A ceramic fiber and a method for producing the same

Abstract

The application provides a ceramic fiber and a preparation method thereof, and relates to the technical field of ceramic fibers, and the preparation method comprises the following steps: (1) uniformly mixing a precursor and a silicazane compound in an organic solvent to obtain a spinning precursor; (2) uniformly mixing the spinning precursor, decaborane and a modified tungsten containing an amino functional group into the organic solvent to obtain a mixed solution; spinning the mixed solution to obtain a raw fiber; and (3) sequentially performing pyrolysis treatment and sintering treatment on the raw fiber to obtain the ceramic fiber. The ceramic fiber provided by the scheme has excellent high-temperature resistance, and the preparation process is simple and low in cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic fibers, in particular to a ceramic fiber and a preparation method thereof. BACKGROUND

[0002] Ceramic fibers are ideal reinforcing materials for high-temperature ceramic matrix composites due to their high-temperature resistance, high strength, corrosion resistance and other advantages, and are widely used in aerospace, nuclear energy, high-temperature structural materials and other fields. However, the high-temperature degradation mechanism of traditional polymer-derived ceramic fibers is mainly derived from the oxidation reaction of silicon and carbon, generating volatile CO and gaseous SiO products, resulting in the formation of a porous structure inside the fiber, and further leading to a significant decrease in strength and modulus.

[0003] Chinese patent CN102807369A discloses a method for preparing continuous silicon carbide fibers. The method adds vinyl-containing cyclic siloxane and silazane into polycarbosilane through physical blending, obtains a precursor fiber through melt spinning, crosslinks the precursor fiber through electron beam irradiation under inert gas, and finally obtains SiC fibers by pyrolysis under inert gas. Although the method is simple and easy to operate, the high-temperature stability is insufficient, and impurities such as free carbon and residual oxygen are easily produced after pyrolysis, resulting in a low ceramic yield. Therefore, there is an urgent need for a ceramic fiber and a preparation method thereof. SUMMARY

[0004] The present application provides a ceramic fiber and a preparation method thereof. The ceramic fiber has excellent high-temperature resistance, and the preparation method is simple, low in cost and high in ceramic yield.

[0005] In a first aspect, the present application provides a preparation method of a ceramic fiber, comprising:

[0006] (1) mixing a precursor and a silazane compound in an organic solvent to obtain a spinning precursor;

[0007] (2) mixing the spinning precursor, decaborane and a modified tungsten containing an amino functional group into an organic solvent to obtain a mixed solution; and spinning the mixed solution to obtain a precursor fiber;

[0008] (3) sequentially performing pyrolysis treatment and sintering treatment on the precursor fiber to obtain the ceramic fiber.

[0009] Preferably, in step (1), the precursor is low-molecular-weight polycarbosilane or high-molecular-weight polycarbosilane; the silazane compound includes vinyl silazane and polysilazane; and the amount of the silazane compound is 2wt%-6wt% of the amount of the precursor.

[0010] Preferably, when the precursor is low-molecular-weight polycarbosilane, the silazane compound is vinylsilazane, and the amount of vinylsilazane is 2wt% to 6wt% of the amount of low-molecular-weight polycarbosilane.

[0011] Preferably, when the precursor is high-molecular-weight polycarbosilane, the silazane compound is polysilazane, and the amount of polysilazane is 2wt% to 4wt% of the amount of high-molecular-weight polycarbosilane.

[0012] Preferably, in step (2), the amount of decaborane is 1wt% to 8wt% of the amount of the spinning precursor.

[0013] Preferably, in step (2), the amount of the amino-functional modified tungsten is 0.1wt% to 0.5wt% of the amount of the spinning precursor.

[0014] Preferably, in step (2), the amino-functional modified tungsten is determined by the following method:

[0015] The tungsten nanoparticles are dispersed in a solvent, and then a silane coupling agent is added for modification treatment to obtain the amino-functional modified tungsten.

[0016] Preferably, the particle size of the tungsten nanoparticles is 30 to 50nm.

[0017] Preferably, the amount of the silane coupling agent is 1wt% to 5wt% of the amount of the tungsten nanoparticles; and the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0018] Preferably, in step (3), the pyrolysis treatment is heating to 200 to 500℃ at a rate of 0.1 to 1.0℃ / min and holding for 1 to 3h, and then heating to 1000 to 1300℃ at a rate of 3 to 7℃ / min and holding for 1 to 3h.

[0019] Preferably, the sintering treatment is at a temperature of 1600 to 1800℃, a heating rate of 8 to 12℃ / min, and a time of 0.5 to 2h.

[0020] Preferably, after the pyrolysis treatment and sintering treatment of the original filament fiber in turn, further comprising: sizing treatment is carried out by using sizing agent, wherein the sizing agent comprises raw materials with the following mass percentages: amino-functional group-containing silicone oil 20%-40%, carboxylated graphene oxide dispersion liquid 2%-6%, titanate coupling agent 1%-5%, non-ionic surfactant 1%-3%, emulsifier 1%-3%, and the rest is water; the carboxylated graphene oxide dispersion liquid comprises carboxylated graphene oxide with a solid content of 2wt%, anionic dispersant with a solid content of 0.1wt%-0.3wt%, and water.

[0021] Preferably, the viscosity of the amino-functional group-containing silicone oil is 800-3000 mPa·s.

