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Double [5]carbohelicene: facile synthesis, chiroptical properties,isomerization study, and lasing application

Science China Chemistry 2025年第1期 233-240页

作者： Peipei liu Yantong li Meng-Xiang Wu Hao Kang xiao-li zhao lin Xu linlin liu xiaodong li Junfeng Fang Zhiwei Fang Ya Cheng Hai-Bo Yang Huakang Yu Xueliang Shi State Key Laboratory of Petroleum Molecular & Process Engineering Shanghai Key Laboratory of Green Chemistry and Chemical ProcessesSchool of Chemistry and Molecular Engineering East China Normal University School of Physics and Optoelectronics South China University of Technology Institute of Polymer Optoelectronic Materials & Devices State Key Laboratory of Luminescent Materials & Devices South China University of Technology School of Physics and Electronic Science Engineering Research Center of Nanophotonics & Advanced Instrument Ministry of EducationEast China Normal University State Key Laboratory of Precision Spectroscopy School of Physics and Electronic Science East China Normal University

Double carbohelicenes have attracted considerable attention due to their aesthetic structures, distinct π-conjugation extension, inherent chirality, and intriguing optical and electronic properties. Herein, the concise de novo synthesis of a new double[5]carbohelicene 1 together with its chiroptical properties, isomerization process and lasing application is presented. 1 was synthesized by a simple protocol involving the formation of a 6,6′-bipentacene as the key intermediate. It is worth noting that1 existed as two diastereomers 1-PP/MM and 1-PM, which were successfully isolated and unambiguously confirmed by Xray crystallography. The optical resolution of the racemic 1-PP/MM was successfully achieved by chiral-phase highperformance liquid chromatography（HPLC）, and 1-PP and 1-MM were characterized by circular dichroism. Interestingly, it was found that 1-PP/MM could be completely isomerized to 1-PM upon heating, and the detailed thermodynamics and kinetics of the isomerization process were systematically investigated. 1-PM exhibited deep-red luminescence with emission maximum at 723 nm and fluorescence quantum yield as high as 32.95%. Consequently, we can showcase the lasing application of 1-PM by doping with epoxy resin to assemble a bottle microlaser spontaneously, which the lasing wavelength is 796.6 nm at a threshold of 0.8 m J cm-2. We believe that our studies, including the facile synthesis methodology, detailed isomerization studies, and lasing application, will shed some light on the design and synthesis of novel carbohelical systems with more functions.

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All-trans retinoic acid promotes smooth muscle cell differentiation of rabbit bone marrow-derived mesenchymal stem cells

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2010年第7期11卷 489-496页

作者： Zhong-yuan SU Ying li xiao-li zhao Ming ZHANG College of life Sciences Zhejiang University Hangzhou 310058 China Zhejiang Academy of Medical Science Hangzhou 310058 China

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. AII-trans retinoic acid increased the expression of myocardin, caldesmon, 22-kDa smooth muscle cell- specific protein （SM22Q）, and SM-myosin heavy chains in rabbit bone marrow-derived mesenchymal stem cells, as detected by reverse transcription polymerase chain reaction （PCR）. Immunostaining of SM22a and SM-myosin heavy chains using monoclonal antibodies also indicated smooth muscle cell differentiation of rabbit bone marrow- derived 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.

关键词： Bone marrow-derived mesenchymal stem cells Smooth muscle cells AII-trans retinoic acid Rabbit

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Effect of vanadium on dynamic continuous cooling transformation behavior of medium-carbon forging steels

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Journal of Iron and Steel Research International 2017年第6期24卷 641-648页

作者： Wei-jun Hui Na xiao xiao-li zhao Yong-jian Zhang Yu-feng Wu School of Mechanical Electronic and Control Engineering Beijing Jiaotong University Beijing 100044 China Faculty of Materials Science and Engineering Kunming University of Science and Technology Kunming 650093 Yunnan China

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.

关键词： Dynamic CCT diagramVanadiumMicroalloyed steelMierostruetureHardness

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Hydrogen-induced delayed fracture of Cu-containing high-strength bolt steel

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Journal of Iron and Steel Research International 2023年第2期30卷 375-383页

作者： xiao-li zhao Cheng-xiang Zhang Yong-jian Zhang Wei-jun Hui Xiu-ming zhao Materials Science and Engineering Research Center School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China School of Materials Science and Engineering Nanjing Institute of TechnologyNanjing211167JiangsuChina

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 *** 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 *** 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 *** 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.

