The experimental determination of the onset of electrical and thermal conductivity percolation thresholds in carbon nanotube-polymer composites

2011 ◽  
Vol 1312 ◽  
Author(s):  
Byung-wook Kim ◽  
Steven Pfeifer ◽  
Sung-Hoon Park ◽  
Prabhakar R. Bandaru
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Percolation Theory ◽  
The Matrix ◽  
Show Evidence ◽  
Percolation Thresholds ◽  
Single Walled Cnts ◽  
Conductivity Contrast ◽  
Walled Cnts

ABSTRACTWe show evidence of electrical and thermal conductivity percolation in polymer based carbon nanotube (CNT) composites, which follow power law variations with respect to the CNT concentrations in the matrix. The experimentally obtained percolation thresholds, i.e., ~ 0.074 vol % for single walled CNTs and ~ 2.0 vol % for multi-walled CNTs, were found to be aspect ratio dependent and in accordance with those determined theoretically from excluded volume percolation theory. A much greater enhancement, over 10 orders of magnitude, was obtained in the electrical conductivity at the percolation threshold, while a smaller increase of ~ 100 % was obtained in the thermal conductivity values. Such a difference is qualitatively explained on the basis of the respective conductivity contrast between the CNT filler and the polymer matrix.

Determination of the Effective Thermal Conductivity Tensor of Heterogeneous Media Using a Self-Consistent Finite Element Method: Application to the Pseudo-percolation Thresholds of Mixtures Containing Nonspherical Inclusions

1999 ◽  
Vol 122 (1) ◽  
pp. 171-175 ◽  
Author(s):  
A. Decarlis ◽  
M. Jaeger ◽  
R. Martin
Keyword(s):  
Thermal Conductivity ◽  
Finite Element Method ◽  
Finite Element ◽  
Effective Thermal Conductivity ◽  
Heterogeneous Media ◽  
The Finite Element Method ◽  
Self Consistent ◽  
Percolation Thresholds ◽  
Element Method

This paper concerns the determination of the effective thermal conductivity of heterogeneous media with randomly dispersed inclusions. Inclusions of arbitrary shape can be considered since the self-consistent problem is solved numerically with the finite element method. Results for many different cases of heterogeneous media with axially symmetrical inclusions are presented. Moreover, the influence of the inclusion’s shape on the pseudo-percolation threshold is investigated. [S0022-1481(00)00801-X]

Phonon Transport in Carbon Nanotube Aerogels

2012 ◽  
Author(s):  
Lin Hu ◽  
Haibin Chen ◽  
Gabriella Coloyan ◽  
Alan J. H. McGaughey
Keyword(s):  
Carbon Nanotube ◽  
Thermal Conductance ◽  
Small Diameter ◽  
Radiation Detectors ◽  
Phonon Transport ◽  
Rotational Angle ◽  
Thermal And Electrical Properties ◽  
Electrical Conductors ◽  
Single Walled Cnts ◽  
Walled Cnts

A carbon nanotube (CNT) aerogel is a low-density network of small diameter single-walled CNTs held together by van del Waals forces. Due to the excellent mechanical, thermal, and electrical properties of individual CNTs and the potential to fuse the junctions in the aerogel, CNT aerogels are candidates for ultralight structural media, radiation detectors, thermal insulators, and electrical conductors. Using molecular dynamics (MD) simulation, we predict the thermal conductance of the junction formed between two CNTs. To access the range of conditions present in the aerogel, we test the effects of different boundary conditions, the CNT lengths, and the rotational angle of the CNTs. A 3-D network model of the aerogel is built that will be used with the MD predictions to estimate the aerogel thermal conductivity.

