阅读说明：本技术 一种高纯纳米氧化铝的制备方法 (Preparation method of high-purity nano aluminum oxide ) 是由 闫德利 魏雨 林玉龙 姚春毅 于 2020-03-16 设计创作，主要内容包括：一种高纯纳米氧化铝的制备方法,其特征在于所述制备方法为：将Al(NO<Sub>3</Sub>)<Sub>3</Sub>和酒石酸的混合溶液缓慢滴加至聚乙烯醇溶胶中,再往混合溶液中加入氨水至碱性,脱水至干凝胶后再不低于1100℃温度下煅烧即得。所述制备方法可控且温和,不会产生传统制备氧化铝过程的氧气,避免氧气对设备的侵蚀；大大避免煅烧过程中氧化铝分子间的团聚,纳米氧化铝均匀度高、粒径分布范围窄、纯度较高,钠含量极低,可满足多领域的特殊应用。(A preparation method of high-purity nano alumina is characterized by comprising the following steps: mixing Al (NO) 3 ) 3 Slowly dripping the mixed solution of tartaric acid and polyvinyl alcohol sol, adding ammonia water into the mixed solution until the mixed solution is alkaline, dehydrating until xerogel, and calcining at the temperature of not lower than 1100 ℃ to obtain the product. The preparation method is controllable and mild, oxygen in the traditional alumina preparation process is not generated, and the corrosion of the oxygen to equipment is avoided; greatly avoiding alumina molecules in the calcining processThe nano alumina has high uniformity, narrow particle size distribution range, high purity and extremely low sodium content, and can meet the special application in multiple fields.)

1. A preparation method of high-purity nano alumina is characterized by comprising the following steps: mixing Al (NO)₃)₃Slowly dripping the mixed solution of tartaric acid and polyvinyl alcohol sol, adding ammonia water into the mixed solution until the mixed solution is alkaline, dehydrating until xerogel, and calcining at the temperature of not lower than 1100 ℃ to obtain the product.

2. The method of claim 1, wherein: the preparation method specifically comprises the following steps:

1) mixing Al (NO)₃)₃·9H₂Dissolving O and tartaric acid in deionized water to obtain a solution A;

2) dissolving polyvinyl alcohol in deionized water of 8-10 times by weight, and heating and stirring until the polyvinyl alcohol is completely dissolved to form uniform sol B;

3) slowly dripping the solution A obtained in the step 1) into the sol B under stirring, and continuously heating and stirring in a water bath for at least 30min to obtain a mixed solution C;

4) adding ammonia water into the solution C under stirring to adjust the pH value to be more than or equal to 9.2 to obtain viscous wet gel D;

5) the wet gel D is firstly subjected to heat preservation at 125-130 ℃ for 30-60 min, then is subjected to heat preservation at 155-160 ℃ for 60-90 min to obtain dry gel, and is ground into powder;

6) and (3) calcining the dry gel powder obtained in the step 5) at the temperature of at least 1100 ℃ for at least 4 hours.

3. The method according to claim 1 or 2, characterized in that: the Al (NO)₃)₃·9H₂O and tartaric acid are dissolved in deionized water according to the molar ratio of 2.3-3.0: 1.

4. The method according to any one of claims 1 to 3, wherein: the content of D-tartaric acid in the tartaric acid is not less than 50 mol%.

5. The method according to claim 1 or 2, characterized in that: the weight average molecular weight of the polyvinyl alcohol is between 6000 and 16000.

6. The method according to any one of claims 2 to 5, wherein: the speed of dripping the solution A into the sol B is 20-30 drops/min.

7. The high-purity nano alumina prepared by the method of any one of claims 1 to 6.

8. The use of the high purity nano alumina of claim 7, wherein the use comprises:

1) use in ceramics; and/or

2) Application in batteries; and/or

3) Application in heat insulating materials; and/or

4) Use in artificial gemstones; and/or

5) Application in semiconductor materials; and/or

6) The application in precision polishing materials.

9. Use according to claim 8, characterized in that said insulating material comprises in particular:

-the high purity nano alumina of claim 7;

-a sunscreen agent;

-reinforcing fibres.

10. Use according to claim 9, characterized in that the thermal insulation material is prepared by the following steps:

1) the high-purity nano alumina powder of claim 7 is uniformly mixed with an opacifier and reinforcing fibers to obtain a mixture;

2) mixing the mixture obtained in the step 1) at a speed of 300-345T/m²Pressing the aluminum oxide nano heat insulation plate.

Technical Field

The invention relates to the technical field of nano metal oxide materials, in particular to a preparation method of high-purity nano aluminum oxide.

Background

The molecular formula of the aluminum oxide is Al₂O₃According to the crystal structure, the crystal is divided into α, gamma, β, rho, kappa, theta and other crystal forms, wherein α -Al₂O₃The crystal form is a high-temperature stable crystal form, has a series of excellent performances such as high melting point, high hardness, high strength and the like, particularly excellent electrical insulation, irradiation resistance, high-temperature resistance and corrosion resistance, and very excellent chemical stability, and becomes an important functional material with military and civil values. The alumina polycrystal material is ideal high-temperature window material, infrared fairing material and wristwatch mirror material due to excellent optical and mechanical properties. Since the sixty-seven decades ago, efforts have been made to develop transparent alumina materials, but due to limitations of methods and processes, the optical transmittance of the prepared alumina materials is very low. Until the end of the last century, with the optimization of raw material preparation processes and the perfection of hot pressing processes, transparent spinel materials with excellent optical properties have not been developed by some. Some research departments in China also begin to develop alumina polycrystalline materials in the 90 s, and the performance indexes of the alumina polycrystalline materials exceed the level of the last century abroad at present and approach or catch up with the similar technical level of the world at one step.

The nano alumina refers to ultrafine alumina particles with the size of less than 100nm, and has good properties in thermal, optical, electrical, magnetic and chemical aspects due to the surface effect, quantum size effect, volume effect and macroscopic quantum tunneling effect of the nano particles, so that the nano alumina is applied to the high-tech fields of traditional industries, new materials, microelectronics, aerospace industries and the like. For example, the nano alpha alumina can improve the compactness, the smoothness, the cold and hot fatigue property, the fracture toughness, the creep resistance and the wear resistance of a high polymer material product of the ceramic; the nano alpha alumina can be used as a far infrared emission material and a thermal insulation material with excellent performance to be applied to chemical fiber products and high-pressure sodium lamps; nano-alpha alumina is also used to prepare YAG laser crystals and electrical insulating materials.

However, the preparation of nano alpha alumina is very difficult because the alpha phase transition temperature is above 1000 ℃, nano precursors (including nano gamma alumina, nano ammonium aluminum carbonate, nano aluminum hydroxide, etc.) must be calcined at a high temperature above 1000 ℃, and the nanoparticles will be seriously agglomerated and sintered in the process, and if the ultrafine alpha alumina is directly prepared by grinding the large-particle-size alpha alumina, the hardness of the alpha alumina is high, the loss of the grinding material is large, the particle size distribution is wide, and the ultrafine alpha alumina with narrow particle size distribution cannot be obtained, so that it is necessary to find a simple and efficient method for preparing monodisperse high-purity low-sodium nano alpha alumina.

The above background disclosure is only for the purpose of assisting understanding of the inventive concept and technical solutions of the present invention, and does not necessarily belong to the prior art of the present patent application, and should not be used for evaluating the novelty and inventive step of the present application in the case that there is no clear evidence that the above content is disclosed at the filing date of the present patent application.

Disclosure of Invention

The invention aims to provide a preparation method of high-purity nano alumina, which is controllable and mild, does not generate oxygen in the traditional alumina preparation process, and avoids the corrosion of the oxygen to equipment; the agglomeration among alumina molecules in the calcining process is greatly avoided, the nano alumina has high uniformity, narrow particle size distribution range, higher purity and extremely low sodium content, and can meet the special application in multiple fields.

