scholarly journals Фононная теплопроводность и фазовые равновесия в наночастицах системы Bi-Sb фрактальной формы

2019 ◽  
Vol 89 (4) ◽  
pp. 556
Author(s):  
А.В. Шишулин ◽  
В.Б. Федосеев ◽  
А.В. Шишулина
Keyword(s):  
Thermal Conductivity ◽  
Mutual Arrangement ◽  
Homogeneous State ◽  
Lattice Vibrations ◽  
Nanoparticle Shape ◽  
Phonon Component ◽  
Complex Morphology ◽  
Coexisting Phases ◽  
Shape Of Nanoparticles ◽  
Mutual Solubilities

AbstractThe thermal conductivity component associated with lattice vibrations is one of the quantities determining the thermoelectric activity of a material. We have simulated the dependences of phase composition and the phonon component of the thermal conductivity associated with it on the shape of nanoparticles of a Bi–Sb alloy with an equiatomic composition and with core–shell configuration. The shape of a particle is simulated by a coefficient corresponding to the extent of deviation of the particle shape from spherical or by its fractal dimension. It is shown that mutual solubilities of components depend on the nanoparticle shape and on the mutual arrangement of coexisting phases, and the thermodynamic equilibrium position for particles with complex morphology corresponds to the homogeneous state. Homogenization of a nanoparticle reduces the phonon component of its thermal conductivity by 70–80%.

scholarly journals Effect of External Charging on Nanoparticle Formation in a Flame

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2891
Author(s):  
Elena Fomenko ◽  
Igor Altman ◽  
Igor E. Agranovski
Keyword(s):  
Negative Ions ◽  
Formation Processes ◽  
Particle Charge ◽  
Mgo Nanoparticles ◽  
Nanoparticle Formation ◽  
Noticeable Change ◽  
Nanoparticle Shape ◽  
Positive Ions ◽  
Direct Interpretation ◽  
Shape Of Nanoparticles

This paper attempts to demonstrate the importance of the nanoparticle charge in the synthesis flame, for the mechanism of their evolution during formation processes. An investigation was made of MgO nanoparticles formed during combustion of magnesium particles. The cubic shape of nanoparticles in an unaffected flame allows for direct interpretation of results on the external flame charging, using a continuous unipolar emission of ions. It was found that the emission of negative ions applied to the flame strongly affects the nanoparticle shape, while the positive ions do not lead to any noticeable change. The demonstrated effect emphasizes the need to take into account all of the phenomena responsible for the particle charge when modeling the nanoparticle formation in flames.

scholarly journals Investigation of thermal conductivity of single-wall carbon nanotubes

2011 ◽  
Vol 15 (2) ◽  
pp. 565-570 ◽  
Author(s):  
Mahmoud Jafari ◽  
Majid Vaezzadeh ◽  
Momhamad Mansouri ◽  
Abazar Hajnorouzi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Theoretical Model ◽  
Potential Energy ◽  
Experimental Results ◽  
Single Wall Carbon Nanotubes ◽  
Lattice Vibrations ◽  
Single Wall Carbon ◽  
Thermal Potential ◽  
Conductivity Behavior

In this paper, the thermal conductivity of Single-wall carbon nanotubes (SWCNTs) is determined by lattice vibrations (phonons) and free elections. The thermal conductivity of SWCNTs is modeled up to 8-300 K and the observed deviations in K-T figures of SWCNTs are explained in terms of phonon vibrations models. An suitable theoretical model is shown for thermal conductivity behavior with respect to temperature and is generalized for experimental results. This model enables us to calculate thermal conductivity SWNTs and Thermal Potential Energy (TPE).

