【作者】 陈阳；

【导师】 李玉香；

【作者基本信息】 山东大学 ， 微电子学与固体电子学， 2016， 硕士

【摘要】 石墨烯是一种单层原子构成的材料,是目前已知的最薄、硬度最大的纳米材料。作为一种新型材料,因其独特的二维结构以及优异的电学、力学等性能,在各个领域掀起了研究的热潮,有可能成为引领多项产业革命的关键材料,在电子设备、航天材料、能源开发等领域拥有广阔的应用前景。在本论文中,我们通过研究辅助插层剂在超临界二氧化碳体系中对石墨烯剥离的影响,确定合适的辅助插层剂和剥离的最佳条件；然后通过一系列的表征手段,对剥离的产物进行分析；最后将剥离得到的石墨烯应用于染料敏化太阳能电池和阻变存储器中。本论文的主要工作和实验成果如下：(1)插层剂Dipp-PDI对石墨剥离的影响在温度为40℃和压强10 MPa条件下,取占石墨的质量百分比分别为0.3%、0.5%、0.8%、1%、3%的N,N’-双(2,6-二异丙基苯基)-3,4,9,10-苝四甲酰二亚胺(Dipp-PDI)依次进行剥离实验,当加入的Dipp-PDI占石墨总质量百分比为0.8%时,剥离得到的石墨烯浓度最高,约0.45 mg/mL.这说明在Dipp-PDI质量占0.8%时,其能够有效的参与到石墨的剥离中,并能够提高剥离得到的石墨烯悬浮液的稳定性。这与其分子之间的强烈的π-π作用有关,能够有效的跟剥离出来的石墨烯结合,有效的防止石墨烯再次发生团聚而沉降。(2)温度和压强对剥离效果的影响在Dipp-PDI占石墨质量为0.8%时,我们研究了在不同温度和压强下,对石墨烯剥离的影响。保持压强10 MPa不变,温度为40℃时剥离得到的石墨烯浓度最高,约为0.44 mg/mL；保持温度40℃不变,随着压强的增大,剥离得到的石墨烯浓度逐渐增大,在20 MPa时剥离得到的浓度最高为0.48 mg/mL.考虑到实验的易操作性和安全性,我们选择15MPa作为最佳的剥离压强,剥离得到的石墨烯浓度约为0.46 mg/mL。(3)石墨烯的尺寸、层数的表征通过对剥离得到的石墨烯进行离心制样进行表征,AFM下可以得到剥离得到的石墨烯层数约为2-4层,样品的尺寸约为几百个nm到1μm,TEM能够更清晰的看到石墨烯的分布、形状,跟AFM结果一致；Raman拉曼光谱的数据显示实验得到的石墨烯缺陷较少,且2D峰峰强较高,说明剥离得到了层数较少、质量较高的石墨烯；X射线衍射剥离得到的石墨烯的衍射峰强度明显减弱,且在(002)的衍射峰20角度变小,说明石墨得到了较好的剥离。(4)石墨烯掺杂的染料敏化太阳能电池将实验剥离得到的石墨烯按照不同的质量百分比跟Ti02混合作为染料敏化太阳能电池(DSSC)的光阳极,制作的太阳能电池跟纯Ti02染料敏化太阳能电池相比,电池的效率得到了显著的提升。其中,当石墨烯所占质量百分比为0.2%时,电池的转换效率最高,为2.12,相比于纯Ti02电池的转换效率1.21,效率提高了75%,效果相当显著。(5)石墨烯增强的POMA基阻变存储器石墨烯增强的POMA基阻变存储器,相比于纯POMA的阻变存储器,器件的性能也有很大的提高。石墨烯增强的POMA基阻变存储器SET和RESET电压明显减小,也意味着功率的损耗减小；且器件在耐久性方面也有显著提高,石墨烯增强的POMA基阻变存储器在循环一百多次后仍然能保持开关比在102-103数量级,且在循环几百次之后,器件虽然开关比减小,但并不会真正闭合,一直在102数量级左右,仍能进行数据的读写操作。更多还原

