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MIcROSTRUcTURAL STUDIES OF FRIcTION STIR WELDED AZ31 MAGNESIUM ALLOY

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Acta Metallurgica Sinica(English Letters) 2004年第5期17卷 747-753页

作者： H.Zhang S.B.Lin L.Wu j.c.feng StateKeyLab.ofAdvancedWeldingProductionTechnology HarbinInstituteofTechnologyHarbin150001China

Friction stir welding achieves the weld in solid phase by locally introducing frictional heating and plastic flow arising from rotation of the welding tool, which results in changes in the local microstructure of magnesium alloy. The purpose in the paper is to study the microstructures of friction stir welded AZ31 magnesium alloy. Residual microstructures, including dynamic re-crystallization zone and nugget structures have been systematically investigated utilizing optical microscopy (OM), scanning electric microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and micro-hardness. AZ31 magnesium alloy has been successfully friction stir welded and exhibits the variations of microstructure including dynamically recrystallized, equaxied grains in the weld nugget. Residual hardness in the nugget was found slightly lower than the parent but not too obvious.

关键词： friction stir welding AZ31magnesium alloy weld nugget thermo- mechanically affected zone microstructure

EFFEcT OF BRAZING TIME ON Tic cERMET/IRON jOINT BRAZED WITH Ag-cu-Zn FILLER METAL

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Acta Metallurgica Sinica(English Letters) 2004年第1期17卷 107-110页

作者： L.X.Zhang j.c.feng Z.R.Li H.j.Liu National Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 ChinaNational Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 ChinaNational Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 ChinaNational Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China

The brazing of Tic cermet to iron was carried out at 1223K for 5-20min using Ag-cu-Zn filler metal. The formation phase and interface structure of the joints were investigated by electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the joint strength was tested by shearing method. The results showed: there occurred three new formation phases, cu(s.s), FeNi and Ag(s.s) in Tic cermet/iron joint. The interface structure was expressed as Tic cermet/cu(s.s)+FeNi/Ag(s.s)+a little cu(s.s)+a little FeNi/cu(s.s)+FeNi/iron, With brazing time increasing, there appeared highest shear strength of the joints, the value of which was up to 252.2MPa when brazing time was 10min.

关键词： brazing Tic cermet interface shear strength

Active metal brazing of SiO2–BN ceramic and Ti plate with Ag–cu–Ti＋BN composite filler

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journal of Materials Science & Technology 2017年第11期33卷 1392-1401页

作者： Z.W.Yang c.L.Wang Y.Wang L.X.Zhang D.P.Wang j.c.feng Tianjin Key Lab of Advanced joining Technology School of Materials Science and Engineering Tianjin University Tianjin 300072 China State Key Lab of Advanced Welding andjoining Harbin Institute of Technology Harbin 150001 China

SiO2–BN ceramic and Ti plate were joined by active brazing in vacuum with Ag–cu–Ti＋BN composite *** effect of BN content,brazing temperature and time on the microstructure and mechanical properties of the brazed joints was *** results showed that a continuous Ti N–Ti B2reaction layer formed adjacent to the SiO2–BN ceramic,whose thickness played a key role in the bonding *** Ti–cu compound layers,Ti2cu,Ti3cu4,Ti cu2and Ti cu4,were observed to border Ti substrate due to the strong affinity of Ti and cu compared with *** central part of the joint was composed of Ag matrix,over which some fine-grains *** added BN particles reacted with Ti in the liquid filler to form fine Ti B whiskers and Ti N particles with low coefficients of thermal expansion（cTE）,leading to the reduction of detrimental residual stress in the joint,and thus improving the joint *** maximum shear strength of 31 MPa was obtained when 3 wt%BN was added in the composite filler,which was 158%higher than that brazed with single Ag–cu–Ti filler *** morphology and thickness of the reaction layer adjacent to the parent materials changed correspondingly with the increase of BN content,brazing temperature and holding *** on the correlation between the microstructural evolution and brazing parameters,the bonding mechanism of SiO2–BN and Ti was discussed.

关键词： SiO2–BN ceramic BN particles Microstructure Mechanical properties

H-and j-aggregation of conjugated small molecules in organic solar cells

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journal of Energy chemistry 2024年第6期93卷 174-192,I0005页

作者： Qiaoqiao Zhao feng He State Key Laboratory of Biobased Material and Green Papermaking Qilu University of TechnologyShandong Academy of SciencesJinan 250353ShangdongChina Shenzhen Grubbs Institute and Department of chemistry Southern University of Science and TechnologyShenzhen 518055GuangdongChina Guangdong Provincial Key Laboratory of catalysis Southern University of Science and TechnologyShenzhen 518055GuangdongChina

As H-and j-aggregation receive more and more attention in the research of organic solar cells(OScs),especially in small molecular systems,deep understanding of aggregation behavior is needed to guide the design of conjugated small molecular structure and the fabrication process of OSc *** this end,this review is ***,the review firstly introduced the basic information about H-and j-aggregation of conjugated small molecules in ***,the characteristics of H-and j-aggregation and the methods to identify them were ***,it reviewed the research progress of H-and j-aggregation of conjugated small molecules in OScs,including the factors influencing H-and j-aggregation in thin film and the effects of H-and j-aggregation on OPV performance.

