Method for producing boron nitride-based composite spherical material by resin-assisted atomization molding

Abstract

The present application relates to a preparation method of resin-assisted atomized forming boron nitride-based composite spherical material, comprising the following steps: mixing uniformly aldehyde group-containing organic matter aqueous solution, amino compound, boron oxide compound and water under heating condition to obtain a high-fluidity uniform liquid resin; adding nitride powder or nano-oxide into the above uniform liquid resin, stirring uniformly to obtain a mixed slurry containing nitride powder or nano-oxide with solid content of 10wt%-30wt% and viscosity of 500-3000 mPa·S; drying and forming the mixed slurry into atomized particles, then performing heat drying treatment and high-temperature heat treatment in a protective atmosphere environment, so that the resin component is converted into boron nitride phase after high-temperature pyrolysis and in-situ nitriding reaction, and a boron nitride-based composite spherical material is obtained. This method forms a precursor spherical body through a resin adhesive, forms a BN phase and nitrides at high temperature, and solves the problem of high-temperature sintering of BN and other nitrides.

Description

Technical fields:

[0001] This invention relates to the field of advanced powder material synthesis technology for advanced nitride ceramics and their composite ceramics, specifically to a method for preparing boron nitride-based multiphase spherical materials by resin-assisted atomization molding. Background technology:

[0002] Ceramic microspheres possess significant application potential in materials science due to their high thermal conductivity, mechanical strength, wear resistance, and chemical stability. They can significantly improve the thermal conductivity of electronic packaging and the automotive industry, enhance the strength and wear resistance of composite materials, and serve as catalyst supports. The superior properties of ceramic microspheres also benefit 3D printing biomimetic materials in the biomedical field and coating materials for high-temperature and corrosive environments. The development of novel ceramic microspheres and their composites will drive technological progress and innovation in related industries.

[0003] Currently, research and development on boron nitride-based composite ceramic microspheres are relatively limited, despite the high application potential and advantages of spherical ceramic particles in many fields. In fact, preparing composite microspheres from boron nitride with other nitrides (such as Si3N4 or AlN) or oxides faces numerous challenges, primarily due to the lack of effective bonding strategies or adhesive materials. Because the surfaces of BN particles and other nitride or oxide particles exhibit very high chemical inertness, effective mass transfer bonding is difficult to achieve at high temperatures, making the preparation and development of composite microspheres containing boron nitride difficult. This significantly limits the development of boron nitride-based ceramic microspheres. Therefore, developing new methods to overcome these difficulties and prepare high-performance BN-containing composite ceramic microspheres to expand the applications of boron nitride and its composite ceramics is particularly important. This will not only fill the current technological gap but also provide significantly broader convenience and practicality for the application of nitride ceramics.

[0004] To address the aforementioned problems, this invention proposes an innovative method utilizing a precursor resin that can act as a binder for sprayed particles at low temperatures and can nitride-form a boron nitride framework that links nitride particles together at high temperatures. With the aid of this resin, the challenge of combining boron nitride particles with other ceramics due to their high-temperature chemical inertness is overcome. This significantly advances the industrial synthesis and production of nitride multiphase ceramic microspheres, and will contribute to improving the applications of boron nitride and its composite phase ceramic microspheres. Summary of the Invention:

[0005] This invention aims to provide a method for preparing boron nitride-based multiphase spherical materials by resin-assisted atomization molding. Using spray granulation technology, this resin is used as a binder to agglomerate and connect other ceramic particles to form a spherical precursor. The resin is then pyrolyzed at high temperature to form a boron nitride phase. Through a pyrolysis nitriding process, other nitride or oxide particles in the precursor spherical structure are nitrided and bonded to boron nitride at their particle edges / outer surfaces, or covalently bonded, thereby forming dense, morphology-invariant boron nitride-based multiphase spherical particles.

[0006] The technical solution to achieve the objective of this invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a boron nitride-based multiphase spherical material by resin-assisted atomization molding, the method comprising the following steps:

[0008] (1) An aqueous solution of an aldehyde-containing organic compound, an amino-containing compound, a boron-containing oxide compound, and water are mixed uniformly under heating conditions to obtain a highly fluid homogeneous liquid resin; the viscosity of the homogeneous liquid resin is greater than that of water and not greater than 50 mPa·s.

[0009] (2) Add nitride powder or nano oxide to the above uniform liquid resin, stir evenly, and obtain a mixed slurry with a solid content of nitride powder or nano oxide between 10wt% and 30wt% and a viscosity between 500 and 3000 mPa·S.

[0010] (3) The mixed slurry is atomized and dried into particles, and then heat-dried at 100-500℃ to obtain composite phase spherical precursor particle powder with spherical morphology.

[0011] (4) The composite phase spherical precursor particles are heat-treated in a protective atmosphere at a temperature range of 1100-1800℃, so that the resin components are transformed into boron nitride phase after high-temperature pyrolysis and in-situ nitriding reaction, thus obtaining boron nitride-based composite phase spherical materials.

