A carbonitride ultrahigh temperature ceramic and a method of making and using the same

Abstract

The application discloses a kind of carbonitride ultrahigh temperature ceramics and its preparation method and application, it is related to the technical field of ultrahigh temperature ceramic materials.The method includes that carbonitride precursor prepared by the reaction of transition metal chloride, polyamine compound and polyol compound is low-temperature crosslinking solidification, then temperature is raised to complete organic-inorganic conversion, finally, the heat treatment product is sintered at high temperature, and carbonitride ultrahigh temperature ceramic is prepared.The application introduces nitrogen source in heat treatment atmosphere, so that carbon thermal reduction and nitriding reaction occur simultaneously in the high-temperature cracking process of precursor, compared with traditional inert gas protection, nitrogen loss at high temperature of precursor is avoided, and high-quality carbonitride ultrahigh temperature ceramic can be simply and efficiently prepared.

Description

Technical Field

[0001] This invention relates to the field of ultra-high temperature ceramic materials technology, specifically to a carbonitride ultra-high temperature ceramic, its preparation method, and its application. Background Technology

[0002] Carbonitride solid solutions, due to the coexistence of metals, ions, and covalent bonds, exhibit excellent corrosion resistance, chemical stability, and thermal stability. Carbonitride ceramics, through the introduction of nitrogen atoms into the carbide sublattice, induce substitution of metal and non-metal sublattice atoms, resulting in electron orbital hybridization and solid solution hardening. This leads to superior mechanical and oxidation resistance compared to carbide ceramics, making them promising for applications in ultra-high temperature fields. Currently, the main technology for preparing ultra-high temperature carbonitride ceramics is the powder high-temperature sintering method. However, this method faces several challenges and limitations in practice, such as high equipment requirements, complex processes, and difficulties in precise molding. Therefore, exploring more efficient, economical, and easy-to-operate preparation methods is of great significance for promoting the practical application of ultra-high temperature carbonitride ceramic materials.

[0003] The precursor conversion method, combined with polymer synthesis, processing, and heat treatment techniques, enables precise control over the shape of ceramics, overcoming the shortcomings of traditional high-temperature hot-pressing sintering of powders. This significantly improves the thermal stability and mechanical properties of ceramic materials, showing broad application prospects in the preparation of ultra-high temperature ceramics. This method can not only regulate the microstructure of ceramic products by changing the composition of the precursor, but also control the particle size and phase distribution of ceramic materials by adjusting the atmosphere, sintering temperature, and sintering time, making it an ideal approach for preparing carbonitride ultra-high temperature ceramics.

[0004] Argon is typically used as a protective gas during the heat treatment stage of the precursor conversion method for preparing ultra-high temperature ceramics to prevent the precursor from contacting air and forming oxides. However, because nitrogen in the carbonitride precursor readily reacts to form small molecules during high-temperature processes, nitrogen source loss occurs, resulting in a low nitrogen content in the final carbonitride ceramics. Furthermore, achieving precise control over the composition of carbonitride ceramics by adjusting the nitrogen content in the precursor is complex, requiring various raw materials and incurring high manufacturing costs. Therefore, exploring suitable heat treatment conditions for carbonitride precursors is crucial for preparing high-performance ultra-high temperature carbonitride ceramics. Summary of the Invention

[0005] This invention addresses the problem of nitrogen loss during high-temperature pyrolysis of carbonitride precursors due to traditional precursor heat treatment processes. It proposes a carbonitride ultra-high temperature ceramic, its preparation method, and its applications. This method introduces a nitrogen source into the heat treatment atmosphere of precursor pyrolysis to regulate and increase the nitrogen content in the carbonitride solid solution. First, the carbonitride precursor undergoes low-temperature cross-linking solidification and organic-inorganic transformation under a nitrogen / ammonia / argon atmosphere, followed by sintering under a nitrogen / argon atmosphere to obtain the carbonitride ultra-high temperature ceramic. This technology, by rationally controlling the partial pressures of nitrogen, ammonia, and argon, enables simultaneous carbothermic reduction and nitriding reactions during the high-temperature pyrolysis of the precursor, thus providing a simple and efficient way to prepare high-quality carbonitride ultra-high temperature ceramics.

