阅读说明：本技术 一种硼酸铝晶须及其制备方法和应用 (Aluminum borate whisker and preparation method and application thereof ) 是由 程艳玲 黎可旭 杨盛凯 张海南 魏世宏 林华泰 于 2019-08-27 设计创作，主要内容包括：本发明属于陶瓷材料领域,公开了一种硼酸铝晶须制备方法和应用。该方法是以水合氯化铝和尿素为原料,将氯化铝和尿素分别溶解在甲醇溶剂中,在一定温度加热溶解后,将尿素溶液加入到氯化铝溶液中,获得澄清透明的稳定前驱盐溶液,持续恒温加热搅拌,获得高浓度的前驱盐溶液,将获得的前驱盐溶液用旋涂法涂覆在Al<Sub>2</Sub>O<Sub>3</Sub>单晶基底上,放入氮化硼坩埚中,在氮气气氛保护下,在1000℃或1200℃进行煅烧,保温5h,最终在基底表面获得硼酸铝晶须,其相的含量与尿素含量和热处理温度有关。该方法制备工艺简单,生产成本低,所制备硼酸铝晶须的纯度高,形貌可控。可作为塑料、金属和陶瓷等的补强材料,用于航天、航空、建材、汽车等领域。(The invention belongs to the field of ceramic materials, and discloses a preparation method and application of aluminum borate whiskers. The method comprises the steps of taking aluminum chlorohydrate and urea as raw materials, respectively dissolving the aluminum chlorohydrate and the urea in a methanol solvent, heating and dissolving at a certain temperature, adding a urea solution into an aluminum chlorohydrate solution to obtain a clear and transparent stable precursor salt solution, continuously heating and stirring at a constant temperature to obtain a high-concentration precursor salt solution, and coating the obtained precursor salt solution on Al by a spin-coating method 2 O 3 Putting a single crystal substrate into a boron nitride crucible, calcining at 1000 ℃ or 1200 ℃ under the protection of nitrogen atmosphere, and preserving heat for 5 hours to finally obtain the aluminum borate whisker on the surface of the substrate, wherein the phase content of the aluminum borate whisker is related to the urea content and the heat treatment temperature. The method has the advantages of simple preparation process, low production cost, high purity of the prepared aluminum borate whisker and controllable appearance. Can be used as a reinforcing material of plastics, metals, ceramics and the like, and is used in the fields of aerospace, aviation, building materials, automobiles and the like.)

1. the preparation method of the aluminum borate whisker is characterized by comprising the following specific preparation steps:

S1, respectively dissolving aluminum chloride and urea in an alcohol solvent, and adding the urea solution into the aluminum chloride solution while stirring after the aluminum chloride and the urea are completely dissolved to obtain a precursor solution;

S2, continuously heating and stirring the precursor salt solution at a constant temperature to evaporate a solvent to obtain a precursor salt concentrated solution;

S3, coating the precursor salt concentrated solution on the cleaned alumina substrate;

And S4, placing the coated substrate in a boron nitride crucible, heating to 1000 ℃ or 1200 ℃ under the protection of nitrogen, and preserving heat to finally obtain the aluminum borate whisker.

2. the method for preparing aluminum borate whiskers as recited in claim 1, wherein: in step S1, the molar ratio of urea to aluminum chloride is 6: 1.

3. The method for preparing aluminum borate whiskers as recited in claim 1, wherein: in the step S1, the mass-to-volume ratio of the aluminum chloride to the alcohol solvent is 0.05-0.10 g/mL, and the mass-to-volume ratio of the urea to the alcohol solvent is 0.05-0.10 g/mL.

4. The method for preparing aluminum borate whiskers as recited in claim 1, wherein: the constant-temperature heating and stirring temperature in the step S2 is 80 ℃; the concentration of aluminum ions in the precursor salt concentrated solution is 0.4142 mol/L.

5. the method for preparing aluminum borate whiskers as recited in claim 1, wherein: in the step S4, the heating rate is 5-10 ℃/min, and the heat preservation time is 2-5 h; the flow rate of the nitrogen-protected atmosphere is more than or equal to 0.4L/min.

6. the method for preparing aluminum borate whiskers as recited in claim 1, wherein: in the step S4, the heating rate is 10 ℃/min, and the heat preservation time is 5 h; the flow rate of the nitrogen-protected atmosphere is 0.4L/min.

7. The method for preparing aluminum borate whiskers as recited in claim 1, wherein: in step S4, the temperature is raised to 1200 ℃.

8. Aluminum borate whiskers produced by the production method according to any one of claims 1 to 7.

9. Use of aluminum borate whiskers of claim 8, in the preparation of plastic, metal, and ceramic reinforcement materials.

10. The use of the aluminum borate whiskers of claim 8 in the preparation of refractory flame retardant coatings, catalyst substrate materials, electronic materials, and electromagnetic wave shielding materials.

