Amorphous Mixtures of Ice and C60 Fullerene

Carbon and ice make up a substantial proportion of our Universe. Recent space exploration has shown that these two chemical species often coexist including on comets, asteroids and in the interstellar medium. Here we prepare mixtures of C60 fullerene and H2O by vapor co-deposition at 90 K with molar C60:H2O ratios ranging from 1:1254 to 1:5. The C60 percolation threshold is found between the 1:132 and 1:48 samples, corresponding to a transition from matrix-isolated C60 molecules to percolating C60 domains that confine the H2O. Below this threshold, the crystallization and thermal desorption properties of H2O are not significantly affected by the C60, whereas the crystallization temperature of H2O is shifted towards higher temperatures for the C60-rich samples. These C60-rich samples also display exotherms corresponding to the crystallization of C60 as the two components undergo phase separation. More than 60 volume percent C60 is required to significantly affect the desorption properties of H2O. A thick blanket of C60 on top of pure amorphous ice is found to display large cracks due to water desorption. These findings may help understand the recently observed unusual surface features and the H2O weather cycle on the 67P/Churyumov–Gerasimenko comet.

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A Personal Journey across Fluorescent Sensing and Logic Associated with Polymers of Various Kinds

Polymers ◽

10.3390/polym11081351 ◽

2019 ◽

Vol 11 (8) ◽

pp. 1351 ◽

Cited By ~ 4

Author(s):

Chao-Yi Yao ◽

Seiichi Uchiyama ◽

A. Prasanna de Silva

Keyword(s):

Phase Separation ◽

Metal Ion ◽

Chemical Species ◽

Polymer Science ◽

Molecular Sensing ◽

Fluorescent Sensing ◽

Molecular Logic ◽

Fluorescent Molecular Sensing ◽

Molecular Scale ◽

Identification Tags

Our experiences concerning fluorescent molecular sensing and logic devices and their intersections with polymer science are the foci of this brief review. Proton-, metal ion- and polarity-responsive cases of these devices are placed in polymeric micro- or nano-environments, some of which involve phase separation. This leads to mapping of chemical species on the nanoscale. These devices also take advantage of thermal properties of some polymers in water in order to reincarnate themselves as thermometers. When the phase separation leads to particles, the latter can be labelled with identification tags based on molecular logic. Such particles also give rise to reusable sensors, although molecular-scale resolution is sacrificed in the process. Polymeric nano-environments also help to organize rather complex molecular logic systems from their simple components. Overall, our little experiences suggest that researchers in sensing and logic would benefit if they assimilate polymer concepts.

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Phase separation in undercooled molten Pd80Si20: Part I

Journal of Materials Research ◽

10.1557/jmr.1999.0493 ◽

1999 ◽

Vol 14 (9) ◽

pp. 3653-3662 ◽

Cited By ~ 31

Author(s):

K. L. Lee ◽

H. W. Kui

Keyword(s):

Growth Rate ◽

Phase Separation ◽

Crystal Growth ◽

Grain Refinement ◽

Crystallization Temperature ◽

Sharp Decrease ◽

Nucleation And Growth ◽

Crystal Growth Rate ◽

Large Undercooling ◽

Kinetic Crystallization

Three different kinds of morphology are found in undercooled Pd80Si20, and they dominate at different undercooling regimens ΔT, defined as ΔT = T1 – Tk, where T1 is the liquidus of Pd80Si20 and Tk is the kinetic crystallization temperature. In the small undercooling regimen, i.e., for ΔT ≤ 190 K, the microstructures are typically dendritic precipitation with a eutecticlike background. In the intermediate undercooling regimen, i.e., for 190 ≤ ΔT ≤ 220 K, spherical morphologies, which arise from nucleation and growth, are identified. In addition, Pd particles are found throughout an entire undercooled specimen. In the large undercooling regimen, i.e., for ΔT ≥ 220 K, a connected structure composed of two subnetworks is found. A sharp decrease in the dimension of the microstructures occurs from the intermediate to the large undercooling regimen. Although the crystalline phases in the intermediate and the large undercooling regimens are the same, the crystal growth rate is too slow to bring about the occurrence of grain refinement. Combining the morphologies observed in the three undercooling regimens and their crystallization behaviors, we conclude that phase separation takes place in undercooled molten Pd80Si20.

