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Liao D.-Q.,Changsha Institute of Mining Research | Xia C.-Y.,KingRay New Materials Science and Technology Co. | Xi X.-M.,Changsha Institute of Mining Research | Zhou C.-X.,Changsha Institute of Mining Research | And 3 more authors.
Journal of Sol-Gel Science and Technology | Year: 2016

The sol–gel method was improved to synthesize the layered Li-rich cathode material Li1.2Ni0.13Co0.13Mn0.54O2 by employing the mixture of polymer polyacrylic acid (PAA) and citric acid as the mixed chelator. The crystal structure, particle morphology and electrochemical performance of the prepared layered Li-rich cathode material are extensively studied by X-ray diffraction spectrometry, scanning electron microscopy, charge–discharge test, cyclic voltammetry and electrochemical impedance spectroscopy techniques. The results show that the Li-rich cathode materials prepared with the new method present explicit layer structure, low level of Li+/Ni2+ disordering, large specific surface area and accurate chemical composition. When measured with electrochemical test system, the prepared material exhibits a high capacity of 274.8 mAh g−1. The excellent performances of the prepared material could be ascribed to the fact that the novel approach combines the advantages of the two chelating agents of PAA and citric acid. Graphical Abstract: [Figure not available: see fulltext.] © 2016, Springer Science+Business Media New York.


Wang W.-N.,Hunan Electrical Power Research Institute | Chen F.-S.,Hunan Electrical Power Research Institute | Wang Z.-Q.,KingRay New Materials Science and Technology Co.
Journal of Systems and Software | Year: 2012

NAND flash memory has become one of the most popular storage media for portable devices, such as MP3 players, MMC cards and solid state drives (SSDs). Due to erase-before-write characteristics of NAND flash memory, wear-leveling strategy is very important in determining the performance and lifetime of NAND flash memory in solid state drives. In this paper, to prolong the lifetime and improve the performance of SSDs with cache, we propose an effective wear-leveling algorithm based on a novel "triple-pool" design. Comparing with previous wear-leveling algorithms, experimental results show that our algorithm lengthens the lifetime and reduces the write amplification. © 2012 Elsevier Inc. All rights reserved.


Xu G.,Central South University | Chen F.,Central South University | Xu G.-P.,KingRay New Materials Science and Technology Co. | Ma C.-D.,Central South University
Cailiao Kexue yu Gongyi/Material Science and Technology | Year: 2010

Thermal residual stress value and it's distribution in flat interface polycrystalline diamond compacts (PDC) was analyzed by using finite element analysis (FEA). On this base, combing with the techniques of non-planar junction and gradient transition, a new PDC combined with non-planar connection and an inner gradient layer between diamond and substrate was presented. The FEA results show that the maximum axial tensile stress in the PCD layer is 126 MPa, which is reduced to 13.2% of that in the conventional planar interface PDC. Besides, the maximum radial tensile stress on the surface and axial tensile stress on the side of PCD layer, is reduced by 82.5% and 94.2% comparing to those of planar interface PDC, respectively. Laboratory tests show that the abrasion ratio and shock strength of the new PDC is 16.43 × 104 and 472 J, which are of the advanced level in China. The excellent service performance of the new PDC is also proved by the field test.


CHEN F.,Central South University | XU G.,Central South University | MA C.-d.,Central South University | XU G.-p.,KingRay New Materials Science and Technology Co.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2010

Thermal residual stresses in polycrystalline diamond compact (PDC) cutter arising from the difference in thermal expansion between the polycrystalline diamond (PCD) and the supporting tungsten carbide substrate after sintering at high pressure and high temperature were investigated using finite element simulation, laboratory tests and theoretical analysis. The obtained results show that although compressive residual stresses exist both in the interface of PCD table and in the most region of PCD table surface, the tensile residual stress, which is a fatal shortage to PDC, can also occur near the outer diameter area of PCD table, and the maximum value is 690 MPa. Distribution of tensile stress in the PCD table is given through experimental results, which is well consistent with the numerical results. This finding may be significant in designing new PDC cutters with lower residual stress and high cutting behavior. © 2010 The Nonferrous Metals Society of China.


Chen F.,Central South University | Xu G.,Central South University | Xu G.-P.,KingRay New Materials Science and Technology Co. | Ma C.-D.,Central South University
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2010

Istron1342 testing machine and Hopkinson pressure bar (SHPB) were used to test the edgewise compressive strength before and after damaged polycrystalline diamond compacts (PDC). The results show that the edgewise compressive strength of PDC increases with the increases of loading speed, and decreases with the increase of diamond table thickness instead. On the other hand, the damage introduced by the impact load as well as the D-value between fore-and-after-damaged PDC increases with the increase of loading speed and diamond table thickness.

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