Compact amorphous SiMN ceramic and preparation method thereof

Abstract

The invention relates to the technical field of ceramic materials, and discloses a compact amorphous SiMN ceramic and a preparation method thereof.The preparation method comprises the steps that an organic metal M source is grafted to a Si-N chain of a silicon nitride precursor, and a Si-M-N polymer precursor is obtained; the Si-M-N polymer precursor is subjected to cracking, and amorphous SiMN ceramic powder is obtained; the amorphous SiMN ceramic powder is pre-formed and then packaged, then synthesis is carried out at high temperature and high pressure, and compact amorphous SiMN ceramic is obtained after cooling and pressure relief; m is one of Hf, Zr and Ti. According to the preparation method disclosed by the invention, additive sintering is avoided, so that impurities and embrittlement effects possibly introduced by a traditional additive are avoided, and the purity and comprehensive performance of the amorphous ceramic material are further improved; the amorphous SiMN ceramic has high compactness and microscopic uniformity, particles are promoted to be fully combined under the high-temperature and high-pressure sintering condition, and the amorphous ceramic with high compactness and a uniform structure is formed.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, in particular to a dense amorphous SiMN ceramic and a preparation method thereof. Background Art

[0002] Amorphous ceramics have attracted widespread attention in recent years due to their lack of long-range ordered structure, highly tunable composition, isotropy, and excellent physical and chemical stability. Compared to traditional polycrystalline ceramics, amorphous ceramics structurally eliminate the influence of grain boundaries, exhibiting superior mechanical properties, wear resistance, and corrosion resistance. Furthermore, amorphous ceramics offer unique advantages in thermal and electrical conductivity, as well as diffusion properties, demonstrating broad application prospects in extreme environment structural components, electrical insulation materials, and functional ceramics.

[0003] Silicon nitride (Si3N4), as a typical covalent ceramic material, has strong atomic bonding and a low self-diffusion coefficient, which makes it extremely difficult to maintain an amorphous structure under normal conditions. It is often prone to crystallization during heat treatment, which limits the preparation of its amorphous ceramics. Traditional amorphous ceramic preparation methods have problems such as the introduction of impurities by sintering aids, difficulties in densification, and non-uniform structures. In addition, due to the high melting point and weak sintering driving force of Si3N4, it is difficult to achieve effective densification without a sintering aid, which often results in a large number of pores remaining in the ceramic, significantly reducing its mechanical and functional properties. Therefore, the development of Si3N4 ceramic preparation technology that does not require a sintering aid and can stably maintain an amorphous structure and achieve densification still faces major challenges.

[0004] Therefore, there is an urgent need for a dense amorphous SiMN ceramic and a preparation method thereof to solve the above technical problems. Summary of the Invention

[0005] The purpose of the present invention is to solve the above technical problems and provide a dense amorphous SiMN ceramic and a preparation method thereof.

[0006] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0007] A method for preparing dense amorphous SiMN ceramics comprises the following steps:

[0008] S1, grafting an organic metal M source onto the Si-N chain of a silicon nitride precursor to obtain a Si-MN polymer precursor;

[0009] S2, cracking the Si-MN polymer precursor to obtain amorphous SiMN ceramic powder;

[0010] S3, preforming the amorphous SiMN ceramic powder and encapsulating it, then synthesizing it under high temperature and high pressure, and cooling and releasing the pressure to obtain dense amorphous SiMN ceramics;

[0011] The M is one of Hf, Zr and Ti.

[0012] Preferably, in step S1, the organic metal M source is tetrakis(dimethylformamide) M, and the silicon nitride precursor is perhydropolysilazane (PHPS).

[0013] Preferably, the amount of perhydropolysilazane used is calculated as Si, the amount of tetrakis(dimethylamide)M used is calculated as M, and the perhydropolysilazane and tetrakis(dimethylamide)M are mixed at different Si:M molar ratios.

[0014] Preferably, the molar ratio of Si:M of perhydropolysilazane and tetrakis(dimethylamino)amide M is (1-3):1.

[0015] Preferably, in an anhydrous and oxygen-free environment, an organic metal M source is grafted onto the Si-N chain of a silicon nitride precursor by a single-source precursor method to prepare a Si-MN polymer precursor.

