A multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic and a preparation method thereof

Abstract

The present application relates to a kind of multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramics and its preparation method.The composition general formula of the nanocomposite ceramics is (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 / SiOC, wherein a+b+c+d+e+f+g+h+i+j=1, and at least 2 of a, b, c, d, e, f, g, h, i, j are not simultaneously 0, x=1 or 2.The preparation method is to react rare earth metal element complex with silicon-based polymer to obtain single-source precursor;the single-source precursor is obtained by crosslinking and high-temperature heat treatment, or ceramic powder is obtained by crosslinking and pyrolysis of single-source precursor, and ceramic bulk is further obtained by high-temperature sintering.The preparation method of the present application is simple and reliable, short cycle, low cost, and can effectively improve the water-oxygen corrosion resistance of the material.

Description

Technical Field

[0001] This invention belongs to the field of structural ceramic material preparation, specifically relating to a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic and its preparation method. Background Technology

[0002] Turbine engines, due to their excellent thrust-to-weight ratio, play a crucial role in commercial and military aircraft, representing a strategic high ground in great power competition. To further improve engine thermal efficiency and thrust, higher turbine inlet gas temperatures are required, subjecting core components such as engine blades to higher temperatures and more demanding service environments. Aero-engine turbine inlet temperatures have already reached over 1600℃. Currently, turbine blades are primarily manufactured using high-performance single-crystal superalloys, employing thermal barrier coatings (TBCs), composite cooling, and double-wall supercooling technologies to enable high-speed operation in such harsh conditions. Further increasing the turbine inlet gas temperature would exceed the temperature resistance limit of single-crystal superalloys, making it difficult to meet requirements even with thermal barrier coatings and various cooling technologies. Therefore, the development of new high-temperature resistant turbine blade materials is urgently needed.

[0003] SiC / SiC ceramic matrix composites have long been considered ideal ultra-high temperature composite materials for thermal protection components in the aerospace field due to their low density, low coefficient of thermal expansion, and excellent high-temperature mechanical properties. Without cooling design, SiC / SiC ceramic matrix composites can withstand temperatures of 1300℃ to 1600℃ with excellent thermal stability, improving engine efficiency and reducing fuel consumption. Furthermore, SiC has a much lower density than high-temperature alloys, significantly reducing engine weight. However, the increasingly harsh operating environment of modern engines forces SiC / SiC ceramic matrix composites to face several serious challenges: high-temperature oxidation, water-oxygen corrosion, and molten salt corrosion. Water-oxygen corrosion is particularly problematic; at high temperatures, water vapor reacts with the SiO2 protective film to form volatile hydroxides. High-speed airflow accelerates the oxidation and volatilization reactions of SiC, leading to structural fragility and significant degradation of mechanical properties. This severely threatens not only engine blades but also core components.

[0004] Environmental barrier coatings (EBCs) can effectively address the aforementioned problems by insulating against water vapor. Among the many EBCs, rare earth silicates possess excellent resistance to water vapor corrosion and are considered one of the most promising EBC candidates. Rare earth silicates mainly include rare earth monosilicates (RE2SiO5) and rare earth disilicates (RE2Si2O7). For single-component rare earth metal EBCs, to address design challenges at higher temperatures, multi-component or high-entropy ceramic designs can be considered, transforming them into multi-component or high-entropy ceramics (HECs). In particular, compared to their single-component compounds, HECs exhibit characteristics such as giant dielectric constants, ultrafast plasma capabilities, good catalytic performance, and excellent capacitance retention; high-entropy non-oxide materials generally possess higher hardness, lower thermal conductivity, and good oxidation resistance. HECs offer a wide range of material systems with diverse properties, making them well-suited for EBC applications.

[0005] In recent years, given the excellent properties of high-entropy ceramics, researchers have attempted to synthesize and develop high-entropy ceramics of rare-earth silicates to obtain even better performance in EBCs. For example, high-entropy ceramics of rare-earth silicates (Ho) have been prepared by solid-state reaction methods. 0.25 Lu 0.25 Yb 0.25 Eu 0.25 The SiO5 powder was tested, and its thermal, mechanical, and matrix corrosion properties were investigated, demonstrating the superiority of high-entropy rare-earth silicate ceramics as EBCs. However, solid-state reaction methods are difficult to prepare single solid solutions with uniform distribution of multiple rare-earth metal elements, and the process is relatively complex, which cannot well meet the needs of existing EBCs. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the first objective of this invention is to provide a multi-element rare-earth silicate / silicon-oxygen-carbon nanocomposite ceramic. The nanocomposite ceramic provided by this invention comprises powder and / or bulk. The nanocomposite ceramic of this invention is produced by a polymer conversion method. Compared to traditional silicon-based ceramics, the ceramics of this invention are all nanocrystalline, exhibiting better resistance to water and oxygen corrosion. Secondly, the nanocomposite ceramic of this invention contains a multi-element rare-earth silicate phase, which possesses excellent resistance to water and oxygen corrosion. Therefore, the nanocomposite ceramic of this invention can compensate for the poor water and oxygen resistance of traditional silicon-based ceramics, resulting in excellent resistance to water and oxygen corrosion within the temperature range of 1200–1500℃. Experimental verification shows that it exhibits excellent resistance to water and oxygen corrosion even after prolonged exposure (100 hours) to water and oxygen.

