Method for in-situ synthesis of diamond by using polymer precursor ceramic

Abstract

The invention belongs to the technical field of ceramic material preparation, and particularly relates to a method for in-situ synthesis of diamond by using polymer precursor ceramic. The raw materials adopted by the method comprise: a liquid polysilazane precursor, the content of which is 78-98% of the total weight of the raw materials; dicumyl peroxide accounting for 2% of the total weight of the raw materials; the content of the divinyl benzene is 0-20% of the total weight of the raw materials; the preparation method comprises the steps of raw material mixing, curing and crosslinking treatment, pyrolysis treatment, first-time ball milling treatment, second-time ball milling treatment, pre-pressing treatment, high-temperature and high-pressure sintering treatment and the like, and the diamond / SiCN ceramic composite material is obtained. Compared with the prior art, the method has an in-situ compounding mechanism, diamond can be formed in the SiCN matrix, directional conversion of free carbon in the SiCN ceramic is achieved, in addition, the process links and the process flow are simplified, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic material preparation, and in particular relates to a method for in-situ synthesis of diamond using polymer precursor ceramics. Background Art

[0002] Diamond, with its high hardness, wear resistance, and high-temperature resistance, is an ideal material for extreme working conditions. However, its high brittleness and tendency to graphitize in high-temperature oxidizing environments, leading to performance degradation, significantly limit its applications. Therefore, the preparation of diamond-ceramic composites has become an important approach to improving material performance.

[0003] Currently, the most common method for preparing diamond-ceramic composites is to co-sinter exogenously added diamond particles with the ceramic. This process, produced under the synergistic effects of high pressure (5-6 GPa) and high temperature (1300-1600°C), involves densifying the exogenously added diamond particles with the ceramic matrix (such as SiC or Al2O3) powder in a solid or semi-molten state, resulting in the preparation of highly dense diamond-ceramic composites. However, this process relies on the introduction of exogenous diamond particles and requires surface modification to improve wettability, which increases the number of steps and costs. Polymer precursor ceramics (PDCs) are a new type of ceramic material prepared by polymer precursor conversion process, which has excellent structure, outstanding high temperature stability and anti-oxidation / corrosion functional properties. The microstructure of polymer precursor ceramics is mainly composed of amorphous regions of tetrahedral coordinated silicon (i.e. SiC x N y ) and free carbon regions composed of numerous carbon nanoclusters. Typical processes include molding, cross-linking and curing, high-temperature pyrolysis, and crystallization of amorphous ceramics. Different processing techniques can significantly affect the microstructure of polymer precursor ceramics during their preparation. Peng et al. (Significant regulation of structure and electrical performance of SiCNceramics through high-pressure sintering. J Am Ceram Soc. 2025; e20639.) introduced a novel synthesis process for polymer precursor ceramics. High-pressure sintering significantly influences the microstructure of the polymer precursor ceramics. High-pressure sintering promotes the formation of free carbon and significantly enhances its structural order, transforming the free carbon phase in the polymer precursor ceramics from amorphous carbon to nanocrystalline graphite. This provides a new direction for optimizing the performance of polymer precursor ceramics. However, in the field of ceramic material preparation, research on the in-situ conversion of diamond using ceramic materials is rarely reported. Existing technologies primarily focus on the preparation of diamond-ceramic composites using exogenous addition methods, which present complex processes and high manufacturing costs. A breakthrough in the in-situ conversion of diamond using ceramic materials could address the shortcomings of traditional processes and open up new avenues for the development of high-performance ceramic-based composites. Summary of the Invention

[0004] The purpose of the present invention is to propose a method for in-situ synthesis of diamond using polymer precursor ceramics. The method adds a metal catalyst FeNi alloy powder during the high-temperature and high-pressure sintering of the polymer precursor ceramics, so that the polymer precursor ceramics are directly converted into diamond under high-pressure conditions, thereby achieving in-situ conversion of the carbon source, thereby synthesizing a new type of diamond / polymer precursor ceramic composite material. The method solves the problems of the existing technology such as complex process, high manufacturing cost, weak interface bonding, and easy damage of diamond at high temperature, and opens up a new path for the development of high-performance ceramic-based composite materials.

