Browsing by Author "Li, Yuan"

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    Electrochemistry of Nanostructured Features on Steel Surface and the Applications
    (2017-12-15) Li, Yuan; Cheng, Frank; Asselin, Edouard; Lu, Qingye(Gemma); Kim, Seonghwan(Sam); Sanati Nezhad, Amir
    Functionalization of pipeline steels through facile nano-techniques is valuable for industrial applications. In this research, the mechanistic aspects of steel corrosion at nanoscale has been studied in order to manipulate the development of corroded nanostructure on pipeline steel. High-performance nanocoatings capable of anti-bioadhesion and self-cleaning have been successfully developed on pipeline steels through facile electrochemical anodization methods. When the X100 pipeline steel is either corroded or passivated in aqueous environments, the development of nanostructures on the steel surface highly depends on the early-stage corrosion behavior, where the thermodynamics and kinetics are affected by the conditions such as surface finish, electrolyte concentration, and electrochemical potential. The nanostructure on steel substrate shows a quick-response to changes of the conditions, either caused by exposure to corrosive electrolytes, or electrochemical potential. The surface features are under a non-equilibrium state lasting from hundreds to thousands of seconds, during which the corrosion processes of the steel were successfully characterized by topographic in-situ mapping through electrochemical atomic force microscopy. It is demonstrated that the corroded nanostructure on pipeline steel can be controlled through manipulating conditions in order to achieve various functions. Nanostructured coating can be fabricated by anodization of pipeline steels in a concentrated alkaline solution. The nanostructure of the coatings can reduce the interactive force between microorganisms and the steel, resulting into anti-bioadhesion to sulfate-reducing bacteria (SRB) and P. aeruginosa. The photocatalytic property of iron oxides in the nanocoatings enables the release of toxic and oxidative reactive oxygen species (ROSs) under light illumination, enhancing the anti-bioadhesion performance up to 99.9 % compared to bare steel. Further treatment by dipping ZnAc solution and annealing allows the formation of ZnFe2O4 in the nanocoating, improving the electrochemical stability of the nanocoating in corrosive environments while maintaining a high performance in anti-bioadhesion and self-cleaning of residual bacteria (up to 99.3 % of total coverage) on the steel.
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    Micromachined Chip Scale Thermal Sensor for Thermal Imaging
    (American Chemical Society, 2018-02-05) Shekhawat, Gajendra; Ramachandran, Srinivasan; Jiryaei Sharahi, Hossein; Sarkar, Souravi; Hujsak, Karl; Li, Yuan; Hagglund, Karl; Kim, Seonghwan; Aden, Gary; Chand, Ami; Dravid, Vinayak
    The lateral resolution of scanning thermal microscopy (SThM) has hitherto never approached that of mainstream atomic force microscopy, mainly due to poor performance of the thermal sensor. Herein, we report a nanomechanical system-based thermal sensor (thermocouple) that enables high lateral resolution that is often required in nanoscale thermal characterization in a wide range of applications. This thermocouple-based probe technology delivers excellent lateral resolution (∼20 nm), extended high-temperature measurements >700 °C without cantilever bending, and thermal sensitivity (∼0.04 °C). The origin of significantly improved figures-of-merit lies in the probe design that consists of a hollow silicon tip integrated with a vertically oriented thermocouple sensor at the apex (low thermal mass) which interacts with the sample through a metallic nanowire (50 nm diameter), thereby achieving high lateral resolution. The efficacy of this approach to SThM is demonstrated by imaging embedded metallic nanostructures in silica core–shell, metal nanostructures coated with polymer films, and metal–polymer interconnect structures. The nanoscale pitch and extremely small thermal mass of the probe promise significant improvements over existing methods and wide range of applications in several fields including semiconductor industry, biomedical imaging, and data storage.