scholarly journals Systematic Structural and Optical Characterization of TiO2 Nanofibers Synthesised by Electrospinning

2021 ◽  
Vol 15 ◽  
pp. 1497-1505
Author(s):  
Oscar Secundino-Sánchez ◽  
José F. Sánchez-Ramírez ◽  
Joel Diaz -Reyes
Keyword(s):  
Phase Transformation ◽  
High Temperatures ◽  
Crystalline Phase ◽  
Annealing Temperature ◽  
Band Gap Energy ◽  
Continuous Change ◽  
Electrospinning Technique ◽  
Tio2 Nanofibers ◽  
Average Grain Size ◽  
High Resolution Tem

TiO2 nanofibers were synthesised by means of the electrospinning technique, which were annealed at high temperatures to achieve the crystalline phase transformation. The chemical stoichiometry of electrospun TiO2 nanofibers was estimated by EDS, finding that at low annealing temperatures excess of oxygen was detected and at high temperatures excess of titanium that originates oxygen vacancies. TEM images show clearly the formation of TiO2 nanofibers (NF’s) that exhibit a homogeneous and continuous aspect without the presence of crystalline defects, whose surface morphology depends strongly on the annealing temperature. The crystalline phase transformation was studied by Raman spectroscopy, which revealed that annealed TiO2 NF’s showed a crystalline phase transformation from pure anatase to, first a mix of anatase-rutile, then pure rutile as the annealing temperature increased, which was corroborated by X-ray diffraction and high-resolution TEM diffraction. The average grain size, inside the NF´s, increased with the crystalline phase transformation from 10 to 24 nm for anatase-TiO2 and from 30 to 47 nm for rutile-TiO2, estimated by using the Scherrer-Debye equation. The band gap energy (Eg), obtained from optical absorption spectra, decreases monotonically, where a local minimum is observed at 700 °C ranged in 3.75 ≤ Eg ≤ 2.42 eV, caused by the anatase → rutile crystalline phase transformation. The photoluminescence shows that radiative bands show a gradual red-shift as the temperature increases due to the continuous change of Eg.

scholarly journals Systematic Structural and Optical Characterization of TiO2 Nanofibres Synthesised by Electrospinning

2021 ◽  
Vol 12 ◽  
pp. 106-115
Author(s):  
Oscar Secundino-Sánchez ◽  
José F. Sánchez-Ramírez ◽  
Joel Diaz-Reyes
Keyword(s):  
Phase Transformation ◽  
High Temperatures ◽  
Crystalline Phase ◽  
Annealing Temperature ◽  
Band Gap Energy ◽  
Continuous Change ◽  
Electrospinning Technique ◽  
Average Grain Size ◽  
High Resolution Tem ◽  
Tem Microscopy

TiO2 nanofibres were synthesised by means of the electrospinning technique, which were annealed at high temperatures to achieve the crystalline phase transformation. The chemical stoichiometry of electrospun TiO2 nanofibres was estimated by EDS, finding that at low annealing temperatures excess of oxygen was detected and at high temperatures excess of titanium that originates oxygen vacancies. TEM images show clearly the formation of TiO2 nanofibres that exhibit a homogeneous and continuous aspect without the presence of crystalline defects, whose surface morphology depends strongly on the annealing temperature. The crystalline phase transformation was studied by Raman spectroscopy, which revealed that annealed TiO2 nanofibres showed a crystalline phase transformation from pure anatase to, first a mix of anatase-rutile, then pure rutile as the annealing temperature increased, which was corroborated by X-ray diffraction and high-resolution TEM microscopy. The average grain size, inside the nanofibres, increased with the crystalline phase transformation from 10 to 24 nm for anatase-TiO2 and from 30 to 47 nm for rutile-TiO2, estimated by using the Scherrer-Debye equation. The band gap energy (Eg), obtained from optical absorption spectra, decreases monotonically, where a local minimum is observed at 700 °C, which is ranged in 3.75  Eg  2.42 eV, caused by the anatase → rutile crystalline phase transformation. The photoluminescence shows that radiative bands present a gradual red-shift as the annealing temperature increases due to the continuous change of Eg.

