TOFTOF: Cold neutron time-of-flight spectrometer

Lohstroh, Wiebke; Evenson, Zachary

doi:10.17815/jlsrf-1-40

Cited by 44 publications

(25 citation statements)

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“…The bulk PdH 0.73 was measured using three spectrometers at the NIST Center for Neutron Research (NCNR) of the National Institute of Standards and Technology (NIST) in the USA; a backscattering spectrometer HFBS [70], a disk chopper time-of-flight spectrometer DCS [71], and a neutron spin echo spectrometer NSE [72,73]. The measurements on the nanocrystalline PdH 0.47 were conducted at the HFBS and at the timeof flight spectrometer TOFTOF [74,75], operated by Technische Universität München, at Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II) in Germany.…”

Section: B Quasielastic Neutron Scatteringmentioning

confidence: 99%

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Hydrogen diffusion in bulk and nanocrystalline palladium: A quasielastic neutron scattering study

et al. 2016

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The diffusion dynamics of hydrogen in bulk and nanocrystalline palladium has been examined using quasielastic neutron scattering (QENS). With respect to bulk PdH0.73, two relaxation processes were found. For both processes, the variation of the relaxation times with momentum transfer was well reproduced by a model of jump diffusion between adjacent octahedral sites. Upon cooling the fast relaxation fraction decreases. The result suggests that the slow relaxation corresponds to jumps between the ground states and the fast one between excited states. In nanocrystalline PdH0.47 with a size of 8 nm, we found a new fast diffusion process with a smaller activation energy in addition to the one observed in the bulk sample. The new process could be due to the motion of hydrogen atoms in the subsurface region where the potential energy surface is substantially modified by surface strain/distortion effects. This is the first QENS experiment that probes hydrogen diffusion within Pd nanoparticles.

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Section: B Quasielastic Neutron Scatteringmentioning

confidence: 99%

“…TOFTOF [74,75] is also a time-of-flight spectrometer similar to DCS in many respects. In the measurements of nanocrystalline PdH x , the incident energy of 0.57 meV was chosen.…”

Section: B Quasielastic Neutron Scatteringmentioning

confidence: 99%

Hydrogen diffusion in bulk and nanocrystalline palladium: A quasielastic neutron scattering study

et al. 2016

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“…Chemical structure of PIM-1 (a) and Matrimid (b).The neutron scattering measurements were performed at the multi-chopper cold neutron timeof-flight spectrometer TOFTOF42 , operated by the Technische Universität München at the Heinz Maier-Leibnitz Zentrum (MLZ) in Garching, Germany. TOFTOF was used in standard configuration with an incident wavelength of l n = 5.0 Å corresponding to a resolution of 85-100 µeV (full width at half maximum) in the q-range used for the VDOS evaluation.…”

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confidence: 99%

Anomalies in the low frequency vibrational density of states for a polymer with intrinsic microporosity – the Boson peak of PIM-1

Zorn

Yin

Lohstroh

et al. 2018

Phys. Chem. Chem. Phys.

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Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. Here, the vibrational density of states (VDOS) for PIM-1, the prototypical polymer with intrinsic microporosity, is investigated by means of inelastic neutron scattering. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid). The measured data show the characteristic low frequency excess contribution to VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. In comparison to the Boson peak of Matrimid, that of PIM-1 is shifted to lower frequencies. This shift is discussed considering the microporous, sponge-like structure of PIM-1 as providing a higher compressibility at the molecular scale than for conventional polymers. For an annealed PIM-1 sample, the Boson peak shifts to higher frequencies in comparison to the un-annealed sample. These changes in the VDOS of the annealed PIM-1 sample are related to changes in the microporous structure as confirmed by X-ray scattering.

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“…In the present work, we focus on the proton diffusion dynamics of the aromatic epoxy resin DGEBA with and without porous nanozeolites (further experimental details in refs. ). These dynamics are coupled to the motions of the DGEBA molecules and thus, the different mobilities of DGEBA molecules, are able to be probed due to the highly incoherent scattering of 1 H in DGEBA relative to the Si and Al atoms of the zeolites structure.…”

Section: Methodsmentioning

confidence: 97%

“…These dynamics are coupled to the motions of the DGEBA molecules and thus, the different mobilities of DGEBA molecules, are able to be probed due to the highly incoherent scattering of 1 H in DGEBA relative to the Si and Al atoms of the zeolites structure. QENS measurements were carried out on the time‐of‐flight spectrometer TOFTOF at the Heinz Maier‐Leibnitz Center (MLZ) in Garching, Germany with an incoming neutron wavelength λ I = 10 Å, yielding an instrumental resolution of ≈50 µeV (full‐width at half‐maximum) and observation of molecular motions on a maximal timescale t 0 ≈ 300 ps. For the TOFTOF experiments, neat DGEBA and DGEBA‐NP were loaded into thin‐walled aluminum sample holders in hollow cylinder geometry with a nominal sample thickness of 0.1 mm.…”

Section: Methodsmentioning

confidence: 99%

Molecular Motion in Viscous DGEBA with Nanoparticles as Seen by Quasi‐Elastic Neutron Scattering

Weidner

Evenson

Zamponi

et al. 2018

Macro Chemistry & Physics

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Pure and filled epoxies are widely used in industry. Nanocomposites especially are affected by interphase regions where properties deviate from bulk. The study of molecular mobility in epoxy monomers is a first step to understanding the molecular dynamics in nanocomposites and their effect on crosslinking in epoxy networks. Here, quasi‐elastic neutron scattering is used to disentangle the molecular motions of monomeric diglycidylether of Bisphenol A (DGEBA) and a suspension of zeolite nanoparticles in DGEBA on a timescale from 2 ps to 5.5 ns. Regarding molecular transport of DGEBA inside the suspension, the particles have no impact on the faster rotational motions. A combination of neutron time‐of‐flight and backscattering spectroscopy reveals a pronounced hindrance of DGEBA molecular dynamics on/in the zeolite particles along with a new type of molecular motion occurring on intermediate timescales. That localized motion is attributed to jump diffusion motions, emanating from interphase effects at the zeolite particles.

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TOFTOF: Cold neutron time-of-flight spectrometer

Cited by 44 publications

References 0 publications

Hydrogen diffusion in bulk and nanocrystalline palladium: A quasielastic neutron scattering study

Hydrogen diffusion in bulk and nanocrystalline palladium: A quasielastic neutron scattering study

Anomalies in the low frequency vibrational density of states for a polymer with intrinsic microporosity – the Boson peak of PIM-1

Molecular Motion in Viscous DGEBA with Nanoparticles as Seen by Quasi‐Elastic Neutron Scattering

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