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Ma S.M.,Shanghai JiaoTong University | Zhang P.,Shanghai JiaoTong University | Ji G.,CNRS Materials and Transformations Unit of UMET | Chen Z.,Shanghai JiaoTong University | And 4 more authors.
Journal of Alloys and Compounds | Year: 2014

In this paper, we reported microstructure and mechanical properties of the in-situ TiB2/Al-Mg-Si composites processed by friction stir processing (FSP). Compared with the initial state, the proper FSP conditions can enhance both the ultimate strength and the elongation of the composite samples obtained from the nugget zone. Detailed microstructure investigation has been performed by synchrotron X-ray diffraction, scanning and transmission electron microscopy and associated electron backscattered diffraction in order to reveal the mechanisms being responsible for the unusual mechanical behaviors. The results show that the initial composite has a grain size of 50-100 μm and the synthesized nanosized TiB2 particles are almost agglomerated to form micrometer sized clusters at grain boundaries. Comparatively, after FSP, the nugget zone is characterized by fine and equiaxed recrystallized grains (1-5 μm in average grain size). The initial clusters are also broken up, while the nanosized TiB2 particles are distributed much more uniformly in the matrix and act as effective pins to interact with dislocations. Hence, the significantly refined grains and the uniform distribution of the nanosized TiB2 particles mainly contribute to the increase of both strength and ductility of the FSPed composites. The strengthening mechanisms are also discussed. © 2014 Elsevier Ltd. All rights reserved.

Li N.,Beijing Institute of Technology | Wang Y.D.,University of Science and Technology Beijing | Liu W.J.,Argonne National Laboratory | An Z.N.,University of Tennessee at Knoxville | And 4 more authors.
Acta Materialia | Year: 2014

Abstract The traditional phenomenological crystallographic theory of martensitic transformations can only explain the change in the shape and crystallographic orientation of a martensitic plate within a single parent crystal. It cannot predict the detailed transformation scenario for preferred selections of martensitic variants or the contributions of partial slip/twinning to local lattice distortion, especially in polycrystalline metals/alloys that exhibit grain-to-grain interactions throughout deformation-induced phase transformation. In this work, synchrotron-based X-ray microdiffraction was used to characterize changes in the local orientation, morphology and strain distribution inside individual martensitic plates, as well as the effect of parent orientation on variant selection in bulk polycrystalline 304 stainless steel (SS) during in situ uniaxial tensile loading at the low temperature of 210 K. It was directly verified that the martensitic phase transformation in the studied 304 SS has two stages, transformation first from γ to ε in the nanoscaled lamella, and then from ε to α′ in the microbands. The selection of martensitic variants was predicted well by the minimum strain work criterion. Phase transformation-induced stress relaxation was evidenced by fluctuations in the (1 1 1) plane lattice strain accompanied by a strain gradient inside the martensitic plate, indicating a load transfer from the transformed grain to its neighbor. This leads to good stress/strain accommodation, as stresses can dissipate from the matrix into martensitic plates and nearby grains. Our experimental observations and theoretical analysis provide an in-depth understanding of the micromechanical behavior, particularly phase transformation-induced plasticity enhancement, of metals containing the metastable phase. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Li M.,CAS Beijing Institute of Applied Physics And Computational Mathematics | Gao C.,Institute of Nuclear Physics and Chemistry | Xu J.,CAS Beijing Institute of Applied Physics And Computational Mathematics
IOP Conference Series: Materials Science and Engineering | Year: 2015

Mechanical properties of material are closely related to the motion of dislocations, and predicting the interactions and resulting collective motion of dislocations is a major task in understanding and modelling plastically deforming materials. A discrete dislocation dynamics model is used to describe the orientation substructure within the microstructure. Discrete dislocation dynamics simulations in three dimensions have been used to examine the role of dislocation multiplication and mobility on the plasticity in small samples under uniaxial compression. In this paper we describe the application of the dislocation dynamics simulations in a cylindrical geometry. The boundary conditions for the simulation were estimated from the distribution of the geometrically necessary dislocation density which was obtained from the orientation map. Numerical studies benchmark could validate the accuracy of the algorithms and the importance of handling the singularity correctly. The results of the simulation explain the formation of the experimentally observed substructure.

