Characteristics of Tio 2 Nanoparticles Synthesized Through Low Temperature Aerosol Process (original) (raw)
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Characteristics of Titania Nanoparticles Synthesized Through Low Temperature Aerosol Process
2005
As one of the important process alternatives for the synthesis of nano materials with lower costs, flexibility and versatility, vapor phase synthesis of titania nano particles continue to attract attention. A low temperature aerosol process for the synthesis of titania nano particles is demonstrated by elucidating the influence of temperature, molar ratio of H 2 O/TiCl 4 and concentration of precursors on particle size and phase composition. This paper highlights the advantages of employing amorphous phase titania powder as solid precursor for its transformation to the rutile phase at temperatures less than 973K through vapor phase hydrolysis of TiCl 4. A mechanistic hypothesis is proposed to explain the catalytic role of water vapor in the enhancement of amorphous to anatase phase transformation at high (15 to 27) molar ratio of H 2 O/TiCl 4 .
Synthesis of TiO2 Nanoparticles Using Chemical Vapor Condensation
MRS Proceedings
Nano-sized TiO2 particles are of interest for many applications, including use as photocatalysts and in heat transfer fluids (nanofluids). In the present study, TiO2 nanoparticles with controllable phase and particle size have been obtained through homogeneous gas-phase nucleation using chemical vapor condensation (CVC). The phase and particle size of TiO2 nanoparticles under various processing conditions have been characterized using x-ray diffraction and transmission electron microscopy. Chamber temperature and pressure were found to be two key parameters affecting particle phase and size. Pure anatase phase was observed for synthesis temperatures as low as 600 °C with chamber pressure varying from 20-50 Torr. When the furnace temperature was increased to 1000 °C at a pressure of 50 Torr, a mixture of anatase and rutile phases was observed, with the predominant phase being anatase. The average particle size under all the experimental conditions was observed to be less than 20 nm.
Journal of The American Ceramic Society, 2004
Three types of tetraalkyl ammonium hydroxides (TANOHs)—namely, tetramethyl ammonium hydroxide (TMNOH), tetraethyl ammonium hydroxide (TENOH), and tetrabutyl ammonium hydroxide (TBNOH)—were used as peptizing agents for the hydrothermal synthesis of nanocrystalline TiO2 powders. X-ray diffractometry, Brunauer-Emmett-Teller surface-area analysis, differential thermal analysis-thermogravimetry, scanning electron microscopy, and transmission electron microscopy were used to characterize the powders. The results showed that the carbon-chain length of TANOHs had a great influence on the particle size, particle shape, and the phase transformation of the hydrothermally derived TiO2 particles. Anatase phase was obtained in all the samples, regardless of the peptizer used, and the particle size increased as the peptizer cation size decreased. In the presence of TMNOH, the particle shape changed from spherical at low concentration to rodlike with increasing TMNOH concentration, whereas a transition from a spherical morphology to an asterisk-like structure was observed in the TENOH peptized samples. However, spherical particles were formed in all the TBNOH peptized samples. The anatase-rutile transition occurred at a lower temperature for the TENOH-derived powders, relative to the other two peptizers.
Vapor synthesis of titania powder by titanium tetrachloride oxidation
AIChE Journal, 1991
Formation of titania particles by vapor-phase oxidation of titanium tetrachloride was studied in an aerosol reactor between 1,200 and 1,723 K. The effect of process variables (reactor residence time, temperature, and reactant concentration) on powder size and phase characteristics was investigated using the differential mobility particle sizer, scanning electron microscopy, and X-ray diffraction. Titania particles were primarily anatase though the rutile weight fraction increased with increasing reactor temperature. The geometric number average diameter of the particles was between 0.13 and 0.35 pm, and the geometric standard deviation of the particle size distribution was about 1.4. The average particle size increased with increasing temperature, inlet TiC1, concentration, and residence time. The observed changes in the particle size distribution were compared with those predicted by solving the aerosol dynamic equation by a sectional method and accounting for coagulation and firstorder chemical reaction. While variations in the process variables resulted in discernible changes in the size of the particles, the spread of the distribution remained rather unaffected.
Formation mechanism of TiO2 nanoparticles in H2O-assisted atmospheric pressure CVS process
Powder Technology, 2011
Atmospheric Pressure Chemical Vapor Synthesis (APCVS) route was used for the synthesis of titania (TiO 2) nanoparticles. The mechanism of nanoparticles formation were investigated by transmission electron microscopy (TEM), X-ray diffraction analysis, nitrogen adsorption technique (BET) and TG-DTA results for assynthesized powders. The effect of precursor temperature, H 2 O effect and effective reaction (ER) zone temperature on the phase structure, nanoparticle size, agglomeration, coagulation, coalescence and nanoparticle morphology were also studied. Also, the effect of thermal velocity on the rate of powder formation, coagulation and coalescence of nanoparticles were discussed theoretically and experimentally. With introducing H 2 O, the appropriate rate of powder formation increased and size, coalescence and coagulation of nanoparticles decreased, significantly. Also, by using H 2 O vapor, the crystallinity of nanoparticles sharply increased. The minimum temperature for the synthesis of full anatase phase in atmospheric pressure was obtained to be 700°C. With increasing precursor temperature, thermal velocity and the rate of powder formation increased. Also, no phase transformation was observed but size, coagulation, coalescence and agglomeration of titania nanoparticles increased whereas the morphology of nanoparticles was similar.
Materials Advances, 2021
The development of titania (TiO2) nanomaterials for next-generation photonic, optoelectronic, and catalytic applications necessitates a facile and cost-effective synthetic methodology for precisely tuning the composition, phase, and morphology at nanometer scales. In this review, an attempt has been made to comprehend the progress of the emerging and rapidly developing synthesis methods evolved for the low-temperature synthesis of titania with a particular emphasis on sub-zero temperature. Insights and understandings of how the temperature affects the characteristic surface properties and morphology of titania, along with a detailed discussion on the material characteristics for various technological device applications are dealt with various methods of analysis. Furthermore, the temperature-dependent morphological (0D–3D) and structural changes and their impact on different energy-harvesting and storage and water remediation applications are elucidated. Thus, this review specifically opens the understanding of different TiO2 polymorph syntheses and their physiochemical comprehension for advanced technological device performance enhancement.
Preparation of titania particles by thermal hydrolysis of TiCl4 in n-propanol solution
Materials Chemistry and Physics, 2003
Titania has been used extensively in pigment, cosmetics, photocatalyst and coating. It has been reported that the spherical powders with a narrow size distribution is the most desired state. In this study, titania powders were synthesized by thermal hydrolysis of TiCl 4 in a mixed solvent of n-propanol and water. The effects of preparation parameters such as synthesis temperature, the concentration of reacting species, the alcohol/water ratio, and the concentration of steric dispersant, were investigated. Hydroxypropyl cellulose (HPC) was used as a steric dispersant in this study. The morphology of the precipitates was controlled by the dielectric constant of the solvent. This can be regulated by changing the volume ratio of n-proponal to water (RH ratio) of the mixed solvent. The titania sample synthesized at an RH ratio of 3 was spherical and uniform-dispersed. Adding HPC made particles more uniformed-dispersed. The titania particles in different solid contents were all spherical, but the particle size increased with an increase of the solid content. The titania particles became not uniform at high synthesized temperature. The effect of the temperature gradient in the solvent plays an important role on the morphology of TiO 2 .