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Evaluating location specific strain rates, temperatures,and accumulated strains in friction welds through microstructure modeling

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Defence Technology（防务技术） 2018年第2期14卷 83-92页

作者： Javed Akram Prasad Rao Kalvala Vikas Jindal mano misra Dept. of Metallurgical Engineering University of Utah Dept. of Metallurgical Engineering Indian Institute of Technology(BHU)

A microstructural simulation method is adopted to predict the location specific strain rates, temperatures, grain evolution, and accumulated strains in the Inconel 718 friction welds. Cellular automata based 2D microstructure model was developed for Inconel 718 alloy using theoretical aspects of dynamic recrystallization. Flow curves were simulated and compared with experimental results using hot deformation parameter obtained from literature work. Using validated model, simulations were performed for friction welds of Inconel 718 alloy generated at three rotational speed i.e., 1200, 1500, and1500 RPM. Results showed the increase in strain rates with increasing rotational speed. These simulated strain rates were found to match with the analytical results. Temperature difference of 150 K was noticed from center to edge of the weld. At all the rotational speeds, the temperature was identical implying steady state temperature(0.89 T_m) attainment.

关键词： Microstructure modeling Dynamic recrystallization Friction welding Inconel 718 EBSD Hot deformation Strain map

Plasmonic-enhanced electrochemical detection of volatile biomarkers with gold functionalized TiO_2 nanotube arrays

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Journal of Materials Science & Technology 2018年第6期34卷 905-913页

作者： Dhiman Bhattacharyya Pankaj Kumar York R.Smith Swomitra K.Mohanty mano misra Department of Metallurgical Engineering University of Utah Department of Chemical Engineering University of Utah

Titania nanotubular arrays （TNA） synthesized via electrochemical anodization is a stable and versatile material, widely studied for photocatalytic and sensing applications, whereas nano-sized gold particles are a known plasmonic material. Semiconductor-metal nanocomposites in isolated, embedded, or encapsulated form, when irradiated with proper light frequency can exhibit localized surface plasmon resonance （LSPR） effect. This effect can result in improved light adsorption and electrical properties of a material. In this study, we report the enhanced visible light photo-response of LSPR induced volatile organic biomarker vapor sensing at room temperature using a Au-embedded TNA electrochemical sensor. Two mechanisms are proposed. One based on classical physics （band theory）, which explains operation under non-irradiated conditions. The second mechanism is based on the coupling of classical and quantum physics （molecular orbitals）, and explains sensor operation under irradiated conditions.

关键词： TiO2 nanotube arrays Au particles Surface plasmon resonance Electrochemical sensor

Low temperature friction stir welding of P91 steel

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Defence Technology（防务技术） 2016年第4期12卷 285-289页

作者： Prasad Rao KALVALA Javed AKRAM mano misra Damodaram RAMACHANDRAN Janaki Ram GABBITA University of Utah Salt Lake City USA SSN College of Engineering Kalavakkam India Indian Institute of Technology Madras Chennai India

Bead-on-plate friction stir welds were made on P91 alloy with low and high rotational speeds(100 and 1000 RPM) to study their effects on weld microstructural changes and impression creep behavior. Temperatures experienced by the stir zone were recorded at the weld tool tip. Different zones of welds were characterized for their microstructural changes, hardness and creep behavior(by impression creep tests). The results were compared with submerged arc fusion weld. Studies revealed that the stir zone temperature with 100 RPM was well below A_(c1) temperature of P91 steel while it was above A_(c3) with 1000 RPM. The results suggest that the microstructural degradation in P91 welds can be controlled by low temperature friction stir welding technique.

关键词： Friction stir welding P91 Low temperature Martensite Carbides Impression creep

Development of a field enhanced photocatalytic device for biocide of coliform bacteria

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Journal of Environmental Sciences 2016年第6期28卷 38-44页

作者： Jeff M.Huber Krista L.Carlson Otakuye Conroy-Ben mano misra Swomitra K.Mohanty Departments of Civil Engineering University of Utah Departments of Metallurgical Engineering University of Utah Departments of Chemical Engineering University of Utah

A field enhanced flow reactor using bias assisted photocatalysis was developed for bacterial disinfection in lab-synthesized and natural waters. The reactor provided complete inactivation of contaminated waters with flow rates of 50 mL/min. The device consisted of titanium dioxide nanotube arrays, with an externally applied bias of up to 6 V. Light intensity, applied voltage, background electrolytes and bacteria concentration were all found to impact the device performance. Complete inactivation of Escherichia coli W3110（- 8 × 10^3CFU/mL） occurred in 15 sec in the reactor irradiated at 25 mW/cm^2 with an applied voltage of 4 V in a 100 ppm NaCl solution. Real world testing was conducted using source water from Emigration Creek in Salt Lake City, Utah. Disinfection of natural creek water proved more challenging, providing complete bacterial inactivation after 25 sec at 6 V. A reduction in bactericidal efficacy was attributed to the presence of inorganic and organic species, as well as the increase in robustness of natural bacteria.

关键词： Titanium dioxide Nanotubes Immobilized Photocatalysis Escherichia coli Inactivation