关键词： H-aggregation j-aggregation Organic solar cells Small molecules Efficiency Stability

Universal insertion of molecules in ionic compounds under pressure

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National Science Review 2024年第1期11卷 120-128页

作者： feng Peng Yanming Ma chris j.Pickard Hanyu Liu Maosheng Miao college of Physics and Electronic Information Luoyang Normal University Department of chemistry and Biochemistry California State University Northridge State Key Laboratory of Superhard Materials & Key Laboratory of Material Simulation Methods and Software of Ministry of Education College of Physics Jilin University International center of Future Science Jilin University Department of Materials Science & Metallurgy University of Cambridge Advanced Institute for Materials Research Tohoku University Department of Earth Science University of California Santa Barbara

Using first-principles calculations and crystal structure search methods, we found that many covalently bonded molecules such as H2, N2, cO2, NH3, H2O and cH4may react with Nac l, a prototype ionic solid,and form stable compounds under pressure while retaining their molecular structure. These molecules,despite whether they are homonuclear or heteronuclear, polar or non-polar, small or large, do not show strong chemical interactions with surrounding Na and cl ions. In contrast, the most stable molecule among all examples, N2, is found to transform into cyclo-N5-anions while reacting with Nac l under high pressures. It provides a new route to synthesize pentazolates, which are promising green energy materials with high energy density. Our work demonstrates a unique and universal hybridization propensity of covalently bonded molecules and solid compounds under pressure. This surprising miscibility suggests possible mixing regions between the molecular and rock layers in the interiors of large planets.

关键词： molecule-solid hybrid materials high-pressure crystal structure prediction density functional theory planet interior

Recent Advances in Deciphering the Mechanisms and Biological Functions of DNA Demethylation

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chinese journal of chemistry 2024年第6期42卷 645-651页

作者： Yang feng Sheng-jun chen Bi-feng Yuan Key Laboratory of Aquatic Product Processing Ministry of Agriculture and Rural AffairsNational R&D Center for Aquatic Product ProcessingSouth China Sea Fisheries Research InstituteChinese Academy of Fishery SciencesGuangzhouGuangdong510300 China School of Public Health Research Center of Public HealthRenmin Hospital of Wuhan UniversityWuhan UniversityWuhanHubei430071 China

5-Methylcytosine (5mc) is a dynamic and reversible epigenetic modification in genomic DNA of higher *** has been well-established that the demethylation of 5mc occurs through the ten-eleven translocation (TET)-mediated oxidation of 5mc followed by thymine DNA glycosylase (TDG)-initiated base excision repair (BER).Recent findings also have identified an alternative pathway of DNA *** this pathway,TET enzymes directly oxidize 5mc to form 5-formylcytosine (5fc) or 5-carboxylcytosine (5cac).These modified bases can undergo direct deformylation or decarboxylation,***,DNA demethylation can also occur through the deamination of 5mc and 5hmc,resulting in the production of thymine and 5-hydroxymethyluracil (5hmU),*** DNA demethylation pathways possess critical functional implications and roles in biological *** Recent Advances article will focus on the studies of mechanisms and biological functions of DNA demethylation,shedding light on the reversible nature of the epigenetic modification of 5mc.

关键词： Epigenetics DNA DNA methylation 5-Methylcytosine Demethylation Mechanisms Biological functions c—c bond cleavage Mass spectrometry

Leflunomide: A versatile additive for defect reduction, enhanced optoelectronic properties and environmental stability of perovskite films

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Nano Research 2024年第4期17卷 2628-2637页

作者： Dingyue Sun Ming Peng Taijin Wang Longju Yi Shizuo Zhang feng Liu Gary j.cheng The Institute of Technological Sciences Wuhan UniversityWuhan 430072China School of Power and Mechanical Engineering Wuhan UniversityWuhan 430072China School of Industrial Engineering Purdue UniversityWest LafayetteIN 47906USA

