Femtosecond laser ultrafast photothermal exsolution

Abstract

Exsolution, as an effective approach to construct particle-decorated interfaces, is still challenging to yield interfacial films rather than isolated particles. Inspired by in vivo near infrared laser photothermal therapy (PTT), using 3 mol.% Y2O3 stabilized tetragonal zirconia polycrystals (3Y-TZP) as host oxide matrix and iron-oxide (Fe3O4/γ-Fe2O3/α-Fe2O3) materials as photothermal modulator and exsolution resource, femtosecond laser ultrafast exsolution approach is presented enabling to conquer this challenge. The key is to trigger photothermal annealing behavior via femtosecond laser ablation to initialize phase transition into tetragonal zirconia (t-ZrO2) and induce columnar crystal growth, where Fe-ions rapidly segregate along grain boundaries and diffuse towards the outmost surface, becoming “frozen” there, highlighting the potential to use photothermal materials and ultrafast heating/quenching behaviors of femtosecond laser ablation for interfacial modification via exsolution. Triggering interfacial iron-oxide coloring exsolution is composition and concentration dependent, indicating photothermal materials themselves and corresponding photothermal transition capacity play a crucial role, initializing at 5wt%, 2wt%, and and 3wt% for Fe3O4-/γ-Fe2O3/α-Fe2O3 embedded 3Y-TZP samples. Due to different photothermal effects, exsolution states of ablated 5wt% Fe3O4-/γ-Fe2O3/α-Fe2O3-embedded 3Y-TZP samples are completely different, complete coverage, exhaustion (ablated away) and partial exsolution (rich in the crystal boundaries of sublayers). This novel exsolution is uniquely featured by up to now the deepest microscale (10 μm from 5 wt%-Fe3O4-3Y-TZP sample) Fe-elemental deficient layer for exsolution and the whole coverage of exsolved materials rather than formation of isolated exsolved particles by other methods. It is believed that femtosecond laser ultrafast photothermal exsolution may pave a good way to modulate interfacial properties for extensive applications in the fields of biology, optics/photonics, energy, catalysis, environment, etc.