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Nowadays, with the rapid development of electronic devices, it is increasingly important to enhance the electrical conductivity of reduced graphene oxide (rGO). Thermal reduction (TR) temperature and time play the most crucial role as they control the electrical conductivity of rGO in terms of removal of oxygen-containing functional (OCF) groups. This work proposes a novel systematic approach for quick calibration of the OCF groups and lattice defects of GO to increase the conductivity by tuning the temperature and exposure time of the sample to the temperature. Single TR (STR) and double TR (DTR) processes were used in the current work, in which samples were exposed to temperatures of 500, 700, and 900 °C for 5 min. Further annealing took place for each sample at the same temperature with various reduction times. The results indicate that the DTR process improved the electrical conductivity of rGO samples. The highest enhancement of rGO500-5, rGO700-5, and rGO900-5 conductivities was 52.36%, 57.58%, and 231.81%, respectively. Consequently, this material can be used as a filler to get a well dispersed nanocomposite by accurate addition of rGO in a matrix, which enhances its electrical properties. Based on x-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and electrical analyses, the plausible STR and DTR mechanism of GO to rGO is effectively proposed.

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In recent years, cheaply available cementitious materials (CMs) are increasingly finding useful applications in construction engineering. This manuscript focused on the development and fabrication of unsaturated polyester resin (UPR)/cementitious material composites to be potentially useful in a variety of construction applications. For this purpose, five types of powders from widely available fillers, i.e., black cement (BC), white cement (WC), plaster of Paris (POP), sand (S), and pit sand (PS), were used. Cement polymer composite (CPC) specimens were prepared by a conventional casting process with various filler contents of 10, 20, 30, and 40 wt %. Neat UPR and CPCs were investigated mechanically by testing their tensile, flexural, compressive, and impact properties. Electron microscopy analysis was used to analyze the relation between the microstructure and mechanical properties of CPCs. The assessment of water absorption was conducted. The highest tensile, flexural, compressive upper yield, and impact strength values were recorded for POP/UPR-10, WC/UPR-10, WC/UPR-40, and POP/UPR-20, respectively. The highest percentages of water absorption were found to be 6.202 and 5.07% for UPR/BC-10 and UPR/BC-20, while the lowest percentages were found to be 1.76 and 1.84% for UPR/S-10 and UPR/S-20, respectively. Based on the finding of this study, the properties of CPCs were found to depend on not only the filler content but also the distribution, particle size, and combination between the filler and the polymer.