[0005] To achieve the above object, the present invention provides a method for in-situ synthesis of diamond using polymer precursor ceramics, wherein the raw materials used in the method include the following components: Liquid polysilazane precursor, the content of which is 78% to 98% by weight of the total raw material; Dicumyl peroxide, content is 2% of the total weight of raw materials; Divinylbenzene, in an amount ranging from 0% to 20% by weight of the total weight of the raw materials; The molecular formula of the liquid polysilazane precursor is shown in the following formula (1): (1); In formula (1), x=2, y=8; The molecular formula of divinylbenzene is shown in the following formula (2): (2).

[0006] Preferably, the mass ratio of the liquid polysilazane precursor, dicumyl peroxide and divinylbenzene is 78:2:20. Preferably, the method comprises the following steps: S1, raw material mixing: under nitrogen atmosphere, uniformly mixing liquid polysilazane precursor, dicumyl peroxide and divinylbenzene according to a mass ratio to obtain a liquid mixture; S2, curing and cross-linking treatment: placing the liquid mixture obtained in step S1 in a vacuum thermosetting chamber for curing and cross-linking treatment under a vacuum environment to obtain a cured product; S3, pyrolysis treatment: under nitrogen atmosphere protection, pyrolyze the solidified material obtained in step S2 in a tube furnace, and cool to room temperature after pyrolysis to obtain a SiCN ceramic block; S4, first ball milling treatment: placing the SiCN ceramic block obtained in step S3 into a ball milling jar and performing a first ball milling treatment using a high-energy ball mill to obtain micro- and nano-scale SiCN ceramic powder; S5, second ball milling treatment: the SiCN ceramic powder obtained in step S4 and the FeNi alloy powder are placed in a ball milling jar at a mass ratio of 1: (1-4), and a second ball milling treatment is performed using a high-energy ball mill to obtain a mixed powder; S6, pre-pressing treatment: taking an appropriate amount of the mixed powder obtained in step S5 and pre-pressing it into a cylinder with a diameter of 10-14 mm and a height of 3-6 mm; S7, high temperature and high pressure sintering treatment: The cylinder obtained in step S6 is placed in a pyrophyllite assembly block, and the block is placed in a six-sided top press. High temperature and high pressure sintering is performed at 5-6 GPa and 1300-1500°C for 10-30 minutes. After slowly cooling and reducing the pressure to room temperature and pressure, in-situ formation of diamond in the SiCN ceramic material can be achieved.

[0007] Preferably, step S1 includes the following steps: The raw materials were placed in a beaker with a magnet, stirred magnetically and vacuumed for 15 min, then the temperature was raised to 90°C and magnetic stirring was continued for 1 h to uniformly mix the raw materials to obtain a liquid mixture.

[0008] Preferably, in step S2, the curing and cross-linking temperature is 120° C., and the curing and cross-linking time is 4 h.

[0009] Preferably, in step S3, the temperature in the tube furnace during pyrolysis is 1300° C., and the pyrolysis time is 4 h.

[0010] Preferably, the first ball milling treatment in step S4 is performed for 1 h, and the second ball milling treatment in step S5 is performed for 10 min.

[0011] Preferably, in step S5, the mass ratio of the SiCN ceramic powder to the FeNi alloy powder is 1:4.

[0012] More preferably, in step S5, the ratio of Fe to Ni in the FeNi alloy powder is 7:3, and the particle size of the FeNi alloy powder is 75 μm.

[0013] Preferably, in step S7, the pressure of the high temperature and high pressure sintering is 5.8 GPa, the temperature is 1500° C., and the sintering time is 30 min.