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High-Throughput Calculations on the Decomposition Reactions of Off-Stoichiometry GeSbTe Alloys for Embedded Memories

Nanomaterials ◽

10.3390/nano11092382 ◽

2021 ◽

Vol 11 (9) ◽

pp. 2382

Author(s):

Omar Abou El Kheir ◽

Marco Bernasconi

Keyword(s):

Phase Separation ◽

Phase Change ◽

High Throughput ◽

Crystallization Temperature ◽

Density Functional ◽

Phase Change Materials ◽

Ternary Phase Diagram ◽

Decomposition Reactions ◽

Embedded Memories ◽

Tie Line

Chalcogenide GeSbTe (GST) alloys are exploited as phase change materials in a variety of applications ranging from electronic non-volatile memories to neuromorphic and photonic devices. In most applications, the prototypical Ge2Sb2Te5 compound along the GeTe-Sb2Te3 pseudobinary line is used. Ge-rich GST alloys, off the pseudobinary tie-line with a crystallization temperature higher than that of Ge2Sb2Te5, are currently explored for embedded phase-change memories of interest for automotive applications. During crystallization, Ge-rich GST alloys undergo a phase separation into pure Ge and less Ge-rich alloys. The detailed mechanisms underlying this transformation are, however, largely unknown. In this work, we performed high-throughput calculations based on Density Functional Theory (DFT) to uncover the most favorable decomposition pathways of Ge-rich GST alloys. The knowledge of the DFT formation energy of all GST alloys in the central part of the Ge-Sb-Te ternary phase diagram allowed us to identify the cubic crystalline phases that are more likely to form during the crystallization of a generic GST alloy. This scheme is exemplified by drawing a decomposition map for alloys on the Ge-Ge1Sb2Te4 tie-line. A map of decomposition propensity is also constructed, which suggests a possible strategy to minimize phase separation by still keeping a high crystallization temperature.

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Origin of colossal magnetoresistance in LaMnO3 manganite

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1424866112 ◽

2015 ◽

Vol 112 (35) ◽

pp. 10869-10872 ◽

Cited By ~ 36

Author(s):

Maria Baldini ◽

Takaki Muramatsu ◽

Mohammad Sherafati ◽

Ho-kwang Mao ◽

Lorenzo Malavasi ◽

...

Keyword(s):

Phase Separation ◽

Percolation Threshold ◽

Memory Effect ◽

Percolation Theory ◽

Colossal Magnetoresistance ◽

Magnetic Clusters ◽

Model Hamiltonian ◽

Large Memory ◽

Crucial Ingredient

Phase separation is a crucial ingredient of the physics of manganites; however, the role of mixed phases in the development of the colossal magnetoresistance (CMR) phenomenon still needs to be clarified. We report the realization of CMR in a single-valent LaMnO3 manganite. We found that the insulator-to-metal transition at 32 GPa is well described using the percolation theory. Pressure induces phase separation, and the CMR takes place at the percolation threshold. A large memory effect is observed together with the CMR, suggesting the presence of magnetic clusters. The phase separation scenario is well reproduced, solving a model Hamiltonian. Our results demonstrate in a clean way that phase separation is at the origin of CMR in LaMnO3.

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Lateral phase separation of phospholipids as a basis for increased permeability of membranes towards fluorescein and other chemical species

The Journal of Membrane Biology ◽

10.1007/bf01868443 ◽

1984 ◽

Vol 80 (3) ◽

pp. 249-256 ◽

Cited By ~ 9

Author(s):

Gillian M. K. Humphries ◽

John P. Lovejoy

Keyword(s):

Phase Separation ◽

Chemical Species ◽

Lateral Phase Separation

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Angle Resolved Thermal Desorption Studies for Poly(methylvinylidene cyanide) and Poly(vinylidenefluoride trifluoroethylene)

MRS Proceedings ◽

10.1557/proc-0947-a03-01 ◽

2006 ◽

Vol 947 ◽

Author(s):

Carolina C. Ilie ◽

P. A. Jacobson ◽

Matt Poulsen ◽

Luis G. Rosa ◽

D. Sahadeva-Reddy ◽

...

