【作者】 卢艳；

【导师】 王福平；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2013， 博士

【摘要】 热电材料可实现热能和电能的直接转换，在温差发电和制冷技术领域有着潜在的应用前景具有非定域π电子共轭体系的导电聚合物因其具有较低的热导率和丰富的电子能带结构，同时还具有资源丰富价格低廉合成工艺简便重量轻柔韧性好等突出优点，其作为潜在的低成本热电材料备受关注目前导电聚合物的热电性能偏低，距离实用化还有相当距离因此，探索提高导电聚合物电传输性能的途径，是导电聚合物热电性能研究需要解决的关键问题本论文通过酸掺杂及纳米碳(石墨烯微片和碳纳米管)复合调控优化聚苯胺的微观结构，研究不同酸掺杂和纳米碳复合对聚苯胺热电性能的影响并探讨聚苯胺与纳米碳间的相互作用及其电热传输机制，为研究和开发新型低成本高性能热电体系提供新的思路和途径对化学聚合法合成的单一酸掺杂和有机-无机混合酸掺杂聚苯胺进行了结构表征和热电性能评价XRD分析表明，掺杂态聚苯胺比本征态聚苯胺结晶度高，适当配比的混合酸有利于提高聚苯胺分子链的有序性和结晶性SEM结果也表明，适当配比的混合酸有利于提高聚苯胺的规整性磺基水杨酸-盐酸(SSA-HCl)和磺基水杨酸-硫酸(SSA-H2SO4)混合酸掺杂聚苯胺的ZT值随温度的升高而增加，适当配比的混合酸掺杂比单一酸掺杂具有更好的热电性能，且在较高的温度时混合酸掺杂比单一酸掺杂更稳定采用原位聚合法制备了聚苯胺与石墨烯微片(PANi/GNs)复合材料，并对其进行了结构表征和热电性能评价PANi/GNs的电导率随温度的升高而降低，而Seebeck系数却随温度的升高而增加PANi/GNs的电导率和Seebeck系数均随GNs含量的增加呈先增大后降低的趋势，而其ZT值却随GNs含量的增加而增加由于聚苯胺和GNs之间存在π-π相互作用，可诱导聚苯胺沿GNs表面生长，使表面形成的聚苯胺分子链构象更为伸展，同时GNs也起到连接聚苯胺链间的载流子跃迁的传导作用，降低了载流子在聚苯胺链间和链内的跃迁激活能，使PANi/GNs复合材料的载流子迁移率显著增加因此，该复合材料的电导率和Seebeck系数得到同时提高由于聚苯胺与GNs之间存在大量界面所导致的声子散射，也有效降低了复合材料的热导率，从而提高了聚苯胺的热电性能通过机械球磨法制备了高GNs含量的PANi/GNs复合材料，研究了制备方式和复合量对微观结构及热电性能的影响相对于原位聚合法制备的PANi/GNs复合材料，机械球磨法所制备PANi/GNs复合材料的电导率随温度的升高几乎没有变化，且随GNs含量的增多显著增加，但当GNs含量为50wt%时，其电导率出现了突增；Seebeck系数随温度的升高而增加，GNs的含量对PANi/GNs的Seebeck系数没有显著的影响；热导率随温度的增加而降低当在PANi/GNs中加入少量的La(NO3)3时，由于显著提高电导率的同时降低了热导率，从而使PANi/GNs的热电性能得到进一步提高将具有较高电导率的碳纳米管(CNTs)加入PANi/GNs复合材料中，利用共同效应CNTs形成的网络结构可增强GNs连接聚苯胺链间的载流子跃迁的传导作用，同时利用散射效应可进一步降低热导率采用原位聚合法制备了PANi/GNs/CNTs复合材料，研究了不同含量的GNs和CNTs对其热电性能的影响由于聚苯胺CNTs和GNs之间均存在π-π相互作用，一方面可诱导聚苯胺沿GNs表面生长，使表面形成的聚苯胺分子链构象更为伸展；另一方面聚苯胺还可沿碳纳米管表面生长，这将降低由于链卷曲在分子链内和链间形成的π-π共轭缺陷，增加了聚苯胺分子链排列的有序度当相对复合量为10wt%时，适当比例的CNTs和GNs试样的ZT值高于仅复合CNTs试样的ZT值将相对复合量提高至30wt%，并在此基础上调节CNTs和GNs的比例，发现加入CNTs可有效提高Seebeck系数并降低热导率当采用机械球磨法制备PANi/GNs/CNTs复合材料时，热电性能也得到进一步的提高但与原位聚合法制备PANi/GNs/CNTs复合材料不同，CNTs的加入会降低Seebeck系数，但通过调节CNTs的加入量可显著提高材料的电导率因此，利用GNs和CNTs的协同作用可进一步提高PANi/GNs复合材料的热电性能更多还原

