A bulk dense amorphous SiBCN ceramic bulk and a preparation method thereof

Abstract

The application discloses a bulk dense amorphous SiBCN ceramic bulk body and a preparation method thereof, relates to an amorphous SiBCN ceramic bulk body and a preparation method thereof, and aims at solving the problem that a bulk dense amorphous SiBCN ceramic bulk body is difficult to be prepared in the prior art. The method comprises the following steps: one, preparation of an organic-inorganic mixed bulk body green compact / powder; and two, preparation of the bulk dense amorphous SiBCN ceramic bulk body. The application is used for the bulk dense amorphous SiBCN ceramic bulk body and the preparation thereof.

Description

TECHNICAL FIELD

[0001] The present application relates to amorphous SiBCN ceramic bulk and its preparation method. BACKGROUND

[0002] Amorphous SiBCN ceramic material is widely used in structural materials and functional materials due to its high specific strength, high temperature oxidation resistance, high thermal stability, and low dielectric constant and dielectric loss. However, due to the large shrinkage and low yield of amorphous SiBCN ceramic prepared by pyrolysis of organic precursor, pure organic precursor pyrolysis cannot produce dense SiBCN bulk, so it is difficult to realize the preparation of large bulk dense amorphous SiBCN bulk ceramic, which to some extent limits the application field of SiBCN ceramic material. Therefore, it is urgent to study the large bulk dense amorphous SiBCN bulk ceramic material. SUMMARY

[0003] The present application solves the problem that the prior art cannot realize the preparation of large bulk dense amorphous SiBCN bulk ceramic, and further provides a large bulk dense amorphous SiBCN ceramic bulk and its preparation method.

[0004] A large bulk dense amorphous SiBCN ceramic bulk, which is composed of a precursor-derived ceramic phase and an amorphous ceramic phase, and the amorphous ceramic phase uniformly fills the voids of the precursor-derived ceramic phase.

[0005] The precursor-derived ceramic phase is obtained by pyrolysis of the precursor at high temperature; and the amorphous ceramic phase is obtained by sintering of the mechanical alloying inorganic amorphous SiBCN powder.

[0006] A preparation method of a large bulk dense amorphous SiBCN ceramic bulk, which is carried out according to the following steps:

[0007] I. Preparation of organic-inorganic mixed bulk green body / powder:

[0008] The mechanical alloying inorganic amorphous SiBCN powder is dispersed in the precursor liquid, and a paste-like organic-inorganic mixed solution is obtained by stirring. The paste-like organic-inorganic mixed solution is vacuum solidified, and after solidification, it is sequentially subjected to crushing and ball milling, or sequentially subjected to crushing, ball milling and pre-pressing, to obtain an organic-inorganic mixed bulk green body / powder; the mass ratio of the precursor liquid to the mechanical alloying inorganic amorphous SiBCN powder is 1:(0.05-0.4).

[0009] or the precursor liquid is solidified under inert atmosphere, and after solidification, the precursor powder is obtained by crushing, and the precursor powder is mixed with the mechanical alloying inorganic amorphous SiBCN powder by ball milling, or the ball milling and pre-pressing are carried out to obtain the organic-inorganic mixed bulk green compact / powder; the mass ratio of the precursor powder to the mechanical alloying inorganic amorphous SiBCN powder is 1:(0.05-0.4);

[0010] II. Preparation of the bulk dense amorphous SiBCN ceramic bulk

[0011] The organic-inorganic mixed bulk green compact / powder is sintered under the conditions of inert atmosphere and a sintering temperature of 1000-1600 DEG C to obtain the dense amorphous SiBCN bulk ceramic material.

[0012] The beneficial effects of the present application are:

[0013] 1. The inorganic amorphous ceramic network structure is generated after the precursor is cracked, and in the sintering process, the inorganic amorphous ceramic network structure provides the driving force for the rearrangement of the original inorganic ceramic powder particles, accelerates the migration of the inorganic ceramic powder particles, and the inorganic powder fills the holes generated after the precursor is cracked, and then the dense bulk ceramic material is obtained. The present application realizes the low-temperature sintering densification of the bulk dense amorphous SiBCN bulk, solves the problem that the pure organic precursor cracking cannot produce the dense SiBCN bulk, and realizes the preparation of the bulk dense amorphous SiBCN ceramic.