[0007] The second objective of this invention is to provide a method for preparing multi-element rare-earth silicate / silicon-oxygen-carbon nanocomposite ceramics. The method utilizes a polymer-to-ceramic conversion process, converting a single-source precursor polymer into multi-element rare-earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder at high temperature, and then preparing nano-ceramic bulk through high-temperature sintering. The resulting ceramic exhibits an average grain size of ≤100 nm for the multi-element rare-earth silicates.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention discloses a multi-element rare-earth silicate / silicon-oxygen-carbon nanocomposite ceramic, with the general formula (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 / SiOC, where 0≤a<1, 0≤b<1, 0≤c<1, 0≤d<1, 0≤e<1, 0≤f<1, 0≤g<1, 0≤h<1, 0≤i<1, 0≤j<1, a+b+c+d+e+f+g+h+i+j=1, and at least two of a,b,c,d,e,f,g,h,i,j are not simultaneously 0, x=1 or 2, in the multi-element rare earth silicate, rare earth metal elements share the cation lattice points of the crystal, forming a single solid solution.

[0010] The nano-multiphase ceramic provided by this invention is 0 when at least two of a, b, c, d, e, f, g, h, i, j are not simultaneously equal to 0, i.e., multi-element rare earth silicate (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 There are at least two metallic elements in it.

[0011] Preferably, the nanocomposite ceramic contains both a uniformly distributed multi-element rare earth silicate phase and a SiOC ceramic phase.

[0012] As a preferred option, the general formula (Yb) a Ho b Er c Lud Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 The multi-element rare earth silicate in / SiOC has a monoclinic crystal structure. The rare earth metal elements Yb, Ho, Er, Lu, Tm, Gd, Tb, Y, La, and Sc atoms share the cation lattice points of the crystal, while Si and O atoms occupy the anion lattice points to form a single solid solution.

[0013] As a preferred option, multi-element rare earth silicates (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 The metal elements in the invention can be in equimolar or non-equimolar ratios. In this invention, the metal elements are in equimolar or near-equimolar ratios, which means they are medium-entropy or high-entropy rare earth silicates.

[0014] As a preferred embodiment, the present invention provides a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic, which is a ceramic powder and / or a ceramic block. The particle size of the ceramic powder is 0.1μm-1000μm, more preferably 5μm-200μm, and the porosity of the ceramic block is 0%-30%, more preferably 0%-10%.

[0015] As a preferred embodiment, the present invention provides a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic, wherein at least one phase in the nanocomposite ceramic has an average grain size of 0.1 nm-100 nm; more preferably 1 nm-70 nm.

[0016] As a preferred embodiment, the present invention provides a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic, wherein the multi-element rare earth silicate (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 The mass fraction is 0.1%-95%, more preferably 20%-85%.

[0017] This invention discloses a method for preparing multi-element rare-earth silicate / silicon-oxygen-carbon nanocomposite ceramics, comprising the following steps:

[0018] (1) Weigh and mix the complex of at least two metal elements among Yb, Ho, Er, Lu, Tm, Gd, Tb, Y, La, and Sc with a silicon-based polymer according to the stoichiometric ratio to obtain chemical raw materials. In an inert atmosphere, dissolve the prepared chemical raw materials in an organic solvent, stir and mix evenly, and then heat to allow a chemical reaction to occur, so that the metal atoms are attached to the molecular chain of the silicon-based polymer through chemical bonds. Finally, remove the solvent to obtain a silicon-based single-source precursor containing at least two rare earth metal elements.

[0019] (2) The silicon-based single-source precursor obtained in step (1) is cross-linked and subjected to high-temperature heat treatment under an inert atmosphere. After completing the "polymer-ceramic" conversion and phase separation and crystallization process, a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic is obtained. The inert gas is argon or nitrogen. The cross-linking temperature is 150-300℃, the heat treatment temperature is 1100-1800℃, preferably 1400-2200℃, and the holding time at the highest temperature is 0.1-20h.

[0020] or

[0021] The silicon-based single-source precursor obtained in step (1) is cross-linked and pyrolyzed under an inert atmosphere to complete the "polymer-ceramic" conversion process, thereby obtaining multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder; the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder is then subjected to high-temperature sintering to obtain multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic bulk. The pyrolysis temperature is 800-1500℃, preferably 800-1300℃, and the high-temperature sintering conditions are: sintering furnace vacuum degree <35Pa, preferably 5Pa, sintering temperature 1000-2000℃, preferably 1500-2200℃, sintering pressure 0-150MPa, holding time 0-600min, and heating rate 5-800℃ / min.

[0022] As a preferred option, the Yb metal complex is selected from ytterbium acetate (III) [C6H9O6Yb], ytterbium chloride (III) [YbCl3], and ytterbium acetylacetonate (III) [C 15 H 21 [O6Yb], Ytterbium nitrate (III) [Yb(NO3)3], Ytterbium carbonate (III) [C3H2O] 10 At least one of Yb2], ytterbium(III) fluoride [F3Yb], and their hydrates. Of course, other Yb metal element complexes can also be used in this invention.

[0023] As a preferred option, the complex of the Ho metal element is selected from holmium(III) acetate [(CH3CO2)3Ho], holmium(III) chloride [HoCl3], and holmium(III) acetylacetone [C 15 H 21 At least one of the following: holmium(III) nitrate [Ho(NO3)3], holmium(III) carbonate [C3O9Ho2], holmium(III) fluoride [F3Ho], and their hydrates. Of course, other Ho metal element complexes can also be used in this invention.

