The generalized oscillator strengths of the dipole-forbidden excitations of the ^(1)A_(2) of H_(2)O and D_(2)O were calculated with the time dependent density functional theory,by taking into account the vibronic effe...The generalized oscillator strengths of the dipole-forbidden excitations of the ^(1)A_(2) of H_(2)O and D_(2)O were calculated with the time dependent density functional theory,by taking into account the vibronic effect.It is found that the vibronic effect converts the dipole-forbidden excitation of the ^(1)A_(2) into a dipole-allowed one,which enhances the intensities of the corresponding generalized oscillator strength in the small squared momentum transfer region.The present investigation shows that the vibronic effect of H_(2)O is slightly stronger than that of D_(2)O,which exhibits a clear isotopic effect.展开更多
Crystalline porous ionic salts(CPISs) represent a new type of porous materials constructed by electrostatic interaction, however, synthesis of CPISs bearing pre-designed functionality while exhibiting permanent porosi...Crystalline porous ionic salts(CPISs) represent a new type of porous materials constructed by electrostatic interaction, however, synthesis of CPISs bearing pre-designed functionality while exhibiting permanent porosity is still challenging. Herein we report the facile synthesis of a series of CPISs 1-3 built from photocatalytic-active polyoxometalate(POM) clusters and cationic Zr-based capsules, which showed open porous frameworks with BET surface area up to 33 m^(2)/g and high activity and selectivity for photodriven aerobic oxidation of alcohols to aldehydes. Compared with the pristine POM cluster {W10}, 1 can promote the reaction in much higher efficiency due to the concerted catalysis of preinstalled {W10} and Zr-based capsule together with open channels. This work highlights the advantage of CPISs as porous heterogeneous catalysts in organic transformation, and may shed light on the rational design of more delicate CPISs-derived functional materials.展开更多
The hydrogen-induced delayed fracture(HIDF)behavior of a 1300-MPa-grade high-strength bolt steel 42CrMoV containing 0.42 wt.%Cu was investigated by constant load tensile test in a pH 3.5 Walpole solution.It is shown t...The hydrogen-induced delayed fracture(HIDF)behavior of a 1300-MPa-grade high-strength bolt steel 42CrMoV containing 0.42 wt.%Cu was investigated by constant load tensile test in a pH 3.5 Walpole solution.It is shown that the addition of Cu is beneficial to enhance the HIDF resistance by~13%.The observation of the fracture surface revealed that the area fraction of brittle crack initiation zone decreased remarkably for the Cu-added steel.Both the corrosion pit depth and the corrosion rate of the Cu-added steel in the Walpole solution are notably decreased,which is primarily because of the formation of a Cu-rich protective compact rust layer and slightly higher corrosion potential.As a result,the absorbed hydrogen content in that solution was also decreased by~21%.It is concluded that the improvement in the HIDF resistance of the tested steel is primarily due to the increase in corrosion resistance and resultant decrease in the absorbed diffusible hydrogen content in the acidic condition.展开更多
Bone marrow-derived mesenchymal stem cells are multipotent stem cells, an attractive resource for regenerative medicine. Accumulating evidence suggests that all-trans retinoic acid plays a key role in the devel- opmen...Bone marrow-derived mesenchymal stem cells are multipotent stem cells, an attractive resource for regenerative medicine. Accumulating evidence suggests that all-trans retinoic acid plays a key role in the devel- opment and differentiation of smooth muscle cells. In the present study, we demonstrate, for the first time, that rabbit bone marrow-derived mesenchymal stem cells differentiate into smooth muscle cells upon the treatment with all-trans retinoic acid. All-trans retinoic acid increased the expression of myocardin, caldesmon, 22-kDa smooth muscle cellspecific protein (SM22α), and SM-myosin heavy chains in rabbit bone marrow-derived mesenchymal stem cells, as detected by reverse transcription polymerase chain reaction (PCR). Immunostaining of SM22α and SM-myosin heavy chains using monoclonal antibodies also indicated smooth muscle cell differentiation of rabbit bone marrowderived mesenchymal stem cells following the treatment with all-trans retinoic acid. In addition, more than 47% of bone marrow-derived mesenchymal stem cells demonstrated the contractile phenotype of smooth muscle cells. Western blot results showed that SM-1 and SM-2 were highly expressed in the differentiated cells. These results suggest that all-trans retinoic acid may serve as a potent agent for functional smooth muscle cell differentiation in tissue engineering.展开更多