[0016] Specifically, the organometallic M sources are tetrakis(dimethylamide) hafnium (TDMAH), tetrakis(dimethylamide) zirconium (TDMAZ), and tetrakis(dimethylamide) titanium (TDMAT). In an inert atmosphere within a double-row tube and glove box, the organometallic M sources are chemically grafted onto the Si-N chain of the silicon nitride precursor, achieving molecular-level regulation.

[0017] Specifically, the mixing process of perhydropolysilazane and tetrakis(dimethylamide)M is as follows:

[0018] In an argon-protected glove box, perhydropolysilazane and tetrakis(dimethylamino)M were added to a schlenk reaction flask equipped with a magnet. After sealing, the schlenk reaction flask was moved out of the glove box, connected to a double-row tube, and the reaction system was replaced with argon. Under the condition of continuous argon flow, magnetic stirring was performed to obtain a Si-MN polymer precursor.

[0019] Preferably, the step S2 is to prepare amorphous SiMN ceramic powder by cracking in NH3 / N2 mixed gas at 800°C for 2 hours.

[0020] Preferably, in the NH3 / N2 mixed gas, the volume ratio of NH3 to N2 is 1:1.

[0021] Preferably, in step S3, the preforming process is: pre-pressing the amorphous SiMN ceramic powder under an inert atmosphere at a pressure of 50 MPa for 10 minutes to obtain a preformed sample.

[0022] Specifically, amorphous SiMN ceramic powder is placed into a BN mold under an inert atmosphere, which can be achieved in a glove box. This preforming process gives the amorphous SiMN ceramic powder a basic shape and a certain mechanical strength, preventing cracking or deformation during subsequent packaging and high-temperature, high-pressure sintering.

[0023] Preferably, in step S3, the packaging process is: packaging the preformed sample with metal molybdenum foil under the protection of an inert atmosphere.

[0024] Specifically, the preformed samples were packaged with metal molybdenum foil in a glove box, which can prevent sample contamination.

[0025] To prevent the samples from being contaminated in high-temperature and high-pressure environments and to avoid composition fluctuations and structural degradation, the pre-pressed samples are encapsulated with metal molybdenum foil to effectively isolate active media such as environmental moisture, oxygen, and carbon, thereby maintaining the purity of the SiMN ceramics and the stability of the amorphous phase.

[0026] Preferably, in step S3, the process of synthesizing under high temperature and high pressure is: keeping the temperature and pressure at 1000-1200° C. for 10 minutes at a synthesis pressure of 1-5 GPa.

[0027] Preferably, in step S3, during the synthesis process under high temperature and high pressure, the temperature is raised to 1000-1200° C. at a heating rate of 60° C. / min.

[0028] Specifically, the high temperature and high pressure synthesis process can use a six-sided hydraulic press.

[0029] The preformed sample, wrapped in molybdenum foil, is placed in the center of a six-sided hydraulic press. A segmented graphite heater is used as the external heating element, and the high-pressure chamber temperature is calibrated using a thermocouple. These synergistic effects create a stable and uniform temperature field, facilitating control of the microstructural evolution of the sample during heat treatment. The six-sided hydraulic press can be a commonly used one in the art, and the structure and use of components such as the segmented graphite heater and thermocouple can also be based on existing technologies.

[0030] Preferably, in step S3, the cooling and decompression process is: after cooling to room temperature by natural heat dissipation, the pressure is slowly released in a staged decompression manner to return to normal pressure.

[0031] Through natural cooling and staged decompression, thermal stress concentration and structural mutation can be effectively avoided, crystallization of the amorphous phase or degradation of mechanical properties can be prevented, and the microstructure and overall integrity of the material can be ensured.

[0032] The present invention discloses a method for preparing dense amorphous SiMN (M=Hf, Zr, Ti) ceramics. The method realizes molecular-level transition metal-modified silicon nitride polymer based on single-source precursor design and combines high-temperature and high-pressure sintering technology to effectively inhibit crystallization behavior, improve the thermal stability and structural uniformity of the material, and simultaneously achieve high densification of amorphous SiMN (M=Hf, Zr, Ti) ceramics without adding any sintering aids.

[0033] This study successfully fabricated high-density amorphous SiMN (M = Hf, Zr, Ti) ceramics at low temperatures and without the addition of external sintering aids, while maintaining the integrity of the amorphous structure. This method provides a stable and controllable process foundation for the structural regulation and engineering applications of amorphous nitride ceramics.