[0024] As a preferred option, the Er metal element complex is selected from erbium(III) acetate [(CH3CO2)3Er], erbium(III) chloride [ErCl3], and erbium(III) acetylacetone [C 15 H 21 At least one of the following: erbium(III) nitrate [Er(NO3)3], erbium(III) carbonate [C3O9Er2], erbium(III) fluoride [F3Er], and their hydrates. Of course, other Er metal element complexes can also be used in this invention.

[0025] As a preferred option, the Lu metal complex is selected from lutetium acetate (III) [(CH3CO2)3Lu], lutetium chloride (III) [LuCl3], and lutetium acetylacetonate (III) [C 15 H 21 O6Lu], lutetium(III) nitrate [Lu(NO3)3] or lutetium(III) carbonate hydrate [C3H2O] 10 At least one of Lu2], lutetium(III) fluoride [F3Lu], and their hydrates. Of course, other Lu metal element complexes can also be used in this invention.

[0026] As a preferred option, the complex of the metal element Tm is selected from thulium acetate (III) [Tm(OOCCH3)3], thulium chloride (III) [TmCl3], and thulium acetylacetonate (III) [C 15 H 21 At least one of the following: thulium(III) nitrate [Tm(NO3)3], thulium(III) carbonate hydrate [C3O9Tm2], thulium(III) fluoride [F3Tm], and their hydrates. Of course, other Tm metal element complexes can also be used in this invention.

[0027] As a preferred option, the Gd metal complex is selected from gadolinium acetate (III) [Gd(CH3CO2)3], gadolinium chloride (III) [GdCl3], and gadolinium acetylacetonate (III) [C 15 H 21At least one of the following: gadolinium(III) nitrate [Gd(NO3)3], gadolinium(III) carbonate [C3O9Gd2], gadolinium(III) fluoride [F3Gd], and their hydrates. Of course, other Gd metal element complexes can also be used in this invention.

[0028] As a preferred option, the complex of the Tb metal element is selected from terbium acetate (III) [C6H9O6Tb], terbium chloride (III) [TbCl3], and terbium acetylacetone (III) [C 15 H 21 At least one of the following: terbium(III) nitrate [Tb(NO3)3], terbium(III) carbonate [C3O9Tb2], terbium(III) fluoride [F3Tb], and their hydrates. Of course, other Tb metal element complexes can also be used in this invention.

[0029] As a preferred option, the complex of metal Y is selected from yttrium(III) acetate [C6H9O6Y], yttrium(III) chloride [YCl3], and yttrium(III) acetylacetone [C 15 H 21 At least one of the following: [O6Y], yttrium(III) nitrate [Y(NO3)3], yttrium(III) carbonate [C3O9Y2], yttrium(III) fluoride [F3Y], and their hydrates. Of course, other Y metal element complexes can also be used in this invention.

[0030] As a preferred option, the complex of the La metal element is selected from lanthanum acetate (III) [C6H9O6La], lanthanum chloride (III) [LaCl3], and lanthanum acetylacetone (III) [C 15 H 21 At least one of the following: [O6La], lanthanum(III) nitrate [La(NO3)3], lanthanum(III) carbonate [C3O9La2], lanthanum(III) fluoride [F3La] and their hydrates; of course, other La metal element complexes can also be used in this invention.

[0031] As a preferred option, the complex of the Sc metal element is selected from scandium(III) acetate [C6H9O6Sc], scandium(III) chloride [ScCl3], and scandium(III) acetylacetone [C 15 H 21 At least one of the following: scandium(III) nitrate [Sc(NO3)3], scandium(III) carbonate [C3O9Sc2], scandium(III) fluoride [F3Sc], and their hydrates; of course, other Sc metal element complexes can also be used in this invention.

[0032] As a preferred embodiment, the silicon-based polymer is one or more of polysiloxane, polycarbosilane, allyl hydrogenated polycarbosilane, vinyl polycarbosilane, and hyperbranched polycarbosilane, preferably polysiloxane. When the silicon-based polymer is preferably polysiloxane, the resulting composite ceramic exhibits the best performance.

[0033] In this invention, the preferred rare earth metal element complex reacts with a portion of the silicon-based polymer to form a multi-element rare earth silicate phase through pyrolysis, while the remaining portion of the silicon-based polymer undergoes pyrolysis to form a SiOC phase, thus forming a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic, i.e., the general chemical formula; (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 / SiOC.

[0034] As a preferred embodiment, the organic solvent is at least one of anhydrous isopropanol or anhydrous xylene.

[0035] As a preferred embodiment, the inert atmosphere is argon and / or nitrogen.

[0036] As a preferred embodiment, the heating temperature is 30-200℃, more preferably 80-150℃, and the heating reaction time is 10-600 min, more preferably 120-180 min.

[0037] The solvent removal method is either vacuum distillation or rotary evaporation. Preferably, vacuum distillation is used for solvent removal, and the heating temperature range during vacuum distillation is 50-80°C. After solvent removal, a silicon-based single-source precursor containing at least two rare earth metal elements is obtained.

[0038] As a further preferred option, the pyrolysis temperature is 800-1500℃ and the holding time is 2-4h.

[0039] In this invention, the obtained silicon-based single-source precursor is heat-treated at a higher temperature (≥1200℃) under inert gas protection to obtain multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic.

[0040] Preferably, the heat treatment temperature is 1300-1800℃ and the holding time is 2-6h.

[0041] The multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder obtained by this invention is sintered at high temperature to obtain multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic bulk.

