An investigation of ZrO2: V nano materials

The structural calculations such as band structure, density of states and optical properties were carried out under the framework of the Density Functional Theory (DFT). A theoretical analysis by computer simulation is expected to clarify the doping effects in detail and compare well with experimental results.
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An investigation of ZrO2:V nano materials JOURNAL OF SCIENCE OF HNUE DOI: 10.18173/2354-1059.2015-0032 Mathematical and Physical Sci., 2015, Vol. 60, No. 7, pp. 55-61 This paper is available online at http://stdb.hnue.edu.vn AN INVESTIGATION OF ZrO2 :V NANO MATERIALS Nguyen Minh Thuy1 , Le Thi Hong Hai2 , Pham Thi Minh Thao2 , Tran Thi May1 , Nguyen Phuong Lien1 and Pham Tien Lam3 1 Facultyof Physics, Hanoi National University of Education 2 Faculty of Chemistry, Hanoi National University of Education 3 Japan Advanced Institute of Science and Technology, Japan Abstract. ZrO2 nanopowders were synthesized using the hydrothermal method in an acid or base (alkaline) environment. The influence of preparation condition on the morphology, crystall phases and particle size in the sample has been investigated in order to obtain highly visible catalytic activity of ZrO2 :V nanocrystals. The ZrO2 :V nanoparticles have a monoclinic phase with average crystal size of 10 - 20 nm and they exhibit long tailed absorption in visible light. FTIR results show the existence of surface OH-groups on the sample, indicating capability of the ZrO2 :V catalyst for biodiesel production. The catalytic activity of ZrO2 :V nanocrystals examined while undergoing ODH n-Butane reaction shows that Vanadium ions play an important role in the active catalytic centers in the reaction. The structural calculations such as band structure, density of states and optical properties were carried out under the framework of the Density Functional Theory (DFT). A theoretical analysis by computer simulation is expected to clarify the doping effects in detail and compare well with experimental results. Keywords: Zirconium, absorption, catalyst, density functional theory.1. Introduction Zirconium ZrO2 is an important ceramic materials that possesses excellent thermal,dielectric, mechanical, chemical and biocompatibility properties [1, 2]. Zirconium is also a usefulcatalysis or an important support material for catalysis, having acidic and alkaline properties[1, 3]. In recent decades, ZrO2 mechanical properties such as elasticity, structural vibration andthermoelasticity) have been widely investigated [2-4]. Zirconium nano-particles will be widelyapplied in high-performance structural engineering ceramics and catalyst industries [1, 2]. Manymethods have been used to obtain ZrO2 nano-particles or superfine powders, including vaporphase hydrolysis, the sol-gel process, the hydrothermal process and the combustion method orreverse micelles. Due to the wide band gap of zirconia (4 - 6 eV) it exhibits poor photocatalyticactivities. However, heterogeneous ion doping adjusts the band gap and can make possible visiblelight absorption of ZrO2 [4]. In this work, ZrO2 and ZrO2 :V nanopowders were synthesized using the hydrothermalmethod. We investigated the influence of the preparation condition on the morphology, crystalReceived October 27, 2015. Accepted November 30, 2015.Contact Nguyen Minh Thuy, e-mail address: thuynm@hnue.edu.vn 55 Nguyen Minh Thuy, Le Thi Hong Hai, Pham Thi Minh Thao and Tran Thi Mayphases and particle size in the sample in order to obtain high visible photoactivity of ZrO2 :Vnanocrystals. A lack of understanding of the electronic structure and impurities existent in ZrO2 :Vnanocrystals leads to continued debate. A theoretical analysis by computer simulation is expectedto clarify the doping effects in detail [5]. With this aim, the plane-wave ultrasoft pseudopotentialsmethod within the framework of the density functional theory (DFT) [6, 7] has been adopted inthis work. At the lattice parameters of supercells where ion doping occurred, electronic structuresand optical properties of the optimized supercells were calculated. Our calculation results havebeen compared with experimental results and other calculated results. Based on these results, themechanism of ZrO2 doped with ion has been discussed.2. Content2.1. Experimental and calculation method V-doped ZrO2 was synthesized by using ZrOCl2 , citric acid (CA), NH4 NO3 , NH3 10%,V2 O5 /NaOH 2 M or HCl 2 M and C2 H5 OH. All chemicals were of analytical reagent grade. PureZirconium powder was prepared using the hydrothermal method and the following procedure:First, ZrOCl2 was added drop by drop to CA and NH4 NO3 solvent (with V2 O5 /NaOH or HClfor the doping process), which was continuously stirred for 20 minutes Then the mixture wastransferred into an autoclave and kept at 190 ◦ C for 24 h. After centrifugation and ...