[0014] The working principle of this invention is that the inventors discovered that due to the unique microstructure of polymer precursor ceramics, during high-temperature and high-pressure sintering, the free carbon phase in the matrix becomes more ordered, resulting in the precipitation of a graphite phase. Using this precipitated graphite phase as the raw material for diamond synthesis eliminates the need for the introduction and pretreatment of exogenous diamond particles, further facilitating the preparation of diamond-ceramic composite materials. Therefore, by adding a metal catalyst, FeNi alloy powder, to the polymer precursor ceramic during high-temperature and high-pressure sintering, the material is directly converted into diamond under high pressure, achieving in-situ conversion of the carbon source and subsequently synthesizing a novel diamond / polymer precursor ceramic composite material.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 1. It has an in-situ composite mechanism: through the catalysis of FeNi, the graphite → diamond phase transition is directly realized in the SiCN matrix, thereby forming a diamond reinforcement phase in the SiCN matrix.

[0016] 2. Achieve directional conversion of free carbon: Use high pressure and high temperature conditions to control the morphology of free carbon and convert it from disordered carbon to diamond.

[0017] 3. Simplified process steps: By directly converting polymer precursors into ceramics, the steps of exogenous diamond addition and surface modification are eliminated, which simplifies the process flow and reduces production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a process flow chart in an embodiment of the present invention; Figure 2 Schematic diagram of the structure of the pyrophyllite assembly block in an embodiment of the present invention; Figure 3 This is an optical photograph of the material finally prepared in Example 1; Figure 4 This is the Raman image of the material finally prepared in Example 1; Figure 5 This is an optical photograph of the material finally prepared in Example 2; Figure 6 This is the Raman map of the material finally prepared in Example 2; Figure 7 This is an optical photograph of the material finally prepared in Example 3; Figure 8 This is the Raman map of the material finally prepared in Example 3; Figure 9 This is the Raman image of the material finally prepared in Comparative Example 1. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0021] There is no particular limitation on the purity of all raw materials in the present invention, and the present invention preferably adopts conventional purity used in the art.

[0022] The devices used in the present invention are not particularly limited and can be devices commonly used in the art.

[0023] Example 1 like Figure 1 As shown, this embodiment provides a method for in-situ synthesis of diamond using a polymer precursor ceramic, comprising the following steps: 1) Mixing the raw materials: Place liquid polysilazane precursor, dicumyl peroxide, and divinylbenzene in a mass ratio of 78:2:20 into a flask with a magnetic stirrer and evacuate for 15 minutes. Then, raise the temperature to 90°C and continue magnetic stirring for 1 hour to obtain a liquid mixture. The molecular formula of the liquid polysilazane precursor is shown in the following formula (1): (1), In formula (1), x=2, y=8; The molecular formula of divinylbenzene is shown in the following formula (2): (2).