Mechanical properties of a newly developed microalloyed bainitic steel were investigated after the hot forging, air cooling and tempering process. The microstructure of the as forged bainitic steel mainly consists of ...Mechanical properties of a newly developed microalloyed bainitic steel were investigated after the hot forging, air cooling and tempering process. The microstructure of the as forged bainitic steel mainly consists of granular bainite and -20 vol. % martensite. The fraction of retained austenite remains unchanged until tempering at 200 ℃, above which it decreases significantly. The increase of tempering temperature leads to decreases of both ultimate tensile strength and total elongation but decreases of both yield strength and reduction of area. The maximum and mini- mum values of impact toughness were observed after tempering at around 200 and 400 ℃, respectively. These effects are mainly attributed to the decomposition of martensite/austenite con stituents and the tempering effects in martensite. The tempering of the forged bainitic steel at around 200 ℃ results in an excellent combination of strength and toughness, which is comparable to that of the conventional quenched and-tempered 40Cr steel. Therefore, low-tempering treatment coupled with post-forging residual stress relieving is a feasible method to further improve the mechanical prooerties of the bainitic foging steel.展开更多
Objective: Human embryonic stem cells (hESCs) have recently been reported as an unlimited source of mesenchymal stem cells (MSCs).The present study not only provides an identical and clinically compliant MSC source de...Objective: Human embryonic stem cells (hESCs) have recently been reported as an unlimited source of mesenchymal stem cells (MSCs).The present study not only provides an identical and clinically compliant MSC source derived from hESCs (hESC-MSCs),but also describes the immunomodulative effects of hESC-MSCs in vitro and in vivo for a carbon tetrachloride (CCl4)-induced liver inflammation model.Methods: Undifferentiated hESCs were treated with Rho-associated kinase (ROCK) inhibitor and induced to fibroblast-looking cells.These cells were tested for their surface markers and multilineage differentiation capability.Further more,we analyzed their immune characteristics by mixed lymphocyte reactions (MLRs) and animal experiments.Results: hESC-MSCs show a homogenous fibroblastic morphology that resembles bone marrow-derived MSCs (BM-MSCs).The cell markers and differentiation potential of hESC-MSCs are also similar to those of BM-MSCs.Unlike their original cells,hESC-MSCs possess poor immunogenicity and can survive and be engrafted into a xenogenic immunocompetent environment.Conclusions: The hESC-MSCs demonstrate strong inhibitory effects on lymphocyte proliferation in vitro and anti-inflammatory infiltration properties in vivo.This study offers information essential to the applications of hESC-MSC-based therapies and evidence for the therapeutic mechanisms of action.展开更多
The thermal stability of retained austenite(RA)and the mechanical properties of the quenched and intercritical annealed 0.1C-5Mn steel with the starting ultrafine lamellar duplex structure of ferrite and retained au...The thermal stability of retained austenite(RA)and the mechanical properties of the quenched and intercritical annealed 0.1C-5Mn steel with the starting ultrafine lamellar duplex structure of ferrite and retained austenite during tempering within the range from 200 to 500°C were studied by X-ray diffraction(XRD),transmission electron microscopy(TEM)and tensile testing.The results showed that there was a slight decrease in the RA volume fraction with increasing tempering temperature up to 400°C.This caused a slight increase in the ultimate tensile strength(UTS)and a slight decrease in the total elongation(TE);thus,the product of UTS to TE(UTS×TE)as high as 31GPa·% was obtained and remained nearly unchanged.However,aportion of the RA began to decompose when tempered at 500°C and thus caused a^35% decrease of the RA fraction and a^16%decrease of the value of UTS×TE.It is concluded that the ultrafine lamellar duplex structure is rather stable and the excellent combination of strength and ductility could be retained with tempering temperature up to 400°C.Thus,thermal processes such as galvanization are feasible for the tested steel provided that their temperatures are not higher than 400°C.展开更多
