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Rashad M.,Chongqing University | Pan F.,Chongqing University | Pan F.,Chongqing Academy of Science and Technology | Tang A.,Chongqing University | And 2 more authors.
Journal of Alloys and Compounds | Year: 2014

Graphene nanoplatelets (GNPs) are novel reinforcing fillers due to their fascinating mechanical properties. However, their unique mechanical properties rapidly devolve as the sheets aggregate due to strong van der Waals forces and π-π attractions, therefore limiting their applications in metal matrix composites. In present work, the rapid aggregation of two-dimensional GNPs is inhibited by intercalating one-dimensional multi-walled carbon nanotubes (MW-CNTs). The long and flexible MW-CNTs bridge adjacent GNPs to form three dimensional hybrid structures which prevent their aggregation, thus resulting in a high contact area between CNTs + GNPs hybrid structure and the matrix. The composite reinforced with hybrid (GNPs and CNTs) reinforcement exhibited higher failure strain than those reinforced with individual GNPs and MW-CNTs. Compared to pure Mg, the Mg-1Al-0.6 wt.%(CNTs + GNPs) composite exhibited improvement in elastic modulus, 0.2% yield strength, ultimate tensile strength and failure strain (+17%; +19%; +15% and +137%, respectively). The impressive increase in tensile failure strain (%) confirmed significant synergetic effect between GNPs and MW-CNTs. © 2014 Elsevier B.V. All rights reserved. Source

Song B.,Southwest University | Song B.,Chongqing University | Guo N.,Southwest University | Guo N.,Chongqing University | And 4 more authors.
Materials and Design | Year: 2014

Twinning can generate the change of texture and a large of twin boundaries, which can greatly influence the mechanical properties of magnesium alloys. Thus, pre-twinning can be considered to be a simple and feasible method to improve the mechanical properties of magnesium alloys. Recently, some studies have confirmed that pre-twinning can be an effective way to enhance the strength, formability and mechanical anisotropy of magnesium alloys. Based on these results, some aspects of the present research on the improvement of mechanical properties via pre-twinning are reviewed. The relevant mechanisms have been summarized. Finally, for this research field, a few critical scientific problems are also proposed. © 2014 Elsevier Ltd. Source

Zhang D.-W.,Peking Union Medical College | He H.-Q.,Chongqing Academy of Science and Technology | Guo S.-X.,Peking Union Medical College
Analytical Biochemistry | Year: 2014

HIV-1 integrase is a key enzyme for retroviral replication. The integrase can perform a palindrome cleavage reaction. In this work, a hairpin DNA probe with a palindromic DNA sequence mimicking the HIV-1 LTR-LTR junction of the 2-LTR circles in its long stem was designed for fluorescence detection of specific restriction-like cleavage activity of HIV-1 integrase. Results showed that the designed probe could be recognized and cleaved by HIV-1 integrase. The palindrome cleavage reaction can be monitored according to the increase in fluorescent signal. The assay can be applied to real-time detection of palindrome cleavage of HIV-1 integrase with advantages of simplicity, high sensitivity, and specificity. © 2014 Elsevier Ltd. All rights reserved. Source

Zhang H.,Chongqing University | Huang G.,Chongqing University | Huang G.,Chongqing Academy of Science and Technology | Wang L.,Chongqing University | Li J.,Chongqing University
Scripta Materialia | Year: 2012

Pre-stretching and annealing treatment was carried out to modify the microstructure of Mg-3Al-1Zn (AZ31) alloy to enhance its formability. The pre-stretched and annealed specimens exhibited lower basal texture intensities and coarser grain sizes and their Erichsen values were increased up to 65% compared with the as-received sheet. The microstructure, macrotexture, mechanical properties and formability of specimens before and after pre-stretching followed by annealing were characterized and compared. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

Chen X.,Chongqing University | Liu L.,Chongqing University | Liu J.,Chongqing University | Pan F.,Chongqing University | Pan F.,Chongqing Academy of Science and Technology
Materials and Design | Year: 2015

The results indicated that addition of Y brought about the formation of I-phase (Mg3Zn6Y) and W-phase (Mg3Zn3Y2) and refined grains in as-cast state. After hot extrusion, there was more and more broken particles dispersing in matrix when Y content ranged from 0 to 3.19wt.%. With increasing Y content, EMI SE was enhanced significantly in extruded state. The alloy with 1.9wt.% Y exhibited the optimal EMI shielding capacity with the SE value of 79-118dB. It was found that good mechanical properties could be achieved by adding very low Y content. The extruded alloy with 0.5wt.% Y presented higher yield strength (268MPa), ultimate tensile strength (334MPa) and good elongation (δ=12.3%) compared with other extruded alloys. A subsequent aging treatment on the extruded alloy with 1.29wt.% Y exhibiting outstanding comprehensive EMI SE and mechanical properties resulted in precipitation of W, β1' and β2' phases, which led to further improvement in EMI SE. The peak-aged sample showed the superior mechanical properties. Based on the microstructure observation, the changes of EMI shielding capacity and mechanical properties have been discussed. © 2014 Elsevier Ltd. Source

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