characterized in that Before the carbon thermal reduction reaction, the method further includes: crushing the precursor.

6. Tantalum and hafnium ceramic nanopowder containing whiskers prepared by the preparation method according to any one of claims 1 to 5, characterized in that: It comprises Ta4HfC5 nanometer powder and Ta4HfC5 whiskers; the diameter of the Ta4HfC5 nanometer powder is 50-200nm, the diameter of the Ta4HfC5 whiskers is 250nm-1μm; the length of the Ta4HfC5 whiskers is 10-50μm.

7. The whisker-containing tantalum and hafnium ceramic nanopowder according to claim 6, characterized in that: The mass percentage of Ta4HfC5 whiskers in the whisker-containing tantalum-hafnium ceramic nanopowder is 30-60%.

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