Electrical, optical, and mechanical percolations of multi-walled carbon nanotube and carbon mesoporous-doped polystyrene composites

2019 ◽  
Vol 54 (1) ◽  
pp. 31-44 ◽  
Author(s):  
Ömer Bahadır Mergen ◽  
Ertan Arda ◽  
Gülşen Akın Evingür
Keyword(s):  
Carbon Nanotube ◽  
Carbon Fiber ◽  
Percolation Theory ◽  
Composite System ◽  
Scattered Light ◽  
Fiber Composites ◽  
Carbon Fiber Composites ◽  
Multi Walled Carbon Nanotube ◽  
Mesoporous Composites ◽  
Percolation Thresholds

In this study, we have investigated and compared electrical, optical, and mechanical properties of polystyrene thin films with added multi-walled carbon nanotube and carbon mesoporous. Surface conductivity ( σ), scattered light intensity ( I sc), and all the mechanical parameters of these composites have increased with increasing the content of carbon filler (multi-walled carbon nanotube or carbon mesoporous) in the polystyrene composites. This behavior in electrical, mechanical, and optical properties of the polystyrene/carbon fiber composites has been explained by classical and site percolation theory, respectively. The electrical percolation thresholds ( R σ) were determined to be 8.0 wt% for polystyrene/multi-walled carbon nanotube and 25.0 wt% for polystyrene/carbon mesoporous composites. The optical percolation thresholds were found to be R op = 0.8 wt.% for polystyrene/multi-walled carbon nanotube and R op = 3.0 wt.% for polystyrene/carbon mesoporous composites. For the polystyrene/carbon mesoporous composite system, it was determined that the mechanical percolation threshold occurred at lower R values than the polystyrene/multi-walled carbon nanotube composite system. The electrical ( β σ), optical ( β op), and mechanical ( β m) critical exponents have been calculated for both of the polystyrene/carbon fiber composites and obtained as compatible with used percolation theory.

FABRICATION OF CARBON NANOTUBE FIELD EFFECT TRANSISTORS WITH OCMC DISPERSED SINGLE-WALLED CARBON NANOTUBES

2010 ◽  
Vol 09 (04) ◽  
pp. 377-381
Author(s):  
KUMAR RAJ ◽  
QING ZHANG ◽  
LIANGYU YAN ◽  
MARY B. CHAN PARK
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Single Walled Carbon Nanotubes ◽  
Oxygen Adsorption ◽  
P Type ◽  
Walled Carbon Nanotubes ◽  
Single Walled Cnts ◽  
Walled Cnts

We report on the fabrication of carbon nanotube field effect transistors (CNTFETs) from dispersed single-walled CNTs using OCMC (O-Carboxymethylchitosan) as the surfactant. The as-prepared devices exhibit p-type as well as ambipolar characteristics due to oxygen adsorption at the metal/nanotube contacts. The Raman scattering from the SWCNTs shows that OCMC disperses CNTs efficiently. Rapid thermal annealing (RTA) at 400°C for 5 min is found to partially remove OCMC from the surface of SWCNTs.

Determination of Thermal Conductivity on Lightweight Concretes

2016 ◽  
Vol 677 ◽  
pp. 163-168
Author(s):  
Lenka Bodnárová ◽  
Jitka Peterková ◽  
Jiri Zach ◽  
Kateřina Sovová
Keyword(s):  
Thermal Conductivity ◽  
High Temperatures ◽  
Structural Changes ◽  
Lightweight Concrete ◽  
Thermal Insulating ◽  
Coefficient Of Thermal Conductivity ◽  
The Matrix ◽  
Wire Method ◽  
Insulating Properties

A range of testing methods were used to study the potential structural changes as a result of the effects of high temperatures on lightweight types of concrete developed above all for fire resistant structures. One such test for monitoring changes in concrete structures is the non-stationary determination of the coefficient of thermal conductivity using the hot wire method. The matrix structure progressively collapses as a result of the effects of high temperatures on the concrete structure ́s surface because erosion takes place of the matrix and aggregate porous structures. The degradation of the porosity of the concrete results in the deterioration of its thermal insulating properties. This paper assesses the dependence of the thermal conductivity coefficient of lightweight concretes on temperature and determines the potential occurrence of structural changes in the lightweight concrete matrix. The results were verified using other methods to determine the concrete ́s resistance to thermal load.

scholarly journals Уменьшение работы выхода при гидрогенизации углеродных нанотрубок в плазме водорода

