Deposition of duplex MAO layer/nanostructured titanium dioxide composite coatings on Mg-1%Ca alloy using a combined technique of air plasma spraying and micro arc oxidation by Daroonparvar, Mohammadreza, Mat Yajid, Muhamad Azizi, Mohd. Yusof, Noordin, Bakhsheshi-Rad, Hamid Reza, Hamzah, Esah, Mardanikivi, Tina