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Zhang H.,CAS Shenyang Institute of Metal Research | Zhang H.,University of Chinese Academy of Sciences | Wang X.H.,CAS Shenyang Institute of Metal Research | Xiang H.M.,Science and Technology of Advanced Functional Composite Laboratory | And 3 more authors.
Applied Physics Letters | Year: 2014

Micro-Raman spectroscopic study and lattice dynamics calculations were conducted to study a recently identified layered ternary carbide, Ti 5Al2C3. The experimental Raman shifts were remarkably consistent with the calculated values. Polarized Raman spectrum was collected in the polycrystalline sample, which confirmed the theoretical symmetry assignment of the Raman modes. In addition, the atomic vibrations of the peaks at 192cm-1, 311cm-1, and 660cm-1 were identified to be the combination of the counterparts in Ti2AlC and Ti3AlC2. © 2014 AIP Publishing LLC.


Zheng L.Y.,CAS Shenyang Institute of Metal Research | Zheng L.Y.,University of Chinese Academy of Sciences | Wang J.Y.,CAS Shenyang Institute of Metal Research | Chen J.X.,CAS Shenyang Institute of Metal Research | And 4 more authors.
Journal of the American Ceramic Society | Year: 2013

Niobium aluminum carbide (Nb4AlC3), as a member of the MAX phases, can retain its stiffness and strength up to over 1400°C, however, the strength at room temperature is relatively low. In this work, Nb5(Si, Al)3 was used to strengthen Nb4AlC 3. Nb4AlC3-Nb5(Si, Al)3 composites with different amount of Nb5(Si, Al)3 were synthesized from the elemental powders by in situ hot-pressing/solid-liquid reaction synthesis process. The RT flexural strength was significantly improved from 370 MPa of monolithic Nb4AlC3 to 432 MPa of Nb 4AlC3-15 vol% Nb5(Si, Al)3 composite without the degradation of its high-temperature mechanical properties. While a slightly decrease in fracture toughness occurs with the increment of Nb 5(Si, Al)3 content. Meanwhile, Transmission electron microscopy (TEM) observations reveal that the interfaces between Nb 4AlC3/Nb4AlC3, Nb 4AlC3/Nb5(Si, Al)3, and Nb 5(Si, Al)3/Nb5(Si, Al)3 are free of amorphous layers, which is also beneficial to its high-temperature mechanical properties. © 2012 The American Ceramic Society.


Zhang H.,CAS Shenyang Institute of Metal Research | Zhang H.,University of Chinese Academy of Sciences | Wang X.H.,CAS Shenyang Institute of Metal Research | Li Z.J.,CAS Shenyang Institute of Metal Research | And 4 more authors.
Materials Science and Engineering A | Year: 2014

A novel twinning platelets strengthened TiC-Ni2AlTi composite was designed and fabricated by an in situ reactive hot-pressing method of blended Ti3AlC2 and Ni powders. Upon de-intercalation of Al from nanolaminated Ti3AlC2 upon heating, TiC twinning platelets with width in submicrometer size were introduced. The obtained composite exhibits excellent wear resistance, high flexural strength, moderate fracture toughness and Vickers hardness. Unexpectedly, the flexural strength of the composite increases with temperature rising from 500 to 800°C, reaching a maximum of 936MPa at 800°C, thereby benefiting the application as cutting tools. © 2013 Elsevier B.V.