Influence of Shape of Nanoparticles on Nanofluid Hydrothermal Behavior

2018 ◽  
pp. 331-388
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Finite Element Method ◽  
Finite Element ◽  
Stream Function ◽  
Shape Factor ◽  
Control Volume ◽  
Flow And Heat Transfer ◽  
Shape Of Nanoparticles ◽  
Stream Function Formulation

The shape of nanoparticles can change the thermal conductivity of nanofluid. So, the effect of shape factor on nanofluid flow and heat transfer has been reported in this chapter. Governing equations are presented in vorticity stream function formulation. Control volume-based finite element method (CVFEM) is utilized to obtain the results. Results indicate that platelet shape has the highest rate of heat transfer.

scholarly journals Nanofluid Thermal Conductivity and Effective Parameters

2018 ◽  
Vol 9 (1) ◽  
pp. 87 ◽  
Author(s):  
Sarah Simpson ◽  
Austin Schelfhout ◽  
Chris Golden ◽  
Saeid Vafaei
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nanoparticle Concentration ◽  
Effective Parameters ◽  
Conductivity Enhancement ◽  
Nanoparticle Shape ◽  
Hybrid Nanofluids ◽  
Different Characteristics ◽  
The Impact ◽  
Base Liquid

Due to the more powerful and miniaturized nature of modern devices, conventional heat-transfer working fluids are not capable of meeting the cooling needs of these systems. Therefore, it is necessary to improve the heat-transfer abilities of commonly used cooling fluids. Recently, nanoparticles with different characteristics have been introduced to base liquids to enhance the overall thermal conductivity. This paper studies the influence of various parameters, including base liquid, temperature, nanoparticle concentration, nanoparticle size, nanoparticle shape, nanoparticle material, and the addition of surfactant, on nanofluid thermal conductivity. The mechanisms of thermal conductivity enhancement by different parameters are discussed. The impact of nanoparticles on the enhanced thermal conductivity of nanofluids is clearly shown through plotting the thermal conductivities of nanofluids as a function of temperature and/or nanoparticle concentration on the same graphs as their respective base liquids. Additionally, the thermal conductivity of hybrid nanofluids, and the effects of the addition of carbon nanotubes on nanofluid thermal conductivity, are studied. Finally, modeling of nanofluid thermal conductivity is briefly reviewed.

Thermal equilibrium at temperatures below 1° absolute

1938 ◽  
Vol 34 (2) ◽  
pp. 301-307 ◽  
Author(s):  
E. S. Shire ◽  
J. F. Allen
Keyword(s):  
Thermal Conductivity ◽  
Liquid Helium ◽  
Thermal Equilibrium ◽  
Lattice Vibrations ◽  
Ammonium Alum

By measuring the resistance of a phosphor bronze wire in thermal equilibrium via various substances with crystals of iron ammonium alum it is shown that the time for thermal equilibrium between the ionic magnets of the salt and its lattice vibrations is less than 0·5 sec. for all temperatures above 0·025° T*. When liquid helium or a german silver tube forms part of the cooled portion of the apparatus, the time for equilibrium is increased to a few seconds for temperatures below 0·4° K. It appears possible that the thermal conductivity of german silver is less than 10−8 cal. cm.−1 sec.−1 degree−1 below 0·05° T*, and there are indications that the thermal conductivity of liquid helium at temperatures below 0·3° K. is small compared with its value at 2° K.

scholarly journals How Do the Size, Charge and Shape of Nanoparticles Affect Amyloid β Aggregation on Brain Lipid Bilayer?

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Yuna Kim ◽  
Ji-Hyun Park ◽  
Hyojin Lee ◽  
Jwa-Min Nam
Keyword(s):  
Lipid Bilayer ◽  
Neuroblastoma Cells ◽  
Amyloid Β ◽  
Random Coil ◽  
Brain Lipid ◽  
Nanoparticle Shape ◽  
Total Brain ◽  
Aβ Aggregation ◽  
Shape Of Nanoparticles ◽  
The Brain

