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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Dealloying and Synthesis of Nanoporous Pt and Au from AgPt and AgAu Binary Alloys

Ganti Mahapatruni, Aditya 31 December 2010 (has links)
A study is presented on the synthesis and characterization of nanoporous AgPt and AgAu alloys after annealing and dealloying in 5% HClO4. Dealloying removes the less-noble atom from the alloy surface to produce nanoporous, highly-interconnected ligaments. Voltammetry of AgPt and AgAu shows the critical potential, Ec, at various potential scan rates. Potential hold current decay experiments on Ag-23Pt and Ag-23Au further show the intrinsic Ec to be 275 mV and 290 mV, respectively. Ec was governed by thermodynamic clustering in the alloys as opposed to dissolution-diffusion kinetic effects. EDX shows the starting 77Ag-23Pt material changes composition after dealloying to about 12Ag-88Pt. XRD indicates the presence of ordering in AgPt via a superlattice (100)-peak for a specific anneal treatment. EIS measurements done on as-annealed and dealloyed AgPt and AgAu samples show the onset of bulk porosity and show that capacitance increase is equal for both alloys at two different dealloying potentials.
2

Dealloying and Synthesis of Nanoporous Pt and Au from AgPt and AgAu Binary Alloys

Ganti Mahapatruni, Aditya 31 December 2010 (has links)
A study is presented on the synthesis and characterization of nanoporous AgPt and AgAu alloys after annealing and dealloying in 5% HClO4. Dealloying removes the less-noble atom from the alloy surface to produce nanoporous, highly-interconnected ligaments. Voltammetry of AgPt and AgAu shows the critical potential, Ec, at various potential scan rates. Potential hold current decay experiments on Ag-23Pt and Ag-23Au further show the intrinsic Ec to be 275 mV and 290 mV, respectively. Ec was governed by thermodynamic clustering in the alloys as opposed to dissolution-diffusion kinetic effects. EDX shows the starting 77Ag-23Pt material changes composition after dealloying to about 12Ag-88Pt. XRD indicates the presence of ordering in AgPt via a superlattice (100)-peak for a specific anneal treatment. EIS measurements done on as-annealed and dealloyed AgPt and AgAu samples show the onset of bulk porosity and show that capacitance increase is equal for both alloys at two different dealloying potentials.
3

Nanoporosity Formation in Ag-Au Alloys

Dursun, Aziz 21 January 2004 (has links)
Selective dissolution also known as dealloying is a corrosion process in which one component of a binary alloy system is selectively removed through an electrochemically controlled process which leads to the formation of a porous metal "sponge" with a porosity that is completely interconnected and random in direction. Nanoporous metals are desirable since they have larger surface areas than an equal volume of non-porous material. Because of their enormous surface area per volume, these highly porous metal electrodes are superior materials for high surface area applications such as in biomedical devices, microfilters and catalysts. Understanding the kinetic processes governing the development of porosity during dealloying and having ability to change the electrochemical conditions will allow us to better control over the average ligament size and distribution in porosity. The basic kinetic processes involved in the formation of these structures are related to such issues as environmental effects and electrochemical conditions on diffusion, microscopic coarsening phenomenon at room temperature and elevated temperatures, alloy passivation, and Gibbs-Thomson effects. The average pore size and distribution was found to depend on the electrolyte composition, dealloying rate, applied potential and time. The porosity was found to significantly coarsen at room temperature during the dealloying process and this coarsening was highly dependent on the applied potential. It is showed that the commonly accepted measurement of the critical potential for alloy dissolution calculated based on extrapolation of anodic polarization data results in an overestimation of this quantity. A series of constant applied potential experiments prove to be a more accurate method for critical potential determination. / Ph. D.
4

Both temple and tomb: difference, desire and death in the sculptures of the Royal museum of central Africa

Morris, Wendy Ann 30 November 2003 (has links)
Both Temple and Tomb is a dissertation in two parts. The first part is an examination and analysis of a collection of 'colonial' sculptures on permanent display in the Royal Museum of Central Africa in Tervuren Belgium. The second part is a reflection on the author's own paintings, drawings and film and an examination of the critical potential of these images in challenging the colonial narratives of the RMCA. Part I presents two arguments. The first is that European aesthetic codes have been used to legitimize the conquest of the Congo and to award sanction to a voyeuristic gaze. The second is that the organization of the sculptures of Africans (and European females) into carefully managed spaces and relationships results in the creation of erotically-charged formations that are intended to afford pleasure to male European spectators. Part II examines the strategies used in Re-Turning the Shadows to disrupt (neo)colonial patterns of viewing that have become ritual and 'naturalized'. Against RMCA narratives that pay homage to the objectivity of science and research, the paintings and film present images that explore multiple subjectivities, mythologizing impulses, and metaphoric allusions. / Art History, Visual Arts & Musicology / M.A. (Visual Arts)
5

Both temple and tomb: difference, desire and death in the sculptures of the Royal museum of central Africa

Morris, Wendy Ann 30 November 2003 (has links)
Both Temple and Tomb is a dissertation in two parts. The first part is an examination and analysis of a collection of 'colonial' sculptures on permanent display in the Royal Museum of Central Africa in Tervuren Belgium. The second part is a reflection on the author's own paintings, drawings and film and an examination of the critical potential of these images in challenging the colonial narratives of the RMCA. Part I presents two arguments. The first is that European aesthetic codes have been used to legitimize the conquest of the Congo and to award sanction to a voyeuristic gaze. The second is that the organization of the sculptures of Africans (and European females) into carefully managed spaces and relationships results in the creation of erotically-charged formations that are intended to afford pleasure to male European spectators. Part II examines the strategies used in Re-Turning the Shadows to disrupt (neo)colonial patterns of viewing that have become ritual and 'naturalized'. Against RMCA narratives that pay homage to the objectivity of science and research, the paintings and film present images that explore multiple subjectivities, mythologizing impulses, and metaphoric allusions. / Art History, Visual Arts and Musicology / M.A. (Visual Arts)

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