【作者】 张甲；

【导师】 王振龙； 胡平安；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2014， 博士

【摘要】 单层石墨烯（Graphene）是由一层碳原子组成的具有六重对称性的二维晶体结构材料，厚度仅为0.34nm，几何结构上被认为是组成其它碳纳米材料的基本单元。石墨烯具有许多优异的物理和化学性能，在基础研究和工业应用中拥有广阔的前景。由于结构决定性能，而性能又决定应用，石墨烯优异的性能发挥首要解决的问题是如何制备符合特定要求的石墨烯及其功能结构。本文基于氧化还原法和化学气相沉积法开展课题研究工作，详细的研究了石墨烯及其功能结构的可控制备；探索了制备掺杂石墨烯的新方法，并将所制备的石墨烯及其功能结构应用于气体检测和构造体材料等方面。首先对氧化还原法制备石墨烯进行了改进，合理选取前驱物和优化反应条件，制备出了尺寸大于100μm的单层氧化石墨烯。通过梯度离心技术成功分离了不同尺寸的氧化石墨烯片，为进一步应用提供了合适的原料。研究了化学气相沉积过程中催化剂的物性、反应装置几何形状、反应温度、碳源浓度、反应时间等参数对石墨烯生长的影响；优化反应参数，制备出了单晶尺寸达几十微米且厚度均一的大面积石墨烯薄膜。该薄膜具有较高的透光率（93.3%~96.5%）和较低的薄膜方阻（540.5~652.6Ω/sq），显著提高了石墨烯薄膜的透明和导电综合性能。研究了常压条件下以甲烷为碳源，石墨烯在铜箔表面的生长规律，结果发现：石墨烯的尺寸和层数随反应时间的延长而增加，铜箔表面出现的碳铜合金纳米颗粒为石墨烯生长提供碳源的新现象。基于本文的实验结果，提出了一种可能的石墨烯生长机理——高浓度碳源下石墨烯表面外延生长。发展了一种基于自由基反应的低温制备大面积掺杂石墨烯薄膜的新方法。通过该方法能在230℃下制备出掺杂量达7.3at%且分布均匀的单层氮掺杂石墨烯薄膜；首次制备出了掺硫量达1.54at%且分布均匀的单层硫掺杂石墨烯薄膜（反应温度300℃）；所制备的掺杂石墨烯薄膜具有可调控的电学性能和优异的氧还原性能。该方法为低温下制备掺杂石墨烯提供了一种通用的技术。发展了一种基于软印刷技术批量制备图案化的氧化石墨烯薄膜阵列的新方法。通过在不同气氛中退火，实现了氧化石墨烯薄膜的还原改性并获得了不同性质的石墨烯薄膜；利用掩膜技术制备出了大规模集成的石墨烯薄膜场效应晶体管。应用石墨烯薄膜器件对氨气进行检测，检测下限可达10ppm，且具有良好的重复性。开发了基于化学气相沉积法制备的石墨烯与二氧化钛薄膜杂化形成的异质结的高性能氧气传感器，实现了常温常压下对氧气的快速高灵敏度检测。其响应时间和回复时间分别193s和135s；检测下极限可达0.0134vol%，且器件的响应率与氧气的浓度在0.0134~100vol%范围内保持良好的线性关系。设计并制备出了具有仿贝壳结构的聚乙烯醇（PVA）与石墨烯复合的高强度及高韧性纤维。采用干纺丝技术将PVA/石墨烯复合纤维纺成弹簧状。详细研究了PVA的含量对于石墨烯复合纤维的形貌和机械性能的影响，探索出当PVA含量约为66%时，石墨烯复合薄膜可纺成连续的具有弹簧结构的纤维。力学测试表明，66%PVA/石墨烯复合弹簧具有超高伸长率（160%~400%）和超强韧性（298.23~639.44J/g）；比氧化石墨烯纤维的伸长率提高了约20~40倍，韧性提高了约30~60倍。最后，从复合弹簧的宏观和微观结构对其机械性能的提高进行了探索性的解释。本文的研究工作可为石墨烯及其功能结构的可控制备和应用研究提供一定的理论与技术支持。更多还原

