Dynamic Covalent Surface Engineering of Highly Reactive Al-Li Alloy Powders for Propellant Application.

Area of Science:

• Materials Science
• Organic Chemistry
• Surface Chemistry

Background:

• Organic functionalization of reactive metal powders is crucial but challenging.
• Al-Li alloys are vital for advanced materials, but their surfaces require protection and enhancement.
• Existing methods often lack efficiency or introduce instability.

Purpose of the Study:

• To develop a new strategy for organic functionalization of Al-Li alloy powders.
• To create a functional dynamic covalent network on the alloy surface.
• To improve the mechanical and combustion properties of Al-Li alloy-based composite solid propellants.

Main Methods:

• Interfacial self-polymerization cross-linking using 4-hydroxyphenylboronic acid (HPBA) monomers.
• Formation of a boroxine structure with dynamic boron-oxygen (B-O) covalent bonds.
• Density Functional Theory (DFT) and Ab initio Molecular Dynamics (AIMD) simulations.

Main Results:

• A functional dynamic covalent network was successfully constructed on Al-Li alloy powders.
• The network exhibits intrinsic self-healing capabilities due to dynamic B-O bonds.
• Strong B-O-Al/Li covalent bonds formed with high adsorption energy (200.167 kJ mol⁻¹).
• Controlled surface morphology effectively blocked corrosive media.
• Enhanced mechanical strength (2.342 MPa) and combustion heat (30.648 MJ kg⁻¹) of propellants.

Conclusions:

• The proposed boroxine chemistry strategy offers an effective method for organic functionalization of reactive metal powders.
• The self-healing, dynamic covalent network significantly improves Al-Li alloy performance.
• This approach holds promise for developing advanced composite solid propellants.