[0034] Working principle:

[0035] The method of the present invention first prepares a Si-MN precursor at the molecular level using a single-source precursor method. Then, using amorphous SiMN (M = Hf, Zr, Ti) ceramics obtained by cracking at 800°C in a NH3 / N2 gas mixture as the raw material, the material is pre-pressed and packaged with metal molybdenum foil. Using a six-sided hydraulic press as high-temperature and high-pressure equipment, the temperature is uniformly raised to the target temperature (1000°C and 1200°C) at pressures of 1GPa, 3GPa, and 5GPa, and maintained for 10 minutes, achieving densification of the amorphous SiMN (M = Hf, Zr, Ti) ceramics without sintering aids. The modification of the transition metals Hf, Zr, and Ti increases the crystallization temperature of SiN, allowing it to remain amorphous at 1200°C and exhibit excellent hardness. This method is simple, does not introduce impurities, and is suitable for the industrial production of high-performance amorphous ceramics.

[0036] The introduction of high-melting-point transition metals (such as Hf, Zr, and Ti) can improve the performance of amorphous ceramics in many aspects: (1) enhancing thermal stability and raising the crystallization temperature; (2) improving the microscopic uniformity of the ceramic by regulating the molecular structure and nitrogen content of the precursor; and (3) imparting higher mechanical strength and greater chemical inertness to the material. Furthermore, MN (M = Hf, Zr, Ti) has high bond energy and a stable structure, forming a synergistic effect with the Si-N network, helping to form a stable amorphous structure and enhance density.

[0037] High temperature and high pressure technology has unique advantages in promoting diffusion, inhibiting crystallization and enhancing structural density. The method of the present invention uses high temperature and high pressure to prepare dense amorphous SiMN (M = Hf, Zr, Ti) ceramics using amorphous SiMN (M = Hf, Zr, Ti) designed with polymer precursors as raw materials. It can effectively achieve the maintenance and densification of the amorphous structure under conditions without sintering aids. The preparation process is simple, the sintering time is short, and the material purity is high. It is suitable for the industrial needs of preparing high-performance amorphous structure ceramics.

[0038] Beneficial effects:

[0039] The amorphous SiMN (M=Hf, Zr, Ti) ceramics of the present invention have excellent amorphous stability: the introduction of transition metal elements (Hf, Zr, Ti) significantly enhances the material's anti-crystallization ability and delays the amorphous-crystal transformation;

[0040] The preparation method of the present invention uses no additives for sintering, thus avoiding the impurities and embrittlement effects that may be introduced by traditional additives, and further improving the purity and comprehensive performance of the amorphous ceramic material.

[0041] The amorphous SiMN (M = Hf, Zr, Ti) ceramics of the present invention have high density and microscopic uniformity. The high temperature and high pressure sintering conditions promote the full bonding of particles to form a highly dense and structurally uniform amorphous ceramic.

[0042] The process of the present invention is highly versatile, and the preparation strategy has good system adaptability and can be extended to the preparation and performance optimization of various silicon nitride-based amorphous ceramic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 XRD patterns of amorphous SiHfN ceramic powder, amorphous SiZrN ceramic powder, and amorphous SiTiN ceramic powder prepared in Examples 1, 7, and 13 of the present invention;

[0044] Figure 2 XRD patterns of Si3N4 ceramics prepared in Comparative Example 3 (5 GPa, 1000°C) and Comparative Example 6 (5 GPa, 1200°C);

[0045] Figure 3 XRD patterns of amorphous SiHfN ceramics prepared in Example 3 (5 GPa, 1000°C) and Example 6 (5 GPa, 1200°C);

[0046] Figure 4 XRD patterns of amorphous SiZrN ceramics prepared in Example 9 (5 GPa, 1000°C) and Example 12 (5 GPa, 1200°C);

[0047] Figure 5 XRD patterns of amorphous SiTiN ceramics prepared in Example 15 (5 GPa, 1000° C.) and Example 18 (5 GPa, 1200° C.);

