Introduction

1. CH3 CH3 CH O CH3 CH3 Ti O CH O CH CH3 O CH3 CH CH3 CH3 Air To mass-spectrometer MFC MFC Ar MFC H2 MFC O2 The Russian Foundation of Basic Research is acknowledged for the support of this work under grant # 10-03-00442. 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 33th International Symposium on Combustion, August 1-6, 2010 Tsinghua University, Beijing, China H2/O2/Ar Flame structure Introduction a Nanocrystalline 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 incarbon-free H2/O2/Ar flame • to study of the H2/O2/Ar flame structure • to explore structure and properties of the TiO2 films b c Experimental setup 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, solidthick curves – modeling Model satisfactorily agrees with experimental data Cooling airflow 300 RPM Rotating disk Properties of nanocrystalline TiO2 films flame substrates probe unit stepper motor Exposition time - 10 s U=4.3 m/s (T=150oC) probe positioner shroudflow burner heater syringe titanium tetraisopropoxide, Ti(OC3H7)4 heater stepper motor Ti(OC3H7)4 syringe needle Exposition time - 20 s Combustible mixture: H2/O2/Ar (13%/14.5%/72.5%)+ 0.1%Ti(OC3H7)4 HRTEM images of TiO2 layers:spherical crystalline particles! =0.45, D=[O2]/([O2]+[Ar])=0.165 Problems in temperature and species measurements Medium diameter <d>=12 nm, σ=1.45 Problem: The flame disturbed by a thermocouple and a probe Solutions: Using thin thermocouples (<0.03 mm) b) probing along burner’s axis on its periphery Problem: The quartz microprobe was clogged by TiO2 particlesin doped flame Solution: discontinuous purge of orifice by tungsten wire (0.05mm) from inside of microprobe Exposition time - 30 s 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 XRD spectra of nano-phase TiO2 crystals (black line), reference data for anatase (red line) and rutile (blue line). Phase-pure anatase (>95%) particles HRTEM images of TiO2 particles deposited on carbon film. Average net film growth rate about 1.4 μm/s Probe unit with electro-magnet and controller The microprobe with tungsten wire inside. Ceramic pipes The thermocouple unit Modeling of H2/O2/Ar flame structure Acknowledgements • 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/