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.

Theoretical phase diagrams of nanowires

2006 ◽  
Vol 21 (11) ◽  
pp. 2829-2834 ◽  
Author(s):  
G. Abudukelimu ◽  
G. Guisbiers ◽  
M. Wautelet
Keyword(s):  
Phase Diagram ◽  
Phase Diagrams ◽  
Binary Systems ◽  
Theoretical Knowledge ◽  
Size Dependent ◽  
Melting Temperatures ◽  
Cohesive Properties ◽  
Shape Effects ◽  
The One ◽  
Classical Thermodynamics

Systems with typical dimensions in the range of 1–100 nm are in an intermediate state between solid and molecular. Such systems are characterized by the fact that the ratio of the number of surface to volume atoms is not small. This is known to lead to size and shape effects on their cohesive properties. In this work, the phase diagram of nanowires was studied in the framework of classical thermodynamics. The roles of the size, shape, and surface tensions were emphasized. The melting temperatures of nanowires of 21 elements were evaluated theoretically. In the case of binary systems, it was shown that the experimental or theoretical knowledge of the size-dependent phase diagrams of a given binary system allows the evaluation of the one of nanowires. The procedure is described in this paper.

A new approach to construct bulk and size-dependent continuous binary solution phase diagrams of alloys

RSC Advances ◽  
2015 ◽  
Vol 5 (117) ◽  
pp. 96323-96327 ◽  
Author(s):  
N. Zhao ◽  
Y. Q. He ◽  
C. C. Yang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Ab Initio ◽  
Phase Diagrams ◽  
Binary Solution ◽  
Solution Phase ◽  
Dynamics Simulation ◽  
New Approach ◽  
Size Dependent

In this work, we report a new approach to construct both bulk and size-dependent continuous binary solution phase diagrams (e.g. the Au–Ag system) by combining ab initio molecular dynamics simulation and nanothermodynamics modeling.

MODELING THE MELTING TEMPERATURE OF METALLIC NANOWIRES

2010 ◽  
Vol 24 (22) ◽  
pp. 2345-2356 ◽  
Author(s):  
Y. J. LI ◽  
W. H. QI ◽  
B. Y. HUANG ◽  
M. P. WANG ◽  
S. Y. XIONG
Keyword(s):  
Melting Temperature ◽  
Present Model ◽  
Dimensional System ◽  
Cross Sectional ◽  
Size Dependent ◽  
Dynamics Simulations ◽  
Low Dimensional ◽  
Sectional Shape ◽  
Temperature Depression ◽  
Melting Temperature Depression

A model is developed to account for the size-dependent melting temperature of pure metallic and bimetallic nanowires, where the effects of the contributions of all surface atoms to the surface area, lattice and surface packing factors and the cross-sectional shape of the nanowires are considered. As the size decreases, the melting temperature functions of pure metallic and bimetallic nanowires decrease almost with the same size-dependent trend. Due to the inclusion of the above effects, the present model can also be applied to investigate the melting temperature depression rate of different low-dimensional system, accurately. The validity of the model is verified by the data of experiments and molecular dynamics simulations.

Thermodynamics: Nano vs. macro

2009 ◽  
Vol 81 (10) ◽  
pp. 1921-1930 ◽  
Author(s):  
Michel Wautelet ◽  
Aram S. Shirinyan
Keyword(s):  
Phase Diagrams ◽  
Melting Temperature ◽  
Two Phase ◽  
Size And Shape ◽  
Shape Effects ◽  
Long Time ◽  
Definition Of ◽  
Classical Thermodynamics

Ordinary macroscopic thermodynamics is applied when the number of atoms in the studied systems is "large". Conditions where nanosystems are "large" with respect to thermodynamics definition are first discussed. In the thermodynamical regime, size and shape effects are known to be important. It has been known for a long time that the melting temperature of nanosystems decreases when their size decreases. A generalization of this leads to the conclusion that phase diagrams are also size- and shape-dependent. In nanosystems, the number of atoms is limited. This differs from classical thermodynamics, where the number of atoms is assumed to be unlimited. The consequences of this difference for the definition of phase diagrams are discussed. In particular, the liquidus and solidus lines have to be carefully defined. The structure of the two-phase nanoparticles also plays a role in the calculation of the phase diagrams.

