Modified sibcn ceramic composite material, preparation method and application thereof

Abstract

The application provides a modified SiBCN ceramic composite material and a preparation method and application thereof, and the modified SiBCN ceramic composite material comprises the following components in percentage by mass: SiBCN ceramic material 85-95%, and rare earth oxide 5-15%. The SiBCN ceramic material is modified by introducing the rare earth oxide, so that high densification can be realized at a temperature lower than 1800 DEG C, the modified SiBCN ceramic composite material has uniform element distribution, high bending strength and excellent high-temperature oxidation resistance, and can be used in extreme environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic composite materials, and in particular relates to a modified SiBCN ceramic composite material and a preparation method and application thereof. Background Art

[0002] Components such as flaps and seals in the tail nozzle extension of aircraft engines operate in a harsh environment of high-speed airflow, high temperatures, and heavy loads for extended periods of time. This places increasingly stringent demands on materials with high strength, high-temperature resistance, corrosion resistance, and wear resistance. As the temperatures of new-generation aircraft engines increase, traditional high-temperature nickel-based alloys, due to their heat resistance and high density, struggle to meet these requirements.

[0003] SiBCN ceramics have attracted widespread attention due to their excellent high-temperature oxidation resistance below 1500°C and excellent structural stability in inert atmospheres below 2000°C. However, traditional preparation processes have significant shortcomings. For example, hot-pressing sintering requires temperatures exceeding 1800°C to achieve high density, resulting in uneven element distribution. Precursor pyrolysis methods also make it difficult to produce high-density SiBCN ceramics.

[0004] Therefore, designing a SiBCN ceramic material with high density, high strength and high-temperature oxidation resistance is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention provides a modified SiBCN ceramic composite material, its preparation method, and its application. By introducing rare earth oxides into the SiBCN ceramic material, the present invention enables high densification at temperatures below 1800°C. Furthermore, the modified SiBCN ceramic composite material exhibits uniform element distribution, high flexural strength, and excellent high-temperature oxidation resistance, making it suitable for use in extreme environments.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a modified SiBCN ceramic composite material, wherein the modified SiBCN ceramic composite material comprises the following components in percentage by mass:

[0008] SiBCN ceramic material 85-95%

[0009] Rare earth oxides 5-15%.

[0010] The present invention modifies SiBCN ceramic materials by introducing rare earth oxides, so that they can achieve high densification at temperatures below 1800°C. In addition, the modified SiBCN ceramic composite material has uniform element distribution, high bending strength and excellent high-temperature oxidation resistance, and can be used in extreme environments.

[0011] In the present invention, the mass content of the SiBCN ceramic material is 85-95%, for example, it can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94% or 95%.

[0012] In the present invention, the mass content of rare earth oxide is 5-15%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%.

[0013] In the present invention, if the mass content of rare earth oxide is too low, a good sintering aid effect cannot be achieved, resulting in insufficient sintering density; if the mass content of rare earth oxide is too high, the material's antioxidant properties will be reduced and the material density will also increase.

[0014] As a preferred technical solution of the present invention, the average particle size of the modified SiBCN ceramic composite material is 150-250 mesh, for example, it can be 250 mesh, 225 mesh, 200 mesh, 170 mesh or 150 mesh, etc., preferably 180-220 mesh.

[0015] In the present invention, the mesh number of the average particle size of the SiBCN ceramic composite material should not be too small. If the mesh number is too small, the powder particle size will be too large and it will be difficult to sinter and form.

[0016] Preferably, the mass content of the rare earth oxide is 8-12%, for example, 8%, 9%, 10%, 11% or 12%.

[0017] Preferably, the rare earth oxide includes any one of Yb2O3, Y2O3 or CeO2 or a combination of at least two thereof, preferably Yb2O3.

