Synthesis of nano-phase TiO2 crystalline films over premixed stagnation flames and the study of the structure of these flames

O.P. Korobeinichev1, A.G. Shmakov1, R.A. Maksyutov1, M.L. Kosinova2, V.S.Sulyaeva2,

A.G.Tereshchenko1, Jong-Shinn Wu3, Huang Chin Chen3

1Institute of Chemical Kinetics and Combustion of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia;2Institute of Inorganic Chemistry of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia;3National Chiao Tung University, Hsinchu, Taiwan

IntroductionNanocrystalline titania (TiO2) films represent a new class

of functional materials, which are promising for producing dye sensitized solar cells and gas-sensors. Nanocrystalline TiO2 films may be synthesized using different methods; however, synthesis of such materials is traditionally carried out in more than a single step. The method of synthesizing particles in one-dimensional laminar premixed ethylene-oxygen stagnation flame, stabilized at a small distance beneath a stationary cooled surface of a rotating disk was proposed early by H. Wang and co-workers [Proc. Comb. Inst. 32 (2009) 1839–1845].

The objective of this study are: to synthesize specimens of nanocrystalline titania (TiO2)

films in carbon-free H2/O2/Ar flame to study of the H2/O2/Ar flame structure to explore structure and properties of the TiO2 films

33th International Symposium on Combustion, August 1-6, 2010Tsinghua University, Beijing, China

Experimental setup

The Russian Foundation of Basic Research is acknowledged for the support of this work under grant # 10-03-00442.

Acknowledgements

Air

Ar

H2

O2

MFC

MFC

MFC

MFC

To mass-spectrometer

Combustible mixture: H2/O2/Ar (13%/14.5%/72.5%)+ 0.1% Ti(OC3H7)4

syringe

stepper motor

stepper motor

heater

heater

syringe needle

probe unit flamesubstrates

Rotating disk

Ti(OC3H7)4

Cooling airflow

burner

probe positioner

shroud flow

300 RPM

H2/O2/Ar Flame structure

Properties of nanocrystalline TiO2 films

Problems in temperature and species measurements

3.5

Керамическая трубка

. Pt, 0.2

PtRh(10%), 0.02

Pt, 0.02

PtRh(10%), 0.2

Ceramic

pipes

Modeling of H2/O2/Ar flame structure

Particle diameter, nm

4 5 6 7 8 9 15 20 25 30 35 4010

Nu

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Problem: The quartz microprobe was clogged by TiO2 particles in doped flame

Solution: discontinuous purge of orifice by tungsten wire (0.05mm) from inside of microprobe

Problem: The flame disturbed by a thermocouple and a probe

Solutions:

a) Using thin thermocouples (<0.03 mm)

b) b) probing along burner’s axis on its periphery

The microprobe with tungsten wire inside.

Probe unit with electro-magnet and controller

U=4.3 m/s (T=150oC)

The thermocouple unit

OPPDIF Code from the Chemkin II Suite

GRI 3.0 mechanism / G.P. Smith, D.M. Golden, M. Frenklach, N.W. Moriarty, B. Eiteneer, M. Goldenberg, C.T. Bowman, R.K. Hanson, S. Song, W.C. Gardiner Jr., V.V. Lissianski, Z. Qin, GRI Mech 3.0. 1999. http://www.me.berkeley.edu/gri_mech/

HRTEM images of TiO2 particles deposited on carbon

film.

Average net film growth rate about

1.4 μm/s

Exposition time - 10 s

Exposition time - 20 s

Exposition time - 30 s

Medium diameter

<d>=12 nm,

σ=1.45

HRTEM images of TiO2 layers: spherical crystalline particles!

Particle size distribution function of TiO2 particles produced at 0.1% Ti(OC3H7)4 loading

(symbols – experiment, curves – lognormal fits to data)

Ultra-narrow size distribution

OO

O

Ti

O

CH

CH3

CH3

CH

CH3

CH3

CH

CH3 CH3

CH

CH3CH3

titanium tetraisopropoxide,

Ti(OC3H7)4

XRD spectra of nano-phase TiO2 crystals (black line), reference data for anatase (red line) and rutile (blue line).

Phase-pure anatase (>95%) particles

=0.45, D=[O2]/([O2]+[Ar])=0.165

Concentration and temperature profiles in H2/O2/Ar flame without additive (a) and with 0.1% Ti(OC3H7)4 (b, c), measured at distance 2.5 mm along burner's axis. Symbols – experiments, solid thick curves – modeling

Model satisfactorily agrees with experimental data

Distance from substrate, mm

024681012

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H2

O2

Distance from substrate, mm024681012

Mo

le fr

act

ion

0,0

2,0e-4

4,0e-4

6,0e-4

8,0e-4

1,0e-3

1,2e-3

1,4e-3

Ti(OC3H7)4

a

c

b

Distance from substrate, mm

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O2

H2O