scholarly journals Structural and optical characterization of the crystalline phase transformation of electrospinning TiO2 nanofibres by high-temperatures annealing

2019 ◽  
Vol 65 (5 Sept-Oct) ◽  
pp. 459
Author(s):  
O. Secundino-Sánchez ◽  
J. Diaz-Reyes ◽  
J. F. Sánchez-Ramírez ◽  
And J.L. Jiménez-Pérez
Keyword(s):  
Phase Transformation ◽  
Raman Scattering ◽  
High Temperatures ◽  
Crystalline Phase ◽  
Annealing Temperature ◽  
Crystal Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Wide Range

The electrospinning technique has been used to synthesize TiO2 nanofibres, which by annealing at high temperatures in a wide range achieves the crystal phase transformation of anatase to rutile passing through the anatase+rutile mixed. The investigated temperature range was 0-1000°C. The TiO2 nanofibres chemical stoichiometry and surface morphology were obtained by Scanning Electron Microscopy and Energy Dispersive Spectrometry. The nanofibres diameter was ranged from 137.0 to 115.3 nm in the annealing temperature interval of 0-1000°C. The influence of the annealing temperature on the structure and crystal phase quality of the TiO2crystal has been investigated by X-ray diffraction and Raman scattering. Clear evidence of nanofibres structural transformation from pure anatase to pure rutile structures, including the quasi-amorphous and anatase+rutile mixed phases has been confirmed by Raman scattering. By X-ray diffraction was found that the nanofibres crystalline phases present as preferential growth direction (101) for anatase and (110) for rutile. The Raman spectroscopy exhibits the anomalous behaviour for band broadening and shifting of Raman bands with increasing crystallite size that form the nanofibres. The room-temperature photoluminescence presents radiative bands whose main band redshifts, from 2.56 to 1.32 eV, as the crystalline phase transforms in the investigated annealing temperature range.

scholarly journals The effect of annealing temperature on the structural, optical, and electrical properties of CdS films

2010 ◽  
Vol 25 (1) ◽  
pp. 189-196 ◽  
Author(s):  
Hulya Metin ◽  
Mehmet Ari ◽  
Selma Erat ◽  
Semra Durmuş ◽  
Mehmet Bozoklu ◽  
...  
Keyword(s):  
Activation Energy ◽  
Phase Transformation ◽  
Electrical Properties ◽  
Electronic Transport ◽  
Annealing Temperature ◽  
Optical Band Gap ◽  
Urbach Energy ◽  
Band Gap Energy ◽  
Optical And Electrical Properties ◽  
Gap Energy

Cadmium sulfide (CdS) photocatalyst films were grown on glass by chemical bath deposition (pH 9.4, 70 °C) and then annealed in nitrogen from 423 K to 823 K in steps of 100 K. The XRD crystallite size increases in a sigmoidal manner from 60 nm to 100 nm while the optical band gap energy decreases from 2.42 eV to 2.28 eV. This trend is paralleled by the decreasing Urbach energy, but only up to 623 K, where it increases again. This is the temperature where the Cd effectively surpasses the phase transformation from cubic to hexagonal, and the activation energy for electronic transport drops by a factor of nearly two.

