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EFFECT OF SILICON CARBIDE VOLUME FRACTION UPON INTERFACE REACTION IN SiC_p/Al COMPOSITES

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中国有色金属学会会刊：英文版 1999年第2期9卷 158-163页

作者： Fan, Tongxiang Shi, Zhongliang Zhang, Di wu, renjie Shanghai Jiao Tong Univ Shanghai China

１ＩＮＴＲＯＤＵＣＴＩＯＮＤｉｓｃｏｎｔｉｎｕｏｕｓｌｙｒｅｉｎｆｏｒｃｅｄｍｅｔａｌｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｓａｒｅｖｅｒｙａｔｒａｃｔｉｖｅｉｎａｅｒｏｓｐａｃｅａｎｄａｕｔｏｍｏｔｉｖｅｉｎｄｕｓｔｒｙｆ... 详细信息

１ＩＮＴＲＯＤＵＣＴＩＯＮＤｉｓｃｏｎｔｉｎｕｏｕｓｌｙｒｅｉｎｆｏｒｃｅｄｍｅｔａｌｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｓａｒｅｖｅｒｙａｔｒａｃｔｉｖｅｉｎａｅｒｏｓｐａｃｅａｎｄａｕｔｏｍｏｔｉｖｅｉｎｄｕｓｔｒｙｆｏｒｔｈｅｉｒｐｒｏｐｅｒｔｉｅｓ...

关键词： SiCp/Al compositeremelting recyclinginterface reactionreinforcement volume

OH regulator of highly dispersed Ru sites on host Pd nanocrystals for selective ethanol electro-oxidation

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Nano Research 2024年第5期17卷 3863-3871页

作者： Zhihe Xiao Yueguang Chen renjie wu Yuwei He Chunfeng Shi Leyu Wang State Key Laboratory of Chemical Resource Engineering College of ChemistryBeijing University of Chemical TechnologyBeijing 100029China Research Institute of Petroleum Processing SINOPECBeijing 100083China

The ethanol oxidation reaction(EOR)is crucial in direct alcohol fuel cells and chemical ***,the electro-oxidation of ethanol molecules to produce acetaldehyde and carbon monoxide can poison the active sites of nanocatalysts,resulting in reduced performance and posing challenges in achieving high activity and selectivity for ethanol *** this study,we employed a dynamic seed-mediated method to precisely modify highly dispersed Ru sites onto well-defined Pd *** oxyphilic Ru sites serve as"OH valves",regulating water dissociation,while the surrounding Pd atomic arrangements control electronic states for the oxidation dehydrogenation of carbonaceous ***,Ru0.040@Pd nanocubes(Ru:Pd=0.04 at.%),featuring(100)facets in Ru-Pd4 configurations,demonstrate an outstanding mass activity of 6.53 A·mgPd^(-1) in EOR under alkaline conditions,which is 6.05 times higher than that of the commercial Pd/C catalyst(1.08 A·mgPd-1).Through in-situ experiments and theoretical investigations,we elucidate that the hydrophilic Ru atoms significantly promote the dynamic evolution of H_(2)O dissociation into OHads species,while the electron redistribution from Ru to adjacent Pd concurrently adjusts the selective oxidation of C_(2) *** host-guest interaction accelerates the subsequent oxidation of carbonaceous intermediates(CH_(3)CO_(ads))to acetate,while preventing the formation of toxic*CHx and*CO species,which constitutes the rate-determining step.

关键词： OH regulator atomic sites ethanol electro-oxidation host-guest interaction

Ligand effect in surface atomic sites of group VI B transition metals on ultrathin Pt nanowires for enhanced oxygen reduction

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Nano Research 2024年第6期17卷 5298-5304页

作者： Yuwei He Yueguang Chen renjie wu Zhihe Xiao Mengxian Li Chunfeng Shi Leyu Wang State Key Laboratory of Chemical Resource Engineering College of ChemistryBeijing University of Chemical TechnologyBeijing 100029China State Key Laboratory of Petroleum Molecular and Process Engineering SINOPEC Research Institute of Petroleum Processing Co.Beijing 100083China

