为提升钛酸铋钠(NBT)基无铅陶瓷电容材料的储能性能,以A位掺杂方式向0.65[Na_(0.5)Bi_(0.5)TiO_(3)]-0.35Sr_(0.7)Bi_(0.2)TiO_(3)中引入MgO,并采用固相烧结法制备了不同摩尔含量(x=0.01~0.06)的0.65[(Na1-x,Mgx)0.5Bi_(0.5)TiO_(3)]-0....为提升钛酸铋钠(NBT)基无铅陶瓷电容材料的储能性能,以A位掺杂方式向0.65[Na_(0.5)Bi_(0.5)TiO_(3)]-0.35Sr_(0.7)Bi_(0.2)TiO_(3)中引入MgO,并采用固相烧结法制备了不同摩尔含量(x=0.01~0.06)的0.65[(Na1-x,Mgx)0.5Bi_(0.5)TiO_(3)]-0.35Sr_(0.7)Bi_(0.2)TiO_(3)(NBT-SBT)陶瓷样品。通过SEM观察和XRD表征,发现随着Mg^(2+)含量的增加,NBT-SBT陶瓷的晶粒尺寸呈先减小后增大的变化,在Mg^(2+)掺入量(x)为0.025时,陶瓷晶粒尺寸最小。介电温谱和电滞回线测试表明该陶瓷为典型的铁电弛豫体,具有较高的介电常数(εr)和电极化强度(Pmax)。在100 k V/cm电场下,(Na0.94,Mg0.06)BT-SBT的可释放能量密度Wrec高达1.65 J/cm^(3),储能效率η为75%,综合性能优于同类NBT基陶瓷样品。结果表明,MgO掺杂的(Na1-x,Mgx)BT-SBT陶瓷具有优异的储能密度和效率,可为电子电力设备等领域的高功率储能电容器件的研究提供参考。展开更多
研究了不同掺量MgO膨胀剂在自然养护、标准养护、限制养护和高温养护条件下对混凝土力学性能的影响,结果表明:随着MgO膨胀剂掺量增大,各养护条件下,混凝土抗压强度均逐渐降低;不同养护条件对混凝土强度影响明显,高温养护下强度发展最快...研究了不同掺量MgO膨胀剂在自然养护、标准养护、限制养护和高温养护条件下对混凝土力学性能的影响,结果表明:随着MgO膨胀剂掺量增大,各养护条件下,混凝土抗压强度均逐渐降低;不同养护条件对混凝土强度影响明显,高温养护下强度发展最快,自然养护下,强度发展最慢;对于C30混凝土,掺20 kg MgO膨胀剂对混凝土强度无明显负面影响;掺MgO膨胀剂混凝土长龄期抗压强度无倒缩现象。展开更多
Dredged marine soils(DMS)have poor engineering properties,which limit their usage in construction projects.This research examines the application of reactive magnesia(rMgO)containing supplementary cementitious materia...Dredged marine soils(DMS)have poor engineering properties,which limit their usage in construction projects.This research examines the application of reactive magnesia(rMgO)containing supplementary cementitious materials(SCMs)to stabilize DMS under ambient and carbon dioxide(CO_(2))curing conditions.Several proprietary experimental tests were conducted to investigate the stabilized DMS.Furthermore,the carbonation-induced mineralogical,thermal,and microstructural properties change of the samples were explored.The findings show that the compressive strength of the stabilized DMS fulfilled the 7-d requirement(0.7-2.1 MPa)for pavement and building foundations.Replacing rMgO with SCMs such as biochar or ground granulated blast-furnace slag(GGBS)altered the engineering properties and particle packing of the stabilized soils,thus influencing their performances.Biochar increased the porosity of the samples,facilitating higher CO_(2) uptake and improved ductility,while GGBS decreased porosity and increased the dry density of the samples,resulting in higher strength.The addition of SCMs also enhanced the water retention capacity and modified the pH of the samples.Microstructural analysis revealed that the hydrated magnesium carbonates precipitated in the carbonated samples provided better cementation effects than brucite formed during rMgO hydration.Moreover,incorporating SCMs reduced the overall global warming potential and energy demand of the rMgO-based systems.The biochar mixes demonstrated lower toxicity and energy consumption.Ultimately,the rMgO and biochar blend can serve as an environmentally friendly additive for soft soil stabilization and permanent fixation of significant amounts of CO_(2) in soils through mineral carbonation,potentially reducing environmental pollution while meeting urbanization needs.展开更多
