A method for preparing silicon nitride fiber

Abstract

The present invention provides a method for preparing silicon nitride fiber, comprising: raw material preparation, preparing a silicon source and a nitrogen source; solution preparation, mixing the silicon source and the nitrogen source and dissolving them in an organic solvent to prepare a solution; adding an appropriate amount of catalyst to promote a mixing reaction between the silicon source and the nitrogen source; fiber preparation, spinning, spraying or rotating the solution through a spinning device to form a preliminary structure of the silicon nitride fiber; gelation, adding a cross-linking agent to carry out a chemical reaction to form a chemical bond between the silicon source and the nitrogen source, so that the preliminary structure of the fiber undergoes gelation to generate silicon nitride gel; heat treatment, in an inert atmosphere, subjecting the silicon nitride gel to a high-temperature heat treatment, wherein the high-temperature heat treatment helps to form a crystal structure of silicon nitride; and surface treatment, subjecting the silicon nitride fiber to a surface treatment agent. The silicon nitride fiber is obtained by mixing polysiloxane, polysiloxane, and ammonia to prepare a solution, spinning the solution, and performing gelation and heat treatment to reduce production costs.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon nitride fiber preparation, and in particular to a method for preparing silicon nitride fiber. Background Art

[0002] Ceramic fibers, with their advantages of light weight, high-temperature resistance, excellent thermal stability, and adjustable thermal conductivity, are often used as reinforcements in high-temperature structural composites. For example, gasoline engines, valvetrains, and adiabatic engines currently require high-strength, low-thermal-conductivity materials to maintain mechanical strength while preventing heat loss. Military applications also require such materials for components like missile nozzle bushings to increase component strength and reduce heat transfer to the metal lining. Therefore, using ceramic fibers for composite toughening can maintain mechanical strength while reducing thermal conductivity.

[0003] Silicon nitride is a typical covalently bonded compound with two crystal forms: α- and β-phases, both belonging to the hexagonal system. α-Si3N4 is a low-temperature stable phase with high hardness and relatively low thermal conductivity, while β-Si3N4 is a high-temperature stable phase with high fracture strength, toughness, and thermal conductivity. Silicon nitride also boasts high thermal stability, strong low- and medium-temperature oxidation resistance, and excellent wear and corrosion resistance, making it widely used in semiconductors, electronics, machinery manufacturing, energy, chemical engineering, aerospace, and other fields. Currently, commercial silicon nitride products include ceramic parts, powders, and whiskers. Silicon nitride whiskers have demonstrated their effectiveness in toughening ceramics. However, research and application of silicon nitride fibers is relatively limited, leaving a significant untapped market. Furthermore, compared to commercially available alumina fibers, silicon nitride fibers offer superior mechanical properties, adjustable thermal conductivity, and thermal stability, making them promising ceramic fibers with enormous potential for application.

[0004] The typical process for preparing silicon nitride fiber materials involves melt spinning precursors such as polysilazane, perhydropolysilazane, and polysilocarbazine, followed by heat treatment in a nitrogen atmosphere to produce silicon nitride fibers. Silicon nitride fibers can then be manufactured into finished products through processes such as spinning, needle punching, or vacuum filtration. However, this method involves expensive precursors and a complex process, resulting in high production costs for silicon nitride fibers. Summary of the Invention

[0005] The present invention provides a method for preparing silicon nitride fibers, which is used to solve the defects in the prior art.

[0006] The present invention provides a method for preparing silicon nitride fiber, comprising:

[0007] Raw material preparation, preparation of silicon source and nitrogen source;

[0008] Solution preparation: mixing the silicon source and the nitrogen source and dissolving them in an organic solvent to prepare a solution; adding an appropriate amount of catalyst to promote the mixing reaction between the silicon source and the nitrogen source;

[0009] Fiber preparation, spinning, spraying or spinning the solution through a spinning device to form the preliminary structure of silicon nitride fiber;

[0010] Gelation, by adding a cross-linking agent to carry out a chemical reaction to form a chemical bond between the silicon source and the nitrogen source, so that the initial structure of the fiber is gelled to form silicon nitride gel;

[0011] Heat treatment: subjecting the silicon nitride gel to high-temperature heat treatment in an inert atmosphere. High-temperature heat treatment helps to form the crystal structure of silicon nitride;

[0012] Surface treatment: The silicon nitride fiber is surface treated with a surface treatment agent.

[0013] According to a method for preparing silicon nitride fibers provided by the present invention, the silicon source is polysiloxane or polysiloxane; and the nitrogen source is ammonia.

