Infrared and Raman study of WO3 tungsten trioxides and WO3, xH2O tungsten trioxide tydrates

Formation of unwanted deposits on steels during their interaction with liquids is an inherent problem that often leads to corrosion, biofouling and results in reduction in durability and function. Here we report a new route to form anti-fouling steel surfaces by electrodeposition of nanoporous tungsten oxide (TO) films. TO-modified steels are as mechanically durable as bare steel and highly tolerant to compressive and tensile stresses due to chemical bonding to the substrate and island-like morphology. When inherently superhydrophilic TO coatings are converted to superhydrophobic, they remain non-wetting even after impingement with yttria-stabilized-zirconia particles, or exposure to ultraviolet light and extreme temperatures. Upon lubrication, these surfaces display omniphobicity against highly contaminating media retaining hitherto unseen mechanical durability. To illustrate the applicability of such a durable coating in biofouling conditions, we modified naval construction steels and surgical instruments and demonstrated significantly reduced marine algal film adhesion, Escherichia coli attachment and blood staining.

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Extremely durable biofouling-resistant metallic surfaces based on electrodeposited nanoporous tungstite films on steel

Proton transfer and superionic conductivity in solids and gels

The phase transformations of 12-tungstophosphoric H3PW12O40-29H2O (29-WPA) acid in the temperature range from ambient temperature to 1150°C were investigated and characterized by differential thermal analysis (DTA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), infrared (ir) and Raman spectroscopies From room temperature to 550°C, 29-WPA passes through a dehydration process, which characterizes the formation of different crystallohydrates, in anhydrous form as well as “denuded” Keggin's anions, the D-phase (PW12O38) During these processes, Keggin's anions are not disturbed too much and they are preserved up to about 550°C The “D” phase is transformed by solid-solid recrystallization at about 600°C in a new monophosphate bronze type compound PW8O26 Unit cell dimensions were calculated from XRPD data (a
o=07515 nm) With the temperature increasing up to 1150°C, novel synthesized cubic bronze passed through three polymorphous phase transitions According to a general formula for monophosphate tungsten bronzes (WO3)2m (PO4)4 all four polymorphs have m=16

Thermally induced phase transformations of 12-tungstophosphoric acid 29-hydrate : synthesis and characterization of PW8O26-type bronzes

Reactivity of different nanometric tungsten oxide was measured by in situ Raman spectroscopy coupled with electrical measurements during the reaction with CH4, CO and NO2 molecules in the temperature range of 50–250°C. Sample with the smallest crystallite size (2 nm) exhibited a strong electrical and Raman response to the presence of these molecules. The formation of a very active form of carbon was observed already at 50°C on the surface of tungsten oxide during the catalytic reactions involving gases containing carbonaceous molecules. Switching the atmosphere from reducing to NO2 oxidizing gas leads to a complete and immediate disappearance of the carbon and the conductivity changes by a factor of 105. No such changes were observed for crystallite sizes of 35 nm. The results are discussed and interpretation based on quasi-chemical reactions is proposed.

M.Pham Thi

Papers

Raman study of WO3 thin films