A liquid silicon carbide ceramic precursor composition and a method for preparing the same, a silicon carbide ceramic material and a method for preparing the same

Abstract

The present application relates to the technical field of ceramic materials, and particularly relates to a liquid silicon carbide ceramic precursor composition and a preparation method thereof, a silicon carbide ceramic material and a preparation method thereof, which do not affect the viscosity and storage stability of the liquid silicon carbide precursor, improve the ceramic yield, and avoid solidification foaming. The liquid silicon carbide ceramic precursor composition comprises a liquid polymer silicon carbide ceramic precursor, a dehydrogenation coupling catalyst and an initiator. The liquid polymer silicon carbide ceramic precursor contains -Si-X and -SiH2- and / or -SiH3. X is one or more of a vinyl group, an ethynyl group and an allyl group. The initiator comprises a free radical thermal polymerization initiator and / or a photopolymerization initiator. The dehydrogenation coupling catalyst comprises one or more of titanium (IV) bis(cyclopentadienyl) diphenoxide, cyclooctadiene-duquinol nickel and a transition metal acetylacetone compound. The composition has good room temperature storage performance and high ceramic yield, and is conducive to inhibiting solidification foaming in the preparation of the silicon carbide ceramic material.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, and particularly relates to a liquid silicon carbide ceramic precursor composition and its preparation method, as well as silicon carbide ceramic materials and their preparation methods. Background Technology

[0002] Compared with classic solid polycarbosilanes, the novel hyperbranched silicon carbide ceramic precursor prepared by Grignard-coupling reduction is in liquid form, which has the advantages of higher ceramic yield and no need for solvent. It can significantly improve the impregnation efficiency of polymer precursor impregnation pyrolysis (PIP) process for preparing ceramic matrix composites and shorten the process cycle.

[0003] When used as an impregnating agent for ceramic matrix composites, an ideal liquid silicon carbide ceramic precursor should simultaneously possess low viscosity, high ceramic yield, and high storage stability. However, simultaneously satisfying these characteristics is extremely challenging. Achieving high ceramic yield often requires high molecular weight, which leads to high viscosity. To achieve both low viscosity and high ceramic yield, a highly reactive molecular structure is required, which typically results in poor storage stability.

[0004] To improve ceramic yield, catalysts are usually added to liquid silicon carbide ceramic precursors. However, existing catalysts (such as Cp2MMe2, M=Ti, Zr, Hf, etc.) can cause room temperature gelation or a significant increase in viscosity in liquid silicon carbide precursors, resulting in a significant decrease in storage stability. This presents a contradiction between high ceramic yield and high storage performance. Furthermore, hydrogen gas is easily generated during dehydrogenation coupling of liquid silicon carbide precursors, leading to solidification and foaming. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a liquid silicon carbide ceramic precursor composition and its preparation method, as well as a silicon carbide ceramic material and its preparation method, so as to significantly improve the ceramic yield and avoid curing foaming while keeping the viscosity and storage stability of the liquid silicon carbide precursor essentially unaffected.

[0006] On one hand, the present invention provides a liquid silicon carbide ceramic precursor composition, comprising a liquid polymer silicon carbide ceramic precursor, a dehydrogenation coupling catalyst, and an initiator. The liquid polymer silicon carbide ceramic precursor composition contains 98.0% to 99.95% by mass, and the liquid polymer silicon carbide ceramic precursor contains -Si-X and -SiH2- and / or -SiH3, wherein X is one or more of vinyl, ethynyl, and allyl groups. The initiator includes a free radical thermal polymerization initiator and / or a photopolymerization initiator. The dehydrogenation coupling catalyst includes one or more of bis(cyclopentadienyl)diphenoxytitanium (IV), cyclooctadiene-duquinone nickel, and transition metal acetylacetone compounds.

[0007] Furthermore, the mass ratio of the initiator to the liquid polymer silicon carbide ceramic precursor is 0.1% to 2%; And / or, the mass ratio of the dehydrogenation coupling catalyst to the liquid polymer silicon carbide ceramic precursor is 0.02% to 1.0%.

[0008] Furthermore, the liquid polymer silicon carbide ceramic precursor comprises a mixture of two or more liquid silicon carbide precursors containing unsaturated groups; And / or, the liquid polymer silicon carbide ceramic precursor comprises a mixture of a liquid silicon carbide precursor containing unsaturated groups and a silicon carbide precursor without unsaturated groups.

[0009] Furthermore, the liquid silicon carbide precursor containing unsaturated groups includes liquid polycarbosilane containing unsaturated groups, the structural formula of which is shown in Formula 1: Formula 1 Wherein, R is methyl or phenyl, X is one or more of -CH=CH2, -C≡CH, and -CH2-CH=CH2, x1 is 0.1~1.0, y1 is 0~0.5, and n1 is 20~100.

[0010] Furthermore, the liquid silicon carbide ceramic precursor composition satisfies: 2% ≤ ≤40%, where m1 is the mass of the compound shown in Formula 1, and x1 is the mass of x1 in Formula 1. The total mass of i kinds of liquid polymer silicon carbide ceramic precursors in the liquid silicon carbide ceramic precursor composition is denoted as i, where i is the number of different types of liquid polymer silicon carbide ceramic precursors in the liquid silicon carbide ceramic precursor composition.

[0011] Furthermore, the transition metal acetylacetone compounds include one or more of aluminum acetylacetone, titanium acetylacetone, titanium acetylacetone diisopropoxy, zirconium acetylacetone, zirconium acetylacetone diethoxy, iron acetylacetone, cobalt acetylacetone, and hafnium acetylacetone. And / or, the free radical thermal polymerization initiator includes one or more of dicumyl peroxide, 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)cyclohexane and 1,3-bis-tert-butylperoxydicumylbenzene; And / or, the photopolymerization initiator includes one or more of 2-hydroxy-2-methylphenylacetone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone.

[0012] On the other hand, the present invention provides a method for preparing the above-mentioned liquid silicon carbide ceramic precursor composition, comprising the following steps: mixing liquid polymer silicon carbide ceramic precursor, initiator and dehydrogenation coupling catalyst uniformly at room temperature to obtain liquid silicon carbide ceramic precursor composition.

[0013] On the other hand, the present invention provides a silicon carbide ceramic material, which is prepared by using the above-mentioned liquid silicon carbide ceramic precursor composition or a liquid silicon carbide ceramic precursor composition obtained by the above-mentioned method for preparing the liquid silicon carbide ceramic precursor composition.

[0014] On the other hand, the present invention provides a method for preparing the above-mentioned silicon carbide ceramic material, comprising the following steps: S1. The liquid silicon carbide ceramic precursor composition is cured and shaped under light irradiation and / or at 120~170°C; S2. Post-curing at 180~280℃; S3. Pyrolysis and ceramization are carried out at 900~1600℃ to obtain ceramic materials.

[0015] Furthermore, the illumination wavelength of S1 is 365 or 405 nm, and the illumination time is 2 to 30 minutes; And / or, in S1, the temperature is increased from room temperature to 120-170℃ at a heating rate of 2-5℃ / min and held for 1-2 hours for curing and shaping.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. This invention uses a liquid polymer silicon carbide ceramic precursor containing carbon-carbon unsaturated bonds and -SiH2- or SiH3- in its molecular structure as the matrix, and simultaneously adds an atypical dehydrogenation coupling catalyst that has no catalytic activity at room temperature and only has a certain catalytic dehydrogenation ability under heating. This catalyst forms a dual curing mechanism combination with the initiator: first, free radical polymerization occurs under light irradiation and / or at 120~170℃; then, a post-curing reaction occurs at 180~280℃ under the action of the dehydrogenation coupling catalyst. This increases the crosslinking density and improves the overall ceramic yield of the liquid silicon carbide ceramic precursor composition. This helps to avoid bubble defects during the curing process and is suitable for the process requirements of typical applications such as impregnation pyrolysis of ceramic matrix composites and coating preparation.

[0017] 2. The liquid silicon carbide ceramic precursor composition of the present invention not only significantly improves the ceramic yield, but also ensures that the room temperature viscosity and storage stability are basically unaffected. It has both good storage performance and high ceramic yield, and the room temperature closed storage period (viscosity not higher than 200 mPa.s) can reach more than 180 days.

[0018] 3. The dehydrogenation coupling catalyst and initiator in the liquid silicon carbide ceramic precursor composition of the present invention are low in sensitivity to oxygen and moisture in the air, easy to use, readily available, and inexpensive. Moreover, due to the small dosage and simple preparation, the liquid silicon carbide ceramic precursor composition of the present invention is economical and cost-effective.

[0019] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objectives and other advantages of this invention can be realized and obtained through the specific points highlighted in the description. Detailed Implementation

[0020] The following examples, taken together with the embodiments of the present invention, are used to illustrate the principles of the invention and are not intended to limit the scope of the invention.

[0021] This invention provides a liquid silicon carbide ceramic precursor composition, comprising a liquid polymer silicon carbide ceramic precursor, a dehydrogenation coupling catalyst, and an initiator. The liquid polymer silicon carbide ceramic precursor composition has a mass percentage content of 98.0% to 99.95%, and the liquid polymer silicon carbide ceramic precursor contains -Si-X and -SiH2- and / or -SiH3, wherein X is one or more of vinyl (-CH=CH2), ethynyl (-C≡CH), and allyl (-CH2-CH=CH2); the initiator includes a free radical thermal polymerization initiator and / or a photopolymerization initiator; the dehydrogenation coupling catalyst includes one or more of di(cyclopentadienyl)diphenoxytitanium(IV) (Cp2Ti(OPh)2), cyclooctadiene-duquinone nickel (Ni(COD)(DQ)), and transition metal acetylacetone compounds.

[0022] In the above system, the initiator can polymerize the unsaturated groups (vinyl, ethynyl, allyl) in the liquid polymer silicon carbide ceramic precursor, and the dehydrogenation coupling catalyst can cause the -SiH2- or -SiH3 to undergo a dehydrogenation coupling post-curing reaction. This is beneficial for the liquid silicon carbide ceramic precursor composition to first undergo polymerization cross-linking and curing during the ceramic preparation process, and then undergo a dehydrogenation coupling cross-linking post-curing reaction. This avoids curing foaming caused by dehydrogenation coupling and improves the ceramic yield.

[0023] Existing dehydrogenation coupling catalysts are mainly used for reaction and structural modification of the host resin, introducing metal elements to regulate dielectric properties. However, they cannot simultaneously maintain the viscosity, molecular structure, and storage characteristics of the host resin. Furthermore, existing dehydrogenation coupling catalysts, such as (Cp2MMe2 (M=Ti,Zr,Hf)), are highly sensitive to air and moisture. In contrast, the dehydrogenation coupling catalyst in this invention acts as a latent dehydrogenation coupling catalyst, which is stable in air and does not react with the components of the liquid silicon carbide ceramic precursor composition at room temperature. This facilitates the preparation of a room-temperature stable, medium-to-high-temperature curing liquid silicon carbide ceramic precursor composition.

