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Universidade Estadual de Campinas

1. Nascente, Pedro Augusto de Paula. Adsor??o e ordenamento moleculares sobre pal?dio (111) : um estudo por HREELS e LEED .

Degree: 1991, Universidade Estadual de Campinas

Resumo: Monocamadas de oxig?nio coadsorvido com acetileno e etileno em uma superf?cie de Pd(111) foram estudadas por Espectroscopia de Alta Resolu??o por Perdas Energ?ticas de El?trons ( "High Resolution Electron Energy Loss Spectroscopy" -HREELS) e Difra??o de El?trons de Baixa Energia ("Low Energy Electron Diffraction" -LEED) a temperaturas de 150 a 320 K. A adsors?o de ambos C2H2 e C2H4 a baixa temperatura resultou em mol?culas quimissorvidas n?o dissociativamente e a pr?-adsors?o de oxig?nio n?o modificou os resultados de LEED e HREELS.? temperatura ambiente ambos C2H2 e C2H4 formaram etilidino (C2H3), que se ordena fracamente na estrutura (?3x?3)R 30?. Descobri que a pr?-adsor??o de oxig?nio induziu melhor ordenamento do C2H3 formado a partir da exposi??o de acetileno, mas n?o do C2H3 derivado da adsors?o de etileno. A sobrecamada de O + C2H3 sobre Pd(111) ? o primeiro caso observado de ordenamento de um adsorvido org?nico induzido pela coadsors?o de oxig?nio. ? proposto que o oxig?nio pr?-adsorvido ajudou no ordenamento da sobrecamada de C2H3 por meio de: (a) remo??o eficiente do hidrog?nio superficial e (b) intera??o atrativa com C2H3 resultando em ordenamento induzido de coadsorvidos; Abstract: Overlayers of oxygen coadsorbed with acetylene and ethylene on a Pd(111) surface have been studied by High Resolution Electron Energy Loss Spectroscopy (HREELS) and Low Energy Electron Diffraction (LEED) in the temperature range of 150 to 320 K. Low temperature adsorption of both C2H2 and C2H4 resulted in non-dissociatively chemisorbed molecules, and the pre-adsorption of oxygen did not change the LEED and HREELS data. At room temperature both C2H2 and C2H4 formed ethylidyne (C2H3), which poorly ordered in a(?3x?3)R 30? structure. It was found that pre-adsorption of oxygen induced better ordering for C2H3 formed from acetylene exposure, but not for C2H3 derived from ethylene adsorption. The O + C2H3 overlayer on Pd(111) is the first observed case of oxygen induced ordering of an organic adsorbate. It is proposed that pre-adsorbed oxygen helped the ordering of the C2H3 overlayer by (a) efficiently removing surface hydrogen and (b) attractively interacting with C2H3 to yield coadsorbate induced ordering Advisors/Committee Members: Castro, Sandra Gra?a Carnicero de, 1949-2000 (advisor).

Subjects/Keywords: Hidrocarbonetos; Cat?lise; Superf?cies (F?sica)

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Nascente, P. A. d. P. (1991). Adsor??o e ordenamento moleculares sobre pal?dio (111) : um estudo por HREELS e LEED . (Thesis). Universidade Estadual de Campinas. Retrieved from http://repositorio.unicamp.br/jspui/handle/REPOSIP/277120

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Nascente, Pedro Augusto de Paula. “Adsor??o e ordenamento moleculares sobre pal?dio (111) : um estudo por HREELS e LEED .” 1991. Thesis, Universidade Estadual de Campinas. Accessed September 20, 2019. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277120.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Nascente, Pedro Augusto de Paula. “Adsor??o e ordenamento moleculares sobre pal?dio (111) : um estudo por HREELS e LEED .” 1991. Web. 20 Sep 2019.

Vancouver:

Nascente PAdP. Adsor??o e ordenamento moleculares sobre pal?dio (111) : um estudo por HREELS e LEED . [Internet] [Thesis]. Universidade Estadual de Campinas; 1991. [cited 2019 Sep 20]. Available from: http://repositorio.unicamp.br/jspui/handle/REPOSIP/277120.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Nascente PAdP. Adsor??o e ordenamento moleculares sobre pal?dio (111) : um estudo por HREELS e LEED . [Thesis]. Universidade Estadual de Campinas; 1991. Available from: http://repositorio.unicamp.br/jspui/handle/REPOSIP/277120

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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