scholarly journals Low Frequency Mechanical Spectroscopy Study of Three Pyrrolidinium Based Ionic Liquids

2015 ◽  
Vol 60 (1) ◽  
pp. 385-390 ◽  
Author(s):  
F. Trequattrini ◽  
A. Paolone ◽  
O. Palumbo ◽  
F.M. Vitucci ◽  
M.A. Navarra ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Relaxation Time ◽  
Glass Transition ◽  
Solid Phase ◽  
Cold Crystallization ◽  
Mechanical Spectroscopy ◽  
Exponential Factor ◽  
Potential Wells ◽  
Thermally Activated ◽  
Crystallization From The Melt

Abstract In this work we present our recent results on three ionic liquids (ILs), which share bis(trifluoromethanesulfonyl)imide (TFSI) as anion and have different pyrrolidinium based cations. By means of a combination of mechanical spectroscopy and thermal analysis, many of the physical processes occurring during cooling down from the liquid phase, can be studied. Depending both on the diverse cation and the different thermal history, crystallization from the melt or glass transition, cold-crystallization, solid-solid phase transitions and thermally activated processes are observed. In one of the ILs, which could be easily undercooled, a prominent thermally activated peak could be observed above the glass transition. The temperature dependence of the relaxation time is approximated by a Vogel-Fulcher-Tamman equation, as usual for fragile glass forming liquids, and the apparent activation energy of W = 0.36 eV with a pre-exponential factor of the relaxation time τ0 = 1.7 · 10−13s were derived supposing jumps between asymmetrical potential wells. The kinetics of the crystallization processes have been studied in the framework of the Johnson-Mehl-Avrami-Kolmogorov theory and the Avrami parameters have been derived for both the crystallization from the melt and for the cold crystallization observed on heating.

Hydrogen Relaxation Process in HiPco Carbon Nanotubes Studied by Mechanical Spectroscopy

2006 ◽  
Vol 115 ◽  
pp. 163-168
Author(s):  
Rosario Cantelli ◽  
Achille Paolone ◽  
S. Roth ◽  
U. Dettlaff
Keyword(s):  
Carbon Nanotubes ◽  
Relaxation Process ◽  
Peak Shift ◽  
Mechanical Spectroscopy ◽  
Debye Relaxation ◽  
Exponential Factor ◽  
Thermally Activated ◽  
Mobile Species ◽  
Quantum Mechanism ◽  
Defect Relaxation

The first mechanical spectroscopy experiments in HiPco carbon nanotubes from room temperature to 3 K revealed a thermally activated relaxation process at about 25 K for frequencies in the kHz range. The peak is due to the presence of a very mobile species performing about 103 jumps per second at the peak temperature. The activation energy obtained by the peak shift with frequency is Ea = 54.7 meV; the value of the pre-exponential factor of the Arrhenius law for the relaxation time, τ0 = 10-14 s, which is typical of point defect relaxation and suggests that the process is originated by the dynamics of hydrogen or by H complexes. The peak is much broader than a single Debye relaxation process, indicating the presence of intense elastic interactions in the highly disordered bundle structure. There are indications that the relaxation process is governed by a quantum mechanism.

Crystal. Liquid and Glass in 2 Dimensions. Analysis of the glass Transition

1985 ◽  
Vol 63 ◽  
Author(s):  
Frédéric Lançon ◽  
Praveen Chaudhari
Keyword(s):  
Molecular Dynamics ◽  
Relaxation Time ◽  
Glass Transition ◽  
Liquid Phase ◽  
Solid Phase ◽  
Amorphous Structure ◽  
Vibratory Motion ◽  
Atomic Vibrations

ABSTRACTA molecular dynamics technique has been used to simulate the melting of a 2-dimensional diatomic crystal and to quench the liquid phase to a solid phase. We demonstrate that a 2-dimensional dense amorphous structure can be obtained and that a 2-dimensional glass transition does exist. Furthermore, atomic vibrations in the liquid can be separated from motion produced by diffusion. The relaxation time during which atoms have a vibratory motion but do not diffuse, diverges to infinity near the observed glass transition. Because of the 2-dimensionality. we are able to display the microscopic processes associated with the glass transition.