[0024] Furthermore, the mass ratio of the initiator to the liquid polymer silicon carbide ceramic precursor is 0.1% to 2%, for example, 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2%, or any combination thereof. Adding an appropriate amount of initiator can effectively improve the ceramic yield. Too low a content is insufficient to achieve adequate curing at medium and low temperatures or under light, while too high an initiator content cannot further improve the ceramic yield and may reduce the storage stability of the liquid silicon carbide ceramic precursor composition and increase the oxygen impurity content of the pyrolysis ceramic products.

[0025] Furthermore, the mass ratio of the free radical thermal polymerization initiator to the liquid polymer silicon carbide ceramic precursor is 0.2% to 0.5% (e.g., 0.2%, 0.3%, 0.4%, 0.5%). This content range can significantly reduce the curing temperature and improve the ceramic yield. At the same time, the liquid silicon carbide ceramic precursor composition has good storage stability and introduces very low oxygen content.

[0026] Furthermore, the mass ratio of photoinitiator to liquid polymer silicon carbide ceramic precursor is 0.5%~1.5% (e.g., 0.5%, 0.8%, 1.0%, 1.3%, 1.5%). This content of photoinitiator can achieve good photoinitiation effect without significantly adversely affecting storage stability. Due to the high polarity of the photoinitiator, higher contents of photoinitiator are difficult to dissolve in the liquid polymer silicon carbide ceramic precursor, which does not lead to a faster curing rate but instead results in poorer room temperature storage stability; when the content of photoinitiator is too low, the curing rate of the liquid silicon carbide ceramic precursor composition is slow.

[0027] Furthermore, the mass ratio of the dehydrogenation coupling catalyst to the liquid polymer silicon carbide ceramic precursor is 0.02% to 1.0%, for example, 0.02%, 0.05%, 0.1%, 0.2%, 0.5%, 1%, or any combination thereof, preferably 0.05% to 0.5%. Unlike existing technologies, in this invention, the dehydrogenation coupling catalyst acts as a latent dehydrogenation coupling catalyst, controlling its mass ratio to the liquid polymer silicon carbide ceramic precursor within the aforementioned range, ensuring no reaction between the components at room temperature. In contrast, existing dehydrogenation coupling catalysts are used to react with and modify the structure of the host resin, introducing metal elements to regulate dielectric properties; however, they cannot simultaneously significantly improve ceramic yield without substantially altering the viscosity, molecular structure, and storage characteristics of the host resin.

[0028] Furthermore, the liquid polymer silicon carbide ceramic precursor, which includes SiH3 end groups, is more readily able to react with dehydrogenation coupling catalysts and solidify.

[0029] In some embodiments, the liquid polymer silicon carbide ceramic precursor comprises a mixture of two or more liquid silicon carbide precursors containing unsaturated groups.

[0030] In some embodiments, the liquid polymer silicon carbide ceramic precursor comprises a mixture of a liquid silicon carbide precursor containing unsaturated groups and a silicon carbide precursor without unsaturated groups. The silicon carbide precursor without unsaturated groups comprises a liquid silicon carbide precursor without unsaturated groups and / or a solid polycarbosilane without unsaturated groups. The mass percentage of the liquid silicon carbide precursor containing unsaturated groups in the liquid polymer silicon carbide ceramic precursor is 20% to 80%, for example, 20%, 30%, 40%, 50%, 60%, 70%, or 80%, which is beneficial for both improving the storage stability of the liquid silicon carbide ceramic precursor composition and the ceramic yield.

[0031] Furthermore, the liquid silicon carbide precursor without unsaturated groups includes one or more of the following: liquid poly(silane-carbosilane), liquid polycarbosilane, and liquid polysilane without unsaturated groups.

[0032] Furthermore, the liquid silicon carbide precursor containing unsaturated groups includes liquid polycarbosilane containing unsaturated groups, the structural formula of which is shown in Formula 1: Formula 1 Wherein, R is methyl (Me) or phenyl (Ph), X is one or more of -CH=CH2, -C≡CH, and -CH2-CH=CH2, x1 is 0.1~1.0 (e.g., 0.1, 0.3, 0.5, 0.7, 1.0), y1 is 0~0.5 (e.g., 0, 0.1, 0.2, 0.3, 0.4, 0.5), and n1 is 20~100 (e.g., 20, 30, 50, 80, 100).

[0033] Furthermore, the structural formula of liquid polycarbosilane without unsaturated groups is shown in Formula 2: Formula 2 Where y2 is 0~0.6 (e.g. 0, 0.1, 0.2, 0.4, 0.6) and n2 is 20~80 (e.g. 20, 30, 40, 50, 60, 70, 80).

[0034] Furthermore, liquid poly(silane-carbosilane) without unsaturated groups includes modified polymethylsilane (mPMS), with the structural formula shown in Formula 3: Formula 3 Where x3 is 0.1~0.2 (e.g. 0.1, 0.13, 0.15, 0.18, 0.2), y3 is 0.1~0.2 (e.g. 0.1, 0.13, 0.15, 0.18, 0.2), and n3 is 20~80 (e.g. 20, 30, 40, 50, 60, 70, 80).

[0035] Furthermore, liquid polysilanes without unsaturated groups include polymethylsilane (PMS), with the structural formula shown in Formula 4: Formula 4 Where n4 is 15~100 (e.g., 15, 30, 50, 80, 100).

[0036] Furthermore, solid polycarbosilanes without unsaturated groups include compounds shown in Formula 5: Formula 5 Wherein, n5 is 15~80 (e.g., 15, 20, 30, 40, 50, 60, 70, 80).

[0037] Furthermore, the compound shown in Formula 5 can be obtained by pyrolysis rearrangement of polydimethylsilane.