Meng S.-J.,Institute of Nuclear Physics and Chemistry | Li Z.-H.,Institute of Nuclear Physics and Chemistry | Qin Y.,Institute of Nuclear Physics and Chemistry | Ye F.,Institute of Nuclear Physics and Chemistry | Xu R.-K.,Institute of Nuclear Physics and Chemistry
Wuli Xuebao/Acta Physica Sinica | Year: 2011

Time-integrated X-ray continuum spectra measured with spherical bent quartz crystal and CCD in aluminum wire array Z-pinches, provide electron temperature by fitting the continuum slope. More data obtained for fitting and markedly reduced influence of line radiation by removing the data superimposed with line spectra, make the temperature in hot core region of plasma more reliable. In experiment of shot No. 09076, the core temperature is around 250 eV, ranging from 241 eV to 258 eV at a 95% confidence level. © 2011 Chinese Physical Society.

Huang Z.,Institute of Nuclear Physics and Chemistry | Yang J.,Institute of Nuclear Physics and Chemistry | Chen F.,Institute of Nuclear Physics and Chemistry
High Energy Density Physics | Year: 2015

Down-scattered neutron spectra for different areal densities and different hot-spot sizes are simulated via using Monte Carlo method. The simulation results indicate that there is a nearly linear relationship between fuel areal density and the yield ratio of down-scattered neutrons to primary neutrons. The linear coefficient varies with areal density and hot-spot size. Single scattered and multiple scattered neutron spectra are simulated to discuss the influence of multiple scattering on down-scattered neutron spectrum. For indirect drive target at SG-III prototype and direct drive target at OMEGA, the effect of CH shell on down-scattered neutron spectrum is simulated. © 2015 Elsevier B.V.

Liu X.,Institute of Nuclear Physics and Chemistry | Zeng G.,Institute of Nuclear Physics and Chemistry | Jiang S.,Institute of Nuclear Physics and Chemistry
Radiation Physics and Chemistry | Year: 2016

In this paper, we introduced a novel 60Co-ray-irradiation-based one-step synthesis method of nano-CdS-reduced graphene oxide composites (CdS/RGO) in aqueous solution. The synthesis approach is simple and green and may be applied in the synthesis of other RGO-metal-sulfide nanocomposites. Sodium thiosulfate was used as a sulfur source. Triethanolamine and glycerol were respectively used as the colloidal stabilizer and radical scavenger. The compositional distribution of the particles in the samples was demonstrated by X-ray diffractometry, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. © 2015 Elsevier Ltd.

Ke J.,Institute of Nuclear Physics and Chemistry | Zhou C.,Institute of Nuclear Physics and Chemistry
IEEE Transactions on Plasma Science | Year: 2014

An empirical method has been used in this paper to estimate the sheath edge of plasma ion sources. Based on Kovaleski's hypothesis in 2006 that the sheath edge from an unmagnetized plasma is coincided with a critical electric field magnitude contour, the sheath edges simulated by a trajectory code were used to calculate Ep and to fit Ep as a function of Te and ne0. A test shows that only half iterations are needed when the initial sheath is set by the empirical method of this paper. This indicates that the using of the empirical method can save much computing time. The deviation of the expression of Ep in Kovaleski's paper and this paper is also discussed. The deviation may be due to the different type of used codes and that the plasma distribution will influence the electric field distribution in sheath edge calculations. © 2014 IEEE.

Wang D.,Institute of Nuclear Physics and Chemistry | Zhang C.,China Academy of Engineering Physics | Zhang J.,Institute of Nuclear Physics and Chemistry
Radiation Measurements | Year: 2015

This work studied a "fission electron-collection" neutron detector via the Monte Carlo method. The detector consists of two metal electrodes, labeled the coated and collection electrodes, mounted in a vacuum. The first electrode is coated with triuranium octoxide. The detector uses the "fission electron-collection" technique, which does not require an intermediate material and directly collects electrons from the coating. This detector can achieve rapid, flat-energy responses, which are important for measuring pulsed neutron sources. This paper presents the physical detection processes and Monte Carlo simulation studies using the Geant4 toolkit. The results indicate that the detector sensitivity is approximately 1.5 × 10-21 [C/(n/cm2)] and the FWHM of response function is 2.5 ns. Additionally, the escaping electrons are characterized, and the detector sensitivity is determined for various coating thicknesses. © 2015 Elsevier Ltd. All rights reserved.