Increasing the utilization efficiency of platinum is critical for advancing proton exchange-membrane fuel cells(PEMFCs).Despite extensive research on catalysts for the cathodic oxygen reduction reaction(ORR),developing highly active and durable Pt-based catalysts that can suppress surface dealloying in corrosive acid conditions remains ***,we report a facile synthesis of bimetallic ultrathin PtM(M=Mo,W,and Cr)nanowires(NWs)composed of group VI B transition metal atomic sites anchored on the *** NWs possess uniform sizes and well-controlled atomic *** to PtW and PtCr catalysts,the PtMo0.05 NWs exhibit the highest half-wave potential of 0.935 V and a mass activity of 1.43 A·mgPt^(−1).Remarkably,they demonstrate a remarkable 23.8-fold enhancement in mass activity compared to commercial Pt/C for ORR,surpassing previously reported Pt-based ***,the PtMo NWs cathode in membrane electrode assembly tests achieves a remarkable peak power density of 1.443 W·cm^(−2)(H_(2)-O_(2)conditions at 80℃),which is 1.09 times that of commercial Pt/*** ligand effect in the bimetallic surface not only facilitates strong coupling between Mo(4d)and Pt(5d)atomic orbitals to hinder atom leaching but also modulates the d-states of active site,significantly optimizing the adsorption of key oxygen(*O and*OH)species and accelerating the rate-determining step in ORR pathways.

关键词： ligand effect oxygen reduction reaction group VI B transition metal ultrathin nanowires multiple oxygen species

High strain rate superplasticity of SiC whisker reinforced pure aluminum composites

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中国有色金属学会会刊：英文版 1999年第3期9卷 500-504页

作者： Xu Xiaojing(许晓静) Zhao Changzheng(赵昌正) Zhang Di(张荻) Shi Zhongliang(施忠良) wu renjie(吴人洁) Shanghai Jiao Tong Univ State Key Lab Met Matrix Composites Shanghai 200030 Peoples R China

A β SiC whisker reinforced pure aluminum composites expected to exhibit high strain rate superplasticity has been successfully fabricated by a new processing route consisting of pressure infiltration, extrusion with a low extrusion ratio and rolling. The composites exhibite a total elongation of 220%～380% in the initial strain rates within 1.0×10 -2 ～1.0×10 -1 s -1 and at 893～903 K. According to differential thermal analysis(DTA) and microstructure observation, it is concluded that an appropriately small amount of liquid phase is necessary to cause a good high strain rate superplasticity in aluminum matrix composites in addition to fine and uniform microstructure.

关键词： high strain rate superplasticity aluminum matrix composites pressure infiltration

Regulatory Mechanisms for Transcriptional Bursting Revealed by an Event-Based Model

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Research 2024年第3期2023卷 217-231页

作者： Renje wu Bangyan Zhou Wei Wang Feng Liu National Laboratory of Solid State Microstructures Department of Physicsand Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093P.R.China Institute for Brain Sciences Nanjing UniversityNanjing 210093P.R.China.

Gene transcription often occurs in discrete bursts, and it can be difficult to deduce the underlying regulatory mechanisms for transcriptional bursting with limited experimental data. Here, we categorize numerous states of single eukaryotic genes and identify 6 essential transcriptional events, each comprising a series of state transitions;transcriptional bursting is characterized as a sequence of 4 events, capable of being organized in various configurations, in addition to the beginning and ending events. By associating transcriptional kinetics with mean durations and recurrence probabilities of the events, we unravel how transcriptional bursting is modulated by various regulators including transcription factors. Through analytical derivation and numerical simulation, this study reveals key state transitions contributing to transcriptional sensitivity and specificity, typical characteristics of burst profiles, global constraints on intrinsic transcriptional noise, major regulatory modes in individual genes and across the genome, and requirements for fast gene induction upon stimulation. It is illustrated how biochemical reactions on different time scales are modulated to separately shape the durations and ordering of the events. Our results suggest that transcriptional patterns are essentially controlled by a shared set of transcriptional events occurring under specific promoter architectures and regulatory modes, the number of which is actually limited.

关键词： kinetics essentially constraints

INTERACTION　OF　PARTICLES　WITH　A　SOLIDIFIED　INTERFACE　DURING　SOLIDIFICATION　OF　METAL　MATRIX　COMPOSITE　REINFORCED　WITH　PARTICLES

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Acta Metallurgica Sinica(English Letters) 1996年第1期9卷 71-78页

作者： CHU Shuangjie WANG Haowei wu renjie LIN Xiaotang(Institute of Composite Materials,Shanghai Jiaotong University,Shanghai 200030,China Shanghai Jiaotong Univ Shanghai China

The interaction of particles with a solid-liquid interface during solidification of metal matrix composites has been investigated theoretically in this *** to the presence of particles in the melt,the shape of the solidification front and solute concentration field in front of solidification interface have been disturbed The thermodynamic method was employed,and a mathematical expression of the shape of the solidification interface and solute concentration field were ***,a theory is developed for evaluation of critical velocities of particles pushed by the solidification interface.A numerical simulation is done in which the critical velocity is evaluated as a function of particle size,thermal conductivity,diffusion coefficient,temperature gradient at the solidification front,the solid-liquid interfacial energy and the melt *** critical velocity is shown to be closely linked to the shape of the solidification interface and solute concentration field, and hence all the parameters also affect the shape of the solidification interface and solute concentration field of the front.