Keyword(s):

Large Deviations ◽

Thermal Desorption ◽

Water Adsorption ◽

Vinylidene Fluoride ◽

Water Desorption ◽

Adsorption And Desorption ◽

Poly Vinylidene Fluoride ◽

Copolymer Poly ◽

Water Species

ABSTRACTWe compare water adsorption and desorption on ferroelectric copolymer poly(vinylidene fluoride-trifluoroethylene), and the dipole ordered polymer poly(methylvinylidene cyanide). The angle-resolved thermal desorption spectra prove that the absorbed water species interacts more strongly with poly(vinylidene fluoride-trifluoroethylene) than with poly(methylvinylidene cyanide). The angle resolved thermal desorption spectra shows large deviations from the cosine distribution for light illuminated poly(vinylidene fluoride-trifluoroethylene). Water desorption from poly(methylvinylidene cyanide) deviates from the cosine distribution without illumination.

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Space exploration with a solar sail coated by materials that undergo thermal desorption

Acta Astronautica ◽

10.1016/j.actaastro.2015.08.007 ◽

2015 ◽

Vol 117 ◽

pp. 231-237 ◽

Cited By ~ 7

Author(s):

Roman Ya. Kezerashvili

Keyword(s):

Thermal Desorption ◽

Space Exploration ◽

Solar Sail

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Giant 1/f Noise in Low-Tc CMR Manganites: Evidence of the Percolation Threshold

MRS Proceedings ◽

10.1557/proc-602-113 ◽

1999 ◽

Vol 602 ◽

Author(s):

V. Podzorov ◽

M. Uehara ◽

M. E. Gershenson ◽

T. Y. Koo ◽

S-W. Cheong

Keyword(s):

Phase Separation ◽

Single Crystal ◽

Percolation Threshold ◽

Single Crystals ◽

Insulator Transition ◽

Metal Insulator Transition ◽

Metal Insulator ◽

Percolation Network

AbstractWe observed a dramatic peak in the 1/f noise at the metal-insulator transition (MIT) in low-Tc, manganites. This many-orders-of-magnitude noise enhancement is observed for both polycrystalline and single-crystal samples of La5/8−y. Pry, Ca3/8MnO3 (y = 0.35 – 0.4) and Pr1−xCaxMnO3 (x = 0.35 – 0.5). This observation strongly suggests that the microscopic phase separation in the low-Tc, manganites causes formation of a percolation network, and that the observed MIT is a percolation threshold. It is shown that the scale of phase separation in polycrystalline samples is much smaller than that in single crystals.

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Incorporation of Carbon Nanofillers Tunes Mechanical and Electrical Percolation in PHBV:PLA Blends

Polymers ◽

10.3390/polym10121371 ◽

2018 ◽

Vol 10 (12) ◽

pp. 1371 ◽

Cited By ~ 3

Author(s):

Jesse Arroyo ◽

Cecily Ryan

Keyword(s):

Phase Separation ◽

Electrical Properties ◽

Percolation Threshold ◽

Mechanical Analysis ◽

Poly Lactic Acid ◽

Peak Reduction ◽

Scanning Calorimetry ◽

Electrical Percolation ◽

Mechanical And Electrical Properties ◽

Electrical Conductivities

Biobased fillers, such as bio-derived cellulose, lignin byproducts, and biochar, can be used to modify the thermal, mechanical, and electrical properties of polymer composites. Biochar (BioC), in particular, is of interest for enhancing thermal and electrical conductivities in composites, and can potentially serve as a bio-derived graphitic carbon alternative for certain composite applications. In this work, we investigate a blended biopolymer system: poly(lactic acid) (PLA)/poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), and addition of carbon black (CB), a commonly used functional filler as a comparison for Kraft lignin-derived BioC. We present calculations and experimental results for phase-separation and nanofiller phase affinity in this system, indicating that the CB localizes in the PHBV phase of the immiscible PHBV:PLA blends. The addition of BioC led to a deleterious reaction with the biopolymers, as indicated by blend morphology, differential scanning calorimetry showing significant melting peak reduction for the PLA phase, and a reduction in melt viscosity. For the CB nanofilled composites, electrical conductivity and dynamic mechanical analysis supported the ability to use phase separation in these blends to tune the percolation of mechanical and electrical properties, with a minimum percolation threshold found for the 80:20 blends of 1.6 wt.% CB. At 2% BioC (approximately the percolation threshold for CB), the 80:20 BioC nanocomposites had a resistance of 3.43 × 10 8 Ω as compared to 2.99 × 10 8 Ω for the CB, indicating that BioC could potentially perform comparably to CB as a conductive nanofiller if the processing challenges can be overcome for higher BioC loadings.

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