[0014] According to a method for preparing silicon nitride fibers provided by the present invention, the catalyst in the solution preparation is one of GaN, Ga, and Fe.

[0015] According to a method for preparing silicon nitride fiber provided by the present invention, the spinning process adopts electrostatic spinning, the solution is injected into the electrostatic spinning equipment, and the voltage, flow rate and distance between the nozzle and the collector of the electrostatic spinning equipment are adjusted.

[0016] According to a method for preparing silicon nitride fibers provided by the present invention, the voltage of the electrospinning is 8-18 kV, the flow rate is 2-6 ml / h, and the distance between the nozzle and the collector is 10-20 cm.

[0017] According to a method for preparing silicon nitride fibers provided by the present invention, during the gelation process, the crosslinking agent in the chemical reaction is methylene bisacrylamide.

[0018] According to a method for preparing silicon nitride fiber provided by the present invention, the inert atmosphere during the heat treatment process is nitrogen or argon.

[0019] According to a preparation method of silicon nitride fiber provided by the present invention, the high-temperature heat treatment temperature of the heat treatment process is 1300-1800°C, the time of the high-temperature heat treatment is 2-6h, the heat treatment process includes heating, heat preservation and cooling, the heating rate of the high-temperature heat treatment is 1-20°C / min, the heating rate or cooling rate of the high-temperature heat treatment is the same, which is 1-20°C / min, or cooling with the furnace during cooling.

[0020] According to a method for preparing silicon nitride fiber provided by the present invention, the surface treatment agent is polyurethane and polyetheretherketone.

[0021] The present invention provides a method for preparing silicon nitride fibers, comprising the steps of mixing polysilicone, polysiloxane and ammonia to prepare a solution, spinning the solution, gelling and heat-treating the solution to obtain silicon nitride fibers, and electrospinning to obtain continuous silicon nitride fibers with high surface smoothness. The silicon nitride fibers are gelled to make their structure more stable, and the obtained silicon nitride fibers are surface-treated to improve the strength, wear resistance and high temperature resistance of the fibers, thereby improving the overall performance of the fibers. The process is simple, and the production cost of the silicon nitride fibers is reduced. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention are described in further detail below in conjunction with the examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention.

[0023] In order to better understand the purpose of the present invention, the present invention is described in further detail below.

[0024] A method for preparing silicon nitride fiber according to an embodiment of the present application includes:

[0025] Raw material preparation, preparation of silicon source and nitrogen source;

[0026] Solution preparation: mixing the silicon source and the nitrogen source and dissolving them in an organic solvent to prepare a solution; adding an appropriate amount of catalyst to promote the mixing reaction between the silicon source and the nitrogen source;

[0027] Fiber preparation, spinning, spraying or spinning the solution through a spinning device to form the preliminary structure of silicon nitride fiber;

[0028] Gelation, by adding a cross-linking agent to carry out a chemical reaction to form a chemical bond between the silicon source and the nitrogen source, so that the initial structure of the fiber is gelled to form silicon nitride gel;

[0029] Heat treatment: subjecting the silicon nitride gel to high-temperature heat treatment in an inert atmosphere. High-temperature heat treatment helps to form the crystal structure of silicon nitride;

[0030] Surface treatment: The silicon nitride fiber is surface treated with a surface treatment agent.

[0031] To further optimize the above technical solution, the silicon source is polysiloxane or polysiloxane; and the nitrogen source is ammonia.

[0032] In order to further optimize the above technical solution, the catalyst in the solution preparation is one of GaN, Ga, and Fe.

[0033] In order to further optimize the above technical solution, electrospinning is adopted in the spinning process, the solution is injected into the electrospinning equipment, and the voltage, flow rate and distance between the nozzle and the collector of the electrospinning equipment are adjusted.

[0034] To further optimize the above technical solution, the voltage of the electrospinning is 8-18 kV, the flow rate is 2-6 ml / h, and the distance between the nozzle and the collector is 10-20 cm.

[0035] To further optimize the above technical solution, during the gelation process, the cross-linking agent in the chemical reaction is methylene bisacrylamide.

[0036] In order to further optimize the above technical solution, the inert atmosphere during the heat treatment process is nitrogen or argon.

[0037] To further optimize the above technical solution, the high-temperature heat treatment temperature of the heat treatment process is 1300-1800°C, the high-temperature heat treatment time is 2-6h, the heat treatment process includes heating, insulation and cooling, the heating rate of the high-temperature heat treatment is 1-20°C / min, the heating rate or cooling rate of the high-temperature heat treatment is the same, 1-20°C / min, or cooling with the furnace during cooling.

