scholarly journals Thermal study of the anatase–rutile structural transitions in sol-gel synthesized titanium dioxide powders

2005 ◽  
Vol 70 (4) ◽  
pp. 675-679 ◽  
Author(s):  
Farias de ◽  
Cecilia Silva ◽  
Thomaz Restivo
Keyword(s):  
Titanium Dioxide ◽  
Crystallite Size ◽  
Anatase Phase ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Metal Chlorides ◽  
Sol Gel Process ◽  
Dta Analysis ◽  
Diffraction Patterns ◽  
Brookite Phase

Titanium dioxide powders were synthesized by the sol?gel process using titanium tetrabutoxide as the precursor. The syntheses were performed in saturated aqueous solutions of KCl, CaCl2, NiCl2, CoCl2 and MnCl2, and in dimethylformamaide (DMF) and dimethylsulfoxide (DMSO) solutions. The obtained X-ray diffraction patterns show that all samples were crystalline (anatase phase) with some minor amounts of a brookite phase. It is worth noting that the anatase phase was obtained independent of any previous or further treatment of the synthesized powder, such as hydrothermal or heat treatment. For the titanium dioxide powders synthesized in saturated aqueous solution of metal chlorides (mean crystallite size = 11 nm), the anatase?rutile transition occurred in the range 455?570 ?C, depending on the considered sample, as verified by DTA analysis. In the powders synthesized in DMF or DMSO solutions (means crystallite size = 6 nm), the same structural transition occurred at 485 ?C.

Self-cleaning Cotton Fabrics

2006 ◽  
Vol 920 ◽  
Author(s):  
Kaihong Qi ◽  
Walid A Daoud ◽  
John Xin ◽  
C.L. Mak
Keyword(s):  
Titanium Dioxide ◽  
Ambient Pressure ◽  
Anatase Phase ◽  
Sol Gel ◽  
Cotton Fabrics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Titanium Dioxide Films ◽  
Sol Gel Process ◽  
Self Cleaning

AbstractNanocrystalline anatase titanium dioxide films were successfully produced on cotton fabrics from alkoxide solutions under ambient pressure using the low temperature sol-gel process. At a temperature as low as 40°C, only anatase phase formed from X-ray diffraction spectroscopy (XRD). Field scanning electron microscopy (FESEM) images show the formation of uniform continuous films of titanium dioxide on cotton fabrics. The self-cleaning properties of these fabrics were evaluated by measuring anti-bacterial activities and the decomposition of a colorant Neolan Blue 2G. The results indicated that anatase treated cotton fabrics exhibited good self-cleaning performance.

Microstructural characteristics and photoluminescence performance of nanograined thermally treated CeO2-TiO2 xerogels

2007 ◽  
Vol 22 (5) ◽  
pp. 1182-1187
Author(s):  
Amita Verma ◽  
A.K. Srivastava ◽  
N. Karar ◽  
Harish Chander ◽  
S.A. Agnihotry
Keyword(s):  
Electron Microscopy ◽  
Crystallite Size ◽  
Sol Gel ◽  
Structural Features ◽  
X Ray Diffraction ◽  
Molar Ratios ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Crystallite Sizes ◽  
Thermally Treated

Nanostructured thermally treated xerogels have been synthesized using a sol-gel process involving cerium (Ce) chloride heptahydrate and titanium (Ti) propoxide mixed in different Ce:Ti molar ratios. Structural features of the xerogels have been correlated with their photoluminescence (PL) response. The crystallite sizes in the samples lie in the nanorange. The x-ray diffraction and transmission electron microscopy results have confirmed the coexistence of CeO2 and TiO2 nanocrystallites in these xerogels. In general, a decrease in the CeO2 crystallite size and an increase in the TiO2 crystallite size are observed in the xerogels as a function of Ti content. Scanning electron microscopy results have evidenced the evolution of ordered structure in the xerogels as a function of TiO2 content. Although both of the phases (CeO2 and TiO2) have exhibited PL in ultraviolet and visible regions, the major luminescence contribution has been made by the CeO2 phase. The largest sized CeO2 crystallites in 1:1 thermally treated xerogel have led to its highest PL response. PL emission in the xerogels is assigned to their nanocrystalline nature and oxygen vacancy-related defects.

