Amorphous SiBCN ceramic block with high density and excellent oxidation resistance and preparation method thereof

Abstract

The present invention relates to an amorphous SiBCN ceramic block with high density and excellent antioxidant properties and a preparation method thereof, belonging to the technical field of high-performance ceramic materials. The preparation method of the amorphous SiBCN ceramic block comprises: solidifying polyborosilazane, crushing, ball milling, and vacuum pyrolysis to obtain an amorphous SiBCN ceramic powder; and subjecting the amorphous SiBCN ceramic powder to spark plasma sintering to obtain an amorphous SiBCN ceramic block. The present invention provides a method for preparing an amorphous SiBCN ceramic block, which can produce an amorphous SiBCN ceramic block with high density, low pore defects, adjustable size, low shrinkage, and excellent antioxidant properties. This method can effectively solve the problems of limited material size and high porosity in the preparation process of traditional SiBCN ceramic blocks.

Description

Technical Field

[0001] The present invention relates to the technical field of high-performance ceramic materials, and in particular to an amorphous SiBCN ceramic block with high density and excellent oxidation resistance and a preparation method thereof. Background Art

[0002] SiBCN ceramics, with their exceptional high-temperature stability, excellent oxidation resistance, good mechanical properties, and low thermal expansion coefficient, have shown broad application potential in the field of high-temperature structural materials and have become the focus of many high-tech fields. There are two main challenges in the actual preparation of large, dense ceramic blocks: first, it is difficult to maintain its amorphous structure while achieving material densification; second, the oxidation resistance needs to be further improved. In addition, traditional preparation methods are limited by the process, which often leads to a large number of pores inside the material, making size control difficult, and the oxidation resistance is difficult to meet higher requirements in application scenarios. Summary of the Invention

[0003] In response to one or more technical problems existing in the prior art, the present invention provides an amorphous SiBCN ceramic block with high density and excellent antioxidant properties and a preparation method thereof. The preparation method of the amorphous SiBCN ceramic block provided by the present invention can obtain an amorphous SiBCN ceramic block with high density, low pore defects, adjustable size, small shrinkage and excellent antioxidant properties, which can meet the preparation needs of large-size, high-quality and high-performance amorphous SiBCN ceramic blocks, and effectively solve the problems of limited material size and multiple pores in the preparation process of traditional SiBCN ceramic blocks.

[0004] In a first aspect, the present invention provides a method for preparing an amorphous SiBCN ceramic block having high density and excellent oxidation resistance, the preparation method comprising:

[0005] After the polyborosilazane is solidified, it is crushed, ball-milled, and vacuum-pyrolyzed to obtain amorphous SiBCN ceramic powder;

[0006] The amorphous SiBCN ceramic powder is subjected to spark plasma sintering to obtain an amorphous SiBCN ceramic block.

[0007] Preferably, the curing is carried out under vacuum conditions, the curing temperature is 300-350° C., and the curing time is 2-4 hours.

[0008] Preferably, the heating rate during the curing process is 0.5-1.5°C / min.

[0009] Preferably, the mass ratio of ball material to water during the ball milling process is 2-4:1:1.5-3, the ball milling speed is 200-400 rpm, and the ball milling time is 4-12 h.

[0010] Preferably, the particle size of the amorphous SiBCN ceramic powder is less than 75 μm.

[0011] Preferably, the vacuum pyrolysis temperature is 1000-1400° C., and the time is 2-6 hours.

[0012] Preferably, the heating rate of the vacuum pyrolysis process is 1-3°C / min.

[0013] Preferably, the spark plasma sintering is performed in an inert atmosphere, with a sintering temperature of 1400-1600° C., a sintering pressure of 30-60 MPa, and a sintering time of 3-15 min.

[0014] In a second aspect, the present invention provides an amorphous SiBCN ceramic block with high density and excellent oxidation resistance, which is prepared by the preparation method described in the first aspect.

