Influence of nitrogen and air atmosphere during thermal treatment on micro and nano sized powders and sintered TiO2 specimens

N Labus,Z.Z Djuric,M.V Nikolic,S Mentus

doi:10.2298/sos1403365l

N Labus, Z.Z Djuric + Show 2 more

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https://doi.org/10.2298/sos1403365l

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Abstract

The influence of air and nitrogen atmosphere during heating on TiO2 nano and micro sized powders as well as sintered polycrystalline specimens was analyzed. Sintering of TiO2 nano and micro powders in air atmosphere was monitored in a dilatometer. Non compacted nano and micro powders were analyzed separately in air and nitrogen atmospheres during heating using thermo gravimetric (TG) and differential thermal analysis (DTA). The anatase to rutile phase transition temperature interval is influenced by the powder particle size and atmosphere change. At lower temperatures for nano TiO2 powder a second order phase transition was detected by both thermal techniques. Polycrystalline specimens obtained by sintering from nano powders were reheated in the dilatometer in nitrogen and air atmosphere, and their shrinkage is found to be different. Powder particle size influence, as well as the air and nitrogen atmosphere influence was discussed.

Highlights

Recent interest in TiO2 is due to its wide band gap semiconductor properties and modulating surface properties
Measured differential thermal analysis (DTA) and TGA diagrams for TiO2 nano and micro powders are shown in fig
Shrinkage and shrinkage rate of the TiO2 nano and micro powders during heating in air are shown in fig

Summary

Introduction

Recent interest in TiO2 is due to its wide band gap semiconductor properties and modulating surface properties. When air and nitrogen atmosphere interchanges are concerned, the pressure of the gases surrounding the bulk specimen can be considered as a comparatively small change on the pressure scale usually observed and has an influence only if the observed oxide is nonstoichiometric [4] Such a small pressure change can become significant if the particular induced point defects concentration is rising with the observed particular state function increase [5,6]. The first phase in this homology group is Ti2O3 and it is morphologically considered an added row on the bulk surface [12] This phase shows the second order phase transition frequently observed by the change in conductance [13]. In this work the observed changes during heating in different atmospheres that produced the final microstructures are all used for the possible deduction and explanation of the underlying processes

Experimental

Results and discussion

Conclusion