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Wen M.,Deakin University | Wen M.,Kunming Institute of Precious Metals | Wen C.,Swinburne University of Technology | Hodgson P.,Deakin University | Li Y.,Deakin University
Corrosion Science | Year: 2012

The oxidation behaviour of a novel Ti with a nanocrystalline (NC) surface layer, made by surface mechanical attrition treatment (SMAT Ti), has been investigated in air at 500∼700 °C. SMAT Ti can react with oxygen and form oxide particles even at 500 °C, while that of coarse-grained Ti (CG Ti) is about 600 °C. Ti shows a different colour at each temperature, which is attributed to the light interference phenomena. The SMAT Ti shows a thicker, denser oxide layer as compared with that of CG Ti. It originates from the numerous grain boundaries and dislocations on the SMAT Ti surface. © 2012 Elsevier Ltd.

Wen M.,Deakin University | Wen M.,Kunming Institute of Precious Metals | Wen C.,Swinburne University of Technology | Hodgson P.,Deakin University | Li Y.,Deakin University
Materials and Design | Year: 2014

Ti and some of its alloys are widely used as orthopedic implants. In the present study, Ti-26Nb-5Ag alloys were prepared by mechanical alloying followed by vacuum furnace sintering or spark plasma sintering (SPS). The microstructure and mechanical properties of the Ti-Nb-Ag alloys were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX), compressive and micro-hardness tests. The effect of different sintering methods on the microstructure and properties of Ti-Nb-Ag alloy was discussed. The results showed that the titanium alloy sintered by vacuum furnace exhibited a microstructure consisting of α, β and a small amount of martensite phase; whilst the SPS sintered alloy exhibited a microstructure consisting of α, β and a small amount of martensite phase, as well as a nanostructured Ag homogeneously distributed at the boundaries of the β phases. The Ti-Nb-Ag alloy sintered by SPS possessed fracture strength nearly 3 times of the alloy sintered by vacuum furnace. © 2013 Elsevier Ltd.

Wen M.,Deakin University | Wen M.,Kunming Institute of Precious Metals | Wen C.,Swinburne University of Technology | Hodgson P.D.,Deakin University | Li Y.C.,Deakin University
Tribology Letters | Year: 2012

Surface mechanical attrition treatment (SMAT), a novel surface severe plastic deformation method, was carried out for titanium (Ti) to create a gradient-structured Ti (SMAT Ti). The tribological behaviour was studied under different loads and dry sliding conditions. The results showed that the deformation layer of SMAT Ti was about 160 μm. The friction and wear results showed that the wear resistance of SMAT Ti was enhanced compared to the coarse-grained (CG) counterpart. SMAT Ti showed abrasive wear under 1 and 5 N, and exhibited abrasive and adhesive wear under 2 N. While CG Ti showed abrasive and adhesive wear under 1-2 N, and exhibited abrasive wear under 5 N for the work hardening effects. © 2011 Springer Science+Business Media, LLC.

Wen M.,Deakin University | Wen M.,Kunming Institute of Precious Metals | Cizek P.,Deakin University | Wen C.,Swinburne University of Technology | And 2 more authors.
Scripta Materialia | Year: 2013

A nanostructured eutectic Ag-Cu alloy with alternate Ag and Cu lamellae was processed by surface mechanical attrition treatment (SMAT). The orientation/phase distributions of the eutectic Ag-Cu before and after SMAT were investigated using transmission electron microscopy combined with automated crystal orientation mapping. After SMAT, the top surface layer was transformed into a composite with isolated Cu phase dispersed in Ag. The interphase boundaries in the top surface layer were changed from the original cube-on-cube and hetero-twin orientation relationships into general large-angle boundaries accordingly. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Xu Y.,Kunming University of Science and Technology | Dong Y.,Kunming Institute of Precious Metals | Shi J.,Kunming University of Science and Technology | Xu M.,Kunming University of Science and Technology | And 2 more authors.
Catalysis Communications | Year: 2011

Au@Pt core-shell nanoparticles were synthesized by a simple one-step ultraviolet irradiation method and were then assembled on functionalized multiwalled carbon nanotubes (MWCNTs) surface. This new type of Au@Pt/MWCNTs composite catalysts was characterized by UV-vis spectrometry, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning TEM, HRTEM, and electrochemical techniques. The results revealed that the Au@Pt nanoparticles with an average diameter less than 5 nm were well coated on the MWCNTs surface. As compared with commercial Pt/C catalysts, the Au@Pt/MWCNTs prepared using Au/Pt atomic ratio of 1:1 exhibited distinctly higher activity and better stability toward methanol oxidation in alkaline media. © 2011 Elsevier B.V. All rights reserved.

Zheng T.,Platinum Technology | He J.,Platinum Technology | Zhao Y.,Platinum Technology | Zhao Y.,Kunming Institute of Precious Metals | Xia W.,Platinum Technology
Journal of Rare Earths | Year: 2014

Precious metal-support interaction plays an important role in thermal stability and catalytic performance of the automotive exhaust catalysts. The support is not only a carrier for active compounds in catalysts but also can improve the dispersion of precious metals and suppress the sintering of precious metals at high temperature; meanwhile, noble metals can also enhance the redox performance and oxygen storage capacity of support. The mechanism of metal-support interactions mainly includes electronic interaction, formation of alloy and inward diffusion of metal into the support or covered by support. The form and degree of precious metal-support interaction depend on many factors, including the content of precious metal, the species of support and metal, and preparation methods. The research results about strong metal-support interaction (SMSI) gave a theory support for developing a kind of new catalyst with excellent performance. This paper reviewed the interaction phenomenon and mechanism of precious metals (Pt, Pd, Rh) and support such as Al 2O3, CeO2, and CeO2-based oxides in automotive exhaust catalysts. The factors that affect SMSI and the catalysts developed by SMSI were also discussed. © 2014 The Chinese Society of Rare Earths.