[0012] Further, in step (1), the ratio of the amount of additional water (in milliliters) to the amount of the aqueous solution of the aldehyde-based organic compound (in milliliters) is in the range of 0.5-5; the molar ratio of the amino compound to the boron oxide compound is 1:(0.2-2); the heating temperature is 45℃~95℃, and the mixture is stirred evenly for 0.2~96 hours until a uniform liquid resin is obtained.

[0013] The solid content in step (2) refers to the proportion of the mass of nitride powder or nano oxide to the total mass of the mixture.

[0014] Further, in step (3), the mixed liquid resin, with the temperature maintained in the range of 25℃ to 90℃, is fed into an atomizing dry granulator with air as the hot air dry flow at a peristaltic feeding speed of 1mL / min to 50mL / min. The atomized particles are dried and shaped to obtain a fluffy white powder with a slight moisture content. After further heat drying treatment in a hot air flow oven at 100℃ to 500℃ for 1 to 48 hours, a composite phase spherical precursor particle powder with spherical morphology is obtained.

[0015] Preferably, the heating / cooling rate range of the heat drying process in step (3) is 1-20℃ / min, and the heat drying gas flow is air, nitrogen, or a mixture of nitrogen and air with an air content of no more than 5% by volume.

[0016] Furthermore, the aqueous solution of the aldehyde-containing organic compound in step (1) is a solution formed by dissolving formaldehyde or acetaldehyde in an aqueous solvent; wherein the content of formaldehyde or acetaldehyde in water is not less than 30 wt.%.

[0017] The boron-containing oxide is at least one of boron trioxide, boric acid, or borax.

[0018] Further, the amino-containing compound in step (1) is a nitrogen-containing compound containing an amino group, and is at least one of a guanidine-containing compound, an azole-containing nitrogen-containing compound, or a triazine-containing nitrogen-containing compound; the guanidine-containing compound is at least one of guanidine carbonate, cyanoguanidine, aminoguanidine, or aminoguanidine bicarbonate.

[0019] The azole-containing nitrogen-containing compound is 3-amino-1,2,4-triazole, and the triazine-containing nitrogen-containing compound is melamine;

[0020] When the system contains triazine or azole nitrogen compounds, a crosslinking inhibitor is added to prevent clumping and maintain a uniform liquid resin state.

[0021] Furthermore, the nitride powder is at least one of boron nitride nanosheets, boron nitride nanoparticles, amorphous boron nitride powder, boron nitride micron or nanofibers, commercial boron nitride powder, aluminum nitride micron or nanoparticle powder, and silicon nitride micron or nanoparticle powder; the nano oxide is at least one of titanium oxide, silicon dioxide, aluminum oxide, lanthanum oxide, molybdenum oxide, cerium oxide, zirconium oxide, yttrium oxide, or magnesium oxide.

[0022] Furthermore, the particle size distribution range of the commercial boron nitride powder is 5-30 micrometers; the average particle size of the aluminum nitride micron powder is 1-10 micrometers; and the average particle size of the silicon nitride micron powder is 1-10 micrometers.

[0023] Furthermore, in step (4), the heating / cooling rate of the heat treatment is 5-100℃ / min, the air flow rate is 10-2000ml / min, and the protective atmosphere is nitrogen, ammonia + nitrogen, or ammonia.

[0024] The atmosphere for heat treatment in the temperature range of 1500-1800℃ is nitrogen.

[0025] The atmosphere for heat treatment in the temperature range of 1100-1400℃ is ammonia or ammonia + nitrogen.

[0026] Secondly, the present invention provides a resin-assisted atomization molding of a boron nitride-based multiphase spherical material, obtained by the aforementioned preparation method. The boron nitride-based multiphase spherical material is a composite phase spherical particle of boron nitride and aluminum nitride, a composite phase spherical particle of boron nitride and silicon nitride, a composite phase spherical particle of boron nitride and boron nitride, or a composite phase spherical particle of boron nitride and oxide, wherein the boron nitride phase is a hexagonal boron nitride phase.

[0027] The boron nitride-based multiphase spherical material of the present invention has a particle size distribution ranging from a few micrometers to more than one hundred micrometers, and the spherical particles have high sphericity, high purity, and strong and dense multiphase connection.

[0028] The spray dryer involved in this invention is a commonly used industrial-grade atomizing dryer and granulator, and there is no need to modify or alter the equipment.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] The resin provided by this invention can be directly transformed into a boron nitride (BN) phase at high temperatures. During the high-temperature process, the direct nitriding reaction can achieve strong nitriding bonding at the edges or surfaces of the original nitride particles, enabling the obtained multiphase other nitride particles or nano-oxides to be well-bonded with the BN phase components, forming a spherical structure of the multiphase components with a high-strength bonding interface.