[0048] Figure 6The hardness of the amorphous SiMN (M = Hf, Zr, Ti) ceramics prepared at 5 GPa and 1000°C in Examples 3, 9, and 15; the hardness of the amorphous SiMN (M = Hf, Zr, Ti) ceramics prepared at 5 GPa and 1200°C in Examples 6, 12, and 18; the hardness of the Si3N4 ceramics prepared in Comparative Examples 3 and 6;

[0049] Figure 7 It is the porosity of the amorphous SiMN (M = Hf, Zr, Ti) ceramics prepared at 5 GPa and 1000°C in Example 3, Example 9, and Example 15; the porosity of the amorphous SiMN (M = Hf, Zr, Ti) ceramics prepared at 5 GPa and 1200°C in Example 6, Example 12, and Example 18; and the porosity of the Si3N4 ceramics prepared in Comparative Examples 3 and 6. DETAILED DESCRIPTION

[0050] The present invention will be further described in detail with reference to specific embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0051] There is no particular limitation on the purity of all raw materials in the present invention, and the present invention adopts conventional purity used in the art.

[0052] The devices used in the present invention are not particularly limited and can be devices commonly used in the art.

[0053] Example 1

[0054] A dense amorphous SiHfN ceramic and a preparation method thereof, comprising the following steps:

[0055] A Si-Hf-N polymer precursor was synthesized via a single-source precursor method using perhydropolysilazane (PHPS) and tetrakis(dimethylamino)hafnium (TDMAH) as raw materials with a Si:Hf molar ratio of 2:1. Amorphous SiHfN ceramic powder was then prepared by pyrolysis in an NH3 / N2 gas mixture at 800°C for 2 hours. After high-energy ball milling and sieving through a 200-mesh sieve, 1.5g of the powder was weighed and loaded into a mold. The mold was then pre-pressed at 50 MPa for 10 minutes to achieve a defined shape and mechanical strength, preventing cracking or deformation during subsequent packaging and high-temperature, high-pressure sintering. The pressed sample was then encapsulated with molybdenum foil to prevent compositional fluctuations and structural degradation under high temperature and high pressure, maintaining the purity and stability of the SiHfN ceramic amorphous phase.

[0056] The encapsulated sample was placed in a high-temperature and high-pressure synthesis chamber, the pressure was increased to 1GPa in 30 minutes, and then the temperature was increased to the target temperature of 1000°C at a heating rate of 60°C / min. After reaching the target temperature, it was kept warm for 10 minutes. After the insulation stage, the sample temperature was reduced to room temperature by natural cooling. Subsequently, a gradual decompression process (from 1GPa to 0.5GPa, and then to 0GPa) was adopted to avoid thermal stress concentration or structural cracks caused by sudden cooling or instantaneous unloading of pressure, and amorphous SiHfN ceramics were prepared.

[0057] Example 2

[0058] The difference between this embodiment and embodiment 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 3 GPa, and the temperature is increased to 1000°C.

[0059] The gradual decompression process is from 3 GPa to 1.5 GPa, from 1.5 GPa to 0.75 GPa, and then to 0 GPa.

[0060] Example 3

[0061] The difference between this embodiment and embodiment 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 5 GPa, and the temperature is increased to 1000°C.

[0062] The gradual decompression process is from 5 GPa to 2.5 GPa, from 2.5 GPa to 1 GPa, and then to 0 GPa.

[0063] Example 4

[0064] The difference between this embodiment and embodiment 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 1 GPa, and the temperature is increased to 1200°C.

[0065] Example 5

[0066] The difference between this embodiment and embodiment 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 3 GPa, and the temperature is increased to 1200°C.

[0067] The gradual decompression process is from 3 GPa to 1.5 GPa, from 1.5 GPa to 0.75 GPa, and then to 0 GPa.

[0068] Example 6

[0069] The difference between this embodiment and embodiment 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 5 GPa, and the temperature is increased to 1200°C.

[0070] The gradual decompression process is from 5 GPa to 2.5 GPa, from 2.5 GPa to 1 GPa, and then to 0 GPa.