[0018] In the present invention, Yb2O3 has a better sintering aid effect than other rare earth oxides, and under high-temperature oxidation, it will form a multiphase oxide layer with SiO2, increasing the viscosity of the oxide layer, thereby reducing the diffusion rate of oxygen and improving the oxidation resistance.

[0019] As a preferred technical solution of the present invention, the modified SiBCN ceramic composite material is cylindrical.

[0020] Preferably, the cylindrical modified SiBCN ceramic composite material has a diameter of 50-60 mm, for example, 50 mm, 52 mm, 54 mm, 56 mm, 58 mm or 60 mm, and a height of 5-8 mm, for example, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm or 8 mm.

[0021] In a second aspect, the present invention provides a method for preparing the modified SiBCN ceramic composite material as described in the first aspect, the preparation method comprising the following steps:

[0022] The modified SiBCN ceramic composite material is obtained by mixing SiBCN ceramic material, silicon powder and rare earth oxide and sintering the mixture.

[0023] The preparation method provided by the present invention has a simple process, low cost, short cycle, and can realize mass production. Densification sintering can be achieved at a temperature below 1800°C, thereby reducing the sintering temperature of SiBCN ceramics and obtaining a high-density ceramic block, solving the problem of high sintering temperature required for the existing preparation of high-density SiBCN ceramics.

[0024] As a preferred technical solution of the present invention, the mass ratio of the SiBCN ceramic material, silicon powder and rare earth oxide is (68-76):(17-19):(5-15), wherein the selection range of the SiBCN ceramic material "68-76" can be, for example, 68, 69, 70, 71, 72, 73, 74, 75 or 76, the selection range of the silicon powder "17-19" can be, for example, 17, 17.5, 18, 18.5 or 19, and the selection range of the rare earth oxide "5-15" can be, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, etc.

[0025] Preferably, the mixing method is ball milling.

[0026] Preferably, the rotation speed of the ball mill is 200-400 rpm, for example, it can be 200 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm.

[0027] Preferably, the mixing time is 4-24 hours, for example, 4 hours, 8 hours, 12 hours, 16 hours, 20 hours or 24 hours.

[0028] Preferably, the ball-to-material ratio of the ball mill is (3-10):1, for example, it can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc.

[0029] It should be noted that the ball-to-material ratio refers to the mass ratio of the grinding balls and the added materials. The type of the grinding balls is not specifically limited. For example, it can be a mixed grinding ball of zirconia grinding balls with sizes of 5 mm and 7 mm, and the mass ratio can be 1:1.

[0030] Preferably, the ball milling comprises wet ball milling.

[0031] It should be noted that those skilled in the art should understand that a solvent needs to be added during the wet ball milling process, and the solvent can be ethanol.

[0032] Preferably, the ball milling is followed by drying.

[0033] Preferably, the drying method includes vacuum drying.

[0034] As a preferred technical solution of the present invention, the sintering method includes spark plasma sintering.

[0035] It should be noted that spark plasma sintering refers to the use of an electric field formed by an external pulsed strong current to remove oxides and adsorbed gases on the surface of powder particles, purify the material, activate the powder surface, and improve the diffusion capacity of the powder surface. The powder is then heated for a short time using a strong current under relatively low mechanical pressure for sintering and densification.

[0036] Preferably, the sintering temperature is 1400-1700°C, for example, 1400°C, 1500°C, 1600°C or 1700°C, and preferably 1500°C.

[0037] In the present invention, if the sintering temperature is too low, the material will not be sintered densely, resulting in high porosity and decreased mechanical strength; if the sintering temperature is too high, the preparation cost of the material will increase, and at a temperature exceeding 1500°C, the grains of the SiC fiber will grow, resulting in a decrease in fiber performance, which is not conducive to subsequent improvement of material performance through fiber toughening.

[0038] Preferably, the sintering heating rate is 50-150°C / min, for example, it can be 50°C / min, 60°C / min, 70°C / min, 80°C / min, 90°C / min, 100°C / min, 110°C / min, 120°C / min, 130°C / min, 140°C / min or 150°C / min, etc.