[0031] This invention creatively introduces BN components, which are difficult to sinter with other nitrides, into spherical precursors in the form of resin precursors with high adhesion. During high-temperature pyrolysis-nitriding, these resin precursors can form a stable aggregate, thus solving the previous technical problem of not being able to prepare spheres from multiple types of nitrides.

[0032] The method of this invention features a simple process flow, eliminating the need for complex steps and significantly simplifying the preparation process. The raw materials used are low-cost and readily available, resulting in significant economic benefits. The required equipment is simple, requiring no special design or modification, making it suitable for large-scale production. During high-temperature pyrolysis, the method of this invention exhibits high safety, reducing safety hazards associated with high-temperature operations.

[0033] The product obtained by this invention has high sphericity and high crystallinity, and the multiphase composition is stable and does not change. These characteristics provide a high raw material base for the production of multiphase nitride bulk ceramics and the formation of multiphase nitride coatings, making it economically valuable and highly versatile.

[0034] The method of this invention effectively solves the problem of difficult sintering and bonding of BN with other nitrides at high temperatures. During high-temperature in-situ nitriding or pyrolysis, the resin transforms into a stable BN phase, serving as a connecting framework for other nitride particles. This ensures the tight bonding of BN and other nitride particles during high-temperature sintering, ultimately forming a dense spherical shape. This not only improves the mechanical strength and thermal stability of the spheres but also solves the problem of maintaining the spherical structure at high temperatures in traditional methods.

[0035] The resin provided by this invention features flexible and controllable composition, facilitating the synthesis of highly spherical and controllable particle size nitride multiphase spherical structures. The resulting product exhibits high crystallinity, low porosity, high strength, and high density. The synthesis process is simple and easy to operate, with streamlined production steps, energy savings, and significant economic benefits. Attached image description:

[0036] To more clearly illustrate the technical solutions and product types of the present invention, the accompanying drawings used in the description of the embodiments are briefly described below. It should be emphasized that these accompanying drawings are only some embodiments of the present invention. For those skilled in the art, there is a possibility that other similar and related accompanying drawings may be extended and derived without creative effort. In the case of similar and related drawings as new creative embodiments, it shall be regarded as an infringement of the present invention.

[0037] Figure 1 The powder XRD diffraction patterns of the nitride multiphase spherical products formed by boron nitride and silicon nitride obtained in Example 1 at 1100°C and 1500°C in nitrogen, respectively;

[0038] Figure 2 This is a SEM image of the nitride multiphase spherical product formed by boron nitride and silicon nitride in nitrogen at 1100°C in Example 1.

[0039] Figure 3This is a SEM image of the nitride multiphase spherical product formed by boron nitride and silicon nitride in nitrogen at 1500°C in Example 1.

[0040] Figure 4 The powder XRD diffraction patterns of the spherical products of homogeneous nitride composites formed by boron nitride and boron nitride nanosheets obtained in Example 2 at 1100℃ and 1500℃ in nitrogen, respectively.

[0041] Figure 5 This is a SEM image of the spherical product formed by the homogeneous nitride composite of boron nitride and boron nitride nanosheets obtained in Example 2 at 1100°C in nitrogen.

[0042] Figure 6 This is a SEM image of the spherical product formed by the homogeneous nitride multiphase composite of boron nitride and boron nitride nanosheets obtained in Example 2 at 1500°C in nitrogen.

[0043] Figure 7 The powder XRD diffraction patterns of boron nitride and boron nitride nanospheres obtained in Examples 3 and 4 at 1500°C in nitrogen, and the spherical products formed by homogeneous nitride multiphase composites with commercial boron nitride bulk powder.

[0044] Figure 8 This is a SEM image of the spherical product formed by the homogeneous nitride multiphase composite of boron nitride and boron nitride nanospheres obtained in Example 3 at 1500°C in nitrogen.

[0045] Figure 9 This is a SEM image of a spherical product formed by homogeneous nitride multiphase composite of boron nitride and commercial boron nitride bulk powder obtained in nitrogen at 1500°C in Example 4.

[0046] Figure 10 The powder XRD diffraction patterns of the pure boron nitride microsphere powder products obtained in Example 5 at 1100°C and 1500°C in nitrogen atmosphere;

[0047] Figure 11 These are SEM images of the pure boron nitride microsphere powder products obtained in Example 5 at 1100°C and 1500°C in nitrogen.

[0048] Figure 12 This is a SEM image of the pure boron nitride microsphere powder product obtained in ammonia at 1100°C in Example 6.

[0049] Figure 13 This is a SEM image of the pure boron nitride microsphere powder product obtained in Example 7 at 1100°C under nitrogen atmosphere.