[0071] Example 7

[0072] A method for preparing dense amorphous SiZrN ceramics comprises the following steps:

[0073] A Si-Zr-N polymer precursor was synthesized via a single-source precursor method using perhydropolysilazane (PHPS) and tetrakis(dimethylamino)zirconium (TDMAZ) as raw materials with a Si:Zr molar ratio of 2:1. Amorphous SiZrN ceramic powder was then prepared by pyrolysis in an NH3 / N2 mixture at 800°C for 2 hours. After high-energy ball milling and sieving through a 200-mesh sieve, 1.5 g of the powder was weighed and loaded into a mold. The mold was then pre-pressed at 50 MPa for 10 minutes to achieve a defined shape and mechanical strength, preventing cracking or deformation during subsequent packaging and high-temperature, high-pressure sintering. The pressed sample was then encapsulated with molybdenum foil to prevent compositional fluctuations and structural degradation under high temperature and high pressure, maintaining the purity and stability of the SiZrN ceramic amorphous phase.

[0074] The encapsulated sample was placed in a high-temperature, high-pressure synthesis chamber. The pressure was increased to 1 GPa over 30 minutes, and then the temperature was increased to a target temperature of 1000°C at a heating rate of 60°C / min. After reaching the target temperature, the sample was kept at this temperature for 10 minutes. After the holding period, the sample temperature was allowed to cool naturally to room temperature. A gradual decompression process (from 1 GPa to 0.5 GPa and then to 0 GPa) was then used to avoid thermal stress concentration or structural cracks caused by sudden cooling or instantaneous pressure relief, thereby producing amorphous SiZrN ceramics.

[0075] Example 8

[0076] The difference between this embodiment and embodiment 7 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 3 GPa, and the temperature is increased to 1000°C.

[0077] The gradual decompression process is from 3 GPa to 1.5 GPa, from 1.5 GPa to 0.75 GPa, and then to 0 GPa.

[0078] Example 9

[0079] The difference between this embodiment and embodiment 7 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 5 GPa, and the temperature is increased to 1000°C.

[0080] The gradual decompression process is from 5 GPa to 2.5 GPa, from 2.5 GPa to 1 GPa, and then to 0 GPa.

[0081] Example 10

[0082] The difference between this embodiment and embodiment 7 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 1 GPa, and the temperature is increased to 1200°C.

[0083] Example 11

[0084] The difference between this embodiment and embodiment 7 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 3 GPa, and the temperature is increased to 1200°C.

[0085] The gradual decompression process is from 3 GPa to 1.5 GPa, from 1.5 GPa to 0.75 GPa, and then to 0 GPa.

[0086] Example 12

[0087] The difference between this embodiment and embodiment 7 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 5 GPa, and the temperature is increased to 1200°C.

[0088] The gradual decompression process is from 5 GPa to 2.5 GPa, from 2.5 GPa to 1 GPa, and then to 0 GPa.

[0089] Example 13

[0090] A method for preparing dense amorphous SiTiN ceramics comprises the following steps:

[0091] A Si-Ti-N polymer precursor was synthesized via a single-source precursor method using perhydropolysilazane (PHPS) and tetrakis(dimethylamino)titanium (TDMAT) as raw materials with a Si:Ti molar ratio of 2:1. Amorphous SiTiN ceramic powder was then prepared by pyrolysis in an NH3 / N2 mixture at 800°C for 2 hours. After high-energy ball milling and sieving through a 200-mesh sieve, 1.5 g of the powder was weighed and loaded into a mold. The mold was then pre-pressed at 50 MPa for 10 minutes to establish a basic shape and sufficient mechanical strength, preventing cracking or deformation during subsequent packaging and high-temperature and high-pressure sintering. The pressed sample was then encapsulated with molybdenum foil to prevent compositional fluctuations and structural degradation under high temperature and high pressure, maintaining the purity and stability of the SiTiN ceramic amorphous phase.

[0092] The encapsulated samples were placed in a high-temperature, high-pressure synthesis chamber, where the pressure was increased to 1 GPa over 30 minutes. The temperature was then raised to a target temperature of 1000°C at a rate of 60°C / min. After reaching the target temperature, the samples were held at that temperature for 10 minutes. After the holding period, the sample temperature was allowed to cool naturally to room temperature. A gradual decompression process (from 1 GPa to 0.5 GPa and then to 0 GPa) was then used to avoid thermal stress concentration or structural cracks caused by sudden cooling or instantaneous pressure relief, resulting in the production of amorphous SiTiN ceramics.

[0093] Example 14

[0094] The difference between this embodiment and embodiment 13 is that the packaged sample is placed in a high-temperature and high-pressure synthesis cavity, the pressure is increased to 3 GPa, and the temperature is increased to 1000°C.

