Millisecond photonic sintering of iron oxide doped alumina ceramic coatings

Evgeniia Gilshtein,Stefan Pfeiffer,Thomas Graule,Jordi Sastre,Yaroslav E Romanyuk,Marta D Rossell,Lovro Gorjan,Rolf Erni,Ayodhya N Tiwari

doi:10.1038/s41598-021-82896-9

Evgeniia Gilshtein, Stefan Pfeiffer + Show 7 more

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https://doi.org/10.1038/s41598-021-82896-9

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Abstract

The sintering of alumina (Al2O3) traditionally occurs at high temperatures (up to ca. 1700 °C) and in significantly long times (up to several hours), which are required for the consolidation of the material by diffusion processes. Here we investigate the photonic sintering of alumina particles using millisecond flash lamp irradiation with extreme heating rates up to 108 K/min. The limitation of the low visible light absorption of alumina is resolved by adding colored α-Fe2O3 nanoparticles, which initiated the grain growth during sintering. After the millisecond-long light pulses from a xenon flash lamp, a bimodal mixture of α-Al2O3 precursor particles was sintered and iron segregation at the grain boundaries was observed. The proposed photonic sintering approach based on doping with colored centers may be extended to other refractory ceramics with low absorption in the visible light range once appropriate high-absorbing dopants are identified.

Highlights

IntroductionThe sintering of alumina (Al2O3) traditionally occurs at high temperatures (up to ca. 1700 °C) and in significantly long times (up to several hours), which are required for the consolidation of the material by diffusion processes
The sintering of alumina (Al2O3) traditionally occurs at high temperatures and in significantly long times, which are required for the consolidation of the material by diffusion processes
The density and uniformity of the prepared coating layer were major factors that affected the multidirectional consolidation during the sintering of α-Al2O3-based films

Summary

Introduction

The sintering of alumina (Al2O3) traditionally occurs at high temperatures (up to ca. 1700 °C) and in significantly long times (up to several hours), which are required for the consolidation of the material by diffusion processes. Laser sintering of bulk A l2O3 with different additives (ZrO2, WO3, and C r2O3) was possible by a continuous-wave C O2 laser with irradiation times below 30 s but a partial melting was observed[13,14] When it comes to thin films or coatings of alumina, one can either sinter a precursor layer deposited by spin coating, dip coating, and electrophoretic deposition followed by annealing in a furnace[15] or grow alumina layer from the vapor phase onto a heated substrate, e.g. by plasma s praying[16]. The main obstacle in the photonic processing of alumina (bandgap of 7–8 eV) is its pristine white color and a high optical reflectance, which limits the absorption of the visible light To circumvent this obstacle, we employ a bimodal mixture of micron- and submicron-sized α-Al2O3 precursor particles together with reddish-brown-colored α-Fe2O3 nanoparticles that boost the optical absorptivity of the precursor layer

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