An alternative solution for the direct formation of?-LiAlO2 was presented by a modified combustion method,to apply it to rather simple systems,utilizing non-oxidizer compounds such as Al2O3 and LiOH,and urea as fuel.L...An alternative solution for the direct formation of?-LiAlO2 was presented by a modified combustion method,to apply it to rather simple systems,utilizing non-oxidizer compounds such as Al2O3 and LiOH,and urea as fuel.LiAlO2 was prepared via non-stoichiometric 1:1,1.5:1 and 2:1 of Li/Al molar ratios at 900 and 1000°C for 5 min.Textural and structural characterization ofγ-LiAlO2 was performed.Also,the effect of different Li/Al molar ratios on material morphology and its stability before high gamma radiation gradients was evaluated.The results showed that the crystal structures of the obtained powders wereγ-LiAlO2 and?-LiAlO2,depending on the Li/Al molar ratio.The results obtained demonstrate that?-LiAlO2 microbricks,polyhedral and laminar shapes can be successfully synthesized with the proposed method and without any subsequent process.Additionally,gamma irradiation showed that the?-LiAlO2 obtained does not decompose,forming only small amounts of Li2CO3.It can be established that the irradiation produces consolidation,which is not favourable for an efficient extraction of tritium.Finally,it could be demonstrated that nitrate precursors are not necessary in the combustion method to produceγ-LiAlO2 with high purity.展开更多
Rock bolts are one of the primary support systems utilized in underground excavations within the civil and mining engineering industries. Rock bolts support the weakened rock mass adjacent to the opening of an excavat...Rock bolts are one of the primary support systems utilized in underground excavations within the civil and mining engineering industries. Rock bolts support the weakened rock mass adjacent to the opening of an excavation by fastening to the more stable, undisturbed formations further from the excavation. The overall response of such a support element has been determined under varying loading conditions in the laboratory and in situ experiments in the past four decades; however, due to the limitations with conventional monitoring methods of capturing strain, there still exists a gap in knowledge associated with an understanding of the geomechanical responses of rock bolts at the microscale. In this paper, we try to address this current gap in scientific knowledge by utilizing a newly developed distributed optical strain sensing(DOS) technology that provides an exceptional spatial resolution of 0.65 mm to capture the strain along the rock bolt. This DOS technology utilizes Rayleigh optical frequency domain reflectometry(ROFDR) which provides unprecedented insight into various mechanisms associated with axially loaded rebar specimens of different embedment lengths, grouting materials, borehole annulus conditions, and borehole diameters. The embedment length of the specimens was found to be the factor that significantly affected the loading of the rebar. The critical embedment length for the fully grouted rock bolts(FGRBs) was systematically determined to be430 mm. The results herein highlight the effects of the variation of these individual parameters on the geomechanical responses FGRBs.展开更多
基金supported by National Institute of Nuclear Research (ININ)Autonomous University of Puebla (BUAP)co-financed by National Council of Science and Technology (CONACYT, México)
文摘An alternative solution for the direct formation of?-LiAlO2 was presented by a modified combustion method,to apply it to rather simple systems,utilizing non-oxidizer compounds such as Al2O3 and LiOH,and urea as fuel.LiAlO2 was prepared via non-stoichiometric 1:1,1.5:1 and 2:1 of Li/Al molar ratios at 900 and 1000°C for 5 min.Textural and structural characterization ofγ-LiAlO2 was performed.Also,the effect of different Li/Al molar ratios on material morphology and its stability before high gamma radiation gradients was evaluated.The results showed that the crystal structures of the obtained powders wereγ-LiAlO2 and?-LiAlO2,depending on the Li/Al molar ratio.The results obtained demonstrate that?-LiAlO2 microbricks,polyhedral and laminar shapes can be successfully synthesized with the proposed method and without any subsequent process.Additionally,gamma irradiation showed that the?-LiAlO2 obtained does not decompose,forming only small amounts of Li2CO3.It can be established that the irradiation produces consolidation,which is not favourable for an efficient extraction of tritium.Finally,it could be demonstrated that nitrate precursors are not necessary in the combustion method to produceγ-LiAlO2 with high purity.
基金Natural Sciences and Engineering Council of Canada(NSERC)the Canadian Department of National Defense+2 种基金MITACSYield Point Inc.the Royal Military College(RMC) Green Team
文摘Rock bolts are one of the primary support systems utilized in underground excavations within the civil and mining engineering industries. Rock bolts support the weakened rock mass adjacent to the opening of an excavation by fastening to the more stable, undisturbed formations further from the excavation. The overall response of such a support element has been determined under varying loading conditions in the laboratory and in situ experiments in the past four decades; however, due to the limitations with conventional monitoring methods of capturing strain, there still exists a gap in knowledge associated with an understanding of the geomechanical responses of rock bolts at the microscale. In this paper, we try to address this current gap in scientific knowledge by utilizing a newly developed distributed optical strain sensing(DOS) technology that provides an exceptional spatial resolution of 0.65 mm to capture the strain along the rock bolt. This DOS technology utilizes Rayleigh optical frequency domain reflectometry(ROFDR) which provides unprecedented insight into various mechanisms associated with axially loaded rebar specimens of different embedment lengths, grouting materials, borehole annulus conditions, and borehole diameters. The embedment length of the specimens was found to be the factor that significantly affected the loading of the rebar. The critical embedment length for the fully grouted rock bolts(FGRBs) was systematically determined to be430 mm. The results herein highlight the effects of the variation of these individual parameters on the geomechanical responses FGRBs.
