Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 291-297). Also available via the Internet.

Thesis (M.Eng.). / Written for the Dept. of Mining and Materials Engineering. Title from title page of PDF (viewed 2009/06/17). Includes bibliographical references.

Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Cesar A. Luongo, Florida State University, College of Engineering, Dept. of Mechanical Engineering. Title and description from dissertation home page (viewed Jan. 13, 2005). Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xv, 129 p.; also includes graphics. Includes bibliographical references. Available online via OhioLINK's ETD Center.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1980. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 233-245).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1980. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 243-252).

Thesis (Ph. D.)--Drexel University, 2006. / Includes abstract. Includes bibliographical references (leaves 167-176).

Micro-electromechanical systems (MEMS) are electrically controlled micro-machines which have been widely used in both industrial applications and scientific research. This technology allows us to use macro-machines to build micro-machines (MEMS) and then use micro-machines to fabricate even smaller structures, namely nano-structures. In this thesis, the concept of Fab on a Chip will be discussed where we construct a palette of MEMS-based micron scale tools including lithography tools, novel atomic deposition sources, atomic mass sensors, thermometers, heaters, shutters and interconnect technologies that allow us to precisely fabricate nanoscale structures and conduct in-situ measurements using these micron scale devices. Such MEMS devices form a novel microscopic nanofabrication system that can be integrated into a single silicon chip. Due to the small dimension of MEMS, fabrication specifications including heat generation, patterning resolution and film deposition precision outperform traditional fabrication in many ways. It will be shown that one gains many advantages by doing nano-lithography and physical vapor deposition at the micron scale. As an application, I will showcase the power of the technique by discussing how we use Fab on a Chip to conduct quench condensation of superconducting Pb thin films where we are able to gently place atoms upon a surface, creating a uniform, disordered amorphous film and precisely tune the superconducting properties. This shows how the new set of techniques for nanofabrication will open up an unexplored regime for the study of the physics of devices and structures with small numbers of atoms.

Sm-Ba-Cu-O (SmBCO), which is a member of rare-earth barium cuprate [(RE)BCO] high-temperature superconductors, has significant potential for practical applications due to its higher critical transition temperature (Tc), higher critical current density (Jc), the so-called ‘peak effect’ characteristic at relatively high applied magnetic field and higher irreversibility field than that of the more established YBCO. The aim of this study is to investigate and overcome the obstacles in fabricating SmBCO bulk superconductors in air, to further improve their superconducting properties and, finally, to scale-up the fabrication of SmBCO single grains, therefore realising the engineering applications of this technologically important material. A modified seeding technique using an MgO-NdBCO generic seed accompanied by a buffer layer has been developed to process the SmBCO system to increase the success rate of growing single domain, bulk SmBCO superconductors in air via a top-seeded melt growth process using a conventional chamber furnace. Subsequently, the effects of doping in SmBCO bulk superconductors on the performance of SmBCO superconductors containing different dopants are discussed based on an analysis of their superconducting properties, including Tc and Jc, and on the microstructures of the samples. Furthermore, the scale-up of SmBCO bulk superconductors has been achieved by the addition of silver to the precursor powders and the introduction of a Y-123 layer beneath the SmBCO bulk pre-forms. Finally, trapped field measurements on successfully grown SmBCO bulk superconductors up to 41 mm in diameter have been performed and used to demonstrate significantly improved field trapping ability due to the optimization of the processing and composition of the SmBCO system. An Ag-SmBCO single grain of diameter 31 mm has achieved 1.033 T at 77 K, which is the highest value of trapped field reported worldwide for SmBCO samples of a similar size grown in air.

A technology that has the potential to liquefy hydrogen and natural gas efficiently is an Active Magnetic Regenerative Liquefier (AMRL). An AMRL exploits the magnetocaloric effect displayed by magnetic materials whereby a reversible temperature change is induced when the material is exposed to a magnetic field. This effect can be used to produce cooling. By using the magnetic materials in a regenerator as the heat storage medium and as the means of work input, one creates an Active Magnetic Regenerator (AMR). Because the adiabatic temperature change is a strong function of temperature for most materials, to span a large temperature range such as that needed to liquefy hydrogen, a number of different materials may be needed to make up one or more regenerators. Single material AMRs have been proven, but layering with more than one material has not. This thesis is a study of AMRs using magnetic refrigerants displaying second-order paramagnetic to ferromagnetic ordering. An analysis of AMR thermodynamics is performed and results are used to define properties of ideal magnetic refrigerants. The design and construction of a novel test apparatus consisting of a conduction-cooled superconducting solenoid and a reciprocating AMR test apparatus are described. A numerical model is developed describing the energy transport in an AMR. Experiments using Gd are performed and results are used to validate the model. A strong relationship between flow phasing is discovered and possible reasons for this phenomenon are discussed. Simulations of AMRs operating in unconventional modes such as at temperatures greater than the transition temperature reveal new insights into AMR behaviour. Simulations of two-material layered AMRs suggest the existence of a jump phenomenon occurring regarding the temperature span. These results are used to explain the experimental results reported by other researchers for a two-material AMR. / Graduate