[0014] 2. Compared with the existing technology which mostly uses various monovalent or multivalent oxide ceramics as sintering aids, the present application uses the precursor ceramic as the main raw material and adds a small amount of inorganic amorphous ceramic powder. The amorphous network structure is formed after the organic precursor is cracked, the sintering activity is high, the sintering of the mechanical alloying SiBCN powder is promoted, and the sintering temperature is reduced and the density and purity of the product are improved. Low-temperature sintering is beneficial to maintaining the amorphous structure (without grain boundaries and dislocations, and grain boundaries and dislocations will be generated after crystallization), and the dense bulk ceramic material prepared by the present application has high strength, good oxidation resistance and excellent wave transmission performance.

[0015] Drawings of the specification

[0016] Figure 1 Flow chart for preparing the bulk dense amorphous SiBCN ceramic bulk of the present application;

[0017] Figure 2 SEM graph of the fracture of the dense amorphous SiBCN ceramic bulk prepared in Example 1;

[0018] Figure 3 TEM graph of the dense amorphous SiBCN ceramic bulk prepared in Example 2;

[0019] Figure 4 TG-DSC graph of the dense amorphous SiBCN ceramic bulk prepared for example three under synthetic air atmosphere;

[0020] Figure 5 Dielectric properties of the dense amorphous SiBCN ceramic bulk prepared for example four, 1 is dielectric constant, 2 is dielectric loss;

[0021] Figure 6 Physical map of the dense amorphous SiBCN ceramic bulk prepared for example two;

[0022] Figure 7 XRD graph of the dense amorphous SiBCN ceramic bulk prepared for example one. DETAILED DESCRIPTION

[0023] Embodiment one: the embodiment is a bulk dense amorphous SiBCN ceramic bulk, which is composed of a precursor-derived ceramic phase and an amorphous ceramic phase, and the amorphous ceramic phase uniformly fills the voids in the precursor-derived ceramic phase.

[0024] The precursor-derived ceramic phase is obtained by pyrolysis of the precursor; and the amorphous ceramic phase is obtained by sintering of the mechanically alloyed inorganic amorphous SiBCN powder.

[0025] The embodiment has the following beneficial effects:

[0026] 1. After pyrolysis of the precursor, an inorganic amorphous ceramic network structure is formed, which provides driving force for rearrangement of the original inorganic ceramic powder particles during sintering, accelerates migration of the inorganic ceramic powder particles, and the inorganic powder fills the pores generated after pyrolysis of the precursor, thereby obtaining a dense bulk ceramic material. The embodiment realizes low-temperature sintering densification of the bulk dense amorphous SiBCN bulk, and solves the problem that pure organic precursors cannot produce dense SiBCN bulk and the difficulty in preparing a bulk dense amorphous SiBCN ceramic.

[0027] 2. Compared with the existing technology which mostly uses various mono- or multi-oxide ceramics as sintering aids, the embodiment uses a precursor ceramic as the main raw material and adds a small amount of inorganic amorphous ceramic powder. The amorphous network structure formed by pyrolysis of the organic precursor has high sintering activity, promotes sintering of the mechanically alloyed SiBCN powder, and is conducive to reducing the sintering temperature and improving the density and purity of the product. Low-temperature sintering is conducive to maintaining the amorphous structure (without grain boundaries and dislocations, etc., and grain boundaries and dislocations will be generated after crystallization). The dense bulk ceramic material prepared by the embodiment has high strength, good oxidation resistance, and excellent wave transmission performance.

[0028] Specific embodiment two: the difference between this embodiment and specific embodiment one is that the precursor is a powder or a liquid, and the precursor is one or a mixture of several of polysilane, polysilazane, polycarbosilane, polyborazane and polyborosilazane. The rest is the same as specific embodiment one.

[0029] Specific embodiment three: the difference between this embodiment and one of specific embodiment one or two is that the mechanical alloying inorganic amorphous SiBCN powder is prepared by high-energy ball milling of a mixed powder containing Si, B, C and N, and Si, B, C and N in the mixed powder are obtained by any combination of Si, carbon material, BN, Si3N4, SiC and B4C. The rest is the same as specific embodiment one or two.

[0030] Specific embodiment four: the difference between this embodiment and one of specific embodiment one to three is that the carbon material is one or a mixture of several of graphite, carbon black, graphene, carbon nanotube, fullerene and diamond; and the BN is one or a mixture of both of c-BN and h-BN. The rest is the same as specific embodiment one to three.

