Force field in coagulation bath at low temperature induced microfibril evolution within PAN nascent fiber and precursor fiber

2020 ◽  
Vol 137 (44) ◽  
pp. 49380 ◽  
Author(s):  
Quan Gao ◽  
Min Jing ◽  
Meiling Chen ◽  
Shengyao Zhao ◽  
Yuxia Wang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Force Field ◽  
Coagulation Bath ◽  
Precursor Fiber ◽  
Nascent Fiber

Molecular dynamics simulation of Al–SiO2 sandwich nanostructure melting and low-temperature energetic reaction behavior

RSC Advances ◽  
2016 ◽  
Vol 6 (64) ◽  
pp. 59313-59318 ◽  
Author(s):  
Jinping Zhang ◽  
Yubing Si ◽  
Can Leng ◽  
Baocheng Yang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Low Temperature ◽  
Force Field ◽  
Melting Temperature ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Reactive Force ◽  
Reactive Force Field ◽  
Reaction Behavior

The heating and low temperature thermite reactions of the Al/SiO2 sandwich nanostructure are investigated by MD simulations in combination with the reactive force field. The results show that the melting temperature of this structure is ∼1400 K.

Optically Active Vibrations of Lithium and α-Sodium Uranium Hexafluorides (LiUF6 and α-NaUF6)

1989 ◽  
Vol 43 (4) ◽  
pp. 714-718 ◽  
Author(s):  
Ken Ohwada
Keyword(s):  
Low Temperature ◽  
Force Field ◽  
Electronic Absorption ◽  
Structural Model ◽  
Electronic Absorption Spectra ◽  
Optically Active ◽  
Lattice Vibrations ◽  
Normal Coordinate ◽  
Valence Force Field ◽  
Intramolecular Vibrations

Normal coordinate analyses of the optically active vibrations of LiUF6 and α-NaUF6 have been made, with the assumption of an idealized structural model. On the basis of the results of this treatment, all of the observed bands so far reported have been successfully assigned to the intramolecular vibrations (UF6−) as well as the optically active lattice vibrations [M+(Li, Na) … UF6−]. The force constants concerning U-F and M-F bonds have been obtained within the framework of the modified valence force field. It has been found that the present analysis, based on a whole crystal, is powerful not only for assigning the optically active lattice vibrations but also for elucidating the vibronic structure of the electronic absorption spectra obtained at low-temperature measurements.

Study on the coagulation process of cellulose nascent fibers with ionic liquid AMIMCl as a solvent during dry-wet spinning

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Jun Song ◽  
Bowen Cheng ◽  
Xiuji Jie ◽  
Yi Liang ◽  
Fei Lu ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Diffusion Coefficient ◽  
Diffusion Rate ◽  
Bath Temperature ◽  
Air Gap ◽  
Coagulation Bath ◽  
Cellulose Solution ◽  
Nascent Fiber ◽  
And Diffusion ◽  
Crystallization Degree

AbstractThe coagulation process of nascent fiber of cellulose with ionic liquid 1- allyl-3-methylimidazolium chloride (AMIMCI) as the solvent was studied during drywet spinning. The diffusion rate and the crystallization situation of nascent fiber were tested, its fracture morphology was observed, and the diffusion coefficient D of solvent and the crystallization degree of nascent fiber were calculated according to relevant equations. The diffusion rate and diffusion coefficient of ionic liquid decrease with cellulose concentration increasing in spinning solution and then remain almost the same when the cellulose mass fraction reaches 7%. With the increase of coagulation bath concentration, the diffusion rate and diffusion coefficient of the solvents increase first and then decrease. When the coagulation bath concentration reaches 5%, the diffusion rate and diffusion coefficient of the solvents are at their maximum. With the increase of coagulation bath temperature and the length of air gap, the diffusion rate and diffusion coefficient of ionic liquid increase slightly. The cellulose solution concentration and the spinning air gap have an influence on the crystallization degree of nascent fiber. With the increase of cellulose solution concentration and the spinning air gap, the crystallization degree of the produced nascent fiber increases slightly, but the coagulation bath temperature basically have no influence on the nascent fiber formation.

