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Title: TEM study of ion beam induced amorphization of minerals

Abstract

Metamicitization is a radiation-induced, periodic-to-aperiodic phase transition caused by alpha-decay events of nuclides in the U[sup 235], U[sup 238] and Th[sup 232] decay series. Despite careful studies of natural specimens, poorly known ages and thermal histories make it difficult to analyze this phenomenon as a function of increasing dose. In this study, ion beam irradiations have been used to simulate the process in many different structure types, including olivine, zircon, zirconolite and neptunite. The irradiations were completed using the HVEM-Tandem facility at Argonne National Laboratory, which links an ion accelerator with a transmission electron microscope, so that the structural change of the target during irradiation can be monitored in situ by electron diffraction. In most cases, complete amorphization of the target occurs within several hours of the ion beam irradiation. The ions used are He, Ne, Ar, Kr and Xe with energy ranges of 200 keV to 1.5 MeV. The electron energy was kept at 300 keV during ion irradiations for in situ observation. Irradiations were performed under a controlled temperature which varies from near liquid helium temperature (15K) to 650 C. Complete amorphization was induced at fractions of one displacement per atom (dpa) damage level in all the mineralsmore » irradiated by Kr and Xe ions at room temperature. Critical amorphization dose increases with the decreasing complexity of the mineral structure, increasing ionicity of the bonding, and increasing irradiation temperature. High resolution transmission electron microscopy has also been performed to study in detail the formation of amorphous domains at low and moderate ion doses. Amorphous domains with the size of displacement cascades (calculated by computer simulations) have been observed.« less

Authors:
;  [1]
  1. (Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Geology)
Publication Date:
OSTI Identifier:
5905745
Alternate Identifier(s):
OSTI ID: 5905745
Report Number(s):
CONF-921058--
Journal ID: ISSN 0016-7592; CODEN: GAAPBC
Resource Type:
Conference
Journal Name:
Geological Society of America, Abstracts with Programs; (United States)
Additional Journal Information:
Journal Volume: 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; Journal ID: ISSN 0016-7592
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 58 GEOSCIENCES; MINERALS; PHYSICAL RADIATION EFFECTS; OLIVINE; ZIRCON; ZIRCONOLITE; ALPHA PARTICLES; AMORPHOUS STATE; ION BEAMS; IRRADIATION; MORPHOLOGICAL CHANGES; PHASE TRANSFORMATIONS; SIMULATION; TRANSMISSION ELECTRON MICROSCOPY; BEAMS; CHARGED PARTICLES; ELECTRON MICROSCOPY; MICROSCOPY; OXIDE MINERALS; RADIATION EFFECTS; SILICATE MINERALS 360605* -- Materials-- Radiation Effects; 580000 -- Geosciences

Citation Formats

Wang, Lu Min, and Ewing, R.C. TEM study of ion beam induced amorphization of minerals. United States: N. p., 1992. Web.
Wang, Lu Min, & Ewing, R.C. TEM study of ion beam induced amorphization of minerals. United States.
Wang, Lu Min, and Ewing, R.C. Wed . "TEM study of ion beam induced amorphization of minerals". United States.
@article{osti_5905745,
title = {TEM study of ion beam induced amorphization of minerals},
author = {Wang, Lu Min and Ewing, R.C.},
abstractNote = {Metamicitization is a radiation-induced, periodic-to-aperiodic phase transition caused by alpha-decay events of nuclides in the U[sup 235], U[sup 238] and Th[sup 232] decay series. Despite careful studies of natural specimens, poorly known ages and thermal histories make it difficult to analyze this phenomenon as a function of increasing dose. In this study, ion beam irradiations have been used to simulate the process in many different structure types, including olivine, zircon, zirconolite and neptunite. The irradiations were completed using the HVEM-Tandem facility at Argonne National Laboratory, which links an ion accelerator with a transmission electron microscope, so that the structural change of the target during irradiation can be monitored in situ by electron diffraction. In most cases, complete amorphization of the target occurs within several hours of the ion beam irradiation. The ions used are He, Ne, Ar, Kr and Xe with energy ranges of 200 keV to 1.5 MeV. The electron energy was kept at 300 keV during ion irradiations for in situ observation. Irradiations were performed under a controlled temperature which varies from near liquid helium temperature (15K) to 650 C. Complete amorphization was induced at fractions of one displacement per atom (dpa) damage level in all the minerals irradiated by Kr and Xe ions at room temperature. Critical amorphization dose increases with the decreasing complexity of the mineral structure, increasing ionicity of the bonding, and increasing irradiation temperature. High resolution transmission electron microscopy has also been performed to study in detail the formation of amorphous domains at low and moderate ion doses. Amorphous domains with the size of displacement cascades (calculated by computer simulations) have been observed.},
doi = {},
journal = {Geological Society of America, Abstracts with Programs; (United States)},
issn = {0016-7592},
number = ,
volume = 24:7,
place = {United States},
year = {1992},
month = {1}
}

Conference:
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