[0042] As a preferred embodiment, the high-temperature sintering is spark plasma sintering, and the sintering conditions are: vacuum degree of sintering furnace <5Pa, temperature 1000-2000℃, sintering pressure 50-100MPa, holding time 10-30min, and heating rate 100-800℃ / min, preferably 100-400℃ / min.

[0043] The average grain size of the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic bulk obtained by this invention is less than 100 nm. After optimization, it can be less than or equal to 60 nm.

[0044] The mass of the multi-element rare-earth silicate / silicon-oxygen-carbon nanocomposite ceramic bulk obtained in this invention continuously increases under water-oxygen conditions at 1200℃, and its parabolic oxidation rate constant (K) increases. p Less than 8.0*10 -1 mg 2 / (cm 4 •h). The parabolic oxidation rate constant (K0) of the optimized multi-element rare-earth silicate nanoceramic bulk at 1200℃. p Less than 7.0*10 -1 mg 2 / (cm 4 •h). The mass of the bulk rare-earth silicate / silicon-oxygen-carbon nanocomposite ceramic under water-oxygen conditions at 1500℃ first increases and then decreases, with the parabolic oxidation rate constant during the decreasing phase being less than -3.0*10. -2 mg 2 / (cm 4 ·h). The parabolic oxidation rate constant (K) of the optimized multi-element rare earth silicate nanoceramic bulk material. p Less than -2.0*10 -2 mg 2 / (cm 4 ·h). Compared to pure SiOC ceramics, its physical oxidation rate constant (K0) at 1200℃ is higher. p The value is 4.677 * 10. -1 mg 2 / (cm 4 ·h). Parabolic oxidation rate constant (K) during the decreasing phase at 1500℃. p The value is -2.078*10. -1 mg 2 / (cm 4 •h). Under the same conditions, the resistance of multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic bulk to water-oxygen corrosion is better than that of pure SiOC ceramic.

[0045] The technical solution of this invention has the following advantages:

[0046] (1) The preparation process of the method described in this invention is simple and easy to implement, and the preparation cycle is short;

[0047] (2) The method described in this invention is beneficial for achieving flexible control and uniform distribution of metal elements at the molecular level;

[0048] (3) The ceramic prepared by this invention has excellent resistance to water and oxygen. The resulting nano-multiphase ceramic bulk has excellent resistance to water and oxygen corrosion at 1200-1500℃, and the oxide layer is continuous and dense.

[0049] This method introduces rare earth metal elements through the chemical reaction of small molecules of complexes with polymers. The types and proportions of various rare earth metal elements can be precisely controlled by adjusting the types and ratios of the complexes. It enables uniform mixing of rare earth metal elements at the molecular level, effectively solving the challenges of forming single-phase solid solutions from multiple elements, achieving uniform distribution of nano-ceramic phases, and coarsening of grains at high temperatures, thereby improving the mechanical properties and oxidation resistance of materials. This method requires simple equipment, has a simple and reliable process, a short preparation cycle, and the potential for large-scale mass production. Attached Figure Description

[0050] Figure 1 This is a flowchart of the preparation process of multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramics according to the present invention.

[0051] Figure 2 The image shows the XRD pattern of the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder obtained in Example 1 of this invention.

[0052] Figure 3 The image shows the XRD pattern of the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder obtained in Example 2 of this invention.

[0053] Figure 4 The image shows the XRD pattern of the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder obtained in Example 3 of this invention.

[0054] Figure 5 The image shows the XRD pattern of the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder obtained in Example 4 of this invention.

[0055] Figure 6 This is a TEM image of the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder obtained in Example 4 of the present invention.

[0056] Figure 7 The image shows the XRD pattern of the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic bulk obtained in Example 5 of this invention.

[0057] Figure 8 This is a cross-sectional SEM image of the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic block obtained in Example 5 of the present invention after water oxidation at 1200℃.

[0058] Figure 9 This is a surface SEM comparison image of the multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic block obtained in Example 5 of the present invention and the ordinary SiOC ceramic block after water oxidation at 1300℃.

[0059] Figure 10 The image shows the XRD pattern of the ceramic powder obtained in Comparative Example 1 of this invention. Detailed Implementation

[0060] The following embodiments further illustrate this description. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the invention.

[0061] Example 1

[0062] According to (Tm) 0.2 Yb 0.3 Er 0.3 Ho 0.3 1 g of ytterbium(III) acetate tetrahydrate, 0.82 g of thulium(III) acetate hydrate, 0.83 g of erbium(III) acetate tetrahydrate, and 0.81 g of holmium(III) acetate hydrate were weighed and dissolved in anhydrous isopropanol. 3.32 g of polysiloxane (PSO) was weighed and mixed evenly. The mixture was stirred at room temperature for 30 min, heated to 150 °C and held for 2 h, allowed to cool naturally and allowed to stand. Isopropanol was removed by vacuum distillation. The mixture was then crosslinked at 250 °C. The single-source precursor was then held at 1100 °C for 3 h in argon to obtain ceramic powder. Subsequently, the powder was heat-treated in argon at 1300 °C, 1400 °C, and 1500 °C for 2 h to obtain the crystallized ceramic.