[0022] The titanate coupling agent comprises at least one of bis(dioctylpyrophosphato) ethylene titanate, chelate 200 type titanate, and isopropyl trioleate.

[0023] Preferably, the non-ionic surfactant comprises at least one of silicone surfactant and fluorine-containing surfactant polymer.

[0024] In a second aspect, the application further provides a ceramic fiber prepared by the preparation method of the first aspect.

[0025] Compared with the prior art, the application has at least the following beneficial effects:

[0026] The ceramic fiber prepared by the application has the following advantages: the amino-functional group-containing modified tungsten and decaborane are introduced, when the decaborane molecules contact with the silicon-nitrogen alkane compound and the nitrogen atom with electron pair in the amino functional group, the strong acid-base interaction combines them together, thereby generating enhanced chemical cross-linking effect and improving the pyrolysis yield; and only simple pyrolysis treatment is needed to realize non-melting treatment. Meanwhile, the nano tungsten can combine with the carbon in the fiber to form tungsten carbide phase at 1200℃ or above, thereby further improving the high-temperature oxidation resistance and high-temperature strength retention rate of the ceramic fiber. DETAILED DESCRIPTION

[0027] To make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme in the embodiments of the application is described clearly and completely below, obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments, and all other embodiments obtained by those skilled in the art without creative labor based on the embodiments in the application belong to the protection scope of the application.

[0028] The following is the concept of the application, the application provides a preparation method of a ceramic fiber, comprising:

[0029] (1) mixing the precursor with a silazane compound to obtain a spinning precursor;

[0030] (2) mixing the spinning precursor, decaborane and modified tungsten containing amino functional groups into an organic solvent to obtain a mixed solution; spinning the mixed solution to obtain a raw fiber;

[0031] (3) sequentially performing pyrolysis treatment and sintering treatment on the raw fiber to obtain a ceramic fiber.

[0032] The ceramic fiber provided by the application has decaborane and modified tungsten containing amino functional groups introduced therein. When the decaborane molecules contact with the siliconazane compound and the nitrogen atom giving an electron pair in the amino functional group, the strong acid-base interaction combines them together, thereby generating enhanced chemical cross-linking effect and improving the pyrolysis yield. Moreover, only simple pyrolysis treatment is needed to realize infusibility treatment. Meanwhile, the nano tungsten can combine with carbon in the fiber to form tungsten carbide at a temperature above 1200℃, thereby further improving the high-temperature oxidation resistance and high-temperature strength retention rate of the ceramic fiber.

[0033] In a preferred embodiment, in step (1), the precursor is a low molecular weight polycarbosilane or a high molecular weight polycarbosilane; the silazane compound includes vinylsilazane and polysilazane; and the amount of the silazane compound is 2wt%-6wt% (for example, can be 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt% or 6wt%) of the amount of the precursor.

[0034] In a more preferred embodiment, when the precursor is a low molecular weight polycarbosilane, the silazane compound is vinylsilazane, and the amount of the vinylsilazane is 2wt%-6wt% (for example, can be 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt% or 6wt%) of the amount of the low molecular weight polycarbosilane.

[0035] In the application, the weight average molecular weight of the low molecular weight polycarbosilane is 1420-1450. Since the ceramic yield of the low molecular weight polycarbosilane is extremely low when pyrolyzed at 1000℃, the chemical cross-linking by introducing vinylsilazane can improve the ceramic yield. It has been proved by experiments that if the amount of the vinylsilazane is higher than 6wt%, the number of molecules with high branching degree and cross-linking degree in the spinning precursor will increase, thereby seriously affecting the spinnability of the subsequent mixed solution, leading to an increase in the broken ends of the ceramic fiber, a change in the diameter of the ceramic fiber, and even a loss of spinnability. If the amount of the vinylsilazane is lower than 2wt%, the cross-linking degree is too low, and the ceramic yield is also low.

[0036] In a more preferred embodiment, when the precursor is high molecular weight polycarbosilane, the silazane compound is polysilazane, and the amount of polysilazane is 2wt% to 4wt% of the amount of high molecular weight polycarbosilane (for example, it can be 2wt%, 2.5wt%, 3wt%, 3.5wt% or 4wt%).

[0037] It should be noted that the weight average molecular weight of high molecular weight polycarbosilane is 2500 to 5000.

[0038] In the present application, the introduction of polysilazane improves the spinning processability and ceramic yield of high molecular weight polycarbosilane, making the viscosity of the mixed solution for spinning suitable, and the uniformity of the as-spun fiber good. Experiments have shown that if the amount of polysilazane is higher than 4wt%, the flowability of the mixed solution for spinning is poor, it is difficult to pass through the spinning nozzle, and stress concentration may occur inside the as-spun fiber, reducing the fiber strength; even it may introduce too much impurity or change the reaction process, leading to incomplete ceramic or side reactions, thereby reducing the ceramic yield. If the amount of polysilazane is less than 2wt%, the viscosity of the mixed solution for spinning is too low, which may lead to the as-spun fiber being thin and fragile, and breaking.

[0039] In a preferred embodiment, in step (2): the amount of decaborane is 1wt% to 8wt% of the amount of spinning precursor (for example, it can be 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt% or 8wt%).

[0040] It should be noted that the purity of decaborane is ≥99%, and it is a colorless crystal at room temperature.

