Reaction mechanism of alumina hollow sphere conversion preparation
Release time: 2025-04-30
The formation of a core-shell structure is crucial for the preparation of hollow sphere materials.
The formation of a core-shell structure is crucial for the preparation of hollow sphere materials. Understanding the formation mechanism of the core-shell structure is essential to exploring the experimental factors affecting alumina hollow sphere bricks. Currently, the formation mechanisms of core-shell structures can be mainly divided into three categories.
(1) Electrostatic Adsorption Mechanism
Electrostatic attraction adsorption relies on the electrostatic force between surface particles and particles with opposite charges in the solution to obtain a core-shell structure. This adsorption does not require any chemical bonds. Particles with opposite charges in the solution are adsorbed onto the core surface through Coulombic force to form a double electric layer. The double electric layer will promote the generation of the electrokinetic potential. The larger the potential, the greater the repulsive force, and the higher the particle dispersibility. When the repulsive force between particles is less than the attractive force between particles, the particles will aggregate. When the electrokinetic potential of the particles reaches zero, the repulsive force between the particles will disappear. During the preparation process, the nanoparticles can be surface-modified first, and a multilayer composite structure can be obtained through a layer-by-layer self-assembly process, and the template can be removed in subsequent processing. The preparation method based on this mechanism has the advantages of simple operation, good product stability, and controllable hollow sphere wall thickness.
(2) Chemical Bonding Mechanism
The chemical bonding mechanism suggests that the core matrix and the coating are bonded together through chemical bonds. Strong chemical bonds promote the formation of a uniform and dense coating, and the coating is difficult to detach. Cui Aili et al. prepared TiO2-Al2O3 core-shell composite particles and characterized the obtained samples using XPS. The binding energy of the 2p electrons of Ti changed before and after coating, indicating the formation of Al-O-Ti chemical bonds.
(3) Supersaturation Mechanism
The supersaturation mechanism suggests that when the pH of the solution reaches a certain fixed value, in a solution with heterogeneous substances, as long as the concentration reaches supersaturation, a large number of nuclei will deposit on the surface of the heterogeneous substances. This is because when the heterogeneous system undergoes nucleation and growth processes, new phases will be generated, thus reducing the increase in surface free energy of the system. Therefore, in a reaction system, crystals will preferentially choose to complete the nucleation and growth process at the heterogeneous interface.
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