[0039] Preferably, the sintering time is 5-30 min, for example, 5 min, 10 min, 15 min, 20 min, 25 min or 30 min.

[0040] Preferably, the pressure during sintering is 30-50 MPa, for example, 30 MPa, 35 MPa, 40 MPa, 45 MPa or 50 MPa.

[0041] As a preferred technical solution of the present invention, the preparation method of the SiBCN ceramic material comprises the following steps:

[0042] (1) mixing the raw material of SiBCN ceramic material and an organic solvent, and performing heat treatment to obtain a SiBCN precursor;

[0043] (2) The SiBCN precursor is subjected to inorganic treatment to obtain a SiBCN ceramic material.

[0044] As a preferred technical solution of the present invention, the raw materials of the SiBCN ceramic material in step (1) include an organic silicon source and an organic boron nitrogen compound.

[0045] Preferably, the organosilicon source comprises polycarbosilane and / or polyborosilazane.

[0046] In the present invention, the phase state of polycarbosilane is not particularly limited. For example, it can be solid or liquid.

[0047] Preferably, the organic boron nitrogen compound comprises polyborazine and / or polyborosilazane.

[0048] Preferably, the organic solvent in step (1) comprises toluene and / or xylene.

[0049] Preferably, the mass ratio of the organosilicon source and the organic boron nitrogen compound is (1-2): (2-1), wherein the selection range of the organosilicon source "1-2" can be, for example, 1, 1.2, 1.4, 1.6, 1.8 or 2, and the selection range of the organic boron nitrogen compound "2-1" can be, for example, 1, 1.2, 1.4, 1.6, 1.8 or 2, etc.

[0050] Preferably, after the raw materials of the SiBCN ceramic material and the organic solvent are mixed in step (1), the concentration of the obtained solution is 40-60wt.%, for example, it can be 40wt.%, 45wt.%, 50wt.%, 55wt.% or 60wt.%.

[0051] Preferably, the heat treatment method in step (1) includes rotary evaporation.

[0052] Preferably, the temperature of the heat treatment in step (1) is 150-200°C, for example, it can be 150°C, 160°C, 170°C, 180°C, 190°C or 200°C.

[0053] Preferably, the heat treatment time in step (1) is 2-4 hours, for example, it can be 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0054] Preferably, the inorganic treatment in step (2) is carried out in an inert atmosphere.

[0055] The present invention does not specifically limit the gas in the inert atmosphere. For example, it can be argon or nitrogen.

[0056] Preferably, the temperature of the inorganic treatment in step (2) is 900-1100°C, for example, it can be 900°C, 950°C, 1000°C, 1050°C or 1100°C.

[0057] Preferably, the holding time of the inorganic treatment in step (2) is 1-3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0058] Preferably, after the inorganic treatment in step (2), a crushing step is also performed.

[0059] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0060] (I) mixing an organosilicon source, an organoboron nitrogen compound, and an organic solvent to obtain a liquid SiBCN precursor having a concentration of 40-60 wt.%, followed by heat treatment in an inert atmosphere at 150-200° C. for 2-4 hours, and quenching to obtain a solid SiBCN precursor;

[0061] Wherein, the mass ratio of the organosilicon source and the organoboron nitrogen compound is (1-2):(2-1);

[0062] (II) In an inert atmosphere, the solid SiBCN precursor is inorganically treated and crushed to obtain an amorphous SiBCN ceramic material;

[0063] The temperature of the inorganic treatment is 900-1100°C, the holding time is 1-3h, and the heating rate is 2-5°C / min;

[0064] (III) ball-milling the amorphous SiBCN ceramic material, silicon powder, and rare earth oxide for 4-24 hours, sieving, drying, and sintering at 30-50 MPa and 1400-1700° C. for 5-30 minutes to obtain a cylindrical modified SiBCN ceramic composite material;

[0065] The mass ratio of SiBCN ceramic material, silicon powder and rare earth oxide is (68-76):(17-19):(5-15), the ball milling speed is 200-400 rpm, the ball-to-material ratio of the ball milling is (3-10):1, and the heating rate of sintering and shaping is 50-150°C / min.

