NMR relaxation rate studies of molecular motions in NaSn, the Laves-phase metal hydride C15-ZrCr(2)H(x) and carbon/epoxy composite materials

Here I present studies of molecular motions in three very different systems: NaSn, which exhibits motion characteristic of both a superionic conductor and a rotor crystal; C15-ZrCr{dollar}sb2{dollar}H{dollar}sb{lcub}rm x{rcub}{dollar} (x {dollar}<{dollar} 0.5), a metal hydride which exhibits unusual characteristics in its hydrogen motion; and, finally a study of the relationship between T{dollar}sb2{dollar} and the degree of cure of carbon/epoxy materials.; NaSn is characterized by Na{dollar}sp+{dollar} ions and stable (Sn{dollar}sb4)sp{lcub}4-{rcub}{dollar} tetrahedra. At high temperatures NaSn displays a disordered solid phase ({dollar}alpha{dollar}-NaSn). The presence of Na{dollar}sp+{dollar} ions suggests that {dollar}alpha{dollar}-NaSn may be a superionic conductor (translationally disordered) and the presence of stable Sn{dollar}sb4{dollar} tetrahedra suggests it may be a rotor crystal (organizationally disordered). The purpose of this study is to gain better understanding of the motions in {dollar}alpha{dollar}-NaSn by monitoring Na and Sn motion using {dollar}sp{lcub}23{rcub}{dollar}Na and {dollar}sp{lcub}119{rcub}{dollar}Sn NMR, respectively.; C15-ZrCr{dollar}sb2{dollar}H{dollar}sb{lcub}rm x{rcub}{dollar} (x {dollar}<{dollar} 0.5) is a Laves phase metal hydride which displays extremely rapid hydrogen motion and a T{dollar}sb1{dollar} peak which cannot be explained by a model employing a single correlation time for the motion. A model employing a Gaussian distribution of correlation times has been used to successfully fit T{dollar}sb1{dollar}, but the origin of this distribution in a crystalline solid solution is not known. The purpose of this study is to better understand the low temperature hydrogen motions occurring in C15-ZrCr{dollar}sb2{dollar}H{dollar}sb{lcub}rm x{rcub}{dollar} by extending the previous NMR measurements using T{dollar}sb{lcub}rm 1p{rcub}{dollar} and T{dollar}sb{lcub}rm 1D{rcub}{dollar}, experiments which effectively push the relaxation peak to lower temperatures.; New techniques for manufacturing carbon/epoxy components are under development which require partial curing of the material. At present, no method for monitoring partial curing exists. T{dollar}sb2{dollar} is a promising monitor of degree of cure because of its sensitivity to changes rates of molecular motions. The purpose of this study is to demonstrate the sensitivity of T{dollar}sb2{dollar} to changes in molecular motion due to curing, and to find a quantitative relationship between T{dollar}sb2{dollar} and the degree of cure for two different carbon/epoxy systems. Measurements of T{dollar}sb2{dollar} were also made on moving towpreg, demonstrating the practical applicability of this technique to on-line measurements.