Electronic waste (e-waste) from nonbiodegradable products present a significant global problem due to its toxic nature and substantial environmental impact. In this study novel electrically conductive biodegradable films of uncured natural rubber (NR) incorporating graphite platelets and chitosan were developed via a latex aqueous microdispersion method. Chitosan was added as a dispersing and thickening agent to encourage the uniform distribution of graphite in the NR matrix at loadings of 20-60 parts per hundred rubbers (phr). FTIR confirmed interactions between NR, graphite, and chitosan. FE-SEM and Synchrotron XTM analyses demonstrated uniform graphite dispersion. The result of XRD revealed the greatest crystallinity at 86.9% with 60 phr graphite loading. Mechanical properties testing indicated a significant increase in Young's modulus to 58.2 MPa, or about 470-fold improvement over the pure NR film. The composite films demonstrated improved thermal and chemical resistance, and their electrical conductivity could rise dramatically to 1.22 x 10-5 S cm-1 at 60 phr graphite loading, or about six orders of magnitude higher than pure NR film. The composite films exhibit antibacterial activity against Staphylococcus aureus and some inhibition against Escherichia coli. In addition, the NR composite films exhibited biodegradability ranging from 16.7% to 25.1% after three months of soil burial, declining with increased graphite loading. These results demonstrate the potential of NR-graphite composites as conductive materials for flexible electronics, such as thin-film electrodes in energy storage devices and sensors.

This manuscript investigated the thermal stability, crystal reconstruction and microstructure evolution of graphite tailing cement mortar subjected to high temperature. Simultaneously, a computational model for heat transfer and degradation considering chemical transformations had been developed by combining multiscale mechanics with the laws of thermodynamics. The results show that 20% graphite tailings can increase the tobermorite crystal content under high temperature and inhibit its transformation into disordered form. Furthermore, the dormant active SiOx in graphite tailing is gradually activated under the action of high temperature, which catalyzes and induces the formation of more belite crystal in graphite tailing cement mortar. Additionally, 40% graphite tailing can promote the generation of anorthite by the induction of high temperature. Finally, a new multi-scale model considering the chemical transformation is established to calculate the hightemperature degradation process of graphite tailing cement mortar.

Frictional heat generated by mechanisms that take service on celestial bodies such as the moon does not dissipate easily owing to the vacuum environment and the low thermal conductivity of celestial soil. Consequently, the temperature of these mechanisms increases significantly. The wear resistance of liquid lubricants at high temperatures degenerates rapidly because the oil film thins out and the oil decomposes. Polytetrafluoroethylene (PTFE) and the soap fiber thickeners of lubricants are susceptible to phase transitions and agglomeration. The wear resistance and thermal stability of lubricants must be improved for mechanisms operating on celestial bodies. The lubricating properties at high temperatures and the thermal stability of fluorinated graphite are excellent. The wear resistance of liquid lubricants for space mechanisms can be improved using fluorinated graphite. In this study, fluorinated-graphite-modified perfluoropolyether (PFPE) greases are prepared using fluorinated graphite with different fluorine-to-carbon ratios and particle sizes, PTFE powders, and D-type PFPE base oil. The thermal behaviors of the materials are characterized using thermogravimetry and differential scanning calorimetry. Electron spectroscopy and X-ray diffraction are used to determine the fluorine-to-carbon ratios and the structures of three types of fluorinated graphite. The effects of different fluorinated graphites on the rheological and tribological properties of the greases are evaluated at 25 degrees C in atmospheric and vacuum environments, as well as at 200 degrees C in a high-temperature vacuum environment. The results show that the decomposition temperature of the three types of fluorinated graphites are higher than 595 degrees C , whereas that of the D-type PFPE base oil is 450 degrees C . The fluorine-to-carbon ratios of C2FJ1002, CFT10, and CF500 fluorinated graphites are 0.92, 0.88, and 1.04, respectively. Among them, the fluorine-to-carbon ratio of the nanoscale fluorinated graphite, CFT10, is the lowest. The (001) reflection of this nanofluorinated graphite is higher than the others; therefore, its (CF)n is greater than those of the others. The nanoscale fluorinated graphite exhibits the most significant thickening effect on grease at room temperature under low shear owing to its larger specific surface area. However, under high-shear and high-temperature conditions, the thickening effects of the three types of fluorinated graphites are almost uniform At high temperatures, the increased interlayer spacing of fluorinated graphite results in more PFPE oil molecules being absorbed, thus resulting in an increase in the shear viscosity of the grease at a shear rate of 10-15 s(-1). The wear-scar diameter of the grease modified by the abovementioned three types of fluorinated graphites under a 25 degrees C vacuum environment decreases by 7.7%, 11.7%, and 13.2%, respectively. The CF500 fluorinated graphite with the highest fluorine-to-carbon ratio demonstrates the best wear resistance in grease. Additionally, it exhibits a decreasing worn function under a 200 degrees C vacuum environment. The C 1s core-level spectra of the wear scars lubricated by the PFPE grease suggest the formation of amorphous carbon on the wear scar due to the degradation of PFPE. However, the C 1s core-level spectra of the wear scars lubricated with grease, which are modified by the CF500 fluorinated graphite, do not suggest the formation of amorphous carbon. The CF500 fluorinated graphite can shield the tribological surface and mitigate the degradation of the PFPE base oil. The higher the fluorine content, the more prominent is the reduction in wear of the PFPE grease in both vacuum and high-temperature vacuum environments. This is primarily attributed to its higher thermal stability and adsorption capacity for PFPE oil molecules, which reduces the chain breakage and carbonization of PFPE. However, reducing the particle size does not significantly reduce wear.