[0015] Preferably, the density of the amorphous SiBCN ceramic block is greater than 2.2 g / cm 3 , porosity is less than 3.5%.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects:

[0017] The present invention can effectively increase the content of the B element in the amorphous SiBCN ceramic powder after pyrolysis and reduce the content of the N element by subjecting the obtained amorphous SiBCN ceramic powder to vacuum pyrolysis, thereby inhibiting the thermal reduction reaction and improving the material's oxidation resistance. The amorphous SiBCN ceramic powder after vacuum pyrolysis is used to prepare amorphous SiBCN ceramic blocks by spark plasma sintering (SPS). This ensures that while maintaining the amorphous structure of the material, its oxidation resistance is significantly improved, resulting in amorphous SiBCN ceramic blocks with high density, low pore defects, adjustable size, low shrinkage rate and excellent oxidation resistance. This can meet the preparation requirements of large-scale, high-quality, high-performance amorphous SiBCN ceramic blocks and effectively solve the problems of limited material size and multiple pores in the preparation process of traditional SiBCN ceramic blocks.

[0018] The amorphous SiBCN ceramic block provided by the present invention has high density, low pore defects, adjustable size, small shrinkage and excellent oxidation resistance, and can meet the use requirements of ultra-high temperature fields such as aerospace and high-temperature structural materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a comparison chart of the oxidation thermogravimetric results of the amorphous SiBCN ceramic powder after vacuum pyrolysis in Example 1 of the present invention and the amorphous SiBCN ceramic powder after argon pyrolysis in Comparative Example 3;

[0021] Figure 2 This is the XRD pattern of the amorphous SiBCN ceramic block prepared in Example 1 of the present invention;

[0022] Figure 3 These are macroscopic and microscopic images of the amorphous SiBCN ceramic block prepared in Example 1 of the present invention;

[0023] Figure 4 These are macroscopic and microscopic images of the amorphous SiBCN ceramic block prepared in Comparative Example 1 of the present invention;

[0024] Figure 5 These are macroscopic and microscopic images of the amorphous SiBCN ceramic block prepared in Comparative Example 2 of the present invention;

[0025] Figure 6 1 is a graph showing the results of an oxidation resistance test (temperature 1400° C., time 2 h) of the amorphous SiBCN ceramic blocks prepared in Example 1 and Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] In a first aspect, the present invention provides a method for preparing an amorphous SiBCN ceramic block having high density and excellent oxidation resistance, the preparation method comprising:

[0028] After the polyborosilazane is solidified, it is crushed, ball-milled, and vacuum-pyrolyzed to obtain amorphous SiBCN ceramic powder;

[0029] The amorphous SiBCN ceramic powder is subjected to spark plasma sintering to obtain an amorphous SiBCN ceramic block.

[0030] The present invention can effectively increase the content of the B element in the amorphous SiBCN ceramic powder after pyrolysis and reduce the content of the N element by subjecting the obtained amorphous SiBCN ceramic powder to vacuum pyrolysis, thereby inhibiting the thermal reduction reaction and improving the material's oxidation resistance. The amorphous SiBCN ceramic powder after vacuum pyrolysis is used to prepare amorphous SiBCN ceramic blocks by spark plasma sintering (SPS). This ensures that while maintaining the amorphous structure of the material, its oxidation resistance is significantly improved, resulting in amorphous SiBCN ceramic blocks with high density, low pore defects, adjustable size, low shrinkage rate and excellent oxidation resistance. This can meet the preparation requirements of large-scale, high-quality, high-performance amorphous SiBCN ceramic blocks and effectively solve the problems of limited material size and multiple pores in the preparation process of traditional SiBCN ceramic blocks.

[0031] According to some preferred embodiments, the curing is performed under vacuum conditions, the curing temperature is 300-350° C., and the curing time is 2-4 hours.

[0032] According to some preferred embodiments, the heating rate during the curing process is 0.5-1.5° C. / min.

[0033] According to some preferred embodiments, the mass ratio of ball material to water during the ball milling process is 2-4:1:1.5-3, the ball milling speed is 200-400 rpm, and the ball milling time is 4-12 h.

[0034] According to some preferred embodiments, the particle size of the amorphous SiBCN ceramic powder is less than 75 μm.

[0035] According to some preferred embodiments, the vacuum pyrolysis is carried out at a temperature of 1000 to 1400° C. and for a time of 2 to 6 hours.

