Search

CN-121990597-A - Preparation method of alpha-phase nano alumina particles based on gas phase heterogeneous nucleation

CN121990597ACN 121990597 ACN121990597 ACN 121990597ACN-121990597-A

Abstract

The invention discloses a method for preparing alpha-phase nano alumina particles based on gas phase heterogeneous nucleation, belonging to the field of nano material preparation. The method comprises the steps of mixing an aluminum salt precursor and alpha-phase alumina seed crystal to form a solution, and spraying the solution into high-temperature flame through atomization. By introducing seed crystal as heterogeneous nucleation template and regulating flame temperature and particle residence time cooperatively, the gas phase species produced by precursor pyrolysis grow epitaxially on the surface of the seed crystal preferentially and alpha-phase nanometer alumina is synthesized directly in one step. The invention solves the difficult problems that the traditional flame method is difficult to directly synthesize alpha phase and needs subsequent calcination, has simple process, is suitable for continuous production, and has high product purity and good dispersibility.

Inventors

  • HU YANJIE
  • JIANG HAO
  • LI CHUNZHONG
  • LIANG PEIRAN

Assignees

  • 华东理工大学

Dates

Publication Date
20260508
Application Date
20260316

Claims (7)

  1. 1. A method for preparing alpha-phase nano alumina particles based on gas phase heterogeneous nucleation is characterized by dissolving an aluminum salt precursor in an organic solvent, adding alpha-phase nano alumina seed crystals to form a precursor solution, atomizing the solution, spraying the solution into high-temperature flame for reaction, and enabling gas phase Al-O clusters generated by pyrolysis of the aluminum salt precursor to be preferentially adsorbed on active sites of the seed crystal by synergistically regulating and controlling the reaction temperature of a flame high-temperature region and the effective residence time of the particles in the high-temperature region, so that the alpha-phase nano alumina particles are directly generated by heterogeneous nucleation and epitaxial growth. The alpha phase content of the synthesized alpha phase nano alumina particles is more than or equal to 80 percent, the primary particle diameter is adjustable within the range of 20 nm-5 mu m, and the grain size distribution is uniform.
  2. 2. The method according to claim 1, wherein the alpha-phase nano alumina seed crystal has a particle size of 1-200 nm and the addition amount is 0.1% -20% of the theoretical alumina yield.
  3. 3. The method according to claim 1, wherein the effective residence time of particles in the flame high temperature zone is 1-100 ms, and the effective reaction volume, the precursor feeding volume flow, the flame supporting gas volume flow and other parameters are regulated and controlled together.
  4. 4. The method of claim 1, wherein the reaction temperature in the flame high temperature zone is 800-2000 ℃ and is regulated and controlled by parameters such as the type of the precursor organic solvent, the type proportion of the flame supporting gas, the volume flow and the like.
  5. 5. The method of any one of claims 1 to 4, wherein the aluminum salt precursor comprises aluminum nitrate, aluminum chloride, aluminum alkoxide, or a combination thereof.
  6. 6. The method of any one of claims 1 to 4, wherein the precursor organic solvent is an alcohol, a ketone, a carboxylic acid, an ester, a hydrocarbon or a combination thereof, or a system mixed with water.
  7. 7. The method according to any one of claims 1 to 4, wherein the flame supporting gas consists of small molecule hydrocarbons such as hydrogen, methane, propane or mixtures thereof with air or oxygen.

Description

Preparation method of alpha-phase nano alumina particles based on gas phase heterogeneous nucleation Technical Field The invention belongs to the technical field of nano material preparation, and particularly relates to a method for directly preparing alpha-phase nano alumina particles in a flame spray pyrolysis process based on a gas phase heterogeneous nucleation mechanism. Background Alumina (Al 2O3) has various crystal forms of gamma, theta, alpha and the like, wherein alpha-phase alumina (corundum) is widely applied to the fields of advanced ceramics, catalyst carriers, wear-resistant coatings, composite material reinforcing phases, optical devices and the like due to the highest thermal stability, chemical inertness, hardness and excellent mechanical, optical and electrical properties. The nano-scale alpha-phase alumina can further improve the performance of the nano-scale alpha-phase alumina in the application scene by virtue of higher specific surface area and surface activity, so that the development of the efficient nano-alpha-phase alumina preparation technology has important significance. The conventional method for preparing alpha-phase alumina needs to convert transition phases (gamma, theta phases) into alpha phases by high-temperature calcination (usually >1200 ℃), which is easy to cause particle sintering, growth and hard agglomeration, and fine dispersed nano particles are difficult to obtain. In order to solve the problem, researchers have developed sol-gel methods, hydrothermal methods, precipitation methods, etc., but these methods have disadvantages of complicated processes, long period, low yield, or the need of using complex additives, etc. Flame Spray Pyrolysis (FSP) has the potential of one-step synthesis as a continuous, high-yield nanoparticle preparation technique. However, the synthesis of pure alpha phase alumina directly by conventional FSP still presents significant challenges. According to classical nucleation theory, in a flame high temperature environment, condensation nucleation of alumina vapor phase species mainly comprises two paths of homogeneous nucleation and heterogeneous nucleation, wherein the homogeneous nucleation needs to overcome a higher thermodynamic barrier, and in a very short residence time of flame (generally <200 ms), the system tends to form metastable transition phases (such as gamma and theta phases) which are easier to generate dynamically, and it is difficult to directly form alpha phases which are the most stable in thermodynamics but have higher nucleation energy barriers. In contrast, heterogeneous nucleation takes pre-added alpha-phase nano alumina seed crystals as a nucleation substrate, and can remarkably reduce nucleation activation energy. Because the seed crystal provides a growth interface with matched structure, the new alumina can directly form alpha phase through an epitaxial growth mechanism, thereby effectively avoiding the generation of metastable phase and providing possibility for realizing high-selectivity synthesis of alpha phase under the flame transient condition. In the existing technology for preparing alumina by a flame method, a heterogeneous nucleation mechanism is not fully utilized, and a seed crystal is not definitely used as a core induction site for heterogeneous nucleation of a gas phase, so that the alpha phase conversion rate is low, and the crystal phase of a product is impure. Therefore, the method for preparing the high-purity alpha-phase nano-alumina by taking the seed crystal induced gas phase heterogeneous nucleation as a core and combining the synergistic regulation and control of flame T-tau parameters can effectively solve the pain point of the prior art, and has important industrial application value and scientific theoretical significance. Disclosure of Invention The invention aims to overcome the defects of the prior art and provide a flame combustion preparation method which takes seed crystal induced gas phase heterogeneous nucleation as a core, has simple process, continuous and high efficiency and lower cost, and can directly prepare high-purity, fine and well-dispersed alpha-phase nano alumina particles. The core concept of the invention is based on classical heterogeneous nucleation and crystal growth theory, and a triple synergistic mechanism for realizing efficient alpha-heterogeneous nucleation in flame gas phase synthesis is disclosed for the first time: (1) And a structural template mechanism is adopted, wherein alpha-phase alumina seed crystals are selected as an active substrate. The stable hexagonal crystal system structure is homogenous with the target product, and provides a crystallographically compatible epitaxial growth template for new alumina species in the flame, so that the interfacial energy barrier of heterogeneous nucleation is effectively reduced; (2) A T-tau cooperative mechanism, namely finding a cooperative regulation rule of temperature (T) and stay time (tau) in a flam