[0038] In some embodiments, the liquid silicon carbide ceramic precursor composition satisfies: 2% ≤ ≤40%, where m1 is the mass of the compound shown in Formula 1, and x1 is the mass of x1 in Formula 1. Let be the total mass of i types of liquid polymer silicon carbide ceramic precursors in the liquid silicon carbide ceramic precursor composition, where i is the number of different types of liquid polymer silicon carbide ceramic precursors in the liquid silicon carbide ceramic precursor composition. When the content is too low, the unsaturated group content is too low, making it difficult to avoid curing and foaming defects in the liquid polymer silicon carbide ceramic precursor. When the concentration is too high, the content of unsaturated groups is too high, and the carbon content of the ceramic products obtained from the pyrolysis of the liquid polymer silicon carbide ceramic precursor is too high, which will significantly reduce the high-temperature oxidation resistance.

[0039] Furthermore, transition metal acetylacetone compounds include aluminum acetylacetone (Al(acac)3), titanium acetylacetone (Ti(acac)4), and titanium acetylacetone diisopropoxy (Ti(acac)2(O)). i One or more of Pr)2), zirconium acetylacetonate (Zr(acac)4), zirconium acetylacetonate diethoxy (Zr(acac)2(OC2H5)2), iron acetylacetonate (Fe(acac)3), cobalt acetylacetonate (Co(acac)3), and hafnium acetylacetonate (Hf(acac)4) can improve the air stability of the liquid silicon carbide ceramic precursor composition while increasing the ceramic yield.

[0040] Furthermore, the free radical thermal polymerization initiator includes one or more of dicumyl peroxide (DCP), 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane (“bis-di-pentane”), 1,1-bis(tert-butylperoxy)cyclohexane (CH), and 1,3-bis-tert-butylperoxydiisopropylbenzene (BIPB). The above initiators have a moderate decomposition temperature, which can reduce the curing temperature of the liquid polymer silicon carbide ceramic precursor, allowing it to undergo polymerization, crosslinking, and curing at a lower temperature. It can also prevent the liquid polymer silicon carbide ceramic precursor from reacting at room temperature, thereby allowing the liquid silicon carbide ceramic precursor composition to maintain a longer storage period.

[0041] Furthermore, the photopolymerization initiator includes one or more of 2-hydroxy-2-methylphenylacetone (PI-1173), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (PI-819), ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (PI-369). This facilitates the post-curing reaction of the liquid polymer silicon carbide ceramic precursor under light irradiation, which first undergoes polymerization crosslinking and curing, followed by dehydrogenation coupling crosslinking. This avoids curing foaming caused by dehydrogenation coupling and improves the ceramic yield.

[0042] Furthermore, the viscosity of the liquid silicon carbide ceramic precursor composition at room temperature is 10 to 200 mPa·s, for example, 10 mPa·s, 50 mPa·s, 100 mPa·s, 150 mPa·s, 200 mPa·s or any combination thereof, preferably 10 to 50 mPa·s.

[0043] Furthermore, the ceramic yield of the liquid silicon carbide ceramic precursor composition is 65% to 91%, for example, 65%, 70%, 75%, 80%, 85%, 90%, 91%, or any combination thereof. The ceramic yield of the liquid silicon carbide ceramic precursor composition of the present invention is calculated as the ratio of the mass of the ceramic material obtained from the liquid silicon carbide ceramic precursor composition to the mass of the liquid polymer silicon carbide ceramic precursor in the liquid silicon carbide ceramic precursor composition.

[0044] Furthermore, the liquid silicon carbide ceramic precursor composition has a sealed storage period of ≥180 days at room temperature (viscosity not exceeding 200 mPa.s). Specifically, the liquid silicon carbide ceramic precursor composition containing photopolymerization initiator should be stored away from light.

[0045] Preferably, the liquid silicon carbide ceramic precursor composition has a sealed storage period (viscosity not exceeding 100 mPa·s) of ≥180 days at room temperature.

[0046] This invention also provides a method for preparing the above-mentioned liquid silicon carbide ceramic precursor composition, comprising the following steps: mixing the liquid polymer silicon carbide ceramic precursor, initiator, and dehydrogenation coupling catalyst uniformly at room temperature to obtain the liquid silicon carbide ceramic precursor composition.

[0047] This invention also provides a silicon carbide ceramic material, which is prepared using the above-described liquid silicon carbide ceramic precursor composition or a liquid silicon carbide ceramic precursor composition prepared according to the above-described method for preparing the liquid silicon carbide ceramic precursor composition.

[0048] This invention also provides a method for preparing the above-mentioned silicon carbide ceramic material, comprising the following steps: S1. The liquid silicon carbide ceramic precursor composition is cured and shaped under light irradiation and / or at 120~170°C; S2. Post-curing at 180~280℃; S3. Pyrolysis and ceramization are carried out at 900~1600℃ to obtain ceramic materials.

[0049] Furthermore, S1 is carried out in an air or nitrogen atmosphere.

[0050] In the above system, a liquid silicon carbide precursor composition is used to prepare silicon carbide ceramic materials through curing and pyrolysis. The liquid silicon carbide ceramic precursor composition is cured by free radical polymerization at low temperature (120~170℃) or under light irradiation, and then cured by dehydrogenation coupling at a higher temperature (180~280℃). This can effectively suppress gas generation and foaming. Finally, the ceramic material is obtained by high-temperature pyrolysis.

[0051] Furthermore, when the initiator in the liquid silicon carbide ceramic precursor composition is a photopolymerization initiator, S1 is cured and shaped under light irradiation. When the initiator in the liquid silicon carbide ceramic precursor composition is a free radical thermal polymerization initiator, S1 is cured and shaped at 120~170℃. When the initiator in the liquid silicon carbide ceramic precursor composition contains both a photopolymerization initiator and a free radical thermal polymerization initiator, S1 is first irradiated with light, and then cured and shaped at 120~170℃.

