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Li Y.,Wuhan University of Science and Technology | Li Y.,University of Science and Technology Beijing | Peng T.,Metallurgical Corporation of China Ltd | Man W.,University of Science and Technology Beijing | And 4 more authors.
RSC Advances | Year: 2016

Ti-bearing electric arc furnace slag (Ti-bearing EAF slag) is the main solid waste generated in the direct reduction iron making process. During the extraction process of Ti from Ti-bearing EAF slag, a by-product containing abundant Si and Al was seldom utilized, thus leading to waste of valuable elements and secondary pollution. In this paper, NaA zeolite (6Na2O·6Al2O3·12SiO2) and sodalite (SOD, 4Na2O·3Al2O3·6SiO2) were synthesized successfully using the by-product as a precursor. The effects of the SiO2/Al2O3 molar ratio (n(SiO2)/n(Al2O3)), H2O/Na2O molar ratio (n(H2O)/n(Na2O)), hydrothermal temperature and time on the crystal phase and microstructure of the prepared zeolites were systematically investigated. The results indicated that NaA zeolite with good crystallinity and cubic morphology was obtained at 140°C for 3 h with n(SiO2)/n(Al2O3) and n(H2O)/n(Na2O) fixed at 2.0:1 and 100:1, respectively. Decreasing n(H2O)/n(Na2O), raising the hydrothermal temperature and prolonging the hydrothermal time were beneficial for the formation of spherical SOD zeolite. The phase transformation between NaA and SOD zeolite was discussed and a mechanism was proposed to explain the phenomenon of these zeolites coexisting in the obtained samples. In addition, the removal performances of Cu2+ in aqueous solutions using zeolites synthesized at different temperatures were studied. The maximum removal capacity of the prepared zeolite can reach 1.346 mmol g-1 for 180 min. © The Royal Society of Chemistry 2016. Source


Peng B.,University of Science and Technology Beijing | Peng B.,Building and Construction Co. | Qiu G.B.,University of Science and Technology Beijing | Yue C.S.,Building and Construction Co. | And 4 more authors.
Materials Research Innovations | Year: 2015

Aluminium nitride whiskers were successfully synthesised by direct nitridation of Al and Al2O3 in graphite crucible under nitrogen atmospheres. The influence of reaction conditions such as molar ratio of Al:Al2O3 and reaction temperature on the formation of the AlN whiskers have been investigated in detail by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction and energy-dispersive X-ray spectroscopy. Through characterising the microstructure and phase constitution of the as-prepared samples, the optimum synthesis conditions of the AlN whiskers were obtained. Moreover, the growth mechanism of AlN whiskers was discussed combining thermodynamic analysis indicating that the AlN whiskers could be grown via vapour-liquid-solid mechanism. © W. S. Maney & Son Ltd 2015. Source


Qiu H.,Metallurgical Corporation of China Ltd | Zhang J.,University of Science and Technology Beijing | Zhu H.,University of Science and Technology Beijing
China's Refractories | Year: 2012

Dense Si 3 N 4 - BN compsite ceramics were fabrica-ted by spark plasma-sintering at 1 500, 1 600 and 1 650 °C under 50 MP a for 5 min using Si 3N 4 and BN powders as starting materials and 2 mass% Al 20 3 and 6 mass% Y 20 3 as sintering additives. The volume fracion ofBN n Si 3N 4 -BN composite powders was chosen as 10%, 20%, and 30%, respectively. The results of XRD and SEM show hat a-Si 3N 4 completely urns nto sintered at 1 650 °C; the addition of BN hinders the growth of Si 3N 4 grains, refining he structure; Vickers hardness and fracture toughness of the composite ceramics decrease with the increase of BN content. Source


Yue C.-S.,University of Science and Technology Beijing | Peng B.,University of Science and Technology Beijing | Peng B.,Metallurgical Corporation of China Ltd | Guo M.,University of Science and Technology Beijing | Zhang M.,University of Science and Technology Beijing
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2011

β-SiAlON whiskers were synthesized from β-SiAlON powder (inducing seed), SiC(basal body), Si powder, Al powder and Al 2O 3 powder. The microstructure, compositions of β-SiAlON whiskers and mechanical property of β-SiAlON/SiC composite were detailed discussed, and the growth mechanisms of β-SiAlON whiskers based on thermodynamic analysis were subsequently developed in this paper. The results shows that (1)the addition of β-SiAlON seed is beneficial to formation of β-SiAlON whisker, and the vapor-liquid-solid (VLS) and vapor-solid (VS) mechanisms could be adopted to explain the behavior of whiskers growth; (2)while the β-SiAlON whiskers grows in VLS mechanisms, the diameter of rodlike and fibrous wiskers is the range of 200-300 nm and the z value of β-SiAlON whisker is about 1.56; whereas in VS mechanisms, the diameter of rodlike and bamboo-like whiskers with well-developed crystalline is the range of 0.5-1.5 μm and the z value is about 1.76; (3)β-SiAlON whisker has improved the fracture strength of β-SiAlON/SiC composites, the higher flexural strength(55.2 MPa) can be obtained from the composites with many whiskers and in higher porosity(32.1%). Source


Hou X.,University of Science and Technology Beijing | Lu X.,University of Science and Technology Beijing | Peng B.,Metallurgical Corporation of China Ltd | Zhao B.,University of Queensland | And 2 more authors.
Corrosion Science | Year: 2012

The oxidation behaviour of hot-pressed β-SiAlON ceramics with different densities has been investigated up to 1853. K in air using thermogravimetry (TG). The microstructures of the oxidised samples were determined by scanning electron microscopy (SEM), and the phases after oxidation were confirmed by X-ray diffraction (XRD). The oxidation kinetics of the higher density sample was diffusion controlled. For the lower density sample, it was controlled by both an interface reaction and diffusion in the early stage but diffusion controlled after a certain time. The oxidation curves can be well described by Chou's model with the "characteristic oxidation time" index introduced. © 2012 Elsevier Ltd. Source

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