The development of perovskite photoelectric devices with excellent performance is largely dependent on the defects in the perovskite *** address this issue,a specific drug,leflunomide(LF,c_(12)H_(9)F_(3)N_(2)O_(2)),was incorporated into the perovskite to reduce defects and improve its photoelectric *** is believed that the c=O bond on LF molecule can interact with the uncoordinated Pb2+of the perovskite,thereby reducing non-radiative *** novel approach of incorporating LF into perovskite films has the potential to revolutionize the development of high-performance perovskite photoelectric *** trifluoromethyl functional(–cF_(3))group on LF can form a protective layer on the surface of the perovskite film,shielding it from water ***,LF can be utilized to alter the nucleation position of perovskite,thus minimizing the number of defects and optimizing the film ***,the LF-doped perovskite film displays low trap density and high photoelectric *** LF-doped perovskite film showed a trap density of 8.28×10^(11),which is notably lower than the 2.04×10^(12) of the perovskite film without *** responsivity and detectivity of the LF-doped perovskite photodetector were 0.771 A/W and 2.81×10^(11) jones,respectively,which are much higher than the 0.23 A/W and 1.06×10^(10) jones of the LF-undoped perovskite ***,the LF-doped photodetector maintained an initial photocurrent of 86%after 30 days of storage in air,indicating drastically increased environmental *** strongly suggests that LF is an effective additive for perovskites utilized in optoelectronic devices with high performance.

关键词： leflunomide additive engineering defect passivation perovskite

A dual-function selection system enables positive selection of multigene cRISPR mutants and negative selection of cas9-free progeny in Arabidopsis

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aBIOTEcH 2024年第2期5卷 140-150页

作者： feng-Zhu Wang Ying Bao Zhenxiang Li Xiangyu Xiong jian-feng Li State Key Laboratory of Biocontrol Guangdong Provincial Key Laboratory of Plant ResourcesSchool of Life SciencesSun Yat-sen UniversityGuangzhou 510275China

The cRISPR/cas9 technology revolutionizes targeted gene knockout in diverse organisms including ***,screening edited alleles,particularly those with multiplex editing,from herbicide-or antibiotic-resistant transgenic plants and segregating out the cas9 transgene represent two laborious *** solutions to facilitate these processes rely on different selection ***,by taking advantage of the opposite functions of a D-amino acid oxidase(DAO)in detoxifying D-serine and in metabolizing non-toxic D-valine to a cytotoxic product,we develop a DAO-based selection system that simultaneously enables the enrichment of multigene edited alleles and elimination of cas9-containing progeny in Arabidopsis *** five DAOs tested in Escherichia coli,the one encoded by Trigonopsis variabilis(TvDAO)could confer slightly stronger D-serine resistance than other *** expression of TvDAO in Arabidopsis allowed a clear distinction between transgenic and nontransgenic plants in both D-serine-conditioned positive selection and D-valine-conditioned negative *** a proof of concept,we combined cRISPR-induced single-strand annealing repair of a dead TvDAO with D-serine-based positive selection to help identify transgenic plants with multiplex editing,where D-serine-resistant plants exhibited considerably higher co-editing frequencies at three endogenous target genes than those selected by ***,D-valine-based negative selection successfully removed cas9 and TvDAO transgenes from the survival offspring carrying inherited ***,this work provides a novel strategy to ease cRISPR mutant identification and cas9 transgene elimination using a single selection marker,which promises more efficient and simplified multiplex cRISPR editing in plants.

关键词： cRISPR Genome editing D-amino acid oxidase cas9-free Selection marker

consumer transparency in the production chain for plant varieties produced using new genomic techniques

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aBIOTEcH 2024年第2期5卷 239-246页

作者： j.M.Lukasiewicz c.c.M.van de Wiel L.A.P.Lotz M.j.M.Smulders Wageningen University&Research P.O.Box 386NL-6700 AJ WageningenThe Netherlands

Plants edited with new genomic techniques(NGTs)currently fall under the Genetically Modified Organisms Directive(2001/18/Ec)in the European *** the proposal of the European commission,NGT plants are partially exempted from the regulations of this *** proposal makes a distinction between two categories of NGT plants:NGT-1 and ***-1 category plants are considered equal to plants obtained through conventional breeding *** plants will not be labelled for the consumer,although they will be labelled as ***-2 category plants may be labelled with additional information as a positive *** of seeds of varieties made with gene editing,but not the products,would mean that most steps in the production chain are transparent,but not the last step towards ***“right to know”and increasing knowledge of gene-edited food is a common theme in food labelling towards ***,we describe current labelling regimes and registers and how these may be applied to provide transparency on gene-edited products to ***,we also look into consumer studies,which indicate a greater acceptance of gene-edited food among consumers,especially when additional benefits such as sustainability are mentioned.

关键词： Labelling New genomic techniques consumer transparency Plant products