The technical scheme adopted by the invention to achieve the aim comprises the following three aspects.

In a first aspect, the invention provides a preparation method of high-purity nano alumina, which comprises the following steps: mixing Al (NO)₃)₃Slowly dripping the mixed solution of tartaric acid and polyvinyl alcohol sol, adding ammonia water into the mixed solution until the mixed solution is alkaline, dehydrating until xerogel, and calcining at the temperature of not lower than 1100 ℃ to obtain the product.

The preparation method of the high-purity nano alumina comprises the following steps:

1) mixing Al (NO)₃)₃·9H₂Dissolving O and tartaric acid in deionized water to obtain a solution A;

2) dissolving polyvinyl alcohol in deionized water of 8-10 times by weight, and heating and stirring until the polyvinyl alcohol is completely dissolved to form uniform sol B;

3) slowly dripping the solution A obtained in the step 1) into the sol B under stirring, and continuously heating and stirring in a water bath for at least 30min to obtain a mixed solution C;

4) adding ammonia water into the solution C under stirring to adjust the pH value to be more than or equal to 9.2 to obtain viscous wet gel D;

5) the wet gel D is firstly subjected to heat preservation at 125-130 ℃ for 30-60 min, then is subjected to heat preservation at 155-160 ℃ for 60-90 min to obtain dry gel, and is ground into powder;

6) and (3) calcining the dry gel powder obtained in the step 5) at the temperature of at least 1100 ℃ for at least 4 hours.

The main chemical reactions occurring in the preparation method of the high-purity nano alumina are shown as the following formulas (1) and (2):

Al(NO₃)₃+3NH₃·H₂O→Al(OH)₃↓+NH₄NO₃(1)

2Al(OH)₃→Al₂O₃+3H₂O↑(2)

the method for preparing the high-purity nano alumina is distributed, the process is controllable and mild, the generated water vapor can be conveniently discharged and can be used for other purposes, such as heating, power generation and the like, oxygen in the traditional process of preparing the alumina is not generated, and the corrosion of the oxygen to equipment is avoided; in the method, polyvinyl alcohol sol is adopted to coat aluminum ions and aluminum hydroxide for calcination to prepare high-purity nano aluminum oxide, the polyvinyl alcohol is coated on the surfaces of aluminum ions and aluminum hydroxide through the coating of the polyvinyl alcohol sol, the contact growth among alumina crystal grains generated in the calcining process is blocked, the agglomeration among alumina molecules in the calcining process can be greatly avoided, further avoiding the grain diameter enlargement and the grain diameter distribution broadening caused by the over-speed growth of the crystal grains, the prepared nano-alumina has high uniformity and narrow grain diameter distribution range, the grains are in a sphere-like shape, the size is nano-scale, the crystal phase is alpha phase, in addition, sodium is not added in the method, the purity of the prepared final product nano aluminum oxide is higher, the sodium content is extremely low, can meet the special application of high-performance ceramics, transparent ceramics, lithium battery diaphragm materials, nanometer heat-insulating materials, artificial gemstones, precision polishing materials, semiconductor materials and the like.

In some preferred embodiments of the present invention, Al (NO) in the step 1)₃)₃·9H₂O and tartaric acid are dissolved in deionized water according to the molar ratio of 2.3-3.0: 1.

In other preferred embodiments of the present invention, the tartaric acid in step 1) has a content of D-tartaric acid of not less than 50 mol%, preferably not less than 60 mol%, more preferably between 66.7 and 75.0 mol%.

In some preferred embodiments of the present invention, Al (NO) in the solution A in the step 1) is₃)₃The molar concentration of (a) is 0.18 to 0.40 mol/L.

In some preferred embodiments of the invention, the heating in step 2) is to a temperature of at least 95 ℃.

In some preferred embodiments of the present invention, the stirring rate in the step 2) is 90 to 150 r/min.

In some preferred embodiments of the present invention, the polyvinyl alcohol in the step 2) has a weight average molecular weight of 6000 to 16000.