An Empirical Potential Function of α-Glycine Derived from Infrared Spectroscopic Data of D-, 13C-, 15N-, and 18O-Labeled Species

1988 ◽  
Vol 43 (8-9) ◽  
pp. 774-792 ◽  
Author(s):  
Masato Kakihana ◽  
Minoru Akiyama ◽  
Tadashi Nagumo ◽  
Makoto Okamoto
Keyword(s):  
Low Temperature ◽  
Force Field ◽  
Normal Modes ◽  
Low Frequency ◽  
Local Symmetry ◽  
Interaction Force ◽  
Force Constants ◽  
Potential Energy Distribution ◽  
Strong Mixing ◽  
Symmetry Coordinates

AbstractThe infrared spectra (4000-100 cm-1) of the α-form crystal ofglycine (NH3+ - CH2 - COO-) and of thirteen isotopic modifications comprising D, 13C, 15N, and 18O were measured at 80 and 290 K. Excellent resolution was reached at the low temperature. In the low temperature spectra the fine structure of the nearly degenerate NH3 and ND3 antisymmetric deformational modes and the CO2-torsional bands in the vicinity of 200 cm-1 for each of the isotopic molecules, which in the low-frequency region are strongly overlapped by a number of lattice modes, clearly showed up. Based upon the frequency data of the 14 isotopic analogs and the precisely known structure of the molecule, a normal coordinate analysis was carried out. 307 observed frequencies were utilized to derive a new empirical valence force field reduced to a set of 50 force constants by a number of restrictive assumptions. The resulting force field reproduced the 307 frequencies with a root-mean- square deviation of 3.32 cm -1. This force field emphasizes the importance of interaction force constants of the in-plane CO2-rocking and CO2-deformational coordinates with the CH2-twisting coordinate, which can come form a significant deviation of this molecule from an ideal Cs-symmetry. The composition of normal vibrations from generally accepted local-symmetry coordinates is given in terms of the potential energy distribution (PED). The PED results indicate that almost all the normal modes below 1600 cm-1 are extensively intermixed group modes, thus precluding a simple normal vibrational decription. Interestingly the PED description for several vibrations associated with the NH3 - CH2 - C fragment exhibits strong mixing between quasi-A′ symmetric and -A″ antisymmetric coordinates with respect to a pseudo molecular symmetry (CCN) plane in this molecule.

Preparation of Polyethersulfone Ultrafiltration Tubular Membranes with Superior Properties

2011 ◽  
Vol 221 ◽  
pp. 216-220 ◽  
Author(s):  
Jun Liu ◽  
En Hua Liu
Keyword(s):  
Low Temperature ◽  
Phase Inversion ◽  
Membrane Preparation ◽  
Coagulation Bath ◽  
Test Results ◽  
Tubular Membrane ◽  
Membrane Performance ◽  
Peg 400 ◽  
Optimized Conditions ◽  
Tubular Membranes

A novel polyethersulfone (PES) tubular membrane preparation by phase inversion via immersion precipitation using N,N-dimethylacetamide (DMAc) as the solvent, PEG-400 as the additive. The effects of membrane preparation conditioans on membrane performance were investigated. It was found that the flux was increased by adding ethanol into the coagulation bath. And the low temperature of coagulation bath also improve membrane’s rejection. Test results show that the flux can be up to 160 L•m-2h-1 and the rejection can reach more than 97% (for ovalbvmin) under optimized conditions.

scholarly journals Diffusion Coefficients of Dimethyl Sulphoxide (DMSO) and H2O in PAN Wet Spinning and Its Influence on Morphology of Nascent Polyacrylonitrile (PAN) Fiber

2013 ◽  
Vol 8 (1) ◽  
pp. 155892501300800 ◽  
Author(s):  
Kai Yi ◽  
Qi Fang Li ◽  
Li Zhang ◽  
Ning Li ◽  
You Zhou ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Diffusion Coefficients ◽  
Bath Temperature ◽  
Coagulation Bath ◽  
Diffusion Activation Energy ◽  
Cross Sectional ◽  
Pan Fiber ◽  
Different Temperatures ◽  
Nascent Fiber ◽  
Coagulation Bath Temperature

