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CN-121990529-A - Preparation method of large-size high-length-diameter-ratio boron nitride fiber

CN121990529ACN 121990529 ACN121990529 ACN 121990529ACN-121990529-A

Abstract

The invention belongs to the technical field of inorganic functional materials, and discloses a preparation method of a large-size high-length-diameter-ratio boron nitride fiber. The method comprises the steps of (1) mixing a boron source and a nitrogen source according to a certain mass ratio, uniformly mixing in a solvent to obtain a precursor solution, (2) adding the precursor solution into a reaction kettle, cooling and crystallizing to room temperature after full reaction, filtering, washing and drying to obtain a white fibrous precursor, (3) calcining the fibrous precursor under a protective atmosphere to obtain a boron nitride fiber primary product, and (4) pickling the boron nitride primary product, filtering, washing and drying to obtain the high-purity boron nitride fiber. The boron nitride fiber prepared by the method has adjustable diameter of 1-300 mu m and length of 500-4000 mu m, the length-diameter ratio is up to 250-2000, and the purity is up to more than 99%. The whole process flow is simple and easy to control, low in cost, energy-saving and environment-friendly, and has obvious advantages in the aspects of manufacturing cost, product performance and the like.

Inventors

  • YE JUNWEI
  • Sun Caobo

Assignees

  • 大连理工大学

Dates

Publication Date
20260508
Application Date
20260129

Claims (6)

  1. 1. The preparation method of the large-size high-length-diameter-ratio boron nitride fiber is characterized by comprising the following steps: Step 1, mixing a boron source, a nitrogen source and an auxiliary agent according to a certain mass ratio, adding a solvent, stirring, adjusting the pH value and the temperature of the solution, and fully reacting to obtain a precursor solution; Step 2, adding the precursor solution obtained in the step 1 into a reaction kettle, regulating and controlling the reaction pressure and the reaction temperature under the stirring condition, slowly cooling after the reaction is finished, cooling and crystallizing to room temperature, filtering, and washing with a solvent to obtain a white fibrous precursor; Step 3, heating the fibrous precursor obtained in the step 2 to 1100-2000 ℃ for heat treatment for 2-20h under protective atmosphere after vacuum drying or freeze drying, and continuously cooling to room temperature under protective atmosphere to obtain a boron nitride fiber primary product; And 4, dispersing the boron nitride fiber primary product obtained in the step 3 in an acid solvent, soaking, stirring, filtering, washing and drying to obtain the high-purity large-size high-length-diameter-ratio boron nitride fiber.
  2. 2. The method for preparing the large-size high-length-diameter-ratio boron nitride fiber according to claim 1, wherein, In the step (1) of the process, The boron source is one of boric acid and metaboric acid; The nitrogen source is one of melamine and urea; the auxiliary agent is one of polyvinylpyrrolidone, polyethylene glycol, sodium hydrogen phosphate, disodium citrate, sodium hydroxide and sodium dodecyl benzene sulfonate; the solvent is one of deionized water, ethanol, isopropanol and tert-butanol.
  3. 3. The method for preparing the large-size high-length-diameter-ratio boron nitride fiber according to claim 1, wherein, In the step (1) of the process, The mass ratio of the nitrogen source to the boron source to the auxiliary agent to the solvent is 1:1-6:0.01-1:60-200; the pH value is 6-8, and besides the auxiliary agent, 0.1mol/L hydrochloric acid solution and 0.1mol/L NaOH solution can be used for adjusting the pH value; The reaction temperature is 10-90 ℃ and the reaction time is 0.5-5 h.
  4. 4. The method for preparing the large-size high-length-diameter-ratio boron nitride fiber according to claim 1, wherein, In the step 2 of the process, the process is carried out, The reaction time is 5-24 h, and the reaction temperature is 100-180 ℃; regulating the pressure in the reaction kettle by using nitrogen, air and helium, wherein the reaction pressure is 0.1-5 MPa; The cooling rate is gradient cooling, and the cooling rate is 0.1-0.5 ℃ per minute above 50 ℃ and 1-3 ℃ per minute below 50 ℃.
  5. 5. The method for preparing the large-size high-length-diameter-ratio boron nitride fiber according to claim 1, wherein, In the step 3 of the method, in the step (3), Vacuum drying temperature is 60-100 ℃, and freeze drying temperature is-40-65 ℃; The protective atmosphere comprises nitrogen, argon, helium or ammonia; The temperature rising rate is 2-15 ℃ per minute, and the temperature reducing rate is 3-10 ℃ per minute.
  6. 6. The method for preparing the large-size high-length-diameter-ratio boron nitride fiber according to claim 1, wherein, In the step 4 of the process, the process is carried out, The acidic solvent is one of 0.01-1 mol/L hydrogen chloride ethanol solution, 0.01-1 mol/L hydrochloric acid aqueous solution, 0.01-1 mol/L hydrochloric acid and hydrofluoric acid aqueous solution.