[0066] In a third aspect, the present invention provides an application of the modified SiBCN ceramic composite material as described in the first aspect, wherein the modified SiBCN ceramic composite material is applied in the field of aerospace.

[0067] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] (1) The present invention modifies SiBCN ceramic materials by introducing rare earth oxides, so that they can achieve high densification at temperatures below 1800°C. In addition, the modified SiBCN ceramic composite material has uniform element distribution, high bending strength and excellent high-temperature oxidation resistance, and can be used in extreme environments.

[0070] (2) The preparation method provided by the present invention has simple process, low cost, short cycle, and can realize mass production. Densification sintering can be achieved at a temperature below 1800°C, which reduces the sintering temperature of SiBCN ceramics and obtains high-density ceramic blocks, solving the problem of high sintering temperature required for the existing preparation of high-density SiBCN ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 It is a line graph showing the density of the SiBCN ceramic composite materials prepared in Examples 1-3 of the present invention and Comparative Examples 1-2 as a function of the Yb2O3 content.

[0072] Figure 2 This is a bar graph showing the variation of the flexural strength of the SiBCN ceramic composite materials prepared in Examples 1-3 of the present invention and Comparative Examples 1-2 with the content of Yb2O3.

[0073] Figure 3 These are non-isothermal oxidation curves of the SiBCN ceramic composite materials prepared in Examples 1-3 of the present invention and Comparative Examples 1-2. DETAILED DESCRIPTION

[0074] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0075] Example 1

[0076] This embodiment provides a modified SiBCN ceramic composite material, which includes the following components in percentage by mass:

[0077] SiBCN ceramic material 95%

[0078] Rare earth oxides 5%;

[0079] The average particle size of the modified SiBCN ceramic composite material is 200 meshes, the rare earth oxide is Yb2O3, and the modified SiBCN ceramic composite material is cylindrical with a diameter of 55 mm and a height of 7 mm.

[0080] This embodiment also provides a method for preparing the modified SiBCN ceramic composite material, the preparation method comprising the following steps:

[0081] (1) The solid polycarbosilane was crushed, and then dissolved in toluene with liquid polyborazine at a mass ratio of 1:1, the concentration was controlled to be 50 wt.%, and mixed on an orbital shaker at a speed of 200 rpm for 4 h to obtain a uniformly mixed liquid SiBCN precursor. The liquid SiBCN precursor was then placed in a 500 mL round-bottom flask and subjected to rotary evaporation in an argon atmosphere at 150 ° C for 4 h. The liquid precursor after rotary evaporation was quenched for 30 min to obtain a solid SiBCN precursor;

[0082] (2) subjecting the solid precursor to inorganic treatment in a tube furnace under an argon atmosphere, and then grinding the obtained product in an agate mortar for 2 h and crushing it to obtain an amorphous SiBCN ceramic material;

[0083] The temperature of the inorganic treatment was 1000°C, the holding time was 1h, and the heating rate was 2°C / min;

[0084] (3) Amorphous SiBCN ceramic material, silicon powder (260-300 mesh) and Yb2O3 were added to a nylon ball mill in a mass ratio of 76:19:5, and ball milled at a speed of 350 rpm in a planetary ball mill for 8 h. The milled slurry was sieved through a 200-mesh sieve, and then the sieved slurry was subjected to rotary evaporation to remove the solvent and vacuum dried at 80°C for 4 h to obtain modified SiBCN powder;

[0085] The mass ratio of the grinding balls, material and ethanol in the ball mill is 10:1:1, and the grinding balls include zirconia grinding balls with sizes of 5 mm and 7 mm, with a mass ratio of 1:1;

[0086] (4) placing the modified SiBCN powder in a cylindrical graphite mold, performing spark plasma sintering, and then cooling the furnace to obtain the cylindrical modified SiBCN ceramic composite material;

[0087] The spark plasma sintering process has a heating rate of 100°C / min, a temperature of 1500°C, a pressure of 30 MPa, and a time of 20 min.

