Flame synthesis of aligned tungsten oxide nanowires

Abstract

Aligned single-crystal WO2.9 nanowires are grown directly from tungsten substrates at high rates using a flame synthesis method. The nanowires have diameters of 20–50nm, lengths >10μm, coverage density of 109–1010cm−2, and growth rates >1μm∕min. Growth occurs by the vapor-solid mechanism, with local gas-phase temperature (∼1720K) and chemical species (O2, H2O, and H2) strategically specified at the substrate for self-synthesis. Advantages of this synthesis method are reduced processing times, absence of necessity for substrate pretreatment or catalysts, scalability for large-area surface coverage, high purity and yield of oriented nanowires, and continuous processing conditions.

Metal-based reactive nanomaterials

“…The precursor materials decompose and the produced metals oxidize in a well-controlled flame yielding a uniform nanosized oxide powder product. More recently, the formation of narrow-sized and specifically shaped nano-oxide particles or nanofibers was achieved by flame synthesis performed over specifically prepared substrates introduced in well-controlled flat flames [82]. Alternately, external electric fields can be used to control the formation of oxide nanoparticles and their agglomeration [83].…”

Synthesis and characterization of tungsten oxide nanorods from chemical vapor deposition-grown tungsten film by low-temperature thermal annealing

“…[20][21][22][23] Tungsten oxide has variant suboxide crystal structures. [24][25][26][27][28] Among these, one of the well-known structures is a monoclinic W 18 O 49 , which is highly anisotropic and shows a good mechanical strength. 29 Various methods based on thermal treatments, vapor phase growth, oxidation, and wet chemical reaction have been reported for preparing W 18 O 49 nanowires.…”

Novel flame-gradient method for synthesis of metal-oxide channels, nanowires and nanorods

“…It is interesting to note that of all the tested transition metals in this study, only the W-oxide structures were coated with a thick layer of highly crystalline carbon. Xu et al [35] reported that the flame synthesis of nanorods composed of W, O and traces (c) (1) of C. Their results suggest that the presence of C is most likely from the deposition of C on the nanowires from carbon-containing species that diffuse from the reaction zone during the processing [35]. The application of HRTEM analysis to our products revealed that a very uniform thick layer of graphite covers the tungsten oxide nanowires.…”