Description

Preparation method of large-size high-length-diameter-ratio boron nitride fiber Technical Field The invention belongs to the technical field of inorganic functional materials, and relates to a preparation method of a large-size high-length-diameter-ratio boron nitride fiber. Background Boron Nitride (BN) is the lightest III-V compound composed of two elements of boron and nitrogen, mainly comprises hexagonal phase h-BN, rhombohedral phase r-BN, cubic phase c-BN and wurtzite w-BN, and has wide application in the fields of aerospace, semiconductors, electronics, metallurgy, cosmetics, ceramics, nuclear industry and the like. The scaly boron nitride is the morphology with the largest industrial application at present, but has wide particle size distribution and easy agglomeration, compared with the fibrous boron nitride, the fibrous boron nitride has better advantages in terms of mechanics, heat, processing and application suitability, and the preparation process is the focus of attention of the current industrial industry and scientific community and still is in the technical research and development stage. The difference of the two types of boron nitride with different appearances is caused by the difference of a two-dimensional layered structure and a one-dimensional continuous structure, the preparation difficulty is attributed to the severe conditions of a strong covalent bond structure, a high melting point and crystal phase transformation, the h-BN layered structure has strong transverse growth tendency, an axially continuous growth fiber structure is difficult to form, and meanwhile, the formation by the traditional metal/polymer melt spinning process is difficult due to the poor plasticity of the boron nitride. In recent years, a research technology is available for preparing boron oxide fibers by high-temperature melting and wire drawing of boron oxide, and then preparing boron nitride fibers by nitriding the boron oxide fibers in an ammonia atmosphere. The other technology is to prepare the organic boron-containing polymer fiber by spinning technology, and prepare the fiber boron nitride by pyrolysis and nitridation, and the method has the problems of harsh synthesis conditions of polymer precursors, higher cost, high fiber shrinkage rate and easiness in crack generation. The invention patent CN117587549 provides a high-conversion boron nitride fiber, a continuous preparation method and a continuous preparation system thereof, which are characterized in that a boron nitride organic precursor (a mixture of aminoborane, aminocycloborane and aniline) is spun to obtain the precursor fiber, then the precursor fiber is coated with protective oil to obtain the precursor fiber with a protective oil layer on the surface, and then the precursor fiber is subjected to curing treatment under an oil-control inert atmosphere and inert atmosphere multi-temperature zone sintering treatment to obtain the boron nitride fiber. The invention patent CN104528671 adopts spray freeze drying technology to control the precursor to nucleate rapidly, avoid crystal growth, obtains flocculent fiber through freeze drying, and prepares porous boron nitride fiber through high temperature heat treatment. The invention patent CN117164365 is to mix and dissolve melamine, boric acid and water in proportion, then pour the mixture into a culture dish to obtain supersaturated precursor, then place (111) oriented nickel-based single crystal superalloy as seed crystal at the bottom center of the culture dish and parallel to the direction of an electric field, place the culture dish in an adjustable electric field, control the volatilization speed of the solvent, regulate the intensity of the electric field and control the orientation to obtain precursor fiber with high orientation, and then obtain boron nitride fiber through calcination treatment. The invention patent CN110629323B adopts the method of cooling the precursor solution by an organic solvent to prepare the boron nitride fiber with the diameter of 80-250nm and the length of 100-300 mu m. The technical methods have the characteristics, but have the problems of low purity, small size, low length-diameter ratio, complex preparation process flow, high energy consumption and the like of the prepared fibers to different degrees. There is a current urgent need to develop methods of preparing high aspect ratio boron nitride fibers. Disclosure of Invention The invention aims to provide a large-size high-length-diameter-ratio boron nitride fiber and a preparation method thereof, which realize the controllable preparation of the boron nitride fiber with adjustable large-size and length-diameter-ratio and high purity (more than 99 percent) and meet the requirements of high-end manufacturing fields of aerospace, semiconductors, nuclear power industry and the like. The technical scheme of the invention is as follows: A preparation method of a large-size high-length-diameter-ratio boron nitride