纳米石墨烯片-正十八烷复合相变材料制备及热物性研究

本文分别制备了纳米石墨烯片质量分数为0%, 0.5%, 1%, 1.5%, 2%的纳米石墨烯片-正十八烷复合相变材料,并通过扫描电镜测试、红外光谱分析、差示扫描量热实验及导热分析等实验对其形貌结构及热物性进行表征和研究.实验表明本文制备的纳米石墨烯-正十八烷复合相变材料具有很好的相变稳定性;当纳米石墨烯片的质量分数达到2%时,复合相变材料的导热系数相对于纯十八烷高出了89.4%.

Preparation and thermophysical properties of graphene nanoplatelets-octadecane phase change composite materials

Latent heat storage mainly uses the latent heat of phase change material (PCM) to realize thermal energy storage and utilization, which is the most important thermal energy storage method at present. However, most of PCMs have the disadvantage of low thermal conductivity, which greatly restricts the thermal response rate and system efficiency of the thermal energy storage system. With the development of nanotechnology, it is expected to improve the thermal conductivity of traditional PCMs by adding high thermal conductivity nanoparticles. In this paper, a novel two-dimensional carbon nanomaterial, graphene is selected as an additive for PCM.In this paper, graphene nanoplatelets-octadecane phase change composite materials are prepared with a two-step method and the mass fractions of graphene nanoplatelets are 0%, 0.5%, 1%, 1.5%, and 2%. Their microstructures, morphologies and thermophysical properties are characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR), differential scanning calorimetry (DSC), and thermal conductivity analysis. The effects of the addition quantity of graphene nanoplatelets on the phase transition temperature, enthalpy, specific heat capacity, thermal conductivity and thermal stability of the composite PCM are compared. The experimental results show that the dispersion stability of the graphene nanoplatelets in the composite system is greatly improved by the addition of dispersant, and the system does not produce obvious agglomeration nor sedimentation after multiple phase transformation cycles. The graphene nanoplatelets still maintain good lamellar structure and homogeneous dispersion in the n-octadecane matrix, and no chemical reaction occurs in the composite process. Comparing with the n-octadecane, the melting point of the composite phase change material decreases slightly, and the freezing point increases slightly. With the increase of graphene nanoplatelets, the latent heat value of graphene nanoplatelets-octadecane composite phase change material decreases gradually. For the composite phase change material with 2.0 wt.% graphene nanoplatelets, the melting enthalpy and solidified enthalpy are reduced by 6.01% and 7.35%, respectively. When the mass fractions of graphene nanoplatelets are 0.5%, 1%, 1.5%, and 2%, the thermal conductivity values of phase change composite materials are nearly 32.4%, 77.4%, 83.1%, and 89.4% higher than the thermal conductivity value of pure octadecane, respectively. Comparing with the significant increase in thermal conductivity, the addition of graphene nanoplatelets has little effect on the phase transition temperature and latent heat of PCM, and still exhibits the good heat storage performance.