Corrosion Resistance Mechanism of Mica-Graphene/Epoxy Composite Coating in CO2-Cl- System.

The working environment for tubing in oil and gas fields is becoming more and more serious due to the exploration of unconventional oil and gas resources, leading to the increasing need for a protective internal coating to be used in tubing. Therefore, a new mica-graphene/epoxy composite coating with different graphene contents (0.0, 0.2, 0.5, 0.7, and 1.0 wt.%) was prepared to improve the tubing resistance to a corrosive medium, an autoclave was used to simulate the working environment, and an electrochemical workstation assisted by three-electrodes was used to study the electrochemical characteristics of the coating. The results showed that the addition of a certain amount of graphene into the mica/epoxy coating significantly improved the corrosion resistance of the composite coating, and when the graphene content increased, the corrosion resistance of the mica/epoxy coating first increased and then decreased when the corrosion current density of a 35 wt.% 800# mica/epoxy coating with a 0.7 wt.% graphene content was the lowest (7.11 × 10-13 A·cm-2), the corrosion potential was the highest (292 mV), the polarization resistance was the largest (3.463 × 109 Ω·cm2), and the corrosion resistance was improved by 89.3% compared to the coating without graphene. Furthermore, the adhesion of the coating with 0.7 wt.% graphene was also the largest (8.81 MPa, increased by 3.4%) and had the smallest diffusion coefficient (1.566 × 107 cm2·s-1, decreased by 76.1%), and the thermal stability improved by 18.6%. Finally, the corrosion resistance mechanism of the composite coating with different graphene contents at different soaking times was revealed based on the electrochemistry and morphology characteristics other than water absorption and contact angle.

Panax notoginseng saponins improve recovery after spinal cord transection by upregulating neurotrophic factors.

Saponins extracted from Panax notoginseng are neuroprotective, but the mechanisms underlying this effect remain unclear. In the present study, we established a rat model of thoracic (T10) spinal cord transection, and injected Panax notoginseng saponins (100 mg/kg) or saline 30 minutes after injury. Locomotor functions were assessed using the Basso, Beattie, and Bresnahan (BBB) scale from 1 to 30 days after injury, and immunohistochemistry was carried out in the ventral horn of the spinal cord at 1 and 7 days to determine expression of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Our results show that at 7-30 days post injury, the BBB score was higher in rats treated with Panax notoginseng saponins than in those that received saline. Furthermore, at 7 days, more NGF- and BDNF-immunoreactive neurons were observed in the ventral horn of the spinal cord of rats that had received Panax notoginseng saponins than in those that received saline. These results indicate that Panax notoginseng saponins caused an upregulation of NGF and BDNF in rats with spinal cord transection, and improved hindlimb motor function.