[0041] In the present application, experiments have shown that if the amount of decaborane is less than 1wt%, it will lead to insufficient crosslinking, and thus insufficient crosslinking will lead to reduced ceramic yield after pyrolysis or even poor mechanical properties of the ceramic fiber; at the same time, due to the low amount of decaborane, the stable crosslinking network formed by the reaction of decaborane and silazane compound has limited effect on the improvement of glass transition temperature, so the subsequent non-melting treatment effect is poor or even softening problems may occur; moreover, the low amount of decaborane also leads to poor high temperature resistance of the prepared ceramic fiber. If the amount of decaborane is higher than 8wt%, the high amount of decaborane will lead to too high viscosity of the mixed solution, even gelation before spinning, and thus continuous as-spun fiber cannot be formed; moreover, the excess decaborane cannot be completely dissolved, which will lead to defects in the as-spun fiber; even the excess decaborane will form too much boron-carbon or boron-nitrogen phase during high temperature pyrolysis, leading to increased brittleness and decreased strength of the as-spun fiber.

[0042] In a preferred embodiment, in step (2), the amount of the modified tungsten containing amino functional groups is 0.1wt% to 0.5wt% of the amount of the spinning precursor (for example, it can be 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt% or 0.5wt%).

[0043] In the present application, it has been proved by experiments that the modified tungsten melts in the pyrolysis process, can combine with carbon in the fiber to form tungsten carbide phase, and further enhance the high temperature oxidation resistance of the ceramic fiber. If the amount of the modified tungsten is less than 0.1wt% of the amount of the spinning precursor, the high temperature enhancement effect on the ceramic fiber is not obvious. However, if the amount of the modified tungsten is more than 0.5wt% of the amount of the spinning precursor, the excess modified tungsten is prone to agglomeration, resulting in defects in the ceramic fiber, affecting the high temperature resistance and mechanical properties of the ceramic fiber, and the introduction of a large amount of particles will increase the viscosity of the mixed solution, affect the spinning, and also generate excess W2C, WC or tungsten silicide in the high temperature pyrolysis process, increasing the brittleness of the ceramic fiber.

[0044] In a preferred embodiment, in step (2), the modified tungsten containing amino functional groups is determined by the following method:

[0045] The tungsten nanoparticles are dispersed in a solvent, and then a silane coupling agent is added for modification treatment to obtain the modified tungsten containing amino functional groups.

[0046] In a preferred embodiment, the particle size of the tungsten nanoparticles is 30nm to 50nm (for example, it can be 30nm, 35nm, 40nm, 45nm or 50nm).

[0047] It should be noted that the particle size of the tungsten nanoparticles refers to the median particle size, also known as D50.

[0048] In the present application, it has been proved by experiments that, under the premise of a certain amount of added modified tungsten, if the particle size of the tungsten nanoparticles is less than 30nm, the specific surface area of the tungsten nanoparticles is too high, which is more prone to agglomeration and difficult to disperse uniformly, and too small modified tungsten may have excessive interfacial reaction with the precursor, affecting the performance of the ceramic fiber. Similarly, if the particle size of the tungsten nanoparticles is greater than 50nm, the large size tungsten nanoparticles are more likely to become a crack source of the ceramic fiber, even lose the nano-enhancing effect and affect the performance of the ceramic fiber. More importantly, since boron elements can form stable boron-tungsten compounds with the modified tungsten at high temperature, by limiting the particle size of the tungsten nanoparticles within the above range, tungsten can also be used as an anchor point to fix boron elements, so that they can work together with decaborane to inhibit the growth of ceramic grains and improve the oxidation resistance; at the same time, the amino groups of the modified tungsten can also work together with the vinyl silazane to increase the interfacial crosslinking density.

[0049] In a preferred embodiment, the amount of silane coupling agent is 1wt% to 5wt% (for example, it can be 1wt%, 2wt%, 3wt%, 4wt% or 5wt%) of the amount of tungsten nanoparticles; the silane coupling agent comprises at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0050] It should be noted that at least one is any one or any mixture of several in any proportion.

[0051] In a preferred embodiment, in step (3): the pyrolysis treatment is to heat up to 200-500℃ (for example, it can be 200℃, 250℃, 300℃, 350℃, 400℃, 450℃ or 500℃) at a rate of 0.1-1.0℃ / min (for example, it can be 0.1℃ / min, 0.2℃ / min, 0.3℃ / min, 0.4℃ / min, 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 0.8℃ / min, 0.9℃ / min or 1.0℃ / min) and keep for 1-3h (for example, it can be 1h, 1.5h, 2h, 2.5h or 3h), then heat up to 1000-1300℃ (for example, it can be 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃ or 1300℃) at a rate of 3-7℃ / min (for example, it can be 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min or 7℃ / min) and keep for 1-3h (for example, it can be 1h, 1.5h, 2h, 2.5h or 3h).

[0052] In the present application, the not-melting treatment and inorganic process of the precursor fiber can be realized by pyrolysis treatment, without complex not-melting treatment operation and high temperature treatment, thereby reducing energy consumption and equipment cost, and being more conducive to large-scale industrial production.