Zheng L.,CAS Shenyang Institute of Metal Research | Zheng L.,University of Chinese Academy of Sciences | Wang J.,CAS Shenyang Institute of Metal Research | Zhou Y.,Science and Technology of Advanced Functional Composite Laboratory
Journal of the American Ceramic Society | Year: 2014

Niobium aluminum carbide (Nb4AlC3), as a member of the MAX phases, can retain its stiffness and strength up to over 1400°C. However, its applications are limited due to its poor oxidation resistance at high temperatures. In this work, silicon pack cementation has been applied to improve the oxidation resistance of Nb4AlC3. After Si pack cementation at 1200°C for 6 h, a dense and uniform silicide coating which was mainly composed of NbSi2 and SiC and well bonded to the matrix was successfully formed on the surface of Nb4AlC3. The Si pack cemented Nb4AlC3 shows excellent oxidation resistance up to 1200°C due to the formation of protective Al2O3 layer. The oxidation kinetics of the cemented Nb4AlC3 obey parabolic law all the way to up to 1200°C, and the parabolic rate constants of cemented Nb4AlC3 are in the same order of magnitude as those of Ti3AlC2 in the temperature range 1000°C-1200°C. However, the oxidation of the cemented Nb 4AlC3 was accelerated after oxidation at 1300°C for about 15 h due to the formation of NbAlO4. © 2013 The American Ceramic Society.


Fang X.M.,CAS Shenyang Institute of Metal Research | Fang X.M.,University of Chinese Academy of Sciences | Wang X.H.,CAS Shenyang Institute of Metal Research | Zhang H.,CAS Shenyang Institute of Metal Research | And 3 more authors.
Journal of Materials Science and Technology | Year: 2015

Nanolaminated Ti3AlC2 honeycomb monolith with parallel and uniform holes has been prepared through a facile extrusion route by using Ti3AlC2 powder as the main raw material. The fabricated honeycomb monolith has high compressive strength of 133±11 and 59±9MPa, along and perpendicular to the extrusion direction, respectively. It also has good electrical conductivity, and excellent match of thermal expansion coefficient with the washcoat material of γ-Al2O3. These combined properties endow the honeycomb monolith a promising candidate as catalysis substrate for cleaning vehicle exhaust. © 2014.


Fang X.,CAS Shenyang Institute of Metal Research | Wang X.,CAS Shenyang Institute of Metal Research | Zhang H.,CAS Shenyang Institute of Metal Research | Li Z.,CAS Shenyang Institute of Metal Research | And 2 more authors.
Advanced Engineering Materials | Year: 2015

A cost-efficient strategy using elemental powders of Ti, Al, and graphite as starting materials is proposed to fabricate conductive Ti2AlC honeycomb monolith. The honeycomb structure is extruded from a plastic feed material composed of the initial powders and several additives. Phase-pure Ti2AlC can be obtained with a direct heating schedule, but the shape of the extruded green body will be destroyed due to thermal explosion in Ti-Al-C strongly exothermic system, which is resulted from the rapid release of latent heat from reactions between the elemental powders during heating process. To avoid the thermal explosion, the honeycomb sample is dwelled at 650 C for 2 h to release latent heat in a controlled manner. As a result, Ti2AlC honeycomb monolith with designed structure is obtained, followed by sintering at elevated temperatures. In addition, the phase evolution and mechanism for pore formation are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Zhang H.,Chinese Academy of Sciences | Zhang H.,University of Chinese Academy of Sciences | Wang X.,Chinese Academy of Sciences | Li Z.,Chinese Academy of Sciences | And 2 more authors.
Journal of Materials Research | Year: 2014

Titanium carbide (TiC) twins are believed to be extremely unstable because of their high twin boundary energy. Here, we report that TiC twins are always presented in platelets with dimensions of 2-3 μm in length and less than 300 nm in width. In-depth microstructural characterizations by high-resolution transmission electron microscopy demonstrate that Al atoms at the twin boundary play a decisive role in stabilizing TiC twins. With different amounts of Al, perfect and defective TiC twins are formed. For perfect twins, three types of twin boundaries can be formed depending on the amount of remaining Al at the twin boundary. With inadequate Al, the TiC twins become defective with certain degrees of deviation from the perfect twin orientation. Based on a detailed analysis of the microstructure of the twin boundaries, a mechanism for the formation and stabilization of TiC twins is proposed. © 2014 Materials Research Society.

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