The hydrogen embrittlement (HE) of a novel microalloyed bainitic forging steel with a strength level of 1100 MPa was evaluated using electrochemical charging and slow strain rate tensile test method with notched round...The hydrogen embrittlement (HE) of a novel microalloyed bainitic forging steel with a strength level of 1100 MPa was evaluated using electrochemical charging and slow strain rate tensile test method with notched round bar specimens. The results show that the susceptibility to HE of the as-forged bainitic forging steel is notably higher than that of the quenched and tempered (Q&T) steel at same strength level, which is ascribed primarily to the presence of a relatively high amount of large blocky martensite/austenite (M/A) constituents of the former. It was found that low-temperature tempering treatment at 200 C could significantly alleviate the susceptibility to HE by a relative decrease of * 35% of the as-forged bainitic forging steel at no expense of strength and ductility, though its resistance to HE is still a little lower than that of the Q&T steel. Thus, it is suggested that efforts concerning refining of the large blocky M/A through optimizing chemical composition and processing route could help to further alleviate the susceptibility to HE of the tested bainitic forging steel.展开更多
Triphenylamine(TPA) derivatives have been widely used as useful building blocks for diverse functional materials because of their excellent redox activity. Most of the molecular structures of TPA-based organic functio...Triphenylamine(TPA) derivatives have been widely used as useful building blocks for diverse functional materials because of their excellent redox activity. Most of the molecular structures of TPA-based organic functional materials contain 4-anisyl groups, which on one hand could reduce their oxidation potential and on the other hand significantly delocalize the spin density of the resultant TPA radical cation species and enhance their stability. However, molecular-level investigation of the redox behavior of triphenylamines consisting of 4-anisyl group and the electronic structures of their radical cation species has not been reported in the literature. Herein, we design a series of triphenylamines consisting of one, two, or three 3,5-di–tert–butyl–4-anisyl groups and investigate their redox behaviors and corresponding radical cation species. We disclose that the resonance hybrid and steric protection could both contribute to the stability of triphenylamine radical cations. Moreover, further oxidation leads to an unexpected oxidative demethylation. The findings in this work may reveal new insights for the understanding of the unique redox properties of 4-anisyl substituted triphenylamines.展开更多
The microstructure and mechanical properties of a V-microalloyed Al-containing medium-Mn steel after hot rolling and intercritical annealing(IA)are explored.The tested steel exhibits a fne multiphase microstructure co...The microstructure and mechanical properties of a V-microalloyed Al-containing medium-Mn steel after hot rolling and intercritical annealing(IA)are explored.The tested steel exhibits a fne multiphase microstructure consisting of bimodal sizes of ferrite and retained austenite plus considerable amount of fne VC and/or M3C precipitates.Physical-chemical phase analysis shows that about 71.0%of the total V is in VC phase and more than 93%of VC particles is less than 5 nm.The calculated precipitation strengthening values of VC are^347 and^234 MPa for the specimens intercritically annealed at 625 and 750℃,respectively.An excellent combination of strength and ductility as high as^50 GPa%and yield strength(YS)of 890 MPa was obtained at intercritical temperature(TIA)of 725℃,although it does not correspond to the maximum precipitation strengthening of VC phase.Therefore,it is suggested that an optimization of TIA corresponding to both excellent combination of strength and ductility and high YS should be further explored through chemical composition and IA process optimization.展开更多
An unexpected bistricyclic aromatic ene AF was synthesized in a tin(Ⅱ)chloride-mediated reductive aromatization reaction.The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crysta...An unexpected bistricyclic aromatic ene AF was synthesized in a tin(Ⅱ)chloride-mediated reductive aromatization reaction.The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crystallography.Interestingly,AF exhibited reversible high-contrast mechanochromism and thermochromism between pale and red color.The obvious chromism is likely ascribed to the conformation transformation and trace amount of diradical species formation upon stimulus.展开更多