In some preferred embodiments of the present invention, the stirring rate in the step 3) is 90 to 120 r/min.

In some preferred embodiments of the present invention, the dropping speed of the solution a into the sol B in the step 3) is 20 to 30 drops/min.

In some preferred embodiments of the present invention, the concentration of the substance of the ammonia water in the step 4) is 0.1 to 0.5 mol/L.

In some preferred embodiments of the invention, the grinding in step 5) is to a powder to at least pass through a 200 mesh screen.

Under the preparation system of the above method, it has also been found that Al (NO)₃)₃·9H₂The O and the tartaric acid containing more D-tartaric acid are mixed and dissolved in the deionized water, the particle size uniformity of the nano alumina can be optimized on the microscopic level of the final product, and the average particle size D of the nano alumina₅₀Is 200nm, has a narrow particle size distribution range, and effectively reduces the agglomerate pile of nano alumina particles caused by high-temperature calcinationThe content and the particle are in a sphere-like shape, the size is nano, the crystal phase is α phase, the purity of the final product nano alumina is high, the sodium content is extremely low, and the special application in multiple fields can be met.

In a second aspect, the invention also provides high-purity nano alumina prepared by the method in the first aspect.

In a third aspect, the present invention also provides the use of the high purity nano alumina of the second aspect, wherein the use comprises:

1) use in ceramics; and/or

2) Application in batteries; and/or

3) Application in heat insulating materials; and/or

4) Use in artificial gemstones; and/or

5) Application in semiconductor materials; and/or

6) The application in precision polishing materials.

In some preferred embodiments of the present invention, the present invention further provides the use of the high purity nano alumina of the second aspect described above in a thermal insulation material, specifically comprising:

-the high purity nano alumina of the second aspect above;

-a sunscreen agent;

-reinforcing fibres.

In other preferred embodiments of the present invention, the opacifier is selected from at least one of zirconium silicate, zirconium oxide, silicon carbide, titanium dioxide or potassium titanate.

In other preferred embodiments of the present invention, the reinforcing fiber is selected from at least one of aramid fiber, orlon fiber, polyester fiber, nylon fiber, vinylon fiber, polypropylene fiber, polyimide fiber, high silica glass fiber, high strength glass fiber, high elastic glass fiber, chemical medium corrosion resistant glass fiber, quartz fiber, mullite fiber, alumina fiber, zirconia fiber, or alumina silicate fiber.

In other preferred embodiments of the present invention, the thermal insulation material is prepared by the steps of:

1) uniformly stirring and dispersing the high-purity nano alumina powder, the opacifier and the reinforcing fibers to obtain a mixture;

2) mixing the mixture obtained in the step 1) at a speed of 300-345T/m²Pressing the aluminum oxide nano heat insulation plate.

In other preferred embodiments of the present invention, the weight ratio of the high-purity nano alumina powder to the opacifier and reinforcing fibers in the heat insulating material is 5-50: 2-10: 1.

The invention has the beneficial effects that:

1) the method for preparing the high-purity nano alumina is distributed, the process is controllable and mild, the generated water vapor can be conveniently discharged and can be used for other purposes, such as heating, power generation and the like, oxygen in the traditional process of preparing the alumina is not generated, and the corrosion of the oxygen to equipment is avoided;

2) the polyvinyl alcohol sol is adopted to coat aluminum ions and aluminum hydroxide for calcination to prepare high-purity nano aluminum oxide, the polyvinyl alcohol is coated on the surfaces of the aluminum ions and the aluminum hydroxide through the coating of the polyvinyl alcohol sol, the contact growth among aluminum oxide crystal grains generated in the calcination process is blocked, the agglomeration among aluminum oxide molecules in the calcination process can be greatly avoided, the phenomenon that the grain size is enlarged and the grain size distribution is widened due to the over-speed growth of the crystal grains is further avoided, the prepared nano aluminum oxide has high uniformity and narrow grain size distribution range, the grains are in a quasi-spherical shape, the size is in a nano level, and the crystal phase is an alpha phase;