[0053] In a preferred embodiment, in step (3), the temperature of the sintering treatment is 1600-1800℃ (for example, it can be 1600℃, 1650℃, 1700℃, 1750℃ or 1800℃), the heating rate is 8-12℃ / min (for example, it can be 8℃ / min, 8.5℃ / min, 9℃ / min, 9.5℃ / min, 10℃ / min, 10.5℃ / min, 11℃ / min, 11.5℃ / min or 12℃ / min), and the time is 0.5-2h (for example, it can be 0.5h, 1h, 1.5h or 2h).

[0054] It should be noted that step (3) is carried out in an inert atmosphere, which includes but is not limited to argon, helium.

[0055] In a preferred embodiment, after the raw silk fibers are sequentially subjected to the pyrolysis treatment and the sintering treatment, the method further comprises: performing sizing treatment using a sizing agent; wherein the sizing agent comprises the following raw materials in mass percentage: 20%-40% of silicone oil containing a double amino functional group, 2%-6% of carboxylated graphene oxide dispersion liquid, 1%-5% of titanate coupling agent, 1%-3% of non-ionic surfactant, 1%-3% of emulsifier, and the rest is water; the carboxylated graphene oxide dispersion liquid comprises carboxylated graphene oxide with a solid content of 2wt%, anionic dispersant with a solid content of 0.1wt%-0.3wt%, and water.

[0056] It should be noted that 20%-40% means any value in the range of 20% to 40%, for example, it can be 20%, 22%, 24%, 25%, 26%, 28%, 30%, 32%, 34%, 35%, 36%, 38% or 40%. 2%-6% means any value in the range of 2% to 6%, for example, it can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5% or 6%. 1%-5% means any value in the range of 1% to 5%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%. 1%-3% means any value in the range of 1% to 3%, for example, it can be 1%, 1.5%, 2%, 2.5% or 3%.

[0057] Specifically, the anionic dispersant is sodium dodecyl sulfate. The size of the carboxylated graphene oxide in the carboxylated graphene oxide dispersion liquid is 2-10μm, and the thickness is 1-3nm. The emulsifier includes at least one of alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether-9, nonylphenol polyoxyethylene ether, and coconut diethanolamide.

[0058] In the present application, the silicone oil containing double amino functional groups can provide flexibility and lubricating performance for the emulsion type sizing agent, the introduced carboxylated graphene oxide not only provides mechanical protection for the protective layer, but also enhances the cohesion of the protective layer through the amidation reaction between the carboxyl group and the amino group in the silicone oil, and the sliding properties between the layers of the carboxylated graphene oxide and the lubricating performance of the silicone oil containing double amino functional groups synergistically act, so that the protective layer formed by the sizing agent has an extremely low friction coefficient, further improving the wear resistance of the ceramic fiber surface. At the same time, the introduced titanate coupling agent can form stable coordination bonds with the oxygen atoms on the surface of the ceramic fiber, the amino groups on the silicone oil, and the carboxyl groups on the carboxylated graphene oxide, which can significantly enhance the interfacial bonding strength between the sizing agent and the ceramic fiber, and at the same time, due to the toughness of the interface, it can also relieve stress concentration when the material deforms, preventing the protective layer from falling off or cracking. Moreover, the non-ionic surfactant has extremely low dynamic surface tension, which can realize instant wetting of the ceramic fiber surface and uniform spreading, improving the sizing uniformity. Therefore, the use of the sizing agent for the sizing treatment of the sintered fiber can further improve the wear resistance of the ceramic fiber.

[0059] In the present application, the sizing agent is an oil-in-water emulsion, water is used as an environmentally friendly dispersion medium to provide a uniform dispersion environment for the raw materials, and can gradually volatilize during film formation without causing environmental pollution, meeting the environmental protection requirements. At the same time, the preparation process is simple, no special equipment and complex operation process are needed, which is convenient for industrialized mass production and application, and significantly reduces the production cost.

[0060] In a preferred embodiment, the viscosity of the silicone oil containing double amino functional groups is 800-3000 mPa·s.

[0061] The titanate coupling agent includes at least one of bis(dioctyl pyrophosphoric acyloxy) ethylene titanate, chelate 200 type titanate, and isopropyl trioleic acyloxy titanate.

[0062] In the present application, experiments have proved that the molecular weight of the silicone oil containing double amino functional groups will affect its viscosity, limiting its viscosity at 25 DEG C to 800-3000 mPa·s, which can not only avoid the uneven sizing of the prepared sizing agent due to the too small molecular weight and too low viscosity of the silicone oil, but also avoid the too large viscosity of the silicone oil when the molecular weight is too large, which affects the dispersion and wettability of the prepared sizing agent.