STRUCTURAL TRANSFORMATION IN NANOPHASE TITANIUM DIOXIDE

1999 ◽  
Vol 13 (05) ◽  
pp. 167-174 ◽  
Author(s):  
MUYING WU ◽  
WEIFENG ZHANG ◽  
ZULIANG DU ◽  
YABIN HUANG
Keyword(s):  
Raman Spectroscopy ◽  
Grain Size ◽  
Phase Transformation ◽  
Titanium Dioxide ◽  
Structural Transformation ◽  
Annealing Temperature ◽  
Sol Gel ◽  
X Ray ◽  
Average Grain Size ◽  
Gel Technique

Nanophase TiO 2 was prepared by a stearic acid sol–gel technique. X-ray measurements showed that the as-prepared sample is anatase TiO 2 phase with an average grain size of 10.4 nm. Raman spectroscopy was used to investigate the structural transformation from anatase-to-rutile in the nanophase TiO 2 annealed at a series of temperatures from 450 to 650°C. The results showed that the transformation took place in a wide annealing temperature range. The related mechanism to the phase transformation is discussed according to nanometer size effect.

scholarly journals Characterization of WO3Thin Films Grown on Silicon by HFMOD

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Joel Díaz-Reyes ◽  
Roberto Castillo-Ojeda ◽  
Miguel Galván-Arellano ◽  
Orlando Zaca-Moran
Keyword(s):  
Crystalline Phase ◽  
Photoelectron Spectroscopy ◽  
Annealing Temperature ◽  
Band Gap Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Radiative Transitions ◽  
Oxide Deposition ◽  
Triclinic Structure ◽  
Hot Filament

We studied the effect of annealing temperature on the physical properties of WO3thin films using different experimental techniques. WO3has been prepared by hot-filament metal oxide deposition (HFMOD). The films, chemical stoichiometry was determined by X-ray photoelectron spectroscopy (XPS). The monoclinic single-phase nature of the as-deposited films, structure was changed to triclinic structure by annealing them at higher temperatures than 400°C, which has been determined by the X-ray diffraction analysis. By Raman scattering is confirmed the change of crystalline phase, of monoclinic to triclinic, since that lattice vibrational modes of as-deposited WO3and annealed at 500°C present clearly differences. WO3band gap energy can be varied from 2.92 to 3.15 eV by annealing WO3from 0 to 500°C as was obtained by transmittance measurements. The photoluminescence response of the as-deposited film presents three radiative transitions observed at 2.85, 2.41, and 2.04 eV that could be associated with oxygen vacancies; the first one is shifted to higher energies as the annealing temperature is increased due to the change of crystalline phase of the WO3.

TEM Analysis of Long-Period Polytypes in SiC—S

1976 ◽  
Vol 34 ◽  
pp. 630-631
Author(s):  
S. Shinozaki ◽  
J. W. Sprys
Keyword(s):  
Electron Diffraction ◽  
Isothermal Annealing ◽  
Tem Analysis ◽  
Long Period ◽  
Transmission Electron ◽  
Average Grain Size ◽  
High Resolution Tem ◽  
Structural Lattice ◽  
The Stability ◽  
Continuous Curves

In reaction sintered SiC (∽ 5um average grain size), about 15% of the grains were found to have long-period structures, which were identifiable by transmission electron microscopy (TEM). In order to investigate the stability of the long-period polytypes at high temperature, crystal structures as well as microstructural changes in the long-period polytypes were analyzed as a function of time in isothermal annealing.Each polytype was analyzed by two methods: (1) Electron diffraction, and (2) Electron micrograph analysis. Fig. 1 shows microdensitometer traces of ED patterns (continuous curves) and calculated intensities (vertical lines) along 10.l row for 6H and 84R (Ramsdell notation). Intensity distributions were calculated based on the Zhdanov notation of (33) for 6H and [ (33)3 (32)2 ]3 for 84R. Because of the dynamical effect in electron diffraction, the observed intensities do not exactly coincide with those intensities obtained by structure factor calculations. Fig. 2 shows the high resolution TEM micrographs, where the striped patterns correspond to direct resolution of the structural lattice periodicities of 6H and 84R structures and the spacings shown in the figures are as expected for those structures.

