A Glassy State of Supersolid Helium

<a></a><a>Quantitative comparison of atomistic simulations with experiment for glass-forming materials is made difficult by the vast mismatch between computationally and experimentally accessible timescales. Recently, we presented results for an epoxy network showing that the computation of specific volume vs. temperature as a function of cooling rate in conjunction with the time–temperature superposition principle (TTSP) enables direct quantitative comparison of simulation with experiment. Here, we follow-up and present results for the translational dynamics of the same material over a temperature range from the rubbery to the glassy state. Using TTSP, we obtain results for translational dynamics out to 10<sup>9</sup> s in TTSP reduced time – a macroscopic timescale. Further, we show that the mean squared displacement (MSD) trends of the network atoms can be collapsed onto a master curve at a reference temperature. The computational master curve is compared with the experimental master curve of the creep compliance for the same network using literature data. We find that the temporal features of the two data sets can be quantitatively compared providing an integrated view relating molecular level dynamics to the macroscopic thermophysical measurement. The time-shift factors needed for the superposition also show excellent agreement with experiment further establishing the veracity of the approach</a>.

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Physical Aging Behavior of a Glassy Polyether

Polymers ◽

10.3390/polym13060954 ◽

2021 ◽

Vol 13 (6) ◽

pp. 954

Author(s):

Xavier Monnier ◽

Sara Marina ◽

Xabier Lopez de Pariza ◽

Haritz Sardón ◽

Jaime Martin ◽

...

Keyword(s):

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Physical Aging ◽

Glassy State ◽

Aging Behavior ◽

Scanning Calorimetry ◽

Narrow Temperature Range ◽

Glass Forming ◽

Fast Scanning Calorimetry

The present work aims to provide insights on recent findings indicating the presence of multiple equilibration mechanisms in physical aging of glasses. To this aim, we have investigated a glass forming polyether, poly(1-4 cyclohexane di-methanol) (PCDM), by following the evolution of the enthalpic state during physical aging by fast scanning calorimetry (FSC). The main results of our study indicate that physical aging persists at temperatures way below the glass transition temperature and, in a narrow temperature range, is characterized by a two steps evolution of the enthalpic state. Altogether, our results indicate that the simple old-standing view of physical aging as triggered by the α relaxation does not hold true when aging is carried out deep in the glassy state.

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Analysis of PLA Composite Filaments Reinforced with Lignin and Polymerised-Lignin-Treated NFC

Polymers ◽

10.3390/polym13132174 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2174

Author(s):

Diana Gregor-Svetec ◽

Mirjam Leskovšek ◽

Blaž Leskovar ◽

Urška Stanković Elesini ◽

Urška Vrabič-Brodnjak

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Scanning Electron Microscopy ◽

Tensile Strength ◽

Glassy State ◽

Nanofibrillated Cellulose ◽

Dynamic Mechanical Properties ◽

Initial Modulus ◽

Surface Modified ◽

Scanning Electron

Polylactic acid (PLA) is one of the most suitable materials for 3D printing. Blending with nanoparticles improves some of its properties, broadening its application possibilities. The article presents a study of composite PLA matrix filaments with added unmodified and lignin/polymerised lignin surface-modified nanofibrillated cellulose (NFC). The influence of untreated and surface-modified NFC on morphological, mechanical, technological, infrared spectroscopic, and dynamic mechanical properties was evaluated for different groups of samples. As determined by the stereo and scanning electron microscopy, the unmodified and surface-modified NFCs with lignin and polymerised lignin were present in the form of plate-shaped agglomerates. The addition of NFC slightly reduced the filaments’ tensile strength, stretchability, and ability to absorb energy, while in contrast, the initial modulus slightly improved. By adding NFC to the PLA matrix, the bending storage modulus (E’) decreased slightly at lower temperatures, especially in the PLA samples with 3 wt% and 5 wt% NFC. When NFC was modified with lignin and polymerised lignin, an increase in E’ was noticed, especially in the glassy state.

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Combined thermal analysis of plant oils

Journal of Thermal Analysis and Calorimetry ◽

10.1007/s10973-020-10470-y ◽

2021 ◽

Author(s):

Kinga Tamási ◽

Kálmán Marossy

Keyword(s):

Thermal Analysis ◽

Differential Scanning Calorimetry ◽

Low Temperature ◽

Glassy State ◽

Mechanical Analysis ◽

Plant Oils ◽

Scanning Calorimetry ◽

Natural Plant ◽

The Moment ◽

Current Reversal

AbstractThe paper deals with the study of seven selected natural plant oils. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermally stimulated discharge (TSD) methods were used. It has been found that most of the oils tested are in a glassy state at low temperature and have multiple transitions in the low temperature range. DSC shows complex melting-like processes or glass transition. For both DMA and TSD, the scaffold supportive method was used and found as a suitable one. DMA and TSD proved more sensitive than DSC and revealed at least two transitions between − 120 and − 40 °C. In the case of three oils (argan, avocado and sunflower), current reversal was observed by TSD; this symptom cannot be fully explained at the moment.