关键词： metal matrix composite solid-liquid interface interaction solidification

Interfacial reaction between the oxidized SiC particles and Al-Mg alloys

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Chinese Science Bulletin 2001年第23期46卷 1948-1952页

作者： SHI Zhongliang GU Mingyuan LIU Junyou LIU Guoquan LEE Jae-chul ZHANG Di wu renjie State Key Lab of Metal Matrix Composites Shanghai Jiao Tong UniversityShanghai 200030China School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Division of Materials Science and Engineering Korea Institute of Sciecne and TechnologyP.O.Box 131CheongryangSeoulKorea

The interfacial reactions of oxidized SiC particles reinforced Al-Mg matrix composites were investigated by the field emission-scanning electron microscopy (FE-SEM), TEM and X-ray diffraction. It was found that the nanoscale MgO forms initially due to the interfacial reaction, then whether it reacts with molten Al continuously or not depends on the content of Mg in the matrix and its covering densification at the surface of particles. When there is not enough Mg in the matrix for the formation of dense MgO layer, MgO will transform into MgAl2O4 crystal owing to the continuous reaction with SiO2 and molten Al. When dense MgO layer forms at the surface of the particles due to the affluence of Mg for the initial reaction, it will protect the inner SiC from the attack of molten Al. However, the reaction products of both MgO and MgAl2O4 are thermo-stable phases at the surface of the particles under high temperature. The results clarify the interfacial reaction route and they are of great value to the

关键词： oxidized SiC particle Al-Mg matrix composite interfa- cial reaction FE-SEM nanoscale MgO MgAl2O4.

In-situ Formed AIN Particulates and TiN Whiskers Mixture Reinforced Al Composite

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Journal of Materials Science & Technology 1996年第5期12卷 365-368页

作者： Chunxiang CUI renjie wu and Guoding ZHANG (Institute of Composite Materials, Shanghai Jiao Tong University, Shanghai 200030, China) Shanghai Jiaotong Univ Shanghai China

The TiNw-AINp/Al composite has been successfully fabricated by gas-liquid reaction method in an intensive electromagnetic mixing and casting in an appropriate cooling condition. The as-cast samples of the composite exhibit a homogeneous distribution of TiNw and AINp, and the in situ formed TiN whisker has a mean diameter of 0.5 μm and mean aspect ratio of 5.8~7.5, and the diameter of the AIN particulates is less than 5 μm. TEM observation indicates that there exist some submicron and nanometer sized in situ formed TiNw-AINp in α-Al matrix. The formation mechanism of in situ formed TiNw and AINp is also discussed

关键词： Al TiN AIN AlN

EFFECT OF REINFORCEMENT VOLUME FRACTION ON PRECIPITATION IN MATRIX OF SiC_p/AI COMPOSITE

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Acta Metallurgica Sinica(English Letters) 1993年第8期6卷 161-167页

作者： LIN Junshan LI Pengxing wu renjie Shanghai Jiao Tong University,Shanghai,China postdoctoral,Institute of Composite Materials,Shanghai Jiaotong University,Shanghai 200030,China Shanghai Jiaotong Univ Shanghai China

The differential scanning calorimetric(DSC) and transmission electron microanalysis (TEM) techniques were used to study the kinetic process of precipitation in matrix of cast SiC_p/2024 *** results showed that precipitation reactions of GP zone and intermediate phase S'(Al_2CuMg)in the composites were accelerated compared with SiC-free material,the peak temperatures of both reactions were *** reaction enthalpies of both the GP zone and intermediate phase S' formation in the matrix were substantially decreased after the addition of *** analysis found that the alloying element Mg segregated at the SiC/Al interfaces,and was depleted in the matrix near the *** precipitation-free zones(PFZ) and precipitation-sparse zones(PSZ) formed near the interfaces,as a results,the volume fraction of precipitates in matrix was reduced.

关键词： SiC_p/2024 composite differential scanning calorimetry precipitation in matrix