[0006] The first objective of this invention is to provide a method for preparing carbonitride ultra-high temperature ceramics, comprising the following steps: Under an inert atmosphere, transition metal chlorides are uniformly dispersed in an organic solvent, polyamine compounds are added, and after a condensation reaction, polyol compounds are added to carry out an end-capping reaction to obtain carbonitride ceramic precursors. Under a certain heat treatment atmosphere, the carbonitride ceramic precursor is cross-linked and cured at 200 ℃~300 ℃, and then the temperature is further raised to 900 ℃~1200 ℃ for organic-inorganic conversion. Subsequently, it is sintered at 1500 ℃~2100 ℃ for 2~6 h under a certain atmosphere to obtain the carbonitride ultra-high temperature ceramic. The transition metal chlorides include one or more of hafnium chloride, zirconium chloride, titanium chloride, and tantalum chloride.

[0007] Preferably, during the organic-inorganic conversion, the heat treatment atmosphere is one or more of argon, nitrogen, and ammonia; during the sintering, the heat treatment atmosphere is nitrogen and / or argon.

[0008] Preferably, the polyamine compound includes ethylenediamine, p-phenylenediamine, dicyandiamide, or propylenediamine.

[0009] Preferably, the polyol compound includes diethanolamine, 1,4-butanediol, methyldiethanolamine, or diisopropanolamine.

[0010] Preferably, the temperature during the condensation reaction is 40~80 ℃; and the temperature during the end-capping reaction is 50~100 ℃.

[0011] Preferably, the molar ratio of the transition metal chloride to the polyamine compound is 1:1 to 1:2.

[0012] Preferably, the molar ratio of the transition metal chloride to the polyol compound is 1:2 to 1:4.

[0013] The second objective of the present invention is to provide a carbonitride ultra-high temperature ceramic prepared by the method according to any one of claims 1 to 7.

[0014] Preferably, the chemical formula of the carbonitride ultra-high temperature ceramic is MeC

[0020] , Figure 2 , ,

[0019] , Figure 3 , Figure 2 , , , Figure 4 , , , Figure 2 N 1-x , where 0 < x < 1; Me is one or more of Hf, Zr, Ti, and Ta.

[0015] The third objective of the present invention is to provide an application of the carbonitride ultra-high temperature ceramic according to claim 8 or 9 in an ultra-high temperature structure.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a carbonitride ultra-high temperature ceramic, its preparation method and application. This method uses nitrogen or ammonia as the heat treatment atmosphere to provide part of the nitrogen source, promoting the simultaneous occurrence of carbothermal reduction and nitridation reactions during the high-temperature pyrolysis of the precursor, which can effectively shorten the reaction time and reduce the reaction temperature; by controlling the partial pressure of nitrogen or ammonia in the heat treatment atmosphere, the C and N element ratios in the ultra-high temperature ceramic can be precisely regulated, and the corresponding carbonitride solid solution can be obtained after sintering; this method has a simple preparation process and low cost, and is suitable for preparing high-performance carbonitride ceramics and their composites.

[0017] The carbonitride ultra-high temperature ceramic prepared by the present invention combines the advantages of carbides and nitrides. It not only has excellent mechanical properties, but also exhibits good ablation resistance and thermophysical properties, and can be widely applied in fields such as thermal protection. Description of the Drawings

[0018] Figure 1 is a schematic process diagram for preparing hafnium carbonitride ceramics in Examples 1 to 4; Figure 2 is the XRD pattern of the hafnium carbonitride ceramics prepared in Examples 1 to 3 and the ceramic provided in Comparative Example 1, where Figure 2 (b) is Figure 2 a partial enlarged view of (a); Figure 3 is the TG curve of the hafnium carbonitride ceramic prepared in Example 1 at an oxygen partial pressure of 20 kPa.

[0019] Figure 4 is the TG-DTG curve of pure HfC ceramic in Reference 1 at different oxygen partial pressures. Detailed Embodiments

[0020] In order to enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and drawings, but the specific embodiments cited shall not be construed as limiting the present invention.

[0021] This invention discloses a method for preparing carbonitride ultra-high temperature ceramics by precursor conversion. The method includes: under a certain heat treatment atmosphere, reacting a transition metal chloride, a polyamine compound, and a polyol compound to prepare a carbonitride precursor, which is then cross-linked and solidified at low temperature; subsequently, heating is performed to complete the organic-inorganic conversion; and finally, the heat-treated product is sintered at high temperature to prepare carbonitride ultra-high temperature ceramics. By introducing a nitrogen source into the heat treatment atmosphere, carbothermic reduction and nitriding reactions occur simultaneously during the high-temperature pyrolysis of the precursor. Compared with traditional inert gas protection, this method avoids nitrogen loss from the precursor at high temperatures and can simply and efficiently prepare high-quality carbonitride ultra-high temperature ceramics.