[0050] Figure 14 The XRD diffraction patterns of the nitride multiphase spherical products formed by boron nitride and aluminum nitride obtained in Example 8 at 1100°C and 1500°C in nitrogen;

[0051] Figure 15 This is a SEM image of the nitride multiphase spherical product formed by boron nitride and aluminum nitride in nitrogen at 1100°C in Example 8.

[0052] Figure 16 This is a SEM image of the nitride multiphase spherical product formed by boron nitride and aluminum nitride in nitrogen at 1500°C in Example 8. Detailed implementation method:

[0053] To better assist those skilled in the art in understanding this invention, practical examples will be used to further describe the details of the invention and to further analyze and clarify its method mechanism. It should be emphasized that the following examples are only used to more clearly illustrate the invention and should not be construed as limiting the scope of protection of this invention in any way. Those skilled in the art can make various improvements and adjustments based on the content of this invention, and these improvements and adjustments should still be included within the scope of protection of this invention.

[0054] Unless otherwise defined, the technical terms used in this invention have the same meaning as commonly understood by those skilled in the art. All raw materials, reagents, instruments, equipment and some consumable materials used in this invention can be purchased from the market or prepared by existing methods.

[0055] The present invention will be further described below with reference to embodiments:

[0056] This invention relates to a method for preparing boron nitride-based multiphase spherical materials by resin-assisted atomization molding, comprising the following four steps:

[0057] Step (1): Mix the aqueous solution of aldehyde-containing organic compound, amino-containing compound, boron-containing oxide compound and water under heating conditions to obtain a highly fluid homogeneous liquid resin; the viscosity of the homogeneous liquid resin is greater than that of water and not greater than 50 mPa·s.

[0058] The amino-containing compound is at least one of guanidine carbonate, cyanoguanidine, aminoguanidine, aminoguanidine bicarbonate, etc.; the boron-containing oxide compound is at least one of boron trioxide, boric acid, or borax, etc.

[0059] The heating temperature is 45℃~95℃, and the mixture is stirred evenly for 0.2~20 hours until a uniform liquid resin is obtained.

[0060] Preferably, the aqueous solution containing aldehyde-containing organic compounds is a solution formed by dissolving formaldehyde or acetaldehyde in an aqueous solvent; wherein the content of formaldehyde or acetaldehyde in the water is not less than 30 wt.%.

[0061] The formation mechanism of the highly fluid, homogeneous liquid resin in this step is as follows: Assuming an amino-containing compound (R-NH2) reacts with an aldehyde-containing organic compound (R-CHO), a condensation reaction occurs. The nitrogen atom in the amino group (-NH2) of the amino-containing compound is a nucleophile with a lone pair of electrons. When it encounters the carbon atom in the aldehyde group (-CHO), it forms an unstable bond, losing one molecule of water and forming an imine bond (C=N). Therefore, in this reaction, a relatively large amount of imine-bonded intermediates and water are initially generated. Subsequently, this intermediate containing multiple imine bonds undergoes an esterification reaction with the hydroxyl group in boric acid, producing water as a byproduct, forming a cross-linked structure with BO bridges, resulting in a resin with a low degree of cross-linking and a BO-linked network. Due to the low degree of cross-linking, the resin exhibits a certain degree of fluidity. By controlling the amount of water, this resin can be prepared into a highly fluid resin colloid.

[0062] Step (2): Add nitride powder or nano oxide to a homogeneous liquid resin and stir until homogeneous to obtain a mixed liquid resin;

[0063] The nitride powder is boron nitride, aluminum nitride, or silicon nitride powder, etc.; the nano oxide is at least one of titanium oxide, silicon dioxide, aluminum oxide, lanthanum oxide, molybdenum oxide, cerium oxide, zirconium oxide, yttrium oxide, or magnesium oxide, etc.

[0064] After being uniformly stirred for 0.1-10 hours within a temperature range of 25-95℃, a mixed liquid resin containing corresponding particles and uniformly dispersed in a uniform liquid resin is obtained. The mixed liquid resin is still in a liquid state, similar to an emulsion, and is called a mixed slurry.

[0065] In this step, the uniform liquid resin is a low-crosslinking and high-flow resin that can interact with the surface of these nitride powders or nano-oxides, so that these nitride powders or nano-oxides form a relatively uniform and unified mixed phase in the resin glue, without any signs of layering, agglomeration or phase separation, and can achieve a high degree of dispersion and uniform mixing.

[0066] Step (3): The mixed liquid resin is atomized and dried into particles, and then heat-dried at 100-500℃ to obtain multiphase spherical precursor particle powder with spherical morphology.

[0067] Specifically, a mixed liquid resin with a temperature maintained in the range of 25-90℃ is fed into an atomizing dryer granulator with air as the hot air dryer at a peristaltic feed rate of 1-50 mL / min. The atomized particles are dried and shaped to obtain a fluffy, slightly moist white powder. The powder is then dried in a hot air dryer oven at 100-500℃ for 1-48 hours to obtain a multiphase spherical precursor particle powder with spherical morphology.

