Abstract

In suspension spraying; two most frequently used solvents are water and ethanol. In this study; we test the potential of using alternative; high-molecular weight solvent and demonstrate the associated advantages. Two organic solvents are directly compared: ethanol (serving as a benchmark; suspension formulated at 10 wt.% solid load) and di-propylene glycol methyl ether (two suspensions at 10 wt.% and 20 wt.%). Submicron 100% alpha-alumina powder is used as a model material to formulate the suspensions. It is shown that the ethanol- and ether-based-feedstock coatings are fully comparable in terms of their microstructure; porosity content; surface roughness as well as hardness. Importantly; the ether-based coatings exhibit slightly higher levels of α-Al2O3 phase when compared to their ethanol-based counterpart (17 wt.% vs. 6 wt.%). The use of 20 wt.% solid load in the ether solvent leads to twofold increase in the deposition rate while - as opposed to ethanol - successfully retaining a dense microstructure. Lastly; the ether is significantly cheaper and safer to handle than ethanol.

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