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HREM imaging of small Pt clusters dispersed in Y-zeolites (1990)

Pan, M. ; Cowley, J. M. ; Chan, I. Y.

Springer

Catalysis letters 5 (1990), S. 1-11

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ISSN: 1572-879X

Keywords: HREM ; small Pt clusters ; zeolites

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract High resolution electron microscopy (HREM) has been used to study dispersed Pt clusters in NaY- and USY-zeolites. All the samples contained 0.8% Pt and were reduced at temperatures of 300 ° C, 500 ° C and 650 ° C. The size of the Pt clusters ranged from a few å up to ∼ 30 å. When the incident electron beam was sufficiently strong, it caused some of the extremely small metal clusters to sinter. This was usually accompanied by zeolite damage. This in-situ sintering must be taken into consideration when interpreting the particle size distribution results obtained solely by TEM, especially for particles that are smaller than 10 å. The minimum phase contrast imaging condition is demonstrated to be more appropriate than optimum defocus for detecting the extremely small Pt clusters inside the zeolite structures.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00772087

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Electron diffraction phenomena observed with a high resolution STEM instrument (1986)

Cowley, J. M.

New York, NY : Wiley-Blackwell

Journal of Electron Microscopy Technique 3 (1986), S. 25-44

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ISSN: 0741-0581

Keywords: Electron diffraction ; Scanning transmission electron microscopy ; Microdiffraction ; In-line holography ; Small particles ; Crystal structure ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Natural Sciences in General

Notes: Because of the high brightness of the cold field emission source used in a dedicated scanning transmission electron microscopy (STEM) instrument, it is possible to focus electrons to a cross-over of width 3Å or less and, with a suitable detection system, to obtain diffraction patterns from specimen regions of this size or greater. Coherent interference effects are visible in shadow images (in-line holograms) and in convergent beam diffraction patterns. Special techniques have been developed for gathering information from the diffraction patterns for application to the study of the structures of crystal defects, crystal surfaces and small particles. Possibilities have been explored for holographic reconstruction from shadow images.

Additional Material: 14 Ill.