EGCFRC的Seebeck效应多类型界面散射强化机理研究

发布时间：2018-04-10 05:38

本文选题：EGCFRC　切入点：热电性能　出处：《西安建筑科技大学》2017年硕士论文

【摘要】：膨胀石墨/碳纤维增强水泥基复合材料(Expanded Graphite/Carbon Fiber Reinforced Cement-based Composites,简写为EGCFRC)是一种可以实现热电相互转换的新型功能材料。它在城市余热利用、建筑结构健康监测和道路低能耗融雪化冰领域具有广泛的应用前景,是智能水泥基复合材料研究与发展的重要方向之一。但目前,EGCFRC-Seebeck系数仍然较低,是制约其大规模应用的关键因素。本文主要通过压制成型工艺制备EGCFRC,分析不同成型压力对EGCFRC电导率与Seebeck效应的影响。利用体视学方法实现了EGCFRC中碳纤维/膨胀石墨与水泥基体间界面,孔隙和微裂纹形成的气/固界面的定量化表征。探究了含水率、不同类型气/固界面,金属氧化物/水泥基体界面以及离子液体/水泥基体界面对EGCFRC电导率及Seebeck系数的影响,获得了EGCFRC多类型界面散射强化机理。主要研究内容和结果如下:(1)借助图像分析方法获得了EGCFRC基体中碳纤维/膨胀石墨与水泥基体间界面,微/纳米孔隙或微裂纹与水泥基体间气/固界面的二维信息,利用体视学原理推导出EGCFRC定量化的三维信息,并建立界面参数与EGCFRC电导率、Seebeck系数间的数学关系。研究结果表明:EGCFRC的电导率随成型压力的增大而呈增加趋势;而EGCFRC中气/固界面含量则随着成型压力的减小而增大,从而引起基体中缺陷密度变大,载流子传输受阻,Seebeck效应获得强化。成型压力为60 MPa时最利于EGCFRC热电性能的提高。(2)探讨了气孔率对EGCFRC热电性能的影响,并通过层切法构造与热流方向呈不同夹角的气/固界面,进一步获得气/固界面对EGCFRC电导率与Seebeck效应的影响机理。研究结果表明:采用压制成型制备EGCFRC,成型压力为60 MPa时,EGCFRC获得最大电导率0.063 S·cm~(-1),较传统成型工艺提高了3个数量级。同时,获得最大功率因数7.26×10~(-4)μWm-1K-2以及最大ZT值2.22×10-7。20 MPa,40 MPa和60 MPa三种成型压力下,气/固界面与热流方向呈90o夹角时,EGCFRC的Seebeck效应得到强化,其中,成型压力为20 MPa时效果最显著。(3)测量了EGCFRC样品的含水率,研究了含水率对EGCFRC热电性能的影响。研究结果表明:含水率的增大可以强化Seebeck效应,但也会降低电导率。在33oC时,当EGCFRC中含水率为14.98%时,获得最大的绝对Seebeck系数11.59μV/oC。在同一温度下,当含水率为11.44%时,获得最大的电导率0.078 S·cm~(-1)以及最大的功率因数7.85×10~(-4)μWm-1K-2。含水率对EGCFRC热电性能的显著影响可以归因于接触电阻的存在、载流子散射、水泥基体的极化效应以及EGCFRC固有的高密度缺陷界面。(4)探讨了水泥基体中Fe_2O_3含量对EGCFRC热电性能的影响。研究结果表明:Fe_2O_3掺量为5.0 wt%时,EGCFRC的电导率和Seebeck效应同时得到提高,在65oC时获得最大绝对Seebeck系数16.80μV/oC和最大电导率0.084 S·cm~(-1);而加入10.0wt%的Fe_2O_3时,EGCFRC的绝对Seebeck系数最大可达20.85μV/oC,但电导率却只有0.036 S·cm~(-1)。(5)研究了不同养护方式、离子液体[Bmim]Br掺量对EGCFRC热电性能的影响规律及机理。研究结果表明:离子液体[Bmim]Br掺量越高,EGCFRC的绝对Seebeck系数越大,电导率越低。预处理后养护可以使[Bmim]Br同时受到机械力与热运动的双重作用而更加均匀地分散在水泥基体中,促进阴阳离子在电极表面的迁移与重排,从而强化EGCFRC的Seebeck效应,但同时会引起电导率降低。[Bmim]Br掺量为3.0 wt%时,直接养护EGCFRC在72oC时获得最大绝对Seebeck系数115.39μV/oC,最大功率因数8.56×10-3 mWm-1K-2;预处理后养护EGCFRC在72oC时获得最大绝对Seebeck系数580.10μV/oC,最大功率因数9.97×10-2mWm-1K-2。
[Abstract]:The expanded graphite / carbon fiber reinforced cement composite (Expanded Graphite/Carbon Fiber Reinforced Cement-based Composites, abbreviated as EGCFRC) is a new type of functional material can achieve the thermoelectric conversion. It makes use of waste heat in the city, structural health monitoring and low energy consumption of road deicing field has a wide application prospect, is one of the important research direction with the development of smart cement based composite materials. But at present, the EGCFRC-Seebeck coefficient is still low, is the key factor that restricts its large-scale application. This paper mainly through the preparation of EGCFRC molding process, analysis of the influence of different molding pressure on the conductivity of EGCFRC and Seebeck effect. The stereo implementation of carbon fiber / EGCFRC expanded graphite and cement the matrix interface method, pore and micro crack formation of the gas / solid interface and quantitative characterization. To explore the different types of moisture. Gas / solid interface, effect of metal oxide / cement matrix interface and the ionic liquid / cement matrix interface of EGCFRC conductivity and Seebeck coefficient, obtained the EGCFRC type interface scattering enhancement mechanism. The main research contents and results are as follows: (1) by means of image analysis method for carbon fiber / matrix with EGCFRC expanded graphite and cement the matrix between the two-dimensional information interface, micro / nano pores or cracks and cement matrix between the gas / solid interface, using stereological 3D information derived from the principle of EGCFRC quantification, and establish the interface parameter and EGCFRC conductivity, mathematical relation among