project viva (1) 2010

Preparation and Characterization of TiO2 nano particles, Effect of Calcination Temperature by sol-gel method: 

Preparation and Characterization of TiO 2 nano particles, Effect of Calcination Temperature by sol-gel method Ajay Rakkesh. R ajayrakkesh@gmail.com

Introduction:: 

Introduction: In recent years, the photocatalytic decomposition of organic pollutants in water has received much attention TiO 2 is the most popular semiconductor used in photocatalytic processes Titanium dioxide (TiO2) is a IV-VI semiconducting material. TiO2 exists in three polymorphs, such as anatase, rutile and brookite. Among these polymorphs, rutile phase is the most thermodynamically stable phase whereas brookite and anatase are metastable and they can be transformed to rutile on heating to high temperature (~600-700 ° C). The bandgap of rutile and anatase forms are 3.03 eV and 3.18 eV. Particles smaller than several tens of nanometers in primary particle diameter (nanoparticles) are of interest for the synthesis of new materials because of their low melting point, special optical properties, high catalytic activity, and unusual mechanical properties compared with their bulk materials. sol-gel technique has been adopted as one of the versatile methods for the preparation of anatase TiO 2 nano particles

Crystal structure of TiO2: 

Crystal structure of TiO 2

Experimental details: 

Experimental details The samples were prepared using the sol-gel method. The chemicals used for the preparation of nano TiO 2 includes ▪ Titanium(IV) isopropoxide (4.65 ml) ▪ Glacial acetic acid (8.95 ml) ▪ water (98.75 ml) ● Titanium (IV) isopropoxide (4.65 mL) was hydrolyzed using 8.95mL glacial acetic acid at 0◦C. ● To this solution 98.75 mL of water was added drop wise under vigorous stirring for 1 h, subsequently, the solution sonicated for 15min in ice bath and continued the stirring for further 4.5 h. ● The solution was ultrasonicated for 15 min in ice bath until a clear solution of TiO2 nanocrystals was formed. ● The prepared solution was kept in dark for nucleation process for 24 h. ● Then, the solution was placed in an oven at the temperature of 70◦C for a period of 12 h for gelation process. ● The gel was then dried at 110 ◦C and obtained powder was crushed well and calcined in a muffle furnace at various temperature for 2 h.

RESULTS AND DISCUSSION X-ray diffraction: 

RESULTS AND DISCUSSION X-ray diffraction Calcination temperature(°c) Crystalline size(nm) 500°c ~ 12 120°c ~ 7 The XRD pattern of the as-prepared TiO 2 showed the presence of very broad peaks. The broad peaks indicate either particles of very small crystalline size, or particles are semi crystalline in nature. All the diffraction lines are assigned well to anatase crystalline phase of titanium dioxide. The XRD pattern is in excellent agreement with a reference pattern (JCPDS 89-4921) of titanium dioxide. It should be noted that only anatase TiO 2 can be detected and no rutile phase can be found in this sample. The crystallite size of the TiO 2 nano particles were found out using Scherer`s formula, The Scherer’s formula is given by d = 0.94 λ / (β cosθ)

Scanning electron microscopy : 

Scanning electron microscopy Selected SEM images of some of the thermally calcinated TiO 2 nanoparticles. The global and uniform particles indicate in images that are coherent together. The particle size is around 11 nm.

Raman spectroscopy : 

Raman spectroscopy The Raman spectra’s for two samples shows the peak positions (cm−1) of 120°c and 500°c heated samples. As expected from the confinement theory all peaks get broader as the crystallite size decreases The broadening and shifts of the Raman line shapes can be explained by the phonon confinement model

Fourier transformation infrared spectroscopy : 

Fourier transformation infrared spectroscopy The FTIR band at 3789 cm¯¹ showed the presence of amide N-H stretching vibrations. It can be observed apparently that strong band in the range of 880 and 450 cm−¹ are associated with the characteristic vibrational modes of TiO 2 . The absorption at 3455 cm−¹ indicates that the presence of hydroxy, which is probably due to the fact that the spectra were not recorded in situ and some readsorption of water from the ambient atmosphere has occurred. The absorption at 1632 cm−¹ may be related to hydroxyl groups of molecular water. The absorption at 2924, 2922 and 2853 cmˉ1 indicates that the presence of alkyl C-H stretching vibrations .

Conclusion: 

Conclusion Anatase TiO 2 nanoparticles were synthesized by the modified sol-gel method, and then calcinated in two different temperatures 120°c and 500°c for 2 hours. The XRD and RAMAN spectra showed that the prepared and characterized TiO 2 nanoparticles are in anatase phase. SEM revealed powder morphology and showed that the particles size around 11 nm. Peaks in Raman Spectra get narrower as the result of calcination and this can be described in broad terms on the basis of phonon confinement theory. In our study, it is observed that the particle size decreases with decreasing calcination temperature. The particles find application as photocatalysis.

PowerPoint Presentation: 

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