TY - JOUR A1 - Schmack, R. A1 - Eckhardt, B. A1 - Koch, G. A1 - Ortel, Erik A1 - Kraehnert, R. T1 - ZnO coatings with controlled pore size, crystallinity and electrical conductivity N2 - Zinc oxide is a wide bandgap semiconductor with unique optical, electrical and catalytic properties. Many of its practical applications rely on the materials pore structure, crystallinity and electrical conductivity. We report a synthesis method for ZnO films with ordered mesopore structure and tuneable crystallinity and electrical conductivity. The synthesis relies on dip-coating of solutions containing micelles of an amphiphilic block copolymer and complexes of Zn2+ ions with aliphatic ligands. A subsequent calcination at 400 °C removes the template and induces crystallization of the pore walls. The pore structure is controlled by the template polymer, whereas the aliphatic ligands control the crystallinity of the pore walls. Complexes with a higher thermal stability result in ZnO films with a higher content of residual carbon, smaller ZnO crystals and therefore lower electrical conductivity. The paper discusses the ability of different types of ligands to assist in the synthesis of mesoporous ZnO and relates the structure and thermal stability of the precursor complexes to the crystallinity and electrical conductivity of the zinc oxide. KW - conductivity KW - EISA KW - pore templating KW - pore size control KW - ligands KW - zinc oxide PY - 2016 DO - https://doi.org/10.5755/j01.ms.22.1.8634 SN - 1392–1320 VL - 22 IS - 1 SP - 74 EP - 81 PB - Kaunas University of Technology, Lithuania AN - OPUS4-35550 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ortel, Erik A1 - Bernicke, M. A1 - Eckhardt, B. A1 - Bernsmeier, D. A1 - Schmack, R. A1 - Kraehnert, R. A1 - Lippitz, Andreas T1 - Synthesis and OER activity of NiO coatings with N2 - Catalysts based on nickel oxide are some of the most active catalysts for the oxygen evolution reaction (OER) in alkaline media. However, preparing catalytic coatings with high surface area and good accessibility of the active sites remains challenging. We present a new approach for the synthesis of homogeneous and binder-free nickel oxide coatings comprising a highly accessible ordered mesopore structure. The synthesis is achieved via evaporation induced self assembly utilizing PEOPB-PEO triblock copolymers as pore template and a chemical complex of Ni2+ and citric acid as precursor. Excessive crystallization behaviour of NiO is avoided by thermal conversion of the precursor into an amorphous Ni carbonate intermediate, followed by transition of the carbonate into the metal oxide. We present a comprehensive analysis of the obtained materials in terms of morphology, crystallinity, surface area, composition, and OER activity of differently calcined catalysts. Retaining a low crystallinity and high surface area during the Synthesis proofs to be the most important factor in obtaining a highly active OER catalyst. KW - XPS KW - nanoparticle KW - catalysis PY - 2016 UR - http://onlinelibrary.wiley.com/doi/10.1002/slct.201600110/abstract DO - https://doi.org/10.1002/slct.201600110 VL - 2016 IS - 3/2016 SP - 482 EP - 489 PB - Wiley Online Library CY - Weinheim AN - OPUS4-35725 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ortel, Erik A1 - Hertwig, Andreas A1 - Berger, D. A1 - Esposito, P. A1 - Rossi, A. M. A1 - Kraehnert, R. A1 - Hodoroaba, Vasile-Dan T1 - New approach on quantification of porosity of thin films via electron-excited X‑ray spectra N2 - One of the crucial characteristics of functionalized thin films is their porosity (i.e., the ratio between the pore volume and the volume of the whole film). Due to the very low amount of material per coated area corresponding to thin films, it is a challenge for analytics to measure the film porosity. In this work, we present an Approach to determine the porosity of thin films by means of electron probe microanalysis (EPMA) either by wavelength-dispersive X-ray spectrometry (WDX) or by energy-dispersive X-ray spectrometry (EDX) with a scanning electron microscope (SEM). The procedure is based on the calculation of the film mass deposition from electron-excited X-ray spectra. The mass deposition is converted into film density by division of measured film thickness. Finally, the film porosity is calculated from the measured film density and the density of bulk, nonporous film material. The general applicability of the procedure to determine the porosity is demonstrated on thin templated mesoporous TiO₂ films, dip-coated on silicon wafer, with controlled porosity in the range of 15 to 50%. The high accuracy of the mass deposition as determined from X-ray spectra was validated with independent methods (ICP-OES and weighing). Furthermore, for the validation of the porosity results, ellipsometry, interference fringes method (IFM), and focused ion beam (FIB) cross sectioning were employed as independent techniques. Hence, the approach proposed in the present study is proven to be suited as a new analytical tool for accurate and relatively fast determination of the porosity of thin films. KW - Porosity KW - X-rays KW - EDX KW - Thin film KW - TiO2 KW - Density KW - Mass deposition KW - STRATAGem PY - 2016 UR - http://pubs.acs.org/doi/abs/10.1021/acs.analchem.6b00847 DO - https://doi.org/10.1021/acs.analchem.6b00847 VL - 88 IS - 14 SP - 7083 EP - 7090 PB - ACS Publications CY - 1155 Sixteenth Street N.W., Washington, DC 20036 AN - OPUS4-36911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -