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2015

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Articles 871 - 874 of 874

Full-Text Articles in Materials Science and Engineering

Phase Transitions And In Situ Dynamics Of Crystal Grain Formation Of Alumina Nanotubes Templated By Vertically Aligned Carbon Nanotubes, L. F. Lampert, A. Barnum, S. W. Smith, J. F. Conley, Jun Jiao Jan 2015

Phase Transitions And In Situ Dynamics Of Crystal Grain Formation Of Alumina Nanotubes Templated By Vertically Aligned Carbon Nanotubes, L. F. Lampert, A. Barnum, S. W. Smith, J. F. Conley, Jun Jiao

Mechanical and Materials Engineering Faculty Publications and Presentations

Phase transitions of amorphous alumina (a-alumina) nanotubes grown by atomic layer deposition and templated by carbon nanotubes were investigated with thermal annealing, transmitted Kikuchi electron diffraction, electron-irradiation-induced crystallization, X-ray diffraction, and X-ray photoelectron spectroscopy. The resulting, engineered alumina nanotube arrays demonstrate a large range of tunable phases that are vital for understanding how alumina nanotube arrays can be applied for uses within biotechnology, catalysis, and other academic and industrial uses.


Anisotropy Of The Reynolds Stress Tensor In The Wakes Of Wind Turbine Arrays In Cartesian Arrangements With Counter-Rotating Rotors, Nicholas Hamilton, Raúl Bayoán Cal Jan 2015

Anisotropy Of The Reynolds Stress Tensor In The Wakes Of Wind Turbine Arrays In Cartesian Arrangements With Counter-Rotating Rotors, Nicholas Hamilton, Raúl Bayoán Cal

Mechanical and Materials Engineering Faculty Publications and Presentations

A 4 × 3 wind turbine array in a Cartesian arrangement was constructed in a wind tunnel setting with four configurations based on the rotational sense of the rotor blades. The fourth row of devices is considered to be in the fully developed turbine canopy for a Cartesian arrangement. Measurements of the flow field were made with stereo particle-image velocimetry immediately upstream and downstream of the selected model turbines. Rotational sense of the turbine blades is evident in the mean spanwise velocity W and the Reynolds shear stress −vw. The flux of kinetic energy is shown to be of greater …


Thermodynamic Grain Size Stabilization Models: An Overview, Mostafa Saber, Carl C. Koch, Ronald O. Scattergood Jan 2015

Thermodynamic Grain Size Stabilization Models: An Overview, Mostafa Saber, Carl C. Koch, Ronald O. Scattergood

Mechanical and Materials Engineering Faculty Publications and Presentations

Grain boundaries in a nanocrystalline microstructure produce an increase in the excess free energy of the system. Grain growth is a consequence of the thermodynamic driving force reducing this excess. Thermodynamic stabilization is an approach based on eliminating the driving force by suitable alloy additions that can produce a metastable equilibrium state at the nanoscale grain size, as opposed to kinetic stabilization where the grain growth mobility is restricted by pinning and/or drag mechanisms. The present paper reviews and compares various models proposed for thermodynamic stabilization.


Estimation Of Transient Temperature Distribution During Quenching, Via A Parabolic Model, Diego E. Lozano, Gabriela Martinez-Solis, Rafael David Mercado-Solis, Rafael Colás, George E. Totten Jan 2015

Estimation Of Transient Temperature Distribution During Quenching, Via A Parabolic Model, Diego E. Lozano, Gabriela Martinez-Solis, Rafael David Mercado-Solis, Rafael Colás, George E. Totten

Mechanical and Materials Engineering Faculty Publications and Presentations

A material-independent model to estimate the transient temperature distribution in a test probe quenched by immersion is presented in this study. This model is based on the assumption that, under one-dimensional unsteady heat conduction, the radial temperature distribution at the end of an interval belongs to the equation of a parabola. The model was validated using AISI 304 stainless steel test probes (Φ8×40 mm and Φ12×60 mm) quenched from 850 to 900 °C in water and in water-based NaNO2 solutions at 25 °C and in canola oil at 50 °C. Additionally, square test probes (20×20×100 mm) were quenched from 550 …