Surface characterization of plasma sprayed oxide materials: estimation of surface acidity using mass titration

Area of Science:

• Materials Science
• Surface Chemistry
• Electrochemistry

Background:

• The point of zero charge (PZC) is critical for understanding oxide material behavior in aqueous solutions.
• Plasma spraying is a common technique for creating oxide coatings, but its effect on surface properties like PZC is not fully characterized.

Purpose of the Study:

• To investigate how plasma spraying affects the PZC of Al2O3-, Cr2O3-, and TiO2-based materials.
• To evaluate the suitability of mass titration for determining the PZC of plasma-sprayed oxide powders and coatings.

Main Methods:

• Mass titration was employed to determine the PZC of initial spray powders and plasma-sprayed materials.
• Experiments included both water-washed and non-washed samples to assess the impact of potential contaminants.
• The study focused on Al2O3, Cr2O3, and TiO2 oxide systems.

Main Results:

• Mass titration proved effective for estimating the surface acidity of coarse oxide powders.
• For most materials, PZC values of plasma-sprayed oxides were comparable to traditionally manufactured oxides.
• Some samples exhibited deviations in mass titration curves, likely due to selective dissolution of contaminants or the material itself.

Conclusions:

• Plasma spraying generally preserves the PZC of common oxide materials, indicating stable surface acidity.
• Mass titration is a viable method for PZC determination of plasma-sprayed oxides, though sample dissolution can influence results.
• Further investigation into dissolution effects is warranted for precise PZC characterization.