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Wang C.,Chinese Academy of Sciences | Zhang W.,Chinese Academy of Sciences | Ren C.,Chinese Academy of Sciences | Huai P.,CAS Shanghai Key Laboratory of Nuclear Radiation and Nuclear Energy Technology | Zhu Z.,Chinese Academy of Sciences
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Molecular dynamics (MD) simulations have been used to study the influence of temperature on defect generation and evolution in nickel and Ni-Fe alloy (with 15% and 50% Fe content) with a 10-keV primary knock-on atom (PKA) at six different temperatures from 0 to 1500 K. The recently available Ni-Fe potential is used with its repulsive part modified by Vörtler. The temporal evolution and temperature dependence of stable defect formation and in-cascade clustering processes are analysed. The number of stable defect and the interstitial clustering fraction are found to increase with temperature whereas the vacancy clustering fraction decreases with temperature. The alloy composition dependence of the stable defect number is also found for the PKA energy considered here. Additionally, a study of the temperature influence on the cluster size distribution is performed, revealing a systematic change in the cluster size distributions, with higher temperature cascades producing larger interstitial clusters. © 2014 Elsevier B.V. All rights reserved. Source

Xu C.,Tsinghua University | Su J.,CAS Shanghai Institute of Applied Physics | Su J.,CAS Shanghai Key Laboratory of Nuclear Radiation and Nuclear Energy Technology | Xu X.,Tsinghua University | And 2 more authors.
Science China Chemistry

Understanding of the bonding nature of uranyl and various ligands is the key for designing robust sequestering agents for uranium extraction from seawater. In this paper thermodynamic properties related to the complexation reaction of uranyl(VI) in aqueous solution (i.e. existing in the form of UO 2(H2O)5 2+) by several typical ligands (L) including acetate (CH3CO2 -), bicarbonate (HOCO2 -), carbonate (CO3 2-), CH3(NH2)CNO- (acetamidoximate, AO-) and glutarimidedioximate (denoted as GDO2-) have been investigated by using relativistic density functional theory (DFT). The geometries, vibrational frequencies, natural net charges, and bond orders of the formed uranyl-L complexes in aqueous solution are studied. Based on the DFT analysis we show that the binding interaction between uranyl and amidoximate ligand is the strongest among the selected complexes. The thermodynamics of the complexation reaction are examined, and the calculated results show that complexation of uranyl with amidoximate ligands is most preferred thermodynamically. Besides, reaction paths of the substitution complexation of solvated uranyl by acetate and AO- have been studied, respectively. We have obtained two minima along the reaction path of solvated uranyl with acetate, the monodentate-acetate complex and the bidentate-acetate one, while only one minimum involving monodentate-AO complex has been located for AO - ligand. Comparing the energy barriers of the two reaction paths, we find that complexation of uranyl with AO- is more difficult in kinetics, though it is more preferable in thermodynamics. These results show that theoretical studies can help to select efficient ligands with fine-tuned thermodynamic and kinetic properties for binding uranyl in seawater. © 2013 Science China Press and Springer-Verlag Berlin Heidelberg. Source

Huang L.,Shanghai University of Engineering Science | Cao Y.,Shanghai University of Engineering Science | Zhao M.,Shanghai University of Engineering Science | Tang Z.,CAS Shanghai Key Laboratory of Nuclear Radiation and Nuclear Energy Technology | Sun Z.,Shanghai University of Engineering Science
Organic and Biomolecular Chemistry

A series of chiral 6-membered ring N-heterocyclic carbene (NHC) precursors based on 3,4-dihydro-quinazoline were synthesized with overall yields of 54-62%. NHCs generated from these precursors show excellent asymmetric catalytic properties for borylation of α,β-unsaturated esters with enantioselectivity of up to 93% with a catalyst content of only 1 mol%. This journal is © the Partner Organisations 2014. Source

Tang Z.,CAS Shanghai Institute of Applied Physics | Tang Z.,CAS Shanghai Key Laboratory of Nuclear Radiation and Nuclear Energy Technology | Cheng G.,Anhui University of Science and Technology | Chen Y.,Guangxi University of Science and Technology | And 2 more authors.
Advanced Powder Technology

Calcium carbonate (CaCO3) particles were modified by a direct blending method using different coupling agents. The changes in the CaCO3 particles were determined using different techniques. Compared with pristine particles, the modified CaCO3 particles show good dispersion, particularly those modified by γ-methacryloxypropyl trimethoxy silane. Results of the thermogravimetric analysis indicated that the coupling agents were adsorbed or anchored on the surface of the CaCO3 particles, thereby hindering aggregation. The formation of covalent bonds [CaOSi] or [CaOTi] was verified using Fourier transform infrared spectroscopy and X-ray diffraction. The modified CaCO3 particles showed more stable colloidal dispersion in ethyl acetate than that of pristine CaCO3 particles. Some silane or titanate coupling agents can be combined with CaCO3 by covalent bonds, thereby changing the surface properties of CaCO3 and enhancing dispersion in many organic media. The hydroxyl groups on the surface of CaCO3 particles can interact with silanol groups or titanate coupling agents forming an organic coating layer. © 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved. Source

Yang J.,CAS Shanghai Institute of Applied Physics | Yan L.,CAS Shanghai Institute of Applied Physics | Yan L.,CAS Shanghai Key Laboratory of Nuclear Radiation and Nuclear Energy Technology | Huai P.,CAS Shanghai Institute of Applied Physics | Huai P.,CAS Shanghai Key Laboratory of Nuclear Radiation and Nuclear Energy Technology
He Jishu/Nuclear Techniques

Background: C/C composites are an attractive choice for components in nuclear reactors because of their excellent performance in high temperature resistance, corrosion resistance and radiation resistance. However, to the best of our knowledge, the radiation research on their morphology and microstructure are scant. Purpose: The aim is to investigate the morphology and microstructure of C/C composites induced by irradiation. Methods: The C/C composites were irradiated with 0.5 MeV and 1 MeV Ar ions at room temperature. The samples prepared before and after irradiation have been characterized by Raman spectroscopy and scanning electron microscope (SEM). Results: With the increment of irradiation dose, the surface defects in the irradiated samples greatly increase. Moreover, some cracks and holes are found in the matrix surfaces, and the largest ones are even up to the size of one micrometer. Conclusion: The surface defects in the matrix caused by 0.5 MeV Ar ion with dose of 2.4×1016 ions·cm-2 are much more than those by 1 MeV Ar ion with dose of 3×1016 ions·cm-2. Source

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