7 research outputs found
Analysis of gas migration patterns in fractured coal rocks under actual mining conditions
Fracture fields in coal rocks are the main channels for gas seepage,
migration, and extraction. The development, evolution, and spatial
distribution of fractures in coal rocks directly affect the permeability of
the coal rock as well as gas migration and flow. In this work, the
Ji-15-14120 mining face at the No. 8 Coal Mine of Pingdingshan Tian’an Coal
Mining Co. Ltd., Pingdingshan, China, was selected as the test site to
develop a full-parameter fracture observation instrument and a dynamic
fracture observation technique. The acquired video information of fractures
in the walls of the boreholes was vectorized and converted to planarly
expanded images on a computer-aided design platform. Based on the relative
spatial distances between the openings of the boreholes, simultaneous planar
images of isolated fractures in the walls of the boreholes along the mining
direction were obtained from the boreholes located at various distances from
the mining face. Using this information, a 3-D fracture network under mining
conditions was established. The gas migration pattern was calculated using a
COMSOL computation platform. The results showed that between 10 hours and 1
day the fracture network controlled the gas-flow, rather than the coal seam
itself. After one day, the migration of gas was completely controlled by the
fractures. The presence of fractures in the overlying rock enables the gas
in coal seam to migrate more easily to the surrounding rocks or extraction
tunnels situated relatively far away from the coal rock. These conclusions
provide an important theoretical basis for gas extraction
Structurally Stable, High-Strength Graphene Oxide/Carbon Nanotube/Epoxy Resin Aerogels as Three-Dimensional Skeletal Precursors for Wave-Absorbing Materials
Three-dimensional (3D) graphene oxide aerogel (GOA) is one of the best fillers for composites for microwave absorption. However, its further development has been hindered by the poor mechanical properties. Methodology to improve the mechanical properties of the aerogel remains an urgent challenge. Herein, graphene oxide/carbon nanotube/epoxy resin composite aerogel (GCEA) was successfully prepared by a facile method. The results showed that the prepared GCEA with the hierarchical and 3D cross-linked structures exhibited excellent compression performance, structural and thermal stability, high hydrophilicity, and microwave absorption. The prepared GCEA recovered from multiple large strain cycles without significant permanent deformation. The minimum reflection loss (RL) was −39.60 dB and the maximum effective absorption bandwidth (EAB) was 2.48 GHz. The development of the enhanced GO aerogels will offer a new approach to the preparation of 3D microwave-absorbing skeletal materials with good mechanical properties
Scalable Synthesis of Monolayer Hexagonal Boron Nitride on Graphene with Giant Bandgap Renormalization
Monolayer hexagonal boron nitride (hBN) has been widely considered a fundamental building block for 2D heterostructures and devices. However, the controlled and scalable synthesis of hBN and its 2D heterostructures has remained a daunting challenge. Here, an hBN/graphene (hBN/G) interface-mediated growth process for the controlled synthesis of high-quality monolayer hBN is proposed and further demonstrated. It is discovered that the in-plane hBN/G interface can be precisely controlled, enabling the scalable epitaxy of unidirectional monolayer hBN on graphene, which exhibits a uniform moir� superlattice consistent with single-domain hBN, aligned to the underlying graphene lattice. Furthermore, it is identified that the deep-ultraviolet emission at 6.12�eV stems from the 1s-exciton state of monolayer hBN with a giant renormalized direct bandgap on graphene. This work provides a viable path for the controlled synthesis of ultraclean, wafer-scale, atomically ordered 2D quantum materials, as well as the fabrication of 2D quantum electronic and optoelectronic devices.Controllable synthesis of monolayer hexagonal boron nitride (hBN) has remained a daunting challenge. An hBN/graphene-interface-mediated growth concept to enable scalable epitaxy of unidirectional high-quality monolayer hBN on graphene substrates is proposed and demonstrated. A uniform moir� superlattice and robust deep-ultraviolet excitonic emission (around 6.12 eV) are achieved in such a monolayer hBN/graphene van der Waals heterostructure.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/172829/1/adma202201387_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/172829/2/adma202201387-sup-0001-SuppMat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/172829/3/adma202201387.pd