[0088] Example 2

[0089] The difference between this embodiment and embodiment 1 is that the amount of Yb2O3 added in step (3) is adjusted so that the mass content of Yb2O3 in the modified SiBCN ceramic composite material is 10%.

[0090] The rest of the preparation methods and parameters remained the same as in Example 1.

[0091] Example 3

[0092] The difference between this embodiment and embodiment 1 is that the amount of Yb2O3 added in step (3) is adjusted so that the mass content of Yb2O3 in the modified SiBCN ceramic composite material is 15%.

[0093] The rest of the preparation methods and parameters remained the same as in Example 1.

[0094] Example 4

[0095] This embodiment provides a modified SiBCN ceramic composite material, which includes the following components in percentage by mass:

[0096] SiBCN ceramic material 92%

[0097] Rare earth oxides 8%;

[0098] The average particle size of the modified SiBCN ceramic composite material is 200 meshes, the rare earth oxide is Yb2O3, and the modified SiBCN ceramic composite material is cylindrical with a diameter of 50 mm and a height of 8 mm.

[0099] This embodiment also provides a method for preparing the modified SiBCN ceramic composite material, the preparation method comprising the following steps:

[0100] (1) The solid polycarbosilane was crushed, and then dissolved in toluene with liquid polyborazine at a mass ratio of 1:1, the concentration was controlled to 40 wt.%, and mixed on an orbital shaker at a speed of 200 rpm for 4 h to obtain a uniformly mixed liquid SiBCN precursor. The liquid SiBCN precursor was then placed in a 500 mL round-bottom flask and subjected to rotary evaporation in an argon atmosphere at 175 ° C for 3 h. The liquid precursor after rotary evaporation was quenched for 30 min to obtain a solid SiBCN precursor;

[0101] (2) subjecting the solid precursor to inorganic treatment in a tube furnace under an argon atmosphere, and then grinding the obtained product in an agate mortar for 2 h and crushing it to obtain an amorphous SiBCN ceramic material;

[0102] The temperature of the inorganic treatment was 900°C, the holding time was 3 h, and the heating rate was 3°C / min.

[0103] (3) Amorphous SiBCN ceramic material, silicon powder (260-300 mesh) and Yb2O3 were added to a nylon ball mill in a mass ratio of 73:19:8, and ball milled at a speed of 200 rpm in a planetary ball mill for 24 h. The ball-milled slurry was sieved through a 200-mesh sieve, and then the sieved slurry was subjected to rotary evaporation to remove the solvent and vacuum dried at 80°C for 4 h to obtain modified SiBCN powder;

[0104] The mass ratio of the grinding balls, material and ethanol in the ball mill is 7:1:1, and the grinding balls include zirconia grinding balls with sizes of 5 mm and 7 mm, with a mass ratio of 1:1;

[0105] (4) placing the modified SiBCN powder in a cylindrical graphite mold, performing spark plasma sintering, and then cooling the furnace to obtain the cylindrical modified SiBCN ceramic composite material;

[0106] The spark plasma sintering process has a heating rate of 50°C / min, a temperature of 1400°C, a pressure of 40 MPa, and a sintering time of 10 min.

[0107] Example 5

[0108] This embodiment provides a modified SiBCN ceramic composite material, which includes the following components in percentage by mass:

[0109] SiBCN ceramic material 92%

[0110] Rare earth oxides 8%;

[0111] The average particle size of the modified SiBCN ceramic composite material is 200 meshes, the rare earth oxide is Yb2O3, and the modified SiBCN ceramic composite material is cylindrical with a diameter of 60 mm and a height of 5 mm.

