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Template-directed synthesis of inorganic heterogeneities and the development of ultrasonic spectroscopy for the analysis of polymers
As polymers are utilized in new applications they encounter environments that push them to their limits. In response to this demand, materials are being engineered on the molecular, meso, and macro levels such that their properties match those required of properties is the incorporation of an inorganic heterogeneity. One of the most effective methods of modifying physical and mechanical properties is the incorporation of an inorganic heterogeneity. Recent advances in controlled SiO2 Sol-gel synthesis have made it possible to created unique heterogeneities of desired dimensions. A detailed investigation of the mechanism of the room temperature sol-gel synthesis of rectangular cross section silica tubes is presented. It is elucidated that tubes are formed by simultaneous template formation and coating with rapidly condensing SiO2. The templates are subsequently dissolved out from within the SiO2 coating yielding tubes whose size and geometry match those of the templates. Knowledge gained in examining the mechanism is utilized to create tubes of desired length and diameter. The process shows promise for fabricating hollow silica shapes of controlled dimension and geometry. The morphology and damage states of complex multicomponent polymeric materials and composites are extremely difficult to characterize by current methods. Traditionally, morphology is characterized via gross differences in electron density (via electron microscopy), chemical nature (staining enhanced electron microscopy) and optical density (via optical microscopy). Ultrasonic spectroscopy is a new technique that utilizes high frequency (10–100 MHz) transducers to transmit and receive sound waves through materials. Sound waves translate via successive perturbations of the medium and consequently the rate and manner in which they are transmitted is a function of the medium's physical and mechanical properties. Hence, morphology is imaged through density or modulus differences regardless of optical clarity. Ultrasonic spectroscopy was applied to the morphological analysis of model polymers containing phase separated spherical heterogeneities, characterization of model reacting systems, and the elucidation of residual strengths in graphite fiber reinforced epoxy laminates exposed to thermal loads. This research resulted in the development of analysis methods that successfully characterized morphology on several levels, monitored gelation and phase separation in situ, and detected thermally induced incipient damage in polymer matrix composites.
Schueneman, Gregory Thomas, "Template-directed synthesis of inorganic heterogeneities and the development of ultrasonic spectroscopy for the analysis of polymers" (1999). Doctoral Dissertations Available from Proquest. AAI9950208.