[0063] In the present application, the titanium atom in the molecular structure of the phthalate coupling agent has a unique coordination ability, which can form stable coordination bonds with the oxygen atoms on the surface of the fiber matrix and the carboxyl / amino groups on the carboxylated graphene oxide / silicone oil. This coordination bond not only significantly enhances the interfacial bonding strength between the protective layer formed by the sizing agent and the fiber matrix, but also strengthens the interaction between the carboxylated graphene oxide and the silicone oil, making the entire composite system form a tightly integrated whole. Moreover, this bonding has a certain toughness, which can still maintain the integrity of the interface when the fiber deforms, effectively relieving stress concentration and preventing the protective layer from falling off or cracking. In addition, the silicone oil containing double amino functional groups is cracked into nano-SiO2 under high temperature conditions, which matches the thermal expansion coefficient of the fiber and has good compatibility. At the same time, the titanate coupling agent can be converted into TiO2, which can form a eutectic phase with SiO2, further enhancing the interfacial bonding strength and heat resistance at high temperatures. Experiments have confirmed that if the amount of titanate coupling agent is less than 1wt%, the Ti content in the sizing agent system is low, which not only reduces the interfacial bonding strength between the protective layer formed by the sizing agent and the fiber, but also weakens the interaction between the carboxylated graphene oxide and the silicone oil, affecting the interface integrity when the material matrix deforms, and affecting the heat resistance of the protective layer at high temperatures. If the amount of titanate coupling agent is more than 5wt%, the amount of titanate coupling agent is too much, and the excess phthalate coupling agent will be physically adsorbed on the surface, forming a weakly bound multilayer, which affects the interfacial bonding strength, adhesion and wear resistance of the protective layer formed by the sizing agent; At the same time, as a surface active substance, excessive titanate coupling agent will destroy the original hydrophilic-lipophilic balance (HLB value) of the emulsion, leading to a decrease in emulsion stability, delamination, demulsification, and loss of application value. After the hydrolysis and condensation of the excess titanate coupling agent, the titanium oxide particles formed will be unevenly attached to the surface of the fiber, rather than forming a continuous and smooth film, which will cause the ceramic fiber to become hard and brittle, and the bundling property to decrease, leading to problems such as hair and broken yarns during subsequent weaving.

[0064] In a preferred embodiment, the non-ionic surfactant comprises at least one of a silicone-based surfactant, a fluorine-containing surfactant polymer. The non-ionic surfactant includes but is not limited to TEGO® Glide 482, TEGO® Glide 410, TEGO® Glide 452, BYK 340, BYK 333, all of which have a dynamic surface tension of <25 mN / m, and preferably BYK-340 which is a fluorine-containing silicone.

[0065] Specifically, the preparation method of the sizing agent is as follows: the silicon oil containing a diamino functional group is dispersed in water, then an emulsifier is added and uniformly mixed to obtain a primary emulsion; the prepared uniformly dispersed carboxylated graphene oxide dispersion liquid and titanate coupling agent are added to the primary emulsion and uniformly mixed under stirring at 40-60℃ to obtain a composite emulsion; the non-ionic surfactant is added to the composite emulsion, then the system is aged under stirring at 300-500 rpm (at this time, the pH value of the system is 6.5-7.0) for 24 h and filtered to obtain the sizing agent.

[0066] In the absence of special instructions, each raw material used in the present application can be a product that can be directly purchased on the market or synthesized by existing methods.

[0067] In the present application, "and / or" appearing between a plurality of technical features means that these technical features are connected in a "and / or" relationship, indicating that it can be any one of these technical features, or a combination of any two or more of these technical features.

[0068] The present application will be further described below by way of examples, but the scope of protection of the present application is not limited to these examples.

[0069] Example 1

[0070] A preparation method of a ceramic fiber:

[0071] (1) 100g of low molecular weight polycarbosilane (MW=1420-1450) and 6g of vinylsilazane were stirred in toluene until completely dissolved to obtain a spinning precursor;

[0072] (2) 10g of tungsten nanoparticles (D50=50nm) were dispersed in 100mL of anhydrous ethanol, and then 0.5g of γ-aminopropyltriethoxysilane (KH550) was added and stirred at 60℃ for 2h, followed by centrifugation at 300rpm for 10min and vacuum drying at 80℃ for 12h to obtain modified tungsten containing an amino functional group;

[0073] 100g of the spinning precursor obtained in step (1), 1.1g of decaborane and 0.1g of modified tungsten containing an amino functional group were added to toluene and uniformly mixed, and stirred at 30℃ for 2h to form a mixed solution; the mixed solution was filtered through a 0.45μm PTFE filter membrane, and then evaporated at 50℃ under reduced pressure for 30min to adjust the viscosity to 300 cP for spinning to obtain a raw fiber;

[0074] (3) The raw fiber is placed in an argon atmosphere, heated at a rate of 0.5°C / min to 200°C and kept for 1 h, then heated at a rate of 5°C / min to 1000°C and kept for 1 h to complete pyrolysis, and then heated at a rate of 10°C / min to 1800°C in an argon atmosphere, kept for 1 h to complete sintering, and then naturally cooled to room temperature to obtain a ceramic fiber.

[0075] Example 2

[0076] Example 2 is basically the same as Example 1, except that 3.2 g of decaborane is added in step (2).

[0077] Specifically, step (2): 100 g of the spinning precursor obtained in step (1), 3.2 g of decaborane and 0.1 g of modified tungsten containing an amino functional group are added to toluene for mixing, and stirred at 30°C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50°C under reduced pressure for 30 min to adjust the viscosity to 300 cP for spinning to obtain a raw fiber.

[0078] Example 3

[0079] Example 3 is basically the same as Example 1, except that 7.6 g of decaborane is added in step (2).

[0080] Specifically, step (2): 100 g of the spinning precursor obtained in step (1), 7.6 g of decaborane and 0.1 g of modified tungsten containing an amino functional group are added to toluene for mixing, and stirred at 30°C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50°C under reduced pressure for 30 min to adjust the viscosity to 300 cP for spinning to obtain a raw fiber.

[0081] Example 4

[0082] Example 4 is basically the same as Example 2, except that 0.3 g of modified tungsten containing an amino functional group is added in step (2).

