Effect of dry-wet cycles on dynamic properties and microstructures of sandstone:Experiments and modelling

Underground pumped storage power plant(UPSP)is an innovative concept for space recycling of abandoned mines.Its realization requires better understanding of the dynamic performance and durability of reservoir rock.This paper conducted ultrasonic detection,split Hopkinson pressure bar(SHPB)impact,mercury intrusion porosimetry(MIP),and backscatter electron observation(BSE)tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage.A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage.The results show that dry-wet cycles decrease the dynamic compressive strength(DCS)with a maximum reduction of 39.40%,the elastic limit strength is reduced from 41.75 to 25.62 MPa.The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle.The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles,which verifies the computational statistics analysis of particle deterioration.The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant.The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.

Fabrication and multiscale characterization of 3D silver containing bioactive glass-ceramic scaffolds

In this work,we fabricated and characterized bioactive 3D glass-ceramic scaffolds with inherent antibacterial properties.The sol-gel(solution-gelation)technique and the sacrificial template method were applied for the fabrication of 3D highly porous scaffolds in the 58.6SiO2-24.9CaO-7.2P2O5-4.2Al2O3–1.5Na2O−1.5K2O–2.1Ag2O system(Ag-BG).This system is known for its advanced bioactive and antibacterial properties.The fabrication of 3D scaffolds has potential applications that impact tissue engineering.The study of the developed scaffolds from macro-characteristics to nano-,revealed a strong correlation between the macroscale properties such as antibacterial action,bioactivity with the microstructural characteristics such as elemental analysis,crystallinity.Elemental homogeneity,morphological,and microstructural characteristics of the scaffolds were studied by scanning electron microscopy associated with energy dispersive spectroscopy(SEM-EDS),transmittance electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR),and UV-visible spectroscopy methods.The compressive strength of the 3D scaffolds was measured within the range of values for glass-ceramic scaffolds with similar compositions,porosity,and pore size.The capability of the scaffolds to form an apatite-like phase was tested by immersing the scaffolds in simulated body fluid(SBF)and the antibacterial response against methicillin-resistant Staphylococcus aureus(MRSA)was studied.The formation of an apatite phase was observed after two weeks of immersion in SBF and the anti-MRSA effect occurs after both direct and indirect exposure.