[0052] Furthermore, the illumination wavelength of S1 is 365 or 405 nm, and the illumination time is 2 to 30 min (e.g., 2 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min).

[0053] Furthermore, in S1, the temperature is increased from room temperature to 120-170℃ (e.g., 120℃, 130℃, 140℃, 150℃, 160℃, 170℃) at a heating rate of 2-5℃ / min (e.g., 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min) and held at that temperature for 1-2 hours (e.g., 1 hour, 1.3 hours, 1.5 hours, 1.8 hours, 2 hours) to solidify and shape the liquid silicon carbide ceramic precursor composition.

[0054] Further, in S2, after demolding the product obtained in S1, it is post-cured under a nitrogen and / or argon atmosphere by heating from room temperature to 180-280℃ (e.g., 180℃, 200℃, 230℃, 250℃, 280℃) at a heating rate of 2-5℃ / min (e.g., 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min) and holding at this temperature for 1-2 hours (e.g., 1 hour, 1.3 hours, 1.5 hours, 1.8 hours, 2 hours). Too fast a heating rate results in excessive thermal stress, while too slow a heating rate leads to excessive curing time.

[0055] In some embodiments, the process of pyrolytic ceramization at 900~1600℃ in S3 includes: heating to 900~1600℃ using a single-stage or two-stage heating method to perform pyrolytic ceramization.

[0056] In some embodiments, the process of pyrolysis ceramization by heating to 900~1600℃ in two stages includes: S31. In a nitrogen or argon atmosphere, heat to 900-1000℃ (e.g., 900℃, 930℃, 950℃, 980℃, 1000℃) at a heating rate of 3-8℃ / min (e.g., 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min). S32. Then, increase the temperature to 1100~1600℃ (e.g., 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, 1600℃) at a heating rate of 1~3℃ (e.g., 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min) and hold for 0.5~2h (e.g., 0.5h, 1h, 1.5h, 2h).

[0057] In the above system, the rapid heating in S31 and the relatively slow heating in S32 help to reduce the thermal stress generated in S3 by the product cured after S2, while ensuring a high pyrolysis efficiency.

[0058] In some embodiments, S3 can be performed by demolding the cured product obtained in S2 and then heating it from room temperature to 900~1600℃ (e.g., 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, 1600℃) for pyrolytic ceramicization, or by continuing to heat the product from the temperature obtained in S2 to 900~1600℃ for pyrolytic ceramicization.

[0059] The present invention will be further described below through specific embodiments.

[0060] The compounds (KH-VHPCS-1, KH-AHPCS-1, KH-AHPCS-2) shown in Formula 1 used in the following examples can all be prepared by existing methods, such as the preparation method described in CN 115678019 A.

[0061] Example 1 In a 25ml capped glass sample vial, 20g of liquid polymer silicon carbide ceramic precursor and 0.04g of titanium acetylacetonate were added. The mixture was stirred thoroughly at room temperature to dissolve the precursors. Then, 0.06g of dicumyl peroxide (DCP) was added at room temperature and mixed thoroughly to dissolve the precursors, yielding a liquid silicon carbide ceramic precursor composition. The liquid polymer silicon carbide ceramic precursor was liquid polycarbosilane (KH-VHPCS-1, abbreviated as V1), with the structural formula shown in Formula 1, where x1 is 0.1, y1 is 0, X is -CH=CH2, R1 is methyl, the number-average molecular weight is 1215, and n1 is 26. It is 10%.

[0062] The liquid silicon carbide ceramic precursor composition was added into a mold and placed in a forced-air drying oven. The temperature was increased from room temperature to 150°C at 3°C / min and held for 2 hours for curing and shaping. After demolding, the cured product was placed in a quartz tube furnace and cured under an argon atmosphere. The temperature was increased from room temperature to 250°C at 3°C / min and held for 2 hours for post-curing. Then, the temperature was increased to 1100°C at 5°C / min and held for 1 hour to obtain 18.2g of silicon carbide ceramic material, i.e., the ceramic yield was 91%.

[0063] Example 2 The difference from Example 1 is that the liquid polymer silicon carbide ceramic precursor is liquid polycarbosilane (KH-AHPCS-1, abbreviated as Al), with the structural formula shown in Formula 1, where x1 is 0.1, y1 is 0.1, R1 is methyl, X is -CH2-CH=CH2, the number average molecular weight is 1150, n1 is 23, DCP is 0.08 g, and titanium acetylacetonate is 0.04 g. It is 10%.

[0064] The liquid silicon carbide ceramic precursor composition was added to a mold and placed in a forced-air drying oven for curing and shaping by raising the temperature from room temperature to 160°C at a rate of 3°C / min and holding for 1 hour. After demolding, the resulting cured product was placed in a quartz tube furnace and post-cured by raising the temperature from room temperature to 260°C at a rate of 3°C / min and holding for 1 hour under an argon atmosphere. The temperature was then raised to 1100°C at a rate of 5°C / min and held for 1 hour. The remaining steps and conditions were the same as in Example 1, yielding 17.2g of silicon carbide ceramic material, i.e., a ceramic yield of 86%.

[0065] Example 3 The difference from Example 1 is that the liquid polymer silicon carbide ceramic precursor is liquid polycarbosilane (KH-AHPCS-2, abbreviated as A2), with the molecular formula shown in Formula 1, where x1 is 0.15, y1 is 0.5, R1 is methyl, X1-CH2-CH=CH2, n1 is 30, and DCP is 0.16g.

