Impact of size, shape and dimension on melting entropy and enthalpy in nanomaterials

2020 ◽  
Author(s):  
Pooja Chaturvedi ◽  
Monika Goyal
Keyword(s):  
Melting Entropy

Influence of the lignin on thermal degradation and melting behaviour of poly(ethylene terephthalate) based composites

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Maurizio Canetti ◽  
Fabio Bertini
Keyword(s):  
Gas Phase ◽  
Ethylene Terephthalate ◽  
Degradation Products ◽  
Melting Behaviour ◽  
Screw Extruder ◽  
Single Screw Extruder ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
Thermal Stability Of ◽  
Melting Entropy

AbstractPoly(ethylene terephthalate) (PET) has been compounded with lignin (L) by a single-screw extruder. The influence of L presence and its content on the thermal stability of PET has been studied by using thermogravimetric analysis. The experiments carried out in oxidative conditions evidenced the barrier effect of L that interferes to the diffusion of the volatile degradation products to the gas phase and at the same time to the diffusion of the oxygen from the gas phase to the PET matrix. The influence of L on the melting behaviour of PET has been investigated on samples submitted to subsequent annealing steps procedure. X-ray techniques were employed to investigate crystallinity and crystal dimensions of pure PET and PET/L composites. Considering the supermolecular and crystal structure of the annealed samples, their melting behaviour was explained assuming small changes in the melting entropy.

Crystal Structure and Melting Entropy of Natural Rubber

2005 ◽  
Vol 38 (4) ◽  
pp. 1223-1231 ◽  
Author(s):  
Attilio Immirzi ◽  
Consiglia Tedesco ◽  
Guglielmo Monaco ◽  
Alan E. Tonelli
Keyword(s):  
Crystal Structure ◽  
Natural Rubber ◽  
Melting Entropy

Melting entropy of Al-based quasicrystals

1999 ◽  
Vol 250-252 ◽  
pp. 829-832 ◽  
Author(s):  
D Holland-Moritz ◽  
I.-R Lu ◽  
G Wilde ◽  
J Schroers ◽  
B Grushko
Keyword(s):  
Melting Entropy

Melting entropy and enthalpy of metallic nanoparticles

2008 ◽  
Vol 62 (24) ◽  
pp. 3954-3956 ◽  
Author(s):  
M. Attarian Shandiz ◽  
A. Safaei
Keyword(s):  
Metallic Nanoparticles ◽  
Melting Entropy

A tentative interpretation of the results of recent X-ray and infra-red studies of liquid water and H 2 O + D 2 O mixtures

1958 ◽  
Vol 247 (1251) ◽  
pp. 472-481 ◽  
Keyword(s):  
Liquid Water ◽  
Room Temperature ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Infra Red ◽  
Stretching Vibration ◽  
Density Of Water ◽  
Absorption Measurements ◽  
Melting Entropy

An idealized model is proposed for the arrangement of the molecules in liquid water which involves essentially a sixfold co-ordination of water molecules with four short OH...O hydrogen bonds of ~2.9 Å length and two long O...O contacts of ~3.6 Å length. An ice-like structure may contribute to a small extent also. This octahedral model has been based on evidence obtained from X-ray and infra-red absorption measurements. The model has been found to be in agreement with the density of water and the melting entropy of ice. The reliability of the radial distribution curves W(r) of liquid water obtained from recent X-ray diffraction measurements is discussed. Infra-red absorption measurements have been made of liquid HDO in excess D 2 O and H 2 O, respectively. The respective O—H and O—D stretching vibration frequencies of liquid HDO have been determined. The position (at 3400 cm -1 ) and shape of the relatively sharp single O—H stretching absorption band of liquid HDO is closely comparable to the corresponding band in liquid interbonding alcohols. The results of the infra-red studies indicate an OH...O distance of 2.86 Å in liquid water at room temperature.

scholarly journals Effect of Size and Shape on the Vibrational and Thermodynamic Properties of Nanomaterials

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
R. Kumar ◽  
G. Sharma ◽  
M. Kumar
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
Size And Shape ◽  
Shape Dependence ◽  
Simple Theoretical Model ◽  
Model Predictions ◽  
Different Shapes ◽  
Debye Frequency ◽  
Good Agreement ◽  
Melting Entropy

A simple theoretical model is developed to study the size and shape dependence of vibrational and thermodynamic properties of nanomaterials. To show the real connection with the nanomaterials we have studied Debye temperature, Debye frequency, melting entropy, and enthalpy in different shapes, namely, spherical, nanowire, and nanofilm of -Fe, Sn, Ag, and In. The results obtained are compared with the experimental data. A good agreement between the model predictions and the experimental data supports the theory developed in the present paper.

The Effect of Variations in Chain Connectivity on Strain-Induced Crystallization in Unvulcanized EPDM Elastomers

1984 ◽  
Vol 57 (4) ◽  
pp. 703-724 ◽  
Author(s):  
B. J. R. Scholtens
Keyword(s):  
Deleterious Effect ◽  
Crystallization Process ◽  
Bond Formation ◽  
Drastic Reduction ◽  
Enhancing Effect ◽  
Strain Induced Crystallization ◽  
The Individual ◽  
Positive Effect ◽  
Induced Crystallization ◽  
Melting Entropy

Abstract The introduction of a small amount of chemical or physical crosslinks has an enhancing effect on SIC in EPDM. This situation results from a decrease in stress relaxation or creep, so that the individual chains are deformed more affinely. At the same time, there is no deleterious effect of crosslinks on the crystallization of nonstretched EPDM because of its copolymeric nature. Therefore, the higher connected chains have a smaller melting entropy upon stretching, which promotes the crystallization process. In both EPDM green rubbers and black compounds, the amount of crystallinity and the end-melting temperature increase considerably with strain, in contrast to literature reports. These are desirable qualities for rubber tack. In spite of the positive effect of a higher chain connectivity on SIC, chain connectivity has a detrimental influence on tack. This effect is the result of a drastic reduction in bond formation caused by diminished material flowability and chain interdiffusion. Hence, we conclude that a tack-grade EPDM should, preferably, contain no branched or lightly crosslinked structures.

Size Effect on Thermal Properties in Low-Dimensional Materials

2010 ◽  
Vol 444 ◽  
pp. 189-218 ◽  
Author(s):  
Ming Zhao ◽  
Qing Jiang
Keyword(s):  
Phase Diagrams ◽  
Melting Temperature ◽  
Binary Solution ◽  
Size Dependent ◽  
Melting Temperatures ◽  
Transition Functions ◽  
Low Dimensional ◽  
Classical Thermodynamics ◽  
S Model ◽  
Melting Entropy

An extension of the classical thermodynamics to nanometer scale has been conducted to elucidate information regarding size dependence of phase transition functions and binary phase diagrams. The theoretical basis of the extension is Lindemanns criterion for solid melting, Motts expression for vibrational melting entropy, and Shis model for size dependent melting temperature. These models are combined into a unified one without adjustable parameters for melting temperatures of nanocrystals. It is shown that the melting temperature of nanocrystals may drop or rise depending on interface conditions and dimensions. The model has been extended and applied to size dependences of melting enthalpy, melting entropy, atomic cohesive energy. Moreover, the above modeling has been utilized to determine the size-dependent continuous binary solution phase diagrams. These thermodynamic approachs have extended the capability of the classical thermodynamics to the thermodynamic phenomena in the nanometer regime.

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