Epitaxial growth of WO3–x needles on (10 0) and (01 0) WC surfaces produced by controlled oxidation with CO2

Abstract

The controlled oxidation with CO₂ of both high surface area (high S_g) and low surface area WC to form WO_3–x needles, has been observed in situ, inside a controlled environment transmission electron microscope (CETEM), and also ex situ, in a standard flow reactor; the tungsten oxide needles, which consist mainly of distorted γ-WO_2.72, propagate in an epitaxial fashion from the (10 0) and (01 0) surfaces of the parent WC crystals; possible mechanisms for the formation of the needles are proposed.