[0066] The liquid silicon carbide ceramic precursor composition was added to a mold and placed in a forced-air drying oven for curing and shaping by raising the temperature from room temperature to 170°C at a rate of 3°C / min and holding for 2 hours. After demolding, the resulting cured product was placed in a quartz tube furnace and post-cured by raising the temperature from room temperature to 270°C at a rate of 3°C / min and holding for 1 hour under an argon atmosphere. The temperature was then raised to 1100°C at a rate of 5°C / min and held for 1 hour. The remaining steps and conditions were the same as in Example 1, yielding 16.0 g of silicon carbide ceramic material, i.e., a ceramic yield of 80%.

[0067] Example 4 In a 25ml glass sample vial with a cap, add 20g of liquid polycarbosilane (brand name KH-VHPCS-1), 0.2g of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (PI-819), and 0.04g of titanium acetylacetonate and stir thoroughly to dissolve.

[0068] The liquid silicon carbide ceramic precursor composition was cured and shaped under a 405 nm LED lamp for 0.5 h, and then post-cured under nitrogen atmosphere by heating from room temperature to 230 °C at a rate of 5 °C / min and holding for 2 h. The resulting cured product was placed in an alumina tube furnace and heated from room temperature to 1600 °C at a rate of 3 °C / min under argon protection and held for 0.5 h to obtain 17.9 g of silicon carbide ceramic material, with a ceramic yield of 89.5%.

[0069] Example 5 In a 25ml capped glass sample vial, add 20g of liquid polycarbosilane (brand name KH-VHPCS-1), 0.3g of ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), and 0.06g of dicumyl peroxide (DCP) and mix well to dissolve; then add 0.04g of titanium acetylacetone and stir thoroughly to dissolve.

[0070] The liquid silicon carbide ceramic precursor composition was cured and shaped under a 405nm LED lamp for 0.5 hours. The resulting cured product was placed in an alumina tube furnace and subjected to pyrolysis under argon protection, with the temperature increased from room temperature to 250℃ at a rate of 3℃ / min and held for 1 hour, followed by a rate increase to 1300℃ at a rate of 5℃ / min and held for 0.5 hours, yielding 17.8g of silicon carbide ceramic material with a ceramic yield of 89.0%.

[0071] Example 6 In a 25ml capped glass sample vial, add 20g of liquid polycarbosilane (KH-VHPCS-1), 0.2g of 2-hydroxy-2-methylphenylacetone (PI-1173), and 0.06g of dicumyl peroxide (DCP) and mix well to dissolve; then add 0.04g of titanium acetylacetone and stir thoroughly to dissolve.

[0072] The liquid silicon carbide ceramic precursor composition was cured under a 365nm LED lamp for 0.5 hours, and then post-cured under nitrogen protection by heating from room temperature to 250℃ at 5℃ / min and holding for 1 hour. The cured product was placed in a quartz tube furnace and heated from room temperature to 1000℃ at 6℃ / mins under argon protection, and then heated to 1200℃ at 2℃ / min and held for 1 hour to obtain 17.9g of silicon carbide ceramic material with a ceramic yield of 89.5%.

[0073] Example 7 In a 25ml capped glass sample vial, add 20g of liquid polycarbosilane (KH-VHPCS-1), 0.2g of 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone (PI-369), and 0.06g of dicumyl peroxide (DCP) and mix well to dissolve; then add 0.04g of titanium acetylacetonate and stir thoroughly to dissolve.

[0074] The liquid silicon carbide ceramic precursor composition was cured under a 365nm LED lamp for 0.5 hours. The cured product was then placed in a quartz tube furnace and heated to 250°C from room temperature at a rate of 3°C / mins and held for 1 hour under argon protection. The temperature was then increased to 1000°C at a rate of 6°C / min and held for 1 hour at a rate of 2°C / min. 17.9 g of silicon carbide ceramic material was obtained, with a ceramic yield of 89.5%.

[0075] Example 8 The difference from Example 1 is that the liquid polymer silicon carbide ceramic precursor is a mixture of all-hydrogen polycarbosilane (KH-HPCS-1, y2 is 0, n is 28) and KH-VHPCS-1 as shown in Formula 2, wherein the mass ratio of the former to the latter is 4:1. The yield was 2%. The liquid silicon carbide ceramic precursor composition was added to a mold and placed in a forced-air drying oven. The temperature was increased from room temperature to 170°C at 3°C / min and held for 2 hours for curing and shaping. After demolding, the cured sample was placed in a quartz tube furnace and cured under argon protection. The temperature was increased from room temperature to 240°C at 3°C / min and held for 1 hour. The temperature was then increased to 1100°C at 5°C / min and held for 1 hour. The remaining steps and conditions were the same as in Example 1, yielding 17.2g of silicon carbide ceramic material, i.e., the ceramic yield was 87%.

[0076] KH-HPCS-1, as referenced in patent 201410398757.0, is obtained by using tetrahydrofuran as a solvent and undergoing Grignard coupling polymerization of chloromethyltrimethoxysilane with magnesium metal scraps followed by reduction with lithium aluminum hydride.

[0077] Example 9 The difference from Example 1 is that the liquid polymer silicon carbide ceramic precursor is a mixture of solid polycarbosilane (produced by Fujian Liya Chemical, with a number average molecular weight of 1500 and n5 of 26) as shown in Formula 5 and KH-VHPCS-1, wherein the mass ratio of the former to the latter is 1:4. It is 8%.