[0095] The gradual decompression process is from 3 GPa to 1.5 GPa, from 1.5 GPa to 0.75 GPa, and then to 0 GPa.

[0096] Example 15

[0097] The difference between this embodiment and embodiment 13 is that the packaged sample is placed in a high-temperature and high-pressure synthesis cavity, the pressure is increased to 5 GPa, and the temperature is increased to 1000°C.

[0098] The gradual decompression process is from 5 GPa to 2.5 GPa, from 2.5 GPa to 1 GPa, and then to 0 GPa.

[0099] Example 16

[0100] The difference between this embodiment and embodiment 13 is that the packaged sample is placed in a high-temperature and high-pressure synthesis cavity, the pressure is increased to 1 GPa, and the temperature is increased to 1200°C.

[0101] Example 17

[0102] The difference between this embodiment and embodiment 13 is that the packaged sample is placed in a high-temperature and high-pressure synthesis cavity, the pressure is increased to 3 GPa, and the temperature is increased to 1200°C.

[0103] The gradual decompression process is from 3 GPa to 1.5 GPa, from 1.5 GPa to 0.75 GPa, and then to 0 GPa.

[0104] Example 18

[0105] The difference between this embodiment and embodiment 13 is that the packaged sample is placed in a high-temperature and high-pressure synthesis cavity, the pressure is increased to 5 GPa, and the temperature is increased to 1200°C.

[0106] The gradual decompression process is from 5 GPa to 2.5 GPa, from 2.5 GPa to 1 GPa, and then to 0 GPa.

[0107] Example 19 (5 GPa, 1000°C)

[0108] The difference between this embodiment and embodiment 3 is that the molar ratio of Si:Hf is 1:1.

[0109] Example 20 (5 GPa, 1000°C)

[0110] The difference between this embodiment and embodiment 3 is that the molar ratio of Si:Hf is 3:1.

[0111] Example 21 (5 GPa, 1200°C)

[0112] The difference between this embodiment and embodiment 6 is that the molar ratio of Si:Hf is 1:1.

[0113] Example 22 (5 GPa, 1200°C)

[0114] The difference between this embodiment and embodiment 6 is that the Si:Hf molar ratio is 3:1.

[0115] Example 23 (5 GPa, 1000°C)

[0116] The difference between this embodiment and embodiment 9 is that the molar ratio of Si:Zr is 1:1.

[0117] Example 24 (5 GPa, 1000°C)

[0118] The difference between this embodiment and embodiment 9 is that the molar ratio of Si:Zr is 3:1.

[0119] Example 25 (5 GPa, 1200°C)

[0120] The difference between this embodiment and embodiment 12 is that the molar ratio of Si:Zr is 1:1.

[0121] Example 26 (5 GPa, 1200°C)

[0122] The difference between this embodiment and embodiment 12 is that the molar ratio of Si:Zr is 3:1.

[0123] Example 27 (5 GPa, 1000°C)

[0124] The difference between this embodiment and embodiment 15 is that the Si:Ti molar ratio is 1:1.

[0125] Example 28 (5 GPa, 1000°C)

[0126] The difference between this embodiment and embodiment 15 is that the Si:Ti molar ratio is 3:1.

[0127] Example 29 (5 GPa, 1200°C)

[0128] The difference between this embodiment and Example 18 is that the Si:Ti molar ratio is 1:1.

[0129] Example 30 (5 GPa, 1200°C)

[0130] The difference between this embodiment and Example 18 is that the Si:Ti molar ratio is 3:1.

[0131] Comparative Example 1

[0132] For comparison, amorphous SiN ceramic powder was prepared using perhydropolysilazane (PHPS) as the raw material by cracking in an NH3 / N2 mixture at 800°C for 2 hours. After high-energy ball milling and passing through a 200-mesh sieve, 1.5g of the amorphous SiN ceramic powder was weighed and loaded into a mold. The mold was then pre-pressed at 50 MPa for 10 minutes to establish a basic shape and a certain mechanical strength, preventing cracking or deformation during subsequent packaging and high-temperature and high-pressure sintering. The pressed sample was then encapsulated with molybdenum foil to prevent compositional fluctuations and structural degradation under high temperature and high pressure, maintaining the purity of the SiN ceramic and the stability of the amorphous phase.

