Key Laboratory of Advanced Special Material and Technology

Chengdu, China

Key Laboratory of Advanced Special Material and Technology

Chengdu, China
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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.


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.


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.


Zhu G.,Sichuan University | Liu Y.,Sichuan University | Liu Y.,Key Laboratory of Advanced Special Material and Technology | Ye J.,Sichuan University
International Journal of Refractory Metals and Hard Materials | Year: 2014

The early high-temperature oxidation behavior of Ti(C,N)-based cermets with equiatomic AlCoCrFeNi high-entropy alloy binder has been studied, as well as the cermet with Ni/Co binder as a reference. Experiments were performed at the temperature range of 800-1100 C in static laboratory air. The micro-structural evolution of the multi-layered oxide scales on the cermets was investigated and the effect of binder phase constituent on the oxidation characteristics of Ti(C,N)-based cermets was evaluated. The results demonstrated that the cermet with AlCoCrFeNi multi-element alloy binder possesses superior oxidation resistance, which is greatly better than that of the cermet with Ni/Co metallic binder under the same condition. We suggest that the formation of a continuous and dense external oxide scale can effectively impede the outward diffusion of volatile tungsten oxides and inward oxygen transport, leading to a remarkable improvement of oxidation resistance. In addition, the enhanced oxidation resistance was related to the high Cr and Al concentration in AlCoCrFeNi binder phase that urges the formation of oxide layers with more efficient passivation effect against oxidation. © 2014 Published by Elsevier Ltd.


Li P.,Sichuan University | Ye J.,Sichuan University | Liu Y.,Sichuan University | Liu Y.,Key Laboratory of Advanced Special Material and Technology | And 2 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2012

Ti(CN)-based cermets were synthesized from Ti(CN)WCMo 2CTaCNiCo composite powders by vacuum-low pressure sintering. The phase evolution and the formation of core-rim structure in Ti(CN)-based cermets were systemically investigated during difference reaction stages at 950-1450 °C. The results show that the secondary carbides such as Mo 2C and TaC are begun to dissolve at 950 °C, finished at 1150 °C, and the solution temperature of WC phase is range from 1150 to 1300 °C, which are result in increase of the cermets lattice constant. At the same time, the inner rim is also formed, and Ti(CN)-based cermets are composed of (Ti, W, Mo, Ta)(CN) and Ni/Co solid solution phase. While at 1350 °C, it was found that the outer rim began to precipitate from the liquid phase with the metal binder. With increase of sintering temperature, mechanical properties of cermets improved obviously were related intimately to the increase of outer rim thickness. © 2012 Elsevier Ltd. All rights reserved.


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.


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.


He L.,Sichuan University | Liu Y.,Sichuan University | Liu Y.,Key Laboratory of Advanced Special Material and Technology | Li J.,Sichuan University | And 2 more authors.
Materials and Design | Year: 2012

High boron Fe-B alloys (1.8wt.% B) with different titanium contents are fabricated by Vacuum Induction Melting (VIM) technique. The integrated mechanical properties of the as-cast alloys are poor, especially the ductility. In this investigation, hot-rolling technology is used to improve the microstructure and mechanical properties. The microstructure analysis shows that hot rolling can reduce the size and improve the distribution of the reinforcements. The mechanical properties testing indicates that the yield strength is unchanged basically, but the tensile strength and elongation are improved greatly by hot rolling, especially the elongation. The content of titanium also has great effects on the microstructures and mechanical properties of the hot-rolled alloys. For the hot-rolled alloys, with the titanium content increasing, the ultimate tensile strength and yield strength first decrease slightly and then increase. The elongation and impact toughness are improved significantly. In particular, when the atomic ratio of Ti to B is 0.5, the reinforcements are almost entirely TiB2 and uniformly distributed in the Fe-matrix. The ternary Fe-B-Ti alloy exhibits balanced mechanical properties: yield strength, ultimate tensile strength, elongation and impact toughness are 334MPa, 602MPa, 16.2% and 213kJ/m2, respectively. © 2011 Elsevier Ltd.


Zhu G.,Sichuan University | Liu Y.,Sichuan University | Liu Y.,Key Laboratory of Advanced Special Material and Technology | Ye J.,Sichuan University
International Journal of Refractory Metals and Hard Materials | Year: 2013

A series of cermets with the varying nominal composition Ti(C0.7 N0.3)-WC-Mo2C-TaC-(Co, Ni)-x(Ce-Co) were prepared via low pressure sintering, to investigate the effect of Ce-Co pre-alloyed powder addition on the microstructure and mechanical properties of Ti(C,N)-based cermets. The Ce-Co content was varied between 0 and 0.8 wt.%, in 0.2 wt.% increments. Experimental results show that the addition of trace Ce-Co pre-alloyed powder can favor the microstructure refinement, improve the particulate dispersion and promote the dissolution of various carbides in binder phase. In addition, energy-dispersive X-ray analysis revealed rare earth cerium was dissolved in the Co/Ni binder, and then the complex solid solution phase containing cerium was formed during the liquid sintering process. The modified microstructure and phase composition by adding rare earth cerium in the form of cobalt pre-alloyed powder results in the high mechanical properties of the cermets. Compared with undoped sample, the cermets doped with 0.6 wt.% Ce-Co pre-alloyed powder showed optimum comprehensive properties: the transverse rupture strength of 1989 MPa, Rockwell hardness of 93.1 HRA and the fracture toughness of 11.01 MPa m1/2, respectively. © 2012 Elsevier Ltd. All rights reserved.


Wang B.,Sichuan University | Wang B.,Xinxiang University | Liu Y.,Sichuan University | Liu Y.,Key Laboratory of Advanced Special Material and Technology | Ye J.,Sichuan University
Physica Scripta | Year: 2013

The lattice parameters, elastic properties, electronic structures and hardness of VC, V4C3 and V8C7 were studied by means of the pseudo-potential plane-waves method using the density function theory (DFT). The present lattice parameters of VC, V4C3 and V8C7 agree well with other theoretical and experimental data. V4C3 and V 8C7 have lower values than VC in bulk modulus, shear modulus and Young's modulus, respectively. According to the analysis of the density of states of VC, V4C3 and V8C7, it was found that a C vacancy leads to the emergence of new peaks near the Fermi level that give a negative contribution to the shear modulus. As the hardness cannot be calculated from DFT directly, a semi-empirical model was used to estimate the hardness. Based on the overlap populations and bond lengths obtained from DFT, the hardness values of VC, V4C3 and V8C7 were evaluated. Furthermore, VC has the highest hardness. © 2013 The Royal Swedish Academy of Sciences.

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