[0068] In this step, the uniformly dispersed nitride powder or nano-oxide forms bonds with resin molecules, resulting in uniform dispersion of these nitride powders or nano-oxides within the mist droplets formed during spraying. In the hot airflow, the mist droplets rapidly dehydrate and dry, forming spherical particles with the lowest energy shape. These spheres are organic / inorganic polymer composite structures formed by the cured resin as the connecting framework and the nitride powder or nano-oxide as the filling phase, thus creating multiphase spherical precursor particle powder with spherical morphology.

[0069] The further thermal drying process of the resin enhances and strengthens the curing of the resin in the spherical particles. The curing mechanism is as follows: Under heating conditions, each monomer in the low-crosslinked resin further crosslinks to form a highly crosslinked structure. The residual amino and aldehyde groups in each monomer react with the reaction sites of adjacent monomers to generate more imine bonds. The hydroxyl groups of boric acid still react with the imine intermediate to form new boron-oxygen (BO) bridge bonds, allowing the monomers to connect with each other through BO bridge bonds. Through multiple crosslinking reactions, multiple monomers are linked together, resulting in a stable, highly crosslinked three-dimensional network structure solid resin. The highly crosslinked three-dimensional network structure solid resin contains a large number of boron-oxygen (BO) bridge bonds and forms a small number of BN bonds.

[0070] Step (4): The multiphase spherical precursor particles are heat-treated in a protective atmosphere at a temperature range of 1100-1800℃, so that the resin is transformed into the boron nitride phase after high-temperature pyrolysis and in-situ nitriding reaction (see Figure 10-13 ), thus obtaining boron nitride-based multiphase spherical materials (see Figure 2 , 3 5, 6, 8, 9, 15 and 16).

[0071] Under nitrogen at temperatures ranging from 1500 to 1800°C, the cured resin in the spherical precursor undergoes thermal decomposition, generating small-molecule waste gas containing hydrogen, carbon, nitrogen, and oxygen that escapes from the spherical reaction zone. Since the BO bonds are simultaneously nitrided into BN bonds, the newly formed BN bonds strengthen the bond between the surrounding boron nitride, aluminum nitride, or silicon nitride particles, ensuring the formation of structurally unchanged spherical nitride multiphase particles at the BN interface. This also ensures the stability of the crystal phases of the aluminum nitride, silicon nitride, and boron nitride particles (see...). Figure 1 , Figure 4 and Figure 7 The strong diffraction peaks in the XRD indicate that the high crystallinity of the aluminum nitride, silicon nitride, and boron nitride particles was not significantly weakened.

[0072] Under ammonia at temperatures ranging from 1100 to 1400°C, the cured resin undergoes thermal decomposition and is eroded by the ammonia gas. Simultaneously, the oxygen-containing portion generates water and detaches from the spherical body. Similarly, the already formed BN bonds maintain the spherical structural arrangement of each nitride particle, thus yielding nitride multiphase spherical particle products (where the amount of nitride or nano-oxide added is not zero) or boron nitride spherical particle products (where the amount of nitride or nano-oxide added is zero).

[0073] Example 1

[0074] 21 g of cyanoguanidine, 30 mL of water, and 15 g of boric acid were added to 20 mL of a 37 wt.% formaldehyde aqueous solution. After heating and stirring at 95 °C for 0.2 hours, 15 g of silicon nitride powder (particle size distribution range of 1-10 micrometers) was added. After uniform stirring at 65 °C for 5 hours, a mixed liquid resin with uniformly dispersed silicon nitride was obtained. The mixed liquid resin at 65 °C was pumped into the hot air flow chamber of the spray drying granulation unit at a feed rate of 5 mL / min using a peristaltic pump. The heat flow temperature in the chamber was set to 200 °C. Spherical powder was collected in the collection tower of the atomizing granulation equipment, and then subjected to hot air drying at 150 °C for 6 hours to obtain multiphase spherical precursor particle powder with spherical morphology. Finally, the multiphase spherical precursor particles were subjected to high-temperature pyrolysis and nitriding reactions in a high-temperature atmosphere furnace with a nitrogen flow rate of 10 ml / min at 1100℃ or 1500℃. After a 6-hour constant-temperature holding process, the particles were cooled to room temperature at the same cooling rate as the heating (10℃ / min). The sample was then removed from the high-temperature atmosphere furnace. The removed sample is the product of the multiphase spherical material of hexagonal boron nitride and silicon nitride (BN / Si3N4).

[0075] In this embodiment, the powder XRD diffraction patterns of the nitride multiphase spherical products were obtained at 1100℃ and 1500℃ in nitrogen atmosphere, respectively, as shown below. Figure 1 As shown, the respective SEM image photos are as follows: Figure 2 and Figure 3 As shown in the figure, this embodiment can obtain a boron nitride-based spherical multiphase material.

