Polymorphism of nanocrystalline TiO<sub>2</sub> prepared in a stagnation flame: formation of the TiO<sub>2</sub>-II phase

Manuputty, Manoel Y.; Dreyer, Jochen A.H.; Yuan, Shijun; Bringley, Eric J.; Botero, María L.; Akroyd, Jethro; Kraft, Markus

doi:10.1039/c8sc02969e

Cited by 50 publications

(72 citation statements)

References 47 publications

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“…Laminar flames are widely used for fundamental studies of soot formation [1][2][3][4] and the synthesis of materials [5][6][7][8]. Characterising such systems with accurate and reliable techniques is vital for understanding the processes controlling particle formation in flames and is an ongoing field of research [9].…”

Section: Introductionmentioning

confidence: 99%

Improved methodology for performing the inverse Abel transform of flame images for color ratio pyrometry

et al. 2019

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A new method is presented for performing the Abel inversion by fitting the line-of-sight projection of a predefined intensity distribution (FLiPPID) to the recorded 2D projections. The aim is to develop a methodology that is less prone to experimental noise when analysing the projection of antisymmetric objects, in this case co-flow diffusion flame images for colour ratio pyrometry. A regression model is chosen for the light emission intensity distribution of the flame cross-section as a function of the radial distance from the flame centre-line. The forward Abel transform of this model function is fitted to the projected light intensity recorded by a colour camera. For each of the three colour channels, the model function requires three fitting parameters to match the radial intensity profile at each height above the burner. This results in a very smooth Abel inversion with no artifacts such as oscillations or negative values of the light source intensity, as is commonly observed for alternative Abel inversion techniques, such as the basis-set expansion (BASEX) or onion-peeling. The advantages of the new FLiPPID method are illustrated by calculating the soot temperature and volume fraction profiles inside a co-flow diffusion flame, both being significantly smoother than those produced by the alternative inversion methods. The developed FLiPPID methodology can be applied to numerous other optical techniques for which smooth inverse Abel transforms are required.

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Section: Introductionmentioning

confidence: 99%

Improved methodology for performing the inverse Abel transform of flame images for color ratio pyrometry

et al. 2019

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“…The XRD and Raman features show a systematic evolution from Mn3O4 products to MnO products at the equivalence ratio is increased (gas-phase O2 decreases). A range of titanium oxide structures was reported for increasing equivalence ratio [13] but a range of metal oxide valence this extensive has not been observed. Experiment C and D demonstrate the manipulation of O2 during particle growth to systematically control the resulting particle oxidation state / structure.…”

Section: Resultsmentioning

confidence: 93%

“…This is in contrast to many titanium oxide and iron oxide studies in premixed flames where full oxidation to TiO2 and Fe2O3 is reported. There are notable exceptions such as a recent report of TiO2-II formation in fuel rich FSRS conditions [13]. In the current study, synthesis of manganese oxide nanoparticles in premixed stagnation flames will be carried out on a stationary deposition surface to further examine competing processes leading to the final oxide product.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Manganese Oxide Nanoparticles in Premixed Flames

Dasappa¹,

Camacho²

2020

Preprint

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Synthesis of manganese oxide nanoparticles was carried out in premixed stagnation flames. The deposition surface was stationary to enable rigorous comparison to flame structure computations using pseudo one-dimensional and full two-dimensional calculations. The pseudo one-dimensional assumption taken by OPPDIF to calculate the flame structure performs reasonably well for the narrow aspect ratio stagnation flow currently studied. Agreement between the measured flame position and both computational methods was within 0.25 cm. The variation in manganese oxidation state in the products observed here is shown to be caused by competing oxidation and particle nucleation processes. Complimentary experimental and modeling studies of flame synthesis were carried out under well-defined boundary conditions to examine this competition. Manganese oxide products having II, II,III, III and IV valence were observed depending on the flame conditions. Unlike iron oxide and titanium oxide systems, complete oxidation to MnO2 is only observed for the most oxidizing growth conditions. The first observation of phase pure MnO by flame synthesis is reported here. Manipulation of the balance between manganese oxidation and particle nucleation through control of the time-temperature-oxygen history may enable selective synthesis of manganese oxide nanoparticles with tailored morphology and oxidation state.

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“…Synthesis of manganese oxide nanoparticles will be carried out in a flame-assisted chemical vapor deposition process. The process is similar to previous FSRS reports [12][13][14] except that a stationary deposition surface is used rather than deposition onto a rotating substrate. The stationary deposition surface enables rigorous modelling of the CVD domain and examination of competing processes leading to the final oxide product.…”

Section: Introductionmentioning

confidence: 88%

“…This is in contrast to many titanium oxide and iron oxide premixed flames studies where full oxidation to TiO2 and Fe2O3 is reported. There are notable exceptions such as a recent report of TiO2-II formation in fuel rich FSRS conditions 12 . The current work is a complementary experimental and modelling study examining formation of nanocrystalline manganese oxides in flames with analysis of thermodynamic barriers to particle nucleation and oxidation.…”

Section: Introductionmentioning

confidence: 99%

Formation of nanocrystalline manganese oxide in flames: oxide phase governed by classical nucleation and size-dependent equilibria

Dasappa

Camacho

2020

CrystEngComm

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Polymorphism of nanocrystalline TiO₂ prepared in a stagnation flame: formation of the TiO₂-II phase

Abstract: Flame-made TiO2 nanoparticles with tunable polymorphs, including the metastable TiO2-II phase, were prepared and a phase formation mechanism was proposed.

Cited by 50 publications

References 47 publications

Improved methodology for performing the inverse Abel transform of flame images for color ratio pyrometry

Improved methodology for performing the inverse Abel transform of flame images for color ratio pyrometry

Synthesis of Manganese Oxide Nanoparticles in Premixed Flames

Formation of nanocrystalline manganese oxide in flames: oxide phase governed by classical nucleation and size-dependent equilibria

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Polymorphism of nanocrystalline TiO2 prepared in a stagnation flame: formation of the TiO2-II phase

Abstract: Flame-made TiO2 nanoparticles with tunable polymorphs, including the metastable TiO2-II phase, were prepared and a phase formation mechanism was proposed.

Cited by 50 publications

References 47 publications

Improved methodology for performing the inverse Abel transform of flame images for color ratio pyrometry

Improved methodology for performing the inverse Abel transform of flame images for color ratio pyrometry

Synthesis of Manganese Oxide Nanoparticles in Premixed Flames

Formation of nanocrystalline manganese oxide in flames: oxide phase governed by classical nucleation and size-dependent equilibria

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Product

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Polymorphism of nanocrystalline TiO₂ prepared in a stagnation flame: formation of the TiO₂-II phase