PHOTOELECTROCHEMICAL STUDY ON SEMICONDUCTOR PROPERTIES OF Ni-BASED ALLOYS OXIDE FILMS FORMED IN 288℃ HIGH TEMPERATURE WATER

The oxide films formed on Ni-based alloys in high temperature water with semiconductor properties were investigated by photoelectrochemical responses.Two Ni-based alloys(Incoloy 800HT and Inconel600) were corroded at 288℃for 100 h in water,and four contributions from the photocurrent are obtained by photoelectrochemical responses.Band gap energy of 2.3 eV is attributed to the presence of nickel hydroxide or nickel-ferrite oxide.Band gap energy of 2.9 and 3.5 eV are attributed to Cr_2O_3 and band gap energy in the range of 4.1-4.3 eV is attributed to the spinel phase Fe_xNi_(1-x)Cr_2O_4.In the photoelectrochemical responses in function of the applied potential tests,the oxide films on Incoloy800HT alloy indicate n type semiconductor in the potential range from -400 mV to +400 mV,and the oxide films on Inconel600 alloy indicate n/p type semiconductor.In addition, the dephasing angle of the photoelectrochemical responses has a 180°evolution at the potential where the semiconductor of oxide film turns from n to p type.