Correction: Wen et al. Fabrication of Dense Gadolinia-Doped Ceria Coatings via Very-Low-Pressure Plasma Spray and Plasma Spray–Physical Vapor Deposition Process. Coatings 2019, 9, 717

The author wishes to make the following correction to this paper [...]

Fabrication of Dense Gadolinia-Doped Ceria Coatings via Very-Low-Pressure Plasma Spray and Plasma Spray–Physical Vapor Deposition Process

Gadolinia-doped ceria (GDC) is a promising electrolyte material for low-temperature solid oxide fuel cells (LT-SOFCs). Many works used ceramic sintering methods to prepare the GDC electrolyte, which was mature and reliable but presented difficulties in rapidly preparing a large area of GDC electrolyte without cracks. The low-pressure plasma spray (LPPS) process has the potential to solve this problem, but few studies have been conducted to date. In this work, submicron GDC powder was agglomerated by a spray drying method to achieve the proper granularity with D50 about 10 μm, and then two dense GDC coatings were fabricated with this agglomerated GDC powder using very-low-pressure plasma spray (VLPPS) and plasma spray–physical vapor deposition (PS-PVD), respectively. The results indicate that the two GDC coatings exhibited similar microstructure but with different densification mechanisms. The VLPPS coating was mainly built up in the form of liquid splats, which had lower mechanical properties due to the lower density and crystallinity, while the PS-PVD coating was co-deposited with the vapor clusters and liquid splats, which had higher density, crystallinity, and mechanical properties. It can therefore be concluded that the GDC coating prepared by PS-PVD is more appropriate for the LT-SOFC application.

Ablation Behavior of Low Pressure Plasma Sprayed TiB2-MoSi2 Composite Coatings

In this work, TiB2-MoSi2 composite coatings with various contents of MoSi2 (20 vol. % and 40 vol. %, respectively) were fabricated on SiC coated C/C substrates by low pressure plasma spray (LPPS) technique. The microstructure and phase composition of the coatings were characterized. The ablation behaviors of the composite coatings were evaluated and compared with the pure TiB2 coating using a plasma flame of about 2200°C. The results showed that MoSi2 was uniformly distributed in the TiB2 matrix. All the coatings kept intact after the ablation for 60s - 180s, indicating their excellent ablation resistance. The addition of MoSi2 had great influence on the ablation behavior of the composite coatings. The TiB2 coating gained mass after the ablation. The mass of the TM20 coating increased firstly (60s and 120s) and then decreased at 180 s. Mass loss was observed for the TM40 coating during the whole procedure of ablation test.

Microstructure and Ablation Property of TaC-SiC Composite Coatings

TaC-based composite coatings containing different contents of SiC (5 vol.%, 10 vol.% and 15 vol.%, respectively) were fabricated by low pressure plasma spray (LPPS) technique. The phase composition and microstructure of the coatings were characterized. The ablation property of the TaC-SiC composite coatings was evaluated by a plasma flame over 2000 oC. The results showed that SiC was uniformly distributed in the composite coatings. The addition of SiC was good for the ablation-resistance of the composite coatings. The mass loss of the composite coatings decreased with increasing the amount of SiC. The mass loss of the TaC-15vol.%SiC composite coating was about 0.15 % after ablation for 60 s, which exhibited the best ablation-resistance among the three kinds of coatings. It was thought that the formed Ta2O5-SiO2 mixed layer on the coating surface contributed to the improved ablation resistance.