Thesis (M.A.)--Cleveland State University, 2009. / Abstract. Title from PDF t.p. (viewed on Sept. 28, 2009). Includes bibliographical references (p. 64-65). Available online via the OhioLINK ETD Center and also available in print.

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains ix, 85 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 63-65).

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: John W. Gillespie, Dept. of Materials Science. Includes bibliographical references.

Thesis (M.Arch.)--University of Hong Kong, 1996. / Includes special study report entitled : Study on transparency. Includes bibliographical references. Also available in print.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Peter F. Green. Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Suresh G. Advani, Dept. of Mechanical Engineering. Includes bibliographical references.

Thesis (M. Sc.)(Geology)--University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains ix, 118 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 117-118).

Macroscopic ductility is promoted in bulk metallic glasses by both composite reinforcements (at low temperatures) and by the activation of viscous flow mechanisms (at high temperatures). It is of fundamental interest to understand deformation physics when both of these strategies are employed at the same time. Despite the quickly growing literature around the room-temperature mechanical properties of metallic glass matrix composites (MGMCs), the deformation behavior of MGMCs over a wide range of temperatures and strain rates has yet to be systematically investigated, especially at high temperatures close to Tg. Here the high temperature compressive behavior of Zr-based MGMCs with in-situ reinforcements is explored systematically over a series of strain rates. Additionally, the volume fraction of second-phase reinforcements was tailored to explore its effect on both inhomogeneous and homogeneous deformation modes. / Singapore-MIT Alliance (SMA)

Made available in DSpace on 2014-08-13T14:50:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-08-05Bitstream added on 2014-08-13T18:01:31Z : No. of bitstreams: 1 000746896.pdf: 3440391 bytes, checksum: 4769422191b2c82210f6239e3eba332e (MD5) / Vidros emissores de luz vêm despertando interesse como potenciais materiais para melhorar a eficiência de células solares comerciais de silício através da conversão descendente de energia onde um fóton da região do visível é convertido em dois fótons na região de ~1000 nm, que é a região da banda proibida do silício. Neste sentido, materiais dopados com íons lantanídeos que são muito promissores devido sua riqueza espectral, tem despertado o interesse nos últimos anos e muitos pares de íons lantanídeos tem sido propostos, dentre eles o par Pr3+-Yb3+, porém sem toda elucidação dos processos de transferência envolvidos. Este trabalho apresenta um estudo realizado em vidros fluoroindatos dopados com íons Pr3+ e co-dopados com íons Pr3+/Yb3+ quanto aos processos de conversão descendente Pr3+→Yb3+ e seus mecanismos. As seguintes composições vítreas foram estudadas: [(100-x) 40InF3-20SrF2-20BaF2- 20ZnF2:xPrF3], (x=0,01; 0,02; 0,05 e 1,0 % mol) e [(99-x) 40InF3-20SrF2-20BaF2- 20ZnF2:1PrF3:xYbF3], (0 ≤ x ≥ 3.0 % mol). O estudo térmico e espectroscópico dessas amostras produzidas pelo método clássico de fusão choque-térmico, mostrou uma boa estabilidade térmica frente à cristalização e uma janela de transparência de até ~ 8 μm, consequência da relativamente baixa energia de modos vibracionais (~500 cm-1) observadas no espectro Raman. As medidas de luminescência nos vidros co-dopados com Pr3+:Yb3+ evidenciaram o processo de conversão descendente de energia, importante para a aplicação em células solares de silício devido a emissão em 980 nm do Yb3+, como resultado da excitação dos íons Pr3+ na região do visível. O processo de conversão descendente de energia se dá por pelo menos três mecanismos, sendo que em dois deles a emissão ocorre a partir dos níveis 3PJ e um a partir do nível 1D2 do íon Pr3+. Valores de eficiência de transferência de 60,8% e 79% foram observados para a amostra... / Glass light emitting in the IR (1000 nm) region have attracted interest as potential materials for improving the efficiency of commercial silicon solar cell through energy downconversion where a photon in the visible region is converted into two photons in the ~1000 nm, which is the region of band gap of silicon. In this sense, materials doped with lanthanide ions that are very promising due to its spectral richness, has aroused interest in recent years and many pairs of lanthanide ions have been proposed, among then the pair Pr3+:Yb3+, but without any elucidation of the transfer processes involved. This work presents a study in fluoroindate glasses doped with Pr3+ and co-doped with Pr3+ / Yb3+ about the down-conversion energy process Pr3+→Yb3+ and the mechanism involved. The vitreous following compositions were used: [(100-x) 40InF3-20SrF2-20BaF2- 20ZnF2:xPrF3], (x=0,01; 0,02; 0,05 e 1,0 % mol) e [(99-x) 40InF3-20SrF2-20BaF2- 20ZnF2:1PrF3 : xYbF3], (0 ≤ x ≥ 3.0 % mol). The spectroscopic and thermal study of these samples produced by the classical method of melting-quenching showed a good thermal stability against crystallization and window transparency of ~ 8 microns, consequence of the relatively low phonon energy (~500 cm-1) seemed in Raman spectra. Measurements of luminescence in the glasses co-doped with Pr3+: Yb3+ showed the down-conversion process important for application in silicon solar cells due to emission at 1000 nm of Yb3+ as a result of excitation of the Pr3+ ions in the visible region. The downconversion process occurs by at least three mechanisms, in that two of then the emission occurs from 3PJ levels and one from the 1D2 level of Pr3+ ion. Transfer efficiency of 60.8% and 79% were observed for the sample containing 1 mol% Pr3+ and 3 mol% Yb3+. After the excitation of the 3PJ levels energy transfer occurs, where first the energy is transferred to an Yb3+ ion by cross relaxation [Pr3+ (3P0 → 1G4)...