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Mesoporous and nanocrystalline sol-gel derived NiTiO3 at the low temperature: Controlling the structure, size and surface area by Ni:Ti molar ratio

Mohammadi, M. R ; Sharif University of Technology | 2010

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  1. Type of Document: Article
  2. DOI: 10.1016/j.solidstatesciences.2010.07.015
  3. Publisher: 2010
  4. Abstract:
  5. Nanocrystalline nickel titanate (NiTiO3) thin films and powders with mesoporous structure were produced at the low temperature of 500 °C by a straightforward particulate sol-gel route. The sols were prepared in various Ni:Ti molar ratios. X-ray diffraction and Fourier transform infrared spectroscopy revealed that the powders contained mixtures of the NiTiO 3 and NiO phases, as well as the anatase-TiO2 and the rutile-TiO2 depending on the annealing temperature and Ni:Ti molar ratio. Moreover, it was found that Ni:Ti molar ratio influences the preferable orientation growth of the nickel titanate, being on (202) planes for the nickel dominant powders (Ni:Ti ≥ 75:25) and on (104) planes for the rest of the powders (Ni:Ti: ≤ 50:50). The average crystallite size of the powders annealed at 500 °C was in the range 1.5-2.4 nm and a gradual increase occurred up to 8 nm by heat treatment at 800 °C. The activation energy of crystal growth decreased with an increase of Ni:Ti molar ratio, calculated in the range 24.93-37.17 kJ/mol. Field emission scanning electron microscope analysis revealed that the deposited thin films had mesoporous and nanocrystalline structure with the average grain size of 20-35 nm. Moreover, atomic force microscope images presented that the thin films had a hill-valley like morphology with roughness mean square in the range 41-57 nm. Based on Brunauer-Emmett-Taylor analysis, the synthesized powders showed mesoporous structure containing pores with needle and plate like shapes. The mesoporous structure of the powders was stable at high annealing temperatures and one of the highest surface areas (i.e., 156 m2/g) reported in the literature was obtained for the powder containing Ni:Ti = 50:50 at 500 °C
  6. Keywords:
  7. Nanocrystalline ; Particulate sol-gel ; Annealing temperatures ; Atomic force microscope images ; Average grain size ; Field emission scanning electron microscopes ; Low temperatures ; Mesoporous ; Mesoporous structures ; Molar ratio ; Nano-crystalline nickel ; Nano-crystalline structures ; Nanocrystallines ; Nickel titanate ; Nickel titanates ; Orientation growth ; Roughness mean squares ; Sol-gel routes ; Surface area ; Synthesized powder ; Taylor analysis ; TiO ; Activation energy ; Annealing ; Crystal growth ; Crystallite size ; Field emission ; Fourier transform infrared spectroscopy ; Fourier transforms ; Gels ; Grain boundaries ; Nickel ; Oxide minerals ; Powders ; Scanning electron microscopy ; Sol-gel process ; Sol-gels ; Sols ; Surface structure ; Thin films ; Titanium dioxide ; Vapor deposition ; X ray diffraction ; X ray powder diffraction ; Nanocrystalline powders
  8. Source: Solid State Sciences ; Volume 12, Issue 9 , 2010 , Pages 1629-1640 ; 12932558 (ISSN)
  9. URL: http://www.sciencedirect.com/science/article/pii/S1293255810002980