[0083] Specifically, step (2): 100 g of the spinning precursor obtained in step (1), 3.2 g of decaborane and 0.3 g of modified tungsten containing an amino functional group are added to toluene for mixing, and stirred at 30°C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50°C under reduced pressure for 30 min to adjust the viscosity to 300 cP for spinning to obtain a raw fiber.

[0084] Example 5

[0085] Example 5 is substantially the same as Example 2, except that the amino-functional modified tungsten added in step (2) is 0.5 g.

[0086] Specifically, step (2): 100 g of the spinning precursor obtained in step (1), 3.2 g of decaborane and 0.5 g of the amino-functional modified tungsten are added into toluene to mix and stir at 30°C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50°C under reduced pressure for 30 min to adjust the viscosity to 300 cP for spinning to obtain the raw fiber.

[0087] Example 6

[0088] A method for preparing a ceramic fiber comprises the following steps:

[0089] (1) 500 g of polymethylsilane is placed in an autoclave and pyrolyzed under pressure at 450°C for 24 h in an inert atmosphere to obtain high molecular weight polycarbosilane with MW = 2500-5000;

[0090] 100 g of the high molecular weight polycarbosilane and 3 g of polysilazane are placed in toluene to mix and stir until completely dissolved to obtain a spinning precursor;

[0091] (2) 10 g of tungsten nanoparticles (D50 = 50 nm) are dispersed in 100 mL of anhydrous ethanol, and then ultrasonicated at a power density of 300 w for 30 min, 0.5 g of γ-aminopropyltriethoxysilane (KH550) is added and stirred at 60°C for 2 h, then centrifuged at 300 rpm for 10 min and vacuum dried at 80°C for 12 h to obtain the amino-functional modified tungsten;

[0092] 100 g of the spinning precursor obtained in step (1), 1.1 g of decaborane and 0.1 g of the amino-functional modified tungsten are added into toluene to mix and stir at 30°C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50°C under reduced pressure for 30 min to adjust the viscosity to 300 cP for spinning to obtain the raw fiber.

[0093] (3) The raw fiber is placed in an argon atmosphere, first heated at a rate of 0.5°C / min to 250°C and kept for 1 h, then heated at a rate of 5°C / min to 1000°C and kept for 1 h to complete the pyrolysis treatment, and then heated at a rate of 10°C / min to 1800°C in an argon atmosphere, kept for 1 h to complete the sintering treatment, and then naturally cooled to room temperature to obtain the ceramic fiber.

[0094] Example 7

[0095] Example 7 is substantially the same as Example 6, except that 3.2 g of decaborane is added in step (2).

[0096] Specifically, step (2): 100 g of the spinning precursor obtained in step (1), 3.2 g of decaborane and 0.1 g of the modified tungsten containing amino functional group are added into toluene for mixing, and stirring at 30 °C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50 °C under reduced pressure for 30 min to adjust the viscosity to 300 cP for spinning to obtain the precursor fiber.

[0097] Example 8

[0098] Example 8 is substantially the same as Example 6, except that 7.6 g of decaborane is added in step (2).

[0099] Specifically, step (2): 100 g of the spinning precursor obtained in step (1), 7.6 g of decaborane and 0.1 g of the modified tungsten containing amino functional group are added into toluene for mixing, and stirring at 30 °C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50 °C under reduced pressure for 30 min to adjust the viscosity to 300 cP for spinning to obtain the precursor fiber.

[0100] Example 9

[0101] Example 9 is substantially the same as Example 7, except that 0.3 g of the modified tungsten containing amino functional group is added in step (2).

[0102] 100 g of the spinning precursor obtained in step (1), 3.2 g of decaborane and 0.3 g of the modified tungsten containing amino functional group are added into toluene for mixing, and stirring at 30 °C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50 °C under reduced pressure for 30 min to adjust the viscosity to 300 cP for spinning to obtain the precursor fiber.

[0103] Example 10

[0104] Example 10 is substantially the same as Example 7, except that 0.5 g of the modified tungsten containing amino functional group is added in step (2).

[0105] Take 100 g of the spinning precursor obtained in step (1), 3.2 g of decaborane and 0.5 g of amino-functional modified tungsten into toluene to mix, and stir at 30°C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50°C under reduced pressure for 30 min to adjust the viscosity to 300 cP for spinning, to obtain the precursor fiber.

[0106] Example 11

[0107] Example 11 is basically the same as Example 1, except that after the precursor fiber is subjected to pyrolysis treatment and sintering treatment in sequence, it further includes: using a sizing agent for sizing treatment.

[0108] The sizing agent includes the following raw materials in mass percentage: amino-functional silicon oil (KGA-9056 purchased from Anhui Keguang) 30%, carboxylated graphene oxide dispersion 2%, titanate coupling agent (isopropyl trioleate titanate KR-TTS) 1%, non-ionic surfactant (TEGO® Glide 410) 1.5%, emulsifier (alkyl phenol polyoxyethylene ether OP-10) 3%, and deionized water 62.5%. The amount of each raw material is indicated below.

