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Continuous-reactor, pH-controlled synthesis of multifunctional mesoporous nanocrystalline anatase aggregates

X-Ray Diffractometer (XRD) application in the research of the phase identification, crystal lattice structure and calculate crystal size
MIAM | 1 Apr 2016

Continuous-reactor, pH-controlled synthesis of multifunctional mesoporous nanocrystalline anatase aggregates

Research Published at: Chemical Engineering Journal, , Volume 287, 1 March 2016, Pages 398-409

https://doi.org/10.1016/j.cej.2015.11.045

Authors: Benedetto Marelli,† Chiara E. Ghezzi,† Jake E. Barralet,‡ Aldo R. Boccaccini,§ and Showan N. Nazhat*,†

  • Department of Mining and Materials Engineering, Faculty of Dentistry, McGill University,
  • Department of Materials Science and Engineering, University of Erlangen-Nuremberg, Germany

Research Method:

For phase identification, X-ray diffraction (XRD) was performed. scanning took place between 20° and 70° (2h) with 0.005°step/second. Background subtraction and smoothening were performed on EVA software. The XRD patterns were compared against JCPDS reference data of anatase (#00-021-1272). Crystallite size was determined using following Scherrer equation:

Dhkl = kλ/(β cosθ)

Where, Dhkl is crystal size in nm, k is 0.89, k is wavelength of Cu radiation (0.1549 nm), b is FWHM (Full Width at Half Maximum) corresponding to (hkl) plane in radians, and h is the Bragg angle corresponding to (hkl) plane in radians.

XRD research fig 

Fig. 3. XRD patterns of TiO2 products synthesized at: (a) 70 °C, (b) 80 °C, and (c) 90 °C compared to anatase reference pattern. Constant conditions: [TiCl4]feed = 0.1 M, pHsteady-state = 3, τ: 30 min.

Rutile peak at 27.5° is evident. At pH 6 the product became amorphous.

XRD research fig 2

Fig. 4. XRD patterns of steady state products compared to anatase reference pattern: The effect of pH: (a) pH 2, (b) pH 3, (c) pH 4, (d) pH 5; constant conditions: T = 80 °C, [TiCl4]feed = 0.1 M, τ = 30 min. The effect of [TiCl4]feed: (e) 0.1 M, (f) 0.2 M, (g) 0.3 M, (h) 0.4 M, (i) 0.5 M; constant conditions: T = 80 °C, pHsteady-state = 3, τ = 30 min.

Results:

  • XRD patterns show all characteristic of body-centered tetragonal anatase phase, according to JCPDS #00-021-1272 (data base);
  • The peaks are broad and low density, indicative of nano-sized-crystals;
  • The average diameters of the anatase crystallites (4.01~ 5.5 nm) nicely agree with the TEM crystallite size data;
  • The peaks overall get shorter and broader, revealing a decrease in crystallinity.
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