[0076] Example 2

[0077] After replacing silicon nitride in Example 1 with boron nitride nanosheet powder, the remaining steps are the same as in Example 1, resulting in a homogeneous multiphase spherical material of hexagonal boron nitride and boron nitride nanosheets (BN / BNNSs), which is in the form of powder particles, such as... Figure 4-6 As shown.

[0078] Example 3

[0079] By replacing the boron nitride nanosheets in Example 2 with boron nitride nanospheres, a homogeneous multiphase spherical material formed by hexagonal boron nitride and boron nitride nanospheres was obtained.

[0080] Example 4

[0081] By replacing the boron nitride nanospheres in Example 3 with commercial boron nitride powder, homogeneous multiphase spherical materials formed by hexagonal boron nitride and large-particle boron nitride bulk materials were obtained.

[0082] Example 5

[0083] In Example 1, no nitride powder was added, i.e., the weight of the nitride powder was changed to 0g, resulting in hexagonal boron nitride spherical particles. SEM images of the nitride multiphase spherical products were obtained at 1100℃ and 1500℃ in nitrogen atmosphere, respectively, as shown below. Figure 11 As shown.

[0084] Example 6

[0085] When nitrogen was replaced with ammonia in Example 5 at 1100°C, boron nitride spherical particles identical to those in Example 5 under nitrogen at 1100°C were obtained. SEM images of these particles are shown below. Figure 12 As shown.

[0086] Example 7

[0087] By replacing 30 mL of water in Example 5 with 10 mL, while keeping the other steps unchanged, a multiphase spherical material with controllable increase in the size of spherical particles was obtained.

[0088] In Examples 5-7, when the solid content of the nitride or oxide particles is 0 wt.%, the resulting spherical material is a pure boron nitride spherical particle powder product. However, the pure boron nitride microspheres obtained by the method of this invention have a very low crystallinity. Even after pyrolysis at temperatures above 1600°C, the spherical particles are still composed of highly isotropic, low-crystallinity, layered boron nitride. Simultaneously, due to the high aldehyde content, which can form a high-viscosity resin with amino groups, the final spherical particles have a large particle size. After heat treatment at higher temperatures, the crystallinity tends to remain low, and the surface remains highly smooth and rounded, with a more uniform and isotropic internal composition. The particle size is in the micrometer range. Low-crystallinity hexagonal boron nitride microspheres can be used as a reinforcing agent for ceramic composites to enhance the toughness and crack resistance of ceramic materials while maintaining good mechanical strength and heat resistance. They are very suitable for reinforcing structures in high-temperature composite ceramics, filling phases in flexible protective coatings under high-temperature extreme environments, and structurally flexible components in high-temperature electrical insulation composites. Compared to the general synthesis method of hexagonal boron nitride spherical particles that typically exhibit high crystallinity due to high temperatures, low-crystallinity hexagonal boron nitride spherical particles demonstrate superior performance in high-temperature flexibility and crack resistance compared to relatively high-crystallinity hexagonal boron nitride spherical particles.

[0089] Example 8

[0090] Replacing silicon nitride with aluminum nitride in Example 1, while keeping other conditions and operations unchanged, yielded a multiphase spherical material of hexagonal boron nitride and aluminum nitride (see Example 1). Figure 15 and Figure 16 However, the sample obtained at 1500℃ contained significant alumina impurities (see...). Figure 14 The XRD pattern calibration is shown in the figure.

[0091] Example 9

[0092] By replacing the cyanoguanidine in Examples 1-4 and 8 with one or a mixture of guanidine carbonate, aminoguanidine, aminoguanidine bicarbonate, 3-amino-1,2,4-triazole, or melamine, similar multiphase spherical materials can be obtained.

[0093] Example 10

[0094] By changing the 30 mL of water in Examples 1-4 and 8-9 to 15, 20, 40, 75, or 100 mL, while keeping other operations unchanged, similar multiphase spherical materials can be obtained. The slight difference is that when the water volume is in the range of 40, 75, or 100 mL, the stirring temperature is between 45 and 80 °C. The difference is that the particle size of the spherical particles gradually decreases with the increase of water volume. When the temperature is below 65 °C, the reaction time needs to be extended to ensure the formation of the resin. This process can take up to 20 hours to complete. In Example 1, since the temperature is a relatively high 95 °C, 0.2 hours is acceptable. In fact, the reaction time is completely controllable between 0.2 and 20 hours.

[0095] Example 11

[0096] In Example 1, the amount of cyanoguanidine used is between 4.1-40g, or the amount of boric acid used is between 3.1-31g, or it is replaced with boron trioxide with an amount between 4-34g, or it is replaced with borax with an amount between 19.1-190g, or the concentration of formaldehyde solution is changed to 30wt.%, or it is replaced with an aqueous solution of acetaldehyde. Changing the amount of boron-containing oxide compound added and the mass of aldehyde-containing organic compound can all yield similar multiphase spherical materials. The difference is that when acetaldehyde is used, with a lower amount of boron-oxygen raw material, the temperature range of the air drying treatment needs to be 400-500℃, and the heat drying time needs to be increased to 36-48 hours to facilitate the pre-removal of some excessive carbon impurities.