[0109] Preparation method of the sizing agent:

[0110] a. In a reaction kettle with stirring device, after adding deionized water, start stirring, slowly add 30 parts of amino-functional silicon oil at 300 rpm, continue stirring for 20 min to make it preliminarily dispersed uniformly in water; then continue to add OP-10 to the system, and shear at 10000 rpm for 30 min to form a primary emulsion;

[0111] b. Carboxylated graphene oxide (COOH content > 5 mmol / g, size 2-10 μm, thickness 1-3 nm) is added to deionized water containing 0.1 wt% sodium dodecyl sulfate, and ultrasonically treated at 1000 w power for 2 h to obtain a carboxylated graphene oxide dispersion with a solid content of 2 wt%; slowly drop 2 parts of the carboxylated graphene oxide dispersion and 1 part of KR-TTS into the primary emulsion of step a, and stir (speed 1000 rpm) at 40°C for 1 h to obtain a composite emulsion;

[0112] c. Add 1.5 parts of TEGO® Glide 410 to the composite emulsion in step b, and stir at 300 rpm for 24 h, and adjust the pH to 6.5-7.0, then filter the aged composite emulsion through a 50 μm microporous filter membrane to remove possible impurities and agglomerated particles to obtain an emulsion type sizing agent.

[0113] Specifically, step (3): the raw fiber is placed in an argon atmosphere, first heated to 200°C at a rate of 0.5°C / min and kept for 1 h, then heated to 1000°C at a rate of 5°C / min and kept for 1 h to complete the pyrolysis treatment, then continue to heat to 1800°C at a rate of 10°C / min in an argon atmosphere, keep for 1 h to complete the sintering treatment, and then naturally cool to room temperature to obtain the initial fiber; the initial fiber is wound around the guide roller, and then passes through the sizing tank, the pressure roller and the oven in sequence, and finally reaches the fiber collector; then the sizing agent is poured into the sizing tank, the initial fiber is fully immersed, and finally the fiber is collected at a speed of 3 m / min to obtain the ceramic fiber.

[0114] Example 12

[0115] Example 12 is basically the same as Example 11, except that the amount of carboxylated graphene oxide dispersion and the amount of titanate coupling agent in the sizing agent are different.

[0116] Specifically, the sizing agent includes the following raw materials by mass percentage: amino-functionalized silicone oil 30%, carboxylated graphene oxide dispersion 4%, titanate coupling agent (isopropyl trioleate titanate KR-TTS) 3%, non-ionic surfactant (TEGO® Glide 410) 1.5%, emulsifier (alkyl phenol polyoxyethylene ether OP-10) 3%, and deionized water 58.5%.

[0117] Comparative Example 1

[0118] Comparative Example 1 is basically the same as Example 1, except that step (2) does not add amino-functionalized modified tungsten.

[0119] Specifically, step (2): 100 g of the spinning precursor obtained in step (1) and 1.1 g of decaborane are added to toluene and mixed, and stirred at 30°C for 2 h to form a mixed solution; the mixed solution is filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50°C under reduced pressure for 30 min to adjust the viscosity to 300 cP before spinning to obtain the raw fiber.

[0120] Comparative Example 2

[0121] Comparative Example 2 is basically the same as Example 1, except that step (2) does not add decaborane.

[0122] Specifically, step (2): 100 g of the spinning precursor obtained in step (1), 0.1 g of modified tungsten containing amino functional groups, and 0.1 g of boron decaboride were added to toluene and stirred for 2 h at 30 °C to form a mixed solution; the mixed solution was filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50 °C under reduced pressure for 30 min to adjust the viscosity to 300 cP before spinning to obtain the raw fiber.

[0123] Comparative Example 3

[0124] Comparative Example 3 is basically the same as Example 1, except that the tungsten is not modified in step (2);

[0125] Specifically, step (2): 100 g of the spinning precursor obtained in step (1), 1.1 g of boron decaboride, and 0.1 g of tungsten nanoparticles (D50 = 50 nm) were added to toluene and stirred for 2 h at 30 °C to form a mixed solution; the mixed solution was filtered through a 0.45 μm PTFE filter membrane, and then evaporated at 50 °C under reduced pressure for 30 min to adjust the viscosity to 300 cP before spinning to obtain the raw fiber.

[0126] Comparative Example 4

[0127] A method for preparing a ceramic fiber:

[0128] (1) 100 g of low molecular weight polycarbosilane (MW = 1420-1450) and 10 g of vinyl silazane were stirred in toluene until completely dissolved to obtain a spinning precursor;

[0129] (2) 100 g of the spinning precursor obtained in step (1) was added to toluene and stirred for 2 h at 30 °C, and the volume of toluene added was controlled to adjust the viscosity of the system to 300 cP before spinning to obtain the raw fiber;

[0130] (3) The raw fiber was placed in a non-melting furnace, which was heated to 140 °C in an air atmosphere for 1 h, then the temperature was increased to 320 °C at a rate of 1 °C / h and held for 2 h, and then cooled to room temperature to obtain a polycarbosilane non-melting fiber. The obtained polycarbosilane non-melting fiber was placed in a high temperature furnace, which was heated to 1500 °C at a rate of 150 °C / h in an argon atmosphere and held for 1 h, and then naturally cooled to room temperature to obtain a ceramic fiber.

[0131] Comparative Example 5

[0132] Comparative Example 5 is basically the same as Example 11, except that the carboxylated graphene oxide dispersion is not added to the sizing agent;

[0133] Specifically, a sizing agent comprises the following raw materials in mass percentage: a silicon oil containing double amino functional groups 30%, a titanate coupling agent (isopropyl trioleate titanate KR-TTS) 1%, a non-ionic surfactant (TEGO® Glide 410) 1.5%, an emulsifier (alkyl phenol polyoxyethylene ether OP-10) 3%, and deionized water 65.5%.