[0133] The encapsulated sample was placed in a high-temperature, high-pressure synthesis chamber, where the pressure was increased to 1 GPa over 30 minutes. The temperature was then raised to a target temperature of 1000°C at a rate of 60°C / min. After reaching the target temperature, the sample was held at that temperature for 10 minutes. Following the holding period, the sample was cooled to room temperature by natural cooling. A gradual decompression process (from 1 GPa to 0.5 GPa and then to 0 GPa) was then employed to avoid thermal stress concentration or structural cracking caused by sudden cooling or instantaneous pressure relief. The Si3N4 ceramic was thus produced.

[0134] Comparative Example 2

[0135] The difference between this embodiment and comparative example 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 3 GPa, and the temperature is increased to 1000°C.

[0136] The gradual decompression process is from 3 GPa to 1.5 GPa, from 1.5 GPa to 0.75 GPa, and then to 0 GPa.

[0137] Comparative Example 3

[0138] The difference between this embodiment and comparative example 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 5 GPa, and the temperature is increased to 1000°C.

[0139] The gradual decompression process is from 5 GPa to 2.5 GPa, from 2.5 GPa to 1 GPa, and then to 0 GPa.

[0140] Comparative Example 4

[0141] The difference between this embodiment and comparative example 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 1 GPa, and the temperature is increased to 1200°C.

[0142] Comparative Example 5

[0143] The difference between this embodiment and comparative example 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 3 GPa, and the temperature is increased to 1200°C.

[0144] The gradual decompression process is from 3 GPa to 1.5 GPa, from 1.5 GPa to 0.75 GPa, and then to 0 GPa.

[0145] Comparative Example 6

[0146] The difference between this embodiment and comparative example 1 is that the packaged sample is placed in a high-temperature and high-pressure synthesis chamber, the pressure is increased to 5 GPa, and the temperature is increased to 1200°C.

[0147] The gradual decompression process is from 5 GPa to 2.5 GPa, from 2.5 GPa to 1 GPa, and then to 0 GPa.

[0148] like Figure 1 Figures 2 and 3 show XRD patterns of amorphous SiHfN ceramic powders, amorphous SiZrN ceramic powders, and amorphous SiTiN ceramic powders prepared in Examples 1, 7, and 13 of the present invention. "SiHfN" in the figure represents the amorphous SiHfN ceramic powder prepared in Example 1; "SiZrN" in the figure represents the amorphous SiZrN ceramic powder prepared in Example 7; and "SiTiN" in the figure represents the amorphous SiTiN ceramic powder prepared in Example 13.

[0149] like Figure 2 Figure 2 shows the XRD patterns of Si3N4 ceramics prepared in Comparative Example 3 (5 GPa, 1000°C) and Comparative Example 6 (5 GPa, 1200°C). The "1000°C" pattern in the figure represents the Si3N4 ceramic prepared in Comparative Example 3; the "1200°C" pattern in the figure represents the Si3N4 ceramic prepared in Comparative Example 6.

[0150] like Figure 3 Figure 2 shows the XRD patterns of amorphous SiHfN ceramics prepared in Example 3 (5 GPa, 1000°C) and Example 6 (5 GPa, 1200°C). The "1000°C" pattern in the figure represents the amorphous SiHfN ceramic prepared in Example 3, while the "1200°C" pattern represents the amorphous SiHfN ceramic prepared in Example 6.

[0151] like Figure 4 As shown in FIG, there are XRD patterns of the amorphous SiZrN ceramics prepared in Example 9 (5 GPa, 1000°C) and Example 12 (5 GPa, 1200°C); “1000°C” in the figure represents the amorphous SiZrN ceramics prepared in Example 9; and “1200°C” in the figure represents the amorphous SiZrN ceramics prepared in Example 12.

[0152] like Figure 5 As shown in the figure, there are XRD patterns of the amorphous SiTiN ceramics prepared in Example 15 (5 GPa, 1000°C) and Example 18 (5 GPa, 1200°C); "1000°C" in the figure represents the amorphous SiTiN ceramic prepared in Example 15; "1200°C" in the figure represents the amorphous SiTiN ceramic prepared in Example 18.