An N.,Jilin University | An N.,Kunming Institute of Precious Metals | Wu P.,Jilin University | Li S.,Jilin University | And 2 more authors.
Applied Surface Science | Year: 2013

Iron oxide supported platinum catalysts were prepared by different methods, including co-precipitation, impregnation and colloid deposition methods. The catalytic properties of these catalysts were investigated for the complete oxidation of formaldehyde. It is found that the catalyst prepared by colloid deposition method (Pt/Fe2O3-CD) exhibited relatively high catalytic activity, which could completely oxidize HCHO even at room temperature. Based on a variety of physical-chemical characterization results, it is proposed that the presence of suitable interaction between Pt particles and iron oxide supports (i.e., PtOFe), which would influence the structure and properties of iron oxide supports, should play a positive role in determining the catalytic activity of Pt/Fe2O3-CD catalyst. © 2013 Elsevier B.V. All rights reserved.

Yu J.,Kunming Institute of Precious Metals | Bi X.,Kunming Institute of Precious Metals | Li Q.,Kunming Institute of Precious Metals
Xiyou Jinshu/Chinese Journal of Rare Metals | Year: 2013

Platinum group metals (PGMs) was a main composition of auto-catalysts, so recovery PGMs from spent auto-catalysts was a main way to resolve the PGMs resource shortage. Various separation methods of PGMs from spent auto-catalysts, for example, traditional precipitation (TP), solvent extraction (SX), ion exchange (IX) and molecule recognition technology (MRT), were reviewed according to 10 year's references and author's research practice. Separation base metals (BMs) from PGMs solution by cation ion exchange was used in recent years, industry practice proved that effectively separation BMs was a key link for separation PGMs each other. Various separation methods of PGMs had different advantages and disadvantages, for example, TP had longer procedure and lower separation efficiency; IX had the disadvantage of lower adsorption capacity and higher investment in apparatus; as to MRT, there was no Independent intellectual property, the price of separation materials and production cost were higher; while, SX had the advantage of higher separation efficiency, higher recovery, oil phase recycled over 100 times, lower cost, larger or smaller production scale, became a key technology of separation PGMs from spent auto-catalysts, and would have a strong potential and broad prospects.

Xie M.-J.,Yunnan University | Yang X.-D.,China Pharmaceutical University | Liu W.-P.,Kunming Institute of Precious Metals | Yan S.-P.,Nankai University | Meng Z.-H.,Kunming Hospital of Population and Health
Journal of Inorganic Biochemistry | Year: 2010

A new insulin-enhancing oxovanadium complex 5-chloro-salicylaldhyde ethylenediamine oxovanadium (V) ([V2O2(μ-O)2L2]) has been synthesized. The complex was characterized by a variety of physical methods, including X-ray crystallography. The X-ray diffraction analysis show a dinuclear complex of two six-coordinate vanadium centers doubly bridged by the oxygen atoms of the Schiff base ligand with a V2O2 diamond core. The complex was administered intragastrically to STZ-diabetic rats for 2weeks. The biological activity results show that the complex at the dose of 10.0 and 20.0mgVkg-1, could significantly decrease the blood glucose level and ameliorate impaired glucose tolerance in STZ-diabetic rats. That results suggested that the complex exerts an antidiabetic effect in STZ-diabetic rats. Furthermore, the complex ([V2O2(μ-O)2L2]) had permeability above 10-5cm/s. The experimental results suggested that the vanadium complex permeates via a passive diffusion mechanism. It was also suggested the complex with salen-type ligands has good lipophilic properties and better oral administration. The cytotoxicity of the complex ([V2O2(μ-O)2L2]) on Caco-2 cells was measured by a decrease of cell viability using the MTT assay suggesting that the chlorine atom at C4 of complex [V2O2(μ-O)2L2] increased cytotoxicity for vanadium complexes. © 2010 Elsevier Inc.

Mao Y.,Kunming Institute of Precious Metals | Wang C.,Kunming Institute of Precious Metals | Yang H.,Kunming Institute of Precious Metals
Materials Letters | Year: 2015

In this work, we demonstrate the synthesis of silver nanowires via a nonaqueous method that employs ethylene glycol to reduce silver nitrate into metallic silver which deposited on the pre-synthesized silver nucleants. The silver nucleants with different morphologies were synthesized by adjusting the reaction temperature and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible spectroscopy (UV-vis). The results indicated that the silver nucleants with dendritic and nanorice morphologies could be prepared under the temperature of 313 K, 353 K, and 393 K, respectively. Specially, it was demonstrated for the first time that the silver nanowires with high aspect ratio and uniformity could be synthesized rapidly via the silver nucleant with the nanorice morphology. © 2014 Elsevier B.V. All rights reserved.

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