Structural, Electrical, and AC-Resistivity Studies of BNT-KN Piezoelectric Ceramics

2020 ◽  
Vol 557 (1) ◽  
pp. 28-42
Author(s):  
Srinivas Pattipaka ◽  
Sweety Bora ◽  
D. Pamu
Keyword(s):  
Dielectric Response ◽  
Sol Gel ◽  
Relaxor Behavior ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Critical Temperatures ◽  
Two Phase ◽  
Structure Morphology ◽  
Sol Gel Process ◽  
Diffraction Patterns

The lead-free (1 – x) Bi0.5Na0.5TiO3 – x KNbO3 (BNT-KN; x = 0 – 0.12) composite ceramics have been synthesized by a sol-gel process. Their structure, morphology, AC conductance and dielectric response were studied systematically. The X-ray diffraction patterns of BNT-KN revealed a morphotropic phase boundary between a rhombohedral and a pseudocubic structure. The temperature-dependent dielectric response of pure BNT revealed two-phase transitions at 200 °C (TR-T or Td) and 320 °C (TC). Furthermore, the critical temperatures were found to shift to lower values with increasing KN concentration. The manifested relaxor behavior was well confirmed by a modified Curie – Weiss law. The hopping conduction mechanism in BNT-KN was characterized through AC-resistivity analysis.

X-ray structure and microstructure determination of the mixed sesquioxides (Eu1−xYbx)2O3prepared by a sol–gel process

2003 ◽  
Vol 36 (6) ◽  
pp. 1411-1416 ◽  
Author(s):  
Z. K. Heiba ◽  
Y. Akin ◽  
W. Sigmund ◽  
Y. S. Hascicek
Keyword(s):  
Crystallite Size ◽  
Rietveld Method ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
X Ray Diffraction ◽  
X Ray ◽  
Profile Fitting ◽  
Cationic Distribution ◽  
Sol Gel Process ◽  
Multiple Orders

Polycrystalline samples of (Eu1−xYbx)2O3(x= 0.0, 0.1, 0.2, 0.5, 0.8, 0.9 and 1.0) were synthesized by a sol–gel process. X-ray diffraction data were collected and the crystal structures were refined by the Rietveld method. All samples are found to have the same crystal system and formed solid solutions over the whole range ofx. The lattice parameters are found to vary linearly with the compositionx. The cationic distribution over the two non-equivalent sites 8band 24dof the space group Ia{\bar 3} is found to be random in the range 0.0 <x≤ 0.5 and preferential in the range 0.5 <x≤ 1.0. Replacing Eu3+and Yb3+by each other introduces slight changes in the atomic coordinates. Crystallite size and microstrain analysis are performed on single and multiple orders for each sample using profile fitting and the Warren–Averbach method. The obtained values of microstrain are correlated with the distribution of the rare earth (RE) ions over the two cationic sites of the structure. The average crystallite size ranges from 35 to 96 nm and the mean-square strain from 0.052 to 0.225 × 10−2.

Structure and microstructure characterization of the mixed sesquioxides (Gd1−xYbx)2O3and (Gd1−xHox)2O3prepared by sol–gel process

2005 ◽  
Vol 38 (2) ◽  
pp. 306-310 ◽  
Author(s):  
Z. K. Heiba ◽  
L. Arda ◽  
Y. S. Hascicek
Keyword(s):  
Crystallite Size ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Rare Earth Ions ◽  
X Ray Diffraction ◽  
Refinement Method ◽  
Cationic Distribution ◽  
Sol Gel Process ◽  
Structure And Microstructure