In Mg-Ca alloys the grain refining mechanism,in particular regarding the role of nucleant substrates,remains the object of debates.Although native MgO is being recognised as a nucleating substrate accounting for grain...In Mg-Ca alloys the grain refining mechanism,in particular regarding the role of nucleant substrates,remains the object of debates.Although native MgO is being recognised as a nucleating substrate accounting for grain refinement of Mg alloys,the possible interactions of MgO with alloying elements that may alter the nucleation potency have not been elucidated yet.Herein,we design casting experiments of Mg-xCa alloys varied qualitatively in number density of native MgO,which are then comprehensively studied by advanced electron microscopy.The results show that grain refinement is enhanced as the particle number density of MgO increases.The native MgO particles are modified by interfacial layers due to the co-segregation of Ca and N solute atoms at the MgO/Mg interface.Using aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy,we reveal the nature of these Ca/N interfacial layers at the atomic scale.Irrespective of the crystallographic termination of MgO,Ca and N co-segregate at the MgO/Mg interface and occupy Mg and O sites,respectively,forming an interfacial structure of a few atomic layers.The interfacial structure is slightly expanded,less ordered and defective compared to the MgO matrix due to compositional deviations,whereby the MgO substrate is altered as a poorer template to nucleate Mg solid.Upon solidification in a TP-1 mould,the impotent MgO particles account for the grain refining mechanism,where they are suggested to participate into nucleation and grain initiation processes in an explosive manner.This work not only reveals the atomic engineering of a substrate through interfacial segregation but also demonstrates the effectiveness of a strategy whereby native MgO particles can be harnessed for grain refinement in Mg-Ca alloys.展开更多
基金supported by the National Natural Science Foundation of China (No.52004044)the Natural Science Foundation of Chongqing,China (No.CSTB2022NSCQ-MSX0801)+3 种基金the Foundation of Chongqing University of Science and Technology,China (No.ckrc2022030)the Graduate Research Innovation Project of Chongqing University of Science and Technology,China (No.YKJCX2220214)the Science and Technology Innovation Training Program of Chongqing University of Science and Technology,China (No.2022046)the College Students’Innovation and Entrepreneurship Training Program of Chongqing University of Science and Technology,China (No.2022007).
文摘为提升钛酸铋钠(NBT)基无铅陶瓷电容材料的储能性能,以A位掺杂方式向0.65[Na_(0.5)Bi_(0.5)TiO_(3)]-0.35Sr_(0.7)Bi_(0.2)TiO_(3)中引入MgO,并采用固相烧结法制备了不同摩尔含量(x=0.01~0.06)的0.65[(Na1-x,Mgx)0.5Bi_(0.5)TiO_(3)]-0.35Sr_(0.7)Bi_(0.2)TiO_(3)(NBT-SBT)陶瓷样品。通过SEM观察和XRD表征,发现随着Mg^(2+)含量的增加,NBT-SBT陶瓷的晶粒尺寸呈先减小后增大的变化,在Mg^(2+)掺入量(x)为0.025时,陶瓷晶粒尺寸最小。介电温谱和电滞回线测试表明该陶瓷为典型的铁电弛豫体,具有较高的介电常数(εr)和电极化强度(Pmax)。在100 k V/cm电场下,(Na0.94,Mg0.06)BT-SBT的可释放能量密度Wrec高达1.65 J/cm^(3),储能效率η为75%,综合性能优于同类NBT基陶瓷样品。结果表明,MgO掺杂的(Na1-x,Mgx)BT-SBT陶瓷具有优异的储能密度和效率,可为电子电力设备等领域的高功率储能电容器件的研究提供参考。
文摘研究了不同掺量MgO膨胀剂在自然养护、标准养护、限制养护和高温养护条件下对混凝土力学性能的影响,结果表明:随着MgO膨胀剂掺量增大,各养护条件下,混凝土抗压强度均逐渐降低;不同养护条件对混凝土强度影响明显,高温养护下强度发展最快,自然养护下,强度发展最慢;对于C30混凝土,掺20 kg MgO膨胀剂对混凝土强度无明显负面影响;掺MgO膨胀剂混凝土长龄期抗压强度无倒缩现象。
基金This work was supported by the Creative Groups of Natural Science Foundation of Hubei Province(Grant No.2021CFA030).Onyekwena Chikezie Chimere is an awardee for the ANSO Scholarship 2020-PhD.Ishrat Hameed Alvi is a recipient of the 2021 PhD ANSO Scholarship.