[0024] 2) Curing and cross-linking treatment: Under nitrogen atmosphere, the prepared liquid mixture is poured into a crucible and placed in a vacuum thermosetting chamber for thermosetting and cross-linking treatment for 4 hours at a temperature of 120°C to obtain a cured product. The use of nitrogen atmosphere protection ensures that the precursor is free from air contact and thus prevents oxidation. 3) Pyrolysis treatment: The solidified product obtained in step 2) is placed in an alumina crucible, which is then placed in a tube furnace and pyrolyzed at 1300°C for 4 hours under a nitrogen atmosphere. After pyrolysis, the solidified product is cooled to room temperature to obtain a SiCN ceramic block. 4) First ball milling: The SiCN ceramic block obtained by pyrolysis in step 3) is placed in a ball mill and subjected to ball milling and pulverization treatment using a high-energy ball mill for 1 hour to obtain micro- and nano-scale SiCN ceramic powders; 5) Second ball milling: The SiCN ceramic powder obtained in step 4) and the FeNi alloy powder were placed in a ball mill at a mass ratio of 1:4 and uniformly mixed for 5 minutes to obtain a mixed powder; In this step, the ratio of Fe to Ni in the FeNi alloy powder is 7:3, and the particle size of the FeNi alloy powder is 75 μm; 6) Pre-pressing: Take an appropriate amount of the mixed powder obtained in step 5) and pre-press it into a cylinder with a diameter of 14 mm and a height of 5 mm; 7) High temperature and high pressure sintering treatment: Take an appropriate amount of the cylinder obtained in step 6) and place it in a pyrophyllite assembly block (the structural diagram of the assembled pyrophyllite assembly block is shown in FIG. Figure 2 As shown in FIG, specifically comprising a pyrophyllite block, a pyrophyllite ring, a steel cap, a steel sheet, a molybdenum sheet, a copper sheet, a magnesium oxide tube, a graphite sheet, a graphite tube and a sample), the pyrophyllite assembly block is placed in a six-sided top press and maintained at 5.8 GPa and 1500 ° C for 30 min for high temperature and high pressure sintering. Then, the residual stress inside the SiCN ceramic / diamond composite material is reduced by slowly cooling and slowly reducing the pressure, thereby realizing in situ generation of diamond in the SiCN ceramic material, thereby obtaining a SiCN ceramic / diamond composite material.

[0025] Figure 3 This is an optical photograph of the diamond / SiCN ceramic composite material obtained in Example 1. Figure 4 Graph 2 shows the Raman pattern of the diamond / SiCN ceramic composite material obtained in Example 1.

[0026] Example 2 The only difference between this embodiment and embodiment 1 is that in step 5), the mass ratio of SiCN ceramic powder to FeNi alloy powder is 1:1.

[0027] Figure 5 This is an optical photograph of the diamond / SiCN ceramic composite material obtained in Example 2. Figure 6 Graph 2 shows the Raman pattern of the diamond / SiCN ceramic composite material obtained in Example 2.

[0028] Example 3 The only difference between this embodiment and embodiment 1 is that in step 5), the mass ratio of SiCN ceramic powder to FeNi alloy powder is 1:2.5.

[0029] Figure 7This is an optical photograph of the diamond / SiCN ceramic composite material obtained in Example 3. Figure 8 3 shows the Raman image of the diamond / SiCN ceramic composite material obtained in Example 3.

[0030] Comparative Example 1 The only difference between this comparative example and Example 1 is that, during the synthesis process, step 5) is omitted, and in step 6), the SiCN ceramic powder obtained in step 4) is directly used to pre-press into a cylinder.

[0031] Figure 9 This is the Raman image of the SiCN ceramic material finally prepared in Comparative Example 1.

[0032] By performing Raman characterization on Examples 1, 2, 3 and Comparative Example 1, the Raman results of Comparative Example 1 are as follows: Figure 9 As shown in Figure 2, it is proved that after mixing the liquid polysilazane precursor, dicumyl peroxide and divinylbenzene in a mass ratio of 78:2:20, the SiCN ceramic powder prepared after high temperature and high pressure sintering will precipitate a highly ordered graphite phase. It is precisely because of the presence of these graphite phases in the SiCN ceramic that a carbon source is provided for the in-situ synthesis of diamond in the SiCN ceramic. The Raman results of Examples 1, 2 and 3 are shown in Figure 2. Figure 4 、 6 As shown in Figures 8 and 8, it is proved that under the catalytic action of FeNi alloys with different mass proportions, the graphite phase in SiCN ceramics is transformed into the diamond phase, realizing the in-situ generation of diamond in SiCN ceramic materials.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for in-situ synthesis of diamond using polymer precursor ceramics, characterized in that: The raw materials used in this method include the following components: Liquid polysilazane precursor, the content of which is 78% to 98% by weight of the total raw material; Dicumyl peroxide, content is 2% of the total weight of raw materials; Divinylbenzene, in an amount ranging from 0% to 20% by weight of the total weight of the raw materials; The molecular formula of the liquid polysilazane precursor is shown in the following formula (1): （1）， In formula (1), x=2, y=8; The molecular formula of divinylbenzene is shown in the following formula (2): （2）。 2. The method for in-situ synthesis of diamond using polymer precursor ceramics according to claim 1, characterized in that: The mass ratio of the liquid polysilazane precursor, dicumyl peroxide and divinylbenzene is 78:2:

20.