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The Structure and Magnetic Properties of Rapidly Quenched Fe72Ni8Nb4Si2B14 Alloy

Materials ◽

10.3390/ma14010005 ◽

2020 ◽

Vol 14 (1) ◽

pp. 5

Author(s):

Lukasz Hawelek ◽

Tymon Warski ◽

Patryk Wlodarczyk ◽

Marcin Polak ◽

Przemyslaw Zackiewicz ◽

...

Keyword(s):

Magnetic Properties ◽

Relaxation Process ◽

Glassy State ◽

Diffraction Method ◽

Soft Magnetic Materials ◽

Process Time ◽

Complex Permeability ◽

Soft Magnetic ◽

Conventional Heat Treatment ◽

Glass Relaxation

The complex structural and magnetic studies of the annealed rapidly quenched Cu-free Fe72Ni8Nb4Si2B14 alloy (metallic ribbons form) are reported here. Based on the calorimetric results, the conventional heat treatment process (with heating rate 10 °C/min and subsequent isothermal annealing for 20 min) for wound toroidal cores has been optimized to obtain the least lossy magnetic properties (for the minimum value of coercivity and magnetic core losses at 50 Hz). For optimal conditions, the complex permeability in the 104–108 Hz frequency range together with core power losses obtained from magnetic induction dependence up to the frequency of 400 kHz was successfully measured. The average and local crystal structure was investigated by the use of the X-ray diffraction method and the transmission electron microscopy observations and proved its fully glassy state. Additionally, for the three temperature values, i.e., 310, 340 and 370 °C, the glass relaxation process study in the function of annealing time was carried out to obtain a deeper insight into the soft magnetic properties: magnetic permeability and cut-off frequency. For this type of Cu-free soft magnetic materials, the control of glass relaxation process (time and temperature) is extremely important to obtain proper magnetic properties.

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Probing Life And Death In The Glassy State Of Cryopreserved Seeds, Fern Spores And Pollen: Fundamental Research To Optimise Ex Situ Preservation.

Cryobiology ◽

10.1016/j.cryobiol.2019.10.065 ◽

2019 ◽

Vol 91 ◽

pp. 161

Author(s):

Dani Ballesteros ◽

Christina Walters ◽

Hugh W. Pritchard

Keyword(s):

Glassy State ◽

Ex Situ ◽

Spores And Pollen ◽

Life And Death ◽

Fundamental Research

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Formation of half-period surface relief gratings in azobenzene containing polymer films

Applied Physics B ◽

10.1007/s00340-020-07500-w ◽

2020 ◽

Vol 126 (9) ◽

Author(s):

Joachim Jelken ◽

Carsten Henkel ◽

Svetlana Santer

Keyword(s):

Polymer Film ◽

Polymer Films ◽

Surface Relief ◽

Incident Light ◽

Glassy State ◽

Polarized Light ◽

Half Period ◽

Polarization Distribution ◽

Linearly Polarized ◽

Set Up

Abstract We study the peculiar response of photo-sensitive polymer films irradiated with a certain type of interference pattern where one interfering beam is S-polarized, while the second one is P-polarized. The polymer film, although in a glassy state, deforms following the local polarization distribution of the incident light, and a surface relief grating (SRG) appears whose period is half the optical one. All other types of interference patterns result in the matching of both periods. The topographical response is triggered by the alignment of photo-responsive azobenzene containing polymer side chains orthogonal to the local electrical field, resulting in a bulk birefringence grating (BBG). We investigate the process of dual grating formation (SRG and BBG) in a polymer film utilizing a dedicated set-up that combines probe beam diffraction and atomic force microscopy (AFM) measurements, and permits acquiring in situ and in real-time information about changes in local topography and birefringence. We find that the SRG maxima appear at the positions of linearly polarized light (tilted by 45° relative to the grating vector), causing the formation of the half-period topography. This permits to inscribe symmetric and asymmetric topography gratings with sub-wavelength period, while changing only slightly the polarization of one of the interfering beams. We demonstrate an easy generation of sawtooth profiles (blazed gratings) with adjustable shape. With these results, we have taken a significant step in understanding the photo-induced deformation of azo-polymer films.

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