关键词： Hydrogen-induced delayed fracture Hydrogen embrittlement High-strength bolt steel Copper Corrosion

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A NEW METHOD FOR NUMERICAL SIMULATION OF TWO TRAINS PASSING BY EACH OTHER AT THE SAME SPEED

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Journal of Hydrodynamics 2010年第5期22卷 697-702页

作者： zhao xiao-li SUN Zhen-xu School of Aerospace Tsinghua University Beijing China State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University Beijing China

A new method is proposed to numerically simulate problems of trains passing by each other at the same speed, and is implemented in UDF language of commercial software Fluent. Because only a half of the computational domain is required and the dynamic mesh technique is avoided, the computational efficiency is greatly improved. A two-dimensional test case is used for validation, which shows that the flow field and the pressure wave during the train-passing events can be correctly calculated by this new method. This method can be easily extended to three-dimensional simulations, to deal with practical problems.

关键词： trains passing by each other rotational symmetry dynamic mesh pressure wave

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Microstructure and mechanical properties of hot-rolled V-microalloyed Al-containing medium-Mn steel

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Journal of Iron and Steel Research International 2020年第5期27卷 537-548页

作者： Ming Lei Wei-jun Hui Jiao-jiao Wang Yong-jian Zhang xiao-li zhao School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China

The microstructure and mechanical properties of a V-microalloyed Al-containing medium-Mn steel after hot rolling and intercritical annealing(IA)are *** 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 ***-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 *** calculated precipitation strengthening values of VC are^347 and^234 MPa for the specimens intercritically annealed at 625 and 750℃,*** 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 ***,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.

关键词： Medium-Mn steel Vanadium Intercritical annealing Microstructure Mechanical property

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Mechanical properties of a microalloyed bainitic steel after hot forging and tempering

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Journal of Iron and Steel Research International 2017年第11期24卷 1085-1094页

作者： Zhi-bao Xu Wei-jun Hui Zhan-hua Wang Yong-jian Zhang xiao-li zhao Xiu-ming zhao School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China z School of Materials Engineering Nanjing Institute of TechnologyNanjing 211167JiangsuChina

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.

关键词： Bainitic forging steel Mechanical property Tempering Microstructure Granular bainite

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Thermal stability of retained austenite and mechanical properties of medium-Mn steel during tempering treatment

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Journal of Iron and Steel Research International 2017年第8期24卷 830-837页

作者： xiao-li zhao Yong-jian Zhang Cheng-wei Shao Wei-jun Hui Han Dong School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Central Iron and Steel Research Institute Beijing 100081China

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 *** results showed that there was a slight decrease in the RA volume fraction with increasing tempering temperature up to 400°*** 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 ***,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×*** 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°***,thermal processes such as galvanization are feasible for the tested steel provided that their temperatures are not higher than 400°C.

关键词： Medium-manganese transformation-induced plasticity steel Tempering Microstructure Mechanical property Retained austenite

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Hydrogen embrittlement of a microalloyed bainitic forging steel

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Journal of Iron and Steel Research International 2019年第9期26卷 1011-1021页

作者： Wei-jun Hui Zhan-hua Wang Zhi-bao Xu Yong-jian Zhang xiao-li zhao Materials Science and Engineering Research Center School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Yantai Branch of China North Industries Group Corporation No. 52 Institute Co. Ltd.Yantai 264003ShandongChina

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.

关键词： Hydrogen embrittlement Bainitic forging steel Microstructure Granular bainite M/A constituent

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Effects of Nitrogen Content and Austenitization Temperature on Precipitation in Niobium Micro-alloyed Steels

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Journal of Iron and Steel Research International 2015年第12期22卷 1164-1173页

作者： Lei CAO Zhong-min YANG Ying CHEN Hui-min WANG xiao-li zhao Central Iron and Steel Research Institute

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.

关键词： nitrogen content austenitization temperature l Nb(C,N) preeipitation alloyed cementite

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