[0097] Example 12

[0098] In Example 11, the nitrides can be replaced by boron nitride nanoparticles, amorphous boron nitride powder, boron nitride micron or nanofibers, commercially available large-particle-size boron nitride powder (5-30 microns), aluminum nitride micron (1-10 microns) or nanoparticles, silicon nitride nanoparticles, or nano-oxide powders, to obtain similar multiphase spherical materials. The difference is that using aluminum nitride nanoparticles will result in increased alumina impurities. When the nitrides are silicon nitride, well-crystallized boron nitride nanosheets, and commercially available boron nitride, the stirring temperature can be in the range of 65-95°C. Increased temperature promotes resin reactivity, and the reaction can be completed in as little as 0.1-1 hour. This yields corresponding nitride composite microspheres and boron nitride and oxide composite microspheres.

[0099] Example 13

[0100] By replacing the hot drying air in Example 12 with ordinary nitrogen or a mixture of nitrogen and air with an air content not exceeding 5% by volume, and by setting the heating / cooling rates to 1, 5, 15, and 20 °C / min, and then changing the subsequent high-temperature pyrolysis heating programs to 5, 15, 40, 60, and 100 °C / min, similar products were obtained.

[0101] Example 14

[0102] After setting the high-temperature pyrolysis temperature in Example 13 to 1600 and 1800℃, and adjusting the airflow to 20, 200, 800, 1400 and 2000 ml / min respectively, the heating rate was in the range of 5-100℃, and the heat treatment time was 4 hours and 1 hour respectively, similar products could be obtained.

[0103] Example 15

[0104] By changing the high-temperature pyrolysis temperature in Example 14 to 1100, 1200 and 1400°C respectively, and changing the protective atmosphere to ammonia or ammonia + nitrogen respectively, the target temperature duration was 12, 8 and 6 hours respectively, and similar products were obtained. The difference was that the alumina impurities in the boron nitride / aluminum nitride multiphase were significantly reduced.

[0105] Example 16

[0106] By changing the solid content of the nitride powder in Example 1 and adjusting the amount of silicon nitride powder added to any amount of 9.56-36g, a product similar to that in Example 1 was obtained. When the amount of silicon nitride powder added was higher than 20g, the particle size of the spherical particles showed a significant increasing trend.

[0107] Example 17

[0108] When the atomization granulation temperature in Example 1 is within the range of 120-200℃, and the temperature is selected within the range of 100-400℃, the drying process generally requires 36-48 hours to completely evaporate the moisture, and similar products are obtained in the same way.

[0109] Without departing from the basic principles, basic raw materials, and basic route of this invention, any non-inventive techniques and processes that make at least one or more substitutions, simplifications, replacements, modifications, improvements, alterations, and additions to experimental steps and raw materials to synthesize boron nitride spherical products or nitride multiphase spherical particle products similar to those produced by this invention, as well as any acts of applying boron nitride spherical products or nitride multiphase spherical particle products prepared using the techniques of this invention to any field, shall be deemed as infringement of the scope of protection of this invention.

[0110] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A method for preparing a boron nitride-based multiphase spherical material by resin-assisted atomization molding, characterized in that, The preparation method includes the following steps: (1) An aqueous solution of an aldehyde-containing organic compound, an amino-containing compound, a boron-containing oxide compound, and water are mixed uniformly under heating conditions to obtain a highly fluid homogeneous liquid resin; the viscosity of the homogeneous liquid resin is greater than that of water and not greater than 50 mPa·s. The aqueous solution containing aldehyde-based organic compounds in step (1) is a solution formed by dissolving formaldehyde or acetaldehyde in an aqueous solvent; wherein the content of formaldehyde or acetaldehyde in water is not less than 30 wt.%. (2) Add nitride powder or nano oxide to the above uniform liquid resin, stir evenly, and obtain a mixed slurry with a solid content of nitride powder or nano oxide between 10wt% and 30wt% and a viscosity between 500 and 3000 mPa·S. The nitride powder is at least one of the following: boron nitride nanosheets, boron nitride nanoparticles, amorphous boron nitride powder, boron nitride micron or nanofibers, commercial boron nitride powder, aluminum nitride micron or nanoparticle powder, and silicon nitride micron or nanoparticle powder. The nano-oxide is at least one of titanium oxide, silicon dioxide, aluminum oxide, lanthanum oxide, molybdenum oxide, cerium oxide, zirconium oxide, yttrium oxide, or magnesium oxide; (3) The mixed slurry is atomized and dried into particles, and then heat-dried at 100-500℃ to obtain composite phase spherical precursor particles with spherical morphology; the composite phase spherical precursor particles are organic / inorganic polymer composite structures with cured resin as the connecting framework and nitride powder or nano oxide as the filling phase. Under heating conditions, each monomer in the low crosslinked resin further crosslinks to form a highly crosslinked structure. The residual amino and aldehyde groups in each monomer react with the reaction sites of adjacent monomers to generate more imine bonds. The hydroxyl groups of boric acid still react with the imine intermediate to form new boron-oxygen (BO) bridge bonds, which allow the monomers to connect with each other through BO bridge bonds. Through multiple crosslinking reactions, multiple monomers are connected together, resulting in a stable highly crosslinked three-dimensional network structure solid resin. The highly crosslinked three-dimensional network structure solid resin contains a large number of boron-oxygen (BO) bridge bonds and forms a small number of BN bonds. (4) The composite phase spherical precursor particles are heat-treated in a protective atmosphere at a temperature range of 1100-1800℃, so that the resin components are transformed into boron nitride phase after high-temperature pyrolysis and in-situ nitriding reaction, thus obtaining boron nitride-based composite phase spherical materials.