[0031] Specific embodiment five: in combination with Figure 1 Specifically, the present embodiment is a method for preparing a bulk dense amorphous SiBCN ceramic bulk, which is carried out according to the following steps:

[0032] I. Preparation of organic-inorganic mixed bulk green body / powder:

[0033] The mechanical alloying inorganic amorphous SiBCN powder is dispersed in the precursor liquid, and a paste-like organic-inorganic mixed solution is obtained by stirring. The paste-like organic-inorganic mixed solution is vacuum solidified, and after solidification, it is sequentially crushed and ball milled, or sequentially crushed, ball milled and pre-pressed, to obtain an organic-inorganic mixed bulk green body / powder; the mass ratio of the precursor liquid to the mechanical alloying inorganic amorphous SiBCN powder is 1:(0.05-0.4);

[0034] or the precursor liquid is solidified under an inert atmosphere, and after solidification, it is crushed to obtain a precursor powder. The precursor powder and the mechanical alloying inorganic amorphous SiBCN powder are ball milled and mixed, or ball milled and mixed and pre-pressed, to obtain an organic-inorganic mixed bulk green body / powder; the mass ratio of the precursor powder to the mechanical alloying inorganic amorphous SiBCN powder is 1:(0.05-0.4);

[0035] II. Preparation of a bulk dense amorphous SiBCN ceramic bulk:

[0036] Sintering the organic-inorganic mixed bulk vitrified powder under inert atmosphere and at a sintering temperature of 1000-1600℃ to obtain a dense amorphous SiBCN bulk ceramic material.

[0037] Sixth Embodiment: The difference between this embodiment and the fifth embodiment is that the mechanical alloying inorganic amorphous SiBCN powder in step one is prepared according to the following steps:

[0038] The mixed powder containing Si, B, C and N is placed in a high-energy ball mill tank under inert atmosphere and at a rotation speed of 400-800r / min for 25-40h, and finally sieved through an 80-200 mesh screen to obtain the mechanical alloying inorganic amorphous SiBCN powder; and the Si, B, C and N in the mixed powder are obtained from any combination of Si, carbon material, BN, Si3N4, SiC and B4C; the carbon material is one or a mixture of several of graphite, carbon black, graphene, carbon nanotube, fullerene and diamond; and the BN is one or a mixture of both of c-BN and h-BN. The rest is the same as the fifth embodiment.

[0039] Seventh Embodiment: The difference between this embodiment and the fifth or sixth embodiment is that the precursor liquid in step one is one or a mixture of several of polysilane, polysilazane, polycarbosilane, polyborazane and polyborosilazane; and the inert atmosphere in steps one and two is one or a mixture of several of argon, nitrogen, ammonia and hydrogen. The rest is the same as the fifth or sixth embodiment.

[0040] Eighth Embodiment: The difference between this embodiment and the fifth to seventh embodiments is that the solidification in step one is carried out at a temperature of 120-350℃ for 2-4h. The rest is the same as the fifth to seventh embodiments.

[0041] Ninth Embodiment: The difference between this embodiment and the fifth to eighth embodiments is that the pre-pressing in step one is one or a combination of cold pressing and cold isostatic pressing; when sintering the organic-inorganic mixed powder in step two, the sintering is spark plasma sintering, hot pressing sintering, gas pressure sintering, hot isostatic pressing sintering or high pressure sintering; and when sintering the organic-inorganic mixed green body in step two, the sintering is pressureless sintering. The rest is the same as the fifth to eighth embodiments.

[0042] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 5 to 9 in that: when the sintering is discharge plasma sintering, it is specifically carried out according to the following steps: heating at a rate of 30℃ / min to 100℃ / min to 1000℃ to 1500℃, and holding at a pressure of 30MPa to 100MPa and a temperature of 1000℃ to 1500℃ for 2min to 10min.

[0043] When the sintering is hot pressing sintering, it is carried out in the following steps: heating at a rate of 3℃ / min to 20℃ / min to 1000℃ to 1600℃, and holding at a pressure of 40MPa to 80MPa and a temperature of 1000℃ to 1600℃ for 30min to 120min.

[0044] When the sintering is pressureless sintering, it is specifically carried out according to the following steps: heating at a rate of 0.5℃ / min to 2℃ / min to 1000℃ to 1600℃, and holding at 1000℃ to 1600℃ for 30min to 240min. Other aspects are the same as in specific embodiments five to nine.