[0063] like Figure 2 As shown, the chemical composition obtained is (Tm) 0.2 Yb 0.3 Er 0.3 Ho 0.3 The XRD pattern of 2SiO5 / SiOC ceramics exhibits two sets of diffraction peaks. The main peak is a rare-earth silicate diffraction peak with a monoclinic crystal structure, indicating that two equal Tm, Yb, Er, and Ho atoms occupy cation sites. At the first Tm, Yb, Er, and Ho site, Tm, Yb, Er, and Ho interact with seven O atoms. 2- Atoms combine to form a twisted (Tm, Yb, Er, Ho)O7 hexagonal pyramid. One corner is shared with two equivalent SiO4 tetrahedra, another with six equivalent (Tm, Yb, Er, Ho)O7 hexagonal pyramids, and yet another with one SiO4 tetrahedron. At the second Tm, Yb, Er, Ho position, Tm, Yb, Er, Ho are combined with eight O atoms. 2- Atomic bonding. Si and O atoms occupy anion lattice sites and combine to form SiO4 tetrahedra, thus forming a solid solution. The secondary peak is a small amount of SiC diffraction peak.

[0064] XRD precision calculations were performed to determine the (Tm) content in the ceramic powder. 0.2 Yb 0.3 Er 0.3 Ho 0.3 The grain size of 2SiO5 crystals is 1.55 nm, (Tm 0.2 Yb 0.3 Er 0.3 Ho 0.3 The cell parameters of 2SiO5 are a = 0.66333 nm, b = 0.68231 nm, and c = 0.89909 nm.

[0065] Example 2

[0066] According to (Tm) 0.2 Yb 0.2 Er 0.2 Ho 0.2 Lu 0.2 The stoichiometric ratio of ytterbium(III) acetate tetrahydrate, 0.82g thulium(III) acetate hydrate, 0.82g erbium(III) acetate tetrahydrate, 0.82g holmium(III) acetate hydrate, and 0.85g lutetium(III) acetate hydrate was weighed and dissolved in anhydrous isopropanol. 4.2g PSO was weighed and the two were mixed evenly. The mixture was stirred at room temperature for 30 minutes, then heated to 150℃ and held for 2 hours. After natural cooling, it was allowed to stand. Isopropanol was removed by vacuum distillation. The mixture was then crosslinked at 250℃. The single-source precursor was then held at 1100℃ in argon for 3 hours to obtain ceramic powder. Subsequently, it was heat-treated in argon at 1300℃, 1400℃, and 1500℃ for 2 hours.

[0067] like Figure 3 As shown, the chemical composition obtained is (Tm) 0.2 Yb 0.2 Er 0.2 Ho 0.2 Lu 0.2 The XRD pattern of the 2SiO5 / SiOC nanoceramics exhibits two sets of diffraction peaks, which are typical diffraction peaks of rare earth metal silicates with monoclinic crystal structures. Specifically, two equal Tm, Yb, Er, Ho, and Lu atoms occupy cation sites. At the first Tm, Yb, Er, Ho, and Lu site, Tm, Yb, Er, Ho, and Lu interact with seven O atoms. 2- Atoms combine to form a twisted (Tm, Yb, Er, Ho, Lu)O7 hexagonal pyramid. The edges are shared with two equivalent SiO4 tetrahedra, six equivalent (Tm, Yb, Er, Ho, Lu)O7 hexagonal pyramids, and one SiO4 tetrahedron. At the second Tm, Yb, Er, Ho, Lu position, Tm, Yb, Er, Ho, Lu are combined with eight O atoms. 2 - Atomic bonding. Si and O atoms occupy anionic lattice sites and combine to form SiO4 tetrahedra, thus forming a solid solution.

[0068] Tm was obtained through XRD refinement calculation. 0.15 Yb 0.25 Er 0.2 Ho 0.2 Lu 0.2 The grain size of 2SiO5 crystals is 1.46 nm, (Tm 0.15 Yb 0.25 Er 0.2 Ho 0.2 Lu 0.2 The cell parameters of 2SiO5 are a = 0.66452 nm, b = 0.68043 nm, and c = 0.8993 nm.

[0069] Example 3

[0070] According to (Yb) 0.2 Er 0.2 Ho 0.2 Lu 0.2 Gd 0.2 The stoichiometric ratio of ytterbium(III) acetate tetrahydrate, 0.94 g gadolinium(III) acetate hydrate, 0.93 g erbium(III) acetate tetrahydrate, 0.96 g holmium(III) acetate hydrate, and 0.94 g lutetium(III) acetate hydrate was weighed and dissolved in anhydrous isopropanol. 4.13 g PSO was weighed and the two were mixed evenly. The mixture was stirred at room temperature for 30 min, heated to 150 °C and held for 2 h, allowed to cool naturally, and the anhydrous isopropanol was removed by vacuum distillation. The mixture was then crosslinked at 250 °C. The single-source precursor was then held at 1100 °C for 3 h in argon to obtain ceramic powder. Subsequently, the powder was heat-treated in argon at 1300 °C, 1400 °C, and 1500 °C for 2 h.

[0071] like Figure 4 As shown, the chemical composition obtained is (Yb 0.2 Er 0.2 Ho 0.2 Lu 0.2 Gd 0.2The XRD pattern of the 2SiO5 / SiOC ceramic powder exhibits two sets of diffraction peaks, which are typical diffraction peaks of rare earth metal silicates with monoclinic crystal structures. Specifically, two equal Lu, Yb, Er, Ho, and Gd atoms occupy cation sites. At the first Lu, Yb, Er, Ho, and Gd site, Lu, Yb, Er, Ho, and Gd interact with seven O atoms. 2 - Atoms combine to form a twisted (Lu, Yb, Er, Ho, Gd)O7 hexagonal pyramid. One corner is shared with two equivalent SiO4 tetrahedra, another with six equivalent (Lu, Yb, Er, Ho, Gd)O7 hexagonal pyramids, and yet another with one SiO4 tetrahedron. At the second Lu, Yb, Er, Ho, Gd position, Lu, Yb, Er, Ho, Gd are combined with eight O atoms. 2 - Atomic bonding. Si and O atoms occupy anionic lattice sites and combine to form SiO4 tetrahedra, thus forming a solid solution.

