2. Material and methods
Ceria nanoparticles were synthesized by chemical precipitation method. Cerium nitrate hexahydrate (Ce (NO3)3? 6H2O, Himedia, Purity of ≥ 99.99%) and 1 N ammonium hydroxide (NH4OH, Himedia, analytical grade) were used as precursor and precipitating agent, respectively. To 0.06 M cerium nitrate precursor in deionized water, ammonium hydroxide was added dropwise with constant stirring while maintaining the pH of the solution at 10. The resultant precipitate was washed with water and dried in vacuum oven at 353 K for 8 h. The dried powder was made into cylindrical pellets with an automatic hydraulic press by applying 5 tons pressure for 30 s. The as pressed pellets were sintered at 1473 K for 5 h and used as a target in Hesperadin beam deposition.
The chemical composition (in weight percentage) of the AISI 304 stainless steel used in the present study is C, 0.08; Cr, 18.35; Mn, 1.84; Ni, 8.54; P, 0.045; S, 0.030; Si, 1.00; the balance being Fe. The AISI 304 substrates of 15 × 15 × 3 mm dimensions were polished using 600, 800 and 1000 grit SiC paper and subsequently cleaned with iso-propanol in ultrasonicator and then air dried. The samples were coated using EBPVD (Hind High Vacuum, Bangalore, Model BC-300 box coater) with a base pressure of 3.75 × 10− 6 Torr. The voltage, substrate temperature and deposition rate was maintained constant for all the depositions at 5 keV, 373 K and 0.2 nm/s, respectively. The thickness of the film during the deposition was monitored using digital thickness monitor and subsequently confirmed using a profilometer (Dektak 6, Veeco, USA).