[0078] The liquid silicon carbide ceramic precursor composition was added to a mold and placed in a forced-air drying oven for curing and shaping by raising the temperature from room temperature to 170°C at a rate of 3°C / min and holding for 2 hours. After demolding, the cured product was placed in a quartz tube furnace and heated to 260°C at a rate of 3°C / min and held for 1 hour under an argon atmosphere. Then, the temperature was raised to 1100°C at a rate of 5°C / min and held for 1 hour. The remaining steps and conditions were the same as in Example 1, yielding 17.0 g of silicon carbide ceramic material, i.e., a ceramic yield of 85%.

[0079] Example 10 The difference from Example 1 is that the liquid polymer silicon carbide ceramic precursor is a mixture of modified polymethylsilane (mPMS, x3 = 0.2, y3 = 0.2, n3 = 35) as shown in Formula 3 and KH-VHPCS-1, wherein the mass ratio of the former to the latter is 1:1. The yield was 5%. The liquid silicon carbide ceramic precursor composition was added to a mold and placed in a forced-air drying oven. The temperature was increased from room temperature to 170°C at 3°C / min and held for 2 hours for curing and shaping. After demolding, the cured product was placed in a quartz tube furnace and heated to 270°C at 3°C / min and held for 1 hour under an argon atmosphere. The temperature was then increased to 1100°C at 5°C / min and held for 1 hour. The remaining steps and conditions were the same as in Example 1, yielding 16.0 g of silicon carbide ceramic material, i.e., the ceramic yield was 80%.

[0080] The preparation method of mPMS refers to patent 201310159751.3, which uses monomer co-sodium condensation polymerization with a molar ratio of MeHSiCl2:Cl2CHSiMeH2:ClCH2SiMe2Cl=0.6:0.2:0.2.

[0081] Example 11 The difference from Example 1 is that the liquid polymer silicon carbide ceramic precursor is a mixture of polymethylsilane (produced by Hunan Bowang Carbon Ceramics Co., Ltd., n4 is 22) as shown in Formula 4 and KH-VHPCS-1, wherein the mass ratio of the former to the latter is 3:7. It is 7%.

[0082] The liquid silicon carbide ceramic precursor composition was added into a mold and placed in a forced-air drying oven. The temperature was increased from room temperature to 170°C at 3°C / min and held for 2 hours for curing and shaping. After demolding, the solid product was placed in a quartz tube furnace and heated to 270°C at 3°C / min and held for 1 hour under an argon atmosphere. The temperature was then increased to 1100°C at 5°C / min and held for 1 hour. The remaining steps and conditions were the same as in Example 1, yielding 17g of silicon carbide ceramic material, i.e., the ceramic yield was 85%.

[0083] The original polymethylsilane had a room temperature storage period of less than one month and a ceramic yield of only 28%. The liquid silicon carbide ceramic precursor composition of Example 11 significantly increased the room temperature storage period and ceramic yield compared to the original polymethylsilane.

[0084] Example 12 The only difference from Example 1 is that the dehydrogenation coupling catalyst is Cp2Ti(OPh)2, while the other steps and conditions are the same as in Example 1.

[0085] Example 13 The only difference from Example 1 is that the dehydrogenation coupling catalyst is Ni(COD)(DQ), while the other steps and conditions are the same as in Example 1.

[0086] Example 14 The only difference from Example 1 is that the amount of titanium acetylacetonate added is 0.004 g, that is, the mass ratio of the dehydrogenation coupling catalyst to the liquid polymer silicon carbide ceramic precursor is 0.02%. The remaining steps and conditions are the same as in Example 1.

[0087] Example 15 The only difference from Example 1 is that the amount of titanium acetylacetonate added is 0.2g, that is, the mass ratio of the dehydrogenation coupling catalyst to the liquid polymer silicon carbide ceramic precursor is 1.0%. The remaining steps and conditions are the same as in Example 1.

[0088] Example 16 The only difference from Example 1 is that the amount of titanium acetylacetonate added is 0.01g, that is, the mass ratio of the dehydrogenation coupling catalyst to the liquid polymer silicon carbide ceramic precursor is 0.05%. The remaining steps and conditions are the same as in Example 1.

[0089] Example 17 The only difference from Example 1 is that the amount of titanium acetylacetonate added is 0.1g, the mass ratio of dehydrogenation coupling catalyst to liquid polymer silicon carbide ceramic precursor is 0.5%, and the remaining steps and conditions are the same as in Example 1.

[0090] Comparative Example 1 Unlike Example 2, titanium acetylacetone was not added in this comparative example, but the other conditions remained the same as in Example 2.

[0091] Comparative Example 2 Unlike Example 3, titanium acetylacetone was not added in this comparative example, but the other conditions remained the same as in Example 3.

[0092] Comparative Example 3 The difference from Example 1 is that no initiator was added, while all other conditions remained the same as in Example 1. Curing and foaming occurred during the preparation of the silicon carbide ceramic material.

[0093] Experimental Example 1 Using a DSC analyzer, the liquid silicon carbide ceramic precursor compositions from each example and comparative example were heated at a heating rate of 10°C / min and a nitrogen atmosphere of 100 ml / min to test their actual dehydrogenation coupling temperatures. The actual dehydrogenation coupling temperatures of Examples 1-11 and Comparative Example 4 were 230-270°C, while those of Comparative Examples 1-3 were greater than 350°C. This indicates that the addition of a dehydrogenation coupling catalyst to the liquid silicon carbide ceramic precursor composition in this invention helps to reduce its dehydrogenation coupling temperature and thus improve its ceramic yield.

[0094] The storage properties, viscosity, ceramic yield, and curing foaming properties of the liquid silicon carbide ceramic precursor compositions of each embodiment and comparative example are summarized in Table 1.