[0045] The beneficial effects of the present invention are verified using the following embodiments:

[0046] Example 1:

[0047] A method for preparing bulk dense amorphous SiBCN ceramic bulk, comprising the following steps:

[0048] I. Preparation of organic-inorganic mixed bulk preforms / powders:

[0049] 2g of mechanically alloyed inorganic amorphous SiBCN powder was dispersed in 18g of polyborosilazane liquid. Then, the mixture was stirred for 5 minutes at 2500 r / min using a vacuum stirrer to obtain a paste-like organic-inorganic mixed solution. The paste-like organic-inorganic mixed solution was placed in a vacuum drying oven and vacuum cured for 4 hours at 170℃. After curing, the mixture was pulverized and then placed in a ball mill jar and ball-milled for 30 minutes at 400 r / min. Finally, the mixture was passed through a 200-mesh sieve to obtain the organic-inorganic mixed powder.

[0050] II. Preparation of bulk, dense, amorphous SiBCN ceramic blocks:

[0051] Organic-inorganic mixed powder was placed in a graphite mold with an inner diameter of 30 mm. Under nitrogen atmosphere, the temperature was raised to 1500 °C at a heating rate of 5 °C / min. The mixture was then hot-pressed and sintered for 1 h under an axial pressure of 60 MPa and a temperature of 1500 °C to obtain a dense amorphous SiBCN ceramic bulk.

[0052] The mechanically alloyed inorganic amorphous SiBCN powder mentioned in step one is prepared according to the following steps:

[0053] A mixed powder containing four elements, Si, B, C and N, was placed in a high-energy ball mill jar and ball-milled for 40 hours under an inert atmosphere and at a speed of 800 r / min. Finally, it was passed through a 100-mesh sieve to obtain mechanically alloyed inorganic amorphous SiBCN powder. The stoichiometric ratio of Si, B, C and N in the mixed powder was 2:1:3:1, and it was obtained by combining Si, graphite and h-BN.

[0054] At high temperatures, organic polyborosilicates are cracked to generate amorphous SiBCN. The recombination of these amorphous SiBCN network structures provides the driving force for the rearrangement of amorphous SiBCN particles prepared by mechanical alloying, enabling the powder produced by mechanical alloying to achieve low-temperature sintering and densification. At the same time, the inorganic powder fills the pores generated after the cracking of the precursor, thus obtaining the corresponding dense amorphous SiBCN bulk. Figure 2 The image shows the SEM image of the fracture surface of the dense amorphous SiBCN ceramic bulk prepared in Example 1. As can be seen from the image, the fracture surface of the bulk is very dense after sintering. The spherical particles are SiBCN powder produced by mechanical alloying. No obvious pores and defects were observed around them (the spherical particles are the material after the organic precursor is cracked), indicating that the pores after the organic precursor is cracked are filled (the filled material is the mechanically alloyed SiBCN phase).

[0055] Figure 7 The image shows the XRD pattern of the dense amorphous SiBCN ceramic bulk prepared in Example 1; as can be seen from the image, the SiBCN ceramic bulk has an amorphous structure.

[0056] The bulk density of the dense amorphous SiBCN ceramic bulk prepared in Example 1 was 2.05 g / cm³. 3 The porosity is 1.6%.

[0057] The dense amorphous SiBCN ceramic bulk prepared in Example 1 was subjected to a three-point bending test. The sample size was 26mm×4mm×3mm (span 20mm), the loading speed was 0.5mm / min, and the bending strength was measured to be 230.5MPa.

[0058] Antioxidant performance was assessed under an air atmosphere with a heating rate of 10℃ / min, at a maximum test temperature of 1500℃. The oxidation performance was determined based on the sample mass change. The prepared dense amorphous SiBCN ceramic bulk exhibited good oxidation resistance; after oxidation at 1500℃ for 5 hours, the mass change was less than 1 wt%.

[0059] Wave transmission performance was tested using the high-Q cavity method. The test sample was a 1 mm thick, 18 mm diameter disc. The test temperature was room temperature, and the frequency range was 18 GHz to 40 GHz. The dense amorphous SiBCN ceramic bulk was found to have a low dielectric loss (dielectric loss tangent less than 0.01) and dielectric constant (around 5.5), indicating that the prepared bulk SiBCN ceramic has excellent wave transmission performance.