[0038] In order to further optimize the above technical solution, the surface treatment agents are polyurethane and polyetheretherketone.

[0039] The preparation method of silicon nitride fiber of the present invention improves the strength, wear resistance and high temperature resistance of the fiber, improves the overall performance of the fiber, and has a simple process flow. The specific embodiment is as follows:

[0040] Example 1

[0041] Raw material preparation, including polysiloxane, polysiloxane and ammonia;

[0042] Solution preparation: polysiloxane, polysiloxane and ammonia are mixed and dissolved in an organic solvent to prepare a solution; an appropriate amount of Fe metal catalyst is added to promote the mixing reaction between the polysiloxane, polysiloxane and ammonia;

[0043] Fiber preparation, spinning, and electrospinning: The solution was injected into the electrospinning equipment with an electrospinning voltage of 8 kV, a flow rate of 2 ml / h, and a distance of 10 cm between the nozzle and the collector to form the preliminary structure of the silicon nitride fiber;

[0044] Gelation: by adding a cross-linking agent, methylene bisacrylamide, to cause a chemical reaction to form chemical bonds between polysiloxane, polysiloxane, and ammonia, so that the initial structure of the fiber is gelled to form silicon nitride gel;

[0045] Heat treatment: subjecting the silicon nitride gel to a high-temperature heat treatment in a nitrogen atmosphere. The high-temperature heat treatment temperature is 1300° C., the high-temperature heat treatment time is 2 hours, the heating rate of the high-temperature heat treatment is 3° C. / min, and the heating rate or cooling rate of the high-temperature heat treatment is the same, 3° C. / min, or cooling with the furnace during cooling. The high-temperature heat treatment helps to form the crystal structure of the silicon nitride;

[0046] Surface treatment: The silicon nitride fiber is surface treated with surface treatment agents polyurethane and polyetheretherketone.

[0047] The thermal conductivity of the prepared silicon nitride fiber is 0.45W / (M·K) and the compressive strength is 3.8Ma.

[0048] Example 2

[0049] Raw material preparation, including polysiloxane, polysiloxane and ammonia;

[0050] Solution preparation: polysiloxane, polysiloxane and ammonia are mixed and dissolved in an organic solvent to prepare a solution; an appropriate amount of Fe metal catalyst is added to promote the mixing reaction between the polysiloxane, polysiloxane and ammonia;

[0051] Fiber preparation, spinning, and electrospinning: The solution was injected into the electrospinning equipment with an electrospinning voltage of 18 kV, a flow rate of 6 ml / h, and a distance of 20 cm between the nozzle and the collector to form the preliminary structure of the silicon nitride fiber;

[0052] Gelation: by adding a cross-linking agent, methylene bisacrylamide, to cause a chemical reaction to form chemical bonds between polysiloxane, polysiloxane, and ammonia, so that the initial structure of the fiber is gelled to form silicon nitride gel;

[0053] Heat treatment: subjecting the silicon nitride gel to a high-temperature heat treatment in a nitrogen atmosphere. The high-temperature heat treatment temperature is 1800° C., the high-temperature heat treatment time is 5 hours, the heating rate of the high-temperature heat treatment is 16° C. / min, and the heating rate or cooling rate of the high-temperature heat treatment is the same, 16° C. / min, or cooling with the furnace during cooling. The high-temperature heat treatment helps to form the crystal structure of the silicon nitride;

[0054] Surface treatment: The silicon nitride fiber is surface treated with surface treatment agents polyurethane and polyetheretherketone.

[0055] The thermal conductivity of the prepared silicon nitride fiber is 0.37W / (M·K) and the compressive strength is 4.3Ma.

