Acoustic properties of novel materials using resonant ultrasound spectroscopy

Resonant Ultrasound Spectroscopy (RUS) is a relatively new acoustic method capable of determining an object's elastic tensor through observation of the object's normal modes of free vibration. This work describes the acoustic properties and characterization of five different novel materials using the RUS technique. The elastic constants of thin film magnesium diboride (MgB2), a Bardeen Cooper Schrieffer (BCS) type superconductor, were measured for the first time and are significantly different from theoretical bulk calculations indicating the presence of strain induced effects. The resonant spectra of arbitrarily shaped bulk magnesium diboride samples were measured and the subsequent investigation, which included Finite Element Analysis (FEA), demonstrated that the samples were not uniform single crystals. In addition to the superconductor MgB2, several other unusual materials were investigated; the elastic constants of thin film columnar silicon carbide were measured to assess changes in material elasticity due to thin film growth mechanisms, the elastic constants of the biological material human dentin were measured to assess variation in elastic constants due to age of the sample donor, the complete elastic tensor of bulk gadolinium scandate (GdScO 3) was measured and sound speeds determined to evaluate applications in acoustic cavity design, and the bulk acoustic sound speed of the colossal magnetoresistant material La0.7Ca0.3MnO3 was determined via RUS for comparison with recently available sound speed measurements obtained using optical pulse methods.