【Abstract】 Thermoelectric (TE) materials can achieve directly heat conversion intoelectricity, which has potential applications in the field of thermoelectric powergeneration and refrigeration technology. Compared with inorganic semiconductormaterials, conducting polymers with delocalized π-electron conjugated possessunique features for application as TE materials because of their wealth structure ofelectronic band, low density, low cost, easy synthesis, and facile processing intoversatile form. Furthermore, polymers inherently possess a low thermal conductivity,which offers them a significant advantage over conventional inorganicthermoelectric materials. However, poor electrical transport properties of polymers,including low electrical conductivity and low Seebeck coefficient, which haveexcluded them as feasible candidates for thermoelectric materials in the past. So it isurgent to find an effective way to improve the electrical transport properties ofconducting polymers.This thesis focused on the preparation and thermoelectricproperties of doped polyaniline and nanocarbon-polyaniline nanocomposites. Theirmechanisms of electrical and thermal transport were also discussed.The structures of polyaniline doped with organic-inorganic hybrid acid werecharacterized and their thermoelectric properties were investigated. XRD analysisshowed that polyaniline doped with appropriate ratio of mixed acid had highercrystallinity than eigenstates polyaniline. SEM also showed that the mixed acid withappropriate ratio could improve the regularity of the molecular chain. The ZT valueof polyaniline doped with SSA-HCl and SSA-H2SO4increases with increasingtemperature and more stable than that of doped with a single acid at highertemperature.The PANi/GNs composites prepared through an in situ polymerization werecharacterized and their thermoelectric performances were evaluated. Theconductivity of PANi/GNs composites decreased but the Seebeck coefficientincreased with increasing temperature. The conductivity and Seebeck coefficient ofPANi/GNs first increased and then decreased with the increasing the percentage ofGNs, while the ZT value increased with the increasing the percentage of GNs. Thepolyaniline grew along the surface of GNs due to π-π interactions between PANi andGNs forming a more extended chain structure during the polymerization process.The electrical conductivity and Seebeck coefficient of PANi/GNs nanocompositeswere higher than that of pure PANi, which could be attributed to the enhancedcarrier mobility in the ordered chain structures of the PANi. The thermal conductivities of the composites, even with high CNTs content, do not change muchand still keep very low values, which is attributed to the phonon scattering effect ofnanointerfaces produced by the PANi/GNs nanostructure.The PANi/GNs composites prepared through mechanical milling werecharacterized and their thermoelectric performances were evaluated. Theconductivity of PANi/GNs composites were almost no change with temperature, butsignificantly increased with the increasing content GNs. Seebeck coefficientincreases with increasing temperature, and no significant effect of GNs content onthe Seebeck coefficient PANi/GNs. Thermal conductivity decreases with increasingtemperature. When adding a small amount of La(NO3)3in PANi/GNs composite, thethermoelectric properties of the PANi/GNs can be further improved.Being network structure CNTs can also be connected to polyaniline chains andenhanced electrical transport.The PANi/GNs/CNTs composites prepared by in situpolymerization were characterized and their thermoelectric performances wereevaluated. The polyaniline grew along the surface of GNs due to π-π interactionsamong PANi, CNTs and GNs forming a more extended chain structure during thepolymerization process. The electrical conductivity and Seebeck coefficient ofPANi/GNs/CNTs nanocomposites were higher than those of pure PANi, which couldbe attributed to the enhanced carrier mobility in the ordered chain structures of thePANi. With the same mass10wt%, ZT value of the composite with the appropriateproportion of CNTs and GNs is larger than that of adding single CNTs. This isbecause GNs can significantly improve electrical conductivity, and more conductivenetwork structures are formed by the addition of CNTs in the composite. Thethermal conductivity of the composites can be further reduced by the scatteringeffect. The incorporation of CNTs can effectively increase the Seebeck coefficientand decrease thermal conductivity by adjusting the ratio of CNTs and GNs when theadded mass up to30wt%. The PANi/GNs/CNTs composites prepared throughmechanical milling were characterized and their thermoelectric performances wereevaluated. The thermoelectric performance of PANi/GNs composites can beimproved by adding an appropriate amount of CNTs. The conductivities of thecomposites can be improved, while their thermal conductivities can be reduced byadjusting the amount of CNTs, which is attributed to the increased phonon scatteringproduced by adding an appropriate amount of CNTs. Therefore, the thermoelectricproperties of iPANi/GNs composite materials can be further improved by exploitingsynergies effect of CNTs and GNs.更多还原