直流脉冲电场作用下纳米洋葱碳相变为金刚石的机理

论文总字数：39464字

摘 要

洋葱碳和纳米金刚石都是碳的同素异构体。探索纳米金刚石与洋葱碳之间相变，不仅有助于了解纳米金刚石的形成起源，而且有助于开辟金刚石与碳同素异形体之间转变的可控工艺，加强纳米金刚石的工业应用。

本文采用直流脉冲电场的放电等离子烧结技术，使用X射线衍射、拉曼光谱、场发射扫描电镜和透射电镜进行测试分析，研究了纳米金刚石与洋葱碳在直流脉冲电场诱导下的相变规律。研究结果表明：纳米金刚石在恰当的工艺参数条件下可以转变为洋葱碳。对不同保温时间烧结出的纳米金刚石样品进行研究，发现保温时间在15min，18min，20min，25min的试样并无明显差别。选定15min的保温时间，对无压不同温度下合成的试样进行研究，发现1400℃是在SPS中纳米金刚石合成洋葱碳的最佳温度，得出SPS中纳米金刚石合成洋葱碳的最佳工艺参数为：无压、1400℃、升温速率25℃/min、保温15min。同时，洋葱碳在金刚石仔晶或者FeNi30催化剂的作用下可以转变为纳米金刚石，但不加催化剂或仔晶时洋葱碳非常稳定，在SPS中1200-1500℃的温度和几十MPa的压力下不能发生相变。总体而言，纳米金刚石可以在直流脉冲电场诱导下相变为洋葱碳，而洋葱碳在直流脉冲电场下相对稳定，需要催化剂或金刚石仔晶才能发生可逆的相变转变为纳米金刚石。

关键词：纳米金刚石；洋葱碳；放电等离子烧结技术；相变

Abstract

Carbon onions and nanodiamonds are both isomers of carbon. Exploring the phase transition between nanodiamonds and carbon onions is not only helpful to understand the formation and origin of nanodiamonds, but also helpful to develop the controllable process for the transformation between diamonds and carbon allotropes, and strengthen the industrial application of nanodiamonds.

In this paper, discharge plasma sintering technology of dc pulsed electric field was used to test and analyze the phase transition law of nanodiamonds and carbon onions under dc pulsed electric field induction by using X-ray diffraction, Raman spectrum, field emission scanning electron microscope and transmission electron microscope. The results show that nanodiamonds can be converted into carbon onions under the right technological parameters. Nanodiamonds sintered with different holding time were studied, and it was found that there was no significant difference between samples with holding time of 15min, 18min, 20min and 25min.The temperature preservation time of 15min was selected to study the samples synthesized at different temperatures without pressure. It was found that 1400℃ was the optimal temperature for the synthesis of carbon onions by nanodiamonds in SPS. The optimal process parameters for the synthesis of carbon onions by nanodiamonds in SPS were as follows: no pressure, 1400℃, temperature rise rate of 25℃/min, and temperature preservation of 15min.At the same time, carbon onions can be transformed into nanodiamonds under the action of diamond seed crystal or FeNi30 catalyst, but without catalyst or seed crystal, carbon onions are very stable, and no phase transition can occur at the temperature of 1200-1500℃ and the pressure of dozens of MPa in SPS. In a word, nanodiamonds can be changed into carbon onions under the induction of dc pulsed electric field, and the carbon onions are relatively stable under the dc pulsed electric field, which require catalyst or diamond crystal to convert into nanodiamonds reversibly.

Keywords: Nanodiamonds; Carbon onions; Spark plasma sintering technology; Phase change

目 录

摘要..................................................................................................................................

目录..................................................................................................................................

第一章 绪论.............................................................................................................1

1.1 引言..........................................................................................................1

1.2 纳米金刚石概述......................................................................................1

1.3 洋葱碳概述..............................................................................................3

1.4 放电等离子烧结（SPS）概述...............................................................6

1.5 纳米金刚石与洋葱碳之间的相变..........................................................7

1.6 本论文的研究意义..................................................................................8

第二章 实验材料与研究方法...............................................................................10

2.1 研究路线................................................................................................10

2.2 实验材料及设备....................................................................................10

2.2.1 实验材料.....................................................................................10

2.2.2 制备样品常用设备.....................................................................11

2.2.3 处理样品仪器.............................................................................13

2.3 分析测试方法........................................................................................13

2.3.1 X射线物相分析.........................................................................13

2.3.2 SEM形貌和粒径分析................................................................14

2.3.3 激光拉曼光谱分析.....................................................................15

2.3.4 透射电镜分析.............................................................................15

第三章 直流脉冲电场诱导下纳米金刚石向洋葱碳的相变研究.......................17

3.1 引言.......................................................................................................17

3.2 实验方法.............................................................................................. 17

3.3 实验结果与分析.................................................................................. 17

3.3.1 SPS保温时间对相变的影响..................................................17

3.3.2 SPS烧结温度对相变的影响..................................................18

3.4 本章小结...............................................................................................22

第四章 直流脉冲电场诱导下洋葱碳向纳米金刚石的相变研究......................24

4.1 引言.....................................................................................................24

4.2 实验方法.............................................................................................24

4.3实验结果与分析............................................................................................24

4.3.1 不同烧结参数下洋葱碳的相变................................................24

4.3.2 催化剂对洋葱碳向纳米金刚石相变的影响............................29

4.3.3 仔晶对洋葱碳向纳米金刚石相变的影响................................32

4.3 本章小结.............................................................................................34

第五章 结论与展望..............................................................................................35

5.1 结论.......................................................................................................35

5.2 展望.......................................................................................................35

参考文献（References）............................................................................................36

致谢..............................................................................................................................41

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