[0153] like Figure 6 Shown are the hardness of the amorphous SiMN (M = Hf, Zr, Ti) ceramics prepared at 5 GPa and 1000 ° C in Example 3, Example 9, and Example 15; the hardness of the amorphous SiMN (M = Hf, Zr, Ti) ceramics prepared at 5 GPa and 1200 ° C in Example 6, Example 12, and Example 18; and the hardness of the Si3N4 ceramics prepared in Comparative Examples 3 and 6.

[0154] like Figure 7 Shown are the porosities of amorphous SiMN (M = Hf, Zr, Ti) ceramics prepared at 5 GPa and 1000°C in Example 3, Example 9, and Example 15; the porosities of amorphous SiMN (M = Hf, Zr, Ti) ceramics prepared at 5 GPa and 1200°C in Example 6, Example 12, and Example 18; and the porosities of Si3N4 ceramics prepared in Comparative Examples 3 and 6.

[0155] "Anti-crystallization ability" and "stable maintenance of amorphous structure" can be judged from XRD data. The most obvious one is Figure 2 Comparison of Si3N4 1200℃ and other SiMN 1200℃ ( Figure 3 、 Figure 4 、 Figure 5 ), Figure 2 The crystallization peak can be seen, but Figures 3 to 5 Still amorphous.

[0156] From the XRD data in the above examples and comparative examples, it can be seen that amorphous SiN crystallizes into α-Si3N4 at 1200℃, while SiMN (M=Hf, Zr, Ti) ceramics still remain amorphous, indicating that the introduction of transition metals effectively improves the material's resistance to crystallization and the prepared ceramics have excellent mechanical properties. In addition, the density of the sample increases with increasing pressure ( Figure 7 ).

[0157] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing dense amorphous SiMN ceramics, characterized by: The following steps are involved: S1, grafting an organic metal M source onto the Si-N chain of a silicon nitride precursor to obtain a Si-MN polymer precursor; S2, cracking the Si-MN polymer precursor to obtain amorphous SiMN ceramic powder; S3, preforming the amorphous SiMN ceramic powder and encapsulating it, then synthesizing it under high temperature and high pressure, and cooling and releasing the pressure to obtain dense amorphous SiMN ceramics; The M is one of Hf, Zr and Ti.

2. The method for preparing a dense amorphous SiMN ceramic according to claim 1, wherein: In the step S1, the organic metal M source is tetrakis(dimethylformamide) M, and the silicon nitride precursor is perhydropolysilazane.

3. The method for preparing a dense amorphous SiMN ceramic according to claim 2, characterized in that: The amount of perhydropolysilazane used is calculated as Si, and the amount of tetrakis(dimethylamide)M used is calculated as M. Perhydropolysilazane and tetrakis(dimethylamide)M are mixed at different Si:M molar ratios.

4. The method for preparing a dense amorphous SiMN ceramic according to claim 1, characterized in that: The step S2 is to prepare amorphous SiMN ceramic powder by cracking in NH3 / N2 mixed gas at 800°C for 2 hours.

5. The method for preparing a dense amorphous SiMN ceramic according to claim 1, characterized in that: In step S3, the preforming process is: pre-pressing the amorphous SiMN ceramic powder under an inert atmosphere at a pressure of 50 MPa for 10 minutes to obtain a pre-formed sample.

6. The method for preparing dense amorphous SiMN ceramics according to claim 5, characterized in that: In step S3, the packaging process is: packaging the preformed sample with metal molybdenum foil under the protection of an inert atmosphere.

7. The method for preparing dense amorphous SiMN ceramics according to claim 1, characterized in that: In step S3, the process of synthesizing under high temperature and high pressure is: keeping the temperature and pressure at 1000-1200° C. for 10 minutes at a synthesis pressure of 1-5 GPa.

8. The method for preparing dense amorphous SiMN ceramics according to claim 1, characterized in that: In the step S3, during the synthesis process under high temperature and high pressure, the temperature is raised to 1000-1200° C. at a heating rate of 60° C. / min.

9. The method for preparing dense amorphous SiMN ceramics according to claim 1, characterized in that: In step S3, the cooling and decompression process is as follows: after cooling to room temperature by natural heat dissipation, the pressure is slowly released in a staged decompression manner to return to normal pressure.

10. Dense amorphous SiMN ceramics prepared by the preparation method according to any one of claims 1 to 9.

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