The influences of nitrogen content and austenitization temperature on Nb(C, N) precipitation in niobium micro-alloyed steels were studied by different methods: optical microscopy, tensile tests, scanning electron m...The influences of nitrogen content and austenitization temperature on Nb(C, N) precipitation in niobium micro-alloyed steels were studied by different methods: optical microscopy, tensile tests, scanning electron mi- croscopy, transmission electron microscopy, physicochemical phase analysis, and small-angle X-ray scattering. The results show that the strength of the steel with high nitrogen content is slightly higher than that of the steel with low nitrogen content. The increase in the nitrogen content does not result in the increase in the amount of Nb(C,N) precipitates, which mainly depends on the niobium content in the steel. The mass fraction of small-sized Nb(C, N) precipitates (1--10 nm) in the steel with high nitrogen content is less than that in the steel with low nitrogen con- tent. After austenitized at 1 150 ℃, a number of large cuboidal and needle-shaped particles are detected in the steel with high nitrogen content, whereas they dissolve after austenitized at 1 200 ℃ and the Nb(C,N) precipitates become finer in both steels. Furthermore, the results also show that part of the nitrogen in steel involves the formation of al- loyed cementite.展开更多
Dynamic continuous cooling transformation (CCT) behavior of medium-carbon forging steels microalloyed with different V contents up to 0.29% was investigated by means of dilatometric measurement, microstructural obse...Dynamic continuous cooling transformation (CCT) behavior of medium-carbon forging steels microalloyed with different V contents up to 0.29% was investigated by means of dilatometric measurement, microstructural observation and hardness measurement. The re- sults showed that the dynamic CCT diagrams were similar and the main difference was that the fields of the transformation products were shifted to the right side of the diagrams with the increase of V content, and this effect was more noticeable with an addition of 0. 290/00 V. The At1 and At3 temperatures showed increasing trends with increasing V content, while the critical cooling rates decreased with increasing V content. The increase of V content re- sulted in significant increase of hardness and this tendency was enhanced with increasing cooling rate until the formation of acicular ferrite (AF). A promising approach of remark- ably improving the toughness of ferritic-pearlitic medium-carbon forging steels with suit- able V addition and the introduction of AF without notable penalty on its strength level was suggested.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12334010,12174259,and 11604003)。
文摘The generalized oscillator strengths of the dipole-forbidden excitations of the ^(1)A_(2) of H_(2)O and D_(2)O were calculated with the time dependent density functional theory,by taking into account the vibronic effect.It is found that the vibronic effect converts the dipole-forbidden excitation of the ^(1)A_(2) into a dipole-allowed one,which enhances the intensities of the corresponding generalized oscillator strength in the small squared momentum transfer region.The present investigation shows that the vibronic effect of H_(2)O is slightly stronger than that of D_(2)O,which exhibits a clear isotopic effect.
基金supported by National Natural Science Foundation of China (Nos. 92161111, 21901037, 21901038)Shanghai Pujiang Program (No. 19PJ1400200)+1 种基金the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher LearningFundamental Research Funds for the Central Universities (No. 2232019G-07)。
文摘Crystalline porous ionic salts(CPISs) represent a new type of porous materials constructed by electrostatic interaction, however, synthesis of CPISs bearing pre-designed functionality while exhibiting permanent porosity is still challenging. Herein we report the facile synthesis of a series of CPISs 1-3 built from photocatalytic-active polyoxometalate(POM) clusters and cationic Zr-based capsules, which showed open porous frameworks with BET surface area up to 33 m^(2)/g and high activity and selectivity for photodriven aerobic oxidation of alcohols to aldehydes. Compared with the pristine POM cluster {W10}, 1 can promote the reaction in much higher efficiency due to the concerted catalysis of preinstalled {W10} and Zr-based capsule together with open channels. This work highlights the advantage of CPISs as porous heterogeneous catalysts in organic transformation, and may shed light on the rational design of more delicate CPISs-derived functional materials.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.52071010).