[0036] According to some preferred embodiments, the heating rate of the vacuum pyrolysis process is 1-3°C / min.

[0037] According to some preferred embodiments, the spark plasma sintering is performed in an inert atmosphere, with a sintering temperature of 1400-1600° C., a sintering pressure of 30-60 MPa, and a sintering time of 3-15 min.

[0038] In a second aspect, the present invention provides an amorphous SiBCN ceramic block with high density and excellent oxidation resistance, which is prepared by the preparation method described in the first aspect.

[0039] The amorphous SiBCN ceramic block provided by the present invention has high density, low pore defects, adjustable size, small shrinkage and excellent oxidation resistance, and can meet the use requirements of ultra-high temperature fields such as aerospace and high-temperature structural materials.

[0040] According to some preferred embodiments, the density of the amorphous SiBCN ceramic block is greater than 2.2 g / cm 3 , porosity is less than 3.5%.

[0041] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the examples. The present invention does not specifically limit the sources of the reagents used in the examples and comparative examples, and they can be directly purchased or synthesized.

[0042] Example 1

[0043] S1. Pour polyborosilazane (PSNB, liquid) into a ceramic boat and then transfer it to a vacuum curing box for curing, wherein the curing temperature is 350°C, the curing time is 2 hours, and the heating rate during the curing process is 1°C / min; the block obtained after curing is crushed by a crusher and then ball-milled using a planetary ball mill, wherein the mass ratio of ball material to water during the ball milling process is 3:1:2, the ball milling speed is 300 rpm, the ball milling time is 10 hours, and the powder is passed through a 200-mesh sieve, and then the cured powder is transferred to a high-temperature tube furnace and pyrolyzed under vacuum conditions, wherein the pyrolysis temperature is 1000°C, the time is 4 hours, and the heating rate during the pyrolysis process is 1°C / min, to obtain amorphous SiBCN ceramic powder;

[0044] S2. Take 5 g of the amorphous SiBCN ceramic powder after vacuum pyrolysis obtained in step S1 and transfer it to a graphite mold. Use spark plasma sintering under an inert atmosphere. The temperature during the spark plasma sintering process is 1500°C, the pressure is 45 MPa, the time is 5 minutes, and the heating rate is 100°C / min to obtain an amorphous SiBCN ceramic block.

[0045] Comparative Example 1

[0046] Amorphous SiBCN ceramic blocks are prepared using the traditional PDC liquid phase molding method:

[0047] S1. Polyborosilazane (PSNB, liquid) was dripped into a polytetrafluoroethylene mold, then transferred to a vacuum curing chamber. The dissolved air in the liquid phase was evacuated and the mixture was initially cured at 220°C for 2 hours. The preliminarily cured sample was removed and transferred to a high-temperature tube furnace, where it was fully cured at 350°C for 2 hours to obtain a cured sample.

[0048] S2. The solidified sample obtained in S1 was pyrolyzed at 1000°C for 2 h. The entire process was carried out in flowing argon gas at a heating rate of 0.5-2°C / min to obtain an amorphous SiBCN ceramic block.

[0049] The inventors found that although the material prepared by this method is dense, it can only be prepared into thin small discs (thickness <2mm). Once the thickness is increased, it will crack during the pyrolysis process.

[0050] Comparative Example 2

[0051] Amorphous SiBCN ceramic blocks are prepared using the traditional PDC powder molding method:

[0052] S1. Pour polyborosilazane (PSNB, liquid) into a ceramic boat and transfer it to a vacuum curing chamber for curing at a temperature of 300-350°C for 2-4 hours at a heating rate of 1°C / min. The resulting block was crushed in a pulverizer and then ball-milled in a planetary ball mill at a ball-to-water ratio of 3:1:2 at a speed of 300 rpm for 10 hours. The solidified powder was then sieved through a 200-mesh sieve to obtain a solidified powder.

[0053] S2. The solidified powder and polyborosilazane precursor (10 wt% of the solidified powder) were mixed in a mortar and pestle, then transferred to a stainless steel mold and pressed into blocks using a hot press at a pressure of 350 MPa, a temperature of 80°C, and a time of 30 min.

