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Li J.,Central South University | Li J.,Hunan Zhengyuan Institute for Energy Storage Materials and Devices | Yang J.,Central South University | Li L.,China Metallurgical Group Corporation | And 5 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2013

The olivine type LiMn0.4Fe0.6PO4 was synthesized via the low temperature solid-state reaction combined with hydrothermal synthesis from Li2CO3, FeC2O4 · 2H2O, MnCO3 and NH4H2PO4. The product from the low temperature solid-state reaction was studied. The structure, particle size and surface morphology of these cathode active materials were investigated by XRD, SEM and TEM. Electrochemical characteristics of the composites were evaluated using galvanostatic charge/discharge tests. The results show that olivine LiMPO4 (M=Fe, Mn) is obtained after the raw materials are fired at 400°C for 4 h. All Li (Mn0.4Fe0.6) PO4 samples are simple pure olive-type phase with a conductive, thin web of carbon surrounding them. The composite synthesized via the low temperature solid-state reaction/hydrothermal synthesis has homogeneous particles of size 100 nm, an initial discharge capacity of 157 mA · h/g at 0.1C and a specific capacity of about 133 mA · h/g after 50 times cycling at 0.5 C rate. They are 1.07 times and 1.21 times of the products from the traditional solid-state, respectively.


Jia Y.,Beijing Jiaotong University | Meng X.,Beijing Jiaotong University | Zhang H.,China Metallurgical Group Corporation
Applied Mechanics and Materials | Year: 2012

The geometric shape of buildings in wind field is an important influencing factor of wind pressure distribution on the buildings. Along with the change of roof shape, wind pressure distributions vary obviously. In this paper, the numerical simulation of the wind pressure for four types of large-span roofs is carried out, using CFX12.0 as computing platform. The characteristics of wind pressure distribution are studied by considering some parameters, such as wind direction, rise-span ratio, and terrain roughness. Wind pressure distribution is greatly affected by wind direction, and the wind pressure on large-span roofs is dominated by suction; the vortex shedding produced by airflow separation is the main factor affecting the characteristics of wind load. © (2012) Trans Tech Publications, Switzerland.


Cen L.H.,Central South University | Cen L.H.,Key Laboratory of System Control and Information Processing | Zhu H.L.,China Metallurgical Group Corporation
Applied Mechanics and Materials | Year: 2013

This paper proposed a parameter identification method for simplified models of open drainage systems. SWMM is used to identify these parameters by taking the rainfall data as the input. Simulations show that the results of the proposed method have high accordance with those of SWMM. The drainage system of Duke University is taken as an example to demonstrate our approach. © (2013) Trans Tech Publications, Switzerland.


Guo G.,The MCC Group | Guo G.,China Jingye Engineering Corporation Ltd | Liu Z.,The MCC Group | Liu Z.,China Jingye Engineering Corporation Ltd | And 5 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

The rupture surface of underreamed ground anchor is essentially important for the bearing mechanism of underreamed ground anchor. In order to observe the shape of rupture surface of sand around underreamed ground anchor during uplifting, a series of model tests on underreamed ground anchor under vertical uplifting were carried out with digital photogrammetry. For the first time, the whole deformation fields of underreamed ground anchor were captured through digital deformation analysis. The results show that the shear bands in the whole process exhibited as long and narrow vertical strips. The shear strain amplitude inside the rupture surface increased. During the process, the sand above the top surface of underreamed section exhibited volumetric compression; while the volume of sand on the side of underreamed section expanded. Based on the analysis, the damage model and bearing capacity calculation method of underreamed ground anchor should be established according to the rupture surface through actual observations.


Zhao Y.,University of Science and Technology Beijing | Gao J.-M.,University of Science and Technology Beijing | Yue Y.,University of Science and Technology Beijing | Peng B.,University of Science and Technology Beijing | And 4 more authors.
International Journal of Minerals, Metallurgy and Materials | Year: 2013

Extraction and separation of nickel and cobalt from saprolite laterite ore were studied by using a method of microwave-assisted hydrothermal leaching and chemical deposition. The effects of leaching temperature and time on the extraction efficiencies of Ni2+ and Co2+ were investigated in detail under microwave conditions. It is shown that the extraction efficiencies of Ni2+ and Co2+ from the ore pre-roasted at 300 C for 5 h were 89.19% and 61.89% when the leaching temperature and time were about 70 C and 60 min, respectively. For the separation process of Ni and Co, the separation of main chemical components was performed by adjusting the pH values of sulfuric leaching solutions using a NaOH solution based on the different pH values of precipitation for metal hydroxides. The final separation efficiencies of Ni and Co were 77.29% and 65.87%, respectively. Furthermore, the separation efficiencies of Fe of 95.36% and Mg of 92.2% were also achieved at the same time. © 2013 University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.