Polycrystalline samples of (Gd1−xYbx)2O3and (Gd1−xHox)2O3(0.0 ≤x≤ 1.0) were synthesized by a sol–gel process. X-ray diffraction data were collected and crystal structure and microstructure analyses were performed using the Rietveld refinement method. All samples were found to have the same crystal system and formed solid solutions over the whole range ofx. For the system (Gd1−xHox)2O3, the cationic distribution over the two non-equivalent sites 8band 24dof the space groupIa\bar{3} were found to be random for all values ofx. For (Gd1−xYbx)2O3, the distribution is random in the range 0.0 <x≤ 0.5 and preferential in the range 0.5 <x≤ 1.0. The lattice parameters are found to vary linearly with the compositionx. Replacing Gd3+and Yb3+, or Gd3+and Ho3+, by each other introduces slight changes in relative atomic coordinates. Crystallite size and microstrain analyses were performed along different crystallographic directions and both are found to vary anisotropically with the composition parameter (x). The obtained values of microstrain are correlated with the distribution of the rare earth ions over the two cationic sites of the structure. The average crystallite size ranges from 45 to 144 nm and the root mean square (r.m.s.) strain from 0.018 to 0.409 × 10−2.

A Study on the Preparation of Nano-Crystalline Barium Titanate Powder by a Sol-Gel Method

2007 ◽  
Vol 121-123 ◽  
pp. 53-56 ◽  
Author(s):  
J. Azadmanjiri ◽  
Hojjatollah K. Salehani ◽  
A. Dehghan Hamedan ◽  
M. Sadeghi
Keyword(s):  
Crystallite Size ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
Uniform Size ◽  
Impedance Analyzer ◽  
X Ray ◽  
Nano Crystalline ◽  
Sol Gel Process ◽  
Different Temperatures ◽  
Scanning Electron

In this work, high purity BaTiO3 (BT) nano-powders by a sol-gel process was prepared with Ba(NO3)2 and Ti(C4H9O)4 materials in order to acquire uniform size grains. The effects of the crystallinity, microstructure of BT nano-powders calcined at different temperatures and dielectric properties of the ceramics were investigated by XRD, SEM and impedance analyzer, respectively. Scanning electron microscopy and X-ray diffraction investigation revealed cubic plates and crystallite size. The results revealed that crystallite size and calcination temperature of BT and influence on the dielectric constant.

Properties and microstructure of thin LiNbO3 films prepared by a sol-gel process

1987 ◽  
Vol 2 (5) ◽  
pp. 595-605 ◽  
Author(s):  
D. P. Partlow ◽  
J. Greggi
Keyword(s):  
Sol Gel ◽  
Epitaxial Films ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
Film Properties ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Oriented Polycrystalline ◽  
Diffraction Patterns ◽  
Gel Processing

Thin LiNbO3 films were prepared from polymerized sol-gel precursor solutions having various concentrations and water:alkoxide ratios in an effort to investigate the effects of these and other processing variables on the resultant film properties and microstructure. Films deposted on silicon substrates were mostly amorphous when pyrolyzed at 435°C for 30 min. Randomly oriented polycrystalline films having distinctive microstnietures were produced using longer heating times or higher temperatures. All of the films exhibited low refractive indices due to porosity, which was attributed to the low level of hydrolysis water required to produce stable polymeric precursor solutions. When single-crystal LiNbO4 was used as the substrate, epitaxial growth of the film resulted. This ideal case establishes the feasibility of producing epitaxial films via sol-gel processing. All films were characterized by transmission electron microscopy (TEM) and thin-film x-ray diffraction patterns.