[0072] Calculation yields (Yb) 0.2 Er 0.2 Ho 0.2 Lu 0.2 Gd 0.2 The crystal size of sodium rare earth silicate 2SiO5 is 1.31 nm, (Yb 0.22 Er 0.2 Ho 0.2 Lu 0.2 Gd 0.18 The cell parameters of 2SiO5 are a = 0.66425 nm, b = 0.68137 nm, and c = 0.90089 nm.

[0073] Example 4

[0074] According to (Yb) 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 The stoichiometric ratio of ytterbium(III) acetate tetrahydrate, 1.01 g of terbium(III) acetate hydrate, 1.02 g of erbium(III) acetate tetrahydrate, 1.04 g of holmium(III) acetate hydrate, and 1.02 g of lutetium(III) acetate hydrate was weighed and dissolved in anhydrous isopropanol. 4.52 g of PSO was weighed and mixed evenly. The mixture was stirred at room temperature for 30 min, heated to 150 °C and held for 2 h, allowed to cool naturally and stand, and the anhydrous isopropanol solution was removed by vacuum distillation. The mixture was then crosslinked at 250 °C. The single-source precursor was then held at 1100 °C for 3 h in argon to obtain ceramic powder. Subsequently, the powder was heat-treated in argon at 1300 °C, 1400 °C, and 1500 °C for 2 h.

[0075] Elemental analysis revealed that the contents of Yb, Ho, Er, Lu, and Tb were approximately in equimolar ratios, resulting in a chemical composition of (Yb...). 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 Nanoceramics of 2SiO5 / SiOC. For example... Figure 5 As shown, its XRD pattern exhibits two sets of diffraction peaks, which are typical diffraction peaks of rare earth metal silicates with monoclinic crystal structures. That is, there are two equal Lu, Yb, Er, Ho, Tb atoms occupying cation sites. At the first Lu, Yb, Er, Ho, Tb site, Lu, Yb, Er, Ho, Tb interact with seven O atoms. 2 - Atoms combine to form a distorted (Lu, Yb, Er, Ho, Tb)O7 hexagonal pyramid. An edge is shared with two equivalent SiO4 tetrahedra, an edge is shared with six equivalent (Lu, Yb, Er, Ho, Tb)O7 hexagonal pyramids, and an edge is shared with one SiO4 tetrahedron. At the second Lu, Yb, Er, Ho, Tb position, Lu, Yb, Er, Ho, Tb are combined with eight O atoms. 2 - Atomic bonding. Si and O atoms occupy anionic lattice sites and combine to form SiO4 tetrahedra, thus forming a solid solution.

[0076] Calculation yields (Yb) 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 The grain size of 2SiO5 crystals is 1.37 nm, such as... Figure 6 As shown in (a), the obtained rare earth silicates are almost all homogeneous (Yb). 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 )2SiO5, Figure 6 (b) Statistics (Yb) 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 The grain size of 2SiO5 is approximately 3.61 nm, which is similar to the results obtained from XRD refinement. Figure 6 (c) shows that the various metal elements in rare earth silicates are evenly distributed. (Yb) 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2The cell parameters of 2SiO5 are a = 0.66437 nm, b = 0.68209 nm, and c = 0.90087 nm.

[0077] Example 5

[0078] According to (Yb) 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 The stoichiometric ratio of ytterbium(III) acetate tetrahydrate, terbium(III) acetate hydrate, erbium(III) acetate tetrahydrate, holmium(III) acetate hydrate, and lutetium(III) acetate hydrate were weighed and dissolved in anhydrous isopropanol. 14.09g of PSO was weighed and mixed evenly. The mixture was stirred at room temperature for 30 min, heated to 150℃ and kept at that temperature for 2 h, allowed to cool naturally and stand, and the anhydrous isopropanol solution was removed by vacuum distillation. The mixture was then placed in a container at 250℃ for crosslinking. Finally, the single-source precursor was kept at 1100℃ in argon for 3 h to obtain ceramic powder.

[0079] The ceramic powder was placed in a graphite mold for spark plasma sintering. The vacuum degree in the furnace was <5 Pa. The temperature was increased to 1500℃ at a heating rate of 100℃ / min, held for 20 min, and the pressure was 50 MPa. Then, it was cooled to room temperature at a cooling rate of 100℃ / min to obtain nano-ceramic bulk material, denoted as (YbErHoLuTb)2SiO5-SPS.

