Authors:Imre Szilágyi, István Sajó, Péter Király, Gábor Tárkányi, Attila Tóth, András Szabó, Katalin Varga-Josepovits, János Madarász, and György Pokol
This article discusses the formation and structure of ammonium tungsten bronzes, (NH4)xWO3−y. As analytical tools, TG/DTA-MS, XRD, SEM, Raman, XPS, and 1H-MAS NMR were used. The well-known α-hexagonal ammonium tungsten bronze (α-HATB, ICDD 42-0452) was thermally reduced and
around 550 °C a hexagonal ammonium tungsten bronze formed, whose structure was similar to α-HATB, but the hexagonal channels
were almost completely empty; thus, this phase was called reduced hexagonal (h-) WO3. In contrast with earlier considerations, it was found that the oxidation state of W atoms influenced at least as much the
cell parameters of α-HATB and h-WO3, as the packing of the hexagonal channels. Between 600 and 650 °C reduced h-WO3 transformed into another ammonium tungsten bronze, whose structure was disputed in the literature. It was found that the
structure of this phase—called β-HATB, (NH4)0.001WO2.79—was hexagonal.
Authors:Viktória Vargha, Avashnee Chetty, Zsolt Sulyok, Judith Mihály, Zsófia Keresztes, András Tóth, István Sajó, László Korecz, Rajesh Anandjiwala, and Lydia Boguslavsky
Surface oxyfluorination had been carried out on polypropylene non-woven fabric (PP NWF) samples of different morphologies and pore sizes. The modified surfaces were characterised by Attenuated Total Reflectance Fourier Transform InfraRed (ATR-FTIR)-spectroscopy, FTIR imaging microscopy, X-Ray Photoelectron Spectroscopy (XPS), Electron Spin Resonance (ESR) spectroscopy, Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM), dynamic rheometry and Thermo-Gravimetry (TG). ATR-FTIR and XPS techniques revealed the presence of –CF, –CF2, –CHF and –C(O)F groups. The formed –C(O)F groups mostly got hydrolysed to –COOH groups. The C=O groups of alpha-haloester, and the C=C stretching of the formed –CF=C(OH)– groups could also be detected. Long-lived radicals could be detected on the functionalised surfaces as middle-chain peroxy radicals by ESR spectroscopy. SEM micrographs showed slight roughening of the oxyfluorinated surfaces. Oxyfluorination had no significant effect on the crystalline structure and phase composition of the PP NWF samples supported by DSC and XRD measurements. The molecular mass of the samples were unaffected by the oxyfluorination treatment as proved by oscillating rheometry. The surface modification, however, significantly affected the thermal decomposition but not affected the thermo-oxidative decomposition of PP NWFs. Different morphologies and pore sizes of PP NWF samples resulted in reproducibility of the findings, although did not substantially affect surface functionalisation.