Highly Aligned Graphene Aerogels for Multifunctional Composites

Stemming from the unique in-plane honeycomb lattice structure and the sp^(2)hybridized carbon atoms bonded by exceptionally strong carbon–carbon bonds,graphene exhibits remarkable anisotropic electrical,mechanical,and thermal properties.To maximize the utilization of graphene’s in-plane properties,pre-constructed and aligned structures,such as oriented aerogels,films,and fibers,have been designed.The unique combination of aligned structure,high surface area,excellent electrical conductivity,mechanical stability,thermal conductivity,and porous nature of highly aligned graphene aerogels allows for tailored and enhanced performance in specific directions,enabling advancements in diverse fields.This review provides a comprehensive overview of recent advances in highly aligned graphene aerogels and their composites.It highlights the fabrication methods of aligned graphene aerogels and the optimization of alignment which can be estimated both qualitatively and quantitatively.The oriented scaffolds endow graphene aerogels and their composites with anisotropic properties,showing enhanced electrical,mechanical,and thermal properties along the alignment at the sacrifice of the perpendicular direction.This review showcases remarkable properties and applications of aligned graphene aerogels and their composites,such as their suitability for electronics,environmental applications,thermal management,and energy storage.Challenges and potential opportunities are proposed to offer new insights into prospects of this material.

Disturbance failure mechanism of highly stressed rock in deep excavation:Current status and prospects

This article reviews the current status on the dynamic behavior of highly stressed rocks under disturbances.Firstly,the experimental apparatus,methods,and theories related to the disturbance dynamics of deep,high-stress rock are reviewed,followed by the introduction of scholars’research on deep rock deformation and failure from an energy perspective.Subsequently,with a backdrop of highstress phenomena in deep hard rock,such as rock bursts and core disking,we delve into the current state of research on rock microstructure analysis and residual stresses from the perspective of studying the energy storage mechanisms in rocks.Thereafter,the current state of research on the mechanical response and the energy dissipation of highly stressed rock formations is briefly retrospected.Finally,the insufficient aspects in the current research on the disturbance and failure mechanisms in deep,highly stressed rock formations are summarized,and prospects for future research are provided.This work provides new avenues for the research on the mechanical response and damage-fracture mechanisms of rocks under high-stress conditions.

Residual stress measurement and analysis of siliceous slate-containing quartz veins

Engineering geological disasters such as rockburst have always been a critical factor affecting the safety of coal mine production.Thus,residual stress is considered a feasible method to explain these geomechanical phenomena.In this study,electron backscatter diffraction(EBSD)and optical microscopy were used to characterize the rock microcosm.A measuring area that met the requirements of X-ray diffraction(XRD)residual stress measurement was determined to account for the mechanism of rock residual stress.Then,the residual stress of a siliceous slate-containing quartz vein was measured and calculated using the sin^(2) ϕ method equipped with an X-ray diffractometer.Analysis of microscopic test results showed homogeneous areas with small particles within the millimeter range,meeting the requirements of XRD stress measurement statistics.Quartz was determined as the calibration mineral for slate samples containing quartz veins.The diffraction patterns of the(324)crystal plane were obtained under different ϕ and φ.The deviation direction of the diffraction peaks was consistent,indicating that the sample tested had residual stress.In addition,the principal residual stress within the quartz vein measured by XRD was compressive,ranging from 10 to 33 MPa.The maximum principal stress was parallel to the vein trend,whereas the minimum principal stress was perpendicular to the vein trend.Furthermore,the content of the low-angle boundary and twin boundary in the quartz veins was relatively high,which enhances the resistance of the rock mass to deformation and promotes the easy formation of strain concentrations,thereby resulting in residual stress.The proposed method for measuring residual stress can serve as a reference for subsequent observation and related research on residual stress in different types of rocks.