The martensitic transformation(MT)lays the foundation for microstructure and performance tailoring of many engineering materials,especially steels,which are with>1.8 billion tons produced per year the most importan...The martensitic transformation(MT)lays the foundation for microstructure and performance tailoring of many engineering materials,especially steels,which are with>1.8 billion tons produced per year the most important material class.The atomic-scale migration path is a long-term challenge for MT dur-ing quenching in high-carbon(nitrogen)steels.Here,we provide direct evidence of(11^(-)2)body-centred tetragonal(BCT)twinned martensite in carbon steels by transmission electron microscopy(TEM)investi-gation,and the increase in tetragonality with the C content matches X-ray diffraction(XRD)results.The specific{11^(-)2}_(BCT)twin planes which are related to the elongated c axis provide essential structural details to revisit the migration path of the atoms in MT.Therefore,the face-centred cubic(FCC)to BCT twin to body-centred cubic(BCC)twin transition pathway and its underlying mechanisms are revealed through direct experimental observation and atomistic simulations.Our findings shed new light on the nature of the martensitic transition,thus providing new opportunities for the nanostructural control of metals and alloys.展开更多
It is very important to develop efficient synthetic strategies for site-specific functionalization of tetrahydroquinolines due to their indispensable roles in pharmaceutical and agrochemical industries.We apply hard/s...It is very important to develop efficient synthetic strategies for site-specific functionalization of tetrahydroquinolines due to their indispensable roles in pharmaceutical and agrochemical industries.We apply hard/soft acid/base(HSAB)theory to selective reduction of quinoline and achieve a series of C3-functionalized tetrahydroquinoline in high to excellent yields(up to 99%)under mild conditions with the catalysis of B(C_(6)F_(5))_(3).A series of in situ NMR reactions are also performed to investigate this cascade reaction.Moreover,AB type monomer 6-(dimethylsilyl)quinoline and AA/BB type monomer 6,6'-biquinoline are synthesized for polymer synthesis,which represents the first example of silicon bridged polytetrahydroquinoline.展开更多
Ti/Zr-based icosahedral quasicrystals are a kind of promising hydrogen storage ma- terials, however their absorption regeneration after oxidation-poisoning has been scarcely studied. This work is intended to investiga...Ti/Zr-based icosahedral quasicrystals are a kind of promising hydrogen storage ma- terials, however their absorption regeneration after oxidation-poisoning has been scarcely studied. This work is intended to investigate the deuterium-storage re- generation of a suction-cast Ti36Zr40Ni20Pd4 quasicrystal. It was found that only through hot vacuuming the quasicrystal could be refreshed from air-flow poisoning to absorb deuterium in two cycles. During the first absorption course, a pregnancy period was observed before the real deuterium uptake while deuterium was loaded rapidly during the second one. The deuterium concentration in the alloy can reach 0.011 mol.D2/（g.M） （corresponding to a hydrogen mass percent of 2.2%. D2 and M denote molecular deuterium and the metallic alloy）. But the loaded deuterium was very difficult to release completely even by eight-stage desorption at different tem- peratures. After the second desorption, the quasicrystal phase remained in a small volume, as though the desorption temperature was beyond the crystallization temperature of the quasicrystal. This probably is attributed to the solution function of residual deuterium in the alloy.展开更多
Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of ...Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of deployable structures(e.g.,solar arrays and antennas).This paper investigates folding stable state of Bi-DCB through the analytical method.Based on Archimedes’helix and energy principle,an analytical model for predicting folding stable state of Bi-DCB was presented.The failure index of Bi-DCB in folding stable state were analyzed using the Tsai-Hill criterion and the maximum stress criterion.Then,a 2400 mm long Bi-DCB was fabricated using autoclave method.The prediction results of the proposed model were compared with experiments and results of two other analytical models.It is shown that the proposed model shows good prediction accuracy.Finally,the effect of geometric parameters on folding stable state of Bi-DCB was further investigated with the aid of the proposed model.展开更多
基金supported by the NSFC(Nos.51931005,51901235,11790292)the NSFC Basic Science Center Program for“Multi-scale Problems in Nonlinear Mechanics”(No.11988102)+1 种基金the Key Research Program of Frontier Sciences(No.QYZDJSSW-JSC011)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB22040302),and the CityU grant 9360161.
