Why are Nano Al Powder surfaces coated?
Nano Al Powder’s activity is expected to be low and less affected by environmental conditions (temperature and humidity) during the storage, transportation, and processing of powder. The product should be stable for long periods of time. However, Aluminum as an active metal can readily react with oxygen in the atmosphere, and form a layer or aluminum oxide film that covers the Nano Al Powder. This reduces the powder’s energy release. In order to avoid the dispersion and homogenization of the system, researchers at home as well as abroad, have used the technique of coating or modifying the surface of Nano-Aluminum Powder to attempt to correct these shortcomings.
Analyse of Nano-Al Powder Surface Coating Technology
Nano Al Powder currently surfaces using a combination of in-situ or surface passivation.
1. Nano Al Powder surface coating
1.1 Passivation mechanism. The strong dipole/dipole interaction means that unpassivated, charged particles remain within the dispersion medium. Through diffusion, uncharged particles react with Ar. Electrons move from the metal layer through the oxide to the oxidant. While the proton H+ itself travels through the metal/oxide interface, electrons pass through the metal-oxide interface. Electrostatic fields are created when positive-charged particles form and accumulate enough to block the redox reaction. Redox is strengthened even before negative charges are fully compensated. The additional metal must be oxidized in order to strengthen the electric field. This will allow the energy barrier effect to stabilize nano-aluminum and improve the anti-oxidation performance.
1.2 The significance of passivation. While nano-aluminum particles are more resistant to oxidation than other powders, this shell layer is not responsible for releasing energy. Consider the entire preparation of nano-aluminum dust, including the size, type, structure and thickness. The shell-coating surface layer is crucial for determining the activity control and antioxidation performance.
2. Nano Al Powder in-situ coating
2.2.1 Method for electric explosion
Electric explosion refers to the application of a pulse current having an energy density equal to 1.0x (106109)A/cm2 onto the aluminum wire. This causes the wire to be heated instantly and then melts. After that, the product is ignited and dispersed in an atmosphere. Finally, the product cools down to create Nano-aluminum pieces. It is important to consider the following aspects when coating in situ with electric explosion: (1) to make sure that active aluminum levels of the nanoaluminum dust reach the micron level of activity (95 to 98%); (2) to improve propellant performance. This coating modifies the fuel’s ability to burn while also preventing the inactivation by oxidation of nano-aluminum. should exhibit a promotion effect. Here is a list of common coating materials that can be used to modify the surface of nano-aluminum dust.
2.2 Chemical method using a wet chemical
For nano-aluminum, the wet chemical process uses Tertiary Amino Aluminum Hydride. It is decomposed under the influence of titanium Isopropoxide. Dark brown color is achieved after adding the catalyst. A coating prevents nano-aluminum from becoming agglomerated during the transformation to black. Nano-aluminum particles are finally formed on the container’s surface.
This process is safe because it uses liquid to produce active aluminum powder. Decomposition rates of tertiary ammonium aluminum hydride, as well as the introduction of organic coating can have an important impact on aluminum powder formation and the shape of composite particles. Other effects of organic matter may also be possible. To summarize, the shell coating is responsible for forming the coating on nano-aluminum dust. It also serves as a catalyst in chemical reaction processes. There are many organic coatings that can produce different results. Future research should focus on this mechanism.
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