Feng X.,Northeastern University China | Feng X.,China Metallurgical Group Corporation | Wang L.,Northeastern University China | Liu Y.,Northeastern University China
Jinshu Xuebao/Acta Metallurgica Sinica | Year: 2016

Effects of welding heat input on the microstructure and dynamic fracture toughness (JId) of the CO2 shielded arc welded joints of Q460 high strength low alloy steel were investigated. The mechanism of effects on the dynamic facture behavior of the welded joint was also discussed. The results showed that there existed the allotriomorphic ferrite at the columnar interface in the fusion zone of welded joint under the condition of low heat input. The morphological characteristics of columnar crystal in the fusion zone gradually decreased and the allotriomorphic ferrite disappeared as the heat input increased. The fusion zone was mainly composed of acicular ferrite, and its average size increased with increasing heat input. The welded joint exhibited the optimal dynamic fracture toughness under the condition of medium heat input while it showed the lowest value under low heat input within the temperature range of -70℃ to room temperature. When the temperature decreased from room temperature to -70℃, the dynamic fracture mechanism of Q460 welded joint changed from ductile fracture to brittle cleavage fracture. Under the condition of low heat input, the allotriomorphic ferrite characterized by the planar growth at the columnar interface in the fusion zone of welded joint can lead to the rapid intergranular crack propagation at low temperature. The fine acicular ferrite in the fusion zone of the welding joint obtained at medium heat input which can hinder the crack propagation during the dynamic fracture at low temperature to the greatest extent is the reason why the welded joint exhibits high dynamic fracture toughness. © All right reserved.


Yu J.-L.,University of Science and Technology Beijing | Zhang M.,University of Science and Technology Beijing | Guo M.,University of Science and Technology Beijing | Peng B.,China Metallurgical Group Corporation
Beijing Keji Daxue Xuebao/Journal of University of Science and Technology Beijing | Year: 2011

Using Bi (NO 3) 3 · 5H 2O and Ti substrates as raw materials and absolute ethyl alcohol as a solvent, oriented Bi 0.5Na 0.5TiO 3 (BNT) ceramics were synthesized by solvothermal method. The phase, micro-mophology and composition of BNT ceramics were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). The effects of factors such as NaOH concentration, [Bi 3+] concentration, surfactants and solvents on the grain phase, micro-mophology and composition of BNT ceramics were systematically studied. The results show that oriented BNT ceramics are successfully obtained when the NaOH concentration, the [Bi 3+] concentration, the addition of polyethylene glycol (PEG) and the solvent are 1 mol · L -1, 0.1 mol · L -1, 1 to 6 mL and absolute ethyl alcohol, respectively. The average size of the BNT grains is in the range of 10 to 20μm.


Chen C.,Xi'an University of Architecture and Technology | Chen C.,Ningbo Institute of Materials Technology and Engineering | Ge F.,Ningbo Institute of Materials Technology and Engineering | Gu W.,Xi'an University of Architecture and Technology | And 4 more authors.
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2015

The VB2 coatings were synthesized by pulsed magnetron co-sputtering on the substrates of Si (100), glass and M2 tool steel, pre-deposited with Ti transition layers. The impact of the frequency of power-supply on the microstructures and mechanical properties of the VB2 coatings was investigated. The VB2 coatings were characterized with X-ray diffraction, scanning electron microscopy, atomic force microscopy and conventional mechanical probes. The results show that depending on the frequency, the VB2 coatings possess improved surface mechanical properties, such as higher hardness, better wear-resistance and lower friction coefficient. As the frequency increased, the surfaces with big columnar-structured grains turned into amorphous-like surfaces with smaller grains and reduced roughness. Grown at 250 kHz, the < 100> preferentially oriented, smooth and compact VB2 coatings had a surface hardness of 43 GPa, and a wear-rate of 7.8×10-16 m3/N m, 300 times lower than that of M2 tool steel. ©, 2015, Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology. All right reserved.

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