[0060] Example 2:

[0061] A method for preparing bulk dense amorphous SiBCN ceramic bulk material, comprising the following steps:

[0062] I. Preparation of organic-inorganic mixed bulk preforms / powders:

[0063] Liquid polyborosilicate was placed in an alumina boat and cured for 4 hours under a nitrogen atmosphere and at a temperature of 170°C. After curing, it was pulverized to obtain polyborosilicate powder. 14g of polyborosilicate powder and 4g of mechanically alloyed inorganic amorphous SiBCN powder were ball-milled for 30 minutes at a speed of 400 r / min. Finally, the powder was passed through a 200-mesh sieve to obtain an organic-inorganic mixed powder. The organic-inorganic mixed powder was placed in a steel mold with an inner diameter of 60 mm and held under an axial pressure of 200 MPa for 5 minutes to obtain an organic-inorganic mixed bulk blank.

[0064] II. Preparation of bulk, dense, amorphous SiBCN ceramic blocks:

[0065] Organic-inorganic mixed bulk blanks were placed in an alumina boat and heated to 1200℃ in a tube furnace under a nitrogen atmosphere at a heating rate of 1℃ / min. The blanks were then sintered without pressure at 1200℃ for 2 hours to obtain dense amorphous SiBCN ceramic bulks.

[0066] The actual product is as shown Figure 6 As shown, Figure 6 This is a photograph of the dense amorphous SiBCN ceramic bulk material prepared in Example 2.

[0067] At high temperatures, organic polyborosilicates decompose to generate amorphous SiBCN. The reorganization of these amorphous SiBCN network structures provides the driving force for the movement of amorphous SiBCN particles prepared by mechanical alloying, enabling the powder produced by mechanical alloying to achieve low-temperature sintering and densification. At the same time, the inorganic amorphous SiBCN powder fills the pores generated after the precursor powder decomposes, thus obtaining the corresponding dense amorphous SiBCN bulk. Figure 3 The image shows a TEM image of the dense amorphous SiBCN ceramic bulk prepared in Example 2. As can be seen from the image, the bulk still maintains an amorphous structure after sintering, and no obvious lattice fringes were observed.

[0068] The bulk density of the dense amorphous SiBCN ceramic bulk prepared in Example 2 was 1.85 g / cm³. 3 The porosity is 0.5%.

[0069] The dense amorphous SiBCN ceramic bulk prepared in Example 2 was subjected to a 3-point bending test. The sample size was 26mm×4mm×3mm (span 20mm), the loading speed was 0.5mm / min, and the bending strength was measured to be 286.5MPa.

[0070] Antioxidant performance was assessed under an air atmosphere with a heating rate of 10℃ / min, at a maximum test temperature of 1500℃. The oxidation performance was determined based on the sample mass change. The prepared SiBCN ceramic exhibited good oxidation resistance; after oxidation at 1500℃ for 5 hours, the mass change was less than 2 wt%.

[0071] Wave transmission performance was tested using the high-Q cavity method. The test sample was a 1 mm thick, 18 mm diameter disc. The test temperature was room temperature, and the frequency range was 18 GHz to 40 GHz. The sintered bulk SiBCN was found to have a low dielectric loss (dielectric loss tangent less than 0.01) and dielectric constant (around 4.3), indicating that the prepared bulk SiBCN ceramic has excellent wave transmission performance.

[0072] Example 3:

[0073] A method for preparing bulk dense amorphous SiBCN ceramic bulk material, comprising the following steps:

[0074] I. Preparation of organic-inorganic mixed bulk preforms / powders:

[0075] Liquid polysilazane was placed in an alumina boat and cured for 4 hours under a nitrogen atmosphere and at a temperature of 150°C. After curing, the liquid was pulverized to obtain polysilazane powder. 8g of polysilazane powder and 2g of mechanically alloyed inorganic amorphous SiBCN powder were ball-milled for 30 minutes at a speed of 400 r / min. Finally, the powder was passed through a 200-mesh sieve to obtain an organic-inorganic mixed powder.

[0076] II. Preparation of bulk, dense, amorphous SiBCN ceramic blocks:

[0077] 3.5g of organic-inorganic mixed powder was placed in a quartz glass sleeve with an inner diameter of 15mm. Under nitrogen atmosphere, the temperature was raised to 1500℃ at a heating rate of 5℃ / min. Then, under the conditions of 150MPa pressure and 1500℃ temperature, it was hot isostatically pressed for 1h to obtain a bulk dense amorphous SiBCN ceramic block.