the Seebeck coefficients. The results show that the conductivity of EGCFRC increases with the molding pressure and increased; while the EGCFRC gas / solid interface was reduced with the molding pressure increases, causing the defects in bulk density change, carrier transport is blocked, Seebeck effect Gain enhancement. The molding pressure is 60 MPa the most conducive to improve the thermoelectric properties of EGCFRC. (2) discussed the effects of porosity on the thermoelectric properties of EGCFRC, and through slicing method to construct different angles of the gas / solid interface and the heat flow direction, further gas / solid interface on the influence mechanism of the electrical conductivity of EGCFRC and Seebeck effect. Research results indicate that the preparation of EGCFRC press molding, molding pressure is 60 MPa, EGCFRC 0.063 S / cm~ maximum conductivity (-1), increased by 3 orders of magnitude compared with the traditional molding process. At the same time, the maximum power factor of 7.26 * 10~ (-4) Wm-1K-2 and the maximum ZT value of 2.22 * 10-7.20 MPa 40 MPa 60 MPa, and three kinds of molding pressure, gas / solid interface and the heat flow direction is 90o angle, the Seebeck effect of EGCFRC was enhanced, the molding pressure is 20 MPa the most significant effect. (3) EGCFRC water samples were measured, on the moisture content of EG Influence of the thermoelectric properties of CFRC. The results show that the increase of water content can enhance the Seebeck effect, but also can reduce theconductivity. In 33oC, when the water content of EGCFRC is 14.98%, Seebeck get the absolute maximum coefficient of 11.59 V/oC. at the same temperature, when the moisture content is 11.44%, the maximum conductivity 0.078 S - cm~ (-1) and the maximum power factor of 7.85 * 10~ (-4) Wm-1K-2. water content had significant influence on the thermoelectric properties of EGCFRC can be attributed to the contact resistance, carrier scattering, polarization effect of cement matrix and EGCFRC inherent defects with high density interface. (4) to investigate the effect of Fe_2O_3 content in cement matrix the thermoelectric properties of EGCFRC. The results show that the content of Fe_2O_3 is 5 wt%, the conductivity and Seebeck effect of EGCFRC were increased at the same time, in the 65oC and get the maximum absolute Seebeck coefficient of 16.80 V/oC and a maximum conductivity of 0. 084 S - cm~ (-1); while the addition of 10.0wt% of Fe_2O_3, the maximum absolute Seebeck coefficient EGCFRC of 20.85 V/oC, but the conductivity is only 0.036 S - cm~ (-1). (5) studied the different curing methods, ionic liquid dosage of [Bmim]Br on the thermoelectric properties of EGCFRC influence and mechanism research. The results show that the ionic liquid [Bmim]Br content is higher, the absolute Seebeck coefficient of EGCFRC, the lower the conductivity. After pretreatment of maintenance can make the [Bmim]Br at the same time is influenced by both mechanical and thermal motion and more evenly dispersed in the cement matrix, promote the migration and rearrangement of ions in the surface of the electrode, thereby strengthening Seebeck the effect of EGCFRC, but it causes the conductivity decreased the dosage of.[Bmim]Br is 3 wt%, direct maintenance EGCFRC get the maximum absolute Seebeck coefficient of 115.39 V/oC at 72oC, the maximum power factor of 8.56 * 10-3 mWm-1K-2; after the pretreatment of EGCFR maintenance The maximum absolute Seebeck coefficient of 580.10 mu V/oC is obtained at 72oC, and the maximum power factor is 9.97 x 10-2mWm-1K-2.

【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34

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