Logarithmic Size-Dependent Melting Temperature of Nanoparticles

2015 ◽  
Vol 119 (21) ◽  
pp. 11929-11933 ◽  
Author(s):  
Zhiyuan Liu ◽  
Xiaohong Sui ◽  
Kai Kang ◽  
Shaojing Qin
Keyword(s):  
Melting Temperature ◽  
Size Dependent

Phase Diagrams of Binary Mixtures of Phenylenediamines and Dihydroxybenzenes

1977 ◽  
Vol 32 (1) ◽  
pp. 98-100
Author(s):  
M. S. Dhillon
Keyword(s):  
Phase Diagrams ◽  
Binary Mixtures ◽  
Melting Temperatures ◽  
Solid Liquid

Abstract Solid - liquid equilibria for o-phenylenediamine + resorcinol, m-phenylenediamine + pyrocatechol, + resorcinol and p-phenylenediamine + pyrocatechol, + resorcinol have been studied by the thaw-melt method. The types and melting temperatures of the complexes formed in theses mixtures were ascertained from the phase diagrams.

Studies on the Melting of DNA

1974 ◽  
Vol 29 (3-4) ◽  
pp. 130-132
Author(s):  
Gokul Chandra Das
Keyword(s):  
Ionic Strength ◽  
Melting Temperature ◽  
Thermal Denaturation ◽  
Spectrophotometric Methods ◽  
Melting Temperatures

Abstract The thermal denaturation of the native DNA in solvents of varying salt concentrations was studied by viscometric and spectrophotometric methods. It was observed that within the molarity range of 0.02 ᴍ to 0.3 ᴍ, the melting temperatures obtained by the two independent methods agreed well, but that at lower ionic strength the agreement was not satisfactory. Both the visco­metric and the spectrophotometric measurements showed an increase of the melting temperature with increasing counterion concentration and a levelling off effect in the neighbourhood of 0.3 ᴍ.

Spinel solid solutions in the systems MgAl2O4–ZnAl2O4 and MgAl2O4–Mg2TiO4

1997 ◽  
Vol 12 (10) ◽  
pp. 2584-2588 ◽  
Author(s):  
M. A. Petrova ◽  
G. A. Mikirticheva ◽  
A. S. Novikova ◽  
V. F. Popova
Keyword(s):  
Solid Solution ◽  
Phase Diagrams ◽  
Melting Temperature ◽  
Solid Solutions ◽  
Spinel Structure ◽  
Room Temperature ◽  
Binary Systems ◽  
Continuous Series ◽  
X Ray ◽  
Spinel Solid Solutions

Phase relations in two binary systems MgAl2O4–ZnAl2O4 and MgAl2O4–Mg2TiO4 have been studied and phase diagrams for them have been constructed. Based on the data of x-ray phase and crystal-optical analyses, the formation of a continuous series of solid solutions with spinel structure between the terminal members of the systems studied has been established. In the MgAl2O4–ZnAl2O4 system the solid solution is stable in the range from room temperature to melting temperature. In the MgAl2O4–Mg2TiO4 system the solid solution decomposes below 1380 °C, yielding the formation of limited regions of homogeneity on the basis of MgAlM2O4 and Mg2+2δ Ti1–δO4. Decomposition of the solid solution is accompanied by crystallization of MgTiO3.

Crystallization in Stretched Polymer Networks. I. trans-Polychloroprene

1967 ◽  
Vol 40 (4) ◽  
pp. 1071-1083 ◽  
Author(s):  
A. N. Gent
Keyword(s):  
Melting Temperature ◽  
Polymer Networks ◽  
Crystal Form ◽  
Simple Extension ◽  
Theoretical Treatment ◽  
Nucleation Kinetics ◽  
Segmental Mobility ◽  
Melting Temperatures ◽  
Direct Measurements ◽  
Stress Changes

Abstract Changes in tensile stress afford a simple means of studying the rates of crystallization and the melting temperatures in crosslinked polymers subjected to simple extension. The form and magnitude of the stress changes in networks of trans-polychloroprene are closely similar to those observed for cis-1:4-polyisoprene and cis-l:4-polybutadiene networks. They are in accord with the formation of oriented crystallites and incompatible with folded chain crystallization at extensions as low as 15 per cent. It seems likely that the present networks do not crystallize by chain folding even in the unstretched state. The large increases in rate of crystallization with extension are approximately accounted for by corresponding increases in the equilibrium melting temperature. Direct measurements of the melting temperature show similar rises with extension. The rise in melting temperature is in good agreement with Flory's theoretical treatment of oriented crystallization at extension ratios of three and higher (when the crystallite orientation is complete) for three networks having different degrees of crosslinking. When referred to a constant segmental mobility, namely, that obtaining at Tg+50° C, the rates of crystallization at various extensions obey a common dependence upon the degree of supercooling. This relation is in fair accord with theories of nucleation kinetics, except at the lowest temperatures where there is some indication of the appearance of a new crystal form.

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