[0095] (1) Viscosity: The viscosity of the liquid silicon carbide ceramic precursor composition at 25°C was measured using a viscometer.

[0096] (2) Storage performance: The liquid silicon carbide ceramic precursor composition was sealed and stored at room temperature (the liquid silicon carbide ceramic precursor composition containing photopolymerization initiator was sealed and stored away from light). The room temperature storage period of Examples 10 and 11 was the longest time with a viscosity not exceeding 200 mPa·s, and the room temperature storage period of all other examples and comparative examples was the longest time with a viscosity not exceeding 100 mPa·s.

[0097] Table 1

[0098] As shown in Table 1, compared with Comparative Examples 1-3, the liquid silicon carbide ceramic precursor compositions in Examples 1-17 include liquid polymer silicon carbide ceramic precursors, dehydrogenation coupling catalysts, and initiators. By controlling the types and contents of each component, the liquid silicon carbide ceramic precursor compositions have good room temperature storage performance, significantly improve ceramic yield, and effectively suppress curing and foaming phenomena during the preparation of silicon carbide ceramic materials.

[0099] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A liquid silicon carbide ceramic precursor composition, characterized in that, The composition comprises a liquid polymer silicon carbide ceramic precursor, a dehydrogenation coupling catalyst, and an initiator. The liquid polymer silicon carbide ceramic precursor composition has a mass percentage content of 98.0% to 99.95%, and the liquid polymer silicon carbide ceramic precursor contains -Si-X and -SiH2- and / or -SiH3, wherein X is one or more of vinyl, ethynyl, and allyl groups. The initiator includes a free radical thermal polymerization initiator and / or a photopolymerization initiator. The dehydrogenation coupling catalyst includes one or more of bis(cyclopentadienyl)diphenoxytitanium (IV), cyclooctadiene-duquinone nickel, and transition metal acetylacetone compounds.

2. The liquid silicon carbide ceramic precursor composition according to claim 1, characterized in that, The mass ratio of the initiator to the liquid polymer silicon carbide ceramic precursor is 0.1% to 2%. And / or, the mass ratio of the dehydrogenation coupling catalyst to the liquid polymer silicon carbide ceramic precursor is 0.02% to 1.0%.

3. The liquid silicon carbide ceramic precursor composition according to claim 1, characterized in that, The liquid polymer silicon carbide ceramic precursor comprises a mixture of two or more liquid silicon carbide precursors containing unsaturated groups. And / or, the liquid polymer silicon carbide ceramic precursor comprises a mixture of a liquid silicon carbide precursor containing unsaturated groups and a silicon carbide precursor without unsaturated groups.

4. The liquid silicon carbide ceramic precursor composition according to claim 3, characterized in that, Liquid silicon carbide precursors containing unsaturated groups include liquid polycarbosilanes containing unsaturated groups, the structural formula of which is shown in Formula 1: Formula 1 Wherein, R is methyl or phenyl, X is one or more of -CH=CH2, -C≡CH, and -CH2-CH=CH2, x1 is 0.1~1.0, y1 is 0~0.5, and n1 is 20~100.

5. The liquid silicon carbide ceramic precursor composition according to claim 4, characterized in that, The liquid silicon carbide ceramic precursor composition satisfies: 2% ≤ ≤40%, where m1 is the mass of the compound shown in Formula 1, and x1 is the mass of x1 in Formula 1. The total mass of i kinds of liquid polymer silicon carbide ceramic precursors in the liquid silicon carbide ceramic precursor composition is denoted as i, where i is the number of different types of liquid polymer silicon carbide ceramic precursors in the liquid silicon carbide ceramic precursor composition.

6. The liquid silicon carbide ceramic precursor composition according to claim 1, characterized in that, Transition metal acetylacetone compounds include one or more of aluminum acetylacetone, titanium acetylacetone, titanium acetylacetone diisopropoxy, zirconium acetylacetone, zirconium acetylacetone diethoxy, iron acetylacetone, cobalt acetylacetone, and hafnium acetylacetone. And / or, the free radical thermal polymerization initiator includes one or more of dicumyl peroxide, 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane, 1,1-bis(tert-butylperoxy)cyclohexane and 1,3-bis-tert-butylperoxydicumylbenzene; And / or, the photopolymerization initiator includes one or more of 2-hydroxy-2-methylphenylacetone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone.

7. A method for preparing the liquid silicon carbide ceramic precursor composition according to any one of claims 1 to 6, characterized in that, The process includes the following steps: mixing the liquid polymer silicon carbide ceramic precursor, initiator, and dehydrogenation coupling catalyst uniformly at room temperature to obtain a liquid silicon carbide ceramic precursor composition.

8. A silicon carbide ceramic material, characterized in that, The liquid silicon carbide ceramic precursor composition is prepared using the liquid silicon carbide ceramic precursor composition according to any one of claims 1-6 or the liquid silicon carbide ceramic precursor composition prepared according to the method of claim 7.

9. A method for preparing the silicon carbide ceramic material according to claim 8, characterized in that, Includes the following steps: S1. The liquid silicon carbide ceramic precursor composition is cured and shaped under light irradiation and / or at 120~170°C; S2. Post-curing at 180~280℃; S3. Pyrolysis and ceramization are carried out at 900~1600℃ to obtain ceramic materials.

10. The method for preparing silicon carbide ceramic material according to claim 9, characterized in that, The illumination wavelength of S1 is 365 or 405 nm, and the illumination time is 2 to 30 minutes. And / or, in S1, the temperature is increased from room temperature to 120-170℃ at a heating rate of 2-5℃ / min and held for 1-2 hours for curing and shaping.

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