【Abstract】 Graphene, a two-dimensional nano-material comprises a single layer carbon atomsarranged in six-membered rings with the thickness of0.34nm. It is considered as anessence of cell of other carbon materials. It exhibits many excellent physical andchemical properties which can be used both in fundamental researches andindustrial applications. Since the the properties are strongly depended on thestructure, the first and the most important thing is preparation of graphene withspecial structure if we want to make the unique properties of graphene become areality. In this thesis, we have focused on the main technology of controllablesynthesis of graphene, chemcial derived graphite oxide (GO) method and chemcialvapor deposition (CVD). Further, we develop a new approach to synthesis of dopedgraphene. Thereby, as-synthesized graphene and its functional structures wereapplied for electrode materials, gas sensor and construction structures.Firstly, we have synthesized the GO by modified Hummers’ method. The GOsheets with single-layer and more than100μm in lateral size were achieved byoptimization of the reaction parameters and precursors. Also, the different sizes ofGO sheets were separated via gradient centrifugation technology, which suppliedthe proper materials for its applications.The effect of the parametres such as properties of catalyst, geometry of chamber,growth temperature, concentrate of carbon source and growth time on the graphenevia CVD, was investigated in detail. Large-scale graphene films with uniformthickness and tens of micrometers of single crystalline domains were synthesized.The graphene films exhibit high transparency (93.3%~96.5%at550nm) and lowsheet resistence (540.5~652.6Ω/sq), which achieved a tradeoffs betweentransparency and conductivity.The mechanism of grwoth graphene on Cu foil using methane as precursor by atmosphere pressure chemcial vapor deposition was investigated. The resultsshowed that the lateral size and layer number of graphene were increasing as growthtime. Meanwhile, we found for the first time that the C-Cu alloy particles suppliedthe carbon sources for the growth of graphene. The hypothesized mechanism,epitaxial graphene layer on the sub-layer under the high concentrate precursor, isproposed based on our experimental results.We have successfully developed a general approach for low temperature growthof large area doped graphene film. The approach involves a free radical reaction.High quality single layer N-doped graphene film with a high N content of7.3at%was successfully synthesized at230oC. S-doped graphene film with S content of1.54at%was also obtained at300oC using this low temperature growth technique.These doped graphenes exhibit controlled electrical properties and outstandingoxygen reduction reaction activity. Our approach also provides an efficient andscalable avenue to synthesize high level doped graphenes with characteristics of lowenergy consumption and low cost, which are key features needed forcommercializationBased on the as-synthesized GO, we have developed a method for fabrication ofpatterned GO thin films array using soft-lithography technique. The properties ofpatterned GO films can be regulated by annealing in different atmosphere. And theintegrated field effect transistors based on annealed GO films can be fabricatedsimply by evaporation of electrodes with shield mask. Then, the devices were usedto detect ammonia gas and achieved a quite good sensitivity of10ppm and stability.In addition, the titanium dioxide (TiO2) was hybrid with as-made graphene filmand formed a heterojunction device, and it was used as oxygen (O2) sensor. Thesensor could achieve a fast response and high sensitivity operated at atmospherepressure and room temperature, benefit by high carrier mobility in grapheme filmaccompany with photoelectric property of TiO2. In detail, the response and recovery time were estimated to be193s and135s, and the detected limitation was down to0.0134%. In addition, it has a quite good linear relationship between theresponsivity of the device and the concentration of O2in the range of0.0134%-100%.Graphene sheets with low defect were exfoliated by electrochemical method,and incorporated into poly(vinyl alcohol, PVA) to form a nacre-like composite film.And then, the PVA/graphene fibers were twist-spun from the composite films. Itwas found the content of PVA had an important effect on the mechanical propertiesof the fiber. When the content increased to~66%, a spring-like PVA/graphene fibercan be achieved. The spring-like fiber shows a super stretchable (160%~400%) andtoughness (298.23~639.44J/g). The elongation and toughness of the fiber haveincreased by20~40times and30~60times, respectively, comparing with those ofthe fiber derived from GO. At last, we have investigated the macro-and micro-structure of the PVA/graphene composite fiber to interpret the mechanism ofenhancement of the mechanical properties.The foundations and results in this thesis would provide some theoretical andtechnical support for synthesis of graphene and its applications.更多还原