Gas Suppression via Copper Interlayers in Magnetron Sputtered Al-Cu₂O Multilayers.

Area of Science:

• Materials Science
• Chemical Engineering
• Metallurgy

Background:

• Successful bonding using thin-foil thermite reactions requires suppressing gas generation and pore formation.
• Understanding vapor production mechanisms in diluted thermites is crucial for optimizing brazing processes.

Purpose of the Study:

• To investigate the effect of copper (Cu) layer thickness on vapor production in aluminum-copper-copper oxide (Al-Cu-Cu2O-Cu) thermite reactions.
• To determine the conditions necessary to eliminate metal vapor production and minimize porosity in thermite-bonded materials.

Main Methods:

• Fabrication of thin film multilayer Al-Cu-Cu2O-Cu foils using magnetron sputtering with varying Cu layer thicknesses (0-100 nm).
• Analysis of reaction mechanisms using slow heating differential scanning calorimetry (DSC).

Main Results:

• Increased Cu layer thickness acted as a diffusion barrier, limiting oxygen transport to the Al fuel.
• Excess Cu addition lowered the reaction temperature below the boiling point of Cu, eliminating metal vapor production.
• Cu vapor production was suppressed with Cu interlayer thickness above 50 nm.

Conclusions:

• Diluting thermite reactions with excess copper effectively suppresses metal vapor production, a key factor in preventing pore formation.
• While metal vapor is eliminated, gas generation from oxygen release persists, resulting in porous final products.
• Further strategies are needed to address gas generation to achieve fully dense, high-quality thermite bonds.