[0022] This invention primarily addresses the technical problem of nitrogen loss during the pyrolysis of carbonitride precursors under conventional heat treatment processes, which prevents the attainment of the target carbonitride solid solution content. Therefore, developing suitable heat treatment process conditions is a crucial step in preparing high-quality carbonitride ceramics.

[0023] To achieve the above objectives, the first aspect of the present invention provides a method for preparing carbonitride ultra-high temperature ceramics, comprising the following steps: Under the protection of an inert gas, nitrogen, or ammonia atmosphere, transition metal chlorides are uniformly dispersed in an organic solvent, polyamine compounds are added, and after a condensation reaction, polyol compounds are added to carry out an end-capping reaction to obtain carbonitride ceramic precursors. Under a certain heat treatment atmosphere, the carbonitride ceramic precursor is cross-linked and cured at 200 ℃~300 ℃, and then the temperature is further raised to 900 ℃~1200 ℃ for organic-inorganic transformation, and then sintered at 1500 ℃~2100 ℃ for 2~6 h to obtain the carbonitride ultra-high temperature ceramic. The transition metal chlorides include one or more of hafnium chloride, zirconium chloride, titanium chloride, and tantalum chloride.

[0024] During the organic-inorganic conversion, the heat treatment atmosphere is one or more of argon, nitrogen, and ammonia; during the sintering, the heat treatment atmosphere is nitrogen and / or argon.

[0025] The polyamine compounds include ethylenediamine, p-phenylenediamine, dicyandiamide, or propylenediamine.

[0026] The polyol compounds include diethanolamine, 1,4-butanediol, methyldiethanolamine, or diisopropanolamine.

[0027] The temperature during the condensation reaction is 40~80 ℃; the temperature during the end-capping reaction is 50~100 ℃.

[0028] The molar ratio of the transition metal chloride to the polyamine compound is 1:1 to 1:2.

[0029] The molar ratio of the transition metal chloride to the polyol compound is 1:2 to 1:4.

[0030] The second aspect of the present invention provides a carbonitride ultra-high temperature ceramic.

[0031] Among them, the chemical formula of the carbonitride ultra-high temperature ceramic is MeC x N 1-x , where 0 < x < 1; Me is one or more of Hf, Zr, Ti, and Ta.

[0032] The third aspect of the present invention provides an application of a carbonitride ultra-high temperature ceramic in an ultra-high temperature structure.

[0033] In one embodiment, as shown in Figure 1 , a preparation method for synthesizing a carbonitride ultra-high temperature ceramic by precursor conversion includes the following steps: Step 1: Uniformly disperse the transition metal chloride in an organic solvent, add a polyamine compound, after condensation reaction, then add a polyol compound, and carry out a capping reaction to obtain a carbonitride ultra-high temperature ceramic precursor.

[0034] Step 2: Place a certain amount of the carbonitride precursor in an alumina crucible, and then place the crucible in a corundum tube furnace, and evacuate and replace the gas 3 times; the gas evacuated and replaced in Step 2 is argon / nitrogen.

[0035] Step 3: Under an argon / nitrogen / ammonia atmosphere, heat the tube furnace to the curing temperature according to the heating program, keep warm, and make the precursor completely cured; the curing temperature in Step 3 is 200 - 300 °C.

[0036] Step 4: After curing, continue to heat to the inorganicization temperature, keep warm for a certain time, complete the organic-inorganic conversion, and then cool to room temperature and take out; the organic-inorganic conversion temperature in Step 4 is 900 - 1,200 °C; the heat treatment atmosphere for the organic-inorganic conversion is one or a mixture of two of argon, nitrogen, and ammonia, and the regulation of the carbonitride ceramic components can be achieved by changing the nitrogen / ammonia / argon partial pressure.

[0037] Step 5: Place the sample obtained in Step 4 in a high-temperature heat treatment furnace, carry out high-temperature sintering under a certain atmosphere, keep warm, and cool with the furnace to room temperature to obtain a carbonitride ceramic.