Degradation of imidazolium ionic liquids in a thermally activated persulfate system

2021 ◽  
Vol 412 ◽  
pp. 128624
Author(s):  
Tian-Lin Ren ◽  
Xi-Wen Ma ◽  
Xiao-Qiong Wu ◽  
Li Yuan ◽  
Yang-Li Lai ◽  
...  
Keyword(s):  
Ionic Liquids ◽  
Imidazolium Ionic Liquids ◽  
Thermally Activated ◽  
Activated Persulfate

Slow Dynamics Due to the Metal-Nonmetal Transition in Liquids

2003 ◽  
Vol 217 (7) ◽  
pp. 803-816 ◽  
Author(s):  
Makoto Yao ◽  
Hirotaka Kohno ◽  
Hiroaki Kajikawa
Keyword(s):  
Relaxation Time ◽  
Glass Transition ◽  
Liquid Glass ◽  
Sound Attenuation ◽  
Slow Dynamics ◽  
Anomalous Increase ◽  
Relaxation Strength ◽  
Transition Range ◽  
Liquid Dynamics ◽  
Nonmetal Transition

AbstractIt is well known that the liquid dynamics slows down on approaching the liquid-gas critical point or the liquid-glass transition. Recently we have found by the sound attenuation measurements that the metal-nonmetal (M-NM) transition also induces slow dynamics. In the M-NM transition range of expanded liquid Hg, we have observed anomalous increase in the sound attenuation due to the structural relaxation process. Assuming a simple Debye-type relaxation, we have estimated that the relaxation time should be of the order of nanoseconds and revealed that the relaxation strength has a broad maximum in the M-NM transition range. Moreover, two types of anomalies have been observed also in the semiconductor-metal (S-M) transition range of liquid Te-Se mixtures. We present the recent experimental results of the sound attenuation measurements and discuss briefly the mechanisms of the slow dynamics in the metal-nonmetal transition range of liquids.

Solidification of Ionic Liquids: Theory and Techniques

2010 ◽  
Vol 63 (4) ◽  
pp. 544 ◽  
Author(s):  
Anja-Verena Mudring
Keyword(s):  
Phase Transition ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Solid Phase ◽  
Soft Materials ◽  
Separation Science ◽  
Vast Number ◽  
Plastic Crystals ◽  
Thermal Fluids ◽  
Solid Phase Transition

Ionic liquids (ILs) have become an important class of solvents and soft materials over the past decades. Despite being salts built by discrete cations and anions, many of them are liquid at room temperature and below. They have been used in a wide variety of applications such as electrochemistry, separation science, chemical synthesis and catalysis, for breaking azeotropes, as thermal fluids, lubricants and additives, for gas storage, for cellulose processing, and photovoltaics. It has been realized that the true advantage of ILs is their modular character. Each specific cation–anion combination is characterized by a unique, characteristic set of chemical and physical properties. Although ILs have been known for roughly a century, they are still a novel class of compounds to exploit due to the vast number of possible ion combinations and one fundamental question remains still inadequately answered: why do certain salts like ILs have such a low melting point and do not crystallize readily? This Review aims to give an insight into the liquid–solid phase transition of ILs from the viewpoint of a solid-state chemist and hopes to contribute to a better understanding of this intriguing class of compounds. It will introduce the fundamental theories of liquid–solid-phase transition and crystallization from melt and solution. Aside form the formation of ideal crystals the development of solid phases with disorder and of lower order like plastic crystals and liquid crystals by ionic liquid compounds are addressed. The formation of ionic liquid glasses is discussed and finally practical techniques, strategies and methods for crystallization of ionic liquids are given.

