Font Size: a A A

Molecular Dynamics Simulation Of Mass And Heat Transfer In Mixture Of Carbon Nanotubes And Small Molecules Excited By Plasma

Posted on:2020-01-27Degree:MasterType:Thesis
Country:ChinaCandidate:Z LiuFull Text:PDF
GTID:2381330590452934Subject:Materials science
Abstract/Summary:PDF Full Text Request
Carbon nanotubes have excellent mechanical,thermal and electrical properties,but good dispersion is the prerequisite for their intrinsic properties.The dispersion process of carbon nanotubes is a key step in its application,because the preparation process of carbon nanotubes will make them form nanoclusters.Traditional dispersion processes such as ultrasonic dispersion,mechanical grinding and surface treatment of carbon nanotubes are unstable,which may destroy their physical structure or the introduction of chemical groups to destroy their properties.Therefore,the dispersion of carbon nanotubes has always been a very complex problem.In this paper,the heat and mass transfer of carbon nanotubes and small molecule mixtures are studied by means of plasma excitation.The effects of plasma excitation on heat transfer of multi-mass aggregates and thermal dispersion of small molecule vaporizable materials are revealed.The microcosmic characterization of carbon nanotubes dispersion was achieved by studying the thermal dispersion method of carbon nanotubes.The effects of dispersed small molecules on the thermal properties of carbon nanotubes were further explored.In view of the short time of plasma excitation,high temperature and nano-scale carbon nanotubes,it is more important to explain the mechanism of heat and mass transfer process under such extreme conditions,so the general experimental research is not competent.With the progress of science and technology,computer simulation has become a powerful tool for studying processes and mechanisms at the limit time and/or space scales.In this paper,molecular dynamics simulation is used as the research method to carry out the following research work:The thermal excitation effect produced by plasma was simulated in asuitable depth of high temperature region.The process and mechanism of heat and mass transfer and dispersion of carbon nanotubes in a polymorphic atomic system consisting of water and carbon nanotubes were investigated under the thermal excitation.The first part is to explore the heat and mass transfer process of carbon nanotubes under thermal excitation,by establishing pure water model and mixing model of carbon nanotubes with water of different lengths.The density distribution,temperature distribution and pressure distribution of the system under ultra-high temperature excitation are analyzed.It is concluded that the boiling of the carbon nanotubes system will intensify compared with pure water environment.At the same time,carbon nanotubes can make the heat spread rapidly and evenly,increase the boiling depth and raise the final temperature.Carbon nanotubes also have a relatively large heat capacity,and have a relatively large heat capacity in the high temperature layer.At the same temperature and density,carbon nanotubes store more heat than water.The second part is to investigate the motion of carbon nanotubes in the polymer under thermal excitation.By calculating the potential of mean force(PMF)of carbon nanotubes in the process of motion,it is found that the free energy of single carbon nanotubes increases gradually with the increase of system temperature,especially when the two carbon nanotubes are far apart,which indicates that the interaction between the two carbon nanotubes is obvious at high temperature.By calculating the temperature distribution and pressure distribution of the system under higher energy excitation,it is found that water boils explosively at high temperature,which converts heat energy into kinetic energy,and also plays an important role in promoting the dispersion of carbon nanotubes.By calculating the mean square displacement(MSD)of the two carbon nanotubes under different excitation conditions and the output of the final position of the carbon nanotubes at the end of the system running time,it is obvious that the carbon nanotubes can achieve better dispersion at higher temperature.The third part is to explore the effect of water molecules in dispersed carbon nanotubes on the thermal properties of carbon nanotubes.The variation of the number of water molecules in carbon nanotubes and their thermal conductivity is calculated.It is concluded that the presence of water molecules can improve the thermal conductivity of carbon nanotubes.This further shows that it is very important to study the dispersion of carbon nanotubes in water system under plasma excitation.Through the above three aspects of work,we have come to the conclusion that under the excitation of plasma,carbon nanotubes can be well dispersed,thestructure of carbon nanotubes will not be destroyed,and the presence of water molecules will not affect the thermal properties of carbon nanotubes,which will play a very important guiding role in the dispersion of carbon nanotubes.
Keywords/Search Tags:molecular dynamics, thermal excitation, carbon nanotubes, mass transfer and heat transfer, dispersion
PDF Full Text Request
Related items