[0038] The sintering time in Step 5 is 2 - 6 h, and the sintering temperature is 1,500 - 2,100 °C; the heat treatment atmosphere is one or a mixture of two of nitrogen and argon. When the nitrogen partial pressure is 100%, the target ceramic product can be obtained at a lower heat treatment temperature.

[0039] One method for preparing a carbonitride ceramic precursor includes the following steps: Step 1) Under room temperature conditions, accurately weigh an appropriate amount of transition metal chloride using the Schlenk operation or in a glove box, dissolve it in an organic solvent, and then stir thoroughly to ensure that the metal chloride is completely dissolved, thereby improving the reactivity and preparing the desired metal-organic solution; wherein, under an inert atmosphere, weigh the transition metal chloride and dissolve it in acetone solution, stirring until the solution turns orange-red, so that it is completely dissolved and the activity is enhanced. Step 2) Weigh out ethylenediamine and add it dropwise to the organometallic solution. Heat and stir to cause the raw materials to undergo condensation and substitution reactions to form a macromolecular skeleton containing Me-N bonds. Step 3) Weigh diethanolamine and add it dropwise to the solution in Step 2). Stir at a certain temperature to allow it to undergo a capping reaction and initiate the formation of a three-dimensional network structure of the precursor. Step 4) The solution obtained in Step 3) is vacuum dried to remove the solvent, and then cross-linked and cured to obtain carbonitride MeC. x N 1-x Organic precursor solid products; In step 1), the transition metal chloride is one or more of the following: hafnium chloride, zirconium chloride, titanium chloride, tantalum chloride, etc.

[0040] In step 2), the molar ratio of metal chloride to ethylenediamine is 1:1 to 1:2. If the ethylenediamine ratio is too high, excess ethylenediamine will be attached to the branch chain or react with diethanolamine in the solution, generating an impurity phase after heat treatment. If the ethylenediamine content is too low, the macromolecular skeleton formed by Me-N bonds will be shortened, resulting in an incomplete reaction.

[0041] The temperature in step 2) is 40~80 ℃. When the temperature is too low, the condensation reaction and substitution reaction cannot be completed, the main chain is too short, and the subsequent ceramic yield is affected. If the temperature is too high, too many branched structures will be formed, the molecular weight will be too large, and the formability of the precursor will be poor.

[0042] In step 3), the molar ratio of metal chloride to diethanolamine is 1:2 to 1:4. When diethanolamine is in excess, it undergoes a substitution reaction, reducing the ceramic yield. Excess diethanolamine will cause diethanolamine to undergo a substitution reaction, reducing the ceramic yield. Insufficient diethanolamine will lead to incomplete end-capping reaction, making it difficult to construct a three-dimensional network structure.

[0043] In step 3), the reaction temperature of diethanolamine with metal chloride is 50~100 ℃. When the temperature is too low, the end-capping reaction is incomplete; when the temperature is too high, a condensation reaction will occur directly to form a solid, and the reaction will end instantaneously, making it impossible to obtain the target precursor structure.

[0044] In one embodiment, a method for preparing a carbonitride ultra-high temperature ceramic includes the following steps: The MeC obtained in step 4) above x N 1-x The organic precursor solid product was subjected to low-temperature crosslinking at 200 ℃~300 ℃, followed by further heating to 900 ℃~1200 ℃, and then sintered at high temperature at 1500 ℃~2100 ℃ for 2~6 h under a certain atmosphere. After cooling to room temperature, MeC was obtained. x N 1-x Single-phase nano-ceramic particles.

[0045] It should be noted that during the organic-inorganic conversion, the heat treatment atmosphere is one or more of argon, nitrogen, and ammonia; during sintering, the heat treatment atmosphere is one or a mixture of two of nitrogen and argon in any proportion. In an argon atmosphere, nitrogen comes only from the precursor, resulting in a low nitrogen content in the obtained carbonitrides. In a nitrogen / ammonia atmosphere, nitrogen / ammonia can act as an external nitrogen source and promote carbothermic reduction and nitriding reactions, enabling the precursor to complete decomposition at a lower heat treatment temperature and obtaining carbonitride ceramics with high nitrogen content. Simultaneously, adjusting the partial pressure of nitrogen / ammonia can control the solid solubility ratio of carbon and nitrogen in the ultra-high temperature ceramic.

