Suspension Plasma Spraying of YPSZ Coatings: Suspension Atomization and Injection

Abstract

Among processes evaluated to produce some parts of or the whole solid-oxide fuel cell, Suspension Plasma Spraying (SPS) is of prime interest. Aqueous suspensions of yttria partially stabilized zirconia atomized into a spray by an internal-mixing co-axial twin-fluid atomizer were injected into a DC plasma jet. The dispersion and stability of the suspensions were enhanced by adjusting the amount of dispersant (ammonium salt of polyacrylic acid, PAA). A polyvinyl alcohol (PVA) was further added to the suspension to tailor its viscosity. The PVA also improved the dispersion and stability of the suspensions. The atomization of optimized formulations is described implementing Weber and Ohnesorge dimensionless numbers as well as gas-to-liquid mass ratio (ALR) value. Drop size distributions changed from monomodal distributions at low We to multimodal distributions when We number increases. The viscosity of the suspensions has a clear influence on the drop size distribution and suspension spray pattern. The secondary fragmentation of the drops due to the plasma jet was evidenced and the final size of the sheared drops was shown to depend on the characteristics of the suspension. Rather dense zirconia coatings have been prepared, which is a promising way to produce electrolyte.

Alumina-zirconia coatings obtained by suspension plasma spraying from highly concentrated aqueous suspensions

“…In spite of this limitation suspensions with a solid loading significantly higher than those reported in previous works can be injected. It is an important achievement because, as explained above in the introduction section, an increase of the suspension solids content involves energy saving and consequently an easier industrial scaling [9,10,14,15].…”

“…However increasing solids content leads to higher viscosity suspensions as a consequence of the exponential growth of viscosity with volume fraction of solids [12]. Moreover, some authors point out that coating properties are strongly dependent on suspension characteristics, finding a relationship between solid loading and coating properties [13][14][15]. Because of the above achieving all feedstock suspension requirements (no agglomeration, long-term stability and low viscosity) with high solid content suspensions as well as assessing the impact of suspension characteristics on coating microstructure and properties is certainly a challenge.…”

Influence of Plasma Intensity on Wear and Erosion Resistance of Conventional and Nanometric WC-Co Coatings Deposited by APS

“…Esta última aumenta con la presión en los recipientes. Para la inyección de suspensiones es preferible la inyección mecánica porque permite tener un chorro de gotas del mismo tamaño y con las mismas velocidades, de esa manera éstas serán mejor tratadas en el plasma [48].…”

Evaluation of hot corrosion of 8YSZ coatings elaborated by suspension plasma spraying

“…8mol% YSZ powder with d 50 of 360nm (d 10 =230nm and d 90 =560nm) supplied by UCM Advanced Ceramics was used to achieve the aqueous suspensions. The solid loading of the suspension was fixed at 20wt.% according to published works by researchers at the Université de Limoges (France) [11][12][13][14][15] in which this value was found to be a good compromise between deposition efficiency and required plasma output. The Beycostat C213 with an amount of 2.1wt.% of YSZ powder was used for dispersing the particles in ethanol.…”