[0078] At high temperatures, organopolysilazanes are cracked to generate amorphous SiCN. The reorganization of these amorphous SiCN network structures provides the driving force for the movement of amorphous SiBCN particles prepared by mechanical alloying, enabling the powder produced by mechanical alloying to achieve low-temperature sintering densification and obtain the corresponding dense bulk.

[0079] The bulk density of the dense amorphous SiBCN ceramic bulk prepared in Example 3 was 2.42 g / cm³. 3 The porosity is 0.4%.

[0080] The dense amorphous SiBCN ceramic bulk prepared in Example 3 was subjected to a 3-point bending test. The sample size was 12mm×3mm×2mm (span 10mm), the loading speed was 0.5mm / min, and the bending strength was measured to be 335.2MPa.

[0081] Antioxidant performance was determined under synthetic air atmosphere, with a heating rate of 10℃ / min and a maximum test temperature of 1500℃. The oxidation performance was judged based on the change in sample mass. Figure 4 The image shows the TG-DSC pattern of the dense amorphous SiBCN ceramic bulk prepared in Example 3 under a synthesis air atmosphere. As can be seen from the image, the prepared SiBCN ceramic has good oxidation resistance; after oxidation at 1500℃ for 5 hours, the mass change rate is less than 2 wt%.

[0082] Example 4:

[0083] A method for preparing bulk dense amorphous SiBCN ceramic bulk material, comprising the following steps:

[0084] I. Preparation of organic-inorganic mixed bulk preforms / powders:

[0085] Liquid polysilazane was placed in an alumina boat and cured for 4 hours under a nitrogen atmosphere and at a temperature of 150°C. After curing, the liquid was pulverized to obtain polysilazane powder. 8g of polysilazane powder and 2g of mechanically alloyed inorganic amorphous SiBCN powder were ball-milled for 30 minutes at a speed of 400 r / min. Finally, the powder was passed through a 200-mesh sieve to obtain an organic-inorganic mixed powder. 4g of the organic-inorganic mixed powder was placed in a steel mold with an inner diameter of 30mm and held under an axial pressure of 200MPa for 5 minutes to obtain a green blank. The green blank was vacuum-sealed and placed in a cold isostatic press. Under a pressure of 200MPa, it was held for 2 minutes to obtain an organic-inorganic mixed block green blank.

[0086] II. Preparation of bulk, dense, amorphous SiBCN ceramic blocks:

[0087] Organic-inorganic mixed bulk blanks were placed in an alumina boat and heated to 1000℃ in a tube furnace under a nitrogen atmosphere at a heating rate of 1℃ / min. The blanks were then sintered without pressure at 1000℃ for 2 hours to obtain a large, dense, amorphous SiBCN ceramic bulk.

[0088] At high temperatures, organopolysilazane decomposes to generate amorphous SiCN. The reorganization of these amorphous SiCN network structures provides the driving force for the movement of amorphous SiBCN particles prepared by mechanical alloying, enabling the powder produced by mechanical alloying to achieve low-temperature sintering and densification. At the same time, the inorganic amorphous SiBCN powder fills the pores generated after the precursor powder decomposes, thus obtaining the corresponding dense amorphous SiBCN bulk.

[0089] The bulk density of the dense amorphous SiBCN ceramic bulk prepared in Example 4 was 1.72 g / cm³. 3 The porosity is 1.3%.

[0090] The dense amorphous SiBCN ceramic bulk prepared in Example 4 was subjected to a 3-point bending test. The sample size was 26mm×4mm×3mm (span 20mm), the loading speed was 0.5mm / min, and the bending strength was measured to be 208.4MPa.

[0091] The oxidation resistance was assessed under an air atmosphere with a heating rate of 10℃ / min, at a maximum test temperature of 1500℃. The oxidation performance was determined based on the sample mass change. The prepared SiBCN ceramic exhibited good oxidation resistance; after oxidation at 1500℃ for 5 hours, the mass change rate was less than 2 wt%.

[0092] The wave transmission performance was tested using the high-Q cavity method. The test sample was a 1mm thick, 18mm diameter disc. The test temperature was room temperature, and the frequency was 18GHz to 40GHz. Figure 5The figure shows the dielectric properties of the dense amorphous SiBCN ceramic bulk prepared in Example 4. 1 represents the dielectric constant, and 2 represents the dielectric loss. As can be seen from the figure, the sintered SiBCN bulk has a low dielectric loss (the dielectric loss tangent is less than 0.01) and a dielectric constant (around 3.5). This indicates that the prepared bulk SiBCN ceramic has excellent wave transmission performance.

