Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: sapphire; bonding. Includes bibliographical references (p. 72-74).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 90-92). Also available via the Internet.

"New high performance optical systems require highly durable, broadband window materials in larger sizes than are currently available. To meet this need, a low cost edge-bonding process was developed for producing large area sapphire windows from smaller, melt-grown blanks. The method uses a polycrystalline alumina interlayer to promote diffusion and single crystal conversion at the interface between two sapphire substrates and produce high strength bonds. The goal of the current research effort is to determine the optimal alumina composition for maximum bond strength. Polycrystalline alumina fillets containing various chemical additives were prepared by tape casting for use in bonding trials. Oriented sapphire blanks were edge bonded in a furnace with special fixtures to accurately align and apply a load to the components during heat treatment. This approach is consistent with and builds upon the methods used in the previous edge-bonding studies. Flexure strength of the bonded samples, as compared to monolithic sapphire, was used as the performance metric. Additional bonding runs were carried out using the highest performing fillet composition in order to provide a sufficient number of specimens to conduct a Weibull analysis of the failure probability of the bonded material as a function of applied stress. A high purity alumina composition containing 3 wt.% SiO2, 0.05 wt.% MgO, and 0.05 wt.% Ti, produced the highest strength bonds. This composition yielded an average fracture strength of 255 MPa (37 kpsi), a Weibull modulus of 8.2, and a characteristic strength of 269 MPa (39 kpsi). These results compare favorably to monolithic sapphire specimens which yielded an average fracture strength of 284 MPa (41 kpsi)."

No description available.

published_or_final_version / Physics / Master / Master of Philosophy

Wide bandgap semiconductors have entered into Naval radar use and will eventually replace vacuum tube and conventional solid-state amplifiers for all modern military radar and communications applications. Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) are on the leading edge of wide bandgap technology and have the performance characteristics to dominate in high power â high bandwidth applications. The Defense Advanced Research Projects Agency (DARPA), Office of Naval Research (ONR) and Missile Defense Agency (MDA) are all sponsoring research projects to apply wide bandgap technology. This thesis studies the effects of changing the substrate material of an existing GaN HEMT from sapphire to diamond through the use of commercially available Silvaco software for modeling and simulation. The unparalleled thermal properties of diamond are expected to dramatically decrease device temperatures and increase component lifetimes and reliability.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Title page, contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / This thesis describes the design and construction of an instrument intended to measure the length noise present in optical materials. The detection of thermoelastic noise in sapphire provides the initial motivation for the instrument, though the intent is to build a system capable of robustly characterising a variety of noise sources in multiple materials. Theoretical modelling is used to design a system that is expected to be dominated by thermoelastic noise. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1295741 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2007

Title page, contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / This thesis describes the design and construction of an instrument intended to measure the length noise present in optical materials. The detection of thermoelastic noise in sapphire provides the initial motivation for the instrument, though the intent is to build a system capable of robustly characterising a variety of noise sources in multiple materials. Theoretical modelling is used to design a system that is expected to be dominated by thermoelastic noise. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1295741 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2007

Thesis (M.Phil.)--University of Hong Kong, 2003. / Includes bibliographical references. Also available in print.