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Wang B.,Sichuan University | Liu Y.,Sichuan University | Liu Y.,Key Laboratory of Advanced Special Material and Technology | Ye J.-W.,Sichuan University | Wang J.,Sichuan University
Computational Materials Science | Year: 2013

The first-principles calculations are performed to investigate structure stability, magnetism, electronic structure and elastic properties of Mo 2FeB2 in nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AF) cases. Density functional theory and ultrasoft pseudopotentials are used in this study. It is found that the lattice parameters of the AF case are more close to the experimental data than the ones of the NM and FM cases, and the AF one has the lowest energy, indicating it is the ground state. All of the cases are stable thermodynamic structures. Furthermore, the AF case expresses more stability than the FM and NM cases because it has the largest formation enthalpy value. The density of states and overlap populations are analyzed for NM, FM and AF cases of Mo2FeB2. B-B and B-Mo are covalent bonding and give the positive to shear modulus. According to the analysis of magnetism, Fe atoms play the key point. The FM and AF cases of Mo2FeB2 have a lower bulk modulus, but higher shear modulus and Young's modulus than of the NM case. It is obvious that the spin restriction can significantly affect the moduli of Mo2FeB 2, and the FM and AF cases show brittle character while the NM one ductile character. © 2013 Elsevier B.V. All rights reserved. Source

Kong Q.,Sichuan University | Lian L.,Sichuan University | Liu Y.,Sichuan University | Liu Y.,Key Laboratory of Advanced Special Material and Technology | Zhang J.,Sichuan University
Materials Letters | Year: 2014

In the present study, Al-Cu alloy with fine grain of ~400 nm has been prepared by mechanical alloying and spark plasma sintering (MA-SPS). Then bulk hierarchical nanoporous copper (BHNPC) was obtained by chemical dealloying of the resultant alloys. Results show that BHNPC possess a highly porosity of ~80% and fine ligament size of about 27 nm that can be prepared without either applied potential or addition of other element such as nickel. Furthermore, compression properties of BHNPC were investigated. The bulk nanoporous copper has a compressive strength of 5.8 MPa. The main failure is brittle fracture, which is probably due to the defects that were generated in the bulk after chemical dealloyed in high concentration alkali solutions. © 2014 Elsevier B.V. Source

Zhu R.,Sichuan University | Liu Y.,Sichuan University | Liu Y.,Key Laboratory of Advanced Special Material and Technology | Ye J.,Sichuan University | Zhang X.,Sichuan University
Journal of Materials Science: Materials in Electronics | Year: 2013

Magnéli phase Ti4O7 was prepared by carbothermal reduction of TiO2 in vacuum. The products synthesized in different carbon black content and heated temperature were investigated by X-ray diffraction, scanning electron microscopy, and ultraviolet-visible (UV-Vis) spectra of products were tested also. The results show that the pure Ti4O7 powder is obtained with carbon black content of 4 wt% at 1,025 C for 2 h in vacuum, their average particle size and BET surface area are about 6.10 μm and 4.107 m2 g-1, respectively. The resistivity of the samples is up to 0.11 Ω cm, and UV-Vis spectra shows the optical absorption bands cover the full range of visible-light wave lengths and extend into near-infrared region. © 2013 Springer Science+Business Media New York. Source

Jun L.,Sichuan University | Ying L.,Sichuan University | Ying L.,Key Laboratory of Advanced Special Material and Technology | Yilong M.,Sichuan University
Journal of Magnetism and Magnetic Materials | Year: 2012

Bulk anisotropic NdFeB/α-Fe nano-composites were obtained directly from alloys of Nd 11Dy 0.5Fe 82.4-xNb xB 6.1 (x=0,0.5,1.0,1.5). High resolution transmission electron microscopy images showed the existence of Nb-rich amorphous grain boundary phase in the alloys with Nb doped. Field emission scanning electron microscope morphologies and X-ray diffraction patterns revealed the grain size and grain alignment of hot pressed and hot deformed nanocomposites. It was found that Nb could refine the grain size and grain texture in hot worked ribbons. Vibrating sample magnetometer results showed that the magnetic properties of the anisotropic nanocomposites were improved with increased Nb doping. The remanence, coercivity and maximum energy product of the bulk anisotropic Nd 11Dy 0.5Fe 80.4Nb 2B 6.1 nanocomposites were 1.04 T, 563 kA/m and 146 kJ/m 3, respectively. © 2012 Elsevier B.V. All rights reserved. Source

Zhong X.,Sichuan University | Liu Y.,Sichuan University | Liu Y.,Key Laboratory of Advanced Special Material and Technology | Li J.,Sichuan University | Wang Y.,Sichuan University
Journal of Magnetism and Magnetic Materials | Year: 2012

FeSiAl is widely used in switching power supply, filter inductors and pulse transformers. But when used under higher frequencies in some particular condition, it is required to reduce its high-frequency loss. Preparing a homogeneous insulating coating with good heat resistance and high resistivity, such as AlN and Al 2O 3, is supposed to be an effective way to reduce eddy current loss, which is less focused on. In this project, mixed AlN and Al 2O 3 insulating layers were prepared on the surface of FeSiAl powders after 30 min exposure at 1100°C in high purity nitrogen atmosphere, by means of surface nitridation and oxidation. The results revealed that the insulating layers increase the electrical resistivity, and hence decrease the loss factor, improve the frequency stability and increase the quality factor, especially in the high-frequency range. The morphologies, microstructure and compositions of the oxidized and nitrided products on the surface were characterized by Scanning Electron Microscopy/Energy Disperse Spectroscopy, X-Ray Diffraction, Transmission Electron Microscopy, Selected Area Electron Diffraction and X-ray Photoelectron Spectroscopy. © 2012 Elsevier B.V. Source

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