[0056] Example 3

[0057] Raw material preparation, including polysiloxane, polysiloxane and ammonia;

[0058] Solution preparation: polysiloxane, polysiloxane and ammonia are mixed and dissolved in an organic solvent to prepare a solution; an appropriate amount of Fe metal catalyst is added to promote the mixing reaction between the polysiloxane, polysiloxane and ammonia;

[0059] Fiber preparation, spinning, and electrospinning: The solution was injected into the electrospinning equipment with an electrospinning voltage of 13 kV, a flow rate of 4 ml / h, and a distance of 15 cm between the nozzle and the collector to form the preliminary structure of the silicon nitride fiber;

[0060] Gelation: by adding a cross-linking agent, methylene bisacrylamide, to cause a chemical reaction to form chemical bonds between polysiloxane, polysiloxane, and ammonia, so that the initial structure of the fiber is gelled to form silicon nitride gel;

[0061] Heat treatment: subjecting the silicon nitride gel to a high-temperature heat treatment in a nitrogen atmosphere at a temperature of 1500° C. for 4 hours and a heating rate of 12° C. / min. The heating rate or cooling rate of the high-temperature heat treatment is the same, 12° C. / min, or the temperature is cooled with the furnace during cooling. The high-temperature heat treatment helps to form the crystal structure of the silicon nitride;

[0062] Surface treatment: The silicon nitride fiber is surface treated with surface treatment agents polyurethane and polyetheretherketone.

[0063] The thermal conductivity of the prepared silicon nitride fiber is 0.49W / (M·K) and the compressive strength is 5.4Ma.

[0064] Example 4

[0065] Raw material preparation, including polysiloxane, polysiloxane and ammonia;

[0066] Solution preparation: polysiloxane, polysiloxane and ammonia are mixed and dissolved in an organic solvent to prepare a solution; an appropriate amount of Fe metal catalyst is added to promote the mixing reaction between the polysiloxane, polysiloxane and ammonia;

[0067] Fiber preparation, spinning, and electrospinning: The solution was injected into the electrospinning equipment with an electrospinning voltage of 11 kV, a flow rate of 3 ml / h, and a distance of 12 cm between the nozzle and the collector to form the preliminary structure of the silicon nitride fiber;

[0068] Gelation: by adding a cross-linking agent, methylene bisacrylamide, to cause a chemical reaction to form chemical bonds between polysiloxane, polysiloxane, and ammonia, so that the initial structure of the fiber is gelled to form silicon nitride gel;

[0069] Heat treatment: subjecting the silicon nitride gel to a high-temperature heat treatment in a nitrogen atmosphere. The high-temperature heat treatment temperature is 1400° C., the high-temperature heat treatment time is 5 hours, the heating rate of the high-temperature heat treatment is 8° C. / min, and the heating rate or cooling rate of the high-temperature heat treatment is the same, 8° C. / min, or cooling with the furnace during cooling. The high-temperature heat treatment helps to form the crystal structure of the silicon nitride;

[0070] Surface treatment: The silicon nitride fiber is surface treated with surface treatment agents polyurethane and polyetheretherketone.

[0071] The thermal conductivity of the prepared silicon nitride fiber is 0.55W / (M·K) and the compressive strength is 4.9Ma.

[0072] Example 5

[0073] Raw material preparation, including polysiloxane, polysiloxane and ammonia;

[0074] Solution preparation: polysiloxane, polysiloxane and ammonia are mixed and dissolved in an organic solvent to prepare a solution; an appropriate amount of Fe metal catalyst is added to promote the mixing reaction between the polysiloxane, polysiloxane and ammonia;

[0075] Fiber preparation, spinning, and electrospinning: The solution was injected into the electrospinning equipment with an electrospinning voltage of 14 kV, a flow rate of 4 ml / h, and a distance of 17 cm between the nozzle and the collector to form the preliminary structure of the silicon nitride fiber;

[0076] Gelation: by adding a cross-linking agent, methylene bisacrylamide, to cause a chemical reaction to form chemical bonds between polysiloxane, polysiloxane, and ammonia, so that the initial structure of the fiber is gelled to form silicon nitride gel;

[0077] Heat treatment: subjecting the silicon nitride gel to a high-temperature heat treatment in a nitrogen atmosphere. The high-temperature heat treatment temperature is 1700° C., the high-temperature heat treatment time is 2 hours, the heating rate of the high-temperature heat treatment is 6° C. / min, and the heating rate or cooling rate of the high-temperature heat treatment is the same, 6° C. / min, or cooling with the furnace during cooling. The high-temperature heat treatment helps to form the crystal structure of the silicon nitride;

[0078] Surface treatment: The silicon nitride fiber is surface treated with surface treatment agents polyurethane and polyetheretherketone.

[0079] The thermal conductivity of the prepared silicon nitride fiber is 0.52W / (M·K) and the compressive strength is 5.6Ma.