2018 ◽  
Vol 44 (10) ◽  
pp. 55
Author(s):  
С.В. Булярский ◽  
Д.А. Богданова ◽  
Е.П. Кицюк ◽  
А.В. Лакалин ◽  
А.А. Павлов ◽  
...  
Keyword(s):  
Experimental Data ◽  
Carbon Nanotube ◽  
Plasma Treatment ◽  
Work Function ◽  
Quantum Mechanical ◽  
Hydrogen Chemisorption ◽  
Quantum Mechanical Calculations ◽  
Single Walled Cnts ◽  
Walled Cnts

AbstractExperimental data showing a decrease in the work function of carbon nanotube (CNT) bundles and arrays hydrogenated in hydrogen-containing plasma are presented. This plasma treatment leads to hydrogen chemisorption on CNTs, which results in a work-function decrease from 4.8 to 3.3 eV. The experimental data confirm quantum-mechanical calculations for single-walled CNTs of variable chirality. Calculations indicate that a decrease in the CNT work function depends on both the properties of CNT and the degree of its passivation by hydrogen.

Impact-resistant carbon nanotube woven films: A molecular dynamics study

Nanoscale ◽  
2021 ◽  
Author(s):  
Fan Wu ◽  
Yushun Zhao ◽  
Yifan Zhao ◽  
Yue Zhao ◽  
Chao Sui ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Carbon Nanotube ◽  
Single Walled Cnts ◽  
Walled Cnts

The fiber-based fabrics have great potentials in impacting protection. Here we proposed a novel nanostructure, where the single-walled CNTs (SWCNTs) was employed to weave plain 2D films. The in-plane mechanical...

Lateral resolution of the electron microbeam analysis

1978 ◽  
Vol 36 (1) ◽  
pp. 542-543
Author(s):  
H.J. Dudek
Keyword(s):  
Quantitative Analysis ◽  
Depth Resolution ◽  
Lateral Resolution ◽  
Cylindrical Particle ◽  
Correction Procedure ◽  
X Ray ◽  
Element Concentrations ◽  
Microbeam Analysis ◽  
The Matrix

The chemical inhomogenities in modern materials such as fibers, phases and inclusions, often have diameters in the region of one micrometer. Using electron microbeam analysis for the determination of the element concentrations one has to know the smallest possible diameter of such regions for a given accuracy of the quantitative analysis.In th is paper the correction procedure for the quantitative electron microbeam analysis is extended to a spacial problem to determine the smallest possible measurements of a cylindrical particle P of high D (depth resolution) and diameter L (lateral resolution) embeded in a matrix M and which has to be analysed quantitative with the accuracy q. The mathematical accounts lead to the following form of the characteristic x-ray intens ity of the element i of a particle P embeded in the matrix M in relation to the intensity of a standard S

Determination of the phase structure of polymerblends by electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 492-493
Author(s):  
Dr. G. Kaemof
Keyword(s):  
Screw Extruder ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Single Screw Extruder ◽  
Transmission Electron ◽  
The Matrix ◽  
Twin Screw ◽  
Special Case ◽  
Microscopic Investigations

A mixture of polycarbonate (PC) and styrene-acrylonitrile-copolymer (SAN) represents a very good example for the efficiency of electron microscopic investigations concerning the determination of optimum production procedures for high grade product properties.The following parameters have been varied:components of charge (PC : SAN 50 : 50, 60 : 40, 70 : 30), kind of compounding machine (single screw extruder, twin screw extruder, discontinuous kneader), mass-temperature (lowest and highest possible temperature).The transmission electron microscopic investigations (TEM) were carried out on ultra thin sections, the PC-phase of which was selectively etched by triethylamine.The phase transition (matrix to disperse phase) does not occur - as might be expected - at a PC to SAN ratio of 50 : 50, but at a ratio of 65 : 35. Our results show that the matrix is preferably formed by the components with the lower melting viscosity (in this special case SAN), even at concentrations of less than 50 %.

Polishing process effect on the image of dispersed precipitates

1984 ◽  
Vol 42 ◽  
pp. 534-535
Author(s):  
C.T. Hu ◽  
C.W. Allen
Keyword(s):  
Matrix Material ◽  
Specimen Preparation ◽  
Second Phase ◽  
Precipitate Particle ◽  
Polishing Process ◽  
Second Phase Particles ◽  
The Matrix ◽  
Surface Profiles ◽  
Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

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