In this study, we demonstrate a novel environmental barrier coating processed from polymer‐derived ceramics (PDCs) with homogeneously distributed sub‐micrometer Y2O3as the filler. Under suitable conditions, dense and crack‐free coatings can be achieved for all the designed compositions with the volumetric content of Y2O3varied from 45 to 93 vol%. To process the PDC SiC–Y2O3composite coatings, Y2O3particles and SiC liquid precursor were uniformly dispersed in hexane and then dip‐coated on SiC substrates. After cross‐linking at 250°C and heat‐treated at 900°C in argon, dense and crack‐free PDC SiC–Y2O3composite coatings were formed. The effect of coating thickness and heat‐treatment temperature on the formation of cracks due to constrained pyrolysis was studied. The critical thickness for realizing crack‐free coatings of three compositions (i.e., 93, 77, and 45 vol% Y2O3) was studied for heat treatment from 1000 to 1300°C using atomic force microscope and scanning electron microscopy. As heat‐treatment temperature increases, the critical coating thickness decreases for the same coating compositions due to enhanced shrinkage at higher temperature. With higher Y2O3content, the critical thickness of the coating increased. The inert Y2O3particles reduce the amount of polymer leading to reduction in the overall constrained shrinkage of the coating during heat treatment.
This content will become publicly available on May 1, 2025
During drying, liquid‐applied particulate coatings develop stress and are consequently prone to stress‐induced defects, such as cracking, curling, and delamination. In this work, the stress development and cracking of coatings, prepared from aqueous silica and zinc oxide particle suspensions, were characterized using cantilever beam deflection with simultaneous imaging of the coating surface. Drying uniformity was improved and lateral or edge‐in drying was discouraged by using thin silicone walls around the perimeter of the cantilever. Coatings prepared from larger monodisperse silica particles (D50∼ 0.9 µm) dried uniformly but had a high critical cracking thickness (>150 µm) that prevented simultaneous study of stress development and cracking. Coatings prepared from smaller silica particles (D50∼ 0.3 µm) cracked readily at low thicknesses but exhibited edge‐in drying that complicated the stress measurement data. This drying nonuniformity was connected to the potential for these small particles to accumulate at the coating surface during drying. Hence, the selection of particle size and density was critical to drying uniformity when characterizing stress development and cracking. Coatings prepared from suspensions of zinc oxide particles (D50∼ 0.4 µm) were well‐suited for these studies, with uniform drying stress peaking at ∼1 MPa. Characteristic features in the stress development data above and below the critical cracking thickness (53 µm) were identified, demonstrating that cantilever beam deflection is a useful tool for studying the effectiveness of crack mitigation methods and the fundamentals of coating fracture during drying.
more » « less- Award ID(s):
- 2011401
- PAR ID:
- 10506810
- Publisher / Repository:
- Journal of the American Ceramic Society
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 107
- Issue:
- 5
- ISSN:
- 0002-7820
- Page Range / eLocation ID:
- 2837 to 2848
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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