[0080] Example 6

[0081] Raw material preparation, including polysiloxane, polysiloxane and ammonia;

[0082] Solution preparation: polysiloxane, polysiloxane and ammonia are mixed and dissolved in an organic solvent to prepare a solution; an appropriate amount of Fe metal catalyst is added to promote the mixing reaction between the polysiloxane, polysiloxane and ammonia;

[0083] Fiber preparation, spinning, and electrospinning: The solution was injected into the electrospinning equipment with an electrospinning voltage of 16 kV, a flow rate of 6 ml / h, and a distance of 15 cm between the nozzle and the collector to form the preliminary structure of the silicon nitride fiber;

[0084] Gelation: by adding a cross-linking agent, methylene bisacrylamide, to cause a chemical reaction to form chemical bonds between polysiloxane, polysiloxane, and ammonia, so that the initial structure of the fiber is gelled to form silicon nitride gel;

[0085] Heat treatment: subjecting the silicon nitride gel to a high-temperature heat treatment in a nitrogen atmosphere. The high-temperature heat treatment temperature is 1300° C., the high-temperature heat treatment time is 3 hours, the heating rate of the high-temperature heat treatment is 9° C. / min, and the heating rate or cooling rate of the high-temperature heat treatment is the same, 9° C. / min, or cooling with the furnace during cooling. The high-temperature heat treatment helps to form the crystal structure of the silicon nitride;

[0086] Surface treatment: The silicon nitride fiber is surface treated with surface treatment agents polyurethane and polyetheretherketone.

[0087] The thermal conductivity of the prepared silicon nitride fiber is 0.39W / (M·K) and the compressive strength is 4.7Ma.

[0088] The equipment used in the present invention is simple, low-cost, and the preparation conditions are mild and controllable. A solution is prepared by mixing polysilicone, polysiloxane and ammonia, and the solution is spun, gelled and heat-treated to obtain silicon nitride fibers. Continuous silicon nitride fibers with high surface smoothness are obtained by electrospinning, and the silicon nitride fibers are gelled to make their structure more stable. The silicon nitride ceramic fibers prepared by the present invention have a smooth surface, and the fiber has high strength and high temperature resistance. It can be used to composite and toughen ceramic matrices and reduce thermal conductivity. It has great application potential in the field of high-temperature structural materials such as aerospace, and has low production costs.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing silicon nitride fiber, characterized in that: include: Raw material preparation, preparation of silicon source and nitrogen source; Solution preparation: mixing a silicon source and a nitrogen source and dissolving them in an organic solvent to prepare a solution; Adding an appropriate amount of catalyst to promote the mixing reaction between the silicon source and the nitrogen source; Fiber preparation, spinning, spraying the solution through a spinning device to form the preliminary structure of silicon nitride fiber; Gelation, by adding a cross-linking agent to carry out a chemical reaction to form a chemical bond between the silicon source and the nitrogen source, so that the initial structure of the fiber is gelled to form silicon nitride gel; Heat treatment: subjecting the silicon nitride gel to high-temperature heat treatment in an inert atmosphere. High-temperature heat treatment helps to form the crystal structure of silicon nitride; Surface treatment, treating the silicon nitride fiber with a surface treatment agent; The silicon source is polysiloxane or polysiloxane; the nitrogen source is ammonia; During the gelation process, the cross-linking agent in the chemical reaction is methylene bisacrylamide.

2. The method for preparing silicon nitride fiber according to claim 1, wherein: The catalyst in the solution preparation is one of GaN, Ga, and Fe.

3. The method for preparing silicon nitride fiber according to claim 1, wherein: The spinning process adopts electrostatic spinning, the solution is injected into the electrostatic spinning device, and the voltage, flow rate and distance between the nozzle and the collector of the electrostatic spinning device are adjusted.

4. The method for preparing silicon nitride fiber according to claim 3, characterized in that: The voltage of the electrospinning is 8-18 kV, the flow rate is 2-6 ml / h, and the distance between the nozzle and the collector is 10-20 cm.

5. The method for preparing silicon nitride fiber according to claim 1, wherein: The inert atmosphere during the heat treatment process is nitrogen or argon.

6. The method for preparing silicon nitride fiber according to claim 1, wherein: The high-temperature heat treatment temperature of the heat treatment process is 1300-1800°C, the high-temperature heat treatment time is 2-6h, the heat treatment process includes heating, heat preservation and cooling, the heating rate of the high-temperature heat treatment is 1-20°C / min, the heating rate or cooling rate of the high-temperature heat treatment is the same, 1-20°C / min, or cooling with the furnace during cooling.

7. The method for preparing silicon nitride fiber according to claim 1, characterized in that: The surface treatment agents are polyurethane and polyetheretherketone.