Tian Q.,Lanzhou University | Tian Q.,Institute of Nuclear Physics and Chemistry | Li J.,Lanzhou University | Xie Q.,Lanzhou University | Wang Q.,Lanzhou University
Materials Chemistry and Physics | Year: 2012

This paper reports morphology-tuned synthesis of arrayed one-dimensional ZnO nanostructures on Agcoated glass substrates from Zn(NO 3) 2 and dimethylamine borane (DMAB) aqueous solutions and their photoluminescence and photocatalytic properties. By adjusting the Zn(NO 3) 2 concentration in the solutions, the ZnO nanoneedle arrays, nanorod arrays, and polycrystal films can be obtained. Low Zn(NO 3) 2 concentrations result in ZnO nanoneedle arrays. The ZnO nanoneedles grow along the 0 {0 0 1} directions. The growth process of the ZnO nanoneedles at low Zn(NO 3) 2 concentrations goes through the formation of the equiaxial ZnO granules, the growth of the equiaxial granules into small nanorods, the growth of the small nanorods into nanoneedles, the growth of the nanoneedles in diameter and length, the growth of the nanoneedles into nano-obelisks, and the growth of the nano-obelisks into thick hexangular rods. So the morphologies of the arrayed 1D ZnO nanostructures can be tuned from arrayed nanoneedles through arrayed nanorods and nano-obelisks to arrayed thick hexagonal rods by controlling the Zn(NO 3) 2 concentration in the DMAB and Zn(NO 3) 2 solutions and/or the deposition time in our process. The ZnO nanoneedle arrays have the largest ratio of the visible to ultraviolet emission and the highest photocatalytic activity. © 2011 Elsevier B.V. All rights reserved.

Yang Y.,Institute of Nuclear Physics and Chemistry | Song H.,Institute of Nuclear Physics and Chemistry | Zhao W.,University of Sichuan | Pu M.,Institute of Nuclear Physics and Chemistry
Journal of Porphyrins and Phthalocyanines | Year: 2011

99mTc(CO)3-TPPS4 was prepared via the precursor [99mTc(CO)3(H2O)3] + and a preliminary investigation on its stability and behavior in Hep2 tumor cells and hepatoma-bearing mice were conducted. Labeling yield and stability of 99mTc(CO)3-TPPS4 was radioactively analyzed by paper chromatography. Hep2 tumor cells were incubated with 99mTc(CO)3-TPPS4 complex system in the substrate and isolated from the substrate for radioactivity count. Then 99mTc(CO)3-TPPS4 complex system was intravenously injected in hepatoma-bearing mice and directly injected in tumor tissue of the mice. Mice were photographed using SPECT. Labeling yields of 99mTc(CO)3-TPPS4 were more than 90% at pH = 7-8, 30 min, in a boiling bath, and it was stable for at least 14 h at pH = 28, rt ∼95 °C. The uptake of 99mTc(CO)3-TPPS 4 in HepG2 tumor cells was only 3-4% with the maximum uptake-time of 20 min. The SPECT images of hepatoma-bearing nude mice showed no uptake or little retention of 99mTc(CO)3-TPPS4 in the tumor tissue. Then the differences between 99mTc(CO) 3-TPPS4 and TPPS4 were analyzed by fluoroscopy and molecular structure. It was found that the paper chromatography, HepG2 tumor cell uptake and the optimized porphyrin ring conformation of 99mTc(CO)3-TPPS4 were quite different from those of TPPS4. It was indicated that 99mTc(CO) 3-TPPS4 had no uptake or little retention in hepatic tumors, unlike those biological behaviors of TPPS4. This may be due to the modification of porphyrin ring conformation of TPPS4 by 99mTc(CO)3 core. © 2011 World Scientific Publishing Company.

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