Nano-indentation investigations of the mechanical properties of thin TiO2, WO3 and their composites layers, deposited by spray pyrolysis

Abstract

The aim of the present work is to determine the indentation hardness (HIT) and indentation modulus (EIT) of pure TiO2 and WO3 thin films, as well as thin films composed of different TiO2 and WO3 proportions and deposited by spray pyrolysis on a stainless-steel (OC 404) substrate. Since the HIT and EIT of the films are properties expected to depend on the phase-chemical composition, morphology, structure and their changes when increasing the WO3 content in the TiO2-WO3 composite film, the correlation between the mechanical and structural properties is also addressed. The obtained results show that HIT and EIT strongly depend on the concentration of the co-deposited WO3. The determined values of HIT and EIT noticeably decrease (in comparison with HIT and EIT of the pure (100 %) TiO2 layer) when very low concentrations of WO3 (up to 2.5 % of W) are co-deposited. At higher concentrations of the co-deposited WO3 (more than 2.5 % of W), the HIT and EIT values increase almost linearly with an increase of the WO3 in the precursor. The observed non-proportional behavior of HIT and EIT is associated with specific changes of the structure and a development of defects in the deposited TiO2-WO3 composite phase, as well as with the increase in the amount of the formed separate WO3 phase (with increasing of WO3 (H2W3O12) in the working solution) surrounded by solitary TiO2 particles. Keywords: inorganic compounds, chemical synthesis, electron microscopy, elastic properties Namen predstavljenega dela je dolo~iti trdoto vtiska (HIT) in modul vtiska (EIT) v tankih filmih iz~istega TiO2 in WO3, kot tudi tankih filmov, sestavljenih iz razli~nih delov TiO2 in WO3, nane{enih s pr{ilno pirolizo na podlago iz nerjavnega jekla (OC 404). Ker se pri~akuje, da sta lastnosti filma HIT in EIT odvisni od kemijske sestave faz, morfologije, strukture in njenih sprememb, ko pove~ujemo dele`WO3 v TiO2-WO3 kompozitnem filmu, se to nana{a tudi na odvisnost med mehanskimi lastnostmi in lastnostmi strukture. Dobljeni rezultati ka`ejo, da sta HIT in EIT mo~no odvisna od koncentracije nane{enega WO3. Dolo~ene vrednosti HIT in EIT se opazno zmanj{ajo (v primerjavi z HIT in EIT plasti iz~istega (100 %) TiO2) ko se nanese WO3 z nizko koncentracijo (do 2,5 % dele`W). Pri nanosih WO3 z vi{jo koncentracijo (nad 2,5 % dele`W), vrednosti HIT in EIT nara{~ata skoraj linearno z pove~evanjem dele`a WO3 v osnovi. Opa`eno neproporcionalno obna{anje HIT in EIT je povezano s specifi~nimi spremembami v strukturi in z razvojem napak v nane{eni TiO2-WO3 kompozitni fazi, kot tudi s pove~anjem koli~ine nastale WO3 faze (pri pove~evanju WO3 (H2W3O12) v delovni raztopini), ki jo obkro`ajo posamezni TiO2 delci.

Sustainable Approach for the Development of TiO2-Based 3D Electrodes for Microsupercapacitors

“…In addition to the well-known electrochemical properties of TiO 2 as an electrode in energy storage systems, TiO 2 has attracted interest primarily because, during the last few years, synthetic routes for thin films with controlled crystallite sizes and shapes and good adhesion to different supports have been reported. TiO 2 thin films can be obtained via several methods [26] including sol-gel processes [27,28], spray pyrolysis [29], pulsed laser deposition [30,31], radio frequency magnetron sputtering (physical vapor deposition (PVD) method [32,33], and atomic layer deposition (ALD) [34]. Once the synthesis of TiO 2 thin films was established, further structuration of TiO 2 thin films on 3D supports was possible, opening the way for developing high-performance microdevices.…”