Sepiolite reinforced PEO layer on AZ 31

What is it about?

The present work deals with the investigation of the incorporation of nanosized ceramic particles (sepiolite) into an oxide layer formed on magnesium alloy AZ31 by plasma electrolytic oxidation (PEO). The actual (true) surface area of the sepiolite particles was determined to be 300 m2 g−1. The particles were exclusively electrostatically stabilized in the used electrolyte without visible sedimentation, at least over 27 days. Using a current controlled pulse regime, the particles are incorporated into the oxide layer simultaneously to the PEO process. The study clearly reveals that the movement and deposition of the particles is based on electrophoresis. Considering the measured mobility of the particles of μ ≈ 6 μm cm V−1 s−1 and a very low field strength in the electrolyte (0.4 V cm−1) the particles velocity was calculated to υ ≈ 2.4 μm s−1. The mass of deposited sepiolite was estimated to approximately 1.2 mg cm−2 under the chosen conditions. The fixation of the deposited particles is caused by sintering due to the heat development of the plasma discharge events.

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Why is it important?

• Particle-enhanced plasma electrolytic oxide film on AZ31 formed with square-wave current pulses of 20 mA cm−2. • The sepiolite particles originally had a real surface area of 300 m2g−1. • The electrostatically stabilized sepiolite containing suspension was stable at least 27 days. • The incorporation of the sepiolite particles (1.2 mg cm−2) occurred preferentially in the discharge crater. • Evidence of electrophoretic deposition of sepiolite at a low field strength of 0.4 V cm−1. • Fixation of the deposited particles takes place by sintering due to the process temperature.