Spontaneous formation of multilayer refractory carbide coatings in a molten salt media

Authors

Loic Constantin, University of Nebraska-LincolnFollow
Lisha Fan, University of Nebraska-LincolnFollow
Mathilde Pouey, CNRS, Bordeaux INP
Jérôme Roger, Université de Bordeaux
Bai Cui, University of Nebraska-LincolnFollow
Jean-François Silvain, CNRS, Bordeaux INP,Follow
Yongfeng Lu, University of Nebraska - LincolnFollow

ORCID IDs

Loic Constantin https://orcid.org/0000-0003-4909-4338

Bai Cui https://orcid.org/0000-0002-0585-6698

Jean-François Silvain https://orcid.org/0000-0002-5881-6833

Yong Feng Lu https://orcid.org/0000-0002-5942-1999

Date of this Version

4-26-2021

Citation

PNAS 2021 Vol. 118 No. 18 e2100663118

https://doi.org/10.1073/pnas.2100663118

Abstract

Refractory materials hold great promise to develop functional multilayer coating for extreme environments and temperature applications but require high temperature and complex synthesis to overcome their strong atomic bonding and form a multilayer structure. Here, a spontaneous reaction producing sophisticated multilayer refractory carbide coatings on carbon fiber (CF) is reported. This approach utilizes a relatively low-temperature (950 °C) moltensalt process for forming refractory carbides. The reaction of titanium (Ti), chromium (Cr), and CF yields a complex, high-quality multilayer carbide coating composed of 1) Cr carbide (Cr₃C₂), 2) Ti carbide, and 3) Cr₃C₂ layers. The layered sequence arises from a difference in metal dissolutions, reactions, and diffusion rates in the salt media. The multilayer-coated CFs act as a permeable oxidation barrier with no crystalline degradation of the CFs after extreme temperature (1,200 °C) and environment (oxyacetylene flame) exposure. The synthesis of high-quality multilayer refractory coating in a fast, efficient, easy, and clean manner may answer the need for industrial applications that develop cheap and reliable extreme environment protection barriers.