In this paper, flexible conductive composite materials were prepared from flexible graphite and carbon fiber by mould pressing, and their micromorphology was studied by SEM. The influence of carbon fiber content on the mechanical properties and electrical conductivity of the flexible conductive composite material was studied, and the corrosion rate of the flexible conductive composite material coupling with galvanized steel in soil with different SO42- concentrations was studied. The results showed that the tensile strength reached 5.82 MPa when the mass ratio of carbon fiber to flexible graphite was 1:20, and the volume resistivity achieved 4.76 x 10-5 Omegam when the mass ratio of carbon fiber to flexible graphite was 1:30. With the increase in molding pressure, tensile strength and electrical conductivity had a slight increase. When the flexible conductive composite material was coupled with galvanized steel, sulfate could accelerate the galvanic cell corrosion between the flexible graphite grounding material and galvanized steel. The increase in the sulfate concentration led to more corrosion acceleration. With the increase in corrosion time, the corrosion potential of the flexible graphite grounding material and galvanized steel coupling body decreased to its lowest at 30 days, and then increased gradually. The corrosion current was the highest at 30 days, and then decreased gradually.

Freeze-thaw (F-T) weathering can alter the geometry of soils and rocks, imposing severe damage to the Earth's surface. However, it has the potential to favor the beneficiation of mineral resources. In this study, we simulated F-T weathering cycles on the graphite ore from Luobei, a seasonally frozen region in China. The deterioration of the graphite ore caused by F-T weathering was characterized by various means, including the P-wave velocity test, uniaxial compression test, optical microscope, and micro X-ray CT. The results showed that the emergence and propagation of surface defects and cracks in the graphite samples under F-T weathering resulted in weakened mechanical properties of the samples. Moreover, comminution and flotation tests indicated that F-T weathering also amplified the selective liberation between graphite and gangue minerals during crushing and grinding, which contributed to improved separation efficiency and flotation recovery of graphite with significantly reduced chemical usage and energy input. Our study offers a promising strategy for improved and more costefficient beneficiation of graphite ores in cold regions where natural F-T weathering occurs.

Green natural rubber (NR) composites reinforced with synthetic graphite platelets, using alginate as a thickening and dispersing agent, were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The fabrication was performed using a latex aqueous microdispersion process. The research demonstrated the effective incorporation of graphite platelets into the NR matrix up to 60 parts per hundred rubbers (phr) without causing agglomeration or phase separation. Graphite incorporation significantly improved the mechanical strength of the composite films. NR with 60 phr of graphite exhibited the highest Young's modulus of 12.3 MPa, roughly 100 times that of the neat NR film. The reinforcement also strongly improved the hydrophilicity of the composite films, resulting in a higher initial water absorption rate compared to the neat NR film. Moreover, the incorporation of graphite significantly improved the chemical resistance of the composite films against nonpolar solvents, such as toluene. The composite films exhibited biodegradability at about 21% to 30% after 90 days in soil. The electrical conductivity of the composite films was considerably enhanced up to 2.18 x 10-4 S/cm at a graphite loading of 60 phr. According to the improved properties, the developed composites have potential applications in electronic substrates.