[0080] like Figure 7 As shown, the chemical composition obtained is (Yb 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 )2SiO5 / SiOC and (Yb 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 The 2Si₂O₇ / SiOC ceramic bulk has a density of 93.85%, and its XRD pattern shows two sets of diffraction peaks (Yb). 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 2SiO5 exhibits typical diffraction peaks of rare-earth metal silicates with a monoclinic crystal structure, indicating that two equal numbers of Lu, Yb, Er, Ho, and Tb atoms occupy cation sites. At the first Lu, Yb, Er, Ho, and Tb site, Lu, Yb, Er, Ho, and Tb interact with seven O atoms. 2- Atoms combine to form a distorted (Lu, Yb, Er, Ho, Tb)O7 hexagonal pyramid. An edge is shared with two equivalent SiO4 tetrahedra, an edge is shared with six equivalent (Lu, Yb, Er, Ho, Tb)O7 hexagonal pyramids, and an edge is shared with one SiO4 tetrahedron. At the second Lu, Yb, Er, Ho, Tb position, Lu, Yb, Er, Ho, Tb are combined with eight O atoms. 2 - Atomic bonding. Si and O atoms occupy anion lattice sites, bonding to form SiO4 tetrahedra, thus forming a solid solution. (Yb 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 )2Si2O7 exhibits typical diffraction peaks of rare-earth metal silicates with a triclinic crystal structure, meaning that four unequal Lu, Yb, Er, Ho, and Tb atoms occupy cation sites. At the first Lu, Yb, Er, Ho, and Tb site, Lu, Yb, Er, Ho, and Tb are geometrically related to seven O atoms in a 7-coordinate pattern. 2 - Atom bonding, at the second Lu, Yb, Er, Ho, Tb position, Lu, Yb, Er, Ho, Tb in an 8-coordinate geometric form with 8 O atoms. 2 - Atom bonding, at the third Lu, Yb, Er, Ho, Tb site, Lu, Yb, Er, Ho, Tb with 6 O atoms. 2 - Atoms combine to form an (Lu, Yb, Er, Ho, Tb)O6 octahedron, sharing corners with seven SiO4 tetrahedra. At the fourth position of Lu, Yb, Er, Ho, and Tb, Lu, Yb, Er, Ho, and Tb are geometrically linked with eight O atoms in an 8-coordinate configuration. 2 - Atoms combine, with Si and O atoms occupying anion lattice sites, combining to form SiO4 tetrahedra, thus forming a solid solution.

[0081] The calculation yields (Yb) in the ceramic block. 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 The grain size of 2SiO5 rare earth silicate crystals is 2.64 nm, (Yb 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 The cell parameters of 2SiO5 are a = 0.66502 nm, b = 0.68107 nm, c = 0.89987 nm; (Yb 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb0.2 The grain size of 2Si2O7 rare earth silicate crystals is 1.43 nm, (Yb 0.2 Er 0.2 Ho 0.2 Lu 0.2 Tb 0.2 The cell parameters of 2Si2O7 are a = 0.65274 nm, b = 0.65543 nm, and c = 1.2008 nm.

[0082] Figure 8 This is a cross-sectional image of (YbErHoLuTb)2SiO5-SPS after water-oxygen corrosion at 1200℃ for 50 h. The water-oxygen layer in the image is continuous and dense, with a thickness of approximately 7.11 μm. Its mass continuously increases, and the parabolic oxidation rate constant (K) is shown. p The value is 6.245*10. -1 mg 2 / (cm 4 •h). The ceramic mass under water-oxygen corrosion at 1500℃ first increases and then decreases, with the parabolic oxidation rate constant (K) during the decreasing phase. p The value is -5.13 * 10. -2 mg 2 / (cm 4 ·h). For pure SiOC ceramics, the physical oxidation rate constant of SiOC at 1200℃ (K p The value is 4.677 * 10. -1 mg 2 / (cm 4 ·h), the parabolic oxidation rate constant (K) during the decreasing phase at 1500℃. p The value is -2.078*10. -1 mg 2 / (cm 4 ·h). Compared to SiOC, its resistance to water and oxygen corrosion has been significantly improved.

[0083] Figure 9 The images show the surface images of (YbErHoLuTb)₂SiO₅-SPS and SiOC ceramics after 100 hours of water-oxygen corrosion at 1300℃. Figure a shows (YbErHoLuTb)₂SiO₅-SPS, and Figure b shows the SiOC ceramic. It is clear from the images that the surface of (YbErHoLuTb)₂SiO₅-SPS in Figure a is dense and crack-free, while the surface of the SiOC ceramic in Figure b shows many cracks, and significant flaking has occurred. Compared to SiOC ceramics and many common silicon-based ceramics, (YbErHoLuTb)₂SiO₅-SPS exhibits superior resistance to water-oxygen corrosion.

[0084] Comparative Example 1

[0085] According to the stoichiometric ratio of Yb₂SiO₅, 5g of ytterbium(III) acetate tetrahydrate was weighed and dissolved in anhydrous isopropanol, and 5g of PSO was weighed and dissolved in anhydrous isopropanol. The two were mixed evenly, heated to 150℃ and held for 2 hours, then allowed to cool naturally. The anhydrous isopropanol was removed by vacuum distillation, and then the mixture was placed at 250℃ for crosslinking. The single-source precursor was then held at 1100℃ for 3 hours in argon to obtain ceramic powder. Subsequently, it was heat-treated in argon at 1300–1500℃ for 2 hours.

[0086] like Figure 10 As shown, the prepared ceramic powder exhibits multiple characteristic peaks, indicating that when there is only one rare earth metal element in the rare earth silicate, the ceramic powder obtained after heat treatment or pyrolysis cannot form a single stable rare earth silicate ceramic. When the temperature is below 1100℃, it is the Yb2SiO5 phase, and when the temperature is above 1300℃, it is the Yb2SiO5 and Yb2Si2O7 phases. However, if it is the previous high-entropy rare earth silicate, its phase is a single phase.

