Determination of Structure and Phase Transition of Light Element Nanocomposites in Mesoporous Silica: Case study of NHBH in MCM-41.
Nanocomposition of molecular crystal ammonia borane (AB) by embedding it in mesoporous silica leads to a remarkable enhancement of the hydrogen storage properties. To investigate the nature of a nanophase AB, we used atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffra...
| Published in: | Journal of the American Chemical Society Vol. 131; no. 38; pp. 13749 - 13756 |
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| Main Authors: | , , , , |
| Format: | Case Study |
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American Chemical Society
9/30/2009
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| Subjects: | |
| Online Access: | View this record in EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=44600327&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 44600327 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 9/30/2009 vid: 131 iid: 38 pid: 997 pub: American Chemical Society artinfo: ui: 44600327 10.1021/ja904901d ppf: 13749 ppct: 7 formats: tig: atl: Determination of Structure and Phase Transition of Light Element Nanocomposites in Mesoporous Silica: Case study of NHBH in MCM-41. aug: au: Hyunjeong Kim Karkamkar, Abhi Autrey, Tom Chupas, Peter Proffen, Thomas affil: Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Pacific Northwest National Laboratory, Richland, Washington 99352 Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 su: Molecular crystals Boranes Optical diffraction Mesoporous materials Nanostructured materials sug: subj: Molecular crystals Boranes Optical diffraction Mesoporous materials Nanostructured materials ab: Nanocomposition of molecular crystal ammonia borane (AB) by embedding it in mesoporous silica leads to a remarkable enhancement of the hydrogen storage properties. To investigate the nature of a nanophase AB, we used atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data to follow the structural evolution of AB embedded within MCM-41 at temperatures ranging from 80 to 300 K. We found that the nanophase AB residing within the mesoporous scaffold does not undergo the structural phase transition at 225 K that was observed in the neat molecular crystal. Rather, it stays in the tetragonal phase over a wide temperature range of 110 to 240 K and starts to lose structural correlation above 240 K. This finding strongly suggests that nanoconfinement of AB within mesoporous scaffolds stabilizes the high-temperature disordered tetragonal phase at a much lower temperature. PDF analyses of composite materials composed of excess AB (i.e., AB:MCM-41 > 1:1) indicates that the excess AB forms aggregates outside the mesoporous scaffold and that these aggregates have structural properties similar to neat AB, that is, the orthorhombic-to-tetragonal structural phase transition is observed at 225 K upon warming. These results may provide important insight into the mechanism behind the enhanced hydrogen storage properties of this system. pubtype: Academic Journal doctype: Case Study src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2009 holdings: @attributes: islocal: N |
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