文摘The hydrogen-induced delayed fracture(HIDF)behavior of a 1300-MPa-grade high-strength bolt steel 42CrMoV containing 0.42 wt.%Cu was investigated by constant load tensile test in a pH 3.5 Walpole solution.It is shown that the addition of Cu is beneficial to enhance the HIDF resistance by~13%.The observation of the fracture surface revealed that the area fraction of brittle crack initiation zone decreased remarkably for the Cu-added steel.Both the corrosion pit depth and the corrosion rate of the Cu-added steel in the Walpole solution are notably decreased,which is primarily because of the formation of a Cu-rich protective compact rust layer and slightly higher corrosion potential.As a result,the absorbed hydrogen content in that solution was also decreased by~21%.It is concluded that the improvement in the HIDF resistance of the tested steel is primarily due to the increase in corrosion resistance and resultant decrease in the absorbed diffusible hydrogen content in the acidic condition.
基金Project supported by the Science and Technology Department of Zhejiang Province (No. J20020579-30116)the Central Hospital of Huzhou City (No. H20010984-32536),Zhejiang Province,China
文摘Bone marrow-derived mesenchymal stem cells are multipotent stem cells, an attractive resource for regenerative medicine. Accumulating evidence suggests that all-trans retinoic acid plays a key role in the devel- opment and differentiation of smooth muscle cells. In the present study, we demonstrate, for the first time, that rabbit bone marrow-derived mesenchymal stem cells differentiate into smooth muscle cells upon the treatment with all-trans retinoic acid. All-trans retinoic acid increased the expression of myocardin, caldesmon, 22-kDa smooth muscle cellspecific protein (SM22α), and SM-myosin heavy chains in rabbit bone marrow-derived mesenchymal stem cells, as detected by reverse transcription polymerase chain reaction (PCR). Immunostaining of SM22α and SM-myosin heavy chains using monoclonal antibodies also indicated smooth muscle cell differentiation of rabbit bone marrowderived mesenchymal stem cells following the treatment with all-trans retinoic acid. In addition, more than 47% of bone marrow-derived mesenchymal stem cells demonstrated the contractile phenotype of smooth muscle cells. Western blot results showed that SM-1 and SM-2 were highly expressed in the differentiated cells. These results suggest that all-trans retinoic acid may serve as a potent agent for functional smooth muscle cell differentiation in tissue engineering.
基金financially supported by the National Key Research&Development Program of China under grant No.2016YFB0300100the Fundamental Research Funds for the Central Universities(No.2014JBM108)the Prospective Joint Study of Industry-University Cooperation of Jiangsu Province under grant No.BY2015009-02
文摘Mechanical properties of a newly developed microalloyed bainitic steel were investigated after the hot forging, air cooling and tempering process. The microstructure of the as forged bainitic steel mainly consists of granular bainite and -20 vol. % martensite. The fraction of retained austenite remains unchanged until tempering at 200 ℃, above which it decreases significantly. The increase of tempering temperature leads to decreases of both ultimate tensile strength and total elongation but decreases of both yield strength and reduction of area. The maximum and mini- mum values of impact toughness were observed after tempering at around 200 and 400 ℃, respectively. These effects are mainly attributed to the decomposition of martensite/austenite con stituents and the tempering effects in martensite. The tempering of the forged bainitic steel at around 200 ℃ results in an excellent combination of strength and toughness, which is comparable to that of the conventional quenched and-tempered 40Cr steel. Therefore, low-tempering treatment coupled with post-forging residual stress relieving is a feasible method to further improve the mechanical prooerties of the bainitic foging steel.