Wetspun nascent PAN fibers were immersed into a DMSO/H2O coagulation bath. Diffusion of DMSO from nascent fiber and that of H2O into nascent fiber were studied at different temperatures and concentrations of coagulation bath. The diffusion coefficient of H2O is larger than that of DMSO. As the coagulation bath temperature increased, the diffusion coefficients of DMSO and H2O increased. Diffusion activation energy of DMSO is smaller than that of H2O during the diffusion. Cross sectional and surface structure of nascent PAN fiber were observed in relation to coagulation ability (the product of diffusion coefficients of two solvents). Coagulation ability was found to have a significant influence on both the cross sectional and surface morphology of nascent fiber. To obtain nascent fiber with circular cross sectional and smooth surface morphology, coagulation ability should be controlled at low value.

Schwingungsspektren und Normalkoordinatenanalyse der Bromo-Iodo-Osmate(IV), [OsBrnI6-n]2-, n = 0-6 / Vibrational Spectra and Normal Coordinate Analysis of Bromo-Iodo-Osmates(IV), [OsBrnI6-n]2-, n = 0-6

1992 ◽  
Vol 47 (12) ◽  
pp. 1667-1672 ◽  
Author(s):  
W. Preetz ◽  
M. Manthey
Keyword(s):  
Low Temperature ◽  
Force Field ◽  
Raman Spectra ◽  
Vibrational Spectra ◽  
Normal Coordinate ◽  
Geometrical Isomers ◽  
Valence Force ◽  
Valence Force Field ◽  
Point Groups ◽  
Ir And Raman

The IR and Raman spectra of the ten bromo-iodo-osmates(IV) [OsBrnI6-n]2-, n = 0-6, including the geometrical isomers for n = 2, 3, 4, have been recorded at low temperature. The vibrational spectra are completely assigned according to point groups Oh, D4h, C4v, C3v, and C2v, as supported by normal coordinate analyses based on a general valence force field. Due to the different trans-influences Br<I in asymmetric axes Br′–Os–I′, the Os–I′ bonds are strengthened and the Os–Br′ bonds are weakened, as indicated by valence force constants, for Os–I′ on average 4% higher and for Os–Br′ 4% lower, as compared with the values calculated for symmetric I–Os–I and Br–Os–Br axes, respectively.

scholarly journals Schwingungsspektren und Normalkoordinatenanalyse der Chloro-Bromo-Osmate(IV), [OsCl„Br6-n]2-, n = 0-6 / Vibrational Spectra and Normal Coordinate Analysis of Chloro-Bromo-Osmates(IV), [OsCl„Br6-n]2-, n = 0-6

1990 ◽  
Vol 45 (3) ◽  
pp. 283-289 ◽  
Author(s):  
W. Preetz ◽  
K. Irmer
Keyword(s):  
Low Temperature ◽  
Force Field ◽  
Vibrational Spectra ◽  
Normal Coordinate ◽  
Geometrical Isomers ◽  
Valence Force ◽  
Valence Force Field ◽  
Trans Influence ◽  
Point Groups ◽  
Ir And Raman

The IR- and Raman spectra of the ten chloro-bromo-osmates(IV) [OsCl„Br6-n]2-, n = 0-6, including the geometrical isomers for n = 2, 3, 4 have been recorded at low temperature (80 K). The vibrational spectra of these complexes are completely assigned according to point groups Oh, D4h, C4v, C3v and C2v, supported by normal coordinate analyses based on a general valence force field. Due to the stronger trans-influence of Br as compared to Cl, in all asymmetric Cl—Os—Br axes the Os—Br bonds are strengthened and the Os—Cl bonds are weakened, indicated by valence force constants for Os— Br approximately 6% higher, for Os—Cl 6% lower, as compared with the values calculated for symmetrical Br—Os—Br and Cl-Os-Cl axes, respectively. The significantly stronger interaction between opposite bonds is revealed by the stretching interaction constants fdd, which are about three times larger than fdd for bonds at right angles.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

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