期刊
NANOSCALE RESEARCH LETTERS
卷 11, 期 -, 页码 -出版社
SPRINGER
DOI: 10.1186/s11671-016-1228-9
关键词
Nanomaterial; Free-volume void; Positron annihilation; Positron trapping
资金
- SAIA (Slovak Academic Information Agency) within National Scholarship Program of Slovak Republic
- Slovak Research and Development Agency [APVV-14-0103, SK-UA-2013-0003]
Structural transformations caused by coarse-grained powdering and fine-grained mechanochemical milling in a dry mode were probed in high-temperature modification of tetra-arsenic tetra-sulfide known as beta-As4S4. In respect to X-ray diffraction analysis, the characteristic sizes of beta-As4S4 crystallites in these coarse-and fine-grained powdered pellets were 90 and 40 nm, respectively. Positron annihilation lifetime spectroscopy was employed to characterize transformations occurred in free-volume structure of these nanoarsenicals. Experimentally measured positron lifetime spectra were parameterized in respect to three-or two-term fitting procedures and respectively compared with those accumulated for single crystalline realgar beta-As4S4 polymorph. The effect of coarse-grained powdering was found to result in generation of large amount of positron and positronium Ps trapping sites inside arsenicals in addition to existing ones. In fine-grained powdered beta-As4S4 pellets, the positron trapping sites with characteristic free volumes close to bi-and tri-atomic vacancies were evidently dominated. These defects were supposed to originate from grain boundary regions and interfacial free volumes near aggregated beta-As4S4 crystallites. Thus, the cumulative production of different positron traps with lifetimes close to defect-related lifetimes in realgar beta-As4S4 polymorph was detected in fine-grained milled samples.
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