# Effect of the Dynamic Porous Structure Generation in Laser Irradiated Multi-Functional Coatings

## TL;DR

This paper introduces a new coating strategy that resists high-power laser damage by generating a porous structure and using endothermic reactions to insulate heat.

## Contribution

The novel dynamic porous structure generation method improves laser resistance through high reflectivity and thermal insulation.

## Key findings

- The coating's reflectivity increased to 93% during laser irradiation, enhancing laser resistance.
- A porous structure formed due to endothermic reactions, providing thermal insulation and preventing substrate melting.
- Under intense laser exposure, the back-surface temperature remained far below the melting point of the aluminum substrate.

## Abstract

Focusing on solving the adverse laser-inducing damage problem, high-power laser-resistant strategies have attracted more attention. In order to improve the laser-resistant property, a novel dynamic porous structure generation idea for laser irradiation was presented in this study, both of high-reflection and reaction endothermic effects. A detailed investigation on phase structure change, optical properties variation, micro-structure evolution, and substrate temperature development during laser irradiation was performed. The initial reflectivity of two coatings at 1064 nm was high, around 80–90%. During laser irradiation, the reflectivity grew continuously, reaching a maximum of 93%. During laser irradiation, a skeleton porous structure formed, promoted by the endothermic reaction of aluminum tri-hydroxide, whose structure contributes to the heat insulation from surface to interior. Thus, the prepared coating showed excellent anti-laser ablation performance, being dependent on its thermal insulation by the reaction-generated porous structure; high reflectivity by surface; and heat dissipation by endothermic reaction. Under 2000 W/cm2, 10 s laser irradiation (spot area is 10 mm × 10 mm), the back-surface temperature is just 159 °C, which is far away from the melting point of aluminum substrate. The coatings and strategy mentioned in this study have a great potential to be applied in the anti-laser field.