Current Search:  Percolation (x)

View All Items

  • CSV Spreadsheet
(1 - 2 of 2)
PERCOLATION STUDY OF NANO-COMPOSITE CONDUCTIVITY USING MONTE CARLO SIMULATIONPERCOLATION
Title
PERCOLATION STUDY OF NANO-COMPOSITE CONDUCTIVITY USING MONTE CARLO SIMULATIONPERCOLATION.
Creator
Bai, Jing, Lin, Kuo-Chi, University of Central Florida
Abstract / Description
A Monte Carlo model is developed for predicting electrical conductivity of carbon nanofiber composite materials. The conductive nanofibers are models as both 2D and 3D network of finite sites that are randomly distributed. The percolation behavior of the network is studied using the Monte Carlo method, which leads to the determination of the percolation threshold. The effect of the nanofiber aspect ratio on the critical nanofiber volume rate is investigated in the current model, each of the...
Show moreA Monte Carlo model is developed for predicting electrical conductivity of carbon nanofiber composite materials. The conductive nanofibers are models as both 2D and 3D network of finite sites that are randomly distributed. The percolation behavior of the network is studied using the Monte Carlo method, which leads to the determination of the percolation threshold. The effect of the nanofiber aspect ratio on the critical nanofiber volume rate is investigated in the current model, each of the nanofibers needs five independent geometrical parameters (i.e., three coordinates in space and two orientation angles) for its identification. There are three controlling parameters for each nanofiber, which includes the nanofiber length, the nanofiber diameter, and the nanofiber aspect ratio. The simulation results reveal a relationship between the fiber aspect ratio and the percolation threshold: the higher the aspect ratio, the lower the threshold. With the simulation results obtained from the Monte Carlo model, the effective electrical conductivity of the composite is then determined by assuming the conductivity is proportional to the ratio of the number of nanofibers forming the largest cluster to the total number of nanofibers. The numerical results indicate that as the volume rate reaches a critical value, the conductivity starts to rise sharply. These obtained simulation results agree fairly with experimental and numerical data published earlier by others. In addition, we investigate the convergence of the current percolation model. We also find the tunneling effect does not affect the critical volume rate greatly. We propose that the percolation model is not scalable as well.
Show less
Date Issued
2009
Identifier
CFE0002644, ucf:48230
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002644
PROCESSING AND STUDY OF CARBON NANOTUBE / POLYMER NANOCOMPOSITES AND POLYMER ELECTROLYTE MATERIALS
Title
PROCESSING AND STUDY OF CARBON NANOTUBE / POLYMER NANOCOMPOSITES AND POLYMER ELECTROLYTE MATERIALS.
Creator
Harish, Muthuraman, Huo, Qun, University of Central Florida
Abstract / Description
The first part of the study deals with the preparation of carbon nanotube/polymer nanocomposite materials. The dispersion of multi-walled carbon nanotubes (MWNTs) using trifluoroacetic acid (TFA) as a co-solvent and its subsequent use in polymer nanocomposite fabrication is reported. The use of carbon nanotube/ polymer nanocomposite system for the fabrication of organic solar cells is also studied. TFA is a strong but volatile acid which is miscible with many commonly used organic solvents....
Show moreThe first part of the study deals with the preparation of carbon nanotube/polymer nanocomposite materials. The dispersion of multi-walled carbon nanotubes (MWNTs) using trifluoroacetic acid (TFA) as a co-solvent and its subsequent use in polymer nanocomposite fabrication is reported. The use of carbon nanotube/ polymer nanocomposite system for the fabrication of organic solar cells is also studied. TFA is a strong but volatile acid which is miscible with many commonly used organic solvents. Our study demonstrates that MWNTs can be effectively purified and readily dispersed in a range of organic solvents including dimethyl formamide (DMF), tetrahydrofuran (THF), and dichloromethane when mixed with 10 vol% trifluoroacetic acid (TFA). X-ray photoelectron spectroscopic analysis revealed that the chemical structure of the TFA-treated MWNTs remained intact without oxidation. The dispersed carbon nanotubes in TFA/THF solution were mixed with poly(methyl methacrylate) (PMMA) to fabricate polymer nanocomposites. A good dispersion of nanotubes in solution and in polymer matrices was observed and confirmed by SEM and optical microscopy study. Low percolation thresholds of electrical conductivity were observed from the fabricated MWNT/PMMA composite films. A carbon nanotube/ polymer nanocomposites system was also used for the fabrication of organic solar cells. A blend of single-wall carbon nanotubes (SWNTs) and poly3-hexylthiophene (P3HT) was used as the active layer in the device. The device characteristics showed that the fabrication of the solar cells was successful without any shorts in the circuit. The second part of the study deals with the preparation and characterization of electrode and electrolyte materials for lithium ion batteries. A system of lithium trifluoroacetate/ PMMA was used for its study as the electrolyte in lithium battery. A variety of different processing conditions were used to prepare the polymer electrolyte system. The conductivity of the electrolyte plays a critical role in the high power output of a battery. A high power output requires fast transport of lithium ions for which the conductivity of the electrolyte must be at least 3 x 10^-4 S/cm. Electrochemical Impedance Spectroscopy (EIS) was used to determine the conductivity of the polymer electrolyte films. Among the different processing conditions used to prepare the polymer electrolyte material, wet films of PMMA/salt system prepared by using 10vol% of TFA in THF showed the best results. At about 70wt% loading of the salt in the polymer, the conductivity obtained was about 1.1 x 10^-2 S/cm. Recently, the use of vanadium oxide material as intercalation host for lithium has gained widespread attention. Sol-gel derived vanadium oxide films were prepared and its use as a cathode material for lithium ion battery was studied. The application of carbon nanotubes in lithium ion battery was explored. A carbon nanotube /block copolymer (P3HT-b-PS) composite was prepared and its potential as an anode material was evaluated.
Show less
Date Issued
2007
Identifier
CFE0001941, ucf:47436
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001941