RESUMEN
This work reports a new means of preparing graphene tubes (GTs) without relying on chemical vapor deposition (CVD) and it's template-free. Surprisingly, we found that under the action of calcium oxide (CaO) and after 1500 °C heat treatment, a large amount of GTs grew on the surface of polyimide (PI). These nanotubes have a maximum diameter of about 600 nm and a length of up to millimeters, and some nanotubes even have a branching structure. We propose a simple, effective and green method which exhibits prospects for large-scale production of GTs using polymeric materials.
RESUMEN
How to construct a functional unit for heat storage by using biomass materials is significant for the exploration of phase change materials (PCMs). In this work, we try to design and construct a functional unit for heat storage by employing a vacuum impregnation method to prepare sugarcane-based shape stabilized phase change materials (SSPCMs) for improving the thermal conductivity of phase change materials (PCMs) and preventing the liquid state leakage of PCMs. The morphologies of the prepared materials are characterized by Scanning electron microscope (SEM) as containing a unique channel structure which is viewed as the key factor for heat storage. X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA) were used to characterize the prepared materials. The results indicated that no chemical reaction occurred between PEG and sugarcane-based biomass during the preparation process and SSPCMs showed great thermal stability. Their thermal properties are measured by using the differential scanning calorimetry (DSC) characterization and show a high melting enthalpy of 140.04 J/g and 94.84% of the relative enthalpy efficiency, illustrating the excellent shape stabilized phase change behavior. Moreover, the highest thermal conductivity of SSPCMs is up to 0.297 W/(mK), which is 28.02% higher than that of the pristine PEG. The excellent capability for thermal energy storage is attributed to the directional thermal conduction skeletons and perfect open channels and the unique anisotropic three-dimensional structure of the SSPCMs. Hence, the unique structure with PEG is testified as the functional unit for heat storage. Comprehensively considering the excellent properties of sugarcane-based materials-providing cheap raw materials via green preparation-it is conceived that sugarcane-based materials could be applied in many energy-related devices with reasonable function unit design.