[0046] This invention provides MeC x N 1-x MeC prepared by ceramic precursor preparation method x N 1-x The ceramic yield reached over 40%, MeC x N 1-x The ceramic exhibits good crystallinity and excellent high-temperature resistance, making it suitable for preparing high-performance carbonitride ceramics and their composites.

[0047] Among them, MeC obtained after high-temperature heat treatment of the precursor x N 1-x The ceramic phase has a uniform composition, fine grains, and excellent high-temperature resistance.

[0048] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0049] Example 1 Step 1: Under an inert atmosphere, 8 g (25 mmol) hafnium tetrachloride was uniformly dispersed in acetone solution. 1.5 g (25 mmol) ethylenediamine was added dropwise while stirring at room temperature for 1 h. The mixture was heated to 50 ℃ and stirred for 2 h to induce a condensation reaction. Then, 5.26 g (50 mmol) diethanolamine was added dropwise. The mixture was heated to 70 ℃ and stirred for 2 h to induce end-capping and polymerization. After the reaction was completed, the mixture was dried under vacuum at -0.1 MPa and 80 ℃ to obtain the solid hafnium carbonitride precursor product.

[0050] Step 2: Place 10 g of hafnium carbonitride precursor in an alumina crucible, then place the crucible in a corundum tube furnace and evacuate and replace it with argon gas 3 times. Step 3: Under N2 atmosphere, heat the tube furnace to 250 ℃ according to the heating program, and hold for 2 h to allow the precursor to crosslink and cure. Step 4: After curing, continue heating to 1000 ℃ according to the heating program, hold for 2 h to complete the organic-inorganic conversion, and then cool to room temperature before taking it out; Step 5: Place the sample obtained in Step 4 in a high-temperature heat treatment furnace, heat it to 1600 ℃ at 10 ℃ / min under N2 atmosphere, hold it at that temperature for 2 h, and then cool it to room temperature with the furnace to obtain hafnium carbonitride ceramic.

[0051] Example 2 Step 1: Under an inert atmosphere, 8 g (25 mmol) of hafnium tetrachloride was uniformly dispersed in an acetone solution. 1.5 g (25 mmol) of ethylenediamine was added dropwise while stirring at room temperature for 1 h. The mixture was heated to 50 ℃ and stirred for 2 h to induce a condensation reaction. Then, 5.26 g (50 mmol) of diethanolamine was added dropwise. The mixture was heated to 70 ℃ and stirred for 2 h to induce end-capping and polymerization. After the reaction was completed, the mixture was vacuum dried at -0.1 MPa and 80 ℃ to obtain the solid hafnium carbonitride precursor product.

[0052] Step 2: Place 10 g of hafnium carbonitride precursor in an alumina crucible, then place the crucible in a corundum tube furnace and evacuate and replace it with argon gas 3 times. Step 3: Under a mixed atmosphere of 50% N2 and 50% Ar, heat the tube furnace to 250 °C according to the heating program, and hold for 2 hours to allow the precursor to crosslink and cure. Step 4: After curing, continue heating to 1000 ℃ according to the heating program, hold for 2 h to complete the organic-inorganic conversion, and then cool to room temperature before taking it out; Step 5: Place the sample obtained in Step 4 in a high-temperature heat treatment furnace, heat it to 1700 ℃ at 10 ℃ / min under a mixed atmosphere of 50% N2 and 50% Ar, hold it at that temperature for 2 h, and then cool it to room temperature with the furnace to obtain hafnium carbonitride ceramic.

[0053] Example 3 Step 1: Under an inert atmosphere, 8 g (25 mmol) of hafnium tetrachloride was uniformly dispersed in an acetone solution. 1.5 g (25 mmol) of ethylenediamine was added dropwise while stirring at room temperature for 1 h. The mixture was heated to 50 °C and stirred for 2 h to induce a condensation reaction. Then, 5.26 g (50 mmol) of diethanolamine was added dropwise. The mixture was heated to 70 °C and stirred for 2 h to induce end-capping and polymerization. After the reaction was completed, the mixture was vacuum dried at -0.1 MPa and 80 °C to obtain the solid hafnium carbonitride precursor product.

