Exploring thermal and mechanical properties of selected transition elements under extreme conditions: Experiments at high pressures and high temperatures

Transition metals (Ti, Zr, Hf, Mo, W, V, Nb, Ta, Pd, Pt, Cu, Ag, and Au) are essential building units of many materials and have important industrial applications. Therefore, it is important to understand their thermal and physical behavior when they are subjected to extreme conditions of pressure and temperature. This dissertation presents: • An improved experimental technique to use lasers for the measurement of thermal conductivity of materials under conditions of very high pressure (P, up to 50 GPa) and temperature (T up to 2500 K). • An experimental study of the phase relationship and physical properties of selected transition metals, which revealed new and unexpected physical effects of thermal conductivity in Zr, and Hf under high P-T. • New phase diagrams created for Hf, Ti and Zr from experimental data. • P-T dependence of the lattice parameters in α-hafnium. Contrary to prior reports, the α-ω phase transition in hafnium has a negative dT/dP slope. • New data on thermodynamic and physical properties of several transition metals and their respective high P-T phase diagrams. • First complete thermodynamic database for solid phases of 13 common transition metals was created. This database has: All the thermochemical data on these elements in their standard state (mostly available and compiled); All the equations of state (EoS) formulated from pressure-volume-temperature data (measured as a part of this study and from literature); Complete thermodynamic data for selected elements from standard to extreme conditions. The thermodynamic database provided by this study can be used with available thermodynamic software to calculate all thermophysical properties and phase diagrams at high P-T conditions. For readers who do not have access to this software, tabulated values of all thermodynamic and volume data for the 13 metals at high P-T are included in the APPENDIX. In the APPENDIX, a description of several other high-pressure studies of selected oxide systems is also included. Thermophysical properties (Cp, H, S, G) of the high P-T ω-phase of Ti, Zr and Hf were determined during the optimization of the EoS parameters and are presented in this study for the first time. These results should have important implications in understanding hexagonal-close-packed to simple-hexagonal phase transitions in transition metals and other materials.

Placing immigrant incorporation: Identity, trust, and civic engagement in Little Havana

Immigrant incorporation in the United States has been a topic of concern and debate since the founding of the nation. Scholars have studied many aspects of the phenomenon, including economic, political, social, and spatial. The most influential paradigm of immigrant incorporation in the US has been, and continues to be, assimilation, and the most important place in and scale at which incorporation occurs is the neighborhood. This dissertation captures both of these integral aspects of immigrant incorporation through its consideration of three dimensions of assimilation – identity, trust, and civic engagement – among Latin American immigrants and American-born Latinos in Little Havana, a predominantly immigrant neighborhood in Miami, Florida. Data discussed in the dissertation were gathered through surveys and interviews as part of a National Science Foundation-funded study carried out in 2005-2006. The combination of quantitative and qualitative data allows for a nuanced understanding of how immigrant incorporation is occurring locally during the first decade of the twentieth century. Findings reveal that overall Latin American immigrants and their American-born offspring appear to be becoming American with regard to their ethnic and racial identities quickly, evidenced through the salience and active employment of panethnic labels, while at the same time they are actively reshaping the identificational structure. The Latino population, however, is not monolithic and is cleaved by diversity within the group, including country of origin and socioeconomic status. These same factors impede group cohesion in terms of trust and its correlate, community. Nevertheless, the historically dominant ancestry group in Little Havana – Cubans – has been able to reach notable levels of trust and build and conserve a more solid sense of community than non-Cuban residents. With respect to civic engagement, neighborhood residents generally participate at rates lower than the overall US population and ethnic subpopulations. This is not the case for political engagement, however, where self-reported voting registration and turnout in Little Havana surpasses that of most benchmarked populations. The empirical evidence presented in this dissertation on the case of Latinos in Little Havana challenges the ways that identity, trust, and civic engagement are conceptualized and theorized, especially among immigrants to the US.