论文总字数：30472字

摘 要

水体沉积物作为生态环境重要组成部分，一直以来是热门研究对象。近年来人们发现沉积物中除导电矿物外，部分有机细菌菌丝也提高了水体沉积物的导电性。探究沉积物中三维导电网络介导长距离电子传输的机理成为新的研究方向。

首先，本课题用机械混匀方式制出不同碳纳米管质量分数的纳米二氧化硅/纳米四氧化三铁/碳纳米管复合材料，采用四端子法测出其电导率。实验结果表明,SiO₂/Fe₃O₄/MWCNT复合材料电导率与碳纳米管掺量关系为：在碳纳米管掺量较少时，复合材料电导率随掺量增加而缓慢增加；当碳纳米管掺量达到一定值（该临界值通常被称为渗滤阈值）时，复合材料电导率剧增，变化幅度达到；而之后随着碳纳米管掺量的增加，复合材料电导率增长开始变得缓慢。

其次，根据实验内容以及复合材料导电机理，我们采用蒙特卡罗思想，建立三维晶格模型。将复合材料组分简化成空间的节点，用随机数确定3D空间节点上每个位置的颗粒成分，使用Hspice求得整个网络等效电阻，改变组分观察复合材料电阻变化，直接观察到复合材料在填料的掺量达到一定值时，等效电阻发生突变的渗滤现象。

最后基于复合材料隧道导电理论，同样采用蒙特卡罗方法，建立沉积物三维导电网络的渗滤模型。通过在空间中随机分布碳纳米管位置，求得仿真网络成功导通的渗滤概率。改变参数分析导通概率及渗滤发生时所需碳纳米管根数变化规律，总结出各向异性情况下碳纳米管的平均长度增加、直径减小等均会提高渗滤概率，减小渗滤阈值。而长度分散度对有机复合导电材料渗滤概率几乎没有影响。

关键词：水体沉积物, 复合材料, 碳纳米管, 渗滤阈值

ABSTRACT

As an important part of the ecological environment, water sediments have been a popular research object. In recent years, it has been found that except the normally conductive metal ions, the electrically conductive bacterial nanowires in the sediment also increase the conductivity of the water deposits. It is a new research direction to explore the conductive mechanism of this organic composite conductive material.

In this study, the mechanical blending method was used to prepare Nano-silica/Nano-ferric oxide/carbon nanotube composites with different mass fractions of carbon nanotubes. The conductivity of the composites was measured by the 4-probe method. Result of the experiment show relationship between the conductivity of the composites and the amount of carbon nanotubes was as follows: when the amount of carbon nanotubes was small, the conductivity of composites increased slowly with the increase of the amount of carbon nanotubes; When the amount of carbon nanotubes reached a certain value which is called the percolation threshold, the conductivity of the composites increased sharply, and the variation range reached ; Then, as the carbon nanotube content increased, the conductivity of composites increased slowly.

According to the experimental content and the conductive mechanism of the composite material, we applied Monte Carlo idea to establish a three-dimensional lattice model. We simplified the composite component into a spatial node and used random numbers to determine the particle composition of each location on the 3D spatial node. The equivalent resistance of the whole network was obtained by Hspice software. The resistivity of the composites was observed by changing the ratio of carbon nanotubes. The percolation phenomenon during which equivalent resistance of the composite material changed abruptly with the amount of carbon nanotubes reaching a certain value was directly observed.

Lastly, based on the quantum tunneling theory of composites, the tunneling model of the three-dimensional sediment conductive network was established by Monte Carlo method. The percolation probability of the successful conduction of the simulation network was obtained by randomly distributing the positions of the carbon nanotubes in space. The conduction probability and root number of carbon nanotubes were analyzed by changing the parameters. It was concluded that the increase of the average length and the diameter reduction of the organic nanowire conductors under anisotropic conditions increased the percolation probability and reduced the percolation threshold. The length dispersion had almost no effect on the percolation threshold of the organic composite conductive material.

KEY WORDS: water sediments, composite material, carbon nanotube, percolation threshold

目 录

摘 要 I

ABSTRACT II

第一章 绪论 1

1.1研究背景 1

1.1.1沉积物污染 1

1.1.2沉积物污染治理 1

1.2沉积物中三维导电网络 2

1.3复合材料 2

1.4复合材料导电机理简介 3

1.4.1渗滤理论 4

1.4.2有效介质理论 4

1.4.3隧道导电理论 5

1.5本文的研究内容与意义 5

第二章 沉积物中三维导电网络的构建与测试 7

2.1实验材料的选取 7

2.2复合材料的制备 8

2.3电导率测试原理与方法 8

2.4电导率测试结果与分析 8

2.5本章小结 10

第三章 沉积物三维导电网络结构与导电行为仿真分析 11

3.1蒙特卡罗仿真分析法简介 11

3.2沉积物三维电阻网络晶格模型的模拟及分析 11

3.2.1相关背景 11

3.2.2设计思路 12

3.2.3结果分析 13

3.3沉积物三维电阻网络渗滤模型的模拟及分析 14

3.3.1相关背景 14

3.3.2设计思路 14

3.3.3结果分析 16

3.4本章小结 19

第四章 总结与展望 20

4.1总结 20

4.2展望 21

致 谢 22

参考文献 23

附录 25

第一章 绪论

1.1研究背景

1.1.1沉积物污染

水是人类社会正常运作必须品之一，随着人口密度增加以及城市发展速度加快，水资源短缺以及水体污染问题逐渐加剧，近些年人们开始意识到此类问题并且加以控制。其中水体沉积物作为水体重要组成部分，必然与水体污染问题密不可分。研究学者将沉积物污染分为两类：重金属和有机物^[1]。

有机物沉积物污染大部分来源于农药的使用。农药自被发明以来被广发应用于农业生产上，但是农药残留物大部分会通过沉降，降水迁移等方式转移到地表水环境中。例如研究学者在珠江三角洲的水体沉积物中就发现了远超常量的有机氯农药^[2]。在武汉东湖表层沉积物中也检测到了久效磷和除虫菊酯类的杀虫剂成分^[3]。另外,这种沉积物还存在渗透进入地下水及更深层的土地导致范围更广的水体污染的可能性^[4]。

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