[0087] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramics, characterized in that, Includes the following steps: (1) Weigh and mix the complex of at least two metal elements among Yb, Ho, Er, Lu, Tm, Gd, Tb, Y, La, and Sc with the silicon-based polymer according to the stoichiometric ratio to obtain chemical raw materials. In an inert atmosphere, dissolve the prepared chemical raw materials in a solvent, stir and mix evenly, and then heat to make a chemical reaction, so that rare earth metal atoms are linked to the molecular chain of the silicon-based polymer through chemical bonds. Finally, remove the solvent to obtain a silicon-based single-source precursor containing at least two rare earth metal elements. (2) The silicon-based single-source precursor obtained in step (1) is cross-linked and subjected to high-temperature heat treatment under an inert atmosphere to complete the "polymer-ceramic" transformation and phase separation and crystallization process, thereby obtaining a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic. The inert gas is argon or nitrogen, the cross-linking temperature is 150-300℃, the heat treatment temperature is 1100-1800℃, and the holding time at the highest temperature is 0.1-20 h; or The silicon-based single-source precursor obtained in step (1) is cross-linked and pyrolyzed under an inert atmosphere to complete the "polymer-ceramic" conversion process, thereby obtaining multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic powder; the ceramic powder is sintered at high temperature to obtain multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic bulk. The pyrolysis temperature is 800-1500℃, and the high-temperature sintering conditions are: sintering furnace vacuum degree <35 Pa, sintering temperature 1000-2000℃, sintering pressure 0-150 MPa, holding time 0-600 min, and heating rate 5-800℃ / min. The general formula for the composition of the rare earth silicate ceramic is (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 / SiOC, where 0≤a<1, 0≤b<1, 0≤c<1, 0≤d<1, 0≤e<1, 0≤f<1, 0≤g<1, 0≤h<1, 0≤i<1, 0≤j<1, a+b+c+d+e+f+g+h+i+j=1, and at least two of a, b, c, d, e, f, g, h, i, j are not simultaneously 0, x=1 or 2, in the multi-element rare earth silicate, rare earth metal elements share the cation lattice points of the crystal to form a single solid solution.

2. The method for preparing a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic according to claim 1, characterized in that: Yb element complexes are selected from at least one of ytterbium acetate (III) and ytterbium acetylacetonate (III); Ho element complexes are selected from at least one of holmium acetate (III) and holmium acetylacetonate (III); Er metal element complexes are selected from at least one of erbium acetate (III) and erbium acetylacetone (III); The Lu metal element complex is selected from at least one of lutetium acetate (III) and lutetium acetylacetone (III); The Tm metal element complex is selected from at least one of thulium acetate (III) and thulium acetylacetone (III); The Gd metal element complex is selected from at least one of gadolinium acetate (III) and gadolinium acetylacetone (III); The Tb metal element complex is selected from at least one of terbium acetate (III) and terbium acetylacetone (III); The Y metal element complex is selected from at least one of yttrium acetate (III) and yttrium acetylacetone (III); The La metal element complex is selected from at least one of lanthanum(III) acetate and lanthanum(III) acetylacetone; The Sc metal element complex is selected from at least one of scandium acetate (III) and scandium acetylacetone (III); The silicon-based polymer is one or more of polysiloxane, polycarbosilane, allyl hydrogenated polycarbosilane, vinyl polycarbosilane, and hyperbranched polycarbosilane; the solvent is anhydrous isopropanol or anhydrous xylene; the inert atmosphere is argon and / or nitrogen; the heating temperature is 30-200℃; the heating reaction time is 10-600 min; and the solvent removal method is vacuum distillation or rotary evaporation. The high-temperature sintering is spark plasma sintering, and the sintering conditions are: vacuum degree of sintering furnace <35 Pa, temperature 1000-2000℃, sintering pressure 50-100 MPa, holding time 10-30 min, and heating rate 100-800℃ / min.

3. The method for preparing a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic according to claim 1, characterized in that: The nanocomposite ceramic contains both a uniformly distributed multi-element rare earth silicate phase and a SiOC ceramic phase.

4. The method for preparing a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic according to claim 1, characterized in that: General formula (Yb) a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 The multi-element rare earth silicate in / SiOC has a monoclinic crystal structure. The rare earth metal elements Yb, Ho, Er, Lu, Tm, Gd, Tb, Y, La, and Sc atoms share the cation lattice of the crystal, while Si and O atoms occupy the anion lattice, forming a single solid solution.

5. The method for preparing a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic according to claim 1, characterized in that: Multi-element rare earth silicates (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 The metallic elements in the composition are either in an equimolar ratio or an unequal molar ratio.

6. The method for preparing a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic according to claim 1, characterized in that: Multi-element rare earth silicates (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 There are at least two rare earth metal elements.

7. The method for preparing a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic according to claim 1, characterized in that: The nano-multiphase ceramic is a ceramic powder or a ceramic block, with the ceramic powder having a particle size of 0.1 μm-1000 μm and the ceramic block having an open porosity of 0%-30%.

8. The method for preparing a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic according to claim 1, characterized in that: The nanocomposite ceramic has at least one phase with an average grain size of 0.1 nm-100 nm.

9. The method for preparing a multi-element rare earth silicate / silicon-oxygen-carbon nanocomposite ceramic according to claim 1, characterized in that: In the nano-composite ceramic, the multi-element rare earth silicate (Yb a Ho b Er c Lu d Tm e Gd f Tb g Y h La i Sc j )2Si x O 2x+3 The mass fraction ranges from 0.1% to 95%.

Images