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Full-Text Articles in Physics
Microstructural Characterization Of An Ultra-High-Performance Polyimide, April Heather Baugher
Microstructural Characterization Of An Ultra-High-Performance Polyimide, April Heather Baugher
Dissertations, Theses, and Masters Projects
The motivation for this study was to further characterize a relatively new high-temperature polymer for application as a matrix resin for carbon fiber composites. The two primary questions addressed in this study dealt with the structural and chemical changes occurring in these polymers on exposure to high temperature.;To investigate the structural changes in the heat-treated samples, a positron annihilation lifetime spectrometer was designed, built and optimized. Because the lifetime of a positron in a material reflects the electronic structure of the material in which it annihilates, measurements by positron annihilation lifetime spectroscopy can be used to investigate changes in a …
Radiation-Induced Luminescence In Terbium-Doped Silicate Glasses, Michael Stuart West
Radiation-Induced Luminescence In Terbium-Doped Silicate Glasses, Michael Stuart West
Dissertations, Theses, and Masters Projects
The purpose of this study is to characterize radiation-induced luminescence of terbium-doped silicate glasses. Experiments performed investigated the optical properties, isothermal time-evolution, and temperature dependence of the radiation-induced luminescence of two commercially available terbium-doped glasses. A problem common to this type of glass is the persistent luminescence, or afterglow, that occurs following the end of excitation from an external source of radiation. While the processes that govern characteristic luminescence of rare earth ions, including terbium, are well understood, the processes that give rise to afterglow in doped glasses are not. Identifying the source of long-term luminescence is essential for controlling …
Propagation Of Rayleigh Waves In Thin Films, Agus A. Ananda
Propagation Of Rayleigh Waves In Thin Films, Agus A. Ananda
Dissertations, Theses, and Masters Projects
With the advent of thin film technology and more recently its applications in microelectronics and control of surface properties, the interest in mechanical properties of thin films has grown tremendously. Mechanical defects such as creep, fracture and adhesion loss, play a very important role in physical instabilities of thin film materials. An acoustic microscope has been built to study mechanical properties of thin-films. The microscope operates at a nominal frequency of 50 MHz. Rayleigh surface waves velocities on the surface of film-substrate systems were measured from V(z) curves generated by the acoustic microscope. V(z) curves are produced from interference between …