[0054] S3. Transfer the green body obtained in step S2 to a high-temperature tube furnace and perform high-temperature pyrolysis under a flowing argon atmosphere to obtain an amorphous SiBCN ceramic block; wherein the heating rate during the high-temperature pyrolysis process is 2°C / min, the high-temperature pyrolysis temperature is 1000°C, and the high-temperature pyrolysis time is 2 hours.

[0055] The inventors found that the method can achieve a dimensional shrinkage of 25% after pyrolysis, and has low density and high porosity.

[0056] Comparative Example 3

[0057] The process is basically the same as Example 1, with the only difference being that pyrolysis is performed under an argon atmosphere in step S1 .

[0058] Comparative Example 4

[0059] The method is basically the same as Example 1, except that the solidified powder is not pyrolyzed under vacuum conditions, but is directly subjected to spark plasma sintering.

[0060] The inventors found that the sintering process of this method resulted in severe dimensional shrinkage.

[0061] The present invention analyzes the elemental composition of the amorphous SiBCN ceramic powder after vacuum pyrolysis of Example 1 and the amorphous SiBCN ceramic powder after argon pyrolysis of Comparative Example 3, as shown in Table 1.

[0062] Table 1. Elemental composition of amorphous SiBCN ceramic powders after vacuum pyrolysis and argon pyrolysis

[0063]

[0064] Table 1 shows that compared with the amorphous SiBCN ceramic powder after argon pyrolysis, the boron content in the amorphous SiBCN ceramic powder after vacuum pyrolysis is significantly increased, which can improve oxidation resistance; the nitrogen content is significantly decreased, which can reduce thermal reduction reactions. This shows that vacuum pyrolysis can improve the oxidation resistance of SiBCN ceramics.

[0065] The present invention performs oxidation thermogravimetric experiments on the amorphous SiBCN ceramic powder after vacuum pyrolysis of Example 1 and the amorphous SiBCN ceramic powder after argon pyrolysis of Comparative Example 3 in a mass spectrometer (room temperature -1500 ° C, flowing air). The oxidation thermogravimetric results are compared with Figure 1 As shown in the figure, the results show that the amorphous SiBCN ceramic powder after vacuum pyrolysis in Example 1 has a small mass change during the entire oxidation process, with a maximum mass loss of only 0.4%, while the amorphous SiBCN ceramic powder after argon pyrolysis in Comparative Example 3 has a maximum mass loss of 1.8% during the entire oxidation process. It can be seen that the oxidation resistance of the SiBCN ceramic powder after vacuum pyrolysis in Example 1 is significantly better than that of the amorphous SiBCN ceramic powder after argon pyrolysis in Comparative Example 3.

[0066] Depend on Figure 2 It can be seen that the XRD spectrum of the amorphous SiBCN ceramic block prepared in Example 1 has no obvious peaks, which proves that the prepared SiBCN ceramic block is amorphous.

[0067] Depend on Figure 3 It can be seen that the amorphous SiBCN ceramic block (diameter 25 mm, thickness 4 mm) prepared in Example 1 has a uniform structure, no obvious pores and cracks in the microstructure, low porosity and high density. The porosity of the amorphous SiBCN ceramic block prepared in Example 1 is measured to be 3.46% and the density is 2.24 g / cm 3 .

[0068] Depend on Figure 4 It can be seen that the amorphous SiBCN ceramic block prepared in Comparative Example 1 has high density, low porosity, uniform microstructure, no obvious pores and cracks, but small size (thickness <2mm); during the preparation process, the size shrinks severely from the solidified state to the pyrolysis state. The porosity of the amorphous SiBCN ceramic block prepared in Comparative Example 1 is measured to be 1.5%, and the density is 2.01g / cm 3The shrinkage rate from the solidified state to the pyrolyzed state is 22.0%. In addition, the inventors found that the preparation method of Comparative Example 1 can only produce thin small amorphous SiBCN ceramic blocks. Once the size increases, it is easy to crack and break during pyrolysis, and it is impossible to form large and dense amorphous SiBCN ceramic blocks. It should be noted that Figure 4 The solidified state refers to the solidified sample obtained after step S1 in comparative example 1, and the pyrolyzed state refers to the amorphous SiBCN ceramic block obtained after step S2 in comparative example 1.