Phase transformation and heterojunction construction of bismuth oxyiodides by grinding-assistant calcination in the presence of thiourea and its photoactivity

2021 ◽  
Author(s):  
Zichen Shen ◽  
Huanzhen Liu ◽  
Xuemei Jia ◽  
Qiaofeng Han ◽  
Huiping Bi
Keyword(s):  
Phase Transformation ◽  
Band Gap ◽  
Layered Structure ◽  
Band Gap Energy ◽  
Gap Energy

Bismuth-rich oxyhalides are promising photocatalysts due to their special layered structure and adjustable band gap energy. In this work, a series of bismuth oxyiodides were fabricated by grinding-assistant calcining in...

Phase transformation of high aluminium fly ash in carbothermal reduction–nitridation at high temperatures

2014 ◽  
Vol 32 (4) ◽  
pp. 399-403
Author(s):  
M. H. Fang ◽  
H. T. Liu ◽  
Z. H. Huang ◽  
J. T. Huang ◽  
Y. G. Liu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Fly Ash ◽  
High Temperatures ◽  
Carbothermal Reduction ◽  
High Aluminium

Crystallization of Amorphous Sputtered NiTi Shape-Memory Alloy Films

1995 ◽  
Vol 398 ◽  
Author(s):  
F.F. Gong ◽  
H.M. Shen ◽  
Y.N. Wang
Keyword(s):  
Shape Memory ◽  
Annealing Temperature ◽  
Optimum Shape ◽  
Niti Shape Memory Alloy ◽  
X Ray Diffraction ◽  
Initial Stage ◽  
Average Grain Size ◽  
Optimum Heat ◽  
Diffraction Patterns ◽  
Optimum Heat Treatment

ABSTRACTThe crystallization of amorphous sputtered NiTi films was investigated for selected heat treatments. From x-ray diffraction patterns, when the films were annealed below the crystallization temperature, the intensity of the broad maximum centered at 2θ = 43.5° increased with increasing the annealing temperature and time. When the films were annealed at 550°C for 0.5hr, parent B2 phase and Ni4Ti3 precipitates appeared. For annealing temperature above 700°C, the films showed embrittlement and volatilization. Therefore the optimum heat treatment for the optimum shape memory effect is found. The average grain size increased slowly in the initial stage of annealing but remained almost unchanged when the films were annealed for more than 1hr. This is because the grain boundary grooving caused by the titanium at a certain temperature volatilization seriously hinder the grain growth.

TiO2 nanofibers fabricated by electrospinning technique and degradation of MO dye under UV light

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Naveen Thakur ◽  
Nikesh Thakur ◽  
Viplove Bhullar ◽  
Saurabh Sharma ◽  
Aman Mahajan ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Fiber Diameter ◽  
Uv Light ◽  
Rutile Phase ◽  
Powder Form ◽  
X Ray Diffraction ◽  
Electrospinning Technique ◽  
Tio2 Nanofibers ◽  
X Ray ◽  
Uv Visible

Abstract Titanium dioxide (TiO2) nanofibers were synthesized by electrospinning to optimize the photocatalytic action efficiency. The synthesis of the fibers was carried out at four different wt% concentrations: 8, 9, 10 & 11% of polymer polyvinylpyrrolidone (PVP). The TiO2 fibers were further calcined at 700 °C to get powder form. The uncalcinated and calcined TiO2 nanofibers were characterized by using X-Ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM) and UV-Visible spectroscopy. Raman spectroscopy confirmed the rutile phase of the calcined TiO2nanofibers in powder form with a crystallite size of 34–38 nm. The surface morphology of the uncalcinated and calcined TiO2 nanofibers was examined by SEM and the fiber diameter found to be 360–540 nm. The optical bandgap of the calcined TiO2 nanofibers was found in the range of 3.29–3.24 eV. The photocatalytic activity of the TiO2 nanofibers as examined for uncalcinated and calcined nanofibers, methyl orange (MO) dye degraded up to 98 and 78%, respectively in 180 min under the exposure of UV light. Uncalcinated TiO2 nanofibers were found more suitable for degradation of MO dye as compared to calcined nanofibers.

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