Browsing by Author "Yang, Yao"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Development of Novel Nanocomposite Photoelectrodes for Photoelectrochemical Cathodic Protection
    (2020-01-08) Yang, Yao; Cheng, Yufeng Frank; Egberts, Philip; Kim, Seonghwan; Shi, Yujun; Jar, Pean Yue Ben
    Novel photoelectrodes are developed for photoelectrochemical cathodic protection (CP) of steels. In a photoelectrochemical CP system, the photoelectrode acts as an anode and absorbs photons to inject electrons from valence band into the conduction band, producing photogenerated holes in the photoelectrode. Then these photogenerated holes are eliminated by hole scavengers and the photoelectrons are utilized to cathodically polarize a steel, making it the cathode. In such a system, the photoelectrode remains intact and converts solar light into electricity for cathodic protection. Compared with conventional CP systems, the photoelectrochemical CP system is more suitable for long-time application in remote areas. To achieve photoelectrochemical CP, photoelectrodes need to work under some conditions. The conduction band potential should be more negative than the corrosion potential of a steel to be protected. High light intensity, efficient hole scavengers and high surface area of the photoelectrode benefit its performance. The electrochemical activity of protected metals and the corrosivity of aqueous environments can affect the performance of this novel CP system. SrTiO3 and ZnO nanorod photoelectrodes are developed for photoelectrochemical CP under ultraviolet (UV) illumination. Compared with SrTiO3 photoelectrode, ZnO nanorod photoelectrode has much higher photoelectrochemical activity due to the high active surface area of ZnO nanorods. Moreover, the methodology of electrodeposition proved to be a more facile and efficient technique for fabrication of a high-performance photoelectrode. Co3O4@ZnO core-shell nanocomposite photoelectrodes are developed to enable photoelectrochemical CP under visible light. The optical absorption edge of the fabricated photoelectrode shifts to the visible light range due to the narrow band gap of Co3O4. Combined with high surface area of ZnO nanorods, the Co3O4@ZnO nanocomposite photoelectrodes achieve high-performance photoelectrochemical CP under visible light. Nano-scaled compounds, i.e., CeO2 and WO3, with energy storage ability are incorporated into the photoelectrodes to develop photoelectrodes for continuous CP with/without illumination. The fabricated CeO2-SrTiO3 and WO3-TiO2-BiVO4 photoelectrodes enable photoelectrochemical CP and energy storage under UV and visible light illumination, respectively. Photocorrosion may occur on passivated carbon steel due to the existence of iron oxides film on the steel surface. The passive film shows a behavior of an n-type semiconductor, and affects the corrosion behavior of the carbon steel under visible light illumination.
  • Thumbnail Image
    ItemOpen Access
    Studies of Circumferential Stress Corrosion Cracking of Pipelines
    (2016) Yang, Yao; Cheng, Frank; Xue, Deyi; Egberts, Philip; El-Badry, Mamdouh
    The circumferential stress corrosion cracking (C-SCC) of X46 and X65 steels in a near-neutral pH environment was studied in this work. The steels were found to be susceptible to SCC. The corrosion and cracking behavior of the steels were investigated. The anodic dissolution at the crack tip was enhanced by stress, contributing to the crack propagation. The increase of corrosion rate was associated with the porous corrosion product. The mechanism of SCC was found to be stress dependent. The SCC process was anodic dissolution dominant under a low stress, while the process was mechanical fracture dominant under a sufficiently high stress. The different SCC behaviors between the steels were studied. Compared with X65 steel, X46 steel contained pearlite and has larger grain size, resulting in better adhesion of corrosion product on the steel and lower mechanical strength. Therefore, X46 steel is more susceptible to mechanical fracture, instead of corrosion.