2. The preparation method according to claim 1, characterized in that, In step (1), the ratio of the amount of additional water to the amount of the aldehyde-based organic aqueous solution is in the range of 0.5-5, and the amounts of the additional water and the aldehyde-based organic aqueous solution are measured in milliliters; the molar ratio of the amino compound to the boron oxide compound is 1:(0.2-2); the heating temperature is 45℃~95℃, and the mixture is stirred evenly for 0.2~96 hours until a uniform liquid resin is obtained; the solid content in step (2) refers to the proportion of the mass of the nitride powder or nano oxide to the total mass of the mixture.

3. The preparation method according to claim 1, characterized in that, In step (3), the mixed liquid resin, with the temperature maintained in the range of 25℃ to 90℃, is fed into the atomizing dry granulator with the temperature range of 120℃ to 300℃ and the hot air dry air flow at a peristaltic feeding speed of 1mL / min to 50mL / min. The atomized particles are dried and shaped to obtain a fluffy white powder with a slight moisture content. After further heat drying in a hot air flow oven at 100℃ to 500℃ for 1 to 48 hours, a composite phase spherical precursor particle powder with spherical morphology is obtained.

4. The preparation method according to claim 3, characterized in that, The heating / cooling rate range of the heat drying process in step (3) is 1-20℃ / min, and the heat drying gas flow is air, nitrogen, or a mixture of nitrogen and air with an air content of no more than 5% by volume.

5. The preparation method according to claim 1, characterized in that, The boron-containing oxide is at least one of boron trioxide, boric acid, or borax.

6. The preparation method according to claim 1, characterized in that, The amino-containing compound in step (1) is a nitrogen-containing compound containing an amino group, and is at least one of a guanidine-containing compound, an azole-containing nitrogen-containing compound, or a triazine-containing nitrogen-containing compound; the guanidine-containing compound is at least one of guanidine carbonate, cyanoguanidine, aminoguanidine, or aminoguanidine bicarbonate. The azole-containing nitrogen-containing compound is 3-amino-1,2,4-triazole, and the triazine-containing nitrogen-containing compound is melamine; When the system contains triazine or azole nitrogen compounds, a crosslinking inhibitor is added to prevent clumping and maintain a uniform liquid resin state.

7. The preparation method according to claim 1, characterized in that: The particle size distribution range of the commercial boron nitride powder is 5-30 micrometers; the average particle size of the aluminum nitride micron powder is 1-10 micrometers; and the average particle size of the silicon nitride micron powder is 1-10 micrometers.

8. The preparation method according to claim 1, characterized in that, In step (4), the heating / cooling rate of the heat treatment is 5-100℃ / min, the air flow rate is 10-2000ml / min, and the protective atmosphere is nitrogen, ammonia + nitrogen or ammonia. The atmosphere for heat treatment in the temperature range of 1500-1800℃ is nitrogen. The atmosphere for heat treatment in the temperature range of 1100-1400℃ is ammonia or ammonia + nitrogen.

9. A resin-assisted atomization molding of boron nitride-based multiphase spherical material, characterized in that, The boron nitride-based multiphase spherical material is obtained by any of the preparation methods described in claims 1-8. It is a composite phase spherical particle of boron nitride and aluminum nitride, a composite phase spherical particle of boron nitride and silicon nitride, a composite phase spherical particle of boron nitride and boron nitride, or a composite phase spherical particle of boron nitride and oxide, wherein the boron nitride phase is a hexagonal boron nitride phase.

10. The multiphase spherical material according to claim 9, characterized in that, The particle size distribution of boron nitride-based multiphase spherical materials ranges from a few micrometers to one hundred micrometers.

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