【Abstract】 Graphene, first successfully exfoliated from graphite by Andre Geim and Konstantin Novoselov, is a single atom material and is known as the thinnest and hardest nanomaterial in the world. As a new material with unique two-dimensional structure and excellent electrical and mechanical properties, graphene and its applications in various fields set off the upsurge of research. It is possible for graphene to become the leading key materials in the field of mobile devices, aerospace, new energy battery, and so on.In this thesis, the exfoliation of graphite into few-layer graphene flakes in supercritical carbon dioxide (scCO2) were investigated. First, the optimal exfoliation conditions of graphite into graphene were determined by investigating the influence of intercalating agent between graphite layers and the temperature and the pressure of the scCO2 system on the yield of graphene nanosheets. After that, the properties of graphene were characterized using AFM, TEM, Raman, and XRD techniques. Finally, the applications of the exfoliated graphene in the dye sensitized solar cell and resistive memory were studied.The main experimental results of this thesis are shown as follows:(1) The Influence of intercalated agent Dipp-PDI on the exfoliation efficiency of graphiteThe exfoliation of graphite were conducted in the system of NMP/scCO2 with Dipp-PDI as an intercalating agent at 40℃ under the pressure of 10 MPa. The weight ratio of Dipp-PDI to graphite (50 mg) were 0.3%,0.5%,0.8%,1%, and 3%, respectively. The highest graphene concentration of 0.44 mg/mL in NMP was achieved when the weight ratio of Dipp-PDI is 0.8%. This indicated that Dipp-PDI can effectively penetrate into graphite interlayers and improve the stability of the graphene suspensions at this concentration. This is attributed to the strong π-π intra-molecular effect which can effectively prevent graphene from aggregation and settlement.(2) The effect of temperature and pressure on the exfoliation of graphiteThe effect of temperature and pressure on the exfoliation of graphite were investigated when the concentration of intercalating agent Dipp-PDI is kept constant to be 0.8%. The appropriate temperature and pressure are obtained about graphene exfoliation. The relative higher graphene yield were obtained when the temperature is 40℃ and 80℃, which is about 0.44 mg/mL and 0.43 mg/mL under the pressure of 10 MPa. The concentration of exfoliated graphene in NMP increased with the increase in pressure from 10 MPa to 20 MPa. The highest concentration of exfoliated graphene was obtained when the pressure was 20 MPa at 40℃, which was about 0.48mg/mL. Considering the safety, the optimal exfoliation pressure was chosen to be 15 MPa under which graphene concentration of 0.46mg/mL is achieved.(3) The characterization in size and number of layers of grapheneThe lateral size and the number of layers of graphene exfoliated in scCO2 system with Dipp-PDI as intercalating agent were characterized using AFM and TEM technology. The results showed that the exfoliated graphene layers were about 2-4 layers, and the lateral size was about from hundreds of nanometers to 1 μm. Raman spectroscopy showed that the intensity of 2D peaks of graphene is high, indicating that the exfoliated graphene has fewer defects. As for the X-ray diffraction, the intensity of diffraction peak of exfoliated graphene decreased significantly, and the 29 angle corresponding to the (002) diffraction peak becomes much smaller, indicating that the graphite was well exfoliated.(4) The applications of graphene in dye-sensitized solar cellThe hybrid of the exfoliated graphene and TiO2 with different weight ratio was used as an anode material in a dye-sensitized solar cell (DSSC). The highest conversion efficiency of the cell was 2.12% which is obtained when the graphene weight ratio is 0.2%. The efficiency increased by 75% compared to that of 1.21% obtained from DSSC fabricated with pure TiO2, indicating that the addition of graphene can significantly improve the solar cell efficiency..(5) The enhancement of graphene on POMA-based resistive switching memoryCompared to the pure POMA-based resistive switching memory (RRAM), the device performance of graphene-enhanced POMA RRAM was greatly improved. The set and reset voltage of graphene-enhanced POMA RRAM decreased obviously, indicating that the power loss was reduced. And the device endurance was increased significantly too. The ON/OFF ratio of graphene-enhanced POMA RRAM can still be kept in the range of 102-103 after one hundred cycles.更多还原