3) mixing Al (NO)₃)₃·9H₂The O and the tartaric acid containing more D-tartaric acid are mixed and dissolved in the deionized water, the particle size uniformity of the nano alumina can be optimized on the microscopic level of the final product, and the average particle size D of the nano alumina₅₀The particle size distribution range is narrow, the content of the agglomerate particle stack of the nano alumina particles caused by high-temperature calcination is effectively reduced, the particles are in a sphere-like shape, the size is nano, the crystal phase is α phase, the purity of the final product nano alumina is high, the sodium content is extremely low, and the special application in multiple fields can be met;

4) sodium is not added in the method, and the prepared final product nano-alumina has high purity and extremely low sodium content, and can meet the special application of high-performance ceramics, transparent ceramics, lithium battery diaphragm materials, nano heat-insulating materials, artificial gemstones, precision polishing materials, semiconductor materials and the like.

The invention adopts the technical scheme to provide the model essay, makes up the defects of the prior art, and has reasonable design and convenient operation.

Drawings

In order to make the aforementioned and other objects, features, and advantages of the invention, as well as others which will become apparent, reference is made to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is an SEM image of high purity nano alumina described in example 1 of the present invention;

FIG. 2 is an XRD image of the high purity nano alumina of example 1 of the present invention;

FIG. 3 is a particle size distribution diagram of the high purity nano alumina according to example 1 of the present invention.

Detailed Description

Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The present invention uses the methods and materials described herein; other suitable methods and materials known in the art may be used. The materials, methods, and examples described herein are illustrative only and are not intended to be limiting. All publications, patent applications, patents, provisional applications, database entries, and other references mentioned herein, and the like, are incorporated by reference herein in their entirety. In case of conflict, the present specification, including definitions, will control.

All percentages, parts, ratios, etc., are by weight unless otherwise indicated; "wt%" means weight percent; "mol%" means mole percent.

Herein, the term "made from … …" is equivalent to "comprising". As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

The conjunction "consisting of … … does not include any elements, steps or components not expressly listed. If present in a claim, the conjunction will limit the claim to the described materials and not to materials not described, but will still include impurities normally associated with those described materials. When the conjunction "consisting of … …" appears in the characterizing portion of the claim, rather than in the immediately preceding portion, it is limited to the elements set forth in the characterizing portion; other elements are not excluded from the claim as a whole.

The conjunction "consisting essentially of … …" is used to define a composition, method, or apparatus that includes additional materials, steps, features, components, or elements in addition to those materials, steps, features, components, or elements that are literally set forth, provided that such additional materials, steps, features, components, or elements do not materially affect the basic and novel characteristics of the claimed invention. The term "consisting essentially of … …" is in the intermediate zone between "comprising" and "consisting of … …".

The term "comprising" is intended to include embodiments encompassed by the terms "consisting essentially of … …" and "consisting of … …". Similarly, the term "consisting essentially of … …" is intended to include embodiments encompassed by the term "consisting of … …".

When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is described, the described range should be understood to include ranges of "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. Where numerical ranges are described herein, unless otherwise stated, the ranges are intended to include the endpoints of the ranges, and all integers and fractions within the ranges.

When the term "about" is used to describe a numerical value or an end point value of a range, the disclosure should be understood to include the specific value or end point referred to.

Furthermore, "or" means "or" unless expressly indicated to the contrary, rather than "or" exclusively. For example, condition a "or" B "applies to any of the following conditions: a is true (or present) and B is false (or not present), a is false (or not present) and B is true (or present), and both a and B are true (or present).

In addition, the indefinite articles "a" and "an" preceding an element or component of the invention are intended to mean no limitation on the number of occurrences (i.e., occurrences) of the element or component. Thus, "a" or "an" should be understood to include one or at least one and the singular forms of an element or component also include the plural unless the singular is explicitly stated.

The materials, methods, and examples described herein are illustrative only and not intended to be limiting unless otherwise specified. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

The present invention is described in detail below.