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URSAKI, Veacheslav; GHIMPU, Lidia; MESTERCA, Raluca; BRANCOVEANU, O.; PRODANA, Mariana; ENACHESCU, Marius; DIMITRACHI, Sergiu; TIGINYANU, Ion. WO3/WS2 composite materials for gas sensor and energy storage applications. In: Materials Science and Condensed Matter Physics. Ediția a 9-a, 25-28 septembrie 2018, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2018, p. 200.
|Materials Science and Condensed Matter Physics
Ediția a 9-a, 2018
Conferința "International Conference on Materials Science and Condensed Matter Physics" |
Chișinău, Moldova, 25-28 septembrie 2018
Transition metal binary compounds, especially oxides and chalcogenides, are material of choice for many applications. Particularly, tungsten trioxide (WO3) has been extensively studied due to its outstanding electrochromic and photochromic properties in the visible and infrared region, high coloration efficiency and relatively low price , which makes it suitable for the construction of smart windows, mirrors, optical shutters and display devices . Tungsten trioxide is also a good photocatalyst, gas sensor, chemical sensor and biosensor, material . On the other hand, tungsten disulfide (WS2) with its unique properties is a promising material for a number of applications such as solid lubricants, catalysts, photosensitive films, electronic and optical devices . Both the materials and their nanocomposites are of great interest for energy storage applications. A variety of technological methods have been applied so far for the production of WO3, WS2 and two-component composite materials. In this paper, we developed technological conditions for obtaining WO3 nanorod arrays by spin coating on tungsten foils or wires, which are further subjected to surfurization by magnetron sputtering. The commercial W foils and wires are cleaned using ethanol and acetone solution and dried before spin coating. A 0.1 M KOH solution in water was spin cast at a rotation speed of 2500 rotation/min for 30 s in the next technological step. The samples with the spin coated solutions were dried in air and subsequently annealed in a tube furnace for ~2 hours at temperatures in the range of 400-700 °C. The scanning electron microscopy analysis of the produced nanorod arrays morphologies proved that 650 °C is the best annealing temperature. The nanorods have a diameter around 100 nm and a length in the micron range. The produced nanorod arrays have been characterized by energy dispersive X-ray (EDX), X-ray diffraction (XRD) analysis, high-resolution scanning transmission electron microscopy (HR-STEM), FTIR and Raman scattering spectroscopy. The EDX analysis shows a stoichiometric WO3 composition, while XRD analysis and Raman spectra suggest the predominance of the monoclinic -WO3 phase, which is also confirmed by the observation of inter-planar 0.351 nm and 0.334 nm spacing in the HR-STEM analysis, corresponding to (012) and (120) reflexes in the XRD pattern. A sulfur film is deposited for sulfurization on the WO3 nanorod arrays by radio-frequency magnetron sputtering with a disc of 99.99 % pure sulfur as target in a deposition chamber evacuated to a pressure of 2.5x10-5 mTorr with a subsequent argon gas pumping at a rate of 50 ml/min to a pressure of 1.9x10-2 mTorr. The magnetron power was maintained at a level of 75 W during the deposition of the sulfur film. The samples were subjected to annealing during 40 minutes at 600-800 oC after the magnetron sputtering to generate a mix phase of WS2/WO3. The prospects of the produced structures for applications in intrinsic fiber optic sensors and energy storage are also discussed in relation with the analysis of cyclic voltammetry data.