[0093] The mechanical alloying method for preparing inorganic amorphous SiBCN powder described in step one of Examples 2 to 4 is the same as that in Example 1.

Claims

1. A method for preparing a bulk dense amorphous SiBCN ceramic bulk, characterized in that... It is done in the following steps: I. Preparation of organic-inorganic mixed bulk preforms / powders: Mechanically alloyed inorganic amorphous SiBCN powder is dispersed in a precursor liquid and stirred to obtain a paste-like organic-inorganic mixed solution. The paste-like organic-inorganic mixed solution is then vacuum-cured, followed by sequential pulverization and ball milling, or sequential pulverization, ball milling, and pre-pressing to obtain an organic-inorganic mixed bulk blank / powder. The mass ratio of the precursor liquid to the mechanically alloyed inorganic amorphous SiBCN powder is 1:(0.05~0.4). Alternatively, the precursor liquid can be solidified under an inert atmosphere, then pulverized to obtain precursor powder. The precursor powder is then ball-milled and mixed with mechanically alloyed inorganic amorphous SiBCN powder, or ball-milled and pre-pressed to obtain an organic-inorganic mixed bulk preform / powder. The mass ratio of the precursor powder to the mechanically alloyed inorganic amorphous SiBCN powder is 1:(0.05~0.4). The precursor liquid is one or a mixture of several of the following: polysilane, polysilazane, polycarbosilane, polyborazane, and polyborosilazane. The mechanically alloyed inorganic amorphous SiBCN powder is prepared according to the following steps: A mixed powder containing four elements, Si, B, C, and N, was placed in a high-energy ball mill jar and ball-milled for 40 hours under an inert atmosphere and at a rotation speed of 800 r / min. Finally, it was passed through a 100-mesh sieve to obtain mechanically alloyed inorganic amorphous SiBCN powder. The stoichiometric ratio of Si, B, C, and N in the mixed powder was 2:1:3:1, and it was composed of Si, graphite, ... h -BN combination is obtained; II. Preparation of bulk, dense, amorphous SiBCN ceramic blocks: Organic-inorganic mixed bulk green body / powder was sintered under an inert atmosphere and at a sintering temperature of 1000℃~1500℃ to obtain dense amorphous SiBCN bulk ceramic material.

2. The method for preparing a bulk dense amorphous SiBCN ceramic bulk according to claim 1, characterized in that... The inert atmosphere mentioned in Step 1 and Step 2 is one or a mixture of several of the following gases: argon, nitrogen, ammonia and hydrogen.

3. The method for preparing a bulk dense amorphous SiBCN ceramic bulk according to claim 1, characterized in that... The curing process described in step one specifically involves curing at a temperature of 120℃~350℃ for 2h~4h.

4. The method for preparing a bulk dense amorphous SiBCN ceramic bulk according to claim 1, characterized in that... The pre-pressing mentioned in step one is one or a combination of cold pressing and cold isostatic pressing; when sintering the organic-inorganic mixed powder in step two, the sintering is spark plasma sintering, hot pressing sintering, gas pressure sintering, hot isostatic pressing sintering or high pressure sintering; when sintering the organic-inorganic mixed green body in step two, the sintering is pressureless sintering.

5. The method for preparing a bulk dense amorphous SiBCN ceramic bulk according to claim 4, characterized in that... When the sintering is discharge plasma sintering, it is specifically carried out according to the following steps: heating to 1000℃~1500℃ at a heating rate of 30℃ / min~100℃ / min, and holding for 2min~10min under the conditions of pressure of 30MPa~100MPa and temperature of 1000℃~1500℃. When the sintering is hot pressing sintering, it is carried out according to the following steps: heating at a rate of 3℃ / min to 20℃ / min to 1000℃ to 1500℃, and holding at a pressure of 40MPa to 80MPa and a temperature of 1000℃ to 1500℃ for 30min to 120min. When the sintering is pressureless sintering, it is carried out according to the following steps: heating at a rate of 0.5℃ / min to 2℃ / min to 1000℃ to 1500℃, and holding at 1000℃ to 1500℃ for 30min to 240min.

6. A bulk, dense, amorphous SiBCN ceramic mass, characterized in that, It was prepared according to the method for preparing bulk dense amorphous SiBCN ceramic bulk as described in any one of claims 1 to 5.

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