[0134] Comparative Example 6

[0135] Comparative Example 6 is basically the same as Example 11, except that no titanate coupling agent is added to the sizing agent.

[0136] Specifically, an emulsion type sizing agent comprises the following raw materials in mass percentage: a silicon oil containing double amino functional groups 30%, a carboxylated graphene oxide dispersion liquid 2%, a non-ionic surfactant (TEGO® Glide 410) 1.5%, an emulsifier (alkyl phenol polyoxyethylene ether OP-10) 3%, and deionized water 63.5%.

[0137] The ceramic fibers prepared in each of the examples and each of the comparative examples are subjected to performance evaluation, and the test performance data are shown in Tables 1 and 2. The tensile strength is obtained at room temperature (25℃), and the tests of the tensile strength and the high-temperature strength retention rate are both in accordance with GB / T 34520.7-2017. The test method of the abrasion rate is in accordance with GB / T 34520.1-2017, and the test method of the friction coefficient is in accordance with T_CSTM 00522-2022.

[0138] Table 1

[0139]

[0140] Table 2

[0141]

[0142] As can be seen from the data in Table 1, the ceramic fibers prepared in the examples of the present application have excellent high-temperature oxidation resistance, significantly improving the strength retention rate of the ceramic fibers at high temperature; and only through simple heat treatment, non-melting treatment is realized. At the same time, the ceramic fibers after sizing treatment have excellent wear resistance, and the tensile strength is also further improved, showing good application prospect.

[0143] The part of the present application not described in detail is the technology known to those skilled in the art.

[0144] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of making a ceramic fiber, characterized by, Comprise: (1) the precursor and silazane compound are placed in an organic solvent to mix, to obtain a spinning precursor; the precursor is a low molecular weight polycarbosilane or a high molecular weight polycarbosilane; when the precursor is a low molecular weight polycarbosilane, the silazane compound is vinyl silazane, and the amount of vinyl silazane is 2wt%-6wt% of the amount of low molecular weight polycarbosilane; when the precursor is a high molecular weight polycarbosilane, the silazane compound is polysilazane, and the amount of polysilazane is 2wt%-4wt% of the amount of high molecular weight polycarbosilane; (2) the spinning precursor, decaborane and amino functional group containing modified tungsten are added to an organic solvent to mix, to obtain a mixed solution; The mixed solution is spun to obtain a raw silk fiber; the amount of decaborane is 1wt%-8wt% of the amount of the spinning precursor; the amount of amino functional group containing modified tungsten is 0.1wt%-0.5wt% of the amount of the spinning precursor; (3) the raw silk fiber is sequentially subjected to pyrolysis treatment and sintering treatment to obtain the ceramic fiber.

2. The production method according to claim 1, characterized by, In step (2): The amino functional group containing modified tungsten is determined by the following method: The tungsten nanoparticles are dispersed in a solvent, and then a silane coupling agent is added for modification treatment to obtain the amino functional group containing modified tungsten.

3. The preparation method according to claim 2, characterized in that, The particle size of the tungsten nanoparticles is 30-50nm.

4. The preparation method according to claim 2, characterized in that, The amount of the silane coupling agent is 1wt%-5wt% of the amount of the tungsten nanoparticles; the silane coupling agent comprises at least one of γ-aminopropyl triethoxysilane, γ-glycidyl ether propyl trimethoxysilane, 3-aminopropyl triethoxysilane and N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane.

5. The preparation method according to claim 1, characterized in that, In step (3): The pyrolysis treatment is to heat to 200-500℃ at a rate of 0.1-1.0℃ / min and keep for 1-3h, and then heat to 1000-1300℃ at a rate of 3-7℃ / min and keep for 1-3h.

6. The method of claim 1, wherein, In step (3): The sintering treatment is at a temperature of 1600-1800℃, a heating rate of 8-12℃ / min and a time of 0.5-2h.

7. The production method according to any one of claims 1 to 6, characterized by, After the raw silk fiber is sequentially subjected to pyrolysis treatment and sintering treatment, it further comprises: sizing treatment with a sizing agent; wherein the sizing agent comprises raw materials in the following mass percentages: double amino functional group containing silicone oil 20%-40%, carboxylated graphene oxide dispersion liquid 2%-6%, titanate coupling agent 1%-5%, non-ionic surfactant 1%-3%, emulsifier 1%-3%, and the rest is water; the carboxylated graphene oxide dispersion liquid comprises carboxylated graphene oxide with a solid content of 2wt%, anionic dispersant with a solid content of 0.1wt%-0.3wt% and water.

8. The preparation method according to claim 7, characterized in that, The viscosity of the double amino functional group containing silicone oil is 800-3000mPa·s; The titanate coupling agent includes at least one of bis(dioctylpyrophosphoryloxy)ethyl titanate, chelate 200 type titanate, isopropyl trioleic acyloxy titanate.

9. The preparation method according to claim 7, characterized in that, The nonionic surfactant includes at least one of organosilicon surfactant, fluorine-containing surfactant polymer.

10. A ceramic fiber, characterized by, The preparation method is prepared by using the preparation method in any one of claims 1 to 9.

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