What does coating nanoparticles mean?
As the name suggests, the process of applying a substance to the surface of a particle to modify it to form a composite particle is called coating of the nanoparticle. It has been found that this process can achieve uniform dispersion between different phase particles, and fully exert the excellent characteristics of different phase particles, and use it as a reinforcing particle. Because aluminum, iron-based, ceramic-based materials can have excellent properties such as high specific strength, wear resistance, small thermal expansion coefficient, and low cost, coating nanoparticles are widely used in aerospace, aviation, automotive, chemical, electronics, etc.
A typical representative of coated nanoparticles
Magnetic nanoparticles are nano-sized particles, generally composed of a magnetic core composed of a metal oxide such as iron, cobalt, or nickel, and a high molecular polymer/silicon/hydroxyapatite shell layer wrapped around a magnetic core. The most common core layer is made of Fe3O4 or γ-Fe2O3 with superparamagnetic or ferromagnetic properties. It has magnetic orientation (targeting). Under the action of external magnetic field, it can realize directional movement, convenient positioning and separation from medium. . Among them, the most common one is peg coated iron oxide nanoparticles.
Several satisfactory research results
Nanomaterials themselves exhibit different properties from conventional materials in terms of optical, thermal, electrical, magnetic, mechanical, physical, and chemical properties due to quantum size effects, surface effects, and macroscopic quantum tunneling effects that conventional materials do not possess. Moreover, the addition of nanoparticles can also improve the performance of traditional organic coatings. This topic has become a hot spot in the field of organic coatings research, and has obtained some satisfactory results:
Using the electromagnetic and optical properties of the nanoparticles to produce a multifunctional coating with stealth function;
The use of nanoparticles has a stronger flop effect, resulting in a more decorative coating for luxury car topcoats;
The addition of nanoparticles can also improve the aging resistance and protective properties of the coating;
Utilizing the absorption of ultraviolet rays by titania nanoparticles to form an ultraviolet shielding coating;
In the field of anti-corrosion coatings, in addition to improving the performance of the coating by adding nanoparticles, the nanoparticles can be further modified by the nanoparticles to improve the protection of the material.
The process of coating nanoparticles (taking SiC as an example)
The principle is to use the coated particles as a nucleation matrix to control the concentration of the coating material between the critical value required for non-uniform nucleation and the critical value required for uniform nucleation, so that the nucleus of the coating material grows on the surface of the coated particles. The key to the process is to control the concentration of the appropriate coating material precipitation reaction and maintain the stable suspension characteristics of the coated particles.
Problems to be solved
At present, the research and application of SiC surface modification and coating at home and abroad are still in the initial stage. Due to various conditions, many related problems have not been solved, such as:
Surface modification of SiC nanoparticles, optimum process conditions for coating process, and modification and coating mechanism;
Development of low-phosphorus plating solution with low energy consumption, less pollution and renewable utilization;
Uniform dispersion of SiC nanoparticles in the plating solution and in the coating layer;
The behavior and mechanism of SiC nanoparticles in the coating layer;
At present, the processes used at home and abroad are relatively high in cost, and require high-pressure, high-temperature conditions and high-purity SiC nanoparticles, or complicated operation, many process flows, resulting in low yield or uneven coating, and is not strong. The quality of the product is not good.
In summary, reducing costs, simplifying steps, and ensuring quality will be an effort in the future.
Latest results: to improve electrochemical performance of electrode materials
At present, a Chinese R&D team has chosen to use nanoparticle surface coatings to improve the performance of lithium-rich electrodes.
The team constructed a carbon shell of NiCo nanoparticles on the prepared nanoparticles, and the resulting LLO@C&NiCo cathode exhibited excellent cycle and rate performance. Analysis shows that LLO@C&NiCo, as the cathode material of lithium battery, exhibits excellent electrochemical performance due to its protective C&NiCo shell. This research has been supported by China's national key research and development plan and national key basic research development plan.