[0054] Step 2: Place 10 g of hafnium carbonitride precursor in an alumina crucible, then place the crucible in a corundum tube furnace and evacuate and replace it with argon gas 3 times. Step 3: Under a mixed atmosphere of 30% N2 and 70% Ar, heat the tube furnace to 300 ℃ according to the heating program, and hold for 2 hours to allow the precursor to crosslink and cure. Step 4: After curing, continue heating to 1100 ℃ according to the heating program, hold for 2 h to complete the organic-inorganic conversion, and then cool to room temperature before taking it out; Step 5: Place the sample obtained in Step 4 in a high-temperature heat treatment furnace, heat it to 1800 ℃ at 10 ℃ / min under a mixed atmosphere of 30% N2 and 70% Ar, hold it at that temperature for 3 h, and then cool it to room temperature with the furnace to obtain hafnium carbonitride ceramic.

[0055] Example 4 Step 1: Under an inert atmosphere, 8 g (25 mmol) of hafnium tetrachloride was uniformly dispersed in an acetone solution. 1.5 g (25 mmol) of ethylenediamine was added dropwise while stirring at room temperature for 1 h. The mixture was heated to 50 ℃ and stirred for 2 h to induce a condensation reaction. Then, 5.26 g (50 mmol) of diethanolamine was added dropwise. The mixture was heated to 70 ℃ and stirred for 2 h to induce end-capping and polymerization. After the reaction was completed, the mixture was vacuum dried at -0.1 MPa and 80 ℃ to obtain the solid hafnium carbonitride precursor product.

[0056] Step 2: Place 10 g of hafnium carbonitride precursor in an alumina crucible, then place the crucible in an alumina tube furnace and evacuate and replace with nitrogen three times. Step 3: Under an NH3 atmosphere, heat the tube furnace to 200 ℃ according to the heating program and hold for 2 h to allow the precursor to crosslink and solidify. Step 4: After curing, continue heating to 900 ℃ according to the heating program, hold for 2 h to complete the organic-inorganic conversion, and then cool to room temperature before taking it out; Step 5: The sample obtained in Step 4 is heated to 1500 ℃ at 10 ℃ / min under N2 atmosphere, held at this temperature for 2 h and then cooled to room temperature in the furnace to obtain hafnium carbonitride ceramic.

[0057] Comparative Example 1 Step 1: Under an inert atmosphere, 8 g (25 mmol) of hafnium tetrachloride was uniformly dispersed in an acetone solution. 1.5 g (25 mmol) of ethylenediamine was added dropwise while stirring at room temperature for 1 h. The mixture was heated to 50 ℃ and stirred for 2 h to induce a condensation reaction. Then, 5.26 g (50 mmol) of diethanolamine was added dropwise. The mixture was heated to 70 ℃ and stirred for 2 h to induce end-capping and polymerization. After the reaction was completed, the mixture was vacuum dried at -0.1 MPa and 80 ℃ to obtain the solid hafnium carbonitride precursor product.

[0058] Step 2: Place 10 g of hafnium carbonitride precursor in an alumina crucible, then place the crucible in a corundum tube furnace and evacuate and replace it with argon gas 3 times. Step 3: Under Ar atmosphere, heat the tube furnace to 300 ℃ according to the heating program and hold for 2 h to allow the precursor to crosslink and solidify. Step 4: After curing, continue heating to 1000 ℃ according to the heating program, hold for 2 h to complete the organic-inorganic conversion, and then cool to room temperature before taking it out; Step 5: Place the sample obtained in Step 4 in a high-temperature heat treatment furnace, heat it to 1700 ℃ at 10 ℃ / min under Ar atmosphere, hold it at that temperature for 2 h, and then cool it to room temperature with the furnace to obtain hafnium carbonitride ceramic with low N content.

[0059] To illustrate the relevant performance of the precursor provided by the present invention, it is described in conjunction with the accompanying drawings.

[0060] Figure 2 The XRD patterns of the ceramics provided in Examples 1-3 and Comparative Example 1 show that the carbonitride ceramics obtained under different heat treatment atmospheres have different C and N solid solution ratios. HfC was obtained under a pure N2 atmosphere. 0.55 N 0.45 HfC was obtained under a mixed atmosphere of 50% N2 and 50% Ar. 0.56 N 0.44 HfC was obtained under a mixed atmosphere of 30% N2 and 70% Ar. 0.67 N 0.33 All are higher than HfC obtained under Ar atmosphere. 0.9 N 0.1 The content of nitrogen (N) in the medium.

