生物炭/二十烷复合定型相变材料制备及其光热、电热转换和储存性能

为解决单一有机相变材料二十烷(n-Eicosane)导热性差及在相变过程中易发生泄漏的问题，本实验选取玉米秸秆作为生物质原料，通过700℃高温热解、KOH刻蚀改性制备了具有多级孔道结构的生物炭(KBC)材料，再通过乙醇熔融、真空浸渍的方法将二十烷封装到生物炭内部孔道，得到了一种生物炭/二十烷(KBC/n-Eicosane)复合定型相变材料。通过SEM、XRD、FTIR等表征手段研究了复合材料的微观结构和形貌，同时利用TG及DSC测试了复合相变材料的热稳定性和储热性能，并探讨了复合相变材料中二十烷不同用量与焓值的关系。结果表明，复合相变材料的焓值与二十烷的用量成正比，当复合相变材料中生物炭与二十烷的质量比为1∶2时，复合相变材料未明显泄漏，定型效果良好，此时对应的熔融焓和凝固焓值分别为121.3 J·g^-1和117.6 J·g^-1，经过100次循环储热和放热性能测试后，未产生渗漏现象，相变焓值亦无明显变化，表明该复合相变材料的储热能力和稳定性较好。此外，还通过模拟太阳光辐射和接入直流电源的方式测试了复合相变材料的光热转换和电热转换能力，结果表明...

Form-stabilized phase change composites based on biochar and n-Eicosane for photo- and electro-thermal conversion and heat storage

To overcome the obstacles of poor thermal conductivity of pure n-Eicosane, a typical single-phase change material, and prevent the melt from leaking during the phase change process, a biochar/n-Eicosane based composite phase change material that possesses high form stabilization, photo- and electric-thermal converting, and enhanced phase change heat transfer was prepared. Firstly, corn straw was selected as the raw material of biomass, and pyrolyzed at higher temperature. Following a KOH etching procedure at 700℃, a biochar support with large surface area and hierarchically interconnected pores were obtained. Then, KBC/n-Eicosane composite phase change materials were prepared by injecting n-Eicosane into biochar skeletons via ethanol melting and vacuum impregnation. The as-prepared composite materials were characterized by SEM, XRD, FTIR and other characterization methods. The thermal stability and heat storage capacity were also tested by TG and DSC. The effect of mass content of n-Eicosane to melting enthalpy and crystallization enthalpy were calculated, and the results reveal that the optimized mass content is m_KBC∶m_n-Eicosane=1∶2 associated with the melting enthalpy and crystallization enthalpy of 121.3 J·g?1 and 117.6 J·g?1, respectively. Notably, after 100 thermal cycles, the melting enthalpy and crystallization enthalpy have negligible changes, and no clear liquid leaking is observed through all thermal cycles, indicating significant thermal storage ability and cycling stability. In addition, the ability of photo- and electro-thermal conversion and storage of the composite phase charge materials were tested by simulated sunlight irradiating and DC power supply powering. The results display that the KBC/n-Eicosane composite phase materials are capable of converting solar energy or electric energy into thermal energy and storing as latent heat with excellent performance. Thus, the as-prepared KBC/n-Eicosane are not merely a phase charge materials with remarkable properties, but can realize varied energy transformation and storage, showing great potential for use in green and renewable energy conversion and storage.