基金Project (No.2007CB947804) supported by the National Basic Research Program (973) of China
文摘Objective: Human embryonic stem cells (hESCs) have recently been reported as an unlimited source of mesenchymal stem cells (MSCs).The present study not only provides an identical and clinically compliant MSC source derived from hESCs (hESC-MSCs),but also describes the immunomodulative effects of hESC-MSCs in vitro and in vivo for a carbon tetrachloride (CCl4)-induced liver inflammation model.Methods: Undifferentiated hESCs were treated with Rho-associated kinase (ROCK) inhibitor and induced to fibroblast-looking cells.These cells were tested for their surface markers and multilineage differentiation capability.Further more,we analyzed their immune characteristics by mixed lymphocyte reactions (MLRs) and animal experiments.Results: hESC-MSCs show a homogenous fibroblastic morphology that resembles bone marrow-derived MSCs (BM-MSCs).The cell markers and differentiation potential of hESC-MSCs are also similar to those of BM-MSCs.Unlike their original cells,hESC-MSCs possess poor immunogenicity and can survive and be engrafted into a xenogenic immunocompetent environment.Conclusions: The hESC-MSCs demonstrate strong inhibitory effects on lymphocyte proliferation in vitro and anti-inflammatory infiltration properties in vivo.This study offers information essential to the applications of hESC-MSC-based therapies and evidence for the therapeutic mechanisms of action.
基金sponsored by the High-level Scientific Research Foundation for the Introduction of Talent of Beijing Jiaotong University(M14RC00010)the Fundamental Research Funds for the Central Universities(No.2014JBM108)
文摘The thermal stability of retained austenite(RA)and the mechanical properties of the quenched and intercritical annealed 0.1C-5Mn steel with the starting ultrafine lamellar duplex structure of ferrite and retained austenite during tempering within the range from 200 to 500°C were studied by X-ray diffraction(XRD),transmission electron microscopy(TEM)and tensile testing.The results showed that there was a slight decrease in the RA volume fraction with increasing tempering temperature up to 400°C.This caused a slight increase in the ultimate tensile strength(UTS)and a slight decrease in the total elongation(TE);thus,the product of UTS to TE(UTS×TE)as high as 31GPa·% was obtained and remained nearly unchanged.However,aportion of the RA began to decompose when tempered at 500°C and thus caused a^35% decrease of the RA fraction and a^16%decrease of the value of UTS×TE.It is concluded that the ultrafine lamellar duplex structure is rather stable and the excellent combination of strength and ductility could be retained with tempering temperature up to 400°C.Thus,thermal processes such as galvanization are feasible for the tested steel provided that their temperatures are not higher than 400°C.
文摘The hydrogen embrittlement (HE) of a novel microalloyed bainitic forging steel with a strength level of 1100 MPa was evaluated using electrochemical charging and slow strain rate tensile test method with notched round bar specimens. The results show that the susceptibility to HE of the as-forged bainitic forging steel is notably higher than that of the quenched and tempered (Q&T) steel at same strength level, which is ascribed primarily to the presence of a relatively high amount of large blocky martensite/austenite (M/A) constituents of the former. It was found that low-temperature tempering treatment at 200 C could significantly alleviate the susceptibility to HE by a relative decrease of * 35% of the as-forged bainitic forging steel at no expense of strength and ductility, though its resistance to HE is still a little lower than that of the Q&T steel. Thus, it is suggested that efforts concerning refining of the large blocky M/A through optimizing chemical composition and processing route could help to further alleviate the susceptibility to HE of the tested bainitic forging steel.
基金financially supported by the National Natural Science Foundation of China (Nos. 22071061 and 52003081)Shanghai Sailing Pro-gram (No. 19YF1412900)Microscale Magnetic Resonance Platform of ECNU。
文摘Triphenylamine(TPA) derivatives have been widely used as useful building blocks for diverse functional materials because of their excellent redox activity. Most of the molecular structures of TPA-based organic functional materials contain 4-anisyl groups, which on one hand could reduce their oxidation potential and on the other hand significantly delocalize the spin density of the resultant TPA radical cation species and enhance their stability. However, molecular-level investigation of the redox behavior of triphenylamines consisting of 4-anisyl group and the electronic structures of their radical cation species has not been reported in the literature. Herein, we design a series of triphenylamines consisting of one, two, or three 3,5-di–tert–butyl–4-anisyl groups and investigate their redox behaviors and corresponding radical cation species. We disclose that the resonance hybrid and steric protection could both contribute to the stability of triphenylamine radical cations. Moreover, further oxidation leads to an unexpected oxidative demethylation. The findings in this work may reveal new insights for the understanding of the unique redox properties of 4-anisyl substituted triphenylamines.