[0061] Figure 3 HfC prepared in Example 1 0.55 N 0.45 The TG curve of the ceramic in an oxygen partial pressure of 20 kPa environment can be seen from the figure. 0.55 N 0.45 The initial oxidation temperature of the ceramic is 450 ℃, which is higher than the oxidation initiation temperature in Reference 1; 450 ℃~700 ℃ stage: HfC0.55 N 0.45 The oxidation process to HfO2; 700 ℃~900 ℃ stage: C oxidation to CO2, this process exhibits a significant rate slowdown. Overall, HfC... 0.55 N 0.45 The oxidation initiation and termination temperatures at each stage all shifted to higher temperatures, indicating that HfC 0.55 N 0.45 Pure HfC ceramics exhibit better high-temperature stability and oxidation resistance.

[0062] Figure 4 The figures are from reference 1, "A thermoanalytical study on the oxidation of ZrC and HfC powders with formation of carbon," Shiro Shimada, Solid State Ionics, 2002: 319-326. The TG-DTG curves of HfC samples at oxygen partial pressures of 40 kPa (A and A'), 20 kPa (B and B'), 10 kPa (C and C'), 5 kPa (D and D'), 1 kPa (E and E'), and 0.5 kPa (F and F') are shown. The figures indicate that the oxidation initiation temperature of HfC is 400℃, independent of oxygen partial pressure. At an oxygen partial pressure of 20 kPa (see...), the oxidation initiation temperature of HfC is... Figure 4 (B and B'): 400℃~660℃ is the process of HfC being oxidized to HfO2; 660℃~740℃ is the process of carbon being oxidized to CO2; oxidation is completed at 740℃.

[0063] This invention provides a method for preparing carbonitride ultra-high temperature ceramics by precursor conversion. First, the carbonitride precursor is cross-linked and cured at low temperature. After curing, it is sintered at high temperature in a nitrogen-containing atmosphere to prepare the carbonitride ultra-high temperature ceramic. This technology promotes simultaneous carbothermic reduction and nitriding reactions during the high-temperature pyrolysis of the precursor, reducing the required reaction temperature and time. Furthermore, the proportion of carbonitrides in the final product can be controlled by adjusting the partial pressure of the atmosphere. The operation is simple and efficient.

[0064] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing carbonitride ultra-high temperature ceramics, characterized in that, Includes the following steps: Under inert gas protection, transition metal chlorides are uniformly dispersed in an organic solvent, polyamine compounds are added, and after condensation reaction, polyol compounds are added to carry out end-capping reaction to obtain carbonitride ceramic precursors. Under a certain heat treatment atmosphere, the carbonitride ceramic precursor is cross-linked and cured at 200℃~300℃, and then the temperature is further raised to 900℃~1200℃ for organic-inorganic conversion. Subsequently, it is sintered at 1500℃~2100℃ for 2~6 h under a certain atmosphere to obtain the carbonitride ultra-high temperature ceramic. The transition metal chlorides include one or more of hafnium chloride, zirconium chloride, titanium chloride, and tantalum chloride. During the organic-inorganic conversion, the heat treatment atmosphere is nitrogen, or nitrogen and argon, or ammonia; during the sintering, the heat treatment atmosphere is nitrogen and / or argon. The polyamine compounds include ethylenediamine, p-phenylenediamine, dicyandiamide, or propylenediamine; The polyol compounds include diethanolamine, 1,4-butanediol, methyldiethanolamine, or diisopropanolamine; The molar ratio of the transition metal chloride to the polyamine compound is 1:1 to 1:2; The molar ratio of the transition metal chloride to the polyol compound is 1:2 to 1:

4.

2. The method for preparing carbonitride ultra-high temperature ceramics according to claim 1, characterized in that, The temperature during the condensation reaction is 40~80℃; the temperature during the end-capping reaction is 50~100℃.

3. A carbonitride ultra-high temperature ceramic prepared by the method of claim 1 or 2.

4. The carbonitride ultra-high temperature ceramic according to claim 3, characterized in that, The chemical formula of the carbonitride ultra-high temperature ceramic is MeC x N 1-x , where 0 < x < 1; Me is one or more of Hf, Zr, Ti, and Ta.

5. The application of the carbonitride ultra-high temperature ceramic according to claim 3 or 4 in ultra-high temperature structures.

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