{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/22606"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/22606","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Structure and melting of small metal particles observed by stem microdiffraction","abstract":"The structure of solvent deposited (Au, Au-Ag, Pt) and vapor deposited (Cu) metal particles $\\approx$10-40 A A was studied by electron microdiffraction in a STEM. A CCD array recorded the microdiffraction patterns with high sensitivity and dynamic range, and low noise Microdiffraction patterns were classified according to whether they had distinct Bragg peaks, or were diffuse. Patterns with distinct Bragg peaks showed low rates of twinning, with an upper bound of $\\approx$14 $\\pm$ 3% in the case of Au-Ag particles. Diffuse patterns indicate that many of the particles are highly disordered, $\\approx$88% in the case of Au particles. The effects of the electron beam on Pt particles were studied further. Crystalline Pt particles up to 40A in diameter become disordered after exposures ranging from less than a second up to 40 minutes. Disordered particles' diffraction patterns were dynamic, with flickers of intensity lasting $\\approx$15 msec (the resolution of the video tape). Pt particles on an amorphous C substrate remained disordered $\\approx$20 min before recrystallizing. The dynamic nature and persistance of the disordered state are reminiscent of Ajayan and Marks's quasimelting theory.","abstract_html":"The structure of solvent deposited (Au, Au-Ag, Pt) and vapor deposited (Cu) metal particles $\\approx$10-40 A A was studied by electron microdiffraction in a STEM. A CCD array recorded the microdiffraction patterns with high sensitivity and dynamic range, and low noise Microdiffraction patterns were classified according to whether they had distinct Bragg peaks, or were diffuse. Patterns with distinct Bragg peaks showed low rates of twinning, with an upper bound of $\\approx$14 $\\pm$ 3% in the case of Au-Ag particles. Diffuse patterns indicate that many of the particles are highly disordered, $\\approx$88% in the case of Au particles. The effects of the electron beam on Pt particles were studied further. Crystalline Pt particles up to 40A in diameter become disordered after exposures ranging from less than a second up to 40 minutes. Disordered particles' diffraction patterns were dynamic, with flickers of intensity lasting $\\approx$15 msec (the resolution of the video tape). Pt particles on an amorphous C substrate remained disordered $\\approx$20 min before recrystallizing. The dynamic nature and persistance of the disordered state are reminiscent of Ajayan and Marks's quasimelting theory.","abstract_has_math":true,"creators":["Contrata, Walter"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Mochel, J.M."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T13:45:17Z","date_published":"2011-05-07T13:45:17Z","updated_at":"2026-07-22T22:25:20Z","subjects":["Physics, Molecular","Physics, Condensed Matter"],"languages":["eng"],"rights":["Copyright 1992 Contrata, Walter"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9215799","(UMI)AAI9215799"],"render_values":[{"text":"AAI9215799","href":null,"code":true},{"text":"(UMI)AAI9215799","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/22606","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Mochel, J.M."]},{"key":"dc:creator","label":"Author","values":["Contrata, Walter"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T13:45:17Z","10000-01-01","1992"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Physics, Molecular","Physics, Condensed Matter"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1992 Contrata, Walter"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9215799","(UMI)AAI9215799","http://hdl.handle.net/2142/22606"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The structure of solvent deposited (Au, Au-Ag, Pt) and vapor deposited (Cu) metal particles $\\approx$10-40 A A was studied by electron microdiffraction in a STEM. A CCD array recorded the microdiffraction patterns with high sensitivity and dynamic range, and low noise Microdiffraction patterns were classified according to whether they had distinct Bragg peaks, or were diffuse. Patterns with distinct Bragg peaks showed low rates of twinning, with an upper bound of $\\approx$14 $\\pm$ 3% in the case of Au-Ag particles. Diffuse patterns indicate that many of the particles are highly disordered, $\\approx$88% in the case of Au particles. The effects of the electron beam on Pt particles were studied further. Crystalline Pt particles up to 40A in diameter become disordered after exposures ranging from less than a second up to 40 minutes. Disordered particles' diffraction patterns were dynamic, with flickers of intensity lasting $\\approx$15 msec (the resolution of the video tape). Pt particles on an amorphous C substrate remained disordered $\\approx$20 min before recrystallizing. The dynamic nature and persistance of the disordered state are reminiscent of Ajayan and Marks's quasimelting theory.","Made available in DSpace on 2011-05-07T13:45:17Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9215799.pdf: 3891449 bytes, checksum: cffc4f51927d59d0e4822051ee521650 (MD5) Previous issue date: 1992","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:58:46Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:27:40-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"]},{"key":"dc:title","label":"Title","values":["Structure and melting of small metal particles observed by stem microdiffraction"]}]}],"canonical_facts":{"dc:contributor":["Mochel, J.M."],"dc:creator":["Contrata, Walter"],"dc:date":["2011-05-07T13:45:17Z","10000-01-01","1992"],"dc:description":["The structure of solvent deposited (Au, Au-Ag, Pt) and vapor deposited (Cu) metal particles $\\approx$10-40 A A was studied by electron microdiffraction in a STEM. A CCD array recorded the microdiffraction patterns with high sensitivity and dynamic range, and low noise Microdiffraction patterns were classified according to whether they had distinct Bragg peaks, or were diffuse. Patterns with distinct Bragg peaks showed low rates of twinning, with an upper bound of $\\approx$14 $\\pm$ 3% in the case of Au-Ag particles. Diffuse patterns indicate that many of the particles are highly disordered, $\\approx$88% in the case of Au particles. The effects of the electron beam on Pt particles were studied further. Crystalline Pt particles up to 40A in diameter become disordered after exposures ranging from less than a second up to 40 minutes. Disordered particles' diffraction patterns were dynamic, with flickers of intensity lasting $\\approx$15 msec (the resolution of the video tape). Pt particles on an amorphous C substrate remained disordered $\\approx$20 min before recrystallizing. The dynamic nature and persistance of the disordered state are reminiscent of Ajayan and Marks's quasimelting theory.","Made available in DSpace on 2011-05-07T13:45:17Z (GMT). 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