Influence of the Time-Temperatur-Profile on Powder Characteristics of Nanocrystalline Anatase (TiO2) produced by Chemica
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1056-HH08-07
Influence of the Time-Temperatur-Profile on Powder Characteristics of Nanocrystalline Anatase (TiO2) produced by Chemical Vapor Synthesis Ruzica Djenadic1, Sankhanilay Roy Chowdhury1, Marina Spasova2, Andreas Gondorf2, Erdal Akyildiz1, and Markus Winterer1 1 Nanoparticle Process Technology, Faculty of Engineering and Cenide, University of DuisburgEssen, Duisburg, 47057, Germany 2 Experimental Physics, Faculty of Physics and CeNIDE, University of Duisburg-Essen, Duisburg, 47057, Germany ABSTRACT Chemical Vapor Synthesis (CVS) is the conversion of molecular species into nanocrystalline particles by chemical reactions in a gas flow reactor. Pure anatase nanoparticles are generated in a hot wall reactor from titanium isopropoxide using different time-temperature-profiles. The time-temperature-profile (T(t)-profile) in the gas phase of the reactor has a profound influence on the particle characteristics such as particle microstructure and surface chemistry and, therefore, on the quality of the powder consisting of nanocrystalline particles. In this study a simple reaction-coagulation-sintering model (CVSSIN) was used to predict influence of the T(t)-profile on the powder characteristics. The as-synthesized anatase powders show a very high degree of crystallinity, primary particle of about 10 nm sizes and a low degree of agglomeration.
INTRODUCTION Nanocrystalline titania, especially anatase, is used for important applications such as photocatalysis and photovoltaics [1, 2]. Nanocrystalline titania can be generated by decomposition of titanium isopropoxide in the gas phase. System is a prototype for CVS because much experimental and theoretical information is available and because the product of the process is – in all relevant cases – crystalline, consisting mostly of anatase. This enables not only a detailed model description of the CVS process but also an extensive characterization of the generated particles and the product powders. In this study we demonstrate the influence of the key CVS-process parameter –T(t)-profile– in the CVS-reactor on the particle generation and the corresponding powder characteristics, especially the degree of agglomeration and surface chemistry.
MODEL A simple reaction-coagulation-sintering model (CVSSIN) [4] is used to describe the CVSprocess assuming stationary, ideal, one-dimensional plug flow, without axial dispersion. Processes, which influence the formation of particles from molecular precursors and powder characteristics such as particle microstructure, morphology, size distribution, and crystallinity are included in the model: conversion of the precursor into monomers (growth species), formation of clusters (primary particles or grains) from monomers, coagulation of primary particles and formation of agglomerates, sintering of the primary particles within the agglomerates, heat exchange (with the hot wall) and heat production by the above processes.
EXPERIMENT Powder Synthesis Nanocrystalline TiO2 powders are synthesized by CVS from titanium-tetra-isopropoxide, TTIP
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