Polymeric Ionic Liquids as CO2Selective Sorbent Coatings for Solid-Phase Microextraction

2010 ◽  
Vol 82 (2) ◽  
pp. 707-713 ◽  
Author(s):  
Qichao Zhao ◽  
Jonathan C. Wajert ◽  
Jared L. Anderson
Keyword(s):  
Ionic Liquids ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Polymeric Ionic Liquids

scholarly journals Predicting the glass transition temperature and viscosity of secondary organic material using molecular composition

2018 ◽  
Vol 18 (9) ◽  
pp. 6331-6351 ◽  
Author(s):  
Wing-Sy Wong DeRieux ◽  
Ying Li ◽  
Peng Lin ◽  
Julia Laskin ◽  
Alexander Laskin ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Chemical Composition ◽  
Organic Compounds ◽  
Molar Mass ◽  
Solid Phase ◽  
Amorphous Solid ◽  
Semi Solid ◽  
Oxygen Atoms

Abstract. Secondary organic aerosol (SOA) accounts for a large fraction of submicron particles in the atmosphere. SOA can occur in amorphous solid or semi-solid phase states depending on chemical composition, relative humidity (RH), and temperature. The phase transition between amorphous solid and semi-solid states occurs at the glass transition temperature (Tg). We have recently developed a method to estimate Tg of pure compounds containing carbon, hydrogen, and oxygen atoms (CHO compounds) with molar mass less than 450 g mol−1 based on their molar mass and atomic O : C ratio. In this study, we refine and extend this method for CH and CHO compounds with molar mass up to ∼ 1100 g mol−1 using the number of carbon, hydrogen, and oxygen atoms. We predict viscosity from the Tg-scaled Arrhenius plot of fragility (viscosity vs. Tg∕T) as a function of the fragility parameter D. We compiled D values of organic compounds from the literature and found that D approaches a lower limit of ∼ 10 (±1.7) as the molar mass increases. We estimated the viscosity of α-pinene and isoprene SOA as a function of RH by accounting for the hygroscopic growth of SOA and applying the Gordon–Taylor mixing rule, reproducing previously published experimental measurements very well. Sensitivity studies were conducted to evaluate impacts of Tg, D, the hygroscopicity parameter (κ), and the Gordon–Taylor constant on viscosity predictions. The viscosity of toluene SOA was predicted using the elemental composition obtained by high-resolution mass spectrometry (HRMS), resulting in a good agreement with the measured viscosity. We also estimated the viscosity of biomass burning particles using the chemical composition measured by HRMS with two different ionization techniques: electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Due to differences in detected organic compounds and signal intensity, predicted viscosities at low RH based on ESI and APPI measurements differ by 2–5 orders of magnitude. Complementary measurements of viscosity and chemical composition are desired to further constrain RH-dependent viscosity in future studies.

Barriers to rotation of the cyclopentadienyl ligand: spin-lattice relaxation time measurements and atom–atom potential calculations on cyclopentadienyl manganese and rhenium tricarbonyl and vanadium tetracarbonyl complexes

1983 ◽  
Vol 61 (4) ◽  
pp. 737-742 ◽  
Author(s):  
D. F. R. Gilson ◽  
G. Gomez ◽  
I. S. Butler ◽  
P. J. Fitzpatrick
Keyword(s):  
Relaxation Time ◽  
Molecular Conformation ◽  
Crystal Packing ◽  
Solid Phase ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Atom Potential

The barriers to cyclopentadienyl ring rotation in the solid phase have been measured by spin-lattice relaxation time methods for the organometallic complexes CpMn(CO)3 (7.24 kJ mol−1), CpRe(CO)3 (7.15 kJ mol−1), and CpV(CO)4 (7.07 kJ mol−1), where Cp = η5-C5H5. Nonbonded atom–atom potential calculations of the barriers in these complexes and in BzCr(CO)3 (Bz = η6-C6H6) show that the molecular conformation of the Mn and Re compounds is determined by crystal packing forces and that concerted ring motions are possible for the cyclopentadienyl complexes, but not for the benzene chromium tricarbonyl.

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