3. A method for in-situ synthesis of diamond using polymer precursor ceramics according to claim 1 or 2, characterized in that: The steps include: S1, raw material mixing: under nitrogen atmosphere, uniformly mixing liquid polysilazane precursor, dicumyl peroxide and divinylbenzene according to a mass ratio to obtain a liquid mixture; S2, curing and cross-linking treatment: placing the liquid mixture obtained in step S1 in a vacuum thermosetting chamber for curing and cross-linking treatment under a vacuum environment to obtain a cured product; S3, pyrolysis treatment: under nitrogen atmosphere protection, pyrolyze the solidified material obtained in step S2 in a tube furnace, and cool to room temperature after pyrolysis to obtain a SiCN ceramic block; S4, first ball milling treatment: placing the SiCN ceramic block obtained in step S3 into a ball milling jar and performing a first ball milling treatment using a high-energy ball mill to obtain micro- and nano-scale SiCN ceramic powder; S5, second ball milling treatment: the SiCN ceramic powder obtained in step S4 and the FeNi alloy powder are placed in a ball milling jar at a mass ratio of 1: (1-4), and a second ball milling treatment is performed using a high-energy ball mill to obtain a mixed powder; S6, pre-pressing treatment: taking an appropriate amount of the mixed powder obtained in step S5 and pre-pressing it into a cylinder with a diameter of 10-14 mm and a height of 3-6 mm; S7, high temperature and high pressure sintering treatment: The cylinder obtained in step S6 is placed in a pyrophyllite assembly block, and the block is placed in a six-sided top press. High temperature and high pressure sintering is performed at 5-6 GPa and 1300-1500°C for 10-30 minutes. After slowly cooling and reducing the pressure to room temperature and pressure, in-situ formation of diamond in the SiCN ceramic material can be achieved.

4. The method for in-situ synthesis of diamond using polymer precursor ceramics according to claim 3, characterized in that: Step S1 includes the following steps: Place the raw materials in a beaker with a magnet, use magnetic stirring and vacuum for 10-15 minutes, then raise the temperature to 80-100°C and continue magnetic stirring for 0.5-1.5 hours to mix them evenly to obtain a liquid mixture.

5. The method for in-situ synthesis of diamond using polymer precursor ceramics according to claim 3, characterized in that: In step S2, the curing and cross-linking temperature is 120-150° C., and the curing and cross-linking time is 3-5 h.

6. The method for in-situ synthesis of diamond using polymer precursor ceramics according to claim 3, characterized in that: In step S3, the temperature in the tube furnace during pyrolysis is 1000-1300°C, and the pyrolysis time is 3-5 hours.

7. The method for in-situ synthesis of diamond using polymer precursor ceramics according to claim 3, characterized in that: The time for the first ball milling treatment in step S4 is 0.5 to 1 hour, and the time for the second ball milling treatment in step S5 is 5 to 10 minutes.

8. The method for in-situ synthesis of diamond using polymer precursor ceramics according to claim 3, characterized in that: In step S5, the mass ratio of the SiCN ceramic powder to the FeNi alloy powder is 1:

4.

9. The method for in-situ synthesis of diamond using polymer precursor ceramics according to claim 8, characterized in that: In step S5, the ratio of Fe to Ni in the FeNi alloy powder is 7:3, and the particle size of the FeNi alloy powder is 75 μm.

10. The method for in-situ synthesis of diamond using polymer precursor ceramics according to claim 3, characterized in that: In step S7, the high temperature and high pressure sintering pressure is 5.8 GPa, the temperature is 1500° C., and the sintering time is 30 min.

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