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Superhydrophobic Ceramic Coatings by Solution Precursor Plasma Spray.

Cai Y, Coyle TW, Azimi G, Mostaghimi J - Sci Rep (2016)

Bottom Line: A rare earth oxide (REO) was selected as the coating material due to its hydrophobic nature, chemical inertness, high temperature stability, and good mechanical properties, and deposited on stainless steel substrates by solution precursor plasma spray (SPPS).The as-sprayed coating demonstrated a hierarchically structured surface topography, which closely resembles superhydrophobic surfaces found in nature.The water contact angle on the SPPS superhydrophobic coating was up to 65% higher than on smooth REO surfaces.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, ON, M5S 3G8, Canada.

ABSTRACT
This work presents a novel coating technique to manufacture ceramic superhydrophobic coatings rapidly and economically. A rare earth oxide (REO) was selected as the coating material due to its hydrophobic nature, chemical inertness, high temperature stability, and good mechanical properties, and deposited on stainless steel substrates by solution precursor plasma spray (SPPS). The effects of various spraying conditions including standoff distance, torch power, number of torch passes, types of solvent and plasma velocity were investigated. The as-sprayed coating demonstrated a hierarchically structured surface topography, which closely resembles superhydrophobic surfaces found in nature. The water contact angle on the SPPS superhydrophobic coating was up to 65% higher than on smooth REO surfaces.

No MeSH data available.


Related in: MedlinePlus

Temperature history and cross-sectional SEM images of selected deposition conditions.(a) Temperature history during depositions for conditions 1, 3 and 5. (b–h) SEM images of various spraying conditions.
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f2: Temperature history and cross-sectional SEM images of selected deposition conditions.(a) Temperature history during depositions for conditions 1, 3 and 5. (b–h) SEM images of various spraying conditions.

Mentions: From the results for conditions 1, 3, and 5 the effect of standoff distance (SD) can be investigated. Figure 2b–d show the cross sectional microstructures of coatings deposited with experimental conditions 1, 3, and 5 respectively and Fig. 2a shows the substrate temperature history for these three conditions. The coatings are porous and rough for all three conditions. Particles observed in the coatings have irregular shapes which is an indication of incomplete melting. This suggests that the coatings were formed mainly by the sintering of incompletely melted particles and aggregates of fully/partially decomposed precipitates from the droplets. Nano-particles were also observed in the coatings. Individual particles of this size would not have sufficient inertia to penetrate the gas boundary layer at the surface of the substrate. The thermophoresis force may have allowed these particles to pass through the boundary layer, or the nano-particles may have formed on the substrate from the condensation of vaporized material. When the standoff distance was increased while all the other parameters were held constant, an increase in the coating porosity, and decreases in the coating thickness and substrate temperature were observed. At long standoff distances, the plasma plume is cooled by the ambient air, resulting in cooler feedstock particles arriving at the substrate. The gas and particle velocities are also reduced at longer standoff distances. The combination of lower momentum and lower feedstock temperature at long standoff distances decreased the adhesion of the feedstock particles when they arrive at the substrate, which resulted in a reduction in the coating thickness and deposition efficiency. This agreed with the SEM images of deposits collected after a single torch pass, that show less material was deposited under condition 5 compared to conditions 1 and 3 (see Supplementary Fig. S2). The lower feedstock temperature at longer standoff distances also explains the increase in coating porosity, due to fewer molten droplets arriving at the substrate and less sintering of the fine particles after deposition. Water contact angles were higher on the coatings deposited at the short standoff distance, which correlates with a higher surface roughness (Supplementary Table S1 and Fig. S5).


Superhydrophobic Ceramic Coatings by Solution Precursor Plasma Spray.

Cai Y, Coyle TW, Azimi G, Mostaghimi J - Sci Rep (2016)

Temperature history and cross-sectional SEM images of selected deposition conditions.(a) Temperature history during depositions for conditions 1, 3 and 5. (b–h) SEM images of various spraying conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835754&req=5

f2: Temperature history and cross-sectional SEM images of selected deposition conditions.(a) Temperature history during depositions for conditions 1, 3 and 5. (b–h) SEM images of various spraying conditions.
Mentions: From the results for conditions 1, 3, and 5 the effect of standoff distance (SD) can be investigated. Figure 2b–d show the cross sectional microstructures of coatings deposited with experimental conditions 1, 3, and 5 respectively and Fig. 2a shows the substrate temperature history for these three conditions. The coatings are porous and rough for all three conditions. Particles observed in the coatings have irregular shapes which is an indication of incomplete melting. This suggests that the coatings were formed mainly by the sintering of incompletely melted particles and aggregates of fully/partially decomposed precipitates from the droplets. Nano-particles were also observed in the coatings. Individual particles of this size would not have sufficient inertia to penetrate the gas boundary layer at the surface of the substrate. The thermophoresis force may have allowed these particles to pass through the boundary layer, or the nano-particles may have formed on the substrate from the condensation of vaporized material. When the standoff distance was increased while all the other parameters were held constant, an increase in the coating porosity, and decreases in the coating thickness and substrate temperature were observed. At long standoff distances, the plasma plume is cooled by the ambient air, resulting in cooler feedstock particles arriving at the substrate. The gas and particle velocities are also reduced at longer standoff distances. The combination of lower momentum and lower feedstock temperature at long standoff distances decreased the adhesion of the feedstock particles when they arrive at the substrate, which resulted in a reduction in the coating thickness and deposition efficiency. This agreed with the SEM images of deposits collected after a single torch pass, that show less material was deposited under condition 5 compared to conditions 1 and 3 (see Supplementary Fig. S2). The lower feedstock temperature at longer standoff distances also explains the increase in coating porosity, due to fewer molten droplets arriving at the substrate and less sintering of the fine particles after deposition. Water contact angles were higher on the coatings deposited at the short standoff distance, which correlates with a higher surface roughness (Supplementary Table S1 and Fig. S5).

Bottom Line: A rare earth oxide (REO) was selected as the coating material due to its hydrophobic nature, chemical inertness, high temperature stability, and good mechanical properties, and deposited on stainless steel substrates by solution precursor plasma spray (SPPS).The as-sprayed coating demonstrated a hierarchically structured surface topography, which closely resembles superhydrophobic surfaces found in nature.The water contact angle on the SPPS superhydrophobic coating was up to 65% higher than on smooth REO surfaces.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, ON, M5S 3G8, Canada.

ABSTRACT
This work presents a novel coating technique to manufacture ceramic superhydrophobic coatings rapidly and economically. A rare earth oxide (REO) was selected as the coating material due to its hydrophobic nature, chemical inertness, high temperature stability, and good mechanical properties, and deposited on stainless steel substrates by solution precursor plasma spray (SPPS). The effects of various spraying conditions including standoff distance, torch power, number of torch passes, types of solvent and plasma velocity were investigated. The as-sprayed coating demonstrated a hierarchically structured surface topography, which closely resembles superhydrophobic surfaces found in nature. The water contact angle on the SPPS superhydrophobic coating was up to 65% higher than on smooth REO surfaces.

No MeSH data available.


Related in: MedlinePlus