Technical Field

the invention belongs to the field of ceramic materials, and particularly relates to an aluminum borate whisker and a preparation method and application thereof.

background

The aluminum borate whisker has stable performance, excellent mechanical performance and great applicability. The heat resistance temperature is 1200 ℃, the Mohs hardness is 7, the tensile strength is 7.84GPa, and the tensile elastic modulus is 392 GPa. Has high elasticity, good mechanical strength, heat resistance, chemical resistance, acid resistance (stable in 1mol/L hydrochloric acid at 70 ℃), electrical insulation and neutron absorption. Can be used as a reinforcing material of plastics, metals, ceramics and the like, and is used in the fields of aerospace, aviation, building materials, automobiles and the like; when the aluminum borate/aluminum borate composite material is used as a reinforcing material, the abrasion of a mold is small, when the content of aluminum borate reaches 30%, the mechanical strength can be enhanced by more than 1 time, and the tensile elastic modulus can be increased by more than two times. The tensile strength can be enhanced by more than 3 times when the material is used as a reinforcing material of light metal; when used as a plastic reinforcing agent, the composite material can play a role in reinforcing a plastic molding product with a tiny and complex shape compared with glass fiber, and endows the product with directionality; can also be used as a reinforcing material for polycarbonate resin. The aluminum borate whisker can also be used for fire-resistant flame-retardant coatings, catalyst base materials, electronic materials and electromagnetic wave shielding materials. The aluminum borate whisker has strong absorption capacity to neutrons, can prevent neutron radiation caused by nuclear change reaction, and has great development and application values.

the preparation method of the aluminum borate whisker mainly comprises a gas phase method, a melting-assisting method and the like. The vapor phase method is characterized in that water vapor is introduced into aluminum fluoride and boron oxide in a gas state at the temperature of 1000-1400 ℃ to obtain aluminum borate whiskers, and the experimental process of the method is difficult to operate; the melting method is characterized in that alumina and boron oxide react at 1200-1400 ℃, the boron oxide simultaneously plays a role of a fluxing agent, and finally the aluminum borate whisker is obtained; the fluxing method comprises adding fluxing agent (such as alkali metal chloride, sulfate or carbonate) into aluminum oxide and boron oxide, growing into whisker at 1000-1200 deg.C, reacting, treating with water, removing fluxing agent, and separating out whisker. The above methods all have the disadvantage of great difficulty in operation.

disclosure of Invention

In order to overcome the defects in the prior art, the invention mainly aims to provide a method for preparing aluminum borate whiskers, which comprises the following steps: the method comprises the steps of taking aluminum chlorohydrate and urea as raw materials, respectively dissolving the aluminum chlorohydrate and the urea in a methanol solvent, heating and dissolving at a certain temperature, slowly adding the urea solution into the aluminum chlorohydrate solution to obtain a clear and transparent stable precursor salt solution, continuously heating and stirring at a constant temperature to obtain a high-concentration precursor salt solution, coating the obtained precursor salt solution on an Al2O3 single crystal substrate by using a spin-coating method, putting the substrate into a boron nitride crucible, respectively calcining at 1000 ℃ and 1200 ℃ under the protection of nitrogen atmosphere, preserving heat for 5 hours, and finally obtaining aluminum borate whiskers on the surface of the substrate. The method has the advantages of easily obtained raw materials, low cost and low synthesis temperature, and can obtain the aluminum borate whisker with high purity without post-treatment.

The invention further aims to provide the boron nitride whisker prepared by the preparation method, and the boron nitride whisker has the advantages of controllable appearance and high purity.

The invention also aims to provide application of the aluminum borate whisker.

The purpose of the invention is realized by the following technical scheme:

The preparation method of the aluminum borate whisker comprises the following specific preparation steps:

S1, respectively dissolving aluminum chloride and urea in an alcohol solvent, and adding the urea solution into the aluminum chloride solution while stirring after the aluminum chloride and the urea are completely dissolved to obtain a precursor solution;

S2, continuously heating and stirring the precursor salt solution at a constant temperature to evaporate a solvent to obtain a precursor salt concentrated solution;

S3, coating the precursor salt concentrated solution on the cleaned alumina substrate;

And S4, placing the coated substrate in a boron nitride crucible, heating to 1000 ℃ or 1200 ℃ under the protection of nitrogen, and preserving heat to finally obtain the aluminum borate whisker.

Preferably, the molar ratio of urea to aluminum chloride in step S1 is 6: 1.

Preferably, in the step S1, the mass-to-volume ratio of the aluminum chloride to the alcohol solvent is 0.05-0.10 g/mL, and the mass-to-volume ratio of the urea to the alcohol solvent is 0.05-0.10 g/mL.

preferably, the constant-temperature heating and stirring temperature in the step S2 is 80 ℃; the concentration of aluminum ions in the precursor salt concentrated solution is 0.4142 mol/L.

Preferably, in the step S4, the temperature rising rate is 5-10 ℃/min, and the heat preservation time is 2-5 h; the flow rate of the nitrogen-protected atmosphere is more than or equal to 0.4L/min.

More preferably, the temperature rising rate in the step S4 is 10 ℃/min, and the heat preservation time is 5 h; the flow rate of the nitrogen-protected atmosphere is 0.4L/min.

preferably, the temperature rise in step S4 is to 1200 ℃.

the aluminum borate whisker prepared by the preparation method.

The aluminum borate whisker is applied to the preparation of plastic, metal and ceramic reinforcing materials.

The aluminum borate whisker is applied to the preparation of fire-resistant flame-retardant coatings, catalyst base materials, electronic materials and electromagnetic wave shielding materials.

compared with the prior art, the invention has the following advantages and effects:

(1) The raw materials required by the invention are from commercial purchase, are cheap and easily available products, and have higher safety coefficient.

(2) The calcination involved in the invention only adopts a commercial common tubular furnace, the required calcination temperature is lower, no toxic product is released in the reaction process, and no protective atmosphere or raw material with low safety coefficient is adopted.

(3) The invention adopts urea as the structure directing agent, and the product has better crystallinity and higher purity.

(4) The invention adopts the boron nitride crucible for heat treatment and introduces the boron source, thus leading the operation to be simpler.

Drawings

Figure 1 is an XRD pattern of the aluminum borate whisker prepared in example 1.

Figure 2 is an SEM topography of the aluminum borate whiskers prepared in example 1.

Figure 3 is an SEM topography of the aluminum borate whiskers prepared in example 2.

Detailed description of the invention

The following examples are presented to further illustrate the present invention and should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.