文摘The martensitic transformation(MT)lays the foundation for microstructure and performance tailoring of many engineering materials,especially steels,which are with>1.8 billion tons produced per year the most important material class.The atomic-scale migration path is a long-term challenge for MT dur-ing quenching in high-carbon(nitrogen)steels.Here,we provide direct evidence of(11^(-)2)body-centred tetragonal(BCT)twinned martensite in carbon steels by transmission electron microscopy(TEM)investi-gation,and the increase in tetragonality with the C content matches X-ray diffraction(XRD)results.The specific{11^(-)2}_(BCT)twin planes which are related to the elongated c axis provide essential structural details to revisit the migration path of the atoms in MT.Therefore,the face-centred cubic(FCC)to BCT twin to body-centred cubic(BCC)twin transition pathway and its underlying mechanisms are revealed through direct experimental observation and atomistic simulations.Our findings shed new light on the nature of the martensitic transition,thus providing new opportunities for the nanostructural control of metals and alloys.
基金supported by the National Natural Science Foundation of China(Grant Nos.21871107,22225104,21975102,22071077).
文摘It is very important to develop efficient synthetic strategies for site-specific functionalization of tetrahydroquinolines due to their indispensable roles in pharmaceutical and agrochemical industries.We apply hard/soft acid/base(HSAB)theory to selective reduction of quinoline and achieve a series of C3-functionalized tetrahydroquinoline in high to excellent yields(up to 99%)under mild conditions with the catalysis of B(C_(6)F_(5))_(3).A series of in situ NMR reactions are also performed to investigate this cascade reaction.Moreover,AB type monomer 6-(dimethylsilyl)quinoline and AA/BB type monomer 6,6'-biquinoline are synthesized for polymer synthesis,which represents the first example of silicon bridged polytetrahydroquinoline.
基金supported by Science and Technology Development Foundation of China Academy of Engineering Physics (No.2007A07002)
文摘Ti/Zr-based icosahedral quasicrystals are a kind of promising hydrogen storage ma- terials, however their absorption regeneration after oxidation-poisoning has been scarcely studied. This work is intended to investigate the deuterium-storage re- generation of a suction-cast Ti36Zr40Ni20Pd4 quasicrystal. It was found that only through hot vacuuming the quasicrystal could be refreshed from air-flow poisoning to absorb deuterium in two cycles. During the first absorption course, a pregnancy period was observed before the real deuterium uptake while deuterium was loaded rapidly during the second one. The deuterium concentration in the alloy can reach 0.011 mol.D2/（g.M） （corresponding to a hydrogen mass percent of 2.2%. D2 and M denote molecular deuterium and the metallic alloy）. But the loaded deuterium was very difficult to release completely even by eight-stage desorption at different tem- peratures. After the second desorption, the quasicrystal phase remained in a small volume, as though the desorption temperature was beyond the crystallization temperature of the quasicrystal. This probably is attributed to the solution function of residual deuterium in the alloy.
基金supported by the National Natural Science Foundation of China(No.52275231)the National Defense Basic Scientific Research Program of China(No.JCKY2019205C002).
文摘Bistable Deployable Composite Boom(Bi-DCB)can achieve bistable function by storing and releasing strain energy,which has a good application prospect in space field.For example,it serves as the main support section of deployable structures(e.g.,solar arrays and antennas).This paper investigates folding stable state of Bi-DCB through the analytical method.Based on Archimedes’helix and energy principle,an analytical model for predicting folding stable state of Bi-DCB was presented.The failure index of Bi-DCB in folding stable state were analyzed using the Tsai-Hill criterion and the maximum stress criterion.Then,a 2400 mm long Bi-DCB was fabricated using autoclave method.The prediction results of the proposed model were compared with experiments and results of two other analytical models.It is shown that the proposed model shows good prediction accuracy.Finally,the effect of geometric parameters on folding stable state of Bi-DCB was further investigated with the aid of the proposed model.