文摘Dredged marine soils(DMS)have poor engineering properties,which limit their usage in construction projects.This research examines the application of reactive magnesia(rMgO)containing supplementary cementitious materials(SCMs)to stabilize DMS under ambient and carbon dioxide(CO_(2))curing conditions.Several proprietary experimental tests were conducted to investigate the stabilized DMS.Furthermore,the carbonation-induced mineralogical,thermal,and microstructural properties change of the samples were explored.The findings show that the compressive strength of the stabilized DMS fulfilled the 7-d requirement(0.7-2.1 MPa)for pavement and building foundations.Replacing rMgO with SCMs such as biochar or ground granulated blast-furnace slag(GGBS)altered the engineering properties and particle packing of the stabilized soils,thus influencing their performances.Biochar increased the porosity of the samples,facilitating higher CO_(2) uptake and improved ductility,while GGBS decreased porosity and increased the dry density of the samples,resulting in higher strength.The addition of SCMs also enhanced the water retention capacity and modified the pH of the samples.Microstructural analysis revealed that the hydrated magnesium carbonates precipitated in the carbonated samples provided better cementation effects than brucite formed during rMgO hydration.Moreover,incorporating SCMs reduced the overall global warming potential and energy demand of the rMgO-based systems.The biochar mixes demonstrated lower toxicity and energy consumption.Ultimately,the rMgO and biochar blend can serve as an environmentally friendly additive for soft soil stabilization and permanent fixation of significant amounts of CO_(2) in soils through mineral carbonation,potentially reducing environmental pollution while meeting urbanization needs.
基金financial support under grant number EP/N007638/1supported by EPSRC under grant number EP/W021080/1
文摘In Mg-Ca alloys the grain refining mechanism,in particular regarding the role of nucleant substrates,remains the object of debates.Although native MgO is being recognised as a nucleating substrate accounting for grain refinement of Mg alloys,the possible interactions of MgO with alloying elements that may alter the nucleation potency have not been elucidated yet.Herein,we design casting experiments of Mg-xCa alloys varied qualitatively in number density of native MgO,which are then comprehensively studied by advanced electron microscopy.The results show that grain refinement is enhanced as the particle number density of MgO increases.The native MgO particles are modified by interfacial layers due to the co-segregation of Ca and N solute atoms at the MgO/Mg interface.Using aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy,we reveal the nature of these Ca/N interfacial layers at the atomic scale.Irrespective of the crystallographic termination of MgO,Ca and N co-segregate at the MgO/Mg interface and occupy Mg and O sites,respectively,forming an interfacial structure of a few atomic layers.The interfacial structure is slightly expanded,less ordered and defective compared to the MgO matrix due to compositional deviations,whereby the MgO substrate is altered as a poorer template to nucleate Mg solid.Upon solidification in a TP-1 mould,the impotent MgO particles account for the grain refining mechanism,where they are suggested to participate into nucleation and grain initiation processes in an explosive manner.This work not only reveals the atomic engineering of a substrate through interfacial segregation but also demonstrates the effectiveness of a strategy whereby native MgO particles can be harnessed for grain refinement in Mg-Ca alloys.