Graphite-reinforced Portland cement composites at alternate ultra-high temperatures

Effects and mechanism of filler content on thermal conductivity of composites: a case study on plasticized polyvinyl chloride/graphite composites

Thermally conductive polymer composites that retain mechanics and processing properties have attracted significant attention because of promising high thermal conductivity. Herein, plasticized polyvinyl chloride (P-PVC)/graphite composites were successfully prepared via melt blending. Following the addition of graphite rising from 0 to 300 phr, the thermal conductivity of P-PVC/graphite composites increases from 0.18 to 3.01 W m−1 K−1. The thermal conductivity of P-PVC/graphite composites with 300 phr graphite is 17 times that of the P-PVC matrix. P-PVC/graphite composites with high thermal conductivity have excellent performance in thermal management for LEDs. Therefore, the high thermal conductivity allows for the LED’s temperature to drop 44%, compared with the P-PVC matrix, at 1.5 V. The notably cooling effect provides the ideas for the future application of the P-PVC/graphite composites in the thermal management for electronic components.

Mechanical Properties of Graphite-Oil Well Cement Composites under High Temperature

Under the condition of heavy oil thermal recovery, the cement sheath is easy to crack in the high temperature environment, resulting in the decrease of cement paste strength, which may further cause sealing failure and oil and gas production safety accidents. In this paper, the influence of graphite on the mechanical properties of cement paste under the simulated thermal recovery of heavy oil was studied, and its mechanism is explored by testing and analyzing the microstructure. The phase composition and microstructure of graphite-cement composites were determined by X-ray diffraction analysis (XRD) and scanning electron microscope (SEM), and the thermogravimetric analyzer (TG/DTG) was used to analyze the heat resistance of the graphite-cement composites. The results show that the addition of graphite significantly improved the strength and deformation resistance of the Class G oil well cement at high temperature (300, 400, and 500 °C) and low temperature (50 °C), and the optimal addition amount is 0.07%. The microscopic analysis shows that the incorporation of graphite promoted the formation of hydration products, and played a role in filling pores and reducing microcracks in cement pastes. At the same time, due to the better thermal conductivity of graphite, it can balance the internal thermal stress of the cement pastes and inhibit the strength decline of cement pastes under high temperature environments. The integrity of cement pastes was guaranteed through the mechanism of "crack deflection" and "crack bridging". The research results of this paper have presented a certain theoretical basis and new ideas for the development of cementing slurry systems in heavy oil thermal recovery wells.