Abstract Here, we studied the effect of the size, shape and surface charge of Au nanoparticles (AuNPs) on amyloid beta (Aβ) aggregation on a total brain lipid-based supported lipid bilayer (brain SLB), a fluid platform that facilitates Aβ-AuNP aggregation process. We found that larger AuNPs induce large and amorphous aggregates on the brain SLB, whereas smaller AuNPs induce protofibrillar Aβ structures. Positively charged AuNPs were more strongly attracted to Aβ than negatively charged AuNPs and the stronger interactions between AuNPs and Aβ resulted in fewer β-sheets and more random coil structures. We also compared spherical AuNPs, gold nanorods (AuNRs) and gold nanocubes (AuNCs) to study the effect of nanoparticle shape on Aβ aggregation on the brain SLB. Aβ was preferentially bound to the long axis of AuNRs and fewer fibrils were formed whereas all the facets of AuNCs interacted with Aβ to produce the fibril networks. Finally, it was revealed that different nanostructures induce different cytotoxicity on neuroblastoma cells, and, overall, smaller Aβ aggregates induce higher cytotoxicity. The results offer insight into the roles of NPs and brain SLB in Aβ aggregation on the cell membrane and can facilitate the understanding of Aβ-nanostructure co-aggregation mechanism and tuning Aβ aggregate structures.

The thermal and electrical conductivity of sodium at low temperatures

1951 ◽  
Vol 209 (1098) ◽  
pp. 368-375 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Low Temperatures ◽  
Lorenz Curve ◽  
Theoretical Work ◽  
Lattice Vibrations ◽  
Lorenz Number ◽  
Recent Theoretical Work ◽  
Metallic Conduction

Modem theories of metallic conduction, based on the quantum interaction of electrons with the lattice vibrations, predict a considerable variation of Lorenz number with temperature. We have carried out measurements of the thermal and electrical conductivity of two rather pure specimens of sodium continuously from 90 to ~ 4° K and derived an experimental Lorenz curve. Considerable deviations from theory are found; these may in part be due to departure of the lattice vibrations from the Debye spectrum. The thermal conductivity, in particular, is compared with the most recent theoretical work, and the predicted minimum at ~ 0.25Θ has not been found.

Thermoelectric Properties of AgBiTe2-Ag2Te Composite

1998 ◽  
Vol 545 ◽  
Author(s):  
Y. Takigawa ◽  
T. Imoto ◽  
T. Sakakibara ◽  
K. Kurosawa
Keyword(s):  
Thermal Conductivity ◽  
Composite Materials ◽  
Grain Boundaries ◽  
Thermoelectric Properties ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Lattice Vibrations ◽  
Thermoelectric Devices ◽  
Long Wavelength ◽  
Prepared Composite

AbstractWe prepared composite materials of AgBiTe2 with several contents of Ag2Te small-size grains for applications to thermoelectric devices. By enhancing long-wavelength phonon scattering at the grain boundaries, lattice thermal conductivity (thermal conductivity due to lattice vibrations) decreased 30% and thus the thermoelectric characteristics were significantly improved.

The thermal conductivity of germanium and silicon between 2 an d 300° K

1957 ◽  
Vol 238 (1215) ◽  
pp. 502-514 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Energy Levels ◽  
Silicon Crystal ◽  
Lattice Vibrations ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Group Iii ◽  
Impurity Atoms ◽  
Type Silicon

The thermal conductivity of single crystals o f pure n -type germanium and of p -type germanium containing from 10 14 to 10 19 group III impurity atoms per cm 3 has been measured from 2 to 90° K . In some cases the readings have been extended up to room temperature. Whereas the low- temperature conductivity of the pure specimens is that which one would expect from a dielectric crystal, the addition of even very amounts of group III impurity decreases the conductivity very considerably and alters its temperature dependence. It is suggested that the extra thermal resistance introduced is due to the scattering of the lattice vibrations by the electrons or holes in the impurity energy levels. The theory of such scattering has been worked out by Ziman, and the experimental results are shown to be in fair agreement with this theory. A pure n -type silicon single crystal and a gold-doped p -type silicon crystal show a behaviour similar to the germanium. The room-temperature conductivity of germanium and silicon is 0⋅64 and 1⋅45 watt units respectively.

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