[0112] This embodiment also provides a method for preparing the modified SiBCN ceramic composite material, the preparation method comprising the following steps:

[0113] (1) The solid polycarbosilane was crushed, and then dissolved in toluene with liquid polyborazine at a mass ratio of 1:1, the concentration was controlled to be 60 wt.%, and mixed on an orbital shaker at a speed of 200 rpm for 4 h to obtain a uniformly mixed liquid SiBCN precursor, and then the liquid SiBCN precursor was placed in a 500 mL round-bottom flask and rotary evaporated in an argon atmosphere at 200 ° C for 2 h. The liquid precursor after rotary evaporation was quenched for 30 min to obtain a solid SiBCN precursor;

[0114] (2) subjecting the solid precursor to inorganic treatment in a tube furnace under an argon atmosphere, and then grinding the obtained product in an agate mortar for 2 h and crushing it to obtain an amorphous SiBCN ceramic material;

[0115] The temperature of the inorganic treatment was 1100°C, the holding time was 1h, and the heating rate was 5°C / min.

[0116] (3) Amorphous SiBCN ceramic material, silicon powder (260-300 mesh) and Yb2O3 were added to a nylon ball mill in a mass ratio of 73:19:8, and ball milled in a planetary ball mill at a speed of 400 pm for 4 h. The milled slurry was sieved through a 200-mesh sieve, and then the sieved slurry was subjected to rotary evaporation to remove the solvent and vacuum dried at 80°C for 4 h to obtain modified SiBCN powder;

[0117] The mass ratio of the grinding balls, material and ethanol in the ball mill is 5:1:1, and the grinding balls include zirconia grinding balls with sizes of 5 mm and 7 mm, with a mass ratio of 1:1;

[0118] (4) placing the modified SiBCN powder in a cylindrical graphite mold, performing spark plasma sintering, and then cooling the furnace to obtain the cylindrical modified SiBCN ceramic composite material;

[0119] The spark plasma sintering process has a heating rate of 150°C / min, a temperature of 1700°C, a pressure of 50 MPa, and a time of 30 min.

[0120] Example 6

[0121] The difference between this embodiment and embodiment 1 is that silicon powder is not added in step (3).

[0122] The rest of the preparation methods and parameters remained the same as in Example 1.

[0123] Example 7

[0124] The difference between this embodiment and embodiment 1 is that the sintering temperature in step (4) is 1300°C.

[0125] The rest of the preparation methods and parameters remained the same as in Example 1.

[0126] Example 8

[0127] The difference between this embodiment and embodiment 1 is that the sintering temperature in step (4) is 1800°C.

[0128] The rest of the preparation methods and parameters remained the same as in Example 1.

[0129] Comparative Example 1

[0130] The difference between this comparative example and Example 1 is that Yb2O3 is not added in step (3).

[0131] The rest of the preparation methods and parameters remained the same as in Example 1.

[0132] Comparative Example 2

[0133] The difference between this comparative example and Example 1 is that the amount of Yb2O3 added in step (3) is adjusted so that the mass content of Yb2O3 in the modified SiBCN ceramic composite material is 20%.

[0134] The rest of the preparation methods and parameters remained the same as in Example 1.

[0135] Performance Testing

[0136] The density, flexural strength and high-temperature oxidation resistance of the modified SiBCN ceramic composite materials prepared in Examples 1-8 and Comparative Examples 1-2 were tested.

[0137] Density test: Use a density meter to test using the Archimedes drainage method.

[0138] Bending strength test: tested using a universal testing machine.

[0139] High temperature oxidation resistance test: A thermogravimetric analyzer was used to test the mass change per unit area of ​​the modified SiBCN ceramic composite material from room temperature to 1200°C in an air atmosphere.