[0069] Depend on Figure 5 It can be seen that the amorphous SiBCN ceramic block prepared in Comparative Example 2 has low density and large porosity, and there are obvious pores and cracks in the microstructure. In addition, the size shrinks severely from the solidified state to the pyrolysis state during the preparation process. The porosity of the amorphous SiBCN ceramic block prepared in Comparative Example 2 is measured to be 22.8%, and the density is 1.62 g / cm 3 , the dimensional shrinkage from the solidified state to the pyrolysis state is about 25%. It should be noted that, Figure 5 The solidified state refers to the material obtained after step S2 of comparative example 2, and the pyrolyzed state refers to the amorphous SiBCN ceramic block obtained after step S3 of comparative example 2.

[0070] Depend on Figure 6 It can be seen that the amorphous SiBCN ceramic blocks obtained in Example 1 and Comparative Example 3 were subjected to an oxidation resistance test in a muffle furnace (temperature of 1400°C and time of 2h). It can be seen that the amorphous SiBCN ceramic block obtained by sintering the SiBCN ceramic powder after argon pyrolysis in Comparative Example 3 was obviously oxidized, and the surface was almost covered with white substance (SiO2), while the amorphous SiBCN ceramic block obtained by sintering the SiBCN ceramic powder after vacuum pyrolysis in Example 1 had only a small amount of white substance. In addition, the mass loss of the amorphous SiBCN ceramic block obtained in Example 1 was about 0.16% before and after the test, and the mass loss of the amorphous SiBCN ceramic block obtained in Comparative Example 3 was about 1.64% before and after the test. It can be seen that the static oxidation resistance of the amorphous SiBCN ceramic block obtained by the vacuum pyrolysis process is significantly better than that of the amorphous SiBCN ceramic block obtained by the vacuum pyrolysis process.

[0071] In summary, the amorphous SiBCN ceramic block prepared by the preparation method of the present invention has high density, low pore defects, adjustable size, small shrinkage and excellent antioxidant performance, which can meet the preparation needs of large-size, high-quality and high-performance amorphous SiBCN ceramic blocks, and effectively solve the problems of limited material size and multiple pores in the preparation process of traditional SiBCN ceramic blocks.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an amorphous SiBCN ceramic block with high density and excellent oxidation resistance, characterized in that: The preparation method comprises: After curing the polyborosilazane, the amorphous SiBCN ceramic powder is obtained by crushing, ball milling and vacuum pyrolysis; the vacuum pyrolysis temperature is 1000-1400° C. and the time is 2-6 hours; The amorphous SiBCN ceramic powder is subjected to spark plasma sintering to obtain an amorphous SiBCN ceramic block; the spark plasma sintering is carried out in an inert atmosphere, with a sintering temperature of 1400-1600° C., a sintering pressure of 30-60 MPa, and a sintering time of 3-15 minutes.

2. The preparation method according to claim 1, characterized in that The curing is carried out under vacuum conditions, the curing temperature is 300-350° C., and the curing time is 2-4 hours.

3. The preparation method according to claim 2, characterized in that The heating rate during the curing process is 0.5-1.5°C / min.

4. The preparation method according to claim 1, characterized in that The mass ratio of ball material to water during the ball milling process is 2-4:1:1.5-3, the ball milling speed is 200-400 rpm, and the ball milling time is 4-12 hours.

5. The preparation method according to claim 1, characterized in that The particle size of the amorphous SiBCN ceramic powder is less than 75 μm.

6. The preparation method according to claim 1, characterized in that The heating rate of the vacuum pyrolysis process is 1-3°C / min.

7. An amorphous SiBCN ceramic block with high density and excellent oxidation resistance, characterized in that: The method is prepared according to any one of claims 1 to 6.

8. The amorphous SiBCN ceramic block according to claim 7, characterized in that: The density of the amorphous SiBCN ceramic block is greater than 2.2 g / cm 3 , porosity is less than 3.5%.

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