Preparation of luminescent inorganic core/shell-structured nanoparticles

2011 ◽  
Vol 1342 ◽  
Author(s):  
Moritz Milde ◽  
Sofia Dembski ◽  
Sabine Rupp ◽  
Carsten Gellermann ◽  
Gerhard Sextl ◽  
...  
Keyword(s):  
Sol Gel ◽  
Core Shell ◽  
X Ray Diffraction ◽  
Coating Solution ◽  
Transmission Electron ◽  
Composition And Structure ◽  
Sol Gel Process ◽  
Shell Composition ◽  
Diffraction Patterns ◽  
Process Annealing

ABSTRACTSiO2 nanoparticles (NPs) were coated with Eu3+-doped calcium phosphate (CP) and Mn2+-doped ZnO to give Zn2SiO4 via a modified Pechini sol-gel process. Annealing at high temperatures resulted in NPs with an amorphous core and a crystalline luminescent shell. It was shown that this procedure can be applied to silica cores with diameters below 300 nm. By transmission electron microscopy, elemental analysis and from X-ray diffraction patterns it was determined that shell composition and structure are influenced by the annealing temperature and pH of the coating solution. Measurements of photoluminescence intensities displayed their dependency on the concentration of dopant in the resulting core/shell NPs.

Structural and Thermal Studies of Titanium Dioxide Gel Modified with Anatase Isostructural Zircon Silicate

2018 ◽  
Vol 930 ◽  
pp. 73-78
Author(s):  
Eduardo Felipe de Carli ◽  
Natali Amarante da Cruz ◽  
Hiana Muniz Garcia ◽  
Jusinei Meireles Stropa ◽  
Lis Regiane Vizolli Favarin ◽  
...  
Keyword(s):  
Phase Transition ◽  
Titanium Dioxide ◽  
Rietveld Method ◽  
Anatase Phase ◽  
Sol Gel ◽  
Thermal Studies ◽  
Rutile Phase ◽  
Structural Rearrangements ◽  
X Ray Diffraction ◽  
X Ray

Important changes in anatase crystal structure are responsible for the consequent anatase-to-rutile phase transition in titanium dioxide powders. In order to investigate several structural rearrangements occurring in anatase phase obtained by hydrolysis-based method such as Sol-Gel method the X-ray diffraction techniques followed by Rietveld method seems to better approach. Several alterations in anatase lattice parameters can occur by doping insertion and the investigation of isostructural zircon silicate can provide interesting ones. In the present paper, the monitoring of anatase structure reordering and the consequent anatase-to-rutile phase transition along the thermal treatment up to higher temperatures were monitored carrying out DSC and XRD characterizations. The insertion of 6 mol% of zircon silicate leads to the fully anatase stabilization up to 900 °C due the control of ordering process, even that a continuous increasing in anatase tetragonality is present during the entire process. We can conclude the reconstructive anatase-to-rutile phase transition is delayed to very higher temperatures can consequence of more stable cross-linked metal oxide bond in anatase phase.

Fe-TiO2 Nanoparticles by Hydrothermal Treatment with Photocatalytic Activity Enhancement

2014 ◽  
Vol 1024 ◽  
pp. 39-43 ◽  
Author(s):  
Siti Aida Ibrahim ◽  
Srimala Sreekantan
Keyword(s):  
Photocatalytic Activity ◽  
Hydrothermal Treatment ◽  
Anatase Phase ◽  
Sol Gel ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Fe Content ◽  
Vis Spectroscopy ◽  
Activity Enhancement ◽  
Brookite Phase

Fe-TiO2nanoparticles with 5-9 nm sizes were prepared by sol gel method subsequently subjected to hydrothermal treatment at 150°C for 6 h. Titanium (IV) isopropoxide and iron (III) nitrate nonahydrate were used as precursor. The morphology, structure and composition of the Fe-TiO2were investigated by X-ray diffraction (XRD), Transmission emission microscopy (TEM) and UV-vis spectroscopy (UV-vis). XRD analysis revealed the prepared samples was dominated with anatase phase and a trace of brookite phase. The TiO2crystallite size was reduced as Fe content was increased. Compared with the pure TiO2nanoparticles, the Fe-TiO2nanoparticles exhibited higher photocatalytic activity in decolorizing methyl orange into non-toxic inorganic products under UV irradiation.

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