[0140] The test results are as follows Figure 1 、 Figure 2 、 Figure 3 and as shown in Table 1.

[0141] Figure 1 A line graph showing the density of the SiBCN ceramic composite materials prepared in Examples 1-3 and Comparative Examples 1-2 as a function of the Yb2O3 content is shown. As can be seen from the graph, the density of the Yb2O3-modified SiBCN ceramics is significantly improved, from 93.77% to 99.60%.

[0142] Figure 2 A bar chart shows the variation of the flexural strength of the SiBCN ceramic composite materials prepared in Examples 1-3 and Comparative Examples 1-2 with the Yb2O3 content. As can be seen from the figure, when the Yb2O3 content reaches 10wt%, the flexural strength of the modified SiBCN ceramic reaches 303.80Mpa. Compared with Comparative Example 1, the flexural strength of Example 2 is increased by 55%.

[0143] Figure 3 The non-isothermal oxidation curves of the SiBCN ceramic composite materials prepared in Examples 1-3 and Comparative Examples 1-2 are shown. As can be seen from the figure, after Yb2O3 modification, the degree of oxidation of the SiBCN ceramic is significantly reduced, but when the Yb2O3 addition content exceeds 10%, the degree of oxidation of the SiBCN ceramic increases.

[0144] Table 1

[0145]

[0146]

[0147] analyze:

[0148] From the above table and Figure 1-3 It can be seen that the present invention modifies the SiBCN ceramic material by introducing rare earth oxides, so that it can achieve high densification at a temperature below 1800°C, and the elements of the modified SiBCN ceramic composite material are evenly distributed, with high bending strength and excellent high-temperature oxidation resistance, and can be used in extreme environments.

[0149] It can be seen from the data results of Example 1 and Example 6 that if silicon powder is not added in step (3), the density and bending strength of the sample will be significantly reduced.

[0150] It can be seen from the data results of Example 1 and Examples 7-8 that if the sintering temperature in step (4) is too low, the sample cannot be sintered, resulting in a significant decrease in density and bending strength; if the sintering temperature in step (4) is too high, it has little effect on the density and bending strength of the sample, but increases the preparation cost.

[0151] It can be seen from the data results of Example 1 and Comparative Example 1 that if Yb2O3 is not added, the density of the sample will be significantly reduced.

[0152] It can be seen from the data results of Example 1 and Comparative Example 2 that if the mass content of Yb2O3 is too high, although the density and bending strength of the prepared material are improved, its high-temperature oxidation resistance is significantly reduced and the overall performance is degraded.

[0153] The applicant states that while the above-described embodiments illustrate the process of the present invention, the present invention is not limited to the above-described process steps, nor does it imply that the present invention must rely on the above-described process steps for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for the raw materials used, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a modified SiBCN ceramic composite material capable of achieving high densification at temperatures below 1800°C, characterized in that: The preparation method of the modified SiBCN ceramic composite material comprises the following steps: Mixing SiBCN ceramic material, silicon powder and rare earth oxide, and sintering to obtain the modified SiBCN ceramic composite material; The mass ratio of the SiBCN ceramic material, silicon powder and rare earth oxide is (68-76):(17-19):(5-15); The sintering method includes spark plasma sintering; The sintering temperature is 1400-1700°C; The sintering heating rate is 50-150°C / min; The sintering time is 5-30min; The pressure during sintering is 30-50 MPa; The rare earth oxide is Yb2O3.

2. The preparation method according to claim 1, characterized in that The average particle size of the modified SiBCN ceramic composite material is 150-250 meshes.

3. The preparation method according to claim 2, characterized in that The average particle size of the modified SiBCN ceramic composite material is 180-220 meshes.

4. The preparation method according to claim 1, characterized in that The modified SiBCN ceramic composite material is cylindrical.