基金This work was supported by the High-level Scientific Research Foundation for the Introduction of Talent of Beijing Jiaotong University(Grant No.M14RC00010).
文摘The microstructure and mechanical properties of a V-microalloyed Al-containing medium-Mn steel after hot rolling and intercritical annealing(IA)are explored.The tested steel exhibits a fne multiphase microstructure consisting of bimodal sizes of ferrite and retained austenite plus considerable amount of fne VC and/or M3C precipitates.Physical-chemical phase analysis shows that about 71.0%of the total V is in VC phase and more than 93%of VC particles is less than 5 nm.The calculated precipitation strengthening values of VC are^347 and^234 MPa for the specimens intercritically annealed at 625 and 750℃,respectively.An excellent combination of strength and ductility as high as^50 GPa%and yield strength(YS)of 890 MPa was obtained at intercritical temperature(TIA)of 725℃,although it does not correspond to the maximum precipitation strengthening of VC phase.Therefore,it is suggested that an optimization of TIA corresponding to both excellent combination of strength and ductility and high YS should be further explored through chemical composition and IA process optimization.
基金Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-05-E00012)Program for Changjiang Scholars and Innovative Research Team in University for financial support+1 种基金the financial supports sponsored by Shanghai Sailing Program(No.19YF1412900)the Fundamental Research Funds for the Central Universities。
文摘An unexpected bistricyclic aromatic ene AF was synthesized in a tin(Ⅱ)chloride-mediated reductive aromatization reaction.The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crystallography.Interestingly,AF exhibited reversible high-contrast mechanochromism and thermochromism between pale and red color.The obvious chromism is likely ascribed to the conformation transformation and trace amount of diradical species formation upon stimulus.
基金Item Sponsored by the CITIC-CBMM Niobium Steel Research and Development Program of China(2013-D065)
文摘The influences of nitrogen content and austenitization temperature on Nb(C, N) precipitation in niobium micro-alloyed steels were studied by different methods: optical microscopy, tensile tests, scanning electron mi- croscopy, transmission electron microscopy, physicochemical phase analysis, and small-angle X-ray scattering. The results show that the strength of the steel with high nitrogen content is slightly higher than that of the steel with low nitrogen content. The increase in the nitrogen content does not result in the increase in the amount of Nb(C,N) precipitates, which mainly depends on the niobium content in the steel. The mass fraction of small-sized Nb(C, N) precipitates (1--10 nm) in the steel with high nitrogen content is less than that in the steel with low nitrogen con- tent. After austenitized at 1 150 ℃, a number of large cuboidal and needle-shaped particles are detected in the steel with high nitrogen content, whereas they dissolve after austenitized at 1 200 ℃ and the Nb(C,N) precipitates become finer in both steels. Furthermore, the results also show that part of the nitrogen in steel involves the formation of al- loyed cementite.
基金financially sponsored by National Key Research & Development Program of China (2016YFB0300103)
文摘Dynamic continuous cooling transformation (CCT) behavior of medium-carbon forging steels microalloyed with different V contents up to 0.29% was investigated by means of dilatometric measurement, microstructural observation and hardness measurement. The re- sults showed that the dynamic CCT diagrams were similar and the main difference was that the fields of the transformation products were shifted to the right side of the diagrams with the increase of V content, and this effect was more noticeable with an addition of 0. 290/00 V. The At1 and At3 temperatures showed increasing trends with increasing V content, while the critical cooling rates decreased with increasing V content. The increase of V content re- sulted in significant increase of hardness and this tendency was enhanced with increasing cooling rate until the formation of acicular ferrite (AF). A promising approach of remark- ably improving the toughness of ferritic-pearlitic medium-carbon forging steels with suit- able V addition and the introduction of AF without notable penalty on its strength level was suggested.