5. The preparation method according to claim 4, characterized in that The cylindrical modified SiBCN ceramic composite material has a diameter of 50-60 mm and a height of 5-8 mm.

6. The preparation method according to claim 1, characterized in that The mixing method is ball milling.

7. The preparation method according to claim 6, characterized in that The rotation speed of the ball mill is 200-400 rpm.

8. The preparation method according to claim 1, characterized in that The mixing time is 4-24h.

9. The preparation method according to claim 6, characterized in that The ball-to-material ratio of the ball mill is (3-10):

1.

10. The preparation method according to claim 6, characterized in that The ball milling is followed by drying.

11. The preparation method according to claim 1, characterized in that The preparation method of the SiBCN ceramic material comprises the following steps: (1) Mixing the raw materials of SiBCN ceramic material and an organic solvent, and then heat treating to obtain a SiBCN precursor; (2) The SiBCN precursor is subjected to inorganic treatment to obtain SiBCN ceramic material.

12. The preparation method according to claim 11, characterized in that The raw materials of the SiBCN ceramic material in step (1) include an organic silicon source and an organic boron nitrogen compound.

13. The preparation method according to claim 12, characterized in that The organosilicon source includes polycarbosilane and / or polyborosilazane.

14. The preparation method according to claim 12, characterized in that The organic boron nitrogen compound includes polyborazine and / or polyborosilazane.

15. The preparation method according to claim 11, characterized in that The organic solvent in step (1) includes toluene and / or xylene.

16. The preparation method according to claim 12, characterized in that The mass ratio of the organic silicon source to the organic boron nitrogen compound is (1-2):(2-1).

17. The preparation method according to claim 11, characterized in that In step (1), the raw materials of the SiBCN ceramic material and the organic solvent are mixed to obtain a solution with a concentration of 40-60 wt.%.

18. The preparation method according to claim 11, characterized in that The heat treatment method in step (1) includes rotary evaporation.

19. The preparation method according to claim 11, characterized in that The temperature of the heat treatment in step (1) is 150-200°C.

20. The preparation method according to claim 11, characterized in that The heat treatment time in step (1) is 2-4 hours.

21. The preparation method according to claim 11, characterized in that The inorganic treatment in step (2) is carried out in an inert atmosphere.

22. The preparation method according to claim 11, characterized in that The temperature of the inorganic treatment in step (2) is 900-1100°C.

23. The preparation method according to claim 11, characterized in that The holding time of the inorganic treatment in step (2) is 1-3 hours.

24. The preparation method according to claim 11, characterized in that After the inorganic treatment in step (2), a crushing step is also performed.

25. The preparation method according to any one of claims 1 to 24, characterized in that: The preparation method comprises the following steps: (I) mixing an organosilicon source, an organoboron nitrogen compound, and an organic solvent to obtain a liquid SiBCN precursor having a concentration of 40-60 wt.%, followed by heat treatment in an inert atmosphere at 150-200° C. for 2-4 hours, and quenching to obtain a solid SiBCN precursor; Wherein, the mass ratio of the organosilicon source and the organoboron nitrogen compound is (1-2):(2-1); (II) In an inert atmosphere, the solid SiBCN precursor is inorganically treated and crushed to obtain a SiBCN ceramic material; The temperature of the inorganic treatment is 900-1100°C, the holding time is 1-3h, and the heating rate is 2-5°C / min; (III) ball-milling the SiBCN ceramic material, silicon powder, and rare earth oxide for 4-24 hours, sieving, drying, and sintering at 30-50 MPa and 1400-1700° C. for 5-30 minutes to obtain a cylindrical modified SiBCN ceramic composite material; The mass ratio of SiBCN ceramic material, silicon powder and rare earth oxide is (68-76):(17-19):(5-15), the ball milling speed is 200-400 rpm, the ball-to-material ratio of the ball milling is (3-10):1, and the heating rate of sintering and shaping is 50-150°C / min.

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